[cfe-commits] r150055 - in /cfe/trunk: include/clang/Basic/DiagnosticGroups.td include/clang/Basic/DiagnosticSemaKinds.td test/Sema/switch.c

[David Blaikie]

On Tue, Feb 7, 2012 at 9:08 PM, Ted Kremenek <kremenek at apple.com> wrote:
> Author: kremenek
> Date: Tue Feb  7 23:08:58 2012
> New Revision: 150055
>
> URL: http://llvm.org/viewvc/llvm-project?rev=150055&view=rev
> Log:
> Move -Wcovered-switch-default out of -Wswitch (and -Wall), and make it an opt-in warning.

I think it's a real pity to separate the two warnings, but I can
understand the limitation/problem. Having this flag under /no/ group
at all does leave me a bit concerned that it'll never be found/used,
though.

As a side note (& I wouldn't've minded a more all-party discussion of
this - though I know it came up once or twice on IRC) Clang's -Wswitch
is under -Wmost (on by default) whereas GCC's -Wswitch is under -Wall
(off by default). One of the possible solutions to this issue (of
-Wcovered-switch-default) I'd considered was to fix this was to make
Clang's -Wswitch behavior consistent with GCC's (thus turning it, and
-Wcovered-switch-default, off by default). Yes, this would still put
-Wcovered-switch-default would be under -Wall & thus, perhaps, still a
bit noisy but it's more likely someone actually wants -Wswitch if they
turn on -Wall & it'd be helpful if they got the other half of that
warning (-Wcovered-switch-default) so -Wswitch was reliable.

> This is a great warning, but it was observed that a ton of real world code violates
> it all the time for (semi-)legitimate reasons.

Last time I brought up any off-by-default warnings Doug seemed to veto
them. (I'm not sure if he's even seen this warning/has an opinion on
it - I'm a bit concerned that he won't like it once he sees it)

> This warnings is fairly pedantic, which is good,
> but not for everyone.

Could we turn it on in the LLVM Makefiles (llvm/Makefile.rules ~ line
650 - I'm not sure if we have to do something else for the cmake
build)? Do we have a way to turn on certain flags only in the presence
of Clang?

>  For example, there is a fair amount of idiomatic code out there
> that does "default: abort()", and similar idioms.
>
> Addresses <rdar://problem/10814651>.
>
> Modified:
>    cfe/trunk/include/clang/Basic/DiagnosticGroups.td
>    cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>    cfe/trunk/test/Sema/switch.c
>
> Modified: cfe/trunk/include/clang/Basic/DiagnosticGroups.td
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticGroups.td?rev=150055&r1=150054&r2=150055&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/Basic/DiagnosticGroups.td (original)
> +++ cfe/trunk/include/clang/Basic/DiagnosticGroups.td Tue Feb  7 23:08:58 2012
> @@ -184,9 +184,9 @@
>  def : DiagGroup<"strict-prototypes">;
>  def StrictSelector : DiagGroup<"strict-selector-match">;
>  def MethodDuplicate : DiagGroup<"duplicate-method-match">;
> -def SwitchEnum     : DiagGroup<"switch-enum">;
>  def CoveredSwitchDefault : DiagGroup<"covered-switch-default">;
> -def Switch         : DiagGroup<"switch", [CoveredSwitchDefault]>;
> +def SwitchEnum     : DiagGroup<"switch-enum">;
> +def Switch         : DiagGroup<"switch">;
>  def Trigraphs      : DiagGroup<"trigraphs">;
>
>  def : DiagGroup<"type-limits">;
>
> Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=150055&r1=150054&r2=150055&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
> +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Tue Feb  7 23:08:58 2012
> @@ -5064,7 +5064,7 @@
>
>  def warn_unreachable_default : Warning<
>   "default label in switch which covers all enumeration values">,
> -  InGroup<CoveredSwitchDefault>;
> +  InGroup<CoveredSwitchDefault>, DefaultIgnore;
>  def warn_not_in_enum : Warning<"case value not in enumerated type %0">,
>   InGroup<Switch>;
>  def err_typecheck_statement_requires_scalar : Error<
>
> Modified: cfe/trunk/test/Sema/switch.c
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/switch.c?rev=150055&r1=150054&r2=150055&view=diff
> ==============================================================================
> --- cfe/trunk/test/Sema/switch.c (original)
> +++ cfe/trunk/test/Sema/switch.c Tue Feb  7 23:08:58 2012
> @@ -1,4 +1,4 @@
> -// RUN: %clang_cc1 -fsyntax-only -verify -Wswitch-enum %s
> +// RUN: %clang_cc1 -fsyntax-only -verify -Wswitch-enum -Wcovered-switch-default %s
>  void f (int z) {
>   while (z) {
>     default: z--;            // expected-error {{statement not in switch}}
>
>
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