closes bpo-34400: Fix undefined behavior in parsetok(). (GH-4439)
Avoid undefined pointer arithmetic with NULL.
(cherry picked from commit 7c4ab2afb17b99eb3f61f9c73cbd548b5e0ad2c0)
Co-authored-by: Zackery Spytz <zspytz@gmail.com>
diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-08-14-03-52-43.bpo-34400.AJD0bz.rst b/Misc/NEWS.d/next/Core and Builtins/2018-08-14-03-52-43.bpo-34400.AJD0bz.rst
new file mode 100644
index 0000000..768f5a2
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2018-08-14-03-52-43.bpo-34400.AJD0bz.rst
@@ -0,0 +1 @@
+Fix undefined behavior in parsetok.c. Patch by Zackery Spytz.
diff --git a/Parser/parsetok.c b/Parser/parsetok.c
index 069cc6b..3189873 100644
--- a/Parser/parsetok.c
+++ b/Parser/parsetok.c
@@ -176,7 +176,7 @@
}
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) {
fprintf(stderr, "no mem for next token\n");