线程也是由两个部分组成的&＃xff1a;
• 一个是线程的内核对象&＃xff0c;操作系统用它来对线程实施管理。内核对象也是系统用来存放线程统计信息的地方。
• 另一个是线程堆栈&＃xff0c;它用于维护线程在执行代码时需要的所有函数参数和局部变量&＃xff08;第1 6章将进一步介绍系统如何管理线程堆栈&＃xff09;。
如何创建线程&＃xff1a;
HANDLE CreateThread( PSECURITY_ATTRIBUTES psa, //安全结构体如果希望内核对象能被子进程继承必须将b I n h e r i t H a n d l e成员被初始化为T R U E DWORD cbStack, //线程堆栈大小 PTHREAD_START_ROUTINE pfnStartAddr, //线程函数地址 PVOID pvParam, //线程参数地址 DWORD fdwCreate, //创建标示&＃xff08;是否立即执行在这指定&＃xff09; PDWORD pdwThreadID //线程ID );1.系统创建内核对象&＃xff0c;使用计数为2、暂停计数为1、退出码为 STILL_ACTIVE&＃xff08;0 x 1 0 3&＃xff09;。
2.分配线程堆栈内存&＃xff0c;并将pvParam&＃xff0c;和ptnStarAddr压入堆栈&＃xff0c;SP指向ptnStarAddr&＃xff0c;IPBaseThreadStart函数所在地址&＃xff08;也就是说代码从此处执行&＃xff09;。
基于C/C&＃43;&＃43;运行库的线程创建函数
unsigned long _beginthreadex(void *security,unsigned stack_size,unsigned *start_address)(void *),void *arglist,unsigned initflag,unsigned *thrdaddr);static unsigned long WINAPI threadstartex (void* ptd){
//Note:ptd is the address of this thread&＃39;s tiddata block.
//Associate the tiddata block with this thread.
TlsSetValue(__tlsindex, ptd);
//Save this thread ID in the tiddata block.
((_ptiddata)ptd)->_tid &＃61; GetCurrentThreadId();
//Initialize floating-point support (code not shown).
//wrap desired thread function in SEH frame to
//handle run-time errors and signal support.
__try {
//Call desired thread function, passing it the desired parameter.
//Pass thread&＃39;s exit code value to _endthreadex.
_endthreadex(
((unsigned(WINAPI *)(void *))(((_ptiddata)ptd)->_initaddr))
(((_ptiddata)ptd)->_initarg));
}
__except(_XcptFilter(GetExceptionCode(), GetExceptionInformation()))
{
//The C run-time&＃39;s exception handler deals with run-time errors
//and signal support; we should never get it here.
_exit(GetExceptionCode()); }
//We never get here; the thread dies in this function.
return(0L);
}
注意到这里((unsigned(WINAPI *)(void *))(((_ptiddata)ptd)->_initaddr))(((_ptiddata)ptd)->_initarg)); //Note:ptd is the address of this thread&＃39;s tiddata block.
//Associate the tiddata block with this thread.
TlsSetValue(__tlsindex, ptd);
//Save this thread ID in the tiddata block.
((_ptiddata)ptd)->_tid &＃61; GetCurrentThreadId();
//Initialize floating-point support (code not shown).
//wrap desired thread function in SEH frame to
//handle run-time errors and signal support.
__try {
//Call desired thread function, passing it the desired parameter.
//Pass thread&＃39;s exit code value to _endthreadex.
_endthreadex(
((unsigned(WINAPI *)(void *))(((_ptiddata)ptd)->_initaddr))
(((_ptiddata)ptd)->_initarg));
}
__except(_XcptFilter(GetExceptionCode(), GetExceptionInformation()))
{
//The C run-time&＃39;s exception handler deals with run-time errors
//and signal support; we should never get it here.
_exit(GetExceptionCode()); }
//We never get here; the thread dies in this function.
return(0L);
}
在_threadstartex函数里面启动了新的线程函数....
后面的代码就是加入一个SEH链处理异常了
前面的代码呢主要是将PTD和线程做关联.
这个过程相当于在新线程外面加了一层包装吧...
在这个包装的过程中系统为线程关联了一个独立的PTD数据块。
在C/C&＃43;&＃43;运行库的基础上线程的创建过程是这样的&＃xff1a;
_beginthreadex&＃xff08;&＃xff09;
----(将线程的启动地址、参数地址存入PTD&＃xff0c;替换CreateThread&＃xff08;&＃xff09;的线程函数地址参数&＃xff0c;和线程参数参数&＃xff0c;为启动threadstartex&＃xff08;&＃xff09;做准备)--------->
CreateThread&＃xff08;&＃xff09;
---(按照正常的过程建立内核对象、分配线程堆栈、并将beginthreadex函数中替换过得参数压入栈&＃xff0c;置CS与IP寄存器指向BaseThreadStart)---->
BaseThreadStart&＃xff08;&＃xff09;
---------------->
threadstartex
----------(为线程关联PTD)--------------->
pfnStartAddr&＃xff08;&＃xff09;
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