void ImageLoader::recursiveLoadLibraries(const LinkContext& context, bool preflightOnly, const RPathChain& loaderRPaths)
{
if ( fState < dyld_image_state_dependents_mapped ) {
// break cycles
fState = dyld_image_state_dependents_mapped;
// get list of libraries this image needs
// 获取image需要的所有的lib的信息
DependentLibraryInfo libraryInfos[fLibraryCount];
this->doGetDependentLibraries(libraryInfos);
// get list of rpaths that this image adds
std::vector<const char*> rpathsFromThisImage;
this->getRPaths(context, rpathsFromThisImage);
const RPathChain thisRPaths(&loaderRPaths, &rpathsFromThisImage);
// try to load each
bool canUsePrelinkingInfo = true;
for(unsigned int i=0; i < fLibraryCount; ++i){
ImageLoader* dependentLib;
bool depLibReExported = false;
bool depLibReRequired = false;
bool depLibCheckSumsMatch = false;
DependentLibraryInfo& requiredLibInfo = libraryInfos[i];
#if DYLD_SHARED_CACHE_SUPPORT
if ( preflightOnly && context.inSharedCache(requiredLibInfo.name) ) {
//如果存在于share_cache之中的lib不需要再lode了，因为在shared cache中的lib不会被卸载
// <rdar://problem/5910137> dlopen_preflight() on image in shared cache leaves it loaded but not objc initialized
// in preflight mode, don't even load dylib that are in the shared cache because they will never be unloaded
setLibImage(i, NULL, false, false);
continue;
}
#endif
try {
dependentLib = context.loadLibrary(requiredLibInfo.name, true, this->getPath(), &thisRPaths);
//static ImageLoader* libraryLocator(const char* libraryName, bool search, const char* origin, const ImageLoader::RPathChain* rpaths)
if ( dependentLib == this ) {
// 循环引用的检测
// found circular reference, perhaps DYLD_LIBARY_PATH is causing this rdar://problem/3684168
dependentLib = context.loadLibrary(requiredLibInfo.name, false, NULL, NULL);
if ( dependentLib != this )
dyld::warn("DYLD_ setting caused circular dependency in %s\n", this->getPath());
}
if ( fNeverUnload )
dependentLib->setNeverUnload();
if ( requiredLibInfo.upward ) {
}
else {
dependentLib->fIsReferencedDownward = true;
}
LibraryInfo actualInfo = dependentLib->doGetLibraryInfo();
depLibReRequired = requiredLibInfo.required;
depLibCheckSumsMatch = ( actualInfo.checksum == requiredLibInfo.info.checksum );
//检查checksum是否一致
depLibReExported = requiredLibInfo.reExported;
if ( ! depLibReExported ) {
// for pre-10.5 binaries that did not use LC_REEXPORT_DYLIB
// 10.5之前的程序没有LC_REXPORT_DYLIB字段，使用这种方法检测
depLibReExported = dependentLib->isSubframeworkOf(context, this) || this->hasSubLibrary(context, dependentLib);
}
// check found library version is compatible
// <rdar://problem/89200806> 0xFFFFFFFF is wildcard that matches any version
if ( (requiredLibInfo.info.minVersion != 0xFFFFFFFF) && (actualInfo.minVersion < requiredLibInfo.info.minVersion) ) {
// record values for possible use by CrashReporter or Finder
// 如果依赖库的版本过低就抛出异常
dyld::throwf("Incompatible library version: %s requires version %d.%d.%d or later, but %s provides version %d.%d.%d",
this->getShortName(), requiredLibInfo.info.minVersion >> 16, (requiredLibInfo.info.minVersion >> 8) & 0xff, requiredLibInfo.info.minVersion & 0xff,
dependentLib->getShortName(), actualInfo.minVersion >> 16, (actualInfo.minVersion >> 8) & 0xff, actualInfo.minVersion & 0xff);
}
// prebinding for this image disabled if any dependent library changed
if ( !depLibCheckSumsMatch )
canUsePrelinkingInfo = false;
// prebinding for this image disabled unless both this and dependent are in the shared cache
if ( !dependentLib->inSharedCache() || !this->inSharedCache() )
//检测share_cache中是否存在需要的lib
canUsePrelinkingInfo = false;
//if ( context.verbosePrebinding ) {
// if ( !requiredLib.checksumMatches )
// fprintf(stderr, "dyld: checksum mismatch, (%u v %u) for %s referencing %s\n",
// requiredLibInfo.info.checksum, actualInfo.checksum, this->getPath(), dependentLib->getPath());
// if ( dependentLib->getSlide() != 0 )
// fprintf(stderr, "dyld: dependent library slid for %s referencing %s\n", this->getPath(), dependentLib->getPath());
//}
}
catch (const char* msg) {
