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From "Farid Zaripov (JIRA)" <j...@apache.org>
Subject [jira] Resolved: (STDCXX-2) [MSVC] std::num_put bad formatting of 0.0 with precision and showpoint
Date Tue, 05 Jun 2007 14:38:25 GMT

     [ https://issues.apache.org/jira/browse/STDCXX-2?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Farid Zaripov resolved STDCXX-2.
--------------------------------

    Resolution: Won't Fix

The problem in the MSVC CRT. 

The expression strm << 0.0; is invokes the __rw_put_num() function, where used the CRT
function snprintf() (num_put.cpp, line 752):

snprintf (buf, size, "%#.2lg", 0.0);

The result of the snprintf() call above is: "0.00".

Info from MSDN:
-----------------------------
Flag '#' means: When used with the g or G format, the # flag forces the output value to contain
a decimal point in all cases and prevents the truncation of trailing zeros.

The precision (".2") means: The precision specifies the maximum number of significant digits
printed.
-----------------------------

The prefix 'l' before type character 'g' here should point to the long double type, but passed
double number (0.0). Anyway this is not causes any problem because of the types double and
long double have the same internal representation on the MSVC.


> [MSVC] std::num_put bad formatting of 0.0 with precision and showpoint
> ----------------------------------------------------------------------
>
>                 Key: STDCXX-2
>                 URL: https://issues.apache.org/jira/browse/STDCXX-2
>             Project: C++ Standard Library
>          Issue Type: Bug
>          Components: 22. Localization
>    Affects Versions: 4.1.2
>         Environment: Windows/MSVC
>            Reporter: Martin Sebor
>            Assignee: Farid Zaripov
>
> When compiled with MSVC (any version), the program below aborts at runtime.
> $ cat t.cpp && cl  -D_RWCONFIG=11s_msvc_7_1 -Ic:/contrib/cygwin/build/sebor/dev-hal/include
-I./../../../../include -Ic:/contrib/cygwin/build/sebor/dev-hal/examples/stdlib/manual/../include
 -Ic:/contrib/cygwin/build/sebor/dev-hal/include/ansi -I./../../../..
> -Ic:/contrib/cygwin/build/sebor/dev-hal -Ic:/contrib/cygwin/build/sebor/dev-hal/examples/stdlib/manual
-I. -nologo -GX -MLd -W3 -Zi -GA -GR -GF -GZ  -c t.cpp && link  -nologo /NODEFAULTLIB:libcpd
/debug /LIBPATH:./../../../../lib /OUT:t.exe t.obj  std11s_msvc_7_1.lib user32.lib t.cpp &&
./t.exe
> #include <cassert>
> #include <sstream>
> int main ()
> {
>     std::ostringstream strm;
>     strm.setf (strm.showpoint);
>     strm.precision (2);
>     strm << 0.0;
>     assert ("0.0" == strm.str ());
> }
> Assertion failed: "0.0" == strm.str (), file t.cpp, line 13

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