Hi, I'm trying to debug some mismatching results from a program compiled with O1,2,3) and without (-O0 or nothing) optimization flags. My thought was to individually turn on optimization flags and see which one changes the program's output. Unfortunately for this plan, the binaries produced using -O1 and those flags said to be turned on by g++ in the manual (-fdefer-pop -fdelayed-branch -fguess-branch-probability -fcprop-registers -fif-conversion -fif-conversion2 -ftree-ccp -ftree-dce -ftree-dominator-opts -ftree-dse -ftree-ter -ftree-lrs -ftree-sra -ftree-copyrename -ftree-fre -ftree-ch -funit-at-a-time -fmerge-constants) do not match. I also tried without -fdelayed-branch b/c it is not supported on my architectures (i386: athlon xp, core duo) and with -fomit-frame-pointer in case that was the difference. I've tried this with g++ versions g++ (GCC) 4.2.3 (Debian 4.2.3-1) and i686-apple-darwin8-g++-4.0.1 (GCC) 4.0.1 (Apple Computer, Inc. build 5363) Is there a way to have g++ tell me which flags it is actually using when compiling a program. E.g. expand -O1 to the individual optimization flags at run time? Anyone have any other suggestions? Thanks much, C.
