Merge pull request #2397 from KLayout/bugfix/issue-2396

Fixed issue #2396 (support weak refs in Python)

src/pya/pya/pyaCallables.cc

@@ -43,6 +43,11 @@ namespace pya
 void
 pya_object_deallocate (PyObject *self)
 {
+  //  Clear weak refs - needed for signal binding and other purposes
+#if PY_VERSION_HEX > 0x03020000
+  PyObject_ClearWeakRefs (self);
+#endif
+
   //  This avoids an assertion in debug builds (Python, gcmodule.c - update_refs).
   //  In short, the GC expects not to see objects with refcount 0 and asserts.
   //  However, due to triggering of signals or similar, the destructor call below

src/pya/pya/pyaModule.cc

@@ -337,6 +337,11 @@ public:
 #if PY_VERSION_HEX >= 0x030D0000
       //  crashes with this option set
       type->tp_flags &= ~Py_TPFLAGS_INLINE_VALUES;
+#endif
+#if PY_VERSION_HEX < 0x03000000
+      type->tp_flags |= Py_TPFLAGS_HAVE_WEAKREFS;
+      type->tp_weaklistoffset = type->tp_basicsize;
+      type->tp_basicsize += sizeof (PyObject *);
 #endif
       type->tp_basicsize += sizeof (PYAObjectBase);
       type->tp_init = &pya_object_init;

testdata/python/basic.py

@@ -22,6 +22,7 @@ import os
 import sys
 import gc
 import copy
+import weakref
 
 # Set this to True to disable some tests involving exceptions
 leak_check = "TEST_LEAK_CHECK" in os.environ
@@ -3352,6 +3353,20 @@ class BasicTest(unittest.TestCase):
     self.assertEqual(bc.str(), "xyz")
     self.assertEqual(bnc.str(), "xyz")
 
+  # weak refs
+  def test_94(self):
+
+    b = pya.B()
+    b.set_str("abc")
+
+    r = weakref.ref(b)
+    self.assertEqual(r() is None, False)
+    self.assertEqual(r().str(), "abc")
+
+    b = None
+    self.assertEqual(r() is None, True)
+
+
 # run unit tests
 if __name__ == '__main__':
   suite = unittest.TestSuite()