On Tue, Dec 6, 2022 at 4:53 PM Alexander Monakov via Gcc <gcc@gcc.gnu.org> wrote: > > Greetings, David, community, > > I'd like to get your input on how GCC command line interface should support > making a "tiered" warning like -Warray-bounds={1,2} an error for "tier 1" > where fewer false positives are expected, and a plain warning otherwise. > > There was a recent thread mentioning the current limitation [1]: > > > This also shows nicely why I don't like warnings with levels, what if I want > > -Werror=array-bounds=2 + -Warray-bounds=1? > > Also in PR 48088 [2] there was a request to make it work for stack size usage: > > > Stumbled on this bug today. I tried to use it in more intricate way: > > > > -Wframe-larger-than=4096 -Werror=frame-larger-than=32768 > > > > which would only warn about any stack more than 4096+, but would fail on > > 32768+. > > > > Does it make sense to implement desired behaviour? > > I guess it's not many '>=number' style options in gcc. > > A problem with implementing DWIM semantics like above for -Wfoo=k > -Werror=foo=n > combination is that technically it changes its current meaning. > > If we don't want to risk that, an alternative is to introduce a new option > for selecting error threshold for a tiered warning, for example: > > -Warray-bounds=2 -Werror-level=array-bounds=1 > > Implementation-wise, we would need to extend common.opt language to annotate > which tier is more inclusive (generally smaller 'n' means fewer warnings, but > for -Wstack-usage and -Wstrict-aliasing it's the other way around).
Implementation-wise one could do a similar trick as we have for global_options vs. global_options_set - add a global_options_error copy (ick!) (and global_options_error_set!?) and have the logic that decides whether a warning is an error pick that set. Of course it's the actual pass that looks at flag_xyz which holds the magic number so that pass would need to be able to see whether it needs to look at both numbers. Btw, does '-Werror=array-bounds=2' imply that =1 kinds are diagnosed as warning? Does it enable -Warray-bounds=2? I think the DWIM behavior isn't all that clear and probably depends on the actual option we want to make it work. Richard. > > Opinions? Does anybody envision problems with going the DWIM way? > > Thanks. > Alexander > > [1] > https://inbox.sourceware.org/gcc-patches/2552ab22-916f-d0fe-2c78-d482f6ad8...@lauterbach.com/ > [2] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=48088#c5