vis_pipe: correctly return non-zero exit status

according to POSIX wait(3p) the return status needs to be checked
and the macro WEXITSTATUS(stat_val) should be used to get the actual
return value on a normal exit. POSIX doesn't specify the value of
stat_val on abnormal exit and thus vis_pipe() should just return
-1 as it does for other errors

closes #1130: vis:pipe returns wrong exit status (when non-zero)

Thanks @pippi1otta for the report and suggestion.

1 files changed, 4 insertions, 1 deletions

diff --git a/vis.c b/vis.c
index 004295b..2a4d6ae 100644
--- a/vis.c
+++ b/vis.c
@@ -1960,7 +1960,10 @@ err:
 	vis->interrupted = false;
 	vis->ui->terminal_restore(vis->ui);
 
-	return status;
+	if (WIFEXITED(status))
+		return WEXITSTATUS(status);
+
+	return -1;
 }
 
 static ssize_t read_buffer(void *context, char *data, size_t len) {