On Fri, Aug 5, 2016 at 10:05 PM, Jim Meyering wrote: > On Fri, Aug 5, 2016 at 10:02 PM, Jim Meyering wrote: >> On Fri, Aug 5, 2016 at 7:32 PM, Norihiro Tanaka wrote: >>> >>> On Fri, 5 Aug 2016 13:29:43 -0700 >>> Jim Meyering wrote: >>> >>>> On Fri, Aug 5, 2016 at 4:30 AM, Norihiro Tanaka wrote: >>>> > dfaoptimize() is not set fast flag even if it is success, but it is wrong. >>>> > If success, dfa matcher uses algorithm for single byte, and it is so fast. >>>> > >>>> > I think this bug does not affect for grep, but it will affect with the >>>> > patch that I just sent to gawk. >>>> >>>> Thank you for the patch. >>>> I was going to push it with the attached slightly updated log message. >>>> Note however that grep does use that -> fast member via dfasearch.c's >>>> use of the dfaisfast function. >>>> But then I realized I should at least verify with "make check", and >>>> found that this makes grep's dfa-match test fail. >>>> Thus, I will not be pushing it as-is. >>> >>> Thanks for review and adjustment. I re-ran all tests including dfa-match, >>> and they were passwd again in my machine. Next, I will re-run them on >>> Fedora24, as my machine is RHEL 6.8 and GCC 4.4.7 which is too old. >>> >>> However, I do not know why dfa-match test fails on your machine. >>> dfa-match test does not use grep. It directly calls dfa functions through >>> dfa-match-aux executable in order to test codes of dfa which grep does >>> not use. dfa-match-aux does not referer to the ->fast member. >> >> I have examined the logs, which suggest it was a false positive in a >> parallelized "make check" run, due to that test's 3-second timeout. I >> have tried repeatedly to reproduce that failure, so far without >> success, but in coreutils development, with parallelized tests, we >> fixed many hard-to-reproduce tests with small timeout limits like this >> -- most of them now use 10 seconds as the limit, so I will change this >> one, too (and several others) with the attached patch. >> >> I have pushed your patch. > > While trying to reproduce that, I ran some tests on OS X and saw > frequent failure of one of the tests, so wrote the attached to work > around what I assume is an aggressive write-to-/dev/null optimization: Dug deeper and saw it was due to grep's own new stdout-vs-/dev/null optimization. I've updated the comment and pushed this: