[Mesa-dev] [PATCH] mesa: handle zero-size buffers in MapBuffer and ranges in MapBufferRange

[Ian Romanick]

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On 08/30/2011 11:54 AM, Ian Romanick wrote:
> On 08/30/2011 10:15 AM, Marek Olaák wrote:
>> Moved from st/mesa.
>> This also fixes an assertion failure in piglit/fdo31934 on gallium drivers.
> 
> So... I guess I don't understand why the mapping can't just fail and set
> GL_OUT_OF_MEMORY.  Returning a pointer to some random bit of storage
> seems like a recipe for bugs that are excruciating for app developers to
> debug.

As another data point, and perhaps Eric can correct me if I'm wrong,
this is what the Intel drivers already do.  In intel_bufferobj_map_range
(intel_buffer_objects.c):

   if (intel_obj->buffer == NULL) {
      obj->Pointer = NULL;
      return NULL;
   }

> I'd be more inclined to return an invalid pointer, like (void
> *)0xdeadbeef, so the reads or writes through it will cause the segfault
> that the app deserves.
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