GCC: program doesn't work with compilation option -O3

Question

I\'m writing a C++ program that doesn\'t work (I get a segmentation fault) when I compile it with optimizations (options -O1, -O2, -O3, etc.), but it works just fine when I

Answer 1

You may be running into an aliasing problem (or it could be a million other things). Look up the -fstrict-aliasing option.

This kind of question is impossible to answer properly without more information.