Program entry function and _security_init_cookie__ function in Windows

The Win32 program is divided into two types:

1. Console (/subsystem:console)

2.GUI (/subsystem:windows)

First look at the console version:

Write a paragraph that is the simplest, or simply use the default main function of the compiler parameter, as follows:

[CPP] view plain copy//EntryFunction.cpp: Defines the entry point for a console application.   #include "stdafx.h" int _tmain (int argc, _tchar* argv[]) {return 0; }

1. Using the/MD option

F9 down to the tag of the main function, F11 back to _tmaincrtstartup () in call stack, and the current file is crtexe.c. As follows:

2. Using the/MT option

F9 down to the tag of the main function, F11 back to _tmaincrtstartup () in call stack, and the current file is crt0.c. As follows:

That is, different runtime links, the implementation of the code is also different. But the name of the entry point function is the same, it is _tmaincrtstartup. This is the startup function (the real entry function) under Windows.

Let's discuss separately what the two do in the entry function.

First look at the _security_init_cookie, this function is the same in the two implementation files, the code is as follows:

[CPP]  View Plain  copy  /***  *__security_init_cookie (cookie)  - init buffer  overrun security cookie.  *  *purpose:  *        initialize the global buffer overrun security cookie which is  used by  *       the /gs compile switch to  detect overwrites to local array variables  *        the potentially corrupt the return address.  this routine  is called  *       at exe/dll startup.  *   *entry:  *  *exit:  *  *exceptions:  *  **************************************** /      Void __cdecl __security_init_cookie ( void)    {       UINT_PTR cookie;       FT  systime={0};       LARGE_INTEGER perfctr;           /*       * do nothing if the global  cookie has already been initialized.  On x86,        * reinitialize the cookie if it has been previously  initialized to a       * value with the high  word 0x0000.  some versions of windows will init        * the cookie in the loader, but using an older  mechanism which forced the       * high word  to zero.&nbsp      */