Boost.Python equivalent of test_private_first_base under pybind11 PR …

…#2672.

pybind/pybind11#2672

SConscript

@@ -9,6 +9,9 @@ env_etc.include_registry.append(
     env_etc.boost_adaptbx_include,
     env_etc.boost_include,
     env_etc.python_include])
+env.SharedLibrary(
+  target="#lib/rwgk_tbx_private_first_base_ext",
+  source="private_first_base_ext.cpp")
 env.SharedLibrary(
   target="#lib/rwgk_tbx_smart_ptr_private_first_base_ext",
   source="smart_ptr_private_first_base_ext.cpp")

private_first_base.py

@@ -0,0 +1,4 @@
+from __future__ import absolute_import, division, print_function
+import boost_adaptbx.boost.python as bp
+ext = bp.import_ext("rwgk_tbx_private_first_base_ext")
+from rwgk_tbx_private_first_base_ext import *

private_first_base_ext.cpp

@@ -0,0 +1,54 @@
+// Boost.Python equivalent of test_private_first_base under
+// pybind11 PR #2672:
+// https://github.com/pybind/pybind11/pull/2672
+
+#include <boost/python/class.hpp>
+#include <boost/python/def.hpp>
+#include <boost/python/manage_new_object.hpp>
+#include <boost/python/module.hpp>
+#include <boost/python/return_value_policy.hpp>
+
+namespace {
+
+struct base {
+  base() : base_id(100) {}
+  virtual ~base() = default;
+  virtual int id() const { return base_id; }
+  base(const base&) = default;
+  int base_id;
+};
+
+struct private_first_base {  // Any class with a virtual function will do.
+  private_first_base() {}
+  virtual void some_other_virtual_function() const {}
+  virtual ~private_first_base() = default;
+  private_first_base(const private_first_base&) = default;
+};
+
+struct drvd : private private_first_base, public base {
+  drvd() {}
+  int id() const override { return 2 * base_id; }
+};
+
+inline drvd* make_drvd() { return new drvd; }
+inline base* make_drvd_up_cast() { return new drvd; }
+
+inline int pass_base(const base* b) { return b->id(); }
+inline int pass_drvd(const drvd* d) { return d->id(); }
+
+}  // namespace
+
+BOOST_PYTHON_MODULE(rwgk_tbx_private_first_base_ext)
+{
+  namespace py = boost::python;
+
+  py::class_<base>("base");
+  py::class_<drvd, py::bases<base>>("drvd");
+
+  py::def("make_drvd", make_drvd,
+          py::return_value_policy<py::manage_new_object>());
+  py::def("make_drvd_up_cast", make_drvd_up_cast,
+          py::return_value_policy<py::manage_new_object>());
+  py::def("pass_base", pass_base);
+  py::def("pass_drvd", pass_drvd);
+}

tst_private_first_base.py

@@ -0,0 +1,29 @@
+from __future__ import absolute_import, division, print_function
+
+import rwgk_tbx.private_first_base as m
+import sys
+
+
+def test_make_drvd_pass_base():
+    d = m.make_drvd()
+    i = m.pass_base(d)
+    assert i == 200
+
+
+def test_make_drvd_up_cast_pass_drvd():
+    b = m.make_drvd_up_cast()
+    # the base return is down-cast immediately.
+    assert b.__class__.__name__ == "drvd"
+    i = m.pass_drvd(b)
+    assert i == 200
+
+
+def run(args):
+  assert not args
+  test_make_drvd_pass_base()
+  test_make_drvd_up_cast_pass_drvd()
+  print("Done.")
+
+
+if (__name__ == "__main__"):
+  run(sys.argv[1:])