main主函数执行完毕后，是否可能会再执行一段代码

可以使用atexit()函数注册一个函数

#include <stdlib.h>

//功能：Processes the specified function at exit.
//格式：int atexit( void ( __cdecl *func )( void ) );
//描述：The atexit function is passed the address of a function (func) to be
// called when the program terminates normally. Successive calls to atexit
//create a register of functions that are executed in LIFO (last-in-first-out)
//order. The functions passed to atexit cannot take parameters. atexit and
//_onexit use the heap to hold the register of functions. Thus, the number of
// functions that can be registered is limited only by heap memory.
int atexit (void (*function)(void));


#include <stdio.h>

void fun1(void);

void fun2(void);

void fun3(void);

void fun4(void);

void main()

{

    atexit(fun1);

    atexit(fun2);

    atexit(fun3);

    atexit(fun4);

    printf("this is executed first.\n");

}

void fun1()
{
    printf("next.\n");
}

void fun2()
{
    printf("executed ");
}

void fun3()
{
    printf("is ");
}

void fun4()
{
    printf("this ");
}