public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "xuejuncao at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/67433] ?: expression returns unexpected value when condition is a bool variable which memory is not true/false Date: Wed, 02 Sep 2015 07:53:00 -0000 [thread overview] Message-ID: <bug-67433-4-TY21OqVE7g@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-67433-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67433 xuejuncao <xuejuncao at gmail dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- Summary|?: expresion returns |?: expression returns |unexpected value when |unexpected value when |condition is a bool |condition is a bool |variable and it's value |variable which memory is |above 1 |not true/false --- Comment #1 from xuejuncao <xuejuncao at gmail dot com> --- #include <stdio.h> #include <stdbool.h> #include <string.h> int main() { union u { bool b; char c; } u; memset((void *)&u, -1, sizeof(u)); bool b = (u.b ? 1 : 0); int i = (u.b ? 1 : 0); int j = (u.b ? 1 : 2); printf("b = %d, i = %d, j = %d\n", b, i, j); return 0; } without optimisation, the output is: b = 1, i = 255, j = 1 with -O2, is: b = 255, i = 255, j = 1
next parent reply other threads:[~2015-09-02 7:53 UTC|newest] Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <bug-67433-4@http.gcc.gnu.org/bugzilla/> 2015-09-02 7:53 ` xuejuncao at gmail dot com [this message] 2015-09-02 7:58 ` pinskia at gcc dot gnu.org 2015-09-02 8:11 ` xuejuncao at gmail dot com 2015-09-02 8:20 ` xuejuncao at gmail dot com 2015-09-02 8:21 ` pinskia at gcc dot gnu.org 2015-09-02 8:22 ` pinskia at gcc dot gnu.org 2015-09-02 8:33 ` pinskia at gcc dot gnu.org 2015-09-02 9:17 ` trippels at gcc dot gnu.org 2015-09-02 10:15 ` xuejuncao at gmail dot com 2015-09-02 10:20 ` rguenth at gcc dot gnu.org 2015-09-02 10:59 ` xuejuncao at gmail dot com
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-67433-4-TY21OqVE7g@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).