On 15 May, Martin Sebor wrote: >> So how about the following then? I stayed with the catch part and added >> a parameter to the warning to let the user decide on the warnings she/he >> wants to get: -Wcatch-value=n. >> -Wcatch-value=1 only warns for polymorphic classes that are caught by >> value (to avoid slicing), -Wcatch-value=2 warns for all classes that >> are caught by value (to avoid copies). And finally -Wcatch-value=3 >> warns for everything not caught by reference to find typos (like pointer >> instead of reference) and bad coding practices. > > It seems reasonable to me. I'm not too fond of multi-level > warnings since few users take advantage of anything but the > default, but this case is simple and innocuous enough that > I don't think it can do harm. > >> >> Bootstrapped and regtested on x86_64-pc-linux-gnu. >> OK for trunk? >> >> If so, would it make sense to add -Wcatch-value=1 to -Wextra or even -Wall? >> I would do this in a seperate patch, becuase I haven't checked what that >> would mean for the testsuite. > > I can't think of a use case for polymorphic slicing that's not > harmful so unless there is a common one that escapes me, I'd say > -Wall.
So that's what I committed after Jason's OK. > What are your thoughts on enhancing the warning to also handle > the rethrow case? > > Also, it seems that a similar warning would be useful even beyond > catch handlers, to help detect slicing when passing arguments to > functions by value. Especially in code that mixes OOP with the > STL (or other template libraries). Have you thought about tackling > that at some point as well? I don't have any plans to handle handle the rethrow case. A general slicing warning would be very nice to have. Actually clang-tidy has one (which is a little buggy, though). Implementing this is over my head, though. I'd rather stick with something less ambitious. > Martin > >> >> Regards, >> Volker