Why not always use compiler optimization?

Question

One of the questions that I asked some time ago had undefined behavior, so compiler optimization was actually causing the program to break.

But if there is no undefi

Answer 1

The reason is that you develop one application (debug build) and your customers run completely different application (release build). If testing resources are low and/or compiler used is not very popular, I would disable optimization for release builds.

MS publishes numerous hotfixes for optimization bugs in their MSVC x86 compiler. Fortunately, I've never encountered one in real life. But this was not the case with other compilers. SH4 compiler in MS Embedded Visual C++ was very buggy.