~bzr-pqm/bzr/bzr.dev

# Copyright (C) 2007, 2009, 2010 Canonical Ltd

#

# 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 2 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, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

from __future__ import absolute_import

import os

import signal

_breakin_signal_number = None

_breakin_signal_name = None

def _debug(signal_number, interrupted_frame):

    import pdb

    import sys

    sys.stderr.write("** %s received, entering debugger\n"

            "** Type 'c' to continue or 'q' to stop the process\n"

            "** Or %s again to quit (and possibly dump core)\n"

            % (_breakin_signal_name, _breakin_signal_name))

    # It seems that on Windows, when sys.stderr is to a PIPE, then we need to

    # flush. Not sure why it is buffered, but that seems to be the case.

    sys.stderr.flush()

    # restore default meaning so that you can kill the process by hitting it

    # twice

    signal.signal(_breakin_signal_number, signal.SIG_DFL)

    try:

        pdb.set_trace()

    finally:

        signal.signal(_breakin_signal_number, _debug)

def determine_signal():

    global _breakin_signal_number

    global _breakin_signal_name

    if _breakin_signal_number is not None:

        return _breakin_signal_number

    # Note: As near as I can tell, Windows is the only one to define SIGBREAK,

    #       and other platforms defined SIGQUIT. There doesn't seem to be a

    #       platform that defines both.

    #       -- jam 2009-07-30

    sigquit = getattr(signal, 'SIGQUIT', None)

    sigbreak = getattr(signal, 'SIGBREAK', None)

    if sigquit is not None:

        _breakin_signal_number = sigquit

        _breakin_signal_name = 'SIGQUIT'

    elif sigbreak is not None:

        _breakin_signal_number = sigbreak

        _breakin_signal_name = 'SIGBREAK'

    return _breakin_signal_number

def hook_debugger_to_signal():

    """Add a signal handler so we drop into the debugger.

    On Unix, this is hooked into SIGQUIT (C-\\), and on Windows, this is

    hooked into SIGBREAK (C-Pause).

    """

    # when sigquit (C-\) or sigbreak (C-Pause) is received go into pdb

    if os.environ.get('BZR_SIGQUIT_PDB', '1') == '0':

        # User explicitly requested we don't support this

        return

    sig = determine_signal()

    if sig is None:

        return

    # print 'hooking into %s' % (_breakin_signal_name,)

    signal.signal(sig, _debug)