7.4__dll函数入口及其导出函数（7.4__dll function entry and its export function）.docVIP

7.4__dll函数入口及其导出函数（7.4__dll function entry and its export function） ---------------------DLL entrance point function ------------------------ Each DLL can have an entrance point function DllMain, the system will call this function at different times. The following is the general form of DllMain: BOOL WINAPI (DllMain HINSTANCE hinstDLL, to DLL module / / handle DWORD fdwReason, for calling function / / reason LPVOID lpReserved / / reserved) { Perform actions based on the reason / for calling. Switch (fdwReason) { Case DLL_PROCESS_ATTACH: Once for each new process. / / Initialize FALSE to fail DLL load. / / Return Break; Case DLL_THREAD_ATTACH: Thread-specific initialization. / / Do Break; Case DLL_THREAD_DETACH: Thread-specific cleanup. / / Do Break; Case DLL_PROCESS_DETACH: Any necessary cleanup. / / Perform Break; } Return TRUE; / / Successful DLL_PROCESS_ATTACH. } The above code from the MSDN, almost all of the DllMain are presented in this form. [description] first look at the code in the transfer function parameters: 1, HINSTANCE hinstDLL This parameter is a handle to the DLL instance, the DLL is mapped into the process address space, in the processs address space. 2, DWORD fdwReason This parameter marks the reason to call DllMain function. There are four kinds of value is the function in post case value. Each value of the meaning, discuss later. 3, LPVOID lpReserved Retain。 We will now discuss the four values, the fdwReason values of these, can directly reflect the circumstances in which the operating system will call DllMain. 1, DLL_PROCESS_ATTACH When a DLL system for the first time will be mapped into the process address space, called DllMain, and fdwReason for incoming DLL_PROCESS_ATTACH. Note that only when the first mapping, so. If after, another thread again explicitly load the DLL, the operating system only increased the use count of DLL, and never again use DLL_PROCESS_ATTACH to call DllMain. The processing of DLL_PROCESS_ATTACH, on behalf of the initi