Canceling pagination caused by execution command from command line aborts readline/gdb

This fixes:

 $ ./gdb program -ex "set height 2" -ex "start"
 ...
 Reading symbols from /home/pedro/gdb/tests/threads...done.
 ---Type <return> to continue, or q <return> to quit---^CQuit  << ctrl-c triggers a Quit

 *type something*
 readline: readline_callback_read_char() called with no handler!
 Aborted
 $

Usually, if an error propagates all the way to the top level, we'll
re-enable stdin, in case the command that was running was a
synchronous command.  That's done in the event loop's actual loop
(event-loop.c:start_event_loop).  However, if a foreground execution
command is run before the event loop starts and throws, nothing is
presently reenabling stdin, which leaves sync_execution set.

When we do start the event loop, because sync_execution is still
(mistakenly) set, display_gdb_prompt removes the readline input
callback, even though stdin is registered in the event loop.  Any
input from here on results in readline aborting.

Such commands are run through catch_command_errors,
catch_command_errors_const, so add the tweak there.

gdb/
2014-07-14  Pedro Alves  <palves@redhat.com>

	PR gdb/17072
	* main.c: Include event-top.h.
	(handle_command_errors): New function.
	(catch_command_errors, catch_command_errors_const): Use it.

gdb/testsuite/
2014-07-14  Pedro Alves  <palves@redhat.com>

	PR gdb/17072
	* gdb.base/paginate-execution-startup.c: New file.
	* gdb.base/paginate-execution-startup.exp: New file.
	* lib/gdb.exp (pagination_prompt): New global.
	(default_gdb_spawn): New procedure, factored out from
	default_gdb_spawn.
	(default_gdb_start): Adjust to call default_gdb_spawn.
	(gdb_spawn): New procedure.

1 files changed, 49 insertions, 12 deletions

diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 50f2481..7a00efb 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -70,6 +70,9 @@ if ![info exists gdb_prompt] then {
     set gdb_prompt "\[(\]gdb\[)\]"
 }
 
+# A regexp that matches the pagination prompt.
+set pagination_prompt "---Type <return> to continue, or q <return> to quit---"
+
 # The variable fullname_syntax_POSIX is a regexp which matches a POSIX 
 # absolute path ie. /foo/ 
 set fullname_syntax_POSIX {/[^\n]*/}
@@ -1426,19 +1429,12 @@ proc gdb_file_cmd { arg } {
     }
 }
 
-#
-# start gdb -- start gdb running, default procedure
-#
-# When running over NFS, particularly if running many simultaneous
-# tests on different hosts all using the same server, things can
-# get really slow.  Give gdb at least 3 minutes to start up.
-#
-proc default_gdb_start { } {
-    global verbose use_gdb_stub
+# Default gdb_spawn procedure.
+
+proc default_gdb_spawn { } {
+    global use_gdb_stub
     global GDB
     global INTERNAL_GDBFLAGS GDBFLAGS
-    global gdb_prompt
-    global timeout
     global gdb_spawn_id
 
     gdb_stop_suppressing_tests
@@ -1469,21 +1465,45 @@ proc default_gdb_start { } {
 	perror "Spawning $GDB failed."
 	return 1
     }
+    set gdb_spawn_id -1
+    return 0
+}
+
+# Default gdb_start procedure.
+
+proc default_gdb_start { } {
+    global gdb_prompt
+    global gdb_spawn_id
+
+    if [info exists gdb_spawn_id] {
+	return 0
+    }
+
+    set res [gdb_spawn]
+    if { $res != 0} {
+	return $res
+    }
+
+    # When running over NFS, particularly if running many simultaneous
+    # tests on different hosts all using the same server, things can
+    # get really slow.  Give gdb at least 3 minutes to start up.
     gdb_expect 360 {
 	-re "\[\r\n\]$gdb_prompt $" {
 	    verbose "GDB initialized."
 	}
 	-re "$gdb_prompt $"	{
 	    perror "GDB never initialized."
+	    unset gdb_spawn_id
 	    return -1
 	}
 	timeout	{
 	    perror "(timeout) GDB never initialized after 10 seconds."
 	    remote_close host
+	    unset gdb_spawn_id
 	    return -1
 	}
     }
-    set gdb_spawn_id -1
+
     # force the height to "unlimited", so no pagers get used
 
     send_gdb "set height 0\n"
@@ -3286,6 +3306,23 @@ proc gdb_clear_suppressed { } {
     set suppress_flag 0
 }
 
+# Spawn the gdb process.
+#
+# This doesn't expect any output or do any other initialization,
+# leaving those to the caller.
+#
+# Overridable function -- you can override this function in your
+# baseboard file.
+
+proc gdb_spawn { } {
+    default_gdb_spawn
+}
+
+# Start gdb running, wait for prompt, and disable the pagers.
+
+# Overridable function -- you can override this function in your
+# baseboard file.
+
 proc gdb_start { } {
     default_gdb_start
 }