On 04/11/2012 05:18 PM, Ian Lance Taylor wrote: > Andrew Haley <a...@redhat.com> writes: > >> On 04/05/2012 01:28 PM, Michael Veksler wrote: >> >>> As for specific warnings, I hate that the the code (a&&b || c&&d), >>> which did not cause a warning on older gcc version now gives a >>> warning. I would not want it on by default since it forces users to >>> write too many parentheses in ((a&&b)||(c&&d)) which makes the >>> expression less readable. What next? Warn about (a*b+c*d) ? I would >>> hate to write ((a*b)+(c*d)). >>> >>> Sure, the precedence of: << vs. +; & vs. == ; & vs. && ; is less >>> clear and deserves a warning, but: & vs. | ; && vs. || ; are at >>> least as common as * vs. + that programmers ought to know them. >> >> Absolutely so, yes. I'd consider this a bug in gcc, just as if it >> warned for arithmetic. > > This one is an interesting case, since there are strong arguments on > both sides. > > I enabled the C++ warning about the precedence of && and || (it's been > in C for many years). It found real bugs in real code, bugs that had > existed for years.
It's the balance with false positives, as usual. If you're looking for a good example of a warning that is useful but still triggers with perfectly legal (and reasonable) code, this is a great example. Andrew.
