[gdb/testsuite] Make Term::wait_for "" match only a prompt

The semantics of Term::wait_for is:
...
    # Accept some output from gdb and update the screen.  WAIT_FOR is
    # a regexp matching the line to wait for.  Return 0 on timeout, 1
    # on success.
    proc wait_for {wait_for} {
...

Note that besides the regexp, also a subsequent gdb prompt is matched.

I recently used wait_for "" in a few test-cases, thinking that this would
match just a prompt, but in fact that's not the case.

Fix this in wait_for, and add a corresponding test in gdb.tui/tuiterm-2.exp.

Tested on x86_64-linux.

2 files changed, 17 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.tui/tuiterm-2.exp b/gdb/testsuite/gdb.tui/tuiterm-2.exp
index e7a0f03..8e838d3 100644
--- a/gdb/testsuite/gdb.tui/tuiterm-2.exp
+++ b/gdb/testsuite/gdb.tui/tuiterm-2.exp
@@ -93,6 +93,19 @@ with_override Term::accept_gdb_output test_accept_gdb_output {
 		}
 		gdb_assert { ![Term::command "foo"] }
 	    }
+
+	    with_test_prefix Term::wait_for {
+		Term::_setup 4 20
+		set send_cnt 0
+		set expect_send {}
+		set action_cnt 0
+		set actions {
+		    {
+			Term::_insert "(gdb) "
+		    }
+		}
+		gdb_assert { [Term::wait_for ""] }
+	    }
 	}
     }
 }
diff --git a/gdb/testsuite/lib/tuiterm.exp b/gdb/testsuite/lib/tuiterm.exp
index dc928ae..41fa554 100644
--- a/gdb/testsuite/lib/tuiterm.exp
+++ b/gdb/testsuite/lib/tuiterm.exp
@@ -789,6 +789,10 @@ namespace eval Term {
 	set fn "wait_for"
 
 	set prompt_wait_for "(^|\\|)$gdb_prompt \$"
+	if { $wait_for == "" } {
+	    set wait_for $prompt_wait_for
+	}
+
 	debug_tui_matching "$fn: regexp: '$wait_for'"
 
 	while 1 {