dylibs.cpp   [plain text]

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#include <stdint.h>
#include <math.h>
#include <unistd.h>
#include <dlfcn.h>
#include <mach/machine.h>

#include <vector>

#include "ld.hpp"
#include "dylibs.h"

namespace ld {
namespace passes {
namespace dylibs {


class WillBeUsed
{
public:
	bool operator()(ld::dylib::File* dylib) const {
		return dylib->willRemoved();
	}
};


void doPass(const Options& opts, ld::Internal& state)
{
//	const bool log = false;
	
	// only optimize dylibs in final linked images
	if ( opts.outputKind() == Options::kObjectFile )
		return;

	// clear "willRemoved" bit on all dylibs
	for (std::vector<ld::dylib::File*>::iterator it = state.dylibs.begin(); it != state.dylibs.end(); ++it) {
		ld::dylib::File* aDylib = *it;
		aDylib->setWillBeRemoved(false);
	}
	for (std::vector<ld::dylib::File*>::iterator it = state.dylibs.begin(); it != state.dylibs.end(); ++it) {
		ld::dylib::File* aDylib = *it;
		// set "willRemoved" bit on implicit dylibs that did not provide any exports
		if ( aDylib->implicitlyLinked() && !aDylib->explicitlyLinked() && !aDylib->providedExportAtom() )
			aDylib->setWillBeRemoved(true);
		// set "willRemoved" bit on dead strippable explicit dylibs that did not provide any exports
		if ( aDylib->explicitlyLinked() && aDylib->deadStrippable() && !aDylib->providedExportAtom() )
			aDylib->setWillBeRemoved(true);
		// set "willRemoved" bit on any unused explicit when -dead_strip_dylibs is used
		if ( opts.deadStripDylibs() && !aDylib->providedExportAtom() )
			aDylib->setWillBeRemoved(true);
	}	
	// remove unused dylibs
	state.dylibs.erase(std::remove_if(state.dylibs.begin(), state.dylibs.end(), WillBeUsed()), state.dylibs.end());
	
	
	// <rdar://problem/9441273> automatically weak-import dylibs when all symbols from it are weak-imported
	for (std::vector<ld::Internal::FinalSection*>::iterator sit=state.sections.begin(); sit != state.sections.end(); ++sit) {
		ld::Internal::FinalSection* sect = *sit;
		for (std::vector<const ld::Atom*>::iterator ait=sect->atoms.begin();  ait != sect->atoms.end(); ++ait) {
			const ld::Atom* atom = *ait;
			const ld::Atom* target = NULL;
			bool targetIsWeakImport = false;
			for (ld::Fixup::iterator fit = atom->fixupsBegin(), end=atom->fixupsEnd(); fit != end; ++fit) {
				if ( fit->firstInCluster() ) 
					target = NULL;
				switch ( fit->binding ) {
					case ld::Fixup::bindingsIndirectlyBound:
						target = state.indirectBindingTable[fit->u.bindingIndex];
						targetIsWeakImport = fit->weakImport;
						break;
					case ld::Fixup::bindingDirectlyBound:
						target = fit->u.target;
						targetIsWeakImport = fit->weakImport;
						break;
                    default:
                        break;   
				}
				if ( (target != NULL) && (target->definition() == ld::Atom::definitionProxy) ) {
					ld::Atom::WeakImportState curWI = target->weakImportState();
					if ( curWI == ld::Atom::weakImportUnset ) {
						// first use of this proxy, set weak-import based on this usage
						(const_cast<ld::Atom*>(target))->setWeakImportState(targetIsWeakImport);
					}
					else {
						// proxy already has weak-importness set, check for weakness mismatch
						bool curIsWeakImport = (curWI == ld::Atom::weakImportTrue);
						if ( curIsWeakImport != targetIsWeakImport ) {
							// found mismatch
							switch ( opts.weakReferenceMismatchTreatment() ) {
								case Options::kWeakReferenceMismatchError:
									throwf("mismatching weak references for symbol: %s", target->name());
								case Options::kWeakReferenceMismatchWeak:
									(const_cast<ld::Atom*>(target))->setWeakImportState(true);
									break;
								case Options::kWeakReferenceMismatchNonWeak:
									(const_cast<ld::Atom*>(target))->setWeakImportState(false);
									break;
							}
						}
					}
				}
			}
		}
	}
	
}


} // namespace dylibs
} // namespace passes 
} // namespace ld