1 //===- lib/Linker/LinkArchives.cpp - Link LLVM objects and libraries ------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file contains routines to handle linking together LLVM bitcode 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/ADT/SetOperations.h" 18 #include "llvm/Bitcode/Archive.h" 19 #include "llvm/Config/config.h" 20 #include <memory> 21 #include <set> 22 using namespace llvm; 23 24 /// GetAllUndefinedSymbols - calculates the set of undefined symbols that still 25 /// exist in an LLVM module. This is a bit tricky because there may be two 26 /// symbols with the same name but different LLVM types that will be resolved to 27 /// each other but aren't currently (thus we need to treat it as resolved). 28 /// 29 /// Inputs: 30 /// M - The module in which to find undefined symbols. 31 /// 32 /// Outputs: 33 /// UndefinedSymbols - A set of C++ strings containing the name of all 34 /// undefined symbols. 35 /// 36 static void 37 GetAllUndefinedSymbols(Module *M, std::set<std::string> &UndefinedSymbols) { 38 std::set<std::string> DefinedSymbols; 39 UndefinedSymbols.clear(); 40 41 // If the program doesn't define a main, try pulling one in from a .a file. 42 // This is needed for programs where the main function is defined in an 43 // archive, such f2c'd programs. 44 Function *Main = M->getFunction("main"); 45 if (Main == 0 || Main->isDeclaration()) 46 UndefinedSymbols.insert("main"); 47 48 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I) 49 if (I->hasName()) { 50 if (I->isDeclaration()) 51 UndefinedSymbols.insert(I->getName()); 52 else if (!I->hasLocalLinkage()) { 53 assert(!I->hasDLLImportLinkage() 54 && "Found dllimported non-external symbol!"); 55 DefinedSymbols.insert(I->getName()); 56 } 57 } 58 59 for (Module::global_iterator I = M->global_begin(), E = M->global_end(); 60 I != E; ++I) 61 if (I->hasName()) { 62 if (I->isDeclaration()) 63 UndefinedSymbols.insert(I->getName()); 64 else if (!I->hasLocalLinkage()) { 65 assert(!I->hasDLLImportLinkage() 66 && "Found dllimported non-external symbol!"); 67 DefinedSymbols.insert(I->getName()); 68 } 69 } 70 71 for (Module::alias_iterator I = M->alias_begin(), E = M->alias_end(); 72 I != E; ++I) 73 if (I->hasName()) 74 DefinedSymbols.insert(I->getName()); 75 76 // Prune out any defined symbols from the undefined symbols set... 77 for (std::set<std::string>::iterator I = UndefinedSymbols.begin(); 78 I != UndefinedSymbols.end(); ) 79 if (DefinedSymbols.count(*I)) 80 UndefinedSymbols.erase(I++); // This symbol really is defined! 81 else 82 ++I; // Keep this symbol in the undefined symbols list 83 } 84 85 /// LinkInArchive - opens an archive library and link in all objects which 86 /// provide symbols that are currently undefined. 87 /// 88 /// Inputs: 89 /// Filename - The pathname of the archive. 90 /// 91 /// Return Value: 92 /// TRUE - An error occurred. 93 /// FALSE - No errors. 94 bool 95 Linker::LinkInArchive(const sys::Path &Filename, bool &is_native) { 96 // Make sure this is an archive file we're dealing with 97 if (!Filename.isArchive()) 98 return error("File '" + Filename.str() + "' is not an archive."); 99 100 // Open the archive file 101 verbose("Linking archive file '" + Filename.str() + "'"); 102 103 // Find all of the symbols currently undefined in the bitcode program. 104 // If all the symbols are defined, the program is complete, and there is 105 // no reason to link in any archive files. 106 std::set<std::string> UndefinedSymbols; 107 GetAllUndefinedSymbols(Composite, UndefinedSymbols); 108 109 if (UndefinedSymbols.empty()) { 110 verbose("No symbols undefined, skipping library '" + Filename.str() + "'"); 111 return false; // No need to link anything in! 112 } 113 114 std::string ErrMsg; 115 std::auto_ptr<Archive> AutoArch ( 116 Archive::OpenAndLoadSymbols(Filename, Context, &ErrMsg)); 117 118 Archive* arch = AutoArch.get(); 119 120 if (!arch) 121 return error("Cannot read archive '" + Filename.str() + 122 "': " + ErrMsg); 123 if (!arch->isBitcodeArchive()) { 124 is_native = true; 125 return false; 126 } 127 is_native = false; 128 129 // Save a set of symbols that are not defined by the archive. Since we're 130 // entering a loop, there's no point searching for these multiple times. This 131 // variable is used to "set_subtract" from the set of undefined symbols. 132 std::set<std::string> NotDefinedByArchive; 133 134 // Save the current set of undefined symbols, because we may have to make 135 // multiple passes over the archive: 136 std::set<std::string> CurrentlyUndefinedSymbols; 137 138 do { 139 CurrentlyUndefinedSymbols = UndefinedSymbols; 140 141 // Find the modules we need to link into the target module. Note that arch 142 // keeps ownership of these modules and may return the same Module* from a 143 // subsequent call. 144 std::set<Module*> Modules; 145 if (!arch->findModulesDefiningSymbols(UndefinedSymbols, Modules, &ErrMsg)) 146 return error("Cannot find symbols in '" + Filename.str() + 147 "': " + ErrMsg); 148 149 // If we didn't find any more modules to link this time, we are done 150 // searching this archive. 151 if (Modules.empty()) 152 break; 153 154 // Any symbols remaining in UndefinedSymbols after 155 // findModulesDefiningSymbols are ones that the archive does not define. So 156 // we add them to the NotDefinedByArchive variable now. 157 NotDefinedByArchive.insert(UndefinedSymbols.begin(), 158 UndefinedSymbols.end()); 159 160 // Loop over all the Modules that we got back from the archive 161 for (std::set<Module*>::iterator I=Modules.begin(), E=Modules.end(); 162 I != E; ++I) { 163 164 // Get the module we must link in. 165 std::string moduleErrorMsg; 166 Module* aModule = *I; 167 if (aModule != NULL) { 168 if (aModule->MaterializeAll(&moduleErrorMsg)) 169 return error("Could not load a module: " + moduleErrorMsg); 170 171 verbose(" Linking in module: " + aModule->getModuleIdentifier()); 172 173 // Link it in 174 if (LinkInModule(aModule, &moduleErrorMsg)) 175 return error("Cannot link in module '" + 176 aModule->getModuleIdentifier() + "': " + moduleErrorMsg); 177 } 178 } 179 180 // Get the undefined symbols from the aggregate module. This recomputes the 181 // symbols we still need after the new modules have been linked in. 182 GetAllUndefinedSymbols(Composite, UndefinedSymbols); 183 184 // At this point we have two sets of undefined symbols: UndefinedSymbols 185 // which holds the undefined symbols from all the modules, and 186 // NotDefinedByArchive which holds symbols we know the archive doesn't 187 // define. There's no point searching for symbols that we won't find in the 188 // archive so we subtract these sets. 189 set_subtract(UndefinedSymbols, NotDefinedByArchive); 190 191 // If there's no symbols left, no point in continuing to search the 192 // archive. 193 if (UndefinedSymbols.empty()) 194 break; 195 } while (CurrentlyUndefinedSymbols != UndefinedSymbols); 196 197 return false; 198 } 199
