maze: Defend against use-after-free

And non-compliant standard C libraries.

2 files changed, 13 insertions, 3 deletions

diff --git a/src/maze.c b/src/maze.c
index cfa010b..3d62485 100644
--- a/src/maze.c
+++ b/src/maze.c
@@ -179,8 +179,18 @@ mf_maze_new(int s, int w, int h)
 }
 
 void
-mf_maze_free(struct mf_maze *m)
+mf_maze_destroy(struct mf_maze **m_p)
 {
-	free(m->walls);
+	struct mf_maze *m;
+
+	if (m_p == NULL || *m_p == NULL) {
+		return;
+	}
+	m = *m_p;
+
+	if (m->walls != NULL) {
+		free(m->walls);
+	}
 	free(m);
+	m = NULL;
 }
diff --git a/src/maze.h b/src/maze.h
index 1f22702..c584c35 100644
--- a/src/maze.h
+++ b/src/maze.h
@@ -33,6 +33,6 @@ struct mf_maze *
 mf_maze_new(int s, int w, int h);
 
 void
-mf_maze_free(struct mf_maze *m);
+mf_maze_destroy(struct mf_maze **m_p);
 
 #endif  /* MF_MAZE_H_ */