hazohelet added a comment. In D140860#4047534 <https://reviews.llvm.org/D140860#4047534>, @aaron.ballman wrote:
> In D140860#4045224 <https://reviews.llvm.org/D140860#4045224>, @dblaikie > wrote: > >> In D140860#4044937 <https://reviews.llvm.org/D140860#4044937>, >> @aaron.ballman wrote: >> >>> In D140860#4031872 <https://reviews.llvm.org/D140860#4031872>, @dblaikie >>> wrote: >>> >>>> The risk now is that this might significantly regress/add new findings for >>>> this warning that may not be sufficiently bug-finding to be worth >>>> immediate cleanup, causing users to have to choose between extensive >>>> lower-value cleanup and disabling the warning entirely. >>>> >>>> Have you/could you run this over a significant codebase to see what sort >>>> of new findings the modified warning finds, to see if they're high quality >>>> bug finding, or mostly noise/check for whether this starts to detect >>>> certain idioms we want to handle differently? >>>> >>>> It might be hard to find a candidate codebase that isn't already >>>> warning-clean with GCC (at least Clang/LLVM wouldn't be a good candidate >>>> because of this) & maybe that's sufficient justification to not worry too >>>> much about this outcome... >>>> >>>> @aaron.ballman curious what your take on this might be >>> >>> Thank you for the ping (and the patience waiting on my response)! >>> >>> I think there's a design here that could make sense to me. >>> >>> Issuing the diagnostic when there is a literal is silly because the literal >>> value is never going to change. However, with a constant expression, the >>> value could change depending on configuration. This begs the question of: >>> what do we do with literals that are expanded from a macro? It looks like >>> we elide the diagnostic in that case, but macros also imply potential >>> configurability. So I think the design that would make sense to me is to >>> treat macro expansions and constant expressions the same way (diagnose) and >>> only elide the diagnostic when there's a (possibly string) literal. WDYT? >> >> Yeah, I'm OK with that - though I also wouldn't feel strongly about ensuring >> we warn on the macro case too - if the incremental improvement to do >> constexpr values is enough for now and a note is left to let someone know >> they could expand it to handle macros. >> >> But equally it's probably not super difficult to check if the literal is >> from a macro source location that differs from the source location of either >> of the operators, I guess? (I guess that check would be needed, so it >> doesn't warn when the macro is literally 'x && y || true' or the like. > > I mostly don't want to insist on dealing with macros in this patch, but it > does leave the diagnostic behavior somewhat inconsistent to my mind. I think > I can live without the macro functionality though, as this is still forward > progress. And yes, you'd need to check the macro location against the > operator location, I believe. Testing for a macro expansion is done with > `SourceLocation::isMacroID()`, in case @hazohelet wants to try to implement > that functionality as well. I ran the diagnostic over `microsoft/lightgbm`, `oneapi-src/oneTBB`, and `rui314/mold` builds. As a result, I found no new warnings from this patch. To my surprise, both unpatched/patched clang does not issue the `-Wlogical-op-parentheses` warning for the following code I mentioned in the previous comment. > https://github.com/oneapi-src/oneTBB/blob/e6e493f96ec8b7e2e2b4d048ed49356eb54ec2a0/src/tbbmalloc/frontend.cpp#L1266 It is because clang does not issue warnings on `x || y && z` and `x && y || z` in the result of macro expansions as of now. I found an issue on GitHub: https://github.com/llvm/llvm-project/issues/19345 > And yes, you'd need to check the macro location against the operator > location, I believe. Testing for a macro expansion is done with > `SourceLocation::isMacroID()`, in case @hazohelet wants to try to implement > that functionality as well. Thanks for your help. I think testing macro location against the operator is already handled in `DiagnoseBinOpPrecedence`, and is somewhat relevant to the issue above. Anyway, I confirm no new instances of parentheses warning in the three repositories above. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D140860/new/ https://reviews.llvm.org/D140860 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
