backport tim_one's checkin of

    revision 2.28 of cmathmodule.c

SF bug 525705:  [2.2] underflow raise OverflowException.
Another year in the quest to out-guess random C behavior.

Added macros Py_ADJUST_ERANGE1(X) and Py_ADJUST_ERANGE2(X, Y).  The latter
is useful for functions with complex results.  Two corrections to errno-
after-libm-call are attempted:

1. If the platform set errno to ERANGE due to underflow, clear errno.
   Some unknown subset of libm versions and link options do this.  It's
   allowed by C89, but I never figured anyone would do it.

2. If the platform did not set errno but overflow occurred, force
   errno to ERANGE.  C89 required setting errno to ERANGE, but C99
   doesn't.  Some unknown subset of libm versions and link options do
   it the C99 way now.

Bugfix candidate, but hold off until some Linux people actually try it,
with and without -lieee.  I'll send a help plea to Python-Dev.

diff --git a/Modules/cmathmodule.c b/Modules/cmathmodule.c
index adf76b8a331dd5e3b228c283d91dd3ad3e1d97e3..6e79680843673858e16cadab98a499b79c4738d2 100644 (file)
--- a/Modules/cmathmodule.c
+++ b/Modules/cmathmodule.c
@@ -337,8 +337,7 @@ math_1(PyObject *args, Py_complex (*func)(Py_complex))
        PyFPE_START_PROTECT("complex function", return 0)
        x = (*func)(x);
        PyFPE_END_PROTECT(x)
-       Py_SET_ERANGE_IF_OVERFLOW(x.real);
-       Py_SET_ERANGE_IF_OVERFLOW(x.imag);
+       Py_ADJUST_ERANGE2(x.real, x.imag);
        if (errno != 0)
                return math_error();
        else