Implementation status: implemented

Synopsis

#include <stdlib.h>

int atexit(void (*func)(void));

Description

Function causes the specified function func to be called when the program terminates normally.

Arguments:
func - a function to be called without arguments when the program terminates normally.

The atexit() function registers the function pointed to by func, to be called without arguments at normal program termination. At normal program termination, all functions registered by the atexit() function are called, in the reverse order of their registration, except that a function is called after any previously registered functions that had already been called at the time it was registered. Normal termination occurs either by a call to exit() or a return from main().

After a successful call to any of the exec functions, any functions previously registered by atexit() are no longer registered.

The functions registered by a call to atexit() must return to ensure that all registered functions are called.

Return value

Upon successful completion, atexit() returns 0; otherwise, it returns -1.

Errors

No errors are defined.

Comments

The application calls sysconf() to obtain the value of {ATEXIT_MAX}, the number of functions that can be registered. There is no way for an application to tell how many functions have already been registered with atexit().
Since the behavior is undefined if the exit() function is called more than once, portable applications calling atexit() must ensure that the exit() function is not called at normal process termination when all functions registered by the atexit() function are called.
All functions registered by the atexit() function are called at normal process termination, which occurs by a call to the exit() function or a return from main() or on the last thread termination, when the behavior is as if the implementation called exit() with a zero argument at thread termination time.
If, at normal process termination, a function registered by the atexit() function is called and a portable application needs to stop further exit() processing, it must call the _exit() function or the _Exit() function or one of the functions which cause abnormal process termination.