[Mesa-dev] [PATCH 7/8] mesa: fix assertion in _mesa_drawbuffers()

[Brian Paul]

On 08/08/2014 07:43 PM, Roland Scheidegger wrote:
> Am 08.08.2014 23:20, schrieb Brian Paul:
>> Fixes failed assertion when _mesa_update_draw_buffers() was called
>> with GL_DRAW_BUFFER == GL_FRONT_AND_BACK.  The piglit gl30basic hit
>> this.
>>
>> Cc: "10.2" <mesa-stable at lists.freedesktop.org>
>> ---
>>   src/mesa/main/buffers.c |    5 +++--
>>   1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/mesa/main/buffers.c b/src/mesa/main/buffers.c
>> index b13a7af..6b4fac9 100644
>> --- a/src/mesa/main/buffers.c
>> +++ b/src/mesa/main/buffers.c
>> @@ -494,10 +494,11 @@ _mesa_drawbuffers(struct gl_context *ctx, GLuint n, const GLenum *buffers,
>>      }
>>
>>      /*
>> -    * If n==1, destMask[0] may have up to four bits set.
>> +    * destMask[0] may have up to four bits set
>> +    * (ex: glDrawBuffer(GL_FRONT_AND_BACK)).
>>       * Otherwise, destMask[x] can only have one bit set.
>>       */
>> -   if (n == 1) {
>> +   if (_mesa_bitcount(destMask[0]) > 1) {
>>         GLuint count = 0, destMask0 = destMask[0];
>>         while (destMask0) {
>>            GLint bufIndex = ffs(destMask0) - 1;
>>
>
> Hmm I don't understand how that could fail. Either you have a winsys
> fbo, in which case n has to be 1, or you have a user fbo, in which case
> you can only have the single color_buffer_x bits.
> What am I missing here?

It happened when called from _mesa_update_draw_buffers() where n = 
MaxDrawBuffers (8) and the user had previously called 
glDrawBuffer(GL_FRONT_AND_BACK).  This could only happen during a 
MakeCurrent() operation.

-Brian