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, 32 insertions, 0 deletions

diff --git a/lib/Sema/SemaTemplateInstantiate.cpp b/lib/Sema/SemaTemplateInstantiate.cpp
index 60de75b917..128dc2f7ff 100644
--- a/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/lib/Sema/SemaTemplateInstantiate.cpp
@@ -153,6 +153,7 @@ Sema::getTemplateInstantiationArgs(NamedDecl *D,
 bool Sema::ActiveTemplateInstantiation::isInstantiationRecord() const {
   switch (Kind) {
   case TemplateInstantiation:
+  case ExceptionSpecInstantiation:
   case DefaultTemplateArgumentInstantiation:
   case DefaultFunctionArgumentInstantiation:
     return true;
@@ -190,6 +191,29 @@ InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
   }
 }
 
+Sema::InstantiatingTemplate::
+InstantiatingTemplate(Sema &SemaRef, SourceLocation PointOfInstantiation,
+                      FunctionDecl *Entity, ExceptionSpecification,
+                      SourceRange InstantiationRange)
+  : SemaRef(SemaRef),
+    SavedInNonInstantiationSFINAEContext(
+                                        SemaRef.InNonInstantiationSFINAEContext)
+{
+  Invalid = CheckInstantiationDepth(PointOfInstantiation,
+                                    InstantiationRange);
+  if (!Invalid) {
+    ActiveTemplateInstantiation Inst;
+    Inst.Kind = ActiveTemplateInstantiation::ExceptionSpecInstantiation;
+    Inst.PointOfInstantiation = PointOfInstantiation;
+    Inst.Entity = reinterpret_cast<uintptr_t>(Entity);
+    Inst.TemplateArgs = 0;
+    Inst.NumTemplateArgs = 0;
+    Inst.InstantiationRange = InstantiationRange;
+    SemaRef.InNonInstantiationSFINAEContext = false;
+    SemaRef.ActiveTemplateInstantiations.push_back(Inst);
+  }
+}
+
 Sema::InstantiatingTemplate::InstantiatingTemplate(Sema &SemaRef,
                                          SourceLocation PointOfInstantiation,
                                          TemplateDecl *Template,
@@ -592,6 +616,13 @@ void Sema::PrintInstantiationStack() {
         << Active->InstantiationRange;
       break;
     }
+
+    case ActiveTemplateInstantiation::ExceptionSpecInstantiation:
+      Diags.Report(Active->PointOfInstantiation,
+                   diag::note_template_exception_spec_instantiation_here)
+        << cast<FunctionDecl>((Decl *)Active->Entity)
+        << Active->InstantiationRange;
+      break;
     }
   }
 }
@@ -609,6 +640,7 @@ llvm::Optional<TemplateDeductionInfo *> Sema::isSFINAEContext() const {
     switch(Active->Kind) {
     case ActiveTemplateInstantiation::DefaultFunctionArgumentInstantiation:
     case ActiveTemplateInstantiation::TemplateInstantiation:
+    case ActiveTemplateInstantiation::ExceptionSpecInstantiation:
       // This is a template instantiation, so there is no SFINAE.
       return llvm::Optional<TemplateDeductionInfo *>();