Re: libstdc++/9548: 64-bit copiling/linking: incorrect results from setf(ios::fixed) or precision(-1)

Re: libstdc++/9548: 64-bit copiling/linking: incorrect results from setf(ios::fixed) or precision(-1)

[paolo]

Synopsis: 64-bit copiling/linking: incorrect results from setf(ios::fixed) or precision(-1)

Responsible-Changed-From-To: unassigned->paolo
Responsible-Changed-By: paolo
Responsible-Changed-When: Mon Feb  3 23:41:49 2003
Responsible-Changed-Why:
    Fixing.
State-Changed-From-To: open->analyzed
State-Changed-By: paolo
State-Changed-When: Mon Feb  3 23:41:49 2003
State-Changed-Why:
    According to 22.2.2.2.2 p11, if (flags & fixed) != 0 then
    str.precision() is specified in the conversion
    specification, even when str.precision is <= 0. Admittedly,
    this is quite a weird situation, which triggers a bug
    in the current library: it prepares a "%.*f" format
    but then calls snprintf without passing the precision field.
    
    Instead of fixing the bug, I'm going to implement the
    resolution of DR231, which is in the "Ready" state:
    according to it str.precision is simply _always_ specified
    in the conversion specification.
    
    Thanks for your report,
    Paolo.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=9548

Re: libstdc++/9548: 64-bit copiling/linking: incorrect results from setf(ios::fixed) or precision(-1)

[axiong]

The following reply was made to PR libstdc++/9548; it has been noted by GNATS.

From: axiong@ca.ibm.com
To: gcc-gnats@gcc.gnu.org, nobody@gcc.gnu.org
Cc:  
Subject: Re: libstdc++/9548: 64-bit copiling/linking: incorrect results from setf(ios::fixed) or
 precision(-1)
Date: Mon, 3 Feb 2003 13:25:16 -0500

 => The C++ source code which was not attached successfully
 /*********************************************************************/
 #include <iostream>
 using namespace std;
 
 int main()
 {
    cout.setf(ios::fixed);
    cout.precision (-1);        // set precision to -1
    cout << "Output 30.5 as: " << 30.5 << "\n";
 
    return 0;
 }
 /**********************************************************************/
 

libstdc++/9548: 64-bit copiling/linking: incorrect results from setf(ios::fixed) or precision(-1)

[axiong]

>Number:         9548
>Category:       libstdc++
>Synopsis:       64-bit copiling/linking: incorrect results from setf(ios::fixed) or precision(-1)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Feb 03 18:16:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     Guan-Zhu (Andrew) Xiong
>Release:        gcc version 3.2
>Organization:
>Environment:
Linux Version 2.4.19
SuSE SLES 8 (ppc) - Kernel 2.4.19-ul1-ppc64-SMP (31)
>Description:
=> for 64-bit g++ compiling/linking: 
   "cout.setf(ios::fixed); cout.precision (-1);" 
   does not work as expected.

=> For the given C++ code, after 64-bit g++ compiling,
   if you run it then you will get output:
   -----------------
   Output 30.5 as: 30

   The correct output should be: 
   -----------------
   Output 30.5 as: 30.500000

=> Refenece: ISO C++ standard
   The value passed to precision(int i) must be greater 
   than zero. If the value is negative the floating point
   insertion operators will use the default value 
   which is 6.
>How-To-Repeat:
1) Compile the given code with "g++ 64-bit compiler"
   - e.g., /opt/cross/bin/powerpc64-linux-g++ -o hello x.C
2) Run it - hello
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: