Add a non-regression test for issue #15

cairocffi/surfaces.py

@@ -25,7 +25,7 @@
 def _make_read_func(file_obj):
     """Return a CFFI callback that reads from a file-like object."""
     @ffi.callback("cairo_read_func_t", error=constants.STATUS_READ_ERROR)
-    def read_func(closure, data, length):
+    def read_func(_closure, data, length):
         string = file_obj.read(length)
         if len(string) < length:  # EOF too early
             return constants.STATUS_READ_ERROR
@@ -40,10 +40,10 @@ def _make_write_func(file_obj):
         return ffi.NULL
 
     @ffi.callback("cairo_write_func_t", error=constants.STATUS_WRITE_ERROR)
-    def read_func(_closure, data, length):
+    def write_func(_closure, data, length):
         file_obj.write(ffi.buffer(data, length))
         return constants.STATUS_SUCCESS
-    return read_func
+    return write_func
 
 
 def _encode_filename(filename):

cairocffi/test_cairo.py

@@ -164,6 +164,25 @@ def test_surface():
     assert_raise_finished(surface.set_fallback_resolution, 3, 4)
 
 
+def test_target_lifetime():
+    # Test our work around for
+    # Related CFFI bug: https://bitbucket.org/cffi/cffi/issue/92/
+    if not hasattr(sys, 'getrefcount'):
+        pytest.xfail()  # PyPy
+    gc.collect()  # Clean up stuff from other tests
+    target = io.BytesIO()
+    initial_refcount = sys.getrefcount(target)
+    assert len(cairocffi.surfaces.KeepAlive.instances) == 0
+    surface = PDFSurface(target, 100, 100)
+    # The target is in a KeepAlive object
+    assert len(cairocffi.surfaces.KeepAlive.instances) == 1
+    assert sys.getrefcount(target) == initial_refcount + 1
+    del surface
+    gc.collect()  # Make sure surface is collected
+    assert len(cairocffi.surfaces.KeepAlive.instances) == 0
+    assert sys.getrefcount(target) == initial_refcount
+
+
 def test_mime_data():
     if cairo_version() < 11000:
         pytest.xfail()