Andrzej Giniewicz wrote: > g++ -c -Q -O0 --help=optimize > 0.flags > g++ -c -Q -O1 --help=optimize > 1.flags > diff 0.flags 1.flags | grep enabled > > the problem is that I was able to add all flags returned by above > commands! Is there some secret things that -O1 do instead of only > lighting those -f*** flags listened by above commands? If above > returned me: When you specify -O0 (or no -O at all) you are telling the compiler to perform no optimization, and therefore all those -f options become no-ops -- the code whose behavior would be modified by their presence has been bypassed entirely. Moreover, as the manual explains, not all optimizations have a corresponding -f flag, some are controlled directly by the -O level. So you absolutely cannot treat -O as being composed of a bunch of -f options. > the problem is that any diagnostic, stwich/case/if for that value > equal HardwareIndexBuffer::IT_32BIT or HardwareIndexBuffer::IT_16BIT > fail, simple cout on it says it's 104... always, every run - every > build with anything more than -O0... it's working on -O0 thought and > -O0 with above flags... anyway for now question is rather about what > more than flags returned by those 3 mentioned lines of shell does -O1 > do because I can just go on with disabling one feature and leaving > rest in place The only way that anyone's going to be able to offer any concrete help is with a testcase that reproduces the problem, something that is standalone and ideally reduced as much as possible. There is a small chance that there is a genuine compiler bug, but a larger chance that some aspect of your code is invoking undefined behavior which results in a program that exhibits seemingly irrational and completely nonsensical behavior. For instance recent versions of gcc can be very sensitive to aliasing violations and signed integer overflow; however that level of strictness is not enabled by default at -O1 so I suspect that it's something else. Brian
