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.


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

Return value

​0​ if the registration succeeds, nonzero value otherwise.


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


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


#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

See also

registers a function to be called on quick_exit invocation
C documentation for atexit

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