On Sun, May 21, 2017 at 12:18 PM, Paul Eggert <egg...@cs.ucla.edu> wrote: > Jim Meyering wrote: >> >> - -Wduplicated-branches complained about three false positives, > > In Emacs, I found -Wduplicated-branches to be useless and I disabled it. > Since it's finding only false alarms in grep, too, I suggest that we disable > it by default at the Gnulib level. My impression is that for GNU code, > -Wduplicated-branches is mostly just the compiler saying "Look how smart I > am!" rather than something that's helpful in finding real bugs.
Hi Paul, I'm inclined to wait for more exposure, and/or to let projects disable it themselves, since two of the three instances it flagged in grep were odd enough that I feel they benefit from the added attention: src/kwset.c:759: ptrdiff_t ret = (IGNORE_DUPLICATE_BRANCH_WARNING src/kwset.c-760- (kwset->trans src/kwset.c-761- ? bmexec_trans (kwset, text, size) src/kwset.c-762- : bmexec_trans (kwset, text, size))); -- src/kwset.c:908: return (IGNORE_DUPLICATE_BRANCH_WARNING src/kwset.c-909- (kwset->trans src/kwset.c-910- ? acexec_trans (kwset, text, size, kwsmatch, longest) src/kwset.c-911- : acexec_trans (kwset, text, size, kwsmatch, longest))); In those cases, the duplication is tied to compiler optimization internals, which makes me think we should have a test to ensure that this very unusual (and kludgey-feeling) technique is still required. I.e., it feels like a technique that a compiler optimizer may perform on its own, rendering this duplication unnecessary.
