As far as I'm concerned, GL_OUT_OF_MEMORY does not work. I get no image if the memory request is too large. In fact, the time it takes to set the first and last entries in the memory array is around 0.001 seconds - until I hit a memory size that GL cannot handle and the time jumps to 10 seconds and I get no image. But no GL error.

So I'll just rely on the time and assume that with a jump like this the memory allocation failed.