commit f45bb585c32b761ded4e8ecd32897a5d205fcf72
author Glen Walker <glen@walker.gen.nz> Tue Aug 16 17:50:43 2016 +1200
committer Glen Walker <glen@walker.gen.nz> Thu Aug 18 09:09:41 2016 +1200
tree 164c9cedbb3c65a1616d75a3ac3d62a99f6a4283
parent e357ed3cc8458fe3c2f202231e22a1fe1148a587

Support keep_alive where nurse may be None

For example keep_alive<0,1>() should work where the return value may sometimes be None. At present a "Could not allocate weak reference!" exception is thrown.
Update documentation to clarify behaviour of keep_alive when nurse is None or does not support weak references.

example/example-keep-alive.cpp

diff --git a/example/example-keep-alive.cpp b/example/example-keep-alive.cpp
index c099aa8..c2aeaee 100644
--- a/example/example-keep-alive.cpp
+++ b/example/example-keep-alive.cpp
@@ -22,6 +22,7 @@
     ~Parent() { std::cout << "Releasing parent." << std::endl; }
     void addChild(Child *) { }
     Child *returnChild() { return new Child(); }
+    Child *returnNullChild() { return nullptr; }
 };
 
 void init_ex_keep_alive(py::module &m) {
@@ -30,7 +31,9 @@
         .def("addChild", &Parent::addChild)
         .def("addChildKeepAlive", &Parent::addChild, py::keep_alive<1, 2>())
         .def("returnChild", &Parent::returnChild)
-        .def("returnChildKeepAlive", &Parent::returnChild, py::keep_alive<1, 0>());
+        .def("returnChildKeepAlive", &Parent::returnChild, py::keep_alive<1, 0>())
+        .def("returnNullChildKeepAliveChild", &Parent::returnNullChild, py::keep_alive<1, 0>())
+        .def("returnNullChildKeepAliveParent", &Parent::returnNullChild, py::keep_alive<0, 1>());
 
     py::class_<Child>(m, "Child")
         .def(py::init<>());

example/example-keep-alive.py

diff --git a/example/example-keep-alive.py b/example/example-keep-alive.py
index ad0176e..187ad53 100644
--- a/example/example-keep-alive.py
+++ b/example/example-keep-alive.py
@@ -31,6 +31,7 @@
     gc.collect()
     print(p)
     p = None
+
 gc.collect()
 print("")
 
@@ -43,4 +44,24 @@
 
 gc.collect()
 print("")
+
+if True:
+    p = Parent()
+    p.returnNullChildKeepAliveChild()
+    gc.collect()
+    print(p)
+    p = None
+
+gc.collect()
+print("")
+
+if True:
+    p = Parent()
+    p.returnNullChildKeepAliveParent()
+    gc.collect()
+    print(p)
+    p = None
+
+gc.collect()
+print("")
 print("Terminating..")

example/example-keep-alive.ref

diff --git a/example/example-keep-alive.ref b/example/example-keep-alive.ref
index 7eb02c5..775aff4 100644
--- a/example/example-keep-alive.ref
+++ b/example/example-keep-alive.ref
@@ -22,4 +22,12 @@
 Releasing parent.
 Releasing child.
 
+Allocating parent.
+<example.Parent object at 0x10eb726c0>
+Releasing parent.
+
+Allocating parent.
+<example.Parent object at 0x10eb726c0>
+Releasing parent.
+
 Terminating..