[Bug math/6786] New: erfc() does not set errno for underflow

[Bug math/6786] New: erfc() does not set errno for underflow

[mtk dot manpages at gmail dot com]

When erfc() is given an argument that causes underflow (e.g., erfc(106.9) on
x8632) it raises an underflow exception.  However, errno is not set.  It should
be set to ERANGE for this case.

Background: 
On error, many glibc math functions both set errno and raise an exception
(fetestexcept(3)).  For example, the following  function all do this: acos(),
asin(), cosh(), sinh(), acosh(), asinh(), exp(), exp2(), ldexp(), log(),
log10(), log2().  However, there is much inconsistency.  Some functions raise an
exception, but don't set errno.  Some functions set errno for some errors, but
not others.  A few set errno, but don't raise an exception.  This series of bug
reports documents deviations from what I consider the ideal: all functions
should BOTH set errno AND raise an exception for all errors.

All of these reports relate to tests on glibc 2.8 (as provided by SUSE 11.0).

-- 
           Summary: erfc() does not set errno for underflow
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
        AssignedTo: aj at suse dot de
        ReportedBy: mtk dot manpages at gmail dot com
                CC: glibc-bugs at sources dot redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=6786

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[Bug math/6786] erfc() does not set errno for underflow

[mtk dot manpages at gmail dot com]

------- Additional Comments From mtk dot manpages at gmail dot com  2008-07-31 08:52 -------
Created an attachment (id=2851)
 --> (http://sourceware.org/bugzilla/attachment.cgi?id=2851&action=view)
test program

(I got the underflow value wrong in my initial report. I think 106.9 gives
underflow with the long double variant.  27 doies the trick for the double
version.)

Sample run showing problem:

$ /tmp/mt_erfc 27
errno == 0
fetestexcept() says:  FE_UNDERFLOW FE_INEXACT
erfc(2.70000000000000000e+01)=5.23704643935262924e-319
0 FE_UNDERFLOW subnormal


-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=6786

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