NAME

atexit — register a function to be called on exit

SYNOPSIS

#include <stdlib.h>

int
atexit(void (*function)(void));

int
atexit_b(void (^function)(void));

DESCRIPTION

The atexit() function registers the given function to be called at program exit, whether via exit(3) or via return from the program's main(). Functions so registered are called in reverse order; no arguments are passed.

If the provided function is located in a library that has been dynamically loaded (e.g. by dlopen()), it will be called when the library is unloaded (due to a call to dlclose()) or at program exit.

The atexit_b() function is like atexit() except the callback is a block pointer instead of a function pointer.

Note: The Block_copy() function (defined in <Blocks.h>) is used by atexit_b() to make a copy of the block, especially for the case when a stack-based block might go out of scope when the subroutine returns.

These functions must not call exit(); if it should be necessary to terminate the process while in such a function, the _exit(2) function should be used. (Alternatively, the function may cause abnormal process termination, for example by calling abort(3).)

At least 32 functions can always be registered, and more are allowed as long as sufficient memory can be allocated.

RETURN VALUES

The atexit() and atexit_b() functions return the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

ERRORS

[ENOMEM]: No memory was available to add the function to the list. The existing list of functions is unmodified.

STANDARDS

The atexit() function conforms to ISO/IEC 9899:1990 (“ISO C90”).

September 6, 2002