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.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@154886 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 16 insertions, 2 deletions

diff --git a/include/clang/Basic/ExceptionSpecificationType.h b/include/clang/Basic/ExceptionSpecificationType.h
index 98cfd297ad..e911bde191 100644
--- a/include/clang/Basic/ExceptionSpecificationType.h
+++ b/include/clang/Basic/ExceptionSpecificationType.h
@@ -16,7 +16,7 @@
 
 namespace clang {
 
-/// \brief The various types of exception specifications that exist in C++0x.
+/// \brief The various types of exception specifications that exist in C++11.
 enum ExceptionSpecificationType {
   EST_None,             ///< no exception specification
   EST_DynamicNone,      ///< throw()
@@ -24,7 +24,8 @@ enum ExceptionSpecificationType {
   EST_MSAny,            ///< Microsoft throw(...) extension
   EST_BasicNoexcept,    ///< noexcept
   EST_ComputedNoexcept, ///< noexcept(expression)
-  EST_Delayed           ///< not known yet
+  EST_Delayed,          ///< not known yet
+  EST_Uninstantiated    ///< not instantiated yet
 };
 
 inline bool isDynamicExceptionSpec(ExceptionSpecificationType ESpecType) {
@@ -35,6 +36,19 @@ inline bool isNoexceptExceptionSpec(ExceptionSpecificationType ESpecType) {
   return ESpecType == EST_BasicNoexcept || ESpecType == EST_ComputedNoexcept;
 }
 
+/// \brief Possible results from evaluation of a noexcept expression.
+enum CanThrowResult {
+  CT_Cannot,
+  CT_Dependent,
+  CT_Can
+};
+
+inline CanThrowResult mergeCanThrow(CanThrowResult CT1, CanThrowResult CT2) {
+  // CanThrowResult constants are ordered so that the maximum is the correct
+  // merge result.
+  return CT1 > CT2 ? CT1 : CT2;
+}
+
 } // end namespace clang
 
 #endif // LLVM_CLANG_BASIC_EXCEPTIONSPECIFICATIONTYPE_H