ld64-302.3.1.tar.gz

[apple/ld64.git] / src / ld / Options.cpp

/* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
 *
 * Copyright (c) 2005-2011 Apple Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_LICENSE_HEADER_END@
 */


#include <sys/types.h>
#include <sys/stat.h>
#include <mach/vm_prot.h>
#include <sys/sysctl.h>
#include <mach-o/dyld.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <spawn.h>
#include <cxxabi.h>
#include <Availability.h>
#include <tapi/tapi.h>

#include <vector>
#include <map>
#include <sstream>

#include "Options.h"
#include "Architectures.hpp"
#include "MachOFileAbstraction.hpp"
#include "Snapshot.h"


// from FunctionNameDemangle.h
extern "C" size_t fnd_get_demangled_name(const char *mangledName, char *outputBuffer, size_t length);


// upward dependency on lto::version()
namespace lto {
        extern const char* version();
        extern unsigned static_api_version();
        extern unsigned runtime_api_version();
}

// magic to place command line in crash reports
const int crashreporterBufferSize = 2000;
static char crashreporterBuffer[crashreporterBufferSize];
#if __MAC_OS_X_VERSION_MIN_REQUIRED >= 1070
        #include <CrashReporterClient.h>
        // hack until ld does not need to build on 10.6 anymore
    struct crashreporter_annotations_t gCRAnnotations 
        __attribute__((section("__DATA," CRASHREPORTER_ANNOTATIONS_SECTION))) 
        = { CRASHREPORTER_ANNOTATIONS_VERSION, 0, 0, 0, 0, 0, 0 };
#else
        extern "C" char* __crashreporter_info__;
        __attribute__((used)) 
        char* __crashreporter_info__ = crashreporterBuffer;
#endif


static bool                     sEmitWarnings = true;
static bool                     sFatalWarnings = false;
static const char*      sWarningsSideFilePath = NULL;
static FILE*            sWarningsSideFile = NULL;
static int                      sWarningsCount = 0;

void warning(const char* format, ...)
{
        ++sWarningsCount;
        if ( sEmitWarnings ) {
                va_list list;
                if ( sWarningsSideFilePath != NULL ) {
                        if ( sWarningsSideFile == NULL )
                                sWarningsSideFile = fopen(sWarningsSideFilePath, "a");
                }
                va_start(list, format);
                fprintf(stderr, "ld: warning: ");
                vfprintf(stderr, format, list);
                fprintf(stderr, "\n");
                if ( sWarningsSideFile != NULL ) {
                        fprintf(sWarningsSideFile, "ld: warning: ");
                        vfprintf(sWarningsSideFile, format, list);
                        fprintf(sWarningsSideFile, "\n");
                        fflush(sWarningsSideFile);
                }
                va_end(list);
        }
}

void throwf(const char* format, ...)
{
        va_list list;
        char*   p;
        va_start(list, format);
        vasprintf(&p, format, list);
        va_end(list);

        const char*     t = p;
        throw t;
}


bool Options::FileInfo::checkFileExists(const Options& options, const char *p)
{
        struct stat statBuffer;
        if (p == NULL) 
          p = path;
        if ( stat(p, &statBuffer) == 0 ) {
                if (p != path) path = strdup(p);
                modTime = statBuffer.st_mtime;
                return true;
        }
        if ( options.dumpDependencyInfo() )
                options.dumpDependency(Options::depNotFound, p);
//      fprintf(stderr, "not found: %s\n", p);
    return false;
}


Options::Options(int argc, const char* argv[])
        : fOutputFile("a.out"), fArchitecture(0), fSubArchitecture(0), fArchitectureName("unknown"), fOutputKind(kDynamicExecutable), 
          fHasPreferredSubType(false), fArchSupportsThumb2(false), fPrebind(false), fBindAtLoad(false), fKeepPrivateExterns(false),
          fNeedsModuleTable(false), fIgnoreOtherArchFiles(false), fErrorOnOtherArchFiles(false), fForceSubtypeAll(false), 
          fInterposeMode(kInterposeNone), fDeadStrip(false), fNameSpace(kTwoLevelNameSpace),
          fDylibCompatVersion(0), fDylibCurrentVersion(0), fDylibInstallName(NULL), fFinalName(NULL), fEntryName(NULL), 
          fBaseAddress(0), fMaxAddress(0x7FFFFFFFFFFFFFFFLL), 
          fBaseWritableAddress(0), fSplitSegs(false),
          fExportMode(kExportDefault), fLibrarySearchMode(kSearchDylibAndArchiveInEachDir),
          fUndefinedTreatment(kUndefinedError), fMessagesPrefixedWithArchitecture(true), 
          fWeakReferenceMismatchTreatment(kWeakReferenceMismatchNonWeak),
          fClientName(NULL),
          fUmbrellaName(NULL), fInitFunctionName(NULL), fDotOutputFile(NULL), fExecutablePath(NULL),
          fBundleLoader(NULL), fDtraceScriptName(NULL), fSegAddrTablePath(NULL), fMapPath(NULL), 
          fDyldInstallPath("/usr/lib/dyld"), fLtoCachePath(NULL), fTempLtoObjectPath(NULL), fOverridePathlibLTO(NULL), fLtoCpu(NULL),
          fZeroPageSize(ULLONG_MAX), fStackSize(0), fStackAddr(0), fSourceVersion(0), fSDKVersion(0), fExecutableStack(false), 
          fNonExecutableHeap(false), fDisableNonExecutableHeap(false),
          fMinimumHeaderPad(32), fSegmentAlignment(4096), 
          fCommonsMode(kCommonsIgnoreDylibs),  fUUIDMode(kUUIDContent), fLocalSymbolHandling(kLocalSymbolsAll), fWarnCommons(false), 
          fVerbose(false), fKeepRelocations(false), fWarnStabs(false),
          fTraceDylibSearching(false), fPause(false), fStatistics(false), fPrintOptions(false),
          fSharedRegionEligible(false), fSharedRegionEligibleForceOff(false), fPrintOrderFileStatistics(false),
          fReadOnlyx86Stubs(false), fPositionIndependentExecutable(false), fPIEOnCommandLine(false),
          fDisablePositionIndependentExecutable(false), fMaxMinimumHeaderPad(false),
          fDeadStripDylibs(false),  fAllowTextRelocs(false), fWarnTextRelocs(false), fKextsUseStubs(false),
          fUsingLazyDylibLinking(false), fEncryptable(true), fEncryptableForceOn(false), fEncryptableForceOff(false),
          fOrderData(true), fMarkDeadStrippableDylib(false),
          fMakeCompressedDyldInfo(true), fMakeCompressedDyldInfoForceOff(false), fNoEHLabels(false),
          fAllowCpuSubtypeMismatches(false), fEnforceDylibSubtypesMatch(false), fUseSimplifiedDylibReExports(false),
          fObjCABIVersion2Override(false), fObjCABIVersion1Override(false), fCanUseUpwardDylib(false),
          fFullyLoadArchives(false), fLoadAllObjcObjectsFromArchives(false), fFlatNamespace(false),
          fLinkingMainExecutable(false), fForFinalLinkedImage(false), fForStatic(false),
          fForDyld(false), fMakeTentativeDefinitionsReal(false), fWhyLoad(false), fRootSafe(false),
          fSetuidSafe(false), fImplicitlyLinkPublicDylibs(true), fAddCompactUnwindEncoding(true),
          fWarnCompactUnwind(false), fRemoveDwarfUnwindIfCompactExists(false),
          fAutoOrderInitializers(true), fOptimizeZeroFill(true), fMergeZeroFill(false), fLogObjectFiles(false),
          fLogAllFiles(false), fTraceDylibs(false), fTraceIndirectDylibs(false), fTraceArchives(false), fTraceEmitJSON(false),
          fOutputSlidable(false), fWarnWeakExports(false), 
          fObjcGcCompaction(false), fObjCGc(false), fObjCGcOnly(false), 
          fDemangle(false), fTLVSupport(false), 
          fVersionLoadCommand(false), fVersionLoadCommandForcedOn(false), 
          fVersionLoadCommandForcedOff(false), fBuildVersionLoadCommand(false), fFunctionStartsLoadCommand(false),
          fFunctionStartsForcedOn(false), fFunctionStartsForcedOff(false),
          fDataInCodeInfoLoadCommand(false), fDataInCodeInfoLoadCommandForcedOn(false), fDataInCodeInfoLoadCommandForcedOff(false),
          fCanReExportSymbols(false), fObjcCategoryMerging(true), fPageAlignDataAtoms(false), 
          fNeedsThreadLoadCommand(false), fEntryPointLoadCommand(false),
          fEntryPointLoadCommandForceOn(false), fEntryPointLoadCommandForceOff(false),
          fSourceVersionLoadCommand(false), 
          fSourceVersionLoadCommandForceOn(false), fSourceVersionLoadCommandForceOff(false), 
          fTargetIOSSimulator(false), fExportDynamic(false), fAbsoluteSymbols(false),
          fAllowSimulatorToLinkWithMacOSX(false), fKeepDwarfUnwind(true),
          fKeepDwarfUnwindForcedOn(false), fKeepDwarfUnwindForcedOff(false),
          fVerboseOptimizationHints(false), fIgnoreOptimizationHints(false),
          fGenerateDtraceDOF(true), fAllowBranchIslands(true), fTraceSymbolLayout(false), 
          fMarkAppExtensionSafe(false), fCheckAppExtensionSafe(false), fForceLoadSwiftLibs(false),
          fSharedRegionEncodingV2(false), fUseDataConstSegment(false),
          fUseDataConstSegmentForceOn(false), fUseDataConstSegmentForceOff(false), fUseTextExecSegment(false),
          fBundleBitcode(false), fHideSymbols(false), fVerifyBitcode(false),
          fReverseMapUUIDRename(false), fDeDupe(true), fVerboseDeDupe(false),
          fReverseMapPath(NULL), fLTOCodegenOnly(false),
          fIgnoreAutoLink(false), fAllowDeadDups(false), fAllowWeakImports(true), fNoInitializers(false), fBitcodeKind(kBitcodeProcess),
          fPlatform(kPlatformUnknown), fDebugInfoStripping(kDebugInfoMinimal), fTraceOutputFile(NULL),
          fMacVersionMin(ld::macVersionUnset), fIOSVersionMin(ld::iOSVersionUnset), fWatchOSVersionMin(ld::wOSVersionUnset),
          fSaveTempFiles(false), fSnapshotRequested(false), fPipelineFifo(NULL),
          fDependencyInfoPath(NULL), fDependencyFileDescriptor(-1), fTraceFileDescriptor(-1), fMaxDefaultCommonAlign(0),
          fUnalignedPointerTreatment(kUnalignedPointerIgnore)
{
        this->checkForClassic(argc, argv);
        this->parsePreCommandLineEnvironmentSettings();
        this->parse(argc, argv);
        this->parsePostCommandLineEnvironmentSettings();
        this->reconfigureDefaults();
        this->checkIllegalOptionCombinations();
        
        if ( this->dumpDependencyInfo() ) {
                this->dumpDependency(depOutputFile, fOutputFile);
                if ( fMapPath != NULL ) 
                this->dumpDependency(depOutputFile, fMapPath);
        }
}

Options::~Options()
{
        if ( fDependencyFileDescriptor != -1 )
                ::close(fDependencyFileDescriptor);

        if ( fTraceFileDescriptor != -1 )
                ::close(fTraceFileDescriptor);
}

bool Options::errorBecauseOfWarnings() const
{
        return (sFatalWarnings && (sWarningsCount > 0));
}


const char*     Options::installPath() const
{
        if ( fDylibInstallName != NULL )
                return fDylibInstallName;
        else if ( fFinalName != NULL )
                return fFinalName;
        else
                return fOutputFile;
}


bool Options::interposable(const char* name) const
{
        switch ( fInterposeMode ) {
                case kInterposeNone:
                        return false;
                case kInterposeAllExternal:
                        return true;
                case kInterposeSome:
                        return fInterposeList.contains(name);
        }
        throw "internal error";
}


bool Options::printWhyLive(const char* symbolName) const
{
        return fWhyLive.contains(symbolName);
}


const char*     Options::dotOutputFile()
{
        return fDotOutputFile;
}


bool Options::hasWildCardExportRestrictList() const
{
        // has -exported_symbols_list which contains some wildcards
        return ((fExportMode == kExportSome) && fExportSymbols.hasWildCards());
}

bool Options::hasWeakBitTweaks() const
{
        // has -exported_symbols_list which contains some wildcards
        return (!fForceWeakSymbols.empty() || !fForceNotWeakSymbols.empty());
}

bool Options::allGlobalsAreDeadStripRoots() const
{
        // -exported_symbols_list means globals are not exported by default
        if ( fExportMode == kExportSome )
                return false;
        //
        switch ( fOutputKind ) {
                case Options::kDynamicExecutable:
                        // <rdar://problem/12839986> Add the -export_dynamic flag 
                        return fExportDynamic;
                case Options::kStaticExecutable:
                        // <rdar://problem/13361218> Support the -export_dynamic flag for xnu
                        return fExportDynamic;
                case Options::kPreload:
                        // by default unused globals in a main executable are stripped
                        return false;
                case Options::kDynamicLibrary:
                case Options::kDynamicBundle:
                case Options::kObjectFile:
                case Options::kDyld:
                case Options::kKextBundle:
                        return true;
        }
        return false;
}


bool Options::keepRelocations()
{
        return fKeepRelocations;
}

bool Options::warnStabs()
{
        return fWarnStabs;
}

const char* Options::executablePath()
{
        return fExecutablePath;
}

uint32_t Options::initialSegProtection(const char* segName) const
{
        for(std::vector<Options::SegmentProtect>::const_iterator it = fCustomSegmentProtections.begin(); it != fCustomSegmentProtections.end(); ++it) {
                if ( strcmp(it->name, segName) == 0 ) {
                        return it->init;
                }
        }
        if ( strcmp(segName, "__TEXT") == 0 ) {
                return ( fUseTextExecSegment ? VM_PROT_READ : (VM_PROT_READ | VM_PROT_EXECUTE) );
        }
        else if ( strcmp(segName, "__TEXT_EXEC") == 0 ) {
                return VM_PROT_READ | VM_PROT_EXECUTE;
        }
        else if ( strcmp(segName, "__PAGEZERO") == 0 ) {
                return 0;
        }
        else if ( strcmp(segName, "__LINKEDIT") == 0 ) {
                return VM_PROT_READ;
        }
        
        // all others default to read-write
        return VM_PROT_READ | VM_PROT_WRITE;
}

uint32_t Options::maxSegProtection(const char* segName) const
{
        // iPhoneOS always uses same protection for max and initial
        // <rdar://problem/11663436> simulator apps need to use MacOSX max-prot
        if ( (fPlatform != kPlatformOSX) && !fTargetIOSSimulator )
                return initialSegProtection(segName);

        for(std::vector<Options::SegmentProtect>::const_iterator it = fCustomSegmentProtections.begin(); it != fCustomSegmentProtections.end(); ++it) {
                if ( strcmp(it->name, segName) == 0 ) {
                        return it->max;
                }
        }
        if ( strcmp(segName, "__PAGEZERO") == 0 ) {
                return 0;
        }
        // all others default to all
        return VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE;
}
        
uint64_t Options::segPageSize(const char* segName) const
{
        for(std::vector<SegmentSize>::const_iterator it=fCustomSegmentSizes.begin(); it != fCustomSegmentSizes.end(); ++it) {
                if ( strcmp(it->name, segName) == 0 )
                        return it->size;
        }
        return fSegmentAlignment;
}

uint64_t Options::customSegmentAddress(const char* segName) const
{
        for(std::vector<SegmentStart>::const_iterator it=fCustomSegmentAddresses.begin(); it != fCustomSegmentAddresses.end(); ++it) {
                if ( strcmp(it->name, segName) == 0 )
                        return it->address;
        }
        // if custom stack in use, model as segment with custom address
        if ( (fStackSize != 0) && (strcmp("__UNIXSTACK", segName) == 0) )
                return fStackAddr - fStackSize;
        return 0;
}

bool Options::hasCustomSegmentAddress(const char* segName) const
{
        for(std::vector<SegmentStart>::const_iterator it=fCustomSegmentAddresses.begin(); it != fCustomSegmentAddresses.end(); ++it) {
                if ( strcmp(it->name, segName) == 0 )
                        return true;
        }
        // if custom stack in use, model as segment with custom address
        if ( (fStackSize != 0) && (strcmp("__UNIXSTACK", segName) == 0) )
                return true;
        return false;
}

bool Options::hasCustomSectionAlignment(const char* segName, const char* sectName) const
{
        for (std::vector<SectionAlignment>::const_iterator it = fSectionAlignments.begin(); it != fSectionAlignments.end(); ++it) {
                if ( (strcmp(it->segmentName, segName) == 0) && (strcmp(it->sectionName, sectName) == 0) )
                        return true;
        }
        if ( fEncryptable && (strcmp(sectName, "__oslogstring") == 0) && (strcmp(segName, "__TEXT") == 0) )
                return true;

        return false;
}

uint8_t Options::customSectionAlignment(const char* segName, const char* sectName) const
{
        for (std::vector<SectionAlignment>::const_iterator it = fSectionAlignments.begin(); it != fSectionAlignments.end(); ++it) {
                if ( (strcmp(it->segmentName, segName) == 0) && (strcmp(it->sectionName, sectName) == 0) )
                        return it->alignment;
        }
        if ( fEncryptable && (strcmp(sectName, "__oslogstring") == 0) && (strcmp(segName, "__TEXT") == 0) )
                return __builtin_ctz(fSegmentAlignment);

        return 0;
}

bool Options::segmentOrderAfterFixedAddressSegment(const char* segName) const
{
        bool nowPinned = false;
        for (std::vector<const char*>::const_iterator it=fSegmentOrder.begin(); it != fSegmentOrder.end(); ++it) {
                if ( strcmp(*it, segName) == 0 )
                        return nowPinned;
                if ( hasCustomSegmentAddress(*it) )
                        nowPinned = true;
        }
        return false;
}

bool Options::hasExportedSymbolOrder()
{
        return (fExportSymbolsOrder.size() > 0);
}

bool Options::exportedSymbolOrder(const char* sym, unsigned int* order) const
{
        NameToOrder::const_iterator pos = fExportSymbolsOrder.find(sym);
        if ( pos != fExportSymbolsOrder.end() ) {
                *order = pos->second;
                return true;
        }
        else {
                *order = 0xFFFFFFFF;
                return false;
        }
}

void Options::loadSymbolOrderFile(const char* fileOfExports, NameToOrder& orderMapping)
{
        // read in whole file
        int fd = ::open(fileOfExports, O_RDONLY, 0);
        if ( fd == -1 )
                throwf("can't open -exported_symbols_order file: %s", fileOfExports);
        struct stat stat_buf;
        ::fstat(fd, &stat_buf);
        char* p = (char*)malloc(stat_buf.st_size);
        if ( p == NULL )
                throwf("can't process -exported_symbols_order file: %s", fileOfExports);

        if ( read(fd, p, stat_buf.st_size) != stat_buf.st_size )
                throwf("can't read -exported_symbols_order file: %s", fileOfExports);

        ::close(fd);

        // parse into symbols and add to unordered_set
        unsigned int count = 0;
        char * const end = &p[stat_buf.st_size];
        enum { lineStart, inSymbol, inComment } state = lineStart;
        char* symbolStart = NULL;
        for (char* s = p; s < end; ++s ) {
                switch ( state ) {
                case lineStart:
                        if ( *s =='#' ) {
                                state = inComment;
                        }
                        else if ( !isspace(*s) ) {
                                state = inSymbol;
                                symbolStart = s;
                        }
                        break;
                case inSymbol:
                        if ( (*s == '\n') || (*s == '\r') ) {
                                *s = '\0';
                                // removing any trailing spaces
                                char* last = s-1;
                                while ( isspace(*last) ) {
                                        *last = '\0';
                                        --last;
                                }
                                orderMapping[symbolStart] = ++count;
                                symbolStart = NULL;
                                state = lineStart;
                        }
                        break;
                case inComment:
                        if ( (*s == '\n') || (*s == '\r') )
                                state = lineStart;
                        break;
                }
        }
        if ( state == inSymbol ) {
                warning("missing line-end at end of file \"%s\"", fileOfExports);
                int len = end-symbolStart+1;
                char* temp = new char[len];
                strlcpy(temp, symbolStart, len);

                // remove any trailing spaces
                char* last = &temp[len-2];
                while ( isspace(*last) ) {
                        *last = '\0';
                        --last;
                }
                orderMapping[temp] = ++count;
        }

        // Note: we do not free() the malloc buffer, because the strings are used by the export-set hash table
}

bool Options::forceWeak(const char* symbolName) const
{
        return fForceWeakSymbols.contains(symbolName);
}

bool Options::forceNotWeak(const char* symbolName) const
{
        return fForceNotWeakSymbols.contains(symbolName);
}

bool Options::forceWeakNonWildCard(const char* symbolName) const
{
        return fForceWeakSymbols.containsNonWildcard(symbolName);
}

bool Options::forceNotWeakNonWildcard(const char* symbolName) const
{
        return fForceNotWeakSymbols.containsNonWildcard(symbolName);
}

bool Options::forceCoalesce(const char* symbolName) const
{
        return fForceCoalesceSymbols.contains(symbolName);
}


bool Options::shouldExport(const char* symbolName) const
{
        switch (fExportMode) {
                case kExportSome:
                        return fExportSymbols.contains(symbolName);
                case kDontExportSome:
                        return ! fDontExportSymbols.contains(symbolName);
                case kExportDefault:
                        return true;
        }
        throw "internal error";
}

bool Options::shouldReExport(const char* symbolName) const
{
        return fReExportSymbols.contains(symbolName);
}

bool Options::keepLocalSymbol(const char* symbolName) const
{
        switch (fLocalSymbolHandling) {
                case kLocalSymbolsAll:
                        return true;
                case kLocalSymbolsNone:
                        return false;
                case kLocalSymbolsSelectiveInclude:
                        return fLocalSymbolsIncluded.contains(symbolName);
                case kLocalSymbolsSelectiveExclude:
                        return ! fLocalSymbolsExcluded.contains(symbolName);
        }
        throw "internal error";
}

const std::vector<const char*>* Options::sectionOrder(const char* segName) const
{ 
        for (std::vector<SectionOrderList>::const_iterator it=fSectionOrder.begin(); it != fSectionOrder.end(); ++it) {
                if ( strcmp(it->segmentName, segName) == 0 )
                        return &it->sectionOrder;
        }
        return NULL;
}

uint32_t Options::minOSversion() const
{
        switch (fPlatform) {
                case kPlatformiOS:
                        return iOSVersionMin();
                case kPlatformOSX:
                        return macosxVersionMin();
                case kPlatformWatchOS:
                        return watchOSVersionMin();
#if SUPPORT_APPLE_TV
                case Options::kPlatform_tvOS:
                        return iOSVersionMin();
#endif
                case kPlatform_bridgeOS:
                        return iOSVersionMin();
                case kPlatformUnknown:
                        return 0;
        }
        return 0;
}

void Options::setArchitecture(cpu_type_t type, cpu_subtype_t subtype, Options::Platform platform)
{
        for (const ArchInfo* t=archInfoArray; t->archName != NULL; ++t) {
                if ( (type == t->cpuType) && (subtype == t->cpuSubType) ) {
                        fArchitecture = type;
                        fSubArchitecture = subtype;
                        fArchitectureName = t->archName;
                        fHasPreferredSubType = t->isSubType;
                        fArchSupportsThumb2 = t->supportsThumb2;
                        if ( fPlatform == kPlatformUnknown)
                                fPlatform = platform;
                        switch ( type ) {
                                case CPU_TYPE_I386:
                                case CPU_TYPE_X86_64:
                                        if ( (fPlatform == kPlatformOSX) && (fOutputKind != Options::kObjectFile) && (fMacVersionMin == ld::macVersionUnset) ) {
                                #ifdef DEFAULT_MACOSX_MIN_VERSION
                                                warning("-macosx_version_min not specified, assuming " DEFAULT_MACOSX_MIN_VERSION);
                                                setMacOSXVersionMin(DEFAULT_MACOSX_MIN_VERSION);
                                #else
                                                warning("-macosx_version_min not specified, assuming 10.6");
                                                fMacVersionMin = ld::mac10_6;
                                #endif          
                                        }
                                        break;
                                case CPU_TYPE_ARM:
                                case CPU_TYPE_ARM64:
                                        if ( (fMacVersionMin == ld::macVersionUnset) && (fIOSVersionMin == ld::iOSVersionUnset) && (fOutputKind != Options::kObjectFile) ) {
                                #if defined(DEFAULT_IPHONEOS_MIN_VERSION)
                                                warning("-ios_version_min not specified, assuming " DEFAULT_IPHONEOS_MIN_VERSION);
                                                setIOSVersionMin(DEFAULT_IPHONEOS_MIN_VERSION);
                                #else
                                                warning("-ios_version_min not specified, assuming 6.0");
                                                setIOSVersionMin("6.0");
                                #endif
                                        }
                                        break;
                        }
                        fLinkSnapshot.recordArch(fArchitectureName);
                        // only use compressed LINKEDIT for:
                        //                      Mac OS X 10.6 or later
                        //                      iOS 3.1 or later
                        if ( !fMakeCompressedDyldInfo && minOS(ld::mac10_6, ld::iOS_3_1) && !fMakeCompressedDyldInfoForceOff )
                                fMakeCompressedDyldInfo = true;
                        // Mac OS X 10.5 and iPhoneOS 2.0 support LC_REEXPORT_DYLIB
                        if ( minOS(ld::mac10_5, ld::iOS_2_0) )
                                fUseSimplifiedDylibReExports = true;
                        return;
                }
        }
        fArchitectureName = "unknown architecture";
}

bool Options::armUsesZeroCostExceptions() const
{
        return ( (fArchitecture == CPU_TYPE_ARM) && (fSubArchitecture == CPU_SUBTYPE_ARM_V7K) );
}

void Options::parseArch(const char* arch)
{
        if ( arch == NULL )
                throw "-arch must be followed by an architecture string";
        for (const ArchInfo* t=archInfoArray; t->archName != NULL; ++t) {
                if ( strcmp(t->archName,arch) == 0 ) {
                        fArchitectureName = arch;
                        fArchitecture = t->cpuType;
                        fSubArchitecture = t->cpuSubType;
                        fHasPreferredSubType = t->isSubType;
                        fArchSupportsThumb2 = t->supportsThumb2;
                        return;
                }
        }
        throwf("unknown/unsupported architecture name for: -arch %s", arch);
}

bool Options::checkForFile(const char* format, const char* dir, const char* rootName, FileInfo& result) const
{
        char possiblePath[strlen(dir)+strlen(rootName)+strlen(format)+8];
        sprintf(possiblePath, format,  dir, rootName);
        bool found = result.checkFileExists(*this, possiblePath);
        if ( fTraceDylibSearching )
                printf("[Logging for XBS]%sfound library: '%s'\n", (found ? " " : " not "), possiblePath);
        return found;
}


Options::FileInfo Options::findLibrary(const char* rootName, bool dylibsOnly) const
{
        FileInfo result;
        const int rootNameLen = strlen(rootName);
        // if rootName ends in .o there is no .a vs .dylib choice
        if ( (rootNameLen > 3) && (strcmp(&rootName[rootNameLen-2], ".o") == 0) ) {
                for (std::vector<const char*>::const_iterator it = fLibrarySearchPaths.begin();
                         it != fLibrarySearchPaths.end();
                         it++) {
                        const char* dir = *it;
                        if ( checkForFile("%s/%s", dir, rootName, result) )
                                return result;
                }
        }
        else {
                bool lookForDylibs = false;
                switch ( fOutputKind ) {
                        case Options::kDynamicExecutable:
                        case Options::kDynamicLibrary:
                        case Options::kDynamicBundle:
                        case Options::kObjectFile:  // <rdar://problem/15914513> 
                                lookForDylibs = true;
                                break;
                        case Options::kStaticExecutable:
                        case Options::kDyld:
                        case Options::kPreload:
                        case Options::kKextBundle:
                                lookForDylibs = false;
                                break;
                }
                switch ( fLibrarySearchMode ) {
                case kSearchAllDirsForDylibsThenAllDirsForArchives:
                                // first look in all directories for just for dylibs
                                if ( lookForDylibs ) {
                                        for (std::vector<const char*>::const_iterator it = fLibrarySearchPaths.begin();
                                                 it != fLibrarySearchPaths.end();
                                                 it++) {
                                                const char* dir = *it;
                                                auto path = std::string(dir) + "/lib" + rootName + ".dylib";
                                                if ( findFile(path, {".tbd"}, result) )
                                                        return result;
                                        }
                                        for (std::vector<const char*>::const_iterator it = fLibrarySearchPaths.begin();
                                                 it != fLibrarySearchPaths.end();
                                                 it++) {
                                                const char* dir = *it;
                                                if ( checkForFile("%s/lib%s.so", dir, rootName, result) )
                                                        return result;
                                        }
                                }
                                // next look in all directories for just for archives
                                if ( !dylibsOnly ) {
                                        for (std::vector<const char*>::const_iterator it = fLibrarySearchPaths.begin();
                                                 it != fLibrarySearchPaths.end();
                                                 it++) {
                                                const char* dir = *it;
                                                if ( checkForFile("%s/lib%s.a", dir, rootName, result) )
                                                        return result;
                                        }
                                }
                                break;

                        case kSearchDylibAndArchiveInEachDir:
                                // look in each directory for just for a dylib then for an archive
                                for (std::vector<const char*>::const_iterator it = fLibrarySearchPaths.begin();
                                         it != fLibrarySearchPaths.end();
                                         it++) {
                                        const char* dir = *it;
                                        auto path = std::string(dir) + "/lib" + rootName + ".dylib";
                                        if ( lookForDylibs && findFile(path, {".tbd"}, result) )
                                                return result;
                                        if ( lookForDylibs && checkForFile("%s/lib%s.so", dir, rootName, result) )
                                                return result;
                                        if ( !dylibsOnly && checkForFile("%s/lib%s.a", dir, rootName, result) )
                                                return result;
                                }
                                break;
                }
        }
        throwf("library not found for -l%s", rootName);
}

Options::FileInfo Options::findFramework(const char* frameworkName) const
{
        if ( frameworkName == NULL )
                throw "-framework missing next argument";
        char temp[strlen(frameworkName)+1];
        strcpy(temp, frameworkName);
        const char* name = temp;
        const char* suffix = NULL;
        char* comma = strchr(temp, ',');
        if ( comma != NULL ) {
                *comma = '\0';
                suffix = &comma[1];
        }
        return findFramework(name, suffix);
}

Options::FileInfo Options::findFramework(const char* rootName, const char* suffix) const
{
        for (const auto* path : fFrameworkSearchPaths) {
                auto possiblePath = std::string(path).append("/").append(rootName).append(".framework/").append(rootName);
                if ( suffix != nullptr ) {
                        char realPath[PATH_MAX];
                        // no symlink in framework to suffix variants, so follow main symlink
                        if ( realpath(possiblePath.c_str(), realPath) != nullptr )
                                possiblePath = std::string(realPath).append(suffix);
                }
        FileInfo result;
                if ( findFile(possiblePath, {".tbd"}, result) )
                        return result;
        }
        // try without suffix
        if ( suffix != NULL )
                return findFramework(rootName, NULL);
        else
                throwf("framework not found %s", rootName);
}

static std::string replace_extension(const std::string &path, const std::string &ext)
{
        auto result = path;
        auto lastSlashIdx = result.find_last_of('/');
        auto lastDotIdx = result.find_last_of('.');
        if (lastDotIdx != std::string::npos && lastDotIdx > lastSlashIdx)
                result.erase(lastDotIdx, std::string::npos);
        if ( ext.size() > 0 && ext[0] == '.' )
                result.append(ext);
        else
                result.append('.' + ext);
        return result;
}

bool Options::findFile(const std::string &path, const std::vector<std::string> &tbdExtensions, FileInfo& result) const
{
        FileInfo tbdInfo;
        for ( const auto &ext : tbdExtensions ) {
                auto newPath = replace_extension(path, ext);
                bool found = tbdInfo.checkFileExists(*this, newPath.c_str());
                if ( fTraceDylibSearching )
                        printf("[Logging for XBS]%sfound library: '%s'\n", (found ? " " : " not "), newPath.c_str());
                if ( found )
                        break;
        }

        FileInfo dylibInfo;
        {
                bool found = dylibInfo.checkFileExists(*this, path.c_str());
                if ( fTraceDylibSearching )
                        printf("[Logging for XBS]%sfound library: '%s'\n", (found ? " " : " not "), path.c_str());
        }

        // There is only a text-based stub file or a dynamic library file.
        if ( tbdInfo.missing() != dylibInfo.missing() ) {
                result = tbdInfo.missing() ? dylibInfo : tbdInfo;
        }
        // There are both - a text-based stub file and a dynamic library file.
        else if ( !tbdInfo.missing() && !dylibInfo.missing() ) {
                // Check if we should prefer the text-based stub file (installapi).
                if (tapi::LinkerInterfaceFile::shouldPreferTextBasedStubFile(tbdInfo.path)) {
                        result = tbdInfo;
                }
                // If the files are still in sync we can use and should use the text-based stub file.
                else if (tapi::LinkerInterfaceFile::areEquivalent(tbdInfo.path, dylibInfo.path)) {
                        result = tbdInfo;
                }
                // Otherwise issue a warning and fall-back to the dynamic library file.
                else {
                        warning("text-based stub file %s and library file %s are out of sync. Falling back to library file for linking.", tbdInfo.path, dylibInfo.path);
                        result = dylibInfo;
                }
        } else {
                return false;
        }

        return true;
}

static bool startsWith(const std::string& str, const std::string& prefix)
{
        return (str.compare(0, prefix.length(), prefix) == 0);
}

static std::string getDirPath(const std::string& path)
{
        std::string::size_type lastSlashPos = path.find_last_of('/');
        if ( lastSlashPos == std::string::npos )
                return "./";
        else
                return path.substr(0, lastSlashPos+1);
}

Options::FileInfo Options::findFile(const std::string &path, const ld::dylib::File* fromDylib) const
{
        FileInfo result;

        // if absolute path and not a .o file, then use SDK prefix
        if ( (path[0] == '/') && (strcmp(&path[path.size()-2], ".o") != 0) ) {
                for (const auto* sdkPathDir : fSDKPaths) {
                        auto possiblePath = std::string(sdkPathDir) + path;
                        if ( findFile(possiblePath, {".tbd"}, result) )
                                return result;
                }
        }

        // expand @ variables
        if ( path[0] == '@' ) {
                if ( startsWith(path, "@executable_path/") && (fExecutablePath != nullptr) ) {
                        std::string exeBasedPath = getDirPath(fExecutablePath) + &path[17];
                        if ( findFile(exeBasedPath, {".tbd"}, result) )
                                return result;
                }
                else if ( startsWith(path, "@loader_path/") && (fromDylib != nullptr) ) {
                        char absPath[PATH_MAX];
                        if ( realpath(fromDylib->path(), absPath) != NULL ) {
                                std::string loaderBasedPath = getDirPath(fromDylib->path()) + &path[13];
                                if ( findFile(loaderBasedPath, {".tbd"}, result) )
                                        return result;
                        }
                }
                else if ( startsWith(path, "@rpath/") ) {
                        // first search any LC_RPATH supplied by dyld that re-exports dylib to be found
                        if ( fromDylib != nullptr ) {
                                for (const char* rp : fromDylib->rpaths() ) {
                                        std::string rpath = rp;
                                        // handle dylib that has LC_RPATH = @loader_path/blah
                                        if ( startsWith(rpath, "@loader_path/") ) {
                                                char absPath[PATH_MAX];
                                                if ( realpath(fromDylib->path(), absPath) != NULL )
                                                        rpath = getDirPath(absPath) + &rpath[13];
                                                else
                                                        rpath = getDirPath(fromDylib->path()) + &rpath[13];
                                        }
                                        std::string rpathBasedPath = rpath + "/" + &path[6];
                                        if ( findFile(rpathBasedPath, {".tbd"}, result) )
                                                return result;
                                }
                        }
                }
        }

        // try raw path
        if ( findFile(path, {".tbd"}, result) )
                return result;

        // not found
        throwf("file not found: %s", path.c_str());
}

// search for indirect dylib first using -F and -L paths first
Options::FileInfo Options::findIndirectDylib(const std::string& installName, const ld::dylib::File* fromDylib) const
{
        FileInfo result;

        auto lastSlashPos = installName.find_last_of('/');
        auto pos = ( lastSlashPos != std::string::npos ) ? lastSlashPos + 1 : 0;
        auto leafName = installName.substr(pos);

        // Is this in a framework?
        // /path/Foo.framework/Foo                                                      ==> true (Foo)
        // /path/Foo.framework/Frameworks/Bar.framework/Bar ==> true (Bar)
        // /path/Foo.framework/Resources/Bar                            ==> false
        bool isFramework = false;
        if ( lastSlashPos != std::string::npos ) {
                auto frameworkDir = std::string("/").append(leafName).append(".framework/");
                if ( installName.rfind(frameworkDir) != std::string::npos )
                        isFramework = true;
        }
        
        // These are abbreviated versions of the routines findFramework and findLibrary above
        // because we already know the final name of the file that we're looking for and so
        // don't need to try variations, just paths. We do need to add the additional bits
        // onto the framework path though.
        if ( isFramework ) {
                auto endPos = installName.rfind(".framework");
                auto beginPos = installName.find_last_of('/', endPos);
                auto leafPath = installName.substr(beginPos);
                for (const auto* dir : fFrameworkSearchPaths) {
                        auto possiblePath = dir + leafPath;
                        if ( findFile(possiblePath, {".tbd"}, result) )
                                return result;
                }
        } else {
                // if this is a .dylib inside a framework, do not search -L paths
                // <rdar://problem/5427952> ld64's re-export cycle detection logic prevents use of X11 libGL on Leopard
                bool embeddedDylib = ( (leafName.size() > 6)
                                        && (leafName.find(".dylib", leafName.size()-6) != std::string::npos)
                                        && (installName.find(".framework/") != std::string::npos) );
                if ( !embeddedDylib ) {
                        for (const auto* dir : fLibrarySearchPaths) {
                                //fprintf(stderr,"Finding Library: %s/%s\n", dir, leafName);
                                std::string possiblePath = dir + std::string("/") + leafName;
                                if ( findFile(possiblePath, {".tbd"}, result) )
                                        return result;
                        }
                }
        }

        // If we didn't find it fall back to findFile.
        return findFile(installName, fromDylib);
}



void Options::parseSegAddrTable(const char* segAddrPath, const char* installPth)
{
        FILE* file = fopen(segAddrPath, "r");
        if ( file == NULL ) {
                warning("-seg_addr_table file cannot be read: %s", segAddrPath);
                return;
        }
        
        char path[PATH_MAX];
        uint64_t firstColumAddress = 0;
        uint64_t secondColumAddress = 0;
        bool hasSecondColumn = false;
        while ( fgets(path, PATH_MAX, file) != NULL ) {
                path[PATH_MAX-1] = '\0';
                char* eol = strchr(path, '\n');
                if ( eol != NULL )
                        *eol = '\0';
                // ignore lines not starting with 0x number
                if ( (path[0] == '0') && (path[1] == 'x') ) {
                        char* p;
                        firstColumAddress = strtoull(path, &p, 16);
                        while ( isspace(*p) )
                                ++p;
                        // see if second column is a number
                        if ( (p[0] == '0') && (p[1] == 'x') ) {
                                secondColumAddress = strtoull(p, &p, 16);
                                hasSecondColumn = true;
                                while ( isspace(*p) )
                                        ++p;
                        }
                        while ( isspace(*p) )
                                ++p;
                        if ( p[0] == '/' ) {
                                // remove any trailing whitespace
                                for(char* end = eol-1; (end > p) && isspace(*end); --end)
                                        *end = '\0';
                                // see if this line is for the dylib being linked
                                if ( strcmp(p, installPth) == 0 ) {
                                        fBaseAddress = firstColumAddress;
                                        if ( hasSecondColumn ) {
                                                fBaseWritableAddress = secondColumAddress;
                                                fSplitSegs = true;
                                        }
                                        break; // out of while loop
                                }
                        }
                }
        }

        fclose(file);
}

void Options::loadFileList(const char* fileOfPaths, ld::File::Ordinal baseOrdinal)
{
        FILE* file;
        const char* comma = strrchr(fileOfPaths, ',');
        const char* prefix = NULL;
        if ( comma != NULL ) {
                // <rdar://problem/5907981> -filelist fails with comma in path
                file = fopen(fileOfPaths, "r");
                if ( file == NULL ) {
                        prefix = comma+1;
                        int realFileOfPathsLen = comma-fileOfPaths;
                        char realFileOfPaths[realFileOfPathsLen+1];
                        strncpy(realFileOfPaths,fileOfPaths, realFileOfPathsLen);
                        realFileOfPaths[realFileOfPathsLen] = '\0';
                        file = fopen(realFileOfPaths, "r");
                        if ( file == NULL )
                                throwf("-filelist file '%s' could not be opened, errno=%d (%s)\n", realFileOfPaths, errno, strerror(errno));
                        if ( this->dumpDependencyInfo() )
                                this->dumpDependency(Options::depFileList, realFileOfPaths);
                }
        }
        else {
                file = fopen(fileOfPaths, "r");
                if ( file == NULL )
                        throwf("-filelist file '%s' could not be opened, errno=%d (%s)\n", fileOfPaths, errno, strerror(errno));
                if ( this->dumpDependencyInfo() )
                        this->dumpDependency(Options::depFileList, fileOfPaths);
        }

        char path[PATH_MAX];
        ld::File::Ordinal previousOrdinal = baseOrdinal;
        while ( fgets(path, PATH_MAX, file) != NULL ) {
                path[PATH_MAX-1] = '\0';
                char* eol = strchr(path, '\n');
                if ( eol != NULL )
                        *eol = '\0';
                if ( prefix != NULL ) {
                        char builtPath[strlen(prefix)+strlen(path)+2];
                        strcpy(builtPath, prefix);
                        strcat(builtPath, "/");
                        strcat(builtPath, path);
           if (fPipelineFifo != NULL) {
                           FileInfo info = FileInfo(builtPath);
                           info.ordinal = previousOrdinal.nextFileListOrdinal();
                           previousOrdinal = info.ordinal;
                           info.fromFileList = true;
              fInputFiles.push_back(info);
           } else {
                           FileInfo info = findFile(builtPath);
                           info.ordinal = previousOrdinal.nextFileListOrdinal();
                           previousOrdinal = info.ordinal;
                           info.fromFileList = true;
                           fInputFiles.push_back(info);
           }
                }
                else {
           if (fPipelineFifo != NULL) {
                           FileInfo info = FileInfo(path);
                           info.ordinal = previousOrdinal.nextFileListOrdinal();
                           previousOrdinal = info.ordinal;
                           info.fromFileList = true;
                           fInputFiles.push_back(info);
           } else {
                           FileInfo info = findFile(path);
                           info.ordinal = previousOrdinal.nextFileListOrdinal();
                           previousOrdinal = info.ordinal;
                           info.fromFileList = true;
                           fInputFiles.push_back(info);
           }
                }
        }
        fclose(file);
}


void Options::SetWithWildcards::remove(const NameSet& toBeRemoved)
{
        for(NameSet::const_iterator it=toBeRemoved.begin(); it != toBeRemoved.end(); ++it) {
                const char* symbolName = *it;
                NameSet::iterator pos = fRegular.find(symbolName);
                if ( pos != fRegular.end() )
                        fRegular.erase(pos);
        }
}

bool Options::SetWithWildcards::hasWildCards(const char* symbol) 
{
        // an exported symbol name containing *, ?, or [ requires wildcard matching
        return ( strpbrk(symbol, "*?[") != NULL );
}

void Options::SetWithWildcards::insert(const char* symbol)
{
        if ( hasWildCards(symbol) )
                fWildCard.push_back(symbol);
        else
                fRegular.insert(symbol);
}

bool Options::SetWithWildcards::contains(const char* symbol, bool* matchBecauseOfWildcard) const
{
        if ( matchBecauseOfWildcard != NULL )
                *matchBecauseOfWildcard = false;
        // first look at hash table on non-wildcard symbols
        if ( fRegular.find(symbol) != fRegular.end() )
                return true;
        // next walk list of wild card symbols looking for a match
        for(std::vector<const char*>::const_iterator it = fWildCard.begin(); it != fWildCard.end(); ++it) {
                if ( wildCardMatch(*it, symbol) ) {
                        if ( matchBecauseOfWildcard != NULL )
                                *matchBecauseOfWildcard = true;
                        return true;
                }
        }
        return false;
}

// Support "foo.o:_bar" to mean symbol _bar in file foo.o
bool Options::SetWithWildcards::containsWithPrefix(const char* symbol, const char* file, bool& wildCardMatch) const
{
        wildCardMatch = false;
        if ( contains(symbol, &wildCardMatch) )
                return true;
        if ( file == NULL )
                return false;
        const char* s = strrchr(file, '/');
        if ( s != NULL )
                file = s+1;
        char buff[strlen(file)+strlen(symbol)+2];
        sprintf(buff, "%s:%s", file, symbol);
        return contains(buff, &wildCardMatch);
}

bool Options::SetWithWildcards::containsNonWildcard(const char* symbol) const
{
        // look at hash table on non-wildcard symbols
        return ( fRegular.find(symbol) != fRegular.end() );
}


std::vector<const char*> Options::exportsData() const
{
        return fExportSymbols.data();
}


std::vector<const char*> Options::SetWithWildcards::data() const
{
        std::vector<const char*> data;
        for (NameSet::iterator it=regularBegin(); it != regularEnd(); ++it) {
                data.push_back(*it);
        }
        for (std::vector<const char*>::const_iterator it=fWildCard.begin(); it != fWildCard.end(); ++it) {
                data.push_back(*it);
        }
        return data;
}

bool Options::SetWithWildcards::inCharRange(const char*& p, unsigned char c) const
{
        ++p; // find end
        const char* b = p;
        while ( *p != '\0' ) {
                if ( *p == ']') {
                        const char* e = p;
                        // found beginining [ and ending ]
                        unsigned char last = '\0';
                        for ( const char* s = b; s < e; ++s ) {
                                if ( *s == '-' ) {
                                        unsigned char next = *(++s);
                                        if ( (last <= c) && (c <= next) )
                                                return true;
                                        ++s;
                                }
                                else {
                                        if ( *s == c )
                                                return true;
                                        last = *s;
                                }
                        }
                        return false;
                }
                ++p;
        }
        return false;
}

bool Options::SetWithWildcards::wildCardMatch(const char* pattern, const char* symbol) const
{
        const char* s = symbol;
        for (const char* p = pattern; *p != '\0'; ++p) {
                switch ( *p ) {
                        case '*':
                                if ( p[1] == '\0' )
                                        return true;
                                for (const char* t = s; *t != '\0'; ++t) {
                                        if ( wildCardMatch(&p[1], t) )
                                                return true;
                                }
                                return false;
                        case '?':
                                if ( *s == '\0' )
                                        return false;
                                ++s;
                                break;
                        case '[':
                                if ( ! inCharRange(p, *s) )
                                        return false;
                                ++s;
                                break;
                        default:
                                if ( *s != *p )
                                        return false;
                                ++s;
                }
        }
        return (*s == '\0');
}


void Options::loadExportFile(const char* fileOfExports, const char* option, SetWithWildcards& set)
{
        if ( fileOfExports == NULL )
                throwf("missing file after %s", option);
        // read in whole file
        int fd = ::open(fileOfExports, O_RDONLY, 0);
        if ( fd == -1 )
                throwf("can't open %s file: %s", option, fileOfExports);
        struct stat stat_buf;
        ::fstat(fd, &stat_buf);
        char* p = (char*)malloc(stat_buf.st_size);
        if ( p == NULL )
                throwf("can't process %s file: %s", option, fileOfExports);

        if ( read(fd, p, stat_buf.st_size) != stat_buf.st_size )
                throwf("can't read %s file: %s", option, fileOfExports);

        if ( this->dumpDependencyInfo() )
                this->dumpDependency(Options::depMisc, fileOfExports);

        ::close(fd);

        // parse into symbols and add to unordered_set
        char * const end = &p[stat_buf.st_size];
        enum { lineStart, inSymbol, inComment } state = lineStart;
        char* symbolStart = NULL;
        for (char* s = p; s < end; ++s ) {
                switch ( state ) {
                case lineStart:
                        if ( *s =='#' ) {
                                state = inComment;
                        }
                        else if ( !isspace(*s) ) {
                                state = inSymbol;
                                symbolStart = s;
                        }
                        break;
                case inSymbol:
                        if ( (*s == '\n') || (*s == '\r') ) {
                                *s = '\0';
                                // removing any trailing spaces
                                char* last = s-1;
                                while ( isspace(*last) ) {
                                        *last = '\0';
                                        --last;
                                }
                                set.insert(symbolStart);
                                symbolStart = NULL;
                                state = lineStart;
                        }
                        break;
                case inComment:
                        if ( (*s == '\n') || (*s == '\r') )
                                state = lineStart;
                        break;
                }
        }
        if ( state == inSymbol ) {
                warning("missing line-end at end of file \"%s\"", fileOfExports);
                int len = end-symbolStart+1;
                char* temp = new char[len];
                strlcpy(temp, symbolStart, len);

                // remove any trailing spaces
                char* last = &temp[len-2];
                while ( isspace(*last) ) {
                        *last = '\0';
                        --last;
                }
                set.insert(temp);
        }

        // Note: we do not free() the malloc buffer, because the strings are used by the export-set hash table
}

void Options::parseAliasFile(const char* fileOfAliases)
{
        // read in whole file
        int fd = ::open(fileOfAliases, O_RDONLY, 0);
        if ( fd == -1 )
                throwf("can't open alias file: %s", fileOfAliases);
        struct stat stat_buf;
        ::fstat(fd, &stat_buf);
        char* p = (char*)malloc(stat_buf.st_size+1);
        if ( p == NULL )
                throwf("can't process alias file: %s", fileOfAliases);

        if ( read(fd, p, stat_buf.st_size) != stat_buf.st_size )
                throwf("can't read alias file: %s", fileOfAliases);
        p[stat_buf.st_size] = '\n';
        ::close(fd);
        if ( this->dumpDependencyInfo() )
                this->dumpDependency(Options::depMisc, fileOfAliases);

        // parse into symbols and add to fAliases
        AliasPair pair;
        char * const end = &p[stat_buf.st_size+1];
        enum { lineStart, inRealName, inBetween, inAliasName, inComment } state = lineStart;
        int lineNumber = 1;
        for (char* s = p; s < end; ++s ) {
                switch ( state ) {
                case lineStart:
                        if ( *s =='#' ) {
                                state = inComment;
                        }
                        else if ( !isspace(*s) ) {
                                state = inRealName;
                                pair.realName = s;
                        }
                        break;
                case inRealName:
                        if ( *s == '\n' ) {
                                warning("line needs two symbols but has only one at line #%d in \"%s\"", lineNumber, fileOfAliases);
                                ++lineNumber;
                                state = lineStart;
                        }
                        else if ( isspace(*s) ) {
                                *s = '\0';
                                state = inBetween;
                        }
                        break;
                case inBetween:
                        if ( *s == '\n' ) {
                                warning("line needs two symbols but has only one at line #%d in \"%s\"", lineNumber, fileOfAliases);
                                ++lineNumber;
                                state = lineStart;
                        }
                        else if ( ! isspace(*s) ) {
                                state = inAliasName;
                                pair.alias = s;
                        }
                        break;
                case inAliasName:
                        if ( *s =='#' ) {
                                *s = '\0';
                                // removing any trailing spaces
                                char* last = s-1;
                                while ( isspace(*last) ) {
                                        *last = '\0';
                                        --last;
                                }
                                fAliases.push_back(pair);
                                state = inComment;
                        }
                        else if ( *s == '\n' ) {
                                *s = '\0';
                                // removing any trailing spaces
                                char* last = s-1;
                                while ( isspace(*last) ) {
                                        *last = '\0';
                                        --last;
                                }
                                fAliases.push_back(pair);
                                state = lineStart;
                        }
                        break;
                case inComment:
                        if ( *s == '\n' )
                                state = lineStart;
                        break;
                }
        }

        // Note: we do not free() the malloc buffer, because the strings therein are used by fAliases
}



void Options::setUndefinedTreatment(const char* treatment)
{
        if ( treatment == NULL )
                throw "-undefined missing [ warning | error | suppress | dynamic_lookup ]";

        if ( strcmp(treatment, "warning") == 0 )
                fUndefinedTreatment = kUndefinedWarning;
        else if ( strcmp(treatment, "error") == 0 )
                fUndefinedTreatment = kUndefinedError;
        else if ( strcmp(treatment, "suppress") == 0 )
                fUndefinedTreatment = kUndefinedSuppress;
        else if ( strcmp(treatment, "dynamic_lookup") == 0 )
                fUndefinedTreatment = kUndefinedDynamicLookup;
        else
                throw "invalid option to -undefined [ warning | error | suppress | dynamic_lookup ]";
}

Options::Treatment Options::parseTreatment(const char* treatment)
{
        if ( treatment == NULL )
                return kNULL;

        if ( strcmp(treatment, "warning") == 0 )
                return kWarning;
        else if ( strcmp(treatment, "error") == 0 )
                return kError;
        else if ( strcmp(treatment, "suppress") == 0 )
                return kSuppress;
        else
                return kInvalid;
}

void Options::setMacOSXVersionMin(const char* version)
{
        uint32_t value;
        if ( !parsePackedVersion32(version, value) ) {
                throwf("-macosx_version_min value malformed: '%s'", version);
        }
        fMacVersionMin = (ld::MacVersionMin)value;
        fPlatform = kPlatformOSX;
}

void Options::setIOSVersionMin(const char* version)
{
        uint32_t value;
        if ( !parsePackedVersion32(version, value) ) {
                throwf("-ios_version_min value malformed: '%s'", version);
        }
        fIOSVersionMin = (ld::IOSVersionMin)value;
        fPlatform = kPlatformiOS;
}


void Options::setWatchOSVersionMin(const char* version)
{
        uint32_t value;
        if ( !parsePackedVersion32(version, value) ) {
                throwf("-watchos_version_min value malformed: '%s'", version);
        }
        fWatchOSVersionMin = (ld::WatchOSVersionMin)value;
        fPlatform = kPlatformWatchOS;
}


bool Options::minOS(ld::MacVersionMin requiredMacMin, ld::IOSVersionMin requirediPhoneOSMin)
{
        if ( fMacVersionMin != ld::macVersionUnset ) {
                return ( fMacVersionMin >= requiredMacMin );
        }
        else {
                return min_iOS(requirediPhoneOSMin);
        }
}

bool Options::min_iOS(ld::IOSVersionMin requirediOSMin)
{
         if ( fWatchOSVersionMin != ld::wOSVersionUnset ) {
                // Hack until we fully track watch and ios versions seperately
                return ( (fWatchOSVersionMin + 0x00070000) >= requirediOSMin);
        }
        else if ( fPlatform == Options::kPlatform_bridgeOS ) {
                // Hack until we fully track bridge and ios versions seperately
                return ( (fIOSVersionMin + 0x00090000) >= requirediOSMin);
        }
        else {
                return ( fIOSVersionMin >= requirediOSMin );
        }
}

void Options::setWeakReferenceMismatchTreatment(const char* treatment)
{
        if ( treatment == NULL )
                throw "-weak_reference_mismatches missing [ error | weak | non-weak ]";

        if ( strcmp(treatment, "error") == 0 )
                fWeakReferenceMismatchTreatment = kWeakReferenceMismatchError;
        else if ( strcmp(treatment, "weak") == 0 )
                fWeakReferenceMismatchTreatment = kWeakReferenceMismatchWeak;
        else if ( strcmp(treatment, "non-weak") == 0 )
                fWeakReferenceMismatchTreatment = kWeakReferenceMismatchNonWeak;
        else
                throw "invalid option to -weak_reference_mismatches [ error | weak | non-weak ]";
}

Options::CommonsMode Options::parseCommonsTreatment(const char* mode)
{
        if ( mode == NULL )
                throw "-commons missing [ ignore_dylibs | use_dylibs | error ]";

        if ( strcmp(mode, "ignore_dylibs") == 0 )
                return kCommonsIgnoreDylibs;
        else if ( strcmp(mode, "use_dylibs") == 0 )
                return kCommonsOverriddenByDylibs;
        else if ( strcmp(mode, "error") == 0 )
                return kCommonsConflictsDylibsError;
        else
                throw "invalid option to -commons [ ignore_dylibs | use_dylibs | error ]";
}

void Options::addDylibOverride(const char* paths)
{
        if ( paths == NULL )
                throw "-dylib_file must followed by two colon separated paths";
        const char* colon = strchr(paths, ':');
        if ( colon == NULL )
                throw "-dylib_file must followed by two colon separated paths";
        int len = colon-paths;
        char* target = new char[len+2];
        strncpy(target, paths, len);
        target[len] = '\0';
        DylibOverride entry;
        entry.installName = target;
        entry.useInstead = &colon[1];   
        fDylibOverrides.push_back(entry);
}

uint64_t Options::parseAddress(const char* addr)
{
        char* endptr;
        uint64_t result = strtoull(addr, &endptr, 16);
        return result;
}

uint32_t Options::parseProtection(const char* prot)
{
        uint32_t result = 0;
        for(const char* p = prot; *p != '\0'; ++p) {
                switch(tolower(*p)) {
                        case 'r':
                                result |= VM_PROT_READ;
                                break;
                        case 'w':
                                result |= VM_PROT_WRITE;
                                break;
                        case 'x':
                                result |= VM_PROT_EXECUTE;
                                break;
                        case '-':
                                break;
                        default:
                                throwf("unknown -segprot lettter in %s", prot);
                }
        }
        return result;
}


//
// Parses number of form A[.B[.B[.D[.E]]]] into a uint64_t where the bits are a24.b10.c10.d10.e10
//
uint64_t Options::parseVersionNumber64(const char* versionString)
{
        uint64_t a = 0;
        uint64_t b = 0;
        uint64_t c = 0;
        uint64_t d = 0;
        uint64_t e = 0;
        char* end;
        a = strtoul(versionString, &end, 10);
        if ( *end == '.' ) {
                b = strtoul(&end[1], &end, 10);
                if ( *end == '.' ) {
                        c = strtoul(&end[1], &end, 10);
                        if ( *end == '.' ) {
                                d = strtoul(&end[1], &end, 10);
                                if ( *end == '.' ) {
                                        e = strtoul(&end[1], &end, 10);
                                }
                        }
                }
        }
        if ( (*end != '\0') || (a > 0xFFFFFF) || (b > 0x3FF) || (c > 0x3FF) || (d > 0x3FF)  || (e > 0x3FF) )
                throwf("malformed 64-bit a.b.c.d.e version number: %s", versionString);

        return (a << 40) | ( b << 30 ) | ( c << 20 ) | ( d << 10 ) | e;
}


uint32_t Options::currentVersion32() const
{
        // warn if it does not fit into 32 bit vers number
        uint32_t a = (fDylibCurrentVersion >> 40) & 0xFFFF;
        uint32_t b = (fDylibCurrentVersion >> 30) & 0xFF;
        uint32_t c = (fDylibCurrentVersion >> 20) & 0xFF;
        uint64_t rep32 = ((uint64_t)a << 40) |  ((uint64_t)b << 30) | ((uint64_t)c << 20);
        if ( rep32 != fDylibCurrentVersion ) {
                warning("truncating -current_version to fit in 32-bit space used by old mach-o format");
                a = (fDylibCurrentVersion >> 40) & 0xFFFFFF;            
                if ( a > 0xFFFF )
                        a = 0xFFFF;
                b = (fDylibCurrentVersion >> 30) & 0x3FF;
                if ( b > 0xFF )
                        b = 0xFF;
                c = (fDylibCurrentVersion >> 20) & 0x3FF;
                if ( c > 0xFF )
                        c = 0xFF;
        }
        return (a << 16) | ( b << 8 ) | c;
}

//
// Parses number of form X[.Y[.Z]] into a uint32_t where the nibbles are xxxx.yy.zz
//
uint32_t Options::parseVersionNumber32(const char* versionString)
{
        uint32_t x = 0;
        uint32_t y = 0;
        uint32_t z = 0;
        char* end;
        x = strtoul(versionString, &end, 10);
        if ( *end == '.' ) {
                y = strtoul(&end[1], &end, 10);
                if ( *end == '.' ) {
                        z = strtoul(&end[1], &end, 10);
                }
        }
        if ( (*end != '\0') || (x > 0xffff) || (y > 0xff) || (z > 0xff) )
                throwf("malformed 32-bit x.y.z version number: %s", versionString);

        return (x << 16) | ( y << 8 ) | z;
}

static const char* cstringSymbolName(const char* orderFileString)
{
        char* result;
        asprintf(&result, "cstring=%s", orderFileString);
        // convert escaped characters
        char* d = result;
        for(const char* s=result; *s != '\0'; ++s, ++d) {
                if ( *s == '\\' ) {
                        ++s;
                        switch ( *s ) {
                                case 'n':
                                        *d = '\n';
                                        break;
                                case 't':
                                        *d = '\t';
                                        break;
                                case 'v':
                                        *d = '\v';
                                        break;
                                case 'b':
                                        *d = '\b';
                                        break;
                                case 'r':
                                        *d = '\r';
                                        break;
                                case 'f':
                                        *d = '\f';
                                        break;
                                case 'a':
                                        *d = '\a';
                                        break;
                                case '\\':
                                        *d = '\\';
                                        break;
                                case '?':
                                        *d = '\?';
                                        break;
                                case '\'':
                                        *d = '\r';
                                        break;
                                case '\"':
                                        *d = '\"';
                                        break;
                                case 'x':
                                        // hexadecimal value of char
                                        {
                                                ++s;
                                                char value = 0;
                                                while ( isxdigit(*s) ) {
                                                        value *= 16;
                                                        if ( isdigit(*s) )
                                                                value += (*s-'0');
                                                        else
                                                                value += ((toupper(*s)-'A') + 10);
                                                        ++s;
                                                }
                                                *d = value;
                                        }
                                        break;
                                default:
                                        if ( isdigit(*s) ) {
                                                // octal value of char
                                                char value = 0;
                                                while ( isdigit(*s) ) {
                                                        value = (value << 3) + (*s-'0');
                                                        ++s;
                                                }
                                                *d = value;
                                        }
                        }
                }
                else {
                        *d = *s;
                }
        }
        *d = '\0';
        return result;
}

void Options::parseOrderFile(const char* path, bool cstring)
{
        // order files override auto-ordering
        fAutoOrderInitializers = false;

        // <rdar://problem/24856050> ld64 should prefer OrderFiles from the SDK over the ones in /
        for (const char* sdkPath : fSDKPaths) {
                char fullPath[PATH_MAX];
                strlcpy(fullPath, sdkPath, PATH_MAX);
                strlcat(fullPath, "/", PATH_MAX);
                strlcat(fullPath, path, PATH_MAX);
                struct stat statBuffer;
                if ( stat(fullPath, &statBuffer) == 0 ) {
                        path = strdup(fullPath);
                        break;
                }
        }

        // read in whole file
        int fd = ::open(path, O_RDONLY, 0);
        if ( fd == -1 )
                throwf("can't open order file: %s", path);
        struct stat stat_buf;
        ::fstat(fd, &stat_buf);
        char* p = (char*)malloc(stat_buf.st_size+1);
        if ( p == NULL )
                throwf("can't process order file: %s", path);
        if ( read(fd, p, stat_buf.st_size) != stat_buf.st_size )
                throwf("can't read order file: %s", path);
        ::close(fd);
        p[stat_buf.st_size] = '\n';
        if ( this->dumpDependencyInfo() )
                this->dumpDependency(Options::depMisc, path);

        // parse into vector of pairs
        char * const end = &p[stat_buf.st_size+1];
        enum { lineStart, inSymbol, inComment } state = lineStart;
        char* symbolStart = NULL;
        for (char* s = p; s < end; ++s ) {
                switch ( state ) {
                case lineStart:
                        if ( *s =='#' ) {
                                state = inComment;
                        }
                        else if ( !isspace(*s) || cstring ) {
                                state = inSymbol;
                                symbolStart = s;
                        }
                        break;
                case inSymbol:
                        if ( (*s == '\n') || (!cstring && (*s == '#')) ) {
                                bool wasComment = (*s == '#');
                                *s = '\0';
                                // removing any trailing spaces
                                char* last = s-1;
                                while ( isspace(*last) ) {
                                        *last = '\0';
                                        --last;
                                }
                                // if there is an architecture prefix, only use this symbol it if matches current arch
                                if ( strncmp(symbolStart, "ppc:", 4) == 0 ) {
                                        symbolStart = NULL;
                                }
                                else if ( strncmp(symbolStart, "ppc64:", 6) == 0 ) {
                                        symbolStart = NULL;
                                }
                                else if ( strncmp(symbolStart, "i386:", 5) == 0 ) {
                                        if ( fArchitecture == CPU_TYPE_I386 )
                                                symbolStart = &symbolStart[5];
                                        else
                                                symbolStart = NULL;
                                }
                                else if ( strncmp(symbolStart, "x86_64:", 7) == 0 ) {
                                        if ( fArchitecture == CPU_TYPE_X86_64 )
                                                symbolStart = &symbolStart[7];
                                        else
                                                symbolStart = NULL;
                                }
                                else if ( strncmp(symbolStart, "arm:", 4) == 0 ) {
                                        if ( fArchitecture == CPU_TYPE_ARM )
                                                symbolStart = &symbolStart[4];
                                        else
                                                symbolStart = NULL;
                                }
                                else if ( strncmp(symbolStart, "arm64:", 6) == 0 ) {
                                        if ( fArchitecture == CPU_TYPE_ARM64 )
                                                symbolStart = &symbolStart[6];
                                        else
                                                symbolStart = NULL;
                                }
                                if ( symbolStart != NULL ) {
                                        char* objFileName = NULL;
                                        char* colon = strstr(symbolStart, ".o:");
                                        if ( colon != NULL ) {
                                                colon[2] = '\0';
                                                objFileName = symbolStart;
                                                symbolStart = &colon[3];
                                        }
                                        else {
                                                colon = strstr(symbolStart, ".o):");
                                                if ( colon != NULL ) {
                                                        colon[3] = '\0';
                                                        objFileName = symbolStart;
                                                        symbolStart = &colon[4];
                                                }
                                        }
                                        // trim leading spaces
                                        while ( isspace(*symbolStart) ) 
                                                ++symbolStart;
                                        Options::OrderedSymbol pair;
                                        if ( cstring )
                                                pair.symbolName = cstringSymbolName(symbolStart);
                                        else
                                                pair.symbolName = symbolStart;
                                        pair.objectFileName = objFileName;
                                        fOrderedSymbols.push_back(pair);
                                }
                                symbolStart = NULL;
                                if ( wasComment )
                                        state = inComment;
                                else
                                        state = lineStart;
                        }
                        break;
                case inComment:
                        if ( *s == '\n' )
                                state = lineStart;
                        break;
                }
        }
        // Note: we do not free() the malloc buffer, because the strings are used by the fOrderedSymbols
}

void Options::parseSectionOrderFile(const char* segment, const char* section, const char* path)
{
        if ( (strcmp(section, "__cstring") == 0) && (strcmp(segment, "__TEXT") == 0) ) {
                parseOrderFile(path, true);
        }
        else if ( (strncmp(section, "__literal",9) == 0) && (strcmp(segment, "__TEXT") == 0) ) {
                warning("sorting of __literal[4,8,16] sections not supported");
        }
        else {
                // ignore section information and append all symbol names to global order file
                parseOrderFile(path, false);
        }
}

void Options::addSection(const char* segment, const char* section, const char* path)
{
        if ( strlen(segment) > 16 )
                throw "-seccreate segment name max 16 chars";
        if ( strlen(section) > 16 ) {
                char* tmp = strdup(section);
                tmp[16] = '\0';
                warning("-seccreate section name (%s) truncated to 16 chars (%s)\n", section, tmp);
                section = tmp;
        }

        // read in whole file
        int fd = ::open(path, O_RDONLY, 0);
        if ( fd == -1 )
                throwf("can't open -sectcreate file: %s", path);
        struct stat stat_buf;
        ::fstat(fd, &stat_buf);
        char* p = (char*)malloc(stat_buf.st_size);
        if ( p == NULL )
                throwf("can't process -sectcreate file: %s", path);
        if ( read(fd, p, stat_buf.st_size) != stat_buf.st_size )
                throwf("can't read -sectcreate file: %s", path);
        ::close(fd);

        // record section to create
        ExtraSection info = { segment, section, path, (uint8_t*)p, (uint64_t)stat_buf.st_size };
        fExtraSections.push_back(info);
}

void Options::addSectionRename(const char* srcSegment, const char* srcSection, const char* dstSegment, const char* dstSection)
{
        if ( strlen(srcSegment) > 16 )
                throw "-rename_section segment name max 16 chars";
        if ( strlen(srcSection) > 16 )
                throw "-rename_section section name max 16 chars";
        if ( strlen(dstSegment) > 16 )
                throw "-rename_section segment name max 16 chars";
        if ( strlen(dstSection) > 16 )
                throw "-rename_section section name max 16 chars";

        SectionRename info;
        info.fromSegment = srcSegment;
        info.fromSection = srcSection;
        info.toSegment = dstSegment;
        info.toSection = dstSection;

        fSectionRenames.push_back(info);
}


void Options::addSegmentRename(const char* srcSegment, const char* dstSegment)
{
        if ( strlen(srcSegment) > 16 )
                throw "-rename_segment segment name max 16 chars";
        if ( strlen(dstSegment) > 16 )
                throw "-rename_segment segment name max 16 chars";

        SegmentRename info;
        info.fromSegment = srcSegment;
        info.toSegment = dstSegment;

        fSegmentRenames.push_back(info);
}



void Options::addSymbolMove(const char* dstSegment, const char* symbolList,
                                                        std::vector<SymbolsMove>& list, const char* optionName)
{
        if ( strlen(dstSegment) > 16 )
                throwf("%s segment name max 16 chars", optionName);
        
        SymbolsMove tmp;
        list.push_back(tmp);
        SymbolsMove& info = list.back();
        info.toSegment = dstSegment;
        loadExportFile(symbolList, optionName, info.symbols);
}
                
bool Options::moveRwSymbol(const char* symName, const char* filePath, const char*& seg, bool& wildCardMatch) const
{
        for (std::vector<SymbolsMove>::const_iterator it=fSymbolsMovesData.begin(); it != fSymbolsMovesData.end(); ++it) {
                const SymbolsMove& info = *it;
                if ( info.symbols.containsWithPrefix(symName, filePath, wildCardMatch)) {
                        seg  = info.toSegment;
                        return true;
                }
        }
        return false;
}

bool Options::moveRoSymbol(const char* symName, const char* filePath, const char*& seg, bool& wildCardMatch) const
{
        for (std::vector<SymbolsMove>::const_iterator it=fSymbolsMovesCode.begin(); it != fSymbolsMovesCode.end(); ++it) {
                const SymbolsMove& info = *it;
                if ( info.symbols.containsWithPrefix(symName, filePath, wildCardMatch)) {
                        seg  = info.toSegment;
                        return true;
                }
        }
        return false;
}

void Options::addSectionAlignment(const char* segment, const char* section, const char* alignmentStr)
{
        if ( strlen(segment) > 16 )
                throw "-sectalign segment name max 16 chars";
        if ( strlen(section) > 16 )
                throw "-sectalign section name max 16 chars";

        // argument to -sectalign is a hexadecimal number
        char* endptr;
        unsigned long value = strtoul(alignmentStr, &endptr, 16);
        if ( *endptr != '\0')
                throw "argument for -sectalign is not a hexadecimal number";
        if ( value > 0x8000 )
                throw "argument for -sectalign must be less than or equal to 0x8000";
        if ( value == 0 ) {
                warning("zero is not a valid -sectalign");
                value = 1;
        }

        // alignment is power of 2 (e.g. page alignment = 12)
        uint8_t alignment = (uint8_t)__builtin_ctz(value);
        if ( (unsigned long)(1 << alignment) != value ) {
                warning("alignment for -sectalign %s %s is not a power of two, using 0x%X",
                        segment, section, 1 << alignment);
        }

        SectionAlignment info = { segment, section, alignment };
        fSectionAlignments.push_back(info);
}

void Options::addLibrary(const FileInfo& info)
{
        // if this library has already been added, don't add again (archives are automatically repeatedly searched)
        for (std::vector<Options::FileInfo>::iterator fit = fInputFiles.begin(); fit != fInputFiles.end(); fit++) {
                if ( strcmp(info.path, fit->path) == 0 ) {
                        // if dylib is specified again but weak, record that it should be weak
                        if ( info.options.fWeakImport )
                                fit->options.fWeakImport = true;
                        return;
                }
        }
        // add to list
        fInputFiles.push_back(info);
}

void Options::warnObsolete(const char* arg)
{
        warning("option %s is obsolete and being ignored", arg);
}


void Options::cannotBeUsedWithBitcode(const char* arg)
{
        if ( fBundleBitcode )
                throwf("%s and -bitcode_bundle (Xcode setting ENABLE_BITCODE=YES) cannot be used together", arg);
}

std::string Options::getVersionString32(uint32_t ver) const
{
        if (ver == 0 || ver >= 0x10000000)
                return "0.0.0";

        unsigned microVersion = ver & 0xFF;
        unsigned minorVersion = (ver >> 8) & 0xFF;
        unsigned majorVersion = (ver >> 16) & 0xFF;
        std::stringstream versionString;
        versionString << majorVersion << "." << minorVersion << "." << microVersion;
        return versionString.str();
}

std::string Options::getVersionString64(uint64_t ver) const
{
        uint64_t a = (ver >> 40) & 0xFFFFFF;
        uint64_t b = (ver >> 30) & 0x3FF;
        uint64_t c = (ver >> 20) & 0x3FF;
        uint64_t d = (ver >> 10) & 0x3FF;
        uint64_t e = ver & 0x3FF;
        std::stringstream versionString;
        versionString << a << "." << b << "." << c << "." << d << "." << e;
        return versionString.str();
}

// Convert X.Y[.Z] to 32-bit value xxxxyyzz
bool Options::parsePackedVersion32(const std::string& versionStr, uint32_t &result)
{
        result = 0;

        if ( versionStr.empty() )
                return false;

        size_t pos = versionStr.find('.');
        if ( pos == std::string::npos )
                return false;

        std::string majorStr = versionStr.substr(0, pos);
        std::string rest = versionStr.substr(pos+1);

        try {
                size_t majorEnd;
                int majorValue = std::stoi(majorStr, &majorEnd);
                if ( majorEnd != majorStr.size() )
                        return false;
                if ( majorValue < 0 )
                        return false;
                if ( majorValue > 65535 )
                        return false;

                std::string minorStr;
                std::string microStr;
                pos = rest.find('.');
                if ( pos == std::string::npos ) {
                        minorStr = rest;
                }
                else {
                        minorStr = rest.substr(0, pos);
                        microStr = rest.substr(pos+1);
                }

                size_t minorEnd;
                int minorValue = std::stoi(minorStr, &minorEnd);
                if ( minorEnd != minorStr.size() )
                        return false;
                if ( minorValue < 0 )
                        return false;
                if ( minorValue > 255 )
                        return false;

                int microValue = 0;
                if ( !microStr.empty() ) {
                        size_t microEnd;
                        microValue = std::stoi(microStr, &microEnd);
                        if ( microEnd != microStr.size() )
                                return false;
                        if ( microValue < 0 )
                                return false;
                        if ( microValue > 255 )
                                return false;
                }

                result = (majorValue << 16) | (minorValue << 8) | microValue;

                return true;
        }
        catch (...) {
                // std::stoi() throws exception on malformed input
                return false;
        }
}

std::string Options::getSDKVersionStr() const
{
        return getVersionString32(fSDKVersion);
}

std::string Options::getPlatformStr() const
{
        switch (fPlatform) {
                case Options::kPlatformOSX:
                        return "MacOSX";
                case Options::kPlatformiOS:
                        if (targetIOSSimulator())
                                return "iPhoneSimulator";
                        else
                                return "iPhoneOS";
                case Options::kPlatformWatchOS:
                        if (targetIOSSimulator())
                                return "watchOS Simulator";
                        else
                                return "watchOS";
#if SUPPORT_APPLE_TV
                case Options::kPlatform_tvOS:
                        if (targetIOSSimulator())
                                return "AppleTVSimulator";
                        else
                                return "AppleTVOS";
                        break;
#endif
                case Options::kPlatform_bridgeOS:
                        return "bridgeOS";
                case Options::kPlatformUnknown:
                        return "Unknown";
        }
}

std::vector<std::string> Options::writeBitcodeLinkOptions() const
{
        std::vector<std::string> linkCommand;
        switch ( fOutputKind ) {
                case Options::kDynamicLibrary:
                        linkCommand.push_back("-dylib");
                        linkCommand.push_back("-compatibility_version");
                        if ( fDylibCompatVersion != 0 ) {
                                linkCommand.push_back(getVersionString32(fDylibCompatVersion));
                        } else {
                                linkCommand.push_back(getVersionString32(currentVersion32()));
                        }
                        if ( fDylibCurrentVersion != 0 ) {
                                linkCommand.push_back("-current_version");
                                linkCommand.push_back(getVersionString64(fDylibCurrentVersion));
                        }
                        linkCommand.push_back("-install_name");
                        linkCommand.push_back(installPath());
                        break;
                case Options::kDynamicExecutable:
                        linkCommand.push_back("-execute");
                        break;
                case Options::kObjectFile:
                        linkCommand.push_back("-r");
                        break;
                default:
                        throwf("could not write bitcode options file output kind\n");
        }

        if (!fImplicitlyLinkPublicDylibs)
                linkCommand.push_back("-no_implicit_dylibs");

        // Add deployment target.
        // Platform is allowed to be unknown for "ld -r".
        switch (fPlatform) {
                case Options::kPlatformOSX:
                        linkCommand.push_back("-macosx_version_min");
                        linkCommand.push_back(getVersionString32((unsigned)fMacVersionMin));
                        break;
                case Options::kPlatformiOS:
                        if (targetIOSSimulator())
                                linkCommand.push_back("-ios_simulator_version_min");
                        else
                                linkCommand.push_back("-ios_version_min");
                        linkCommand.push_back(getVersionString32((unsigned)fIOSVersionMin));
                        break;
                case Options::kPlatformWatchOS:
                        if (targetIOSSimulator())
                                linkCommand.push_back("-watchos_simulator_version_min");
                        else
                                linkCommand.push_back("-watchos_version_min");
                        linkCommand.push_back(getVersionString32((unsigned)fIOSVersionMin));
                        break;
#if SUPPORT_APPLE_TV
                case Options::kPlatform_tvOS:
                        if (targetIOSSimulator())
                                linkCommand.push_back("-tvos_simulator_version_min");
                        else
                                linkCommand.push_back("-tvos_version_min");
                        linkCommand.push_back(getVersionString32((unsigned)fIOSVersionMin));
                        break;
#endif
                case Options::kPlatform_bridgeOS:
                        linkCommand.push_back("-bridgeos_version_min");
                        linkCommand.push_back(getVersionString32((unsigned)fIOSVersionMin));
                        break;
                case Options::kPlatformUnknown:
                        if ( fOutputKind != Options::kObjectFile ) {
                                throwf("platform is unknown for final bitcode bundle,"
                                           "deployment target and min version is required for -bitcode_bundle");
                        }
                        break;
        }


        // entry name
        if ( fEntryName ) {
                linkCommand.push_back("-e");
                linkCommand.push_back(fEntryName);
        }

        // Write rpaths
        if (!fRPaths.empty()) {
                for (std::vector<const char*>::const_iterator it=fRPaths.begin(); it != fRPaths.end(); ++it) {
                        linkCommand.push_back("-rpath");
                        linkCommand.push_back(*it);
                }
        }

        // Other bitcode compatiable options
        if ( fObjCABIVersion1Override ) {
                linkCommand.push_back("-objc_abi_version");
                linkCommand.push_back("1");
        } else if ( fObjCABIVersion2Override ) {
                linkCommand.push_back("-objc_abi_version");
                linkCommand.push_back("2");
        }
        if ( fExecutablePath ) {
                linkCommand.push_back("-executable_path");
                linkCommand.push_back(fExecutablePath);
        }
        if ( fDeadStrip )
                linkCommand.push_back("-dead_strip");
        if ( fExportDynamic )
                linkCommand.push_back("-export_dynamic");
        if ( fMarkAppExtensionSafe && fCheckAppExtensionSafe )
                linkCommand.push_back("-application_extension");

        if ( fSourceVersionLoadCommandForceOn )
                linkCommand.push_back("-add_source_version");
        if ( fSourceVersion != 0 ) {
                linkCommand.push_back("-source_version");
                linkCommand.push_back(getVersionString64(fSourceVersion));
        }

        // linker flag added by swift driver
        // rdar://problem/20108072
        if ( !fObjcCategoryMerging )
                linkCommand.push_back("-no_objc_category_merging");

        return linkCommand;
}

//
// Process all command line arguments.
//
// The only error checking done here is that each option is valid and if it has arguments
// that they too are valid.
//
// The general rule is "last option wins", i.e. if both -bundle and -dylib are specified,
// whichever was last on the command line is used.
//
// Error check for invalid combinations of options is done in checkIllegalOptionCombinations()
//
void Options::parse(int argc, const char* argv[])
{
    // Store the original args in the link snapshot.
    fLinkSnapshot.recordRawArgs(argc, argv);
    
        // pass one builds search list from -L and -F options
        this->buildSearchPaths(argc, argv);

        // reduce re-allocations
        fInputFiles.reserve(32);

        // pass two parse all other options
        for(int i=1; i < argc; ++i) {
                const char* arg = argv[i];

                if ( arg[0] == '-' ) {
            // by default, copy one arg to the snapshot link command, and do no file copying
            int snapshotArgIndex = i;
            int snapshotArgCount = -1; // -1 means compute count based on change in index
            int snapshotFileArgIndex = -1; // -1 means no data file parameter to arg

                        // Since we don't care about the files passed, just the option names, we do this here.
                        if (fPrintOptions)
                                fprintf (stderr, "[Logging ld64 options]\t%s\n", arg);

                        if ( (arg[1] == 'L') || (arg[1] == 'F') ) {
                snapshotArgCount = 0; // stripped out of link snapshot
                                if (arg[2] == '\0')
                                        ++i;
                                // previously handled by buildSearchPaths()
                        }
                        // The one gnu style option we have to keep compatibility
                        // with gcc. Might as well have the single hyphen one as well.
                        else if ( (strcmp(arg, "--help") == 0)
                                          || (strcmp(arg, "-help") == 0)) {
                                fprintf (stdout, "ld64: For information on command line options please use 'man ld'.\n");
                                exit (0);
                        }
                        else if ( strcmp(arg, "-arch") == 0 ) {
                                parseArch(argv[++i]);
                        }
                        else if ( strcmp(arg, "-dynamic") == 0 ) {
                                // default
                        }
                        else if ( strcmp(arg, "-static") == 0 ) {
                                fForStatic = true;
                                if ( (fOutputKind != kObjectFile) && (fOutputKind != kKextBundle) ) {
                                        fOutputKind = kStaticExecutable;
                                }
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-dylib") == 0 ) {
                                fOutputKind = kDynamicLibrary;
                        }
                        else if ( strcmp(arg, "-bundle") == 0 ) {
                                fOutputKind = kDynamicBundle;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-dylinker") == 0 ) {
                                fOutputKind = kDyld;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-execute") == 0 ) {
                                if ( fOutputKind != kStaticExecutable )
                                        fOutputKind = kDynamicExecutable;
                        }
                        else if ( strcmp(arg, "-preload") == 0 ) {
                                fOutputKind = kPreload;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-r") == 0 ) {
                                fOutputKind = kObjectFile;
                        }
                        else if ( strcmp(arg, "-kext") == 0 ) {
                                fOutputKind = kKextBundle;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-o") == 0 ) {
                snapshotArgCount = 0;
                                fOutputFile = argv[++i];
                fLinkSnapshot.setSnapshotName(fOutputFile);
                        }
                        else if ( strncmp(arg, "-lazy-l", 7) == 0 ) {
                snapshotArgCount = 0;
                                FileInfo info = findLibrary(&arg[7], true);
                                info.options.fLazyLoad = true;
                                info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                                addLibrary(info);
                                fUsingLazyDylibLinking = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-lto_library") == 0 ) {
                snapshotFileArgIndex = 1;
                                fOverridePathlibLTO = argv[++i];
                                if ( fOverridePathlibLTO == NULL )
                                        throw "missing argument to -lto_library";
                        }
                        else if ( strcmp(arg, "-cache_path_lto") == 0 ) {
                                fLtoCachePath = argv[++i];
                                if ( fLtoCachePath == NULL )
                                        throw "missing argument to -cache_path_lto";
                        }
                        else if ( strcmp(arg, "-prune_interval_lto") == 0 ) {
                                const char* value = argv[++i];
                                if ( value == NULL )
                                        throw "missing argument to -prune_interval_lto";
                                char* endptr;
                                fLtoPruneInterval = strtoul(value, &endptr, 10);
                                if ( *endptr != '\0')
                                        throw "invalid argument for -prune_interval_lto";
                        }
                        else if ( strcmp(arg, "-prune_after_lto") == 0 ) {
                                const char* value = argv[++i];
                                if ( value == NULL )
                                        throw "missing argument to -prune_after_lto";
                                char* endptr;
                                fLtoPruneAfter = strtoul(value, &endptr, 10);
                                if ( *endptr != '\0')
                                        throw "invalid argument for -prune_after_lto";
                        }
                        else if ( strcmp(arg, "-max_relative_cache_size_lto") == 0 ) {
                                const char* value = argv[++i];
                                if ( value == NULL )
                                        throw "missing argument to -max_relative_cache_size_lto";
                                char* endptr;
                                fLtoMaxCacheSize = strtoul(value, &endptr, 10);
                                if ( *endptr != '\0')
                                        throw "invalid argument for -max_relative_cache_size_lto";
                                if (fLtoMaxCacheSize > 100)
                                        throw "Expect a value between 0 and 100 for -max_relative_cache_size_lto";
                        }
                        else if ( (arg[1] == 'l') && (strncmp(arg,"-lazy_",6) !=0) ) {
                snapshotArgCount = 0;
                                FileInfo info = findLibrary(&arg[2]);
                                info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                                addLibrary(info);
                        }
                        // This causes a dylib to be weakly bound at
                        // link time.  This corresponds to weak_import.
                        else if ( strncmp(arg, "-weak-l", 7) == 0 ) {
                // SNAPSHOT FIXME: what should we do for link snapshots? (ignore for now)
                snapshotArgCount = 0;
                                FileInfo info = findLibrary(&arg[7]);
                                info.options.fWeakImport = true;
                                info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                                addLibrary(info);
                        }
                        // Avoid lazy binding.
                        else if ( strcmp(arg, "-bind_at_load") == 0 ) {
                                fBindAtLoad = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-twolevel_namespace") == 0 ) {
                                fNameSpace = kTwoLevelNameSpace;
                        }
                        else if ( strcmp(arg, "-flat_namespace") == 0 ) {
                                fNameSpace = kFlatNameSpace;
                                cannotBeUsedWithBitcode(arg);
                        }
                        // Also sets a bit to ensure dyld causes everything
                        // in the namespace to be flat.
                        // ??? Deprecate
                        else if ( strcmp(arg, "-force_flat_namespace") == 0 ) {
                                fNameSpace = kForceFlatNameSpace;
                                cannotBeUsedWithBitcode(arg);
                        }
                        // Similar to --whole-archive.
                        else if ( strcmp(arg, "-all_load") == 0 ) {
                                fFullyLoadArchives = true;
                        }
                        else if ( strcmp(arg, "-noall_load") == 0) {
                                warnObsolete(arg);
                        }
                        // Similar to -all_load
                        else if ( strcmp(arg, "-ObjC") == 0 ) {
                                fLoadAllObjcObjectsFromArchives = true;
                        }
                        // Similar to -all_load, but for the following archive only.
                        else if ( strcmp(arg, "-force_load") == 0 ) {
                                FileInfo info = findFile(argv[++i]);
                                info.options.fForceLoad = true;
                                info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                                addLibrary(info);
                        }
                        // Library versioning.
                        else if ( (strcmp(arg, "-dylib_compatibility_version") == 0)
                                          || (strcmp(arg, "-compatibility_version") == 0)) {
                                 const char* vers = argv[++i];
                                 if ( vers == NULL )
                                        throw "-dylib_compatibility_version missing <version>";
                                fDylibCompatVersion = parseVersionNumber32(vers);
                        }
                        else if ( (strcmp(arg, "-dylib_current_version") == 0)
                                          || (strcmp(arg, "-current_version") == 0)) {
                                 const char* vers = argv[++i];
                                 if ( vers == NULL )
                                        throw "-dylib_current_version missing <version>";
                                fDylibCurrentVersion = parseVersionNumber64(vers);
                        }
                        else if ( strcmp(arg, "-sectorder") == 0 ) {
                                 if ( (argv[i+1]==NULL) || (argv[i+2]==NULL) || (argv[i+3]==NULL) )
                                        throw "-sectorder missing <segment> <section> <file-path>";
                snapshotFileArgIndex = 3;
                                parseSectionOrderFile(argv[i+1], argv[i+2], argv[i+3]);
                                i += 3;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-order_file") == 0 ) {
                snapshotFileArgIndex = 1;
                                parseOrderFile(argv[++i], false);
                        }
                        else if ( strcmp(arg, "-order_file_statistics") == 0 ) {
                                fPrintOrderFileStatistics = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        // ??? Deprecate segcreate.
                        // -sectcreate puts whole files into a section in the output.
                        else if ( (strcmp(arg, "-sectcreate") == 0) || (strcmp(arg, "-segcreate") == 0) ) {
                                 if ( (argv[i+1]==NULL) || (argv[i+2]==NULL) || (argv[i+3]==NULL) )
                                        throw "-sectcreate missing <segment> <section> <file-path>";
                snapshotFileArgIndex = 3;
                                addSection(argv[i+1], argv[i+2], argv[i+3]);
                                i += 3;
                        }
                        // Since we have a full path in binary/library names we need to be able to override it.
                        else if ( (strcmp(arg, "-dylib_install_name") == 0)
                                          || (strcmp(arg, "-dylinker_install_name") == 0)
                                          || (strcmp(arg, "-install_name") == 0)) {
                                fDylibInstallName = argv[++i];
                if ( fDylibInstallName == NULL )
                                        throw "-install_name missing <path>";
                        }
                        // Sets the base address of the output.
                        else if ( (strcmp(arg, "-seg1addr") == 0) || (strcmp(arg, "-image_base") == 0) ) {
                                 const char* address = argv[++i];
                                 if ( address == NULL )
                                        throwf("%s missing <address>", arg);
                                fBaseAddress = parseAddress(address);
                                uint64_t temp = ((fBaseAddress+fSegmentAlignment-1) & (-fSegmentAlignment)); 
                                if ( fBaseAddress != temp ) {
                                        warning("-seg1addr not %lld byte aligned, rounding up", fSegmentAlignment);
                                        fBaseAddress = temp;
                                }
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-e") == 0 ) {
                                fEntryName = argv[++i];
                        }
                        // Same as -@ from the FSF linker.
                        else if ( strcmp(arg, "-filelist") == 0 ) {
                 snapshotArgCount = 0;
                                 const char* path = argv[++i];
                                 if ( (path == NULL) || (path[0] == '-') )
                                        throw "-filelist missing <path>";
                                 ld::File::Ordinal baseOrdinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                                 loadFileList(path, baseOrdinal);
                        }
                        else if ( strcmp(arg, "-keep_private_externs") == 0 ) {
                                cannotBeUsedWithBitcode(arg);
                                fKeepPrivateExterns = true;
                        }
                        else if ( strcmp(arg, "-final_output") == 0 ) {
                                fFinalName = argv[++i];
                        }
                        // Ensure that all calls to exported symbols go through lazy pointers.  Multi-module
                        // just ensures that this happens for cross object file boundaries.
                        else if ( (strcmp(arg, "-interposable") == 0) || (strcmp(arg, "-multi_module") == 0)) {
                                switch ( fInterposeMode ) {
                                        case kInterposeNone:
                                        case kInterposeAllExternal:
                                                fInterposeMode = kInterposeAllExternal;
                                                break;
                                        case kInterposeSome:
                                                // do nothing, -interposable_list overrides -interposable"
                                                break;
                                }
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-interposable_list") == 0 ) {
                snapshotFileArgIndex = 1;
                                fInterposeMode = kInterposeSome;
                                loadExportFile(argv[++i], "-interposable_list", fInterposeList);
                                cannotBeUsedWithBitcode(arg);
                        }
                        // Default for -interposable/-multi_module/-single_module.
                        else if ( strcmp(arg, "-single_module") == 0 ) {
                                fInterposeMode = kInterposeNone;
                        }
                        else if ( strcmp(arg, "-exported_symbols_list") == 0 ) {
                snapshotFileArgIndex = 1;
                                if ( fExportMode == kDontExportSome )
                                        throw "can't use -exported_symbols_list and -unexported_symbols_list";
                                fExportMode = kExportSome;
                                loadExportFile(argv[++i], "-exported_symbols_list", fExportSymbols);
                        }
                        else if ( strcmp(arg, "-unexported_symbols_list") == 0 ) {
                snapshotFileArgIndex = 1;
                                if ( fExportMode == kExportSome )
                                        throw "can't use -unexported_symbols_list and -exported_symbols_list";
                                fExportMode = kDontExportSome;
                                loadExportFile(argv[++i], "-unexported_symbols_list", fDontExportSymbols);
                        }
                        else if ( strcmp(arg, "-exported_symbol") == 0 ) {
                                if ( fExportMode == kDontExportSome )
                                        throw "can't use -exported_symbol and -unexported_symbols";
                                fExportMode = kExportSome;
                                fExportSymbols.insert(argv[++i]);
                        }
                        else if ( strcmp(arg, "-unexported_symbol") == 0 ) {
                                if ( fExportMode == kExportSome )
                                        throw "can't use -unexported_symbol and -exported_symbol";
                                fExportMode = kDontExportSome;
                                fDontExportSymbols.insert(argv[++i]);
                        }
                        else if ( strcmp(arg, "-non_global_symbols_no_strip_list") == 0 ) {
                snapshotFileArgIndex = 1;
                                if ( fLocalSymbolHandling == kLocalSymbolsSelectiveExclude )
                                        throw "can't use -non_global_symbols_no_strip_list and -non_global_symbols_strip_list";
                                fLocalSymbolHandling = kLocalSymbolsSelectiveInclude;
                                loadExportFile(argv[++i], "-non_global_symbols_no_strip_list", fLocalSymbolsIncluded);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-non_global_symbols_strip_list") == 0 ) {
                snapshotFileArgIndex = 1;
                                if ( fLocalSymbolHandling == kLocalSymbolsSelectiveInclude )
                                        throw "can't use -non_global_symbols_no_strip_list and -non_global_symbols_strip_list";
                                fLocalSymbolHandling = kLocalSymbolsSelectiveExclude;
                                loadExportFile(argv[++i], "-non_global_symbols_strip_list", fLocalSymbolsExcluded);
                                cannotBeUsedWithBitcode(arg);
                        }
                        // ??? Deprecate
                        else if ( strcmp(arg, "-no_arch_warnings") == 0 ) {
                                 fIgnoreOtherArchFiles = true;
                        }
                        else if ( strcmp(arg, "-force_cpusubtype_ALL") == 0 ) {
                                fForceSubtypeAll = true;
                                fAllowCpuSubtypeMismatches = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        // Similar to -weak-l but uses the absolute path name to the library.
                        else if ( strcmp(arg, "-weak_library") == 0 ) {
                // SNAPSHOT FIXME: what should we do for link snapshots? (ignore for now)
                snapshotArgCount = 0;
                                FileInfo info = findFile(argv[++i]);
                                info.options.fWeakImport = true;
                                info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                                addLibrary(info);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-lazy_library") == 0 ) {
                // SNAPSHOT FIXME: what should we do for link snapshots? (ignore for now)
                snapshotArgCount = 0;
                                FileInfo info = findFile(argv[++i]);
                                info.options.fLazyLoad = true;
                                info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                                addLibrary(info);
                                fUsingLazyDylibLinking = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-framework") == 0 ) {
                snapshotArgCount = 0;
                                FileInfo info = findFramework(argv[++i]);
                                info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                                addLibrary(info);
                        }
                        else if ( strcmp(arg, "-weak_framework") == 0 ) {
                // SNAPSHOT FIXME: what should we do for link snapshots? (ignore for now)
                snapshotArgCount = 0;
                                FileInfo info = findFramework(argv[++i]);
                                info.options.fWeakImport = true;
                                info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                                addLibrary(info);
                        }
                        else if ( strcmp(arg, "-lazy_framework") == 0 ) {
                // SNAPSHOT FIXME: what should we do for link snapshots? (ignore for now)
                snapshotArgCount = 0;
                                FileInfo info = findFramework(argv[++i]);
                                info.options.fLazyLoad = true;
                                info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                                addLibrary(info);
                                fUsingLazyDylibLinking = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-search_paths_first") == 0 ) {
                                // previously handled by buildSearchPaths()
                        }
                        else if ( strcmp(arg, "-search_dylibs_first") == 0 ) {
                                // previously handled by buildSearchPaths()
                        }
                        else if ( strcmp(arg, "-undefined") == 0 ) {
                setUndefinedTreatment(argv[++i]);
                                cannotBeUsedWithBitcode(arg);
                        }
                        // Debugging output flag.
                        else if ( strcmp(arg, "-arch_multiple") == 0 ) {
                                 fMessagesPrefixedWithArchitecture = true;
                        }
                        // Specify what to do with relocations in read only
                        // sections like .text.  Could be errors, warnings,
                        // or suppressed.  Currently we do nothing with the
                        // flag.
                        else if ( strcmp(arg, "-read_only_relocs") == 0 ) {
                                switch ( parseTreatment(argv[++i]) ) {
                                        case kNULL:
                                        case kInvalid:
                                                throw "-read_only_relocs missing [ warning | error | suppress ]";
                                        case kWarning:
                                                fWarnTextRelocs = true;
                                                fAllowTextRelocs = true;
                                                cannotBeUsedWithBitcode(arg);
                                                break;
                                        case kSuppress:
                                                fWarnTextRelocs = false;
                                                fAllowTextRelocs = true;
                                                cannotBeUsedWithBitcode(arg);
                                                break;
                                        case kError:
                                                fWarnTextRelocs = false;
                                                fAllowTextRelocs = false;
                                                break;
                                }
                        }
                        else if ( strcmp(arg, "-sect_diff_relocs") == 0 ) {
                                warnObsolete(arg);
                                ++i;
                        }
                        // Warn, error or make strong a mismatch between weak
                        // and non-weak references.
                        else if ( strcmp(arg, "-weak_reference_mismatches") == 0 ) {
                setWeakReferenceMismatchTreatment(argv[++i]);
                        }
                        // For a deployment target of 10.3 and earlier ld64 will
                        // prebind an executable with 0s in all addresses that
                        // are prebound.  This can then be fixed up by update_prebinding
                        // later.  Prebinding is less useful on 10.4 and greater.
                        else if ( strcmp(arg, "-prebind") == 0 ) {
                                fPrebind = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-noprebind") == 0 ) {
                                warnObsolete(arg);
                                fPrebind = false;
                        }
                        else if ( strcmp(arg, "-prebind_allow_overlap") == 0 ) {
                                warnObsolete(arg);
                        }
                        else if ( strcmp(arg, "-prebind_all_twolevel_modules") == 0 ) {
                                warnObsolete(arg);
                        }
                        else if ( strcmp(arg, "-noprebind_all_twolevel_modules") == 0 ) {
                                warnObsolete(arg);
                        }
                        else if ( strcmp(arg, "-nofixprebinding") == 0 ) {
                                warnObsolete(arg);
                        }
                        // This should probably be deprecated when we respect -L and -F
                        // when searching for libraries.
                        else if ( strcmp(arg, "-dylib_file") == 0 ) {
                // ignore for snapshot because a stub dylib will be created in the snapshot
                 snapshotArgCount = 0;
                                 addDylibOverride(argv[++i]);
                                cannotBeUsedWithBitcode(arg);
                        }
                        // What to expand @executable_path to if found in dependent dylibs
                        else if ( strcmp(arg, "-executable_path") == 0 ) {
                                 fExecutablePath = argv[++i];
                                 if ( (fExecutablePath == NULL) || (fExecutablePath[0] == '-') )
                                        throw "-executable_path missing <path>";
                                // if a directory was passed, add / to end
                                // <rdar://problem/5171880> ld64 can't find @executable _path relative dylibs from our umbrella frameworks
                                struct stat statBuffer;
                                if ( stat(fExecutablePath, &statBuffer) == 0 ) {
                                        if ( (statBuffer.st_mode & S_IFMT) == S_IFDIR ) {
                                                char* pathWithSlash = new char[strlen(fExecutablePath)+2];
                                                strcpy(pathWithSlash, fExecutablePath);
                                                strcat(pathWithSlash, "/");
                                                fExecutablePath = pathWithSlash;
                                        }
                                }
                        }
                        // Aligns all segments to the power of 2 boundary specified.
                        else if ( strcmp(arg, "-segalign") == 0 ) {
                                const char* size = argv[++i];
                                if ( size == NULL )
                                        throw "-segalign missing <size>";
                                fSegmentAlignment = parseAddress(size);
                                uint8_t alignment = (uint8_t)__builtin_ctz(fSegmentAlignment);
                                uint32_t p2aligned = (1 << alignment);
                                if ( p2aligned != fSegmentAlignment ) {
                                        warning("alignment for -segalign %s is not a power of two, using 0x%X", size, p2aligned);
                                        fSegmentAlignment = p2aligned;
                                }
                                cannotBeUsedWithBitcode(arg);
                        }
                        // Puts a specified segment at a particular address that must
                        // be a multiple of the segment alignment.
                        else if ( strcmp(arg, "-segaddr") == 0 ) {
                                SegmentStart seg;
                                seg.name = argv[++i];
                                 if ( (seg.name == NULL) || (argv[i+1] == NULL) )
                                        throw "-segaddr missing segName Adddress";
                                seg.address = parseAddress(argv[++i]);
                                uint64_t temp = ((seg.address+fSegmentAlignment-1) & (-fSegmentAlignment)); 
                                if ( seg.address != temp )
                                        warning("-segaddr %s not %lld byte aligned", seg.name, fSegmentAlignment);
                                fCustomSegmentAddresses.push_back(seg);
                                cannotBeUsedWithBitcode(arg);
                        }
                        // ??? Deprecate when we deprecate split-seg.
                        else if ( strcmp(arg, "-segs_read_only_addr") == 0 ) {
                                fBaseAddress = parseAddress(argv[++i]);
                                cannotBeUsedWithBitcode(arg);
                        }
                        // ??? Deprecate when we deprecate split-seg.
                        else if ( strcmp(arg, "-segs_read_write_addr") == 0 ) {
                                fBaseWritableAddress = parseAddress(argv[++i]);
                                fSplitSegs = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        // ??? Deprecate when we get rid of basing at build time.
                        else if ( strcmp(arg, "-seg_addr_table") == 0 ) {
                snapshotFileArgIndex = 1;
                                const char* name = argv[++i];
                                if ( name == NULL )
                                        throw "-seg_addr_table missing argument";
                                fSegAddrTablePath = name;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-seg_addr_table_filename") == 0 ) {
                                warnObsolete(arg);
                                ++i;
                        }
                        else if ( strcmp(arg, "-segprot") == 0 ) {
                                SegmentProtect seg;
                                seg.name = argv[++i];
                                 if ( (seg.name == NULL) || (argv[i+1] == NULL) || (argv[i+2] == NULL) )
                                        throw "-segprot missing segName max-prot init-prot";
                                seg.max = parseProtection(argv[++i]);
                                seg.init = parseProtection(argv[++i]);
                                if ( strcmp(seg.name, "__LINKEDIT") == 0 )
                                        warning("-segprot cannot be used to modify __LINKEDIT protections");
                                else
                                        fCustomSegmentProtections.push_back(seg);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-pagezero_size") == 0 ) {
                                 const char* size = argv[++i];
                                 if ( size == NULL )
                                        throw "-pagezero_size missing <size>";
                                fZeroPageSize = parseAddress(size);
                                uint64_t temp = fZeroPageSize & (-4096); // page align
                                if ( (fZeroPageSize != temp)  )
                                        warning("-pagezero_size not page aligned, rounding down");
                                 fZeroPageSize = temp;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-stack_addr") == 0 ) {
                                 const char* address = argv[++i];
                                 if ( address == NULL )
                                        throw "-stack_addr missing <address>";
                                fStackAddr = parseAddress(address);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-stack_size") == 0 ) {
                                 const char* size = argv[++i];
                                 if ( size == NULL )
                                        throw "-stack_size missing <address>";
                                fStackSize = parseAddress(size);
                        }
                        else if ( strcmp(arg, "-allow_stack_execute") == 0 ) {
                                fExecutableStack = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-allow_heap_execute") == 0 ) {
                                fDisableNonExecutableHeap = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-sectalign") == 0 ) {
                                 if ( (argv[i+1]==NULL) || (argv[i+2]==NULL) || (argv[i+3]==NULL) )
                                        throw "-sectalign missing <segment> <section> <file-path>";
                                addSectionAlignment(argv[i+1], argv[i+2], argv[i+3]);
                                i += 3;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-sectorder_detail") == 0 ) {
                                warnObsolete(arg);
                        }
                        else if ( strcmp(arg, "-sectobjectsymbols") == 0 ) {
                                warnObsolete(arg);
                                i += 2;
                        }
                        else if ( strcmp(arg, "-bundle_loader") == 0 ) {
                snapshotFileArgIndex = 1;
                                fBundleLoader = argv[++i];
                                if ( (fBundleLoader == NULL) || (fBundleLoader[0] == '-') )
                                        throw "-bundle_loader missing <path>";
                                FileInfo info = findFile(fBundleLoader);
                                info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                                info.options.fBundleLoader = true;
                                fInputFiles.push_back(info);
                        }
                        else if ( strcmp(arg, "-private_bundle") == 0 ) {
                                warnObsolete(arg);
                        }
                        else if ( strcmp(arg, "-twolevel_namespace_hints") == 0 ) {
                                // FIX FIX
                        }
                        // Use this flag to set default behavior for deployement targets.
                        else if ( strcmp(arg, "-macosx_version_min") == 0 ) {
                                const char* macVers = argv[++i];
                                if ( macVers == NULL )
                                        throw "-macosx_version_min missing version argument";
                                const char* envMacVers = getenv("MACOSX_DEPLOYMENT_TARGET");
                                const char* enviPhoneVers = getenv("IPHONEOS_DEPLOYMENT_TARGET");
                                if ( (envMacVers != NULL) && (enviPhoneVers != NULL) ) {
                                        // <rdar://problem/13774329> when conflicting deployments set, break tie by looking at syslibroot
                                        warning("both MACOSX_DEPLOYMENT_TARGET and IPHONEOS_DEPLOYMENT_TARGET are set");
                                        if ( !fSDKPaths.empty() ) {
                                                const char* sysrootPath = fSDKPaths.back();
                                                const char* lastSlash = strrchr(sysrootPath, '/');
                                                if ( strstr(lastSlash, "Simulator") != NULL ) 
                                                        setIOSVersionMin(enviPhoneVers);
                                                else
                                                        setMacOSXVersionMin(macVers);
                                        }
                                        else {
                                                setMacOSXVersionMin(macVers);
                                        }
                                }
                                else {
                                        setMacOSXVersionMin(macVers);
                                }
                        }
                        else if ( (strcmp(arg, "-ios_version_min") == 0) || (strcmp(arg, "-iphoneos_version_min") == 0) ) {
                                const char* vers = argv[++i];
                                if ( vers == NULL )
                                        throw "-ios_version_min missing version argument";
                                setIOSVersionMin(vers);
                        }
                        else if ( strcmp(arg, "-ios_simulator_version_min") == 0 ) {
                                const char* vers = argv[++i];
                                if ( vers == NULL )
                                        throw "-ios_simulator_version_min missing version argument";
                                setIOSVersionMin(vers);
                                fTargetIOSSimulator = true;
                        }
                        else if ( strcmp(arg, "-watchos_version_min") == 0 ) {
                                const char* vers = argv[++i];
                                if ( vers == NULL )
                                        throw "-watchos_version_min missing version argument";
                                setWatchOSVersionMin(vers);
                        }
                        else if ( strcmp(arg, "-watchos_simulator_version_min") == 0 ) {
                                const char* vers = argv[++i];
                                if ( vers == NULL )
                                        throw "-watchos_simulator_version_min missing version argument";
                                setWatchOSVersionMin(vers);
                                fTargetIOSSimulator = true;
                        }
        #if SUPPORT_APPLE_TV
                        else if ( strcmp(arg, "-tvos_version_min") == 0 ) {
                                const char* vers = argv[++i];
                                if ( vers == NULL )
                                        throw "-tvos_version_min missing version argument";
                                setIOSVersionMin(vers);
                                fPlatform = kPlatform_tvOS;
                        }
                        else if ( strcmp(arg, "-tvos_simulator_version_min") == 0 ) {
                                const char* vers = argv[++i];
                                if ( vers == NULL )
                                        throw "-tvos_simulator_version_min missing version argument";
                                setIOSVersionMin(vers);
                                fPlatform = kPlatform_tvOS;
                                fTargetIOSSimulator = true;
                        }
        #endif
                        else if ( strcmp(arg, "-bridgeos_version_min") == 0 ) {
                                const char* vers = argv[++i];
                                if ( vers == NULL )
                                        throw "-bridgeos_version_min missing version argument";
                                setIOSVersionMin(vers);
                                fPlatform = kPlatform_bridgeOS;
                        }
                        else if ( strcmp(arg, "-multiply_defined") == 0 ) {
                                //warnObsolete(arg);
                                ++i;
                        }
                        else if ( strcmp(arg, "-multiply_defined_unused") == 0 ) {
                                warnObsolete(arg);
                                ++i;
                        }
                        else if ( strcmp(arg, "-nomultidefs") == 0 ) {
                                warnObsolete(arg);
                        }
                        // Display each file in which the argument symbol appears and whether
                        // the file defines or references it.  This option takes an argument
                        // as -y<symbol> note that there is no space.
                        else if ( strncmp(arg, "-y", 2) == 0 ) {
                                warnObsolete("-y");
                        }
                        // Same output as -y, but output <arg> number of undefined symbols only.
                        else if ( strcmp(arg, "-Y") == 0 ) {
                                //warnObsolete(arg);
                                ++i;
                        }
                        // This option affects all objects linked into the final result.
                        else if ( strcmp(arg, "-m") == 0 ) {
                                warnObsolete(arg);
                        }
                        else if ( (strcmp(arg, "-why_load") == 0) || (strcmp(arg, "-whyload") == 0) ) {
                                 fWhyLoad = true;
                        }
                        else if ( strcmp(arg, "-why_live") == 0 ) {
                                 const char* name = argv[++i];
                                if ( name == NULL )
                                        throw "-why_live missing symbol name argument";
                                fWhyLive.insert(name);
                        }
                        else if ( strcmp(arg, "-u") == 0 ) {
                                const char* name = argv[++i];
                                if ( name == NULL )
                                        throw "-u missing argument";
                                fInitialUndefines.push_back(name);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-U") == 0 ) {
                                const char* name = argv[++i];
                                if ( name == NULL )
                                        throw "-U missing argument";
                                fAllowedUndefined.insert(name);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-s") == 0 ) {
                                warnObsolete(arg);
                                fLocalSymbolHandling = kLocalSymbolsNone;
                                fDebugInfoStripping = Options::kDebugInfoNone;
                        }
                        else if ( strcmp(arg, "-x") == 0 ) {
                                fLocalSymbolHandling = kLocalSymbolsNone;
                        }
                        else if ( strcmp(arg, "-S") == 0 ) {
                                fDebugInfoStripping = Options::kDebugInfoNone;
                        }
                        else if ( strcmp(arg, "-X") == 0 ) {
                                warnObsolete(arg);
                        }
                        else if ( strcmp(arg, "-Si") == 0 ) {
                                warnObsolete(arg);
                                fDebugInfoStripping = Options::kDebugInfoFull;
                        }
                        else if ( strcmp(arg, "-b") == 0 ) {
                                warnObsolete(arg);
                        }
                        else if ( strcmp(arg, "-Sn") == 0 ) {
                                warnObsolete(arg);
                                fDebugInfoStripping = Options::kDebugInfoFull;
                        }
                        else if ( strcmp(arg, "-Sp") == 0 ) {
                                warnObsolete(arg);
                        }
                        else if ( strcmp(arg, "-dead_strip") == 0 ) {
                                fDeadStrip = true;
                        }
                        else if ( strcmp(arg, "-no_dead_strip_inits_and_terms") == 0 ) {
                                fDeadStrip = true;
                        }
                        else if ( strcmp(arg, "-w") == 0 ) {
                                // previously handled by buildSearchPaths()
                        }
                        else if ( strcmp(arg, "-fatal_warnings") == 0 ) {
                                // previously handled by buildSearchPaths()
                        }
                        else if ( strcmp(arg, "-arch_errors_fatal") == 0 ) {
                                fErrorOnOtherArchFiles = true;
                        }
                        else if ( strcmp(arg, "-M") == 0 ) {
                                // FIX FIX
                        }
                        else if ( strcmp(arg, "-headerpad") == 0 ) {
                                const char* size = argv[++i];
                                if ( size == NULL )
                                        throw "-headerpad missing argument";
                                 fMinimumHeaderPad = parseAddress(size);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-headerpad_max_install_names") == 0 ) {
                                // ignore -headerpad_max_install_names when compiling with bitcode
                                // rdar://problem/20748962
                                if ( fBundleBitcode )
                                        warning("-headerpad_max_install_names is ignored when used with -bitcode_bundle (Xcode setting ENABLE_BITCODE=YES)");
                                else
                                        fMaxMinimumHeaderPad = true;
                        }
                        else if ( strcmp(arg, "-t") == 0 ) {
                                fLogAllFiles = true;
                        }
                        else if ( strcmp(arg, "-whatsloaded") == 0 ) {
                                fLogObjectFiles = true;
                        }
                        else if ( strcmp(arg, "-A") == 0 ) {
                                warnObsolete(arg);
                                 ++i;
                        }
                        else if ( strcmp(arg, "-umbrella") == 0 ) {
                                const char* name = argv[++i];
                                if ( name == NULL )
                                        throw "-umbrella missing argument";
                                fUmbrellaName = name;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-allowable_client") == 0 ) {
                                const char* name = argv[++i];

                                if ( name == NULL )
                                        throw "-allowable_client missing argument";

                                fAllowableClients.push_back(name);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-client_name") == 0 ) {
                                const char* name = argv[++i];

                                if ( name == NULL )
                                        throw "-client_name missing argument";

                                fClientName = name;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-sub_umbrella") == 0 ) {
                                const char* name = argv[++i];
                                if ( name == NULL )
                                        throw "-sub_umbrella missing argument";
                                 fSubUmbellas.push_back(name);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-sub_library") == 0 ) {
                                const char* name = argv[++i];
                                if ( name == NULL )
                                        throw "-sub_library missing argument";
                                 fSubLibraries.push_back(name);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-init") == 0 ) {
                                const char* name = argv[++i];
                                if ( name == NULL )
                                        throw "-init missing argument";
                                fInitFunctionName = name;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-dot") == 0 ) {
                                const char* name = argv[++i];
                                if ( name == NULL )
                                        throw "-dot missing argument";
                                fDotOutputFile = name;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-warn_commons") == 0 ) {
                                fWarnCommons = true;
                        }
                        else if ( strcmp(arg, "-commons") == 0 ) {
                                fCommonsMode = parseCommonsTreatment(argv[++i]);
                        }
                        else if ( strcmp(arg, "-keep_relocs") == 0 ) {
                                fKeepRelocations = true;
                        }
                        else if ( strcmp(arg, "-warn_stabs") == 0 ) {
                                fWarnStabs = true;
                        }
                        else if ( strcmp(arg, "-pause") == 0 ) {
                                fPause = true;
                        }
                        else if ( strcmp(arg, "-print_statistics") == 0 ) {
                                fStatistics = true;
                        }
                        else if ( strcmp(arg, "-d") == 0 ) {
                                fMakeTentativeDefinitionsReal = true;
                        }
                        else if ( strcmp(arg, "-v") == 0 ) {
                                // previously handled by buildSearchPaths()
                        }
                        else if ( strcmp(arg, "-Z") == 0 ) {
                                // previously handled by buildSearchPaths()
                        }
                        else if ( strcmp(arg, "-syslibroot") == 0 ) {
                snapshotArgCount = 0;
                                ++i;
                                // previously handled by buildSearchPaths()
                        }
                        else if ( strcmp(arg, "-bitcode_bundle") == 0 ) {
                                snapshotArgCount = 0;
                                // previously handled by buildSearchPaths()
                        }
                        else if ( strcmp(arg, "-no_uuid") == 0 ) {
                                fUUIDMode = kUUIDNone;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-random_uuid") == 0 ) {
                                fUUIDMode = kUUIDRandom;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-dtrace") == 0 ) {
                snapshotFileArgIndex = 1;
                                const char* name = argv[++i];
                                if ( name == NULL )
                                        throw "-dtrace missing argument";
                                fDtraceScriptName = name;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-root_safe") == 0 ) {
                                fRootSafe = true;
                        }
                        else if ( strcmp(arg, "-setuid_safe") == 0 ) {
                                fSetuidSafe = true;
                        }
                        else if ( strcmp(arg, "-alias") == 0 ) {
                                Options::AliasPair pair;
                                pair.realName = argv[++i];
                                if ( pair.realName == NULL )
                                        throw "missing argument to -alias";
                                pair.alias = argv[++i];
                                if ( pair.alias == NULL )
                                        throw "missing argument to -alias";
                                fAliases.push_back(pair);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-alias_list") == 0 ) {
                snapshotFileArgIndex = 1;
                                parseAliasFile(argv[++i]);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-save-temps") == 0 ) {
                                fSaveTempFiles = true;
                        }
                        else if ( strcmp(arg, "-bitcode_hide_symbols") == 0 ) {
                                fHideSymbols = true;
                        }
                        else if ( strcmp(arg, "-bitcode_verify") == 0 ) {
                                fVerifyBitcode = true;
                        }
                        else if ( strcmp(arg, "-bitcode_symbol_map") == 0) {
                                fReverseMapPath = argv[++i];
                                if ( fReverseMapPath == NULL )
                                        throw "missing argument to -bitcode_symbol_map";
                                struct stat statbuf;
                                int ret = ::stat(fReverseMapPath, &statbuf);
                                if ( ret == 0 && S_ISDIR(statbuf.st_mode)) {
                                        char tempPath[PATH_MAX];
                                        sprintf(tempPath, "%s/XXXXXX", fReverseMapPath);
                                        int tempFile = ::mkstemp(tempPath);
                                        if (tempFile == -1)
                                                throwf("could not write file to symbol map directory: %s", fReverseMapPath);
                                        ::close(tempFile);
                                        fReverseMapTempPath = std::string(tempPath);
                                        fReverseMapUUIDRename = true;
                                } else
                                        fReverseMapTempPath = std::string(fReverseMapPath);
                        }
                        else if ( strcmp(argv[i], "-flto-codegen-only") == 0) {
                                fLTOCodegenOnly = true;
                        }
                        else if ( strcmp(argv[i], "-ignore_auto_link") == 0) {
                                fIgnoreAutoLink = true;
                        }
                        else if ( strcmp(argv[i], "-allow_dead_duplicates") == 0) {
                                fAllowDeadDups = true;
                        }
                        else if ( strcmp(argv[i], "-bitcode_process_mode") == 0 ) {
                                const char* bitcode_type = argv[++i];
                                if ( bitcode_type == NULL )
                                        throw "missing argument to -bitcode_process_mode";
                                else if ( strcmp(bitcode_type, "strip") == 0 )
                                        fBitcodeKind = kBitcodeStrip;
                                else if ( strcmp(bitcode_type, "marker") == 0 )
                                        fBitcodeKind = kBitcodeMarker;
                                else if ( strcmp(bitcode_type, "data") == 0 )
                                        fBitcodeKind = kBitcodeAsData;
                                else if ( strcmp(bitcode_type, "bitcode") == 0 )
                                        fBitcodeKind = kBitcodeProcess;
                                else
                                        throw "unknown argument to -bitcode_process_mode {strip,marker,data,bitcode}";
                        }
                        else if ( strcmp(arg, "-rpath") == 0 ) {
                                const char* path = argv[++i];
                                if ( path == NULL )
                                        throw "missing argument to -rpath";
                                fRPaths.push_back(path);
                        }
                        else if ( strcmp(arg, "-read_only_stubs") == 0 ) {
                                fReadOnlyx86Stubs = true;
                        }
                        else if ( strcmp(arg, "-slow_stubs") == 0 ) {
                                warnObsolete(arg);
                        }
                        else if ( strcmp(arg, "-map") == 0 ) {
                                fMapPath = argv[++i];
                                if ( fMapPath == NULL )
                                        throw "missing argument to -map";
                        }
                        else if ( strcmp(arg, "-pie") == 0 ) {
                                fPositionIndependentExecutable = true;
                                fPIEOnCommandLine = true;
                        }
                        else if ( strcmp(arg, "-no_pie") == 0 ) {
                                fDisablePositionIndependentExecutable = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strncmp(arg, "-reexport-l", 11) == 0 ) {
                // SNAPSHOT FIXME: what should we do for link snapshots? (ignore for now)
                snapshotArgCount = 0;
                                FileInfo info = findLibrary(&arg[11], true);
                                info.options.fReExport = true;
                                info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                                addLibrary(info);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-reexport_library") == 0 ) {
                // SNAPSHOT FIXME: what should we do for link snapshots? (ignore for now)
                snapshotArgCount = 0;
                                FileInfo info = findFile(argv[++i]);
                                info.options.fReExport = true;
                                info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                                addLibrary(info);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-reexport_framework") == 0 ) {
                // SNAPSHOT FIXME: what should we do for link snapshots? (ignore for now)
                snapshotArgCount = 0;
                                FileInfo info = findFramework(argv[++i]);
                                info.options.fReExport = true;
                                info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                                addLibrary(info);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strncmp(arg, "-upward-l", 9) == 0 ) {
                // SNAPSHOT FIXME: what should we do for link snapshots? (ignore for now)
                snapshotArgCount = 0;
                                FileInfo info = findLibrary(&arg[9], true);
                                info.options.fUpward = true;
                                info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                                addLibrary(info);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-upward_library") == 0 ) {
                // SNAPSHOT FIXME: what should we do for link snapshots? (ignore for now)
                snapshotArgCount = 0;
                                FileInfo info = findFile(argv[++i]);
                                info.options.fUpward = true;
                                info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                                addLibrary(info);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-upward_framework") == 0 ) {
                // SNAPSHOT FIXME: what should we do for link snapshots? (ignore for now)
                snapshotArgCount = 0;
                                FileInfo info = findFramework(argv[++i]);
                                info.options.fUpward = true;
                                info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                                addLibrary(info);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-dead_strip_dylibs") == 0 ) {
                                fDeadStripDylibs = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-no_implicit_dylibs") == 0 ) {
                                fImplicitlyLinkPublicDylibs = false;
                        }
                        else if ( strcmp(arg, "-new_linker") == 0 ) {
                                // ignore
                        }
                        else if ( strcmp(arg, "-no_encryption") == 0 ) {
                                fEncryptableForceOff = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-encryptable") == 0 ) {
                                fEncryptableForceOn = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-no_compact_unwind") == 0 ) {
                                fAddCompactUnwindEncoding = false;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-mllvm") == 0 ) {
                                const char* opts = argv[++i];
                                if ( opts == NULL )
                                        throw "missing argument to -mllvm";
                                fLLVMOptions.push_back(opts);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-mcpu") == 0 ) {
                                const char* cpu = argv[++i];
                                if ( cpu == NULL )
                                        throw "missing argument to -mcpu";
                                fLtoCpu = cpu;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-no_order_inits") == 0 ) {
                                fAutoOrderInitializers = false;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-no_order_data") == 0 ) {
                                fOrderData = false;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-seg_page_size") == 0 ) {
                                SegmentSize seg;
                                seg.name = argv[++i];
                                 if ( (seg.name == NULL) || (argv[i+1] == NULL) )
                                        throw "-seg_page_size missing segName Adddress";
                                seg.size = parseAddress(argv[++i]);
                                uint64_t temp = seg.size & (-4096); // page align
                                if ( (seg.size != temp)  )
                                        warning("-seg_page_size %s not 4K aligned, rounding down", seg.name);
                                fCustomSegmentSizes.push_back(seg);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-mark_dead_strippable_dylib") == 0 ) {
                                fMarkDeadStrippableDylib = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-exported_symbols_order") == 0 ) {
                snapshotFileArgIndex = 1;
                                loadSymbolOrderFile(argv[++i], fExportSymbolsOrder);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-no_compact_linkedit") == 0 ) {
                                warnObsolete("-no_compact_linkedit");
                        }
                        else if ( strcmp(arg, "-no_eh_labels") == 0 ) {
                                fNoEHLabels = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-warn_compact_unwind") == 0 ) {
                                fWarnCompactUnwind = true;
                        }
                        else if ( strcmp(arg, "-allow_sub_type_mismatches") == 0 ) {
                                fAllowCpuSubtypeMismatches = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-no_zero_fill_sections") == 0 ) {
                                fOptimizeZeroFill = false;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-merge_zero_fill_sections") == 0 ) {
                                fMergeZeroFill = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-objc_abi_version") == 0 ) {
                                const char* version = argv[++i];
                                 if ( version == NULL )
                                        throw "-objc_abi_version missing version number";
                                if ( strcmp(version, "2") == 0 ) {
                                        fObjCABIVersion1Override = false;
                                        fObjCABIVersion2Override = true;
                                }
                                else if ( strcmp(version, "1") == 0 ) {
                                        fObjCABIVersion1Override = true;
                                        fObjCABIVersion2Override = false;
                                }
                                else
                                        warning("ignoring unrecognized argument (%s) to -objc_abi_version", version);
                        }
                        else if ( strcmp(arg, "-warn_weak_exports") == 0 ) {
                                fWarnWeakExports = true;
                        }
                        else if ( strcmp(arg, "-objc_gc_compaction") == 0 ) {
                                fObjcGcCompaction = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-objc_gc") == 0 ) {
                                fObjCGc = true;
                                if ( fObjCGcOnly ) { 
                                        warning("-objc_gc overriding -objc_gc_only");
                                        fObjCGcOnly = false;    
                                }
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-objc_gc_only") == 0 ) {
                                fObjCGcOnly = true;
                                if ( fObjCGc ) { 
                                        warning("-objc_gc_only overriding -objc_gc");
                                        fObjCGc = false;        
                                }
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-demangle") == 0 ) {
                                fDemangle = true;
                        }
                        else if ( strcmp(arg, "-version_load_command") == 0 ) {
                                fVersionLoadCommandForcedOn = true;
                                fVersionLoadCommandForcedOff = false;
                        }
                        else if ( strcmp(arg, "-no_version_load_command") == 0 ) {
                                fVersionLoadCommandForcedOff = true;
                                fVersionLoadCommandForcedOn = false;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-function_starts") == 0 ) {
                                fFunctionStartsForcedOn = true;
                                fFunctionStartsForcedOff = false;
                        }
                        else if ( strcmp(arg, "-no_function_starts") == 0 ) {
                                fFunctionStartsForcedOff = true;
                                fFunctionStartsForcedOn = false;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-no_data_in_code_info") == 0 ) {
                                fDataInCodeInfoLoadCommandForcedOff = true;
                                fDataInCodeInfoLoadCommandForcedOn = false;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-data_in_code_info") == 0 ) {
                                fDataInCodeInfoLoadCommandForcedOn  = true;
                                fDataInCodeInfoLoadCommandForcedOff = false;
                        }
                        else if ( strcmp(arg, "-object_path_lto") == 0 ) {
                                fTempLtoObjectPath = argv[++i];
                                if ( fTempLtoObjectPath == NULL )
                                        throw "missing argument to -object_path_lto";
                        }
                        else if ( strcmp(arg, "-no_objc_category_merging") == 0 ) {
                                fObjcCategoryMerging = false;
                        }
                        else if ( strcmp(arg, "-force_symbols_weak_list") == 0 ) {
                snapshotFileArgIndex = 1;
                                loadExportFile(argv[++i], "-force_symbols_weak_list", fForceWeakSymbols);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-force_symbols_not_weak_list") == 0 ) {
                snapshotFileArgIndex = 1;
                                loadExportFile(argv[++i], "-force_symbols_not_weak_list", fForceNotWeakSymbols);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-force_symbol_weak") == 0 ) {
                                const char* symbol = argv[++i];
                                if ( symbol == NULL )
                                        throw "-force_symbol_weak missing <symbol>";
                                fForceWeakSymbols.insert(symbol);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-force_symbol_not_weak") == 0 ) {
                                const char* symbol = argv[++i];
                                if ( symbol == NULL )
                                        throw "-force_symbol_not_weak missing <symbol>";
                                fForceNotWeakSymbols.insert(symbol);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-reexported_symbols_list") == 0 ) {
                snapshotFileArgIndex = 1;
                                if ( fExportMode == kExportSome )
                                        throw "can't use -exported_symbols_list and -reexported_symbols_list";
                                loadExportFile(argv[++i], "-reexported_symbols_list", fReExportSymbols);
                        }
                        else if ( strcmp(arg, "-dyld_env") == 0 ) {
                                const char* envarg = argv[++i];
                                if ( envarg == NULL )
                                        throw "-dyld_env missing ENV=VALUE";
                                if ( strchr(envarg, '=') == NULL )
                                        throw "-dyld_env missing ENV=VALUE";
                                fDyldEnvironExtras.push_back(envarg);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-page_align_data_atoms") == 0 ) {
                                fPageAlignDataAtoms = true;
                                cannotBeUsedWithBitcode(arg);
                        } 
                        else if (strcmp(arg, "-debug_snapshot") == 0) {
                fLinkSnapshot.setSnapshotMode(Snapshot::SNAPSHOT_DEBUG);
                fSnapshotRequested = true;
                                cannotBeUsedWithBitcode(arg);
            }
                        else if (strcmp(arg, "-snapshot_dir") == 0) {
                                const char* path = argv[++i];
                                if ( path == NULL )
                                        throw "-snapshot_dir missing path";
                                fLinkSnapshot.setSnapshotMode(Snapshot::SNAPSHOT_DEBUG);
                                fLinkSnapshot.setSnapshotPath(path);
                                fSnapshotRequested = true;
                                cannotBeUsedWithBitcode(arg);
            }
                        else if ( strcmp(arg, "-new_main") == 0 ) {
                                fEntryPointLoadCommandForceOn = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-no_new_main") == 0 ) {
                                fEntryPointLoadCommandForceOff = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-source_version") == 0 ) {
                                 const char* vers = argv[++i];
                                 if ( vers == NULL )
                                        throw "-source_version missing <version>";
                                fSourceVersion = parseVersionNumber64(vers);
                        }
                        else if ( strcmp(arg, "-add_source_version") == 0 ) {
                                fSourceVersionLoadCommandForceOn = true;
                        }
                        else if ( strcmp(arg, "-no_source_version") == 0 ) {
                                fSourceVersionLoadCommandForceOff = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-sdk_version") == 0 ) {
                                 const char* vers = argv[++i];
                                 if ( vers == NULL )
                                        throw "-sdk_version missing <version>";
                                fSDKVersion = parseVersionNumber32(vers);
                        }
                        else if ( strcmp(arg, "-dependent_dr_info") == 0 ) {
                                warnObsolete(arg);
                        }
                        else if ( strcmp(arg, "-no_dependent_dr_info") == 0 ) {
                                warnObsolete(arg);
                        }
                        else if ( strcmp(arg, "-kexts_use_stubs") == 0 ) {
                                fKextsUseStubs = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(argv[i], "-dependency_info") == 0 ) {
                snapshotArgCount = 0;
                                ++i;
                                // previously handled by buildSearchPaths()
                        }
                        else if ( strcmp(arg, "-export_dynamic") == 0 ) {
                                fExportDynamic = true;
                        }
                        else if ( strcmp(arg, "-force_symbols_coalesce_list") == 0 ) {
                snapshotFileArgIndex = 1;
                                loadExportFile(argv[++i], "-force_symbols_coalesce_list", fForceCoalesceSymbols);
                        }
                        else if ( strcmp(arg, "-add_linker_option") == 0 ) {
                                // ex: -add_linker_option '-framework Foundation'
                                const char* optString = argv[++i];
                                if ( optString == NULL )
                                        throw "-add_linker_option missing <option>";
                                // break up into list of tokens at whitespace
                                std::vector<const char*> opts;
                                char* buffer = strdup(optString);
                                char* start = buffer;
                                for (char* s = buffer; ; ++s) {
                                        if ( isspace(*s)  ) {
                                                *s = '\0';
                                                opts.push_back(start);
                                                start = s+1;
                                        }
                                        else if ( *s == '\0' ) {
                                                opts.push_back(start);
                                                break;
                                        }
                                }
                                fLinkerOptions.push_back(opts);
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-allow_simulator_linking_to_macosx_dylibs") == 0 ) {
                                fAllowSimulatorToLinkWithMacOSX = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-keep_dwarf_unwind") == 0 ) {
                                fKeepDwarfUnwindForcedOn = true;
                                fKeepDwarfUnwindForcedOff = false;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-no_keep_dwarf_unwind") == 0 ) {
                                fKeepDwarfUnwindForcedOn = false;
                                fKeepDwarfUnwindForcedOff = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-verbose_optimization_hints") == 0 ) {
                                fVerboseOptimizationHints = true;
                        }
                        else if ( strcmp(arg, "-ignore_optimization_hints") == 0 ) {
                                fIgnoreOptimizationHints = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-no_dtrace_dof") == 0 ) {
                                fGenerateDtraceDOF = false;
                        }
                        else if ( strcmp(arg, "-rename_section") == 0 ) {
                                 if ( (argv[i+1]==NULL) || (argv[i+2]==NULL) || (argv[i+3]==NULL) || (argv[i+4]==NULL) )
                                        throw "-rename_section missing <segment> <section> <segment> <section>";
                                addSectionRename(argv[i+1], argv[i+2], argv[i+3], argv[i+4]);
                                i += 4;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-rename_segment") == 0 ) {
                                 if ( (argv[i+1]==NULL) || (argv[i+2]==NULL) )
                                        throw "-rename_segment missing <existing-segment> <new-segment>";
                                addSegmentRename(argv[i+1], argv[i+2]);
                                i += 2;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-move_to_ro_segment") == 0 ) {
                                 if ( (argv[i+1]==NULL) || (argv[i+2]==NULL) )
                                        throw "-move_to_ro_segment missing <segment> <symbol-list-file>";
                                addSymbolMove(argv[i+1], argv[i+2], fSymbolsMovesCode, "-move_to_ro_segment");
                                i += 2;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-move_to_rw_segment") == 0 ) {
                                 if ( (argv[i+1]==NULL) || (argv[i+2]==NULL) )
                                        throw "-move_to_rw_segment missing <segment> <symbol-list-file>";
                                addSymbolMove(argv[i+1], argv[i+2], fSymbolsMovesData, "-move_to_rw_segment");
                                i += 2;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-trace_symbol_layout") == 0 ) {
                                fTraceSymbolLayout = true;
                        }
                        else if ( strcmp(arg, "-no_branch_islands") == 0 ) {
                                fAllowBranchIslands = false;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-segment_order") == 0 ) {
                                // ex: -segment_order __TEXT:__DATA:__JUNK
                                const char* optString = argv[++i];
                                if ( optString == NULL )
                                        throw "-segment_order missing colon separated <segment-list>";
                                if ( !fSegmentOrder.empty() )
                                        throw "-segment_order used more than once";
                                // break up into list of tokens at colon
                                char* buffer = strdup(optString);
                                char* start = buffer;
                                for (char* s = buffer; ; ++s) {
                                        if ( *s == ':'  ) {
                                                *s = '\0';
                                                fSegmentOrder.push_back(start);
                                                start = s+1;
                                        }
                                        else if ( *s == '\0' ) {
                                                fSegmentOrder.push_back(start);
                                                break;
                                        }
                                }
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-section_order") == 0 ) {
                                // ex: -section_order __DATA  __data:__const:__nl_pointers
                                 if ( (argv[i+1]==NULL) || (argv[i+2]==NULL) )
                                        throw "-section_order missing <segment> <section-list>";
                                const char* segName = argv[++i];
                                const char* optString = argv[++i];
                                if ( sectionOrder(segName) != NULL )
                                        throwf("-section_order %s ... used more than once", segName);
                                SectionOrderList dummy;
                                fSectionOrder.push_back(dummy);
                                SectionOrderList& entry = fSectionOrder.back();
                                entry.segmentName = segName;
                                // break up into list of tokens at colon
                                char* buffer = strdup(optString);
                                char* start = buffer;
                                for (char* s = buffer; ; ++s) {
                                        if ( *s == ':'  ) {
                                                *s = '\0';
                                                entry.sectionOrder.push_back(start);
                                                start = s+1;
                                        }
                                        else if ( *s == '\0' ) {
                                                entry.sectionOrder.push_back(start);
                                                break;
                                        }
                                }
                                cannotBeUsedWithBitcode(arg);
                        }                       
                        else if ( strcmp(arg, "-application_extension") == 0 ) {
                                fMarkAppExtensionSafe = true;
                                fCheckAppExtensionSafe = true;
                        }
                        else if ( strcmp(arg, "-no_application_extension") == 0 ) {
                                fMarkAppExtensionSafe = false;
                                fCheckAppExtensionSafe = false;
                        }
                        else if ( strcmp(arg, "-add_ast_path") == 0 ) {
                                const char* path = argv[++i];
                                if ( path == NULL )
                                        throw "-add_ast_path missing <option>";
                                fASTFilePaths.push_back(path);
                        }
                        else if ( strcmp(arg, "-force_load_swift_libs") == 0 ) {
                                fForceLoadSwiftLibs = true;
                        }
                        else if ( strcmp(arg, "-not_for_dyld_shared_cache") == 0 ) {
                                fSharedRegionEligibleForceOff = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-dirty_data_list") == 0 ) {
                                 if ( argv[i+1] == NULL )
                                        throw "-dirty_data_list missing <symbol-list-file>";
                                addSymbolMove("__DATA_DIRTY", argv[i+1], fSymbolsMovesData, "-dirty_data_list");
                                ++i;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-data_const") == 0 ) {
                                fUseDataConstSegmentForceOn = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-no_data_const") == 0 ) {
                                fUseDataConstSegmentForceOff = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-text_exec") == 0 ) {
                                fUseTextExecSegment = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-add_split_seg_info") == 0) {
                                fSharedRegionEligible = true;
                                cannotBeUsedWithBitcode(arg);
                        }
                        else if ( strcmp(arg, "-no_deduplicate") == 0 ) {
                                fDeDupe = false;
                        }
                        else if ( strcmp(arg, "-verbose_deduplicate") == 0 ) {
                                fVerboseDeDupe = true;
                        }
                        else if ( strcmp(arg, "-max_default_common_align") == 0 ) {
                                const char* alignStr = argv[++i];
                                if ( alignStr == NULL )
                                        throw "-max_default_common_align missing <align-value>";
                                // argument is a hexadecimal number
                                char* endptr;
                                unsigned long value = strtoul(alignStr, &endptr, 16);
                                if ( *endptr != '\0')
                                        throw "argument for -max_default_common_align is not a hexadecimal number";
                                if ( value > 0x8000 )
                                        throw "argument for -max_default_common_align must be less than or equal to 0x8000";
                                if ( value == 0 ) {
                                        warning("zero is not a valid -max_default_common_align");
                                        value = 1;
                                }
                                // alignment is power of 2 
                                uint8_t alignment = (uint8_t)__builtin_ctz(value);
                                if ( (unsigned long)(1 << alignment) != value ) {
                                        warning("alignment for -max_default_common_align is not a power of two, using 0x%X", 1 << alignment);
                                }
                                fMaxDefaultCommonAlign = alignment;
                        }
                        else if ( strcmp(argv[i], "-no_weak_imports") == 0 ) {
                                fAllowWeakImports = false;
                        }
                        else if ( strcmp(argv[i], "-no_inits") == 0 ) {
                                fNoInitializers = true;
                        }
                        // put this last so that it does not interfer with other options starting with 'i'
                        else if ( strncmp(arg, "-i", 2) == 0 ) {
                                const char* colon = strchr(arg, ':');
                                if ( colon == NULL )
                                        throwf("unknown option: %s", arg);
                                Options::AliasPair pair;
                                char* temp = new char[colon-arg];
                                strlcpy(temp, &arg[2], colon-arg-1);
                                pair.realName = &colon[1];
                                pair.alias = temp;
                                fAliases.push_back(pair);
                        }
                        else {
                                throwf("unknown option: %s", arg);
                        }
            
            if (snapshotArgCount == -1)
                snapshotArgCount = i-snapshotArgIndex+1;
            if (snapshotArgCount > 0)
                fLinkSnapshot.addSnapshotLinkArg(snapshotArgIndex, snapshotArgCount, snapshotFileArgIndex);
                }
                else {
                        FileInfo info = findFile(arg);
                        info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)i);
                        if ( strcmp(&info.path[strlen(info.path)-2], ".a") == 0 )
                                addLibrary(info);
                        else
                                fInputFiles.push_back(info);
                }
        }
        
        // if a -lazy option was used, implicitly link in lazydylib1.o
        if ( fUsingLazyDylibLinking ) {
                FileInfo info = findLibrary("lazydylib1.o");
                info.ordinal = ld::File::Ordinal::makeArgOrdinal((uint16_t)argc);
                addLibrary(info);
        }
    
    if (fSnapshotRequested)
        fLinkSnapshot.createSnapshot();
}



//
// -syslibroot <path> is used for SDK support.
// The rule is that all search paths (both explicit and default) are
// checked to see if they exist in the SDK.  If so, that path is
// replaced with the sdk prefixed path.  If not, that search path
// is used as is.  If multiple -syslibroot options are specified
// their directory structures are logically overlayed and files
// from sdks specified earlier on the command line used before later ones.

void Options::buildSearchPaths(int argc, const char* argv[])
{
        bool addStandardLibraryDirectories = true;
        std::vector<const char*> libraryPaths;
        std::vector<const char*> frameworkPaths;
        libraryPaths.reserve(10);
        frameworkPaths.reserve(10);
        // scan through argv looking for -L, -F, -Z, and -syslibroot options
        for(int i=0; i < argc; ++i) {
                if ( (argv[i][0] == '-') && (argv[i][1] == 'L') ) {
                        const char* libSearchDir = &argv[i][2];
                        // Allow either "-L{path}" or "-L {path}".
                        if (argv[i][2] == '\0') {
                                // -L {path}.  Make sure there is an argument following this.
                                const char* path = argv[++i];
                                if ( path == NULL )
                                        throw "-L missing argument";
                                libSearchDir = path;
                        }
                        if ( libSearchDir[0] == '\0' ) 
                                throw "-L must be immediately followed by a directory path (no space)";
                        libraryPaths.push_back(libSearchDir);
                }
                else if ( (argv[i][0] == '-') && (argv[i][1] == 'F') ) {
                        const char* frameworkSearchDir = &argv[i][2];
                        // Allow either "-F{path}" or "-F {path}".
                        if (argv[i][2] == '\0') {
                                // -F {path}.  Make sure there is an argument following this.
                                const char* path = argv[++i];
                                if ( path == NULL )
                                        throw "-F missing argument";
                                frameworkSearchDir = path;
                        }
                        if ( frameworkSearchDir[0] == '\0' ) 
                                throw "-F must be immediately followed by a directory path (no space)";
                        frameworkPaths.push_back(frameworkSearchDir);
                }
                else if ( strcmp(argv[i], "-Z") == 0 )
                        addStandardLibraryDirectories = false;
                else if ( strcmp(argv[i], "-v") == 0 ) {
                        fVerbose = true;
                        extern const char ldVersionString[];
                        fprintf(stderr, "%s", ldVersionString);
                        fprintf(stderr, "configured to support archs: %s\n", ALL_SUPPORTED_ARCHS);
                         // if only -v specified, exit cleanly
                         if ( argc == 2 ) {
                                const char* ltoVers = lto::version();
                                if ( ltoVers != NULL )
                                        fprintf(stderr, "LTO support using: %s (static support for %d, runtime is %d)\n",
                                                        ltoVers, lto::static_api_version(), lto::runtime_api_version());
                                fprintf(stderr, "TAPI support using: %s\n", tapi::Version::getFullVersionAsString().c_str());
                                exit(0);
                        }
                }
                else if ( strcmp(argv[i], "-syslibroot") == 0 ) {
                        const char* path = argv[++i];
                        if ( path == NULL )
                                throw "-syslibroot missing argument";
                        fSDKPaths.push_back(path);
                }
                else if ( strcmp(argv[i], "-search_paths_first") == 0 ) {
                        fLibrarySearchMode = kSearchDylibAndArchiveInEachDir;
                }
                else if ( strcmp(argv[i], "-search_dylibs_first") == 0 ) {
                        fLibrarySearchMode = kSearchAllDirsForDylibsThenAllDirsForArchives;
                }
                else if ( strcmp(argv[i], "-w") == 0 ) {
                        sEmitWarnings = false;
                }
                else if ( strcmp(argv[i], "-fatal_warnings") == 0 ) {
                        sFatalWarnings = true;
                }
                else if ( strcmp(argv[i], "-dependency_info") == 0 ) {
                         const char* path = argv[++i];
                         if ( path == NULL )
                                throw "-dependency_info missing <path>";
                        fDependencyInfoPath = path;
                }
                else if ( strcmp(argv[i], "-bitcode_bundle") == 0 ) {
                        fBundleBitcode = true;
                }
        }
        int standardLibraryPathsStartIndex = libraryPaths.size();
        int standardFrameworkPathsStartIndex = frameworkPaths.size();
        if ( addStandardLibraryDirectories ) {
                libraryPaths.push_back("/usr/lib");
                libraryPaths.push_back("/usr/local/lib");

                frameworkPaths.push_back("/Library/Frameworks/");
                frameworkPaths.push_back("/System/Library/Frameworks/");
                // <rdar://problem/5433882> remove /Network/Library/Frameworks from default search path
        }

        // <rdar://problem/5829579> Support for configure based hacks 
        // if last -syslibroot is /, then ignore all syslibroots
        if ( fSDKPaths.size() > 0 ) {
                if ( strcmp(fSDKPaths.back(), "/") == 0 ) {
                        fSDKPaths.clear();
                }
        }

        // now merge sdk and library paths to make real search paths
        fLibrarySearchPaths.reserve(libraryPaths.size()*(fSDKPaths.size()+1));
        int libIndex = 0;
        for (std::vector<const char*>::iterator it = libraryPaths.begin(); it != libraryPaths.end(); ++it, ++libIndex) {
                const char* libDir = *it;
                bool sdkOverride = false;
                if ( libDir[0] == '/' ) {
                        char betterLibDir[PATH_MAX];
                        if ( strstr(libDir, "/..") != NULL ) {
                                if ( realpath(libDir, betterLibDir) != NULL )
                                        libDir = strdup(betterLibDir);
                        }
                        const int libDirLen = strlen(libDir);
                        for (std::vector<const char*>::iterator sdkit = fSDKPaths.begin(); sdkit != fSDKPaths.end(); sdkit++) {
                                const char* sdkDir = *sdkit;
                                const int sdkDirLen = strlen(sdkDir);
                                char newPath[libDirLen + sdkDirLen+4];
                                strcpy(newPath, sdkDir);
                                if ( newPath[sdkDirLen-1] == '/' )
                                        newPath[sdkDirLen-1] = '\0';
                                strcat(newPath, libDir);
                                struct stat statBuffer;
                                if ( stat(newPath, &statBuffer) == 0 ) {
                                        if ( (statBuffer.st_mode & S_IFDIR) == 0 ) {
                                                warning("-syslibroot and -L combined path '%s' is not a directory", newPath);
                                        }
                                        else {
                                                fLibrarySearchPaths.push_back(strdup(newPath));
                                                sdkOverride = true;
                                        }
                                }
                        }
                }
                if ( !sdkOverride ) {
                        if ( (libIndex >= standardLibraryPathsStartIndex) && (fSDKPaths.size() == 1) ) {
                                // <rdar://problem/6438270> -syslibroot should skip standard search paths not in the SDK
                                // if one SDK is specified and a standard library path is not in the SDK, don't use it
                        }
                        else {
                                struct stat statBuffer;
                                if ( stat(libDir, &statBuffer) == 0 ) {
                                        if ( (statBuffer.st_mode & S_IFDIR) == 0 )
                                                warning("-L path '%s' is not a directory", libDir);
                                        else
                                                fLibrarySearchPaths.push_back(libDir);
                                }
                                else if ( !addStandardLibraryDirectories || (strcmp(libDir, "/usr/local/lib") != 0) ) {
                                        warning("directory not found for option '-L%s'", libDir);
                                }
                        }
                }
        }


        // now merge sdk and framework paths to make real search paths
        fFrameworkSearchPaths.reserve(frameworkPaths.size()*(fSDKPaths.size()+1));
        int frameIndex = 0;
        for (std::vector<const char*>::iterator it = frameworkPaths.begin(); it != frameworkPaths.end(); ++it, ++frameIndex) {
                const char* frameworkDir = *it;
                bool sdkOverride = false;
                if ( frameworkDir[0] == '/' ) {
                        char betterFrameworkDir[PATH_MAX];
                        if ( strstr(frameworkDir, "/..") != NULL ) {
                                if ( realpath(frameworkDir, betterFrameworkDir) != NULL )
                                        frameworkDir = strdup(betterFrameworkDir);
                        }
                        const int frameworkDirLen = strlen(frameworkDir);
                        for (std::vector<const char*>::iterator sdkit = fSDKPaths.begin(); sdkit != fSDKPaths.end(); sdkit++) {
                                const char* sdkDir = *sdkit;
                                const int sdkDirLen = strlen(sdkDir);
                                char newPath[frameworkDirLen + sdkDirLen+4];
                                strcpy(newPath, sdkDir);
                                if ( newPath[sdkDirLen-1] == '/' )
                                        newPath[sdkDirLen-1] = '\0';
                                strcat(newPath, frameworkDir);
                                struct stat statBuffer;
                                if ( stat(newPath, &statBuffer) == 0 ) {
                                        if ( (statBuffer.st_mode & S_IFDIR) == 0 ) {
                                                warning("-syslibroot and -F combined path '%s' is not a directory", newPath);
                                        }
                                        else {
                                                fFrameworkSearchPaths.push_back(strdup(newPath));
                                                sdkOverride = true;
                                        }
                                }
                        }
                }
                if ( !sdkOverride ) {
                        if ( (frameIndex >= standardFrameworkPathsStartIndex) && (fSDKPaths.size() == 1) ) {
                                // <rdar://problem/6438270> -syslibroot should skip standard search paths not in the SDK
                                // if one SDK is specified and a standard library path is not in the SDK, don't use it
                        }
                        else {
                                struct stat statBuffer;
                                if ( stat(frameworkDir, &statBuffer) == 0 ) {
                                        if ( (statBuffer.st_mode & S_IFDIR) == 0 )
                                                warning("-F path '%s' is not a directory", frameworkDir);
                                        else
                                                fFrameworkSearchPaths.push_back(frameworkDir);
                                }
                                else if ( !addStandardLibraryDirectories || (strcmp(frameworkDir, "/Library/Frameworks/") != 0) ) {
                                        warning("directory not found for option '-F%s'", frameworkDir);
                                }
                        }
                }
        }

        if ( fVerbose ) {
                fprintf(stderr,"Library search paths:\n");
                for (std::vector<const char*>::iterator it = fLibrarySearchPaths.begin();
                         it != fLibrarySearchPaths.end();
                         it++)
                        fprintf(stderr,"\t%s\n", *it);
                fprintf(stderr,"Framework search paths:\n");
                for (std::vector<const char*>::iterator it = fFrameworkSearchPaths.begin();
                         it != fFrameworkSearchPaths.end();
                         it++)
                        fprintf(stderr,"\t%s\n", *it);
        }
}

// this is run before the command line is parsed
void Options::parsePreCommandLineEnvironmentSettings()
{
        if ((getenv("LD_TRACE_ARCHIVES") != NULL)
                || (getenv("RC_TRACE_ARCHIVES") != NULL))
            fTraceArchives = true;

        if ((getenv("LD_TRACE_DYLIBS") != NULL)
                || (getenv("RC_TRACE_DYLIBS") != NULL)) {
            fTraceDylibs = true;
                fTraceIndirectDylibs = true;
        }
        
        if ((getenv("LD_TRACE_DEPENDENTS") != NULL)) {
                
                fTraceEmitJSON = true;
        }

        if (getenv("RC_TRACE_DYLIB_SEARCHING") != NULL) {
            fTraceDylibSearching = true;
        }

        if (getenv("LD_PRINT_OPTIONS") != NULL)
                fPrintOptions = true;

        if (fTraceDylibs || fTraceArchives || fTraceEmitJSON)
                fTraceOutputFile = getenv("LD_TRACE_FILE");

        if (getenv("LD_PRINT_ORDER_FILE_STATISTICS") != NULL)
                fPrintOrderFileStatistics = true;

        if (getenv("LD_SPLITSEGS_NEW_LIBRARIES") != NULL)
                fSplitSegs = true;
                
        if (getenv("LD_NO_ENCRYPT") != NULL) {
                fEncryptable = false;
                fMarkAppExtensionSafe = true; // temporary
                fCheckAppExtensionSafe = false;
        }

        if (getenv("LD_APPLICATION_EXTENSION_SAFE") != NULL) {
                fMarkAppExtensionSafe = true;
                fCheckAppExtensionSafe = false;
        }
        
        if (getenv("LD_ALLOW_CPU_SUBTYPE_MISMATCHES") != NULL)
                fAllowCpuSubtypeMismatches = true;
        
        if (getenv("LD_DYLIB_CPU_SUBTYPES_MUST_MATCH") != NULL)
                fEnforceDylibSubtypesMatch = true;
        
        sWarningsSideFilePath = getenv("LD_WARN_FILE");
        
        const char* customDyldPath = getenv("LD_DYLD_PATH");
        if ( customDyldPath != NULL ) 
                fDyldInstallPath = customDyldPath;
    
    const char* debugArchivePath = getenv("LD_DEBUG_SNAPSHOT");
    if (debugArchivePath != NULL) {
        fLinkSnapshot.setSnapshotMode(Snapshot::SNAPSHOT_DEBUG);
        if (strlen(debugArchivePath) > 0)
            fLinkSnapshot.setSnapshotPath(debugArchivePath);
        fSnapshotRequested = true;
    }

    const char* pipeFdString = getenv("LD_PIPELINE_FIFO");
    if (pipeFdString != NULL) {
                fPipelineFifo = pipeFdString;
    }
}


// this is run after the command line is parsed
void Options::parsePostCommandLineEnvironmentSettings()
{
        // when building a dynamic main executable, default any use of @executable_path to output path
        if ( fExecutablePath == NULL && (fOutputKind == kDynamicExecutable) ) {
                fExecutablePath = fOutputFile;
        }

        // allow build system to set default seg_addr_table
        if ( fSegAddrTablePath == NULL )
                fSegAddrTablePath = getenv("LD_SEG_ADDR_TABLE");

        // allow build system to turn on prebinding
        if ( !fPrebind ) {
                fPrebind = ( getenv("LD_PREBIND") != NULL );
        }
        
        // allow build system to force on dead-code-stripping
        if ( !fDeadStrip ) {
                if ( getenv("LD_DEAD_STRIP") != NULL ) {
                        switch (fOutputKind) {
                                case Options::kDynamicLibrary:
                                case Options::kDynamicExecutable:
                                case Options::kDynamicBundle:
                                        fDeadStrip = true;
                                        break;
                                case Options::kPreload:
                                case Options::kObjectFile:
                                case Options::kDyld:
                                case Options::kStaticExecutable:
                                case Options::kKextBundle:
                                        break;
                        }
                }
        }
        
        // allow build system to force on -warn_commons
        if ( getenv("LD_WARN_COMMONS") != NULL )
                fWarnCommons = true;
        
        // allow B&I to set default -source_version
        if ( fSourceVersion == 0 ) {
                const char* vers = getenv("RC_ProjectSourceVersion");
                if ( vers != NULL )
                        fSourceVersion = parseVersionNumber64(vers);
        }
                
}


static bool sharedCacheEligiblePath(const char* path)
{
        return ( (strncmp(path, "/usr/lib/", 9) == 0) || (strncmp(path, "/System/Library/", 16) == 0) );
}

void Options::reconfigureDefaults()
{
        // sync reader options
        switch ( fOutputKind ) {
                case Options::kObjectFile:
                        fForFinalLinkedImage = false;
                        break;
                case Options::kDyld:
                        fForDyld = true;
                        fForFinalLinkedImage = true;
                        fNoEHLabels = true;
                        break;
                case Options::kDynamicLibrary:
                case Options::kDynamicBundle:
                case Options::kKextBundle:
                        fForFinalLinkedImage = true;
                        fNoEHLabels = true;
                        break;
                case Options::kDynamicExecutable:
                case Options::kStaticExecutable:
                case Options::kPreload:
                        fLinkingMainExecutable = true;
                        fForFinalLinkedImage = true;
                        fNoEHLabels = true;
                        break;
        }

        // set default min OS version
        if ( (fMacVersionMin == ld::macVersionUnset) && (fIOSVersionMin == ld::iOSVersionUnset) && (fWatchOSVersionMin == ld::wOSVersionUnset) ) {
                // if neither -macosx_version_min nor -iphoneos_version_min used, try environment variables
                const char* macVers = getenv("MACOSX_DEPLOYMENT_TARGET");
                const char* iPhoneVers = getenv("IPHONEOS_DEPLOYMENT_TARGET");
                const char* iOSVers = getenv("IOS_DEPLOYMENT_TARGET");
                const char* wOSVers = getenv("WATCHOS_DEPLOYMENT_TARGET");
                if ( macVers != NULL )
                        setMacOSXVersionMin(macVers);
                else if ( iPhoneVers != NULL )
                        setIOSVersionMin(iPhoneVers);
                else if ( iOSVers != NULL )
                        setIOSVersionMin(iOSVers);
                else if ( wOSVers != NULL )
                        setWatchOSVersionMin(wOSVers);
                else {
                        // if still nothing, set default based on architecture
                        switch ( fArchitecture ) {
                                case CPU_TYPE_I386:
                                case CPU_TYPE_X86_64:
                                        if ( (fOutputKind != Options::kObjectFile) && (fOutputKind != Options::kPreload) ) {
                        #ifdef DEFAULT_MACOSX_MIN_VERSION
                                                warning("-macosx_version_min not specified, assuming " DEFAULT_MACOSX_MIN_VERSION);
                                                setMacOSXVersionMin(DEFAULT_MACOSX_MIN_VERSION);
                        #else
                                                warning("-macosx_version_min not specified, assuming 10.6");
                                                setMacOSXVersionMin("10.6");
                        #endif          
                                        }
                                        break;
                                case CPU_TYPE_ARM:
                                        if ( (fOutputKind != Options::kObjectFile) && (fOutputKind != Options::kPreload) ) {
                        #if defined(DEFAULT_IPHONEOS_MIN_VERSION)
                                                warning("-ios_version_min not specified, assuming " DEFAULT_IPHONEOS_MIN_VERSION);
                                                setIOSVersionMin(DEFAULT_IPHONEOS_MIN_VERSION);
                        #else
                                                if ( fSubArchitecture == CPU_SUBTYPE_ARM_V7K ) {
                                                        warning("-watchos_version_min not specified, assuming 2.0");
                                                        setWatchOSVersionMin("2.0");
                                                }
                                                else {
                                                        warning("-ios_version_min not specified, assuming 6.0");
                                                        setIOSVersionMin("6.0");
                                                }
                        #endif
                                        }
                                        break;
                                default:
                                        // architecture will be infered later by examining .o files
                                        break;
                        }
                }
        }


        // adjust min based on architecture
        switch ( fArchitecture ) {
                case CPU_TYPE_I386:
                        if ( (fPlatform == kPlatformOSX) && (fMacVersionMin < ld::mac10_4) ) {
                                //warning("-macosx_version_min should be 10.4 or later for i386");
                                fMacVersionMin = ld::mac10_4;
                        }
                        break;
                case CPU_TYPE_X86_64:
                        if ( (fPlatform == kPlatformOSX) && (fMacVersionMin < ld::mac10_4) ) {
                                //warning("-macosx_version_min should be 10.4 or later for x86_64");
                                fMacVersionMin = ld::mac10_4;
                        }
                        break;
                case CPU_TYPE_ARM64:
                        if ( (fPlatform == kPlatformiOS) && (fIOSVersionMin < ld::iOS_7_0) ) {
                                //warning("-mios_version_min should be 7.0 or later for arm64");
                                fIOSVersionMin = ld::iOS_7_0;
                        }
                        break;
        }
        
        // default to adding functions start for dynamic code, static code must opt-in
        switch ( fOutputKind ) {
                case Options::kPreload:
                case Options::kStaticExecutable:
                case Options::kKextBundle:
                        if ( fDataInCodeInfoLoadCommandForcedOn )
                                fDataInCodeInfoLoadCommand = true;
                        if ( fFunctionStartsForcedOn )
                                fFunctionStartsLoadCommand = true;
                        break;
                case Options::kObjectFile:
                        if ( !fDataInCodeInfoLoadCommandForcedOff )
                                fDataInCodeInfoLoadCommand = true;
                        if ( fFunctionStartsForcedOn )
                                fFunctionStartsLoadCommand = true;
                        break;
                case Options::kDynamicExecutable:
                case Options::kDyld:
                case Options::kDynamicLibrary:
                case Options::kDynamicBundle:
                        if ( !fDataInCodeInfoLoadCommandForcedOff )
                                fDataInCodeInfoLoadCommand = true;
                        if ( !fFunctionStartsForcedOff )
                                fFunctionStartsLoadCommand = true;
                        break;
        }
                
        // adjust kext type based on architecture
        if ( fOutputKind == kKextBundle ) {
                switch ( fArchitecture ) {
                        case CPU_TYPE_X86_64:
                                // x86_64 uses new MH_KEXT_BUNDLE type
                                fMakeCompressedDyldInfo = false;
                                fMakeCompressedDyldInfoForceOff = true;
                                fAllowTextRelocs = true;
                                fUndefinedTreatment = kUndefinedDynamicLookup;
                                break;
                        case CPU_TYPE_ARM64:
                                // arm64 uses new MH_KEXT_BUNDLE type
                                fMakeCompressedDyldInfo = false;
                                fMakeCompressedDyldInfoForceOff = true;
                                fAllowTextRelocs = false; 
                                fKextsUseStubs = true;
                                fUndefinedTreatment = kUndefinedDynamicLookup;
                                break;
                        case CPU_TYPE_ARM:
                                if ( min_iOS(ld::iOS_5_0) ) {
                    // iOS 5.0 and later use new MH_KEXT_BUNDLE type
                    fMakeCompressedDyldInfo = false;
                    fMakeCompressedDyldInfoForceOff = true;
                                        // kexts are PIC in iOS 6.0 and later
                                        fAllowTextRelocs = !min_iOS(ld::iOS_6_0);
                                        fKextsUseStubs = !fAllowTextRelocs;
                    fUndefinedTreatment = kUndefinedDynamicLookup;
                                        break;
                                }
                                // else use object file
                        case CPU_TYPE_I386:
                                // use .o files
                                fOutputKind = kObjectFile;
                                break;
                }
        }

        // disable implicit dylibs when targeting 10.3
        // <rdar://problem/5451987> add option to disable implicit load commands for indirectly used public dylibs
        if ( !minOS(ld::mac10_4, ld::iOS_2_0) )
                fImplicitlyLinkPublicDylibs = false;


        // allow build system to force linker to ignore -prebind
        if ( getenv("LD_FORCE_NO_PREBIND") != NULL )
                fPrebind = false;                       

        // allow build system to force linker to ignore -seg_addr_table
        if ( getenv("LD_FORCE_NO_SEG_ADDR_TABLE") != NULL )
                   fSegAddrTablePath = NULL;

        // check for base address specified externally
        if ( (fSegAddrTablePath != NULL) &&  (fOutputKind == Options::kDynamicLibrary) ) {
                parseSegAddrTable(fSegAddrTablePath, this->installPath());
                // HACK to support seg_addr_table entries that are physical paths instead of install paths
                if ( fBaseAddress == 0 ) {
                        if ( strcmp(this->installPath(), "/usr/lib/libstdc++.6.dylib") == 0 ) {
                                parseSegAddrTable(fSegAddrTablePath, "/usr/lib/libstdc++.6.0.4.dylib");
                                if ( fBaseAddress == 0 )
                                        parseSegAddrTable(fSegAddrTablePath, "/usr/lib/libstdc++.6.0.9.dylib");
                        }
                                
                        else if ( strcmp(this->installPath(), "/usr/lib/libz.1.dylib") == 0 ) 
                                parseSegAddrTable(fSegAddrTablePath, "/usr/lib/libz.1.2.3.dylib");
                                
                        else if ( strcmp(this->installPath(), "/usr/lib/libutil.dylib") == 0 ) 
                                parseSegAddrTable(fSegAddrTablePath, "/usr/lib/libutil1.0.dylib");
                }               
        }
        
        // split segs only allowed for dylibs
        if ( fSplitSegs ) {
        // split seg only supported for i386, and arm.
        switch ( fArchitecture ) {
            case CPU_TYPE_I386:
                if ( fOutputKind != Options::kDynamicLibrary )
                    fSplitSegs = false;
                // make sure read and write segments are proper distance apart
                if ( fSplitSegs && (fBaseWritableAddress-fBaseAddress != 0x10000000) )
                    fBaseWritableAddress = fBaseAddress + 0x10000000;
                break;
            case CPU_TYPE_ARM:
                if ( fOutputKind != Options::kDynamicLibrary ) {
                    fSplitSegs = false;
                                }
                                else {
                                        // make sure read and write segments are proper distance apart
                                        if ( fSplitSegs && (fBaseWritableAddress-fBaseAddress != 0x08000000) )
                                                fBaseWritableAddress = fBaseAddress + 0x08000000;
                                }
                break;
            default:
                fSplitSegs = false;
                fBaseAddress = 0;
                fBaseWritableAddress = 0;
                }
        }

        // set too-large size
        switch ( fArchitecture ) {
                case CPU_TYPE_I386:
                        fMaxAddress = 0xFFFFFFFF;
                        break;
                case CPU_TYPE_X86_64:
                        break;
                case CPU_TYPE_ARM:
                        switch ( fOutputKind ) {
                                case Options::kDynamicExecutable:
                                case Options::kDynamicLibrary:
                                case Options::kDynamicBundle:
                                        // user land code is limited to low 1GB
                                        fMaxAddress = 0x2FFFFFFF;
                                        break;
                                case Options::kStaticExecutable:
                                case Options::kObjectFile:
                                case Options::kDyld:
                                case Options::kPreload:
                                case Options::kKextBundle:
                                        fMaxAddress = 0xFFFFFFFF;
                                        break;
                        }
                        // range check -seg1addr for ARM
                        if ( fBaseAddress > fMaxAddress ) {
                                warning("ignoring -seg1addr 0x%08llX.  Address out of range.", fBaseAddress);
                                fBaseAddress = 0;
                        }
                        break;
        }

        // <rdar://problem/6138961> -r implies no prebinding for all architectures
        if ( fOutputKind == Options::kObjectFile )
                fPrebind = false;                       

        // disable prebinding depending on arch and min OS version
        if ( fPrebind ) {
                switch ( fArchitecture ) {
                        case CPU_TYPE_I386:
                                if ( fMacVersionMin == ld::mac10_4 ) {
                                        // in 10.4 only split seg dylibs are prebound
                                        if ( (fOutputKind != Options::kDynamicLibrary) || ! fSplitSegs )
                                                fPrebind = false;
                                }
                                else if ( fMacVersionMin >= ld::mac10_5 ) {
                                        // in 10.5 nothing is prebound
                                        fPrebind = false;
                                }
                                else if ( fIOSVersionMin != ld::iOSVersionUnset ) {
                                        // nothing in simulator is prebound
                                        fPrebind = false;
                                }
                                else {
                                        // in 10.3 and earlier only dylibs and main executables could be prebound
                                        switch ( fOutputKind ) {
                                                case Options::kDynamicExecutable:
                                                case Options::kDynamicLibrary:
                                                        // only main executables and dylibs can be prebound
                                                        break;
                                                case Options::kStaticExecutable:
                                                case Options::kDynamicBundle:
                                                case Options::kObjectFile:
                                                case Options::kDyld:
                                                case Options::kPreload:
                                                case Options::kKextBundle:
                                                        // disable prebinding for everything else
                                                        fPrebind = false;
                                                        break;
                                        }
                                }
                                break;
                        case CPU_TYPE_X86_64:
                                fPrebind = false;
                                break;
            case CPU_TYPE_ARM:
                                switch ( fOutputKind ) {
                                        case Options::kDynamicExecutable:
                                        case Options::kDynamicLibrary:
                                                // only main executables and dylibs can be prebound
                                                break;
                                        case Options::kStaticExecutable:
                                        case Options::kDynamicBundle:
                                        case Options::kObjectFile:
                                        case Options::kDyld:
                                        case Options::kPreload:
                                        case Options::kKextBundle:
                                                // disable prebinding for everything else
                                                fPrebind = false;
                                                break;
                                }
                                break;
                }
        }

        // only prebound images can be split-seg
        if ( fSplitSegs && !fPrebind )
                fSplitSegs = false;

        // determine if info for shared region should be added
        if ( fOutputKind == Options::kDynamicLibrary ) {
                if ( minOS(ld::mac10_5, ld::iOS_3_1) )
                        if ( !fPrebind && !fSharedRegionEligibleForceOff )
                                if ( sharedCacheEligiblePath(this->installPath()) )
                                        fSharedRegionEligible = true;
        }
        else if ( fOutputKind == Options::kDyld ) {
        // <rdar://problem/10111122> Enable dyld to be put into the dyld shared cache
        fSharedRegionEligible = true;
        }

        // automatically use __DATA_CONST in iOS dylibs
        if ( fSharedRegionEligible && minOS(ld::mac10_Future, ld::iOS_9_0) && !fUseDataConstSegmentForceOff && !fTargetIOSSimulator) {
                fUseDataConstSegment = true;
        }
        if ( fUseDataConstSegmentForceOn ) {
                fUseDataConstSegment = true;
        }
        // A -kext for iOS 10 ==>  -data_const, -text_exec, -add_split_seg_info
        if ( (fOutputKind == Options::kKextBundle) && minOS(ld::mac10_Future, ld::iOS_10_0) && (fArchitecture == CPU_TYPE_ARM64) ) {
                fUseDataConstSegment = true;
                fUseTextExecSegment = true;
                fSharedRegionEligible = true;
        }
        if ( fUseDataConstSegment ) {
                addSectionRename("__DATA", "__got",                             "__DATA_CONST", "__got");
                addSectionRename("__DATA", "__la_symbol_ptr",   "__DATA_CONST", "__la_symbol_ptr");
                addSectionRename("__DATA", "__nl_symbol_ptr",   "__DATA_CONST", "__nl_symbol_ptr");
                addSectionRename("__DATA", "__const",                   "__DATA_CONST", "__const");
                addSectionRename("__DATA", "__cfstring",                "__DATA_CONST", "__cfstring");
                addSectionRename("__DATA", "__mod_init_func",   "__DATA_CONST", "__mod_init_func");
                addSectionRename("__DATA", "__mod_term_func",   "__DATA_CONST", "__mod_term_func");
                addSectionRename("__DATA", "__objc_classlist",  "__DATA_CONST", "__objc_classlist");
                addSectionRename("__DATA", "__objc_nlclslist",  "__DATA_CONST", "__objc_nlclslist");
                addSectionRename("__DATA", "__objc_catlist",    "__DATA_CONST", "__objc_catlist");
                addSectionRename("__DATA", "__objc_nlcatlist",  "__DATA_CONST", "__objc_nlcatlist");
                addSectionRename("__DATA", "__objc_protolist",  "__DATA_CONST", "__objc_protolist");
                addSectionRename("__DATA", "__objc_imageinfo",  "__DATA_CONST", "__objc_imageinfo");
                addSectionRename("__DATA", "__objc_const",          "__DATA_CONST", "__objc_const");
        }
        if ( fUseTextExecSegment ) {
                addSectionRename("__TEXT", "__text",                            "__TEXT_EXEC", "__text");
                addSectionRename("__TEXT", "__stubs",                           "__TEXT_EXEC", "__stubs");
        }
        
        // Use V2 shared cache info when targetting newer OSs
        if ( fSharedRegionEligible && minOS(ld::mac10_12, ld::iOS_9_0)) {
                fSharedRegionEncodingV2 = true;
                if ( fPlatform == kPlatformOSX ) {
                        fSharedRegionEncodingV2 = false;
                        // <rdar://problem/24772435> only use v2 for Swift dylibs on Mac OS X
                        if ( strncmp(this->installPath(), "/System/Library/PrivateFrameworks/Swift/", 40) == 0 )
                                fSharedRegionEncodingV2 = true;
                        // <rdar://problem/31428120> an other OS frameworks that use swift need v2
                        for (const char* searchPath  : fLibrarySearchPaths ) {
                                if ( strstr(searchPath, "xctoolchain/usr/lib/swift/macos") != NULL ) {
                                        fSharedRegionEncodingV2 = true;
                                        break;
                                }
                        }
                }
                fIgnoreOptimizationHints = true;
        }

        // figure out if module table is needed for compatibility with old ld/dyld
        if ( fOutputKind == Options::kDynamicLibrary ) {
                switch ( fArchitecture ) {
                        case CPU_TYPE_I386:
                                if ( fIOSVersionMin != ld::iOSVersionUnset ) // simulator never needs modules
                                        break;
                        case CPU_TYPE_ARM:
                                if ( fPrebind )
                                        fNeedsModuleTable = true; // redo_prebinding requires a module table
                                break;
                }
        }
        
        // <rdar://problem/5366363> -r -x implies -S
        if ( (fOutputKind == Options::kObjectFile) && (fLocalSymbolHandling == kLocalSymbolsNone) )
                fDebugInfoStripping = Options::kDebugInfoNone;                  

        // <rdar://problem/15252891> -r implies -no_uuid
        if ( fOutputKind == Options::kObjectFile )
                fUUIDMode = kUUIDNone;

        // choose how to process unwind info
        switch ( fArchitecture ) {
                case CPU_TYPE_I386:             
                case CPU_TYPE_X86_64:           
                case CPU_TYPE_ARM64:            
                        switch ( fOutputKind ) {
                                case Options::kObjectFile:
                                case Options::kStaticExecutable:
                                case Options::kPreload:
                                case Options::kKextBundle:
                                        fAddCompactUnwindEncoding = false;
                                        break;
                                case Options::kDyld:
                                case Options::kDynamicLibrary:
                                case Options::kDynamicBundle:
                                case Options::kDynamicExecutable:
                                        //if ( fAddCompactUnwindEncoding && (fVersionMin >= ld::mac10_6) )
                                        //      fRemoveDwarfUnwindIfCompactExists = true;
                                        break;
                        }
                        break;
                case CPU_TYPE_ARM:
                        if ( armUsesZeroCostExceptions() )  {
                                switch ( fOutputKind ) {
                                        case Options::kObjectFile:
                                        case Options::kStaticExecutable:
                                        case Options::kPreload:
                                        case Options::kKextBundle:
                                                fAddCompactUnwindEncoding = false;
                                                break;
                                        case Options::kDyld:
                                        case Options::kDynamicLibrary:
                                        case Options::kDynamicBundle:
                                        case Options::kDynamicExecutable:
                                                fAddCompactUnwindEncoding = true;
                                                break;
                                }
                        }
                        else {
                                fAddCompactUnwindEncoding = false;
                                fRemoveDwarfUnwindIfCompactExists = false;
                        }
                        break;
                case 0:
                        // if -arch is missing, assume we don't want compact unwind info
                        fAddCompactUnwindEncoding = false;
                        break;
        }
                
        // only iOS executables should be encryptable
        switch ( fOutputKind ) {
                case Options::kObjectFile:
                case Options::kDyld:
                case Options::kStaticExecutable:
                case Options::kPreload:
                case Options::kKextBundle:
                        fEncryptable = false;
                        break;
                case Options::kDynamicExecutable:
                        break;
                case Options::kDynamicLibrary:
                case Options::kDynamicBundle:
                        // <rdar://problem/16293398> Add LC_ENCRYPTION_INFO load command to bundled frameworks
                        if ( !min_iOS(ld::iOS_7_0) )
                                fEncryptable = false;
                        break;
        }
        if ( (fArchitecture != CPU_TYPE_ARM) && (fArchitecture != CPU_TYPE_ARM64)
         )
                fEncryptable = false;
        if ( fEncryptableForceOn )
                fEncryptable = true;
        else if ( fEncryptableForceOff )
                fEncryptable = false;

        // don't move inits in dyld because dyld wants certain
        // entries point at stable locations at the start of __text
        if ( fOutputKind == Options::kDyld ) 
                fAutoOrderInitializers = false;
                
                
        // disable __data ordering for some output kinds
        switch ( fOutputKind ) {
                case Options::kObjectFile:
                case Options::kDyld:
                case Options::kStaticExecutable:
                case Options::kPreload:
                case Options::kKextBundle:
                        fOrderData = false;
                        break;
                case Options::kDynamicExecutable:
                case Options::kDynamicLibrary:
                case Options::kDynamicBundle:
                        break;
        }
        
        // only use compressed LINKEDIT for final linked images
        switch ( fOutputKind ) {
                case Options::kDynamicExecutable:
                case Options::kDynamicLibrary:
                case Options::kDynamicBundle:
                        break;
                case Options::kPreload:
                case Options::kStaticExecutable:
                case Options::kObjectFile:
                case Options::kDyld:
                case Options::kKextBundle:
                        fMakeCompressedDyldInfoForceOff = true;
                        break;
        }
        if ( fMakeCompressedDyldInfoForceOff ) 
                fMakeCompressedDyldInfo = false;

        
        // only use compressed LINKEDIT for:
        //                      Mac OS X 10.6 or later
        //                      iOS 3.1 or later
        if ( fMakeCompressedDyldInfo ) {
                if ( !minOS(ld::mac10_6, ld::iOS_3_1) )
                        fMakeCompressedDyldInfo = false;
        }

        // only ARM and x86_64 enforces that cpu-sub-types must match
        switch ( fArchitecture ) {
                case CPU_TYPE_ARM:
                        break;
                case CPU_TYPE_X86_64:
                        fEnforceDylibSubtypesMatch = false;
                        break;
                case CPU_TYPE_I386:
                case CPU_TYPE_ARM64:
                        fEnforceDylibSubtypesMatch = false;
                        break;
        }
                
                
        // only final linked images can not optimize zero fill sections
        if ( fOutputKind == Options::kObjectFile )
                fOptimizeZeroFill = true;

        // all undefines in -r mode
//      if ( fOutputKind == Options::kObjectFile )
//              fUndefinedTreatment = kUndefinedSuppress;

        // only dynamic final linked images should warn about use of commmons
        if ( fWarnCommons ) {
                switch ( fOutputKind ) {
                        case Options::kDynamicExecutable:
                        case Options::kDynamicLibrary:
                        case Options::kDynamicBundle:
                                break;
                        case Options::kPreload:
                        case Options::kStaticExecutable:
                        case Options::kObjectFile:
                        case Options::kDyld:
                        case Options::kKextBundle:
                                fWarnCommons = false;
                                break;
                }
        }
        
        // Mac OS X 10.5 and iPhoneOS 2.0 support LC_REEXPORT_DYLIB
        if ( minOS(ld::mac10_5, ld::iOS_2_0) )
                fUseSimplifiedDylibReExports = true;
        
        // Mac OS X 10.7 and iOS 4.2 support LC_LOAD_UPWARD_DYLIB
        if ( minOS(ld::mac10_7, ld::iOS_4_2) && (fOutputKind == kDynamicLibrary) )
                fCanUseUpwardDylib = true;
                
        // MacOSX 10.7 defaults to PIE
        if ( (fArchitecture == CPU_TYPE_I386)
                && (fOutputKind == kDynamicExecutable)
                && (fMacVersionMin >= ld::mac10_7) ) {
                        fPositionIndependentExecutable = true;
        }

        // armv7 for iOS4.3 defaults to PIE
        if ( (fArchitecture == CPU_TYPE_ARM) 
                && fArchSupportsThumb2
                && (fOutputKind == kDynamicExecutable) 
                && min_iOS(ld::iOS_4_3) ) {
                        fPositionIndependentExecutable = true;
        }

        // <rdar://problem/24535196> x86_64 defaults PIE (regardless of minOS version)
        if ( (fArchitecture == CPU_TYPE_X86_64) && (fOutputKind == kDynamicExecutable) && (fMacVersionMin >= ld::mac10_6) )
                fPositionIndependentExecutable = true;

        // Simulator defaults to PIE
        if ( fTargetIOSSimulator && (fOutputKind == kDynamicExecutable) )
                fPositionIndependentExecutable = true;

        // -no_pie anywhere on command line disable PIE
        if ( fDisablePositionIndependentExecutable )
                fPositionIndependentExecutable = false;

        // arm64 is always PIE
        if ( ((fArchitecture == CPU_TYPE_ARM64)
          )
        && (fOutputKind == kDynamicExecutable) ) {
                fPositionIndependentExecutable = true;
                if ( fDisablePositionIndependentExecutable )
                        warning("-no_pie ignored for arm64");
        }

        // set fOutputSlidable
        switch ( fOutputKind ) {
                case Options::kObjectFile:
                        fOutputSlidable = false;
                        break;
                case Options::kStaticExecutable:
                case Options::kDynamicExecutable:
                        fOutputSlidable = fPositionIndependentExecutable;
                        break;
                case Options::kPreload:
                        fOutputSlidable = fPIEOnCommandLine;
                        break;
                case Options::kDyld:
                case Options::kDynamicLibrary:
                case Options::kDynamicBundle:
                case Options::kKextBundle:
                        fOutputSlidable = true;
                        break;
        }

        // let linker know if thread local variables are supported
        if ( fMacVersionMin >= ld::mac10_7 ) {
                fTLVSupport = true;
        }
        else if ( ((fArchitecture == CPU_TYPE_ARM64)
               )
             && min_iOS(ld::iOS_8_0) ) {
                fTLVSupport = true;
        }
        else if ( (fArchitecture == CPU_TYPE_ARM) && min_iOS(ld::iOS_9_0) ) {
                fTLVSupport = true;
        }
        else if ( fTargetIOSSimulator && (fArchitecture == CPU_TYPE_X86_64) && min_iOS(ld::iOS_8_0) ) {
                fTLVSupport = true;
        }
        else if ( fTargetIOSSimulator && (fArchitecture == CPU_TYPE_I386) && min_iOS(ld::iOS_9_0) ) {
                fTLVSupport = true;
        }

        // default to adding version load command for dynamic code, static code must opt-in
        switch ( fOutputKind ) {
                case Options::kObjectFile:
                        fVersionLoadCommand = false;
                        break;
                case Options::kStaticExecutable:
                case Options::kPreload:
                case Options::kKextBundle:
                        if ( fVersionLoadCommandForcedOn )
                                fVersionLoadCommand = true;
                        break;
                case Options::kDynamicExecutable:
                case Options::kDyld:
                case Options::kDynamicLibrary:
                case Options::kDynamicBundle:
                        if ( !fVersionLoadCommandForcedOff )
                                fVersionLoadCommand = true;
                        break;
        }
        
        // support re-export of individual symbols in MacOSX 10.7 and iOS 4.2
        if ( (fOutputKind == kDynamicLibrary) && minOS(ld::mac10_7, ld::iOS_4_2) )
                fCanReExportSymbols = true;
        
        // ObjC optimization is only in dynamic final linked images
        switch ( fOutputKind ) {
                case Options::kObjectFile:
                case Options::kStaticExecutable:
                case Options::kPreload:
                case Options::kKextBundle:
                case Options::kDyld:
                        fObjcCategoryMerging = false;
                        break;
                case Options::kDynamicExecutable:
                case Options::kDynamicLibrary:
                case Options::kDynamicBundle:
                        break;
        }

        // i386 main executables linked on Mac OS X 10.7 default to NX heap
        // regardless of target unless overriden with -allow_heap_execute anywhere
        // on the command line
        if ( (fArchitecture == CPU_TYPE_I386) && (fOutputKind == kDynamicExecutable) && !fDisableNonExecutableHeap)
                fNonExecutableHeap = true;
                
        // Use LC_MAIN instead of LC_UNIXTHREAD for newer OSs
        switch ( fOutputKind ) {
                case Options::kDynamicExecutable:
                        if ( fEntryPointLoadCommandForceOn ) {
                                fEntryPointLoadCommand = true;
                                if ( fEntryName == NULL ) 
                                        fEntryName = "_main";
                        }
                        else if ( fEntryPointLoadCommandForceOff ) {
                                fNeedsThreadLoadCommand = true;
                                if ( fEntryName == NULL ) 
                                        fEntryName = "start";
                        }
                        else {
                                // <rdar://problem/16310363> Linker should look for "_main" not "start" when building for sim regardless of min OS
                                if ( minOS(ld::mac10_8, ld::iOS_6_0) || fTargetIOSSimulator ) {
                                        fEntryPointLoadCommand = true;
                                        if ( fEntryName == NULL ) 
                                                fEntryName = "_main";
                                        if ( strcmp(fEntryName, "start") == 0 ) {
                                                warning("Ignoring '-e start' because entry point 'start' is not used for the targeted OS version");
                                                fEntryName = "_main";
                                        }
                                } 
                                else {
                                        fNeedsThreadLoadCommand = true;
                                        if ( fEntryName == NULL ) 
                                                fEntryName = "start";
                                }
                        }
                        break;
                case Options::kObjectFile:
                case Options::kKextBundle:
                case Options::kDynamicLibrary:
                case Options::kDynamicBundle:
                        break;
                        
                case Options::kStaticExecutable:
                case Options::kPreload:
                case Options::kDyld:
                        fNeedsThreadLoadCommand = true;
                        if ( fEntryName == NULL ) 
                                fEntryName = "start";  // Perhaps these should have no default and require -e
                        break;
        }
        
        // add LC_SOURCE_VERSION
        switch ( fOutputKind ) {
                case Options::kDynamicExecutable:
                case Options::kKextBundle:
                case Options::kDynamicLibrary:
                case Options::kDynamicBundle:
                case Options::kDyld:
                case Options::kStaticExecutable:
                        if ( fSourceVersionLoadCommandForceOn ) {
                                fSourceVersionLoadCommand = true;
                        }
                        else if ( fSourceVersionLoadCommandForceOff ) {
                                fSourceVersionLoadCommand = false;
                        }
                        else {
                                if ( minOS(ld::mac10_8, ld::iOS_6_0) ) {
                                        fSourceVersionLoadCommand = true;
                                }
                                else
                                        fSourceVersionLoadCommand = false;
                        }
                        break;
                case Options::kObjectFile:
                case Options::kPreload:
                        fSourceVersionLoadCommand = false;
                        break;
        }

        // if -sdk_version not on command line, infer from -syslibroot
        if ( (fSDKVersion == 0) && (fSDKPaths.size() > 0) ) {
                const char* sdkPath = fSDKPaths.front();
                const char* end = &sdkPath[strlen(sdkPath)-1];
                while ( !isdigit(*end) && (end > sdkPath) )
                        --end;
                const char* start = end-1;
                while ( (isdigit(*start) || (*start == '.')) && (start > sdkPath))
                        --start;
                char sdkVersionStr[32];
                int len = end-start+1;
                if ( len > 2 ) {
                        strlcpy(sdkVersionStr, start+1, len);
                        fSDKVersion = parseVersionNumber32(sdkVersionStr);
                }
        }
        
        // if -sdk_version and -syslibroot not used, but targeting MacOSX, use current OS version
        if ( (fSDKVersion == 0) && (fMacVersionMin != ld::macVersionUnset) ) {
                // special case if RC_ProjectName and MACOSX_DEPLOYMENT_TARGET are both set that sdkversion=minos
                if ( getenv("RC_ProjectName") && getenv("MACOSX_DEPLOYMENT_TARGET") ) {
                        fSDKVersion = fMacVersionMin;
                }
                else {
                        int mib[2] = { CTL_KERN, KERN_OSRELEASE };
                        char kernVersStr[100];
                        size_t strlen = sizeof(kernVersStr);
                        if ( sysctl(mib, 2, kernVersStr, &strlen, NULL, 0) != -1 ) {
                                uint32_t kernVers = parseVersionNumber32(kernVersStr);
                                int minor = (kernVers >> 16) - 4;  // kernel major version is 4 ahead of x in 10.x
                                fSDKVersion = 0x000A0000 + (minor << 8);
                        }
                }
        }
        
        // allow trie based absolute symbols if targeting new enough OS
        if ( fMakeCompressedDyldInfo ) {
                if ( minOS(ld::mac10_9, ld::iOS_7_0) ) {
                        fAbsoluteSymbols = true;
                }
        }
        
        // <rdar://problem/12959510> iOS main executables now default to 16KB page size
        if ( (fIOSVersionMin != ld::iOSVersionUnset) && (fOutputKind == Options::kDynamicExecutable) ) {
                // <rdar://problem/13070042> Only third party apps should have 16KB page segments by default
                if ( fEncryptable ) {
                        if ( fSegmentAlignment == 4096 )
                                fSegmentAlignment = 4096*4;
                }
        }
  
        // <rdar://problem/12258065> ARM64 needs 16KB page size for user land code
        // <rdar://problem/15974532> make armv7[s] use 16KB pages in user land code for iOS 8 or later
        if ( fSegmentAlignment == 4096 ) {
                switch ( fOutputKind ) {
                        case Options::kDynamicExecutable:
                        case Options::kDynamicLibrary:
                        case Options::kDynamicBundle:
                        case Options::kDyld:
                                if ( ((fArchitecture == CPU_TYPE_ARM64)
                     )
                                || ((fArchitecture == CPU_TYPE_ARM) && min_iOS(ld::iOS_7_0)) ) {
                                        fSegmentAlignment = 4096*4;
                                }
                                break;
                        case Options::kStaticExecutable:
                        case Options::kKextBundle:
                                // <rdar://problem/14676611> 16KB segments for arm64 kexts
                                if ( ((fArchitecture == CPU_TYPE_ARM64)
                     )
                                    && min_iOS(ld::iOS_9_0) ) {
                                        fSegmentAlignment = 4096*4;
                                }
                                break;
                        case Options::kObjectFile:
                        case Options::kPreload:
                                break;
                }
        }



        // <rdar://problem/13624134> linker should not convert dwarf unwind if .o file has compact unwind section
        switch ( fOutputKind ) {
                case Options::kDynamicExecutable:
                case Options::kDynamicLibrary:
                case Options::kDynamicBundle:
                case Options::kDyld:
                        if ( fKeepDwarfUnwindForcedOn ) {
                                fKeepDwarfUnwind = true;
                        }
                        else if ( fKeepDwarfUnwindForcedOff ) {
                                fKeepDwarfUnwind = false;
                        }
                        else {
                                if ( minOS(ld::mac10_9, ld::iOS_7_0) ) 
                                        fKeepDwarfUnwind = false;
                                else
                                        fKeepDwarfUnwind = true;
                        }
                        break;
                case Options::kKextBundle:
                case Options::kStaticExecutable:
                case Options::kObjectFile:
                case Options::kPreload:
                        fKeepDwarfUnwind = true;
                        break;
        }
        
        // Make sure -image_base matches alignment
        uint64_t alignedBaseAddress = (fBaseAddress+fSegmentAlignment-1) & (-fSegmentAlignment);
        if ( alignedBaseAddress != fBaseAddress ) {
                warning("base address 0x%llX is not properly aligned. Changing it to 0x%llX", fBaseAddress, alignedBaseAddress);
                fBaseAddress = alignedBaseAddress;
        }

        // If -dirty_data_list not specified, look in $SDKROOT/AppleInternal/DirtyDataFiles/<dylib>.dirty for dirty data list
        if ( fSymbolsMovesData.empty() && fUseDataConstSegment && ( fDylibInstallName != NULL) && !fSDKPaths.empty() ) {
                const char* dylibLeaf = strrchr(fDylibInstallName, '/');
                if ( dylibLeaf ) {
                        char path[PATH_MAX];
                        strlcpy(path , fSDKPaths.front(), sizeof(path));
                        strlcat(path , "/AppleInternal/DirtyDataFiles", sizeof(path));
                        strlcat(path , dylibLeaf, sizeof(path));
                        strlcat(path , ".dirty", sizeof(path));
                        FileInfo info;
                        if ( info.checkFileExists(*this, path) )
                                addSymbolMove("__DATA_DIRTY", path, fSymbolsMovesData, "-dirty_data_list");
                }
        }


        // <rdar://problem/32138080> Automatically use OrderFiles found in the AppleInternal SDK
        if ( (fFinalName != NULL) && fOrderedSymbols.empty() && !fSDKPaths.empty() ) {
                char path[PATH_MAX];
                strlcpy(path , fSDKPaths.front(), sizeof(path));
                strlcat(path , "/AppleInternal/OrderFiles/", sizeof(path));
                strlcat(path , fFinalName, sizeof(path));
                strlcat(path , ".order", sizeof(path));
                FileInfo info;
                if ( info.checkFileExists(*this, path) )
                        parseOrderFile(path, false);
        }

        // <rdar://problem/20503811> Reduce the default alignment of structures/arrays to save memory in embedded systems
        if ( fMaxDefaultCommonAlign == 0 ) {
                if ( fOutputKind == Options::kPreload )
                        fMaxDefaultCommonAlign = 8;
                else
                        fMaxDefaultCommonAlign = 15;
        }

        // Add warnings for issues likely to cause OS verification issues
        if ( fSharedRegionEligible && !fRPaths.empty() ) {
                // <rdar://problem/18719327> warn if -rpath is used with OS dylibs
                warning("OS dylibs should not add rpaths (linker option: -rpath) (Xcode build setting: LD_RUNPATH_SEARCH_PATHS)");
        }
        if ( (fOutputKind == Options::kDynamicLibrary) && (fDylibInstallName != NULL) && (fFinalName != NULL) && sharedCacheEligiblePath(fFinalName) ) {
                if ( strncmp(fDylibInstallName, "@rpath", 6) == 0 )
                        warning("OS dylibs should not use @rpath for -install_name.  Use absolute path instead");
                if ( strcmp(fDylibInstallName, fFinalName) != 0 ) {
                        bool different = true;
                        // some projects end up with double slash in -final_output path
                        if ( strstr(fFinalName, "//") != NULL ) {
                                char fixedPath[strlen(fFinalName)+1];
                                char* t = fixedPath;
                                bool lastWasSlash = false;
                                for (const char* s=fFinalName; *s != '\0'; ++s) {
                                        if ( *s == '/' ) {
                                                if ( !lastWasSlash )
                                                        *t++ = *s;
                                                lastWasSlash = true;
                                        }
                                        else {
                                                *t++ = *s;
                                                lastWasSlash = false;
                                        }
                                }
                                *t = '\0';
                                different = (strcmp(fDylibInstallName, fixedPath) != 0);
                        }
                        if ( different )
                                warning("OS dylibs -install_name should match its real absolute path");
                }
        }

        // set if unaligned pointers are warnings or errors
        if ( fMacVersionMin >= ld::mac10_12 ) {
                // ignore unaligned pointers when targeting older macOS versions
                if ( fSharedRegionEligible )
                        fUnalignedPointerTreatment = Options::kUnalignedPointerWarning;
                else
                        fUnalignedPointerTreatment = Options::kUnalignedPointerIgnore;
        }
        else if ( min_iOS(ld::iOS_10_0) ) {
                fUnalignedPointerTreatment = Options::kUnalignedPointerWarning;
        }
        else {
                fUnalignedPointerTreatment = Options::kUnalignedPointerIgnore;
        }

}

void Options::checkIllegalOptionCombinations()
{
        // check -undefined setting
        switch ( fUndefinedTreatment ) {
                case kUndefinedError:
                        // always legal
                        break;
                case kUndefinedDynamicLookup:
                        switch (fPlatform) {
                                case kPlatformOSX:
                                        break;
                                case kPlatformiOS:
                                case kPlatformWatchOS:
                                case kPlatform_bridgeOS:
                #if SUPPORT_APPLE_TV
                                case kPlatform_tvOS:
                #endif
                                        if ( fOutputKind != kKextBundle )
                                                warning("-undefined dynamic_lookup is deprecated on %s", platformName(fPlatform));
                                        break;
                                default:
                                        break;
                        }
                        break;
                case kUndefinedWarning:
                case kUndefinedSuppress:
                        // requires flat namespace
                        if ( fNameSpace == kTwoLevelNameSpace )
                                throw "can't use -undefined warning or suppress with -twolevel_namespace";
                        break;
        }

        // unify -sub_umbrella with dylibs
        for (std::vector<const char*>::iterator it = fSubUmbellas.begin(); it != fSubUmbellas.end(); it++) {
                const char* subUmbrella = *it;
                bool found = false;
                for (std::vector<Options::FileInfo>::iterator fit = fInputFiles.begin(); fit != fInputFiles.end(); fit++) {
                        Options::FileInfo& info = *fit;
                        const char* lastSlash = strrchr(info.path, '/');
                        if ( lastSlash == NULL )
                                lastSlash = info.path - 1;
                        std::string path(&lastSlash[1]);
                        auto idx = path.find(".tbd", path.size() - 4);
                        if (idx != std::string::npos)
                                path.erase(idx);
                        if ( path == subUmbrella ) {
                                info.options.fReExport = true;
                                found = true;
                fLinkSnapshot.recordSubUmbrella(info.path);
                                break;
                        }
                }
                if ( ! found  )
                        warning("-sub_umbrella %s does not match a supplied dylib", subUmbrella);
        }

        // unify -sub_library with dylibs
        for (std::vector<const char*>::iterator it = fSubLibraries.begin(); it != fSubLibraries.end(); it++) {
                const char* subLibrary = *it;
                bool found = false;
                for (std::vector<Options::FileInfo>::iterator fit = fInputFiles.begin(); fit != fInputFiles.end(); fit++) {
                        Options::FileInfo& info = *fit;
                        const char* lastSlash = strrchr(info.path, '/');
                        if ( lastSlash == NULL )
                                lastSlash = info.path - 1;
                        const char* dot = strchr(&lastSlash[1], '.');
                        if ( dot == NULL )
                                dot = &lastSlash[strlen(lastSlash)];
                        if ( strncmp(&lastSlash[1], subLibrary, dot-lastSlash-1) == 0 ) {
                                info.options.fReExport = true;
                                found = true;
                fLinkSnapshot.recordSubLibrary(info.path);
                                break;
                        }
                }
                if ( ! found  )
                        warning("-sub_library %s does not match a supplied dylib", subLibrary);
        }

        // sync reader options
        if ( fNameSpace != kTwoLevelNameSpace ) {
                fFlatNamespace = true;
                switch (fPlatform) {
                        case kPlatformOSX:
                                break;
                        case kPlatformiOS:
                        case kPlatformWatchOS:
                        case kPlatform_bridgeOS:
        #if SUPPORT_APPLE_TV
                        case Options::kPlatform_tvOS:
        #endif
                                warning("-flat_namespace is deprecated on %s", platformName(fPlatform));
                                break;
                        default:
                                break;
                }
        }


        // check -stack_addr
        if ( fStackAddr != 0 ) {
                switch (fArchitecture) {
                        case CPU_TYPE_I386:
            case CPU_TYPE_ARM:
                                if ( fStackAddr > 0xFFFFFFFF )
                                        throw "-stack_addr must be < 4G for 32-bit processes";
                                break;
                        case CPU_TYPE_X86_64:
                        case CPU_TYPE_ARM64:
                                break;
                }
                if ( (fStackAddr & -4096) != fStackAddr )
                        throw "-stack_addr must be multiples of 4K";
                if ( fStackSize  == 0 )
                        throw "-stack_addr must be used with -stack_size";
        }

        // check -stack_size
        if ( fStackSize != 0 ) {
                switch (fArchitecture) {
                        case CPU_TYPE_I386:
                                if ( fPlatform == kPlatformOSX ) {
                                        if ( fStackSize > 0xFFFFFFFF )
                                                throw "-stack_size must be < 4GB for 32-bit processes";
                                        if ( fStackAddr == 0 )
                                                fStackAddr = 0xC0000000;
                                        if ( (fStackAddr > 0xB0000000) && ((fStackAddr-fStackSize) < 0xB0000000)  )
                                                warning("custom stack placement overlaps and will disable shared region");
                                }
                                else {
                                        if ( fStackSize > 0x1F000000 )
                                                throw "-stack_size must be < 496MB";
                                        if ( fStackAddr == 0 )
                                                fStackAddr = 0xC0000000;
                                }
                                break;
            case CPU_TYPE_ARM:
                                if ( fStackSize > 0x1F000000 )
                                        throw "-stack_size must be < 496MB";
                                if ( fStackAddr == 0 )
                                        fStackAddr = 0x1F000000;
                if ( fStackAddr > 0x20000000)
                    throw "-stack_addr must be < 0x20000000 for arm";
                                break;
                        case CPU_TYPE_X86_64:
                                if ( fPlatform == kPlatformOSX ) {
                                        if ( fStackSize > 0x10000000000 )
                                                throw "-stack_size must be <= 1TB";
                                        if ( fStackAddr == 0 ) {
                                                fStackAddr = 0x00007FFF5C000000LL;
                                        }
                                }
                                else {
                                        if ( fStackSize > 0x20000000 )
                                                throw "-stack_size must be <= 512MB";
                                        if ( fStackAddr == 0 ) {
                                                fStackAddr = 0x120000000;
                                }
                                break;
                        case CPU_TYPE_ARM64:
                                if ( fStackSize > 0x20000000 )
                                        throw "-stack_size must be <= 512MB";
                                if ( fStackAddr == 0 )
                                        fStackAddr = 0x120000000;
                                }
                                break;
                }
                if ( (fStackSize & (-fSegmentAlignment)) != fStackSize )
                        throwf("-stack_size must be multiple of segment alignment (%lldKB)", fSegmentAlignment/1024);
                switch ( fOutputKind ) {
                        case Options::kDynamicExecutable:
                        case Options::kStaticExecutable:
                                // custom stack size only legal when building main executable
                                break;
                        case Options::kDynamicLibrary:
                        case Options::kDynamicBundle:
                        case Options::kObjectFile:
                        case Options::kDyld:
                        case Options::kPreload:
                        case Options::kKextBundle:
                                throw "-stack_size option can only be used when linking a main executable";
                }
                if ( fStackSize > fStackAddr )
                        throwf("-stack_size (0x%08llX) must be smaller than -stack_addr (0x%08llX)", fStackSize, fStackAddr);
        }

        // check that -allow_stack_execute is only used with main executables
        if ( fExecutableStack ) {
                switch ( fOutputKind ) {
                        case Options::kDynamicExecutable:
                        case Options::kStaticExecutable:
                                // -allow_stack_execute size only legal when building main executable
                                break;
                        case Options::kDynamicLibrary:
                        case Options::kDynamicBundle:
                        case Options::kObjectFile:
                        case Options::kDyld:
                        case Options::kPreload:
                        case Options::kKextBundle:
                                throw "-allow_stack_execute option can only be used when linking a main executable";
                }
        }

        // check that -allow_heap_execute is only used with i386 main executables
        if ( fDisableNonExecutableHeap ) {
                if ( fArchitecture != CPU_TYPE_I386 )
                        throw "-allow_heap_execute option can only be used when linking for i386";
                switch ( fOutputKind ) {
                        case Options::kDynamicExecutable:
                                // -allow_heap_execute only legal when building main executable
                                break;
                        case Options::kStaticExecutable:
                        case Options::kDynamicLibrary:
                        case Options::kDynamicBundle:
                        case Options::kObjectFile:
                        case Options::kDyld:
                        case Options::kPreload:
                        case Options::kKextBundle:
                                throw "-allow_heap_execute option can only be used when linking a main executable";
                }
        }

        // check -client_name is only used when making a bundle or main executable
        if ( fClientName != NULL ) {
                switch ( fOutputKind ) {
                        case Options::kDynamicExecutable:
                        case Options::kDynamicBundle:
                                break;
                        case Options::kStaticExecutable:
                        case Options::kDynamicLibrary:
                        case Options::kObjectFile:
                        case Options::kDyld:
                        case Options::kPreload:
                        case Options::kKextBundle:
                                throw "-client_name can only be used with -bundle";
                }
        }
        
        // check -init is only used when building a dylib
        if ( (fInitFunctionName != NULL) && (fOutputKind != Options::kDynamicLibrary) )
                throw "-init can only be used with -dynamiclib";

        // check -bundle_loader only used with -bundle
        if ( (fBundleLoader != NULL) && (fOutputKind != Options::kDynamicBundle) )
                throw "-bundle_loader can only be used with -bundle";

        // check -dtrace not used with -r
        if ( (fDtraceScriptName != NULL) && (fOutputKind == Options::kObjectFile) )
                throw "-dtrace can only be used when creating final linked images";

        // check -d can only be used with -r
        if ( fMakeTentativeDefinitionsReal && (fOutputKind != Options::kObjectFile) )
                throw "-d can only be used with -r";

        // check that -root_safe is not used with -r
        if ( fRootSafe && (fOutputKind == Options::kObjectFile) )
                throw "-root_safe cannot be used with -r";

        // check that -setuid_safe is not used with -r
        if ( fSetuidSafe && (fOutputKind == Options::kObjectFile) )
                throw "-setuid_safe cannot be used with -r";

        // <rdar://problem/12781832> compiler driver no longer uses -objc_abi_version, it uses -ios_simulator_version_min instead
        if ( !fObjCABIVersion1Override && !fObjCABIVersion2Override && fTargetIOSSimulator )
                fObjCABIVersion2Override = true;

        // rdar://problem/4718189 map ObjC class names to new runtime names
        bool alterObjC1ClassNamesToObjC2 = false;
        switch (fArchitecture) {
                case CPU_TYPE_I386:
                        // i386 only uses new symbols when using objc2 ABI
                        if ( fObjCABIVersion2Override )
                                alterObjC1ClassNamesToObjC2 = true;
                        break;
                case CPU_TYPE_X86_64:
                case CPU_TYPE_ARM:
                case CPU_TYPE_ARM64:
                        alterObjC1ClassNamesToObjC2 = true;
                        break;
        }

        // make sure all required exported symbols exist
        std::vector<const char*> impliedExports;
        for (NameSet::iterator it=fExportSymbols.regularBegin(); it != fExportSymbols.regularEnd(); ++it) {
                const char* name = *it;
                const int len = strlen(name);
                if ( (strcmp(&name[len-3], ".eh") == 0) || (strncmp(name, ".objc_category_name_", 20) == 0) ) {
                        // never export .eh symbols
                        warning("ignoring %s in export list", name);
                }
                else if ( (fArchitecture == CPU_TYPE_I386) && !fObjCABIVersion2Override && (strncmp(name, "_OBJC_CLASS_$", 13) == 0) ) {
                        warning("ignoring Objc2 Class symbol %s in i386 export list", name);
                        fRemovedExports.insert(name);
                }
                else if ( alterObjC1ClassNamesToObjC2 && (strncmp(name, ".objc_class_name_", 17) == 0) ) {
                        // linking ObjC2 ABI, but have ObjC1 ABI name in export list.  Change it to intended name
                        fRemovedExports.insert(name);
                        char* temp;
                        asprintf(&temp, "_OBJC_CLASS_$_%s", &name[17]);
                        impliedExports.push_back(temp);
                        asprintf(&temp, "_OBJC_METACLASS_$_%s", &name[17]);
                        impliedExports.push_back(temp);
                }
                else {
                        fInitialUndefines.push_back(name);
                }
        }
        fExportSymbols.remove(fRemovedExports);
        for (std::vector<const char*>::iterator it=impliedExports.begin(); it != impliedExports.end(); ++it) {
                const char* name = *it;
                fExportSymbols.insert(name);
                fInitialUndefines.push_back(name);
        }

        // make sure all required re-exported symbols exist
        for (NameSet::iterator it=fReExportSymbols.regularBegin(); it != fReExportSymbols.regularEnd(); ++it) {
                fInitialUndefines.push_back(*it);
        }
        
        // make sure that -init symbol exists
        if ( fInitFunctionName != NULL )
                fInitialUndefines.push_back(fInitFunctionName);

        // make sure that entry symbol exists
        switch ( fOutputKind ) {
                case Options::kDynamicExecutable:
                case Options::kStaticExecutable:
                case Options::kDyld:
                case Options::kPreload:
                        fInitialUndefines.push_back(fEntryName);
                        break;
                case Options::kDynamicLibrary:
                case Options::kDynamicBundle:
                case Options::kObjectFile:
                case Options::kKextBundle:
                        break;
        }

        // make sure every alias base exists
        for (std::vector<AliasPair>::iterator it=fAliases.begin(); it != fAliases.end(); ++it) {
                fInitialUndefines.push_back(it->realName);
        }

        // check custom segments
        if ( fCustomSegmentAddresses.size() != 0 ) {
                // verify no segment is in zero page
                if ( fZeroPageSize != ULLONG_MAX ) {
                        for (std::vector<SegmentStart>::iterator it = fCustomSegmentAddresses.begin(); it != fCustomSegmentAddresses.end(); ++it) {
                                if ( it->address < fZeroPageSize )
                                        throwf("-segaddr %s 0x%llX conflicts with -pagezero_size", it->name, it->address);
                        }
                }
                // verify no duplicates
                for (std::vector<SegmentStart>::iterator it = fCustomSegmentAddresses.begin(); it != fCustomSegmentAddresses.end(); ++it) {
                        for (std::vector<SegmentStart>::iterator it2 = fCustomSegmentAddresses.begin(); it2 != fCustomSegmentAddresses.end(); ++it2) {
                                if ( (it->address == it2->address) && (it != it2) )
                                        throwf("duplicate -segaddr addresses for %s and %s", it->name, it2->name);
                        }
                        // a custom segment address of zero will disable the use of a zero page
                        if ( it->address == 0 )
                                fZeroPageSize = 0;
                }
        }

        if ( fZeroPageSize == ULLONG_MAX ) {
                // zero page size not specified on command line, set default
                switch (fArchitecture) {
                        case CPU_TYPE_I386:
                        case CPU_TYPE_ARM:
                                // first 4KB for 32-bit architectures
                                fZeroPageSize = 0x1000;
                                break;
                        case CPU_TYPE_ARM64:
                        case CPU_TYPE_X86_64:
                                // first 4GB for x86_64 on all OS's
                                fZeroPageSize = 0x100000000ULL;
                                break;
                        default:
                                // if -arch not used, default to 4K zero-page
                                fZeroPageSize = 0x1000;
                }
        }
        else {
                switch ( fOutputKind ) {
                        case Options::kDynamicExecutable:
                        case Options::kStaticExecutable:
                                // -pagezero_size size only legal when building main executable
                                break;
                        case Options::kDynamicLibrary:
                        case Options::kDynamicBundle:
                        case Options::kObjectFile:
                        case Options::kDyld:
                        case Options::kPreload:
                        case Options::kKextBundle:
                                if ( fZeroPageSize != 0 )
                                        throw "-pagezero_size option can only be used when linking a main executable";
                }
        }

        // if main executable with custom base address, model zero page as custom segment
        if ( (fOutputKind == Options::kDynamicExecutable) && (fBaseAddress != 0) && (fZeroPageSize != 0) ) {
                SegmentStart seg;
                seg.name = "__PAGEZERO";
                seg.address = 0;;
                fCustomSegmentAddresses.push_back(seg);
        }

        // -dead_strip and -r are incompatible
        if ( fDeadStrip && (fOutputKind == Options::kObjectFile) )
                throw "-r and -dead_strip cannot be used together";

        // can't use -rpath unless targeting 10.5 or later
        if ( fRPaths.size() > 0 ) {
                if ( !minOS(ld::mac10_5, ld::iOS_2_0) )
                        throw "-rpath can only be used when targeting Mac OS X 10.5 or later";
                switch ( fOutputKind ) {
                        case Options::kDynamicExecutable:
                        case Options::kDynamicLibrary:
                        case Options::kDynamicBundle:
                                break;
                        case Options::kStaticExecutable:
                        case Options::kObjectFile:
                        case Options::kDyld:
                        case Options::kPreload:
                        case Options::kKextBundle:
                                throw "-rpath can only be used when creating a dynamic final linked image";
                }
        }
        
        if ( fPositionIndependentExecutable ) {
                switch ( fOutputKind ) {
                        case Options::kDynamicExecutable:
                                // check -pie is only used when building a dynamic main executable for 10.5
                                if ( !minOS(ld::mac10_5, ld::iOS_4_2) ) {
                                        if ( fIOSVersionMin == ld::iOSVersionUnset )
                                                throw "-pie can only be used when targeting Mac OS X 10.5 or later";
                                        else
                                                throw "-pie can only be used when targeting iOS 4.2 or later";
                                }
                                break;
                        case Options::kStaticExecutable:
                        case Options::kPreload:
                                // -pie is ok with -static or -preload
                                break;
                        case Options::kDynamicLibrary:
                        case Options::kDynamicBundle:
                                warning("-pie being ignored. It is only used when linking a main executable");
                                fPositionIndependentExecutable = false;
                                break;
                        case Options::kObjectFile:
                        case Options::kDyld:
                        case Options::kKextBundle:
                                throw "-pie can only be used when linking a main executable";
                }
        }
        
        // check -read_only_relocs is not used with x86_64
        if ( fAllowTextRelocs ) {
                if ( (fArchitecture == CPU_TYPE_X86_64) && (fOutputKind != kKextBundle) ) {
                        warning("-read_only_relocs cannot be used with x86_64");
                        fAllowTextRelocs = false;
                }
        }
        
        // check -mark_auto_dead_strip is only used with dylibs
        if ( fMarkDeadStrippableDylib ) {
                if ( fOutputKind != Options::kDynamicLibrary ) {
                        warning("-mark_auto_dead_strip can only be used when creating a dylib");
                        fMarkDeadStrippableDylib = false;
                }
        }
        
        // -force_cpusubtype_ALL is not supported for ARM
        if ( fForceSubtypeAll ) {
                if ( fArchitecture == CPU_TYPE_ARM ) {
                        warning("-force_cpusubtype_ALL will become unsupported for ARM architectures");
                }
        }
        
        // -reexported_symbols_list can only be used with -dynamiclib
        if ( !fReExportSymbols.empty() ) {
                if ( fOutputKind != Options::kDynamicLibrary )
                        throw "-reexported_symbols_list can only used used when created dynamic libraries";
                if ( !minOS(ld::mac10_7, ld::iOS_4_2) )
                        throw "targeted OS version does not support -reexported_symbols_list";
        }
        
        // -dyld_env can only be used with main executables
        if ( (fOutputKind != Options::kDynamicExecutable) && (fDyldEnvironExtras.size() != 0) )
                throw "-dyld_env can only used used when created main executables";

        // -segment_order can only be used with -preload or -static
        if ( !fSegmentOrder.empty() && ((fOutputKind != Options::kPreload) && (fOutputKind != kStaticExecutable)) )
                throw "-segment_order can only used used with -preload output";

        // warn about bitcode option combinations
        if ( !fBundleBitcode ) {
                if ( fVerifyBitcode )
                        warning("-bitcode_verify is ignored without -bitcode_bundle");
                else if ( fHideSymbols )
                        warning("-bitcode_hide_symbols is ignored without -bitcode_bundle");
        }
        if ( fReverseMapPath != NULL && !fHideSymbols ) {
                throw "-bitcode_symbol_map can only be used with -bitcode_hide_symbols";
        }
        // auto fix up the process type for strip -S.
        // when there is only one input and output type is object file, downgrade kBitcodeProcess to kBitcodeAsData.
        if ( fOutputKind == Options::kObjectFile && fInputFiles.size() == 1 && fBitcodeKind == Options::kBitcodeProcess )
                fBitcodeKind = Options::kBitcodeAsData;

        // <rdar://problem/17598404> warn if building an embedded iOS dylib for pre-iOS 8
        // <rdar://problem/18935714> How can we suppress "ld: warning: embedded dylibs/frameworks only run on iOS 8 or later" when building XCTest?
        if ( (fOutputKind == Options::kDynamicLibrary) && (fIOSVersionMin != ld::iOSVersionUnset) && (fDylibInstallName != NULL) ) {
                if ( !min_iOS(ld::iOS_8_0) && (fDylibInstallName[0] == '@') && !fEncryptableForceOff )
                        warning("embedded dylibs/frameworks only run on iOS 8 or later");
        }

        // bridgeOS always generates new load command
        if ( fVersionLoadCommand && (fPlatform == kPlatform_bridgeOS) ) {
                fBuildVersionLoadCommand = true;
        }

        // produce nicer error when no input
        if ( fInputFiles.empty() ) {
                throw "no object files specified";
        }
}       


void Options::checkForClassic(int argc, const char* argv[])
{
        // scan options
        bool archFound = false;
        bool staticFound = false;
        bool dtraceFound = false;
        bool kextFound = false;
        bool rFound = false;
        bool creatingMachKernel = false;
        bool newLinker = false;
        
        // build command line buffer in case ld crashes
#if __MAC_OS_X_VERSION_MIN_REQUIRED >= 1070
        CRSetCrashLogMessage(crashreporterBuffer);
#endif
        const char* srcRoot = getenv("SRCROOT");
        if ( srcRoot != NULL ) {
                strlcpy(crashreporterBuffer, "SRCROOT=", crashreporterBufferSize);
                strlcat(crashreporterBuffer, srcRoot, crashreporterBufferSize);
                strlcat(crashreporterBuffer, "\n", crashreporterBufferSize);
        }
#ifdef LD_VERS
        strlcat(crashreporterBuffer, LD_VERS, crashreporterBufferSize);
        strlcat(crashreporterBuffer, "\n", crashreporterBufferSize);
#endif
        strlcat(crashreporterBuffer, "ld ", crashreporterBufferSize);
        for(int i=1; i < argc; ++i) {
                strlcat(crashreporterBuffer, argv[i], crashreporterBufferSize);
                strlcat(crashreporterBuffer, " ", crashreporterBufferSize);
        }

        for(int i=0; i < argc; ++i) {
                const char* arg = argv[i];
                if ( arg[0] == '-' ) {
                        if ( strcmp(arg, "-arch") == 0 ) {
                                parseArch(argv[++i]);
                                archFound = true;
                        }
                        else if ( strcmp(arg, "-static") == 0 ) {
                                staticFound = true;
                        }
                        else if ( strcmp(arg, "-kext") == 0 ) {
                                kextFound = true;
                        }
                        else if ( strcmp(arg, "-dtrace") == 0 ) {
                                dtraceFound = true;
                        }
                        else if ( strcmp(arg, "-r") == 0 ) {
                                rFound = true;
                        }
                        else if ( strcmp(arg, "-new_linker") == 0 ) {
                                newLinker = true;
                        }
                        else if ( strcmp(arg, "-classic_linker") == 0 ) {
                                // ld_classic does not understand this option, so remove it
                                for(int j=i; j < argc; ++j)
                                        argv[j] = argv[j+1];
                                warning("using ld_classic");
                                this->gotoClassicLinker(argc-1, argv);
                        }
                        else if ( strcmp(arg, "-o") == 0 ) {
                                const char* outfile = argv[++i];
                                if ( (outfile != NULL) && (strstr(outfile, "/mach_kernel") != NULL) )
                                        creatingMachKernel = true;
                        }
                }
        }
}

void Options::gotoClassicLinker(int argc, const char* argv[])
{
        argv[0] = "ld_classic";
        // ld_classic does not support -iphoneos_version_min, so change
        for(int j=0; j < argc; ++j) {
                if ( (strcmp(argv[j], "-iphoneos_version_min") == 0) || (strcmp(argv[j], "-ios_version_min") == 0) ) {
                        argv[j] = "-macosx_version_min";
                        if ( j < argc-1 )
                                argv[j+1] = "10.5";
                        break;
                }
        }
        // ld classic does not understand -kext (change to -static -r)
        for(int j=0; j < argc; ++j) {
                if ( strcmp(argv[j], "-kext") == 0) 
                        argv[j] = "-r";
                else if ( strcmp(argv[j], "-dynamic") == 0) 
                        argv[j] = "-static";
        }
        // ld classic does not understand -demangle 
        for(int j=0; j < argc; ++j) {
                if ( strcmp(argv[j], "-demangle") == 0) 
                        argv[j] = "-noprebind";
        }
        // in -v mode, print command line passed to ld_classic
        for(int i=0; i < argc; ++i) {
                if ( strcmp(argv[i], "-v") == 0 ) {
                        for(int j=0; j < argc; ++j)
                                printf("%s ", argv[j]);
                        printf("\n");
                        break;
                }
        }
        char rawPath[PATH_MAX];
        char path[PATH_MAX];
        uint32_t bufSize = PATH_MAX;
        if ( _NSGetExecutablePath(rawPath, &bufSize) != -1 ) {
                if ( realpath(rawPath, path) != NULL ) {
                        char* lastSlash = strrchr(path, '/');
                        if ( lastSlash != NULL ) {
                                strcpy(lastSlash+1, "ld_classic");
                                argv[0] = path;
                                execvp(path, (char**)argv);
                        }
                }
        }
        // in case of error in above, try searching for ld_classic via PATH
        execvp(argv[0], (char**)argv);
        fprintf(stderr, "can't exec ld_classic\n");
        exit(1);
}


// Note, returned string buffer is own by this function.
// It should not be freed
// It will be reused, so clients need to strdup() if they want
// to use it long term.
const char* Options::demangleSymbol(const char* sym) const
{
        // only try to demangle symbols if -demangle on command line
        if ( !fDemangle )
                return sym;

        static size_t size = 1024;
        static char* buff = (char*)malloc(size);
        
#if DEMANGLE_SWIFT
        // only try to demangle symbols that look like Swift symbols
        if ( strncmp(sym, "__T", 3) == 0 ) {
                size_t demangledSize = fnd_get_demangled_name(&sym[1], buff, size);
                if ( demangledSize > size ) {
                        size = demangledSize+2;
                        buff = (char*)realloc(buff, size);
                        demangledSize = fnd_get_demangled_name(&sym[1], buff, size);
                }
                if ( demangledSize != 0 )
                        return buff;
        }
#endif

        // only try to demangle symbols that look like C++ symbols
        if ( strncmp(sym, "__Z", 3) != 0 )
                return sym;

        int status;
        char* result = abi::__cxa_demangle(&sym[1], buff, &size, &status); 
        if ( result != NULL ) {
                // if demangling successful, keep buffer for next demangle
                buff = result;
                return buff;
        }
        return sym;
}


void Options::dumpDependency(uint8_t opcode, const char* path) const
{
        if ( !this->dumpDependencyInfo() ) 
                return;

        // one time open() of -dependency_info file
        if ( fDependencyFileDescriptor == -1 ) {
                fDependencyFileDescriptor = open(this->dependencyInfoPath(), O_WRONLY | O_TRUNC | O_CREAT, 0666);
                if ( fDependencyFileDescriptor == -1 )
                        throwf("Could not open or create -dependency_info file: %s", this->dependencyInfoPath());

                // write header
                uint8_t version = depLinkerVersion;
                if ( write(fDependencyFileDescriptor, &version, 1) == -1 )
                        throwf("write() to -dependency_info failed, errno=%d", errno);
                extern const char ldVersionString[];
                if ( write(fDependencyFileDescriptor, ldVersionString, strlen(ldVersionString)+1) == -1 )
                        throwf("write() to -dependency_info failed, errno=%d", errno);
        }

        char realPath[PATH_MAX];
        if ( path[0] != '/' ) {
                if ( realpath(path, realPath) != NULL ) {
                        path = realPath;
                }
        }

        if ( write(fDependencyFileDescriptor, &opcode, 1) == -1 )
                throwf("write() to -dependency_info failed, errno=%d", errno);
        if ( write(fDependencyFileDescriptor, path, strlen(path)+1) == -1 )
                throwf("write() to -dependency_info failed, errno=%d", errno);

        //fprintf(stderr, "0x%02X %s\n", opcode, path);
}


void Options::writeToTraceFile(const char* buffer, size_t len) const
{
        // one time open() of custom LD_TRACE_FILE
        if ( fTraceFileDescriptor == -1 ) {
                if ( fTraceOutputFile != NULL ) {
                        fTraceFileDescriptor = open(fTraceOutputFile, O_WRONLY | O_APPEND | O_CREAT, 0666);
                        if ( fTraceFileDescriptor == -1 )
                                throwf("Could not open or create trace file (errno=%d): %s", errno, fTraceOutputFile);
                }
                else {
                        fTraceFileDescriptor = fileno(stderr);
                }
        }

        while (len > 0) {
                ssize_t amountWritten = write(fTraceFileDescriptor, buffer, len);
                if ( amountWritten == -1 )
                        /* Failure to write shouldn't fail the build. */
                        return;
                buffer += amountWritten;
                len -= amountWritten;
        }
}