std::atexit

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Utilities library

Type support (basic types, RTTI, type traits)

Dynamic memory management

Error handling

Program utilities

Variadic functions

Date and time

Function objects

initializer_list (C++11)

bitset

hash (C++11)

Relational operators

rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=

optional, any and variant (C++17)

optional

any

variant

in_placein_place_typein_place_indexin_place_tin_place_type_tin_place_index_t

Pairs and tuples

pair

tuple (C++11)

apply (C++17)

make_from_tuple (C++17)

piecewise_construct_t (C++11)

piecewise_construct (C++11)

integer_sequence (C++14)

Swap, forward and move

swap

exchange (C++14)

forward (C++11)

move (C++11)

move_if_noexcept (C++11)

Elementary string conversions

to_chars (C++17)

from_chars (C++17)

chars_format (C++17)

Type operations

declval (C++11)

as_const (C++17)

 

Program support utilities

Program termination
abort exit quick_exit (C++11) _Exit (C++11)	atexit at_quick_exit (C++11) EXIT_SUCCESSEXIT_FAILURE
Communicating with the environment
system	getenv
Signals
signal raise sig_atomic_t	SIG_DFLSIG_IGN SIG_ERR
Signal types
SIGABRTSIGFPESIGILLSIGINTSIGSEGVSIGTERM
Non-local jumps
setjmp
longjmp
Types
jmp_buf

 

Defined in header <cstdlib>
int atexit( /*c-atexit-handler*/* func ); int atexit( /*atexit-handler*/* func );	(1)
extern "C++" using /*atexit-handler*/ = void(); // exposition-only extern "C" using /*c-atexit-handler*/ = void(); // exposition-only	(2)

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

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) 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

See also

at_quick_exit (C++11)	registers a function to be called on quick_exit invocation (function)
C documentation for atexit