On Tue, Nov 15, 2016 at 5:22 PM, Hal Finkel <hfin...@anl.gov> wrote: > ----- Original Message ----- >> From: "Aaron Ballman via cfe-commits" <cfe-commits@lists.llvm.org> >> To: "Joshua Hurwitz" <hurwi...@google.com> >> Cc: "cfe-commits" <cfe-commits@lists.llvm.org> >> Sent: Tuesday, November 15, 2016 12:17:28 PM >> Subject: Re: [PATCH] Warning for main returning a bool. >> >> On Fri, Oct 14, 2016 at 1:17 PM, Joshua Hurwitz via cfe-commits >> <cfe-commits@lists.llvm.org> wrote: >> > See attached. >> > >> > Returning a bool from main is a special case of return type >> > mismatch. The >> > common convention when returning a bool is that 'true' (== 1) >> > indicates >> > success and 'false' (== 0) failure. But since main expects a return >> > value of >> > 0 on success, returning a bool is usually unintended. >> >> I am not convinced that this is a high-value diagnostic. Returning a >> Boolean from main() may or may not be a bug (the returned value is >> generally a convention more than anything else). Also, why Boolean >> and >> not, say, long long or float? > > I've seen this error often enough, but I think we need to be careful about > false positives here. I recommend that we check only for explicit uses of > boolean immediates (i.e. return true; or return false;) -- these are often > bugs.
I could get behind that. > Aaron, I disagree that the return value is just some kind of convention. It > has a clear meaning. For many hosted environments, certainly. Freestanding implementations? Much less so, but I suppose this behavior is still reasonable enough for them (not to mention, there may not even *be* a main() for a freestanding implementation). > Furthermore, the behavior of the system can be quite different for a non-zero > exit code than otherwise, and users who don't understand what's going on can > find it very difficult to understand what's going wrong. That's a fair point, but my question still stands -- why only Boolean values, and not "return 0x1234567800000000ULL;" or "return 1.2;"? Combining with your idea above, if the check flagged instances where a literal of non-integral type (other than Boolean) is returned from main(), that seems like good value. ~Aaron > > Thanks again, > Hal > >> >> ~Aaron >> >> > >> > _______________________________________________ >> > cfe-commits mailing list >> > cfe-commits@lists.llvm.org >> > http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits >> > >> _______________________________________________ >> cfe-commits mailing list >> cfe-commits@lists.llvm.org >> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits >> > > -- > Hal Finkel > Lead, Compiler Technology and Programming Languages > Leadership Computing Facility > Argonne National Laboratory _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
