Keep one fd free for the predicates themselves.

Otherwise -empty may start failing once the dircache grows.

It's still possible to cause failures with

    $ bfs some/big/dir -empty 3</dev/null

because one more fd than expected will be allocated, but that's not a
common case.  It could be worked around by reading /proc/self/fd/ at
startup.

1 files changed, 3 insertions, 3 deletions

diff --git a/eval.c b/eval.c
index 01da7a4..10379a3 100644
--- a/eval.c
+++ b/eval.c
@@ -402,9 +402,9 @@ static int infer_nopenfd() {
 		}
 	}
 
-	// Account for std{in,out,err}
-	if (ret > 3) {
-		ret -= 3;
+	// Account for std{in,out,err}, and allow one free for the predicates
+	if (ret > 4) {
+		ret -= 4;
 	}
 
 	return ret;