This documentation is archived and is not being maintained.


Processes the specified function at exit.

int atexit(
   void (__cdecl *func )( void )



Function to be called.

atexit returns 0 if successful, or a nonzero value if an error occurs.

The atexit function is passed the address of a function (func) to be called when the program terminates normally. Successive calls to atexit create a register of functions that are executed in last-in, first-out (LIFO) order. The functions passed to atexit cannot take parameters. atexit and _onexit use the heap to hold the register of functions. Thus, the number of functions that can be registered is limited only by heap memory.

The code in the atexit function should not contain any dependency on any DLL which could have already been unloaded when the atexit function is called.

To generate an ANSI-compliant application, use the ANSI-standard atexit function (rather than the similar _onexit function).

Routine Required header Compatibility



ANSI, Windows 95, Windows 98, Windows 98 Second Edition, Windows Millennium Edition, Windows NT 4.0, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003

This program pushes four functions onto the stack of functions to be executed when atexit is called. When the program exits, these programs are executed on a last in, first out basis.

// crt_atexit.c
#include <stdlib.h>
#include <stdio.h>

void fn1( void ), fn2( void ), fn3( void ), fn4( void );

int main( void )
   atexit( fn1 );
   atexit( fn2 );
   atexit( fn3 );
   atexit( fn4 );
   printf( "This is executed first.\n" );

void fn1()
   printf( "next.\n" );

void fn2()
   printf( "executed " );

void fn3()
   printf( "is " );

void fn4()
   printf( "This " );


This is executed first.
This is executed next.