作为通用的跨平台高性能线程库，在很多跨平台的项目中都可以看见pthread的身影。pthread本身的实现比较优雅，APIs使用起来也很方便。

但在Windows下使用静态编译的pthread时要特别注意一下，必须显式的调用如下四个函数，否则pthread用到的一些全局变量会没有被初始化，导致所有的pthread的APIs调用都crash.

BOOL pthread_win32_process_attach_np (void);

BOOL pthread_win32_process_detach_np (void);

BOOL pthread_win32_thread_attach_np (void);

BOOL pthread_win32_thread_detach_np (void);

pthread官方文档对此有如下的明确说明：

These functions contain the code normally run via dllMain when the library is used as a dll but which need to be called explicitly by an application when the library is statically linked.

You will need to call pthread_win32_process_attach_np() before you can call any pthread routines when statically linking.

You should call pthread_win32_process_detach_np() before exiting your application to clean up.

pthread_win32_thread_attach_np() is currently a no-op, but pthread_win32_thread_detach_np() is needed to clean up the implicit pthread handle that is allocated to a Win32 thread if it calls certain pthreads routines. Call this routine when the Win32 thread exits.

These functions invariably return TRUE except for pthread_win32_process_attach_np() which will return FALSE if pthreads-win32 initialisation fails.

通过函数的名字我们不难猜测出如下调用顺序

在程序开始的时候要调用：

BOOL pthread_win32_process_attach_np (void);

BOOL pthread_win32_thread_attach_np (void);

在程序退出时要调用：

BOOL pthread_win32_thread_detach_np (void);

BOOL pthread_win32_process_detach_np (void);

比较通用的做法是在模块Load和UnLoad的时候做这个attach和detach操作，如下面所示：

/* Callback for our DLL so we can initialize pthread */ 
 
BOOL WINAPI DllMain( HANDLE hinstDLL, DWORD fdwReason, LPVOID lpvReserved ) 
{ 
#ifdef PTW32_STATIC_LIB 
    switch( fdwReason ) 
    { 
        case DLL_PROCESS_ATTACH: 
            pthread_win32_process_attach_np(); 
        case DLL_THREAD_ATTACH: 
            pthread_win32_thread_attach_np(); 
            break; 
        case DLL_THREAD_DETACH: 
            pthread_win32_thread_detach_np(); 
            break; 
        case DLL_PROCESS_DETACH: 
            pthread_win32_thread_detach_np(); 
            pthread_win32_process_detach_np(); 
            break; 
    } 
#endif 
    return TRUE; 
} 

注意： PTW32_STATIC_LIB 宏为pthread静态编译的标志，这个可以通过pthread.h的配置或者CFLAGS传递进来。

BOOL WINAPI DllMain (HINSTANCE hinstDll, DWORD fdwReason, LPVOID lpvReserved) 
{ 
  BOOL result = PTW32_TRUE; 
  switch (fdwReason) 
    { 
    case DLL_PROCESS_ATTACH: 
      result = pthread_win32_process_attach_np (); 
      break; 
    case DLL_THREAD_ATTACH: 
      /* 
       * A thread is being created 
       */ 
      result = pthread_win32_thread_attach_np (); 
      break; 
    case DLL_THREAD_DETACH: 
      /* 
       * A thread is exiting cleanly 
       */ 
      result = pthread_win32_thread_detach_np (); 
      break; 
    case DLL_PROCESS_DETACH: 
      (void) pthread_win32_thread_detach_np (); 
      result = pthread_win32_process_detach_np (); 
      break; 
    } 
  return (result); 
} /* DllMain */ 

#ifdef PTW32_STATIC_LIB  
static void detach_ptw32(void)  
{  
    pthread_win32_thread_detach_np();  
    pthread_win32_process_detach_np();  
}  
#endif  

#ifdef PTW32_STATIC_LIB  
    pthread_win32_process_attach_np();  
    pthread_win32_thread_attach_np();  
    atexit(detach_ptw32);  
#endif