[Intel-gfx] [PATCH i-g-t 1/3] lib/core: Avoid unused result in backtrace printing

[Chris Wilson]

Quoting Tvrtko Ursulin (2017-11-03 12:56:14)
> 
> On 03/11/2017 12:10, Chris Wilson wrote:
> > Quoting Tvrtko Ursulin (2017-11-03 12:04:15)
> >>
> >> On 03/11/2017 11:52, Chris Wilson wrote:
> >>> Quoting Tvrtko Ursulin (2017-11-03 11:47:54)
> >>>> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> >>>>
> >>>> Add helpers for direct write to stderr to consolidate the code
> >>>> and avoid the unused result warning in build.
> >>>>
> >>>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> >>>> ---
> >>>>    lib/igt_core.c | 23 ++++++++++++++++-------
> >>>>    1 file changed, 16 insertions(+), 7 deletions(-)
> >>>>
> >>>> diff --git a/lib/igt_core.c b/lib/igt_core.c
> >>>> index 538a4472e209..351859eaa04c 100644
> >>>> --- a/lib/igt_core.c
> >>>> +++ b/lib/igt_core.c
> >>>> @@ -1239,7 +1239,7 @@ static const char hex[] = "0123456789abcdef";
> >>>>    static void
> >>>>    xputch(int c)
> >>>>    {
> >>>> -       write(STDERR_FILENO, (const void *) &c, 1);
> >>>> +       igt_assert_eq(write(STDERR_FILENO, (const void *) &c, 1), 1);
> >>>
> >>> Infinite recursion, you can't use an assert from inside the assert
> >>> handler.
> >>
> >> I thought it is the signal handler. Tested sending some signals and it
> >> survived. If there is a flaw there could instead nerf them with void
> >> cast, don't know.
> > 
> > I do recall these are meant to be fail safe, so using something like
> > assert which may end up here again is no-no. igt_ignore_warn()?
> 
> But then on the other hand igt_fail seems to have handling for exit 
> handlers using igt_asserts. Which suggests what I've done might be fine 
> after all.

Otoh, where does the assert go if we fail to write to stderr? I do not
like the means by which we are meant to be writing the death throes to
cause further output. These routines are the lowest level and meant to
be impervious, callable from any context, calling back up into igt is a
layering violation.
-Chris