It is possible to emit signal in PySide with invalid signature, that will lead
to application crash with stack trace leading to internals of PySide/Shiboken.

Consider example:

import sys
from PySide import QtCore, QtGui

class A(QtCore.QObject):
    sig = QtCore.Signal(object)

    def __init__(self):
        super(A, self).__init__()

        print "A.__init__({0})".format(self)

        self.sig.connect(self.slot)

    def wrong_emit(self):
        # Incorrect call.
        # self.sig.emit(self)
        self.sig.emit()

    @QtCore.Slot(object)
    def slot(self, object):
        print "A.slot({0}, {1})".format(self, object)

app = QtGui.QApplication(sys.argv)

o = A()
o.wrong_emit()

#sys.exit(app.exec_())


Debugging such errors in Python looks impossible, PySide definitely should have
some kind of handler for signals that emitted with incorrect signature.