shared_ptr.cpp

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/*
 * This file is part of KnowRob, please consult
 * https://github.com/knowrob/knowrob for license details.
 */
 
#include <knowrob/Logger.h>
#include <knowrob/ThreadPool.h>
#include <knowrob/integration/python/gil.h>
#include <knowrob/integration/python/converter/shared_ptr.h>
 
#define KNOWROB_PY_USE_SHARED_PTR_DELETER_QUEUE
 
namespace boost::python::converter {
    void shared_ptr_deleter::operator()(void const *) {
        // This is needed to release the Python GIL when the shared_ptr is deleted.
        // Otherwise, if the shared_ptr is deleted in a C++ thread,
        // Python will crash because the GIL is not acquired.
        // There was also a debate about adding this to boost which was not really conclusive
        // ite seems.
        // @see https://github.com/boostorg/python/pull/11
 
#ifdef KNOWROB_PY_USE_SHARED_PTR_DELETER_QUEUE
        static knowrob::ThreadPool gil_pool(1);
        // release the shared_ptr such that we can call reset in a worker thread
        auto released_ptr = owner.release();
        // a lambda worker that will lock the GIL and delete the pointer.
        // note that calling reset in the current thread directly may cause deadlocks.
        auto runner = std::make_shared<knowrob::ThreadPool::LambdaRunner>(
            [released_ptr](const knowrob::ThreadPool::LambdaRunner::StopChecker &) {
                knowrob::py::gil_lock gil;
                handle<> ptr_handle(released_ptr);
                ptr_handle.reset();
            });
        gil_pool.pushWork(runner, [](const std::exception &e) {
            KB_WARN("an exception occurred when deleting ptr: {}.", e.what());
            throw;
        });
#else
        knowrob::py::gil_lock gil;
        owner.reset();
#endif
    }
}
 
namespace boost {
    // This is needed for boost::python to work with std::shared_ptr.
    // @see https://stackoverflow.com/questions/46435509/boostpython-stdshared-ptr-to-stdshared-ptr
    template<class T>
    T *get_pointer(std::shared_ptr<T> p) { return p.get(); }
}