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, 9 insertions, 0 deletions

diff --git a/lib/AST/Type.cpp b/lib/AST/Type.cpp
index c82aeaadd4..10c1adc875 100644
--- a/lib/AST/Type.cpp
+++ b/lib/AST/Type.cpp
@@ -1546,6 +1546,13 @@ FunctionProtoType::FunctionProtoType(QualType result, const QualType *args,
       else if (epi.NoexceptExpr->isInstantiationDependent())
         setInstantiationDependent();
     }
+  } else if (getExceptionSpecType() == EST_Uninstantiated) {
+    // Store the function decl from which we will resolve our
+    // exception specification.
+    FunctionDecl **slot = reinterpret_cast<FunctionDecl**>(argSlot + numArgs);
+    *slot = epi.ExceptionSpecDecl;
+    // This exception specification doesn't make the type dependent, because
+    // it's not instantiated as part of instantiating the type.
   }
 
   if (epi.ConsumedArguments) {
@@ -1629,6 +1636,8 @@ void FunctionProtoType::Profile(llvm::FoldingSetNodeID &ID, QualType Result,
       ID.AddPointer(epi.Exceptions[i].getAsOpaquePtr());
   } else if (epi.ExceptionSpecType == EST_ComputedNoexcept && epi.NoexceptExpr){
     epi.NoexceptExpr->Profile(ID, Context, false);
+  } else if (epi.ExceptionSpecType == EST_Uninstantiated) {
+    ID.AddPointer(epi.ExceptionSpecDecl->getCanonicalDecl());
   }
   if (epi.ConsumedArguments) {
     for (unsigned i = 0; i != NumArgs; ++i)