Common reasons for bugs in release version not present in debug mode

Question

What are the typical reasons for bugs and abnormal program behavior that manifest themselves only in release compilation mode but which do not occur when in debug mode?

Answer 1

That is possible, if you have conditional compilation so that the debug code and release code are different, and there is a bug in the code that is only use in the release mode.

Other than that, it's not possible. There are difference in how debug code and release code are compiled, and differences in how code is executed if run under a debugger or not, but if any of those differences cause anything other than a performance difference, the problem was there all along.

In the debug version the error might not be occuring (because the timing or memory allocation is different), but that doesn't mean that the error is not there. There may also be other factors that are not related to the debug mode that changes the timing of the code, causing the error to occur or not, but it all boils down to the fact that if the code was correct, the error would not occur in any of the situations.

So, no, the debug version is not OK just because you can run it without getting an error. If an error occurs when you run it in release mode, it's not because of the release mode, it's because the error was there from the start.