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From "Farid Zaripov (JIRA)" <j...@apache.org>
Subject [jira] Commented: (STDCXX-819) [_MSC_VER] Binary representation of the numeric_limits<>::quiet_NaN() and numeric_limits<>::signaling_NaN() is different from binary representation in native STL
Date Tue, 01 Apr 2008 18:12:27 GMT

    [ https://issues.apache.org/jira/browse/STDCXX-819?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12584237#action_12584237
] 

Farid Zaripov commented on STDCXX-819:
--------------------------------------

As a result the following program outputs the deffirent results:
{noformat}
#include <float.h>
#include <iostream>
#include <limits>

int main ()
{
    std::cout << _copysign (1., std::numeric_limits<double>::quiet_NaN ()) <<
'\n';
    std::cout << _copysign (1., -std::numeric_limits<double>::quiet_NaN ()) <<
'\n';
    std::cout << _copysign (1., std::numeric_limits<double>::signaling_NaN ())
<< '\n';
    std::cout << _copysign (1., -std::numeric_limits<double>::signaling_NaN ())
<< '\n';

    return 0;
}
{noformat}

The result in MSVC STL:
{noformat}
1
-1
1
-1
{noformat}

The result in stdcxx:
{noformat}
-1
-1
1
1
{noformat}


> [_MSC_VER] Binary representation of the numeric_limits<>::quiet_NaN() and numeric_limits<>::signaling_NaN()
is different from binary representation in native STL
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: STDCXX-819
>                 URL: https://issues.apache.org/jira/browse/STDCXX-819
>             Project: C++ Standard Library
>          Issue Type: Bug
>          Components: 26. Numerics
>    Affects Versions: 4.1.2, 4.1.3, 4.1.4, 4.2.0
>         Environment: MSVC and ICC/Windows
>            Reporter: Farid Zaripov
>             Fix For: 4.2.1
>
>
> The binary representation of NAN's in stdcxx:
> {noformat}
> #define _RWSTD_FLT_QNAN_BITS  { 0, 0, '\xc0', '\xff' }
> #define _RWSTD_FLT_SNAN_BITS  { '\x1', 0, '\x80', '\x7f' }
> #define _RWSTD_DBL_QNAN_BITS  { 0, 0, 0, 0, 0, 0, '\xf8', '\xff' }
> #define _RWSTD_DBL_SNAN_BITS  { '\x1', 0, 0, 0, 0, 0, '\xf0', '\x7f' }
> #define _RWSTD_LDBL_QNAN_BITS  { 0, 0, 0, 0, 0, 0, '\xf8', '\xff' }
> #define _RWSTD_LDBL_SNAN_BITS  { '\x1', 0, 0, 0, 0, 0, '\xf0', '\x7f' }
> {noformat}
> The binary representation of the same things in MSVC STL:
> {noformat}
> #define _RWSTD_FLT_QNAN_BITS  { 0, 0, '\xc0', '\x7f' }
> #define _RWSTD_FLT_SNAN_BITS  { '\x1', 0, '\xc0', '\x7f' }
> #define _RWSTD_DBL_QNAN_BITS  { 0, 0, 0, 0, 0, 0, '\xf8', '\x7f' }
> #define _RWSTD_DBL_SNAN_BITS  { '\x1', 0, 0, 0, 0, 0, '\xf8', '\x7f' }
> #define _RWSTD_LDBL_QNAN_BITS  { 0, 0, 0, 0, 0, 0, '\xf8', '\x7f' }
> #define _RWSTD_LDBL_SNAN_BITS  { '\x1', 0, 0, 0, 0, 0, '\xf8', '\x7f' }
> {noformat}

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