[Mesa-dev] [PATCH v2] egl/dri2: Fix GCC maybe-uninitialized warning.

[Matt Turner]

On Wed, Mar 25, 2015 at 4:15 PM, Jan Vesely <jan.vesely at rutgers.edu> wrote:
> On Wed, 2015-03-25 at 18:55 -0400, Ilia Mirkin wrote:
>> On Wed, Mar 25, 2015 at 6:51 PM, Jan Vesely <jan.vesely at rutgers.edu> wrote:
>> > On Fri, 2015-03-06 at 23:54 -0800, Vinson Lee wrote:
>> >> egl_dri2.c: In function ‘dri2_bind_tex_image’:
>> >> egl_dri2.c:1240:4: warning: ‘format’ may be used uninitialized in this function [-Wmaybe-uninitialized]
>> >>     (*dri2_dpy->tex_buffer->setTexBuffer2)(dri2_ctx->dri_context,
>> >>     ^
>> >>
>> >> Suggested-by: Ilia Mirkin <imirkin at alum.mit.edu>
>> >> Signed-off-by: Vinson Lee <vlee at freedesktop.org>
>> >> ---
>> >>  src/egl/drivers/dri2/egl_dri2.c | 6 ++++--
>> >>  1 file changed, 4 insertions(+), 2 deletions(-)
>> >>
>> >> diff --git a/src/egl/drivers/dri2/egl_dri2.c b/src/egl/drivers/dri2/egl_dri2.c
>> >> index d503196..c5c475d 100644
>> >> --- a/src/egl/drivers/dri2/egl_dri2.c
>> >> +++ b/src/egl/drivers/dri2/egl_dri2.c
>> >> @@ -1226,7 +1226,8 @@ dri2_bind_tex_image(_EGLDriver *drv,
>> >>        format = __DRI_TEXTURE_FORMAT_RGBA;
>> >>        break;
>> >>     default:
>> >> -      assert(0);
>> >> +      _eglError(EGL_BAD_SURFACE, "unrecognized format");
>> >> +      return EGL_FALSE;
>> >
>> > does using:
>> > unreachable("unrecognized format");
>> > instead of
>> > assert(0);
>> > fix the warning?
>>
>> unreachable is for *truly* unreachable code... it sounded like this
>> was reachable with bad input.
>
> maybe I misunderstood the situation.
> since there is assert(0) I assumed it can never happen.
> combination of assert(0) and return is very confusing:
> either the code is reachable and should have a correct error path (in
> which case there should not be assert(0)),
> or the code is not reachable in which case unreachable does just fine
> and you should not have the error path.
>
> it looks to me that using assert and return just makes sure that the
> error path is never run on debug build.
>
> anyway, it was just a suggestion. I won't argue one way or another,
> since I don't work with/understand those parts of the code.

I agree. If the code had an assert(0) it's pretty clearly a case for
unreachable.