Am 22.03.22 um 17:38 schrieb Paul Eggert: > Today, Carlo Arenas pointed out[1] that GNU grep didn't work around > PCRE2 bug 2642, which Git grep has a workaround for. While installing > a GNU grep patch to fix this[2] I noticed that Git's workaround > appears to be too pessimistic: on older PCRE2 libraries Git grep sets > PCRE2_NO_START_OPTIMIZE even when PCRE2_CASELESS is not set. > > Attached is a patch to Git that I just now cobbled up and have not > even compiled, much less tested. Please feel free to ignore it, as it > would merely improve performance on older, buggy PCRE2 libraries and > that might not be worth your trouble. I'm sending this email as more > of a thank-you for letting us know indirectly of the PCRE2 bug. > > [1]: https://lists.gnu.org/r/grep-devel/2022-03/msg00004.html > [2]: https://lists.gnu.org/r/grep-devel/2022-03/msg00005.html Interesting. So you say bug 2642 [3] requires the flag PCRE2_CASELESS (i.e. --ignore-case) to be triggered. (That's probably documented in Bugzilla, but I'm not authorized to access it.) However, the looser check works around another bug, if only by accident. I believe it was fixed upstream by [4]. That other bug was discussed in the thread Carlo linked to, which started at [5]. You should be able to reproduce it with something like this (search for leading white-space in a Unicode haystack): $ echo ' Halló' | grep -P '^\s' An affected version of PCRE2 would loop forever. However, I can only test any of that with CI jobs, not locally, so please take my findings with a heap of salt. René [3] https://bugs.exim.org/show_bug.cgi?id=2642 [4] https://github.com/PhilipHazel/pcre2/commit/e0c6029 [5] https://lore.kernel.org/git/20220129172542.GB2581@xxxxxxxxxx/
