Mark> If you have time, could you try the attached patch and report what
    Mark> gets printed when cmath.exp(710+1.5j) is called?  On my machine, I
    Mark> get:
    ...

Looks similar here:

    % ./python
    Python 3.0 (r30:67503, Dec  3 2008, 14:46:39)
    [GCC 4.2.2] on sunos5
    Type "help", "copyright", "credits" or "license" for more information.
    >>> import cmath
    >>> cmath.exp(complex(710.0, 1.5))
    r.real, r.imag: 1.58027e+307, Inf
    Py_IS_INFINITY(r.real), Py_IS_INFINITY(r.imag): 0, 1
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    OverflowError: math range error

If I then comment back out your two printf statements and recompile, it once
again fails to raise OverflowError:

    % ./python
    Python 3.0 (r30:67503, Dec  3 2008, 14:46:39)
    [GCC 4.2.2] on sunos5
    Type "help", "copyright", "credits" or "license" for more information.
    >>> import cmath ; cmath.exp(complex(710.0, 1.5))
    (1.5802653829857376e+307+inf*j)

Very weird.  If I uncomment either of your printf statements OverflowError
seems to be raised as expected.  It's as if some register bit isn't being
set unless you reference r.real or r.imag multiple times.

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