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, 10 insertions, 0 deletions

diff --git a/clang/test/SemaTemplate/instantiate-declref.cpp b/clang/test/SemaTemplate/instantiate-declref.cpp
index ced56dfc6ab..7d4a2ff6a3f 100644
--- a/clang/test/SemaTemplate/instantiate-declref.cpp
+++ b/clang/test/SemaTemplate/instantiate-declref.cpp
@@ -105,3 +105,13 @@ namespace test1 {
   }
   template void f(int const &); // expected-note {{requested here}}
 }
+
+namespace test2 {
+  template<typename T> void f() {
+    T::error; // expected-error {{no member}}
+  }
+  void g() {
+    // This counts as an odr-use, so should trigger the instantiation of f<int>.
+    (void)&f<int>; // expected-note {{here}}
+  }
+}