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

I work on a large engineering application, and every now and then we see release only crashes and other problems reported by clients. Our code has 37 files (out of around 6000) where we have this at the top of the file, to turn off optimization to fix such crashes:

#pragma optimize( "", off)

(We use Microsoft Visual C++ native, 2015, but it is true for just about any compiler, except maybe Intel Fortran 2016 update 2 where we have not yet turned of any optimizations.)

If you search through the Microsoft Visual Studio feedback site you can find some optimization bugs there as well. We occasionally log some of ours (if you can reproduce it easily enough with a small section of code and you are willing to take the time) and they do get fixed, but sadly others get introduced again. smiles

Compilers are programs written by people, and any big program has bugs, trust me on that. The compiler optimization options most certainly has bugs and turning on optimization can certainly introduce bugs in your program.