Allow references to objects held by smart pointers (#533)

tests/test_smart_ptr.py

@@ -1,3 +1,4 @@
+import pytest
 from pybind11_tests import ConstructorStats
 
 
@@ -124,3 +125,74 @@ def test_unique_nodelete():
     del o
     cstats = ConstructorStats.get(MyObject4)
     assert cstats.alive() == 1  # Leak, but that's intentional
+
+
+def test_shared_ptr_and_references():
+    from pybind11_tests.smart_ptr import SharedPtrRef, A
+
+    s = SharedPtrRef()
+    stats = ConstructorStats.get(A)
+    assert stats.alive() == 2
+
+    ref = s.ref  # init_holder_helper(holder_ptr=false, owned=false)
+    assert stats.alive() == 2
+    assert s.set_ref(ref)
+    with pytest.raises(RuntimeError) as excinfo:
+        assert s.set_holder(ref)
+    assert "Unable to cast from non-held to held instance" in str(excinfo.value)
+
+    copy = s.copy  # init_holder_helper(holder_ptr=false, owned=true)
+    assert stats.alive() == 3
+    assert s.set_ref(copy)
+    assert s.set_holder(copy)
+
+    holder_ref = s.holder_ref  # init_holder_helper(holder_ptr=true, owned=false)
+    assert stats.alive() == 3
+    assert s.set_ref(holder_ref)
+    assert s.set_holder(holder_ref)
+
+    holder_copy = s.holder_copy  # init_holder_helper(holder_ptr=true, owned=true)
+    assert stats.alive() == 3
+    assert s.set_ref(holder_copy)
+    assert s.set_holder(holder_copy)
+
+    del ref, copy, holder_ref, holder_copy, s
+    assert stats.alive() == 0
+
+
+def test_shared_ptr_from_this_and_references():
+    from pybind11_tests.smart_ptr import SharedFromThisRef, B
+
+    s = SharedFromThisRef()
+    stats = ConstructorStats.get(B)
+    assert stats.alive() == 2
+
+    ref = s.ref  # init_holder_helper(holder_ptr=false, owned=false, bad_wp=false)
+    assert stats.alive() == 2
+    assert s.set_ref(ref)
+    assert s.set_holder(ref)  # std::enable_shared_from_this can create a holder from a reference
+
+    bad_wp = s.bad_wp  # init_holder_helper(holder_ptr=false, owned=false, bad_wp=true)
+    assert stats.alive() == 2
+    assert s.set_ref(bad_wp)
+    with pytest.raises(RuntimeError) as excinfo:
+        assert s.set_holder(bad_wp)
+    assert "Unable to cast from non-held to held instance" in str(excinfo.value)
+
+    copy = s.copy  # init_holder_helper(holder_ptr=false, owned=true, bad_wp=false)
+    assert stats.alive() == 3
+    assert s.set_ref(copy)
+    assert s.set_holder(copy)
+
+    holder_ref = s.holder_ref  # init_holder_helper(holder_ptr=true, owned=false, bad_wp=false)
+    assert stats.alive() == 3
+    assert s.set_ref(holder_ref)
+    assert s.set_holder(holder_ref)
+
+    holder_copy = s.holder_copy  # init_holder_helper(holder_ptr=true, owned=true, bad_wp=false)
+    assert stats.alive() == 3
+    assert s.set_ref(holder_copy)
+    assert s.set_holder(holder_copy)
+
+    del ref, bad_wp, copy, holder_ref, holder_copy, s
+    assert stats.alive() == 0