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Object: pad out BSD archive members to 8-bytes 

ld64 requires its archive members to be 8-byte aligned for 64-bit
content and 4-byte aligned for 32-bit content.  Opt for the larger
alignment requirement.  This ensures that ld64 can consume archives
generated by llvm-ar.

Thanks to Kevin Enderby for the hint about the ld64/cctools behaviours!

Resolves PR28361!

llvm-svn: 294615
This commit is contained in:
Saleem Abdulrasool 2017-02-09 19:29:35 +00:00
parent 2f1f1616ae
commit 111cd669e9
2 changed files with 17 additions and 5 deletions
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12
llvm/lib/Object/ArchiveWriter.cpp
View File

@ -395,18 +395,28 @@ llvm::writeArchive(StringRef ArcName,
std::vector<unsigned> MemberOffset;
for (const NewArchiveMember &M : NewMembers) {
MemoryBufferRef File = M.Buf->getMemBufferRef();
unsigned Padding = 0;
unsigned Pos = Out.tell();
MemberOffset.push_back(Pos);
// 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.
if (Kind == object::Archive::K_BSD)
Padding = OffsetToAlignment(M.Buf->getBufferSize(), 8);
printMemberHeader(Out, Kind, Thin,
sys::path::filename(M.Buf->getBufferIdentifier()),
StringMapIndexIter, M.ModTime, M.UID, M.GID, M.Perms,
M.Buf->getBufferSize());
M.Buf->getBufferSize() + Padding);
if (!Thin)
Out << File.getBuffer();
while (Padding--)
Out << '\n';
if (Out.tell() % 2)
Out << '\n';
}

10
llvm/test/Object/archive-format.test
View File

@ -32,10 +32,12 @@ 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 24 `
BSD-NEXT: 0123456789abcde{{.....}}bar.
BSD-SAME: #1/16 0 0 0 644 20 `
BSD-NEXT: 0123456789abcdefzed.
BSD-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:]]}}
BSD-NEXT: #1/20 0 0 0 644 28 `
BSD-NEXT: 0123456789abcdef{{....}}zed.
RUN: rm -f test.a
RUN: llvm-ar --format=gnu rcT test.a 0123456789abcde 0123456789abcdef