[Sema] Tweak incomplete enum types on MSVC ABI targets

Enums without an explicit, fixed, underlying type are implicitly given a
fixed 'int' type for ABI compatibility with MSVC.  However, we can
enforce the standard-mandated rules on these types as-if we didn't know
this fact if the tag is not part of a definition.

llvm-svn: 249667

1 files changed, 4 insertions, 2 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 23d4491d04c..fcc40955836 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -11769,8 +11769,10 @@ Decl *Sema::ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK,
         EnumUnderlying = Context.IntTy.getTypePtr();
 
     } else if (Context.getTargetInfo().getCXXABI().isMicrosoft()) {
-      // Microsoft enums are always of int type.
-      EnumUnderlying = Context.IntTy.getTypePtr();
+      if (getLangOpts().MSVCCompat || TUK == TUK_Definition) {
+        // Microsoft enums are always of int type.
+        EnumUnderlying = Context.IntTy.getTypePtr();
+      }
     }
   }