[Mesa-dev] [PATCH] mesa: Don't check (offset + size <= bufObj->Size) in BindBufferRange.

[Ian Romanick]

On 02/07/2013 05:54 PM, Paul Berry wrote:
> In the documentation for BindBufferRange, OpenGL specs from 3.0
> through 4.1 contain this language:
>
>      "The error INVALID_VALUE is generated if size is less than or
>      equal to zero or if offset + size is greater than the value of
>      BUFFER_SIZE."
>
> This text was dropped from OpenGL 4.2, and it does not appear in the
> GLES 3.0 spec.
>
> Presumably the reason for the change is because come clients change
> the size of the buffer after calling BindBufferRange.  We don't want
> to generate an error at the time of the BindBufferRange call just
> because the old size of the buffer was too small, when the buffer is
> about to be resized.
>
> Since this is a deliberate relaxation of error conditions in order to
> allow clients to work, it seems sensible to apply it to all versions
> of GL, not just GL 4.2 and above.
>
> (Note that there is no danger of this change allowing a client to
> access data beyond the end of a buffer.  We already have code to
> ensure that that doesn't happen in the case where the client shrinks
> the buffer after calling BindBufferRange).
>
> Eliminates a spurious error message in the gles3 conformance test
> "transform_feedback_offset_size".
> ---
>   src/mesa/main/bufferobj.c | 7 -------
>   1 file changed, 7 deletions(-)
>
> diff --git a/src/mesa/main/bufferobj.c b/src/mesa/main/bufferobj.c
> index 7c06938..b82ba7b 100644
> --- a/src/mesa/main/bufferobj.c
> +++ b/src/mesa/main/bufferobj.c
> @@ -2152,13 +2152,6 @@ _mesa_BindBufferRange(GLenum target, GLuint index,
>                        (int) size);
>            return;
>         }
> -
> -      if (offset + size > bufObj->Size) {
> -         _mesa_error(ctx, GL_INVALID_VALUE,
> -                     "glBindBufferRange(offset + size %d > buffer size %d)",
> -                     (int) (offset + size), (int) (bufObj->Size));
> -         return;
> -      }
>      }
>
>      switch (target) {
>

For some reason, this change makes one of the UBO tests fail... while 
making the transform feedback tests not get an error.  Sigh... I'll look 
in to it...