[FFmpeg-devel] [PATCH v2] avformat/avio: Don't use incompatible function pointer type for call

[Tomas Härdin]

sön 2023-09-10 klockan 12:07 +0200 skrev Andreas Rheinhardt:
> It is undefined behaviour even in cases where it works
> (it works because it is only a const uint8_t* vs. uint8_t*
> difference).
> Instead use a macro to produce two functions with the required
> types to be const-correct and type-safe.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
> ---
>  libavformat/avio.c | 98 +++++++++++++++++++++++---------------------
> --
>  1 file changed, 50 insertions(+), 48 deletions(-)
> 
> diff --git a/libavformat/avio.c b/libavformat/avio.c
> index ab1c19a58d..9783cb1881 100644
> --- a/libavformat/avio.c
> +++ b/libavformat/avio.c
> @@ -353,63 +353,67 @@ fail:
>      return ret;
>  }
>  
> -static inline int retry_transfer_wrapper(URLContext *h, uint8_t
> *buf,
> -                                         int size, int size_min,
> -                                         int
> (*transfer_func)(URLContext *h,
> -                                                             
> uint8_t *buf,
> -                                                              int
> size))
> -{
> -    int ret, len;
> -    int fast_retries = 5;
> -    int64_t wait_since = 0;
> -
> -    len = 0;
> -    while (len < size_min) {
> -        if (ff_check_interrupt(&h->interrupt_callback))
> -            return AVERROR_EXIT;
> -        ret = transfer_func(h, buf + len, size - len);
> -        if (ret == AVERROR(EINTR))
> -            continue;
> -        if (h->flags & AVIO_FLAG_NONBLOCK)
> -            return ret;
> -        if (ret == AVERROR(EAGAIN)) {
> -            ret = 0;
> -            if (fast_retries) {
> -                fast_retries--;
> -            } else {
> -                if (h->rw_timeout) {
> -                    if (!wait_since)
> -                        wait_since = av_gettime_relative();
> -                    else if (av_gettime_relative() > wait_since + h-
> >rw_timeout)
> -                        return AVERROR(EIO);
> -                }
> -                av_usleep(1000);
> -            }
> -        } else if (ret == AVERROR_EOF)
> -            return (len > 0) ? len : AVERROR_EOF;
> -        else if (ret < 0)
> -            return ret;
> -        if (ret) {
> -            fast_retries = FFMAX(fast_retries, 2);
> -            wait_since = 0;
> -        }
> -        len += ret;
> -    }
> -    return len;
> +#define RETRY_TRANSFER_WRAPPER(RW,
> CONST)                                     \
> +static inline int retry_ ## RW ## _wrapper(URLContext *h, CONST
> uint8_t *buf, \
> +                                           int size, int
> size_min,            \
> +                                           int (*RW ##
> _func)(URLContext *h,  \
> +                                                              CONST
> uint8_t *buf, \
> +                                                              int
> size))      \
> +{                                                                   
>           \
> +    int ret,
> len;                                                             \
> +    int fast_retries =
> 5;                                                     \
> +    int64_t wait_since =
> 0;                                                   \
> +                                                                    
>           \
> +    len =
> 0;                                                                  \
> +    while (len < size_min)
> {                                                  \
> +        if (ff_check_interrupt(&h-
> >interrupt_callback))                       \
> +            return
> AVERROR_EXIT;                                              \
> +        ret = RW ## _func(h,  buf + len, size -
> len);                         \
> +        if (ret ==
> AVERROR(EINTR))                                            \
> +           
> continue;                                                         \
> +        if (h->flags &
> AVIO_FLAG_NONBLOCK)                                    \
> +            return
> ret;                                                       \
> +        if (ret == AVERROR(EAGAIN))
> {                                         \
> +            ret =
> 0;                                                          \
> +            if (fast_retries)
> {                                               \
> +                fast_retries--
> ;                                               \
> +            } else
> {                                                          \
> +                if (h->rw_timeout)
> {                                          \
> +                    if
> (!wait_since)                                          \
> +                        wait_since =
> av_gettime_relative();                   \
> +                    else if (av_gettime_relative() > wait_since + h-
> >rw_timeout) \
> +                        return
> AVERROR(EIO);                                  \
> +               
> }                                                             \
> +               
> av_usleep(1000);                                              \
> +           
> }                                                                 \
> +        } else if (ret ==
> AVERROR_EOF)                                        \
> +            return (len > 0) ? len :
> AVERROR_EOF;                             \
> +        else if (ret <
> 0)                                                     \
> +            return
> ret;                                                       \
> +        if (ret)
> {                                                            \
> +            fast_retries = FFMAX(fast_retries,
> 2);                            \
> +            wait_since =
> 0;                                                   \
> +       
> }                                                                    
> \
> +        len +=
> ret;                                                           \
> +   
> }                                                                    
>      \
> +    return
> len;                                                               \
>  }
>  
> +RETRY_TRANSFER_WRAPPER(read, )
> +RETRY_TRANSFER_WRAPPER(write, const)
> +
>  int ffurl_read(URLContext *h, unsigned char *buf, int size)
>  {
>      if (!(h->flags & AVIO_FLAG_READ))
>          return AVERROR(EIO);
> -    return retry_transfer_wrapper(h, buf, size, 1, h->prot-
> >url_read);
> +    return retry_read_wrapper(h, buf, size, 1, h->prot->url_read);
>  }
>  
>  int ffurl_read_complete(URLContext *h, unsigned char *buf, int size)
>  {
>      if (!(h->flags & AVIO_FLAG_READ))
>          return AVERROR(EIO);
> -    return retry_transfer_wrapper(h, buf, size, size, h->prot-
> >url_read);
> +    return retry_read_wrapper(h, buf, size, size, h->prot-
> >url_read);
>  }
>  
>  int ffurl_write(URLContext *h, const unsigned char *buf, int size)
> @@ -420,9 +424,7 @@ int ffurl_write(URLContext *h, const unsigned
> char *buf, int size)
>      if (h->max_packet_size && size > h->max_packet_size)
>          return AVERROR(EIO);
>  
> -    return retry_transfer_wrapper(h, (unsigned char *)buf, size,
> size,
> -                                  (int (*)(struct URLContext *,
> uint8_t *, int))
> -                                  h->prot->url_write);
> +    return retry_write_wrapper(h, buf, size, size, h->prot-
> >url_write);
>  }
>  
>  int64_t ffurl_seek(URLContext *h, int64_t pos, int whence)

Fair enough.

/Tomas