public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "18307130172 at fudan dot edu.cn" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/106131] New: -fstrict-aliasing breaks normal program that does not use any pointer or reference Date: Wed, 29 Jun 2022 02:05:06 +0000 [thread overview] Message-ID: <bug-106131-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106131 Bug ID: 106131 Summary: -fstrict-aliasing breaks normal program that does not use any pointer or reference Product: gcc Version: 12.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: 18307130172 at fudan dot edu.cn Target Milestone: --- Target: x86_64-pc-linux-gnu Created attachment 53220 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53220&action=edit preprocessed source file My program does not use any pointer or reference but is affected by -fstrict-aliasing. Here is a minimal example to manifest this issue: #include <vector> #include <iostream> using Pair = std::pair<int, int>; std::vector<Pair> f = {{0, -11}, {0, -8}, {1, 2}}; int foo(Pair x, Pair y) { return std::max(x.second, y.second); } int main() { for (int J = 0; J < 1; J++) { f[J] = f[0]; if(J == 0) f[J] = f[2]; std::cout << foo(f[J], f[1]) << std::endl; } } Save it to main.cpp and compile it with: g++ -O2 main.cpp The expected output should be "2", but the optimized build output "-8". If compiled with "-O2 -fno-strict-aliasing", the output is correct.
next reply other threads:[~2022-06-29 2:05 UTC|newest] Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-06-29 2:05 18307130172 at fudan dot edu.cn [this message] 2022-06-29 2:09 ` [Bug c++/106131] " 18307130172 at fudan dot edu.cn 2022-06-29 2:36 ` pinskia at gcc dot gnu.org 2022-06-29 9:26 ` redi at gcc dot gnu.org 2022-06-29 19:20 ` [Bug c++/106131] [10/11/12/13 Regression] " pinskia at gcc dot gnu.org 2022-06-29 19:21 ` pinskia at gcc dot gnu.org 2022-06-29 19:38 ` mpolacek at gcc dot gnu.org 2022-06-29 19:39 ` [Bug tree-optimization/106131] " mpolacek at gcc dot gnu.org 2022-06-29 19:39 ` mpolacek at gcc dot gnu.org 2022-06-30 0:50 ` 18307130172 at fudan dot edu.cn 2022-06-30 6:47 ` rguenther at suse dot de 2022-06-30 7:57 ` rguenth at gcc dot gnu.org 2022-06-30 8:31 ` rguenth at gcc dot gnu.org 2022-07-01 6:53 ` cvs-commit at gcc dot gnu.org 2022-07-01 6:54 ` [Bug tree-optimization/106131] [10/11/12 " rguenth at gcc dot gnu.org 2022-07-19 11:38 ` cvs-commit at gcc dot gnu.org 2022-10-11 13:04 ` [Bug tree-optimization/106131] [10/11 " cvs-commit at gcc dot gnu.org 2022-10-14 10:47 ` [Bug tree-optimization/106131] [10 " cvs-commit at gcc dot gnu.org 2022-10-14 10:48 ` rguenth 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-106131-4@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).