commit shift count needs to be initialized to -1

An initial value of zero for commit shift count means we can erroneously fail a
parse when we back up to zero shifts.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/pdarun.h b/src/pdarun.h
index dfabfea5..a5427576 100644
--- a/src/pdarun.h
+++ b/src/pdarun.h
@@ -317,6 +317,12 @@ struct pda_run
 
 	long steps;
 	long target_steps;
+
+
+	/* The shift count simply tracks the number of shifts that have happend.
+	 * The commit shift count is the shift count when the last commit occurred.
+	 * If we back up to this number of shifts then we decide we cannot proceed.
+	 * The commit shift count is initialized to -1. */
 	long shift_count;
 	long commit_shift_count;