cross_module_gil_utils.cpp

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/*
    tests/cross_module_gil_utils.cpp -- tools for acquiring GIL from a different module

    Copyright (c) 2019 Google LLC

    All rights reserved. Use of this source code is governed by a
    BSD-style license that can be found in the LICENSE file.
*/
#include <pybind11/pybind11.h>
#include <cstdint>

// This file mimics a DSO that makes pybind11 calls but does not define a
// PYBIND11_MODULE. The purpose is to test that such a DSO can create a
// py::gil_scoped_acquire when the running thread is in a GIL-released state.
//
// Note that we define a Python module here for convenience, but in general
// this need not be the case. The typical scenario would be a DSO that implements
// shared logic used internally by multiple pybind11 modules.

namespace {

namespace py = pybind11;
void gil_acquire() { py::gil_scoped_acquire gil; }

constexpr char kModuleName[] = "cross_module_gil_utils";

#if PY_MAJOR_VERSION >= 3
struct PyModuleDef moduledef = {
    PyModuleDef_HEAD_INIT,
    kModuleName,
    NULL,
    0,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL
};
#else
PyMethodDef module_methods[] = {
    {NULL, NULL, 0, NULL}
};
#endif

}  // namespace

extern "C" PYBIND11_EXPORT
#if PY_MAJOR_VERSION >= 3
PyObject* PyInit_cross_module_gil_utils()
#else
void initcross_module_gil_utils()
#endif
{

    PyObject* m =
#if PY_MAJOR_VERSION >= 3
        PyModule_Create(&moduledef);
#else
        Py_InitModule(kModuleName, module_methods);
#endif

    if (m != NULL) {
        static_assert(
            sizeof(&gil_acquire) == sizeof(void*),
            "Function pointer must have the same size as void*");
        PyModule_AddObject(m, "gil_acquire_funcaddr",
                           PyLong_FromVoidPtr(reinterpret_cast<void*>(&gil_acquire)));
    }

#if PY_MAJOR_VERSION >= 3
    return m;
#endif
}