http://blog.csdn.net/psusong/archive/2010/01/14/5189659.aspx
pthread 靜態(tài)編譯版本在Windows下使用時(shí)的注意事項(xiàng)
作為通用的跨平臺(tái)高性能線程庫(kù)，在很多跨平臺(tái)的項(xiàng)目中都可以看見(jiàn)pthread的身影。pthread本身的實(shí)現(xiàn)比較優(yōu)雅，APIs使用起來(lái)也很方便。
但在Windows下使用靜態(tài)編譯的pthread時(shí)要特別注意一下，必須顯式的調(diào)用如下四個(gè)函數(shù)，否則pthread用到的一些全局變量會(huì)沒(méi)有被初始化，導(dǎo)致所有的pthread的APIs調(diào)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官方文檔對(duì)此有如下的明確說(shuō)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.
通過(guò)函數(shù)的名字我們不難猜測(cè)出如下調(diào)用順序
在程序開(kāi)始的時(shí)候要調(diào)用：
BOOL pthread_win32_process_attach_np (void);
BOOL pthread_win32_thread_attach_np (void);
在程序退出時(shí)要調(diào)用：
BOOL pthread_win32_thread_detach_np (void);
BOOL pthread_win32_process_detach_np (void);
比較通用的做法是在模塊Load和UnLoad的時(shí)候做這個(gè)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 宏為pthread靜態(tài)編譯的標(biāo)志，這個(gè)可以通過(guò)pthread.h的配置或者CFLAGS傳遞進(jìn)來(lái)。
下面是pthread的官方的dll.c的實(shí)現(xiàn)
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 */
也就是說(shuō)pthread官方代碼在動(dòng)態(tài)編譯的版本中主動(dòng)做了這個(gè)attach和detach操作。
而靜態(tài)編譯版本由于沒(méi)有一個(gè)合適的地方來(lái)做這件事，就將attach和detach的的操作扔給用戶來(lái)完成了。
上面的代碼是針對(duì)調(diào)用方是Dll的情況做的初始化，如果調(diào)用方不是Dll呢？對(duì)此可以參照如下做法，雖然很暴力，但很簡(jiǎn)單，可以工作
1）定義如下函數(shù)
#ifdef PTW32_STATIC_LIB
static void detach_ptw32(void)
{
pthread_win32_thread_detach_np();
pthread_win32_process_detach_np();
}
#endif
2）在你的主程序的入口處，一般而言是main()中做如下調(diào)用即可
#ifdef PTW32_STATIC_LIB
pthread_win32_process_attach_np();
pthread_win32_thread_attach_np();
atexit(detach_ptw32);
#endif
也就是用atexit()將detach工作掛接到程序中去，使得程序在退出的時(shí)候可以對(duì)pthread進(jìn)行detach.