[FFmpeg-devel] [RFC] avdevice: lock to minor version of avformat

[Diederick C. Niehorster]

FWIW, the macro
#define AV_MAKE_MAJOR_MINOR_FUNC_NAME(name,major,minor)
AV_GLUE(av,name)AV_GLUE(_version_,major)AV_GLUE(_,minor)
doesn't compile on patchwork
(https://patchwork.ffmpeg.org/check/49062/), but worked fine for me on
MSVC. Is MSVC non-compliant somehow? Suggestions appreciated, I'm no
star in C macros.

In any case, this is a discussion starter, so let it not compiling not
hold us back from that.

Cheers,
Dee

On Sun, Dec 26, 2021 at 6:17 PM Diederick Niehorster <dcnieho at gmail.com> wrote:
>
> As per discussion on the list (
> https://ffmpeg.org/pipermail/ffmpeg-devel/2021-June/281513.html, see
> especially https://ffmpeg.org/pipermail/ffmpeg-devel/2021-June/281586.html),
> to resolve the the unholy ABI-relationship between libavdevice and
> libavformat and allow easier working on the part of the avdevice API
> that lives in avformat, lock avdevice to a specific major and minor
> version of avformat.
>
> Signed-off-by: Diederick Niehorster <dcnieho at gmail.com>
> ---
>  libavdevice/avdevice.c | 10 ++++++++++
>  libavdevice/version.h  | 10 ++++++++++
>  libavformat/utils.c    |  5 +++++
>  libavformat/version.h  | 11 +++++++++++
>  libavutil/macros.h     |  2 ++
>  5 files changed, 38 insertions(+)
>
> diff --git a/libavdevice/avdevice.c b/libavdevice/avdevice.c
> index 8f460c7564..b608ec532f 100644
> --- a/libavdevice/avdevice.c
> +++ b/libavdevice/avdevice.c
> @@ -38,6 +38,16 @@ unsigned avdevice_version(void)
>      return LIBAVDEVICE_VERSION_INT;
>  }
>
> +unsigned avdevice_version_same_minor()
> +{
> +    // check version of loaded lavf has same major and minor version as
> +    // this library was compiled against
> +    if ((avformat_version_same_minor()) & ~0xFF != (LIBAVFORMAT_VERSION_INT & ~0xFF))
> +        abort();
> +
> +    return avformat_version();
> +}
> +
>  const char * avdevice_configuration(void)
>  {
>      return FFMPEG_CONFIGURATION;
> diff --git a/libavdevice/version.h b/libavdevice/version.h
> index 41f568d6b0..4c511a7f53 100644
> --- a/libavdevice/version.h
> +++ b/libavdevice/version.h
> @@ -26,6 +26,7 @@
>   */
>
>  #include "libavutil/version.h"
> +#include "libavutil/macros.h"
>
>  #define LIBAVDEVICE_VERSION_MAJOR  59
>  #define LIBAVDEVICE_VERSION_MINOR   1
> @@ -48,4 +49,13 @@
>   */
>  #define FF_API_DEVICE_CAPABILITIES (LIBAVDEVICE_VERSION_MAJOR < 60)
>
> +/**
> + * avdevice_version_same_minor() expands to a function with
> + * the same minor and major version it was compiled against
> + * encoded in it. Enables linking locking to the minor version
> + * of other libraries they were compiled against.
> + */
> +#define avdevice_version_same_minor AV_MAKE_MAJOR_MINOR_FUNC_NAME(device,LIBAVFORMAT_VERSION_MAJOR,LIBAVFORMAT_VERSION_MINOR)
> +unsigned avdevice_version_same_minor();
> +
>  #endif /* AVDEVICE_VERSION_H */
> diff --git a/libavformat/utils.c b/libavformat/utils.c
> index 332ba534d2..607a777c3f 100644
> --- a/libavformat/utils.c
> +++ b/libavformat/utils.c
> @@ -63,6 +63,11 @@ unsigned avformat_version(void)
>      return LIBAVFORMAT_VERSION_INT;
>  }
>
> +unsigned avformat_version_same_minor()
> +{
> +    return avformat_version();
> +}
> +
>  const char *avformat_configuration(void)
>  {
>      return FFMPEG_CONFIGURATION;
> diff --git a/libavformat/version.h b/libavformat/version.h
> index 379a68cc7c..2423800687 100644
> --- a/libavformat/version.h
> +++ b/libavformat/version.h
> @@ -28,6 +28,7 @@
>   */
>
>  #include "libavutil/version.h"
> +#include "libavutil/macros.h"
>
>  // Major bumping may affect Ticket5467, 5421, 5451(compatibility with Chromium)
>  // Also please add any ticket numbers that you believe might be affected here
> @@ -63,4 +64,14 @@
>
>
>  #define FF_API_R_FRAME_RATE            1
> +
> +/**
> + * avformat_version_same_minor() expands to a function with
> + * the same minor and major version it was compiled against
> + * encoded in it. Enables linking locking to the minor version
> + * of other libraries they were compiled against.
> + */
> +#define avformat_version_same_minor AV_MAKE_MAJOR_MINOR_FUNC_NAME(format,LIBAVFORMAT_VERSION_MAJOR,LIBAVFORMAT_VERSION_MINOR)
> +unsigned avformat_version_same_minor();
> +
>  #endif /* AVFORMAT_VERSION_H */
> diff --git a/libavutil/macros.h b/libavutil/macros.h
> index 2a7567c3ea..dda1bf6452 100644
> --- a/libavutil/macros.h
> +++ b/libavutil/macros.h
> @@ -73,6 +73,8 @@
>   * @}
>   */
>
> +#define AV_MAKE_MAJOR_MINOR_FUNC_NAME(name,major,minor) AV_GLUE(av,name)AV_GLUE(_version_,major)AV_GLUE(_,minor)
> +
>  #define AV_PRAGMA(s) _Pragma(#s)
>
>  #define FFALIGN(x, a) (((x)+(a)-1)&~((a)-1))
> --
> 2.28.0.windows.1
>