public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "joseph at codesourcery dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/59448] Code generation doesn't respect C11 address-dependency Date: Tue, 10 Dec 2013 17:47:00 -0000 [thread overview] Message-ID: <bug-59448-4-FShxPWVHMQ@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-59448-4@http.gcc.gnu.org/bugzilla/> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59448 --- Comment #3 from joseph at codesourcery dot com <joseph at codesourcery dot com> --- The code generated appears fully in accordance with the semantics of C11. You refer to 5.1.2.4#14, the definition of "carries a dependency". The term "carries a dependency" is used outside its own definition only in the definition of "dependency-ordered before". This testcase contains no instances of "dependency-ordered before", because any such instance must directly or indirectly involve a case of "A performs a release operation on an atomic object M, and, in another thread, B performs a consume operation on M and reads a value written by any side effect in the release sequence headed by A", and the test involves no atomic objects. "dependency-ordered before", in turn, is only used in the definition of "inter-thread happens before", which is only used in the definition of "happens before". Please provide a complete testcase, using _Atomic or <stdatomic.h> (and so using GCC 4.9, of course) that demonstrates any bug: that is, that does not contain a data race according to the C11 definition, but where GCC has reordered code in a way that introduces one (and so one can be demonstrated by enough iterations of the threads in the testcase) - or where the code generated fails some other semantics associated with "happens before", such as those for "visible side effect" and "visible sequence of side effects". I expect any such bug, and fix, would probably not be a front-end issue but an issue with the atomic built-in functions failing to ensure appropriate ordering in the presence of dependencies involving atomic operations (dependencies not involving such operations having no effects on C11 semantics).
next prev parent reply other threads:[~2013-12-10 17:47 UTC|newest] Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-12-10 12:07 [Bug target/59448] New: ARM code " algrant at acm dot org 2013-12-10 14:19 ` [Bug c/59448] Code " rearnsha at gcc dot gnu.org 2013-12-10 16:43 ` algrant at acm dot org 2013-12-10 17:47 ` joseph at codesourcery dot com [this message] 2013-12-12 18:07 ` [Bug middle-end/59448] " algrant at acm dot org 2013-12-16 14:38 ` joseph at codesourcery dot com 2014-01-20 8:52 ` algrant at acm dot org 2014-01-20 9:02 ` pinskia at gcc dot gnu.org 2014-01-20 10:13 ` algrant at acm dot org 2014-01-20 14:21 ` joseph at codesourcery dot com 2014-01-23 22:28 ` torvald at gcc dot gnu.org 2014-02-17 10:26 ` algrant at acm dot org 2014-02-17 21:03 ` torvald at gcc dot gnu.org 2014-02-17 22:22 ` algrant at acm dot org 2014-10-28 10:56 ` ramana at gcc dot gnu.org 2014-10-28 12:48 ` amacleod at redhat dot com 2014-10-28 13:43 ` joseph at codesourcery dot com 2014-10-28 17:37 ` t.p.northover at gmail dot com 2014-10-29 1:48 ` joseph at codesourcery dot com 2014-10-29 9:23 ` torvald at gcc dot gnu.org 2014-10-30 21:08 ` torvald at gcc dot gnu.org 2014-10-30 22:16 ` filter-gcc at preshing dot com 2014-11-24 12:13 ` filter-gcc at preshing dot com 2015-01-14 13:59 ` amacleod at redhat dot com 2022-01-15 1:47 ` pinskia at gcc dot gnu.org 2022-01-15 1:53 ` pinskia 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-59448-4-FShxPWVHMQ@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).