modern objective-c translator. ifdef'out 
__weak and __block when rewriting.
// rdar://11236342



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@154592 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Rewrite/RewriteModernObjC.cpp b/lib/Rewrite/RewriteModernObjC.cpp
index fd621a2..ba62ad3 100644
--- a/lib/Rewrite/RewriteModernObjC.cpp
+++ b/lib/Rewrite/RewriteModernObjC.cpp
@@ -5726,7 +5726,12 @@
     Preamble += "#ifndef KEEP_ATTRIBUTES\n";  // We use this for clang tests.
     Preamble += "#define __attribute__(X)\n";
     Preamble += "#endif\n";
+    Preamble += "#ifndef __weak\n";
     Preamble += "#define __weak\n";
+    Preamble += "#endif\n";
+    Preamble += "#ifndef __block\n";
+    Preamble += "#define __block\n";
+    Preamble += "#endif\n";
   }
   else {
     Preamble += "#define __block\n";