It's more the fact that that's /all/ the warning improvement has found so far. If it was 8 false positives & also found 80 actionable bugs/bad code, that'd be one thing.
Now, admittedly, maybe it would help find bugs that people usually catch with a unit test, etc but never make it to checked in code - that's always harder to evaluate though Google has some infrastructure for it at least. On Tue, Apr 10, 2018 at 9:07 AM John McCall <rjmcc...@gmail.com> wrote: > If you have a concrete suggestion of how to suppress this warning for > user-defined operators just in unit tests, great. I don’t think 8 > easily-suppressed warnings is an unacceptably large false-positive problem, > though. Most warnings have similar problems, and the standard cannot > possibly be “must never fire on code where the programmer is actually happy > with the behavior”. > > John. > On Tue, Apr 10, 2018 at 17:12 Nico Weber <tha...@chromium.org> wrote: > >> "False positive" means "warning fires but didn't find anything >> interesting", not "warning fires while being technically correct". So all >> these instances do count as false positives. >> >> clang tries super hard to make sure that every time a warning fires, it >> is useful for a dev to fix it. If you build with warnings enabled, that >> should be a rewarding experience. Often, this means dialing back a warning >> to not warn in cases where it would make sense in theory when in practice >> the warning doesn't find much compared to the amount of noise it generates. >> This is why for example clang's -Woverloaded-virtual is usable while gcc's >> isn't (or wasn't last I checked a while ago) – gcc fires always when it's >> technically correct to do so, clang only when it actually matters in >> practice. >> >> On Tue, Apr 10, 2018 at 10:21 AM, Roman Lebedev via Phabricator via >> cfe-commits <firstname.lastname@example.org> wrote: >> >>> lebedev.ri added a comment. >>> >>> In https://reviews.llvm.org/D44883#1063003, @thakis wrote: >>> >>> > This landing made our clang trunk bots do an evaluation of this >>> warning :-P It fired 8 times, all false positives, and all from unit tests >>> testing that operator= works for self-assignment. ( >>> https://chromium-review.googlesource.com/c/chromium/src/+/1000856 has >>> the exact details) It looks like the same issue exists in LLVM itself too, >>> https://reviews.llvm.org/D45082 >>> >>> >>> Right, i guess i only built the chrome binary itself, not the tests, >>> good to know... >>> >>> > Now tests often need warning suppressions for things like this, and >>> this in itself doesn't seem horrible. However, this change takes a warning >>> that was previously 100% noise-free in practice and makes it pretty noisy – >>> without a big benefit in practice. I get that it's beneficial in theory, >>> but that's true of many warnings. >>> > >>> > Based on how this warning does in practice, I think it might be better >>> for the static analyzer, which has a lower bar for false positives. >>> >>> Noisy in the sense that it correctly diagnoses a self-assignment where >>> one **intended** to have self-assignment. >>> And unsurprisingly, it happened in the unit-tests, as was expected ^ in >>> previous comments. >>> **So far** there are no truly false-positives noise (at least no reports >>> of it). >>> >>> We could help workaround that the way i initially suggested, by keeping >>> this new part of the diag under it's own sub-flag, >>> and suggest to disable it for tests. But yes, that >>> >> >>> >>> Repository: >>> rC Clang >>> >>> https://reviews.llvm.org/D44883 >>> >>> >>> >>> _______________________________________________ >>> cfe-commits mailing list >>> email@example.com >>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits >>> >>
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