Can compiler optimization introduce bugs?

Question

Today I had a discussion with a friend of mine and we debated for a couple of hours about \"compiler optimization\".

I defended the point that sometimes

Answer 1

To combine the other posts:

1. Compilers do occasionally have bugs in their code, like most software. The "smart people" argument is completely irrelevant to this, as NASA satellites and other apps built by smart people also have bugs. The coding that does optimization is different coding from that which doesn't, so if the bug happens to be in the optimizer then indeed your optimized code may contain errors while your non-optimized code will not.

2. As Mr. Shiny and New pointed out, it's possible for code that is naive with regard to concurrency and/or timing issues to run satisfactorily without optimization yet fail with optimization as this may change the timing of execution. You could blame such a problem on the source code, but if it will only manifest when optimized, some people might blame optimization.