Report errors that occur when closing files

Otherwise we miss write errors that occur when flushing the cache.

1 files changed, 3 insertions, 1 deletions

diff --git a/expr.h b/expr.h
index 0eba0da..c0e2b92 100644
--- a/expr.h
+++ b/expr.h
@@ -219,7 +219,9 @@ void dump_expr(CFILE *cfile, const struct expr *expr, bool verbose);
 
 /**
  * Free an expression tree.
+ *
+ * @return 0 if successful, -1 on error.
  */
-void free_expr(struct expr *expr);
+int free_expr(struct expr *expr);
 
 #endif // EXPR_H