Improve our handling of reference binding for subobjects of

temporaries. There are actually several interrelated fixes here:

  - When converting an object to a base class, it's only an lvalue
  cast when the original object was an lvalue and we aren't casting
  pointer-to-derived to pointer-to-base. Previously, we were
  misclassifying derived-to-base casts of class rvalues as lvalues,
  causing various oddities (including problems with reference binding
  not extending the lifetimes of some temporaries).

  - Teach the code for emitting a reference binding how to look
  through no-op casts and parentheses directly, since
  Expr::IgnoreParenNoOpCasts is just plain wrong for this. Also, make
  sure that we properly look through multiple levels of indirection
  from the temporary object, but destroy the actual temporary object;
  this fixes the reference-binding issue mentioned above.

  - Teach Objective-C message sends to bind the result as a temporary
    when needed. This is actually John's change, but it triggered the
    reference-binding problem above, so it's included here. Now John
    can actually test his return-slot improvements.

llvm-svn: 104434

1 files changed, 8 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGExprAgg.cpp b/clang/lib/CodeGen/CGExprAgg.cpp
index aa32bb8..7b0c316 100644
--- a/clang/lib/CodeGen/CGExprAgg.cpp
+++ b/clang/lib/CodeGen/CGExprAgg.cpp
@@ -216,6 +216,14 @@ void AggExprEmitter::VisitCastExpr(CastExpr *E) {
     break;
   }
 
+  case CastExpr::CK_DerivedToBase:
+  case CastExpr::CK_BaseToDerived:
+  case CastExpr::CK_UncheckedDerivedToBase: {
+    assert(0 && "cannot perform hierarchy conversion in EmitAggExpr: "
+                "should have been unpacked before we got here");
+    break;
+  }
+
   // FIXME: Remove the CK_Unknown check here.
   case CastExpr::CK_Unknown:
   case CastExpr::CK_NoOp: