stdlib/FreeBSD/atexit.3

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  32 .\"     @(#)atexit.3    8.1 (Berkeley) 6/4/93
  33 .\" $FreeBSD: src/lib/libc/stdlib/atexit.3,v 1.11 2007/01/09 00:28:09 imp Exp $
  34 .\"
  35 .Dd May 20, 2008
  36 .Dt ATEXIT 3
  37 .Os
  38 .Sh NAME
  39 .Nm atexit
  40 .Nd register a function to be called on exit
  41 .Sh SYNOPSIS
  42 .In stdlib.h
  43 .Ft int
  44 .Fn atexit "void (*func)(void)"
  45 #ifdef UNIFDEF_BLOCKS
  46 .Ft int
  47 .Fn atexit_b "void (^block)(void)"
  48 #endif
  49 .Sh DESCRIPTION
  50 The
  51 .Fn atexit
  52 function
  53 registers the function
  54 .Fa func
  55 to be called at program exit, whether via
  56 .Xr exit 3
  57 or via return from the program's
  58 .Fn main .
  59 Functions so registered are called in reverse order;
  60 no arguments are passed.
  61 #ifdef UNIFDEF_BLOCKS
  62 .Pp
  63 The
  64 .Fn atexit_b
  65 function is like
  66 .Fn atexit
  67 except the callback is a block pointer instead of a function pointer.
  68 .Bd -ragged -offset indent
  69 Note: The
  70 .Fn Block_copy
  71 function (defined in
  72 .In Blocks.h )
  73 is used by
  74 .Fn atexit_b
  75 to make a copy of the block, especially for the case when a stack-based
  76 block might go out of scope when the subroutine returns.
  77 .Ed
  78 #endif
  79 .Pp
  80 These callbacks must not call
  81 .Fn exit ;
  82 if it should be necessary to terminate the process while in such a
  83 function, the
  84 .Xr _exit 2
  85 function should be used.
  86 (Alternatively, the callbacks may cause abnormal
  87 process termination, for example by calling
  88 .Xr abort 3 . )
  89 .Pp
  90 At least 32 callbacks can always be registered;
  91 more are allowed as long as sufficient memory can be allocated.
  92 .\" XXX {ATEXIT_MAX} is not implemented yet
  93 .Sh RETURN VALUES
  94 #ifdef UNIFDEF_BLOCKS
  95 .ds ATEXIT_B atexit_b
  96 #endif
  97 .Rv -std atexit \*[ATEXIT_B]
  98 .Sh ERRORS
  99 .Bl -tag -width Er
 100 .It Bq Er ENOMEM
 101 No memory was available to add the function to the list.
 102 The existing list of functions is unmodified.
 103 .El
 104 .Sh SEE ALSO
 105 .Xr exit 3
 106 .Sh STANDARDS
 107 The
 108 .Fn atexit
 109 function
 110 conforms to
 111 .St -isoC .