1 files changed, 82 insertions, 0 deletions
diff --git a/bzrlib/breakin.py b/bzrlib/breakin.py
new file mode 100644
index 0000000..d55baa0
--- /dev/null
+++ b/bzrlib/breakin.py
@@ -0,0 +1,82 @@
+# 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)