[FFmpeg-devel] [PATCH 1/3] avcodec/cbs_h266_syntax_template: Don't omit unused function parameter

[Andreas Rheinhardt]

Andreas Rheinhardt:
> The calls to the sei_decoded_picture_hash read and write functions
> are performed with four pointer arguments; just because one
> of them is unused by the callees does not mean that they
> can be omitted: This is undefined behaviour.
> (This was not recognized because the SEI_MESSAGE_RW macro
> contains casts.)
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
> ---
> I found this via UBSan test failures with Clang 17,
> but actually there are compiler warnings for this:
> -Wcast-function-type for GCC and old Clang
> and -Wcast-function-type in conjunction with
> -Wno-cast-function-type-strict (without the latter,
> Clang warns about conversions with different pointer
> types, like int (*)(void*)->int (*)(struct Foo*);
> the latter typically lead to UB (when used in a call),
> but are actually common).
> 
>  libavcodec/cbs_h266_syntax_template.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavcodec/cbs_h266_syntax_template.c b/libavcodec/cbs_h266_syntax_template.c
> index 26ee7a420b..e75f2f6971 100644
> --- a/libavcodec/cbs_h266_syntax_template.c
> +++ b/libavcodec/cbs_h266_syntax_template.c
> @@ -3430,7 +3430,7 @@ static int FUNC(slice_header) (CodedBitstreamContext *ctx, RWContext *rw,
>  static int FUNC(sei_decoded_picture_hash) (CodedBitstreamContext *ctx,
>                                             RWContext *rw,
>                                             H266RawSEIDecodedPictureHash *
> -                                           current)
> +                                           current, SEIMessageState *unused)
>  {
>      int err, c_idx, i;
>  

Will apply this patchset tomorrow unless there are objections.

- Andreas