public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/65892] gcc fails to implement N685 aliasing of union members Date: Wed, 09 Sep 2015 14:25:00 -0000 [thread overview] Message-ID: <bug-65892-4-X6rJQoRC2s@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-65892-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65892 --- Comment #15 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Melissa from comment #12) > A C++ conversion of the original example is below. I asked about the word > "read" on the C++ Standard Discussion (std-discussion) mailing list, because > it probably should also allow writing if it allows reads. Up to C++14 the wording said "inspect" which was changed to use "read" by http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1719 so I think limiting to reads and not writes is intended. (In reply to joseph@codesourcery.com from comment #14) > That C++ wording doesn't have any obvious bearing on what "it is > permitted" is intended to be an exception to - the general > implementation-defined nature of type punning (which I think was the > original intent in C90), or the aliasing rules. C++ doesn't support any type-punning, only reading from the common initial sequence (where the types must be compatible), so I think it can only be an exception to the aliasing rules.
next prev parent reply other threads:[~2015-09-09 14:25 UTC|newest] Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-04-25 23:59 [Bug c/65892] New: " msebor at gcc dot gnu.org 2015-04-26 0:11 ` [Bug c/65892] " pinskia at gcc dot gnu.org 2015-04-26 0:15 ` pinskia at gcc dot gnu.org 2015-04-26 0:17 ` pinskia at gcc dot gnu.org 2015-04-26 17:50 ` pinskia at gcc dot gnu.org 2015-04-26 18:00 ` msebor at gcc dot gnu.org 2015-04-27 9:00 ` rguenth at gcc dot gnu.org 2015-04-27 14:57 ` msebor at gcc dot gnu.org 2015-04-28 17:08 ` joseph at codesourcery dot com 2015-05-13 16:02 ` msebor at gcc dot gnu.org 2015-05-21 11:41 ` mpolacek at gcc dot gnu.org 2015-09-09 0:39 ` myriachan at gmail dot com 2015-09-09 0:43 ` myriachan at gmail dot com 2015-09-09 13:44 ` joseph at codesourcery dot com 2015-09-09 14:25 ` redi at gcc dot gnu.org [this message] 2015-09-09 14:42 ` redi at gcc dot gnu.org 2015-09-09 15:59 ` msebor at gcc dot gnu.org 2018-04-23 14:27 ` joseph at codesourcery 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-65892-4-X6rJQoRC2s@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).