#include <stdio.h>
#include <pthread.h>

void* func(void* arg) {
  printf("Hello World\n");
  return NULL;
}

int main() {

  pthread_t t; // 定義一個線程
  pthread_create(&t, NULL, func, NULL); // 創(chuàng)建線程并且執(zhí)行函數(shù) func 

  // wait unit thread t finished
  pthread_join(t, NULL); // 主線程等待線程 t 執(zhí)行完成然后主線程才繼續(xù)往下執(zhí)行

  printf("thread t has finished\n");
  return 0;
}

clang helloworld.c -o helloworld.out -lpthread
或者
gcc helloworld.c -o helloworld.out -lpthread

int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
                          void *(*start_routine) (void *), void *arg);

import threading

def func():
	print("Hello World")


if __name__ == '__main__':
	t = threading.Thread(target=func)
	t.start()
	t.join()

    def start(self):
        if not self._initialized:
            raise RuntimeError("thread.__init__() not called")

        if self._started.is_set():
            raise RuntimeError("threads can only be started once")

        with _active_limbo_lock:
            _limbo[self] = self
        try:
            _start_new_thread(self._bootstrap, ())
        except Exception:
            with _active_limbo_lock:
                del _limbo[self]
            raise
        self._started.wait()
 

    def run(self):
        try:
            if self._target is not None:
                self._target(*self._args, **self._kwargs)
        finally:
            # Avoid a refcycle if the thread is running a function with
            # an argument that has a member that points to the thread.
            del self._target, self._args, self._kwargs

    def _bootstrap(self):
        try:
            self._bootstrap_inner()
        except:
            if self._daemonic and _sys is None:
                return
            raise

    def _bootstrap_inner(self):
        try:
            self._set_ident()
            self._set_tstate_lock()
            if _HAVE_THREAD_NATIVE_ID:
                self._set_native_id()
            self._started.set()
            with _active_limbo_lock:
                _active[self._ident] = self
                del _limbo[self]

            if _trace_hook:
                _sys.settrace(_trace_hook)
            if _profile_hook:
                _sys.setprofile(_profile_hook)

            try:
                self.run()
            except:
                self._invoke_excepthook(self)
        finally:
            self._delete()

long
PyThread_start_new_thread(void (*func)(void *), void *arg)
{
    pthread_t th;
    int status;
    pthread_attr_t attrs;
    size_t      tss;

    if (!initialized)
        PyThread_init_thread();

    if (pthread_attr_init(&attrs) != 0)
        return -1;
    tss = (_pythread_stacksize != 0) ? _pythread_stacksize
                                     : THREAD_STACK_SIZE;
    if (tss != 0) {
        if (pthread_attr_setstacksize(&attrs, tss) != 0) {
            pthread_attr_destroy(&attrs);
            return -1;
        }
    }
    pthread_attr_setscope(&attrs, PTHREAD_SCOPE_SYSTEM);

    status = pthread_create(&th,
                             &attrs,
                             (void* (*)(void *))func,
                             (void *)arg
                             ); // 創(chuàng)建新線程執(zhí)行函數(shù) func，也就是傳遞過來的函數(shù) t_bootstrap（函數(shù)內容見下方）
    // 在執(zhí)行完上面的代碼之后線程就會立即執(zhí)行了不需要像 Python 當中的線程一樣需要調用 start
    pthread_attr_destroy(&attrs);
    if (status != 0)
        return -1;

    pthread_detach(th);

    return (long) th;
}

static void
t_bootstrap(void *boot_raw)
{
    struct bootstate *boot = (struct bootstate *) boot_raw;
    PyThreadState *tstate;
    PyObject *res;

    tstate = boot->tstate;
    tstate->thread_id = PyThread_get_thread_ident();
    _PyThreadState_Init(tstate);
    PyEval_AcquireThread(tstate);
    nb_threads++;
    // boot->func 就是從 Python 層面?zhèn)鬟f過來的 _bootstrap 
    // PyEval_CallObjectWithKeywords 就是調用 Python 層面的函數(shù)
    // 下面這行代碼就是在創(chuàng)建線程后執(zhí)行的 Python 代碼
    res = PyEval_CallObjectWithKeywords(
        boot->func, boot->args, boot->keyw);
    if (res == NULL) {
        if (PyErr_ExceptionMatches(PyExc_SystemExit))
            PyErr_Clear();
        else {
            PyObject *file;
            PySys_WriteStderr(
                "Unhandled exception in thread started by ");
            file = PySys_GetObject("stderr");
            if (file != NULL && file != Py_None)
                PyFile_WriteObject(boot->func, file, 0);
            else
                PyObject_Print(boot->func, stderr, 0);
            PySys_WriteStderr("\n");
            PyErr_PrintEx(0);
        }
    }
    else
        Py_DECREF(res);
    Py_DECREF(boot->func);
    Py_DECREF(boot->args);
    Py_XDECREF(boot->keyw);
    PyMem_DEL(boot_raw);
    nb_threads--;
    PyThreadState_Clear(tstate);
    PyThreadState_DeleteCurrent();
    PyThread_exit_thread();
}

def recv(socket):
  while True:
    try:
      data = socket.recv() # 接收到數(shù)據(jù)了
    	return data
    except BlockingIOError:
      yield # 讓出 CPU 的執(zhí)行權，也就是將協(xié)程暫停，讓其他協(xié)程運行起來

def event_loop():
  coroutines = [...]
  while coroutines.is_not_empty():
    coroutine = get_a_coroutine(coroutines)
    res = coroutine.run() # 當程序從這里返回的時候要么是協(xié)程停下來了，要么是協(xié)程執(zhí)行完成了
    if coroutine.is_not_finished():
      append(coroutines)