[Mesa-dev] [PATCH] list: add some iterator debug

[Jason Ekstrand]

Yeah, that's a GNU extension. It also works in clang but not MSVC which is 
used to build NIR.

On May 25, 2019 13:30:29 Rob Clark <robdclark at gmail.com> wrote:

> On Sat, May 25, 2019 at 11:13 AM Ilia Mirkin <imirkin at alum.mit.edu> wrote:
>>
>> On Sat, May 25, 2019 at 2:03 PM Rob Clark <robdclark at gmail.com> wrote:
>> >
>> > From: Rob Clark <robdclark at chromium.org>
>> >
>> > Debugging use of unsafe iterators when you should have used the _safe
>> > version sucks.  Add some DEBUG build support to catch and assert if
>> > someone does that.
>> >
>> > I didn't update the UPPERCASE verions of the iterators.  They should
>> > probably be deprecated/removed.
>> >
>> > Signed-off-by: Rob Clark <robdclark at chromium.org>
>> > ---
>> >  src/util/list.h | 23 ++++++++++++++++++-----
>> >  1 file changed, 18 insertions(+), 5 deletions(-)
>> >
>> > diff --git a/src/util/list.h b/src/util/list.h
>> > index 09d1b4cae64..6d89a42b226 100644
>> > --- a/src/util/list.h
>> > +++ b/src/util/list.h
>> > @@ -43,6 +43,13 @@
>> >  #include <assert.h>
>> >  #include "c99_compat.h"
>> >
>> > +#ifdef DEBUG
>> > +#  define LIST_DEBUG 1
>> > +#else
>> > +#  define LIST_DEBUG 0
>> > +#endif
>> > +
>> > +#define list_assert(cond, msg)  ({ if (LIST_DEBUG) assert((cond) && msg); })
>>
>> Not sure if it's worth worrying about, but this style of macro
>> definition can be dangerous. One might use it as
>>
>> if (x) list_assert()
>> else blah;
>>
>> With the macro defined as-is, the "else blah" will get attached to the
>> if in the macro. I believe the common style is to do do {}while(0) to
>> avoid such issues (or to use an inline function). Alternatively, just
>> define it differently for LIST_DEBUG vs not.
>>
>
> I think the ({ ... }) should save the day..
>
> (hmm, is that c99 or a gnu thing?  I've it isn't avail on some
> compilers I guess we should disable list_assert() for those?)
>
> BR,
> -R
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