Hello, I'm trying to understand something that appears to me that it shouldn't be happening. For the project I'm working on, I'm one of 6 developers, we were using optimization option -Os. For reasons beyond the scope of this question, we've switched from this to -O2. On my CentOS 6.5, 64 bit, system, I'm using gcc 4.4.7. On the CentOS 6.0 - 6.2, 32 bit systems we build for, we're using gcc 4.4.4. I could find docs for 4.4.7 online (https://gcc.gnu.org/onlinedocs/gcc-4.4.7/gcc/). >From these docs, I found the following: -Os disables the following optimization flags: -falign-functions -falign-jumps -falign-loops -falign-labels -freorder-blocks -freorder-blocks-and-partition -fprefetch-loop-arrays -ftree-vect-loop-version Today, while doing some further research into optimization options, and investigating the -march= option, I found a gem of an option which I didn't know existed before: --help=. After a little bit of experimentation I did the following: $ gcc -Q -O2 --help=optimizers > O2settings $ gcc -Q -Os --help=optimizers > Ossettings I then diff'd them: gvimdiff O2settings Ossettings. What I wasn't expecting is that the only difference between the two files is: O2settings: -finline-functions [disabled] Ossettings: -finline-functions [enabled] Since I'm new to these options, am I doing it incorrectly? Is this compiler implementation broken? Is this normal for RHEL (from which CentOS is derived)? Any help in understanding this would be good. Just for the record the following options, which the docs say should be different but aren't: align-functions: enabled align-jumps: enabled align-labels: enabled align-loops: disabled reorder-blocks: enabled reorder-blocks-and-patition: disabled prefetch-loop-arrays: disabled tree-vect-loop-version: enabled Andy
