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std::atexit

Defined in header `<cstdlib>`
extern "C" int atexit( void (*func)() );
extern "C++" int atexit( void (*func)() );

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.

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).

Exceptions

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

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;
}

Output:

returning from main
at exit #2
at exit #1