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Issue #2487. math.ldexp(x, n) raised OverflowError when n was large and

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negative; fix to return an (appropriately signed) zero instead.
This commit is contained in:
Mark Dickinson 2008-05-09 17:54:23 +00:00
parent 8bd5334a9e
commit f8476c1573
3 changed files with 78 additions and 13 deletions
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68
Modules/mathmodule.c
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@ -349,23 +349,65 @@ static PyObject *
math_ldexp(PyObject *self, PyObject *args)
{
double x, r;
int exp;
if (! PyArg_ParseTuple(args, "di:ldexp", &x, &exp))
PyObject *oexp;
long exp;
if (! PyArg_ParseTuple(args, "dO:ldexp", &x, &oexp))
return NULL;
errno = 0;
PyFPE_START_PROTECT("in math_ldexp", return 0)
r = ldexp(x, exp);
PyFPE_END_PROTECT(r)
if (Py_IS_FINITE(x) && Py_IS_INFINITY(r))
errno = ERANGE;
/* Windows MSVC8 sets errno = EDOM on ldexp(NaN, i);
we unset it to avoid raising a ValueError here. */
if (errno == EDOM)
if (PyLong_Check(oexp)) {
/* on overflow, replace exponent with either LONG_MAX
or LONG_MIN, depending on the sign. */
exp = PyLong_AsLong(oexp);
if (exp == -1 && PyErr_Occurred()) {
if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
if (Py_SIZE(oexp) < 0) {
exp = LONG_MIN;
}
else {
exp = LONG_MAX;
}
PyErr_Clear();
}
else {
/* propagate any unexpected exception */
return NULL;
}
}
}
else if (PyInt_Check(oexp)) {
exp = PyInt_AS_LONG(oexp);
}
else {
PyErr_SetString(PyExc_TypeError,
"Expected an int or long as second argument "
"to ldexp.");
return NULL;
}
if (x == 0. || !Py_IS_FINITE(x)) {
/* NaNs, zeros and infinities are returned unchanged */
r = x;
errno = 0;
} else if (exp > INT_MAX) {
/* overflow */
r = copysign(Py_HUGE_VAL, x);
errno = ERANGE;
} else if (exp < INT_MIN) {
/* underflow to +-0 */
r = copysign(0., x);
errno = 0;
} else {
errno = 0;
PyFPE_START_PROTECT("in math_ldexp", return 0);
r = ldexp(x, (int)exp);
PyFPE_END_PROTECT(r);
if (Py_IS_INFINITY(r))
errno = ERANGE;
}
if (errno && is_error(r))
return NULL;
else
return PyFloat_FromDouble(r);
return PyFloat_FromDouble(r);
}
PyDoc_STRVAR(math_ldexp_doc,