]> git.saurik.com Git - apple/ld64.git/blobdiff - src/ld.cpp
ld64-77.1.tar.gz
[apple/ld64.git] / src / ld.cpp
index e98df10b0c335dd3f1cad8fcbafbb85d8bb543be..a2a56b9d538548cfd2cd6d8c0d90aca11d4e678d 100644 (file)
@@ -1,6 +1,5 @@
-/* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
- *
- * Copyright (c) 2005-2006 Apple Computer, Inc. All rights reserved.
+/* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-*
+ * Copyright (c) 2005-2007 Apple Inc. All rights reserved.
  *
  * @APPLE_LICENSE_HEADER_START@
  *
 #include <sys/sysctl.h>
 #include <fcntl.h>
 #include <errno.h>
+#include <limits.h>
 #include <unistd.h>
 #include <mach/mach_time.h>
 #include <mach/vm_statistics.h>
 #include <mach/mach_init.h>
 #include <mach/mach_host.h>
 #include <mach-o/fat.h>
-
+#include <dlfcn.h>
 
 #include <string>
+#include <map>
 #include <set>
 #include <string>
 #include <vector>
 #include <list>
 #include <algorithm>
 #include <ext/hash_map>
+#include <dlfcn.h>
+#include <AvailabilityMacros.h>
 
 #include "Options.h"
 
 #include "MachOReaderDylib.hpp"
 #include "MachOWriterExecutable.hpp"
 
-#include "SectCreate.h"
-
-#if 0
-static void dumpAtom(ObjectFile::Atom* atom)
-{
-       //printf("atom:    %p\n", atom);
-
-       // name
-       printf("name:    %s\n",  atom->getDisplayName());
-
-       // scope
-       switch ( atom->getScope() ) {
-               case ObjectFile::Atom::scopeTranslationUnit:
-                       printf("scope:   translation unit\n");
-                       break;
-               case ObjectFile::Atom::scopeLinkageUnit:
-                       printf("scope:   linkage unit\n");
-                       break;
-               case ObjectFile::Atom::scopeGlobal:
-                       printf("scope:   global\n");
-                       break;
-               default:
-                       printf("scope:   unknown\n");
-       }
-
-       // kind
-       switch ( atom->getDefinitinonKind() ) {
-               case ObjectFile::Atom::kRegularDefinition:
-                       printf("kind:     regular\n");
-                       break;
-               case ObjectFile::Atom::kWeakDefinition:
-                       printf("kind:     weak\n");
-                       break;
-               case ObjectFile::Atom::kTentativeDefinition:
-                       printf("kind:     tentative\n");
-                       break;
-               case ObjectFile::Atom::kExternalDefinition:
-                       printf("kind:     import\n");
-                       break;
-               case ObjectFile::Atom::kExternalWeakDefinition:
-                       printf("kind:     weak import\n");
-                       break;
-               default:
-                       printf("scope:   unknown\n");
-       }
-
-       // segment and section
-       printf("section: %s,%s\n", atom->getSegment().getName(), atom->getSectionName());
-
-       // attributes
-       printf("attrs:   ");
-       if ( atom->dontDeadStrip() )
-               printf("dont-dead-strip ");
-       if ( atom->isZeroFill() )
-               printf("zero-fill ");
-       printf("\n");
-
-       // size
-       printf("size:    0x%012llX\n", atom->getSize());
-
-       // content
-       uint8_t content[atom->getSize()];
-       atom->copyRawContent(content);
-       printf("content: ");
-       if ( strcmp(atom->getSectionName(), "__cstring") == 0 ) {
-               printf("\"%s\"", content);
-       }
-       else {
-               for (unsigned int i=0; i < sizeof(content); ++i)
-                       printf("%02X ", content[i]);
-       }
-       printf("\n");
-
-       // references
-       std::vector<ObjectFile::Reference*>&  references = atom->getReferences();
-       const int refCount = references.size();
-       printf("references: (%u)\n", refCount);
-       for (int i=0; i < refCount; ++i) {
-               ObjectFile::Reference* ref = references[i];
-               printf("   %s\n", ref->getDescription());
-       }
-
-       // attributes
+#define LLVM_SUPPORT 0
+#if LLVM_SUPPORT
+#include "LLVMReader.hpp"
+#endif
 
-}
+#include "OpaqueSection.hpp"
 
-#endif
 
 class CStringComparor
 {
@@ -158,7 +82,7 @@ class Section : public ObjectFile::Section
 public:
        static Section* find(const char* sectionName, const char* segmentName, bool zeroFill);
        static void             assignIndexes();
-
+       const char*             getName() { return fSectionName; }
 private:
                                        Section(const char* sectionName, const char* segmentName, bool zeroFill);
 
@@ -167,6 +91,7 @@ private:
                bool operator()(Section* left, Section* right);
        };
 
+       typedef __gnu_cxx::hash_map<const char*, uint32_t, __gnu_cxx::hash<const char*>, CStringEquals> NameToOrdinal;
        typedef __gnu_cxx::hash_map<const char*, class Section*, __gnu_cxx::hash<const char*>, CStringEquals> NameToSection;
        //typedef std::map<const char*, class Section*, CStringComparor> NameToSection;
 
@@ -176,15 +101,18 @@ private:
 
        static NameToSection                    fgMapping;
        static std::vector<Section*>    fgSections;
+       static NameToOrdinal                    fgSegmentDiscoverOrder;
 };
 
 Section::NameToSection Section::fgMapping;
 std::vector<Section*>  Section::fgSections;
+Section::NameToOrdinal Section::fgSegmentDiscoverOrder;
 
 Section::Section(const char* sectionName, const char* segmentName, bool zeroFill)
  : fSectionName(sectionName), fSegmentName(segmentName), fZeroFill(zeroFill)
 {
-       //fprintf(stderr, "new Section(%s, %s)\n", sectionName, segmentName);
+       this->fIndex = fgSections.size();
+       //fprintf(stderr, "new Section(%s, %s) => %p, %u\n", sectionName, segmentName, this, this->getIndex());
 }
 
 Section* Section::find(const char* sectionName, const char* segmentName, bool zeroFill)
@@ -202,7 +130,6 @@ Section* Section::find(const char* sectionName, const char* segmentName, bool ze
 
        // does not exist, so make a new one
        Section* sect = new Section(sectionName, segmentName, zeroFill);
-       sect->fIndex = fgMapping.size();
        fgMapping[sectionName] = sect;
        fgSections.push_back(sect);
 
@@ -211,6 +138,10 @@ Section* Section::find(const char* sectionName, const char* segmentName, bool ze
                find("__textcoal_nt", "__TEXT", false);
        }
 
+       // remember segment discovery order
+       if ( fgSegmentDiscoverOrder.find(segmentName) == fgSegmentDiscoverOrder.end() ) 
+               fgSegmentDiscoverOrder[segmentName] = fgSegmentDiscoverOrder.size();
+
        return sect;
 }
 
@@ -224,29 +155,24 @@ int Section::Sorter::segmentOrdinal(const char* segName)
                return 3;
        if ( strcmp(segName, "__OBJC") == 0 )
                return 4;
+       if ( strcmp(segName, "__OBJC2") == 0 )
+               return 5;
        if ( strcmp(segName, "__LINKEDIT") == 0 )
                return INT_MAX; // linkedit segment should always sort last
        else
-               return 5;
+               return fgSegmentDiscoverOrder[segName]+6;
 }
 
 
 bool Section::Sorter::operator()(Section* left, Section* right)
 {
        // Segment is primary sort key
-       const char* leftSegName = left->fSegmentName;
-       const char* rightSegName = right->fSegmentName;
-       int segNameCmp = strcmp(leftSegName, rightSegName);
-       if ( segNameCmp != 0 )
-       {
-               int leftSegOrdinal = segmentOrdinal(leftSegName);
-               int rightSegOrdinal = segmentOrdinal(rightSegName);
-               if ( leftSegOrdinal < rightSegOrdinal )
-                       return true;
-               if ( leftSegOrdinal == rightSegOrdinal )
-                       return segNameCmp < 0;
+       int leftSegOrdinal = segmentOrdinal(left->fSegmentName);
+       int rightSegOrdinal = segmentOrdinal(right->fSegmentName);
+       if ( leftSegOrdinal < rightSegOrdinal )
+               return true;
+       if ( leftSegOrdinal > rightSegOrdinal )
                return false;
-       }
 
        // zerofill section sort to the end
        if ( !left->fZeroFill && right->fZeroFill )
@@ -259,8 +185,8 @@ bool Section::Sorter::operator()(Section* left, Section* right)
 }
 
 void Section::assignIndexes()
-{
-       //printf("unsorted:\n");
+{      
+       //printf("unsorted sections:\n");
        //for (std::vector<Section*>::iterator it=fgSections.begin(); it != fgSections.end(); it++) {
        //      printf("section: name=%s, segment: name=%s, discovery order=%d\n", (*it)->fSectionName, (*it)->fSegmentName, (*it)->fIndex);
        //}
@@ -273,63 +199,89 @@ void Section::assignIndexes()
        for (std::vector<Section*>::iterator it=fgSections.begin(); it != fgSections.end(); it++)
                (*it)->fIndex = newOrder++;
 
-       //printf("sorted:\n");
+       //printf("sorted sections:\n");
        //for (std::vector<Section*>::iterator it=fgSections.begin(); it != fgSections.end(); it++) {
-       //      printf("section: name=%s\n", (*it)->fSectionName);
+       //      printf("section: index=%d, obj=%p, name=%s\n", (*it)->fIndex, (*it), (*it)->fSectionName);
        //}
 }
 
-class Linker {
+class Linker : public ObjectFile::Reader::DylibHander {
 public:
                                                Linker(int argc, const char* argv[]);
 
+       const char*                     getArchPrefix();
+       const char*                     architectureName();
+       bool                            showArchitectureInErrors();
+       bool                            isInferredArchitecture();
        void                            createReaders();
        void                            createWriter();
-       void                            addInputFile(ObjectFile::Reader* reader);
+       void                            addInputFile(ObjectFile::Reader* reader, const Options::FileInfo& );
        void                            setOutputFile(ExecutableFile::Writer* writer);
        void                            link();
-
+       void                            optimize();
+       
+       // implemenation from ObjectFile::Reader::DylibHander
+       virtual ObjectFile::Reader* findDylib(const char* installPath, const char* fromPath);
 
 private:
+       struct WhyLiveBackChain
+       {
+               WhyLiveBackChain*       previous;
+               const char*                     name;
+       };
+
        ObjectFile::Reader*     createReader(const Options::FileInfo&);
        void                            addAtom(ObjectFile::Atom& atom);
        void                            addAtoms(std::vector<class ObjectFile::Atom*>& atoms);
        void                            buildAtomList();
+       void                            processDylibs();
+       void                            updateContraints(ObjectFile::Reader* reader);
+       void                            loadAndResolve();
+       void                            processDTrace();
+       void                            checkObjC();
        void                            loadUndefines();
+       void                            checkUndefines();
        void                            addWeakAtomOverrides();
        void                            resolveReferences();
-       void                            deadStrip();
+       void                            deadStripResolve();
+       void                            addLiveRoot(const char* name);
+       ObjectFile::Atom*       findAtom(const Options::OrderedSymbol& pair);
+       void                            logArchive(ObjectFile::Reader* reader);
+       void                            sortSections();
        void                            sortAtoms();
        void                            tweakLayout();
        void                            writeDotOutput();
        static bool                     minimizeStab(ObjectFile::Reader::Stab& stab);
        static const char*      truncateStabString(const char* str);
-       void                            collectStabs();
+       void                            collectDebugInfo();
        void                            writeOutput();
        ObjectFile::Atom*       entryPoint();
        ObjectFile::Atom*       dyldHelper();
        const char*                     assureFullPath(const char* path);
-       void                            markLive(ObjectFile::Atom* atom, std::set<ObjectFile::Atom*>& liveAtoms);
-       void                            collectStabs(ObjectFile::Reader* reader);
-       void                            synthesizeStabs(ObjectFile::Reader* reader);
+       void                            markLive(ObjectFile::Atom& atom, Linker::WhyLiveBackChain* previous);
+       void                            collectStabs(ObjectFile::Reader* reader, std::map<const class ObjectFile::Atom*, uint32_t>& atomOrdinals);
+       void                            synthesizeDebugNotes(std::vector<class ObjectFile::Atom*>& allAtomsByReader);
        void                            printStatistics();
        void                            printTime(const char* msg, uint64_t partTime, uint64_t totalTime);
        char*                           commatize(uint64_t in, char* out);
        void                            getVMInfo(vm_statistics_data_t& info);
        cpu_type_t                      inferArchitecture();
-
-       void                            resolve(ObjectFile::Reference* reference);
-       void                            resolveFrom(ObjectFile::Reference* reference);
-       void                            addJustInTimeAtoms(const char* name);
+       void                            addDtraceProbe(ObjectFile::Atom& atom, uint32_t offsetInAtom, const char* probeName);
+       void                            checkDylibClientRestrictions(ObjectFile::Reader* reader);
+       void                            logDylib(ObjectFile::Reader* reader, bool indirect);
+       
+       void                                                                    resolve(ObjectFile::Reference* reference);
+       void                                                                    resolveFrom(ObjectFile::Reference* reference);
+       std::vector<class ObjectFile::Atom*>*   addJustInTimeAtoms(const char* name);
+       void                                                                    addJustInTimeAtomsAndMarkLive(const char* name);
 
        ObjectFile::Reader*     addDylib(ObjectFile::Reader* reader, const Options::FileInfo& info, uint64_t mappedLen);
        ObjectFile::Reader*     addObject(ObjectFile::Reader* reader, const Options::FileInfo& info, uint64_t mappedLen);
        ObjectFile::Reader*     addArchive(ObjectFile::Reader* reader, const Options::FileInfo& info, uint64_t mappedLen);
-       void                            addIndirectLibraries(ObjectFile::Reader* reader);
-       bool                            haveIndirectLibrary(const char* path, ObjectFile::Reader* reader);
-       bool                            haveDirectLibrary(const char* path);
 
        void                            logTraceInfo(const char* format, ...);
+
+
        class SymbolTable
        {
        public:
@@ -339,20 +291,34 @@ private:
                ObjectFile::Atom*       find(const char* name);
                unsigned int            getRequireCount() { return fRequireCount; }
                void                            getNeededNames(bool andWeakDefintions, std::vector<const char*>& undefines);
-       private:
                typedef __gnu_cxx::hash_map<const char*, ObjectFile::Atom*, __gnu_cxx::hash<const char*>, CStringEquals> Mapper;
+       private:
                Linker&                         fOwner;
                Mapper                          fTable;
                unsigned int            fRequireCount;
        };
 
-       struct AtomSorter
+       class AtomSorter
        {
-               bool operator()(ObjectFile::Atom* left, ObjectFile::Atom* right);
+       public:
+               AtomSorter(std::map<const ObjectFile::Atom*, uint32_t>* map) : fOverriddenOrdinalMap(map) {}
+               bool operator()(const ObjectFile::Atom* left, const ObjectFile::Atom* right);
+       private:
+               std::map<const ObjectFile::Atom*, uint32_t>*    fOverriddenOrdinalMap;
        };
 
        typedef std::map<const char*, uint32_t, CStringComparor> SectionOrder;
 
+       struct DTraceProbeInfo {
+               DTraceProbeInfo(const ObjectFile::Atom* a, uint32_t o, const char* n) : atom(a), offset(o), probeName(n) {}
+               const ObjectFile::Atom*                 atom;
+               uint32_t                                                offset;
+               const char*                                             probeName;
+       };
+       typedef __gnu_cxx::hash_map<const char*, std::vector<DTraceProbeInfo>, __gnu_cxx::hash<const char*>, CStringEquals>     ProviderToProbes;
+       typedef __gnu_cxx::hash_set<const char*, __gnu_cxx::hash<const char*>, CStringEquals>  CStringSet;
+       typedef __gnu_cxx::hash_map<const char*, ObjectFile::Reader*, __gnu_cxx::hash<const char*>, CStringEquals>      InstallNameToReader;
+
        struct IndirectLibrary {
                const char*                                                     path;
                uint64_t                                                        fileLen;
@@ -365,29 +331,44 @@ private:
 
        Options                                                                                         fOptions;
        SymbolTable                                                                                     fGlobalSymbolTable;
-       unsigned int                                                                            fWeakSymbolsAddedCount;
+       uint32_t                                                                                        fNextInputOrdinal;
        std::vector<class ObjectFile::Reader*>                          fInputFiles;
        ExecutableFile::Writer*                                                         fOutputFile;
-       std::vector<ExecutableFile::DyLibUsed>                          fDynamicLibraries;
-       std::list<IndirectLibrary>                                                      fIndirectDynamicLibraries;
+       InstallNameToReader                                                                     fDylibMap;
+       std::map<ObjectFile::Reader*,DynamicLibraryOptions> fDylibOptionsMap;
+       std::set<ObjectFile::Reader*>                                           fDylibsProcessed;
+       ObjectFile::Reader*                                                                     fBundleLoaderReader;
        std::vector<class ObjectFile::Reader*>                          fReadersThatHaveSuppliedAtoms;
        std::vector<class ObjectFile::Atom*>                            fAllAtoms;
+       std::set<class ObjectFile::Reader*>                                     fArchiveReaders;
+       std::set<class ObjectFile::Reader*>                                     fArchiveReadersLogged;
        std::set<class ObjectFile::Atom*>                                       fDeadAtoms;
+       std::set<ObjectFile::Atom*>                                                     fLiveAtoms;
+       std::set<ObjectFile::Atom*>                                                     fLiveRootAtoms;
        std::vector<class ObjectFile::Reader::Stab>                     fStabs;
+       std::vector<class ObjectFile::Atom*>                            fAtomsWithUnresolvedReferences;
+       std::vector<DTraceProbeInfo>                                            fDtraceProbes;
+       std::vector<DTraceProbeInfo>                                            fDtraceProbeSites;
+       std::vector<DTraceProbeInfo>                                            fDtraceIsEnabledSites;
+       std::map<const ObjectFile::Atom*,CStringSet>            fDtraceAtomToTypes;
        bool                                                                                            fCreateUUID;
+       bool                                                                                            fCanScatter;
        SectionOrder                                                                            fSectionOrder;
-       unsigned int                                                                            fNextSortOrder;
-       unsigned int                                                                            fNextObjectFileOrder;
        cpu_type_t                                                                                      fArchitecture;
+       const char*                                                                                     fArchitectureName;
+       bool                                                                                            fArchitectureInferred;
        bool                                                                                            fDirectLibrariesComplete;
+       bool                                                                                            fBiggerThanTwoGigOutput;
        uint64_t                                                                                        fOutputFileSize;
+       uint64_t                                                                                        fTotalZeroFillSize;
+       uint64_t                                                                                        fTotalSize;
        uint64_t                                                                                        fStartTime;
        uint64_t                                                                                        fStartCreateReadersTime;
        uint64_t                                                                                        fStartCreateWriterTime;
        uint64_t                                                                                        fStartBuildAtomsTime;
-       uint64_t                                                                                        fStartLoadUndefinesTime;
-       uint64_t                                                                                        fStartResolveTime;
+       uint64_t                                                                                        fStartLoadAndResolveTime;
        uint64_t                                                                                        fStartSortTime;
+       uint64_t                                                                                        fStartDebugTime;
        uint64_t                                                                                        fStartWriteTime;
        uint64_t                                                                                        fEndTime;
        uint64_t                                                                                        fTotalObjectSize;
@@ -396,28 +377,69 @@ private:
        uint32_t                                                                                        fTotalArchivesLoaded;
        uint32_t                                                                                        fTotalDylibsLoaded;
        vm_statistics_data_t                                                            fStartVMInfo;
+       ObjectFile::Reader::ObjcConstraint                                      fCurrentObjCConstraint;
+       ObjectFile::Reader::CpuConstraint                                       fCurrentCpuConstraint;
+       bool                                                                                            fObjcReplacmentClasses;
+       bool                                                                                            fAllDirectDylibsLoaded;
 };
 
 
 Linker::Linker(int argc, const char* argv[])
-       : fOptions(argc, argv), fGlobalSymbolTable(*this), fOutputFile(NULL), fCreateUUID(false), fNextSortOrder(1),
-         fNextObjectFileOrder(1), fArchitecture(0), fDirectLibrariesComplete(false), fOutputFileSize(0), fTotalObjectSize(0),
-         fTotalArchiveSize(0),  fTotalObjectLoaded(0), fTotalArchivesLoaded(0), fTotalDylibsLoaded(0)
+       : fOptions(argc, argv), fGlobalSymbolTable(*this), fNextInputOrdinal(1), fOutputFile(NULL), fBundleLoaderReader(NULL), 
+         fCreateUUID(false), fCanScatter(true),
+         fArchitecture(0), fArchitectureInferred(false), fDirectLibrariesComplete(false), fBiggerThanTwoGigOutput(false),
+         fOutputFileSize(0), fTotalZeroFillSize(0), fTotalSize(0), fTotalObjectSize(0),
+         fTotalArchiveSize(0),  fTotalObjectLoaded(0), fTotalArchivesLoaded(0), fTotalDylibsLoaded(0),
+         fCurrentObjCConstraint(ObjectFile::Reader::kObjcNone), fCurrentCpuConstraint(ObjectFile::Reader::kCpuAny),
+         fObjcReplacmentClasses(false), fAllDirectDylibsLoaded(false)
 {
        fStartTime = mach_absolute_time();
        if ( fOptions.printStatistics() )
                getVMInfo(fStartVMInfo);
-               
+
        fArchitecture = fOptions.architecture();
        if ( fArchitecture == 0 ) {
                // -arch not specified, scan .o files to figure out what it should be
                fArchitecture = inferArchitecture();
+               fArchitectureInferred = true;
+       }
+       switch (fArchitecture) {
+               case CPU_TYPE_POWERPC:
+                       fArchitectureName = "ppc";
+                       break;
+               case CPU_TYPE_POWERPC64:
+                       fArchitectureName = "ppc64";
+                       break;
+               case CPU_TYPE_I386:
+                       fArchitectureName = "i386";
+                       break;
+               case CPU_TYPE_X86_64:
+                       fArchitectureName = "x86_64";
+                       break;
+               default:
+                       fArchitectureName = "unknown architecture";
+                       break;
        }
 }
 
+const char*    Linker::architectureName()
+{
+       return fArchitectureName;
+}
+
+bool Linker::showArchitectureInErrors()
+{
+       return fOptions.printArchPrefix();
+}
+
+bool Linker::isInferredArchitecture()
+{
+       return fArchitectureInferred;
+}
+
 cpu_type_t Linker::inferArchitecture()
 {
-       // scan all input files, looking for a thin .o file.  
+       // scan all input files, looking for a thin .o file.
        // the first one found is presumably the architecture to link
        uint8_t buffer[sizeof(mach_header_64)];
        std::vector<Options::FileInfo>& files = fOptions.getInputFiles();
@@ -428,39 +450,45 @@ cpu_type_t Linker::inferArchitecture()
                        ::close(fd);
                        if ( amount >= (ssize_t)sizeof(buffer) ) {
                                if ( mach_o::relocatable::Reader<ppc>::validFile(buffer) ) {
-                                       fprintf(stderr, "ld64 warning: -arch not used, infering -arch ppc based on %s\n", it->path);
+                                       //fprintf(stderr, "ld: warning -arch not used, infering -arch ppc based on %s\n", it->path);
                                        return CPU_TYPE_POWERPC;
                                }
                                else if ( mach_o::relocatable::Reader<ppc64>::validFile(buffer) ) {
-                                       fprintf(stderr, "ld64 warning: -arch not used, infering -arch ppc64 based on %s\n", it->path);
+                                       //fprintf(stderr, "ld: warning -arch not used, infering -arch ppc64 based on %s\n", it->path);
                                        return CPU_TYPE_POWERPC64;
                                }
                                else if ( mach_o::relocatable::Reader<x86>::validFile(buffer) ) {
-                                       fprintf(stderr, "ld64 warning: -arch not used, infering -arch i386 based on %s\n", it->path);
+                                       //fprintf(stderr, "ld: warning -arch not used, infering -arch i386 based on %s\n", it->path);
                                        return CPU_TYPE_I386;
                                }
+                               else if ( mach_o::relocatable::Reader<x86_64>::validFile(buffer) ) {
+                                       //fprintf(stderr, "ld: warning -arch not used, infering -arch x86_64 based on %s\n", it->path);
+                                       return CPU_TYPE_X86_64;
+                               }
                        }
                }
        }
-       
+
        // no thin .o files found, so default to same architecture this was built as
-       fprintf(stderr, "ld64 warning: -arch not specified\n");
+       fprintf(stderr, "ld: warning -arch not specified\n");
 #if __ppc__
        return CPU_TYPE_POWERPC;
 #elif __i386__
        return CPU_TYPE_I386;
 #elif __ppc64__
        return CPU_TYPE_POWERPC64;
+#elif __x86_64__
+       return CPU_TYPE_X86_64;
 #else
        #error unknown default architecture
 #endif
 }
 
 
-void Linker::addInputFile(ObjectFile::Reader* reader)
+void Linker::addInputFile(ObjectFile::Reader* reader, const Options::FileInfo& info)
 {
-       reader->setSortOrder(fNextObjectFileOrder++);
        fInputFiles.push_back(reader);
+       fDylibOptionsMap[reader] = info.options;
 }
 
 void Linker::setOutputFile(ExecutableFile::Writer* writer)
@@ -468,16 +496,86 @@ void Linker::setOutputFile(ExecutableFile::Writer* writer)
        fOutputFile = writer;
 }
 
+class InSet
+{
+public:
+       InSet(std::set<ObjectFile::Atom*>& deadAtoms) : fDeadAtoms(deadAtoms) {}
+
+       bool operator()(ObjectFile::Atom*& atom) const {
+               return ( fDeadAtoms.count(atom) != 0 );
+       }
+
+private:
+       std::set<ObjectFile::Atom*>& fDeadAtoms;
+};
+
+void Linker::loadAndResolve()
+{
+       fStartLoadAndResolveTime = mach_absolute_time();
+       if ( fOptions.deadStrip() == Options::kDeadStripOff ) {
+               // without dead-code-stripping:
+               // find atoms to resolve all undefines
+               this->loadUndefines();
+               // verify nothing is missing
+               this->checkUndefines();
+               // once all undefines fulfill, then bind all references
+               this->resolveReferences();
+               // remove atoms weak atoms that have been overridden
+               fAllAtoms.erase(std::remove_if(fAllAtoms.begin(), fAllAtoms.end(), InSet(fDeadAtoms)), fAllAtoms.end());
+       }
+       else {
+               // with dead code stripping:
+               // start binding references from roots,
+               this->deadStripResolve();
+               // verify nothing is missing
+               this->checkUndefines();
+       }
+}
+
+void Linker::optimize()
+{
+       std::vector<class ObjectFile::Atom*> newAtoms;
+
+       const int readerCount = fInputFiles.size();
+       for (int i=0; i < readerCount; ++i) {
+               fInputFiles[i]->optimize(fAllAtoms, newAtoms, fNextInputOrdinal);
+       }
+       // note: When writer start generating stubs and non-lazy-pointers for all architecture, do not insert
+       // newAtoms into fGlobalSymbolTable. Instead directly insert them in fAllAtoms and set their order appropriately.
+       this->addAtoms(newAtoms);
+
+       // Some of the optimized atoms may not have identified section properly, if they
+       // were created before optimizer produces corrosponding real atom. Here, input
+       // file readers are not able to patch it themselves because Section::find() is
+       // linker specific.
+       for(std::vector<class ObjectFile::Atom*>::iterator itr = fAllAtoms.begin();
+               itr != fAllAtoms.end(); ++itr) {
+
+               ObjectFile::Atom *atom = *itr;
+               if (atom->getSectionName() && !atom->getSection())
+                       atom->setSection(Section::find(atom->getSectionName(), atom->getSegment().getName(), atom->isZeroFill()));
+       }
+
+       if ( fOptions.deadStrip() != Options::kDeadStripOff ) {
+               fLiveAtoms.clear();
+        deadStripResolve();
+    }
+    else
+        resolveReferences();
+}
+
 void Linker::link()
 {
        this->buildAtomList();
-       this->loadUndefines();
-       this->resolveReferences();
-       this->deadStrip();
-       this->sortAtoms();
+       this->loadAndResolve();
+       this->optimize();
+       this->checkObjC();
+       this->processDTrace();
        this->tweakLayout();
+       this->sortSections();
+       this->sortAtoms();
        this->writeDotOutput();
-       this->collectStabs();
+       this->collectDebugInfo();
        this->writeOutput();
        this->printStatistics();
 
@@ -491,7 +589,7 @@ void Linker::printTime(const char* msg, uint64_t partTime, uint64_t totalTime)
        if ( sUnitsPerSecond == 0 ) {
                struct mach_timebase_info timeBaseInfo;
                if ( mach_timebase_info(&timeBaseInfo) == KERN_SUCCESS ) {
-                       sUnitsPerSecond = 1000000000LL * timeBaseInfo.denom / timeBaseInfo.numer;
+                       sUnitsPerSecond = 1000000000ULL * timeBaseInfo.denom / timeBaseInfo.numer;
                        //fprintf(stderr, "sUnitsPerSecond=%llu\n", sUnitsPerSecond);
                }
        }
@@ -545,14 +643,14 @@ void Linker::printStatistics()
                getVMInfo(endVMInfo);
 
                uint64_t totalTime = fEndTime - fStartTime;
-               printTime("ld64 total time", totalTime, totalTime);
+               printTime("ld total time", totalTime, totalTime);
                printTime(" option parsing time",       fStartCreateReadersTime -       fStartTime,                                     totalTime);
                printTime(" object file processing",fStartCreateWriterTime -    fStartCreateReadersTime,        totalTime);
                printTime(" output file setup",         fStartBuildAtomsTime -          fStartCreateWriterTime,         totalTime);
-               printTime(" build atom list",           fStartLoadUndefinesTime -       fStartBuildAtomsTime,           totalTime);
-               printTime(" load undefines",            fStartResolveTime -                     fStartLoadUndefinesTime,        totalTime);
-               printTime(" resolve references",        fStartSortTime -                        fStartResolveTime,                      totalTime);
-               printTime(" sort output",                       fStartWriteTime -                       fStartSortTime,                         totalTime);
+               printTime(" build atom list",           fStartLoadAndResolveTime -      fStartBuildAtomsTime,           totalTime);
+               printTime(" resolve references",        fStartSortTime -                        fStartLoadAndResolveTime,       totalTime);
+               printTime(" sort output",                       fStartDebugTime -                       fStartSortTime,                         totalTime);
+               printTime(" process debug info",        fStartWriteTime -                       fStartDebugTime,                        totalTime);
                printTime(" write output",                      fEndTime -                                      fStartWriteTime,                        totalTime);
                fprintf(stderr, "pageins=%u, pageouts=%u, faults=%u\n", endVMInfo.pageins-fStartVMInfo.pageins,
                                                                                endVMInfo.pageouts-fStartVMInfo.pageouts, endVMInfo.faults-fStartVMInfo.faults);
@@ -569,23 +667,34 @@ inline void Linker::addAtom(ObjectFile::Atom& atom)
        // add to list of all atoms
        fAllAtoms.push_back(&atom);
 
-       // add atom's references's names to symbol table as to-be-resolved-later
-       std::vector<class ObjectFile::Reference*>& references = atom.getReferences();
-       for (std::vector<ObjectFile::Reference*>::iterator it=references.begin(); it != references.end(); it++) {
-               ObjectFile::Reference* reference = *it;
-               if ( reference->isTargetUnbound() ) {
-                       fGlobalSymbolTable.require(reference->getTargetName());
+       if ( fOptions.deadStrip() == Options::kDeadStripOff ) {
+               // not dead-stripping code, so add atom's references's names to symbol table as to-be-resolved-later
+               std::vector<class ObjectFile::Reference*>& references = atom.getReferences();
+               for (std::vector<ObjectFile::Reference*>::iterator it=references.begin(); it != references.end(); it++) {
+                       ObjectFile::Reference* reference = *it;
+                       if ( reference->getTargetBinding() == ObjectFile::Reference::kUnboundByName )
+                               fGlobalSymbolTable.require(reference->getTargetName());
+                       if ( reference->getFromTargetBinding() == ObjectFile::Reference::kUnboundByName )
+                               fGlobalSymbolTable.require(reference->getFromTargetName());
+                       if ( reference->getTargetBinding() == ObjectFile::Reference::kDontBind )
+                               addDtraceProbe(atom, reference->getFixUpOffset(), reference->getTargetName());
+               }
+               // update total size info (except for __ZEROPAGE atom)
+               if ( atom.getSegment().isContentReadable() ) {
+                       fTotalSize += atom.getSize();
+                       if ( atom.isZeroFill() )
+                               fTotalZeroFillSize += atom.getSize();
                }
-               if ( reference->hasFromTarget() && reference->isFromTargetUnbound() )
-                       fGlobalSymbolTable.require(reference->getFromTargetName());
+       }
+       else {
+               if ( atom.dontDeadStrip() )
+                       fLiveRootAtoms.insert(&atom);
        }
 
        // if in global namespace, add atom itself to symbol table
        ObjectFile::Atom::Scope scope = atom.getScope();
        const char* name = atom.getName();
        if ( (scope != ObjectFile::Atom::scopeTranslationUnit) && (name != NULL) ) {
-               fGlobalSymbolTable.add(atom);
-
                // update scope based on export list (possible that globals are downgraded to private_extern)
                if ( (scope == ObjectFile::Atom::scopeGlobal) && fOptions.hasExportRestrictList() ) {
                        bool doExport = fOptions.shouldExport(name);
@@ -593,33 +702,107 @@ inline void Linker::addAtom(ObjectFile::Atom& atom)
                                atom.setScope(ObjectFile::Atom::scopeLinkageUnit);
                        }
                }
+               // add to symbol table
+               fGlobalSymbolTable.add(atom);
        }
 
        // record section orders so output file can have same order
-       atom.setSection(Section::find(atom.getSectionName(), atom.getSegment().getName(), atom.isZeroFill()));
+       if (atom.getSectionName())
+               atom.setSection(Section::find(atom.getSectionName(), atom.getSegment().getName(), atom.isZeroFill()));
+}
+
+void Linker::updateContraints(ObjectFile::Reader* reader)
+{
+       // check objc objects were compiled compatibly
+       ObjectFile::Reader::ObjcConstraint objcAddition = reader->getObjCConstraint();
+       if ( reader->getInstallPath() == NULL ) {
+               // adding a .o file
+               switch ( fCurrentObjCConstraint ) {
+                       case ObjectFile::Reader::kObjcNone:
+                               fCurrentObjCConstraint = objcAddition;
+                               break;
+                       case ObjectFile::Reader::kObjcRetainRelease:
+                       case ObjectFile::Reader::kObjcRetainReleaseOrGC:
+                       case ObjectFile::Reader::kObjcGC:
+                               if ( (fCurrentObjCConstraint != objcAddition) && (objcAddition != ObjectFile::Reader::kObjcNone) ) 
+                                       throwf("%s built with different Garbage Collection settings", reader->getPath());
+                               break;
+               }
+       }
+       if ( reader->objcReplacementClasses() )
+               fObjcReplacmentClasses = true;
 
-       // assign order in which this atom was originally seen
-       if ( atom.getSortOrder() == 0 )
-               fNextSortOrder = atom.setSortOrder(fNextSortOrder);
+       // check cpu sub-types
+       ObjectFile::Reader::CpuConstraint  cpuAddition = reader->getCpuConstraint();
+       switch ( fCurrentCpuConstraint ) {
+               case ObjectFile::Reader::kCpuAny:
+                       fCurrentCpuConstraint = cpuAddition;
+                       break;
+               case ObjectFile::Reader::kCpuG3:
+                       switch ( cpuAddition ) {
+                               case ObjectFile::Reader::kCpuAny:
+                               case ObjectFile::Reader::kCpuG3:
+                                       break;
+                               case ObjectFile::Reader::kCpuG4:
+                               case ObjectFile::Reader::kCpuG5:
+                                       // previous file for G3 this one is more contrained, use it
+                                       fCurrentCpuConstraint = cpuAddition;
+                                       break;
+                       }
+                       break;
+               case ObjectFile::Reader::kCpuG4:
+                       switch ( cpuAddition ) {
+                               case ObjectFile::Reader::kCpuAny:
+                               case ObjectFile::Reader::kCpuG3:
+                               case ObjectFile::Reader::kCpuG4:
+                                       break;
+                               case ObjectFile::Reader::kCpuG5:
+                                       // previous file for G5 this one is more contrained, use it
+                                       fCurrentCpuConstraint = cpuAddition;
+                                       break;
+                       }
+                       break;
+               case ObjectFile::Reader::kCpuG5:
+                       // G5 can run everything
+                       break;
+       }
 }
 
 inline void Linker::addAtoms(std::vector<class ObjectFile::Atom*>& atoms)
 {
-       bool first = true; // assume all atoms are from same reader
+       bool scanAll = fOptions.readerOptions().fFullyLoadArchives || fOptions.readerOptions().fLoadAllObjcObjectsFromArchives;
+       bool first = true; 
        for (std::vector<ObjectFile::Atom*>::iterator it=atoms.begin(); it != atoms.end(); it++) {
-               if ( first ) {
+               // usually we only need to get the first atom's reader, but
+               // with -all_load all atoms from all .o files come come back together
+               // so we need to scan all atoms
+               if ( first || scanAll ) {
                        // update fReadersThatHaveSuppliedAtoms
                        ObjectFile::Reader* reader = (*it)->getFile();
                        if ( std::find(fReadersThatHaveSuppliedAtoms.begin(), fReadersThatHaveSuppliedAtoms.end(), reader)
                                        == fReadersThatHaveSuppliedAtoms.end() ) {
                                fReadersThatHaveSuppliedAtoms.push_back(reader);
-                       }
+                               updateContraints(reader);                               
+                       }       
                }
                this->addAtom(**it);
                first = false;
        }
 }
 
+void Linker::logArchive(ObjectFile::Reader* reader)
+{
+       if ( (fArchiveReaders.count(reader) != 0) && (fArchiveReadersLogged.count(reader) == 0) ) {
+               fArchiveReadersLogged.insert(reader);
+               const char* fullPath = reader->getPath();
+               char realName[MAXPATHLEN];
+               if ( realpath(fullPath, realName) != NULL )
+                       fullPath = realName;
+               logTraceInfo("[Logging for XBS] Used static archive: %s\n", fullPath);
+       }
+}
+
+
 void Linker::buildAtomList()
 {
        fStartBuildAtomsTime = mach_absolute_time();
@@ -633,15 +816,19 @@ void Linker::buildAtomList()
        this->addAtoms(fOutputFile->getAtoms());
 
        // each reader contributes atoms
-       const int readerCount = fInputFiles.size();
-       for (int i=0; i < readerCount; ++i) {
-               this->addAtoms(fInputFiles[i]->getAtoms());
+       for (std::vector<class ObjectFile::Reader*>::iterator it=fInputFiles.begin(); it != fInputFiles.end(); it++) {
+               ObjectFile::Reader* reader = *it;
+               std::vector<class ObjectFile::Atom*>& atoms = reader->getAtoms();
+               this->addAtoms(atoms);
+               if ( fOptions.readerOptions().fTraceArchives && (atoms.size() != 0) ) 
+                       logArchive(reader);
        }
 
        // extra command line section always at end
        std::vector<Options::ExtraSection>& extraSections = fOptions.extraSections();
        for( std::vector<Options::ExtraSection>::iterator it=extraSections.begin(); it != extraSections.end(); ++it) {
-               this->addAtoms(SectCreate::MakeReader(it->segmentName, it->sectionName, it->path, it->data, it->dataLen)->getAtoms());
+               this->addAtoms((new opaque_section::Reader(it->segmentName, it->sectionName, it->path, it->data, it->dataLen, fNextInputOrdinal))->getAtoms());
+               fNextInputOrdinal += it->dataLen;
        }
 }
 
@@ -656,7 +843,6 @@ static const char* pathLeafName(const char* path)
 
 void Linker::loadUndefines()
 {
-       fStartLoadUndefinesTime = mach_absolute_time();
        // keep looping until no more undefines were added in last loop
        unsigned int undefineCount = 0xFFFFFFFF;
        while ( undefineCount != fGlobalSymbolTable.getRequireCount() ) {
@@ -667,133 +853,199 @@ void Linker::loadUndefines()
                        const char* name = *it;
                        ObjectFile::Atom* possibleAtom = fGlobalSymbolTable.find(name);
                        if ( (possibleAtom == NULL)
-                         || ((possibleAtom->getDefinitionKind()==ObjectFile::Atom::kWeakDefinition) && (fOptions.outputKind() != Options::kObjectFile) && (possibleAtom->getScope() == ObjectFile::Atom::scopeGlobal)) )
-                               this->addJustInTimeAtoms(name);
+                         || ((possibleAtom->getDefinitionKind()==ObjectFile::Atom::kWeakDefinition) 
+                         && (fOptions.outputKind() != Options::kObjectFile) 
+                         && (possibleAtom->getScope() == ObjectFile::Atom::scopeGlobal)) ) {
+                               std::vector<class ObjectFile::Atom*>* atoms = this->addJustInTimeAtoms(name);
+                               if ( atoms != NULL ) 
+                                       delete atoms;
+                       }
                }
        }
+}
 
-       if ( fOptions.outputKind() != Options::kObjectFile ) {
-               // error out on any remaining undefines
-               bool doPrint = true;
-               bool doError = true;
-               switch ( fOptions.undefinedTreatment() ) {
-                       case Options::kUndefinedError:
-                               break;
-                       case Options::kUndefinedDynamicLookup:
-                               doError = false;
-                               break;
-                       case Options::kUndefinedWarning:
-                               doError = false;
-                               break;
-                       case Options::kUndefinedSuppress:
-                               doError = false;
-                               doPrint = false;
-                               break;
+// temp hack for rdar://problem/4718189 map ObjC class names to new runtime names
+class ExportedObjcClass
+{
+public:
+       ExportedObjcClass(Options& opt) : fOptions(opt)  {}
+
+       bool operator()(const char* name) const {
+               if ( fOptions.shouldExport(name) ) {
+                       if ( strncmp(name, ".objc_class_name_", 17) == 0 )
+                               return true;
+                       if ( strncmp(name, "_OBJC_CLASS_$_", 14) == 0 )
+                               return true;
+                       if ( strncmp(name, "_OBJC_METACLASS_$_", 18) == 0 )
+                               return true;
                }
-               std::vector<const char*> unresolvableUndefines;
-               fGlobalSymbolTable.getNeededNames(false, unresolvableUndefines);
-               const int unresolvableCount = unresolvableUndefines.size();
-               int unresolvableExportsCount  = 0;
-               if ( unresolvableCount != 0 ) {
-                       if ( doPrint ) {
-                               fprintf(stderr, "can't resolve symbols:\n");
-                               for (int i=0; i < unresolvableCount; ++i) {
-                                       const char* name = unresolvableUndefines[i];
-                                       fprintf(stderr, "  %s, referenced from:\n", name);
-                                       // scan all atoms for references
-                                       bool foundAtomReference = false;
-                                       for (std::vector<ObjectFile::Atom*>::iterator it=fAllAtoms.begin(); it != fAllAtoms.end(); it++) {
-                                               ObjectFile::Atom* atom = *it;
-                                               std::vector<class ObjectFile::Reference*>& references = atom->getReferences();
-                                               for (std::vector<ObjectFile::Reference*>::iterator rit=references.begin(); rit != references.end(); rit++) {
-                                                       ObjectFile::Reference* reference = *rit;
-                                                       if ( reference->isTargetUnbound() ) {
-                                                               if ( strcmp(reference->getTargetName(), name) == 0 ) {
-                                                                       fprintf(stderr, "      %s in %s\n", atom->getDisplayName(), pathLeafName(atom->getFile()->getPath()));
-                                                                       foundAtomReference = true;
-                                                               }
+               //fprintf(stderr, "%s is not exported\n", name);
+               return false;
+       }
+private:
+       Options& fOptions;
+};
+
+
+void Linker::checkUndefines()
+{
+       // error out on any remaining undefines
+       bool doPrint = true;
+       bool doError = true;
+       switch ( fOptions.undefinedTreatment() ) {
+               case Options::kUndefinedError:
+                       break;
+               case Options::kUndefinedDynamicLookup:
+                       doError = false;
+                       break;
+               case Options::kUndefinedWarning:
+                       doError = false;
+                       break;
+               case Options::kUndefinedSuppress:
+                       doError = false;
+                       doPrint = false;
+                       break;
+       }
+       std::vector<const char*> unresolvableUndefines;
+       fGlobalSymbolTable.getNeededNames(false, unresolvableUndefines);
+
+       // temp hack for rdar://problem/4718189 map ObjC class names to new runtime names
+       // ignore unresolved references to Objc class names that are listed in -exported_symbols_list
+       if ( fOptions.hasExportRestrictList() )
+               unresolvableUndefines.erase(std::remove_if(unresolvableUndefines.begin(), unresolvableUndefines.end(), ExportedObjcClass(fOptions)), unresolvableUndefines.end());
+
+       const int unresolvableCount = unresolvableUndefines.size();
+       int unresolvableExportsCount  = 0;
+       if ( unresolvableCount != 0 ) {
+               if ( doPrint ) {
+                       if ( fOptions.printArchPrefix() )
+                               fprintf(stderr, "Undefined symbols for architecture %s:\n", fArchitectureName);
+                       else
+                               fprintf(stderr, "Undefined symbols:\n");
+                       for (int i=0; i < unresolvableCount; ++i) {
+                               const char* name = unresolvableUndefines[i];
+                               fprintf(stderr, "  \"%s\", referenced from:\n", name);
+                               // scan all atoms for references
+                               bool foundAtomReference = false;
+                               for (std::vector<ObjectFile::Atom*>::iterator it=fAllAtoms.begin(); it != fAllAtoms.end(); it++) {
+                                       ObjectFile::Atom* atom = *it;
+                                       std::vector<class ObjectFile::Reference*>& references = atom->getReferences();
+                                       for (std::vector<ObjectFile::Reference*>::iterator rit=references.begin(); rit != references.end(); rit++) {
+                                               ObjectFile::Reference* reference = *rit;
+                                               if ( reference->getTargetBinding() == ObjectFile::Reference::kUnboundByName ) {
+                                                       if ( strcmp(reference->getTargetName(), name) == 0 ) {
+                                                               fprintf(stderr, "      %s in %s\n", atom->getDisplayName(), pathLeafName(atom->getFile()->getPath()));
+                                                               foundAtomReference = true;
                                                        }
-                                                       if ( reference->hasFromTarget() && reference->isFromTargetUnbound() ) {
-                                                               if ( strcmp(reference->getFromTargetName(), name) == 0 ) {
-                                                                       fprintf(stderr, "      %s in %s\n", atom->getDisplayName(), pathLeafName(atom->getFile()->getPath()));
-                                                                       foundAtomReference = true;
-                                                               }
+                                               }
+                                               if ( reference->getFromTargetBinding() == ObjectFile::Reference::kUnboundByName ) {
+                                                       if ( strcmp(reference->getFromTargetName(), name) == 0 ) {
+                                                               fprintf(stderr, "      %s in %s\n", atom->getDisplayName(), pathLeafName(atom->getFile()->getPath()));
+                                                               foundAtomReference = true;
                                                        }
                                                }
                                        }
-                                       // scan command line options
-                                       if  ( !foundAtomReference && fOptions.hasExportRestrictList() && fOptions.shouldExport(name) ) {
-                                               fprintf(stderr, "     -exported_symbols_list command line option\n");
-                                               ++unresolvableExportsCount;
-                                       }
+                               }
+                               // scan command line options
+                               if  ( !foundAtomReference && fOptions.hasExportRestrictList() && fOptions.shouldExport(name) ) {
+                                       fprintf(stderr, "     -exported_symbols_list command line option\n");
+                                       ++unresolvableExportsCount;
                                }
                        }
-                       if ( doError && (unresolvableCount > unresolvableExportsCount) ) // last check should be removed.  It exists so broken projects still build
-                               throw "symbol(s) not found";
-               }
-
-               // now verify that -init routine exists
-               if ( fOptions.initFunctionName() != NULL ) {
-                       if ( fGlobalSymbolTable.find(fOptions.initFunctionName()) == NULL )
-                               throwf("symbol %s not found for -init", fOptions.initFunctionName());
                }
+               if ( doError ) 
+                       throw "symbol(s) not found";
        }
 }
 
 
 
-void Linker::addJustInTimeAtoms(const char* name)
+std::vector<class ObjectFile::Atom*>* Linker::addJustInTimeAtoms(const char* name)
 {
        // when creating final linked image, writer gets first chance
        if ( fOptions.outputKind() != Options::kObjectFile ) {
                std::vector<class ObjectFile::Atom*>* atoms = fOutputFile->getJustInTimeAtomsFor(name);
                if ( atoms != NULL ) {
                        this->addAtoms(*atoms);
-                       delete atoms;
                        //fprintf(stderr, "addJustInTimeAtoms(%s) => found in file %s\n", name, fOutputFile->getPath() );
-                       return;  // found a definition, no need to search anymore
+                       return atoms;  // found a definition, no need to search anymore
                }
        }
 
-       // give direct readers a chance
+       // give readers a chance
        for (std::vector<class ObjectFile::Reader*>::iterator it=fInputFiles.begin(); it != fInputFiles.end(); it++) {
                ObjectFile::Reader* reader = *it;
                if ( reader != NULL ) {
                        // if this reader is a static archive that has the symbol we need, pull in all atoms in that module
                        // if this reader is a dylib that exports the symbol we need, have it synthesize an atom for us.
+                       //fprintf(stderr, "addJustInTimeAtoms(%s), looking in reader %s\n", name, reader->getPath() );
                        std::vector<class ObjectFile::Atom*>* atoms = reader->getJustInTimeAtomsFor(name);
                        if ( atoms != NULL ) {
                                this->addAtoms(*atoms);
-                               delete atoms;
-                               //fprintf(stderr, "addJustInTimeAtoms(%s) => found in file %s\n", name, fInputFiles[i]->getPath() );
-                               return;  // found a definition, no need to search anymore
+                               //fprintf(stderr, "addJustInTimeAtoms(%s) => found in file %s\n", name, reader->getPath() );
+                               if ( fOptions.readerOptions().fTraceArchives ) {
+                                       logArchive(reader);
+                               }
+                               // if this is a weak definition in a dylib
+                               if ( (atoms->size() == 1) && (reader->getInstallPath() != NULL) && (atoms->at(0)->getDefinitionKind() == ObjectFile::Atom::kExternalWeakDefinition) ) {
+                                       // keep looking for a non-weak definition
+                               }
+                               else {
+                                       // found a definition, no need to search anymore
+                                       return atoms;  
+                               }
                        }
                }
        }
 
-       // give indirect readers a chance
-       for (std::list<IndirectLibrary>::iterator it=fIndirectDynamicLibraries.begin(); it != fIndirectDynamicLibraries.end(); it++) {
-               ObjectFile::Reader* reader = it->reader;
-               if ( reader != NULL ) {
-                       std::vector<class ObjectFile::Atom*>* atoms = reader->getJustInTimeAtomsFor(name);
-                       if ( atoms != NULL ) {
-                               this->addAtoms(*atoms);
-                               //fprintf(stderr, "addJustInTimeAtoms(%s) => found in file %s\n", name, reader->getPath() );
-                               delete atoms;
-                               return;  // found a definition, no need to search anymore
+       // for two level namesapce, give all implicitly link dylibs a chance
+       if ( fOptions.nameSpace() == Options::kTwoLevelNameSpace ) {
+               for (InstallNameToReader::iterator it=fDylibMap.begin(); it != fDylibMap.end(); it++) {
+                       if ( it->second->implicitlyLinked() ) {
+                               //fprintf(stderr, "addJustInTimeAtoms(%s), looking in implicitly linked %s\n", name, it->second->getPath() );
+                               std::vector<class ObjectFile::Atom*>* atoms = it->second->getJustInTimeAtomsFor(name);
+                               if ( atoms != NULL ) {
+                                       this->addAtoms(*atoms);
+                                       //fprintf(stderr, "addJustInTimeAtoms(%s) => found in file %s\n", name, reader->getPath() );
+                                       // if this is a weak definition in a dylib
+                                       if ( (atoms->size() == 1) && (atoms->at(0)->getDefinitionKind() == ObjectFile::Atom::kExternalWeakDefinition) ) {
+                                               // keep looking for a non-weak definition
+                                       }
+                                       else {
+                                               // found a definition, no need to search anymore
+                                               return atoms;  
+                                       }
+                               }
+                       }
+               }
+       }
+
+       // for flat namespace, give indirect dylibs
+       if ( fOptions.nameSpace() != Options::kTwoLevelNameSpace ) {
+               for (InstallNameToReader::iterator it=fDylibMap.begin(); it != fDylibMap.end(); it++) {
+                       if ( ! it->second->explicitlyLinked() ) {
+                               std::vector<class ObjectFile::Atom*>* atoms = it->second->getJustInTimeAtomsFor(name);
+                               if ( atoms != NULL ) {
+                                       this->addAtoms(*atoms);
+                                       //fprintf(stderr, "addJustInTimeAtoms(%s) => found in file %s\n", name, reader->getPath() );
+                                       return atoms;  // found a definition, no need to search anymore
+                               }
                        }
                }
        }
 
        // when creating .o file, writer goes last (this is so any static archives will be searched above)
-       if ( (fOptions.outputKind() == Options::kObjectFile) || (fOptions.undefinedTreatment() != Options::kUndefinedError) ) {
+       if (    (fOptions.outputKind() == Options::kObjectFile) 
+               ||  (fOptions.undefinedTreatment() != Options::kUndefinedError)
+               ||      fOptions.someAllowedUndefines() ) {
                ObjectFile::Atom* atom = fOutputFile->getUndefinedProxyAtom(name);
                if ( atom != NULL ) {
                        this->addAtom(*atom);
-                       return;
+                       return NULL;
                }
        }
        //fprintf(stderr, "addJustInTimeAtoms(%s) => not found\n", name);
+       return NULL;
 }
 
 void Linker::resolve(ObjectFile::Reference* reference)
@@ -802,7 +1054,7 @@ void Linker::resolve(ObjectFile::Reference* reference)
        const char* targetName = reference->getTargetName();
        ObjectFile::Atom* target = fGlobalSymbolTable.find(targetName);
        if ( target == NULL ) {
-               fprintf(stderr, "can't resolve: %s\n", targetName);
+               fprintf(stderr, "Undefined symbol: %s\n", targetName);
        }
        reference->setTarget(*target, reference->getTargetOffset());
 }
@@ -813,7 +1065,7 @@ void Linker::resolveFrom(ObjectFile::Reference* reference)
        const char* fromTargetName = reference->getFromTargetName();
        ObjectFile::Atom* fromTarget = fGlobalSymbolTable.find(fromTargetName);
        if ( fromTarget == NULL ) {
-               fprintf(stderr, "can't resolve: %s\n", fromTargetName);
+               fprintf(stderr, "Undefined symbol: %s\n", fromTargetName);
        }
        reference->setFromTarget(*fromTarget);
 }
@@ -821,33 +1073,20 @@ void Linker::resolveFrom(ObjectFile::Reference* reference)
 
 void Linker::resolveReferences()
 {
-       fStartResolveTime = mach_absolute_time();
        // note: the atom list may grow during this loop as libraries supply needed atoms
        for (unsigned int j=0; j < fAllAtoms.size(); ++j) {
                ObjectFile::Atom* atom = fAllAtoms[j];
                std::vector<class ObjectFile::Reference*>& references = atom->getReferences();
                for (std::vector<ObjectFile::Reference*>::iterator it=references.begin(); it != references.end(); it++) {
                        ObjectFile::Reference* reference = *it;
-                       if ( reference->isTargetUnbound() )
+                       if ( reference->getTargetBinding() == ObjectFile::Reference::kUnboundByName )
                                this->resolve(reference);
-                       if ( reference->hasFromTarget() && reference->isFromTargetUnbound() )
+                       if ( reference->getFromTargetBinding() == ObjectFile::Reference::kUnboundByName )
                                this->resolveFrom(reference);
                }
        }
 }
 
-class InSet
-{
-public:
-       InSet(std::set<ObjectFile::Atom*>& deadAtoms) : fDeadAtoms(deadAtoms) {}
-
-       bool operator()(ObjectFile::Atom*& atom) const {
-               return ( fDeadAtoms.count(atom) != 0 );
-       }
-
-private:
-       std::set<ObjectFile::Atom*>& fDeadAtoms;
-};
 
 // used to remove stabs associated with atoms that won't be in output file
 class NotInSet
@@ -867,98 +1106,822 @@ private:
 };
 
 
-class DeadStrippable
+class NotLive
 {
 public:
-       DeadStrippable()  {}
+       NotLive(std::set<ObjectFile::Atom*>& set) : fLiveAtoms(set)  {}
 
        bool operator()(ObjectFile::Atom*& atom) const {
-               //if ( ! atom->dontDeadStrip() )
+               //if ( fLiveAtoms.count(atom) == 0 )
                //      fprintf(stderr, "dead strip %s\n", atom->getDisplayName());
-               return ( ! atom->dontDeadStrip() );
+               return ( fLiveAtoms.count(atom) == 0 );
        }
+private:
+       std::set<ObjectFile::Atom*>& fLiveAtoms;
 };
 
-void Linker::markLive(ObjectFile::Atom* atom, std::set<ObjectFile::Atom*>& liveAtoms)
+
+void Linker::addJustInTimeAtomsAndMarkLive(const char* name)
 {
-       if ( liveAtoms.count(atom) == 0 ) {
-               // this atom is live
-               liveAtoms.insert(atom);
-               // so don't dead strip
-               atom->setDontDeadStrip();
+       std::vector<class ObjectFile::Atom*>* atoms = this->addJustInTimeAtoms(name);
+       if ( atoms != NULL ) {
+               if ( fOptions.allGlobalsAreDeadStripRoots() ) {
+                       for (std::vector<ObjectFile::Atom*>::iterator it=atoms->begin(); it != atoms->end(); it++) {
+                               ObjectFile::Atom* atom = *it;
+                               if ( atom->getScope() ==  ObjectFile::Atom::scopeGlobal ) {
+                                       WhyLiveBackChain rootChain;
+                                       rootChain.previous = NULL;
+                                       rootChain.name = atom->getDisplayName();
+                                       this->markLive(*atom, &rootChain);
+                               }
+                       }
+               }
+               delete atoms;
+       }
+}
 
+void Linker::markLive(ObjectFile::Atom& atom, struct Linker::WhyLiveBackChain* previous)
+{
+       if ( fLiveAtoms.count(&atom) == 0 ) {
+               // if -whylive cares about this symbol, then dump chain
+               if ( (previous->name != NULL) && fOptions.printWhyLive(previous->name) ) {
+                       int depth = 0;
+                       for(WhyLiveBackChain* p = previous; p != NULL; p = p->previous, ++depth) {
+                               for(int i=depth; i > 0; --i)
+                                       fprintf(stderr, "  ");
+                               fprintf(stderr, "%s\n", p->name);
+                       }
+               }
+               // set up next chain
+               WhyLiveBackChain thisChain;
+               thisChain.previous = previous;
+               // this atom is live
+               fLiveAtoms.insert(&atom);
+               // update total size info (except for __ZEROPAGE atom)
+               if ( atom.getSegment().isContentReadable() ) {
+                       fTotalSize += atom.getSize();
+                       if ( atom.isZeroFill() )
+                               fTotalZeroFillSize += atom.getSize();
+               }
                // and all atoms it references
-               std::vector<class ObjectFile::Reference*>& references = atom->getReferences();
+               std::vector<class ObjectFile::Reference*>& references = atom.getReferences();
                for (std::vector<ObjectFile::Reference*>::iterator it=references.begin(); it != references.end(); it++) {
                        ObjectFile::Reference* reference = *it;
-                       // mark target of reference as live
-                       this->markLive(&reference->getTarget(), liveAtoms);
-                       // mark from-target (if it exists) as live
-                       if ( reference->hasFromTarget() )
-                               this->markLive(&reference->getFromTarget(), liveAtoms);
+                       if ( reference->getTargetBinding() == ObjectFile::Reference::kUnboundByName ) {
+                               // look in global symbol table
+                               const char* targetName = reference->getTargetName();
+                               ObjectFile::Atom* target = fGlobalSymbolTable.find(targetName);
+                               if ( target == NULL ) {
+                                       // load archives or dylibs
+                                       this->addJustInTimeAtomsAndMarkLive(targetName);
+                               }
+                               // look again
+                               target = fGlobalSymbolTable.find(targetName);
+                               if ( target != NULL ) {
+                                       reference->setTarget(*target, reference->getTargetOffset());
+                               }
+                               else {
+                                       // mark as undefined, for later error processing
+                                       fAtomsWithUnresolvedReferences.push_back(&atom);
+                                       fGlobalSymbolTable.require(targetName);
+                               }
+                       }
+                       switch ( reference->getTargetBinding() ) {
+                               case ObjectFile::Reference::kBoundDirectly:
+                               case ObjectFile::Reference::kBoundByName:
+                                       thisChain.name = reference->getTargetName();
+                                       markLive(reference->getTarget(), &thisChain);
+                                       break;
+                               case ObjectFile::Reference::kDontBind:
+                                       addDtraceProbe(atom, reference->getFixUpOffset(), reference->getTargetName());
+                                       break;
+                               case ObjectFile::Reference::kUnboundByName:
+                                       // do nothing
+                                       break;
+                       }
+                       // do the same as above, for "from target"
+                       if ( reference->getFromTargetBinding() == ObjectFile::Reference::kUnboundByName ) {
+                               // look in global symbol table
+                               const char* targetName = reference->getFromTargetName();
+                               ObjectFile::Atom* target = fGlobalSymbolTable.find(targetName);
+                               if ( target == NULL ) {
+                                       // load archives or dylibs
+                                       this->addJustInTimeAtomsAndMarkLive(targetName);
+                               }
+                               // look again
+                               target = fGlobalSymbolTable.find(targetName);
+                               if ( target != NULL ) {
+                                       reference->setFromTarget(*target);
+                               }
+                               else {
+                                       // mark as undefined, for later error processing
+                                       fGlobalSymbolTable.require(targetName);
+                               }
+                       }
+                       switch ( reference->getFromTargetBinding() ) {
+                               case ObjectFile::Reference::kBoundDirectly:
+                               case ObjectFile::Reference::kBoundByName:
+                                       thisChain.name = reference->getFromTargetName();
+                                       markLive(reference->getFromTarget(), &thisChain);
+                                       break;
+                               case ObjectFile::Reference::kUnboundByName:
+                               case ObjectFile::Reference::kDontBind:
+                                       // do nothing
+                                       break;
+                       }
                }
        }
 }
 
-void Linker::deadStrip()
-{
-       if ( fOptions.deadStrip() != Options::kDeadStripOff ) {
-               std::set<ObjectFile::Atom*> liveAtoms;
-
-               // mark main() and all atoms reachable from it as live
-               ObjectFile::Atom* entryPoint = this->entryPoint();
-               if ( entryPoint != NULL )
-                       markLive(entryPoint, liveAtoms);
-
-               ObjectFile::Atom* dyldHelper = this->dyldHelper();
-               if ( dyldHelper != NULL )
-                       markLive(dyldHelper, liveAtoms);
-
-               // mark initializers and all atoms reachable from them as live
-               // mark all exported atoms and atoms reachable from them as live
-               Section* initSection = Section::find("__mod_init_func", "__DATA", false);
-               Section* termSection = Section::find("__mod_term_func", "__DATA", false);
-               const bool globalsAreRoots = ( fOptions.outputKind() != Options::kDynamicExecutable );
-               for (std::vector<ObjectFile::Atom*>::iterator it=fAllAtoms.begin(); it != fAllAtoms.end(); it++) {
-                       ObjectFile::Atom* atom = *it;
-                       //fprintf(stderr,"%d %s\n", atom->dontDeadStrip(), atom->getDisplayName());
-                       if ( (globalsAreRoots && (atom->getScope() == ObjectFile::Atom::scopeGlobal))
-                               || (atom->getSection() == initSection) || (atom->getSection() == termSection) )
-                               markLive(atom, liveAtoms);
-               }
 
-               // now remove dead strippable atoms from fAllAtoms
-               fAllAtoms.erase(std::remove_if(fAllAtoms.begin(), fAllAtoms.end(), DeadStrippable()), fAllAtoms.end());
+void Linker::addLiveRoot(const char* name)
+{
+       ObjectFile::Atom* target = fGlobalSymbolTable.find(name);
+       if ( target == NULL ) {
+               this->addJustInTimeAtomsAndMarkLive(name);
+               target = fGlobalSymbolTable.find(name);
        }
-       else {
-               //printf("Stripping atoms:\n");
-               //for (std::set<ObjectFile::Atom*>::iterator it=fDeadAtoms.begin(); it != fDeadAtoms.end(); it++) {
-               //      printf("\t%s\n", (*it)->getDisplayName());
-               //}
+       if ( target != NULL )
+               fLiveRootAtoms.insert(target);
+}
 
-               // if not dead stripping, just remove atoms weak atoms that have been overridden
-               fAllAtoms.erase(std::remove_if(fAllAtoms.begin(), fAllAtoms.end(), InSet(fDeadAtoms)), fAllAtoms.end());
+
+void Linker::deadStripResolve()
+{
+       // add main() to live roots
+       ObjectFile::Atom* entryPoint = this->entryPoint();
+       if ( entryPoint != NULL )
+               fLiveRootAtoms.insert(entryPoint);
+
+       // add dyld_stub_binding_helper() to live roots
+       ObjectFile::Atom* dyldHelper = this->dyldHelper();
+       if ( dyldHelper != NULL )
+               fLiveRootAtoms.insert(dyldHelper);
+
+       // add -exported_symbols_list, -init, and -u entries to live roots
+       std::vector<const char*>& initialUndefines = fOptions.initialUndefines();
+       for (std::vector<const char*>::iterator it=initialUndefines.begin(); it != initialUndefines.end(); it++)
+               addLiveRoot(*it);
+
+       // in some cases, every global scope atom in initial .o files is a root
+       if ( fOptions.allGlobalsAreDeadStripRoots() ) {
+               for (std::vector<ObjectFile::Atom*>::iterator it=fAllAtoms.begin(); it != fAllAtoms.end(); it++) {
+                       ObjectFile::Atom* atom = *it;
+                       if ( (atom->getScope() == ObjectFile::Atom::scopeGlobal) && (fDeadAtoms.count(atom) == 0) )
+                               fLiveRootAtoms.insert(atom);
+               }
+       }
+
+       // mark all roots as live, and all atoms they reference
+       for (std::set<ObjectFile::Atom*>::iterator it=fLiveRootAtoms.begin(); it != fLiveRootAtoms.end(); it++) {
+               WhyLiveBackChain rootChain;
+               rootChain.previous = NULL;
+               rootChain.name = (*it)->getDisplayName();
+               markLive(**it, &rootChain);
+       }
+
+       // it is possible that there are unresolved references that can be resolved now
+       // this can happen if the first reference to a common symbol in an archive.
+       // common symbols are not in the archive TOC, but the .o could have been pulled in later.
+       // <rdar://problem/4654131> ld64 while linking cc1 [ when dead_strip is ON]
+       for (std::vector<ObjectFile::Atom*>::iterator it=fAtomsWithUnresolvedReferences.begin(); it != fAtomsWithUnresolvedReferences.end(); it++) {
+               std::vector<class ObjectFile::Reference*>& references = (*it)->getReferences();
+               for (std::vector<ObjectFile::Reference*>::iterator rit=references.begin(); rit != references.end(); rit++) {
+                       ObjectFile::Reference* reference = *rit;
+                       if ( reference->getTargetBinding() == ObjectFile::Reference::kUnboundByName ) {
+                               ObjectFile::Atom* target = fGlobalSymbolTable.find(reference->getTargetName());
+                               if ( target != NULL ) {
+                                       reference->setTarget(*target, reference->getTargetOffset());
+                                       fLiveAtoms.insert(target);
+                                       // by just adding this atom to fLiveAtoms set, we are assuming it has no
+                                       // references, which is true for commons.
+                                       if ( target->getDefinitionKind() != ObjectFile::Atom::kTentativeDefinition )
+                                               fprintf(stderr, "warning: ld64 internal error %s is not a tentative definition\n", target->getDisplayName());
+                               }
+                       }
+                       if ( reference->getFromTargetBinding() == ObjectFile::Reference::kUnboundByName ) {
+                               ObjectFile::Atom* target = fGlobalSymbolTable.find(reference->getFromTargetName());
+                               if ( target != NULL ) {
+                                       reference->setFromTarget(*target);
+                                       fLiveAtoms.insert(target);
+                                       // by just adding this atom to fLiveAtoms set, we are assuming it has no
+                                       // references, which is true for commons.
+                                       if ( target->getDefinitionKind() != ObjectFile::Atom::kTentativeDefinition )
+                                               fprintf(stderr, "warning: ld64 internal error %s is not a tentative definition\n", target->getDisplayName());
+                               }
+                       }
+               }
+       }
+
+       // now remove all non-live atoms from fAllAtoms
+       fAllAtoms.erase(std::remove_if(fAllAtoms.begin(), fAllAtoms.end(), NotLive(fLiveAtoms)), fAllAtoms.end());
+}
+
+void Linker::checkObjC()
+{
+       // check dylibs
+       switch ( fCurrentObjCConstraint ) {
+               case ObjectFile::Reader::kObjcNone:
+                       // can link against any dylib
+                       break;
+               case ObjectFile::Reader::kObjcRetainRelease:
+                       // cannot link against GC-only dylibs
+                       for (InstallNameToReader::iterator it=fDylibMap.begin(); it != fDylibMap.end(); it++) {
+                               if ( it->second->explicitlyLinked() ) {
+                                       if ( it->second->getObjCConstraint() == ObjectFile::Reader::kObjcGC )
+                                               throwf("this linkage unit uses Retain/Release.  It cannot link against the GC-only dylib: %s", it->second->getPath());
+                               }
+                       }
+                       break;
+               case ObjectFile::Reader::kObjcRetainReleaseOrGC:
+                       // can link against GC or RR dylibs
+                       break;
+               case ObjectFile::Reader::kObjcGC:
+                       // cannot link against RR-only dylibs
+                       for (InstallNameToReader::iterator it=fDylibMap.begin(); it != fDylibMap.end(); it++) {
+                               if ( it->second->explicitlyLinked() ) {
+                                       if ( it->second->getObjCConstraint() == ObjectFile::Reader::kObjcRetainRelease )
+                                               throwf("this linkage unit requires GC.  It cannot link against Retain/Release dylib: %s", it->second->getPath());
+                               }
+                       }
+                       break;
+       }
+       
+       // synthesize __OBJC __image_info atom if needed
+       if ( fCurrentObjCConstraint != ObjectFile::Reader::kObjcNone ) {
+               this->addAtom(fOutputFile->makeObjcInfoAtom(fCurrentObjCConstraint, fObjcReplacmentClasses));
+       }
+}
+
+void Linker::addDtraceProbe(ObjectFile::Atom& atom, uint32_t offsetInAtom, const char* probeName)
+{
+       if ( probeName != NULL ) {
+               if ( strncmp(probeName, "___dtrace_probe$", 16) == 0 ) 
+                       fDtraceProbeSites.push_back(DTraceProbeInfo(&atom, offsetInAtom, probeName));
+               else if ( strncmp(probeName, "___dtrace_isenabled$", 20) == 0 ) 
+                       fDtraceIsEnabledSites.push_back(DTraceProbeInfo(&atom, offsetInAtom, probeName));
+               else if ( strncmp(probeName, "___dtrace_", 10) == 0 )
+                       fDtraceAtomToTypes[&atom].insert(probeName);
+               else if ( fOptions.dTrace() && (strncmp(probeName, "__dtrace_probe$", 15) == 0) ) 
+                       fDtraceProbes.push_back(DTraceProbeInfo(&atom, offsetInAtom, probeName));
        }
 }
 
+static uint8_t pointerKind(cpu_type_t arch)
+{
+       switch ( arch ) {
+               case CPU_TYPE_POWERPC:
+                       return ppc::kPointer;
+               case CPU_TYPE_POWERPC64:
+                       return ppc64::kPointer;
+               case CPU_TYPE_I386:
+                       return x86::kPointer;
+               case CPU_TYPE_X86_64:
+                       return x86_64::kPointer;
+       }
+       throw "uknown architecture";
+}
 
+static uint8_t pcRelKind(cpu_type_t arch)
+{
+       switch ( arch ) {
+               case CPU_TYPE_POWERPC:
+                       return ppc::kPointerDiff32;
+               case CPU_TYPE_POWERPC64:
+                       return ppc64::kPointerDiff32;
+               case CPU_TYPE_I386:
+                       return x86::kPointerDiff;
+               case CPU_TYPE_X86_64:
+                       return x86_64::kPointerDiff32;
+       }
+       throw "uknown architecture";
+}
+
+typedef uint8_t* (*oldcreatedof_func_t) (const char*, cpu_type_t, unsigned int, const char*[], const char*[], uint64_t offsetsInDOF[], size_t* size);
+typedef uint8_t* (*createdof_func_t)(cpu_type_t, unsigned int, const char*[], unsigned int, const char*[], const char*[], uint64_t offsetsInDOF[], size_t* size);
 
+
+void Linker::processDTrace()
+{
+       // handle dtrace 2.0 static probes
+       if ( (fOptions.outputKind() != Options::kObjectFile) && ((fDtraceProbeSites.size() != 0) || (fDtraceIsEnabledSites.size() != 0)) ) {
+               // partition probes by provider name
+               // The symbol names looks like:
+               //      "___dtrace_isenabled$" provider-name "$" probe-name [ "$"... ]
+               //      "___dtrace_probe$" provider-name "$" probe-name [ "$"... ]
+               ProviderToProbes providerToProbes;
+               std::vector<DTraceProbeInfo> emptyList;
+               for(std::vector<DTraceProbeInfo>::iterator it = fDtraceProbeSites.begin(); it != fDtraceProbeSites.end(); ++it) {
+                       const char* providerStart = &it->probeName[16];
+                       const char* providerEnd = strchr(providerStart, '$');
+                       if ( providerEnd != NULL ) {
+                               char providerName[providerEnd-providerStart+1];
+                               strlcpy(providerName, providerStart, providerEnd-providerStart+1);
+                               ProviderToProbes::iterator pos = providerToProbes.find(providerName);
+                               if ( pos == providerToProbes.end() ) {
+                                       const char* dup = strdup(providerName);
+                                       providerToProbes[dup] = emptyList;
+                               }
+                               providerToProbes[providerName].push_back(*it);
+                       }
+               }
+               for(std::vector<DTraceProbeInfo>::iterator it = fDtraceIsEnabledSites.begin(); it != fDtraceIsEnabledSites.end(); ++it) {
+                       const char* providerStart = &it->probeName[20];
+                       const char* providerEnd = strchr(providerStart, '$');
+                       if ( providerEnd != NULL ) {
+                               char providerName[providerEnd-providerStart+1];
+                               strlcpy(providerName, providerStart, providerEnd-providerStart+1);
+                               ProviderToProbes::iterator pos = providerToProbes.find(providerName);
+                               if ( pos == providerToProbes.end() ) {
+                                       const char* dup = strdup(providerName);
+                                       providerToProbes[dup] = emptyList;
+                               }
+                               providerToProbes[providerName].push_back(*it);
+                       }
+               }
+               
+               // create a DOF section for each provider
+               int dofIndex=1;
+               CStringSet sectionNamesUsed;
+               for(ProviderToProbes::iterator pit = providerToProbes.begin(); pit != providerToProbes.end(); ++pit, ++dofIndex) {
+                       const char* providerName = pit->first;
+                       const std::vector<DTraceProbeInfo>& probes = pit->second;
+
+                       // open library and find dtrace_create_dof()
+                       void* handle = dlopen("/usr/lib/libdtrace.dylib", RTLD_LAZY);
+                       if ( handle == NULL )
+                               throwf("couldn't dlopen() /usr/lib/libdtrace.dylib: %s\n", dlerror());
+                       createdof_func_t pCreateDOF = (createdof_func_t)dlsym(handle, "dtrace_ld_create_dof");
+                       if ( pCreateDOF == NULL )
+                               throwf("couldn't find \"dtrace_ld_create_dof\" in /usr/lib/libdtrace.dylib: %s\n", dlerror());
+                       // build list of typedefs/stability infos for this provider
+                       CStringSet types;
+                       for(std::vector<DTraceProbeInfo>::const_iterator it = probes.begin(); it != probes.end(); ++it) {
+                               std::map<const ObjectFile::Atom*,CStringSet>::iterator pos = fDtraceAtomToTypes.find(it->atom);
+                               if ( pos != fDtraceAtomToTypes.end() ) {
+                                       for(CStringSet::iterator sit = pos->second.begin(); sit != pos->second.end(); ++sit) {
+                                               const char* providerStart = strchr(*sit, '$')+1;
+                                               const char* providerEnd = strchr(providerStart, '$');
+                                               if ( providerEnd != NULL ) {
+                                                       char aProviderName[providerEnd-providerStart+1];
+                                                       strlcpy(aProviderName, providerStart, providerEnd-providerStart+1);
+                                                       if ( strcmp(aProviderName, providerName) == 0 )
+                                                               types.insert(*sit);
+                                               }
+                                       }
+                               }
+                       }
+                       int typeCount = types.size();
+                       const char* typeNames[typeCount];
+                       //fprintf(stderr, "types for %s:\n", providerName);
+                       uint32_t index = 0;
+                       for(CStringSet::iterator it = types.begin(); it != types.end(); ++it) {
+                               typeNames[index] = *it;
+                               //fprintf(stderr, "\t%s\n", *it);
+                               ++index;
+                       }
+                       
+                       // build list of probe/isenabled sites
+                       const uint32_t probeCount = probes.size();
+                       const char* probeNames[probeCount];
+                       const char* funtionNames[probeCount];
+                       uint64_t offsetsInDOF[probeCount];
+                       index = 0;
+                       for(std::vector<DTraceProbeInfo>::const_iterator it = probes.begin(); it != probes.end(); ++it) {
+                               probeNames[index] = it->probeName;
+                               funtionNames[index] = it->atom->getName();
+                               offsetsInDOF[index] = 0;
+                               ++index;
+                       }
+                       // call dtrace library to create DOF section
+                       size_t dofSectionSize;
+                       uint8_t* p = (*pCreateDOF)(fArchitecture, typeCount, typeNames, probeCount, probeNames, funtionNames, offsetsInDOF, &dofSectionSize);
+                       if ( p != NULL ) {
+                               char sectionName[18];
+                               strcpy(sectionName, "__dof_");
+                               strlcpy(&sectionName[6], providerName, 10);
+                               // create unique section name so each DOF is in its own section
+                               if ( sectionNamesUsed.count(sectionName) != 0 ) {
+                                       sectionName[15] = '0';
+                                       sectionName[16] = '\0';
+                                       while ( sectionNamesUsed.count(sectionName) != 0 )
+                                               ++sectionName[15];
+                               }
+                               sectionNamesUsed.insert(sectionName);
+                               char symbolName[strlen(providerName)+64];
+                               sprintf(symbolName, "__dtrace_dof_for_provider_%s", providerName);
+                               opaque_section::Reader* reader = new opaque_section::Reader("__TEXT", sectionName, 
+                                                                                                               "dtrace", p, dofSectionSize, fNextInputOrdinal, symbolName);
+                               fNextInputOrdinal += dofSectionSize;
+                               // add references
+                               for (uint32_t i=0; i < probeCount; ++i) {
+                                       uint64_t offset = offsetsInDOF[i];
+                                       //fprintf(stderr, "%s offset[%d]=0x%08llX\n", providerName, i, offset);
+                                       if ( offset > dofSectionSize )
+                                               throwf("offsetsInDOF[i]=%0llX > dofSectionSize=%0lX\n", i, offset, dofSectionSize);
+                                       reader->addSectionReference(pcRelKind(fArchitecture), offset, probes[i].atom, probes[i].offset, reader->getAtoms()[0], 0);
+                               }
+                               this->addAtoms(reader->getAtoms());
+                       }
+                       else {
+                               throw "error creating dtrace DOF section";
+                       }
+               }
+       }
+       // create a __DATA __dof section iff -dtrace option was used and static probes were found in .o files
+       else if ( fOptions.dTrace() && (fDtraceProbes.size() != 0) ) {
+               const uint32_t probeCount = fDtraceProbes.size();
+               const char* labels[probeCount];
+               const char* funtionNames[probeCount];
+               uint64_t offsetsInDOF[probeCount];
+
+               // open libray and find dtrace_ld64_create_dof()
+               void* handle = dlopen("/usr/lib/libdtrace.dylib", RTLD_LAZY);
+               if ( handle == NULL )
+                       throwf("couldn't dlopen() /usr/lib/libdtrace.dylib: %s\n", dlerror());
+               oldcreatedof_func_t pCreateDOF = (oldcreatedof_func_t)dlsym(handle, "dtrace_ld64_create_dof");
+               if ( pCreateDOF == NULL )
+                       throwf("couldn't find \"dtrace_ld64_create_dof\" in /usr/lib/libdtrace.dylib: %s\n", dlerror());
+
+               // build argument list
+               uint32_t index = 0;
+               for(std::vector<DTraceProbeInfo>::iterator it = fDtraceProbes.begin(); it != fDtraceProbes.end(); ++it) {
+                       labels[index] = it->probeName;
+                       funtionNames[index] = it->atom->getName();
+                       offsetsInDOF[index] = 0;
+                       ++index;
+               }
+               size_t dofSectionSize;
+               // call dtrace library to create DOF section
+               uint8_t* p = (*pCreateDOF)(fOptions.dTraceScriptName(), fArchitecture, probeCount, labels, funtionNames, offsetsInDOF, &dofSectionSize);
+               if ( p != NULL ) {
+                       opaque_section::Reader* reader = new opaque_section::Reader("__DATA", "__dof", "dtrace", p, dofSectionSize, fNextInputOrdinal);
+                       fNextInputOrdinal += dofSectionSize;
+                       // add references
+                       for (uint32_t i=0; i < probeCount; ++i) {
+                               uint64_t offset = offsetsInDOF[i];
+                               if ( offset > dofSectionSize )
+                                       throwf("offsetsInDOF[i]=%0llX > dofSectionSize=%0lX\n", i, offset, dofSectionSize);
+                               reader->addSectionReference(pointerKind(fArchitecture), offset, fDtraceProbes[i].atom, fDtraceProbes[i].offset);
+                       }
+                       this->addAtoms(reader->getAtoms());
+               }
+               else {
+                       throw "error created dtrace DOF section";
+               }
+       }
+}
+
+
+static bool matchesObjectFile(ObjectFile::Atom* atom, const char* objectFileLeafName)
+{
+       if ( objectFileLeafName == NULL )
+               return true;
+       const char* atomFullPath = atom->getFile()->getPath();
+       const char* lastSlash = strrchr(atomFullPath, '/');
+       if ( lastSlash != NULL ) {
+               if ( strcmp(&lastSlash[1], objectFileLeafName) == 0 )
+                       return true;
+       }
+       else {
+               if ( strcmp(atomFullPath, objectFileLeafName) == 0 )
+                       return true;
+       }
+       return false;
+}
+
+
+static bool usesAnonymousNamespace(const char* symbol)
+{
+       return ( (strncmp(symbol, "__Z", 3) == 0) && (strstr(symbol, "_GLOBAL__N_") != NULL) );
+}
+
+
+//
+//  convert:
+//             __ZN20_GLOBAL__N__Z5main2v3barEv                                        =>  _ZN-3barEv
+//             __ZN37_GLOBAL__N_main.cxx_00000000_493A01A33barEv       =>  _ZN-3barEv
+//
+static void canonicalizeAnonymousName(const char* inSymbol, char outSymbol[])
+{
+       const char* globPtr = strstr(inSymbol, "_GLOBAL__N_");
+       while ( isdigit(*(--globPtr)) )
+               ; // loop
+       char* endptr;
+       unsigned long length = strtoul(globPtr+1, &endptr, 10);
+       const char* globEndPtr = endptr + length;
+       int startLen = globPtr-inSymbol+1;
+       memcpy(outSymbol, inSymbol, startLen);
+       outSymbol[startLen] = '-';
+       strcpy(&outSymbol[startLen+1], globEndPtr);
+}
+
+
+ObjectFile::Atom* Linker::findAtom(const Options::OrderedSymbol& orderedSymbol)
+{
+       ObjectFile::Atom* atom = fGlobalSymbolTable.find(orderedSymbol.symbolName);
+       if ( atom != NULL ) {
+               if ( matchesObjectFile(atom, orderedSymbol.objectFileName) )
+                       return atom;
+       }
+       else {
+               // slow case.  The requested symbol is not in symbol table, so might be static function
+               static SymbolTable::Mapper hashTableOfTranslationUnitScopedSymbols;
+               static SymbolTable::Mapper hashTableOfSymbolsWithAnonymousNamespace;
+               static bool built = false;
+               // build a hash_map the first time
+               if ( !built ) {
+                       for (std::vector<ObjectFile::Atom*>::iterator it=fAllAtoms.begin(); it != fAllAtoms.end(); it++) {
+                               atom = *it;
+                               const char* name = atom->getName();
+                               if ( name != NULL) {
+                                       if ( usesAnonymousNamespace(name) ) {
+                                               // symbol that uses anonymous namespace
+                                               char canonicalName[strlen(name)+2];
+                                               canonicalizeAnonymousName(name, canonicalName);
+                                               const char* hashName = strdup(canonicalName);
+                                               SymbolTable::Mapper::iterator pos = hashTableOfSymbolsWithAnonymousNamespace.find(hashName);
+                                               if ( pos == hashTableOfSymbolsWithAnonymousNamespace.end() )
+                                                       hashTableOfSymbolsWithAnonymousNamespace[hashName] = atom;
+                                               else
+                                                       hashTableOfSymbolsWithAnonymousNamespace[hashName] = NULL;      // collision, denote with NULL
+                                       }
+                                       else if ( atom->getScope() == ObjectFile::Atom::scopeTranslationUnit ) {
+                                               // static function or data
+                                               SymbolTable::Mapper::iterator pos = hashTableOfTranslationUnitScopedSymbols.find(name);
+                                               if ( pos == hashTableOfTranslationUnitScopedSymbols.end() )
+                                                       hashTableOfTranslationUnitScopedSymbols[name] = atom;
+                                               else
+                                                       hashTableOfTranslationUnitScopedSymbols[name] = NULL;   // collision, denote with NULL
+                                       }
+                               }
+                       }
+                       //fprintf(stderr, "built hash table of %lu static functions\n", hashTableOfTranslationUnitScopedSymbols.size());
+                       built = true;
+               }
+
+               // look for name in hashTableOfTranslationUnitScopedSymbols
+               SymbolTable::Mapper::iterator pos = hashTableOfTranslationUnitScopedSymbols.find(orderedSymbol.symbolName);
+               if ( pos != hashTableOfTranslationUnitScopedSymbols.end() ) {
+                       if ( (pos->second != NULL) && matchesObjectFile(pos->second, orderedSymbol.objectFileName) ) {
+                               //fprintf(stderr, "found %s in hash table\n", orderedSymbol.symbolName);
+                               return pos->second;
+                       }
+                       if ( pos->second == NULL )
+                       // name is in hash table, but atom is NULL, so that means there are duplicates, so we use super slow way
+                       for (std::vector<ObjectFile::Atom*>::iterator it=fAllAtoms.begin(); it != fAllAtoms.end(); it++) {
+                               atom = *it;
+                               if ( atom->getScope() == ObjectFile::Atom::scopeTranslationUnit ) {
+                                       const char* name = atom->getName();
+                                       if ( (name != NULL) && (strcmp(name, orderedSymbol.symbolName) == 0) ) {
+                                               if ( matchesObjectFile(atom, orderedSymbol.objectFileName) ) {
+                                                       if ( fOptions.printOrderFileStatistics() )
+                                                               fprintf(stderr, "ld: warning %s specified in order_file but it exists in multiple .o files. "
+                                                                               "Prefix symbol with .o filename in order_file to disambiguate\n", orderedSymbol.symbolName);
+                                                       return atom;
+                                               }
+                                       }
+                               }
+                       }
+               }
+               
+               // look for name in hashTableOfSymbolsWithAnonymousNamespace
+               if ( usesAnonymousNamespace(orderedSymbol.symbolName) ) {
+                       // symbol that uses anonymous namespace
+                       char canonicalName[strlen(orderedSymbol.symbolName)+2];
+                       canonicalizeAnonymousName(orderedSymbol.symbolName, canonicalName);
+                       SymbolTable::Mapper::iterator pos = hashTableOfSymbolsWithAnonymousNamespace.find(canonicalName);
+                       if ( pos != hashTableOfSymbolsWithAnonymousNamespace.end() ) {
+                               if ( (pos->second != NULL) && matchesObjectFile(pos->second, orderedSymbol.objectFileName) ) {
+                                       //fprintf(stderr, "found %s in anonymous namespace hash table\n", canonicalName);
+                                       return pos->second;
+                               }
+                               if ( pos->second == NULL )
+                               // name is in hash table, but atom is NULL, so that means there are duplicates, so we use super slow way
+                               for (std::vector<ObjectFile::Atom*>::iterator it=fAllAtoms.begin(); it != fAllAtoms.end(); it++) {
+                                       atom = *it;
+                                       const char* name = atom->getName();
+                                       if ( (name != NULL) && usesAnonymousNamespace(name) ) {
+                                               char canonicalAtomName[strlen(name)+2];
+                                               canonicalizeAnonymousName(name, canonicalAtomName);
+                                               if ( strcmp(canonicalAtomName, canonicalName) == 0 ) {
+                                                       if ( matchesObjectFile(atom, orderedSymbol.objectFileName) ) {
+                                                               if ( fOptions.printOrderFileStatistics() )
+                                                                       fprintf(stderr, "ld: warning %s specified in order_file but it exists in multiple .o files. "
+                                                                               "Prefix symbol with .o filename in order_file to disambiguate\n", orderedSymbol.symbolName);
+                                                               return atom;
+                                                       }
+                                               }
+                                       }
+                               }
+                       }
+               }
+       }
+       return NULL;
+}
+
+
+void Linker::sortSections()
+{
+       Section::assignIndexes();
+}
+
+
+//
+// Linker::sortAtoms()
+//
+// The purpose of this method is to take the graph of all Atoms and produce an ordered
+// sequence of atoms.  The constraints are that: 1) all Atoms of the same Segment must
+// be contiguous, 2)  all Atoms of the same Section must be contigous, 3) Atoms specified
+// in an order_file are seqenced as in the order_file and before Atoms not specified,
+// 4) Atoms in the same section from the same .o file should be contiguous and sequenced
+// in the same order they were in the .o file, 5) Atoms in the same Section but which came
+// from different .o files should be sequenced in the same order that the .o files
+// were passed to the linker (i.e. command line order).
+//
+// The way this is implemented is that the linker passes a "base ordinal" to each Reader
+// as it is constructed.  The reader should construct it Atoms so that calling getOrdinal()
+// on its atoms returns a contiguous range of values starting at the base ordinal.  Then
+// sorting is just sorting by section, then by ordinal.
+//
+// If an order_file is specified, it gets more complicated.  First, an override-ordinal map
+// is created.  It causes the sort routine to ignore the value returned by getOrdinal() and
+// use the override value instead.  Next some Atoms must be layed out consecutively
+// (e.g. hand written assembly that does not end with return, but rather falls into
+// the next label).  This is modeled in Readers via a "kFollowOn" reference.  The use of
+// kFollowOn refernces produces "clusters" of atoms that must stay together.
+// If an order_file tries to move one atom, it may need to move a whole cluster.  The
+// algorithm to do this models clusters using two maps.  The "starts" maps maps any
+// atom in a cluster to the first Atom in the cluster.  The "nexts" maps an Atom in a
+// cluster to the next Atom in the cluster.  With this in place, while processing an
+// order_file, if any entry is in a cluster (in "starts" map), then the entire cluster is
+// given ordinal overrides.
+//
 void Linker::sortAtoms()
 {
        fStartSortTime = mach_absolute_time();
-       Section::assignIndexes();
-       std::sort(fAllAtoms.begin(), fAllAtoms.end(), Linker::AtomSorter());
+       // if -order_file is used, build map of atom ordinal overrides
+       std::map<const ObjectFile::Atom*, uint32_t>* ordinalOverrideMap = NULL;
+       std::map<const ObjectFile::Atom*, uint32_t> theOrdinalOverrideMap;
+       const bool log = false;
+       if ( fOptions.orderedSymbols().size() != 0 ) {
+               // first make a pass to find all follow-on references and build start/next maps
+               // which are a way to represent clusters of atoms that must layout together
+               std::map<const ObjectFile::Atom*, const ObjectFile::Atom*> followOnStarts;
+               std::map<const ObjectFile::Atom*, const ObjectFile::Atom*> followOnNexts;
+               for (std::vector<ObjectFile::Atom*>::iterator ait=fAllAtoms.begin(); ait != fAllAtoms.end(); ait++) {
+                       ObjectFile::Atom* atom = *ait;
+                       std::vector<class ObjectFile::Reference*>& references = atom->getReferences();
+                       for (std::vector<ObjectFile::Reference*>::iterator rit=references.begin(); rit != references.end(); rit++) {
+                               ObjectFile::Reference* ref = *rit;
+                               if ( ref->getKind() == 1 ) {    // FIX FIX
+                                       ObjectFile::Atom* targetAtom = &ref->getTarget();
+                                       if ( log ) fprintf(stderr, "ref %s -> %s", atom->getDisplayName(), targetAtom->getDisplayName());
+                                       std::map<const ObjectFile::Atom*, const ObjectFile::Atom*>::iterator startFrom = followOnStarts.find(atom);
+                                       std::map<const ObjectFile::Atom*, const ObjectFile::Atom*>::iterator startTo = followOnStarts.find(targetAtom);
+                                       if ( (startFrom == followOnStarts.end()) && (startTo == followOnStarts.end()) ) {
+                                               // this is first time we've seen either atom, make simple cluster of the two
+                                               if ( log ) fprintf(stderr, "  new cluster\n");
+                                               followOnStarts[atom] = atom;
+                                               followOnStarts[targetAtom] = atom;
+                                               followOnNexts[atom] = targetAtom;
+                                               followOnNexts[targetAtom] = NULL;
+                                       }
+                                       else if ( (startFrom != followOnStarts.end()) && (startTo == followOnStarts.end()) && (followOnNexts[atom] == NULL) ) {
+                                               // atom is at end of an existing cluster, so append target to end of cluster
+                                               if ( log ) fprintf(stderr, "  end of cluster starting with %s\n", followOnStarts[atom]->getDisplayName());
+                                               followOnNexts[atom] = targetAtom;
+                                               followOnNexts[targetAtom] = NULL;
+                                               followOnStarts[targetAtom] = followOnStarts[atom];
+                                       }
+                                       else {
+                                               // gerneral case of inserting into an existing cluster
+                                               if ( followOnNexts[atom] != NULL ) {
+                                                       // an atom with two follow-ons is illegal
+                                                       fprintf(stderr, "ld: warning can't order %s because both %s and %s must follow it\n",
+                                                                               atom->getDisplayName(), targetAtom->getDisplayName(), followOnNexts[atom]->getDisplayName());
+                                               }
+                                               else {
+                                                       // there already exists an atom that says target must be its follow-on
+                                                       const ObjectFile::Atom* originalStart = startTo->second;
+                                                       const ObjectFile::Atom* originalPrevious = originalStart;
+                                                       while ( followOnNexts[originalPrevious] != targetAtom )
+                                                               originalPrevious = followOnNexts[originalPrevious];
+                                                       bool otherIsAlias = (originalPrevious->getSize() == 0);
+                                                       bool thisIsAlias = (atom->getSize() == 0);
+                                                       if ( !otherIsAlias && !thisIsAlias ) {
+                                                               fprintf(stderr, "ld: warning can't order %s because both %s and %s must preceed it\n",
+                                                                                       targetAtom->getDisplayName(), originalPrevious->getDisplayName(), atom->getDisplayName());
+                                                       }
+                                                       else if ( otherIsAlias ) {
+                                                               if ( originalPrevious == originalStart ) {
+                                                                       // other is alias at start of cluster, make this the new start of cluster
+                                                                       if ( log ) fprintf(stderr, "  becomes new start of cluster previous starting with %s\n", originalStart->getDisplayName());
+                                                                       followOnNexts[atom] = originalPrevious;
+                                                                       for(const ObjectFile::Atom* nextAtom = atom; nextAtom != NULL; nextAtom = followOnNexts[nextAtom])
+                                                                               followOnStarts[nextAtom] = atom;
+                                                               }
+                                                               else {
+                                                                       // other is alias in middle of cluster, insert new atom before it
+                                                                       if ( log ) fprintf(stderr, "  insert into cluster starting with %s before alias %s\n", originalStart->getDisplayName(), originalPrevious->getDisplayName());
+                                                                       followOnStarts[atom] = originalStart;
+                                                                       followOnNexts[atom] = originalPrevious;
+                                                                       for(const ObjectFile::Atom* a = originalStart; a != NULL; a = followOnNexts[a]) {
+                                                                               if ( followOnNexts[a] == originalPrevious ) {
+                                                                                       followOnNexts[a] = atom;
+                                                                                       break;
+                                                                               }
+                                                                       }
+                                                               }
+                                                       }
+                                                       else {
+                                                               // this is alias, so it can go inbetween originalPrevious and targetAtom
+                                                               if ( log ) fprintf(stderr, "  insert into cluster starting with %s after %s\n", originalStart->getDisplayName(), originalPrevious->getDisplayName());
+                                                               followOnStarts[atom] = originalStart;
+                                                               followOnNexts[atom] = followOnNexts[originalPrevious];
+                                                               followOnNexts[originalPrevious] = atom;
+                                                       }
+                                               }
+                                       }
+                               }
+                       }
+               }
+
+               if ( log ) {
+                       for(std::map<const ObjectFile::Atom*, const ObjectFile::Atom*>::iterator it = followOnStarts.begin(); it != followOnStarts.end(); ++it)
+                               fprintf(stderr, "start %s -> %s\n", it->first->getDisplayName(), it->second->getDisplayName());
+
+                       for(std::map<const ObjectFile::Atom*, const ObjectFile::Atom*>::iterator it = followOnNexts.begin(); it != followOnNexts.end(); ++it)
+                               fprintf(stderr, "next %s -> %s\n", it->first->getDisplayName(), (it->second != NULL) ? it->second->getDisplayName() : "null");
+               }
+
+               // with the start/next maps of follow-on atoms we can process the order file and produce override ordinals
+               ordinalOverrideMap = &theOrdinalOverrideMap;
+               uint32_t index = 0;
+               uint32_t matchCount = 0;
+               std::vector<Options::OrderedSymbol>& orderedSymbols = fOptions.orderedSymbols();
+               for(std::vector<Options::OrderedSymbol>::iterator it = orderedSymbols.begin(); it != orderedSymbols.end(); ++it) {
+                       ObjectFile::Atom* atom = this->findAtom(*it);
+                       if ( atom != NULL ) {
+                               std::map<const ObjectFile::Atom*, const ObjectFile::Atom*>::iterator start = followOnStarts.find(atom);
+                               if ( start != followOnStarts.end() ) {
+                                       // this symbol for the order file corresponds to an atom that is in a cluster that must lay out together
+                                       for(const ObjectFile::Atom* nextAtom = start->second; nextAtom != NULL; nextAtom = followOnNexts[nextAtom]) {
+                                               std::map<const ObjectFile::Atom*, uint32_t>::iterator pos = theOrdinalOverrideMap.find(nextAtom);
+                                               if ( pos == theOrdinalOverrideMap.end() ) {
+                                                       theOrdinalOverrideMap[nextAtom] = index++;
+                                                       if (log ) fprintf(stderr, "override ordinal %u assigned to %s in cluster from %s\n", index, nextAtom->getDisplayName(), nextAtom->getFile()->getPath());
+                                               }
+                                               else {
+                                                       if (log ) fprintf(stderr, "could not order %s as %u because it was already laid out earlier by %s as %u\n",
+                                                                                       atom->getDisplayName(), index, followOnStarts[atom]->getDisplayName(), theOrdinalOverrideMap[atom] );
+                                               }
+                                       }
+                               }
+                               else {
+                                       theOrdinalOverrideMap[atom] = index;
+                                       if (log ) fprintf(stderr, "override ordinal %u assigned to %s from %s\n", index, atom->getDisplayName(), atom->getFile()->getPath());
+                               }
+                       }
+                       else {
+                               ++matchCount;
+                               //fprintf(stderr, "can't find match for order_file entry %s/%s\n", it->objectFileName, it->symbolName);
+                       }
+                        ++index;
+               }
+               if ( fOptions.printOrderFileStatistics() && (fOptions.orderedSymbols().size() != matchCount) ) {
+                       fprintf(stderr, "ld: warning only %u out of %lu order_file symbols were applicable\n", matchCount, fOptions.orderedSymbols().size() );
+               }
+       }
+
+       // sort atoms
+       std::sort(fAllAtoms.begin(), fAllAtoms.end(), Linker::AtomSorter(ordinalOverrideMap));
+
        //fprintf(stderr, "Sorted atoms:\n");
        //for (std::vector<ObjectFile::Atom*>::iterator it=fAllAtoms.begin(); it != fAllAtoms.end(); it++) {
-       //      fprintf(stderr, "\t%s\n", (*it)->getDisplayName());
+       //      fprintf(stderr, "\t%p, %u  %s\n", (*it)->getSection(), (*it)->getSection()->getIndex(), (*it)->getDisplayName());
        //}
 }
 
 
-
 // make sure given addresses are within reach of branches, etc
 void Linker::tweakLayout()
 {
+       // > 2GB images need their large zero fill atoms sorted to the end to keep access with +/- 2GB
+       if ( fTotalSize > 0x7F000000 ) {
+               fBiggerThanTwoGigOutput = true;
+
+               if ( (fTotalSize-fTotalZeroFillSize) > 0x7F000000 )
+                       throwf("total output size exceeds 2GB (%lldMB)", (fTotalSize-fTotalZeroFillSize)/(1024*1024));          
+
+               // move very large (>1MB) zero fill atoms to a new section at very end
+               Section* hugeZeroFills = Section::find("__huge", "__DATA", true);
+               for (std::vector<ObjectFile::Atom*>::iterator it=fAllAtoms.begin(); it != fAllAtoms.end(); it++) {
+                       ObjectFile::Atom* atom = *it;
+                       if ( atom->isZeroFill() && (atom->getSize() > 1024*1024) && atom->getSegment().isContentReadable() )
+                               atom->setSection(hugeZeroFills);
+               }
+       }
 }
 
 
@@ -978,18 +1941,9 @@ void Linker::writeDotOutput()
                                ObjectFile::Atom* atom = *it;
                                if ( atom->getFile() != fOutputFile ) {
                                        const char* name = atom->getDisplayName();
-                                       // don't create nodes for stubs, lazy pointers or non-lazy pointers
-                                       const char* lastDollar = strrchr(name, '$');
-                                       if ( lastDollar != NULL ) {
-                                               if ( (strcmp(lastDollar, "$stub") == 0) || (strcmp(lastDollar, "$lazy_ptr") == 0) || (strcmp(lastDollar, "$non_lazy_ptr") == 0) )
-                                                       continue;
-                                       }
                                        if ( (atom->getDefinitionKind() == ObjectFile::Atom::kExternalDefinition)
                                          || (atom->getDefinitionKind() == ObjectFile::Atom::kExternalWeakDefinition) ) {
-                                               char temp[strlen(name)+2];
-                                               strcpy(temp, name);
-                                               temp[strlen(name)-7] = '\0'; // strip trailing "$import"
-                                               fprintf(out, "\t%s [ shape = plaintext ];\n", temp);
+                                               fprintf(out, "\taddr%p [ shape = plaintext, label = \"%s\" ];\n", atom, name);
                                        }
                                        else if ( strcmp(atom->getSectionName(), "__cstring") == 0 ) {
                                                char cstring[atom->getSize()+2];
@@ -1021,37 +1975,7 @@ void Linker::writeDotOutput()
                                                ObjectFile::Atom* toAtom = &(reference->getTarget());
                                                if ( seenTargets.count(toAtom) == 0 ) {
                                                        seenTargets.insert(toAtom);
-                                                       const char* toName = toAtom->getDisplayName();
-                                                       const char* lastDollar = strrchr(toName, '$');
-                                                       if ( (lastDollar != NULL) && (strcmp(lastDollar, "$stub") == 0) ) {
-                                                               char temp[strlen(toName)+2];
-                                                               strcpy(temp, toName);
-                                                               temp[strlen(toName)-5] = '\0'; // strip trailing "$stub"
-                                                               fprintf(out, "\taddr%p -> %s;\n", fromAtom, temp);
-                                                       }
-                                                       else if ( lastDollar != NULL && (strcmp(lastDollar, "$non_lazy_ptr") == 0) ) {
-                                                               ObjectFile::Atom* nonLazyTargetAtom = &(toAtom->getReferences()[0]->getTarget());
-                                                               if ( (nonLazyTargetAtom->getDefinitionKind() == ObjectFile::Atom::kExternalDefinition)
-                                                                 || (nonLazyTargetAtom->getDefinitionKind() == ObjectFile::Atom::kExternalWeakDefinition) ) {
-                                                                       char temp[strlen(toName)+2];
-                                                                       strcpy(temp, toName);
-                                                                       temp[strlen(toName)-13] = '\0'; // strip trailing "$non_lazy_ptr"
-                                                                       fprintf(out, "\taddr%p -> %s;\n", fromAtom, temp);
-                                                               }
-                                                               else {
-                                                                       fprintf(out, "\taddr%p -> addr%p;\n", fromAtom, nonLazyTargetAtom);
-                                                               }
-                                                       }
-                                                       else {
-                                                               // don't list references from stubs, lazy pointers or non-lazy pointers
-                                                               const char* name = fromAtom->getDisplayName();
-                                                               const char* lastDollar = strrchr(name, '$');
-                                                               if ( lastDollar != NULL ) {
-                                                                       if ( (strcmp(lastDollar, "$stub") == 0) || (strcmp(lastDollar, "$lazy_ptr") == 0) || (strcmp(lastDollar, "$non_lazy_ptr") == 0) )
-                                                                               continue;
-                                                               }
-                                                               fprintf(out, "\taddr%p -> addr%p;\n", fromAtom, toAtom);
-                                                       }
+                                                       fprintf(out, "\taddr%p -> addr%p;\n", fromAtom, toAtom);
                                                }
                                        }
                                }
@@ -1065,11 +1989,7 @@ void Linker::writeDotOutput()
                                if ( atom->getFile() != fOutputFile )
                                        if ( (atom->getDefinitionKind() == ObjectFile::Atom::kExternalDefinition)
                                          || (atom->getDefinitionKind() == ObjectFile::Atom::kExternalWeakDefinition) ) {
-                                               const char* name = atom->getDisplayName();
-                                               char temp[strlen(name)+2];
-                                               strcpy(temp, name);
-                                               temp[strlen(name)-7] = '\0'; // strip trailing "$import"
-                                               fprintf(out, "%s; ", temp);
+                                               fprintf(out, "addr%p; ", atom);
                                        }
                        }
                        fprintf(out, "};\n ");
@@ -1079,7 +1999,7 @@ void Linker::writeDotOutput()
                        fclose(out);
                }
                else {
-                       fprintf(stderr, "ld64 warning: could not write dot output file: %s\n", dotOutFilePath);
+                       fprintf(stderr, "ld: warning could not write dot output file: %s\n", dotOutFilePath);
                }
        }
 }
@@ -1094,14 +2014,14 @@ ObjectFile::Atom* Linker::entryPoint()
                case Options::kDyld:
                        entryPoint = fGlobalSymbolTable.find(fOptions.entryName());
                        if ( entryPoint == NULL ) {
-                               throwf("could not find entry point: %s", fOptions.entryName());
+                               throwf("could not find entry point \"%s\" (perhaps missing crt1.o)", fOptions.entryName());
                        }
                        break;
                case Options::kDynamicLibrary:
                        if ( fOptions.initFunctionName() != NULL ) {
                                entryPoint = fGlobalSymbolTable.find(fOptions.initFunctionName());
                                if ( entryPoint == NULL ) {
-                                       throwf("could not find -init function: %s", fOptions.initFunctionName());
+                                       throwf("could not find -init function: \"%s\"", fOptions.initFunctionName());
                                }
                        }
                        break;
@@ -1136,7 +2056,7 @@ const char* Linker::assureFullPath(const char* path)
 //
 // The stab strings are of the form:
 //             <name> ':' <type-code> <number-pari>
-//  but the <name> contain a colon. 
+//  but the <name> contain a colon.
 //  For C++ <name> may contain a double colon (e.g. std::string:f(0,1) )
 //  For Objective-C name may contain a colon instead square bracket (e.g. [Foo doit:]:f(0,1) )
 //
@@ -1200,8 +2120,9 @@ bool Linker::minimizeStab(ObjectFile::Reader::Stab& stab)
        }
 }
 
-struct HeaderRange { 
-       std::vector<ObjectFile::Reader::Stab>::iterator begin; 
+
+struct HeaderRange {
+       std::vector<ObjectFile::Reader::Stab>::iterator begin;
        std::vector<ObjectFile::Reader::Stab>::iterator end;
        int                                                                                             parentRangeIndex;
        uint32_t                                                                                sum;
@@ -1217,19 +2138,25 @@ typedef __gnu_cxx::hash_map<const char*, std::vector<uint32_t>, __gnu_cxx::hash<
 static PathToSums sKnownBINCLs;
 
 
-void Linker::collectStabs(ObjectFile::Reader* reader)
+void Linker::collectStabs(ObjectFile::Reader* reader, std::map<const class ObjectFile::Atom*, uint32_t>& atomOrdinals)
 {
        bool log = false;
        bool minimal = ( fOptions.readerOptions().fDebugInfoStripping == ObjectFile::ReaderOptions::kDebugInfoMinimal );
        std::vector<class ObjectFile::Reader::Stab>* readerStabs = reader->getStabs();
        if ( readerStabs == NULL )
                return;
-               
+
        if ( log ) fprintf(stderr, "processesing %lu stabs for %s\n", readerStabs->size(), reader->getPath());
-       // Find all (possibly nested) BINCL/EINCL ranges and their checksums
        std::vector<HeaderRange> ranges;
        int curRangeIndex = -1;
        int count = 0;
+       ObjectFile::Atom* atomWithLowestOrdinal = NULL;
+       ObjectFile::Atom* atomWithHighestOrdinal = NULL;
+       uint32_t highestOrdinal = 0;
+       uint32_t lowestOrdinal = UINT_MAX;
+       std::vector<std::pair<ObjectFile::Atom*,ObjectFile::Atom*> > soRanges;
+       // 1) find all (possibly nested) BINCL/EINCL ranges and their checksums
+       // 2) find all SO/SO ranges and the first/last atom own by a FUN stab therein
        for(std::vector<class ObjectFile::Reader::Stab>::iterator it=readerStabs->begin(); it != readerStabs->end(); ++it) {
                ++count;
                switch ( it->type ) {
@@ -1239,7 +2166,7 @@ void Linker::collectStabs(ObjectFile::Reader* reader)
                                        range.begin = it;
                                        range.end = readerStabs->end();
                                        range.parentRangeIndex = curRangeIndex;
-                                       range.sum = it->value; 
+                                       range.sum = it->value;
                                        range.sumPrecomputed = (range.sum != 0);
                                        range.useEXCL = false;
                                        range.cannotEXCL = false;
@@ -1250,15 +2177,30 @@ void Linker::collectStabs(ObjectFile::Reader* reader)
                                break;
                        case N_EINCL:
                                if ( curRangeIndex == -1 ) {
-                                       fprintf(stderr, "ld64 warning: EINCL missing BINCL in %s\n", reader->getPath());
+                                       fprintf(stderr, "ld: warning EINCL missing BINCL in %s\n", reader->getPath());
                                }
                                else {
                                        ranges[curRangeIndex].end = it+1;
                                        if ( log ) fprintf(stderr, "[%d->%d]EINCL %s\n", curRangeIndex, ranges[curRangeIndex].parentRangeIndex, it->string);
                                        curRangeIndex = ranges[curRangeIndex].parentRangeIndex;
                                }
-                               break;                          
+                               break;
                        case N_FUN:
+                               {
+                                       std::map<const class ObjectFile::Atom*, uint32_t>::iterator pos = atomOrdinals.find(it->atom);
+                                       if ( pos != atomOrdinals.end() ) {
+                                               uint32_t ordinal = pos->second;
+                                               if ( ordinal > highestOrdinal ) {
+                                                       highestOrdinal = ordinal;
+                                                       atomWithHighestOrdinal = it->atom;
+                                               }
+                                               if ( ordinal < lowestOrdinal ) {
+                                                       lowestOrdinal = ordinal;
+                                                       atomWithLowestOrdinal = it->atom;
+                                               }
+                                       }
+                               }
+                               // fall through
                        case N_BNSYM:
                        case N_ENSYM:
                        case N_LBRAC:
@@ -1269,9 +2211,22 @@ void Linker::collectStabs(ObjectFile::Reader* reader)
                                if ( curRangeIndex != -1 ) {
                                        ranges[curRangeIndex].cannotEXCL = true;
                                        if ( fOptions.warnStabs() )
-                                               fprintf(stderr, "ld64: cannot do BINCL/EINCL optimzation because of stabs kinds in %s for %s\n", ranges[curRangeIndex].begin->string, reader->getPath());
+                                               fprintf(stderr, "ld: cannot do BINCL/EINCL optimzation because of stabs kinds in %s for %s\n", ranges[curRangeIndex].begin->string, reader->getPath());
                                }
                                break;
+                       case N_SO:
+                               if ( (it->string != NULL) && (strlen(it->string) > 0) ) {
+                                       // start SO, reset hi/low FUN tracking
+                                       atomWithLowestOrdinal = NULL;
+                                       atomWithHighestOrdinal = NULL;
+                                       highestOrdinal = 0;
+                                       lowestOrdinal = UINT_MAX;
+                               }
+                               else {
+                                       // end SO, record hi/low atoms for this SO range
+                                       soRanges.push_back(std::make_pair<ObjectFile::Atom*,ObjectFile::Atom*>(atomWithLowestOrdinal, atomWithHighestOrdinal));
+                               }
+                               // fall through
                        default:
                                if ( curRangeIndex != -1 ) {
                                        if ( ! ranges[curRangeIndex].sumPrecomputed ) {
@@ -1289,34 +2244,42 @@ void Linker::collectStabs(ObjectFile::Reader* reader)
                                                ranges[curRangeIndex].sum += sum;
                                        }
                                }
-                               
+
                }
        }
        if ( log ) fprintf(stderr, "processesed %d stabs for %s\n", count, reader->getPath());
        if ( curRangeIndex != -1 )
-               fprintf(stderr, "ld64 warning: BINCL (%s) missing EINCL in %s\n", ranges[curRangeIndex].begin->string, reader->getPath());
-               
+               fprintf(stderr, "ld: warning BINCL (%s) missing EINCL in %s\n", ranges[curRangeIndex].begin->string, reader->getPath());
+
        // if no BINCLs
        if ( ranges.size() == 0 ) {
-               if ( minimal ) {
-                       // only copy minimal stabs
-                       for(std::vector<ObjectFile::Reader::Stab>::iterator it=readerStabs->begin(); it != readerStabs->end(); ++it) {
-                               if ( minimizeStab(*it) )
-                                       fStabs.push_back(*it);
+               int soIndex = 0;
+               for(std::vector<ObjectFile::Reader::Stab>::iterator it=readerStabs->begin(); it != readerStabs->end(); ++it) {
+                       // copy minimal or all stabs
+                       ObjectFile::Reader::Stab stab = *it;
+                       if ( !minimal || minimizeStab(stab) ) {
+                               if ( stab.type == N_SO ) {
+                                       if ( (stab.string != NULL) && (strlen(stab.string) > 0) ) {
+                                               // starting SO is associated with first atom
+                                               stab.atom = soRanges[soIndex].first;
+                                       }
+                                       else {
+                                               // ending SO is associated with last atom
+                                               stab.atom = soRanges[soIndex].second;
+                                               ++soIndex;
+                                       }
+                               }
+                               fStabs.push_back(stab);
                        }
                }
-               else {
-                       // copy all stabs
-                       fStabs.insert(fStabs.end(), readerStabs->begin(), readerStabs->end());
-               }
                return;
        }
-                       
+
        //fprintf(stderr, "BINCL/EINCL info for %s\n", reader->getPath());
        //for(std::vector<HeaderRange>::iterator it=ranges.begin(); it != ranges.end(); ++it) {
        //      fprintf(stderr, "%08X %s\n", it->sum, it->begin->string);
        //}
-       
+
        // see if any of these BINCL/EINCL ranges have already been seen and therefore can be replaced with EXCL
        for(std::vector<HeaderRange>::iterator it=ranges.begin(); it != ranges.end(); ++it) {
                if ( ! it->cannotEXCL ) {
@@ -1347,10 +2310,11 @@ void Linker::collectStabs(ObjectFile::Reader* reader)
                        }
                }
        }
-       
+
        // add a new set of stabs with BINCL/EINCL runs that have been seen before, replaced with EXCLs
        curRangeIndex = -1;
        const int maxRangeIndex = ranges.size();
+       int soIndex = 0;
        for(std::vector<ObjectFile::Reader::Stab>::iterator it=readerStabs->begin(); it != readerStabs->end(); ++it) {
                switch ( it->type ) {
                        case N_BINCL:
@@ -1360,7 +2324,7 @@ void Linker::collectStabs(ObjectFile::Reader* reader)
                                                HeaderRange& range = ranges[curRangeIndex];
                                                ObjectFile::Reader::Stab stab = *it;
                                                stab.value = range.sum; // BINCL and EXCL have n_value set to checksum
-                                               if ( range.useEXCL ) 
+                                               if ( range.useEXCL )
                                                        stab.type = N_EXCL;     // transform BINCL into EXCL
                                                if ( !minimal )
                                                        fStabs.push_back(stab);
@@ -1374,11 +2338,24 @@ void Linker::collectStabs(ObjectFile::Reader* reader)
                                                fStabs.push_back(*it);
                                        curRangeIndex = ranges[curRangeIndex].parentRangeIndex;
                                }
-                               break;                          
+                               break;
                        default:
                                if ( (curRangeIndex == -1) || !ranges[curRangeIndex].useEXCL ) {
-                                       if ( !minimal || minimizeStab(*it) )
-                                               fStabs.push_back(*it);
+                                       ObjectFile::Reader::Stab stab = *it;
+                                       if ( !minimal || minimizeStab(stab) ) {
+                                               if ( stab.type == N_SO ) {
+                                                       if ( (stab.string != NULL) && (strlen(stab.string) > 0) ) {
+                                                               // starting SO is associated with first atom
+                                                               stab.atom = soRanges[soIndex].first;
+                                                       }
+                                                       else {
+                                                               // ending SO is associated with last atom
+                                                               stab.atom = soRanges[soIndex].second;
+                                                               ++soIndex;
+                                                       }
+                                               }
+                                               fStabs.push_back(stab);
+                                       }
                                }
                }
        }
@@ -1386,163 +2363,209 @@ void Linker::collectStabs(ObjectFile::Reader* reader)
 }
 
 
-void Linker::synthesizeStabs(ObjectFile::Reader* reader)
+// used to prune out atoms that don't need debug notes generated
+class NoDebugNoteAtom
 {
-       // synthesize "debug notes" and add them to master stabs vector
-       const char* dirPath = NULL;
-       const char* filename = NULL;
-       bool wroteStartSO = false;
-       std::vector<const char*> seenFiles;
-       for (std::vector<class ObjectFile::Atom*>::iterator it=fAllAtoms.begin(); it != fAllAtoms.end(); ++it) {
-               ObjectFile::Atom* atom = *it;
-               if ( atom->getFile() == reader ) {
-                       const char* name = atom->getName();
-                       if ( (name != NULL) && (name[0] == '_' ) && (atom->getSymbolTableInclusion() != ObjectFile::Atom::kSymbolTableNotIn) ) {
-                               const char* newDirPath;
-                               const char* newFilename;
-                               if ( atom->getTranslationUnitSource(&newDirPath, &newFilename) ) {
-                                       // need SO's whenever the translation unit source file changes
-                                       if ( newFilename != filename ) {
-                                               if ( filename != NULL ) {
-                                                       // translation unit change, emit ending SO
-                                                       ObjectFile::Reader::Stab endFileStab;
-                                                       endFileStab.atom                = NULL;
-                                                       endFileStab.type                = N_SO;
-                                                       endFileStab.other               = 1;
-                                                       endFileStab.desc                = 0;
-                                                       endFileStab.value               = 0;
-                                                       endFileStab.string              = "";
-                                                       fStabs.push_back(endFileStab);
-                                               }
-                                               // new translation unit, emit start SO's
-                                               ObjectFile::Reader::Stab dirPathStab;
-                                               dirPathStab.atom                = NULL;
-                                               dirPathStab.type                = N_SO;
-                                               dirPathStab.other               = 0;
-                                               dirPathStab.desc                = 0;
-                                               dirPathStab.value               = 0;
-                                               dirPathStab.string              = newDirPath;
-                                               fStabs.push_back(dirPathStab);
-                                               ObjectFile::Reader::Stab fileStab;
-                                               fileStab.atom           = NULL;
-                                               fileStab.type           = N_SO;
-                                               fileStab.other          = 0;
-                                               fileStab.desc           = 0;
-                                               fileStab.value          = 0;
-                                               fileStab.string         = newFilename;
-                                               fStabs.push_back(fileStab);
-                                               // Synthesize OSO for start of file
-                                               ObjectFile::Reader::Stab objStab;
-                                               objStab.atom            = NULL;
-                                               objStab.type            = N_OSO;
-                                               objStab.other           = 0;
-                                               objStab.desc            = 1;
-                                               objStab.value           = reader->getModificationTime();
-                                               objStab.string          = assureFullPath(reader->getPath());
-                                               fStabs.push_back(objStab);
-                                               wroteStartSO = true;
-                                       }
-                                       filename = newFilename;
-                                       dirPath = newDirPath;
-                                       seenFiles.push_back(filename);
-                                       if ( atom->getSegment().isContentExecutable() && (strncmp(atom->getSectionName(), "__text", 6) == 0) ) {
-                                               // Synthesize BNSYM and start FUN stabs
-                                               ObjectFile::Reader::Stab beginSym;
-                                               beginSym.atom           = atom;
-                                               beginSym.type           = N_BNSYM;
-                                               beginSym.other          = 1;
-                                               beginSym.desc           = 0;
-                                               beginSym.value          = 0;
-                                               beginSym.string         = "";
-                                               fStabs.push_back(beginSym);
-                                               ObjectFile::Reader::Stab startFun;
-                                               startFun.atom           = atom;
-                                               startFun.type           = N_FUN;
-                                               startFun.other          = 1;
-                                               startFun.desc           = 0;
-                                               startFun.value          = 0;
-                                               startFun.string         = name;
-                                               fStabs.push_back(startFun);
-                                               // Synthesize any SOL stabs needed
-                                               std::vector<ObjectFile::LineInfo>* lineInfo = atom->getLineInfo();
-                                               if ( lineInfo != NULL ) {
-                                                       // might be nice to set the source file path to seenFiles so it does not show up in SOLs
-                                                       const char* curFile = NULL;
-                                                       for (std::vector<ObjectFile::LineInfo>::iterator it = lineInfo->begin(); it != lineInfo->end(); ++it) {
-                                                               if ( it->fileName != curFile ) {
-                                                                       bool alreadySeen = false;
-                                                                       for (std::vector<const char*>::iterator sit = seenFiles.begin(); sit != seenFiles.end(); ++sit) {
-                                                                               if ( strcmp(it->fileName, *sit) == 0 ) {
-                                                                                       alreadySeen = true;
-                                                                                       break;
-                                                                               }
-                                                                       }
-                                                                       if ( ! alreadySeen ) {
-                                                                               seenFiles.push_back(it->fileName);
-                                                                               ObjectFile::Reader::Stab sol;
-                                                                               sol.atom                = 0;
-                                                                               sol.type                = N_SOL;
-                                                                               sol.other               = 0;
-                                                                               sol.desc                = 0;
-                                                                               sol.value               = 0;
-                                                                               sol.string              = it->fileName;
-                                                                               fStabs.push_back(sol);
-                                                                       }
-                                                                       curFile = it->fileName;
-                                                               }
+public:
+       NoDebugNoteAtom(const std::map<class ObjectFile::Reader*, uint32_t>& readersWithDwarfOrdinals)
+                       : fReadersWithDwarfOrdinals(readersWithDwarfOrdinals) {}
+
+       bool operator()(const ObjectFile::Atom* atom) const {
+               if ( atom->getSymbolTableInclusion() == ObjectFile::Atom::kSymbolTableNotIn )
+                       return true;
+               if ( atom->getName() == NULL )
+                       return true;
+               if ( fReadersWithDwarfOrdinals.find(atom->getFile()) == fReadersWithDwarfOrdinals.end() )
+                       return true;
+               return false;
+       }
+
+private:
+       const std::map<class ObjectFile::Reader*, uint32_t>& fReadersWithDwarfOrdinals;
+};
+
+// used to sort atoms with debug notes
+class ReadersWithDwarfSorter
+{
+public:
+       ReadersWithDwarfSorter(const std::map<class ObjectFile::Reader*, uint32_t>& readersWithDwarfOrdinals,
+                                                  const std::map<const class ObjectFile::Atom*, uint32_t>& atomOrdinals)
+                       : fReadersWithDwarfOrdinals(readersWithDwarfOrdinals), fAtomOrdinals(atomOrdinals) {}
+
+       bool operator()(const ObjectFile::Atom* left, const ObjectFile::Atom* right) const
+       {
+               // first sort by reader
+               unsigned int leftReaderIndex  = fReadersWithDwarfOrdinals.find(left->getFile())->second;
+               unsigned int rightReaderIndex = fReadersWithDwarfOrdinals.find(right->getFile())->second;
+               if ( leftReaderIndex != rightReaderIndex )
+                       return (leftReaderIndex < rightReaderIndex);
+
+               // then sort by atom ordinal
+               unsigned int leftAtomIndex  = fAtomOrdinals.find(left)->second;
+               unsigned int rightAtomIndex = fAtomOrdinals.find(right)->second;
+               return leftAtomIndex < rightAtomIndex;
+       }
+
+private:
+       const std::map<class ObjectFile::Reader*, uint32_t>& fReadersWithDwarfOrdinals;
+       const std::map<const class ObjectFile::Atom*, uint32_t>& fAtomOrdinals;
+};
+
+
+
+
+
+void Linker::synthesizeDebugNotes(std::vector<class ObjectFile::Atom*>& allAtomsByReader)
+{
+       // synthesize "debug notes" and add them to master stabs vector
+       const char* dirPath = NULL;
+       const char* filename = NULL;
+       bool wroteStartSO = false;
+       bool useZeroOSOModTime = (getenv("RC_RELEASE") != NULL);
+       __gnu_cxx::hash_set<const char*, __gnu_cxx::hash<const char*>, CStringEquals>  seenFiles;
+       for (std::vector<ObjectFile::Atom*>::iterator it=allAtomsByReader.begin(); it != allAtomsByReader.end(); it++) {
+               ObjectFile::Atom* atom = *it;
+               const char* newDirPath;
+               const char* newFilename;
+               //fprintf(stderr, "debug note for %s\n", atom->getDisplayName());
+               if ( atom->getTranslationUnitSource(&newDirPath, &newFilename) ) {
+                       // need SO's whenever the translation unit source file changes
+                       if ( newFilename != filename ) {
+                               // gdb like directory SO's to end in '/', but dwarf DW_AT_comp_dir usually does not have trailing '/'
+                               if ( (newDirPath != NULL) && (strlen(newDirPath) > 1 ) && (newDirPath[strlen(newDirPath)-1] != '/') )
+                                       asprintf((char**)&newDirPath, "%s/", newDirPath);
+                               if ( filename != NULL ) {
+                                       // translation unit change, emit ending SO
+                                       ObjectFile::Reader::Stab endFileStab;
+                                       endFileStab.atom                = NULL;
+                                       endFileStab.type                = N_SO;
+                                       endFileStab.other               = 1;
+                                       endFileStab.desc                = 0;
+                                       endFileStab.value               = 0;
+                                       endFileStab.string              = "";
+                                       fStabs.push_back(endFileStab);
+                               }
+                               // new translation unit, emit start SO's
+                               ObjectFile::Reader::Stab dirPathStab;
+                               dirPathStab.atom                = NULL;
+                               dirPathStab.type                = N_SO;
+                               dirPathStab.other               = 0;
+                               dirPathStab.desc                = 0;
+                               dirPathStab.value               = 0;
+                               dirPathStab.string              = newDirPath;
+                               fStabs.push_back(dirPathStab);
+                               ObjectFile::Reader::Stab fileStab;
+                               fileStab.atom           = NULL;
+                               fileStab.type           = N_SO;
+                               fileStab.other          = 0;
+                               fileStab.desc           = 0;
+                               fileStab.value          = 0;
+                               fileStab.string         = newFilename;
+                               fStabs.push_back(fileStab);
+                               // Synthesize OSO for start of file
+                               ObjectFile::Reader::Stab objStab;
+                               objStab.atom            = NULL;
+                               objStab.type            = N_OSO;
+                               objStab.other           = 0;
+                               objStab.desc            = 1;
+                               objStab.value           = useZeroOSOModTime ? 0 : atom->getFile()->getModificationTime();
+                               objStab.string          = assureFullPath(atom->getFile()->getPath());
+                               fStabs.push_back(objStab);
+                               wroteStartSO = true;
+                               // add the source file path to seenFiles so it does not show up in SOLs
+                               seenFiles.insert(newFilename);
+                       }
+                       filename = newFilename;
+                       dirPath = newDirPath;
+                       if ( atom->getSegment().isContentExecutable() && (strncmp(atom->getSectionName(), "__text", 6) == 0) ) {
+                               // Synthesize BNSYM and start FUN stabs
+                               ObjectFile::Reader::Stab beginSym;
+                               beginSym.atom           = atom;
+                               beginSym.type           = N_BNSYM;
+                               beginSym.other          = 1;
+                               beginSym.desc           = 0;
+                               beginSym.value          = 0;
+                               beginSym.string         = "";
+                               fStabs.push_back(beginSym);
+                               ObjectFile::Reader::Stab startFun;
+                               startFun.atom           = atom;
+                               startFun.type           = N_FUN;
+                               startFun.other          = 1;
+                               startFun.desc           = 0;
+                               startFun.value          = 0;
+                               startFun.string         = atom->getName();
+                               fStabs.push_back(startFun);
+                               // Synthesize any SOL stabs needed
+                               std::vector<ObjectFile::LineInfo>* lineInfo = atom->getLineInfo();
+                               if ( lineInfo != NULL ) {
+                                       const char* curFile = NULL;
+                                       for (std::vector<ObjectFile::LineInfo>::iterator it = lineInfo->begin(); it != lineInfo->end(); ++it) {
+                                               if ( it->fileName != curFile ) {
+                                                       if ( seenFiles.count(it->fileName) == 0 ) {
+                                                               seenFiles.insert(it->fileName);
+                                                               ObjectFile::Reader::Stab sol;
+                                                               sol.atom                = 0;
+                                                               sol.type                = N_SOL;
+                                                               sol.other               = 0;
+                                                               sol.desc                = 0;
+                                                               sol.value               = 0;
+                                                               sol.string              = it->fileName;
+                                                               fStabs.push_back(sol);
                                                        }
+                                                       curFile = it->fileName;
                                                }
-                                               // Synthesize end FUN and ENSYM stabs
-                                               ObjectFile::Reader::Stab endFun;
-                                               endFun.atom                     = atom;
-                                               endFun.type                     = N_FUN;
-                                               endFun.other            = 0;
-                                               endFun.desc                     = 0;
-                                               endFun.value            = 0;
-                                               endFun.string           = "";
-                                               fStabs.push_back(endFun);
-                                               ObjectFile::Reader::Stab endSym;
-                                               endSym.atom                     = atom;
-                                               endSym.type                     = N_ENSYM;
-                                               endSym.other            = 1;
-                                               endSym.desc                     = 0;
-                                               endSym.value            = 0;
-                                               endSym.string           = "";
-                                               fStabs.push_back(endSym);
                                        }
-                                       else {
-                                               ObjectFile::Reader::Stab globalsStab;
-                                               if ( atom->getScope() == ObjectFile::Atom::scopeTranslationUnit ) {
-                                                       // Synthesize STSYM stab for statics
-                                                       const char* name = atom->getName();
-                                                       if ( name[0] == '_' ) {
-                                                               globalsStab.atom                = atom;
-                                                               globalsStab.type                = N_STSYM;
-                                                               globalsStab.other               = 1;
-                                                               globalsStab.desc                = 0;
-                                                               globalsStab.value               = 0;
-                                                               globalsStab.string              = name;
-                                                               fStabs.push_back(globalsStab);
-                                                       }
-                                               }
-                                               else {
-                                                       // Synthesize GSYM stab for other globals (but not .eh exception frame symbols)
-                                                       const char* name = atom->getName();
-                                                       if ( (name[0] == '_') && (strcmp(atom->getSectionName(), "__eh_frame") != 0) ) {
-                                                               globalsStab.atom                = atom;
-                                                               globalsStab.type                = N_GSYM;
-                                                               globalsStab.other               = 1;
-                                                               globalsStab.desc                = 0;
-                                                               globalsStab.value               = 0;
-                                                               globalsStab.string              = name;
-                                                               fStabs.push_back(globalsStab);
-                                                       }
-                                               }
+                               }
+                               // Synthesize end FUN and ENSYM stabs
+                               ObjectFile::Reader::Stab endFun;
+                               endFun.atom                     = atom;
+                               endFun.type                     = N_FUN;
+                               endFun.other            = 0;
+                               endFun.desc                     = 0;
+                               endFun.value            = 0;
+                               endFun.string           = "";
+                               fStabs.push_back(endFun);
+                               ObjectFile::Reader::Stab endSym;
+                               endSym.atom                     = atom;
+                               endSym.type                     = N_ENSYM;
+                               endSym.other            = 1;
+                               endSym.desc                     = 0;
+                               endSym.value            = 0;
+                               endSym.string           = "";
+                               fStabs.push_back(endSym);
+                       }
+                       else {
+                               ObjectFile::Reader::Stab globalsStab;
+                               if ( atom->getScope() == ObjectFile::Atom::scopeTranslationUnit ) {
+                                       // Synthesize STSYM stab for statics
+                                       const char* name = atom->getName();
+                                       if ( name[0] == '_' ) {
+                                               globalsStab.atom                = atom;
+                                               globalsStab.type                = N_STSYM;
+                                               globalsStab.other               = 1;
+                                               globalsStab.desc                = 0;
+                                               globalsStab.value               = 0;
+                                               globalsStab.string              = name;
+                                               fStabs.push_back(globalsStab);
+                                       }
+                               }
+                               else {
+                                       // Synthesize GSYM stab for other globals (but not .eh exception frame symbols)
+                                       const char* name = atom->getName();
+                                       if ( (name[0] == '_') && (strcmp(atom->getSectionName(), "__eh_frame") != 0) ) {
+                                               globalsStab.atom                = atom;
+                                               globalsStab.type                = N_GSYM;
+                                               globalsStab.other               = 1;
+                                               globalsStab.desc                = 0;
+                                               globalsStab.value               = 0;
+                                               globalsStab.string              = name;
+                                               fStabs.push_back(globalsStab);
                                        }
                                }
                        }
                }
        }
+
        if ( wroteStartSO ) {
                //  emit ending SO
                ObjectFile::Reader::Stab endFileStab;
@@ -1556,11 +2579,18 @@ void Linker::synthesizeStabs(ObjectFile::Reader* reader)
        }
 }
 
-void Linker::collectStabs()
+
+
+
+void Linker::collectDebugInfo()
 {
+       std::map<const class ObjectFile::Atom*, uint32_t>       atomOrdinals;
+       fStartDebugTime = mach_absolute_time();
        if ( fOptions.readerOptions().fDebugInfoStripping != ObjectFile::ReaderOptions::kDebugInfoNone ) {
-               fStabs.reserve(1024); // try to minimize re-allocations
-               // get stabs from each reader, in command line order
+
+               // determine mixture of stabs and dwarf
+               bool someStabs = false;
+               bool someDwarf = false;
                for (std::vector<class ObjectFile::Reader*>::iterator it=fReadersThatHaveSuppliedAtoms.begin();
                                it != fReadersThatHaveSuppliedAtoms.end();
                                it++) {
@@ -1568,17 +2598,16 @@ void Linker::collectStabs()
                        if ( reader != NULL ) {
                                switch ( reader->getDebugInfoKind() ) {
                                        case ObjectFile::Reader::kDebugInfoNone:
-                                               // do nothing
                                                break;
                                        case ObjectFile::Reader::kDebugInfoStabs:
-                                               collectStabs(reader);
+                                               someStabs = true;
                                                break;
                                        case ObjectFile::Reader::kDebugInfoDwarf:
-                                               synthesizeStabs(reader);
+                                               someDwarf = true;
                                                fCreateUUID = true;
                                                break;
                                    case ObjectFile::Reader::kDebugInfoStabsUUID:
-                                               collectStabs(reader);
+                                               someStabs = true;
                                                fCreateUUID = true;
                                                break;
                                        default:
@@ -1586,18 +2615,83 @@ void Linker::collectStabs()
                                }
                        }
                }
-               // remove stabs associated with atoms that won't be in output
-               std::set<class ObjectFile::Atom*>       allAtomsSet;
-               allAtomsSet.insert(fAllAtoms.begin(), fAllAtoms.end());
-               fStabs.erase(std::remove_if(fStabs.begin(), fStabs.end(), NotInSet(allAtomsSet)), fStabs.end());
+
+               if ( someDwarf || someStabs ) {
+                       // try to minimize re-allocations
+                       fStabs.reserve(1024);
+
+                       // make mapping from atoms to ordinal
+                       uint32_t ordinal = 1;
+                       for (std::vector<ObjectFile::Atom*>::iterator it=fAllAtoms.begin(); it != fAllAtoms.end(); it++) {
+                               atomOrdinals[*it] = ordinal++;
+                       }
+               }
+
+               // process all dwarf .o files as a batch
+               if ( someDwarf ) {
+                       // make mapping from readers with dwarf to ordinal
+                       std::map<class ObjectFile::Reader*, uint32_t>   readersWithDwarfOrdinals;
+                       uint32_t readerOrdinal = 1;
+                       for (std::vector<class ObjectFile::Reader*>::iterator it=fReadersThatHaveSuppliedAtoms.begin();
+                                       it != fReadersThatHaveSuppliedAtoms.end();
+                                       it++) {
+                               ObjectFile::Reader* reader = *it;
+                               if ( (reader != NULL) && (reader->getDebugInfoKind() == ObjectFile::Reader::kDebugInfoDwarf) ) {
+                                       readersWithDwarfOrdinals[reader] = readerOrdinal++;
+                               }
+                       }
+
+                       // make a vector of atoms
+                       std::vector<class ObjectFile::Atom*> allAtomsByReader(fAllAtoms.begin(), fAllAtoms.end());
+                       // remove those not from a reader that has dwarf
+                       allAtomsByReader.erase(std::remove_if(allAtomsByReader.begin(), allAtomsByReader.end(),
+                                                               NoDebugNoteAtom(readersWithDwarfOrdinals)), allAtomsByReader.end());
+                       // sort by reader then atom ordinal
+                       std::sort(allAtomsByReader.begin(), allAtomsByReader.end(), ReadersWithDwarfSorter(readersWithDwarfOrdinals, atomOrdinals));
+                       // add debug notes for each atom
+                       this->synthesizeDebugNotes(allAtomsByReader);
+               }
+
+               // process all stabs .o files one by one
+               if ( someStabs ) {
+                       // get stabs from each reader, in command line order
+                       for (std::vector<class ObjectFile::Reader*>::iterator it=fReadersThatHaveSuppliedAtoms.begin();
+                                       it != fReadersThatHaveSuppliedAtoms.end();
+                                       it++) {
+                               ObjectFile::Reader* reader = *it;
+                               if ( reader != NULL ) {
+                                       switch ( reader->getDebugInfoKind() ) {
+                                               case ObjectFile::Reader::kDebugInfoDwarf:
+                                               case ObjectFile::Reader::kDebugInfoNone:
+                                                       // do nothing
+                                                       break;
+                                               case ObjectFile::Reader::kDebugInfoStabs:
+                                               case ObjectFile::Reader::kDebugInfoStabsUUID:
+                                                       collectStabs(reader, atomOrdinals);
+                                                       break;
+                                               default:
+                                                       throw "Unhandled type of debug information";
+                                       }
+                               }
+                       }
+                       // remove stabs associated with atoms that won't be in output
+                       std::set<class ObjectFile::Atom*>       allAtomsSet;
+                       allAtomsSet.insert(fAllAtoms.begin(), fAllAtoms.end());
+                       fStabs.erase(std::remove_if(fStabs.begin(), fStabs.end(), NotInSet(allAtomsSet)), fStabs.end());
+               }
        }
 }
 
 void Linker::writeOutput()
 {
+       if ( fOptions.forceCpuSubtypeAll() )
+               fCurrentCpuConstraint = ObjectFile::Reader::kCpuAny;
+               
        fStartWriteTime = mach_absolute_time();
        // tell writer about each segment's atoms
-       fOutputFileSize = fOutputFile->write(fAllAtoms, fStabs, this->entryPoint(), this->dyldHelper(), (fCreateUUID && fOptions.emitUUID()));
+       fOutputFileSize = fOutputFile->write(fAllAtoms, fStabs, this->entryPoint(), this->dyldHelper(),
+                                                                                       fCreateUUID, fCanScatter, 
+                                                                                       fCurrentCpuConstraint, fBiggerThanTwoGigOutput);
 }
 
 ObjectFile::Reader* Linker::createReader(const Options::FileInfo& info)
@@ -1624,7 +2718,7 @@ ObjectFile::Reader* Linker::createReader(const Options::FileInfo& info)
                                uint32_t fileOffset = OSSwapBigToHostInt32(archs[i].offset);
                                len = OSSwapBigToHostInt32(archs[i].size);
                                // if requested architecture is page aligned within fat file, then remap just that portion of file
-                               if ( (fileOffset && 0x00000FFF) == 0 ) {
+                               if ( (fileOffset & 0x00000FFF) == 0 ) {
                                        // unmap whole file
                                        munmap((caddr_t)p, info.fileLen);
                                        // re-map just part we need
@@ -1644,51 +2738,167 @@ ObjectFile::Reader* Linker::createReader(const Options::FileInfo& info)
        switch (fArchitecture) {
                case CPU_TYPE_POWERPC:
                        if ( mach_o::relocatable::Reader<ppc>::validFile(p) )
-                               return this->addObject(mach_o::relocatable::Reader<ppc>::make(p, info.path, info.modTime, fOptions.readerOptions()), info, len);
-                       else if ( mach_o::dylib::Reader<ppc>::validFile(p) )
-                               return this->addDylib(mach_o::dylib::Reader<ppc>::make(p, len, info.path, fOptions.readerOptions()), info, len);
+                               return this->addObject(new mach_o::relocatable::Reader<ppc>::Reader(p, info.path, info.modTime, fOptions.readerOptions(), fNextInputOrdinal), info, len);
+                       else if ( mach_o::dylib::Reader<ppc>::validFile(p, info.options.fBundleLoader) )
+                               return this->addDylib(new mach_o::dylib::Reader<ppc>::Reader(p, len, info.path, info.options.fBundleLoader, fOptions.readerOptions(), fNextInputOrdinal), info, len);
                        else if ( mach_o::archive::Reader<ppc>::validFile(p, len) )
-                               return this->addArchive(mach_o::archive::Reader<ppc>::make(p, len, info.path, info.modTime, fOptions.readerOptions()), info, len);
+                               return this->addArchive(new mach_o::archive::Reader<ppc>::Reader(p, len, info.path, info.modTime, fOptions.readerOptions(), fNextInputOrdinal), info, len);
                        break;
                case CPU_TYPE_POWERPC64:
                        if ( mach_o::relocatable::Reader<ppc64>::validFile(p) )
-                               return this->addObject(mach_o::relocatable::Reader<ppc64>::make(p, info.path, info.modTime, fOptions.readerOptions()), info, len);
-                       else if ( mach_o::dylib::Reader<ppc64>::validFile(p) )
-                               return this->addDylib(mach_o::dylib::Reader<ppc64>::make(p, len, info.path, fOptions.readerOptions()), info, len);
+                               return this->addObject(new mach_o::relocatable::Reader<ppc64>::Reader(p, info.path, info.modTime, fOptions.readerOptions(), fNextInputOrdinal), info, len);
+                       else if ( mach_o::dylib::Reader<ppc64>::validFile(p, info.options.fBundleLoader) )
+                               return this->addDylib(new mach_o::dylib::Reader<ppc64>::Reader(p, len, info.path, info.options.fBundleLoader, fOptions.readerOptions(), fNextInputOrdinal), info, len);
                        else if ( mach_o::archive::Reader<ppc64>::validFile(p, len) )
-                               return this->addArchive(mach_o::archive::Reader<ppc64>::make(p, len, info.path, info.modTime, fOptions.readerOptions()), info, len);
+                               return this->addArchive(new mach_o::archive::Reader<ppc64>::Reader(p, len, info.path, info.modTime, fOptions.readerOptions(), fNextInputOrdinal), info, len);
                        break;
                case CPU_TYPE_I386:
                        if ( mach_o::relocatable::Reader<x86>::validFile(p) )
-                               return this->addObject(mach_o::relocatable::Reader<x86>::make(p, info.path, info.modTime, fOptions.readerOptions()), info, len);
-                       else if ( mach_o::dylib::Reader<x86>::validFile(p) )
-                               return this->addDylib(mach_o::dylib::Reader<x86>::make(p, len, info.path, fOptions.readerOptions()), info, len);
+                               return this->addObject(new mach_o::relocatable::Reader<x86>::Reader(p, info.path, info.modTime, fOptions.readerOptions(), fNextInputOrdinal), info, len);
+                       else if ( mach_o::dylib::Reader<x86>::validFile(p, info.options.fBundleLoader) )
+                               return this->addDylib(new mach_o::dylib::Reader<x86>::Reader(p, len, info.path, info.options.fBundleLoader, fOptions.readerOptions(), fNextInputOrdinal), info, len);
                        else if ( mach_o::archive::Reader<x86>::validFile(p, len) )
-                               return this->addArchive(mach_o::archive::Reader<x86>::make(p, len, info.path, info.modTime, fOptions.readerOptions()), info, len);
+                               return this->addArchive(new mach_o::archive::Reader<x86>::Reader(p, len, info.path, info.modTime, fOptions.readerOptions(), fNextInputOrdinal), info, len);
+                       break;
+               case CPU_TYPE_X86_64:
+                       if ( mach_o::relocatable::Reader<x86_64>::validFile(p) )
+                               return this->addObject(new mach_o::relocatable::Reader<x86_64>::Reader(p, info.path, info.modTime, fOptions.readerOptions(), fNextInputOrdinal), info, len);
+                       else if ( mach_o::dylib::Reader<x86_64>::validFile(p, info.options.fBundleLoader) )
+                               return this->addDylib(new mach_o::dylib::Reader<x86_64>::Reader(p, len, info.path, info.options.fBundleLoader, fOptions.readerOptions(), fNextInputOrdinal), info, len);
+                       else if ( mach_o::archive::Reader<x86_64>::validFile(p, len) )
+                               return this->addArchive(new mach_o::archive::Reader<x86_64>::Reader(p, len, info.path, info.modTime, fOptions.readerOptions(), fNextInputOrdinal), info, len);
                        break;
        }
 
+#if LLVM_SUPPORT
+       if ( LLVMReader::validFile(p, info.path, fArchitecture, fOptions) ) {
+               return this->addObject(LLVMReader::make(p, info.path, info.modTime, fOptions), info, len);
+       }
+#endif
        // error handling
        if ( ((fat_header*)p)->magic == OSSwapBigToHostInt32(FAT_MAGIC) ) {
-               const char* archName = "unknown";
-               switch (fArchitecture) {
-                       case CPU_TYPE_POWERPC:
-                               archName = "ppc";
-                               break;
-                       case CPU_TYPE_POWERPC64:
-                               archName = "ppc64";
-                               break;
-                       case CPU_TYPE_I386:
-                               archName = "i386";
-                               break;
-               }
-               throwf("missing required architecture %s in fat file", archName);
+               throwf("missing required architecture %s in file", fArchitectureName);
        }
        else {
                throw "file is not of required architecture";
        }
 }
 
+void Linker::logDylib(ObjectFile::Reader* reader, bool indirect)
+{
+       if ( fOptions.readerOptions().fTraceDylibs ) {
+               const char* fullPath = reader->getPath();
+               char realName[MAXPATHLEN];
+               if ( realpath(fullPath, realName) != NULL )
+                       fullPath = realName;
+               if ( indirect )
+                       logTraceInfo("[Logging for XBS] Used indirect dynamic library: %s\n", fullPath);
+               else
+                       logTraceInfo("[Logging for XBS] Used dynamic library: %s\n", fullPath);
+       }
+}
+
+
+
+ObjectFile::Reader* Linker::findDylib(const char* installPath, const char* fromPath)
+{
+       //fprintf(stderr, "findDylib(%s, %s)\n", installPath, fromPath);
+       InstallNameToReader::iterator pos = fDylibMap.find(installPath);
+       if ( pos != fDylibMap.end() ) {
+               return pos->second;
+       }
+       else {
+               // allow -dylib_path option to override indirect library to use
+               for (std::vector<Options::DylibOverride>::iterator dit = fOptions.dylibOverrides().begin(); dit != fOptions.dylibOverrides().end(); ++dit) {
+                       if ( strcmp(dit->installName,installPath) == 0 ) {\
+                               try {
+                                       Options::FileInfo info = fOptions.findFile(dit->useInstead);
+                                       ObjectFile::Reader* reader = this->createReader(info);
+                                       fDylibMap[strdup(installPath)] = reader;
+                                       this->logDylib(reader, true);
+                                       return reader;
+                               }
+                               catch (const char* msg) {
+                                       fprintf(stderr, "ld: warning ignoring -dylib_file option, %s\n", msg);
+                               }
+                       }
+               }
+               char newPath[MAXPATHLEN];
+               // handle @loader_path
+               if ( strncmp(installPath, "@loader_path/", 13) == 0 ) {
+                       strcpy(newPath, fromPath);
+                       char* addPoint = strrchr(newPath,'/');
+                       if ( addPoint != NULL )
+                               strcpy(&addPoint[1], &installPath[13]);
+                       else
+                               strcpy(newPath, &installPath[13]);
+                       installPath = newPath;
+               }
+               // note: @executable_path case is handled inside findFileUsingPaths()
+               // search for dylib using -F and -L paths
+               Options::FileInfo info = fOptions.findFileUsingPaths(installPath);
+               try {
+                       ObjectFile::Reader* reader = this->createReader(info);
+                       fDylibMap[strdup(installPath)] = reader;
+                       this->logDylib(reader, true);
+                       return reader;
+               }
+               catch (const char* msg) {
+                       throwf("in %s, %s", info.path, msg);
+               }
+       }
+}
+
+
+void Linker::processDylibs()
+{
+       fAllDirectDylibsLoaded = true;
+
+       // mark all dylibs initially specified as required and check if they can be used
+       for (InstallNameToReader::iterator it=fDylibMap.begin(); it != fDylibMap.end(); it++) {
+               it->second->setExplicitlyLinked();
+               this->checkDylibClientRestrictions(it->second);
+       }
+       
+       // keep processing dylibs until no more dylibs are added
+       unsigned long lastMapSize = 0;
+       while ( lastMapSize != fDylibMap.size() ) {
+               lastMapSize = fDylibMap.size();
+               // can't iterator fDylibMap while modifying it, so use temp buffer
+               std::vector<ObjectFile::Reader*> currentUnprocessedReaders;
+               for (InstallNameToReader::iterator it=fDylibMap.begin(); it != fDylibMap.end(); it++) {
+                       if ( fDylibsProcessed.count(it->second) == 0 )
+                               currentUnprocessedReaders.push_back(it->second);
+               }
+               for (std::vector<ObjectFile::Reader*>::iterator it=currentUnprocessedReaders.begin(); it != currentUnprocessedReaders.end(); it++) {
+                       fDylibsProcessed.insert(*it);
+                       (*it)->processIndirectLibraries(this);
+               }
+       }
+       
+       // go back over original dylibs and mark sub frameworks as re-exported
+       if ( fOptions.outputKind() == Options::kDynamicLibrary ) {
+               const char* myLeaf = strrchr(fOptions.installPath(), '/');
+               if ( myLeaf != NULL ) {
+                       for (std::vector<class ObjectFile::Reader*>::iterator it=fInputFiles.begin(); it != fInputFiles.end(); it++) {
+                               ObjectFile::Reader* reader = *it;
+                               const char* childParent = reader->parentUmbrella();
+                               if ( childParent != NULL ) {
+                                       if ( strcmp(childParent, &myLeaf[1]) == 0 ) {
+                                               // set re-export bit of info
+                                               std::map<ObjectFile::Reader*,DynamicLibraryOptions>::iterator pos = fDylibOptionsMap.find(reader);
+                                               if ( pos != fDylibOptionsMap.end() ) {
+                                                       pos->second.fReExport = true;
+                                               }
+                                       }
+                               }
+                       }
+               }
+       }
+       
+}
+
+       
 
 void Linker::createReaders()
 {
@@ -1703,7 +2913,7 @@ void Linker::createReaders()
                // ignore /usr/lib/dyld on command line in crt.o build
                if ( strcmp(entry.path, "/usr/lib/dyld") != 0 ) {
                        try {
-                               this->addInputFile(this->createReader(entry));
+                               this->addInputFile(this->createReader(entry), entry);
                        }
                        catch (const char* msg) {
                                if ( strstr(msg, "architecture") != NULL ) {
@@ -1711,7 +2921,7 @@ void Linker::createReaders()
                                                // ignore, because this is about an architecture not in use
                                        }
                                        else {
-                                               fprintf(stderr, "ld64 warning: in %s, %s\n", entry.path, msg);
+                                               fprintf(stderr, "ld: warning in %s, %s\n", entry.path, msg);
                                        }
                                }
                                else {
@@ -1721,115 +2931,16 @@ void Linker::createReaders()
                }
        }
 
-       // add first level of indirect dylibs
-       fDirectLibrariesComplete = true;
-       for (std::vector<ExecutableFile::DyLibUsed>::iterator it=fDynamicLibraries.begin(); it != fDynamicLibraries.end(); it++) {
-               this->addIndirectLibraries(it->reader);
-       }
-
-       // indirect handling depends on namespace
-       switch ( fOptions.nameSpace() ) {
-               case Options::kFlatNameSpace:
-               case Options::kForceFlatNameSpace:
-                       // with flat namespace, blindly load all indirect libraries
-                       // the indirect list will grow as indirect libraries are loaded
-                       for (std::list<IndirectLibrary>::iterator it=fIndirectDynamicLibraries.begin(); it != fIndirectDynamicLibraries.end(); it++) {
-                               try {
-                                       it->reader = this->createReader(fOptions.findFile(it->path));
-                                       it->reader->setSortOrder(fNextObjectFileOrder++);
-                               }
-                               catch (const char* msg) {
-                                       fprintf(stderr, "ld64 warning: indirect library %s could not be loaded: %s\n", it->path, msg);
-                               }
-                       }
-                       break;
-
-               case Options::kTwoLevelNameSpace:
-                       // with two-level namespace we only want to use indirect libraries that are re-exported through a library that is used
-                       {
-                               bool indirectAdded = true;
-                               while ( indirectAdded ) {
-                                       indirectAdded = false;
-                                       // instantiate a reader for each indirect library and try to find parent that re-exports it
-                                       for (std::list<IndirectLibrary>::iterator it=fIndirectDynamicLibraries.begin(); it != fIndirectDynamicLibraries.end(); it++) {
-                                               if ( it->reader == NULL ) {
-                                                       try {
-                                                               it->reader = this->createReader(fOptions.findFile(it->path));
-                                                               it->reader->setSortOrder(fNextObjectFileOrder++);
-                                                               indirectAdded = true;
-                                                       }
-                                                       catch (const char* msg) {
-                                                               fprintf(stderr, "ld64 warning: indirect library %s could not be loaded: %s\n", it->path, msg);
-                                                       }
-                                               }
-                                               // if an indirect library does not have an assigned parent, look for one
-                                               if ( (it->reader != NULL) && (it->reExportedViaDirectLibrary == NULL) ) {
-                                                       it->reExportedViaDirectLibrary = this->findDirectLibraryWhichReExports(*it);
-                                               }
-                                       }
-                               }
-                       }
-                       break;
-       }
-
-       // add relevant indirect libraries to the end of fDynamicLibraries
-       for (std::list<IndirectLibrary>::iterator it=fIndirectDynamicLibraries.begin(); it != fIndirectDynamicLibraries.end(); it++) {
-               if ( (it->reader != NULL) && (it->reExportedViaDirectLibrary != NULL) || (fOptions.nameSpace() != Options::kTwoLevelNameSpace) ) {
-                       ExecutableFile::DyLibUsed dylibInfo;
-                       dylibInfo.reader = it->reader;
-                       dylibInfo.options.fWeakImport = false;
-                       dylibInfo.options.fReExport = false;
-                       dylibInfo.options.fInstallPathOverride = NULL;
-                       dylibInfo.indirect = true;
-                       dylibInfo.directReader = it->reExportedViaDirectLibrary;
-                       fDynamicLibraries.push_back(dylibInfo);
-                       if ( fOptions.readerOptions().fTraceIndirectDylibs ) {
-                               const char* fullPath = it->reader->getPath();
-                               char realName[MAXPATHLEN];
-                               if ( realpath(fullPath, realName) != NULL )
-                                       fullPath = realName;
-                               logTraceInfo("[Logging for XBS] Used indirect dynamic library: %s\n", fullPath);
-                       }
-               }
-       }
-}
-
-
-ObjectFile::Reader* Linker::findDirectLibraryWhichReExports(IndirectLibrary& indirectLib)
-{
-       // ask each parent if they re-export this dylib
-       for (std::set<ObjectFile::Reader*>::iterator pit=indirectLib.parents.begin(); pit != indirectLib.parents.end(); pit++) {
-               if ( (*pit)->reExports(indirectLib.reader) ) {
-                       ObjectFile::Reader* lib = *pit;
-                       // first check if we found a direct library, if so return it
-                       for (std::vector<ExecutableFile::DyLibUsed>::iterator dit=fDynamicLibraries.begin(); dit != fDynamicLibraries.end(); dit++) {
-                               if ( dit->reader == lib && dit->indirect == false )
-                                       return lib;
-                       }
-                       // otherwise search indirects for parent and see how it is reexported
-                       for (std::list<IndirectLibrary>::iterator iit=fIndirectDynamicLibraries.begin(); iit != fIndirectDynamicLibraries.end(); iit++) {
-                               if ( iit->reader == lib ) {
-                                       ObjectFile::Reader* lib2 = this->findDirectLibraryWhichReExports(*iit);
-                                       if ( lib2 != NULL )
-                                               return lib2;
-                               }
-                       }
-               }
-       }
-       return NULL;
+       this->processDylibs();
 }
 
 
 
 ObjectFile::Reader* Linker::addArchive(ObjectFile::Reader* reader, const Options::FileInfo& info, uint64_t mappedLen)
 {
-       if (fOptions.readerOptions().fTraceArchives) {
-               const char* fullPath = reader->getPath();
-               char realName[MAXPATHLEN];
-               if ( realpath(fullPath, realName) != NULL )
-                       fullPath = realName;
-               logTraceInfo("[Logging for XBS] Used static archive: %s\n", fullPath);
-       }
+       fNextInputOrdinal += mappedLen;
+       // remember which readers are archives because they are logged differently
+       fArchiveReaders.insert(reader);
 
        // update stats
        fTotalArchiveSize += mappedLen;
@@ -1839,57 +2950,49 @@ ObjectFile::Reader* Linker::addArchive(ObjectFile::Reader* reader, const Options
 
 ObjectFile::Reader* Linker::addObject(ObjectFile::Reader* reader, const Options::FileInfo& info, uint64_t mappedLen)
 {
+       fNextInputOrdinal += mappedLen;
+       // any .o files that don't have MH_SUBSECTIONS_VIA_SYMBOLS, that means a generated .o file can't
+       if ( (fOptions.outputKind() == Options::kObjectFile) && !reader->canScatterAtoms() )
+               fCanScatter = false;
+
        // update stats
        fTotalObjectSize += mappedLen;
        ++fTotalObjectLoaded;
        return reader;
 }
 
-ObjectFile::Reader* Linker::addDylib(ObjectFile::Reader* reader, const Options::FileInfo& info, uint64_t mappedLen)
-{
-       if ( reader->getInstallPath() == NULL ) {
-               // this is a "blank" stub
-               // silently ignore it
-               return reader;
-       }
-
-       if ( fDirectLibrariesComplete ) {
-               this->addIndirectLibraries(reader);
-       }
-       else {
-               if ( fOptions.readerOptions().fTraceDylibs ) {
-                       const char* fullPath = reader->getPath();
-                       char realName[MAXPATHLEN];
-                       if ( realpath(fullPath, realName) != NULL )
-                               fullPath = realName;
-                       logTraceInfo("[Logging for XBS] Used dynamic library: %s\n", fullPath);
-               }
-               ExecutableFile::DyLibUsed dylibInfo;
-               dylibInfo.reader = reader;
-               dylibInfo.options = info.options;
-               dylibInfo.indirect = false;
-               dylibInfo.directReader = NULL;
-               fDynamicLibraries.push_back(dylibInfo);
-       
 
-               // Verify that a client is allowed to link to this dylib.  There are three cases.
-               bool okToLink = true;
-               const char* outputFilePath = fOptions.installPath();
-               const char* outputFilePathLastSlash = strrchr(outputFilePath, '/');
-               if ( reader->parentUmbrella() != NULL ) {
+void Linker::checkDylibClientRestrictions(ObjectFile::Reader* reader)
+{
+       // Check for any restrictions on who can link with this dylib  
+       const char* readerParentName = reader->parentUmbrella() ;
+       std::vector<const char*>* clients = reader->getAllowableClients();
+       if ( (readerParentName != NULL) || (clients != NULL) ) {
+               // only dylibs that are in an umbrella or have a client list need verification
+               const char* installName = fOptions.installPath();
+               const char* installNameLastSlash = strrchr(installName, '/');
+               bool isParent = false;
+               bool isSibling = false;
+               bool isAllowableClient = false;
+               // There are three cases:
+               if ( (readerParentName != NULL) && (installNameLastSlash != NULL) ) {
                        // case 1) The dylib has a parent umbrella, and we are creating the parent umbrella
-                       okToLink = ( (outputFilePathLastSlash != NULL) && (strcmp(&outputFilePathLastSlash[1], reader->parentUmbrella()) == 0) );
-               }
-               
-               if ( !okToLink && (reader->parentUmbrella() != NULL) ) {
+                       isParent = ( strcmp(&installNameLastSlash[1], readerParentName) == 0 );
+                       
+                       // hack to support umbrella variants that encode the variant name in the install name 
+                       // e.g. CoreServices_profile
+                       if ( !isParent ) {
+                               const char* underscore = strchr(&installNameLastSlash[1], '_');
+                               if ( underscore != NULL ) {
+                                       isParent = ( strncmp(&installNameLastSlash[1], readerParentName, underscore-installNameLastSlash-1) == 0 );
+                               }
+                       }
+                       
                        // case 2) The dylib has a parent umbrella, and we are creating a sibling with the same parent
-                       okToLink = ( (outputFilePathLastSlash != NULL) 
-                                       && (fOptions.umbrellaName() != NULL) 
-                                       && (strcmp(fOptions.umbrellaName(), reader->parentUmbrella()) == 0) );
+                       isSibling = ( (fOptions.umbrellaName() != NULL) && (strcmp(fOptions.umbrellaName(), readerParentName) == 0) );
                }
 
-               std::vector<const char*>* clients = reader->getAllowableClients();
-               if ( !okToLink && (clients != NULL) ) {
+               if ( !isParent && !isSibling && (clients != NULL) ) {
                        // case 3) the dylib has a list of allowable clients, and we are creating one of them
                        const char* clientName = fOptions.clientName();
                        int clientNameLen = 0;
@@ -1898,96 +3001,82 @@ ObjectFile::Reader* Linker::addDylib(ObjectFile::Reader* reader, const Options::
                                clientNameLen = strlen(clientName);
                        }
                        else {
-                               // infer client name from output path (e.g. xxx/libfoo.A.dylib --> foo, Bar.framework/Bar --> Bar)
-                               clientName = outputFilePath;
+                               // infer client name from output path (e.g. xxx/libfoo_variant.A.dylib --> foo, Bar.framework/Bar_variant --> Bar)
+                               clientName = installName;
+                               clientNameLen = strlen(clientName);
                                // starts after last slash
-                               if ( outputFilePathLastSlash != NULL )
-                                       clientName = &outputFilePathLastSlash[1];
+                               if ( installNameLastSlash != NULL )
+                                       clientName = &installNameLastSlash[1];
                                if ( strncmp(clientName, "lib", 3) == 0 )
                                        clientName = &clientName[3];
                                // up to first dot
                                const char* firstDot = strchr(clientName, '.');
-                               if ( firstDot == NULL )
-                                       clientNameLen = strlen(clientName);
-                               else
+                               if ( firstDot != NULL )
                                        clientNameLen = firstDot - clientName;
+                               // up to first underscore
+                               const char* firstUnderscore = strchr(clientName, '_');
+                               if ( (firstUnderscore != NULL) && ((firstUnderscore - clientName) < clientNameLen) )
+                                       clientNameLen = firstUnderscore - clientName;
                        }
-                       
+
                        // Use clientName to check if this dylib is able to link against the allowable clients.
                        for (std::vector<const char*>::iterator it = clients->begin(); it != clients->end(); it++) {
                                if ( strncmp(*it, clientName, clientNameLen) == 0 )
-                                       okToLink = true;
+                                       isAllowableClient = true;
                        }
                }
        
-               // error out if we are not allowed to link
-               if ( ! okToLink )
-                       //throwf("'%s' is a subframework. Link against the umbrella framework '%s.framework' instead.",
-                       fprintf(stderr, "'%s' is a subframework. Link against the umbrella framework '%s.framework' instead.",
-                                       reader->getPath(), reader->parentUmbrella());
-       }
-       
-       // update stats
-       ++fTotalDylibsLoaded;
-
-       return reader;
-}
-
-
-void Linker::addIndirectLibraries(ObjectFile::Reader* reader)
-{
-       std::vector<const char*>* dependentLibs = reader->getDependentLibraryPaths();
-       if ( dependentLibs != NULL ) {
-               for (std::vector<const char*>::iterator it=dependentLibs->begin(); it != dependentLibs->end(); it++) {
-                       if ( this->haveDirectLibrary(*it) ) {
-                               // do nothing, direct library already exists
-                       }
-                       else if ( this->haveIndirectLibrary(*it, reader) ) {
-                               // side effect of haveIndirectLibrary() added reader to parent list
+               if ( !isParent && !isSibling && !isAllowableClient ) {
+                       if ( readerParentName != NULL ) {
+                               throwf("cannot link directly with %s.  Link against the umbrella framework '%s.framework' instead.", 
+                                       reader->getPath(), readerParentName);
                        }
                        else {
-                               // add to list of indirect libraries
-                               IndirectLibrary indirectLib;
-                               indirectLib.path = *it;
-                               indirectLib.fileLen = 0;
-                               indirectLib.reader = NULL;
-                               indirectLib.parents.insert(reader);
-                               indirectLib.reExportedViaDirectLibrary = NULL;
-                               fIndirectDynamicLibraries.push_back(indirectLib);
-                               //fprintf(stderr, "add indirect library: %s\n", *it);
+                               throwf("cannot link directly with %s", reader->getPath());
                        }
                }
        }
+
+
 }
 
-bool Linker::haveIndirectLibrary(const char* path, ObjectFile::Reader* parentReader)
+ObjectFile::Reader* Linker::addDylib(ObjectFile::Reader* reader, const Options::FileInfo& info, uint64_t mappedLen)
 {
-       for (std::list<IndirectLibrary>::iterator it=fIndirectDynamicLibraries.begin(); it != fIndirectDynamicLibraries.end(); it++) {
-               if ( strcmp(path, it->path) == 0 ) {
-                       it->parents.insert(parentReader);
-                       return true;
+       fNextInputOrdinal += mappedLen;
+       if ( (reader->getInstallPath() == NULL) && !info.options.fBundleLoader ) {
+               // this is a "blank" stub
+               // silently ignore it
+               return reader;
+       }
+       // add to map of loaded dylibs
+       const char* installPath = reader->getInstallPath();
+       if ( installPath != NULL ) {
+               InstallNameToReader::iterator pos = fDylibMap.find(installPath);
+               if ( pos == fDylibMap.end() ) {
+                       fDylibMap[strdup(installPath)] = reader;
                }
-               if ( it->reader != NULL ) {
-                       const char* installPath = it->reader->getInstallPath();
-                       if ( (installPath != NULL) && (strcmp(path, installPath) == 0) )
-                               return true;
+               else {
+                       InstallNameToReader::iterator pos2 = fDylibMap.find(reader->getPath());
+                       if ( pos2 == fDylibMap.end() ) 
+                               fDylibMap[strdup(reader->getPath())] = reader;
+                       else
+                               fprintf(stderr, "ld: warning, duplicate dylib %s\n", reader->getPath());
                }
        }
-       return false;
-}
+       else if ( info.options.fBundleLoader )
+               fBundleLoaderReader = reader;
 
-bool Linker::haveDirectLibrary(const char* path)
-{
-       for (std::vector<ExecutableFile::DyLibUsed>::iterator it=fDynamicLibraries.begin(); it != fDynamicLibraries.end(); it++) {
-               if ( strcmp(path, it->reader->getPath()) == 0 )
-                       return true;
-               const char* installPath = it->reader->getInstallPath();
-               if ( (installPath != NULL) && (strcmp(path, installPath) == 0) )
-                       return true;
-       }
-       return false;
+       // log direct readers
+       if ( !fAllDirectDylibsLoaded ) 
+               this->logDylib(reader, false);
+
+       // update stats
+       ++fTotalDylibsLoaded;
+
+       return reader;
 }
 
+
 void Linker::logTraceInfo (const char* format, ...)
 {
        static int trace_file = -1;
@@ -2029,16 +3118,71 @@ void Linker::logTraceInfo (const char* format, ...)
 void Linker::createWriter()
 {
        fStartCreateWriterTime = mach_absolute_time();
+
+       // make a vector out of all required dylibs in fDylibMap
+       std::vector<ExecutableFile::DyLibUsed>  dynamicLibraries;
+       // need to preserve command line order 
+       for (std::vector<class ObjectFile::Reader*>::iterator it=fInputFiles.begin(); it != fInputFiles.end(); it++) {
+               ObjectFile::Reader* reader = *it;
+               for (InstallNameToReader::iterator mit=fDylibMap.begin(); mit != fDylibMap.end(); mit++) {
+                       if ( reader == mit->second ) {
+                               ExecutableFile::DyLibUsed dylibInfo;
+                               dylibInfo.reader = reader;
+                               dylibInfo.options = fDylibOptionsMap[reader];
+                               dynamicLibraries.push_back(dylibInfo);
+                               break;
+                       }
+               }
+       }
+       // then add any other dylibs
+       for (InstallNameToReader::iterator it=fDylibMap.begin(); it != fDylibMap.end(); it++) {
+               if ( it->second->implicitlyLinked()  ) {
+                       // if not already in dynamicLibraries
+                       bool alreadyInDynamicLibraries = false;
+                       for (std::vector<ExecutableFile::DyLibUsed>::iterator dit=dynamicLibraries.begin(); dit != dynamicLibraries.end(); dit++) {
+                               if ( dit->reader == it->second ) {
+                                       alreadyInDynamicLibraries = true;
+                                       break;
+                               }
+                       }
+                       if ( ! alreadyInDynamicLibraries ) {    
+                               ExecutableFile::DyLibUsed dylibInfo;
+                               dylibInfo.reader = it->second;
+                               std::map<ObjectFile::Reader*,DynamicLibraryOptions>::iterator pos = fDylibOptionsMap.find(it->second);
+                               if ( pos != fDylibOptionsMap.end() ) {
+                                       dylibInfo.options = pos->second;
+                               }
+                               else {
+                                       dylibInfo.options.fWeakImport = false;          // FIX ME
+                                       dylibInfo.options.fReExport = false;
+                                       dylibInfo.options.fBundleLoader = false;
+                               }
+                               dynamicLibraries.push_back(dylibInfo);
+                       }
+               }
+       }
+       if ( fBundleLoaderReader != NULL ) {
+               ExecutableFile::DyLibUsed dylibInfo;
+               dylibInfo.reader = fBundleLoaderReader;
+               dylibInfo.options.fWeakImport = false;          
+               dylibInfo.options.fReExport = false;
+               dylibInfo.options.fBundleLoader = true;
+               dynamicLibraries.push_back(dylibInfo);
+       }
+
        const char* path = fOptions.getOutputFilePath();
        switch ( fArchitecture ) {
                case CPU_TYPE_POWERPC:
-                       this->setOutputFile(new mach_o::executable::Writer<ppc>(path, fOptions, fDynamicLibraries));
+                       this->setOutputFile(new mach_o::executable::Writer<ppc>(path, fOptions, dynamicLibraries));
                        break;
                case CPU_TYPE_POWERPC64:
-                       this->setOutputFile(new mach_o::executable::Writer<ppc64>(path, fOptions, fDynamicLibraries));
+                       this->setOutputFile(new mach_o::executable::Writer<ppc64>(path, fOptions, dynamicLibraries));
                        break;
                case CPU_TYPE_I386:
-                       this->setOutputFile(new mach_o::executable::Writer<x86>(path, fOptions, fDynamicLibraries));
+                       this->setOutputFile(new mach_o::executable::Writer<x86>(path, fOptions, dynamicLibraries));
+                       break;
+               case CPU_TYPE_X86_64:
+                       this->setOutputFile(new mach_o::executable::Writer<x86_64>(path, fOptions, dynamicLibraries));
                        break;
                default:
                        throw "unknown architecture";
@@ -2062,32 +3206,43 @@ void Linker::SymbolTable::require(const char* name)
 }
 
 // convenience labels for 2-dimensional switch statement
-enum {
+enum AllDefinitionCombinations {
        kRegAndReg                              = (ObjectFile::Atom::kRegularDefinition << 3)   | ObjectFile::Atom::kRegularDefinition,
        kRegAndWeak                             = (ObjectFile::Atom::kRegularDefinition << 3)   | ObjectFile::Atom::kWeakDefinition,
        kRegAndTent                             = (ObjectFile::Atom::kRegularDefinition << 3)   | ObjectFile::Atom::kTentativeDefinition,
        kRegAndExtern                   = (ObjectFile::Atom::kRegularDefinition << 3)   | ObjectFile::Atom::kExternalDefinition,
        kRegAndExternWeak               = (ObjectFile::Atom::kRegularDefinition << 3)   | ObjectFile::Atom::kExternalWeakDefinition,
+       kRegAndAbsolute                 = (ObjectFile::Atom::kRegularDefinition << 3)   | ObjectFile::Atom::kAbsoluteSymbol,
        kWeakAndReg                             = (ObjectFile::Atom::kWeakDefinition << 3)              | ObjectFile::Atom::kRegularDefinition,
        kWeakAndWeak                    = (ObjectFile::Atom::kWeakDefinition << 3)              | ObjectFile::Atom::kWeakDefinition,
        kWeakAndTent                    = (ObjectFile::Atom::kWeakDefinition << 3)              | ObjectFile::Atom::kTentativeDefinition,
        kWeakAndExtern                  = (ObjectFile::Atom::kWeakDefinition << 3)              | ObjectFile::Atom::kExternalDefinition,
        kWeakAndExternWeak              = (ObjectFile::Atom::kWeakDefinition << 3)              | ObjectFile::Atom::kExternalWeakDefinition,
+       kWeakAndAbsolute                = (ObjectFile::Atom::kWeakDefinition << 3)              | ObjectFile::Atom::kAbsoluteSymbol,
        kTentAndReg                             = (ObjectFile::Atom::kTentativeDefinition << 3) | ObjectFile::Atom::kRegularDefinition,
        kTentAndWeak                    = (ObjectFile::Atom::kTentativeDefinition << 3) | ObjectFile::Atom::kWeakDefinition,
        kTentAndTent                    = (ObjectFile::Atom::kTentativeDefinition << 3) | ObjectFile::Atom::kTentativeDefinition,
        kTentAndExtern                  = (ObjectFile::Atom::kTentativeDefinition << 3) | ObjectFile::Atom::kExternalDefinition,
        kTentAndExternWeak              = (ObjectFile::Atom::kTentativeDefinition << 3) | ObjectFile::Atom::kExternalWeakDefinition,
+       kTentAndAbsolute                = (ObjectFile::Atom::kTentativeDefinition << 3) | ObjectFile::Atom::kAbsoluteSymbol,
        kExternAndReg                   = (ObjectFile::Atom::kExternalDefinition << 3)  | ObjectFile::Atom::kRegularDefinition,
        kExternAndWeak                  = (ObjectFile::Atom::kExternalDefinition << 3)  | ObjectFile::Atom::kWeakDefinition,
        kExternAndTent                  = (ObjectFile::Atom::kExternalDefinition << 3)  | ObjectFile::Atom::kTentativeDefinition,
        kExternAndExtern                = (ObjectFile::Atom::kExternalDefinition << 3)  | ObjectFile::Atom::kExternalDefinition,
        kExternAndExternWeak    = (ObjectFile::Atom::kExternalDefinition << 3)  | ObjectFile::Atom::kExternalWeakDefinition,
+       kExternAndAbsolute              = (ObjectFile::Atom::kExternalDefinition << 3)  | ObjectFile::Atom::kAbsoluteSymbol,
        kExternWeakAndReg               = (ObjectFile::Atom::kExternalWeakDefinition << 3) | ObjectFile::Atom::kRegularDefinition,
        kExternWeakAndWeak              = (ObjectFile::Atom::kExternalWeakDefinition << 3) | ObjectFile::Atom::kWeakDefinition,
        kExternWeakAndTent              = (ObjectFile::Atom::kExternalWeakDefinition << 3) | ObjectFile::Atom::kTentativeDefinition,
        kExternWeakAndExtern    = (ObjectFile::Atom::kExternalWeakDefinition << 3) | ObjectFile::Atom::kExternalDefinition,
-       kExternWeakAndExternWeak= (ObjectFile::Atom::kExternalWeakDefinition << 3) | ObjectFile::Atom::kExternalWeakDefinition
+       kExternWeakAndExternWeak= (ObjectFile::Atom::kExternalWeakDefinition << 3) | ObjectFile::Atom::kExternalWeakDefinition,
+       kExternWeakAndAbsolute  = (ObjectFile::Atom::kExternalWeakDefinition << 3) | ObjectFile::Atom::kAbsoluteSymbol,
+       kAbsoluteAndReg                 = (ObjectFile::Atom::kAbsoluteSymbol << 3)              | ObjectFile::Atom::kRegularDefinition,
+       kAbsoluteAndWeak                = (ObjectFile::Atom::kAbsoluteSymbol << 3)              | ObjectFile::Atom::kWeakDefinition,
+       kAbsoluteAndTent                = (ObjectFile::Atom::kAbsoluteSymbol << 3)              | ObjectFile::Atom::kTentativeDefinition,
+       kAbsoluteAndExtern              = (ObjectFile::Atom::kAbsoluteSymbol << 3)              | ObjectFile::Atom::kExternalDefinition,
+       kAbsoluteAndExternWeak  = (ObjectFile::Atom::kAbsoluteSymbol << 3)              | ObjectFile::Atom::kExternalWeakDefinition,
+       kAbsoluteAndAbsolute    = (ObjectFile::Atom::kAbsoluteSymbol << 3)              | ObjectFile::Atom::kAbsoluteSymbol
 };
 
 bool Linker::SymbolTable::add(ObjectFile::Atom& newAtom)
@@ -2101,7 +3256,7 @@ bool Linker::SymbolTable::add(ObjectFile::Atom& newAtom)
                existingAtom = pos->second;
        if ( existingAtom != NULL ) {
                // already have atom with same name in symbol table
-               switch ( (existingAtom->getDefinitionKind() << 3) | newAtom.getDefinitionKind() ) {
+               switch ( (AllDefinitionCombinations)((existingAtom->getDefinitionKind() << 3) | newAtom.getDefinitionKind()) ) {
                        case kRegAndReg:
                                throwf("duplicate symbol %s in %s and %s\n", name, newAtom.getFile()->getPath(), existingAtom->getFile()->getPath());
                        case kRegAndWeak:
@@ -2111,6 +3266,12 @@ bool Linker::SymbolTable::add(ObjectFile::Atom& newAtom)
                        case kRegAndTent:
                                // ignore new tentative atom, because we already have a regular one
                                useNew = false;
+                               if ( newAtom.getSize() > existingAtom->getSize() ) {
+                                       fprintf(stderr, "ld: warning for symbol %s tentative definition of size %llu from %s is "
+                                                                       "is smaller than the real definition of size %llu from %s\n",
+                                                                       newAtom.getDisplayName(), newAtom.getSize(), newAtom.getFile()->getPath(),
+                                                                       existingAtom->getSize(), existingAtom->getFile()->getPath());
+                               }
                                break;
                        case kRegAndExtern:
                                // ignore external atom, because we already have a one
@@ -2120,13 +3281,16 @@ bool Linker::SymbolTable::add(ObjectFile::Atom& newAtom)
                                // ignore external atom, because we already have a one
                                useNew = false;
                                break;
+                       case kRegAndAbsolute:
+                               throwf("duplicate symbol %s in %s and %s\n", name, newAtom.getFile()->getPath(), existingAtom->getFile()->getPath());
+                               break;
                        case kWeakAndReg:
                                // replace existing weak atom with regular one
                                break;
                        case kWeakAndWeak:
                                // have another weak atom, use whichever has largest alignment requirement
                                // because codegen of some client may require alignment
-                               useNew = ( newAtom.getAlignment() > existingAtom->getAlignment() );
+                               useNew = ( newAtom.getAlignment().trailingZeros() > existingAtom->getAlignment().trailingZeros() );
                                break;
                        case kWeakAndTent:
                                // replace existing weak atom with tentative one ???
@@ -2139,8 +3303,17 @@ bool Linker::SymbolTable::add(ObjectFile::Atom& newAtom)
                                // keep weak atom, at runtime external one may override
                                useNew = false;
                                break;
+                       case kWeakAndAbsolute:
+                               // replace existing weak atom with absolute one
+                               break;
                        case kTentAndReg:
                                // replace existing tentative atom with regular one
+                               if ( newAtom.getSize() < existingAtom->getSize() ) {
+                                       fprintf(stderr, "ld: warning for symbol %s tentative definition of size %llu from %s is "
+                                                                       "being replaced by a real definition of size %llu from %s\n",
+                                                                       newAtom.getDisplayName(), existingAtom->getSize(), existingAtom->getFile()->getPath(),
+                                                                       newAtom.getSize(), newAtom.getFile()->getPath());
+                               }
                                break;
                        case kTentAndWeak:
                                // replace existing tentative atom with weak one ???
@@ -2149,6 +3322,10 @@ bool Linker::SymbolTable::add(ObjectFile::Atom& newAtom)
                                // use largest
                                if ( newAtom.getSize() < existingAtom->getSize() ) {
                                        useNew = false;
+                               } 
+                               else {
+                                       if ( newAtom.getAlignment().trailingZeros() < existingAtom->getAlignment().trailingZeros() )
+                                               fprintf(stderr, "ld: warning alignment lost in merging tentative definition %s\n", newAtom.getDisplayName());
                                }
                                break;
                        case kTentAndExtern:
@@ -2157,13 +3334,13 @@ bool Linker::SymbolTable::add(ObjectFile::Atom& newAtom)
                                switch ( fOwner.fOptions.commonsMode() ) {
                                        case Options::kCommonsIgnoreDylibs:
                                                if ( fOwner.fOptions.warnCommons() )
-                                                       fprintf(stderr, "ld64: using common symbol %s from %s and ignoring defintion from dylib %s\n",
+                                                       fprintf(stderr, "ld: using common symbol %s from %s and ignoring defintion from dylib %s\n",
                                                                        existingAtom->getName(), existingAtom->getFile()->getPath(), newAtom.getFile()->getPath());
                                                useNew = false;
                                                break;
                                        case Options::kCommonsOverriddenByDylibs:
                                                if ( fOwner.fOptions.warnCommons() )
-                                                       fprintf(stderr, "ld64: replacing common symbol %s from %s with true definition from dylib %s\n",
+                                                       fprintf(stderr, "ld: replacing common symbol %s from %s with true definition from dylib %s\n",
                                                                        existingAtom->getName(), existingAtom->getFile()->getPath(), newAtom.getFile()->getPath());
                                                break;
                                        case Options::kCommonsConflictsDylibsError:
@@ -2171,6 +3348,9 @@ bool Linker::SymbolTable::add(ObjectFile::Atom& newAtom)
                                                                existingAtom->getName(), existingAtom->getFile()->getPath(), newAtom.getFile()->getPath());
                                }
                                break;
+                       case kTentAndAbsolute:
+                               // replace tentative with absolute (can't size check because absolutes have no size)
+                               break;
                        case kExternAndReg:
                                // replace external atom with regular one
                                break;
@@ -2182,12 +3362,12 @@ bool Linker::SymbolTable::add(ObjectFile::Atom& newAtom)
                                switch ( fOwner.fOptions.commonsMode() ) {
                                        case Options::kCommonsIgnoreDylibs:
                                                if ( fOwner.fOptions.warnCommons() )
-                                                       fprintf(stderr, "ld64: using common symbol %s from %s and ignoring defintion from dylib %s\n",
+                                                       fprintf(stderr, "ld: using common symbol %s from %s and ignoring defintion from dylib %s\n",
                                                                        newAtom.getName(), newAtom.getFile()->getPath(), existingAtom->getFile()->getPath());
                                                break;
                                        case Options::kCommonsOverriddenByDylibs:
                                                if ( fOwner.fOptions.warnCommons() )
-                                                       fprintf(stderr, "ld64: replacing defintion of %s from dylib %s with common symbol from %s\n",
+                                                       fprintf(stderr, "ld: replacing defintion of %s from dylib %s with common symbol from %s\n",
                                                                        newAtom.getName(), existingAtom->getFile()->getPath(), newAtom.getFile()->getPath());
                                                useNew = false;
                                                break;
@@ -2202,6 +3382,9 @@ bool Linker::SymbolTable::add(ObjectFile::Atom& newAtom)
                                // keep strong dylib atom, ignore weak one
                                useNew = false;
                                break;
+                       case kExternAndAbsolute:
+                               // replace external atom with absolute one
+                               break;
                        case kExternWeakAndReg:
                                // replace existing weak external with regular
                                break;
@@ -2213,12 +3396,12 @@ bool Linker::SymbolTable::add(ObjectFile::Atom& newAtom)
                                switch ( fOwner.fOptions.commonsMode() ) {
                                        case Options::kCommonsIgnoreDylibs:
                                                if ( fOwner.fOptions.warnCommons() )
-                                                       fprintf(stderr, "ld64: using common symbol %s from %s and ignoring defintion from dylib %s\n",
+                                                       fprintf(stderr, "ld: using common symbol %s from %s and ignoring defintion from dylib %s\n",
                                                                        newAtom.getName(), newAtom.getFile()->getPath(), existingAtom->getFile()->getPath());
                                                break;
                                        case Options::kCommonsOverriddenByDylibs:
                                                if ( fOwner.fOptions.warnCommons() )
-                                                       fprintf(stderr, "ld64: replacing defintion of %s from dylib %s with common symbol from %s\n",
+                                                       fprintf(stderr, "ld: replacing defintion of %s from dylib %s with common symbol from %s\n",
                                                                        newAtom.getName(), existingAtom->getFile()->getPath(), newAtom.getFile()->getPath());
                                                useNew = false;
                                                break;
@@ -2234,8 +3417,36 @@ bool Linker::SymbolTable::add(ObjectFile::Atom& newAtom)
                                // keep existing external weak
                                useNew = false;
                                break;
+                       case kExternWeakAndAbsolute:
+                               // replace existing weak external with absolute
+                               break;
+                       case kAbsoluteAndReg:
+                               throwf("duplicate symbol %s in %s and %s\n", name, newAtom.getFile()->getPath(), existingAtom->getFile()->getPath());
+                       case kAbsoluteAndWeak:
+                               // ignore new weak atom, because we already have a non-weak one
+                               useNew = false;
+                               break;
+                       case kAbsoluteAndTent:
+                               // ignore new tentative atom, because we already have a regular one
+                               useNew = false;
+                               break;
+                       case kAbsoluteAndExtern:
+                               // ignore external atom, because we already have a one
+                               useNew = false;
+                               break;
+                       case kAbsoluteAndExternWeak:
+                               // ignore external atom, because we already have a one
+                               useNew = false;
+                               break;
+                       case kAbsoluteAndAbsolute:
+                               throwf("duplicate symbol %s in %s and %s\n", name, newAtom.getFile()->getPath(), existingAtom->getFile()->getPath());
+                               break;
                }
        }
+       if ( (existingAtom != NULL) && (newAtom.getScope() != existingAtom->getScope()) ) {
+               fprintf(stderr, "ld: warning %s has different visibility (%d) in %s and (%d) in %s\n", 
+                       newAtom.getDisplayName(), newAtom.getScope(), newAtom.getFile()->getPath(), existingAtom->getScope(), existingAtom->getFile()->getPath());
+       }
        if ( useNew ) {
                fTable[name] = &newAtom;
                if ( existingAtom != NULL )
@@ -2271,31 +3482,70 @@ void Linker::SymbolTable::getNeededNames(bool andWeakDefintions, std::vector<con
 
 
 
-bool Linker::AtomSorter::operator()(ObjectFile::Atom* left, ObjectFile::Atom* right)
+bool Linker::AtomSorter::operator()(const ObjectFile::Atom* left, const ObjectFile::Atom* right)
 {
+       if ( left == right )
+               return false;
+
        // first sort by section order (which is already sorted by segment)
        unsigned int leftSectionIndex  =  left->getSection()->getIndex();
        unsigned int rightSectionIndex = right->getSection()->getIndex();
        if ( leftSectionIndex != rightSectionIndex)
                return (leftSectionIndex < rightSectionIndex);
 
-       // then sort by .o file order
-       ObjectFile::Reader* leftReader = left->getFile();
-       ObjectFile::Reader* rightReader = right->getFile();
-       if ( leftReader !=  rightReader )
-               return leftReader->getSortOrder() < rightReader->getSortOrder();
-
-       // lastly sort by atom within a .o file
-       return left->getSortOrder() < right->getSortOrder();
+       // if a -order_file is specified, then sorting is altered to sort those symbols first
+       if ( fOverriddenOrdinalMap != NULL ) {
+               std::map<const ObjectFile::Atom*, uint32_t>::iterator leftPos  = fOverriddenOrdinalMap->find(left);
+               std::map<const ObjectFile::Atom*, uint32_t>::iterator rightPos = fOverriddenOrdinalMap->find(right);
+               std::map<const ObjectFile::Atom*, uint32_t>::iterator end = fOverriddenOrdinalMap->end();
+               if ( leftPos != end ) {
+                       if ( rightPos != end ) {
+                               // both left and right are overridden, so compare overridden ordinals
+                               return leftPos->second < rightPos->second;
+                       }
+                       else {
+                               // left is overridden and right is not, so left < right
+                               return true;
+                       }
+               }
+               else {
+                       if ( rightPos != end ) {
+                               // right is overridden and left is not, so right < left
+                               return false;
+                       }
+                       else {
+                               // neither are overridden, do default sort
+                               // fall into default sorting below
+                       }
+               }
+       }
+       
+       // the __common section can have real or tentative definitions
+       // we want the real ones to sort before tentative ones
+       bool leftIsTent  =  (left->getDefinitionKind() == ObjectFile::Atom::kTentativeDefinition);
+       bool rightIsTent =  (right->getDefinitionKind() == ObjectFile::Atom::kTentativeDefinition);
+       if ( leftIsTent != rightIsTent )
+               return rightIsTent; 
+       
+       // lastly sort by atom ordinal.  this is already sorted by .o order
+       return left->getOrdinal() < right->getOrdinal();
 }
 
 
 int main(int argc, const char* argv[])
 {
+       const char* archName = NULL;
+       bool showArch = false;
+       bool archInferred = false;
        try {
                // create linker object given command line arguments
                Linker ld(argc, argv);
 
+               // save error message prefix
+               archName = ld.architectureName();
+               archInferred = ld.isInferredArchitecture();
+               showArch = ld.showArchitectureInErrors();
+
                // open all input files
                ld.createReaders();
 
@@ -2306,10 +3556,14 @@ int main(int argc, const char* argv[])
                ld.link();
        }
        catch (const char* msg) {
-               fprintf(stderr, "ld64 failed: %s\n", msg);
+               if ( archInferred )
+                       fprintf(stderr, "ld: %s for inferred architecture %s\n", msg, archName);
+               else if ( showArch )
+                       fprintf(stderr, "ld: %s for architecture %s\n", msg, archName);
+               else
+                       fprintf(stderr, "ld: %s\n", msg);
                return 1;
        }
 
-
        return 0;
 }