libstdc++/8949: numeric_limits<>::denorm_min() and is_iec559 problems.

[johnb at stl dot sarov dot ru]

>Number:         8949
>Category:       libstdc++
>Synopsis:       numeric_limits<>::denorm_min() and is_iec559 problems.
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Dec 15 06:46:01 PST 2002
>Closed-Date:
>Last-Modified:
>Originator:     Eugeny Belov
>Release:        gcc version 3.2 20020903 (Red Hat Linux 8.0 3.2-7)
>Organization:
>Environment:
Red Hat Linux 8.0
>Description:
I found some problems with numeric_limits class:

1. In case denormalization is not presented (numeric_limits<>::has_denorm == false) numeric_limits<float;double;long double>::denorm_min() should be equal to corresponding numeric_limits<float;double;long double>::min(). (minimum positive normalized value, see ISO|IEC 14882 14882 "C++" 18.2.1.2(49-51))

  As an effect there is:

2. numeric_limits<float;double;long double>::denorm_min()
should be > 0.0 as stated in ISO|IEC 10967-1 "Language Independend Arithmetic" (see also ISO|IEC 14882 "C++" 18.2.1.2(49-51))

3. Possibly I am wrong here, but please look also for is_iec559 member for short,int,long types, it looks that these types shouldn`t have it set to true.

See small testcase attached also.
>How-To-Repeat:
Compile and run testcase with g++. You`ll see some failed messages.

>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
----gnatsweb-attachment----
Content-Type: text/plain; name="test18_2.cpp"
Content-Disposition: inline; filename="test18_2.cpp"

#include <limits>
#include <cassert>
#include <iostream>

using namespace std;

#define CHK(condition)  if (!(condition)) printf ("check for: %s : Failed!\n",#condition);


int main(int, char *[])
{

    CHK(0 <  numeric_limits<float>::denorm_min());
    CHK(0 <  numeric_limits<double>::denorm_min());
    CHK(0 <  numeric_limits<long double>::denorm_min());

    if (numeric_limits<float>::has_denorm == denorm_absent)
      CHK( numeric_limits<float>::denorm_min() ==  numeric_limits<float>::min());

    if (numeric_limits<double>::has_denorm == denorm_absent)
     CHK( numeric_limits<double>::denorm_min() == numeric_limits<double>::min());

    if (numeric_limits<long double>::has_denorm == denorm_absent)
     CHK( numeric_limits<long double>::denorm_min() == numeric_limits<long double>::min());

    CHK(! numeric_limits<short>::is_iec559);
    CHK(! numeric_limits<unsigned short>::is_iec559);
    CHK(! numeric_limits<int>::is_iec559);
    CHK(! numeric_limits<unsigned int>::is_iec559);
    CHK(! numeric_limits<long>::is_iec559);
    CHK(! numeric_limits<unsigned long>::is_iec559);


  return (0);
}