Created attachment 92635 [details]
Patch against git 6ec210989fa10847091f06fcfcab77dd07618dff
Mesa crashes instead of returning GL_INVALID_ENUM when GL_NONE is passed as an argument to glReadBuffer.
Attached is a patch to achieve the desired behavior.
Can you post the backtrace? GL_NONE is a valid value for glReadBuffer() and there seems toe be plenty of Piglit tests using this so you might be hitting some corner case here.
Created attachment 92646 [details]
The source code line in
Fixed with commit f7c118ffbfdafaccd4ec05d4a040d07e120c5090
on Feb 20, 2017 at 08:43:58.
(provided by the Example extension).