Repaired a comment and asserted a precondition.
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index 09f7135..8c86c38 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -18,7 +18,7 @@
#endif
/* RED_FLAG 12-Oct-2000 Tim
- * What CHECK does if errno != 0 and x is a NaN is a platform-dependent crap
+ * What CHECK does if errno == 0 and x is a NaN is a platform-dependent crap
* shoot. Most (but not all!) platforms will end up setting errno to ERANGE
* then, but EDOM is probably better.
*/
@@ -38,6 +38,7 @@
is_error(double x)
{
int result = 1; /* presumption of guilt */
+ assert(errno); /* non-zero errno is a precondition for calling */
if (errno == EDOM)
PyErr_SetString(PyExc_ValueError, "math domain error");
else if (errno == ERANGE) {