From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Thu, 9 Jul 2015 19:48:06 +0000 (+0000)
Subject: llvm-ar: Pad the symbol table to 4 bytes.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=7255090cd339bc93902b5f28fa73eb2d5556de64;p=oota-llvm.git

llvm-ar: Pad the symbol table to 4 bytes.

It looks like ld64 requires it. With this we seem to be able to bootstrap using
llvm-ar+/usr/bin/true instead of ar+ranlib (currently on stage2).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241842 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Object/ArchiveWriter.cpp b/lib/Object/ArchiveWriter.cpp
index c485b34a081..1148c847549 100644
--- a/lib/Object/ArchiveWriter.cpp
+++ b/lib/Object/ArchiveWriter.cpp
@@ -237,8 +237,11 @@ writeSymbolTable(raw_fd_ostream &Out, object::Archive::Kind Kind,
     print32(Out, Kind, StringTable.size()); // byte count of the string table
   Out << StringTable;
 
-  if (Out.tell() % 2)
-    Out << '\0';
+  // ld64 requires the next member header to start at an offset that is
+  // 4 bytes aligned.
+  unsigned Pad = OffsetToAlignment(Out.tell(), 4);
+  while (Pad--)
+    Out.write(uint8_t(0));
 
   // Patch up the size of the symbol table now that we know how big it is.
   unsigned Pos = Out.tell();
diff --git a/test/Object/archive-symtab.test b/test/Object/archive-symtab.test
index 5de2f2b5e1d..5f648ebc109 100644
--- a/test/Object/archive-symtab.test
+++ b/test/Object/archive-symtab.test
@@ -87,3 +87,11 @@ MACHO: trivial-object-test2.macho-x86-64
 MACHO-NEXT: 0000000000000000 t _bar
 MACHO-NEXT: 0000000000000001 T _foo
 MACHO-NEXT: 0000000000000002 T _main
+
+Test that we pad the symbol table so that it ends in a multiple of 4 bytes:
+8 + 60 + 36 == 104
+RUN: rm -f %t.a
+RUN: llvm-ar --format=bsd rcs %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        `