Don't modify archive members unless really needed.

For whatever reason ld64 requires that member headers (not the member
themselves) should be aligned. The only way to do that is to edit the
previous member so that it ends at an aligned boundary.

Since modifying data put in an archive is an undesirable property,
llvm-ar should only do it when it is absolutely necessary.

llvm-svn: 295765

include/llvm/Object/Archive.h

@@ -212,6 +212,7 @@ public:
     K_GNU,
     K_MIPS64,
     K_BSD,
+    K_DARWIN,
     K_DARWIN64,
     K_COFF
   };

lib/Object/ArchiveWriter.cpp

@@ -122,12 +122,26 @@ static void printWithSpacePadding(raw_fd_ostream &OS, T Data, unsigned Size,
   }
 }
 
+static bool isBSDLike(object::Archive::Kind Kind) {
+  switch (Kind) {
+  case object::Archive::K_GNU:
+    return false;
+  case object::Archive::K_BSD:
+  case object::Archive::K_DARWIN:
+    return true;
+  case object::Archive::K_MIPS64:
+  case object::Archive::K_DARWIN64:
+  case object::Archive::K_COFF:
+    llvm_unreachable("not supported for writting");
+  }
+}
+
 static void print32(raw_ostream &Out, object::Archive::Kind Kind,
                     uint32_t Val) {
-  if (Kind == object::Archive::K_GNU)
+  if (isBSDLike(Kind))
-    support::endian::Writer<support::big>(Out).write(Val);
-  else
     support::endian::Writer<support::little>(Out).write(Val);
+  else
+    support::endian::Writer<support::big>(Out).write(Val);
 }
 
 static void printRestOfMemberHeader(
@@ -178,7 +192,7 @@ printMemberHeader(raw_fd_ostream &Out, object::Archive::Kind Kind, bool Thin,
                   std::vector<unsigned>::iterator &StringMapIndexIter,
                   const sys::TimePoint<std::chrono::seconds> &ModTime,
                   unsigned UID, unsigned GID, unsigned Perms, unsigned Size) {
-  if (Kind == object::Archive::K_BSD)
+  if (isBSDLike(Kind))
     return printBSDMemberHeader(Out, Name, ModTime, UID, GID, Perms, Size);
   if (!useStringTable(Thin, Name))
     return printGNUSmallMemberHeader(Out, Name, ModTime, UID, GID, Perms, Size);
@@ -285,10 +299,10 @@ writeSymbolTable(raw_fd_ostream &Out, object::Archive::Kind Kind,
 
     if (!HeaderStartOffset) {
       HeaderStartOffset = Out.tell();
-      if (Kind == object::Archive::K_GNU)
+      if (isBSDLike(Kind))
-        printGNUSmallMemberHeader(Out, "", now(Deterministic), 0, 0, 0, 0);
-      else
         printBSDMemberHeader(Out, "__.SYMDEF", now(Deterministic), 0, 0, 0, 0);
+      else
+        printGNUSmallMemberHeader(Out, "", now(Deterministic), 0, 0, 0, 0);
       BodyStartOffset = Out.tell();
       print32(Out, Kind, 0); // number of entries or bytes
     }
@@ -307,7 +321,7 @@ writeSymbolTable(raw_fd_ostream &Out, object::Archive::Kind Kind,
         return EC;
       NameOS << '\0';
       MemberOffsetRefs.push_back(MemberNum);
-      if (Kind == object::Archive::K_BSD)
+      if (isBSDLike(Kind))
         print32(Out, Kind, NameOffset);
       print32(Out, Kind, 0); // member offset
     }
@@ -318,12 +332,12 @@ writeSymbolTable(raw_fd_ostream &Out, object::Archive::Kind Kind,
 
   // ld64 prefers the cctools type archive which pads its string table to a
   // boundary of sizeof(int32_t).
-  if (Kind == object::Archive::K_BSD)
+  if (isBSDLike(Kind))
     for (unsigned P = OffsetToAlignment(NameOS.tell(), sizeof(int32_t)); P--;)
       NameOS << '\0';
 
   StringRef StringTable = NameOS.str();
-  if (Kind == object::Archive::K_BSD)
+  if (isBSDLike(Kind))
     print32(Out, Kind, StringTable.size()); // byte count of the string table
   Out << StringTable;
 
@@ -342,10 +356,10 @@ writeSymbolTable(raw_fd_ostream &Out, object::Archive::Kind Kind,
   // Patch up the number of symbols.
   Out.seek(BodyStartOffset);
   unsigned NumSyms = MemberOffsetRefs.size();
-  if (Kind == object::Archive::K_GNU)
+  if (isBSDLike(Kind))
-    print32(Out, Kind, NumSyms);
-  else
     print32(Out, Kind, NumSyms * 8);
+  else
+    print32(Out, Kind, NumSyms);
 
   Out.seek(Pos);
   return BodyStartOffset + 4;
@@ -357,8 +371,7 @@ llvm::writeArchive(StringRef ArcName,
                    bool WriteSymtab, object::Archive::Kind Kind,
                    bool Deterministic, bool Thin,
                    std::unique_ptr<MemoryBuffer> OldArchiveBuf) {
-  assert((!Thin || Kind == object::Archive::K_GNU) &&
+  assert((!Thin || !isBSDLike(Kind)) && "Only the gnu format has a thin mode");
-         "Only the gnu format has a thin mode");
   SmallString<128> TmpArchive;
   int TmpArchiveFD;
   if (auto EC = sys::fs::createUniqueFile(ArcName + ".temp-archive-%%%%%%%.a",
@@ -388,7 +401,7 @@ llvm::writeArchive(StringRef ArcName,
   }
 
   std::vector<unsigned> StringMapIndexes;
-  if (Kind != object::Archive::K_BSD)
+  if (!isBSDLike(Kind))
     writeStringTable(Out, ArcName, NewMembers, StringMapIndexes, Thin);
 
   std::vector<unsigned>::iterator StringMapIndexIter = StringMapIndexes.begin();
@@ -404,7 +417,7 @@ llvm::writeArchive(StringRef ArcName,
     // 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.
-    if (Kind == object::Archive::K_BSD)
+    if (Kind == object::Archive::K_DARWIN)
       Padding = OffsetToAlignment(M.Buf->getBufferSize(), 8);
 
     printMemberHeader(Out, Kind, Thin,
@@ -424,7 +437,7 @@ llvm::writeArchive(StringRef ArcName,
   if (MemberReferenceOffset) {
     Out.seek(MemberReferenceOffset);
     for (unsigned MemberNum : MemberOffsetRefs) {
-      if (Kind == object::Archive::K_BSD)
+      if (isBSDLike(Kind))
         Out.seek(Out.tell() + 4); // skip over the string offset
       print32(Out, Kind, MemberOffset[MemberNum]);
     }

test/Object/archive-extract.test

@@ -43,10 +43,10 @@
 CHECK-GNU: 1465 2004-11-19 03:01:31.000000000 very_long_bytecode_file_name.bc
 
 ; RUN: rm -f %t.a
-; RUN: llvm-ar -format bsd rcU %t.a very_long_bytecode_file_name.bc
+; RUN: llvm-ar -format darwin rcU %t.a very_long_bytecode_file_name.bc
-; RUN: env TZ=GMT llvm-ar tv %t.a | FileCheck %s -check-prefix CHECK-BSD
+; RUN: env TZ=GMT llvm-ar tv %t.a | FileCheck %s -check-prefix CHECK-DARWIN
 
-CHECK-BSD: 1472 2004-11-19 03:01:31.000000000 very_long_bytecode_file_name.bc
+CHECK-DARWIN: 1472 2004-11-19 03:01:31.000000000 very_long_bytecode_file_name.bc
 
 RUN: not llvm-ar x %p/Inputs/GNU.a foo.o 2>&1 | FileCheck --check-prefix=NOTFOUND %s
 NOTFOUND: foo.o was not found

test/Object/archive-format.test

@@ -32,12 +32,23 @@ RUN: llvm-ar --format=bsd rc %t.a 0123456789abcde 0123456789abcdef
 RUN: cat %t.a | FileCheck -strict-whitespace --check-prefix=BSD %s
 
 BSD:      !<arch>
-BSD-NEXT: #1/20           0           0     0     644     28        `
+BSD-NEXT: #1/20           0           0     0     644     24        `
+BSD-NEXT: 0123456789abcde{{.....}}bar.
+BSD-SAME: #1/16           0           0     0     644     20        `
+BSD-NEXT: 0123456789abcdefzed.
+
+RUN: rm -f %t.a
+RUN: llvm-ar --format=darwin rc %t.a 0123456789abcde 0123456789abcdef
+RUN: cat %t.a | FileCheck -strict-whitespace --check-prefix=DARWIN %s
+
+DARWIN:      !<arch>
+DARWIN-NEXT: #1/20           0           0     0     644     28        `
 Each [[:space:]] matches a newline.  We explicitly match 3 newlines, as the
 fourth newline is implicitly consumed by FileCheck and cannot be matched.
-BSD-NEXT: 0123456789abcde{{.....}}bar.{{[[:space:]][[:space:]][[:space:]]}}
+DARWIN-NEXT: 0123456789abcde{{.....}}bar.{{[[:space:]][[:space:]][[:space:]]}}
-BSD-NEXT: #1/20           0           0     0     644     28        `
+DARWIN-NEXT: #1/20           0           0     0     644     28        `
-BSD-NEXT: 0123456789abcdef{{....}}zed.
+DARWIN-NEXT: 0123456789abcdef{{....}}zed.
+
 
 RUN: rm -f test.a
 RUN: llvm-ar --format=gnu rcT test.a 0123456789abcde 0123456789abcdef

test/Object/archive-pad.test

@@ -0,0 +1,19 @@
+Test that only the darwin format needs to modify archive members to
+avoid a ld64 bug.
+
+RUN: echo foo > %t.o
+
+RUN: rm -f %t.a
+RUN: llvm-ar -format=bsd rc %t.a %t.o
+RUN: llvm-ar p %t.a > %bsd.o
+RUN: cmp %bsd.o %t.o
+
+RUN: rm -f %t.a
+RUN: llvm-ar -format=gnu rc %t.a %t.o
+RUN: llvm-ar p %t.a > %gnu.o
+RUN: cmp %gnu.o %t.o
+
+RUN: rm -f %t.a
+RUN: llvm-ar -format=darwin rc %t.a %t.o
+RUN: llvm-ar p %t.a > %darwin.o
+RUN: not cmp %darwin.o %t.o

tools/llvm-ar/llvm-ar.cpp

@@ -87,13 +87,14 @@ static cl::opt<bool> MRI("M", cl::desc(""));
 static cl::opt<std::string> Plugin("plugin", cl::desc("plugin (ignored for compatibility"));
 
 namespace {
-enum Format { Default, GNU, BSD };
+enum Format { Default, GNU, BSD, DARWIN };
 }
 
 static cl::opt<Format>
     FormatOpt("format", cl::desc("Archive format to create"),
               cl::values(clEnumValN(Default, "default", "default"),
                          clEnumValN(GNU, "gnu", "gnu"),
+                         clEnumValN(DARWIN, "darwin", "darwin"),
                          clEnumValN(BSD, "bsd", "bsd")));
 
 static std::string Options;
@@ -623,8 +624,9 @@ computeNewArchiveMembers(ArchiveOperation Operation,
 }
 
 static object::Archive::Kind getDefaultForHost() {
-  return Triple(sys::getProcessTriple()).isOSDarwin() ? object::Archive::K_BSD
+  return Triple(sys::getProcessTriple()).isOSDarwin()
-                                                      : object::Archive::K_GNU;
+             ? object::Archive::K_DARWIN
+             : object::Archive::K_GNU;
 }
 
 static object::Archive::Kind getKindFromMember(const NewArchiveMember &Member) {
@@ -633,7 +635,7 @@ static object::Archive::Kind getKindFromMember(const NewArchiveMember &Member) {
 
   if (OptionalObject)
     return isa<object::MachOObjectFile>(**OptionalObject)
-               ? object::Archive::K_BSD
+               ? object::Archive::K_DARWIN
                : object::Archive::K_GNU;
 
   // squelch the error in case we had a non-object file
@@ -672,6 +674,11 @@ performWriteOperation(ArchiveOperation Operation,
       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;
   }
 
   std::pair<StringRef, std::error_code> Result =