mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-08-04 08:59:19 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 11

SF bug 705231: Assertion failed, python aborts.

Browse source 
float_pow():  Don't let the platform pow() raise -1.0 to an integer power
anymore; at least glibc gets it wrong in some cases.  Note that
math.pow() will continue to deliver wrong (but platform-native) results
in such cases.
This commit is contained in:
Tim Peters 2003-05-24 20:18:24 +00:00
parent 0ed39577dd
commit e87568dd9a
3 changed files with 61 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

44
Objects/floatobject.c
View file

@ -572,10 +572,39 @@ float_pow(PyObject *v, PyObject *w, PyObject *z)
}
return PyFloat_FromDouble(0.0);
}
if (iv < 0.0 && iw != floor(iw)) {
PyErr_SetString(PyExc_ValueError,
"negative number cannot be raised to a fractional power");
return NULL;
if (iv < 0.0) {
/* Whether this is an error is a mess, and bumps into libm
* bugs so we have to figure it out ourselves.
*/
if (iw != floor(iw)) {
PyErr_SetString(PyExc_ValueError, "negative number "
"cannot be raised to a fractional power");
return NULL;
}
/* iw is an exact integer, albeit perhaps a very large one.
* -1 raised to an exact integer should never be exceptional.
* Alas, some libms (chiefly glibc as of early 2003) return
* NaN and set EDOM on pow(-1, large_int) if the int doesn't
* happen to be representable in a *C* integer. That's a
* bug; we let that slide in math.pow() (which currently
* reflects all platform accidents), but not for Python's **.
*/
if (iv == -1.0 && !Py_IS_INFINITY(iw) && iw == iw) {
/* XXX the "iw == iw" was to weed out NaNs. This
* XXX doesn't actually work on all platforms.
*/
/* Return 1 if iw is even, -1 if iw is odd; there's
* no guarantee that any C integral type is big
* enough to hold iw, so we have to check this
* indirectly.
*/
ix = floor(iw * 0.5) * 2.0;
return PyFloat_FromDouble(ix == iw ? 1.0 : -1.0);
}
/* Else iv != -1.0, and overflow or underflow are possible.
* Unless we're to write pow() ourselves, we have to trust
* the platform to do this correctly.
*/
}
errno = 0;
PyFPE_START_PROTECT("pow", return NULL)
@ -583,8 +612,11 @@ float_pow(PyObject *v, PyObject *w, PyObject *z)
PyFPE_END_PROTECT(ix)
Py_ADJUST_ERANGE1(ix);
if (errno != 0) {
assert(errno == ERANGE);
PyErr_SetFromErrno(PyExc_OverflowError);
/* We don't expect any errno value other than ERANGE, but
* the range of libm bugs appears unbounded.
*/
PyErr_SetFromErrno(errno == ERANGE ? PyExc_OverflowError :
PyExc_ValueError);
return NULL;
}
return PyFloat_FromDouble(ix);