Re: [FFmpeg-devel] [PATCH] configure: check for sysctl.h explicitly

[Aman Karmani <ffmpeg@tmm1.net>]

On Tue, Jan 17, 2023 at 3:23 AM Andreas Rheinhardt <
andreas.rheinhardt@outlook.com> wrote:

> Aman Karmani:
> > From: Aman Karmani <aman@tmm1.net>
> >
> > HAVE_SYSCTL is used to guard #include <sys/sysctl.h>, so make sure
> > we only define it when that header is present.
> >
> > In recent glibc, the header was removed:
> > https://sourceware.org/pipermail/glibc-cvs/2020q2/069366.html
> >
> > Signed-off-by: Aman Karmani <aman@tmm1.net>
> > ---
> >     configure: check for sysctl.h explicitly
> >
> >     HAVE_SYSCTL is used to guard #include <sys/sysctl.h>, so make sure we
> >     only define it when that header is present.
> >
> >     In recent glibc, the header was removed:
> >     https://sourceware.org/pipermail/glibc-cvs/2020q2/069366.html
> >
> >     Signed-off-by: Aman Karmani aman@tmm1.net
> >
> > Published-As:
> https://github.com/ffstaging/FFmpeg/releases/tag/pr-ffstaging-49%2Ftmm1%2Fsysctl-chk-v1
> > Fetch-It-Via: git fetch https://github.com/ffstaging/FFmpeg
> pr-ffstaging-49/tmm1/sysctl-chk-v1
> > Pull-Request: https://github.com/ffstaging/FFmpeg/pull/49
> >
> >  configure | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/configure b/configure
> > index df69d39669..d2e0ec402d 100755
> > --- a/configure
> > +++ b/configure
> > @@ -6282,7 +6282,7 @@ check_func  setrlimit
> >  check_struct "sys/stat.h" "struct stat" st_mtim.tv_nsec -D_BSD_SOURCE
> >  check_func  strerror_r
> >  check_func  sysconf
> > -check_func  sysctl
> > +check_func_headers sys/sysctl.h sysctl
> >  check_func  usleep
> >
> >  check_func_headers conio.h kbhit
> >
> > base-commit: 01f46f18dbcdf323ceb4fdff7358cf3ca71366e6
>
> What exactly do we need from said header? You intend to include it if it
> available, but we should only include it if it needed.


Seems like sysctl.h defines sysctl() on various BSD. See
https://www.freebsd.org/cgi/man.cgi?sysctl(3)

It is used by libavutil/cpu.c as follows:

#if HAVE_SYSCTL
#if HAVE_SYS_PARAM_H
#include <sys/param.h>
#endif
#include <sys/types.h>
#include <sys/sysctl.h>
#endif


>
> - Andreas
>
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