Fix relative thin archive path handling

[gbreynoo]

Summary

This fixes some thin archive relative path issues, paths are shortened where possible and paths are output correctly when using the display table command.

[ruiu]

include/llvm/Object/ArchiveWriter.h

39–40 ↗

(On Diff #191083)

This function is supposed to compute an archive relative path (as the name says), and it now has ForceRelative flag? That's confusing.

[rupprecht]

test/tools/llvm-ar/thin-archive.test

8

I'm not able to reproduce any differences against GNU ar based on these test cases.

Can you clarify what it is that you're fixing?

[gbreynoo]

Update after Rui's comment.

The thought was originally to avoid changes to addMember but this may be clearer.

[gbreynoo]

In response to rupprecht:

Currently on Windows absolute paths in an archive can have mixed slashes e.g.
C:\llvm-build\test\tools\llvm-ar\Output\thin-archive.test.tmp/foo/elf.o/
And to select the member the path must be matched exactly.

llvm-ar -t 'absolute archive path' outputs the above as:
C:\llvm-build\test\tools\llvm-ar\Output\thin-archive.test.tmp/C:\llvm-build\test\tools\llvm-ar\Output\thin-archive.test.tmp/foo/elf.o

Relative member paths will be converted to absolute paths in some cases.

Relative paths currently are not computed correctly in some cases, for example:
when in directory foo which contains elf.o
llvm-ar.exe rTc ../relative-1.ar elf.o
The member path becomes ../elf.o rather than foo/elf.o

These relative path issues are also found when flattening thin-archives e.g.

The following files are present:

• reduce-thin-path.test.tmp/elf.o
• reduce-thin-path.test.tmp/baz/internal.a

internal.a has a member ../elf.o/

When in directory reduce-thin-path.test.tmp/foo call below:
llvm-ar.exe" "rTc" "C:\llvm-build\test\tools\llvm-ar\Output\reduce-thin-path.test.tmp/foo/bar/external.ar" "../baz/internal.ar"

The member is squashed to the following:
../baz\../elf.o/
However it should be ../../elf.o

After some experimenting in gnu-ar there may be similar issues regarding relative thin archive paths but I don't believe we should follow suit if we can help it.

[ruiu]

Let P1 and P2 be pathnames. IIUC, the problem we want to solve is to how to compute a relative path from the last directory of P1 to P2. Is this correct?

If so, I guess the following scheme may be simpler than the current one:

1. Canonicalize both P1 and P2 by converting backslashes to slashes.
2. Remove common prefixes from P1 and P2
3. Count the number of slashes in P1. Let N be that number.
4. Concatenate "../../../../...." (repeated N times) and P2. This is the result.

Here is an example when P1 = "foo/bar/baz/quux" and P2="foo/x/y".

1. Canonicalize them (in this case this is a no-op)
2. P1 becomes "bar/baz/quux", P2 becomes "x/y".
3. N = 2
4. "../../x/y"

lib/Object/ArchiveWriter.cpp

23–1

This lambda doesn't capture anything, you probably should consider moving this outside of this function.

23–1

Create instances of SmallString and populate their contents as a side-effect seems a bit awkward. You could instead make your helper function (which is currently named getDotlessAbsolutePath) to return an std::string.

26

Flip the condition and return early. Err would be a better name, as it can be read as "if error". Currently it is "if ret" which is a bit less readable.

[gbreynoo]

The problem with working out the paths is if either are in the form foo/../bar/. I don't believe your above suggestion would work for paths with internal ../.

lib/Object/ArchiveWriter.cpp

23–1

Made a change as you've suggested but the use of SmallString is due to remove__dots() and I didn't want a second conversion to std::string.

23–1

The lambda was to keep it local to this function, i'd rather keep it unless others really disagree.

[gbreynoo]

ping

If the reasons for these changes are unclear I'll be happy to clarify.

Thanks

[rupprecht]

Sorry, this patch dropped off my radar. I'm not sure I'll get to it this or next week, but I'll make sure to review it eventually (unless ruiu does it sooner).

[ruiu]

Sorry, I though that I replied to this thread.

In D59491#1436706, @gbreynoo wrote:

The problem with working out the paths is if either are in the form foo/../bar/. I don't believe your above suggestion would work for paths with internal ../.

You can just call remove_dots to remove all internal .., no?

[gbreynoo]

Hi Rui, thanks for the feedback. I'm unsure what changes would better fit what we have outlined in past comments:

Suggested implementation:

Canonicalize both P1 and P2 by converting backslashes to slashes(including calls to remove_dots).
Remove common prefixes from P1 and P2
Count the number of slashes in P1. Let N be that number.
Concatenate "../../../../...." (repeated N times) and P2. This is the result.

My understanding of the current implementation:

Calls to getDotlessAbsolute path to canonicalize, includes call to remove_dots()
In cases where this isnt possible return P2
Remove common prefixes using two iterators
Construct a path with the number of "../" required using one iterator, I thought this would be more efficient than constructing the remaining P1 path to count slashes
Append the remaining P2 path using the iterator.

Any further suggestions would be appreciated,

Thanks

[gbreynoo]

I've attempted to make "computeArchiveRelativePath" clearer and errors are now propagated to the caller to deal with rather than just returning the "To" argument.

[ruiu]

LGTM

[hintonda]

This change seems to have caused the following error:

Writer.cpp.o.d -o lib/Object/CMakeFiles/LLVMObject.dir/ArchiveWriter.cpp.o -c /Users/dhinton/projects/llvm_project/monorepo/llvm-project/llvm/lib/Object/ArchiveWriter.cpp
In file included from /Users/dhinton/projects/llvm_project/monorepo/llvm-project/llvm/lib/Object/ArchiveWriter.cpp:13:
In file included from /Users/dhinton/projects/llvm_project/monorepo/llvm-project/llvm/include/llvm/Object/ArchiveWriter.h:16:
In file included from /Users/dhinton/projects/llvm_project/monorepo/llvm-project/llvm/include/llvm/ADT/StringRef.h:12:
In file included from /Users/dhinton/projects/llvm_project/monorepo/llvm-project/llvm/include/llvm/ADT/STLExtras.h:20:
In file included from /Users/dhinton/projects/llvm_project/monorepo/llvm-project/llvm/include/llvm/ADT/SmallVector.h:19:
In file included from /Users/dhinton/projects/llvm_project/monorepo/llvm-project/llvm/include/llvm/Support/MathExtras.h:18:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/algorithm:1278:14: error: type 'llvm::sys::path::const_iterator' does not provide a call operator

if (!__pred(*__first1, *__first2))
     ^~~~~~

/Users/dhinton/projects/llvm_project/monorepo/llvm-project/llvm/lib/Object/ArchiveWriter.cpp:523:12: note: in instantiation of function template specialization 'std::__1::mismatch<llvm::sys::path::const_itera
tor, llvm::sys::path::const_iterator, llvm::sys::path::const_iterator>' requested here

std::mismatch(sys::path::begin(DirFrom), sys::path::end(DirFrom),
     ^

1 error generated.

[gribozavr]

Sorry, I reverted this change in r362413, it was breaking the build.

[gbreynoo]

Thanks hintonda and gribozavr, I will look into that build issue before I recommit.

[gbreynoo]

Fixed a reapplied:
rG5d5078e341f5: [llvm-ar] Reapply Fix relative thin archive path handling

lib/Object/ArchiveWriter.cpp

-//===- ArchiveWriter.cpp - ar File Format implementation --------*- C++ -*-===//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-//
-// This file defines the writeArchive function.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Object/ArchiveWriter.h"
-#include "llvm/ADT/ArrayRef.h"
-#include "llvm/ADT/StringRef.h"
-#include "llvm/BinaryFormat/Magic.h"
-#include "llvm/IR/LLVMContext.h"
-#include "llvm/Object/Archive.h"
-#include "llvm/Object/ObjectFile.h"
-#include "llvm/Object/SymbolicFile.h"
-#include "llvm/Support/EndianStream.h"
-#include "llvm/Support/Errc.h"
-#include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/Format.h"
-#include "llvm/Support/Path.h"
-#include "llvm/Support/ToolOutputFile.h"
-#include "llvm/Support/raw_ostream.h"
-
-#include <map>
-
-#if !defined(_MSC_VER) && !defined(__MINGW32__)
-#include <unistd.h>
-#else
-#include <io.h>
-#endif
-
-using namespace llvm;
-
-NewArchiveMember::NewArchiveMember(MemoryBufferRef BufRef)
-    : Buf(MemoryBuffer::getMemBuffer(BufRef, false)),
-      MemberName(BufRef.getBufferIdentifier()) {}
-
-Expected<NewArchiveMember>
-NewArchiveMember::getOldMember(const object::Archive::Child &OldMember,
-                               bool Deterministic) {
-  Expected<llvm::MemoryBufferRef> BufOrErr = OldMember.getMemoryBufferRef();
-  if (!BufOrErr)
-    return BufOrErr.takeError();
-
-  NewArchiveMember M;
-  M.Buf = MemoryBuffer::getMemBuffer(*BufOrErr, false);
-  M.MemberName = M.Buf->getBufferIdentifier();
-  if (!Deterministic) {
-    auto ModTimeOrErr = OldMember.getLastModified();
-    if (!ModTimeOrErr)
-      return ModTimeOrErr.takeError();
-    M.ModTime = ModTimeOrErr.get();
-    Expected<unsigned> UIDOrErr = OldMember.getUID();
-    if (!UIDOrErr)
-      return UIDOrErr.takeError();
-    M.UID = UIDOrErr.get();
-    Expected<unsigned> GIDOrErr = OldMember.getGID();
-    if (!GIDOrErr)
-      return GIDOrErr.takeError();
-    M.GID = GIDOrErr.get();
-    Expected<sys::fs::perms> AccessModeOrErr = OldMember.getAccessMode();
-    if (!AccessModeOrErr)
-      return AccessModeOrErr.takeError();
-    M.Perms = AccessModeOrErr.get();
-  }
-  return std::move(M);
-}
-
-Expected<NewArchiveMember> NewArchiveMember::getFile(StringRef FileName,
-                                                     bool Deterministic) {
-  sys::fs::file_status Status;
-  int FD;
-  if (auto EC = sys::fs::openFileForRead(FileName, FD))
-    return errorCodeToError(EC);
-  assert(FD != -1);
-
-  if (auto EC = sys::fs::status(FD, Status))
-    return errorCodeToError(EC);
-
-  // Opening a directory doesn't make sense. Let it fail.
-  // Linux cannot open directories with open(2), although
-  // cygwin and *bsd can.
-  if (Status.type() == sys::fs::file_type::directory_file)
-    return errorCodeToError(make_error_code(errc::is_a_directory));
-
-  ErrorOr<std::unique_ptr<MemoryBuffer>> MemberBufferOrErr =
-      MemoryBuffer::getOpenFile(FD, FileName, Status.getSize(), false);
-  if (!MemberBufferOrErr)
-    return errorCodeToError(MemberBufferOrErr.getError());
-
-  if (close(FD) != 0)
-    return errorCodeToError(std::error_code(errno, std::generic_category()));
-
-  NewArchiveMember M;
-  M.Buf = std::move(*MemberBufferOrErr);
-  M.MemberName = M.Buf->getBufferIdentifier();
-  if (!Deterministic) {
-    M.ModTime = std::chrono::time_point_cast<std::chrono::seconds>(
-        Status.getLastModificationTime());
-    M.UID = Status.getUser();
-    M.GID = Status.getGroup();
-    M.Perms = Status.permissions();
-  }
-  return std::move(M);
-}
-
-template <typename T>
-static void printWithSpacePadding(raw_ostream &OS, T Data, unsigned Size) {
-  uint64_t OldPos = OS.tell();
-  OS << Data;
-  unsigned SizeSoFar = OS.tell() - OldPos;
-  assert(SizeSoFar <= Size && "Data doesn't fit in Size");
-  OS.indent(Size - SizeSoFar);
-}
-
-static bool isDarwin(object::Archive::Kind Kind) {
-  return Kind == object::Archive::K_DARWIN ||
-         Kind == object::Archive::K_DARWIN64;
-}
-
-static bool isBSDLike(object::Archive::Kind Kind) {
-  switch (Kind) {
-  case object::Archive::K_GNU:
-  case object::Archive::K_GNU64:
-    return false;
-  case object::Archive::K_BSD:
-  case object::Archive::K_DARWIN:
-  case object::Archive::K_DARWIN64:
-    return true;
-  case object::Archive::K_COFF:
-    break;
-  }
-  llvm_unreachable("not supported for writting");
-}
-
-template <class T>
-static void print(raw_ostream &Out, object::Archive::Kind Kind, T Val) {
-  support::endian::write(Out, Val,
-                         isBSDLike(Kind) ? support::little : support::big);
-}
-
-static void printRestOfMemberHeader(
-    raw_ostream &Out, const sys::TimePoint<std::chrono::seconds> &ModTime,
-    unsigned UID, unsigned GID, unsigned Perms, unsigned Size) {
-  printWithSpacePadding(Out, sys::toTimeT(ModTime), 12);
-
-  // The format has only 6 chars for uid and gid. Truncate if the provided
-  // values don't fit.
-  printWithSpacePadding(Out, UID % 1000000, 6);
-  printWithSpacePadding(Out, GID % 1000000, 6);
-
-  printWithSpacePadding(Out, format("%o", Perms), 8);
-  printWithSpacePadding(Out, Size, 10);
-  Out << "`\n";
-}
-
-static void
-printGNUSmallMemberHeader(raw_ostream &Out, StringRef Name,
-                          const sys::TimePoint<std::chrono::seconds> &ModTime,
-                          unsigned UID, unsigned GID, unsigned Perms,
-                          unsigned Size) {
-  printWithSpacePadding(Out, Twine(Name) + "/", 16);
-  printRestOfMemberHeader(Out, ModTime, UID, GID, Perms, Size);
-}
-
-static void
-printBSDMemberHeader(raw_ostream &Out, uint64_t Pos, StringRef Name,
-                     const sys::TimePoint<std::chrono::seconds> &ModTime,
-                     unsigned UID, unsigned GID, unsigned Perms,
-                     unsigned Size) {
-  uint64_t PosAfterHeader = Pos + 60 + Name.size();
-  // Pad so that even 64 bit object files are aligned.
-  unsigned Pad = OffsetToAlignment(PosAfterHeader, 8);
-  unsigned NameWithPadding = Name.size() + Pad;
-  printWithSpacePadding(Out, Twine("#1/") + Twine(NameWithPadding), 16);
-  printRestOfMemberHeader(Out, ModTime, UID, GID, Perms,
-                          NameWithPadding + Size);
-  Out << Name;
-  while (Pad--)
-    Out.write(uint8_t(0));
-}
-
-static bool useStringTable(bool Thin, StringRef Name) {
-  return Thin || Name.size() >= 16 || Name.contains('/');
-}
-
-static bool is64BitKind(object::Archive::Kind Kind) {
-  switch (Kind) {
-  case object::Archive::K_GNU:
-  case object::Archive::K_BSD:
-  case object::Archive::K_DARWIN:
-  case object::Archive::K_COFF:
-    return false;
-  case object::Archive::K_DARWIN64:
-  case object::Archive::K_GNU64:
-    return true;
-  }
-  llvm_unreachable("not supported for writting");
-}
-
-static void
-printMemberHeader(raw_ostream &Out, uint64_t Pos, raw_ostream &StringTable,
-                  StringMap<uint64_t> &MemberNames, object::Archive::Kind Kind,
-                  bool Thin, const NewArchiveMember &M,
-                  sys::TimePoint<std::chrono::seconds> ModTime, unsigned Size) {
-  if (isBSDLike(Kind))
-    return printBSDMemberHeader(Out, Pos, M.MemberName, ModTime, M.UID, M.GID,
-                                M.Perms, Size);
-  if (!useStringTable(Thin, M.MemberName))
-    return printGNUSmallMemberHeader(Out, M.MemberName, ModTime, M.UID, M.GID,
-                                     M.Perms, Size);
-  Out << '/';
-  uint64_t NamePos;
-  if (Thin) {
-    NamePos = StringTable.tell();
-    StringTable << M.MemberName << "/\n";
-  } else {
-    auto Insertion = MemberNames.insert({M.MemberName, uint64_t(0)});
-    if (Insertion.second) {
-      Insertion.first->second = StringTable.tell();
-      StringTable << M.MemberName << "/\n";
-    }
-    NamePos = Insertion.first->second;
-  }
-  printWithSpacePadding(Out, NamePos, 15);
-  printRestOfMemberHeader(Out, ModTime, M.UID, M.GID, M.Perms, Size);
-}
-
-namespace {
-struct MemberData {
-  std::vector<unsigned> Symbols;
-  std::string Header;
-  StringRef Data;
-  StringRef Padding;
-};
-} // namespace
-
-static MemberData computeStringTable(StringRef Names) {
-  unsigned Size = Names.size();
-  unsigned Pad = OffsetToAlignment(Size, 2);
-  std::string Header;
-  raw_string_ostream Out(Header);
-  printWithSpacePadding(Out, "//", 48);
-  printWithSpacePadding(Out, Size + Pad, 10);
-  Out << "`\n";
-  Out.flush();
-  return {{}, std::move(Header), Names, Pad ? "\n" : ""};
-}
-
-static sys::TimePoint<std::chrono::seconds> now(bool Deterministic) {
-  using namespace std::chrono;
-
-  if (!Deterministic)
-    return time_point_cast<seconds>(system_clock::now());
-  return sys::TimePoint<seconds>();
-}
-
-static bool isArchiveSymbol(const object::BasicSymbolRef &S) {
-  uint32_t Symflags = S.getFlags();
-  if (Symflags & object::SymbolRef::SF_FormatSpecific)
-    return false;
-  if (!(Symflags & object::SymbolRef::SF_Global))
-    return false;
-  if (Symflags & object::SymbolRef::SF_Undefined)
-    return false;
-  return true;
-}
-
-static void printNBits(raw_ostream &Out, object::Archive::Kind Kind,
-                       uint64_t Val) {
-  if (is64BitKind(Kind))
-    print<uint64_t>(Out, Kind, Val);
-  else
-    print<uint32_t>(Out, Kind, Val);
-}
-
-static void writeSymbolTable(raw_ostream &Out, object::Archive::Kind Kind,
-                             bool Deterministic, ArrayRef<MemberData> Members,
-                             StringRef StringTable) {
-  // We don't write a symbol table on an archive with no members -- except on
-  // Darwin, where the linker will abort unless the archive has a symbol table.
-  if (StringTable.empty() && !isDarwin(Kind))
-    return;
-
-  unsigned NumSyms = 0;
-  for (const MemberData &M : Members)
-    NumSyms += M.Symbols.size();
-
-  unsigned Size = 0;
-  unsigned OffsetSize = is64BitKind(Kind) ? sizeof(uint64_t) : sizeof(uint32_t);
-
-  Size += OffsetSize; // Number of entries
-  if (isBSDLike(Kind))
-    Size += NumSyms * OffsetSize * 2; // Table
-  else
-    Size += NumSyms * OffsetSize; // Table
-  if (isBSDLike(Kind))
-    Size += OffsetSize; // byte count
-  Size += StringTable.size();
-  // ld64 expects the members to be 8-byte aligned for 64-bit content and at
-  // least 4-byte aligned for 32-bit content.  Opt for the larger encoding
-  // uniformly.
-  // We do this for all bsd formats because it simplifies aligning members.
-  unsigned Alignment = isBSDLike(Kind) ? 8 : 2;
-  unsigned Pad = OffsetToAlignment(Size, Alignment);
-  Size += Pad;
-
-  if (isBSDLike(Kind)) {
-    const char *Name = is64BitKind(Kind) ? "__.SYMDEF_64" : "__.SYMDEF";
-    printBSDMemberHeader(Out, Out.tell(), Name, now(Deterministic), 0, 0, 0,
-                         Size);
-  } else {
-    const char *Name = is64BitKind(Kind) ? "/SYM64" : "";
-    printGNUSmallMemberHeader(Out, Name, now(Deterministic), 0, 0, 0, Size);
-  }
-
-  uint64_t Pos = Out.tell() + Size;
-
-  if (isBSDLike(Kind))
-    printNBits(Out, Kind, NumSyms * 2 * OffsetSize);
-  else
-    printNBits(Out, Kind, NumSyms);
-
-  for (const MemberData &M : Members) {
-    for (unsigned StringOffset : M.Symbols) {
-      if (isBSDLike(Kind))
-        printNBits(Out, Kind, StringOffset);
-      printNBits(Out, Kind, Pos); // member offset
-    }
-    Pos += M.Header.size() + M.Data.size() + M.Padding.size();
-  }
-
-  if (isBSDLike(Kind))
-    // byte count of the string table
-    printNBits(Out, Kind, StringTable.size());
-  Out << StringTable;
-
-  while (Pad--)
-    Out.write(uint8_t(0));
-}
-
-static Expected<std::vector<unsigned>>
-getSymbols(MemoryBufferRef Buf, raw_ostream &SymNames, bool &HasObject) {
-  std::vector<unsigned> Ret;
-
-  // In the scenario when LLVMContext is populated SymbolicFile will contain a
-  // reference to it, thus SymbolicFile should be destroyed first.
-  LLVMContext Context;
-  std::unique_ptr<object::SymbolicFile> Obj;
-  if (identify_magic(Buf.getBuffer()) == file_magic::bitcode) {
-    auto ObjOrErr = object::SymbolicFile::createSymbolicFile(
-        Buf, file_magic::bitcode, &Context);
-    if (!ObjOrErr) {
-      // FIXME: check only for "not an object file" errors.
-      consumeError(ObjOrErr.takeError());
-      return Ret;
-    }
-    Obj = std::move(*ObjOrErr);
-  } else {
-    auto ObjOrErr = object::SymbolicFile::createSymbolicFile(Buf);
-    if (!ObjOrErr) {
-      // FIXME: check only for "not an object file" errors.
-      consumeError(ObjOrErr.takeError());
-      return Ret;
-    }
-    Obj = std::move(*ObjOrErr);
-  }
-
-  HasObject = true;
-  for (const object::BasicSymbolRef &S : Obj->symbols()) {
-    if (!isArchiveSymbol(S))
-      continue;
-    Ret.push_back(SymNames.tell());
-    if (auto EC = S.printName(SymNames))
-      return errorCodeToError(EC);
-    SymNames << '\0';
-  }
-  return Ret;
-}
-
-static Expected<std::vector<MemberData>>
-computeMemberData(raw_ostream &StringTable, raw_ostream &SymNames,
-                  object::Archive::Kind Kind, bool Thin, bool Deterministic,
-                  ArrayRef<NewArchiveMember> NewMembers) {
-  static char PaddingData[8] = {'\n', '\n', '\n', '\n', '\n', '\n', '\n', '\n'};
-
-  // This ignores the symbol table, but we only need the value mod 8 and the
-  // symbol table is aligned to be a multiple of 8 bytes
-  uint64_t Pos = 0;
-
-  std::vector<MemberData> Ret;
-  bool HasObject = false;
-
-  // Deduplicate long member names in the string table and reuse earlier name
-  // offsets. This especially saves space for COFF Import libraries where all
-  // members have the same name.
-  StringMap<uint64_t> MemberNames;
-
-  // UniqueTimestamps is a special case to improve debugging on Darwin:
-  //
-  // The Darwin linker does not link debug info into the final
-  // binary. Instead, it emits entries of type N_OSO in in the output
-  // binary's symbol table, containing references to the linked-in
-  // object files. Using that reference, the debugger can read the
-  // debug data directly from the object files. Alternatively, an
-  // invocation of 'dsymutil' will link the debug data from the object
-  // files into a dSYM bundle, which can be loaded by the debugger,
-  // instead of the object files.
-  //
-  // For an object file, the N_OSO entries contain the absolute path
-  // path to the file, and the file's timestamp. For an object
-  // included in an archive, the path is formatted like
-  // "/absolute/path/to/archive.a(member.o)", and the timestamp is the
-  // archive member's timestamp, rather than the archive's timestamp.
-  //
-  // However, this doesn't always uniquely identify an object within
-  // an archive -- an archive file can have multiple entries with the
-  // same filename. (This will happen commonly if the original object
-  // files started in different directories.) The only way they get
-  // distinguished, then, is via the timestamp. But this process is
-  // unable to find the correct object file in the archive when there
-  // are two files of the same name and timestamp.
-  //
-  // Additionally, timestamp==0 is treated specially, and causes the
-  // timestamp to be ignored as a match criteria.
-  //
-  // That will "usually" work out okay when creating an archive not in
-  // deterministic timestamp mode, because the objects will probably
-  // have been created at different timestamps.
-  //
-  // To ameliorate this problem, in deterministic archive mode (which
-  // is the default), on Darwin we will emit a unique non-zero
-  // timestamp for each entry with a duplicated name. This is still
-  // deterministic: the only thing affecting that timestamp is the
-  // order of the files in the resultant archive.
-  //
-  // See also the functions that handle the lookup:
-  // in lldb: ObjectContainerBSDArchive::Archive::FindObject()
-  // in llvm/tools/dsymutil: BinaryHolder::GetArchiveMemberBuffers().
-  bool UniqueTimestamps = Deterministic && isDarwin(Kind);
-  std::map<StringRef, unsigned> FilenameCount;
-  if (UniqueTimestamps) {
-    for (const NewArchiveMember &M : NewMembers)
-      FilenameCount[M.MemberName]++;
-    for (auto &Entry : FilenameCount)
-      Entry.second = Entry.second > 1 ? 1 : 0;
-  }
-
-  for (const NewArchiveMember &M : NewMembers) {
-    std::string Header;
-    raw_string_ostream Out(Header);
-
-    MemoryBufferRef Buf = M.Buf->getMemBufferRef();
-    StringRef Data = Thin ? "" : Buf.getBuffer();
-
-    // ld64 expects the members to be 8-byte aligned for 64-bit content and at
-    // least 4-byte aligned for 32-bit content.  Opt for the larger encoding
-    // uniformly.  This matches the behaviour with cctools and ensures that ld64
-    // is happy with archives that we generate.
-    unsigned MemberPadding =
-        isDarwin(Kind) ? OffsetToAlignment(Data.size(), 8) : 0;
-    unsigned TailPadding = OffsetToAlignment(Data.size() + MemberPadding, 2);
-    StringRef Padding = StringRef(PaddingData, MemberPadding + TailPadding);
-
-    sys::TimePoint<std::chrono::seconds> ModTime;
-    if (UniqueTimestamps)
-      // Increment timestamp for each file of a given name.
-      ModTime = sys::toTimePoint(FilenameCount[M.MemberName]++);
-    else
-      ModTime = M.ModTime;
-    printMemberHeader(Out, Pos, StringTable, MemberNames, Kind, Thin, M,
-                      ModTime, Buf.getBufferSize() + MemberPadding);
-    Out.flush();
-
-    Expected<std::vector<unsigned>> Symbols =
-        getSymbols(Buf, SymNames, HasObject);
-    if (auto E = Symbols.takeError())
-      return std::move(E);
-
-    Pos += Header.size() + Data.size() + Padding.size();
-    Ret.push_back({std::move(*Symbols), std::move(Header), Data, Padding});
-  }
-  // If there are no symbols, emit an empty symbol table, to satisfy Solaris
-  // tools, older versions of which expect a symbol table in a non-empty
-  // archive, regardless of whether there are any symbols in it.
-  if (HasObject && SymNames.tell() == 0)
-    SymNames << '\0' << '\0' << '\0';
-  return Ret;
-}
-
-namespace llvm {
-// Compute the relative path from From to To.
-std::string computeArchiveRelativePath(StringRef From, StringRef To) {
-  if (sys::path::is_absolute(From) || sys::path::is_absolute(To))
-    return To;
-
-  StringRef DirFrom = sys::path::parent_path(From);
-  auto FromI = sys::path::begin(DirFrom);
-  auto ToI = sys::path::begin(To);
-  while (*FromI == *ToI) {
-    ++FromI;
-    ++ToI;
-  }
-
-  SmallString<128> Relative;
-  for (auto FromE = sys::path::end(DirFrom); FromI != FromE; ++FromI)
-    sys::path::append(Relative, "..");
-
-  for (auto ToE = sys::path::end(To); ToI != ToE; ++ToI)
-    sys::path::append(Relative, *ToI);
-
-  // Replace backslashes with slashes so that the path is portable between *nix
-  // and Windows.
-  return sys::path::convert_to_slash(Relative);
-}
-
-Error writeArchive(StringRef ArcName, ArrayRef<NewArchiveMember> NewMembers,
-                   bool WriteSymtab, object::Archive::Kind Kind,
-                   bool Deterministic, bool Thin,
-                   std::unique_ptr<MemoryBuffer> OldArchiveBuf) {
-  assert((!Thin || !isBSDLike(Kind)) && "Only the gnu format has a thin mode");
-
-  SmallString<0> SymNamesBuf;
-  raw_svector_ostream SymNames(SymNamesBuf);
-  SmallString<0> StringTableBuf;
-  raw_svector_ostream StringTable(StringTableBuf);
-
-  Expected<std::vector<MemberData>> DataOrErr = computeMemberData(
-      StringTable, SymNames, Kind, Thin, Deterministic, NewMembers);
-  if (Error E = DataOrErr.takeError())
-    return E;
-  std::vector<MemberData> &Data = *DataOrErr;
-
-  if (!StringTableBuf.empty())
-    Data.insert(Data.begin(), computeStringTable(StringTableBuf));
-
-  // We would like to detect if we need to switch to a 64-bit symbol table.
-  if (WriteSymtab) {
-    uint64_t MaxOffset = 0;
-    uint64_t LastOffset = MaxOffset;
-    for (const auto &M : Data) {
-      // Record the start of the member's offset
-      LastOffset = MaxOffset;
-      // Account for the size of each part associated with the member.
-      MaxOffset += M.Header.size() + M.Data.size() + M.Padding.size();
-      // We assume 32-bit symbols to see if 32-bit symbols are possible or not.
-      MaxOffset += M.Symbols.size() * 4;
-    }
-
-    // The SYM64 format is used when an archive's member offsets are larger than
-    // 32-bits can hold. The need for this shift in format is detected by
-    // writeArchive. To test this we need to generate a file with a member that
-    // has an offset larger than 32-bits but this demands a very slow test. To
-    // speed the test up we use this environment variable to pretend like the
-    // cutoff happens before 32-bits and instead happens at some much smaller
-    // value.
-    const char *Sym64Env = std::getenv("SYM64_THRESHOLD");
-    int Sym64Threshold = 32;
-    if (Sym64Env)
-      StringRef(Sym64Env).getAsInteger(10, Sym64Threshold);
-
-    // If LastOffset isn't going to fit in a 32-bit varible we need to switch
-    // to 64-bit. Note that the file can be larger than 4GB as long as the last
-    // member starts before the 4GB offset.
-    if (LastOffset >= (1ULL << Sym64Threshold)) {
-      if (Kind == object::Archive::K_DARWIN)
-        Kind = object::Archive::K_DARWIN64;
-      else
-        Kind = object::Archive::K_GNU64;
-    }
-  }
-
-  Expected<sys::fs::TempFile> Temp =
-      sys::fs::TempFile::create(ArcName + ".temp-archive-%%%%%%%.a");
-  if (!Temp)
-    return Temp.takeError();
-
-  raw_fd_ostream Out(Temp->FD, false);
-  if (Thin)
-    Out << "!<thin>\n";
-  else
-    Out << "!<arch>\n";
-
-  if (WriteSymtab)
-    writeSymbolTable(Out, Kind, Deterministic, Data, SymNamesBuf);
-
-  for (const MemberData &M : Data)
-    Out << M.Header << M.Data << M.Padding;
-
-  Out.flush();
-
-  // At this point, we no longer need whatever backing memory
-  // was used to generate the NewMembers. On Windows, this buffer
-  // could be a mapped view of the file we want to replace (if
-  // we're updating an existing archive, say). In that case, the
-  // rename would still succeed, but it would leave behind a
-  // temporary file (actually the original file renamed) because
-  // a file cannot be deleted while there's a handle open on it,
-  // only renamed. So by freeing this buffer, this ensures that
-  // the last open handle on the destination file, if any, is
-  // closed before we attempt to rename.
-  OldArchiveBuf.reset();
-
-  return Temp->keep(ArcName);
-}
-
-} // namespace llvm
+//===- ArchiveWriter.cpp - ar File Format implementation --------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the writeArchive function.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Object/ArchiveWriter.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/BinaryFormat/Magic.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/Object/Archive.h"
+#include "llvm/Object/ObjectFile.h"
+#include "llvm/Object/SymbolicFile.h"
+#include "llvm/Support/EndianStream.h"
+#include "llvm/Support/Errc.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/Format.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/ToolOutputFile.h"
+#include "llvm/Support/raw_ostream.h"
+
+#include <map>
+
+#if !defined(_MSC_VER) && !defined(__MINGW32__)
+#include <unistd.h>
+#else
+#include <io.h>
+#endif
+
+using namespace llvm;
+
+NewArchiveMember::NewArchiveMember(MemoryBufferRef BufRef)
+    : Buf(MemoryBuffer::getMemBuffer(BufRef, false)),
+      MemberName(BufRef.getBufferIdentifier()) {}
+
+Expected<NewArchiveMember>
+NewArchiveMember::getOldMember(const object::Archive::Child &OldMember,
+                               bool Deterministic) {
+  Expected<llvm::MemoryBufferRef> BufOrErr = OldMember.getMemoryBufferRef();
+  if (!BufOrErr)
+    return BufOrErr.takeError();
+
+  NewArchiveMember M;
+  M.Buf = MemoryBuffer::getMemBuffer(*BufOrErr, false);
+  M.MemberName = M.Buf->getBufferIdentifier();
+  if (!Deterministic) {
+    auto ModTimeOrErr = OldMember.getLastModified();
+    if (!ModTimeOrErr)
+      return ModTimeOrErr.takeError();
+    M.ModTime = ModTimeOrErr.get();
+    Expected<unsigned> UIDOrErr = OldMember.getUID();
+    if (!UIDOrErr)
+      return UIDOrErr.takeError();
+    M.UID = UIDOrErr.get();
+    Expected<unsigned> GIDOrErr = OldMember.getGID();
+    if (!GIDOrErr)
+      return GIDOrErr.takeError();
+    M.GID = GIDOrErr.get();
+    Expected<sys::fs::perms> AccessModeOrErr = OldMember.getAccessMode();
+    if (!AccessModeOrErr)
+      return AccessModeOrErr.takeError();
+    M.Perms = AccessModeOrErr.get();
+  }
+  return std::move(M);
+}
+
+Expected<NewArchiveMember> NewArchiveMember::getFile(StringRef FileName,
+                                                     bool Deterministic) {
+  sys::fs::file_status Status;
+  int FD;
+  if (auto EC = sys::fs::openFileForRead(FileName, FD))
+    return errorCodeToError(EC);
+  assert(FD != -1);
+
+  if (auto EC = sys::fs::status(FD, Status))
+    return errorCodeToError(EC);
+
+  // Opening a directory doesn't make sense. Let it fail.
+  // Linux cannot open directories with open(2), although
+  // cygwin and *bsd can.
+  if (Status.type() == sys::fs::file_type::directory_file)
+    return errorCodeToError(make_error_code(errc::is_a_directory));
+
+  ErrorOr<std::unique_ptr<MemoryBuffer>> MemberBufferOrErr =
+      MemoryBuffer::getOpenFile(FD, FileName, Status.getSize(), false);
+  if (!MemberBufferOrErr)
+    return errorCodeToError(MemberBufferOrErr.getError());
+
+  if (close(FD) != 0)
+    return errorCodeToError(std::error_code(errno, std::generic_category()));
+
+  NewArchiveMember M;
+  M.Buf = std::move(*MemberBufferOrErr);
+  M.MemberName = M.Buf->getBufferIdentifier();
+  if (!Deterministic) {
+    M.ModTime = std::chrono::time_point_cast<std::chrono::seconds>(
+        Status.getLastModificationTime());
+    M.UID = Status.getUser();
+    M.GID = Status.getGroup();
+    M.Perms = Status.permissions();
+  }
+  return std::move(M);
+}
+
+template <typename T>
+static void printWithSpacePadding(raw_ostream &OS, T Data, unsigned Size) {
+  uint64_t OldPos = OS.tell();
+  OS << Data;
+  unsigned SizeSoFar = OS.tell() - OldPos;
+  assert(SizeSoFar <= Size && "Data doesn't fit in Size");
+  OS.indent(Size - SizeSoFar);
+}
+
+static bool isDarwin(object::Archive::Kind Kind) {
+  return Kind == object::Archive::K_DARWIN ||
+         Kind == object::Archive::K_DARWIN64;
+}
+
+static bool isBSDLike(object::Archive::Kind Kind) {
+  switch (Kind) {
+  case object::Archive::K_GNU:
+  case object::Archive::K_GNU64:
+    return false;
+  case object::Archive::K_BSD:
+  case object::Archive::K_DARWIN:
+  case object::Archive::K_DARWIN64:
+    return true;
+  case object::Archive::K_COFF:
+    break;
+  }
+  llvm_unreachable("not supported for writting");
+}
+
+template <class T>
+static void print(raw_ostream &Out, object::Archive::Kind Kind, T Val) {
+  support::endian::write(Out, Val,
+                         isBSDLike(Kind) ? support::little : support::big);
+}
+
+static void printRestOfMemberHeader(
+    raw_ostream &Out, const sys::TimePoint<std::chrono::seconds> &ModTime,
+    unsigned UID, unsigned GID, unsigned Perms, unsigned Size) {
+  printWithSpacePadding(Out, sys::toTimeT(ModTime), 12);
+
+  // The format has only 6 chars for uid and gid. Truncate if the provided
+  // values don't fit.
+  printWithSpacePadding(Out, UID % 1000000, 6);
+  printWithSpacePadding(Out, GID % 1000000, 6);
+
+  printWithSpacePadding(Out, format("%o", Perms), 8);
+  printWithSpacePadding(Out, Size, 10);
+  Out << "`\n";
+}
+
+static void
+printGNUSmallMemberHeader(raw_ostream &Out, StringRef Name,
+                          const sys::TimePoint<std::chrono::seconds> &ModTime,
+                          unsigned UID, unsigned GID, unsigned Perms,
+                          unsigned Size) {
+  printWithSpacePadding(Out, Twine(Name) + "/", 16);
+  printRestOfMemberHeader(Out, ModTime, UID, GID, Perms, Size);
+}
+
+static void
+printBSDMemberHeader(raw_ostream &Out, uint64_t Pos, StringRef Name,
+                     const sys::TimePoint<std::chrono::seconds> &ModTime,
+                     unsigned UID, unsigned GID, unsigned Perms,
+                     unsigned Size) {
+  uint64_t PosAfterHeader = Pos + 60 + Name.size();
+  // Pad so that even 64 bit object files are aligned.
+  unsigned Pad = OffsetToAlignment(PosAfterHeader, 8);
+  unsigned NameWithPadding = Name.size() + Pad;
+  printWithSpacePadding(Out, Twine("#1/") + Twine(NameWithPadding), 16);
+  printRestOfMemberHeader(Out, ModTime, UID, GID, Perms,
+                          NameWithPadding + Size);
+  Out << Name;
+  while (Pad--)
+    Out.write(uint8_t(0));
+}
+
+static bool useStringTable(bool Thin, StringRef Name) {
+  return Thin || Name.size() >= 16 || Name.contains('/');
+}
+
+static bool is64BitKind(object::Archive::Kind Kind) {
+  switch (Kind) {
+  case object::Archive::K_GNU:
+  case object::Archive::K_BSD:
+  case object::Archive::K_DARWIN:
+  case object::Archive::K_COFF:
+    return false;
+  case object::Archive::K_DARWIN64:
+  case object::Archive::K_GNU64:
+    return true;
+  }
+  llvm_unreachable("not supported for writting");
+}
+
+static void
+printMemberHeader(raw_ostream &Out, uint64_t Pos, raw_ostream &StringTable,
+                  StringMap<uint64_t> &MemberNames, object::Archive::Kind Kind,
+                  bool Thin, const NewArchiveMember &M,
+                  sys::TimePoint<std::chrono::seconds> ModTime, unsigned Size) {
+  if (isBSDLike(Kind))
+    return printBSDMemberHeader(Out, Pos, M.MemberName, ModTime, M.UID, M.GID,
+                                M.Perms, Size);
+  if (!useStringTable(Thin, M.MemberName))
+    return printGNUSmallMemberHeader(Out, M.MemberName, ModTime, M.UID, M.GID,
+                                     M.Perms, Size);
+  Out << '/';
+  uint64_t NamePos;
+  if (Thin) {
+    NamePos = StringTable.tell();
+    StringTable << M.MemberName << "/\n";
+  } else {
+    auto Insertion = MemberNames.insert({M.MemberName, uint64_t(0)});
+    if (Insertion.second) {
+      Insertion.first->second = StringTable.tell();
+      StringTable << M.MemberName << "/\n";
+    }
+    NamePos = Insertion.first->second;
+  }
+  printWithSpacePadding(Out, NamePos, 15);
+  printRestOfMemberHeader(Out, ModTime, M.UID, M.GID, M.Perms, Size);
+}
+
+namespace {
+struct MemberData {
+  std::vector<unsigned> Symbols;
+  std::string Header;
+  StringRef Data;
+  StringRef Padding;
+};
+} // namespace
+
+static MemberData computeStringTable(StringRef Names) {
+  unsigned Size = Names.size();
+  unsigned Pad = OffsetToAlignment(Size, 2);
+  std::string Header;
+  raw_string_ostream Out(Header);
+  printWithSpacePadding(Out, "//", 48);
+  printWithSpacePadding(Out, Size + Pad, 10);
+  Out << "`\n";
+  Out.flush();
+  return {{}, std::move(Header), Names, Pad ? "\n" : ""};
+}
+
+static sys::TimePoint<std::chrono::seconds> now(bool Deterministic) {
+  using namespace std::chrono;
+
+  if (!Deterministic)
+    return time_point_cast<seconds>(system_clock::now());
+  return sys::TimePoint<seconds>();
+}
+
+static bool isArchiveSymbol(const object::BasicSymbolRef &S) {
+  uint32_t Symflags = S.getFlags();
+  if (Symflags & object::SymbolRef::SF_FormatSpecific)
+    return false;
+  if (!(Symflags & object::SymbolRef::SF_Global))
+    return false;
+  if (Symflags & object::SymbolRef::SF_Undefined)
+    return false;
+  return true;
+}
+
+static void printNBits(raw_ostream &Out, object::Archive::Kind Kind,
+                       uint64_t Val) {
+  if (is64BitKind(Kind))
+    print<uint64_t>(Out, Kind, Val);
+  else
+    print<uint32_t>(Out, Kind, Val);
+}
+
+static void writeSymbolTable(raw_ostream &Out, object::Archive::Kind Kind,
+                             bool Deterministic, ArrayRef<MemberData> Members,
+                             StringRef StringTable) {
+  // We don't write a symbol table on an archive with no members -- except on
+  // Darwin, where the linker will abort unless the archive has a symbol table.
+  if (StringTable.empty() && !isDarwin(Kind))
+    return;
+
+  unsigned NumSyms = 0;
+  for (const MemberData &M : Members)
+    NumSyms += M.Symbols.size();
+
+  unsigned Size = 0;
+  unsigned OffsetSize = is64BitKind(Kind) ? sizeof(uint64_t) : sizeof(uint32_t);
+
+  Size += OffsetSize; // Number of entries
+  if (isBSDLike(Kind))
+    Size += NumSyms * OffsetSize * 2; // Table
+  else
+    Size += NumSyms * OffsetSize; // Table
+  if (isBSDLike(Kind))
+    Size += OffsetSize; // byte count
+  Size += StringTable.size();
+  // ld64 expects the members to be 8-byte aligned for 64-bit content and at
+  // least 4-byte aligned for 32-bit content.  Opt for the larger encoding
+  // uniformly.
+  // We do this for all bsd formats because it simplifies aligning members.
+  unsigned Alignment = isBSDLike(Kind) ? 8 : 2;
+  unsigned Pad = OffsetToAlignment(Size, Alignment);
+  Size += Pad;
+
+  if (isBSDLike(Kind)) {
+    const char *Name = is64BitKind(Kind) ? "__.SYMDEF_64" : "__.SYMDEF";
+    printBSDMemberHeader(Out, Out.tell(), Name, now(Deterministic), 0, 0, 0,
+                         Size);
+  } else {
+    const char *Name = is64BitKind(Kind) ? "/SYM64" : "";
+    printGNUSmallMemberHeader(Out, Name, now(Deterministic), 0, 0, 0, Size);
+  }
+
+  uint64_t Pos = Out.tell() + Size;
+
+  if (isBSDLike(Kind))
+    printNBits(Out, Kind, NumSyms * 2 * OffsetSize);
+  else
+    printNBits(Out, Kind, NumSyms);
+
+  for (const MemberData &M : Members) {
+    for (unsigned StringOffset : M.Symbols) {
+      if (isBSDLike(Kind))
+        printNBits(Out, Kind, StringOffset);
+      printNBits(Out, Kind, Pos); // member offset
+    }
+    Pos += M.Header.size() + M.Data.size() + M.Padding.size();
+  }
+
+  if (isBSDLike(Kind))
+    // byte count of the string table
+    printNBits(Out, Kind, StringTable.size());
+  Out << StringTable;
+
+  while (Pad--)
+    Out.write(uint8_t(0));
+}
+
+static Expected<std::vector<unsigned>>
+getSymbols(MemoryBufferRef Buf, raw_ostream &SymNames, bool &HasObject) {
+  std::vector<unsigned> Ret;
+
+  // In the scenario when LLVMContext is populated SymbolicFile will contain a
+  // reference to it, thus SymbolicFile should be destroyed first.
+  LLVMContext Context;
+  std::unique_ptr<object::SymbolicFile> Obj;
+  if (identify_magic(Buf.getBuffer()) == file_magic::bitcode) {
+    auto ObjOrErr = object::SymbolicFile::createSymbolicFile(
+        Buf, file_magic::bitcode, &Context);
+    if (!ObjOrErr) {
+      // FIXME: check only for "not an object file" errors.
+      consumeError(ObjOrErr.takeError());
+      return Ret;
+    }
+    Obj = std::move(*ObjOrErr);
+  } else {
+    auto ObjOrErr = object::SymbolicFile::createSymbolicFile(Buf);
+    if (!ObjOrErr) {
+      // FIXME: check only for "not an object file" errors.
+      consumeError(ObjOrErr.takeError());
+      return Ret;
+    }
+    Obj = std::move(*ObjOrErr);
+  }
+
+  HasObject = true;
+  for (const object::BasicSymbolRef &S : Obj->symbols()) {
+    if (!isArchiveSymbol(S))
+      continue;
+    Ret.push_back(SymNames.tell());
+    if (auto EC = S.printName(SymNames))
+      return errorCodeToError(EC);
+    SymNames << '\0';
+  }
+  return Ret;
+}
+
+static Expected<std::vector<MemberData>>
+computeMemberData(raw_ostream &StringTable, raw_ostream &SymNames,
+                  object::Archive::Kind Kind, bool Thin, bool Deterministic,
+                  ArrayRef<NewArchiveMember> NewMembers) {
+  static char PaddingData[8] = {'\n', '\n', '\n', '\n', '\n', '\n', '\n', '\n'};
+
+  // This ignores the symbol table, but we only need the value mod 8 and the
+  // symbol table is aligned to be a multiple of 8 bytes
+  uint64_t Pos = 0;
+
+  std::vector<MemberData> Ret;
+  bool HasObject = false;
+
+  // Deduplicate long member names in the string table and reuse earlier name
+  // offsets. This especially saves space for COFF Import libraries where all
+  // members have the same name.
+  StringMap<uint64_t> MemberNames;
+
+  // UniqueTimestamps is a special case to improve debugging on Darwin:
+  //
+  // The Darwin linker does not link debug info into the final
+  // binary. Instead, it emits entries of type N_OSO in in the output
+  // binary's symbol table, containing references to the linked-in
+  // object files. Using that reference, the debugger can read the
+  // debug data directly from the object files. Alternatively, an
+  // invocation of 'dsymutil' will link the debug data from the object
+  // files into a dSYM bundle, which can be loaded by the debugger,
+  // instead of the object files.
+  //
+  // For an object file, the N_OSO entries contain the absolute path
+  // path to the file, and the file's timestamp. For an object
+  // included in an archive, the path is formatted like
+  // "/absolute/path/to/archive.a(member.o)", and the timestamp is the
+  // archive member's timestamp, rather than the archive's timestamp.
+  //
+  // However, this doesn't always uniquely identify an object within
+  // an archive -- an archive file can have multiple entries with the
+  // same filename. (This will happen commonly if the original object
+  // files started in different directories.) The only way they get
+  // distinguished, then, is via the timestamp. But this process is
+  // unable to find the correct object file in the archive when there
+  // are two files of the same name and timestamp.
+  //
+  // Additionally, timestamp==0 is treated specially, and causes the
+  // timestamp to be ignored as a match criteria.
+  //
+  // That will "usually" work out okay when creating an archive not in
+  // deterministic timestamp mode, because the objects will probably
+  // have been created at different timestamps.
+  //
+  // To ameliorate this problem, in deterministic archive mode (which
+  // is the default), on Darwin we will emit a unique non-zero
+  // timestamp for each entry with a duplicated name. This is still
+  // deterministic: the only thing affecting that timestamp is the
+  // order of the files in the resultant archive.
+  //
+  // See also the functions that handle the lookup:
+  // in lldb: ObjectContainerBSDArchive::Archive::FindObject()
+  // in llvm/tools/dsymutil: BinaryHolder::GetArchiveMemberBuffers().
+  bool UniqueTimestamps = Deterministic && isDarwin(Kind);
+  std::map<StringRef, unsigned> FilenameCount;
+  if (UniqueTimestamps) {
+    for (const NewArchiveMember &M : NewMembers)
+      FilenameCount[M.MemberName]++;
+    for (auto &Entry : FilenameCount)
+      Entry.second = Entry.second > 1 ? 1 : 0;
+  }
+
+  for (const NewArchiveMember &M : NewMembers) {
+    std::string Header;
+    raw_string_ostream Out(Header);
+
+    MemoryBufferRef Buf = M.Buf->getMemBufferRef();
+    StringRef Data = Thin ? "" : Buf.getBuffer();
+
+    // ld64 expects the members to be 8-byte aligned for 64-bit content and at
+    // least 4-byte aligned for 32-bit content.  Opt for the larger encoding
+    // uniformly.  This matches the behaviour with cctools and ensures that ld64
+    // is happy with archives that we generate.
+    unsigned MemberPadding =
+        isDarwin(Kind) ? OffsetToAlignment(Data.size(), 8) : 0;
+    unsigned TailPadding = OffsetToAlignment(Data.size() + MemberPadding, 2);
+    StringRef Padding = StringRef(PaddingData, MemberPadding + TailPadding);
+
+    sys::TimePoint<std::chrono::seconds> ModTime;
+    if (UniqueTimestamps)
+      // Increment timestamp for each file of a given name.
+      ModTime = sys::toTimePoint(FilenameCount[M.MemberName]++);
+    else
+      ModTime = M.ModTime;
+    printMemberHeader(Out, Pos, StringTable, MemberNames, Kind, Thin, M,
+                      ModTime, Buf.getBufferSize() + MemberPadding);
+    Out.flush();
+
+    Expected<std::vector<unsigned>> Symbols =
+        getSymbols(Buf, SymNames, HasObject);
+    if (auto E = Symbols.takeError())
+      return std::move(E);
+
+    Pos += Header.size() + Data.size() + Padding.size();
+    Ret.push_back({std::move(*Symbols), std::move(Header), Data, Padding});
+  }
+  // If there are no symbols, emit an empty symbol table, to satisfy Solaris
+  // tools, older versions of which expect a symbol table in a non-empty
+  // archive, regardless of whether there are any symbols in it.
+  if (HasObject && SymNames.tell() == 0)
+    SymNames << '\0' << '\0' << '\0';
+  return Ret;
+}
+
+namespace llvm {
+// Compute the relative path from From to To.
+std::string computeArchiveRelativePath(StringRef From, StringRef To) {
+  auto getDotlessAbsolutePath = [](StringRef P) -> ErrorOr<SmallString<128>> {
+    SmallString<128> Ret = P;
+    std::error_code Err = sys::fs::make_absolute(Ret);
+    if (Err)
+      return Err;
+    sys::path::remove_dots(Ret, /*removedotdot*/ true);
+#ifdef _WIN32
+    // Canonicalise '\\' to '/' as sys::path::const_iterator may return a UNC
+    // specifier. It also returns the first directory separator after a drive
+    // letter or UNC specifier as a component of the path.
+    std::replace(Ret.begin(), Ret.end(), '\\', '/');
+#endif
+    return Ret;
+  };
+
+  ErrorOr<SmallString<128>> PathToOrErr = getDotlessAbsolutePath(To);
+  ErrorOr<SmallString<128>> DirFromOrErr =
+      getDotlessAbsolutePath(sys::path::parent_path(From));
+  if (!PathToOrErr || !DirFromOrErr)
+    return sys::path::convert_to_slash(To);
+
+  const SmallString<128> &PathTo = *PathToOrErr;
+  const SmallString<128> &DirFrom = *DirFromOrErr;
+
+  auto FromS = sys::path::begin(DirFrom);
+  auto FromI = FromS;
+  auto ToI = sys::path::begin(PathTo);
+  while (*FromI == *ToI) {
+    ++FromI;
+    ++ToI;
+  }
+
+  // Can't construct a relative path between different roots
+  if ((FromI == FromS) && !sys::path::root_name(PathTo).empty())
+    return PathTo.str();
+
+  SmallString<128> Relative;
+  for (auto FromE = sys::path::end(DirFrom); FromI != FromE; ++FromI)
+    sys::path::append(Relative, sys::path::Style::posix, "..");
+
+  for (auto ToE = sys::path::end(PathTo); ToI != ToE; ++ToI)
+    sys::path::append(Relative, sys::path::Style::posix, *ToI);
+
+  return Relative.str();
+}
+
+Error writeArchive(StringRef ArcName, ArrayRef<NewArchiveMember> NewMembers,
+                   bool WriteSymtab, object::Archive::Kind Kind,
+                   bool Deterministic, bool Thin,
+                   std::unique_ptr<MemoryBuffer> OldArchiveBuf) {
+  assert((!Thin || !isBSDLike(Kind)) && "Only the gnu format has a thin mode");
+
+  SmallString<0> SymNamesBuf;
+  raw_svector_ostream SymNames(SymNamesBuf);
+  SmallString<0> StringTableBuf;
+  raw_svector_ostream StringTable(StringTableBuf);
+
+  Expected<std::vector<MemberData>> DataOrErr = computeMemberData(
+      StringTable, SymNames, Kind, Thin, Deterministic, NewMembers);
+  if (Error E = DataOrErr.takeError())
+    return E;
+  std::vector<MemberData> &Data = *DataOrErr;
+
+  if (!StringTableBuf.empty())
+    Data.insert(Data.begin(), computeStringTable(StringTableBuf));
+
+  // We would like to detect if we need to switch to a 64-bit symbol table.
+  if (WriteSymtab) {
+    uint64_t MaxOffset = 0;
+    uint64_t LastOffset = MaxOffset;
+    for (const auto &M : Data) {
+      // Record the start of the member's offset
+      LastOffset = MaxOffset;
+      // Account for the size of each part associated with the member.
+      MaxOffset += M.Header.size() + M.Data.size() + M.Padding.size();
+      // We assume 32-bit symbols to see if 32-bit symbols are possible or not.
+      MaxOffset += M.Symbols.size() * 4;
+    }
+
+    // The SYM64 format is used when an archive's member offsets are larger than
+    // 32-bits can hold. The need for this shift in format is detected by
+    // writeArchive. To test this we need to generate a file with a member that
+    // has an offset larger than 32-bits but this demands a very slow test. To
+    // speed the test up we use this environment variable to pretend like the
+    // cutoff happens before 32-bits and instead happens at some much smaller
+    // value.
+    const char *Sym64Env = std::getenv("SYM64_THRESHOLD");
+    int Sym64Threshold = 32;
+    if (Sym64Env)
+      StringRef(Sym64Env).getAsInteger(10, Sym64Threshold);
+
+    // If LastOffset isn't going to fit in a 32-bit varible we need to switch
+    // to 64-bit. Note that the file can be larger than 4GB as long as the last
+    // member starts before the 4GB offset.
+    if (LastOffset >= (1ULL << Sym64Threshold)) {
+      if (Kind == object::Archive::K_DARWIN)
+        Kind = object::Archive::K_DARWIN64;
+      else
+        Kind = object::Archive::K_GNU64;
+    }
+  }
+
+  Expected<sys::fs::TempFile> Temp =
+      sys::fs::TempFile::create(ArcName + ".temp-archive-%%%%%%%.a");
+  if (!Temp)
+    return Temp.takeError();
+
+  raw_fd_ostream Out(Temp->FD, false);
+  if (Thin)
+    Out << "!<thin>\n";
+  else
+    Out << "!<arch>\n";
+
+  if (WriteSymtab)
+    writeSymbolTable(Out, Kind, Deterministic, Data, SymNamesBuf);
+
+  for (const MemberData &M : Data)
+    Out << M.Header << M.Data << M.Padding;
+
+  Out.flush();
+
+  // At this point, we no longer need whatever backing memory
+  // was used to generate the NewMembers. On Windows, this buffer
+  // could be a mapped view of the file we want to replace (if
+  // we're updating an existing archive, say). In that case, the
+  // rename would still succeed, but it would leave behind a
+  // temporary file (actually the original file renamed) because
+  // a file cannot be deleted while there's a handle open on it,
+  // only renamed. So by freeing this buffer, this ensures that
+  // the last open handle on the destination file, if any, is
+  // closed before we attempt to rename.
+  OldArchiveBuf.reset();
+
+  return Temp->keep(ArcName);
+}
+
+} // namespace llvm

test/tools/llvm-ar/reduce-thin-path.test

+RUN: rm -rf %t && mkdir -p %t/foo/bar/
+RUN: mkdir -p %t/baz/
+RUN: yaml2obj %S/Inputs/elf.yaml -o %t/elf.o
+
+RUN: cd %t && llvm-ar rTc %t/baz/internal.ar elf.o
+RUN: cd %t/foo && llvm-ar rTc %t/foo/bar/external.ar ../baz/internal.ar
+
+RUN: FileCheck -input-file=%t/foo/bar/external.ar %s
+
+CHECK: {{^}}../../elf.o/

test/tools/llvm-ar/thin-archive.test

+RUN: rm -rf %t && mkdir -p %t/foo/bar/
+
+RUN: yaml2obj %S/Inputs/elf.yaml -o %t/foo/elf.o
+RUN: cp %t/foo/elf.o %t/foo/bar/elf.o
+RUN: cp %t/foo/bar/elf.o %t/delete.o
+
+Test that modules can be added with absolute paths when the archive is created using an absolute path
+
+RUN: llvm-ar rTc %t/absolute-1.ar %t/foo/elf.o %t/delete.o %t/foo/bar/elf.o
+RUN: llvm-ar dT %t/absolute-1.ar delete.o
+
+RUN: FileCheck -input-file=%t/absolute-1.ar --check-prefixes=THIN,CHECK %s -DPATH=%/t/
+RUN: llvm-ar t %t/absolute-1.ar | FileCheck %s -DPATH=%/t/
+
+Test that modules can be added with absolute paths when the archive is created using a relative path
+
+RUN: llvm-ar rTc Output/%basename_t.tmp/absolute-2.ar %t/foo/elf.o %t/delete.o %t/foo/bar/elf.o
+RUN: llvm-ar dT Output/%basename_t.tmp/absolute-2.ar %t/delete.o
+
+RUN: FileCheck -input-file=%t/absolute-2.ar --check-prefixes=THIN,CHECK %s -DPATH=%/t/
+RUN: llvm-ar t %t/absolute-2.ar | FileCheck %s -DPATH=%/t/
+
+These tests must be run in %t/foo. cd %t is included on each line to make debugging this test case easier.
+
+Test that modules can be added with relative paths when the archive is created using a relative path
+
+RUN: cd %t/foo && llvm-ar rTc ../relative-1.ar elf.o ../delete.o bar/elf.o
+RUN: cd %t/foo && llvm-ar dT ../relative-1.ar delete.o
+
+RUN: FileCheck -input-file=%t/relative-1.ar --check-prefixes=THIN,CHECK %s -DPATH=
+RUN: llvm-ar t %t/relative-1.ar | FileCheck %s -DPATH=%/t/
+
+Test that modules can be added with relative paths when the archive is created using a absolute path
+
+RUN: cd %t/foo && llvm-ar rTc %t/relative-2.ar elf.o ../delete.o bar/elf.o
+cd %t/foo && llvm-ar dT %t/relative-2.ar delete.o
+
+FileCheck -input-file=%t/relative-2.ar --check-prefixes=THIN,CHECK %s -DPATH=
+llvm-ar t %t/relative-2.ar | FileCheck %s -DPATH=%/t/
+
+THIN: !<thin>
+
+CHECK-NOT: delete.o
+CHECK: {{^}}[[PATH]]foo/elf.o
+CHECK: {{^}}[[PATH]]foo/bar/elf.o
 No newline at end of file

tools/llvm-ar/llvm-ar.cpp

-//===-- llvm-ar.cpp - LLVM archive librarian utility ----------------------===//
-//
-// 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
-//
-//===----------------------------------------------------------------------===//
-//
-// Builds up (relatively) standard unix archive files (.a) containing LLVM
-// bitcode or other files.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/ADT/StringSwitch.h"
-#include "llvm/ADT/Triple.h"
-#include "llvm/IR/LLVMContext.h"
-#include "llvm/Object/Archive.h"
-#include "llvm/Object/ArchiveWriter.h"
-#include "llvm/Object/MachO.h"
-#include "llvm/Object/ObjectFile.h"
-#include "llvm/Support/Chrono.h"
-#include "llvm/Support/CommandLine.h"
-#include "llvm/Support/Errc.h"
-#include "llvm/Support/FileSystem.h"
-#include "llvm/Support/Format.h"
-#include "llvm/Support/FormatVariadic.h"
-#include "llvm/Support/InitLLVM.h"
-#include "llvm/Support/LineIterator.h"
-#include "llvm/Support/MemoryBuffer.h"
-#include "llvm/Support/Path.h"
-#include "llvm/Support/Process.h"
-#include "llvm/Support/StringSaver.h"
-#include "llvm/Support/TargetSelect.h"
-#include "llvm/Support/ToolOutputFile.h"
-#include "llvm/Support/WithColor.h"
-#include "llvm/Support/raw_ostream.h"
-#include "llvm/ToolDrivers/llvm-dlltool/DlltoolDriver.h"
-#include "llvm/ToolDrivers/llvm-lib/LibDriver.h"
-
-#if !defined(_MSC_VER) && !defined(__MINGW32__)
-#include <unistd.h>
-#else
-#include <io.h>
-#endif
-
-using namespace llvm;
-
-// The name this program was invoked as.
-static StringRef ToolName;
-
-// The basename of this program.
-static StringRef Stem;
-
-const char RanlibHelp[] = R"(
-OVERVIEW: LLVM Ranlib (llvm-ranlib)
-
-  This program generates an index to speed access to archives
-
-USAGE: llvm-ranlib <archive-file>
-
-OPTIONS:
-  -help                             - Display available options
-  -version                          - Display the version of this program
-)";
-
-const char ArHelp[] = R"(
-OVERVIEW: LLVM Archiver
-
-USAGE: llvm-ar [options] [-]<operation>[modifiers] [relpos] <archive> [files]
-       llvm-ar -M [<mri-script]
-
-OPTIONS:
-  --format              - Archive format to create
-    =default            -   default
-    =gnu                -   gnu
-    =darwin             -   darwin
-    =bsd                -   bsd
-  --plugin=<string>     - Ignored for compatibility
-  --help                - Display available options
-  --version             - Display the version of this program
-
-OPERATIONS:
-  d - delete [files] from the archive
-  m - move [files] in the archive
-  p - print [files] found in the archive
-  q - quick append [files] to the archive
-  r - replace or insert [files] into the archive
-  s - act as ranlib
-  t - display contents of archive
-  x - extract [files] from the archive
-
-MODIFIERS:
-  [a] - put [files] after [relpos]
-  [b] - put [files] before [relpos] (same as [i])
-  [c] - do not warn if archive had to be created
-  [D] - use zero for timestamps and uids/gids (default)
-  [i] - put [files] before [relpos] (same as [b])
-  [l] - ignored for compatibility
-  [L] - add archive's contents
-  [o] - preserve original dates
-  [P] - use full names when matching (implied for thin archives)
-  [s] - create an archive index (cf. ranlib)
-  [S] - do not build a symbol table
-  [T] - create a thin archive
-  [u] - update only [files] newer than archive contents
-  [U] - use actual timestamps and uids/gids
-  [v] - be verbose about actions taken
-)";
-
-void printHelpMessage() {
-  if (Stem.contains_lower("ranlib"))
-    outs() << RanlibHelp;
-  else if (Stem.contains_lower("ar"))
-    outs() << ArHelp;
-}
-
-// Show the error message and exit.
-LLVM_ATTRIBUTE_NORETURN static void fail(Twine Error) {
-  WithColor::error(errs(), ToolName) << Error << ".\n";
-  printHelpMessage();
-  exit(1);
-}
-
-static void failIfError(std::error_code EC, Twine Context = "") {
-  if (!EC)
-    return;
-
-  std::string ContextStr = Context.str();
-  if (ContextStr.empty())
-    fail(EC.message());
-  fail(Context + ": " + EC.message());
-}
-
-static void failIfError(Error E, Twine Context = "") {
-  if (!E)
-    return;
-
-  handleAllErrors(std::move(E), [&](const llvm::ErrorInfoBase &EIB) {
-    std::string ContextStr = Context.str();
-    if (ContextStr.empty())
-      fail(EIB.message());
-    fail(Context + ": " + EIB.message());
-  });
-}
-
-static SmallVector<const char *, 256> PositionalArgs;
-
-static bool MRI;
-
-namespace {
-enum Format { Default, GNU, BSD, DARWIN, Unknown };
-}
-
-static Format FormatType = Default;
-
-static std::string Options;
-
-// This enumeration delineates the kinds of operations on an archive
-// that are permitted.
-enum ArchiveOperation {
-  Print,           ///< Print the contents of the archive
-  Delete,          ///< Delete the specified members
-  Move,            ///< Move members to end or as given by {a,b,i} modifiers
-  QuickAppend,     ///< Quickly append to end of archive
-  ReplaceOrInsert, ///< Replace or Insert members
-  DisplayTable,    ///< Display the table of contents
-  Extract,         ///< Extract files back to file system
-  CreateSymTab     ///< Create a symbol table in an existing archive
-};
-
-// Modifiers to follow operation to vary behavior
-static bool AddAfter = false;        ///< 'a' modifier
-static bool AddBefore = false;       ///< 'b' modifier
-static bool Create = false;          ///< 'c' modifier
-static bool OriginalDates = false;   ///< 'o' modifier
-static bool CompareFullPath = false; ///< 'P' modifier
-static bool OnlyUpdate = false;      ///< 'u' modifier
-static bool Verbose = false;         ///< 'v' modifier
-static bool Symtab = true;           ///< 's' modifier
-static bool Deterministic = true;    ///< 'D' and 'U' modifiers
-static bool Thin = false;            ///< 'T' modifier
-static bool AddLibrary = false;      ///< 'L' modifier
-
-// Relative Positional Argument (for insert/move). This variable holds
-// the name of the archive member to which the 'a', 'b' or 'i' modifier
-// refers. Only one of 'a', 'b' or 'i' can be specified so we only need
-// one variable.
-static std::string RelPos;
-
-// This variable holds the name of the archive file as given on the
-// command line.
-static std::string ArchiveName;
-
-// This variable holds the list of member files to proecess, as given
-// on the command line.
-static std::vector<StringRef> Members;
-
-// Static buffer to hold StringRefs.
-static BumpPtrAllocator Alloc;
-
-// Extract the member filename from the command line for the [relpos] argument
-// associated with a, b, and i modifiers
-static void getRelPos() {
-  if (PositionalArgs.empty())
-    fail("Expected [relpos] for a, b, or i modifier");
-  RelPos = PositionalArgs[0];
-  PositionalArgs.erase(PositionalArgs.begin());
-}
-
-// Get the archive file name from the command line
-static void getArchive() {
-  if (PositionalArgs.empty())
-    fail("An archive name must be specified");
-  ArchiveName = PositionalArgs[0];
-  PositionalArgs.erase(PositionalArgs.begin());
-}
-
-// Copy over remaining items in PositionalArgs to our Members vector
-static void getMembers() {
-  for (auto &Arg : PositionalArgs)
-    Members.push_back(Arg);
-}
-
-std::vector<std::unique_ptr<MemoryBuffer>> ArchiveBuffers;
-std::vector<std::unique_ptr<object::Archive>> Archives;
-
-static object::Archive &readLibrary(const Twine &Library) {
-  auto BufOrErr = MemoryBuffer::getFile(Library, -1, false);
-  failIfError(BufOrErr.getError(), "Could not open library " + Library);
-  ArchiveBuffers.push_back(std::move(*BufOrErr));
-  auto LibOrErr =
-      object::Archive::create(ArchiveBuffers.back()->getMemBufferRef());
-  failIfError(errorToErrorCode(LibOrErr.takeError()),
-              "Could not parse library");
-  Archives.push_back(std::move(*LibOrErr));
-  return *Archives.back();
-}
-
-static void runMRIScript();
-
-// Parse the command line options as presented and return the operation
-// specified. Process all modifiers and check to make sure that constraints on
-// modifier/operation pairs have not been violated.
-static ArchiveOperation parseCommandLine() {
-  if (MRI) {
-    if (!PositionalArgs.empty() || !Options.empty())
-      fail("Cannot mix -M and other options");
-    runMRIScript();
-  }
-
-  // Keep track of number of operations. We can only specify one
-  // per execution.
-  unsigned NumOperations = 0;
-
-  // Keep track of the number of positional modifiers (a,b,i). Only
-  // one can be specified.
-  unsigned NumPositional = 0;
-
-  // Keep track of which operation was requested
-  ArchiveOperation Operation;
-
-  bool MaybeJustCreateSymTab = false;
-
-  for (unsigned i = 0; i < Options.size(); ++i) {
-    switch (Options[i]) {
-    case 'd':
-      ++NumOperations;
-      Operation = Delete;
-      break;
-    case 'm':
-      ++NumOperations;
-      Operation = Move;
-      break;
-    case 'p':
-      ++NumOperations;
-      Operation = Print;
-      break;
-    case 'q':
-      ++NumOperations;
-      Operation = QuickAppend;
-      break;
-    case 'r':
-      ++NumOperations;
-      Operation = ReplaceOrInsert;
-      break;
-    case 't':
-      ++NumOperations;
-      Operation = DisplayTable;
-      break;
-    case 'x':
-      ++NumOperations;
-      Operation = Extract;
-      break;
-    case 'c':
-      Create = true;
-      break;
-    case 'l': /* accepted but unused */
-      break;
-    case 'o':
-      OriginalDates = true;
-      break;
-    case 'P':
-      CompareFullPath = true;
-      break;
-    case 's':
-      Symtab = true;
-      MaybeJustCreateSymTab = true;
-      break;
-    case 'S':
-      Symtab = false;
-      break;
-    case 'u':
-      OnlyUpdate = true;
-      break;
-    case 'v':
-      Verbose = true;
-      break;
-    case 'a':
-      getRelPos();
-      AddAfter = true;
-      NumPositional++;
-      break;
-    case 'b':
-      getRelPos();
-      AddBefore = true;
-      NumPositional++;
-      break;
-    case 'i':
-      getRelPos();
-      AddBefore = true;
-      NumPositional++;
-      break;
-    case 'D':
-      Deterministic = true;
-      break;
-    case 'U':
-      Deterministic = false;
-      break;
-    case 'T':
-      Thin = true;
-      // Thin archives store path names, so P should be forced.
-      CompareFullPath = true;
-      break;
-    case 'L':
-      AddLibrary = true;
-      break;
-    default:
-      fail(std::string("unknown option ") + Options[i]);
-    }
-  }
-
-  // At this point, the next thing on the command line must be
-  // the archive name.
-  getArchive();
-
-  // Everything on the command line at this point is a member.
-  getMembers();
-
-  if (NumOperations == 0 && MaybeJustCreateSymTab) {
-    NumOperations = 1;
-    Operation = CreateSymTab;
-    if (!Members.empty())
-      fail("The s operation takes only an archive as argument");
-  }
-
-  // Perform various checks on the operation/modifier specification
-  // to make sure we are dealing with a legal request.
-  if (NumOperations == 0)
-    fail("You must specify at least one of the operations");
-  if (NumOperations > 1)
-    fail("Only one operation may be specified");
-  if (NumPositional > 1)
-    fail("You may only specify one of a, b, and i modifiers");
-  if (AddAfter || AddBefore) {
-    if (Operation != Move && Operation != ReplaceOrInsert)
-      fail("The 'a', 'b' and 'i' modifiers can only be specified with "
-           "the 'm' or 'r' operations");
-  }
-  if (OriginalDates && Operation != Extract)
-    fail("The 'o' modifier is only applicable to the 'x' operation");
-  if (OnlyUpdate && Operation != ReplaceOrInsert)
-    fail("The 'u' modifier is only applicable to the 'r' operation");
-  if (AddLibrary && Operation != QuickAppend)
-    fail("The 'L' modifier is only applicable to the 'q' operation");
-
-  // Return the parsed operation to the caller
-  return Operation;
-}
-
-// Implements the 'p' operation. This function traverses the archive
-// looking for members that match the path list.
-static void doPrint(StringRef Name, const object::Archive::Child &C) {
-  if (Verbose)
-    outs() << "Printing " << Name << "\n";
-
-  Expected<StringRef> DataOrErr = C.getBuffer();
-  failIfError(DataOrErr.takeError());
-  StringRef Data = *DataOrErr;
-  outs().write(Data.data(), Data.size());
-}
-
-// Utility function for printing out the file mode when the 't' operation is in
-// verbose mode.
-static void printMode(unsigned mode) {
-  outs() << ((mode & 004) ? "r" : "-");
-  outs() << ((mode & 002) ? "w" : "-");
-  outs() << ((mode & 001) ? "x" : "-");
-}
-
-// Implement the 't' operation. This function prints out just
-// the file names of each of the members. However, if verbose mode is requested
-// ('v' modifier) then the file type, permission mode, user, group, size, and
-// modification time are also printed.
-static void doDisplayTable(StringRef Name, const object::Archive::Child &C) {
-  if (Verbose) {
-    Expected<sys::fs::perms> ModeOrErr = C.getAccessMode();
-    failIfError(ModeOrErr.takeError());
-    sys::fs::perms Mode = ModeOrErr.get();
-    printMode((Mode >> 6) & 007);
-    printMode((Mode >> 3) & 007);
-    printMode(Mode & 007);
-    Expected<unsigned> UIDOrErr = C.getUID();
-    failIfError(UIDOrErr.takeError());
-    outs() << ' ' << UIDOrErr.get();
-    Expected<unsigned> GIDOrErr = C.getGID();
-    failIfError(GIDOrErr.takeError());
-    outs() << '/' << GIDOrErr.get();
-    Expected<uint64_t> Size = C.getSize();
-    failIfError(Size.takeError());
-    outs() << ' ' << format("%6llu", Size.get());
-    auto ModTimeOrErr = C.getLastModified();
-    failIfError(ModTimeOrErr.takeError());
-    // Note: formatv() only handles the default TimePoint<>, which is in
-    // nanoseconds.
-    // TODO: fix format_provider<TimePoint<>> to allow other units.
-    sys::TimePoint<> ModTimeInNs = ModTimeOrErr.get();
-    outs() << ' ' << formatv("{0:%b %e %H:%M %Y}", ModTimeInNs);
-    outs() << ' ';
-  }
-
-  if (C.getParent()->isThin()) {
-    StringRef ParentDir = sys::path::parent_path(ArchiveName);
-    if (!ParentDir.empty())
-      outs() << ParentDir << '/';
-  }
-  outs() << Name << "\n";
-}
-
-static StringRef normalizePath(StringRef Path) {
-  return CompareFullPath ? Path : sys::path::filename(Path);
-}
-
-// Implement the 'x' operation. This function extracts files back to the file
-// system.
-static void doExtract(StringRef Name, const object::Archive::Child &C) {
-  // Retain the original mode.
-  Expected<sys::fs::perms> ModeOrErr = C.getAccessMode();
-  failIfError(ModeOrErr.takeError());
-  sys::fs::perms Mode = ModeOrErr.get();
-
-  int FD;
-  failIfError(sys::fs::openFileForWrite(sys::path::filename(Name), FD,
-                                        sys::fs::CD_CreateAlways,
-                                        sys::fs::F_None, Mode),
-              Name);
-
-  {
-    raw_fd_ostream file(FD, false);
-
-    // Get the data and its length
-    Expected<StringRef> BufOrErr = C.getBuffer();
-    failIfError(BufOrErr.takeError());
-    StringRef Data = BufOrErr.get();
-
-    // Write the data.
-    file.write(Data.data(), Data.size());
-  }
-
-  // If we're supposed to retain the original modification times, etc. do so
-  // now.
-  if (OriginalDates) {
-    auto ModTimeOrErr = C.getLastModified();
-    failIfError(ModTimeOrErr.takeError());
-    failIfError(
-        sys::fs::setLastAccessAndModificationTime(FD, ModTimeOrErr.get()));
-  }
-
-  if (close(FD))
-    fail("Could not close the file");
-}
-
-static bool shouldCreateArchive(ArchiveOperation Op) {
-  switch (Op) {
-  case Print:
-  case Delete:
-  case Move:
-  case DisplayTable:
-  case Extract:
-  case CreateSymTab:
-    return false;
-
-  case QuickAppend:
-  case ReplaceOrInsert:
-    return true;
-  }
-
-  llvm_unreachable("Missing entry in covered switch.");
-}
-
-static void performReadOperation(ArchiveOperation Operation,
-                                 object::Archive *OldArchive) {
-  if (Operation == Extract && OldArchive->isThin())
-    fail("extracting from a thin archive is not supported");
-
-  bool Filter = !Members.empty();
-  {
-    Error Err = Error::success();
-    for (auto &C : OldArchive->children(Err)) {
-      Expected<StringRef> NameOrErr = C.getName();
-      failIfError(NameOrErr.takeError());
-      StringRef Name = NameOrErr.get();
-
-      if (Filter) {
-        auto I = find_if(Members, [Name](StringRef Path) {
-          return Name == normalizePath(Path);
-        });
-        if (I == Members.end())
-          continue;
-        Members.erase(I);
-      }
-
-      switch (Operation) {
-      default:
-        llvm_unreachable("Not a read operation");
-      case Print:
-        doPrint(Name, C);
-        break;
-      case DisplayTable:
-        doDisplayTable(Name, C);
-        break;
-      case Extract:
-        doExtract(Name, C);
-        break;
-      }
-    }
-    failIfError(std::move(Err));
-  }
-
-  if (Members.empty())
-    return;
-  for (StringRef Name : Members)
-    WithColor::error(errs(), ToolName) << "'" << Name << "' was not found\n";
-  exit(1);
-}
-
-static void addChildMember(std::vector<NewArchiveMember> &Members,
-                           const object::Archive::Child &M,
-                           bool FlattenArchive = false) {
-  if (Thin && !M.getParent()->isThin())
-    fail("Cannot convert a regular archive to a thin one");
-  Expected<NewArchiveMember> NMOrErr =
-      NewArchiveMember::getOldMember(M, Deterministic);
-  failIfError(NMOrErr.takeError());
-  // If the child member we're trying to add is thin, use the path relative to
-  // the archive it's in, so the file resolves correctly.
-  if (Thin && FlattenArchive) {
-    StringSaver Saver(Alloc);
-    Expected<std::string> FileNameOrErr = M.getFullName();
-    failIfError(FileNameOrErr.takeError());
-    NMOrErr->MemberName =
-        Saver.save(computeArchiveRelativePath(ArchiveName, *FileNameOrErr));
-  }
-  if (FlattenArchive &&
-      identify_magic(NMOrErr->Buf->getBuffer()) == file_magic::archive) {
-    Expected<std::string> FileNameOrErr = M.getFullName();
-    failIfError(FileNameOrErr.takeError());
-    object::Archive &Lib = readLibrary(*FileNameOrErr);
-    // When creating thin archives, only flatten if the member is also thin.
-    if (!Thin || Lib.isThin()) {
-      Error Err = Error::success();
-      // Only Thin archives are recursively flattened.
-      for (auto &Child : Lib.children(Err))
-        addChildMember(Members, Child, /*FlattenArchive=*/Thin);
-      failIfError(std::move(Err));
-      return;
-    }
-  }
-  Members.push_back(std::move(*NMOrErr));
-}
-
-static void addMember(std::vector<NewArchiveMember> &Members,
-                      StringRef FileName, bool FlattenArchive = false) {
-  Expected<NewArchiveMember> NMOrErr =
-      NewArchiveMember::getFile(FileName, Deterministic);
-  failIfError(NMOrErr.takeError(), FileName);
-  StringSaver Saver(Alloc);
-  // For regular archives, use the basename of the object path for the member
-  // name. For thin archives, use the full relative paths so the file resolves
-  // correctly.
-  NMOrErr->MemberName =
-      Thin ? Saver.save(computeArchiveRelativePath(ArchiveName, FileName))
-           : sys::path::filename(NMOrErr->MemberName);
-  if (FlattenArchive &&
-      identify_magic(NMOrErr->Buf->getBuffer()) == file_magic::archive) {
-    object::Archive &Lib = readLibrary(FileName);
-    // When creating thin archives, only flatten if the member is also thin.
-    if (!Thin || Lib.isThin()) {
-      Error Err = Error::success();
-      // Only Thin archives are recursively flattened.
-      for (auto &Child : Lib.children(Err))
-        addChildMember(Members, Child, /*FlattenArchive=*/Thin);
-      failIfError(std::move(Err));
-      return;
-    }
-  }
-  Members.push_back(std::move(*NMOrErr));
-}
-
-enum InsertAction {
-  IA_AddOldMember,
-  IA_AddNewMember,
-  IA_Delete,
-  IA_MoveOldMember,
-  IA_MoveNewMember
-};
-
-static InsertAction computeInsertAction(ArchiveOperation Operation,
-                                        const object::Archive::Child &Member,
-                                        StringRef Name,
-                                        std::vector<StringRef>::iterator &Pos) {
-  if (Operation == QuickAppend || Members.empty())
-    return IA_AddOldMember;
-
-  auto MI = find_if(
-      Members, [Name](StringRef Path) { return Name == normalizePath(Path); });
-
-  if (MI == Members.end())
-    return IA_AddOldMember;
-
-  Pos = MI;
-
-  if (Operation == Delete)
-    return IA_Delete;
-
-  if (Operation == Move)
-    return IA_MoveOldMember;
-
-  if (Operation == ReplaceOrInsert) {
-    StringRef PosName = normalizePath(RelPos);
-    if (!OnlyUpdate) {
-      if (PosName.empty())
-        return IA_AddNewMember;
-      return IA_MoveNewMember;
-    }
-
-    // We could try to optimize this to a fstat, but it is not a common
-    // operation.
-    sys::fs::file_status Status;
-    failIfError(sys::fs::status(*MI, Status), *MI);
-    auto ModTimeOrErr = Member.getLastModified();
-    failIfError(ModTimeOrErr.takeError());
-    if (Status.getLastModificationTime() < ModTimeOrErr.get()) {
-      if (PosName.empty())
-        return IA_AddOldMember;
-      return IA_MoveOldMember;
-    }
-
-    if (PosName.empty())
-      return IA_AddNewMember;
-    return IA_MoveNewMember;
-  }
-  llvm_unreachable("No such operation");
-}
-
-// We have to walk this twice and computing it is not trivial, so creating an
-// explicit std::vector is actually fairly efficient.
-static std::vector<NewArchiveMember>
-computeNewArchiveMembers(ArchiveOperation Operation,
-                         object::Archive *OldArchive) {
-  std::vector<NewArchiveMember> Ret;
-  std::vector<NewArchiveMember> Moved;
-  int InsertPos = -1;
-  StringRef PosName = normalizePath(RelPos);
-  if (OldArchive) {
-    Error Err = Error::success();
-    for (auto &Child : OldArchive->children(Err)) {
-      int Pos = Ret.size();
-      Expected<StringRef> NameOrErr = Child.getName();
-      failIfError(NameOrErr.takeError());
-      StringRef Name = NameOrErr.get();
-      if (Name == PosName) {
-        assert(AddAfter || AddBefore);
-        if (AddBefore)
-          InsertPos = Pos;
-        else
-          InsertPos = Pos + 1;
-      }
-
-      std::vector<StringRef>::iterator MemberI = Members.end();
-      InsertAction Action =
-          computeInsertAction(Operation, Child, Name, MemberI);
-      switch (Action) {
-      case IA_AddOldMember:
-        addChildMember(Ret, Child, /*FlattenArchive=*/Thin);
-        break;
-      case IA_AddNewMember:
-        addMember(Ret, *MemberI);
-        break;
-      case IA_Delete:
-        break;
-      case IA_MoveOldMember:
-        addChildMember(Moved, Child, /*FlattenArchive=*/Thin);
-        break;
-      case IA_MoveNewMember:
-        addMember(Moved, *MemberI);
-        break;
-      }
-      if (MemberI != Members.end())
-        Members.erase(MemberI);
-    }
-    failIfError(std::move(Err));
-  }
-
-  if (Operation == Delete)
-    return Ret;
-
-  if (!RelPos.empty() && InsertPos == -1)
-    fail("Insertion point not found");
-
-  if (RelPos.empty())
-    InsertPos = Ret.size();
-
-  assert(unsigned(InsertPos) <= Ret.size());
-  int Pos = InsertPos;
-  for (auto &M : Moved) {
-    Ret.insert(Ret.begin() + Pos, std::move(M));
-    ++Pos;
-  }
-
-  if (AddLibrary) {
-    assert(Operation == QuickAppend);
-    for (auto &Member : Members)
-      addMember(Ret, Member, /*FlattenArchive=*/true);
-    return Ret;
-  }
-
-  std::vector<NewArchiveMember> NewMembers;
-  for (auto &Member : Members)
-    addMember(NewMembers, Member, /*FlattenArchive=*/Thin);
-  Ret.reserve(Ret.size() + NewMembers.size());
-  std::move(NewMembers.begin(), NewMembers.end(),
-            std::inserter(Ret, std::next(Ret.begin(), InsertPos)));
-
-  return Ret;
-}
-
-static object::Archive::Kind getDefaultForHost() {
-  return Triple(sys::getProcessTriple()).isOSDarwin()
-             ? object::Archive::K_DARWIN
-             : object::Archive::K_GNU;
-}
-
-static object::Archive::Kind getKindFromMember(const NewArchiveMember &Member) {
-  Expected<std::unique_ptr<object::ObjectFile>> OptionalObject =
-      object::ObjectFile::createObjectFile(Member.Buf->getMemBufferRef());
-
-  if (OptionalObject)
-    return isa<object::MachOObjectFile>(**OptionalObject)
-               ? object::Archive::K_DARWIN
-               : object::Archive::K_GNU;
-
-  // squelch the error in case we had a non-object file
-  consumeError(OptionalObject.takeError());
-  return getDefaultForHost();
-}
-
-static void performWriteOperation(ArchiveOperation Operation,
-                                  object::Archive *OldArchive,
-                                  std::unique_ptr<MemoryBuffer> OldArchiveBuf,
-                                  std::vector<NewArchiveMember> *NewMembersP) {
-  std::vector<NewArchiveMember> NewMembers;
-  if (!NewMembersP)
-    NewMembers = computeNewArchiveMembers(Operation, OldArchive);
-
-  object::Archive::Kind Kind;
-  switch (FormatType) {
-  case Default:
-    if (Thin)
-      Kind = object::Archive::K_GNU;
-    else if (OldArchive)
-      Kind = OldArchive->kind();
-    else if (NewMembersP)
-      Kind = !NewMembersP->empty() ? getKindFromMember(NewMembersP->front())
-                                   : getDefaultForHost();
-    else
-      Kind = !NewMembers.empty() ? getKindFromMember(NewMembers.front())
-                                 : getDefaultForHost();
-    break;
-  case GNU:
-    Kind = object::Archive::K_GNU;
-    break;
-  case BSD:
-    if (Thin)
-      fail("Only the gnu format has a thin mode");
-    Kind = object::Archive::K_BSD;
-    break;
-  case DARWIN:
-    if (Thin)
-      fail("Only the gnu format has a thin mode");
-    Kind = object::Archive::K_DARWIN;
-    break;
-  case Unknown:
-    llvm_unreachable("");
-  }
-
-  Error E =
-      writeArchive(ArchiveName, NewMembersP ? *NewMembersP : NewMembers, Symtab,
-                   Kind, Deterministic, Thin, std::move(OldArchiveBuf));
-  failIfError(std::move(E), ArchiveName);
-}
-
-static void createSymbolTable(object::Archive *OldArchive) {
-  // When an archive is created or modified, if the s option is given, the
-  // resulting archive will have a current symbol table. If the S option
-  // is given, it will have no symbol table.
-  // In summary, we only need to update the symbol table if we have none.
-  // This is actually very common because of broken build systems that think
-  // they have to run ranlib.
-  if (OldArchive->hasSymbolTable())
-    return;
-
-  performWriteOperation(CreateSymTab, OldArchive, nullptr, nullptr);
-}
-
-static void performOperation(ArchiveOperation Operation,
-                             object::Archive *OldArchive,
-                             std::unique_ptr<MemoryBuffer> OldArchiveBuf,
-                             std::vector<NewArchiveMember> *NewMembers) {
-  switch (Operation) {
-  case Print:
-  case DisplayTable:
-  case Extract:
-    performReadOperation(Operation, OldArchive);
-    return;
-
-  case Delete:
-  case Move:
-  case QuickAppend:
-  case ReplaceOrInsert:
-    performWriteOperation(Operation, OldArchive, std::move(OldArchiveBuf),
-                          NewMembers);
-    return;
-  case CreateSymTab:
-    createSymbolTable(OldArchive);
-    return;
-  }
-  llvm_unreachable("Unknown operation.");
-}
-
-static int performOperation(ArchiveOperation Operation,
-                            std::vector<NewArchiveMember> *NewMembers) {
-  // Create or open the archive object.
-  ErrorOr<std::unique_ptr<MemoryBuffer>> Buf =
-      MemoryBuffer::getFile(ArchiveName, -1, false);
-  std::error_code EC = Buf.getError();
-  if (EC && EC != errc::no_such_file_or_directory)
-    fail("error opening '" + ArchiveName + "': " + EC.message() + "!");
-
-  if (!EC) {
-    Error Err = Error::success();
-    object::Archive Archive(Buf.get()->getMemBufferRef(), Err);
-    EC = errorToErrorCode(std::move(Err));
-    failIfError(EC,
-                "error loading '" + ArchiveName + "': " + EC.message() + "!");
-    if (Archive.isThin())
-      CompareFullPath = true;
-    performOperation(Operation, &Archive, std::move(Buf.get()), NewMembers);
-    return 0;
-  }
-
-  assert(EC == errc::no_such_file_or_directory);
-
-  if (!shouldCreateArchive(Operation)) {
-    failIfError(EC, Twine("error loading '") + ArchiveName + "'");
-  } else {
-    if (!Create) {
-      // Produce a warning if we should and we're creating the archive
-      WithColor::warning(errs(), ToolName)
-          << "creating " << ArchiveName << "\n";
-    }
-  }
-
-  performOperation(Operation, nullptr, nullptr, NewMembers);
-  return 0;
-}
-
-static void runMRIScript() {
-  enum class MRICommand { AddLib, AddMod, Create, Delete, Save, End, Invalid };
-
-  ErrorOr<std::unique_ptr<MemoryBuffer>> Buf = MemoryBuffer::getSTDIN();
-  failIfError(Buf.getError());
-  const MemoryBuffer &Ref = *Buf.get();
-  bool Saved = false;
-  std::vector<NewArchiveMember> NewMembers;
-
-  for (line_iterator I(Ref, /*SkipBlanks*/ false), E; I != E; ++I) {
-    StringRef Line = *I;
-    Line = Line.split(';').first;
-    Line = Line.split('*').first;
-    Line = Line.trim();
-    if (Line.empty())
-      continue;
-    StringRef CommandStr, Rest;
-    std::tie(CommandStr, Rest) = Line.split(' ');
-    Rest = Rest.trim();
-    if (!Rest.empty() && Rest.front() == '"' && Rest.back() == '"')
-      Rest = Rest.drop_front().drop_back();
-    auto Command = StringSwitch<MRICommand>(CommandStr.lower())
-                       .Case("addlib", MRICommand::AddLib)
-                       .Case("addmod", MRICommand::AddMod)
-                       .Case("create", MRICommand::Create)
-                       .Case("delete", MRICommand::Delete)
-                       .Case("save", MRICommand::Save)
-                       .Case("end", MRICommand::End)
-                       .Default(MRICommand::Invalid);
-
-    switch (Command) {
-    case MRICommand::AddLib: {
-      object::Archive &Lib = readLibrary(Rest);
-      {
-        Error Err = Error::success();
-        for (auto &Member : Lib.children(Err))
-          addChildMember(NewMembers, Member, /*FlattenArchive=*/Thin);
-        failIfError(std::move(Err));
-      }
-      break;
-    }
-    case MRICommand::AddMod:
-      addMember(NewMembers, Rest);
-      break;
-    case MRICommand::Create:
-      Create = true;
-      if (!ArchiveName.empty())
-        fail("Editing multiple archives not supported");
-      if (Saved)
-        fail("File already saved");
-      ArchiveName = Rest;
-      break;
-    case MRICommand::Delete: {
-      StringRef Name = normalizePath(Rest);
-      llvm::erase_if(NewMembers,
-                     [=](NewArchiveMember &M) { return M.MemberName == Name; });
-      break;
-    }
-    case MRICommand::Save:
-      Saved = true;
-      break;
-    case MRICommand::End:
-      break;
-    case MRICommand::Invalid:
-      fail("Unknown command: " + CommandStr);
-    }
-  }
-
-  // Nothing to do if not saved.
-  if (Saved)
-    performOperation(ReplaceOrInsert, &NewMembers);
-  exit(0);
-}
-
-static bool handleGenericOption(StringRef arg) {
-  if (arg == "-help" || arg == "--help") {
-    printHelpMessage();
-    return true;
-  }
-  if (arg == "-version" || arg == "--version") {
-    cl::PrintVersionMessage();
-    return true;
-  }
-  return false;
-}
-
-static int ar_main(int argc, char **argv) {
-  SmallVector<const char *, 0> Argv(argv, argv + argc);
-  StringSaver Saver(Alloc);
-  cl::ExpandResponseFiles(Saver, cl::TokenizeGNUCommandLine, Argv);
-  for (size_t i = 1; i < Argv.size(); ++i) {
-    StringRef Arg = Argv[i];
-    const char *match;
-    auto MatchFlagWithArg = [&](const char *expected) {
-      size_t len = strlen(expected);
-      if (Arg == expected) {
-        if (++i >= Argv.size())
-          fail(std::string(expected) + " requires an argument");
-        match = Argv[i];
-        return true;
-      }
-      if (Arg.startswith(expected) && Arg.size() > len && Arg[len] == '=') {
-        match = Arg.data() + len + 1;
-        return true;
-      }
-      return false;
-    };
-    if (handleGenericOption(Argv[i]))
-      return 0;
-    if (Arg == "--") {
-      for (; i < Argv.size(); ++i)
-        PositionalArgs.push_back(Argv[i]);
-      break;
-    }
-    if (Arg[0] == '-') {
-      if (Arg.startswith("--"))
-        Arg = Argv[i] + 2;
-      else
-        Arg = Argv[i] + 1;
-      if (Arg == "M") {
-        MRI = true;
-      } else if (MatchFlagWithArg("format")) {
-        FormatType = StringSwitch<Format>(match)
-                         .Case("default", Default)
-                         .Case("gnu", GNU)
-                         .Case("darwin", DARWIN)
-                         .Case("bsd", BSD)
-                         .Default(Unknown);
-        if (FormatType == Unknown)
-          fail(std::string("Invalid format ") + match);
-      } else if (MatchFlagWithArg("plugin")) {
-        // Ignored.
-      } else {
-        Options += Argv[i] + 1;
-      }
-    } else if (Options.empty()) {
-      Options += Argv[i];
-    } else {
-      PositionalArgs.push_back(Argv[i]);
-    }
-  }
-  ArchiveOperation Operation = parseCommandLine();
-  return performOperation(Operation, nullptr);
-}
-
-static int ranlib_main(int argc, char **argv) {
-  bool ArchiveSpecified = false;
-  for (int i = 1; i < argc; ++i) {
-    if (handleGenericOption(argv[i])) {
-      return 0;
-    } else {
-      if (ArchiveSpecified)
-        fail("Exactly one archive should be specified");
-      ArchiveSpecified = true;
-      ArchiveName = argv[i];
-    }
-  }
-  return performOperation(CreateSymTab, nullptr);
-}
-
-int main(int argc, char **argv) {
-  InitLLVM X(argc, argv);
-  ToolName = argv[0];
-
-  llvm::InitializeAllTargetInfos();
-  llvm::InitializeAllTargetMCs();
-  llvm::InitializeAllAsmParsers();
-
-  Stem = sys::path::stem(ToolName);
-  if (Stem.contains_lower("dlltool"))
-    return dlltoolDriverMain(makeArrayRef(argv, argc));
-
-  if (Stem.contains_lower("ranlib"))
-    return ranlib_main(argc, argv);
-
-  if (Stem.contains_lower("lib"))
-    return libDriverMain(makeArrayRef(argv, argc));
-
-  if (Stem.contains_lower("ar"))
-    return ar_main(argc, argv);
-  fail("Not ranlib, ar, lib or dlltool!");
-}
+//===-- llvm-ar.cpp - LLVM archive librarian utility ----------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Builds up (relatively) standard unix archive files (.a) containing LLVM
+// bitcode or other files.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/StringSwitch.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/Object/Archive.h"
+#include "llvm/Object/ArchiveWriter.h"
+#include "llvm/Object/MachO.h"
+#include "llvm/Object/ObjectFile.h"
+#include "llvm/Support/Chrono.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Errc.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Format.h"
+#include "llvm/Support/FormatVariadic.h"
+#include "llvm/Support/InitLLVM.h"
+#include "llvm/Support/LineIterator.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/Process.h"
+#include "llvm/Support/StringSaver.h"
+#include "llvm/Support/TargetSelect.h"
+#include "llvm/Support/ToolOutputFile.h"
+#include "llvm/Support/WithColor.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/ToolDrivers/llvm-dlltool/DlltoolDriver.h"
+#include "llvm/ToolDrivers/llvm-lib/LibDriver.h"
+
+#if !defined(_MSC_VER) && !defined(__MINGW32__)
+#include <unistd.h>
+#else
+#include <io.h>
+#endif
+
+using namespace llvm;
+
+// The name this program was invoked as.
+static StringRef ToolName;
+
+// The basename of this program.
+static StringRef Stem;
+
+const char RanlibHelp[] = R"(
+OVERVIEW: LLVM Ranlib (llvm-ranlib)
+
+  This program generates an index to speed access to archives
+
+USAGE: llvm-ranlib <archive-file>
+
+OPTIONS:
+  -help                             - Display available options
+  -version                          - Display the version of this program
+)";
+
+const char ArHelp[] = R"(
+OVERVIEW: LLVM Archiver
+
+USAGE: llvm-ar [options] [-]<operation>[modifiers] [relpos] <archive> [files]
+       llvm-ar -M [<mri-script]
+
+OPTIONS:
+  --format              - Archive format to create
+    =default            -   default
+    =gnu                -   gnu
+    =darwin             -   darwin
+    =bsd                -   bsd
+  --plugin=<string>     - Ignored for compatibility
+  --help                - Display available options
+  --version             - Display the version of this program
+
+OPERATIONS:
+  d - delete [files] from the archive
+  m - move [files] in the archive
+  p - print [files] found in the archive
+  q - quick append [files] to the archive
+  r - replace or insert [files] into the archive
+  s - act as ranlib
+  t - display contents of archive
+  x - extract [files] from the archive
+
+MODIFIERS:
+  [a] - put [files] after [relpos]
+  [b] - put [files] before [relpos] (same as [i])
+  [c] - do not warn if archive had to be created
+  [D] - use zero for timestamps and uids/gids (default)
+  [i] - put [files] before [relpos] (same as [b])
+  [l] - ignored for compatibility
+  [L] - add archive's contents
+  [o] - preserve original dates
+  [P] - use full names when matching (implied for thin archives)
+  [s] - create an archive index (cf. ranlib)
+  [S] - do not build a symbol table
+  [T] - create a thin archive
+  [u] - update only [files] newer than archive contents
+  [U] - use actual timestamps and uids/gids
+  [v] - be verbose about actions taken
+)";
+
+void printHelpMessage() {
+  if (Stem.contains_lower("ranlib"))
+    outs() << RanlibHelp;
+  else if (Stem.contains_lower("ar"))
+    outs() << ArHelp;
+}
+
+// Show the error message and exit.
+LLVM_ATTRIBUTE_NORETURN static void fail(Twine Error) {
+  WithColor::error(errs(), ToolName) << Error << ".\n";
+  printHelpMessage();
+  exit(1);
+}
+
+static void failIfError(std::error_code EC, Twine Context = "") {
+  if (!EC)
+    return;
+
+  std::string ContextStr = Context.str();
+  if (ContextStr.empty())
+    fail(EC.message());
+  fail(Context + ": " + EC.message());
+}
+
+static void failIfError(Error E, Twine Context = "") {
+  if (!E)
+    return;
+
+  handleAllErrors(std::move(E), [&](const llvm::ErrorInfoBase &EIB) {
+    std::string ContextStr = Context.str();
+    if (ContextStr.empty())
+      fail(EIB.message());
+    fail(Context + ": " + EIB.message());
+  });
+}
+
+static SmallVector<const char *, 256> PositionalArgs;
+
+static bool MRI;
+
+namespace {
+enum Format { Default, GNU, BSD, DARWIN, Unknown };
+}
+
+static Format FormatType = Default;
+
+static std::string Options;
+
+// This enumeration delineates the kinds of operations on an archive
+// that are permitted.
+enum ArchiveOperation {
+  Print,           ///< Print the contents of the archive
+  Delete,          ///< Delete the specified members
+  Move,            ///< Move members to end or as given by {a,b,i} modifiers
+  QuickAppend,     ///< Quickly append to end of archive
+  ReplaceOrInsert, ///< Replace or Insert members
+  DisplayTable,    ///< Display the table of contents
+  Extract,         ///< Extract files back to file system
+  CreateSymTab     ///< Create a symbol table in an existing archive
+};
+
+// Modifiers to follow operation to vary behavior
+static bool AddAfter = false;        ///< 'a' modifier
+static bool AddBefore = false;       ///< 'b' modifier
+static bool Create = false;          ///< 'c' modifier
+static bool OriginalDates = false;   ///< 'o' modifier
+static bool CompareFullPath = false; ///< 'P' modifier
+static bool OnlyUpdate = false;      ///< 'u' modifier
+static bool Verbose = false;         ///< 'v' modifier
+static bool Symtab = true;           ///< 's' modifier
+static bool Deterministic = true;    ///< 'D' and 'U' modifiers
+static bool Thin = false;            ///< 'T' modifier
+static bool AddLibrary = false;      ///< 'L' modifier
+
+// Relative Positional Argument (for insert/move). This variable holds
+// the name of the archive member to which the 'a', 'b' or 'i' modifier
+// refers. Only one of 'a', 'b' or 'i' can be specified so we only need
+// one variable.
+static std::string RelPos;
+
+// This variable holds the name of the archive file as given on the
+// command line.
+static std::string ArchiveName;
+
+// This variable holds the list of member files to proecess, as given
+// on the command line.
+static std::vector<StringRef> Members;
+
+// Static buffer to hold StringRefs.
+static BumpPtrAllocator Alloc;
+
+// Extract the member filename from the command line for the [relpos] argument
+// associated with a, b, and i modifiers
+static void getRelPos() {
+  if (PositionalArgs.empty())
+    fail("Expected [relpos] for a, b, or i modifier");
+  RelPos = PositionalArgs[0];
+  PositionalArgs.erase(PositionalArgs.begin());
+}
+
+// Get the archive file name from the command line
+static void getArchive() {
+  if (PositionalArgs.empty())
+    fail("An archive name must be specified");
+  ArchiveName = PositionalArgs[0];
+  PositionalArgs.erase(PositionalArgs.begin());
+}
+
+// Copy over remaining items in PositionalArgs to our Members vector
+static void getMembers() {
+  for (auto &Arg : PositionalArgs)
+    Members.push_back(Arg);
+}
+
+std::vector<std::unique_ptr<MemoryBuffer>> ArchiveBuffers;
+std::vector<std::unique_ptr<object::Archive>> Archives;
+
+static object::Archive &readLibrary(const Twine &Library) {
+  auto BufOrErr = MemoryBuffer::getFile(Library, -1, false);
+  failIfError(BufOrErr.getError(), "Could not open library " + Library);
+  ArchiveBuffers.push_back(std::move(*BufOrErr));
+  auto LibOrErr =
+      object::Archive::create(ArchiveBuffers.back()->getMemBufferRef());
+  failIfError(errorToErrorCode(LibOrErr.takeError()),
+              "Could not parse library");
+  Archives.push_back(std::move(*LibOrErr));
+  return *Archives.back();
+}
+
+static void runMRIScript();
+
+// Parse the command line options as presented and return the operation
+// specified. Process all modifiers and check to make sure that constraints on
+// modifier/operation pairs have not been violated.
+static ArchiveOperation parseCommandLine() {
+  if (MRI) {
+    if (!PositionalArgs.empty() || !Options.empty())
+      fail("Cannot mix -M and other options");
+    runMRIScript();
+  }
+
+  // Keep track of number of operations. We can only specify one
+  // per execution.
+  unsigned NumOperations = 0;
+
+  // Keep track of the number of positional modifiers (a,b,i). Only
+  // one can be specified.
+  unsigned NumPositional = 0;
+
+  // Keep track of which operation was requested
+  ArchiveOperation Operation;
+
+  bool MaybeJustCreateSymTab = false;
+
+  for (unsigned i = 0; i < Options.size(); ++i) {
+    switch (Options[i]) {
+    case 'd':
+      ++NumOperations;
+      Operation = Delete;
+      break;
+    case 'm':
+      ++NumOperations;
+      Operation = Move;
+      break;
+    case 'p':
+      ++NumOperations;
+      Operation = Print;
+      break;
+    case 'q':
+      ++NumOperations;
+      Operation = QuickAppend;
+      break;
+    case 'r':
+      ++NumOperations;
+      Operation = ReplaceOrInsert;
+      break;
+    case 't':
+      ++NumOperations;
+      Operation = DisplayTable;
+      break;
+    case 'x':
+      ++NumOperations;
+      Operation = Extract;
+      break;
+    case 'c':
+      Create = true;
+      break;
+    case 'l': /* accepted but unused */
+      break;
+    case 'o':
+      OriginalDates = true;
+      break;
+    case 'P':
+      CompareFullPath = true;
+      break;
+    case 's':
+      Symtab = true;
+      MaybeJustCreateSymTab = true;
+      break;
+    case 'S':
+      Symtab = false;
+      break;
+    case 'u':
+      OnlyUpdate = true;
+      break;
+    case 'v':
+      Verbose = true;
+      break;
+    case 'a':
+      getRelPos();
+      AddAfter = true;
+      NumPositional++;
+      break;
+    case 'b':
+      getRelPos();
+      AddBefore = true;
+      NumPositional++;
+      break;
+    case 'i':
+      getRelPos();
+      AddBefore = true;
+      NumPositional++;
+      break;
+    case 'D':
+      Deterministic = true;
+      break;
+    case 'U':
+      Deterministic = false;
+      break;
+    case 'T':
+      Thin = true;
+      // Thin archives store path names, so P should be forced.
+      CompareFullPath = true;
+      break;
+    case 'L':
+      AddLibrary = true;
+      break;
+    default:
+      fail(std::string("unknown option ") + Options[i]);
+    }
+  }
+
+  // At this point, the next thing on the command line must be
+  // the archive name.
+  getArchive();
+
+  // Everything on the command line at this point is a member.
+  getMembers();
+
+  if (NumOperations == 0 && MaybeJustCreateSymTab) {
+    NumOperations = 1;
+    Operation = CreateSymTab;
+    if (!Members.empty())
+      fail("The s operation takes only an archive as argument");
+  }
+
+  // Perform various checks on the operation/modifier specification
+  // to make sure we are dealing with a legal request.
+  if (NumOperations == 0)
+    fail("You must specify at least one of the operations");
+  if (NumOperations > 1)
+    fail("Only one operation may be specified");
+  if (NumPositional > 1)
+    fail("You may only specify one of a, b, and i modifiers");
+  if (AddAfter || AddBefore) {
+    if (Operation != Move && Operation != ReplaceOrInsert)
+      fail("The 'a', 'b' and 'i' modifiers can only be specified with "
+           "the 'm' or 'r' operations");
+  }
+  if (OriginalDates && Operation != Extract)
+    fail("The 'o' modifier is only applicable to the 'x' operation");
+  if (OnlyUpdate && Operation != ReplaceOrInsert)
+    fail("The 'u' modifier is only applicable to the 'r' operation");
+  if (AddLibrary && Operation != QuickAppend)
+    fail("The 'L' modifier is only applicable to the 'q' operation");
+
+  // Return the parsed operation to the caller
+  return Operation;
+}
+
+// Implements the 'p' operation. This function traverses the archive
+// looking for members that match the path list.
+static void doPrint(StringRef Name, const object::Archive::Child &C) {
+  if (Verbose)
+    outs() << "Printing " << Name << "\n";
+
+  Expected<StringRef> DataOrErr = C.getBuffer();
+  failIfError(DataOrErr.takeError());
+  StringRef Data = *DataOrErr;
+  outs().write(Data.data(), Data.size());
+}
+
+// Utility function for printing out the file mode when the 't' operation is in
+// verbose mode.
+static void printMode(unsigned mode) {
+  outs() << ((mode & 004) ? "r" : "-");
+  outs() << ((mode & 002) ? "w" : "-");
+  outs() << ((mode & 001) ? "x" : "-");
+}
+
+// Implement the 't' operation. This function prints out just
+// the file names of each of the members. However, if verbose mode is requested
+// ('v' modifier) then the file type, permission mode, user, group, size, and
+// modification time are also printed.
+static void doDisplayTable(StringRef Name, const object::Archive::Child &C) {
+  if (Verbose) {
+    Expected<sys::fs::perms> ModeOrErr = C.getAccessMode();
+    failIfError(ModeOrErr.takeError());
+    sys::fs::perms Mode = ModeOrErr.get();
+    printMode((Mode >> 6) & 007);
+    printMode((Mode >> 3) & 007);
+    printMode(Mode & 007);
+    Expected<unsigned> UIDOrErr = C.getUID();
+    failIfError(UIDOrErr.takeError());
+    outs() << ' ' << UIDOrErr.get();
+    Expected<unsigned> GIDOrErr = C.getGID();
+    failIfError(GIDOrErr.takeError());
+    outs() << '/' << GIDOrErr.get();
+    Expected<uint64_t> Size = C.getSize();
+    failIfError(Size.takeError());
+    outs() << ' ' << format("%6llu", Size.get());
+    auto ModTimeOrErr = C.getLastModified();
+    failIfError(ModTimeOrErr.takeError());
+    // Note: formatv() only handles the default TimePoint<>, which is in
+    // nanoseconds.
+    // TODO: fix format_provider<TimePoint<>> to allow other units.
+    sys::TimePoint<> ModTimeInNs = ModTimeOrErr.get();
+    outs() << ' ' << formatv("{0:%b %e %H:%M %Y}", ModTimeInNs);
+    outs() << ' ';
+  }
+
+  if (C.getParent()->isThin()) {
+    if (!sys::path::is_absolute(Name)) {
+      StringRef ParentDir = sys::path::parent_path(ArchiveName);
+      if (!ParentDir.empty())
+        outs() << sys::path::convert_to_slash(ParentDir) << '/';
+    }
+  }
+  outs() << Name << "\n";
+}
+
+static StringRef normalizePath(StringRef Path) {
+  return CompareFullPath ? Path : sys::path::filename(Path);
+}
+
+// Implement the 'x' operation. This function extracts files back to the file
+// system.
+static void doExtract(StringRef Name, const object::Archive::Child &C) {
+  // Retain the original mode.
+  Expected<sys::fs::perms> ModeOrErr = C.getAccessMode();
+  failIfError(ModeOrErr.takeError());
+  sys::fs::perms Mode = ModeOrErr.get();
+
+  int FD;
+  failIfError(sys::fs::openFileForWrite(sys::path::filename(Name), FD,
+                                        sys::fs::CD_CreateAlways,
+                                        sys::fs::F_None, Mode),
+              Name);
+
+  {
+    raw_fd_ostream file(FD, false);
+
+    // Get the data and its length
+    Expected<StringRef> BufOrErr = C.getBuffer();
+    failIfError(BufOrErr.takeError());
+    StringRef Data = BufOrErr.get();
+
+    // Write the data.
+    file.write(Data.data(), Data.size());
+  }
+
+  // If we're supposed to retain the original modification times, etc. do so
+  // now.
+  if (OriginalDates) {
+    auto ModTimeOrErr = C.getLastModified();
+    failIfError(ModTimeOrErr.takeError());
+    failIfError(
+        sys::fs::setLastAccessAndModificationTime(FD, ModTimeOrErr.get()));
+  }
+
+  if (close(FD))
+    fail("Could not close the file");
+}
+
+static bool shouldCreateArchive(ArchiveOperation Op) {
+  switch (Op) {
+  case Print:
+  case Delete:
+  case Move:
+  case DisplayTable:
+  case Extract:
+  case CreateSymTab:
+    return false;
+
+  case QuickAppend:
+  case ReplaceOrInsert:
+    return true;
+  }
+
+  llvm_unreachable("Missing entry in covered switch.");
+}
+
+static void performReadOperation(ArchiveOperation Operation,
+                                 object::Archive *OldArchive) {
+  if (Operation == Extract && OldArchive->isThin())
+    fail("extracting from a thin archive is not supported");
+
+  bool Filter = !Members.empty();
+  {
+    Error Err = Error::success();
+    for (auto &C : OldArchive->children(Err)) {
+      Expected<StringRef> NameOrErr = C.getName();
+      failIfError(NameOrErr.takeError());
+      StringRef Name = NameOrErr.get();
+
+      if (Filter) {
+        auto I = find_if(Members, [Name](StringRef Path) {
+          return Name == normalizePath(Path);
+        });
+        if (I == Members.end())
+          continue;
+        Members.erase(I);
+      }
+
+      switch (Operation) {
+      default:
+        llvm_unreachable("Not a read operation");
+      case Print:
+        doPrint(Name, C);
+        break;
+      case DisplayTable:
+        doDisplayTable(Name, C);
+        break;
+      case Extract:
+        doExtract(Name, C);
+        break;
+      }
+    }
+    failIfError(std::move(Err));
+  }
+
+  if (Members.empty())
+    return;
+  for (StringRef Name : Members)
+    WithColor::error(errs(), ToolName) << "'" << Name << "' was not found\n";
+  exit(1);
+}
+
+static void addChildMember(std::vector<NewArchiveMember> &Members,
+                           const object::Archive::Child &M,
+                           bool FlattenArchive = false) {
+  if (Thin && !M.getParent()->isThin())
+    fail("Cannot convert a regular archive to a thin one");
+  Expected<NewArchiveMember> NMOrErr =
+      NewArchiveMember::getOldMember(M, Deterministic);
+  failIfError(NMOrErr.takeError());
+  // If the child member we're trying to add is thin, use the path relative to
+  // the archive it's in, so the file resolves correctly.
+  if (Thin && FlattenArchive) {
+    StringSaver Saver(Alloc);
+    Expected<StringRef> NameOrErr = M.getName();
+    failIfError(NameOrErr.takeError());
+    Expected<std::string> FileNameOrErr = M.getFullName();
+    failIfError(FileNameOrErr.takeError());
+
+    std::string MemberPath;
+    if (sys::path::is_absolute(*NameOrErr) &&
+        sys::path::is_absolute(*FileNameOrErr)) {
+      MemberPath = sys::path::convert_to_slash(*FileNameOrErr);
+    } else {
+      MemberPath = computeArchiveRelativePath(ArchiveName, *FileNameOrErr);
+    }
+
+    NMOrErr->MemberName = Saver.save(MemberPath);
+  }
+  if (FlattenArchive &&
+      identify_magic(NMOrErr->Buf->getBuffer()) == file_magic::archive) {
+    Expected<std::string> FileNameOrErr = M.getFullName();
+    failIfError(FileNameOrErr.takeError());
+    object::Archive &Lib = readLibrary(*FileNameOrErr);
+    // When creating thin archives, only flatten if the member is also thin.
+    if (!Thin || Lib.isThin()) {
+      Error Err = Error::success();
+      // Only Thin archives are recursively flattened.
+      for (auto &Child : Lib.children(Err))
+        addChildMember(Members, Child, /*FlattenArchive=*/Thin);
+      failIfError(std::move(Err));
+      return;
+    }
+  }
+  Members.push_back(std::move(*NMOrErr));
+}
+
+static void addMember(std::vector<NewArchiveMember> &Members,
+                      StringRef FileName, bool FlattenArchive = false) {
+  Expected<NewArchiveMember> NMOrErr =
+      NewArchiveMember::getFile(FileName, Deterministic);
+  failIfError(NMOrErr.takeError(), FileName);
+  StringSaver Saver(Alloc);
+  // For regular archives, use the basename of the object path for the member
+  // name. For thin archives, use the full relative paths so the file resolves
+  // correctly.
+  auto getThinMemberPath = [](StringRef FileName) -> std::string {
+    if (sys::path::is_absolute(FileName)) {
+      return sys::path::convert_to_slash(FileName);
+    }
+    return computeArchiveRelativePath(ArchiveName, FileName);
+  };
+
+  NMOrErr->MemberName = Thin ? Saver.save(getThinMemberPath(FileName))
+                             : sys::path::filename(NMOrErr->MemberName);
+  if (FlattenArchive &&
+      identify_magic(NMOrErr->Buf->getBuffer()) == file_magic::archive) {
+    object::Archive &Lib = readLibrary(FileName);
+    // When creating thin archives, only flatten if the member is also thin.
+    if (!Thin || Lib.isThin()) {
+      Error Err = Error::success();
+      // Only Thin archives are recursively flattened.
+      for (auto &Child : Lib.children(Err))
+        addChildMember(Members, Child, /*FlattenArchive=*/Thin);
+      failIfError(std::move(Err));
+      return;
+    }
+  }
+  Members.push_back(std::move(*NMOrErr));
+}
+
+enum InsertAction {
+  IA_AddOldMember,
+  IA_AddNewMember,
+  IA_Delete,
+  IA_MoveOldMember,
+  IA_MoveNewMember
+};
+
+static InsertAction computeInsertAction(ArchiveOperation Operation,
+                                        const object::Archive::Child &Member,
+                                        StringRef Name,
+                                        std::vector<StringRef>::iterator &Pos) {
+  if (Operation == QuickAppend || Members.empty())
+    return IA_AddOldMember;
+
+  auto MI = find_if(
+      Members, [Name](StringRef Path) { return Name == normalizePath(Path); });
+
+  if (MI == Members.end())
+    return IA_AddOldMember;
+
+  Pos = MI;
+
+  if (Operation == Delete)
+    return IA_Delete;
+
+  if (Operation == Move)
+    return IA_MoveOldMember;
+
+  if (Operation == ReplaceOrInsert) {
+    StringRef PosName = normalizePath(RelPos);
+    if (!OnlyUpdate) {
+      if (PosName.empty())
+        return IA_AddNewMember;
+      return IA_MoveNewMember;
+    }
+
+    // We could try to optimize this to a fstat, but it is not a common
+    // operation.
+    sys::fs::file_status Status;
+    failIfError(sys::fs::status(*MI, Status), *MI);
+    auto ModTimeOrErr = Member.getLastModified();
+    failIfError(ModTimeOrErr.takeError());
+    if (Status.getLastModificationTime() < ModTimeOrErr.get()) {
+      if (PosName.empty())
+        return IA_AddOldMember;
+      return IA_MoveOldMember;
+    }
+
+    if (PosName.empty())
+      return IA_AddNewMember;
+    return IA_MoveNewMember;
+  }
+  llvm_unreachable("No such operation");
+}
+
+// We have to walk this twice and computing it is not trivial, so creating an
+// explicit std::vector is actually fairly efficient.
+static std::vector<NewArchiveMember>
+computeNewArchiveMembers(ArchiveOperation Operation,
+                         object::Archive *OldArchive) {
+  std::vector<NewArchiveMember> Ret;
+  std::vector<NewArchiveMember> Moved;
+  int InsertPos = -1;
+  StringRef PosName = normalizePath(RelPos);
+  if (OldArchive) {
+    Error Err = Error::success();
+    for (auto &Child : OldArchive->children(Err)) {
+      int Pos = Ret.size();
+      Expected<StringRef> NameOrErr = Child.getName();
+      failIfError(NameOrErr.takeError());
+      StringRef Name = NameOrErr.get();
+      if (Name == PosName) {
+        assert(AddAfter || AddBefore);
+        if (AddBefore)
+          InsertPos = Pos;
+        else
+          InsertPos = Pos + 1;
+      }
+
+      std::vector<StringRef>::iterator MemberI = Members.end();
+      InsertAction Action =
+          computeInsertAction(Operation, Child, Name, MemberI);
+      switch (Action) {
+      case IA_AddOldMember:
+        addChildMember(Ret, Child, /*FlattenArchive=*/Thin);
+        break;
+      case IA_AddNewMember:
+        addMember(Ret, *MemberI);
+        break;
+      case IA_Delete:
+        break;
+      case IA_MoveOldMember:
+        addChildMember(Moved, Child, /*FlattenArchive=*/Thin);
+        break;
+      case IA_MoveNewMember:
+        addMember(Moved, *MemberI);
+        break;
+      }
+      if (MemberI != Members.end())
+        Members.erase(MemberI);
+    }
+    failIfError(std::move(Err));
+  }
+
+  if (Operation == Delete)
+    return Ret;
+
+  if (!RelPos.empty() && InsertPos == -1)
+    fail("Insertion point not found");
+
+  if (RelPos.empty())
+    InsertPos = Ret.size();
+
+  assert(unsigned(InsertPos) <= Ret.size());
+  int Pos = InsertPos;
+  for (auto &M : Moved) {
+    Ret.insert(Ret.begin() + Pos, std::move(M));
+    ++Pos;
+  }
+
+  if (AddLibrary) {
+    assert(Operation == QuickAppend);
+    for (auto &Member : Members)
+      addMember(Ret, Member, /*FlattenArchive=*/true);
+    return Ret;
+  }
+
+  std::vector<NewArchiveMember> NewMembers;
+  for (auto &Member : Members)
+    addMember(NewMembers, Member, /*FlattenArchive=*/Thin);
+  Ret.reserve(Ret.size() + NewMembers.size());
+  std::move(NewMembers.begin(), NewMembers.end(),
+            std::inserter(Ret, std::next(Ret.begin(), InsertPos)));
+
+  return Ret;
+}
+
+static object::Archive::Kind getDefaultForHost() {
+  return Triple(sys::getProcessTriple()).isOSDarwin()
+             ? object::Archive::K_DARWIN
+             : object::Archive::K_GNU;
+}
+
+static object::Archive::Kind getKindFromMember(const NewArchiveMember &Member) {
+  Expected<std::unique_ptr<object::ObjectFile>> OptionalObject =
+      object::ObjectFile::createObjectFile(Member.Buf->getMemBufferRef());
+
+  if (OptionalObject)
+    return isa<object::MachOObjectFile>(**OptionalObject)
+               ? object::Archive::K_DARWIN
+               : object::Archive::K_GNU;
+
+  // squelch the error in case we had a non-object file
+  consumeError(OptionalObject.takeError());
+  return getDefaultForHost();
+}
+
+static void performWriteOperation(ArchiveOperation Operation,
+                                  object::Archive *OldArchive,
+                                  std::unique_ptr<MemoryBuffer> OldArchiveBuf,
+                                  std::vector<NewArchiveMember> *NewMembersP) {
+  std::vector<NewArchiveMember> NewMembers;
+  if (!NewMembersP)
+    NewMembers = computeNewArchiveMembers(Operation, OldArchive);
+
+  object::Archive::Kind Kind;
+  switch (FormatType) {
+  case Default:
+    if (Thin)
+      Kind = object::Archive::K_GNU;
+    else if (OldArchive)
+      Kind = OldArchive->kind();
+    else if (NewMembersP)
+      Kind = !NewMembersP->empty() ? getKindFromMember(NewMembersP->front())
+                                   : getDefaultForHost();
+    else
+      Kind = !NewMembers.empty() ? getKindFromMember(NewMembers.front())
+                                 : getDefaultForHost();
+    break;
+  case GNU:
+    Kind = object::Archive::K_GNU;
+    break;
+  case BSD:
+    if (Thin)
+      fail("Only the gnu format has a thin mode");
+    Kind = object::Archive::K_BSD;
+    break;
+  case DARWIN:
+    if (Thin)
+      fail("Only the gnu format has a thin mode");
+    Kind = object::Archive::K_DARWIN;
+    break;
+  case Unknown:
+    llvm_unreachable("");
+  }
+
+  Error E =
+      writeArchive(ArchiveName, NewMembersP ? *NewMembersP : NewMembers, Symtab,
+                   Kind, Deterministic, Thin, std::move(OldArchiveBuf));
+  failIfError(std::move(E), ArchiveName);
+}
+
+static void createSymbolTable(object::Archive *OldArchive) {
+  // When an archive is created or modified, if the s option is given, the
+  // resulting archive will have a current symbol table. If the S option
+  // is given, it will have no symbol table.
+  // In summary, we only need to update the symbol table if we have none.
+  // This is actually very common because of broken build systems that think
+  // they have to run ranlib.
+  if (OldArchive->hasSymbolTable())
+    return;
+
+  performWriteOperation(CreateSymTab, OldArchive, nullptr, nullptr);
+}
+
+static void performOperation(ArchiveOperation Operation,
+                             object::Archive *OldArchive,
+                             std::unique_ptr<MemoryBuffer> OldArchiveBuf,
+                             std::vector<NewArchiveMember> *NewMembers) {
+  switch (Operation) {
+  case Print:
+  case DisplayTable:
+  case Extract:
+    performReadOperation(Operation, OldArchive);
+    return;
+
+  case Delete:
+  case Move:
+  case QuickAppend:
+  case ReplaceOrInsert:
+    performWriteOperation(Operation, OldArchive, std::move(OldArchiveBuf),
+                          NewMembers);
+    return;
+  case CreateSymTab:
+    createSymbolTable(OldArchive);
+    return;
+  }
+  llvm_unreachable("Unknown operation.");
+}
+
+static int performOperation(ArchiveOperation Operation,
+                            std::vector<NewArchiveMember> *NewMembers) {
+  // Create or open the archive object.
+  ErrorOr<std::unique_ptr<MemoryBuffer>> Buf =
+      MemoryBuffer::getFile(ArchiveName, -1, false);
+  std::error_code EC = Buf.getError();
+  if (EC && EC != errc::no_such_file_or_directory)
+    fail("error opening '" + ArchiveName + "': " + EC.message() + "!");
+
+  if (!EC) {
+    Error Err = Error::success();
+    object::Archive Archive(Buf.get()->getMemBufferRef(), Err);
+    EC = errorToErrorCode(std::move(Err));
+    failIfError(EC,
+                "error loading '" + ArchiveName + "': " + EC.message() + "!");
+    if (Archive.isThin())
+      CompareFullPath = true;
+    performOperation(Operation, &Archive, std::move(Buf.get()), NewMembers);
+    return 0;
+  }
+
+  assert(EC == errc::no_such_file_or_directory);
+
+  if (!shouldCreateArchive(Operation)) {
+    failIfError(EC, Twine("error loading '") + ArchiveName + "'");
+  } else {
+    if (!Create) {
+      // Produce a warning if we should and we're creating the archive
+      WithColor::warning(errs(), ToolName)
+          << "creating " << ArchiveName << "\n";
+    }
+  }
+
+  performOperation(Operation, nullptr, nullptr, NewMembers);
+  return 0;
+}
+
+static void runMRIScript() {
+  enum class MRICommand { AddLib, AddMod, Create, Delete, Save, End, Invalid };
+
+  ErrorOr<std::unique_ptr<MemoryBuffer>> Buf = MemoryBuffer::getSTDIN();
+  failIfError(Buf.getError());
+  const MemoryBuffer &Ref = *Buf.get();
+  bool Saved = false;
+  std::vector<NewArchiveMember> NewMembers;
+
+  for (line_iterator I(Ref, /*SkipBlanks*/ false), E; I != E; ++I) {
+    StringRef Line = *I;
+    Line = Line.split(';').first;
+    Line = Line.split('*').first;
+    Line = Line.trim();
+    if (Line.empty())
+      continue;
+    StringRef CommandStr, Rest;
+    std::tie(CommandStr, Rest) = Line.split(' ');
+    Rest = Rest.trim();
+    if (!Rest.empty() && Rest.front() == '"' && Rest.back() == '"')
+      Rest = Rest.drop_front().drop_back();
+    auto Command = StringSwitch<MRICommand>(CommandStr.lower())
+                       .Case("addlib", MRICommand::AddLib)
+                       .Case("addmod", MRICommand::AddMod)
+                       .Case("create", MRICommand::Create)
+                       .Case("delete", MRICommand::Delete)
+                       .Case("save", MRICommand::Save)
+                       .Case("end", MRICommand::End)
+                       .Default(MRICommand::Invalid);
+
+    switch (Command) {
+    case MRICommand::AddLib: {
+      object::Archive &Lib = readLibrary(Rest);
+      {
+        Error Err = Error::success();
+        for (auto &Member : Lib.children(Err))
+          addChildMember(NewMembers, Member, /*FlattenArchive=*/Thin);
+        failIfError(std::move(Err));
+      }
+      break;
+    }
+    case MRICommand::AddMod:
+      addMember(NewMembers, Rest);
+      break;
+    case MRICommand::Create:
+      Create = true;
+      if (!ArchiveName.empty())
+        fail("Editing multiple archives not supported");
+      if (Saved)
+        fail("File already saved");
+      ArchiveName = Rest;
+      break;
+    case MRICommand::Delete: {
+      StringRef Name = normalizePath(Rest);
+      llvm::erase_if(NewMembers,
+                     [=](NewArchiveMember &M) { return M.MemberName == Name; });
+      break;
+    }
+    case MRICommand::Save:
+      Saved = true;
+      break;
+    case MRICommand::End:
+      break;
+    case MRICommand::Invalid:
+      fail("Unknown command: " + CommandStr);
+    }
+  }
+
+  // Nothing to do if not saved.
+  if (Saved)
+    performOperation(ReplaceOrInsert, &NewMembers);
+  exit(0);
+}
+
+static bool handleGenericOption(StringRef arg) {
+  if (arg == "-help" || arg == "--help") {
+    printHelpMessage();
+    return true;
+  }
+  if (arg == "-version" || arg == "--version") {
+    cl::PrintVersionMessage();
+    return true;
+  }
+  return false;
+}
+
+static int ar_main(int argc, char **argv) {
+  SmallVector<const char *, 0> Argv(argv, argv + argc);
+  StringSaver Saver(Alloc);
+  cl::ExpandResponseFiles(Saver, cl::TokenizeGNUCommandLine, Argv);
+  for (size_t i = 1; i < Argv.size(); ++i) {
+    StringRef Arg = Argv[i];
+    const char *match;
+    auto MatchFlagWithArg = [&](const char *expected) {
+      size_t len = strlen(expected);
+      if (Arg == expected) {
+        if (++i >= Argv.size())
+          fail(std::string(expected) + " requires an argument");
+        match = Argv[i];
+        return true;
+      }
+      if (Arg.startswith(expected) && Arg.size() > len && Arg[len] == '=') {
+        match = Arg.data() + len + 1;
+        return true;
+      }
+      return false;
+    };
+    if (handleGenericOption(Argv[i]))
+      return 0;
+    if (Arg == "--") {
+      for (; i < Argv.size(); ++i)
+        PositionalArgs.push_back(Argv[i]);
+      break;
+    }
+    if (Arg[0] == '-') {
+      if (Arg.startswith("--"))
+        Arg = Argv[i] + 2;
+      else
+        Arg = Argv[i] + 1;
+      if (Arg == "M") {
+        MRI = true;
+      } else if (MatchFlagWithArg("format")) {
+        FormatType = StringSwitch<Format>(match)
+                         .Case("default", Default)
+                         .Case("gnu", GNU)
+                         .Case("darwin", DARWIN)
+                         .Case("bsd", BSD)
+                         .Default(Unknown);
+        if (FormatType == Unknown)
+          fail(std::string("Invalid format ") + match);
+      } else if (MatchFlagWithArg("plugin")) {
+        // Ignored.
+      } else {
+        Options += Argv[i] + 1;
+      }
+    } else if (Options.empty()) {
+      Options += Argv[i];
+    } else {
+      PositionalArgs.push_back(Argv[i]);
+    }
+  }
+  ArchiveOperation Operation = parseCommandLine();
+  return performOperation(Operation, nullptr);
+}
+
+static int ranlib_main(int argc, char **argv) {
+  bool ArchiveSpecified = false;
+  for (int i = 1; i < argc; ++i) {
+    if (handleGenericOption(argv[i])) {
+      return 0;
+    } else {
+      if (ArchiveSpecified)
+        fail("Exactly one archive should be specified");
+      ArchiveSpecified = true;
+      ArchiveName = argv[i];
+    }
+  }
+  return performOperation(CreateSymTab, nullptr);
+}
+
+int main(int argc, char **argv) {
+  InitLLVM X(argc, argv);
+  ToolName = argv[0];
+
+  llvm::InitializeAllTargetInfos();
+  llvm::InitializeAllTargetMCs();
+  llvm::InitializeAllAsmParsers();
+
+  Stem = sys::path::stem(ToolName);
+  if (Stem.contains_lower("dlltool"))
+    return dlltoolDriverMain(makeArrayRef(argv, argc));
+
+  if (Stem.contains_lower("ranlib"))
+    return ranlib_main(argc, argv);
+
+  if (Stem.contains_lower("lib"))
+    return libDriverMain(makeArrayRef(argv, argc));
+
+  if (Stem.contains_lower("ar"))
+    return ar_main(argc, argv);
+  fail("Not ranlib, ar, lib or dlltool!");
+}