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libstdc++/9922: numeric_limits<double>::quiet_NaN() returns 0
- From: mail at Franosch dot org
- To: gcc-gnats at gcc dot gnu dot org
- Date: 3 Mar 2003 16:52:44 -0000
- Subject: libstdc++/9922: numeric_limits<double>::quiet_NaN() returns 0
- Reply-to: mail at Franosch dot org
>Number: 9922
>Category: libstdc++
>Synopsis: numeric_limits<double>::quiet_NaN() returns 0
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: unassigned
>State: open
>Class: change-request
>Submitter-Id: net
>Arrival-Date: Mon Mar 03 16:56:01 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator: mail at Franosch dot org
>Release: gcc 3.2
>Organization:
>Environment:
Suse Linux 8.0
>Description:
Although the i386 architecture has support for NaN and infinity, numeric_limits<double>::quiet_NaN() and numeric_limits<double>::infinity() return 0.
The correct output of the program below would be
inf
nan
It is
0
0
instead.
#include <limits>
#include <iostream>
using namespace std;
int main() {
cerr << numeric_limits<double>::infinity() << endl;
cerr << numeric_limits<double>::quiet_NaN() << endl;
}
I know that numeric_limits<double>::has_quiet_NaN is false and therefore, returning any value in numeric_limits<double>::quiet_NaN() would not be a bug in the strict sense. But I'd consider it a serious flaw in implementation. Please fix that, as workarounds are rather ugly.
Thank you.
>How-To-Repeat:
Compile the program above with g++, execute and watch output.
>Fix:
I don't know enough about implementation details of gcc/libstdc++ across all supported architectures to provide a fix. But changing
__glibcpp_float_quiet_NaN 0.0F
to
__glibcpp_float_quiet_NaN NAN
(in case NAN is defined by <cmath>) should be trivial (same with INFINITY).
>Release-Note:
>Audit-Trail:
>Unformatted: