[-fms-extensions] Allow missing exception specifications in redeclarations as an extension

Microsoft's ATL headers make use of this MSVC extension, add support for
it and issue a diagnostic under -Wmicrosoft-exception-spec.

This fixes PR25265.

llvm-svn: 250854

1 files changed, 8 insertions, 4 deletions

diff --git a/clang/lib/Sema/SemaExceptionSpec.cpp b/clang/lib/Sema/SemaExceptionSpec.cpp
index a4356f6941b..a18824f1552 100644
--- a/clang/lib/Sema/SemaExceptionSpec.cpp
+++ b/clang/lib/Sema/SemaExceptionSpec.cpp
@@ -285,10 +285,14 @@ bool Sema::CheckEquivalentExceptionSpec(FunctionDecl *Old, FunctionDecl *New) {
         NewProto->getExtProtoInfo().withExceptionSpec(ESI)));
   }
 
-  // Allow missing exception specifications in redeclarations as an extension,
-  // when declaring a replaceable global allocation function.
-  if (New->isReplaceableGlobalAllocationFunction() &&
-      ESI.Type != EST_ComputedNoexcept) {
+  if (getLangOpts().MicrosoftExt && ESI.Type != EST_ComputedNoexcept) {
+    // Allow missing exception specifications in redeclarations as an extension.
+    DiagID = diag::ext_ms_missing_exception_specification;
+    ReturnValueOnError = false;
+  } else if (New->isReplaceableGlobalAllocationFunction() &&
+             ESI.Type != EST_ComputedNoexcept) {
+    // Allow missing exception specifications in redeclarations as an extension,
+    // when declaring a replaceable global allocation function.
     DiagID = diag::ext_missing_exception_specification;
     ReturnValueOnError = false;
   } else {