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* [Bug c++/57066] New: std::logb(-inf) returns wrong value
@ 2013-04-25  7:01 bolero.murakami at gmail dot com
  2013-04-25  8:05 ` [Bug c++/57066] [4.7/4.8/4.9 Regression] " rguenth at gcc dot gnu.org
                   ` (9 more replies)
  0 siblings, 10 replies; 11+ messages in thread
From: bolero.murakami at gmail dot com @ 2013-04-25  7:01 UTC (permalink / raw)
  To: gcc-bugs


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57066

             Bug #: 57066
           Summary: std::logb(-inf) returns wrong value
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: bolero.murakami@gmail.com


auto inf = std::numeric_limits<double>::infinity();
std::cout << std::logb(-inf) << std::endl;

"-inf" is output.
it is wrong.

std::logb(-inf) should returns +inf.
> F.9.3.11 The logb functions
> - logb(±∞) returns +∞.
>From gcc-bugs-return-420917-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Thu Apr 25 07:08:12 2013
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From: "glisse at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/57064] [clarification requested] Which overload with ref-qualifier should be called?
Date: Thu, 25 Apr 2013 07:08:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idW064

--- Comment #7 from Marc Glisse <glisse at gcc dot gnu.org> 2013-04-25 07:08:07 UTC ---
(In reply to comment #6)
> void f(A &&a)
> {
>     std::move(a).p();
> }
>
> _Z1fO1A:
>         .cfi_startproc
>         jmp     _ZNR1A1pEv@PLT  #
>         .cfi_endproc
>
> Then this looks like a bug in 4.8.1.

Indeed, I get s/R/O/ with 4.9.

> But then are we in agreement that a.p() in that function above should call the
> lvalue-ref overload?

Yes.

> It does make the feature sligthly less useful for me. It
> would require writing:
>
>     return std::move(std::move(std::move(std::move(QString("%1 %2 %3 %4")
>                                                    .arg(42))
>                                           .arg(47))
>                                .arg(-42))
>                      .arg(-47));

Why? You are not naming those return values, so they are still rvalues and will
use the && overload. (not sure why Qstring doesn't provide a mutating interface
for arg)


^ permalink raw reply	[flat|nested] 11+ messages in thread
end of thread, other threads:[~2013-05-03  8:59 UTC | newest]

Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2013-04-25  7:01 [Bug c++/57066] New: std::logb(-inf) returns wrong value bolero.murakami at gmail dot com
2013-04-25  8:05 ` [Bug c++/57066] [4.7/4.8/4.9 Regression] " rguenth at gcc dot gnu.org
2013-04-25  8:41 ` mpolacek at gcc dot gnu.org
2013-04-25 10:26 ` [Bug tree-optimization/57066] " mpolacek at gcc dot gnu.org
2013-04-25 11:47 ` mpolacek at gcc dot gnu.org
2013-04-25 13:43 ` mpolacek at gcc dot gnu.org
2013-04-25 15:52 ` mpolacek at gcc dot gnu.org
2013-04-25 15:52 ` mpolacek at gcc dot gnu.org
2013-05-03  8:55 ` [Bug tree-optimization/57066] [4.7/4.8 " mpolacek at gcc dot gnu.org
2013-05-03  8:59 ` mpolacek at gcc dot gnu.org
2013-05-03  8:59 ` mpolacek at gcc dot gnu.org

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