Returns True when v==0, and yet 0 is not a power of 2.

Further, this technique - correctly applied - is essentially #9 in the list.

According to the C spec, this is expression is undefined for v == 0.

So it might return true, or return false, or start NetHack, or wipe your disk. In other words: Strictly speaken, that function is not allowed to be called for v == 0.

Mesa is a GL renderer. POT only matters in 3D for things like texture sizes. Textures aren't allowed to have zero-sized dimensions. The check for v == 0 occurs far higher up the stack than where this function's used.

We're not writing bad code, we promise. :3