WG14 DR496

[aaron.ballman]

Summary

This DR was discussed at the WG14 meeting in Albuquerque and the outcome was that member-designator wording could safely be replaced by "subobject", which will be the Proposed Technical Corrigendum coming out of that meeting. This patch removes the extension warning we were issuing in these situations.

[rsmith]

Thanks!

[aaron.ballman]

Commit in r318796.

include/clang/Basic/DiagnosticSemaKinds.td

 def err_offsetof_record_type : Error<
   "offsetof requires struct, union, or class type, %0 invalid">;
 def err_offsetof_array_type : Error<"offsetof requires array type, %0 invalid">;
-def ext_offsetof_extended_field_designator : Extension<
-  "using extended field designator is an extension">,
-  InGroup<DiagGroup<"extended-offsetof">>;
 def ext_offsetof_non_pod_type : ExtWarn<"offset of on non-POD type %0">,
   InGroup<InvalidOffsetof>;
 def ext_offsetof_non_standardlayout_type : ExtWarn<

lib/Sema/SemaExpr.cpp

       && RequireCompleteType(BuiltinLoc, ArgTy,
                              diag::err_offsetof_incomplete_type, TypeRange))
     return ExprError();
-  
-  // offsetof with non-identifier designators (e.g. "offsetof(x, a.b[c])") are a
-  // GCC extension, diagnose them.
-  // FIXME: This diagnostic isn't actually visible because the location is in
-  // a system header!
-  if (Components.size() != 1)
-    Diag(BuiltinLoc, diag::ext_offsetof_extended_field_designator)
-      << SourceRange(Components[1].LocStart, Components.back().LocEnd);
-  
   bool DidWarnAboutNonPOD = false;
   QualType CurrentType = ArgTy;
   SmallVector<OffsetOfNode, 4> Comps;

test/CXX/drs/dr4xx.cpp

     U<__builtin_offsetof(A, n)>::type a;
     U<__builtin_offsetof(T, n)>::type b; // expected-error +{{}} expected-warning 0+{{}}
     // as an extension, we allow the member-designator to include array indices
-    g(__builtin_offsetof(A, a[0])).h<int>(); // expected-error {{extension}}
-    g(__builtin_offsetof(A, a[N])).h<int>(); // expected-error {{extension}}
-    U<__builtin_offsetof(A, a[0])>::type c; // expected-error {{extension}}
-    U<__builtin_offsetof(A, a[N])>::type d; // expected-error {{extension}} expected-error +{{}} expected-warning 0+{{}}
+    g(__builtin_offsetof(A, a[0])).h<int>();
+    g(__builtin_offsetof(A, a[N])).h<int>();
+    U<__builtin_offsetof(A, a[0])>::type c;
+    U<__builtin_offsetof(A, a[N])>::type d; // expected-error +{{}} expected-warning 0+{{}}
   }
 }