commit 3e26e42c905852394fa136f1cc564dac98b56166
author Zackery Spytz <zspytz@gmail.com> Mon Aug 20 21:11:40 2018 -0600
committer Benjamin Peterson <benjamin@python.org> Mon Aug 20 20:11:40 2018 -0700
tree aab8651b7351b994e334daf42d0b102689a6d8d7
parent cdbf50cba1664f72ae6621a89c324a32fea70377

bpo-34400: Fix more undefined behavior in parsetok.c (GH-8833)

Parser/parsetok.c

diff --git a/Parser/parsetok.c b/Parser/parsetok.c
index b9c9fe8..a1580e6 100644
--- a/Parser/parsetok.c
+++ b/Parser/parsetok.c
@@ -252,11 +252,13 @@
             }
         }
 #endif
-        if (a >= tok->line_start)
+        if (a != NULL && a >= tok->line_start) {
             col_offset = Py_SAFE_DOWNCAST(a - tok->line_start,
                                           intptr_t, int);
-        else
+        }
+        else {
             col_offset = -1;
+        }
 
         if ((err_ret->error =
              PyParser_AddToken(ps, (int)type, str,