108 lines
2.9 KiB
C
108 lines
2.9 KiB
C
/*
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* Copyright (c) 1990 Regents of the University of California.
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* All rights reserved.
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*
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* %sccs.include.redist.c%
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*
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* This function is a modified version of atexit.c
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*/
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/*
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FUNCTION
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<<on_exit>>---request execution of function with argument at program exit
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INDEX
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on_exit
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ANSI_SYNOPSIS
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#include <stdlib.h>
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int on_exit (void (*<[function]>)(int, void *), void *<[arg]>);
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TRAD_SYNOPSIS
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#include <stdlib.h>
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int on_exit ((<[function]>, <[arg]>)
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void (*<[function]>)(int, void *);
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void *<[arg]>;
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DESCRIPTION
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You can use <<on_exit>> to enroll functions in a list of functions that
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will be called when your program terminates normally. The argument is
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a pointer to a user-defined function which takes two arguments. The
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first is the status code passed to exit and the second argument is of type
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pointer to void. The function must not return a result. The value
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of <[arg]> is registered and passed as the argument to <[function]>.
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The functions are kept in a LIFO stack; that is, the last function
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enrolled by <<atexit>> or <<on_exit>> will be the first to execute when
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your program exits. You can intermix functions using <<atexit>> and
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<<on_exit>>.
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There is no built-in limit to the number of functions you can enroll
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in this list; however, after every group of 32 functions is enrolled,
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<<atexit>>/<<on_exit>> will call <<malloc>> to get space for the next part
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of the list. The initial list of 32 functions is statically allocated, so
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you can always count on at least that many slots available.
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RETURNS
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<<on_exit>> returns <<0>> if it succeeds in enrolling your function,
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<<-1>> if it fails (possible only if no space was available for
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<<malloc>> to extend the list of functions).
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PORTABILITY
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<<on_exit>> is a non-standard glibc extension
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Supporting OS subroutines required: None
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*/
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#include <stddef.h>
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#include <stdlib.h>
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#include <reent.h>
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/*
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* Register a function to be performed at exit.
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*/
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int
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_DEFUN (on_exit,
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(fn, arg),
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_VOID _EXFUN ((*fn), (int, _PTR)) _AND
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_PTR arg)
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{
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struct _on_exit_args * args;
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register struct _atexit *p;
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void (*x)(void) = (void (*)(void))fn;
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/* _REENT_SMALL on_exit() doesn't allow more than the required 32 entries. */
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#ifdef _REENT_SMALL
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p = &_REENT->_atexit;
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if (p->_ind >= _ATEXIT_SIZE)
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return -1;
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args = p->_on_exit_args_ptr;
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if (args == NULL)
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{
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args = malloc (sizeof * p->_on_exit_args_ptr);
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if (args == NULL)
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return -1;
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args->_fntypes = 0;
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p->_on_exit_args_ptr = args;
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}
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#else
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if ((p = _REENT->_atexit) == NULL)
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_REENT->_atexit = p = &_REENT->_atexit0;
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if (p->_ind >= _ATEXIT_SIZE)
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{
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if ((p = (struct _atexit *) malloc (sizeof *p)) == NULL)
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return -1;
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p->_ind = 0;
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p->_on_exit_args._fntypes = 0;
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p->_next = _REENT->_atexit;
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_REENT->_atexit = p;
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}
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args = & p->_on_exit_args;
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#endif
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args->_fntypes |= (1 << p->_ind);
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args->_fnargs[p->_ind] = arg;
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p->_fns[p->_ind++] = x;
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return 0;
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}
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