Boost.Python equivalent of test_smart_ptr_private_first_base under py…

…bind11 PR #2672.

pybind/pybind11#2672 (comment)

README.md

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+# Experimental stuff using cctbx_project/libtbx build tools.
+
+## Example bootstrap
+```
+cd clone  # Any name.
+git clone https://github.com/SCons/scons.git
+git clone https://github.com/cctbx/boost.git
+git clone https://github.com/cctbx/cctbx_project.git
+git clone https://github.com/rwgk/rwgk_tbx.git
+mkdir bintbx  # Any other name.
+cd bintbx
+python3 ../cctbx_project/libtbx/configure.py --compiler=clang rwgk_tbx
+source setpaths.sh
+make
+libtbx.python ../rwgk_tbx/tst_smart_ptr_private_first_base.py
+```

SConscript

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+import libtbx.load_env
+Import("env_etc", "env_no_includes_boost_python_ext")
+env = env_no_includes_boost_python_ext.Clone()
+env_etc.enable_more_warnings(env=env)
+env_etc.include_registry.append(
+  env=env,
+  paths=[
+    env_etc.libtbx_include,
+    env_etc.boost_adaptbx_include,
+    env_etc.boost_include,
+    env_etc.python_include])
+env.SharedLibrary(
+  target="#lib/rwgk_tbx_smart_ptr_private_first_base_ext",
+  source="smart_ptr_private_first_base_ext.cpp")

libtbx_config

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+{
+  "optional_modules": ["boost"]
+}

smart_ptr_private_first_base.py

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+from __future__ import absolute_import, division, print_function
+import boost_adaptbx.boost.python as bp
+ext = bp.import_ext("rwgk_tbx_smart_ptr_private_first_base_ext")
+from rwgk_tbx_smart_ptr_private_first_base_ext import *

smart_ptr_private_first_base_ext.cpp

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+// Boost.Python equivalent of test_smart_ptr_private_first_base under
+// pybind11 PR #2672:
+// https://github.com/pybind/pybind11/pull/2672#issuecomment-748543648
+
+#include <boost/python/class.hpp>
+#include <boost/python/def.hpp>
+#include <boost/python/module.hpp>
+
+#include <memory>
+
+namespace {
+
+struct base {
+  base() : base_id(100) {}
+  virtual ~base() = default;
+  virtual int id() const { return base_id; }
+  int base_id;
+};
+
+struct private_first_base {  // Any class with a virtual function will do.
+  virtual void some_other_virtual_function() const {}
+  virtual ~private_first_base() = default;
+};
+
+struct drvd : private private_first_base, public base {
+  int id() const override { return 2 * base_id; }
+};
+
+inline std::shared_ptr<drvd> make_shared_drvd() {
+  return std::shared_ptr<drvd>(new drvd);
+}
+
+inline int pass_shared_base(std::shared_ptr<base> b) { return b->id(); }
+
+}  // namespace
+
+BOOST_PYTHON_MODULE(rwgk_tbx_smart_ptr_private_first_base_ext)
+{
+  namespace py = boost::python;
+
+  py::class_<base, std::shared_ptr<base>>("base");
+  py::class_<drvd, py::bases<base>, std::shared_ptr<drvd>>("drvd");
+
+  py::def("make_shared_drvd", make_shared_drvd);
+  py::def("pass_shared_base", pass_shared_base);
+}

tst_smart_ptr_private_first_base.py

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+from __future__ import absolute_import, division, print_function
+
+import rwgk_tbx.smart_ptr_private_first_base as m
+import sys
+
+def run(args):
+  assert not args
+  d = m.make_shared_drvd()
+  i = m.pass_shared_base(d)
+  assert i == 200
+  print("Done.")
+
+if (__name__ == "__main__"):
+  run(sys.argv[1:])