src/ld/passes/dylibs.cpp

   1 /* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
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  24
  25
  26 #include <stdint.h>
  27 #include <math.h>
  28 #include <unistd.h>
  29 #include <dlfcn.h>
  30 #include <mach/machine.h>
  31
  32 #include <vector>
  33
  34 #include "ld.hpp"
  35 #include "dylibs.h"
  36
  37 namespace ld {
  38 namespace passes {
  39 namespace dylibs {
  40
  41
  42 class WillBeUsed
  43 {
  44 public:
  45         bool operator()(ld::dylib::File* dylib) const {
  46                 return dylib->willRemoved();
  47         }
  48 };
  49
  50
  51 void doPass(const Options& opts, ld::Internal& state)
  52 {
  53 //      const bool log = false;
  54
  55         // only optimize dylibs in final linked images
  56         if ( opts.outputKind() == Options::kObjectFile )
  57                 return;
  58
  59         // clear "willRemoved" bit on all dylibs
  60         for (std::vector<ld::dylib::File*>::iterator it = state.dylibs.begin(); it != state.dylibs.end(); ++it) {
  61                 ld::dylib::File* aDylib = *it;
  62                 aDylib->setWillBeRemoved(false);
  63         }
  64         for (std::vector<ld::dylib::File*>::iterator it = state.dylibs.begin(); it != state.dylibs.end(); ++it) {
  65                 ld::dylib::File* aDylib = *it;
  66                 // set "willRemoved" bit on implicit dylibs that did not provide any exports
  67                 if ( aDylib->implicitlyLinked() && !aDylib->explicitlyLinked() && !aDylib->providedExportAtom() )
  68                         aDylib->setWillBeRemoved(true);
  69                 // set "willRemoved" bit on dead strippable explicit dylibs that did not provide any exports
  70                 if ( aDylib->explicitlyLinked() && aDylib->deadStrippable() && !aDylib->providedExportAtom() )
  71                         aDylib->setWillBeRemoved(true);
  72                 // set "willRemoved" bit on any unused explicit when -dead_strip_dylibs is used
  73                 if ( opts.deadStripDylibs() && !aDylib->providedExportAtom() )
  74                         aDylib->setWillBeRemoved(true);
  75         }
  76         // remove unused dylibs
  77         state.dylibs.erase(std::remove_if(state.dylibs.begin(), state.dylibs.end(), WillBeUsed()), state.dylibs.end());
  78
  79
  80         // <rdar://problem/9441273> automatically weak-import dylibs when all symbols from it are weak-imported
  81         for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
  82                 ld::Internal::FinalSection* sect = *sit;
  83                 for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
  84                         const ld::Atom* atom = *ait;
  85                         const ld::Atom* target = NULL;
  86                         bool targetIsWeakImport = false;
  87                         for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
  88                                 if ( fit->firstInCluster() )
  89                                         target = NULL;
  90                                 switch ( fit->binding ) {
  91                                         case ld::Fixup::bindingsIndirectlyBound:
  92                                                 target = state.indirectBindingTable[fit->u.bindingIndex];
  93                                                 targetIsWeakImport = fit->weakImport;
  94                                                 break;
  95                                         case ld::Fixup::bindingDirectlyBound:
  96                                                 target = fit->u.target;
  97                                                 targetIsWeakImport = fit->weakImport;
  98                                                 break;
  99                     default:
 100                         break;
 101                                 }
 102                                 if ( (target != NULL) && (target->definition() == ld::Atom::definitionProxy) ) {
 103                                         ld::Atom::WeakImportState curWI = target->weakImportState();
 104                                         if ( curWI == ld::Atom::weakImportUnset ) {
 105                                                 // first use of this proxy, set weak-import based on this usage
 106                                                 (const_cast<ld::Atom*>(target))->setWeakImportState(targetIsWeakImport);
 107                                         }
 108                                         else {
 109                                                 // proxy already has weak-importness set, check for weakness mismatch
 110                                                 bool curIsWeakImport = (curWI == ld::Atom::weakImportTrue);
 111                                                 if ( curIsWeakImport != targetIsWeakImport ) {
 112                                                         // found mismatch
 113                                                         switch ( opts.weakReferenceMismatchTreatment() ) {
 114                                                                 case Options::kWeakReferenceMismatchError:
 115                                                                         throwf("mismatching weak references for symbol: %s", target->name());
 116                                                                 case Options::kWeakReferenceMismatchWeak:
 117                                                                         (const_cast<ld::Atom*>(target))->setWeakImportState(true);
 118                                                                         break;
 119                                                                 case Options::kWeakReferenceMismatchNonWeak:
 120                                                                         (const_cast<ld::Atom*>(target))->setWeakImportState(false);
 121                                                                         break;
 122                                                         }
 123                                                 }
 124                                         }
 125                                 }
 126                         }
 127                 }
 128         }
 129
 130 }
 131
 132
 133 } // namespace dylibs
 134 } // namespace passes
 135 } // namespace ld