[FFmpeg-devel] [PATCH 04/21] avformat: Redo cleanup of demuxer upon read_header() failure

[Michael Niedermayer]

On Sun, Mar 22, 2020 at 04:47:39AM +0100, Andreas Rheinhardt wrote:
> If reading the header fails, the demuxer's read_close() function (if
> existing) is not called automatically; instead several demuxers call it
> via "goto fail" in read_header().
> 
> This commit intends to change this by adding a flag to AVInputFormat
> that can be used to set on a per-AVInputFormat basis whether read_close()
> should be called generically after an error during read_header().
> 
> The flag controlling this behaviour has been added because it might be
> unsafe to call read_close() generally (e.g. this might lead to
> read_close() being called twice and this might e.g. lead to double-frees
> if av_free() instead of av_freep() is used; or a size field has not
> been reset after freeing the elements (see the mov demuxer for an
> example of this)). Yet the intention is to check and fix all demuxers
> and make the flag redundant in the medium run.
> 
> The flag has been added to a new internal field of AVInputFormat,
> flags_internal. When it has become redundant, it can be removed again
> at the next major version bump.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
> ---
>  libavformat/avformat.h |  7 +++++++
>  libavformat/utils.c    | 11 +++++++++--
>  2 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/libavformat/avformat.h b/libavformat/avformat.h
> index 9b9b634ec3..50b90788b1 100644
> --- a/libavformat/avformat.h
> +++ b/libavformat/avformat.h
> @@ -780,6 +780,13 @@ typedef struct AVInputFormat {
>       * @see avdevice_capabilities_free() for more details.
>       */
>      int (*free_device_capabilities)(struct AVFormatContext *s, struct AVDeviceCapabilitiesQuery *caps);
> +
> +#define FF_INPUTFORMAT_HEADER_CLEANUP 0x0001 /**< read_close() should be called
> +                                                  on read_header() failure */
> +    /**
> +     * Can use flags: FF_INPUTFORMAT_HEADER_CLEANUP
> +     */
> +    int flags_internal;
>  } AVInputFormat;
>  /**
>   * @}

This feature is a good idea.

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Observe your enemies, for they first find out your faults. -- Antisthenes
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