在C语言中，“主进程结束”与“调用在atexit中注册的任何函数”之间缺少链接

Question

In C, when the main process ends -- how does it know to call any functions registered with atexit() ?

I understand how atexit() works, but I don't understand the communication between "Main process ending" and "call any functions registered with atexit() " I'm being a bit redundant.

Thanks!

Answer 1

In C, the main() function is actually called by some other function, which is built into the runtime. This function, after the main() function ends, does a few more things to clean up. One of them is to call any functions which have been registered with the atexit() . This function actually stores some kind of static list of function pointers, which will be called by the runtime after main() .

Answer 2

From the C standard [PDF Link] (5.1.2.2.3):

a return from the initial call to the main function is equivalent to calling the exit function with the value returned by the main function as its argument; reaching the } that terminates the main function returns a value of 0 .

It is the responsibility of the exit function to call the functions registered with atexit (see 7.20.4.3 in the standard for a description of everything that exit does).