When running blender --debug-gpu Display which debug facilities are available. One of these, in order of preference: - OpenGL 4.3 - KHR_debug - ARB_debug_output - AMD_debug_output All messages are logged now, not just errors. Will probably turn some of these off later. GL_DEBUG_OUTPUT_SYNCHRONOUS lets us break on errors and backtrace to the exact trouble spot. Callers of GPU_string_marker no longer pass in a message length, just the message itself (null terminated). Apple provides no GL debug logging features.