https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71618
Martin Sebor <msebor at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED CC| |msebor at gcc dot gnu.org Resolution|--- |INVALID --- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> --- I suspect you're missing an aspect of GCC optimization options that's not very apparent from reading the manual alone and that's been the topic of enough similar questions in the past to get its own FAQ entry: https://gcc.gnu.org/wiki/FAQ#optimization-options Basically, -ON options are more than just aggregates of -fxxx options. They may implicitly enable additional optimizations that other optimizations need to do their work. (You may find the output of gcc -help=optimizers helpful here, though it too needs to be interpreted with the above caveat in mind.) I resolve this bug as Invalid because it doesn't report a problem but, IIUC, rather asks a question. I suggest to ask questions about using GCC on the gcc-help list. If you do think there is a problem with GCC or its documentation, please open a new bug and describe what you think is wrong and what you expect.