On Thu, 7 Apr 2016 17:51:26 +0200
Michael Niedermayer <mich...@niedermayer.cc> wrote:
> Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc>
> ---
> libavformat/format.c | 16 ++++++++++------
> 1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/libavformat/format.c b/libavformat/format.c
> index 15fe167..f0abb5d 100644
> --- a/libavformat/format.c
> +++ b/libavformat/format.c
> @@ -62,20 +62,24 @@ void av_register_input_format(AVInputFormat *format)
> {
> AVInputFormat **p = last_iformat;
>
> - format->next = NULL;
> - while(*p || avpriv_atomic_ptr_cas((void * volatile *)p, NULL, format))
> + // Note, format could be added after the first 2 checks but that implies
> that *p is no longer NULL
> + while(p != &format->next && !format->next && avpriv_atomic_ptr_cas((void
> * volatile *)p, NULL, format))
> p = &(*p)->next;
> - last_iformat = &format->next;
> +
> + if (!format->next)
> + last_iformat = &format->next;
> }
>
> void av_register_output_format(AVOutputFormat *format)
> {
> AVOutputFormat **p = last_oformat;
>
> - format->next = NULL;
> - while(*p || avpriv_atomic_ptr_cas((void * volatile *)p, NULL, format))
> + // Note, format could be added after the first 2 checks but that implies
> that *p is no longer NULL
> + while(p != &format->next && !format->next && avpriv_atomic_ptr_cas((void
> * volatile *)p, NULL, format))
> p = &(*p)->next;
> - last_oformat = &format->next;
> +
> + if (!format->next)
> + last_oformat = &format->next;
> }
>
> int av_match_ext(const char *filename, const char *extensions)
This is a giant heap of crap, and it's probably not easy to do much
better. Have you considered just using a mutex instead? We have the
equivalent of pthread_init_once on all platforms now.
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