public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "hewillk at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug libstdc++/99752] New: ranges::find_end should return empty subrange when search range is empty Date: Wed, 24 Mar 2021 14:19:26 +0000 [thread overview] Message-ID: <bug-99752-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99752 Bug ID: 99752 Summary: ranges::find_end should return empty subrange when search range is empty Product: gcc Version: 11.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: libstdc++ Assignee: unassigned at gcc dot gnu.org Reporter: hewillk at gmail dot com Target Milestone: --- In ranges::find_end implementation: 674 else 675 { 676 auto __i = ranges::next(__first1, __last1); 677 if (__first2 == __last2) 678 return {__i, __i}; when the examined range is not bidirectional_range and the search range is empty, we still do the ranges::next call, this makes the following code infinite loop: #include <algorithm> #include <ranges> int main() { auto r = std::views::iota(0); std::ranges::empty_view<int> e; std::ranges::find_end(r, e); } But according to the [alg.find.end]: "i be last1 if [first2, last2) is empty", so I think this is a library bug since in such case ranges::find_end never return. Same situations in ranges::rotate with performance loss in more rare conditions: 1573 { 1574 auto __lasti = ranges::next(__first, __last); 1575 if (__first == __middle) 1576 return {__lasti, __lasti}; 1577 if (__last == __middle) 1578 return {std::move(__first), std::move(__lasti)};
next reply other threads:[~2021-03-24 14:19 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-03-24 14:19 hewillk at gmail dot com [this message] 2021-03-24 14:48 ` [Bug libstdc++/99752] " hewillk at gmail dot com 2021-03-24 14:53 ` hewillk at gmail dot com 2021-03-24 14:56 ` redi at gcc dot gnu.org
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=bug-99752-4@http.gcc.gnu.org/bugzilla/ \ --to=gcc-bugzilla@gcc.gnu.org \ --cc=gcc-bugs@gcc.gnu.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).