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

3e26e42c · Zackery Spytz · Benjamin Peterson · cdbf50cb · 3e26e42c
Commit 3e26e42c authored Aug 20, 2018 by Zackery Spytz Committed by Benjamin Peterson Aug 20, 2018
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Parser/parsetok.c Parser/parsetok.c +4 -2

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--- a/Parser/parsetok.c
+++ b/Parser/parsetok.c
@@ -252,11 +252,13 @@ parsetok(struct tok_state *tok, grammar *g, int start, perrdetail *err_ret,
            }
        }
 #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,