[Bug math/5680] New: math functions (atanh, log, log1p) are inconsistent in treatment of errno

["dickinsm at gmail dot com" <sourceware-bugzilla at sourceware dot org>]

In version 2.5 of glibc, on SuSE Linux 10.2, it appears that the libm functions atanh, log and log1p (and 
possibly others) are inconsistent in their handling of singularities:

log(0.0) returns -Infinity and sets errno = ERANGE
log1p(-1.0) returns -Infinity and doesn't set errno
atanh(-1.0) returns -Infinity and sets errno = EDOM.

According to the C99 standard (appendix F), and IEEE-754r, all of these operations should behave in 
the same way---they should all return -Infinity and raise the "divide-by-zero" exception. This makes 
sense mathematically:  all three function calls correspond to singularities of log type.  Admittedly, the 
C99 standard has little to say about errno, but I don't understand why these three calls behave 
differently with respect to setting of errno.

-- 
           Summary: math functions (atanh, log, log1p) are inconsistent in
                    treatment of errno
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: math
        AssignedTo: aj at suse dot de
        ReportedBy: dickinsm at gmail dot com
                CC: glibc-bugs at sources dot redhat dot com
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://sourceware.org/bugzilla/show_bug.cgi?id=5680

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