[Mesa-dev] default texture buffer object

[Dave Airlie]

On Mon, Jan 14, 2013 at 5:09 AM, Eric Anholt <eric at anholt.net> wrote:
> Dave Airlie <airlied at gmail.com> writes:
>
>> Hi,
>>
>> so the gallium state tracker falls over with one of the TBO tests and
>> I wsa wondering what the correct solution is.
>>
>> After the tests run, the test leaves the fragment shader bound, but
>> has deleted the texture object and the buffer object,
>> so we just have the ctx->Shared->DefaultTex[TEXTURE_BUFFER_INDEX],
>> however since this has no buffer object bound
>> the code falls over.
>>
>> Now the docs say the results of sampling from an tbo with no buffer
>> object is undefined, but crashing isn't probably the right solution
>>
>> The intel driver seems to deal with there being no backing BO by
>> binding an object at address 0 with w/h = 0.
>
> I actually had written a test to make sure that rendering with no BO
> didn't crash, before realizing that you actually were allowed to crash
> for "undefined" behavior.  I'd be tempted to just fix the test that's
> unintentionally testing this and if we want to avoid the crash, put in
> the independent test for it.  Let me know if you want that.

Yeah I suppose that makes more sense, fixing the formats test is just
a matter of putting
glUseProgram(0) at the end before we go back to glClear, but it might
be good to have an
explicit test to just avoid the crash.

Dave.