On 26.08.24 19:56, Thiago Macieira wrote: > The Lakos Rule says that methods that only methods with wide contracts should > be noexcept. That is, if your method has a precondition, it should not be > noexcept. > > This is apparently predicated on the fact that the preconditions will be > implementable as C++ contracts some time in the future and that some compilers > or compilation modes may turn contract verifications into runtime checks. > Moreover, said checks can be implemented by throwing an exception indicating a > contract violation. Alternatively, an application could replace the Qt > assertion handler with one that throws (which is currently not possible > because qt_assert is noexcept, therefore this replacement is not supported). > > I'd like to request Qt code not obey that rule. In my opinion, it's a defect > in the contract implementation rather than on Qt code. The *pre* condition > indicates something that must be true before the method is called and > therefore the method's own noexcept specification does not apply *yet*.
I don't see a proposal for an alternative rule in the above. Please provide a) a new rule and b) rationale for it. Bonus points for being implementable in a static checker like Clazy or Axivion. Background: The Lakos Rule has been the status quo for the last decade in C++ and Qt. It is easy to explain and should be pretty straight-forward to check. I don't think we as the Qt project are qualified to come up with a rule that differs from what std is doing, so I strongly suggest not to try. Alternatively, we need _very_ good reasons to diverge from what std is doing, not just one developer's hunch. Allowing Q_ASSERT to throw into QtTest would be a big step towards better testing of failure conditions, something that surely becomes more important over time as pressure from legislators on unsafe-memory language libraries increases. Any function in-between that's incorrectly marked as noexcept prevents that check from working, until it can be fixed in the next major release (removing noexcept is BiC). So not only do we have _no_ incentive to diverge from std, we also have a rather large incentive to keep doing what std is doing. Thanks, Marc -- Marc Mutz <marc.m...@qt.io> (he/his) Principal Software Engineer The Qt Company Erich-Thilo-Str. 10 12489 Berlin, Germany www.qt.io Geschäftsführer: Mika Pälsi, Juha Varelius, Jouni Lintunen Sitz der Gesellschaft: Berlin, Registergericht: Amtsgericht Charlottenburg, HRB 144331 B -- Development mailing list Development@qt-project.org https://lists.qt-project.org/listinfo/development
