llvm-ar: Move archive writer to Object.

[pcc]

Summary

No functional change intended, other than some minor changes to certain
diagnostics.

[• rafael]

We really need a better way of handling diagnostics in lib/Object, but this is fine for now with some nits.

I will try to code something to untangle diagnostics and error handling in general.

include/llvm/Object/ArchiveWriter.h

10

writeArchive.

lib/Object/ArchiveWriter.cpp

92

Please add a FIXME about using endian.h

include/llvm/Object/ArchiveWriter.h

+//===- ArchiveWriter.h - ar archive file format writer ----------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Declares the WriteArchive function for writing an archive file.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_OBJECT_ARCHIVEWRITER_H
+#define LLVM_OBJECT_ARCHIVEWRITER_H
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Object/Archive.h"
+#include "llvm/Support/FileSystem.h"
+
+namespace llvm {
+
+class NewArchiveIterator {
+  bool IsNewMember;
+  StringRef Name;
+
+  object::Archive::child_iterator OldI;
+
+  StringRef NewFilename;
+
+public:
+  NewArchiveIterator(object::Archive::child_iterator I, StringRef Name);
+  NewArchiveIterator(StringRef I, StringRef Name);
+  NewArchiveIterator();
+  bool isNewMember() const;
+  StringRef getName() const;
+
+  object::Archive::child_iterator getOld() const;
+
+  StringRef getNew() const;
+  llvm::ErrorOr<int> getFD(sys::fs::file_status &NewStatus) const;
+  const sys::fs::file_status &getStatus() const;
+};
+
+std::pair<StringRef, std::error_code>
+WriteArchive(StringRef ArcName, std::vector<NewArchiveIterator> &NewMembers,
+             bool WriteSymtab);
+
+}
+
+#endif

lib/Object/ArchiveWriter.cpp

+//===- ArchiveWriter.cpp - ar File Format implementation --------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the WriteArchive function.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Object/ArchiveWriter.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/Object/Archive.h"
+#include "llvm/Object/ObjectFile.h"
+#include "llvm/Object/SymbolicFile.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 <unistd.h>
+
+using namespace llvm;
+
+NewArchiveIterator::NewArchiveIterator() {}
+
+NewArchiveIterator::NewArchiveIterator(object::Archive::child_iterator I,
+                                       StringRef Name)
+    : IsNewMember(false), Name(Name), OldI(I) {}
+
+NewArchiveIterator::NewArchiveIterator(StringRef NewFilename, StringRef Name)
+    : IsNewMember(true), Name(Name), NewFilename(NewFilename) {}
+
+StringRef NewArchiveIterator::getName() const { return Name; }
+
+bool NewArchiveIterator::isNewMember() const { return IsNewMember; }
+
+object::Archive::child_iterator NewArchiveIterator::getOld() const {
+  assert(!IsNewMember);
+  return OldI;
+}
+
+StringRef NewArchiveIterator::getNew() const {
+  assert(IsNewMember);
+  return NewFilename;
+}
+
+llvm::ErrorOr<int>
+NewArchiveIterator::getFD(sys::fs::file_status &NewStatus) const {
+  assert(IsNewMember);
+  int NewFD;
+  if (auto EC = sys::fs::openFileForRead(NewFilename, NewFD))
+    return EC;
+  assert(NewFD != -1);
+
+  if (auto EC = sys::fs::status(NewFD, NewStatus))
+    return EC;
+
+  // Opening a directory doesn't make sense. Let it fail.
+  // Linux cannot open directories with open(2), although
+  // cygwin and *bsd can.
+  if (NewStatus.type() == sys::fs::file_type::directory_file)
+    return make_error_code(std::errc::is_a_directory);
+
+  return NewFD;
+}
+
+template <typename T>
+static void printWithSpacePadding(raw_fd_ostream &OS, T Data, unsigned Size,
+          bool MayTruncate = false) {
+  uint64_t OldPos = OS.tell();
+  OS << Data;
+  unsigned SizeSoFar = OS.tell() - OldPos;
+  if (Size > SizeSoFar) {
+    unsigned Remaining = Size - SizeSoFar;
+    for (unsigned I = 0; I < Remaining; ++I)
+      OS << ' ';
+  } else if (Size < SizeSoFar) {
+    assert(MayTruncate && "Data doesn't fit in Size");
+    // Some of the data this is used for (like UID) can be larger than the
+    // space available in the archive format. Truncate in that case.
+    OS.seek(OldPos + Size);
+  }
+}
+
+static void print32BE(raw_fd_ostream &Out, unsigned Val) {
+  for (int I = 3; I >= 0; --I) {
+    char V = (Val >> (8 * I)) & 0xff;
+    Out << V;
+  }
+}
+
+static void printRestOfMemberHeader(raw_fd_ostream &Out,
+                                    const sys::TimeValue &ModTime, unsigned UID,
+                                    unsigned GID, unsigned Perms,
+                                    unsigned Size) {
+  printWithSpacePadding(Out, ModTime.toEpochTime(), 12);
+  printWithSpacePadding(Out, UID, 6, true);
+  printWithSpacePadding(Out, GID, 6, true);
+  printWithSpacePadding(Out, format("%o", Perms), 8);
+  printWithSpacePadding(Out, Size, 10);
+  Out << "`\n";
+}
+
+static void printMemberHeader(raw_fd_ostream &Out, StringRef Name,
+                              const sys::TimeValue &ModTime, unsigned UID,
+                              unsigned GID, unsigned Perms, unsigned Size) {
+  printWithSpacePadding(Out, Twine(Name) + "/", 16);
+  printRestOfMemberHeader(Out, ModTime, UID, GID, Perms, Size);
+}
+
+static void printMemberHeader(raw_fd_ostream &Out, unsigned NameOffset,
+                              const sys::TimeValue &ModTime, unsigned UID,
+                              unsigned GID, unsigned Perms, unsigned Size) {
+  Out << '/';
+  printWithSpacePadding(Out, NameOffset, 15);
+  printRestOfMemberHeader(Out, ModTime, UID, GID, Perms, Size);
+}
+
+static void writeStringTable(raw_fd_ostream &Out,
+                             ArrayRef<NewArchiveIterator> Members,
+                             std::vector<unsigned> &StringMapIndexes) {
+  unsigned StartOffset = 0;
+  for (ArrayRef<NewArchiveIterator>::iterator I = Members.begin(),
+                                              E = Members.end();
+       I != E; ++I) {
+    StringRef Name = I->getName();
+    if (Name.size() < 16)
+      continue;
+    if (StartOffset == 0) {
+      printWithSpacePadding(Out, "//", 58);
+      Out << "`\n";
+      StartOffset = Out.tell();
+    }
+    StringMapIndexes.push_back(Out.tell() - StartOffset);
+    Out << Name << "/\n";
+  }
+  if (StartOffset == 0)
+    return;
+  if (Out.tell() % 2)
+    Out << '\n';
+  int Pos = Out.tell();
+  Out.seek(StartOffset - 12);
+  printWithSpacePadding(Out, Pos - StartOffset, 10);
+  Out.seek(Pos);
+}
+
+// Returns the offset of the first reference to a member offset.
+static ErrorOr<unsigned>
+writeSymbolTable(raw_fd_ostream &Out, ArrayRef<NewArchiveIterator> Members,
+                 ArrayRef<MemoryBufferRef> Buffers,
+                 std::vector<unsigned> &MemberOffsetRefs) {
+  unsigned StartOffset = 0;
+  unsigned MemberNum = 0;
+  std::string NameBuf;
+  raw_string_ostream NameOS(NameBuf);
+  unsigned NumSyms = 0;
+  LLVMContext Context;
+  for (ArrayRef<NewArchiveIterator>::iterator I = Members.begin(),
+                                              E = Members.end();
+       I != E; ++I, ++MemberNum) {
+    MemoryBufferRef MemberBuffer = Buffers[MemberNum];
+    ErrorOr<std::unique_ptr<object::SymbolicFile>> ObjOrErr =
+        object::SymbolicFile::createSymbolicFile(
+            MemberBuffer, sys::fs::file_magic::unknown, &Context);
+    if (!ObjOrErr)
+      continue;  // FIXME: check only for "not an object file" errors.
+    object::SymbolicFile &Obj = *ObjOrErr.get();
+
+    if (!StartOffset) {
+      printMemberHeader(Out, "", sys::TimeValue::now(), 0, 0, 0, 0);
+      StartOffset = Out.tell();
+      print32BE(Out, 0);
+    }
+
+    for (const object::BasicSymbolRef &S : Obj.symbols()) {
+      uint32_t Symflags = S.getFlags();
+      if (Symflags & object::SymbolRef::SF_FormatSpecific)
+        continue;
+      if (!(Symflags & object::SymbolRef::SF_Global))
+        continue;
+      if (Symflags & object::SymbolRef::SF_Undefined)
+        continue;
+      if (auto EC = S.printName(NameOS))
+        return EC;
+      NameOS << '\0';
+      ++NumSyms;
+      MemberOffsetRefs.push_back(MemberNum);
+      print32BE(Out, 0);
+    }
+  }
+  Out << NameOS.str();
+
+  if (StartOffset == 0)
+    return 0;
+
+  if (Out.tell() % 2)
+    Out << '\0';
+
+  unsigned Pos = Out.tell();
+  Out.seek(StartOffset - 12);
+  printWithSpacePadding(Out, Pos - StartOffset, 10);
+  Out.seek(StartOffset);
+  print32BE(Out, NumSyms);
+  Out.seek(Pos);
+  return StartOffset + 4;
+}
+
+std::pair<StringRef, std::error_code>
+llvm::WriteArchive(StringRef ArcName,
+                   std::vector<NewArchiveIterator> &NewMembers,
+                   bool WriteSymtab) {
+  SmallString<128> TmpArchive;
+  int TmpArchiveFD;
+  if (auto EC = sys::fs::createUniqueFile(ArcName + ".temp-archive-%%%%%%%.a",
+                                          TmpArchiveFD, TmpArchive))
+    return std::make_pair(ArcName, EC);
+
+  tool_output_file Output(TmpArchive, TmpArchiveFD);
+  raw_fd_ostream &Out = Output.os();
+  Out << "!<arch>\n";
+
+  std::vector<unsigned> MemberOffsetRefs;
+
+  std::vector<std::unique_ptr<MemoryBuffer>> Buffers;
+  std::vector<MemoryBufferRef> Members;
+  std::vector<sys::fs::file_status> NewMemberStatus;
+
+  for (unsigned I = 0, N = NewMembers.size(); I < N; ++I) {
+    NewArchiveIterator &Member = NewMembers[I];
+    MemoryBufferRef MemberRef;
+
+    if (Member.isNewMember()) {
+      StringRef Filename = Member.getNew();
+      NewMemberStatus.resize(NewMemberStatus.size() + 1);
+      sys::fs::file_status &Status = NewMemberStatus.back();
+      ErrorOr<int> FD = Member.getFD(Status);
+      if (auto EC = FD.getError())
+        return std::make_pair(Filename, EC);
+      ErrorOr<std::unique_ptr<MemoryBuffer>> MemberBufferOrErr =
+          MemoryBuffer::getOpenFile(FD.get(), Filename, Status.getSize(),
+                                    false);
+      if (auto EC = MemberBufferOrErr.getError())
+        return std::make_pair(Filename, EC);
+      if (close(FD.get()) != 0)
+        return std::make_pair(Filename,
+                              std::error_code(errno, std::generic_category()));
+      Buffers.push_back(std::move(MemberBufferOrErr.get()));
+      MemberRef = Buffers.back()->getMemBufferRef();
+    } else {
+      object::Archive::child_iterator OldMember = Member.getOld();
+      ErrorOr<MemoryBufferRef> MemberBufferOrErr =
+          OldMember->getMemoryBufferRef();
+      if (auto EC = MemberBufferOrErr.getError())
+        return std::make_pair("", EC);
+      MemberRef = MemberBufferOrErr.get();
+    }
+    Members.push_back(MemberRef);
+  }
+
+  unsigned MemberReferenceOffset = 0;
+  if (WriteSymtab) {
+    ErrorOr<unsigned> MemberReferenceOffsetOrErr =
+        writeSymbolTable(Out, NewMembers, Members, MemberOffsetRefs);
+    if (auto EC = MemberReferenceOffsetOrErr.getError())
+      return std::make_pair(ArcName, EC);
+    MemberReferenceOffset = MemberReferenceOffsetOrErr.get();
+  }
+
+  std::vector<unsigned> StringMapIndexes;
+  writeStringTable(Out, NewMembers, StringMapIndexes);
+
+  unsigned MemberNum = 0;
+  unsigned LongNameMemberNum = 0;
+  unsigned NewMemberNum = 0;
+  std::vector<unsigned> MemberOffset;
+  for (std::vector<NewArchiveIterator>::iterator I = NewMembers.begin(),
+                                                 E = NewMembers.end();
+       I != E; ++I, ++MemberNum) {
+
+    unsigned Pos = Out.tell();
+    MemberOffset.push_back(Pos);
+
+    MemoryBufferRef File = Members[MemberNum];
+    if (I->isNewMember()) {
+      StringRef FileName = I->getNew();
+      const sys::fs::file_status &Status = NewMemberStatus[NewMemberNum];
+      NewMemberNum++;
+
+      StringRef Name = sys::path::filename(FileName);
+      if (Name.size() < 16)
+        printMemberHeader(Out, Name, Status.getLastModificationTime(),
+                          Status.getUser(), Status.getGroup(),
+                          Status.permissions(), Status.getSize());
+      else
+        printMemberHeader(Out, StringMapIndexes[LongNameMemberNum++],
+                          Status.getLastModificationTime(), Status.getUser(),
+                          Status.getGroup(), Status.permissions(),
+                          Status.getSize());
+    } else {
+      object::Archive::child_iterator OldMember = I->getOld();
+      StringRef Name = I->getName();
+
+      if (Name.size() < 16)
+        printMemberHeader(Out, Name, OldMember->getLastModified(),
+                          OldMember->getUID(), OldMember->getGID(),
+                          OldMember->getAccessMode(), OldMember->getSize());
+      else
+        printMemberHeader(Out, StringMapIndexes[LongNameMemberNum++],
+                          OldMember->getLastModified(), OldMember->getUID(),
+                          OldMember->getGID(), OldMember->getAccessMode(),
+                          OldMember->getSize());
+    }
+
+    Out << File.getBuffer();
+
+    if (Out.tell() % 2)
+      Out << '\n';
+  }
+
+  if (MemberReferenceOffset) {
+    Out.seek(MemberReferenceOffset);
+    for (unsigned MemberNum : MemberOffsetRefs)
+      print32BE(Out, MemberOffset[MemberNum]);
+  }
+
+  Output.keep();
+  Out.close();
+  sys::fs::rename(TmpArchive, ArcName);
+  return std::make_pair("", std::error_code());
+}

lib/Object/CMakeLists.txt

 add_llvm_library(LLVMObject
   Archive.cpp
+  ArchiveWriter.cpp
   Binary.cpp
   COFFObjectFile.cpp
   COFFYAML.cpp
   ELF.cpp
   ELFObjectFile.cpp
   ELFYAML.cpp
   Error.cpp
   IRObjectFile.cpp

tools/llvm-ar/llvm-ar.cpp

 // bitcode or other files.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Object/Archive.h"
+#include "llvm/Object/ArchiveWriter.h"
 #include "llvm/Object/ObjectFile.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/LineIterator.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/MemoryBuffer.h"

 #include <io.h>
 #endif
 
 using namespace llvm;
 
 // The name this program was invoked as.
 static StringRef ToolName;
 
-static const char *TemporaryOutput;
-static int TmpArchiveFD = -1;
-
 // Show the error message and exit.
 LLVM_ATTRIBUTE_NORETURN static void fail(Twine Error) {
   outs() << ToolName << ": " << Error << ".\n";
-  if (TmpArchiveFD != -1)
-    close(TmpArchiveFD);
-  if (TemporaryOutput)
-    sys::fs::remove(TemporaryOutput);
   exit(1);
 }
 
 static void failIfError(std::error_code EC, Twine Context = "") {
   if (!EC)
     return;
 
   std::string ContextStr = Context.str();
case DisplayTable:
       break;
     case Extract:
       doExtract(Name, I);
       break;
     }
   }
 }
 
-namespace {
-class NewArchiveIterator {
-  bool IsNewMember;
-  StringRef Name;
-
-  object::Archive::child_iterator OldI;
-
-  StringRef NewFilename;
-
-public:
-  NewArchiveIterator(object::Archive::child_iterator I, StringRef Name);
-  NewArchiveIterator(StringRef I, StringRef Name);
-  NewArchiveIterator();
-  bool isNewMember() const;
-  StringRef getName() const;
-
-  object::Archive::child_iterator getOld() const;
-
-  StringRef getNew() const;
-  int getFD(sys::fs::file_status &NewStatus) const;
-  const sys::fs::file_status &getStatus() const;
-};
-}
-
-NewArchiveIterator::NewArchiveIterator() {}
-
-NewArchiveIterator::NewArchiveIterator(object::Archive::child_iterator I,
-                                       StringRef Name)
-    : IsNewMember(false), Name(Name), OldI(I) {}
-
-NewArchiveIterator::NewArchiveIterator(StringRef NewFilename, StringRef Name)
-    : IsNewMember(true), Name(Name), NewFilename(NewFilename) {}
-
-StringRef NewArchiveIterator::getName() const { return Name; }
-
-bool NewArchiveIterator::isNewMember() const { return IsNewMember; }
-
-object::Archive::child_iterator NewArchiveIterator::getOld() const {
-  assert(!IsNewMember);
-  return OldI;
-}
-
-StringRef NewArchiveIterator::getNew() const {
-  assert(IsNewMember);
-  return NewFilename;
-}
-
-int NewArchiveIterator::getFD(sys::fs::file_status &NewStatus) const {
-  assert(IsNewMember);
-  int NewFD;
-  failIfError(sys::fs::openFileForRead(NewFilename, NewFD), NewFilename);
-  assert(NewFD != -1);
-
-  failIfError(sys::fs::status(NewFD, NewStatus), NewFilename);
-
-  // Opening a directory doesn't make sense. Let it fail.
-  // Linux cannot open directories with open(2), although
-  // cygwin and *bsd can.
-  if (NewStatus.type() == sys::fs::file_type::directory_file)
-    failIfError(make_error_code(errc::is_a_directory), NewFilename);
-
-  return NewFD;
-}
-
 template <typename T>
 void addMember(std::vector<NewArchiveIterator> &Members, T I, StringRef Name,
                int Pos = -1) {
   NewArchiveIterator NI(I, Name);
   if (Pos == -1)
     Members.push_back(NI);
   else
     Members[Pos] = NI;
for (auto &Member : Members) {
     StringRef Name = sys::path::filename(Member);
     addMember(Ret, Member, Name, Pos);
     ++Pos;
   }
 
   return Ret;
 }
 
-template <typename T>
-static void printWithSpacePadding(raw_fd_ostream &OS, T Data, unsigned Size,
-          bool MayTruncate = false) {
-  uint64_t OldPos = OS.tell();
-  OS << Data;
-  unsigned SizeSoFar = OS.tell() - OldPos;
-  if (Size > SizeSoFar) {
-    unsigned Remaining = Size - SizeSoFar;
-    for (unsigned I = 0; I < Remaining; ++I)
-      OS << ' ';
-  } else if (Size < SizeSoFar) {
-    assert(MayTruncate && "Data doesn't fit in Size");
-    // Some of the data this is used for (like UID) can be larger than the
-    // space available in the archive format. Truncate in that case.
-    OS.seek(OldPos + Size);
-  }
-}
-
-static void print32BE(raw_fd_ostream &Out, unsigned Val) {
-  for (int I = 3; I >= 0; --I) {
-    char V = (Val >> (8 * I)) & 0xff;
-    Out << V;
-  }
-}
-
-static void printRestOfMemberHeader(raw_fd_ostream &Out,
-                                    const sys::TimeValue &ModTime, unsigned UID,
-                                    unsigned GID, unsigned Perms,
-                                    unsigned Size) {
-  printWithSpacePadding(Out, ModTime.toEpochTime(), 12);
-  printWithSpacePadding(Out, UID, 6, true);
-  printWithSpacePadding(Out, GID, 6, true);
-  printWithSpacePadding(Out, format("%o", Perms), 8);
-  printWithSpacePadding(Out, Size, 10);
-  Out << "`\n";
-}
-
-static void printMemberHeader(raw_fd_ostream &Out, StringRef Name,
-                              const sys::TimeValue &ModTime, unsigned UID,
-                              unsigned GID, unsigned Perms, unsigned Size) {
-  printWithSpacePadding(Out, Twine(Name) + "/", 16);
-  printRestOfMemberHeader(Out, ModTime, UID, GID, Perms, Size);
-}
-
-static void printMemberHeader(raw_fd_ostream &Out, unsigned NameOffset,
-                              const sys::TimeValue &ModTime, unsigned UID,
-                              unsigned GID, unsigned Perms, unsigned Size) {
-  Out << '/';
-  printWithSpacePadding(Out, NameOffset, 15);
-  printRestOfMemberHeader(Out, ModTime, UID, GID, Perms, Size);
-}
-
-static void writeStringTable(raw_fd_ostream &Out,
-                             ArrayRef<NewArchiveIterator> Members,
-                             std::vector<unsigned> &StringMapIndexes) {
-  unsigned StartOffset = 0;
-  for (ArrayRef<NewArchiveIterator>::iterator I = Members.begin(),
-                                              E = Members.end();
-       I != E; ++I) {
-    StringRef Name = I->getName();
-    if (Name.size() < 16)
-      continue;
-    if (StartOffset == 0) {
-      printWithSpacePadding(Out, "//", 58);
-      Out << "`\n";
-      StartOffset = Out.tell();
-    }
-    StringMapIndexes.push_back(Out.tell() - StartOffset);
-    Out << Name << "/\n";
-  }
-  if (StartOffset == 0)
-    return;
-  if (Out.tell() % 2)
-    Out << '\n';
-  int Pos = Out.tell();
-  Out.seek(StartOffset - 12);
-  printWithSpacePadding(Out, Pos - StartOffset, 10);
-  Out.seek(Pos);
-}
-
-// Returns the offset of the first reference to a member offset.
-static unsigned writeSymbolTable(raw_fd_ostream &Out,
-                                 ArrayRef<NewArchiveIterator> Members,
-                                 ArrayRef<MemoryBufferRef> Buffers,
-                                 std::vector<unsigned> &MemberOffsetRefs) {
-  unsigned StartOffset = 0;
-  unsigned MemberNum = 0;
-  std::string NameBuf;
-  raw_string_ostream NameOS(NameBuf);
-  unsigned NumSyms = 0;
-  LLVMContext &Context = getGlobalContext();
-  for (ArrayRef<NewArchiveIterator>::iterator I = Members.begin(),
-                                              E = Members.end();
-       I != E; ++I, ++MemberNum) {
-    MemoryBufferRef MemberBuffer = Buffers[MemberNum];
-    ErrorOr<std::unique_ptr<object::SymbolicFile>> ObjOrErr =
-        object::SymbolicFile::createSymbolicFile(
-            MemberBuffer, sys::fs::file_magic::unknown, &Context);
-    if (!ObjOrErr)
-      continue;  // FIXME: check only for "not an object file" errors.
-    object::SymbolicFile &Obj = *ObjOrErr.get();
-
-    if (!StartOffset) {
-      printMemberHeader(Out, "", sys::TimeValue::now(), 0, 0, 0, 0);
-      StartOffset = Out.tell();
-      print32BE(Out, 0);
-    }
-
-    for (const object::BasicSymbolRef &S : Obj.symbols()) {
-      uint32_t Symflags = S.getFlags();
-      if (Symflags & object::SymbolRef::SF_FormatSpecific)
-        continue;
-      if (!(Symflags & object::SymbolRef::SF_Global))
-        continue;
-      if (Symflags & object::SymbolRef::SF_Undefined)
-        continue;
-      failIfError(S.printName(NameOS));
-      NameOS << '\0';
-      ++NumSyms;
-      MemberOffsetRefs.push_back(MemberNum);
-      print32BE(Out, 0);
-    }
-  }
-  Out << NameOS.str();
-
-  if (StartOffset == 0)
-    return 0;
-
-  if (Out.tell() % 2)
-    Out << '\0';
-
-  unsigned Pos = Out.tell();
-  Out.seek(StartOffset - 12);
-  printWithSpacePadding(Out, Pos - StartOffset, 10);
-  Out.seek(StartOffset);
-  print32BE(Out, NumSyms);
-  Out.seek(Pos);
-  return StartOffset + 4;
-}
-
-static void
-performWriteOperation(ArchiveOperation Operation, object::Archive *OldArchive,
-                      std::vector<NewArchiveIterator> &NewMembers) {
-  SmallString<128> TmpArchive;
-  failIfError(sys::fs::createUniqueFile(ArchiveName + ".temp-archive-%%%%%%%.a",
-                                        TmpArchiveFD, TmpArchive));
-
-  TemporaryOutput = TmpArchive.c_str();
-  tool_output_file Output(TemporaryOutput, TmpArchiveFD);
-  raw_fd_ostream &Out = Output.os();
-  Out << "!<arch>\n";
-
-  std::vector<unsigned> MemberOffsetRefs;
-
-  std::vector<std::unique_ptr<MemoryBuffer>> Buffers;
-  std::vector<MemoryBufferRef> Members;
-  std::vector<sys::fs::file_status> NewMemberStatus;
-
-  for (unsigned I = 0, N = NewMembers.size(); I < N; ++I) {
-    NewArchiveIterator &Member = NewMembers[I];
-    MemoryBufferRef MemberRef;
-
-    if (Member.isNewMember()) {
-      StringRef Filename = Member.getNew();
-      NewMemberStatus.resize(NewMemberStatus.size() + 1);
-      sys::fs::file_status &Status = NewMemberStatus.back();
-      int FD = Member.getFD(Status);
-      ErrorOr<std::unique_ptr<MemoryBuffer>> MemberBufferOrErr =
-          MemoryBuffer::getOpenFile(FD, Filename, Status.getSize(), false);
-      failIfError(MemberBufferOrErr.getError(), Filename);
-      if (close(FD) != 0)
-        fail("Could not close file");
-      Buffers.push_back(std::move(MemberBufferOrErr.get()));
-      MemberRef = Buffers.back()->getMemBufferRef();
-    } else {
-      object::Archive::child_iterator OldMember = Member.getOld();
-      ErrorOr<MemoryBufferRef> MemberBufferOrErr =
-          OldMember->getMemoryBufferRef();
-      failIfError(MemberBufferOrErr.getError());
-      MemberRef = MemberBufferOrErr.get();
-    }
-    Members.push_back(MemberRef);
-  }
-
-  unsigned MemberReferenceOffset = 0;
-  if (Symtab) {
-    MemberReferenceOffset =
-        writeSymbolTable(Out, NewMembers, Members, MemberOffsetRefs);
-  }
-
-  std::vector<unsigned> StringMapIndexes;
-  writeStringTable(Out, NewMembers, StringMapIndexes);
-
-  unsigned MemberNum = 0;
-  unsigned LongNameMemberNum = 0;
-  unsigned NewMemberNum = 0;
-  std::vector<unsigned> MemberOffset;
-  for (std::vector<NewArchiveIterator>::iterator I = NewMembers.begin(),
-                                                 E = NewMembers.end();
-       I != E; ++I, ++MemberNum) {
-
-    unsigned Pos = Out.tell();
-    MemberOffset.push_back(Pos);
-
-    MemoryBufferRef File = Members[MemberNum];
-    if (I->isNewMember()) {
-      StringRef FileName = I->getNew();
-      const sys::fs::file_status &Status = NewMemberStatus[NewMemberNum];
-      NewMemberNum++;
-
-      StringRef Name = sys::path::filename(FileName);
-      if (Name.size() < 16)
-        printMemberHeader(Out, Name, Status.getLastModificationTime(),
-                          Status.getUser(), Status.getGroup(),
-                          Status.permissions(), Status.getSize());
-      else
-        printMemberHeader(Out, StringMapIndexes[LongNameMemberNum++],
-                          Status.getLastModificationTime(), Status.getUser(),
-                          Status.getGroup(), Status.permissions(),
-                          Status.getSize());
-    } else {
-      object::Archive::child_iterator OldMember = I->getOld();
-      StringRef Name = I->getName();
-
-      if (Name.size() < 16)
-        printMemberHeader(Out, Name, OldMember->getLastModified(),
-                          OldMember->getUID(), OldMember->getGID(),
-                          OldMember->getAccessMode(), OldMember->getSize());
-      else
-        printMemberHeader(Out, StringMapIndexes[LongNameMemberNum++],
-                          OldMember->getLastModified(), OldMember->getUID(),
-                          OldMember->getGID(), OldMember->getAccessMode(),
-                          OldMember->getSize());
-    }
-
-    Out << File.getBuffer();
-
-    if (Out.tell() % 2)
-      Out << '\n';
-  }
-
-  if (MemberReferenceOffset) {
-    Out.seek(MemberReferenceOffset);
-    for (unsigned MemberNum : MemberOffsetRefs)
-      print32BE(Out, MemberOffset[MemberNum]);
-  }
-
-  Output.keep();
-  Out.close();
-  sys::fs::rename(TemporaryOutput, ArchiveName);
-  TemporaryOutput = nullptr;
-}
-
 static void
 performWriteOperation(ArchiveOperation Operation, object::Archive *OldArchive,
                       std::vector<NewArchiveIterator> *NewMembersP) {
   if (NewMembersP) {
-    performWriteOperation(Operation, OldArchive, *NewMembersP);
+    std::pair<StringRef, std::error_code> Result =
+        WriteArchive(ArchiveName, *NewMembersP, Symtab);
+    failIfError(Result.second, Result.first);
     return;
   }
   std::vector<NewArchiveIterator> NewMembers =
       computeNewArchiveMembers(Operation, OldArchive);
-  performWriteOperation(Operation, OldArchive, NewMembers);
+  auto Result = WriteArchive(ArchiveName, NewMembers, Symtab);
+  failIfError(Result.second, Result.first);
 }
 
 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