That's a non solution for existing code that already calls GetPixel 20 million times. It's not like I'm saying C is the best possible way to write new code. I

That's a non solution for existing code that already calls GetPixel 20 million times. It's not like I'm saying C is the best possible way to write new code. I'm just commenting why this matters for performance, and “remove all undefined behavior" from C compilers is a non-starter. Now go write Rust for all I care.