Put macro redefinition warnings under -Wmacro-redefined

[rnk]

Summary

This is consistent with -Wbuiltin-macro-redefined, and puts this common
extension warning under a flag.

[rsmith]

LGTM

include/clang/Basic/DiagnosticGroups.td

51–52

Do you think there's value in making BuiltinMacroRedefined a subgroup of MacroRedefined? I'm torn here -- logically one is a subset of the other, but redefining a builtin macro is a more serious offense.

[rnk]

Thanks!

include/clang/Basic/DiagnosticGroups.td

51–52

I'd leave it as is. No need to impose artificial hierarchy. Users might accidentally suppress -Wbuiltin-macro-redefined with -Wno-macro-redefined.

[rnk]

Closed by commit rL205591 (authored by @rnk).

include/clang/Basic/DiagnosticGroups.td

 def EnumConversion : DiagGroup<"enum-conversion">;
 def EnumTooLarge : DiagGroup<"enum-too-large">;
 def NonLiteralNullConversion : DiagGroup<"non-literal-null-conversion">;
 def NullConversion : DiagGroup<"null-conversion">;
 def ImplicitConversionFloatingPointToBool :
   DiagGroup<"implicit-conversion-floating-point-to-bool">;
 def ObjCLiteralConversion : DiagGroup<"objc-literal-conversion">;
 def BadArrayNewLength : DiagGroup<"bad-array-new-length">;
+def MacroRedefined : DiagGroup<"macro-redefined">;
 def BuiltinMacroRedefined : DiagGroup<"builtin-macro-redefined">;
 def BuiltinRequiresHeader : DiagGroup<"builtin-requires-header">;
 def C99Compat : DiagGroup<"c99-compat">;
 def CXXCompat: DiagGroup<"c++-compat">;
 def ExternCCompat : DiagGroup<"extern-c-compat">;
 def KeywordCompat : DiagGroup<"keyword-compat">;
 def GNUCaseRange : DiagGroup<"gnu-case-range">;
 def CastAlign : DiagGroup<"cast-align">;
 def : DiagGroup<"cast-qual">;

include/clang/Basic/DiagnosticLexKinds.td

 def ext_pp_warning_directive : Extension<"#warning is a language extension">;
 
 def ext_pp_extra_tokens_at_eol : ExtWarn<
   "extra tokens at end of #%0 directive">, InGroup<ExtraTokens>;
   
 def ext_pp_comma_expr : Extension<"comma operator in operand of #if">;
 def ext_pp_bad_vaargs_use : Extension<
   "__VA_ARGS__ can only appear in the expansion of a C99 variadic macro">;
-def ext_pp_macro_redef : ExtWarn<"%0 macro redefined">;
+def ext_pp_macro_redef : ExtWarn<"%0 macro redefined">, InGroup<MacroRedefined>;
 def ext_variadic_macro : Extension<"variadic macros are a C99 feature">,
   InGroup<VariadicMacros>;
 def warn_cxx98_compat_variadic_macro : Warning<
   "variadic macros are incompatible with C++98">,
   InGroup<CXX98CompatPedantic>, DefaultIgnore;
 def ext_named_variadic_macro : Extension<
   "named variadic macros are a GNU extension">, InGroup<VariadicMacros>;
 def err_embedded_include : Error<

test/Misc/warning-flags.c

(2) It prevents us adding new warnings to Clang that have no -W flag.  All
     new warnings should have -W flags.
 
     If you add a new warning without a flag, this test will fail.  To fix
     this test, simply add a warning group to that warning.
 
 
 The list of warnings below should NEVER grow.  It should gradually shrink to 0.
 
-CHECK: Warnings without flags (106):
+CHECK: Warnings without flags (105):
 CHECK-NEXT:   ext_delete_void_ptr_operand
 CHECK-NEXT:   ext_expected_semi_decl_list
 CHECK-NEXT:   ext_explicit_specialization_storage_class
 CHECK-NEXT:   ext_implicit_lib_function_decl
 CHECK-NEXT:   ext_many_braces_around_scalar_init
 CHECK-NEXT:   ext_missing_declspec
 CHECK-NEXT:   ext_missing_whitespace_after_macro_name
 CHECK-NEXT:   ext_new_paren_array_nonconst
 CHECK-NEXT:   ext_plain_complex
-CHECK-NEXT:   ext_pp_macro_redef
 CHECK-NEXT:   ext_template_arg_extra_parens
 CHECK-NEXT:   ext_typecheck_comparison_of_pointer_integer
 CHECK-NEXT:   ext_typecheck_cond_incompatible_operands
 CHECK-NEXT:   ext_typecheck_cond_incompatible_operands_nonstandard
 CHECK-NEXT:   ext_typecheck_ordered_comparison_of_function_pointers
 CHECK-NEXT:   ext_typecheck_ordered_comparison_of_pointer_integer
 CHECK-NEXT:   ext_using_undefined_std
 CHECK-NEXT:   pp_include_next_absolute_path

test/Preprocessor/macro_redefined.c

+// RUN: %clang_cc1 %s -Eonly -verify -Wno-all -Wmacro-redefined -DCLI_MACRO=1 -DWMACRO_REDEFINED
+// RUN: %clang_cc1 %s -Eonly -verify -Wno-all -Wno-macro-redefined -DCLI_MACRO=1
+
+#ifndef WMACRO_REDEFINED
+// expected-no-diagnostics
+#endif
+
+#ifdef WMACRO_REDEFINED
+// expected-note@1 {{previous definition is here}}
+// expected-warning@+2 {{macro redefined}}
+#endif
+#define CLI_MACRO
+
+#ifdef WMACRO_REDEFINED
+// expected-note@+3 {{previous definition is here}}
+// expected-warning@+3 {{macro redefined}}
+#endif
+#define REGULAR_MACRO
+#define REGULAR_MACRO 1