Using my PR 7827, I saw that test_refleaks_in_decompressor___init__() of test_lzma leaks 100 handles on Windows.

Extract of the code:

    @support.refcount_test
    def test_refleaks_in_decompressor___init__(self):
        gettotalrefcount = support.get_attribute(sys, 'gettotalrefcount')
        lzd = LZMADecompressor()
        refs_before = gettotalrefcount()
        for i in range(100):
            lzd.__init__()
        self.assertAlmostEqual(gettotalrefcount() - refs_before, 0, delta=10)


The test comes from bpo-31787: commit d019bc8319ea35e93bf4baa38098ff1b57cd3ee5.

In _lzmamodule.c

    self->lock = PyThread_allocate_lock();

This seems leak some resource.  But I'm not sure this lock contains refcnt on Windows.

Have a look at #23224 and PR 7822.

> This seems leak some resource.  But I'm not sure this lock contains refcnt on Windows.

PR 7827 checks for leaks of Windows handles, this issue is about Windows handles, not Python reference leaks. But a Windows lock may use a Windows handle internally, I don't know :-)

It seems like test_bz2 has the same issue, but I'm not sure:
https://github.com/python/cpython/pull/7827#issuecomment-398810849

I four times tried to update this issue, and only the forth one was successful. Other attempts was failed because "Edit Error: someone else has edited this issue (nosy, components, versions)." This is an extreme case of race condition in real life.

New changeset 9b7cf757213cf4d7ae1d436d86ad53f5ba362d55 by Victor Stinner in branch 'master':
bpo-33916: Fix bz2 and lzma init when called twice (GH-7843)
https://github.com/python/cpython/commit/9b7cf757213cf4d7ae1d436d86ad53f5ba362d55

New changeset efc6bf66a58e96c12116d65984ac69b0f36f85de by Miss Islington (bot) in branch '3.7':
bpo-33916: Fix bz2 and lzma init when called twice (GH-7843)
https://github.com/python/cpython/commit/efc6bf66a58e96c12116d65984ac69b0f36f85de

New changeset 1094891b2e3eafef464819acd4cd04cfd2b59661 by Victor Stinner in branch '3.6':
bpo-33916: Fix bz2 and lzma init when called twice (GH-7843) (GH-7872)
https://github.com/python/cpython/commit/1094891b2e3eafef464819acd4cd04cfd2b59661

It seems like Python 2.7 is inaffected by the bug:

static int
BZ2File_init(BZ2FileObject *self, PyObject *args, PyObject *kwargs)
{
    ...
#ifdef WITH_THREAD
    if (!self->lock) {
        self->lock = PyThread_allocate_lock();
    }

    if (!self->lock) {
        PyErr_SetString(PyExc_MemoryError, "unable to allocate lock");
        goto error;
    }
#endif
    ...
}

I fixed the leak in Python 3.6, 3.7 and master. I close the issue.