LLVM API Documentation
00001 //===- lib/Linker/LinkArchives.cpp - Link LLVM objects and libraries ------===// 00002 // 00003 // The LLVM Compiler Infrastructure 00004 // 00005 // This file was developed by the LLVM research group and is distributed under 00006 // the University of Illinois Open Source License. See LICENSE.TXT for details. 00007 // 00008 //===----------------------------------------------------------------------===// 00009 // 00010 // This file contains routines to handle linking together LLVM bytecode files, 00011 // and to handle annoying things like static libraries. 00012 // 00013 //===----------------------------------------------------------------------===// 00014 00015 #include "llvm/Linker.h" 00016 #include "llvm/Module.h" 00017 #include "llvm/ModuleProvider.h" 00018 #include "llvm/ADT/SetOperations.h" 00019 #include "llvm/Bytecode/Reader.h" 00020 #include "llvm/Bytecode/Archive.h" 00021 #include "llvm/Config/config.h" 00022 #include <memory> 00023 #include <set> 00024 using namespace llvm; 00025 00026 /// GetAllDefinedSymbols - Modifies its parameter DefinedSymbols to contain the 00027 /// name of each externally-visible symbol defined in M. 00028 /// 00029 static void 00030 GetAllDefinedSymbols(Module *M, std::set<std::string> &DefinedSymbols) { 00031 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I) 00032 if (I->hasName() && !I->isExternal() && !I->hasInternalLinkage()) 00033 DefinedSymbols.insert(I->getName()); 00034 for (Module::global_iterator I = M->global_begin(), E = M->global_end(); 00035 I != E; ++I) 00036 if (I->hasName() && !I->isExternal() && !I->hasInternalLinkage()) 00037 DefinedSymbols.insert(I->getName()); 00038 } 00039 00040 /// GetAllUndefinedSymbols - calculates the set of undefined symbols that still 00041 /// exist in an LLVM module. This is a bit tricky because there may be two 00042 /// symbols with the same name but different LLVM types that will be resolved to 00043 /// each other but aren't currently (thus we need to treat it as resolved). 00044 /// 00045 /// Inputs: 00046 /// M - The module in which to find undefined symbols. 00047 /// 00048 /// Outputs: 00049 /// UndefinedSymbols - A set of C++ strings containing the name of all 00050 /// undefined symbols. 00051 /// 00052 static void 00053 GetAllUndefinedSymbols(Module *M, std::set<std::string> &UndefinedSymbols) { 00054 std::set<std::string> DefinedSymbols; 00055 UndefinedSymbols.clear(); 00056 00057 // If the program doesn't define a main, try pulling one in from a .a file. 00058 // This is needed for programs where the main function is defined in an 00059 // archive, such f2c'd programs. 00060 Function *Main = M->getMainFunction(); 00061 if (Main == 0 || Main->isExternal()) 00062 UndefinedSymbols.insert("main"); 00063 00064 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I) 00065 if (I->hasName()) { 00066 if (I->isExternal()) 00067 UndefinedSymbols.insert(I->getName()); 00068 else if (!I->hasInternalLinkage()) 00069 DefinedSymbols.insert(I->getName()); 00070 } 00071 for (Module::global_iterator I = M->global_begin(), E = M->global_end(); 00072 I != E; ++I) 00073 if (I->hasName()) { 00074 if (I->isExternal()) 00075 UndefinedSymbols.insert(I->getName()); 00076 else if (!I->hasInternalLinkage()) 00077 DefinedSymbols.insert(I->getName()); 00078 } 00079 00080 // Prune out any defined symbols from the undefined symbols set... 00081 for (std::set<std::string>::iterator I = UndefinedSymbols.begin(); 00082 I != UndefinedSymbols.end(); ) 00083 if (DefinedSymbols.count(*I)) 00084 UndefinedSymbols.erase(I++); // This symbol really is defined! 00085 else 00086 ++I; // Keep this symbol in the undefined symbols list 00087 } 00088 00089 /// LinkInArchive - opens an archive library and link in all objects which 00090 /// provide symbols that are currently undefined. 00091 /// 00092 /// Inputs: 00093 /// Filename - The pathname of the archive. 00094 /// 00095 /// Return Value: 00096 /// TRUE - An error occurred. 00097 /// FALSE - No errors. 00098 bool 00099 Linker::LinkInArchive(const sys::Path &Filename) { 00100 00101 // Make sure this is an archive file we're dealing with 00102 if (!Filename.isArchive()) 00103 return error("File '" + Filename.toString() + "' is not an archive."); 00104 00105 // Open the archive file 00106 verbose("Linking archive file '" + Filename.toString() + "'"); 00107 00108 // Find all of the symbols currently undefined in the bytecode program. 00109 // If all the symbols are defined, the program is complete, and there is 00110 // no reason to link in any archive files. 00111 std::set<std::string> UndefinedSymbols; 00112 GetAllUndefinedSymbols(Composite, UndefinedSymbols); 00113 00114 if (UndefinedSymbols.empty()) { 00115 verbose("No symbols undefined, skipping library '" + 00116 Filename.toString() + "'"); 00117 return false; // No need to link anything in! 00118 } 00119 00120 std::string ErrMsg; 00121 std::auto_ptr<Archive> AutoArch ( 00122 Archive::OpenAndLoadSymbols(Filename,&ErrMsg)); 00123 00124 Archive* arch = AutoArch.get(); 00125 00126 if (!arch) 00127 return error("Cannot read archive '" + Filename.toString() + 00128 "': " + ErrMsg); 00129 00130 // Save a set of symbols that are not defined by the archive. Since we're 00131 // entering a loop, there's no point searching for these multiple times. This 00132 // variable is used to "set_subtract" from the set of undefined symbols. 00133 std::set<std::string> NotDefinedByArchive; 00134 00135 // While we are linking in object files, loop. 00136 while (true) { 00137 00138 // Find the modules we need to link into the target module 00139 std::set<ModuleProvider*> Modules; 00140 arch->findModulesDefiningSymbols(UndefinedSymbols, Modules); 00141 00142 // If we didn't find any more modules to link this time, we are done 00143 // searching this archive. 00144 if (Modules.empty()) 00145 break; 00146 00147 // Any symbols remaining in UndefinedSymbols after 00148 // findModulesDefiningSymbols are ones that the archive does not define. So 00149 // we add them to the NotDefinedByArchive variable now. 00150 NotDefinedByArchive.insert(UndefinedSymbols.begin(), 00151 UndefinedSymbols.end()); 00152 00153 // Loop over all the ModuleProviders that we got back from the archive 00154 for (std::set<ModuleProvider*>::iterator I=Modules.begin(), E=Modules.end(); 00155 I != E; ++I) { 00156 00157 // Get the module we must link in. 00158 std::auto_ptr<Module> AutoModule( (*I)->releaseModule() ); 00159 Module* aModule = AutoModule.get(); 00160 00161 verbose(" Linking in module: " + aModule->getModuleIdentifier()); 00162 00163 // Link it in 00164 if (LinkInModule(aModule)) 00165 return error("Cannot link in module '" + 00166 aModule->getModuleIdentifier() + "': " + Error); 00167 } 00168 00169 // Get the undefined symbols from the aggregate module. This recomputes the 00170 // symbols we still need after the new modules have been linked in. 00171 GetAllUndefinedSymbols(Composite, UndefinedSymbols); 00172 00173 // At this point we have two sets of undefined symbols: UndefinedSymbols 00174 // which holds the undefined symbols from all the modules, and 00175 // NotDefinedByArchive which holds symbols we know the archive doesn't 00176 // define. There's no point searching for symbols that we won't find in the 00177 // archive so we subtract these sets. 00178 set_subtract(UndefinedSymbols, NotDefinedByArchive); 00179 00180 // If there's no symbols left, no point in continuing to search the 00181 // archive. 00182 if (UndefinedSymbols.empty()) 00183 break; 00184 } 00185 00186 return false; 00187 }