stdlib/FreeBSD/atexit.3

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  32 .\"     @(#)atexit.3    8.1 (Berkeley) 6/4/93
  33 .\" $FreeBSD$
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  35 .Dd September 6, 2002
  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 (*function)(void)"
  45 #ifdef UNIFDEF_BLOCKS
  46 .Ft int
  47 .Fn atexit_b "void (^function)(void)"
  48 #endif
  49 .Sh DESCRIPTION
  50 The
  51 .Fn atexit
  52 function
  53 registers the given
  54 .Fa function
  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 .Pp
  62 If the provided
  63 .Fa function
  64 is located in a library that has been dynamically loaded (e.g. by
  65 .Fn dlopen ) Ns ,
  66 it will be called when the library is unloaded (due to a call
  67 to
  68 .Fn dlclose )
  69 or at program exit.
  70 #ifdef UNIFDEF_BLOCKS
  71 .Pp
  72 The
  73 .Fn atexit_b
  74 function is like
  75 .Fn atexit
  76 except the callback is a block pointer instead of a function pointer.
  77 .Bd -ragged -offset indent
  78 Note: The
  79 .Fn Block_copy
  80 function (defined in
  81 .In Blocks.h )
  82 is used by
  83 .Fn atexit_b
  84 to make a copy of the block, especially for the case when a stack-based
  85 block might go out of scope when the subroutine returns.
  86 .Ed
  87 #endif
  88 .Pp
  89 These functions must not call
  90 .Fn exit ;
  91 if it should be necessary to terminate the process while in such a
  92 function, the
  93 .Xr _exit 2
  94 function should be used.
  95 (Alternatively, the function may cause abnormal
  96 process termination, for example by calling
  97 .Xr abort 3 . )
  98 .Pp
  99 At least 32 functions can always be registered,
 100 and more are allowed as long as sufficient memory can be allocated.
 101 .\" XXX {ATEXIT_MAX} is not implemented yet
 102 .Sh RETURN VALUES
 103 #ifdef UNIFDEF_BLOCKS
 104 .ds ATEXIT_B atexit_b
 105 #endif
 106 .Rv -std atexit \*[ATEXIT_B]
 107 .Sh ERRORS
 108 .Bl -tag -width Er
 109 .It Bq Er ENOMEM
 110 No memory was available to add the function to the list.
 111 The existing list of functions is unmodified.
 112 .El
 113 .Sh SEE ALSO
 114 .Xr exit 3
 115 .Sh STANDARDS
 116 The
 117 .Fn atexit
 118 function
 119 conforms to
 120 .St -isoC .