blob: ea99583b1d80b74e1b445df70bc0371bec050a2a [file] [log] [blame]
//===- PDB.cpp ------------------------------------------------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "PDB.h"
#include "Chunks.h"
#include "Config.h"
#include "DebugTypes.h"
#include "Driver.h"
#include "SymbolTable.h"
#include "Symbols.h"
#include "TypeMerger.h"
#include "Writer.h"
#include "lld/Common/ErrorHandler.h"
#include "lld/Common/Timer.h"
#include "lld/Common/Threads.h"
#include "llvm/DebugInfo/CodeView/DebugFrameDataSubsection.h"
#include "llvm/DebugInfo/CodeView/DebugSubsectionRecord.h"
#include "llvm/DebugInfo/CodeView/GlobalTypeTableBuilder.h"
#include "llvm/DebugInfo/CodeView/LazyRandomTypeCollection.h"
#include "llvm/DebugInfo/CodeView/MergingTypeTableBuilder.h"
#include "llvm/DebugInfo/CodeView/RecordName.h"
#include "llvm/DebugInfo/CodeView/SymbolDeserializer.h"
#include "llvm/DebugInfo/CodeView/SymbolRecordHelpers.h"
#include "llvm/DebugInfo/CodeView/SymbolSerializer.h"
#include "llvm/DebugInfo/CodeView/TypeDeserializer.h"
#include "llvm/DebugInfo/CodeView/TypeDumpVisitor.h"
#include "llvm/DebugInfo/CodeView/TypeIndexDiscovery.h"
#include "llvm/DebugInfo/CodeView/TypeStreamMerger.h"
#include "llvm/DebugInfo/MSF/MSFBuilder.h"
#include "llvm/DebugInfo/MSF/MSFCommon.h"
#include "llvm/DebugInfo/PDB/GenericError.h"
#include "llvm/DebugInfo/PDB/Native/DbiModuleDescriptorBuilder.h"
#include "llvm/DebugInfo/PDB/Native/DbiStream.h"
#include "llvm/DebugInfo/PDB/Native/DbiStreamBuilder.h"
#include "llvm/DebugInfo/PDB/Native/GSIStreamBuilder.h"
#include "llvm/DebugInfo/PDB/Native/InfoStream.h"
#include "llvm/DebugInfo/PDB/Native/InfoStreamBuilder.h"
#include "llvm/DebugInfo/PDB/Native/NativeSession.h"
#include "llvm/DebugInfo/PDB/Native/PDBFile.h"
#include "llvm/DebugInfo/PDB/Native/PDBFileBuilder.h"
#include "llvm/DebugInfo/PDB/Native/PDBStringTableBuilder.h"
#include "llvm/DebugInfo/PDB/Native/TpiHashing.h"
#include "llvm/DebugInfo/PDB/Native/TpiStream.h"
#include "llvm/DebugInfo/PDB/Native/TpiStreamBuilder.h"
#include "llvm/DebugInfo/PDB/PDB.h"
#include "llvm/Object/COFF.h"
#include "llvm/Object/CVDebugRecord.h"
#include "llvm/Support/BinaryByteStream.h"
#include "llvm/Support/CRC.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/Errc.h"
#include "llvm/Support/FormatVariadic.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/ScopedPrinter.h"
#include <memory>
using namespace llvm;
using namespace llvm::codeview;
using llvm::object::coff_section;
namespace lld {
namespace coff {
static ExitOnError exitOnErr;
static Timer totalPdbLinkTimer("PDB Emission (Cumulative)", Timer::root());
static Timer addObjectsTimer("Add Objects", totalPdbLinkTimer);
static Timer typeMergingTimer("Type Merging", addObjectsTimer);
static Timer symbolMergingTimer("Symbol Merging", addObjectsTimer);
static Timer globalsLayoutTimer("Globals Stream Layout", totalPdbLinkTimer);
static Timer tpiStreamLayoutTimer("TPI Stream Layout", totalPdbLinkTimer);
static Timer diskCommitTimer("Commit to Disk", totalPdbLinkTimer);
namespace {
class DebugSHandler;
class PDBLinker {
friend DebugSHandler;
PDBLinker(SymbolTable *symtab)
: alloc(), symtab(symtab), builder(alloc), tMerger(alloc) {
// This isn't strictly necessary, but link.exe usually puts an empty string
// as the first "valid" string in the string table, so we do the same in
// order to maintain as much byte-for-byte compatibility as possible.
/// Emit the basic PDB structure: initial streams, headers, etc.
void initialize(llvm::codeview::DebugInfo *buildId);
/// Add natvis files specified on the command line.
void addNatvisFiles();
/// Link CodeView from each object file in the symbol table into the PDB.
void addObjectsToPDB();
/// Link info for each import file in the symbol table into the PDB.
void addImportFilesToPDB(ArrayRef<OutputSection *> outputSections);
/// Link CodeView from a single object file into the target (output) PDB.
/// When a precompiled headers object is linked, its TPI map might be provided
/// externally.
void addObjFile(ObjFile *file, CVIndexMap *externIndexMap = nullptr);
/// Produce a mapping from the type and item indices used in the object
/// file to those in the destination PDB.
/// If the object file uses a type server PDB (compiled with /Zi), merge TPI
/// and IPI from the type server PDB and return a map for it. Each unique type
/// server PDB is merged at most once, so this may return an existing index
/// mapping.
/// If the object does not use a type server PDB (compiled with /Z7), we merge
/// all the type and item records from the .debug$S stream and fill in the
/// caller-provided objectIndexMap.
Expected<const CVIndexMap &> mergeDebugT(ObjFile *file,
CVIndexMap *objectIndexMap);
/// Reads and makes available a PDB.
Expected<const CVIndexMap &> maybeMergeTypeServerPDB(ObjFile *file);
/// Merges a precompiled headers TPI map into the current TPI map. The
/// precompiled headers object will also be loaded and remapped in the
/// process.
Error mergeInPrecompHeaderObj(ObjFile *file, CVIndexMap *objectIndexMap);
/// Reads and makes available a precompiled headers object.
/// This is a requirement for objects compiled with cl.exe /Yu. In that
/// case, the referenced object (which was compiled with /Yc) has to be loaded
/// first. This is mainly because the current object's TPI stream has external
/// references to the precompiled headers object.
/// If the precompiled headers object was already loaded, this function will
/// simply return its (remapped) TPI map.
Expected<const CVIndexMap &> aquirePrecompObj(ObjFile *file);
/// Adds a precompiled headers object signature -> TPI mapping.
std::pair<CVIndexMap &, bool /*already there*/>
registerPrecompiledHeaders(uint32_t signature);
void mergeSymbolRecords(ObjFile *file, const CVIndexMap &indexMap,
std::vector<ulittle32_t *> &stringTableRefs,
BinaryStreamRef symData);
/// Add the section map and section contributions to the PDB.
void addSections(ArrayRef<OutputSection *> outputSections,
ArrayRef<uint8_t> sectionTable);
/// Write the PDB to disk and store the Guid generated for it in *Guid.
void commit(codeview::GUID *guid);
// Print statistics regarding the final PDB
void printStats();
BumpPtrAllocator alloc;
SymbolTable *symtab;
pdb::PDBFileBuilder builder;
TypeMerger tMerger;
/// PDBs use a single global string table for filenames in the file checksum
/// table.
DebugStringTableSubsection pdbStrTab;
llvm::SmallString<128> nativePath;
std::vector<pdb::SecMapEntry> sectionMap;
/// Type index mappings of type server PDBs that we've loaded so far.
std::map<codeview::GUID, CVIndexMap> typeServerIndexMappings;
/// Type index mappings of precompiled objects type map that we've loaded so
/// far.
std::map<uint32_t, CVIndexMap> precompTypeIndexMappings;
// For statistics
uint64_t globalSymbols = 0;
uint64_t moduleSymbols = 0;
uint64_t publicSymbols = 0;
class DebugSHandler {
PDBLinker &linker;
/// The object file whose .debug$S sections we're processing.
ObjFile &file;
/// The result of merging type indices.
const CVIndexMap &indexMap;
/// The DEBUG_S_STRINGTABLE subsection. These strings are referred to by
/// index from other records in the .debug$S section. All of these strings
/// need to be added to the global PDB string table, and all references to
/// these strings need to have their indices re-written to refer to the
/// global PDB string table.
DebugStringTableSubsectionRef cVStrTab;
/// The DEBUG_S_FILECHKSMS subsection. As above, these are referred to
/// by other records in the .debug$S section and need to be merged into the
/// PDB.
DebugChecksumsSubsectionRef checksums;
/// The DEBUG_S_INLINEELINES subsection. There can be only one of these per
/// object file.
DebugInlineeLinesSubsectionRef inlineeLines;
/// The DEBUG_S_FRAMEDATA subsection(s). There can be more than one of
/// these and they need not appear in any specific order. However, they
/// contain string table references which need to be re-written, so we
/// collect them all here and re-write them after all subsections have been
/// discovered and processed.
std::vector<DebugFrameDataSubsectionRef> newFpoFrames;
/// Pointers to raw memory that we determine have string table references
/// that need to be re-written. We first process all .debug$S subsections
/// to ensure that we can handle subsections written in any order, building
/// up this list as we go. At the end, we use the string table (which must
/// have been discovered by now else it is an error) to re-write these
/// references.
std::vector<ulittle32_t *> stringTableReferences;
DebugSHandler(PDBLinker &linker, ObjFile &file, const CVIndexMap &indexMap)
: linker(linker), file(file), indexMap(indexMap) {}
void handleDebugS(lld::coff::SectionChunk &debugS);
mergeInlineeLines(DebugChecksumsSubsection *newChecksums);
void finish();
// Visual Studio's debugger requires absolute paths in various places in the
// PDB to work without additional configuration:
static void pdbMakeAbsolute(SmallVectorImpl<char> &fileName) {
// The default behavior is to produce paths that are valid within the context
// of the machine that you perform the link on. If the linker is running on
// a POSIX system, we will output absolute POSIX paths. If the linker is
// running on a Windows system, we will output absolute Windows paths. If the
// user desires any other kind of behavior, they should explicitly pass
// /pdbsourcepath, in which case we will treat the exact string the user
// passed in as the gospel and not normalize, canonicalize it.
if (sys::path::is_absolute(fileName, sys::path::Style::windows) ||
sys::path::is_absolute(fileName, sys::path::Style::posix))
// It's not absolute in any path syntax. Relative paths necessarily refer to
// the local file system, so we can make it native without ending up with a
// nonsensical path.
if (config->pdbSourcePath.empty()) {
// Try to guess whether /PDBSOURCEPATH is a unix path or a windows path.
// Since PDB's are more of a Windows thing, we make this conservative and only
// decide that it's a unix path if we're fairly certain. Specifically, if
// it starts with a forward slash.
SmallString<128> absoluteFileName = config->pdbSourcePath;
sys::path::Style guessedStyle = absoluteFileName.startswith("/")
? sys::path::Style::posix
: sys::path::Style::windows;
sys::path::append(absoluteFileName, guessedStyle, fileName);
sys::path::native(absoluteFileName, guessedStyle);
sys::path::remove_dots(absoluteFileName, true, guessedStyle);
fileName = std::move(absoluteFileName);
// A COFF .debug$H section is currently a clang extension. This function checks
// if a .debug$H section is in a format that we expect / understand, so that we
// can ignore any sections which are coincidentally also named .debug$H but do
// not contain a format we recognize.
static bool canUseDebugH(ArrayRef<uint8_t> debugH) {
if (debugH.size() < sizeof(object::debug_h_header))
return false;
auto *header =
reinterpret_cast<const object::debug_h_header *>(;
debugH = debugH.drop_front(sizeof(object::debug_h_header));
return header->Magic == COFF::DEBUG_HASHES_SECTION_MAGIC &&
header->Version == 0 &&
header->HashAlgorithm == uint16_t(GlobalTypeHashAlg::SHA1_8) &&
(debugH.size() % 8 == 0);
static Optional<ArrayRef<uint8_t>> getDebugH(ObjFile *file) {
SectionChunk *sec =
SectionChunk::findByName(file->getDebugChunks(), ".debug$H");
if (!sec)
return llvm::None;
ArrayRef<uint8_t> contents = sec->getContents();
if (!canUseDebugH(contents))
return None;
return contents;
static ArrayRef<GloballyHashedType>
getHashesFromDebugH(ArrayRef<uint8_t> debugH) {
debugH = debugH.drop_front(sizeof(object::debug_h_header));
uint32_t count = debugH.size() / sizeof(GloballyHashedType);
return {reinterpret_cast<const GloballyHashedType *>(, count};
static void addTypeInfo(pdb::TpiStreamBuilder &tpiBuilder,
TypeCollection &typeTable) {
// Start the TPI or IPI stream header.
// Flatten the in memory type table and hash each type.
typeTable.ForEachRecord([&](TypeIndex ti, const CVType &type) {
auto hash = pdb::hashTypeRecord(type);
if (auto e = hash.takeError())
fatal("type hashing error");
tpiBuilder.addTypeRecord(type.RecordData, *hash);
Expected<const CVIndexMap &>
PDBLinker::mergeDebugT(ObjFile *file, CVIndexMap *objectIndexMap) {
ScopedTimer t(typeMergingTimer);
if (!file->debugTypesObj)
return *objectIndexMap; // no Types stream
// Precompiled headers objects need to save the index map for further
// reference by other objects which use the precompiled headers.
if (file->debugTypesObj->kind == TpiSource::PCH) {
uint32_t pchSignature = file->pchSignature.getValueOr(0);
if (pchSignature == 0)
fatal("No signature found for the precompiled headers OBJ (" +
file->getName() + ")");
// When a precompiled headers object comes first on the command-line, we
// update the mapping here. Otherwise, if an object referencing the
// precompiled headers object comes first, the mapping is created in
// aquirePrecompObj(), thus we would skip this block.
if (!objectIndexMap->isPrecompiledTypeMap) {
auto r = registerPrecompiledHeaders(pchSignature);
if (r.second)
"A precompiled headers OBJ with the same signature was already "
"provided! (" +
file->getName() + ")");
objectIndexMap = &r.first;
if (file->debugTypesObj->kind == TpiSource::UsingPDB) {
// Look through type servers. If we've already seen this type server,
// don't merge any type information.
return maybeMergeTypeServerPDB(file);
CVTypeArray &types = *file->debugTypes;
if (file->debugTypesObj->kind == TpiSource::UsingPCH) {
// This object was compiled with /Yu, so process the corresponding
// precompiled headers object (/Yc) first. Some type indices in the current
// object are referencing data in the precompiled headers object, so we need
// both to be loaded.
Error e = mergeInPrecompHeaderObj(file, objectIndexMap);
if (e)
return std::move(e);
// Drop LF_PRECOMP record from the input stream, as it has been replaced
// with the precompiled headers Type stream in the mergeInPrecompHeaderObj()
// call above. Note that we can't just call Types.drop_front(), as we
// explicitly want to rebase the stream.
CVTypeArray::Iterator firstType = types.begin();
// Fill in the temporary, caller-provided ObjectIndexMap.
if (config->debugGHashes) {
ArrayRef<GloballyHashedType> hashes;
std::vector<GloballyHashedType> ownedHashes;
if (Optional<ArrayRef<uint8_t>> debugH = getDebugH(file))
hashes = getHashesFromDebugH(*debugH);
else {
ownedHashes = GloballyHashedType::hashTypes(types);
hashes = ownedHashes;
if (auto err = mergeTypeAndIdRecords(
tMerger.globalIDTable, tMerger.globalTypeTable,
objectIndexMap->tpiMap, types, hashes, file->pchSignature))
fatal("codeview::mergeTypeAndIdRecords failed: " +
} else {
if (auto err = mergeTypeAndIdRecords(tMerger.iDTable, tMerger.typeTable,
objectIndexMap->tpiMap, types,
fatal("codeview::mergeTypeAndIdRecords failed: " +
return *objectIndexMap;
Expected<const CVIndexMap &> PDBLinker::maybeMergeTypeServerPDB(ObjFile *file) {
Expected<llvm::pdb::NativeSession *> pdbSession = findTypeServerSource(file);
if (!pdbSession)
return pdbSession.takeError();
pdb::PDBFile &pdbFile = pdbSession.get()->getPDBFile();
pdb::InfoStream &info = cantFail(pdbFile.getPDBInfoStream());
auto it = typeServerIndexMappings.emplace(info.getGuid(), CVIndexMap());
CVIndexMap &indexMap = it.first->second;
if (!it.second)
return indexMap; // already merged
// Mark this map as a type server map.
indexMap.isTypeServerMap = true;
Expected<pdb::TpiStream &> expectedTpi = pdbFile.getPDBTpiStream();
if (auto e = expectedTpi.takeError())
fatal("Type server does not have TPI stream: " + toString(std::move(e)));
pdb::TpiStream *maybeIpi = nullptr;
if (pdbFile.hasPDBIpiStream()) {
Expected<pdb::TpiStream &> expectedIpi = pdbFile.getPDBIpiStream();
if (auto e = expectedIpi.takeError())
fatal("Error getting type server IPI stream: " + toString(std::move(e)));
maybeIpi = &*expectedIpi;
if (config->debugGHashes) {
// PDBs do not actually store global hashes, so when merging a type server
// PDB we have to synthesize global hashes. To do this, we first synthesize
// global hashes for the TPI stream, since it is independent, then we
// synthesize hashes for the IPI stream, using the hashes for the TPI stream
// as inputs.
auto tpiHashes = GloballyHashedType::hashTypes(expectedTpi->typeArray());
Optional<uint32_t> endPrecomp;
// Merge TPI first, because the IPI stream will reference type indices.
if (auto err =
mergeTypeRecords(tMerger.globalTypeTable, indexMap.tpiMap,
expectedTpi->typeArray(), tpiHashes, endPrecomp))
fatal("codeview::mergeTypeRecords failed: " + toString(std::move(err)));
// Merge IPI.
if (maybeIpi) {
auto ipiHashes =
GloballyHashedType::hashIds(maybeIpi->typeArray(), tpiHashes);
if (auto err =
mergeIdRecords(tMerger.globalIDTable, indexMap.tpiMap,
indexMap.ipiMap, maybeIpi->typeArray(), ipiHashes))
fatal("codeview::mergeIdRecords failed: " + toString(std::move(err)));
} else {
// Merge TPI first, because the IPI stream will reference type indices.
if (auto err = mergeTypeRecords(tMerger.typeTable, indexMap.tpiMap,
fatal("codeview::mergeTypeRecords failed: " + toString(std::move(err)));
// Merge IPI.
if (maybeIpi) {
if (auto err = mergeIdRecords(tMerger.iDTable, indexMap.tpiMap,
indexMap.ipiMap, maybeIpi->typeArray()))
fatal("codeview::mergeIdRecords failed: " + toString(std::move(err)));
return indexMap;
Error PDBLinker::mergeInPrecompHeaderObj(ObjFile *file,
CVIndexMap *objectIndexMap) {
const PrecompRecord &precomp =
Expected<const CVIndexMap &> e = aquirePrecompObj(file);
if (!e)
return e.takeError();
const CVIndexMap &precompIndexMap = *e;
if (precompIndexMap.tpiMap.empty())
return Error::success();
assert(precomp.getStartTypeIndex() == TypeIndex::FirstNonSimpleIndex);
assert(precomp.getTypesCount() <= precompIndexMap.tpiMap.size());
// Use the previously remapped index map from the precompiled headers.
precompIndexMap.tpiMap.begin() +
return Error::success();
static bool equals_path(StringRef path1, StringRef path2) {
#if defined(_WIN32)
return path1.equals_lower(path2);
return path1.equals(path2);
// Find by name an OBJ provided on the command line
static ObjFile *findObjWithPrecompSignature(StringRef fileNameOnly,
uint32_t precompSignature) {
for (ObjFile *f : ObjFile::instances) {
StringRef currentFileName = sys::path::filename(f->getName());
if (f->pchSignature.hasValue() &&
f->pchSignature.getValue() == precompSignature &&
equals_path(fileNameOnly, currentFileName))
return f;
return nullptr;
std::pair<CVIndexMap &, bool /*already there*/>
PDBLinker::registerPrecompiledHeaders(uint32_t signature) {
auto insertion = precompTypeIndexMappings.insert({signature, CVIndexMap()});
CVIndexMap &indexMap = insertion.first->second;
if (!insertion.second)
return {indexMap, true};
// Mark this map as a precompiled types map.
indexMap.isPrecompiledTypeMap = true;
return {indexMap, false};
Expected<const CVIndexMap &> PDBLinker::aquirePrecompObj(ObjFile *file) {
const PrecompRecord &precomp =
// First, check if we already loaded the precompiled headers object with this
// signature. Return the type index mapping if we've already seen it.
auto r = registerPrecompiledHeaders(precomp.getSignature());
if (r.second)
return r.first;
CVIndexMap &indexMap = r.first;
// Cross-compile warning: given that Clang doesn't generate LF_PRECOMP
// records, we assume the OBJ comes from a Windows build of cl.exe. Thusly,
// the paths embedded in the OBJs are in the Windows format.
SmallString<128> precompFileName = sys::path::filename(
precomp.getPrecompFilePath(), sys::path::Style::windows);
// link.exe requires that a precompiled headers object must always be provided
// on the command-line, even if that's not necessary.
auto precompFile =
findObjWithPrecompSignature(precompFileName, precomp.Signature);
if (!precompFile)
return createFileError(
addObjFile(precompFile, &indexMap);
return indexMap;
static bool remapTypeIndex(TypeIndex &ti, ArrayRef<TypeIndex> typeIndexMap) {
if (ti.isSimple())
return true;
if (ti.toArrayIndex() >= typeIndexMap.size())
return false;
ti = typeIndexMap[ti.toArrayIndex()];
return true;
static void remapTypesInSymbolRecord(ObjFile *file, SymbolKind symKind,
MutableArrayRef<uint8_t> recordBytes,
const CVIndexMap &indexMap,
ArrayRef<TiReference> typeRefs) {
MutableArrayRef<uint8_t> contents =
for (const TiReference &ref : typeRefs) {
unsigned byteSize = ref.Count * sizeof(TypeIndex);
if (contents.size() < ref.Offset + byteSize)
fatal("symbol record too short");
// This can be an item index or a type index. Choose the appropriate map.
ArrayRef<TypeIndex> typeOrItemMap = indexMap.tpiMap;
bool isItemIndex = ref.Kind == TiRefKind::IndexRef;
if (isItemIndex && indexMap.isTypeServerMap)
typeOrItemMap = indexMap.ipiMap;
MutableArrayRef<TypeIndex> tIs(
reinterpret_cast<TypeIndex *>( + ref.Offset), ref.Count);
for (TypeIndex &ti : tIs) {
if (!remapTypeIndex(ti, typeOrItemMap)) {
log("ignoring symbol record of kind 0x" + utohexstr(symKind) + " in " +
file->getName() + " with bad " + (isItemIndex ? "item" : "type") +
" index 0x" + utohexstr(ti.getIndex()));
ti = TypeIndex(SimpleTypeKind::NotTranslated);
static void
recordStringTableReferenceAtOffset(MutableArrayRef<uint8_t> contents,
uint32_t offset,
std::vector<ulittle32_t *> &strTableRefs) {
contents =
ulittle32_t *index = reinterpret_cast<ulittle32_t *>(;
static void
recordStringTableReferences(SymbolKind kind, MutableArrayRef<uint8_t> contents,
std::vector<ulittle32_t *> &strTableRefs) {
// For now we only handle S_FILESTATIC, but we may need the same logic for
// S_DEFRANGE and S_DEFRANGE_SUBFIELD. However, I cannot seem to generate any
// PDBs that contain these types of records, so because of the uncertainty
// they are omitted here until we can prove that it's necessary.
switch (kind) {
case SymbolKind::S_FILESTATIC:
// FileStaticSym::ModFileOffset
recordStringTableReferenceAtOffset(contents, 8, strTableRefs);
case SymbolKind::S_DEFRANGE:
log("Not fixing up string table reference in S_DEFRANGE / "
static SymbolKind symbolKind(ArrayRef<uint8_t> recordData) {
const RecordPrefix *prefix =
reinterpret_cast<const RecordPrefix *>(;
return static_cast<SymbolKind>(uint16_t(prefix->RecordKind));
/// MSVC translates S_PROC_ID_END to S_END, and S_[LG]PROC32_ID to S_[LG]PROC32
static void translateIdSymbols(MutableArrayRef<uint8_t> &recordData,
TypeCollection &iDTable) {
RecordPrefix *prefix = reinterpret_cast<RecordPrefix *>(;
SymbolKind kind = symbolKind(recordData);
if (kind == SymbolKind::S_PROC_ID_END) {
prefix->RecordKind = SymbolKind::S_END;
// In an object file, GPROC32_ID has an embedded reference which refers to the
// single object file type index namespace. This has already been translated
// to the PDB file's ID stream index space, but we need to convert this to a
// symbol that refers to the type stream index space. So we remap again from
// ID index space to type index space.
if (kind == SymbolKind::S_GPROC32_ID || kind == SymbolKind::S_LPROC32_ID) {
SmallVector<TiReference, 1> refs;
auto content = recordData.drop_front(sizeof(RecordPrefix));
CVSymbol sym(recordData);
discoverTypeIndicesInSymbol(sym, refs);
assert(refs.size() == 1);
assert(refs.front().Count == 1);
TypeIndex *ti =
reinterpret_cast<TypeIndex *>( + refs[0].Offset);
// `ti` is the index of a FuncIdRecord or MemberFuncIdRecord which lives in
// the IPI stream, whose `FunctionType` member refers to the TPI stream.
// Note that LF_FUNC_ID and LF_MEMFUNC_ID have the same record layout, and
// in both cases we just need the second type index.
if (!ti->isSimple() && !ti->isNoneType()) {
CVType funcIdData = iDTable.getType(*ti);
SmallVector<TypeIndex, 2> indices;
discoverTypeIndices(funcIdData, indices);
assert(indices.size() == 2);
*ti = indices[1];
kind = (kind == SymbolKind::S_GPROC32_ID) ? SymbolKind::S_GPROC32
: SymbolKind::S_LPROC32;
prefix->RecordKind = uint16_t(kind);
/// Copy the symbol record. In a PDB, symbol records must be 4 byte aligned.
/// The object file may not be aligned.
static MutableArrayRef<uint8_t>
copyAndAlignSymbol(const CVSymbol &sym, MutableArrayRef<uint8_t> &alignedMem) {
size_t size = alignTo(sym.length(), alignOf(CodeViewContainer::Pdb));
assert(size >= 4 && "record too short");
assert(size <= MaxRecordLength && "record too long");
assert(alignedMem.size() >= size && "didn't preallocate enough");
// Copy the symbol record and zero out any padding bytes.
MutableArrayRef<uint8_t> newData = alignedMem.take_front(size);
alignedMem = alignedMem.drop_front(size);
memcpy(,, sym.length());
memset( + sym.length(), 0, size - sym.length());
// Update the record prefix length. It should point to the beginning of the
// next record.
auto *prefix = reinterpret_cast<RecordPrefix *>(;
prefix->RecordLen = size - 2;
return newData;
struct ScopeRecord {
ulittle32_t ptrParent;
ulittle32_t ptrEnd;
struct SymbolScope {
ScopeRecord *openingRecord;
uint32_t scopeOffset;
static void scopeStackOpen(SmallVectorImpl<SymbolScope> &stack,
uint32_t curOffset, CVSymbol &sym) {
SymbolScope s;
s.scopeOffset = curOffset;
s.openingRecord = const_cast<ScopeRecord *>(
reinterpret_cast<const ScopeRecord *>(sym.content().data()));
s.openingRecord->ptrParent = stack.empty() ? 0 : stack.back().scopeOffset;
static void scopeStackClose(SmallVectorImpl<SymbolScope> &stack,
uint32_t curOffset, InputFile *file) {
if (stack.empty()) {
warn("symbol scopes are not balanced in " + file->getName());
SymbolScope s = stack.pop_back_val();
s.openingRecord->ptrEnd = curOffset;
static bool symbolGoesInModuleStream(const CVSymbol &sym, bool isGlobalScope) {
switch (sym.kind()) {
case SymbolKind::S_GDATA32:
case SymbolKind::S_CONSTANT:
// We really should not be seeing S_PROCREF and S_LPROCREF in the first place
// since they are synthesized by the linker in response to S_GPROC32 and
// S_LPROC32, but if we do see them, don't put them in the module stream I
// guess.
case SymbolKind::S_PROCREF:
case SymbolKind::S_LPROCREF:
return false;
// S_UDT records go in the module stream if it is not a global S_UDT.
case SymbolKind::S_UDT:
return !isGlobalScope;
// S_GDATA32 does not go in the module stream, but S_LDATA32 does.
case SymbolKind::S_LDATA32:
return true;
static bool symbolGoesInGlobalsStream(const CVSymbol &sym, bool isGlobalScope) {
switch (sym.kind()) {
case SymbolKind::S_CONSTANT:
case SymbolKind::S_GDATA32:
// S_LDATA32 goes in both the module stream and the globals stream.
case SymbolKind::S_LDATA32:
case SymbolKind::S_GPROC32:
case SymbolKind::S_LPROC32:
// We really should not be seeing S_PROCREF and S_LPROCREF in the first place
// since they are synthesized by the linker in response to S_GPROC32 and
// S_LPROC32, but if we do see them, copy them straight through.
case SymbolKind::S_PROCREF:
case SymbolKind::S_LPROCREF:
return true;
// S_UDT records go in the globals stream if it is a global S_UDT.
case SymbolKind::S_UDT:
return isGlobalScope;
return false;
static void addGlobalSymbol(pdb::GSIStreamBuilder &builder, uint16_t modIndex,
unsigned symOffset, const CVSymbol &sym) {
switch (sym.kind()) {
case SymbolKind::S_CONSTANT:
case SymbolKind::S_UDT:
case SymbolKind::S_GDATA32:
case SymbolKind::S_LDATA32:
case SymbolKind::S_PROCREF:
case SymbolKind::S_LPROCREF:
case SymbolKind::S_GPROC32:
case SymbolKind::S_LPROC32: {
SymbolRecordKind k = SymbolRecordKind::ProcRefSym;
if (sym.kind() == SymbolKind::S_LPROC32)
k = SymbolRecordKind::LocalProcRef;
ProcRefSym ps(k);
ps.Module = modIndex;
// For some reason, MSVC seems to add one to this value.
ps.Name = getSymbolName(sym);
ps.SumName = 0;
ps.SymOffset = symOffset;
llvm_unreachable("Invalid symbol kind!");
void PDBLinker::mergeSymbolRecords(ObjFile *file, const CVIndexMap &indexMap,
std::vector<ulittle32_t *> &stringTableRefs,
BinaryStreamRef symData) {
ArrayRef<uint8_t> symsBuffer;
cantFail(symData.readBytes(0, symData.getLength(), symsBuffer));
SmallVector<SymbolScope, 4> scopes;
// Iterate every symbol to check if any need to be realigned, and if so, how
// much space we need to allocate for them.
bool needsRealignment = false;
unsigned totalRealignedSize = 0;
auto ec = forEachCodeViewRecord<CVSymbol>(
symsBuffer, [&](CVSymbol sym) -> llvm::Error {
unsigned realignedSize =
alignTo(sym.length(), alignOf(CodeViewContainer::Pdb));
needsRealignment |= realignedSize != sym.length();
totalRealignedSize += realignedSize;
return Error::success();
// If any of the symbol record lengths was corrupt, ignore them all, warn
// about it, and move on.
if (ec) {
warn("corrupt symbol records in " + file->getName());
// If any symbol needed realignment, allocate enough contiguous memory for
// them all. Typically symbol subsections are small enough that this will not
// cause fragmentation.
MutableArrayRef<uint8_t> alignedSymbolMem;
if (needsRealignment) {
void *alignedData =
alloc.Allocate(totalRealignedSize, alignOf(CodeViewContainer::Pdb));
alignedSymbolMem = makeMutableArrayRef(
reinterpret_cast<uint8_t *>(alignedData), totalRealignedSize);
// Iterate again, this time doing the real work.
unsigned curSymOffset = file->moduleDBI->getNextSymbolOffset();
ArrayRef<uint8_t> bulkSymbols;
symsBuffer, [&](CVSymbol sym) -> llvm::Error {
// Align the record if required.
MutableArrayRef<uint8_t> recordBytes;
if (needsRealignment) {
recordBytes = copyAndAlignSymbol(sym, alignedSymbolMem);
sym = CVSymbol(recordBytes);
} else {
// Otherwise, we can actually mutate the symbol directly, since we
// copied it to apply relocations.
recordBytes = makeMutableArrayRef(
const_cast<uint8_t *>(, sym.length());
// Discover type index references in the record. Skip it if we don't
// know where they are.
SmallVector<TiReference, 32> typeRefs;
if (!discoverTypeIndicesInSymbol(sym, typeRefs)) {
log("ignoring unknown symbol record with kind 0x" +
return Error::success();
// Re-map all the type index references.
remapTypesInSymbolRecord(file, sym.kind(), recordBytes, indexMap,
// An object file may have S_xxx_ID symbols, but these get converted to
// "real" symbols in a PDB.
translateIdSymbols(recordBytes, tMerger.getIDTable());
sym = CVSymbol(recordBytes);
// If this record refers to an offset in the object file's string table,
// add that item to the global PDB string table and re-write the index.
recordStringTableReferences(sym.kind(), recordBytes, stringTableRefs);
// Fill in "Parent" and "End" fields by maintaining a stack of scopes.
if (symbolOpensScope(sym.kind()))
scopeStackOpen(scopes, curSymOffset, sym);
else if (symbolEndsScope(sym.kind()))
scopeStackClose(scopes, curSymOffset, file);
// Add the symbol to the globals stream if necessary. Do this before
// adding the symbol to the module since we may need to get the next
// symbol offset, and writing to the module's symbol stream will update
// that offset.
if (symbolGoesInGlobalsStream(sym, scopes.empty())) {
file->moduleDBI->getModuleIndex(), curSymOffset, sym);
if (symbolGoesInModuleStream(sym, scopes.empty())) {
// Add symbols to the module in bulk. If this symbol is contiguous
// with the previous run of symbols to add, combine the ranges. If
// not, close the previous range of symbols and start a new one.
if ( == bulkSymbols.end()) {
bulkSymbols = makeArrayRef(,
bulkSymbols.size() + sym.length());
} else {
bulkSymbols = recordBytes;
curSymOffset += sym.length();
return Error::success();
// Add any remaining symbols we've accumulated.
// Allocate memory for a .debug$S / .debug$F section and relocate it.
static ArrayRef<uint8_t> relocateDebugChunk(BumpPtrAllocator &alloc,
SectionChunk &debugChunk) {
uint8_t *buffer = alloc.Allocate<uint8_t>(debugChunk.getSize());
assert(debugChunk.getOutputSectionIdx() == 0 &&
"debug sections should not be in output sections");
return makeArrayRef(buffer, debugChunk.getSize());
static pdb::SectionContrib createSectionContrib(const Chunk *c, uint32_t modi) {
OutputSection *os = c ? c->getOutputSection() : nullptr;
pdb::SectionContrib sc;
memset(&sc, 0, sizeof(sc));
sc.ISect = os ? os->sectionIndex : llvm::pdb::kInvalidStreamIndex;
sc.Off = c && os ? c->getRVA() - os->getRVA() : 0;
sc.Size = c ? c->getSize() : -1;
if (auto *secChunk = dyn_cast_or_null<SectionChunk>(c)) {
sc.Characteristics = secChunk->header->Characteristics;
sc.Imod = secChunk->file->moduleDBI->getModuleIndex();
ArrayRef<uint8_t> contents = secChunk->getContents();
JamCRC crc(0);
sc.DataCrc = crc.getCRC();
} else {
sc.Characteristics = os ? os->header.Characteristics : 0;
sc.Imod = modi;
sc.RelocCrc = 0; // FIXME
return sc;
static uint32_t
translateStringTableIndex(uint32_t objIndex,
const DebugStringTableSubsectionRef &objStrTable,
DebugStringTableSubsection &pdbStrTable) {
auto expectedString = objStrTable.getString(objIndex);
if (!expectedString) {
warn("Invalid string table reference");
return 0;
return pdbStrTable.insert(*expectedString);
void DebugSHandler::handleDebugS(lld::coff::SectionChunk &debugS) {
DebugSubsectionArray subsections;
ArrayRef<uint8_t> relocatedDebugContents = SectionChunk::consumeDebugMagic(
relocateDebugChunk(linker.alloc, debugS), debugS.getSectionName());
BinaryStreamReader reader(relocatedDebugContents, support::little);
exitOnErr(reader.readArray(subsections, relocatedDebugContents.size()));
for (const DebugSubsectionRecord &ss : subsections) {
// Ignore subsections with the 'ignore' bit. Some versions of the Visual C++
// runtime have subsections with this bit set.
if (uint32_t(ss.kind()) & codeview::SubsectionIgnoreFlag)
switch (ss.kind()) {
case DebugSubsectionKind::StringTable: {
assert(!cVStrTab.valid() &&
"Encountered multiple string table subsections!");
case DebugSubsectionKind::FileChecksums:
assert(!checksums.valid() &&
"Encountered multiple checksum subsections!");
case DebugSubsectionKind::Lines:
// We can add the relocated line table directly to the PDB without
// modification because the file checksum offsets will stay the same.
case DebugSubsectionKind::InlineeLines:
assert(!inlineeLines.valid() &&
"Encountered multiple inlinee lines subsections!");
case DebugSubsectionKind::FrameData: {
// We need to re-write string table indices here, so save off all
// frame data subsections until we've processed the entire list of
// subsections so that we can be sure we have the string table.
DebugFrameDataSubsectionRef fds;
case DebugSubsectionKind::Symbols: {
linker.mergeSymbolRecords(&file, indexMap, stringTableReferences,
case DebugSubsectionKind::CrossScopeImports:
case DebugSubsectionKind::CrossScopeExports:
// These appear to relate to cross-module optimization, so we might use
// these for ThinLTO.
case DebugSubsectionKind::ILLines:
case DebugSubsectionKind::FuncMDTokenMap:
case DebugSubsectionKind::TypeMDTokenMap:
case DebugSubsectionKind::MergedAssemblyInput:
// These appear to relate to .Net assembly info.
case DebugSubsectionKind::CoffSymbolRVA:
// Unclear what this is for.
warn("ignoring unknown debug$S subsection kind 0x" +
utohexstr(uint32_t(ss.kind())) + " in file " + toString(&file));
static Expected<StringRef>
getFileName(const DebugStringTableSubsectionRef &strings,
const DebugChecksumsSubsectionRef &checksums, uint32_t fileID) {
auto iter = checksums.getArray().at(fileID);
if (iter == checksums.getArray().end())
return make_error<CodeViewError>(cv_error_code::no_records);
uint32_t offset = iter->FileNameOffset;
return strings.getString(offset);
DebugSHandler::mergeInlineeLines(DebugChecksumsSubsection *newChecksums) {
auto newInlineeLines = std::make_shared<DebugInlineeLinesSubsection>(
*newChecksums, inlineeLines.hasExtraFiles());
for (const InlineeSourceLine &line : inlineeLines) {
TypeIndex inlinee = line.Header->Inlinee;
uint32_t fileID = line.Header->FileID;
uint32_t sourceLine = line.Header->SourceLineNum;
ArrayRef<TypeIndex> typeOrItemMap =
indexMap.isTypeServerMap ? indexMap.ipiMap : indexMap.tpiMap;
if (!remapTypeIndex(inlinee, typeOrItemMap)) {
log("ignoring inlinee line record in " + file.getName() +
" with bad inlinee index 0x" + utohexstr(inlinee.getIndex()));
SmallString<128> filename =
exitOnErr(getFileName(cVStrTab, checksums, fileID));
newInlineeLines->addInlineSite(inlinee, filename, sourceLine);
if (inlineeLines.hasExtraFiles()) {
for (uint32_t extraFileId : line.ExtraFiles) {
filename = exitOnErr(getFileName(cVStrTab, checksums, extraFileId));
return newInlineeLines;
void DebugSHandler::finish() {
pdb::DbiStreamBuilder &dbiBuilder = linker.builder.getDbiBuilder();
// We should have seen all debug subsections across the entire object file now
// which means that if a StringTable subsection and Checksums subsection were
// present, now is the time to handle them.
if (!cVStrTab.valid()) {
if (checksums.valid())
fatal(".debug$S sections with a checksums subsection must also contain a "
"string table subsection");
if (!stringTableReferences.empty())
warn("No StringTable subsection was encountered, but there are string "
"table references");
// Rewrite string table indices in the Fpo Data and symbol records to refer to
// the global PDB string table instead of the object file string table.
for (DebugFrameDataSubsectionRef &fds : newFpoFrames) {
const ulittle32_t *reloc = fds.getRelocPtr();
for (codeview::FrameData fd : fds) {
fd.RvaStart += *reloc;
fd.FrameFunc =
translateStringTableIndex(fd.FrameFunc, cVStrTab, linker.pdbStrTab);
for (ulittle32_t *ref : stringTableReferences)
*ref = translateStringTableIndex(*ref, cVStrTab, linker.pdbStrTab);
// Make a new file checksum table that refers to offsets in the PDB-wide
// string table. Generally the string table subsection appears after the
// checksum table, so we have to do this after looping over all the
// subsections.
auto newChecksums = std::make_unique<DebugChecksumsSubsection>(linker.pdbStrTab);
for (FileChecksumEntry &fc : checksums) {
SmallString<128> filename =
exitOnErr(dbiBuilder.addModuleSourceFile(*file.moduleDBI, filename));
newChecksums->addChecksum(filename, fc.Kind, fc.Checksum);
// Rewrite inlinee item indices if present.
if (inlineeLines.valid())
void PDBLinker::addObjFile(ObjFile *file, CVIndexMap *externIndexMap) {
if (file->mergedIntoPDB)
file->mergedIntoPDB = true;
// Before we can process symbol substreams from .debug$S, we need to process
// type information, file checksums, and the string table. Add type info to
// the PDB first, so that we can get the map from object file type and item
// indices to PDB type and item indices.
CVIndexMap objectIndexMap;
auto indexMapResult =
mergeDebugT(file, externIndexMap ? externIndexMap : &objectIndexMap);
// If the .debug$T sections fail to merge, assume there is no debug info.
if (!indexMapResult) {
if (!config->warnDebugInfoUnusable) {
warn("Cannot use debug info for '" + toString(file) + "' [LNK4099]\n" +
">>> failed to load reference " +
ScopedTimer t(symbolMergingTimer);
pdb::DbiStreamBuilder &dbiBuilder = builder.getDbiBuilder();
DebugSHandler dsh(*this, *file, *indexMapResult);
// Now do all live .debug$S and .debug$F sections.
for (SectionChunk *debugChunk : file->getDebugChunks()) {
if (!debugChunk->live || debugChunk->getSize() == 0)
if (debugChunk->getSectionName() == ".debug$S") {
if (debugChunk->getSectionName() == ".debug$F") {
ArrayRef<uint8_t> relocatedDebugContents =
relocateDebugChunk(alloc, *debugChunk);
FixedStreamArray<object::FpoData> fpoRecords;
BinaryStreamReader reader(relocatedDebugContents, support::little);
uint32_t count = relocatedDebugContents.size() / sizeof(object::FpoData);
exitOnErr(reader.readArray(fpoRecords, count));
// These are already relocated and don't refer to the string table, so we
// can just copy it.
for (const object::FpoData &fd : fpoRecords)
// Do any post-processing now that all .debug$S sections have been processed.
// Add a module descriptor for every object file. We need to put an absolute
// path to the object into the PDB. If this is a plain object, we make its
// path absolute. If it's an object in an archive, we make the archive path
// absolute.
static void createModuleDBI(pdb::PDBFileBuilder &builder) {
pdb::DbiStreamBuilder &dbiBuilder = builder.getDbiBuilder();
SmallString<128> objName;
for (ObjFile *file : ObjFile::instances) {
bool inArchive = !file->parentName.empty();
objName = inArchive ? file->parentName : file->getName();
StringRef modName = inArchive ? file->getName() : StringRef(objName);
file->moduleDBI = &exitOnErr(dbiBuilder.addModuleInfo(modName));
ArrayRef<Chunk *> chunks = file->getChunks();
uint32_t modi = file->moduleDBI->getModuleIndex();
for (Chunk *c : chunks) {
auto *secChunk = dyn_cast<SectionChunk>(c);
if (!secChunk || !secChunk->live)
pdb::SectionContrib sc = createSectionContrib(secChunk, modi);
static PublicSym32 createPublic(Defined *def) {
PublicSym32 pub(SymbolKind::S_PUB32);
pub.Name = def->getName();
if (auto *d = dyn_cast<DefinedCOFF>(def)) {
if (d->getCOFFSymbol().isFunctionDefinition())
pub.Flags = PublicSymFlags::Function;
} else if (isa<DefinedImportThunk>(def)) {
pub.Flags = PublicSymFlags::Function;
OutputSection *os = def->getChunk()->getOutputSection();
assert(os && "all publics should be in final image");
pub.Offset = def->getRVA() - os->getRVA();
pub.Segment = os->sectionIndex;
return pub;
// Add all object files to the PDB. Merge .debug$T sections into IpiData and
// TpiData.
void PDBLinker::addObjectsToPDB() {
ScopedTimer t1(addObjectsTimer);
for (ObjFile *file : ObjFile::instances)
// Construct TPI and IPI stream contents.
ScopedTimer t2(tpiStreamLayoutTimer);
addTypeInfo(builder.getTpiBuilder(), tMerger.getTypeTable());
addTypeInfo(builder.getIpiBuilder(), tMerger.getIDTable());
ScopedTimer t3(globalsLayoutTimer);
// Compute the public and global symbols.
auto &gsiBuilder = builder.getGsiBuilder();
std::vector<PublicSym32> publics;
symtab->forEachSymbol([&publics](Symbol *s) {
// Only emit defined, live symbols that have a chunk.
auto *def = dyn_cast<Defined>(s);
if (def && def->isLive() && def->getChunk())
if (!publics.empty()) {
publicSymbols = publics.size();
// Sort the public symbols and add them to the stream.
parallelSort(publics, [](const PublicSym32 &l, const PublicSym32 &r) {
return l.Name < r.Name;
for (const PublicSym32 &pub : publics)
void PDBLinker::printStats() {
if (!config->showSummary)
SmallString<256> buffer;
raw_svector_ostream stream(buffer);
stream << center_justify("Summary", 80) << '\n'
<< std::string(80, '-') << '\n';
auto print = [&](uint64_t v, StringRef s) {
stream << format_decimal(v, 15) << " " << s << '\n';
"Input OBJ files (expanded from all cmd-line inputs)");
print(typeServerIndexMappings.size(), "PDB type server dependencies");
print(precompTypeIndexMappings.size(), "Precomp OBJ dependencies");
print(tMerger.getTypeTable().size() + tMerger.getIDTable().size(),
"Merged TPI records");
print(pdbStrTab.size(), "Output PDB strings");
print(globalSymbols, "Global symbol records");
print(moduleSymbols, "Module symbol records");
print(publicSymbols, "Public symbol records");
void PDBLinker::addNatvisFiles() {
for (StringRef file : config->natvisFiles) {
ErrorOr<std::unique_ptr<MemoryBuffer>> dataOrErr =
if (!dataOrErr) {
warn("Cannot open input file: " + file);
builder.addInjectedSource(file, std::move(*dataOrErr));
static codeview::CPUType toCodeViewMachine(COFF::MachineTypes machine) {
switch (machine) {
return codeview::CPUType::X64;
return codeview::CPUType::ARM7;
return codeview::CPUType::ARM64;
return codeview::CPUType::ARMNT;
return codeview::CPUType::Intel80386;
llvm_unreachable("Unsupported CPU Type");
// Mimic MSVC which surrounds arguments containing whitespace with quotes.
// Double double-quotes are handled, so that the resulting string can be
// executed again on the cmd-line.
static std::string quote(ArrayRef<StringRef> args) {
std::string r;
for (StringRef a : args) {
if (!r.empty())
r.push_back(' ');
bool hasWS = a.find(' ') != StringRef::npos;
bool hasQ = a.find('"') != StringRef::npos;
if (hasWS || hasQ)
if (hasQ) {
SmallVector<StringRef, 4> s;
a.split(s, '"');
r.append(join(s, "\"\""));
} else {
if (hasWS || hasQ)
return r;
static void fillLinkerVerRecord(Compile3Sym &cs) {
cs.Machine = toCodeViewMachine(config->machine);
// Interestingly, if we set the string to, then when trying to view
// local variables WinDbg emits an error that private symbols are not present.
// By setting this to a valid MSVC linker version string, local variables are
// displayed properly. As such, even though it is not representative of
// LLVM's version information, we need this for compatibility.
cs.Flags = CompileSym3Flags::None;
cs.VersionBackendBuild = 25019;
cs.VersionBackendMajor = 14;
cs.VersionBackendMinor = 10;
cs.VersionBackendQFE = 0;
// MSVC also sets the frontend to since this is specifically for the
// linker module (which is by definition a backend), so we don't need to do
// anything here. Also, it seems we can use "LLVM Linker" for the linker name
// without any problems. Only the backend version has to be hardcoded to a
// magic number.
cs.VersionFrontendBuild = 0;
cs.VersionFrontendMajor = 0;
cs.VersionFrontendMinor = 0;
cs.VersionFrontendQFE = 0;
cs.Version = "LLVM Linker";
static void addCommonLinkerModuleSymbols(StringRef path,
pdb::DbiModuleDescriptorBuilder &mod,
BumpPtrAllocator &allocator) {
ObjNameSym ons(SymbolRecordKind::ObjNameSym);
EnvBlockSym ebs(SymbolRecordKind::EnvBlockSym);
Compile3Sym cs(SymbolRecordKind::Compile3Sym);
ons.Name = "* Linker *";
ons.Signature = 0;
ArrayRef<StringRef> args = makeArrayRef(config->argv).drop_front();
std::string argStr = quote(args);
SmallString<64> cwd;
if (config->pdbSourcePath.empty())
cwd = config->pdbSourcePath;
SmallString<64> exe = config->argv[0];
ons, allocator, CodeViewContainer::Pdb));
cs, allocator, CodeViewContainer::Pdb));
ebs, allocator, CodeViewContainer::Pdb));
static void addLinkerModuleCoffGroup(PartialSection *sec,
pdb::DbiModuleDescriptorBuilder &mod,
OutputSection &os,
BumpPtrAllocator &allocator) {
// If there's a section, there's at least one chunk
const Chunk *firstChunk = *sec->chunks.begin();
const Chunk *lastChunk = *sec->chunks.rbegin();
// Emit COFF group
CoffGroupSym cgs(SymbolRecordKind::CoffGroupSym);
cgs.Name = sec->name;
cgs.Segment = os.sectionIndex;
cgs.Offset = firstChunk->getRVA() - os.getRVA();
cgs.Size = lastChunk->getRVA() + lastChunk->getSize() - firstChunk->getRVA();
cgs.Characteristics = sec->characteristics;
// Somehow .idata sections & sections groups in the debug symbol stream have
// the "write" flag set. However the section header for the corresponding
// .idata section doesn't have it.
if (cgs.Name.startswith(".idata"))
cgs.Characteristics |= llvm::COFF::IMAGE_SCN_MEM_WRITE;
cgs, allocator, CodeViewContainer::Pdb));
static void addLinkerModuleSectionSymbol(pdb::DbiModuleDescriptorBuilder &mod,
OutputSection &os,
BumpPtrAllocator &allocator) {
SectionSym sym(SymbolRecordKind::SectionSym);
sym.Alignment = 12; // 2^12 = 4KB
sym.Characteristics = os.header.Characteristics;
sym.Length = os.getVirtualSize();
sym.Name =;
sym.Rva = os.getRVA();
sym.SectionNumber = os.sectionIndex;
sym, allocator, CodeViewContainer::Pdb));
// Skip COFF groups in MinGW because it adds a significant footprint to the
// PDB, due to each function being in its own section
if (config->mingw)
// Output COFF groups for individual chunks of this section.
for (PartialSection *sec : os.contribSections) {
addLinkerModuleCoffGroup(sec, mod, os, allocator);
// Add all import files as modules to the PDB.
void PDBLinker::addImportFilesToPDB(ArrayRef<OutputSection *> outputSections) {
if (ImportFile::instances.empty())
std::map<std::string, llvm::pdb::DbiModuleDescriptorBuilder *> dllToModuleDbi;
for (ImportFile *file : ImportFile::instances) {
if (!file->live)
if (!file->thunkSym)
if (!file->thunkLive)
std::string dll = StringRef(file->dllName).lower();
llvm::pdb::DbiModuleDescriptorBuilder *&mod = dllToModuleDbi[dll];
if (!mod) {
pdb::DbiStreamBuilder &dbiBuilder = builder.getDbiBuilder();
SmallString<128> libPath = file->parentName;
// Name modules similar to MSVC's link.exe.
// The first module is the simple dll filename
llvm::pdb::DbiModuleDescriptorBuilder &firstMod =
pdb::SectionContrib sc =
createSectionContrib(nullptr, llvm::pdb::kInvalidStreamIndex);
// The second module is where the import stream goes.
mod = &exitOnErr(dbiBuilder.addModuleInfo("Import:" + file->dllName));
DefinedImportThunk *thunk = cast<DefinedImportThunk>(file->thunkSym);
Chunk *thunkChunk = thunk->getChunk();
OutputSection *thunkOS = thunkChunk->getOutputSection();
ObjNameSym ons(SymbolRecordKind::ObjNameSym);
Compile3Sym cs(SymbolRecordKind::Compile3Sym);
Thunk32Sym ts(SymbolRecordKind::Thunk32Sym);
ScopeEndSym es(SymbolRecordKind::ScopeEndSym);
ons.Name = file->dllName;
ons.Signature = 0;
ts.Name = thunk->getName();
ts.Parent = 0;
ts.End = 0;
ts.Next = 0;
ts.Thunk = ThunkOrdinal::Standard;
ts.Length = thunkChunk->getSize();
ts.Segment = thunkOS->sectionIndex;
ts.Offset = thunkChunk->getRVA() - thunkOS->getRVA();
ons, alloc, CodeViewContainer::Pdb));
cs, alloc, CodeViewContainer::Pdb));
SmallVector<SymbolScope, 4> scopes;
CVSymbol newSym = codeview::SymbolSerializer::writeOneSymbol(
ts, alloc, CodeViewContainer::Pdb);
scopeStackOpen(scopes, mod->getNextSymbolOffset(), newSym);
newSym = codeview::SymbolSerializer::writeOneSymbol(es, alloc,
scopeStackClose(scopes, mod->getNextSymbolOffset(), file);
pdb::SectionContrib sc =
createSectionContrib(thunk->getChunk(), mod->getModuleIndex());
// Creates a PDB file.
void createPDB(SymbolTable *symtab,
ArrayRef<OutputSection *> outputSections,
ArrayRef<uint8_t> sectionTable,
llvm::codeview::DebugInfo *buildId) {
ScopedTimer t1(totalPdbLinkTimer);
PDBLinker pdb(symtab);
pdb.addSections(outputSections, sectionTable);
ScopedTimer t2(diskCommitTimer);
codeview::GUID guid;
memcpy(&buildId->PDB70.Signature, &guid, 16);
void PDBLinker::initialize(llvm::codeview::DebugInfo *buildId) {
exitOnErr(builder.initialize(4096)); // 4096 is blocksize
buildId->Signature.CVSignature = OMF::Signature::PDB70;
// Signature is set to a hash of the PDB contents when the PDB is done.
memset(buildId->PDB70.Signature, 0, 16);
buildId->PDB70.Age = 1;
// Create streams in MSF for predefined streams, namely
// PDB, TPI, DBI and IPI.
for (int i = 0; i < (int)pdb::kSpecialStreamCount; ++i)
// Add an Info stream.
auto &infoBuilder = builder.getInfoBuilder();
// Add an empty DBI stream.
pdb::DbiStreamBuilder &dbiBuilder = builder.getDbiBuilder();
// Technically we are not link.exe 14.11, but there are known cases where
// debugging tools on Windows expect Microsoft-specific version numbers or
// they fail to work at all. Since we know we produce PDBs that are
// compatible with LINK 14.11, we set that version number here.
dbiBuilder.setBuildNumber(14, 11);
void PDBLinker::addSections(ArrayRef<OutputSection *> outputSections,
ArrayRef<uint8_t> sectionTable) {
// It's not entirely clear what this is, but the * Linker * module uses it.
pdb::DbiStreamBuilder &dbiBuilder = builder.getDbiBuilder();
nativePath = config->pdbPath;
uint32_t pdbFilePathNI = dbiBuilder.addECName(nativePath);
auto &linkerModule = exitOnErr(dbiBuilder.addModuleInfo("* Linker *"));
addCommonLinkerModuleSymbols(nativePath, linkerModule, alloc);
// Add section contributions. They must be ordered by ascending RVA.
for (OutputSection *os : outputSections) {
addLinkerModuleSectionSymbol(linkerModule, *os, alloc);
for (Chunk *c : os->chunks) {
pdb::SectionContrib sc =
createSectionContrib(c, linkerModule.getModuleIndex());
// The * Linker * first section contrib is only used along with /INCREMENTAL,
// to provide trampolines thunks for incremental function patching. Set this
// as "unused" because LLD doesn't support /INCREMENTAL link.
pdb::SectionContrib sc =
createSectionContrib(nullptr, llvm::pdb::kInvalidStreamIndex);
// Add Section Map stream.
ArrayRef<object::coff_section> sections = {
(const object::coff_section *),
sectionTable.size() / sizeof(object::coff_section)};
sectionMap = pdb::DbiStreamBuilder::createSectionMap(sections);
// Add COFF section header stream.
dbiBuilder.addDbgStream(pdb::DbgHeaderType::SectionHdr, sectionTable));
void PDBLinker::commit(codeview::GUID *guid) {
ExitOnError exitOnErr((config->pdbPath + ": ").str());
// Write to a file.
exitOnErr(builder.commit(config->pdbPath, guid));
static uint32_t getSecrelReloc() {
switch (config->machine) {
case AMD64:
case I386:
case ARMNT:
case ARM64:
llvm_unreachable("unknown machine type");
// Try to find a line table for the given offset Addr into the given chunk C.
// If a line table was found, the line table, the string and checksum tables
// that are used to interpret the line table, and the offset of Addr in the line
// table are stored in the output arguments. Returns whether a line table was
// found.
static bool findLineTable(const SectionChunk *c, uint32_t addr,
DebugStringTableSubsectionRef &cVStrTab,
DebugChecksumsSubsectionRef &checksums,
DebugLinesSubsectionRef &lines,
uint32_t &offsetInLinetable) {
ExitOnError exitOnErr;
uint32_t secrelReloc = getSecrelReloc();
for (SectionChunk *dbgC : c->file->getDebugChunks()) {
if (dbgC->getSectionName() != ".debug$S")
// Build a mapping of SECREL relocations in dbgC that refer to `c`.
DenseMap<uint32_t, uint32_t> secrels;
for (const coff_relocation &r : dbgC->getRelocs()) {
if (r.Type != secrelReloc)
if (auto *s = dyn_cast_or_null<DefinedRegular>(
if (s->getChunk() == c)
secrels[r.VirtualAddress] = s->getValue();
ArrayRef<uint8_t> contents =
SectionChunk::consumeDebugMagic(dbgC->getContents(), ".debug$S");
DebugSubsectionArray subsections;
BinaryStreamReader reader(contents, support::little);
exitOnErr(reader.readArray(subsections, contents.size()));
for (const DebugSubsectionRecord &ss : subsections) {
switch (ss.kind()) {
case DebugSubsectionKind::StringTable: {
assert(!cVStrTab.valid() &&
"Encountered multiple string table subsections!");
case DebugSubsectionKind::FileChecksums:
assert(!checksums.valid() &&
"Encountered multiple checksum subsections!");
case DebugSubsectionKind::Lines: {
ArrayRef<uint8_t> bytes;
auto ref = ss.getRecordData();
exitOnErr(ref.readLongestContiguousChunk(0, bytes));
size_t offsetInDbgC = - dbgC->getContents().data();
// Check whether this line table refers to C.
auto i = secrels.find(offsetInDbgC);
if (i == secrels.end())
// Check whether this line table covers Addr in C.
DebugLinesSubsectionRef linesTmp;
uint32_t offsetInC = i->second + linesTmp.header()->RelocOffset;
if (addr < offsetInC || addr >= offsetInC + linesTmp.header()->CodeSize)
assert(!lines.header() &&
"Encountered multiple line tables for function!");
offsetInLinetable = addr - offsetInC;
if (cVStrTab.valid() && checksums.valid() && lines.header())
return true;
return false;
// Use CodeView line tables to resolve a file and line number for the given
// offset into the given chunk and return them, or None if a line table was
// not found.
Optional<std::pair<StringRef, uint32_t>>
getFileLineCodeView(const SectionChunk *c, uint32_t addr) {
ExitOnError exitOnErr;
DebugStringTableSubsectionRef cVStrTab;
DebugChecksumsSubsectionRef checksums;
DebugLinesSubsectionRef lines;
uint32_t offsetInLinetable;
if (!findLineTable(c, addr, cVStrTab, checksums, lines, offsetInLinetable))
return None;
Optional<uint32_t> nameIndex;
Optional<uint32_t> lineNumber;
for (LineColumnEntry &entry : lines) {
for (const LineNumberEntry &ln : entry.LineNumbers) {
LineInfo li(ln.Flags);
if (ln.Offset > offsetInLinetable) {
if (!nameIndex) {
nameIndex = entry.NameIndex;
lineNumber = li.getStartLine();
StringRef filename =
exitOnErr(getFileName(cVStrTab, checksums, *nameIndex));
return std::make_pair(filename, *lineNumber);
nameIndex = entry.NameIndex;
lineNumber = li.getStartLine();
if (!nameIndex)
return None;
StringRef filename = exitOnErr(getFileName(cVStrTab, checksums, *nameIndex));
return std::make_pair(filename, *lineNumber);
} // namespace coff
} // namespace lld