public inbox for gcc-prs@sourceware.org help / color / mirror / Atom feed
From: Thomas Kunert <kunert@physik.tu-dresden.de> To: nobody@gcc.gnu.org Cc: gcc-prs@gcc.gnu.org, Subject: Re: c++/9982: placement new returns wrong value Date: Fri, 07 Mar 2003 13:26:00 -0000 [thread overview] Message-ID: <20030307132600.22182.qmail@sources.redhat.com> (raw) The following reply was made to PR c++/9982; it has been noted by GNATS. From: Thomas Kunert <kunert@physik.tu-dresden.de> To: bangerth@dealii.org, gcc-bugs@gcc.gnu.org, gcc-prs@gcc.gnu.org, kunert@physik.tu-dresden.de, nobody@gcc.gnu.org, gcc-gnats@gcc.gnu.org Cc: Subject: Re: c++/9982: placement new returns wrong value Date: Fri, 07 Mar 2003 14:21:54 +0100 bangerth@dealii.org wrote: > Synopsis: placement new returns wrong value > > State-Changed-From-To: open->closed > State-Changed-By: bangerth > State-Changed-When: Thu Mar 6 19:41:07 2003 > State-Changed-Why: > This is not a bug. For array expressions, the compiler puts > the number of array elements into the first slot (pointed to > by the placement argument), and only then the elements of the > array. This is so because delete[] needs this information. > There is no delete[] corresponding to the placement new[], hence this is useless. In many cases the compiler actually seems to figure that out: changing the line A * b = new(a) A[3]; to A * b = new((void*)a) A[3]; makes a and b pointing to the same position. Why is the difference here? But you are right, the standard seems to allow any behavior. However, this makes operator new(a)[] pretty much useless, since the final position of the new array is undefined and one does not even know the necessary size of the provided memory region. Thomas http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=9982
next reply other threads:[~2003-03-07 13:26 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2003-03-07 13:26 Thomas Kunert [this message] -- strict thread matches above, loose matches on Subject: below -- 2003-03-06 19:41 bangerth 2003-03-06 18:46 kunert
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=20030307132600.22182.qmail@sources.redhat.com \ --to=kunert@physik.tu-dresden.de \ --cc=gcc-prs@gcc.gnu.org \ --cc=nobody@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).