python/test/test_weakreferences.py

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# Version: MPL 1.1/GPL 2.0/LGPL 2.1
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# The Original Code is the Python XPCOM language bindings.
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# ActiveState Tool Corp.
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#   Mark Hammond <markh@activestate.com> (original author)
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# test_weakreferences.py - Test our weak reference implementation.
from xpcom import components, _xpcom
import xpcom.server, xpcom.client
from pyxpcom_test_tools import suite_from_functions, testmain

try:
    from sys import gettotalrefcount
except ImportError:
    # Not a Debug build - assume no references (can't be leaks then :-)
    gettotalrefcount = lambda: 0

num_alive = 0

class koTestSimple:
    _com_interfaces_ = [components.interfaces.nsIInputStream]
    def __init__(self):
        global num_alive
        num_alive += 1
    def __del__(self):
        global num_alive
        num_alive -= 1
    def close( self ):
        pass

def test():
    ob = xpcom.server.WrapObject( koTestSimple(), components.interfaces.nsIInputStream)

    if num_alive != 1: raise RuntimeError, "Eeek - there are %d objects alive" % (num_alive,)

    # Check we can create a weak reference to our object.
    wr = xpcom.client.WeakReference(ob)
    if num_alive != 1: raise RuntimeError, "Eeek - there are %d objects alive" % (num_alive,)

    # Check we can call methods via the weak reference.
    if wr() is None: raise RuntimeError, "Our weak-reference is returning None before it should!"
    wr().close()

    ob  = None # This should kill the object.
    if num_alive != 0: raise RuntimeError, "Eeek - there are %d objects alive" % (num_alive,)
    if wr() is not None: raise RuntimeError, "Our weak-reference is not returning None when it should!"

    # Now a test that we can get a _new_ interface from the weak reference - ie,
    # an IID the real object has never previously been queried for
    # (this behaviour previously caused a bug - never again ;-)
    ob = xpcom.server.WrapObject( koTestSimple(), components.interfaces.nsISupports)
    if num_alive != 1: raise RuntimeError, "Eeek - there are %d objects alive" % (num_alive,)
    wr = xpcom.client.WeakReference(ob, components.interfaces.nsIInputStream)
    if num_alive != 1: raise RuntimeError, "Eeek - there are %d objects alive" % (num_alive,)
    wr() # This would die once upon a time ;-)
    ob  = None # This should kill the object.
    if num_alive != 0: raise RuntimeError, "Eeek - there are %d objects alive" % (num_alive,)
    if wr() is not None: raise RuntimeError, "Our weak-reference is not returning None when it should!"

def test_refcount(num_loops=-1):
    # Do the test lots of times - can help shake-out ref-count bugs.
    if num_loops == -1: num_loops = 10
    for i in xrange(num_loops):
        test()

        if i==0:
            # First loop is likely to "leak" as we cache things.
            # Leaking after that is a problem.
            num_refs = gettotalrefcount()

    lost = gettotalrefcount() - num_refs
    # Sometimes we get spurious counts off by 1 or 2.
    # This can't indicate a real leak, as we have looped
    # more than twice!
    if abs(lost)>2:
        print "*** Lost %d references" % (lost,)

# Make this test run under our std test suite
def suite():
    return suite_from_functions(test_refcount)

if __name__=='__main__':
    testmain()