Permit Exception Spec mismatch with NoThrow on inherited Virtual

As reported here: https://bugs.llvm.org/show_bug.cgi?id=42100

This fairly common pattern ends up being an error in MinGW, so relax it
in all cases to a warning.

llvm-svn: 362434

1 files changed, 15 insertions, 3 deletions

diff --git a/clang/lib/Sema/SemaExceptionSpec.cpp b/clang/lib/Sema/SemaExceptionSpec.cpp
index 8f3ebc29b52..5274532b0ff 100644
--- a/clang/lib/Sema/SemaExceptionSpec.cpp
+++ b/clang/lib/Sema/SemaExceptionSpec.cpp
@@ -744,6 +744,7 @@ bool Sema::handlerCanCatch(QualType HandlerType, QualType ExceptionType) {
 bool Sema::CheckExceptionSpecSubset(const PartialDiagnostic &DiagID,
                                     const PartialDiagnostic &NestedDiagID,
                                     const PartialDiagnostic &NoteID,
+                                    const PartialDiagnostic &NoThrowDiagID,
                                     const FunctionProtoType *Superset,
                                     SourceLocation SuperLoc,
                                     const FunctionProtoType *Subset,
@@ -790,6 +791,16 @@ bool Sema::CheckExceptionSpecSubset(const PartialDiagnostic &DiagID,
     return CheckParamExceptionSpec(NestedDiagID, NoteID, Superset, SuperLoc,
                                    Subset, SubLoc);
 
+  // Allow __declspec(nothrow) to be missing on redeclaration as an extension in
+  // some cases.
+  if (NoThrowDiagID.getDiagID() != 0 && SubCanThrow == CT_Can &&
+      SuperCanThrow == CT_Cannot && SuperEST == EST_NoThrow) {
+    Diag(SubLoc, NoThrowDiagID);
+    if (NoteID.getDiagID() != 0)
+      Diag(SuperLoc, NoteID);
+    return true;
+  }
+
   // If the subset contains everything or the superset contains nothing, we've
   // failed.
   if ((SubCanThrow == CT_Can && SubEST != EST_Dynamic) ||
@@ -919,9 +930,9 @@ bool Sema::CheckExceptionSpecCompatibility(Expr *From, QualType ToType) {
   //     void (*q)(void (*) throw(int)) = p;
   //   }
   // ... because it might be instantiated with T=int.
-  return CheckExceptionSpecSubset(PDiag(DiagID), PDiag(NestedDiagID), PDiag(),
-                                  ToFunc, From->getSourceRange().getBegin(),
-                                  FromFunc, SourceLocation()) &&
+  return CheckExceptionSpecSubset(
+             PDiag(DiagID), PDiag(NestedDiagID), PDiag(), PDiag(), ToFunc,
+             From->getSourceRange().getBegin(), FromFunc, SourceLocation()) &&
          !getLangOpts().CPlusPlus17;
 }
 
@@ -953,6 +964,7 @@ bool Sema::CheckOverridingFunctionExceptionSpec(const CXXMethodDecl *New,
   return CheckExceptionSpecSubset(PDiag(DiagID),
                                   PDiag(diag::err_deep_exception_specs_differ),
                                   PDiag(diag::note_overridden_virtual_function),
+                                  PDiag(diag::ext_override_exception_spec),
                                   Old->getType()->getAs<FunctionProtoType>(),
                                   Old->getLocation(),
                                   New->getType()->getAs<FunctionProtoType>(),