llvm-ar: Don't add an unnecessary alignment in gnu mode.

This is mostly for getting stricter testing in preparation for future
changes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@314000 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Object/ArchiveWriter.cpp

@@ -351,7 +351,8 @@ writeSymbolTable(raw_fd_ostream &Out, object::Archive::Kind Kind,
 
   // ld64 requires the next member header to start at an offset that is
   // 4 bytes aligned.
-  unsigned Pad = OffsetToAlignment(Out.tell(), 4);
+  unsigned Alignment = isBSDLike(Kind) ? 4 : 2;
+  unsigned Pad = OffsetToAlignment(Out.tell(), Alignment);
   while (Pad--)
     Out.write(uint8_t(0));
 

test/Object/archive-symtab.test

@@ -122,3 +122,11 @@ RUN: llvm-ar --format=bsd rcsU %t.a %p/Inputs/trivial-object-test.macho-x86-64
 RUN: FileCheck --check-prefix=MACHO-SYMTAB-ALIGN %s < %t.a
 MACHO-SYMTAB-ALIGN: !<arch>
 MACHO-SYMTAB-ALIGN-NEXT: #1/12           {{..........}}  0     0     0       36        `
+
+With a gnu symbol table we only align to two
+8 + 60 + 14 = 82
+RUN: rm -f %t.a
+RUN: llvm-ar --format=gnu rcsD %t.a %p/Inputs/trivial-object-test.macho-x86-64
+RUN: FileCheck --check-prefix=GNU-SYMTAB-ALIGN %s < %t.a
+GNU-SYMTAB-ALIGN: !<arch>
+GNU-SYMTAB-ALIGN-NEXT: /               0           0     0     0       14        `