Implement DR1330 in C++11 mode, to support libstdc++4.7 which uses it.

We have a new flavor of exception specification, EST_Uninstantiated. A function
type with this exception specification carries a pointer to a FunctionDecl, and
the exception specification for that FunctionDecl is instantiated (if needed)
and used in the place of the function type's exception specification.

When a function template declaration with a non-trivial exception specification
is instantiated, the specialization's exception specification is set to this
new 'uninstantiated' kind rather than being instantiated immediately.

Expr::CanThrow has migrated onto Sema, so it can instantiate exception specs
on-demand. Also, any odr-use of a function triggers the instantiation of its
exception specification (the exception specification could be needed by IRGen).
In passing, fix two places where a DeclRefExpr was created but the corresponding
function was not actually marked odr-used. We used to get away with this, but
don't any more.

Also fix a bug where instantiating an exception specification which refers to
function parameters resulted in a crash. We still have the same bug in default
arguments, which I'll be looking into next.

This, plus a tiny patch to fix libstdc++'s common_type, is enough for clang to
parse (and, in very limited testing, support) all of libstdc++4.7's standard
headers.

llvm-svn: 154886

1 files changed, 3 insertions, 4 deletions

diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 5511fc00f55..a66378e5178 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -4181,10 +4181,7 @@ TreeTransform<Derived>::TransformFunctionProtoType(TypeLocBuilder &TLB,
                                                    unsigned ThisTypeQuals) {
   // Transform the parameters and return type.
   //
-  // We instantiate in source order, with the return type first followed by
-  // the parameters, because users tend to expect this (even if they shouldn't
-  // rely on it!).
-  //
+  // We are required to instantiate the params and return type in source order.
   // When the function has a trailing return type, we instantiate the
   // parameters before the return type,  since the return type can then refer
   // to the parameters themselves (via decltype, sizeof, etc.).
@@ -4230,6 +4227,8 @@ TreeTransform<Derived>::TransformFunctionProtoType(TypeLocBuilder &TLB,
       return QualType();
   }
 
+  // FIXME: Need to transform the exception-specification too.
+
   QualType Result = TL.getType();
   if (getDerived().AlwaysRebuild() ||
       ResultType != T->getResultType() ||