Cleanup a fixme by using a specific diagnostic for subscripting

a pointer to void.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@133912 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Basic/DiagnosticSemaKinds.td

@@ -2838,6 +2838,8 @@ def err_subscript_function_type : Error<
   "subscript of pointer to function type %0">;
 def err_subscript_incomplete_type : Error<
   "subscript of pointer to incomplete type %0">;
+def ext_gnu_subscript_void_type : Extension<
+  "subscript of a pointer to void is a GNU extension">, InGroup<PointerArith>;
 def err_typecheck_member_reference_struct_union : Error<
   "member reference base type %0 is not a structure or union">;
 def err_typecheck_member_reference_ivar : Error<

lib/Sema/SemaExpr.cpp

@@ -3092,9 +3092,8 @@ Sema::CreateBuiltinArraySubscriptExpr(Expr *Base, SourceLocation LLoc,
 
   if (ResultType->isVoidType() && !getLangOptions().CPlusPlus) {
     // GNU extension: subscripting on pointer to void
-    // FIXME: Use a better warning for this.
+    Diag(LLoc, diag::ext_gnu_subscript_void_type)
-    Diag(LLoc, diag::ext_gnu_void_ptr)
+      << BaseExpr->getSourceRange();
-      << 0 << BaseExpr->getSourceRange();
 
     // C forbids expressions of unqualified void type from being l-values.
     // See IsCForbiddenLValueType.

test/Sema/pointer-addition.c

@@ -9,7 +9,7 @@ void a(S* b, void* c) {
   c += 1;    // expected-warning {{arithmetic on a pointer to void is a GNU extension}}
   c--;       // expected-warning {{arithmetic on a pointer to void is a GNU extension}}
   c -= 1;    // expected-warning {{arithmetic on a pointer to void is a GNU extension}}
-  (void) c[1]; // expected-warning {{arithmetic on a pointer to void is a GNU extension}}
+  (void) c[1]; // expected-warning {{subscript of a pointer to void is a GNU extension}}
   b = 1+b;   // expected-error {{arithmetic on a pointer to an incomplete type}}
   /* The next couple tests are only pedantic warnings in gcc */
   void (*d)(S*,void*) = a;