1 //===- lib/Linker/LinkArchives.cpp - Link LLVM objects and libraries ------===//
3 // The LLVM Compiler Infrastructure
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.
8 //===----------------------------------------------------------------------===//
10 // This file contains routines to handle linking together LLVM bytecode 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/Bytecode/Reader.h"
20 #include "llvm/Bytecode/Archive.h"
21 #include "llvm/Config/config.h"
26 /// GetAllDefinedSymbols - Modifies its parameter DefinedSymbols to contain the
27 /// name of each externally-visible symbol defined in M.
30 GetAllDefinedSymbols(Module *M, std::set<std::string> &DefinedSymbols) {
31 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
32 if (I->hasName() && !I->isExternal() && !I->hasInternalLinkage())
33 DefinedSymbols.insert(I->getName());
34 for (Module::global_iterator I = M->global_begin(), E = M->global_end();
36 if (I->hasName() && !I->isExternal() && !I->hasInternalLinkage())
37 DefinedSymbols.insert(I->getName());
40 /// GetAllUndefinedSymbols - calculates the set of undefined symbols that still
41 /// exist in an LLVM module. This is a bit tricky because there may be two
42 /// symbols with the same name but different LLVM types that will be resolved to
43 /// each other but aren't currently (thus we need to treat it as resolved).
46 /// M - The module in which to find undefined symbols.
49 /// UndefinedSymbols - A set of C++ strings containing the name of all
50 /// undefined symbols.
53 GetAllUndefinedSymbols(Module *M, std::set<std::string> &UndefinedSymbols) {
54 std::set<std::string> DefinedSymbols;
55 UndefinedSymbols.clear();
57 // If the program doesn't define a main, try pulling one in from a .a file.
58 // This is needed for programs where the main function is defined in an
59 // archive, such f2c'd programs.
60 Function *Main = M->getMainFunction();
61 if (Main == 0 || Main->isExternal())
62 UndefinedSymbols.insert("main");
64 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
67 UndefinedSymbols.insert(I->getName());
68 else if (!I->hasInternalLinkage()) {
69 assert(!I->hasDLLImportLinkage()
70 && "Found dllimported non-external symbol!");
71 DefinedSymbols.insert(I->getName());
74 for (Module::global_iterator I = M->global_begin(), E = M->global_end();
78 UndefinedSymbols.insert(I->getName());
79 else if (!I->hasInternalLinkage()) {
80 assert(!I->hasDLLImportLinkage()
81 && "Found dllimported non-external symbol!");
82 DefinedSymbols.insert(I->getName());
86 // Prune out any defined symbols from the undefined symbols set...
87 for (std::set<std::string>::iterator I = UndefinedSymbols.begin();
88 I != UndefinedSymbols.end(); )
89 if (DefinedSymbols.count(*I))
90 UndefinedSymbols.erase(I++); // This symbol really is defined!
92 ++I; // Keep this symbol in the undefined symbols list
95 /// LinkInArchive - opens an archive library and link in all objects which
96 /// provide symbols that are currently undefined.
99 /// Filename - The pathname of the archive.
102 /// TRUE - An error occurred.
103 /// FALSE - No errors.
105 Linker::LinkInArchive(const sys::Path &Filename) {
107 // Make sure this is an archive file we're dealing with
108 if (!Filename.isArchive())
109 return error("File '" + Filename.toString() + "' is not an archive.");
111 // Open the archive file
112 verbose("Linking archive file '" + Filename.toString() + "'");
114 // Find all of the symbols currently undefined in the bytecode program.
115 // If all the symbols are defined, the program is complete, and there is
116 // no reason to link in any archive files.
117 std::set<std::string> UndefinedSymbols;
118 GetAllUndefinedSymbols(Composite, UndefinedSymbols);
120 if (UndefinedSymbols.empty()) {
121 verbose("No symbols undefined, skipping library '" +
122 Filename.toString() + "'");
123 return false; // No need to link anything in!
127 std::auto_ptr<Archive> AutoArch (
128 Archive::OpenAndLoadSymbols(Filename,&ErrMsg));
130 Archive* arch = AutoArch.get();
133 return error("Cannot read archive '" + Filename.toString() +
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 // While we are linking in object files, loop.
144 // Find the modules we need to link into the target module
145 std::set<ModuleProvider*> Modules;
146 if (!arch->findModulesDefiningSymbols(UndefinedSymbols, Modules, &ErrMsg))
147 return error("Cannot find symbols in '" + Filename.toString() +
150 // If we didn't find any more modules to link this time, we are done
151 // searching this archive.
155 // Any symbols remaining in UndefinedSymbols after
156 // findModulesDefiningSymbols are ones that the archive does not define. So
157 // we add them to the NotDefinedByArchive variable now.
158 NotDefinedByArchive.insert(UndefinedSymbols.begin(),
159 UndefinedSymbols.end());
161 // Loop over all the ModuleProviders that we got back from the archive
162 for (std::set<ModuleProvider*>::iterator I=Modules.begin(), E=Modules.end();
165 // Get the module we must link in.
166 std::auto_ptr<Module> AutoModule( (*I)->releaseModule() );
167 Module* aModule = AutoModule.get();
169 verbose(" Linking in module: " + aModule->getModuleIdentifier());
172 if (LinkInModule(aModule))
173 return error("Cannot link in module '" +
174 aModule->getModuleIdentifier() + "': " + Error);
177 // Get the undefined symbols from the aggregate module. This recomputes the
178 // symbols we still need after the new modules have been linked in.
179 GetAllUndefinedSymbols(Composite, UndefinedSymbols);
181 // At this point we have two sets of undefined symbols: UndefinedSymbols
182 // which holds the undefined symbols from all the modules, and
183 // NotDefinedByArchive which holds symbols we know the archive doesn't
184 // define. There's no point searching for symbols that we won't find in the
185 // archive so we subtract these sets.
186 set_subtract(UndefinedSymbols, NotDefinedByArchive);
188 // If there's no symbols left, no point in continuing to search the
190 if (UndefinedSymbols.empty())