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 /// GetAllUndefinedSymbols - calculates the set of undefined symbols that still
27 /// exist in an LLVM module. This is a bit tricky because there may be two
28 /// symbols with the same name but different LLVM types that will be resolved to
29 /// each other but aren't currently (thus we need to treat it as resolved).
32 /// M - The module in which to find undefined symbols.
35 /// UndefinedSymbols - A set of C++ strings containing the name of all
36 /// undefined symbols.
39 GetAllUndefinedSymbols(Module *M, std::set<std::string> &UndefinedSymbols) {
40 std::set<std::string> DefinedSymbols;
41 UndefinedSymbols.clear();
43 // If the program doesn't define a main, try pulling one in from a .a file.
44 // This is needed for programs where the main function is defined in an
45 // archive, such f2c'd programs.
46 Function *Main = M->getFunction("main");
47 if (Main == 0 || Main->isDeclaration())
48 UndefinedSymbols.insert("main");
50 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
52 if (I->isDeclaration())
53 UndefinedSymbols.insert(I->getName());
54 else if (!I->hasInternalLinkage()) {
55 assert(!I->hasDLLImportLinkage()
56 && "Found dllimported non-external symbol!");
57 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 // Prune out any defined symbols from the undefined symbols set...
73 for (std::set<std::string>::iterator I = UndefinedSymbols.begin();
74 I != UndefinedSymbols.end(); )
75 if (DefinedSymbols.count(*I))
76 UndefinedSymbols.erase(I++); // This symbol really is defined!
78 ++I; // Keep this symbol in the undefined symbols list
81 /// LinkInArchive - opens an archive library and link in all objects which
82 /// provide symbols that are currently undefined.
85 /// Filename - The pathname of the archive.
88 /// TRUE - An error occurred.
89 /// FALSE - No errors.
91 Linker::LinkInArchive(const sys::Path &Filename) {
93 // Make sure this is an archive file we're dealing with
94 if (!Filename.isArchive())
95 return error("File '" + Filename.toString() + "' is not an archive.");
97 // Open the archive file
98 verbose("Linking archive file '" + Filename.toString() + "'");
100 // Find all of the symbols currently undefined in the bytecode program.
101 // If all the symbols are defined, the program is complete, and there is
102 // no reason to link in any archive files.
103 std::set<std::string> UndefinedSymbols;
104 GetAllUndefinedSymbols(Composite, UndefinedSymbols);
106 if (UndefinedSymbols.empty()) {
107 verbose("No symbols undefined, skipping library '" +
108 Filename.toString() + "'");
109 return false; // No need to link anything in!
113 std::auto_ptr<Archive> AutoArch (
114 Archive::OpenAndLoadSymbols(Filename,&ErrMsg));
116 Archive* arch = AutoArch.get();
119 return error("Cannot read archive '" + Filename.toString() +
122 // Save a set of symbols that are not defined by the archive. Since we're
123 // entering a loop, there's no point searching for these multiple times. This
124 // variable is used to "set_subtract" from the set of undefined symbols.
125 std::set<std::string> NotDefinedByArchive;
127 // Save the current set of undefined symbols, because we may have to make
128 // multiple passes over the archive:
129 std::set<std::string> CurrentlyUndefinedSymbols;
132 CurrentlyUndefinedSymbols = UndefinedSymbols;
134 // Find the modules we need to link into the target module
135 std::set<ModuleProvider*> Modules;
136 if (!arch->findModulesDefiningSymbols(UndefinedSymbols, Modules, &ErrMsg))
137 return error("Cannot find symbols in '" + Filename.toString() +
140 // If we didn't find any more modules to link this time, we are done
141 // searching this archive.
145 // Any symbols remaining in UndefinedSymbols after
146 // findModulesDefiningSymbols are ones that the archive does not define. So
147 // we add them to the NotDefinedByArchive variable now.
148 NotDefinedByArchive.insert(UndefinedSymbols.begin(),
149 UndefinedSymbols.end());
151 // Loop over all the ModuleProviders that we got back from the archive
152 for (std::set<ModuleProvider*>::iterator I=Modules.begin(), E=Modules.end();
155 // Get the module we must link in.
156 std::string moduleErrorMsg;
157 std::auto_ptr<Module> AutoModule((*I)->releaseModule( &moduleErrorMsg ));
158 Module* aModule = AutoModule.get();
160 if (aModule != NULL) {
161 verbose(" Linking in module: " + aModule->getModuleIdentifier());
164 if (LinkInModule(aModule, &moduleErrorMsg)) {
165 return error("Cannot link in module '" +
166 aModule->getModuleIdentifier() + "': " + moduleErrorMsg);
171 // Get the undefined symbols from the aggregate module. This recomputes the
172 // symbols we still need after the new modules have been linked in.
173 GetAllUndefinedSymbols(Composite, UndefinedSymbols);
175 // At this point we have two sets of undefined symbols: UndefinedSymbols
176 // which holds the undefined symbols from all the modules, and
177 // NotDefinedByArchive which holds symbols we know the archive doesn't
178 // define. There's no point searching for symbols that we won't find in the
179 // archive so we subtract these sets.
180 set_subtract(UndefinedSymbols, NotDefinedByArchive);
182 // If there's no symbols left, no point in continuing to search the
184 if (UndefinedSymbols.empty())
186 } while (CurrentlyUndefinedSymbols != UndefinedSymbols);