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 b51d28780b160b0589a4124aca6fe1b434bddaf0..fb1e69ec4c20a1f4dd92f86bae8e8a1e1e7fff92 100644 (file)
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -5169,6 +5169,18 @@ do_watch(PQExpBuffer query_buf, double sleep)
        pclose(pagerpipe);
        restore_sigpipe_trap();
    }
+   else
+   {
+       /*
+        * 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.  We only do this when not
+        * using a pager, because pagers are expected to restore the screen to
+        * a sane state on exit.
+        */
+       fprintf(stdout, "\n");
+       fflush(stdout);
+   }
 
 #ifdef HAVE_POSIX_DECL_SIGWAIT
    /* Disable the interval timer. */