fix stream_prev() for invalid (negative) stream

Now that the parent stream is stored as a position, the validity
of a stream can't anymore be tested by checking if its number
is non-negative because inside a struct position stream number
are stored as an unsigned (and changing it to signed would halve
the maximum number of stream).

So, add a check against input_stream_nr before returning the
previous stream.

Fixes: 4c6cbe557c48205f9b3d2aae4c166cd66446b240
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/tokenize.c b/tokenize.c
index d68fbcd8..ca842f52 100644
--- a/tokenize.c
+++ b/tokenize.c
@@ -66,7 +66,10 @@ int stream_prev(int stream)
 {
 	if (stream < 0 || stream > input_stream_nr)
 		return -1;
-	return input_streams[stream].pos.stream;
+	stream = input_streams[stream].pos.stream;
+	if (stream > input_stream_nr)
+		return -1;
+	return stream;
 }
 
 static struct position stream_pos(stream_t *stream)