1 //===- lib/Linker/LinkArchives.cpp - Link LLVM objects and libraries ------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains routines to handle linking together LLVM bitcode files,
11 // and to handle annoying things like static libraries.
13 //===----------------------------------------------------------------------===//
15 #include "llvm/Linker.h"
16 #include "llvm/Module.h"
17 #include "llvm/ModuleProvider.h"
18 #include "llvm/ADT/SetOperations.h"
19 #include "llvm/Bitcode/Archive.h"
20 #include "llvm/Config/config.h"
25 /// GetAllUndefinedSymbols - calculates the set of undefined symbols that still
26 /// exist in an LLVM module. This is a bit tricky because there may be two
27 /// symbols with the same name but different LLVM types that will be resolved to
28 /// each other but aren't currently (thus we need to treat it as resolved).
31 /// M - The module in which to find undefined symbols.
34 /// UndefinedSymbols - A set of C++ strings containing the name of all
35 /// undefined symbols.
38 GetAllUndefinedSymbols(Module *M, std::set<std::string> &UndefinedSymbols) {
39 std::set<std::string> DefinedSymbols;
40 UndefinedSymbols.clear();
42 // If the program doesn't define a main, try pulling one in from a .a file.
43 // This is needed for programs where the main function is defined in an
44 // archive, such f2c'd programs.
45 Function *Main = M->getFunction("main");
46 if (Main == 0 || Main->isDeclaration())
47 UndefinedSymbols.insert("main");
49 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
51 if (I->isDeclaration())
52 UndefinedSymbols.insert(I->getName());
53 else if (!I->hasInternalLinkage()) {
54 assert(!I->hasDLLImportLinkage()
55 && "Found dllimported non-external symbol!");
56 DefinedSymbols.insert(I->getName());
60 for (Module::global_iterator I = M->global_begin(), E = M->global_end();
63 if (I->isDeclaration())
64 UndefinedSymbols.insert(I->getName());
65 else if (!I->hasInternalLinkage()) {
66 assert(!I->hasDLLImportLinkage()
67 && "Found dllimported non-external symbol!");
68 DefinedSymbols.insert(I->getName());
72 for (Module::alias_iterator I = M->alias_begin(), E = M->alias_end();
75 const GlobalValue *Aliased = I->getAliasedGlobal();
76 if (Aliased->isDeclaration())
77 UndefinedSymbols.insert(I->getName());
79 DefinedSymbols.insert(I->getName());
82 // Prune out any defined symbols from the undefined symbols set...
83 for (std::set<std::string>::iterator I = UndefinedSymbols.begin();
84 I != UndefinedSymbols.end(); )
85 if (DefinedSymbols.count(*I))
86 UndefinedSymbols.erase(I++); // This symbol really is defined!
88 ++I; // Keep this symbol in the undefined symbols list
91 /// LinkInArchive - opens an archive library and link in all objects which
92 /// provide symbols that are currently undefined.
95 /// Filename - The pathname of the archive.
98 /// TRUE - An error occurred.
99 /// FALSE - No errors.
101 Linker::LinkInArchive(const sys::Path &Filename, bool &is_native) {
102 // Make sure this is an archive file we're dealing with
103 if (!Filename.isArchive())
104 return error("File '" + Filename.toString() + "' is not an archive.");
106 // Open the archive file
107 verbose("Linking archive file '" + Filename.toString() + "'");
109 // Find all of the symbols currently undefined in the bitcode program.
110 // If all the symbols are defined, the program is complete, and there is
111 // no reason to link in any archive files.
112 std::set<std::string> UndefinedSymbols;
113 GetAllUndefinedSymbols(Composite, UndefinedSymbols);
115 if (UndefinedSymbols.empty()) {
116 verbose("No symbols undefined, skipping library '" +
117 Filename.toString() + "'");
118 return false; // No need to link anything in!
122 std::auto_ptr<Archive> AutoArch (
123 Archive::OpenAndLoadSymbols(Filename,&ErrMsg));
125 Archive* arch = AutoArch.get();
128 return error("Cannot read archive '" + Filename.toString() +
130 if (!arch->isBitcodeArchive()) {
136 // Save a set of symbols that are not defined by the archive. Since we're
137 // entering a loop, there's no point searching for these multiple times. This
138 // variable is used to "set_subtract" from the set of undefined symbols.
139 std::set<std::string> NotDefinedByArchive;
141 // Save the current set of undefined symbols, because we may have to make
142 // multiple passes over the archive:
143 std::set<std::string> CurrentlyUndefinedSymbols;
146 CurrentlyUndefinedSymbols = UndefinedSymbols;
148 // Find the modules we need to link into the target module
149 std::set<ModuleProvider*> Modules;
150 if (!arch->findModulesDefiningSymbols(UndefinedSymbols, Modules, &ErrMsg))
151 return error("Cannot find symbols in '" + Filename.toString() +
154 // If we didn't find any more modules to link this time, we are done
155 // searching this archive.
159 // Any symbols remaining in UndefinedSymbols after
160 // findModulesDefiningSymbols are ones that the archive does not define. So
161 // we add them to the NotDefinedByArchive variable now.
162 NotDefinedByArchive.insert(UndefinedSymbols.begin(),
163 UndefinedSymbols.end());
165 // Loop over all the ModuleProviders that we got back from the archive
166 for (std::set<ModuleProvider*>::iterator I=Modules.begin(), E=Modules.end();
169 // Get the module we must link in.
170 std::string moduleErrorMsg;
171 std::auto_ptr<Module> AutoModule((*I)->releaseModule( &moduleErrorMsg ));
172 if (!moduleErrorMsg.empty())
173 return error("Could not load a module: " + moduleErrorMsg);
175 Module* aModule = AutoModule.get();
177 if (aModule != NULL) {
178 verbose(" Linking in module: " + aModule->getModuleIdentifier());
181 if (LinkInModule(aModule, &moduleErrorMsg)) {
182 return error("Cannot link in module '" +
183 aModule->getModuleIdentifier() + "': " + moduleErrorMsg);
188 // Get the undefined symbols from the aggregate module. This recomputes the
189 // symbols we still need after the new modules have been linked in.
190 GetAllUndefinedSymbols(Composite, UndefinedSymbols);
192 // At this point we have two sets of undefined symbols: UndefinedSymbols
193 // which holds the undefined symbols from all the modules, and
194 // NotDefinedByArchive which holds symbols we know the archive doesn't
195 // define. There's no point searching for symbols that we won't find in the
196 // archive so we subtract these sets.
197 set_subtract(UndefinedSymbols, NotDefinedByArchive);
199 // If there's no symbols left, no point in continuing to search the
201 if (UndefinedSymbols.empty())
203 } while (CurrentlyUndefinedSymbols != UndefinedSymbols);