[FFmpeg-devel] [PATCH 1/7] ffprobe: Change string_validation to int, its accessed via AVOption as int

Stefano Sabatini stefasab at gmail.com
Fri Feb 6 11:20:03 CET 2015

On date Thursday 2015-02-05 23:03:56 +0100, Michael Niedermayer encoded:
> On Thu, Feb 05, 2015 at 12:10:12PM +0100, Stefano Sabatini wrote:
> > On date Wednesday 2015-02-04 16:10:03 +0100, Michael Niedermayer encoded:
> > > > the enum might be a different data type than int, it might have
> > > > a different sizeof() than sizeof(int), av_opt accessing it could
> > > > fail.
> > 
> > Is it a theoretical difference or does it affect some
> > platform/compiler? In that case, could be a defect in the
> > platform/compiler?
> gcc on some embeded platforms seems to use types smaller than int
> when it can by default. You can get the same behavior with
> -fshort-enums on x86 if you like to try,
> gcc on linux x86  will also use int64_t if a enum constant is too
> large for 32bit idependant of the short enum flag
> > 
> > From my reading of the C spec, enums and int should be treated in the
> > same way by the compiler, but I'm probably wrong.
> Enumeration specifiers
> ...
> 4 Each enumerated type shall be compatible with char, a signed integer type, or an
>   unsigned integer type. The choice of type is implementation-defined,110) but shall be
>   capable of representing the values of all the members of the enumeration. The
>   enumerated type is incomplete until after the } that terminates the list of enumerator
>   declarations.

Thanks for taking the time for elaborating this reply. I'm fine with
the patch.

Still better would be to extend av_opt() code as you suggested. Also
documenting this shouldn't be bad (and I guess we have a lot of places
where we use enums in options, right?).
FFmpeg = Funny and Fundamental Mere Plastic Evil God

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