python
diff --git a/‎Misc/NEWS.d/next/Core and Builtins/2018-08-14-03-52-43.bpo-34400.AJD0bz.rst‎
Lines changed: 1 addition & 0 deletions b/‎Misc/NEWS.d/next/Core and Builtins/2018-08-14-03-52-43.bpo-34400.AJD0bz.rst‎
Lines changed: 1 addition & 0 deletions
diff --git a/‎Parser/parsetok.c‎
Lines changed: 1 addition & 1 deletion b/‎Parser/parsetok.c‎
Lines changed: 1 addition & 1 deletion
@@ -0,0 +1 @@
+Fix undefined behavior in parsetok.c.  Patch by Zackery Spytz.
@@ -225,7 +225,7 @@ parsetok(struct tok_state *tok, grammar *g, int start, perrdetail *err_ret,
         }
         else
             started = 1;
-        len = b - a; /* XXX this may compute NULL - NULL */
+        len = a != NULL && b != NULL ? b - a : 0;
         str = (char *) PyObject_MALLOC(len + 1);
         if (str == NULL) {
             err_ret->error = E_NOMEM;
Original file line number	Diff line number	Diff line change
@@ -0,0 +1 @@
	1	+ Fix undefined behavior in parsetok.c. Patch by Zackery Spytz.
Original file line number	Diff line number	Diff line change
@@ -225,7 +225,7 @@ parsetok(struct tok_state tok, grammar g, int start, perrdetail *err_ret,
225	225	}
226	226	else
227	227	started = 1;
228		- len = b - a; /* XXX this may compute NULL - NULL */
	228	+ len = a != NULL && b != NULL ? b - a : 0;
229	229	str = (char *) PyObject_MALLOC(len + 1);
230	230	if (str == NULL) {
231	231	err_ret->error = E_NOMEM;