NAME¶

std::atexit - std::atexit

Synopsis¶

Defined in header <cstdlib>
int atexit( /*c-atexit-handler*/* func ); (until C++11)
int atexit( /*atexit-handler*/* func );
int atexit( /*c-atexit-handler*/* func ) noexcept; (since C++11)
int atexit( /*atexit-handler*/* func ) noexcept; (1)
extern "C++" using /*atexit-handler*/ = void(); //
exposition-only (2)
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 (until C++11)
between static object constructors and the calls to atexit: see
std::exit
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 (since C++11)
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

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.

Parameters¶

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

Return value¶

0 if the registration succeeds, nonzero value otherwise.

Notes¶

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

Example¶

// Run this code

#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) || (result_2 != 0)) {
std::cerr << "Registration failed\n";
return EXIT_FAILURE;
}

std::cout << "returning from main\n";
return EXIT_SUCCESS;
}

Output:¶

returning from main
at exit #2
at exit #1

See also¶

abort causes abnormal program termination (without cleaning up)
(function)
exit causes normal program termination with cleaning up
(function)
quick_exit causes quick program termination without completely cleaning up
(C++11) (function)
at_quick_exit registers a function to be called on std::quick_exit invocation
(C++11) (function)