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.

6 files changed, 310 insertions, 20 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 7a5abe0..df5a9df 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,12 @@
 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.
+
+2014-07-14  Pedro Alves  <palves@redhat.com>
+
 	* exceptions.c (catch_command_errors, catch_command_errors_const):
 	Moved to main.c.
 	* exceptions.h (catch_command_errors_ftype)
diff --git a/gdb/main.c b/gdb/main.c
index 1d77bd3..b51ff89 100644
--- a/gdb/main.c
+++ b/gdb/main.c
@@ -46,6 +46,7 @@
 #include "filenames.h"
 #include "filestuff.h"
 #include <signal.h>
+#include "event-top.h"
 
 /* The selected interpreter.  This will be used as a set command
    variable, so it should always be malloc'ed - since
@@ -337,6 +338,25 @@ captured_command_loop (void *data)
   return 1;
 }
 
+/* Handle command errors thrown from within
+   catch_command_errors/catch_command_errors_const.  */
+
+static int
+handle_command_errors (volatile struct gdb_exception e)
+{
+  if (e.reason < 0)
+    {
+      exception_print (gdb_stderr, e);
+
+      /* If any exception escaped to here, we better enable stdin.
+	 Otherwise, any command that calls async_disable_stdin, and
+	 then throws, will leave stdin inoperable.  */
+      async_enable_stdin ();
+      return 0;
+    }
+  return 1;
+}
+
 /* Type of the command callback passed to catch_command_errors.  */
 
 typedef void (catch_command_errors_ftype) (char *, int);
@@ -353,10 +373,7 @@ catch_command_errors (catch_command_errors_ftype *command,
     {
       command (arg, from_tty);
     }
-  exception_print (gdb_stderr, e);
-  if (e.reason < 0)
-    return 0;
-  return 1;
+  return handle_command_errors (e);
 }
 
 /* Type of the command callback passed to catch_command_errors_const.  */
@@ -375,10 +392,7 @@ catch_command_errors_const (catch_command_errors_const_ftype *command,
     {
       command (arg, from_tty);
     }
-  exception_print (gdb_stderr, e);
-  if (e.reason < 0)
-    return 0;
-  return 1;
+  return handle_command_errors (e);
 }
 
 /* Arguments of --command option and its counterpart.  */
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index f504db6..c0207c4 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,16 @@
 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.
+
+2014-07-14  Pedro Alves  <palves@redhat.com>
+
 	* lib/gdb.exp (gdb_assert): New procedure.
 	* gdb.trace/backtrace.exp (gdb_backtrace_tdp_4): Use it.
 
diff --git a/gdb/testsuite/gdb.base/paginate-execution-startup.c b/gdb/testsuite/gdb.base/paginate-execution-startup.c
new file mode 100644
index 0000000..e741785
--- /dev/null
+++ b/gdb/testsuite/gdb.base/paginate-execution-startup.c
@@ -0,0 +1,32 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2014 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <unistd.h>
+
+static void
+after_sleep (void)
+{
+  return; /* after sleep */
+}
+
+int
+main (void)
+{
+  sleep (3);
+  after_sleep ();
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.base/paginate-execution-startup.exp b/gdb/testsuite/gdb.base/paginate-execution-startup.exp
new file mode 100644
index 0000000..dc713ec
--- /dev/null
+++ b/gdb/testsuite/gdb.base/paginate-execution-startup.exp
@@ -0,0 +1,189 @@
+# Copyright (C) 2014 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# A collection of tests related to pagination resulting from running
+# execution commands directly from the command line, with "-ex".
+
+standard_testfile
+
+if {[build_executable "failed to prepare" $testfile $srcfile debug] == -1} {
+    return -1
+}
+
+set file_arg $binfile
+if [is_remote host] {
+  set file_arg [remote_download host $file_arg]
+}
+
+global GDBFLAGS
+set saved_gdbflags $GDBFLAGS
+
+# Returns true if the board can 'gdb -ex "start"', false otherwise.
+
+proc probe_can_run_cmdline  {} {
+    global srcfile file_arg
+    global saved_gdbflags GDBFLAGS
+    global gdb_prompt
+
+    set GDBFLAGS $saved_gdbflags
+    append GDBFLAGS " -ex \"set height 0\""
+    append GDBFLAGS " -ex \"start\""
+    append GDBFLAGS " --args \"$file_arg\""
+
+    with_test_prefix "probe support" {
+	set test "run to main"
+
+	gdb_exit
+	set res [gdb_spawn]
+	if { $res != 0} {
+	    fail $test
+	    return -1
+	}
+
+	set res -1
+	gdb_test_multiple "" $test {
+	    -re "main .* at .*$srcfile.*$gdb_prompt $" {
+		set res 1
+		pass $test
+	    }
+	    -re "Don't know how to run.*$gdb_prompt $" {
+		set res 0
+		unsupported $test
+	    }
+	}
+
+	# In case the board file wants to send further commands.
+	gdb_test_no_output "set height unlimited"
+	return $res
+    }
+}
+
+# Check that we handle pagination correctly when it triggers due to an
+# execution command entered directly on the command line.
+
+proc test_fg_execution_pagination_return {} {
+    global file_arg
+    global saved_gdbflags GDBFLAGS
+    global gdb_prompt pagination_prompt
+
+    set GDBFLAGS $saved_gdbflags
+    append GDBFLAGS " -ex \"set height 2\""
+    append GDBFLAGS " -ex \"start\""
+    append GDBFLAGS " --args \"$file_arg\""
+
+    with_test_prefix "return" {
+	set test "run to pagination"
+
+	gdb_exit
+	set res [gdb_spawn]
+	if { $res != 0} {
+	    fail $test
+	    return $res
+	}
+	gdb_test_multiple "" $test {
+	    -re "$pagination_prompt$" {
+		pass $test
+	    }
+	    -re "$gdb_prompt $" {
+		fail $test
+	    }
+	}
+
+	send_gdb "\n"
+
+	set saw_pagination_prompt 0
+	set test "send \\n to GDB"
+	gdb_test_multiple "" $test {
+	    -re "$pagination_prompt$" {
+		set saw_pagination_prompt 1
+		send_gdb "\n"
+		exp_continue
+	    }
+	    -notransfer -re "<return>" {
+		# Otherwise gdb_test_multiple considers this an error.
+		exp_continue
+	    }
+	    -re "$gdb_prompt $" {
+		gdb_assert $saw_pagination_prompt $test
+	    }
+	}
+
+	gdb_test "p 1" " = 1" "GDB accepts further input"
+
+	# In case the board file wants to send further commands.
+	gdb_test_no_output "set height unlimited"
+    }
+}
+
+# Check that we handle canceling pagination correctly when it triggers
+# due to an execution command entered directly on the command line.
+
+proc test_fg_execution_pagination_cancel { how } {
+    global file_arg
+    global saved_gdbflags GDBFLAGS
+    global gdb_prompt pagination_prompt
+
+    set GDBFLAGS $saved_gdbflags
+
+    append GDBFLAGS " -ex \"set height 2\""
+    append GDBFLAGS " -ex \"start\""
+    append GDBFLAGS " --args \"$file_arg\""
+
+    with_test_prefix "cancel with $how" {
+	set test "run to pagination"
+
+	gdb_exit
+	set res [gdb_spawn]
+	if { $res != 0} {
+	    fail $test
+	    return $res
+	}
+	gdb_test_multiple "" $test {
+	    -re "$pagination_prompt$" {
+		pass $test
+	    }
+	    -notransfer -re "<return>" {
+		# Otherwise gdb_test_multiple considers this an error.
+		exp_continue
+	    }
+	}
+
+	set test "cancel pagination"
+	if { $how == "ctrl-c" } {
+	    send_gdb "\003"
+	} else {
+	    send_gdb "q\n"
+
+	}
+	gdb_test_multiple "" $test {
+	    -re "Quit\r\n$gdb_prompt $" {
+		pass $test
+	    }
+	}
+
+	gdb_test "p 1" " = 1" "GDB accepts further input"
+
+	# In case the board file wants to send further commands.
+	gdb_test_no_output "set height unlimited"
+    }
+}
+
+if {[probe_can_run_cmdline] > 0} {
+    test_fg_execution_pagination_return
+    test_fg_execution_pagination_cancel "ctrl-c"
+    test_fg_execution_pagination_cancel "quit"
+}
+
+set GDBFLAGS $saved_gdbflags
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
 }