Fix \watch's interaction with libedit on ^C.

When you hit ^C, the terminal driver in Unix-like systems echoes "^C" as
well as sending an interrupt signal (depending on stty settings).  At
least libedit (but maybe also libreadline) is then confused about the
current cursor location, and corrupts the display if you try to scroll
back.  Fix, by moving to a new line before the next prompt is displayed.

Back-patch to all supported released.

Author: Pavel Stehule 
Reported-by: Tom Lane 
Discussion: https://postgr.es/m/3278793.1626198638%40sss.pgh.pa.us

diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index d1ee795cb60744de47b726004cbcd8acc95a92e5..062c79ccbd1fe277cfeaa232889c1e1d5cc560c0 100644 (file)
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -4992,6 +4992,14 @@ do_watch(PQExpBuffer query_buf, double sleep)
        sigint_interrupt_enabled = false;
    }
 
+   /*
+    * If the terminal driver echoed "^C", libedit/libreadline might be
+    * confused about the cursor position.  Therefore, inject a newline
+    * before the next prompt is displayed.
+    */
+   fprintf(stdout, "\n");
+   fflush(stdout);
+
    pg_free(title);
    return (res >= 0);
 }