On Mon, 21 Nov 2016 09:58:33 -0500
"Gregory J. Wolfe" <gregory.wo...@kodakalaris.com> wrote:
> (1) Multi-threading support requires knowing the number of CPUs available.
> When building with MinGW on a Windows system, both gcc and Windows run
> time functions are available to get this information. However, when Windows
> threading has been selected, the Windows function should be used, not the
> gcc function. This avoids creating an unnecessary dependency on the gcc
> thread library.
>
> (2) When ALL threading support is disabled, the build should not create a
> dependency on ANY thread library.
>
> Signed-off-by: Gregory J. Wolfe <gregory.wo...@kodakalaris.com>
> ---
> libavutil/cpu.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/libavutil/cpu.c b/libavutil/cpu.c
> index f5785fc..3843778 100644
> --- a/libavutil/cpu.c
> +++ b/libavutil/cpu.c
> @@ -258,10 +258,15 @@ int av_cpu_count(void)
> static volatile int printed;
>
> int nb_cpus = 1;
> +#if HAVE_THREADS
> #if HAVE_WINRT
> SYSTEM_INFO sysinfo;
> #endif
> -#if HAVE_SCHED_GETAFFINITY && defined(CPU_COUNT)
> + // if HAVE_W32THREADS and HAVE_GETPROCESSAFFINITYMASK, we will use
> + // Windows GetProcessAffinityMask() instead of gcc library function
> + // sched_getaffinity(). This avoids creating a dependency on the gcc
> + // thread library that we don't need/want.
> +#if HAVE_SCHED_GETAFFINITY && defined(CPU_COUNT) && !(HAVE_W32THREADS &&
> HAVE_GETPROCESSAFFINITYMASK)
> cpu_set_t cpuset;
>
> CPU_ZERO(&cpuset);
> @@ -286,6 +291,7 @@ int av_cpu_count(void)
> GetNativeSystemInfo(&sysinfo);
> nb_cpus = sysinfo.dwNumberOfProcessors;
> #endif
> +#endif
>
> if (!printed) {
> av_log(NULL, AV_LOG_DEBUG, "detected %d logical cores\n", nb_cpus);
Wouldn't it be better to move the HAVE_GETPROCESSAFFINITYMASK case
above HAVE_SCHED_GETAFFINITY, and avoid making the ifdeffery mess
worse? GetProcessAffinityMask is available on every supported Windows
and could as well be replaced by "ifdef _WIN32" instead.
Also, technically you might have to stop the configure script to stop
linking to libpthread. I'm not sure what exactly stops it from doing
that in your case.
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