Don't construct unique_ptr around unowned pointers (#478)
If we need to initialize a holder around an unowned instance, and the
holder type is non-copyable (i.e. a unique_ptr), we currently construct
the holder type around the value pointer, but then never actually
destruct the holder: the holder destructor is called only for the
instance that actually has `inst->owned = true` set.
This seems no pointer, however, in creating such a holder around an
unowned instance: we never actually intend to use anything that the
unique_ptr gives us: and, in fact, do not want the unique_ptr (because
if it ever actually got destroyed, it would cause destruction of the
wrapped pointer, despite the fact that that wrapped pointer isn't
owned).
This commit changes the logic to only create a unique_ptr holder if we
actually own the instance, and to destruct via the constructed holder
whenever we have a constructed holder--which will now only be the case
for owned-unique-holder or shared-holder types.
Other changes include:
* Added test for non-movable holder constructor/destructor counts
The three alive assertions now pass, before #478 they fail with counts
of 2/2/1 respectively, because of the unique_ptr that we don't want and
don't destroy (because we don't *want* its destructor to run).
* Return cstats reference; fix ConstructStats doc
Small cleanup to the #478 test code, and fix to the ConstructStats
documentation (the static method definition should use `reference` not
`reference_internal`).
* Rename inst->constructed to inst->holder_constructed
This makes it clearer exactly what it's referring to.
diff --git a/tests/test_issues.py b/tests/test_issues.py
index 208cf3b..6f84f77 100644
--- a/tests/test_issues.py
+++ b/tests/test_issues.py
@@ -201,3 +201,20 @@
assert cstats.alive() == 1
del child, parent
assert cstats.alive() == 0
+
+def test_non_destructed_holders():
+ """ Issue #478: unique ptrs constructed and freed without destruction """
+ from pybind11_tests import SpecialHolderObj
+
+ a = SpecialHolderObj(123)
+ b = a.child()
+
+ assert a.val == 123
+ assert b.val == 124
+
+ cstats = SpecialHolderObj.holder_cstats()
+ assert cstats.alive() == 1
+ del b
+ assert cstats.alive() == 1
+ del a
+ assert cstats.alive() == 0