#define PY_SSIZE_T_CLEAN
#include <Python.h>

#include <assert.h>
#include <pthread.h>
#include <unistd.h>

int tracefunc(PyObject *, PyFrameObject *, int, PyObject *)
{
    return 0;
}

void*
thread_body(void*)
{
    PyGILState_STATE gilstate = PyGILState_Ensure();
    PyEval_SetTrace(&tracefunc, Py_None);
    PyGILState_Release(gilstate);
    return NULL;
}

PyObject*
trace_in_thread(PyObject*, PyObject*)
{
    pthread_t thread;
    int ret = pthread_create(&thread, NULL, &thread_body, NULL);
    assert(0 == ret);

    Py_BEGIN_ALLOW_THREADS
    ret = pthread_join(thread, NULL);
    assert(0 == ret);
    Py_END_ALLOW_THREADS

    Py_RETURN_NONE;
}

static PyMethodDef methods[] = {
        {"trace_in_thread", trace_in_thread, METH_NOARGS, "Call PyEval_SetTrace in a thread"},
        {NULL, NULL, 0, NULL},
};

static struct PyModuleDef moduledef = {PyModuleDef_HEAD_INIT, "testext", "", -1, methods};

PyMODINIT_FUNC
PyInit_testext(void)
{
    return PyModule_Create(&moduledef);
}