Make gdb.base/long-inferior-output.exp fail fast

A local change I was working on had a bug that made GDB lose inferior
output, which was caught by the gdb.base/long-inferior-output.exp
testcase.  While debugging the problem, I found it useful to have the
testcase fail quickly when it noticed output was missing.

Also, tighten the regexes to make sure that we don't get
spurious/repeated/bogus output between each "this is line number ..."
line.

gdb/testsuite/ChangeLog:
yyyy-mm-dd  Pedro Alves  <pedro@palves.net>

	* gdb.base/long-inferior-output.exp: Don't set "more" when we see
	an unexpected "this is line number" number.

Change-Id: I53e8499bd8fdbf961431a7f2a94d263da6a9f573

1 files changed, 28 insertions, 3 deletions

diff --git a/gdb/testsuite/gdb.base/long-inferior-output.exp b/gdb/testsuite/gdb.base/long-inferior-output.exp
index 294786f..c0e1802 100644
--- a/gdb/testsuite/gdb.base/long-inferior-output.exp
+++ b/gdb/testsuite/gdb.base/long-inferior-output.exp
@@ -47,21 +47,46 @@ if { ![runto_main] } then {
 set printing_done_line [gdb_get_line_number "printing done"]
 gdb_test "break $printing_done_line" ".*" "set breakpoint after printing"
 
-send_gdb "continue\n"
+gdb_test_multiple "continue" "" {
+    -re "Continuing\.\r\n" {
+	pass $gdb_test_name
+    }
+}
 
 set expected_lines 3000
 set more 1
 set i 0
 while {$more} {
     set more 0
+
+    # Make sure that we don't get spurious/repeated/bogus output
+    # between each "this is line number ..."  line, with an anchor.
+    # But consume any output that precedes the first line, because
+    # when testing against GDBserver, we'll get:
+    #
+    #   continue
+    #   Continuing.
+    #   PASS: gdb.base/long-inferior-output.exp: continue
+    #   Remote debugging from host ::1, port 40044
+    #   this is line number 0
+    #   ...
+    if {$i != 0} {
+	set anchor "^"
+    } else {
+	set anchor ""
+    }
+
     gdb_expect {
 	-i $inferior_spawn_id
-	-ex "this is line number $i" {
+	-re "${anchor}this is line number $i\r\n" {
 	    incr i
-           if {$i != $expected_lines} {
+	    if {$i != $expected_lines} {
 		set more 1
 	    }
 	}
+	-re "this is line number \[^\r\n\]*\r\n" {
+	    # If we see this, we've lost output.
+	}
     }
 }