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include/xo/pyutil/pyutil.hpp

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+/* @file pyutil.hpp
+ *
+ * utility stuff to be used across multiple pybind11 .cpp files
+ */
+
+#pragma once
+
+#include "xo/refcnt/Refcounted.hpp"
+#include "xo/refcnt/Unowned.hpp"
+#include <pybind11/pybind11.h>
+
+/* xo::ref::intrusive_ptr<T> is an intrusively-reference-counted pointer.
+ * always safe to create one from a T* p
+ * (since refcount is directly accessible from p)
+ *
+ * Need declaration like this before any pybind11 bindings
+ * that expose an object of types like
+ * (a) intrusive_ptr<T> or
+ * (b) T * / T const * / T & / T const & to python.
+ * If this were not done,  pybind11 would by default use unique_ptr<intrusive_ptr<T>>
+ * (ok but inefficient) or unique_ptr<T> (fatal!)
+ */
+PYBIND11_DECLARE_HOLDER_TYPE(T, xo::ref::intrusive_ptr<T>, true);
+
+/* xo::ref::unowned_ptr<T> is an unmanaged pointer.
+ * use this for immortal objects that pybind11 must not delete.
+ */
+PYBIND11_DECLARE_HOLDER_TYPE(T, xo::ref::unowned_ptr<T>, true);
+
+/* end pyutil.hpp */