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From: "vincent-srcware at vinc17 dot net" <sourceware-bugzilla@sourceware.org> To: glibc-bugs-regex@sourceware.org Subject: [Bug regex/29560] New: Wrong result with backreferences (test for non-prime numbers) Date: Thu, 08 Sep 2022 11:43:53 +0000 [thread overview] Message-ID: <bug-29560-132@http.sourceware.org/bugzilla/> (raw) https://sourceware.org/bugzilla/show_bug.cgi?id=29560 Bug ID: 29560 Summary: Wrong result with backreferences (test for non-prime numbers) Product: glibc Version: 2.31 Status: UNCONFIRMED Severity: normal Priority: P2 Component: regex Assignee: unassigned at sourceware dot org Reporter: vincent-srcware at vinc17 dot net CC: drepper.fsp at gmail dot com Target Milestone: --- Created attachment 14327 --> https://sourceware.org/bugzilla/attachment.cgi?id=14327&action=edit Testcase written in C zira:~> echo "1111111111111" | grep --color=always -E '^(11+)\1+$|^1?$' 1111111111111 with no colors, i.e. the matched portion is empty. This is incorrect: there shouldn't be any match, as there are 13 digits 1 and 13 is a prime number. This bug was initially reported in 2017 here: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=884075 https://debbugs.gnu.org/cgi/bugreport.cgi?bug=29613 It was also added in Bug 11053 comment 6, but Bug 11053 was actually a different bug. If the "|^1?$" part is replaced by "|^$" (matching an empty string), the issue still occurs, but if I remove it or replace it by a regexp that cannot match an empty string, the issue no longer occurs. I've attached a testcase written in C (almost the same as the one from Bug 11053 comment 6), using regcomp and regexec. This bug is still there in glibc 2.35 (Ubuntu 22.04.1 LTS / riscv64). -- You are receiving this mail because: You are on the CC list for the bug.
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