LinkArchives.cpp revision 4ca8e710681cd932775ef2f10af81a018b253770
1//===- lib/Linker/LinkArchives.cpp - Link LLVM objects and libraries ------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by the LLVM research group and is distributed under 6// the University of Illinois Open Source License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file contains routines to handle linking together LLVM bytecode files, 11// and to handle annoying things like static libraries. 12// 13//===----------------------------------------------------------------------===// 14 15#include "llvm/Linker.h" 16#include "llvm/Module.h" 17#include "llvm/ModuleProvider.h" 18#include "llvm/ADT/SetOperations.h" 19#include "llvm/Bytecode/Reader.h" 20#include "llvm/Bytecode/Archive.h" 21#include "llvm/Config/config.h" 22#include <memory> 23#include <set> 24#include <iostream> 25 26using namespace llvm; 27 28/// GetAllDefinedSymbols - Modifies its parameter DefinedSymbols to contain the 29/// name of each externally-visible symbol defined in M. 30/// 31static void 32GetAllDefinedSymbols(Module *M, std::set<std::string> &DefinedSymbols) { 33 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I) 34 if (I->hasName() && !I->isExternal() && !I->hasInternalLinkage()) 35 DefinedSymbols.insert(I->getName()); 36 for (Module::giterator I = M->gbegin(), E = M->gend(); I != E; ++I) 37 if (I->hasName() && !I->isExternal() && !I->hasInternalLinkage()) 38 DefinedSymbols.insert(I->getName()); 39} 40 41/// GetAllUndefinedSymbols - calculates the set of undefined symbols that still 42/// exist in an LLVM module. This is a bit tricky because there may be two 43/// symbols with the same name but different LLVM types that will be resolved to 44/// each other but aren't currently (thus we need to treat it as resolved). 45/// 46/// Inputs: 47/// M - The module in which to find undefined symbols. 48/// 49/// Outputs: 50/// UndefinedSymbols - A set of C++ strings containing the name of all 51/// undefined symbols. 52/// 53static void 54GetAllUndefinedSymbols(Module *M, std::set<std::string> &UndefinedSymbols) { 55 std::set<std::string> DefinedSymbols; 56 UndefinedSymbols.clear(); 57 58 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I) 59 if (I->hasName()) { 60 if (I->isExternal()) 61 UndefinedSymbols.insert(I->getName()); 62 else if (!I->hasInternalLinkage()) 63 DefinedSymbols.insert(I->getName()); 64 } 65 for (Module::giterator I = M->gbegin(), E = M->gend(); I != E; ++I) 66 if (I->hasName()) { 67 if (I->isExternal()) 68 UndefinedSymbols.insert(I->getName()); 69 else if (!I->hasInternalLinkage()) 70 DefinedSymbols.insert(I->getName()); 71 } 72 73 // Prune out any defined symbols from the undefined symbols set... 74 for (std::set<std::string>::iterator I = UndefinedSymbols.begin(); 75 I != UndefinedSymbols.end(); ) 76 if (DefinedSymbols.count(*I)) 77 UndefinedSymbols.erase(I++); // This symbol really is defined! 78 else 79 ++I; // Keep this symbol in the undefined symbols list 80} 81 82/// LinkInArchive - opens an archive library and link in all objects which 83/// provide symbols that are currently undefined. 84/// 85/// Inputs: 86/// Filename - The pathname of the archive. 87/// 88/// Return Value: 89/// TRUE - An error occurred. 90/// FALSE - No errors. 91bool 92Linker::LinkInArchive(const sys::Path &Filename) { 93 94 // Make sure this is an archive file we're dealing with 95 if (!Filename.isArchive()) 96 return error("File '" + Filename.toString() + "' is not an archive."); 97 98 // Open the archive file 99 verbose("Linking archive file '" + Filename.toString() + "'"); 100 101 // Find all of the symbols currently undefined in the bytecode program. 102 // If all the symbols are defined, the program is complete, and there is 103 // no reason to link in any archive files. 104 std::set<std::string> UndefinedSymbols; 105 GetAllUndefinedSymbols(Composite, UndefinedSymbols); 106 107 if (UndefinedSymbols.empty()) { 108 verbose("No symbols undefined, skipping library '" + 109 Filename.toString() + "'"); 110 return false; // No need to link anything in! 111 } 112 113 std::string ErrMsg; 114 std::auto_ptr<Archive> AutoArch ( 115 Archive::OpenAndLoadSymbols(Filename,&ErrMsg)); 116 117 Archive* arch = AutoArch.get(); 118 119 if (!arch) 120 return error("Cannot read archive '" + Filename.toString() + 121 "': " + ErrMsg); 122 123 // Save a set of symbols that are not defined by the archive. Since we're 124 // entering a loop, there's no point searching for these multiple times. This 125 // variable is used to "set_subtract" from the set of undefined symbols. 126 std::set<std::string> NotDefinedByArchive; 127 128 // While we are linking in object files, loop. 129 while (true) { 130 131 // Find the modules we need to link into the target module 132 std::set<ModuleProvider*> Modules; 133 arch->findModulesDefiningSymbols(UndefinedSymbols, Modules); 134 135 // If we didn't find any more modules to link this time, we are done 136 // searching this archive. 137 if (Modules.empty()) 138 break; 139 140 // Any symbols remaining in UndefinedSymbols after 141 // findModulesDefiningSymbols are ones that the archive does not define. So 142 // we add them to the NotDefinedByArchive variable now. 143 NotDefinedByArchive.insert(UndefinedSymbols.begin(), 144 UndefinedSymbols.end()); 145 146 // Loop over all the ModuleProviders that we got back from the archive 147 for (std::set<ModuleProvider*>::iterator I=Modules.begin(), E=Modules.end(); 148 I != E; ++I) { 149 150 // Get the module we must link in. 151 std::auto_ptr<Module> AutoModule( (*I)->releaseModule() ); 152 Module* aModule = AutoModule.get(); 153 154 // Link it in 155 if (this->LinkInModule(aModule)) 156 return error("Cannot link in module '" + 157 aModule->getModuleIdentifier() + "': " + Error); 158 } 159 160 // Get the undefined symbols from the aggregate module. This recomputes the 161 // symbols we still need after the new modules have been linked in. 162 GetAllUndefinedSymbols(Composite, UndefinedSymbols); 163 164 // At this point we have two sets of undefined symbols: UndefinedSymbols 165 // which holds the undefined symbols from all the modules, and 166 // NotDefinedByArchive which holds symbols we know the archive doesn't 167 // define. There's no point searching for symbols that we won't find in the 168 // archive so we subtract these sets. 169 set_subtract<std::set<std::string>,std::set<std::string> >( 170 UndefinedSymbols,NotDefinedByArchive); 171 172 // If there's no symbols left, no point in continuing to search the 173 // archive. 174 if (UndefinedSymbols.empty()) 175 break; 176 } 177 178 return false; 179} 180