88 lines
2.2 KiB
C
88 lines
2.2 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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/*
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FUNCTION
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<<atexit>>---request execution of functions at program exit
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INDEX
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atexit
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ANSI_SYNOPSIS
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#include <stdlib.h>
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int atexit (void (*<[function]>)(void));
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TRAD_SYNOPSIS
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#include <stdlib.h>
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int atexit ((<[function]>)
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void (*<[function]>)();
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DESCRIPTION
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You can use <<atexit>> 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 must not require arguments and
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must not return a result).
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The functions are kept in a LIFO stack; that is, the last function
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enrolled by <<atexit>> will be the first to execute when your program
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exits.
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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>> will call <<malloc>> to get space for the next part of the
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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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<<atexit>> 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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<<atexit>> is required by the ANSI standard, which also specifies that
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implementations must support enrolling at least 32 functions.
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Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,
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<<lseek>>, <<read>>, <<sbrk>>, <<write>>.
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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 (atexit,
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(fn),
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_VOID _EXFUN ((*fn), (_VOID)))
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{
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register struct _atexit *p;
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/* _REENT_SMALL atexit() doesn't allow more than the required 32 entries. */
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#ifndef _REENT_SMALL
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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->_next = _REENT->_atexit;
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_REENT->_atexit = p;
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}
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#else
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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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#endif
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p->_fns[p->_ind++] = fn;
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return 0;
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}
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