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

1 files changed, 11 insertions, 1 deletions

diff --git a/llvm/lib/Object/ArchiveWriter.cpp b/llvm/lib/Object/ArchiveWriter.cpp
index 45047240c3b..fc827d321d9 100644
--- a/llvm/lib/Object/ArchiveWriter.cpp
+++ b/llvm/lib/Object/ArchiveWriter.cpp
@@ -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';
   }