//===- InputFiles.cpp -----------------------------------------------------===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

#include "InputFiles.h"

#include "Chunks.h"

#include "Config.h"

#include "Driver.h"

#include "SymbolTable.h"

#include "Symbols.h"

#include "lld/Common/ErrorHandler.h"

#include "lld/Common/Memory.h"

#include "llvm-c/lto.h"

#include "llvm/ADT/SmallVector.h"

#include "llvm/ADT/Triple.h"

#include "llvm/ADT/Twine.h"

#include "llvm/BinaryFormat/COFF.h"

#include "llvm/Object/Binary.h"

#include "llvm/Object/COFF.h"

#include "llvm/Support/Casting.h"

#include "llvm/Support/Endian.h"

#include "llvm/Support/Error.h"

#include "llvm/Support/ErrorOr.h"

#include "llvm/Support/FileSystem.h"

#include "llvm/Support/Path.h"

#include "llvm/Target/TargetOptions.h"

#include <cstring>

#include <system_error>

#include <utility>

using namespace llvm;

using namespace llvm::COFF;

using namespace llvm::object;

using namespace llvm::support::endian;

using llvm::Triple;

using llvm::support::ulittle32_t;

namespace lld {

namespace coff {

std::vector<ObjFile *> ObjFile::Instances;

std::vector<ImportFile *> ImportFile::Instances;

std::vector<BitcodeFile *> BitcodeFile::Instances;

/// Checks that Source is compatible with being a weak alias to Target.

/// If Source is Undefined and has no weak alias set, makes it a weak

/// alias to Target.

static void checkAndSetWeakAlias(SymbolTable *Symtab, InputFile *F,

                                 Symbol *Source, Symbol *Target) {

  if (auto *U = dyn_cast<Undefined>(Source)) {

    if (U->WeakAlias && 
U->WeakAlias != Target2
) {

      // Weak aliases as produced by GCC are named in the form

      // .weak.<weaksymbol>.<othersymbol>, where <othersymbol> is the name

      // of another symbol emitted near the weak symbol.

      // Just use the definition from the first object file that defined

      // this weak symbol.

      if (Config->MinGW)

        return;

      Symtab->reportDuplicate(Source, F);

    }

    U->WeakAlias = Target;

  }

}

ArchiveFile::ArchiveFile(MemoryBufferRef M) : InputFile(ArchiveKind, M) {}

void ArchiveFile::parse() {

  // Parse a MemoryBufferRef as an archive file.

  File = CHECK(Archive::create(MB), this);

  // Read the symbol table to construct Lazy objects.

  for (const Archive::Symbol &Sym : File->symbols())

    Symtab->addLazy(this, Sym);

}

// Returns a buffer pointing to a member file containing a given symbol.

void ArchiveFile::addMember(const Archive::Symbol *Sym) {

  const Archive::Child &C =

      CHECK(Sym->getMember(),

            "could not get the member for symbol " + Sym->getName());

  // Return an empty buffer if we have already returned the same buffer.

  if (!Seen.insert(C.getChildOffset()).second)

    return;

  Driver->enqueueArchiveMember(C, Sym->getName(), getName());

}

std::vector<MemoryBufferRef> getArchiveMembers(Archive *File) {

  std::vector<MemoryBufferRef> V;

  Error Err = Error::success();

  for (const ErrorOr<Archive::Child> &COrErr : File->children(Err)) {

    Archive::Child C =

        CHECK(COrErr,

              File->getFileName() + ": could not get the child of the archive");

    MemoryBufferRef MBRef =

        CHECK(C.getMemoryBufferRef(),

              File->getFileName() +

                  ": could not get the buffer for a child of the archive");

    V.push_back(MBRef);

  }

  if (Err)

    fatal(File->getFileName() +

          ": Archive::children failed: " + toString(std::move(Err)));

  return V;

}

void ObjFile::parse() {

  // Parse a memory buffer as a COFF file.

  std::unique_ptr<Binary> Bin = CHECK(createBinary(MB), this);

  if (auto *Obj = dyn_cast<COFFObjectFile>(Bin.get())) {

    Bin.release();

    COFFObj.reset(Obj);

  } else {

    fatal(toString(this) + " is not a COFF file");

  }

  // Read section and symbol tables.

  initializeChunks();

  initializeSymbols();

}

const coff_section* ObjFile::getSection(uint32_t I) {

  const coff_section *Sec;

  if (auto EC = COFFObj->getSection(I, Sec))

    fatal("getSection failed: #" + Twine(I) + ": " + EC.message());

  return Sec;

}

// We set SectionChunk pointers in the SparseChunks vector to this value

// temporarily to mark comdat sections as having an unknown resolution. As we

// walk the object file's symbol table, once we visit either a leader symbol or

// an associative section definition together with the parent comdat's leader,

// we set the pointer to either nullptr (to mark the section as discarded) or a

// valid SectionChunk for that section.

static SectionChunk *const PendingComdat = reinterpret_cast<SectionChunk *>(1);

void ObjFile::initializeChunks() {

  uint32_t NumSections = COFFObj->getNumberOfSections();

  Chunks.reserve(NumSections);

  SparseChunks.resize(NumSections + 1);

  for (uint32_t I = 1; I < NumSections + 1; 
++I2.63k
) {

    const coff_section *Sec = getSection(I);

    if (Sec->Characteristics & IMAGE_SCN_LNK_COMDAT)

      SparseChunks[I] = PendingComdat;

    else

      SparseChunks[I] = readSection(I, nullptr, "");

  }

}

SectionChunk *ObjFile::readSection(uint32_t SectionNumber,

                                   const coff_aux_section_definition *Def,

                                   StringRef LeaderName) {

  const coff_section *Sec = getSection(SectionNumber);

  StringRef Name;

  if (auto EC = COFFObj->getSectionName(Sec, Name))

    fatal("getSectionName failed: #" + Twine(SectionNumber) + ": " +

          EC.message());

  if (Name == ".drectve") {

    ArrayRef<uint8_t> Data;

    COFFObj->getSectionContents(Sec, Data);

    Directives = std::string((const char *)Data.data(), Data.size());

    return nullptr;

  }

  if (Name == ".llvm_addrsig") {

    AddrsigSec = Sec;

    return nullptr;

  }

  // Object files may have DWARF debug info or MS CodeView debug info

  // (or both).

  //

  // DWARF sections don't need any special handling from the perspective

  // of the linker; they are just a data section containing relocations.

  // We can just link them to complete debug info.

  //

  // CodeView needs linker support. We need to interpret debug info,

  // and then write it to a separate .pdb file.

  // Ignore DWARF debug info unless /debug is given.

  if (!Config->Debug && 
Name.startswith(".debug_")1.77k
)

    return nullptr;

  if (Sec->Characteristics & llvm::COFF::IMAGE_SCN_LNK_REMOVE)

    return nullptr;

  auto *C = make<SectionChunk>(this, Sec);

  if (Def)

    C->Checksum = Def->CheckSum;

  // CodeView sections are stored to a different vector because they are not

  // linked in the regular manner.

  if (C->isCodeView())

    DebugChunks.push_back(C);

  else if (Config->GuardCF != GuardCFLevel::Off && 
Name == ".gfids$y"109
)

    GuardFidChunks.push_back(C);

  else if (Config->GuardCF != GuardCFLevel::Off && 
Name == ".gljmp$y"99
)

    GuardLJmpChunks.push_back(C);

  else if (Name == ".sxdata")

    SXDataChunks.push_back(C);

  else if (Config->TailMerge && 
Sec->NumberOfRelocations == 01.61k
 &&

           
Name == ".rdata"1.33k
 && 
LeaderName.startswith("??_C@")44
)

    // COFF sections that look like string literal sections (i.e. no

    // relocations, in .rdata, leader symbol name matches the MSVC name mangling

    // for string literals) are subject to string tail merging.

    MergeChunk::addSection(C);

  else

    Chunks.push_back(C);

  return C;

}

void ObjFile::readAssociativeDefinition(

    COFFSymbolRef Sym, const coff_aux_section_definition *Def) {

  readAssociativeDefinition(Sym, Def, Def->getNumber(Sym.isBigObj()));

}

void ObjFile::readAssociativeDefinition(COFFSymbolRef Sym,

                                        const coff_aux_section_definition *Def,

                                        uint32_t ParentIndex) {

  SectionChunk *Parent = SparseChunks[ParentIndex];

  int32_t SectionNumber = Sym.getSectionNumber();

  auto Diag = [&]() {

    StringRef Name, ParentName;

    COFFObj->getSymbolName(Sym, Name);

    const coff_section *ParentSec = getSection(ParentIndex);

    COFFObj->getSectionName(ParentSec, ParentName);

    error(toString(this) + ": associative comdat " + Name + " (sec " +

          Twine(SectionNumber) + ") has invalid reference to section " +

          ParentName + " (sec " + Twine(ParentIndex) + ")");

  };

  if (Parent == PendingComdat) {

    // This can happen if an associative comdat refers to another associative

    // comdat that appears after it (invalid per COFF spec) or to a section

    // without any symbols.

    Diag();

    return;

  }

  // Check whether the parent is prevailing. If it is, so are we, and we read

  // the section; otherwise mark it as discarded.

  if (Parent) {

    SectionChunk *C = readSection(SectionNumber, Def, "");

    SparseChunks[SectionNumber] = C;

    if (C) {

      C->Selection = IMAGE_COMDAT_SELECT_ASSOCIATIVE;

      Parent->addAssociative(C);

    }

  } else {

    SparseChunks[SectionNumber] = nullptr;

  }

}

void ObjFile::recordPrevailingSymbolForMingw(

    COFFSymbolRef Sym, DenseMap<StringRef, uint32_t> &PrevailingSectionMap) {

  // For comdat symbols in executable sections, where this is the copy

  // of the section chunk we actually include instead of discarding it,

  // add the symbol to a map to allow using it for implicitly

  // associating .[px]data$<func> sections to it.

  int32_t SectionNumber = Sym.getSectionNumber();

  SectionChunk *SC = SparseChunks[SectionNumber];

  if (SC && SC->getOutputCharacteristics() & IMAGE_SCN_MEM_EXECUTE) {

    StringRef Name;

    COFFObj->getSymbolName(Sym, Name);

    PrevailingSectionMap[Name] = SectionNumber;

  }

}

void ObjFile::maybeAssociateSEHForMingw(

    COFFSymbolRef Sym, const coff_aux_section_definition *Def,

    const DenseMap<StringRef, uint32_t> &PrevailingSectionMap) {

  StringRef Name;

  COFFObj->getSymbolName(Sym, Name);

  if (Name.consume_front(".pdata$") || 
Name.consume_front(".xdata$")19
) {

    // For MinGW, treat .[px]data$<func> as implicitly associative to

    // the symbol <func>.

    auto ParentSym = PrevailingSectionMap.find(Name);

    if (ParentSym != PrevailingSectionMap.end())

      readAssociativeDefinition(Sym, Def, ParentSym->second);

  }

}

Symbol *ObjFile::createRegular(COFFSymbolRef Sym) {

  SectionChunk *SC = SparseChunks[Sym.getSectionNumber()];

  if (Sym.isExternal()) {

    StringRef Name;

    COFFObj->getSymbolName(Sym, Name);

    if (SC)

      return Symtab->addRegular(this, Name, Sym.getGeneric(), SC);

    // For MinGW symbols named .weak.* that point to a discarded section,

    // don't create an Undefined symbol. If nothing ever refers to the symbol,

    // everything should be fine. If something actually refers to the symbol

    // (e.g. the undefined weak alias), linking will fail due to undefined

    // references at the end.

    if (Config->MinGW && Name.startswith(".weak."))

      return nullptr;

    return Symtab->addUndefined(Name, this, false);

  }

  if (SC)

    return make<DefinedRegular>(this, /*Name*/ "", /*IsCOMDAT*/ false,

                                /*IsExternal*/ false, Sym.getGeneric(), SC);

  return nullptr;

}

void ObjFile::initializeSymbols() {

  uint32_t NumSymbols = COFFObj->getNumberOfSymbols();

  Symbols.resize(NumSymbols);

  SmallVector<std::pair<Symbol *, uint32_t>, 8> WeakAliases;

  std::vector<uint32_t> PendingIndexes;

  PendingIndexes.reserve(NumSymbols);

  DenseMap<StringRef, uint32_t> PrevailingSectionMap;

  std::vector<const coff_aux_section_definition *> ComdatDefs(

      COFFObj->getNumberOfSections() + 1);

  for (uint32_t I = 0; I < NumSymbols; 
++I4.96k
) {

    COFFSymbolRef COFFSym = check(COFFObj->getSymbol(I));

    bool PrevailingComdat;

    if (COFFSym.isUndefined()) {

      Symbols[I] = createUndefined(COFFSym);

    } else if (COFFSym.isWeakExternal()) {

      Symbols[I] = createUndefined(COFFSym);

      uint32_t TagIndex = COFFSym.getAux<coff_aux_weak_external>()->TagIndex;

      WeakAliases.emplace_back(Symbols[I], TagIndex);

    } else if (Optional<Symbol *> OptSym =

                   createDefined(COFFSym, ComdatDefs, PrevailingComdat)) {

      Symbols[I] = *OptSym;

      if (Config->MinGW && 
PrevailingComdat398
)

        recordPrevailingSymbolForMingw(COFFSym, PrevailingSectionMap);

    } else {

      // createDefined() returns None if a symbol belongs to a section that

      // was pending at the point when the symbol was read. This can happen in

      // two cases:

      // 1) section definition symbol for a comdat leader;

      // 2) symbol belongs to a comdat section associated with another section.

      // In both of these cases, we can expect the section to be resolved by

      // the time we finish visiting the remaining symbols in the symbol

      // table. So we postpone the handling of this symbol until that time.

      PendingIndexes.push_back(I);

    }

    I += COFFSym.getNumberOfAuxSymbols();

  }

  for (uint32_t I : PendingIndexes) {

    COFFSymbolRef Sym = check(COFFObj->getSymbol(I));

    if (const coff_aux_section_definition *Def = Sym.getSectionDefinition()) {

      if (Def->Selection == IMAGE_COMDAT_SELECT_ASSOCIATIVE)

        readAssociativeDefinition(Sym, Def);

      else if (Config->MinGW)

        maybeAssociateSEHForMingw(Sym, Def, PrevailingSectionMap);

    }

    if (SparseChunks[Sym.getSectionNumber()] == PendingComdat) {

      StringRef Name;

      COFFObj->getSymbolName(Sym, Name);

      log("comdat section " + Name +

          " without leader and unassociated, discarding");

      continue;

    }

    Symbols[I] = createRegular(Sym);

  }

  for (auto &KV : WeakAliases) {

    Symbol *Sym = KV.first;

    uint32_t Idx = KV.second;

    checkAndSetWeakAlias(Symtab, this, Sym, Symbols[Idx]);

  }

}

Symbol *ObjFile::createUndefined(COFFSymbolRef Sym) {

  StringRef Name;

  COFFObj->getSymbolName(Sym, Name);

  return Symtab->addUndefined(Name, this, Sym.isWeakExternal());

}

void ObjFile::handleComdatSelection(COFFSymbolRef Sym, COMDATType &Selection,

                                    bool &Prevailing, DefinedRegular *Leader) {

  if (Prevailing)

    return;

  // There's already an existing comdat for this symbol: `Leader`.

  // Use the comdats's selection field to determine if the new

  // symbol in `Sym` should be discarded, produce a duplicate symbol

  // error, etc.

  SectionChunk *LeaderChunk = nullptr;

  COMDATType LeaderSelection = IMAGE_COMDAT_SELECT_ANY;

  if (Leader->Data) {

    LeaderChunk = Leader->getChunk();

    LeaderSelection = LeaderChunk->Selection;

  } else {

    // FIXME: comdats from LTO files don't know their selection; treat them

    // as "any".

    Selection = LeaderSelection;

  }

  if ((Selection == IMAGE_COMDAT_SELECT_ANY &&

       
LeaderSelection == IMAGE_COMDAT_SELECT_LARGEST20
) ||

      
(40
Selection == IMAGE_COMDAT_SELECT_LARGEST40
 &&

       
LeaderSelection == IMAGE_COMDAT_SELECT_ANY11
)) {

    // cl.exe picks "any" for vftables when building with /GR- and

    // "largest" when building with /GR. To be able to link object files

    // compiled with each flag, "any" and "largest" are merged as "largest".

    LeaderSelection = Selection = IMAGE_COMDAT_SELECT_LARGEST;

  }

  // Other than that, comdat selections must match.  This is a bit more

  // strict than link.exe which allows merging "any" and "largest" if "any"

  // is the first symbol the linker sees, and it allows merging "largest"

  // with everything (!) if "largest" is the first symbol the linker sees.

  // Making this symmetric independent of which selection is seen first

  // seems better though.

  // (This behavior matches ModuleLinker::getComdatResult().)

  if (Selection != LeaderSelection) {

    log(("conflicting comdat type for " + toString(*Leader) + ": " +

         Twine((int)LeaderSelection) + " in " + toString(Leader->getFile()) +

         " and " + Twine((int)Selection) + " in " + toString(this))

            .str());

    Symtab->reportDuplicate(Leader, this);

    return;

  }

  switch (Selection) {

  case IMAGE_COMDAT_SELECT_NODUPLICATES:

    Symtab->reportDuplicate(Leader, this);

    break;

  case IMAGE_COMDAT_SELECT_ANY:

    // Nothing to do.

    break;

  case IMAGE_COMDAT_SELECT_SAME_SIZE:

    if (LeaderChunk->getSize() != getSection(Sym)->SizeOfRawData)

      Symtab->reportDuplicate(Leader, this);

    break;

  case IMAGE_COMDAT_SELECT_EXACT_MATCH: {

    SectionChunk NewChunk(this, getSection(Sym));

    // link.exe only compares section contents here and doesn't complain

    // if the two comdat sections have e.g. different alignment.

    // Match that.

    if (LeaderChunk->getContents() != NewChunk.getContents())

      Symtab->reportDuplicate(Leader, this);

    break;

  }

  case IMAGE_COMDAT_SELECT_ASSOCIATIVE:

    // createDefined() is never called for IMAGE_COMDAT_SELECT_ASSOCIATIVE.

    // (This means lld-link doesn't produce duplicate symbol errors for

    // associative comdats while link.exe does, but associate comdats

    // are never extern in practice.)

    llvm_unreachable("createDefined not called for associative comdats");

  case IMAGE_COMDAT_SELECT_LARGEST:

    if (LeaderChunk->getSize() < getSection(Sym)->SizeOfRawData) {

      // Replace the existing comdat symbol with the new one.

      StringRef Name;

      COFFObj->getSymbolName(Sym, Name);

      // FIXME: This is incorrect: With /opt:noref, the previous sections

      // make it into the final executable as well. Correct handling would

      // be to undo reading of the whole old section that's being replaced,

      // or doing one pass that determines what the final largest comdat

      // is for all IMAGE_COMDAT_SELECT_LARGEST comdats and then reading

      // only the largest one.

      replaceSymbol<DefinedRegular>(Leader, this, Name, /*IsCOMDAT*/ true,

                                    /*IsExternal*/ true, Sym.getGeneric(),

                                    nullptr);

      Prevailing = true;

    }

    break;

  case IMAGE_COMDAT_SELECT_NEWEST:

    llvm_unreachable("should have been rejected earlier");

  }

}

Optional<Symbol *> ObjFile::createDefined(

    COFFSymbolRef Sym,

    std::vector<const coff_aux_section_definition *> &ComdatDefs,

    bool &Prevailing) {

  Prevailing = false;

  auto GetName = [&]() {

    StringRef S;

    COFFObj->getSymbolName(Sym, S);

    return S;

  };

  if (Sym.isCommon()) {

    auto *C = make<CommonChunk>(Sym);

    Chunks.push_back(C);

    return Symtab->addCommon(this, GetName(), Sym.getValue(), Sym.getGeneric(),

                             C);

  }

  if (Sym.isAbsolute()) {

    StringRef Name = GetName();

    // Skip special symbols.

    if (Name == "@comp.id")

      return nullptr;

    if (Name == "@feat.00") {

      Feat00Flags = Sym.getValue();

      return nullptr;

    }

    if (Sym.isExternal())

      return Symtab->addAbsolute(Name, Sym);

    return make<DefinedAbsolute>(Name, Sym);

  }

  int32_t SectionNumber = Sym.getSectionNumber();

  if (SectionNumber == llvm::COFF::IMAGE_SYM_DEBUG)

    return nullptr;

  if (llvm::COFF::isReservedSectionNumber(SectionNumber))

    fatal(toString(this) + ": " + GetName() +

          " should not refer to special section " + Twine(SectionNumber));

  if ((uint32_t)SectionNumber >= SparseChunks.size())

    fatal(toString(this) + ": " + GetName() +

          " should not refer to non-existent section " + Twine(SectionNumber));

  // Comdat handling.

  // A comdat symbol consists of two symbol table entries.

  // The first symbol entry has the name of the section (e.g. .text), fixed

  // values for the other fields, and one auxilliary record.

  // The second symbol entry has the name of the comdat symbol, called the

  // "comdat leader".

  // When this function is called for the first symbol entry of a comdat,

  // it sets ComdatDefs and returns None, and when it's called for the second

  // symbol entry it reads ComdatDefs and then sets it back to nullptr.

  // Handle comdat leader.

  if (const coff_aux_section_definition *Def = ComdatDefs[SectionNumber]) {

    ComdatDefs[SectionNumber] = nullptr;

    DefinedRegular *Leader;

    if (Sym.isExternal()) {

      std::tie(Leader, Prevailing) =

          Symtab->addComdat(this, GetName(), Sym.getGeneric());

    } else {

      Leader = make<DefinedRegular>(this, /*Name*/ "", /*IsCOMDAT*/ false,

                                    /*IsExternal*/ false, Sym.getGeneric());

      Prevailing = true;

    }

    if (Def->Selection < (int)IMAGE_COMDAT_SELECT_NODUPLICATES ||

        // Intentionally ends at IMAGE_COMDAT_SELECT_LARGEST: link.exe

        // doesn't understand IMAGE_COMDAT_SELECT_NEWEST either.

        Def->Selection > (int)IMAGE_COMDAT_SELECT_LARGEST) {

      fatal("unknown comdat type " + std::to_string((int)Def->Selection) +

            " for " + GetName() + " in " + toString(this));

    }

    COMDATType Selection = (COMDATType)Def->Selection;

    if (Leader->isCOMDAT())

      handleComdatSelection(Sym, Selection, Prevailing, Leader);

    if (Prevailing) {

      SectionChunk *C = readSection(SectionNumber, Def, GetName());

      SparseChunks[SectionNumber] = C;

      C->Sym = cast<DefinedRegular>(Leader);

      C->Selection = Selection;

      cast<DefinedRegular>(Leader)->Data = &C->Repl;

    } else {

      SparseChunks[SectionNumber] = nullptr;

    }

    return Leader;

  }

  // Prepare to handle the comdat leader symbol by setting the section's

  // ComdatDefs pointer if we encounter a non-associative comdat.

  if (SparseChunks[SectionNumber] == PendingComdat) {

    if (const coff_aux_section_definition *Def = Sym.getSectionDefinition()) {

      if (Def->Selection != IMAGE_COMDAT_SELECT_ASSOCIATIVE)

        ComdatDefs[SectionNumber] = Def;

    }

    return None;

  }

  return createRegular(Sym);

}

MachineTypes ObjFile::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))

    fatal("broken import library");

  // Read names and create an __imp_ symbol.

  StringRef Name = Saver.save(StringRef(Buf + sizeof(*Hdr)));

  StringRef ImpName = Saver.save("__imp_" + Name);

  const char *NameStart = Buf + sizeof(coff_import_header) + Name.size() + 1;

  DLLName = StringRef(NameStart);

  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;

  }

  this->Hdr = Hdr;

  ExternalName = ExtName;

  ImpSym = Symtab->addImportData(ImpName, this);

  // If this was a duplicate, we logged an error but may continue;

  // in this case, ImpSym is nullptr.

  if (!ImpSym)

    return;

  if (Hdr->getType() == llvm::COFF::IMPORT_CONST)

    static_cast<void>(Symtab->addImportData(Name, this));

  // 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)

    ThunkSym = Symtab->addImportThunk(

        Name, cast_or_null<DefinedImportData>(ImpSym), Hdr->Machine);

}

void BitcodeFile::parse() {

  Obj = check(lto::InputFile::create(MemoryBufferRef(

      MB.getBuffer(), Saver.save(ParentName + MB.getBufferIdentifier()))));

  std::vector<std::pair<Symbol *, bool>> Comdat(Obj->getComdatTable().size());

  for (size_t I = 0; I != Obj->getComdatTable().size(); 
++I23
)

    // FIXME: lto::InputFile doesn't keep enough data to do correct comdat

    // selection handling.

    Comdat[I] = Symtab->addComdat(this, Saver.save(Obj->getComdatTable()[I]));

  for (const lto::InputFile::Symbol &ObjSym : Obj->symbols()) {

    StringRef SymName = Saver.save(ObjSym.getName());

    int ComdatIndex = ObjSym.getComdatIndex();

    Symbol *Sym;

    if (ObjSym.isUndefined()) {

      Sym = Symtab->addUndefined(SymName, this, false);

    } else if (ObjSym.isCommon()) {

      Sym = Symtab->addCommon(this, SymName, ObjSym.getCommonSize());

    } else if (ObjSym.isWeak() && 
ObjSym.isIndirect()17
) {

      // Weak external.

      Sym = Symtab->addUndefined(SymName, this, true);

      std::string Fallback = ObjSym.getCOFFWeakExternalFallback();

      Symbol *Alias = Symtab->addUndefined(Saver.save(Fallback));

      checkAndSetWeakAlias(Symtab, this, Sym, Alias);

    } else if (ComdatIndex != -1) {

      if (SymName == Obj->getComdatTable()[ComdatIndex])

        Sym = Comdat[ComdatIndex].first;

      else if (Comdat[ComdatIndex].second)

        Sym = Symtab->addRegular(this, SymName);

      else

        Sym = Symtab->addUndefined(SymName, this, false);

    } else {

      Sym = Symtab->addRegular(this, SymName);

    }

    Symbols.push_back(Sym);

    if (ObjSym.isUsed())

      Config->GCRoot.push_back(Sym);

  }

  Directives = Obj->getCOFFLinkerOpts();

}

MachineTypes BitcodeFile::getMachineType() {

  switch (Triple(Obj->getTargetTriple()).getArch()) {

  case Triple::x86_64:

    return AMD64;

  case Triple::x86:

    return I386;

  case Triple::arm:

    return ARMNT;

  case Triple::aarch64:

    return ARM64;

  default:

    return IMAGE_FILE_MACHINE_UNKNOWN;

  }

}

} // namespace coff

} // namespace lld

// Returns the last element of a path, which is supposed to be a filename.

static StringRef getBasename(StringRef Path) {

  return sys::path::filename(Path, sys::path::Style::windows);

}

// Returns a string in the format of "foo.obj" or "foo.obj(bar.lib)".

std::string lld::toString(const coff::InputFile *File) {

  if (!File)

    return "<internal>";

  if (File->ParentName.empty())

    return File->getName();

  return (getBasename(File->ParentName) + "(" + getBasename(File->getName()) +

          ")")

      .str();

}