[FFmpeg-devel] [PATCH 2/3] lavfi/psnr: rename pow2 to pow_2

Clément Bœsch u at pkh.me
Mon Mar 27 01:39:21 EEST 2017

On Sun, Mar 26, 2017 at 06:17:57PM -0400, Ronald S. Bultje wrote:
> > I'll improve the message, but basically the djgpp libc can be configured
> > to be POSIX only, where these functions functions and macro (pow2, PI) are
> > not defined. We could do that in the configure (-D_POSIX_SOURCE).
> >
> > Unfortunately, DJGPP does not have posix_memalign(), and will lack its own
> > memalign function we use in lavu/mem.c if we use -D_POSIX_SOURCE. (we
> > could use the recently defunct memalign hack, but better use the proper
> > allocation function).
> I'm not sure I understand. The user might have installed djgpp instead of
> libc. But we have no influence whatsoever over how the user compiled djgpp,
> so FFmpeg should work with as well as without a posix-compiled djgpp, right?

pow2() and memalign() prototypes and macros like PI are exposed
conditionally in their respective headers. So if you have _POSIX_SOURCE
defined in your code and include math.h or stdlib.h, you will not see
these symbols (even though they are present in the djgpp libc).

Clément B.
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