On Sun, Jan 30, 2022 at 07:27:24AM +0100, Andreas Rheinhardt wrote:
> This is in preparation for actually adding such contexts
> and e.g. moving fields only used by the main thread to
> the corresponding "Main" context.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

This breaks build on mingw64

src/libavcodec/dxva2_mpeg2.c:42:50: warning: ‘struct MPVDecContext’ declared inside parameter list will not be visible outside of this definition or declaration
                                     const struct MPVDecContext *s,
                                                  ^~~~~~~~~~~~~
src/libavcodec/dxva2_mpeg2.c: In function ‘fill_picture_parameters’:
src/libavcodec/dxva2_mpeg2.c:45:39: error: dereferencing pointer to incomplete type ‘const struct MPVDecContext’
     const Picture *current_picture = s->current_picture_ptr;
                                       ^~
src/libavcodec/dxva2_mpeg2.c: At top level:
src/libavcodec/dxva2_mpeg2.c:108:53: warning: ‘struct MPVDecContext’ declared inside parameter list will not be visible outside of this definition or declaration
                                        const struct MPVDecContext *s,
                                                     ^~~~~~~~~~~~~
src/libavcodec/dxva2_mpeg2.c: In function ‘fill_quantization_matrices’:
src/libavcodec/dxva2_mpeg2.c:115:18: error: dereferencing pointer to incomplete type ‘const struct MPVDecContext’
         int n = s->idsp.idct_permutation[ff_zigzag_direct[i]];
                  ^~
src/libavcodec/dxva2_mpeg2.c:115:13: warning: variable ‘n’ set but not used [-Wunused-but-set-variable]
         int n = s->idsp.idct_permutation[ff_zigzag_direct[i]];
             ^
src/libavcodec/dxva2_mpeg2.c: At top level:
src/libavcodec/dxva2_mpeg2.c:124:37: warning: ‘struct MPVDecContext’ declared inside parameter list will not be visible outside of this definition or declaration
                        const struct MPVDecContext *s,
                                     ^~~~~~~~~~~~~
src/libavcodec/dxva2_mpeg2.c: In function ‘fill_slice’:
src/libavcodec/dxva2_mpeg2.c:129:21: error: dereferencing pointer to incomplete type ‘const struct MPVDecContext’
     int is_field = s->picture_structure != PICT_FRAME;
                     ^~
src/libavcodec/dxva2_mpeg2.c: In function ‘commit_bitstream_and_slice_buffer’:
src/libavcodec/dxva2_mpeg2.c:157:10: error: dereferencing pointer to incomplete type ‘const struct MPVDecContext’
         s->current_picture_ptr->hwaccel_picture_private;
          ^~
src/libavcodec/dxva2_mpeg2.c: In function ‘dxva2_mpeg2_start_frame’:
src/libavcodec/dxva2_mpeg2.c:260:10: error: dereferencing pointer to incomplete type ‘const struct MPVDecContext’
         s->current_picture_ptr->hwaccel_picture_private;
          ^~
src/libavcodec/dxva2_mpeg2.c:266:41: warning: passing argument 3 of ‘fill_picture_parameters’ from incompatible pointer type [-Wincompatible-pointer-types]
     fill_picture_parameters(avctx, ctx, s, &ctx_pic->pp);
                                         ^
src/libavcodec/dxva2_mpeg2.c:40:13: note: expected ‘const struct MPVDecContext *’ but argument is of type ‘const struct MPVDecContext * const’
 static void fill_picture_parameters(AVCodecContext *avctx,
             ^~~~~~~~~~~~~~~~~~~~~~~
src/libavcodec/dxva2_mpeg2.c:267:44: warning: passing argument 3 of ‘fill_quantization_matrices’ from incompatible pointer type [-Wincompatible-pointer-types]
     fill_quantization_matrices(avctx, ctx, s, &ctx_pic->qm);
                                            ^
src/libavcodec/dxva2_mpeg2.c:106:13: note: expected ‘const struct MPVDecContext *’ but argument is of type ‘const struct MPVDecContext * const’
 static void fill_quantization_matrices(AVCodecContext *avctx,
             ^~~~~~~~~~~~~~~~~~~~~~~~~~
src/libavcodec/dxva2_mpeg2.c: In function ‘dxva2_mpeg2_decode_slice’:
src/libavcodec/dxva2_mpeg2.c:280:10: error: dereferencing pointer to incomplete type ‘const struct MPVDecContext’
         s->current_picture_ptr->hwaccel_picture_private;
          ^~
src/libavcodec/dxva2_mpeg2.c:293:23: warning: passing argument 2 of ‘fill_slice’ from incompatible pointer type [-Wincompatible-pointer-types]
     fill_slice(avctx, s, &ctx_pic->slice[ctx_pic->slice_count++], position,
                       ^
src/libavcodec/dxva2_mpeg2.c:123:13: note: expected ‘const struct MPVDecContext *’ but argument is of type ‘const struct MPVDecContext * const’
 static void fill_slice(AVCodecContext *avctx,
             ^~~~~~~~~~
src/libavcodec/dxva2_mpeg2.c: In function ‘dxva2_mpeg2_end_frame’:
src/libavcodec/dxva2_mpeg2.c:302:10: error: dereferencing pointer to incomplete type ‘struct MPVDecContext’
         s->current_picture_ptr->hwaccel_picture_private;
          ^~
src/libavcodec/dxva2_mpeg2.c:312:33: warning: passing argument 1 of ‘ff_mpeg_draw_horiz_band’ from incompatible pointer type [-Wincompatible-pointer-types]
         ff_mpeg_draw_horiz_band(s, 0, avctx->height);
                                 ^
In file included from src/libavcodec/dxva2_mpeg2.c:27:0:
src/libavcodec/mpegvideo.h:606:6: note: expected ‘MPVContext * {aka struct MPVContext *}’ but argument is of type ‘struct MPVDecContext * const’
 void ff_mpeg_draw_horiz_band(MPVContext *s, int y, int h);
      ^~~~~~~~~~~~~~~~~~~~~~~
src/ffbuild/common.mak:78: recipe for target 'libavcodec/dxva2_mpeg2.o' failed
make: *** [libavcodec/dxva2_mpeg2.o] Error 1
make: *** Waiting for unfinished jobs....

[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

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