"It's not the compiler" is always a good first-approximation. And then bizarre things happen.. I ran into this with MSVC just a few months back. After an updat

"It's not the compiler" is always a good first-approximation. And then bizarre things happen.. I ran into this with MSVC just a few months back. After an update of the compiler, a bizarre display issue emerged with lines criss-crossing the screen. Turning off optimizations to debug made the problem go away. Eventually tracked down the issue to the following line of code: if (abs(delta.y) > abs(delta.x)) { … changing this to: bool yDominant = abs(delta.y) > abs(delta.x); if (yDominant) { … fixed the problem. Yikes! I don't know if they fixed the optimization in question by now.