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"""
Replacement for the Python standard library's atexit.py.
Whereas the standard :mod:`atexit` module only defines :func:`atexit.register`,
this replacement module also defines :func:`unregister`.
This module also fixes a the issue that exceptions raised by an exit handler is
printed twice when the standard :mod:`atexit` is used.
"""
from __future__ import absolute_import
from __future__ import division
import sys
import threading
import traceback
import atexit as std_atexit
from pwnlib.context import context
__all__ = ['register', 'unregister']
_lock = threading.Lock()
_ident = 0
_handlers = {}
def register(func, *args, **kwargs):
"""register(func, *args, **kwargs)
Registers a function to be called on program termination. The function will
be called with positional arguments `args` and keyword arguments `kwargs`,
i.e. ``func(*args, **kwargs)``. The current `context` is recorded and will
be the one used when the handler is run.
E.g. to suppress logging output from an exit-handler one could write::
with context.local(log_level = 'error'):
atexit.register(handler)
An identifier is returned which can be used to unregister the exit-handler.
This function can be used as a decorator::
@atexit.register
def handler():
...
Notice however that this will bind ``handler`` to the identifier and not the
actual exit-handler. The exit-handler can then be unregistered with::
atexit.unregister(handler)
This function is thread safe.
"""
global _ident
with _lock:
ident = _ident
_ident += 1
_handlers[ident] = (func, args, kwargs, vars(context))
return ident
def unregister(ident):
"""unregister(ident)
Remove the exit-handler identified by `ident` from the list of registered
handlers. If `ident` isn't registered this is a no-op.
"""
if ident in _handlers:
del _handlers[ident]
def _run_handlers():
"""_run_handlers()
Run registered exit-handlers. They run in the reverse order of which they
were registered.
If a handler raises an exception, it will be printed but nothing else
happens, i.e. other handlers will be run and `sys.excepthook` will not be
called for that reason.
"""
context.clear()
for _ident, (func, args, kwargs, ctx) in \
sorted(_handlers.items(), reverse = True):
try:
with context.local(**ctx):
func(*args, **kwargs)
except SystemExit:
pass
except Exception:
# extract the current exception and rewind the traceback to where it
# originated
typ, val, tb = sys.exc_info()
traceback.print_exception(typ, val, tb.tb_next)
# if there's already an exitfunc registered be sure to run that too
if hasattr(sys, "exitfunc"):
register(sys.exitfunc)
if sys.version_info[0] < 3:
sys.exitfunc = _run_handlers
else:
std_atexit.register(_run_handlers)
|
