lld/COFF/InputFiles.cpp - toolchain/llvm-project - Gitiles

 //===- InputFiles.cpp -----------------------------------------------------===//
 //
 //                             The LLVM Linker
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//

 #include "Chunks.h"
 #include "Error.h"
 #include "InputFiles.h"
 #include "Symbols.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/LTO/LTOModule.h"
 #include "llvm/Object/COFF.h"
 #include "llvm/Support/COFF.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/raw_ostream.h"

 using namespace llvm::COFF;
 using namespace llvm::object;
 using namespace llvm::support::endian;
 using llvm::RoundUpToAlignment;
 using llvm::Triple;
 using llvm::support::ulittle32_t;
 using llvm::sys::fs::file_magic;
 using llvm::sys::fs::identify_magic;

 namespace lld {
 namespace coff {

 int InputFile::NextIndex = 0;

 // Returns the last element of a path, which is supposed to be a filename.
 static StringRef getBasename(StringRef Path) {
   size_t Pos = Path.find_last_of("\\/");
   if (Pos == StringRef::npos)
     return Path;
   return Path.substr(Pos + 1);
 }

 // Returns a string in the format of "foo.obj" or "foo.obj(bar.lib)".
 std::string InputFile::getShortName() {
   if (ParentName == "")
     return getName().lower();
   std::string Res = (getBasename(ParentName) + "(" +
                      getBasename(getName()) + ")").str();
   return StringRef(Res).lower();
 }

 void ArchiveFile::parse() {
   // Parse a MemoryBufferRef as an archive file.
   auto ArchiveOrErr = Archive::create(MB);
   error(ArchiveOrErr, "Failed to parse static library");
   File = std::move(ArchiveOrErr.get());

   // Allocate a buffer for Lazy objects.
   size_t NumSyms = File->getNumberOfSymbols();
   size_t BufSize = NumSyms * sizeof(Lazy);
   Lazy *Buf = (Lazy *)Alloc.Allocate(BufSize, llvm::alignOf<Lazy>());
   LazySymbols.reserve(NumSyms);

   // Read the symbol table to construct Lazy objects.
   uint32_t I = 0;
   for (const Archive::Symbol &Sym : File->symbols()) {
     auto *B = new (&Buf[I++]) Lazy(this, Sym);
     // Skip special symbol exists in import library files.
     if (B->getName() != "__NULL_IMPORT_DESCRIPTOR")
       LazySymbols.push_back(B);
   }

   // Seen is a map from member files to boolean values. Initially
   // all members are mapped to false, which indicates all these files
   // are not read yet.
   for (const Archive::Child &Child : File->children())
     Seen[Child.getChildOffset()].clear();
 }

 // Returns a buffer pointing to a member file containing a given symbol.
 // This function is thread-safe.
 MemoryBufferRef ArchiveFile::getMember(const Archive::Symbol *Sym) {
   auto ItOrErr = Sym->getMember();
   error(ItOrErr,
         Twine("Could not get the member for symbol ") + Sym->getName());
   Archive::child_iterator It = ItOrErr.get();

   // Return an empty buffer if we have already returned the same buffer.
   if (Seen[It->getChildOffset()].test_and_set())
     return MemoryBufferRef();
   ErrorOr<MemoryBufferRef> Ret = It->getMemoryBufferRef();
   error(Ret, Twine("Could not get the buffer for the member defining symbol ") +
                  Sym->getName());
   return *Ret;
 }

 void ObjectFile::parse() {
   // Parse a memory buffer as a COFF file.
   auto BinOrErr = createBinary(MB);
   error(BinOrErr, "Failed to parse object file");
   std::unique_ptr<Binary> Bin = std::move(BinOrErr.get());

   if (auto *Obj = dyn_cast<COFFObjectFile>(Bin.get())) {
     Bin.release();
     COFFObj.reset(Obj);
   } else {
     error(Twine(getName()) + " is not a COFF file.");
   }

   // Read section and symbol tables.
   initializeChunks();
   initializeSymbols();
   initializeSEH();
 }

 void ObjectFile::initializeChunks() {
   uint32_t NumSections = COFFObj->getNumberOfSections();
   Chunks.reserve(NumSections);
   SparseChunks.resize(NumSections + 1);
   for (uint32_t I = 1; I < NumSections + 1; ++I) {
     const coff_section *Sec;
     StringRef Name;
     std::error_code EC = COFFObj->getSection(I, Sec);
     error(EC, Twine("getSection failed: ") + Name);
     EC = COFFObj->getSectionName(Sec, Name);
     error(EC, Twine("getSectionName failed: ") + Name);
     if (Name == ".sxdata") {
       SXData = Sec;
       continue;
     }
     if (Name == ".drectve") {
       ArrayRef<uint8_t> Data;
       COFFObj->getSectionContents(Sec, Data);
       Directives = std::string((const char *)Data.data(), Data.size());
       continue;
     }
     // Skip non-DWARF debug info. MSVC linker converts the sections into
     // a PDB file, but we don't support that.
     if (Name == ".debug" || Name.startswith(".debug$"))
       continue;
     // We want to preserve DWARF debug sections only when /debug is on.
     if (!Config->Debug && Name.startswith(".debug"))
       continue;
     if (Sec->Characteristics & llvm::COFF::IMAGE_SCN_LNK_REMOVE)
       continue;
     auto *C = new (Alloc) SectionChunk(this, Sec);
     Chunks.push_back(C);
     SparseChunks[I] = C;
   }
 }

 void ObjectFile::initializeSymbols() {
   uint32_t NumSymbols = COFFObj->getNumberOfSymbols();
   SymbolBodies.reserve(NumSymbols);
   SparseSymbolBodies.resize(NumSymbols);
   llvm::SmallVector<Undefined *, 8> WeakAliases;
   int32_t LastSectionNumber = 0;
   for (uint32_t I = 0; I < NumSymbols; ++I) {
     // Get a COFFSymbolRef object.
     auto SymOrErr = COFFObj->getSymbol(I);
     error(SymOrErr, Twine("broken object file: ") + getName());

     COFFSymbolRef Sym = SymOrErr.get();

     const void *AuxP = nullptr;
     if (Sym.getNumberOfAuxSymbols())
       AuxP = COFFObj->getSymbol(I + 1)->getRawPtr();
     bool IsFirst = (LastSectionNumber != Sym.getSectionNumber());

     SymbolBody *Body = nullptr;
     if (Sym.isUndefined()) {
       Body = createUndefined(Sym);
     } else if (Sym.isWeakExternal()) {
       Body = createWeakExternal(Sym, AuxP);
       WeakAliases.push_back((Undefined *)Body);
     } else {
       Body = createDefined(Sym, AuxP, IsFirst);
     }
     if (Body) {
       SymbolBodies.push_back(Body);
       SparseSymbolBodies[I] = Body;
     }
     I += Sym.getNumberOfAuxSymbols();
     LastSectionNumber = Sym.getSectionNumber();
   }
   for (Undefined *U : WeakAliases)
     U->WeakAlias = SparseSymbolBodies[(uintptr_t)U->WeakAlias];
 }

 Undefined *ObjectFile::createUndefined(COFFSymbolRef Sym) {
   StringRef Name;
   COFFObj->getSymbolName(Sym, Name);
   return new (Alloc) Undefined(Name);
 }

 Undefined *ObjectFile::createWeakExternal(COFFSymbolRef Sym, const void *AuxP) {
   StringRef Name;
   COFFObj->getSymbolName(Sym, Name);
   auto *U = new (Alloc) Undefined(Name);
   auto *Aux = (const coff_aux_weak_external *)AuxP;
   U->WeakAlias = (Undefined *)(uintptr_t)Aux->TagIndex;
   return U;
 }

 Defined *ObjectFile::createDefined(COFFSymbolRef Sym, const void *AuxP,
                                    bool IsFirst) {
   StringRef Name;
   if (Sym.isCommon()) {
     auto *C = new (Alloc) CommonChunk(Sym);
     Chunks.push_back(C);
     return new (Alloc) DefinedCommon(this, Sym, C);
   }
   if (Sym.isAbsolute()) {
     COFFObj->getSymbolName(Sym, Name);
     // Skip special symbols.
     if (Name == "@comp.id")
       return nullptr;
     // COFF spec 5.10.1. The .sxdata section.
     if (Name == "@feat.00") {
       if (Sym.getValue() & 1)
         SEHCompat = true;
       return nullptr;
     }
     return new (Alloc) DefinedAbsolute(Name, Sym);
   }
   if (Sym.getSectionNumber() == llvm::COFF::IMAGE_SYM_DEBUG)
     return nullptr;

   // Nothing else to do without a section chunk.
   auto *SC = cast_or_null<SectionChunk>(SparseChunks[Sym.getSectionNumber()]);
   if (!SC)
     return nullptr;

   // Handle associative sections
   if (IsFirst && AuxP) {
     auto *Aux = reinterpret_cast<const coff_aux_section_definition *>(AuxP);
     if (Aux->Selection == IMAGE_COMDAT_SELECT_ASSOCIATIVE)
       if (auto *ParentSC = cast_or_null<SectionChunk>(
               SparseChunks[Aux->getNumber(Sym.isBigObj())]))
         ParentSC->addAssociative(SC);
   }

   auto *B = new (Alloc) DefinedRegular(this, Sym, SC);
   if (SC->isCOMDAT() && Sym.getValue() == 0 && !AuxP)
     SC->setSymbol(B);

   return B;
 }

 void ObjectFile::initializeSEH() {
   if (!SEHCompat || !SXData)
     return;
   ArrayRef<uint8_t> A;
   COFFObj->getSectionContents(SXData, A);
   if (A.size() % 4 != 0)
     error(".sxdata must be an array of symbol table indices");
   auto *I = reinterpret_cast<const ulittle32_t *>(A.data());
   auto *E = reinterpret_cast<const ulittle32_t *>(A.data() + A.size());
   for (; I != E; ++I)
     SEHandlers.insert(SparseSymbolBodies[*I]);
 }

 MachineTypes ObjectFile::getMachineType() {
   if (COFFObj)
     return static_cast<MachineTypes>(COFFObj->getMachine());
   return IMAGE_FILE_MACHINE_UNKNOWN;
 }

 StringRef ltrim1(StringRef S, const char *Chars) {
   if (!S.empty() && strchr(Chars, S[0]))
     return S.substr(1);
   return S;
 }

 void ImportFile::parse() {
   const char *Buf = MB.getBufferStart();
   const char *End = MB.getBufferEnd();
   const auto *Hdr = reinterpret_cast<const coff_import_header *>(Buf);

   // Check if the total size is valid.
   if ((size_t)(End - Buf) != (sizeof(*Hdr) + Hdr->SizeOfData))
     error("broken import library");

   // Read names and create an __imp_ symbol.
   StringRef Name = StringAlloc.save(StringRef(Buf + sizeof(*Hdr)));
   StringRef ImpName = StringAlloc.save(Twine("__imp_") + Name);
   const char *NameStart = Buf + sizeof(coff_import_header) + Name.size() + 1;
   DLLName = StringRef(NameStart).lower();
   StringRef ExtName;
   switch (Hdr->getNameType()) {
   case IMPORT_ORDINAL:
     ExtName = "";
     break;
   case IMPORT_NAME:
     ExtName = Name;
     break;
   case IMPORT_NAME_NOPREFIX:
     ExtName = ltrim1(Name, "?@_");
     break;
   case IMPORT_NAME_UNDECORATE:
     ExtName = ltrim1(Name, "?@_");
     ExtName = ExtName.substr(0, ExtName.find('@'));
     break;
   }
   ImpSym = new (Alloc) DefinedImportData(DLLName, ImpName, ExtName, Hdr);
   SymbolBodies.push_back(ImpSym);

   // If type is function, we need to create a thunk which jump to an
   // address pointed by the __imp_ symbol. (This allows you to call
   // DLL functions just like regular non-DLL functions.)
   if (Hdr->getType() != llvm::COFF::IMPORT_CODE)
     return;
   ThunkSym = new (Alloc) DefinedImportThunk(Name, ImpSym, Hdr->Machine);
   SymbolBodies.push_back(ThunkSym);
 }

 void BitcodeFile::parse() {
   std::string Err;
   M.reset(LTOModule::createFromBuffer(MB.getBufferStart(),
                                       MB.getBufferSize(),
                                       llvm::TargetOptions(), Err));
   if (!Err.empty())
     error(Err);

   llvm::StringSaver Saver(Alloc);
   for (unsigned I = 0, E = M->getSymbolCount(); I != E; ++I) {
     lto_symbol_attributes Attrs = M->getSymbolAttributes(I);
     if ((Attrs & LTO_SYMBOL_SCOPE_MASK) == LTO_SYMBOL_SCOPE_INTERNAL)
       continue;

     StringRef SymName = Saver.save(M->getSymbolName(I));
     int SymbolDef = Attrs & LTO_SYMBOL_DEFINITION_MASK;
     if (SymbolDef == LTO_SYMBOL_DEFINITION_UNDEFINED) {
       SymbolBodies.push_back(new (Alloc) Undefined(SymName));
     } else {
       bool Replaceable =
           (SymbolDef == LTO_SYMBOL_DEFINITION_TENTATIVE || // common
            (Attrs & LTO_SYMBOL_COMDAT) ||                  // comdat
            (SymbolDef == LTO_SYMBOL_DEFINITION_WEAK &&     // weak external
             (Attrs & LTO_SYMBOL_ALIAS)));
       SymbolBodies.push_back(new (Alloc) DefinedBitcode(this, SymName,
                                                         Replaceable));
     }
   }

   Directives = M->getLinkerOpts();
 }

 MachineTypes BitcodeFile::getMachineType() {
   if (!M)
     return IMAGE_FILE_MACHINE_UNKNOWN;
   switch (Triple(M->getTargetTriple()).getArch()) {
   case Triple::x86_64:
     return AMD64;
   case Triple::x86:
     return I386;
   case Triple::arm:
     return ARMNT;
   default:
     return IMAGE_FILE_MACHINE_UNKNOWN;
   }
 }

 } // namespace coff
 } // namespace lld
	//===- InputFiles.cpp -----------------------------------------------------===//
	//
	// The LLVM Linker
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//

	#include "Chunks.h"
	#include "Error.h"
	#include "InputFiles.h"
	#include "Symbols.h"
	#include "llvm/ADT/STLExtras.h"
	#include "llvm/LTO/LTOModule.h"
	#include "llvm/Object/COFF.h"
	#include "llvm/Support/COFF.h"
	#include "llvm/Support/Debug.h"
	#include "llvm/Support/Endian.h"
	#include "llvm/Support/raw_ostream.h"

	using namespace llvm::COFF;
	using namespace llvm::object;
	using namespace llvm::support::endian;
	using llvm::RoundUpToAlignment;
	using llvm::Triple;
	using llvm::support::ulittle32_t;
	using llvm::sys::fs::file_magic;
	using llvm::sys::fs::identify_magic;

	namespace lld {
	namespace coff {

	int InputFile::NextIndex = 0;

	// Returns the last element of a path, which is supposed to be a filename.
	static StringRef getBasename(StringRef Path) {
	size_t Pos = Path.find_last_of("\\/");
	if (Pos == StringRef::npos)
	return Path;
	return Path.substr(Pos + 1);
	}

	// Returns a string in the format of "foo.obj" or "foo.obj(bar.lib)".
	std::string InputFile::getShortName() {
	if (ParentName == "")
	return getName().lower();
	std::string Res = (getBasename(ParentName) + "(" +
	getBasename(getName()) + ")").str();
	return StringRef(Res).lower();
	}

	void ArchiveFile::parse() {
	// Parse a MemoryBufferRef as an archive file.
	auto ArchiveOrErr = Archive::create(MB);
	error(ArchiveOrErr, "Failed to parse static library");
	File = std::move(ArchiveOrErr.get());

	// Allocate a buffer for Lazy objects.
	size_t NumSyms = File->getNumberOfSymbols();
	size_t BufSize = NumSyms * sizeof(Lazy);
	Lazy Buf = (Lazy )Alloc.Allocate(BufSize, llvm::alignOf<Lazy>());
	LazySymbols.reserve(NumSyms);

	// Read the symbol table to construct Lazy objects.
	uint32_t I = 0;
	for (const Archive::Symbol &Sym : File->symbols()) {
	auto *B = new (&Buf[I++]) Lazy(this, Sym);
	// Skip special symbol exists in import library files.
	if (B->getName() != "__NULL_IMPORT_DESCRIPTOR")
	LazySymbols.push_back(B);
	}

	// Seen is a map from member files to boolean values. Initially
	// all members are mapped to false, which indicates all these files
	// are not read yet.
	for (const Archive::Child &Child : File->children())
	Seen[Child.getChildOffset()].clear();
	}

	// Returns a buffer pointing to a member file containing a given symbol.
	// This function is thread-safe.
	MemoryBufferRef ArchiveFile::getMember(const Archive::Symbol *Sym) {
	auto ItOrErr = Sym->getMember();
	error(ItOrErr,
	Twine("Could not get the member for symbol ") + Sym->getName());
	Archive::child_iterator It = ItOrErr.get();

	// Return an empty buffer if we have already returned the same buffer.
	if (Seen[It->getChildOffset()].test_and_set())
	return MemoryBufferRef();
	ErrorOr<MemoryBufferRef> Ret = It->getMemoryBufferRef();
	error(Ret, Twine("Could not get the buffer for the member defining symbol ") +
	Sym->getName());
	return *Ret;
	}

	void ObjectFile::parse() {
	// Parse a memory buffer as a COFF file.
	auto BinOrErr = createBinary(MB);
	error(BinOrErr, "Failed to parse object file");
	std::unique_ptr<Binary> Bin = std::move(BinOrErr.get());

	if (auto *Obj = dyn_cast<COFFObjectFile>(Bin.get())) {
	Bin.release();
	COFFObj.reset(Obj);
	} else {
	error(Twine(getName()) + " is not a COFF file.");
	}

	// Read section and symbol tables.
	initializeChunks();
	initializeSymbols();
	initializeSEH();
	}

	void ObjectFile::initializeChunks() {
	uint32_t NumSections = COFFObj->getNumberOfSections();
	Chunks.reserve(NumSections);
	SparseChunks.resize(NumSections + 1);
	for (uint32_t I = 1; I < NumSections + 1; ++I) {
	const coff_section *Sec;
	StringRef Name;
	std::error_code EC = COFFObj->getSection(I, Sec);
	error(EC, Twine("getSection failed: ") + Name);
	EC = COFFObj->getSectionName(Sec, Name);
	error(EC, Twine("getSectionName failed: ") + Name);
	if (Name == ".sxdata") {
	SXData = Sec;
	continue;
	}
	if (Name == ".drectve") {
	ArrayRef<uint8_t> Data;
	COFFObj->getSectionContents(Sec, Data);
	Directives = std::string((const char *)Data.data(), Data.size());
	continue;
	}
	// Skip non-DWARF debug info. MSVC linker converts the sections into
	// a PDB file, but we don't support that.
	if (Name == ".debug" \|\| Name.startswith(".debug$"))
	continue;
	// We want to preserve DWARF debug sections only when /debug is on.
	if (!Config->Debug && Name.startswith(".debug"))
	continue;
	if (Sec->Characteristics & llvm::COFF::IMAGE_SCN_LNK_REMOVE)
	continue;
	auto *C = new (Alloc) SectionChunk(this, Sec);
	Chunks.push_back(C);
	SparseChunks[I] = C;
	}
	}

	void ObjectFile::initializeSymbols() {
	uint32_t NumSymbols = COFFObj->getNumberOfSymbols();
	SymbolBodies.reserve(NumSymbols);
	SparseSymbolBodies.resize(NumSymbols);
	llvm::SmallVector<Undefined *, 8> WeakAliases;
	int32_t LastSectionNumber = 0;
	for (uint32_t I = 0; I < NumSymbols; ++I) {
	// Get a COFFSymbolRef object.
	auto SymOrErr = COFFObj->getSymbol(I);
	error(SymOrErr, Twine("broken object file: ") + getName());

	COFFSymbolRef Sym = SymOrErr.get();

	const void *AuxP = nullptr;
	if (Sym.getNumberOfAuxSymbols())
	AuxP = COFFObj->getSymbol(I + 1)->getRawPtr();
	bool IsFirst = (LastSectionNumber != Sym.getSectionNumber());

	SymbolBody *Body = nullptr;
	if (Sym.isUndefined()) {
	Body = createUndefined(Sym);
	} else if (Sym.isWeakExternal()) {
	Body = createWeakExternal(Sym, AuxP);
	WeakAliases.push_back((Undefined *)Body);
	} else {
	Body = createDefined(Sym, AuxP, IsFirst);
	}
	if (Body) {
	SymbolBodies.push_back(Body);
	SparseSymbolBodies[I] = Body;
	}
	I += Sym.getNumberOfAuxSymbols();
	LastSectionNumber = Sym.getSectionNumber();
	}
	for (Undefined *U : WeakAliases)
	U->WeakAlias = SparseSymbolBodies[(uintptr_t)U->WeakAlias];
	}

	Undefined *ObjectFile::createUndefined(COFFSymbolRef Sym) {
	StringRef Name;
	COFFObj->getSymbolName(Sym, Name);
	return new (Alloc) Undefined(Name);
	}

	Undefined ObjectFile::createWeakExternal(COFFSymbolRef Sym, const void AuxP) {
	StringRef Name;
	COFFObj->getSymbolName(Sym, Name);
	auto *U = new (Alloc) Undefined(Name);
	auto Aux = (const coff_aux_weak_external )AuxP;
	U->WeakAlias = (Undefined *)(uintptr_t)Aux->TagIndex;
	return U;
	}

	Defined ObjectFile::createDefined(COFFSymbolRef Sym, const void AuxP,
	bool IsFirst) {
	StringRef Name;
	if (Sym.isCommon()) {
	auto *C = new (Alloc) CommonChunk(Sym);
	Chunks.push_back(C);
	return new (Alloc) DefinedCommon(this, Sym, C);
	}
	if (Sym.isAbsolute()) {
	COFFObj->getSymbolName(Sym, Name);
	// Skip special symbols.
	if (Name == "@comp.id")
	return nullptr;
	// COFF spec 5.10.1. The .sxdata section.
	if (Name == "@feat.00") {
	if (Sym.getValue() & 1)
	SEHCompat = true;
	return nullptr;
	}
	return new (Alloc) DefinedAbsolute(Name, Sym);
	}
	if (Sym.getSectionNumber() == llvm::COFF::IMAGE_SYM_DEBUG)
	return nullptr;

	// Nothing else to do without a section chunk.
	auto *SC = cast_or_null<SectionChunk>(SparseChunks[Sym.getSectionNumber()]);
	if (!SC)
	return nullptr;

	// Handle associative sections
	if (IsFirst && AuxP) {
	auto Aux = reinterpret_cast<const coff_aux_section_definition >(AuxP);
	if (Aux->Selection == IMAGE_COMDAT_SELECT_ASSOCIATIVE)
	if (auto *ParentSC = cast_or_null<SectionChunk>(
	SparseChunks[Aux->getNumber(Sym.isBigObj())]))
	ParentSC->addAssociative(SC);
	}

	auto *B = new (Alloc) DefinedRegular(this, Sym, SC);
	if (SC->isCOMDAT() && Sym.getValue() == 0 && !AuxP)
	SC->setSymbol(B);

	return B;
	}

	void ObjectFile::initializeSEH() {
	if (!SEHCompat \|\| !SXData)
	return;
	ArrayRef<uint8_t> A;
	COFFObj->getSectionContents(SXData, A);
	if (A.size() % 4 != 0)
	error(".sxdata must be an array of symbol table indices");
	auto I = reinterpret_cast<const ulittle32_t >(A.data());
	auto E = reinterpret_cast<const ulittle32_t >(A.data() + A.size());
	for (; I != E; ++I)
	SEHandlers.insert(SparseSymbolBodies[*I]);
	}

	MachineTypes ObjectFile::getMachineType() {
	if (COFFObj)
	return static_cast<MachineTypes>(COFFObj->getMachine());
	return IMAGE_FILE_MACHINE_UNKNOWN;
	}

	StringRef ltrim1(StringRef S, const char *Chars) {
	if (!S.empty() && strchr(Chars, S[0]))
	return S.substr(1);
	return S;
	}

	void ImportFile::parse() {
	const char *Buf = MB.getBufferStart();
	const char *End = MB.getBufferEnd();
	const auto Hdr = reinterpret_cast<const coff_import_header >(Buf);

	// Check if the total size is valid.
	if ((size_t)(End - Buf) != (sizeof(*Hdr) + Hdr->SizeOfData))
	error("broken import library");

	// Read names and create an __imp_ symbol.
	StringRef Name = StringAlloc.save(StringRef(Buf + sizeof(*Hdr)));
	StringRef ImpName = StringAlloc.save(Twine("__imp_") + Name);
	const char *NameStart = Buf + sizeof(coff_import_header) + Name.size() + 1;
	DLLName = StringRef(NameStart).lower();
	StringRef ExtName;
	switch (Hdr->getNameType()) {
	case IMPORT_ORDINAL:
	ExtName = "";
	break;
	case IMPORT_NAME:
	ExtName = Name;
	break;
	case IMPORT_NAME_NOPREFIX:
	ExtName = ltrim1(Name, "?@_");
	break;
	case IMPORT_NAME_UNDECORATE:
	ExtName = ltrim1(Name, "?@_");
	ExtName = ExtName.substr(0, ExtName.find('@'));
	break;
	}
	ImpSym = new (Alloc) DefinedImportData(DLLName, ImpName, ExtName, Hdr);
	SymbolBodies.push_back(ImpSym);

	// If type is function, we need to create a thunk which jump to an
	// address pointed by the __imp_ symbol. (This allows you to call
	// DLL functions just like regular non-DLL functions.)
	if (Hdr->getType() != llvm::COFF::IMPORT_CODE)
	return;
	ThunkSym = new (Alloc) DefinedImportThunk(Name, ImpSym, Hdr->Machine);
	SymbolBodies.push_back(ThunkSym);
	}

	void BitcodeFile::parse() {
	std::string Err;
	M.reset(LTOModule::createFromBuffer(MB.getBufferStart(),
	MB.getBufferSize(),
	llvm::TargetOptions(), Err));
	if (!Err.empty())
	error(Err);

	llvm::StringSaver Saver(Alloc);
	for (unsigned I = 0, E = M->getSymbolCount(); I != E; ++I) {
	lto_symbol_attributes Attrs = M->getSymbolAttributes(I);
	if ((Attrs & LTO_SYMBOL_SCOPE_MASK) == LTO_SYMBOL_SCOPE_INTERNAL)
	continue;

	StringRef SymName = Saver.save(M->getSymbolName(I));
	int SymbolDef = Attrs & LTO_SYMBOL_DEFINITION_MASK;
	if (SymbolDef == LTO_SYMBOL_DEFINITION_UNDEFINED) {
	SymbolBodies.push_back(new (Alloc) Undefined(SymName));
	} else {
	bool Replaceable =
	(SymbolDef == LTO_SYMBOL_DEFINITION_TENTATIVE \|\| // common
	(Attrs & LTO_SYMBOL_COMDAT) \|\| // comdat
	(SymbolDef == LTO_SYMBOL_DEFINITION_WEAK && // weak external
	(Attrs & LTO_SYMBOL_ALIAS)));
	SymbolBodies.push_back(new (Alloc) DefinedBitcode(this, SymName,
	Replaceable));
	}
	}

	Directives = M->getLinkerOpts();
	}

	MachineTypes BitcodeFile::getMachineType() {
	if (!M)
	return IMAGE_FILE_MACHINE_UNKNOWN;
	switch (Triple(M->getTargetTriple()).getArch()) {
	case Triple::x86_64:
	return AMD64;
	case Triple::x86:
	return I386;
	case Triple::arm:
	return ARMNT;
	default:
	return IMAGE_FILE_MACHINE_UNKNOWN;
	}
	}

	} // namespace coff
	} // namespace lld