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//===- lib/Linker/LinkArchives.cpp - Link LLVM objects and libraries ------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains routines to handle linking together LLVM bitcode files,
// and to handle annoying things like static libraries.
//
//===----------------------------------------------------------------------===//
#include "llvm/Linker.h"
#include "llvm/ADT/SetOperations.h"
#include "llvm/Bitcode/Archive.h"
#include "llvm/IR/Module.h"
#include <memory>
#include <set>
using namespace llvm;
/// GetAllUndefinedSymbols - calculates the set of undefined symbols that still
/// exist in an LLVM module. This is a bit tricky because there may be two
/// symbols with the same name but different LLVM types that will be resolved to
/// each other but aren't currently (thus we need to treat it as resolved).
///
/// Inputs:
/// M - The module in which to find undefined symbols.
///
/// Outputs:
/// UndefinedSymbols - A set of C++ strings containing the name of all
/// undefined symbols.
///
static void
GetAllUndefinedSymbols(Module *M, std::set<std::string> &UndefinedSymbols) {
std::set<std::string> DefinedSymbols;
UndefinedSymbols.clear();
// If the program doesn't define a main, try pulling one in from a .a file.
// This is needed for programs where the main function is defined in an
// archive, such f2c'd programs.
Function *Main = M->getFunction("main");
if (Main == 0 || Main->isDeclaration())
UndefinedSymbols.insert("main");
for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
if (I->hasName()) {
if (I->isDeclaration())
UndefinedSymbols.insert(I->getName());
else if (!I->hasLocalLinkage()) {
assert(!I->hasDLLImportLinkage()
&& "Found dllimported non-external symbol!");
DefinedSymbols.insert(I->getName());
}
}
for (Module::global_iterator I = M->global_begin(), E = M->global_end();
I != E; ++I)
if (I->hasName()) {
if (I->isDeclaration())
UndefinedSymbols.insert(I->getName());
else if (!I->hasLocalLinkage()) {
assert(!I->hasDLLImportLinkage()
&& "Found dllimported non-external symbol!");
DefinedSymbols.insert(I->getName());
}
}
for (Module::alias_iterator I = M->alias_begin(), E = M->alias_end();
I != E; ++I)
if (I->hasName())
DefinedSymbols.insert(I->getName());
// Prune out any defined symbols from the undefined symbols set...
for (std::set<std::string>::iterator I = UndefinedSymbols.begin();
I != UndefinedSymbols.end(); )
if (DefinedSymbols.count(*I))
UndefinedSymbols.erase(I++); // This symbol really is defined!
else
++I; // Keep this symbol in the undefined symbols list
}
/// LinkInArchive - opens an archive library and link in all objects which
/// provide symbols that are currently undefined.
///
/// Inputs:
/// Filename - The pathname of the archive.
///
/// Return Value:
/// TRUE - An error occurred.
/// FALSE - No errors.
bool
Linker::LinkInArchive(const sys::Path &Filename, bool &is_native) {
// Make sure this is an archive file we're dealing with
if (!Filename.isArchive())
return error("File '" + Filename.str() + "' is not an archive.");
// Open the archive file
verbose("Linking archive file '" + Filename.str() + "'");
// Find all of the symbols currently undefined in the bitcode program.
// If all the symbols are defined, the program is complete, and there is
// no reason to link in any archive files.
std::set<std::string> UndefinedSymbols;
GetAllUndefinedSymbols(Composite, UndefinedSymbols);
if (UndefinedSymbols.empty()) {
verbose("No symbols undefined, skipping library '" + Filename.str() + "'");
return false; // No need to link anything in!
}
std::string ErrMsg;
std::auto_ptr<Archive> AutoArch (
Archive::OpenAndLoadSymbols(Filename, Context, &ErrMsg));
Archive* arch = AutoArch.get();
if (!arch)
return error("Cannot read archive '" + Filename.str() +
"': " + ErrMsg);
if (!arch->isBitcodeArchive()) {
is_native = true;
return false;
}
is_native = false;
// Save a set of symbols that are not defined by the archive. Since we're
// entering a loop, there's no point searching for these multiple times. This
// variable is used to "set_subtract" from the set of undefined symbols.
std::set<std::string> NotDefinedByArchive;
// Save the current set of undefined symbols, because we may have to make
// multiple passes over the archive:
std::set<std::string> CurrentlyUndefinedSymbols;
do {
CurrentlyUndefinedSymbols = UndefinedSymbols;
// Find the modules we need to link into the target module. Note that arch
// keeps ownership of these modules and may return the same Module* from a
// subsequent call.
SmallVector<Module*, 16> Modules;
if (!arch->findModulesDefiningSymbols(UndefinedSymbols, Modules, &ErrMsg))
return error("Cannot find symbols in '" + Filename.str() +
"': " + ErrMsg);
// If we didn't find any more modules to link this time, we are done
// searching this archive.
if (Modules.empty())
break;
// Any symbols remaining in UndefinedSymbols after
// findModulesDefiningSymbols are ones that the archive does not define. So
// we add them to the NotDefinedByArchive variable now.
NotDefinedByArchive.insert(UndefinedSymbols.begin(),
UndefinedSymbols.end());
// Loop over all the Modules that we got back from the archive
for (SmallVectorImpl<Module*>::iterator I=Modules.begin(), E=Modules.end();
I != E; ++I) {
// Get the module we must link in.
std::string moduleErrorMsg;
Module* aModule = *I;
if (aModule != NULL) {
if (aModule->MaterializeAll(&moduleErrorMsg))
return error("Could not load a module: " + moduleErrorMsg);
verbose(" Linking in module: " + aModule->getModuleIdentifier());
// Link it in
if (LinkInModule(aModule, &moduleErrorMsg))
return error("Cannot link in module '" +
aModule->getModuleIdentifier() + "': " + moduleErrorMsg);
}
}
// Get the undefined symbols from the aggregate module. This recomputes the
// symbols we still need after the new modules have been linked in.
GetAllUndefinedSymbols(Composite, UndefinedSymbols);
// At this point we have two sets of undefined symbols: UndefinedSymbols
// which holds the undefined symbols from all the modules, and
// NotDefinedByArchive which holds symbols we know the archive doesn't
// define. There's no point searching for symbols that we won't find in the
// archive so we subtract these sets.
set_subtract(UndefinedSymbols, NotDefinedByArchive);
// If there's no symbols left, no point in continuing to search the
// archive.
if (UndefinedSymbols.empty())
break;
} while (CurrentlyUndefinedSymbols != UndefinedSymbols);
return false;
}
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