It may even be a good idea to move asinh, copysign and log1p to a new
file Python/pymath.c and add compensatory implementations of acosh,
atanh and expm1, too. The math related code in pyport.h could then be
moved to Include/pymath.h. In the past some people have asked me to
implement the reverse hyperbolic functions for the math module.

This is beyond a simple fix for the cmath module and should be discussed
on the python-dev list first.