Objective-C++ ARC: do not mangle __unsafe_unretained lifetime

qualifiers, so that an __unsafe_unretained-qualified type T in ARC code
will have the same mangling as T in non-ARC code, improving ABI
interoperability. This works now because we infer or require a
lifetime qualifier everywhere one can appear in an external
interface. Another part of <rdar://problem/9595486>.

llvm-svn: 133306

1 files changed, 7 insertions, 2 deletions

diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index a77fe5f48ab..5f0b2a6eff8 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -1472,7 +1472,6 @@ void CXXNameMangler::mangleQualifiers(Qualifiers Quals) {
   //   <type> ::= U "__strong"
   //   <type> ::= U "__weak"
   //   <type> ::= U "__autoreleasing"
-  //   <type> ::= U "__unsafe_unretained"
   case Qualifiers::OCL_None:
     break;
     
@@ -1489,7 +1488,13 @@ void CXXNameMangler::mangleQualifiers(Qualifiers Quals) {
     break;
     
   case Qualifiers::OCL_ExplicitNone:
-    LifetimeName = "__unsafe_unretained";
+    // The __unsafe_unretained qualifier is *not* mangled, so that
+    // __unsafe_unretained types in ARC produce the same manglings as the
+    // equivalent (but, naturally, unqualified) types in non-ARC, providing
+    // better ABI compatibility.
+    //
+    // It's safe to do this because unqualified 'id' won't show up
+    // in any type signatures that need to be mangled.
     break;
   }
   if (!LifetimeName.empty())