Manually reimplement MutualExclusion

Author: mstorsjo

clang/include/clang/Basic/Attr.td

@@ -4388,16 +4388,13 @@ def MSStruct : InheritableAttr {
   let Spellings = [GCC<"ms_struct">];
   let Subjects = SubjectList<[Record]>;
   let Documentation = [MSStructDocs];
-  let SimpleHandler = 1;
 }
 
 def GCCStruct : InheritableAttr {
   let Spellings = [GCC<"gcc_struct">];
   let Subjects = SubjectList<[Record]>;
   let Documentation = [MSStructDocs]; // Covers this attribute too.
-  let SimpleHandler = 1;
 }
-def : MutualExclusions<[MSStruct, GCCStruct]>;
 
 def DLLExport : InheritableAttr, TargetSpecificAttr<TargetHasDLLImportExport> {
   let Spellings = [Declspec<"dllexport">, GCC<"dllexport">];

clang/lib/Sema/SemaDeclAttr.cpp

@@ -6172,6 +6172,27 @@ static void handleMSConstexprAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   D->addAttr(::new (S.Context) MSConstexprAttr(S.Context, AL));
 }
 
+static void handleMSStructAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+  if (const auto *First = D->getAttr<GCCStructAttr>()) {
+    S.Diag(AL.getLoc(), diag::err_attributes_are_not_compatible)
+        << AL << First << 0;
+    S.Diag(First->getLocation(), diag::note_conflicting_attribute);
+    return;
+  }
+
+  D->addAttr(::new (S.Context) MSStructAttr(S.Context, AL));
+}
+
+static void handleGCCStructAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+  if (const auto *First = D->getAttr<MSStructAttr>()) {
+    S.Diag(AL.getLoc(), diag::err_attributes_are_not_compatible)
+        << AL << First << 0;
+    S.Diag(First->getLocation(), diag::note_conflicting_attribute);
+    return;
+  }
+  D->addAttr(::new (S.Context) GCCStructAttr(S.Context, AL));
+}
+
 static void handleAbiTagAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   SmallVector<StringRef, 4> Tags;
   for (unsigned I = 0, E = AL.getNumArgs(); I != E; ++I) {
@@ -7910,6 +7931,14 @@ ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D, const ParsedAttr &AL,
   case ParsedAttr::AT_VTablePointerAuthentication:
     handleVTablePointerAuthentication(S, D, AL);
     break;
+
+  case ParsedAttr::AT_MSStruct:
+    handleMSStructAttr(S, D, AL);
+    break;
+
+  case ParsedAttr::AT_GCCStruct:
+    handleGCCStructAttr(S, D, AL);
+    break;
   }
 }