[Mesa-dev] [PATCH v2] mesa/pbo: Handle zero width, height or depth when validating access

[Ilia Mirkin]

On Wed, Sep 2, 2015 at 6:29 AM, Neil Roberts <neil at linux.intel.com> wrote:
> It's legal to call glTexSubImage with zero values for the width,
> height or depth. Previously this was breaking the PBO access
> validation because it tries to work out the last pixel accessed by
> getting the pixel at height-1 and depth-1 which would end up with
> bogus values.
>
> This was causing GL errors to be generated during the Piglit
> texsubimage test, although the test was passing anyway.
>
> v2: Also check for width == 0. Don't validate the start pointer if any
>     of the dimensions are zero.

Reviewed-by: Ilia Mirkin <imirkin at alum.mit.edu>

Note that the spec text you referred to earlier said to error if
anything out of bounds *would be accessed*, but if any of the dims are
0, then nothing is accessed...

> ---
>  src/mesa/main/pbo.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/src/mesa/main/pbo.c b/src/mesa/main/pbo.c
> index 0c16025..7762324 100644
> --- a/src/mesa/main/pbo.c
> +++ b/src/mesa/main/pbo.c
> @@ -103,6 +103,12 @@ _mesa_validate_pbo_access(GLuint dimensions,
>        /* no buffer! */
>        return GL_FALSE;
>
> +   /* If the size of the image is zero then no pixels are accessed so we
> +    * don't need to check anything else.
> +    */
> +   if (width == 0 || height == 0 || depth == 0)
> +      return GL_TRUE;
> +
>     /* get the offset to the first pixel we'll read/write */
>     start = _mesa_image_offset(dimensions, pack, width, height,
>                                format, type, 0, 0, 0);
> --
> 1.9.3
>