[FFmpeg-devel] Re: [PR] avutil/mem: Add av_malloc_with_paddingz() (PR #21509)

[Kieran Kunhya via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

On Mon, 19 Jan 2026, 04:22 michaelni via ffmpeg-devel, <
ffmpeg-devel@ffmpeg.org> wrote:

> PR #21509 opened by michaelni
> URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21509
> Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21509.patch
>
> Add a av_malloc() that adds padding like AV_INPUT_BUFFER_PADDING_SIZE
> and clears it.
>
> This is a operation we commonly use so this function should simplify
> many cases
>
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
>
>
> >From cc424b2a5568ee35a3435ff58a84d2a18c1c6843 Mon Sep 17 00:00:00 2001
> From: Michael Niedermayer <michael@niedermayer.cc>
> Date: Mon, 19 Jan 2026 05:15:23 +0100
> Subject: [PATCH] avutil/mem: Add av_malloc_with_paddingz()
>
> Add a av_malloc() that adds padding like AV_INPUT_BUFFER_PADDING_SIZE
> and clears it.
>
> This is a operation we commonly use so this function should simplify
> many cases
>
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavutil/mem.c | 10 ++++++++++
>  libavutil/mem.h | 13 +++++++++++++
>  2 files changed, 23 insertions(+)
>
> diff --git a/libavutil/mem.c b/libavutil/mem.c
> index b205d3fb25..aac7ef4d12 100644
> --- a/libavutil/mem.c
> +++ b/libavutil/mem.c
> @@ -261,6 +261,16 @@ void *av_mallocz(size_t size)
>      return ptr;
>  }
>
> +void *av_malloc_with_paddingz(size_t size, size_t padding)
> +{
> +    if (size > SIZE_MAX - padding)
> +        return NULL;
> +    uint8_t *p = av_malloc(size + padding);
> +    if(p)
> +        memset(p + size, 0, padding);
> +    return p;
> +}
> +
>  void *av_calloc(size_t nmemb, size_t size)
>  {
>      size_t result;
> diff --git a/libavutil/mem.h b/libavutil/mem.h
> index ab7648ac57..6a4c144f18 100644
> --- a/libavutil/mem.h
> +++ b/libavutil/mem.h
> @@ -129,6 +129,19 @@ void *av_malloc(size_t size) av_malloc_attrib
> av_alloc_size(1);
>   */
>  void *av_mallocz(size_t size) av_malloc_attrib av_alloc_size(1);
>
> +/**
> + * Allocate a memory block with alignment suitable for all memory accesses
> + * (including vectors if available on the CPU)
> + *
> + * An additional padding will be allocated and cleared.
> + *
> + * @param size Size in bytes for the memory block to be allocated
> + * @param padding Size in bytes of padding allocated and zeroed after
> size.
> + * @return Pointer to the allocated block, or `NULL` if it cannot be
> allocated
> + * @see av_malloc()
> + */
> +void *av_malloc_with_paddingz(size_t size, size_t padding)
> av_malloc_attrib av_alloc_size(1);
> +
>  /**
>   * Allocate a memory block for an array with av_malloc().
>   *
> --
> 2.52.0
>
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Seems a bit wordy. av_malloc_paddedz instead?

Kieran
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