< cpp‎ | utility‎ | program
Program support utilities
Program termination
Communicating with the environment
Signal types
Non-local jumps
Defined in header <cstdlib>
int atexit( /*c-atexit-handler*/* func );
int atexit( /*atexit-handler*/* func );
extern "C++" using /*atexit-handler*/ = void(); // exposition-only
extern "C" using /*c-atexit-handler*/ = void(); // exposition-only

Registers the function pointed to by func to be called on normal program termination (via std::exit() or returning from the main function)

The functions will be called during the destruction of the static objects, in reverse order: if A was registered before B, then the call to B is made before the call to A. Same applies to the ordering between static object constructors and the calls to atexit: see std::exit (until C++11)
The functions may be called concurrently with the destruction of the objects with static storage duration and with each other, maintaining the guarantee that if registration of A was sequenced-before the registration of B, then the call to B is sequenced-before the call to A, same applies to the sequencing between static object constructors and calls to atexit: see std::exit (since C++11)

The same function may be registered more than once.

If a function exits via an exception, std::terminate is called.

atexit is thread-safe: calling the function from several threads does not induce a data race.

The implementation is guaranteed to support the registration of at least 32 functions. The exact limit is implementation-defined.


[edit] Parameters

func - pointer to a function to be called on normal program termination

[edit] Return value

0 if the registration succeeds, nonzero value otherwise.

[edit] Notes

The two overloads are distinct because the types of the parameter func are distinct (language linkage is part of its type)

[edit] Exceptions

(none) (until C++11)
noexcept specification:  
(since C++11)

[edit] Example

#include <iostream>
#include <cstdlib>
void atexit_handler_1() 
    std::cout << "at exit #1\n";
void atexit_handler_2() 
    std::cout << "at exit #2\n";
int main() 
    const int result_1 = std::atexit(atexit_handler_1);
    const int result_2 = std::atexit(atexit_handler_2);
    if ((result_1 != 0) or (result_2 != 0)) {
        std::cerr << "Registration failed\n";
        return EXIT_FAILURE;
    std::cout << "returning from main\n";
    return EXIT_SUCCESS;


returning from main
at exit #2
at exit #1

[edit] See also

causes abnormal program termination (without cleaning up)
(function) [edit]
causes normal program termination with cleaning up
(function) [edit]
causes quick program termination without completely cleaning up
(function) [edit]
registers a function to be called on quick_exit invocation
(function) [edit]
C documentation for atexit