Repaired a comment and asserted a precondition.

diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index 09f7135077ef7debf5cdfc0cb711d0ffa7396dcc..8c86c386f34d10715a8f210c930ac15b8658a12c 100644 (file)
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -18,7 +18,7 @@ extern double modf (double, double *);
 #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 @@ static int
 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) {