[FFmpeg-devel] Moving if(constant expression) to preprocessor?

Axel Holzinger aholzinger
Sat Sep 18 18:00:40 CEST 2010

Hi Vlado and all,

Vladimir Pantelic wrote:
> On 09/18/2010 01:02 PM, Axel Holzinger wrote:
> > Hi all,
> > 
> > if compiling FFmpeg code with zero optimisations (even without
> > code elimination) there are linker errors (undefined references to

> > functions or structs) that come from constructs like i.e. the 
> > following in libavcodec/allcodecs.c:
> > 
> > if(CONFIG_##X##_HWACCEL) av_register_hwaccel(&x##_hwaccel); )
> > 
> > The runtime (lower case) "if" leads to an undefined 
> reference, because 
> > it is evaluated at runtime and not at compile time.
> > 
> > If dead code eliminitation optimisation is on, this isn't an
> > but with optimisations completely off it is.
> as far as ffmpeg is concerned, "dead code eliminitation" is a 
> prerequisite to build it, you cannot do without.

Now that's exactly the prerequisite I would like to overcome.

"You cannot" is quite absurd here, isn't it? If at all I think it's a
matter of We or I don't want.


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