[FFmpeg-devel] [PATCH] avcodec/ffv1enc_template: use FF_PTR_ADD to add offsets to a pointer

[FFmpeg-devel] [PATCH] avcodec/ffv1enc_template: use FF_PTR_ADD to add offsets to a pointer

[James Almer]

Fixes: libavcodec\ffv1enc_template.c:75:79: runtime error: applying zero offset to null pointer
Signed-off-by: James Almer <jamrial@gmail.com>
---
Untested, as gcc-usan on Linux x86_64 doesn't complain about it, but it can be seen in
https://fate.ffmpeg.org/report.cgi?time=20250622122557&slot=amd64-clang-cl-msvc-asan

 libavcodec/ffv1enc_template.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/ffv1enc_template.c b/libavcodec/ffv1enc_template.c
index aaf82159ee..7edfd2dc0f 100644
--- a/libavcodec/ffv1enc_template.c
+++ b/libavcodec/ffv1enc_template.c
@@ -72,7 +72,7 @@ RENAME(encode_line)(FFV1Context *f, FFV1SliceContext *sc,
         int diff, context;
 
         context = RENAME(get_context)(f->quant_tables[p->quant_table_index],
-                                      sample[0] + x, sample[1] + x, sample[2] + x);
+                                      sample[0] + x, sample[1] + x, FF_PTR_ADD(sample[2], x));
         diff    = sample[0][x] - RENAME(predict)(sample[0] + x, sample[1] + x);
 
         if (context < 0) {
-- 
2.50.0

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[FFmpeg-devel] [PATCH 2/2] avcodec/mss2dsp: use FF_PTR_ADD to add offsets to a pointer

[James Almer]

Fixes: libavcodec/mss2dsp.c:59:14: runtime error: applying zero offset to null pointer

Signed-off-by: James Almer <jamrial@gmail.com>
---
Untested, as gcc-usan on Linux x86_64 doesn't complain about it, but it can be seen in
https://fate.ffmpeg.org/report.cgi?time=20250622122557&slot=amd64-clang-cl-msvc-asan

 libavcodec/mss2dsp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/mss2dsp.c b/libavcodec/mss2dsp.c
index cc39dd637f..4180c65577 100644
--- a/libavcodec/mss2dsp.c
+++ b/libavcodec/mss2dsp.c
@@ -56,7 +56,7 @@ static av_always_inline void mss2_blit_wmv9_template(uint8_t *dst,
                 }
             }
         }
-        mask +=  mask_stride;
+        FF_PTR_ADD(mask, mask_stride);
         dst  +=   dst_stride;
         srcy +=  srcy_stride;
         srcu += srcuv_stride * (r & 1);
-- 
2.50.0

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[FFmpeg-devel] [PATCH v2 2/2] avcodec/mss2dsp: use FF_PTR_ADD to add offsets to a pointer

[James Almer]

Fixes: libavcodec/mss2dsp.c:59:14: runtime error: applying zero offset to null pointer

Signed-off-by: James Almer <jamrial@gmail.com>
---
Untested, as gcc-usan on Linux x86_64 doesn't complain about it, but it can be seen in
https://fate.ffmpeg.org/report.cgi?time=20250622122557&slot=amd64-clang-cl-msvc-asan

 libavcodec/mss2dsp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/mss2dsp.c b/libavcodec/mss2dsp.c
index cc39dd637f..ace92ef9c7 100644
--- a/libavcodec/mss2dsp.c
+++ b/libavcodec/mss2dsp.c
@@ -56,7 +56,7 @@ static av_always_inline void mss2_blit_wmv9_template(uint8_t *dst,
                 }
             }
         }
-        mask +=  mask_stride;
+        mask  = FF_PTR_ADD(mask, mask_stride);
         dst  +=   dst_stride;
         srcy +=  srcy_stride;
         srcu += srcuv_stride * (r & 1);
-- 
2.50.0

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Re: [FFmpeg-devel] [PATCH] avcodec/ffv1enc_template: use FF_PTR_ADD to add offsets to a pointer

[Kacper Michajlow]

On Sun, 22 Jun 2025 at 15:49, James Almer
<jamrial-at-gmail.com@ffmpeg.org> wrote:
>
> Fixes: libavcodec\ffv1enc_template.c:75:79: runtime error: applying zero offset to null pointer
> Signed-off-by: James Almer <jamrial@gmail.com>
> ---
> Untested, as gcc-usan on Linux x86_64 doesn't complain about it, but it can be seen in
clang-usan also reproduces this on Linux x86_64.

> https://fate.ffmpeg.org/report.cgi?time=20250622122557&slot=amd64-clang-cl-msvc-asan
>
>  libavcodec/ffv1enc_template.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/libavcodec/ffv1enc_template.c b/libavcodec/ffv1enc_template.c
> index aaf82159ee..7edfd2dc0f 100644
> --- a/libavcodec/ffv1enc_template.c
> +++ b/libavcodec/ffv1enc_template.c
> @@ -72,7 +72,7 @@ RENAME(encode_line)(FFV1Context *f, FFV1SliceContext *sc,
>          int diff, context;
>
>          context = RENAME(get_context)(f->quant_tables[p->quant_table_index],
> -                                      sample[0] + x, sample[1] + x, sample[2] + x);
> +                                      sample[0] + x, sample[1] + x, FF_PTR_ADD(sample[2], x));

Doesn't work. FF_PTR_ADD checks offset (x) only, but the issue here is
that sample[2]==NULL.

- Kacper
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Re: [FFmpeg-devel] [PATCH] avcodec/ffv1enc_template: use FF_PTR_ADD to add offsets to a pointer

[Kacper Michajlow]

On Sun, 22 Jun 2025 at 16:50, Kacper Michajlow <kasper93@gmail.com> wrote:
>
> On Sun, 22 Jun 2025 at 15:49, James Almer
> <jamrial-at-gmail.com@ffmpeg.org> wrote:
> >
> > Fixes: libavcodec\ffv1enc_template.c:75:79: runtime error: applying zero offset to null pointer
> > Signed-off-by: James Almer <jamrial@gmail.com>
> > ---
> > Untested, as gcc-usan on Linux x86_64 doesn't complain about it, but it can be seen in
> clang-usan also reproduces this on Linux x86_64.
>
> > https://fate.ffmpeg.org/report.cgi?time=20250622122557&slot=amd64-clang-cl-msvc-asan
> >
> >  libavcodec/ffv1enc_template.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/libavcodec/ffv1enc_template.c b/libavcodec/ffv1enc_template.c
> > index aaf82159ee..7edfd2dc0f 100644
> > --- a/libavcodec/ffv1enc_template.c
> > +++ b/libavcodec/ffv1enc_template.c
> > @@ -72,7 +72,7 @@ RENAME(encode_line)(FFV1Context *f, FFV1SliceContext *sc,
> >          int diff, context;
> >
> >          context = RENAME(get_context)(f->quant_tables[p->quant_table_index],
> > -                                      sample[0] + x, sample[1] + x, sample[2] + x);
> > +                                      sample[0] + x, sample[1] + x, FF_PTR_ADD(sample[2], x));
>
> Doesn't work. FF_PTR_ADD checks offset (x) only, but the issue here is
> that sample[2]==NULL.

To be more precise, the patch fixes, "applying zero offset to null
pointer", but on next iteration it complains about:
ffv1enc_template.c:75:69: runtime error: applying non-zero offset 2 to
null pointer

- Kacper
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Re: [FFmpeg-devel] [PATCH v2 2/2] avcodec/mss2dsp: use FF_PTR_ADD to add offsets to a pointer

[Kacper Michajlow]

On Sun, 22 Jun 2025 at 15:54, James Almer
<jamrial-at-gmail.com@ffmpeg.org> wrote:
>
> Fixes: libavcodec/mss2dsp.c:59:14: runtime error: applying zero offset to null pointer
>
> Signed-off-by: James Almer <jamrial@gmail.com>
> ---
> Untested, as gcc-usan on Linux x86_64 doesn't complain about it, but it can be seen in
> https://fate.ffmpeg.org/report.cgi?time=20250622122557&slot=amd64-clang-cl-msvc-asan
>
>  libavcodec/mss2dsp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/libavcodec/mss2dsp.c b/libavcodec/mss2dsp.c
> index cc39dd637f..ace92ef9c7 100644
> --- a/libavcodec/mss2dsp.c
> +++ b/libavcodec/mss2dsp.c
> @@ -56,7 +56,7 @@ static av_always_inline void mss2_blit_wmv9_template(uint8_t *dst,
>                  }
>              }
>          }
> -        mask +=  mask_stride;
> +        mask  = FF_PTR_ADD(mask, mask_stride);

I can confirm this fixes the mss2-region test. Though I didn't check
the code if similar to other example wouldn't "non-zero offset"
warning come up. At least the test passes. Thanks.

- Kacper
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