NAME
	  setjmp, longjmp, _setjmp, _longjmp - Saves and restores the
	  current execution context

     LIBRARY
	  Standard C Library  (libc.a)

     SYNOPSIS
	  #include <setjmp.h>
	  int setjmp (
	       jmp_buf environment );
	  void longjmp (
	       jmp_buf environment,
	       int value );
	  int _setjmp (
	       jmp_buf environment );
	  void _longjmp	(
	       jmp_buf environment,
	       int value );


     PARAMETERS
	  environment
		    Specifies an address for a jmp_buf structure.

	  value	    Specifies any nonzero value.


     DESCRIPTION
	  The setjmp() and longjmp() functions are useful when han-
	  dling	errors and interrupts encountered in low-level func-
	  tions	of a program.

	  The setjmp() function	saves the current stack	context	and
	  signal mask in the buffer specified by the environment
	  parameter.

	  The longjmp()	function restores the stack context and	signal
	  mask that were saved by the setjmp() function	in the
	  corresponding	environment buffer. After the longjmp()	func-
	  tion runs, program execution continues as if the correspond-
	  ing call to the setjmp() function had	just returned the
	  value	of the value parameter.	The function that called the
	  setjmp() function must not have returned before the comple-
	  tion of the longjmp()	function. The setjmp() function	and
	  the longjmp()	function save and restore the signal mask,
	  while	_setjmp() and _longjmp() manipulate only the stack
	  context.

	  As it	bypasses the usual function call and return mechan-
	  isms,	the longjmp() function executes	correctly in contexts
	  of interrupts, signals, and any of their associated
	  functions.  However, if the longjmp()	function is invoked
	  from a nested	signal handler (that is, from a	function
	  invoked as a result of a signal raised during	the handling
	  of another signal), the behavior is undefined.

     NOTES
	  The reentrant	versions of the	setjmp() and longjmp() func-
	  tions	are identical in behavior to the _setjmp() and
	  _longjmp()

	  The System V versions	of the setjmp()	and longjmp() func-
	  tions, which are equivalent to _setjmp() and _longjmp()
	  respectively,	are also supported for compatibility.  To use
	  the System V versions	of setjmp() and	longjmp(), you must
	  link with the	libsys5	library	before you link	with libc.


	  AES Support Level:
			 Full use


     CAUTION
	  If the longjmp() function is called with an environment
	  parameter that was not previously set	by the setjmp()	func-
	  tion,	or if the function that	made the corresponding call to
	  the setjmp() function	has already returned, then the results
	  of the longjmp() function are	undefined. If the longjmp()
	  function detects such	a condition, it	calls the longjmper-
	  ror()	function. If longjmperror() returns, the program is
	  aborted.  The	default	version	of longjmperror() prints an
	  error	message	to standard error and returns. Users wishing
	  to exit more gracefully can write their own versions of the
	  longjmperror() program.


	  If automatic and register variables are changed after	the
	  setjmp(), their values are indeterminate after the
	  longjmp().  You cannot assume	that these variables are
	  restored to what they	were when the setjmp() was called. Nor
	  can you assume that they are set to whatever value they had
	  when the function sequence containing	the longjmp() was
	  started.


	  If you want them to retain the values	they had when the
	  function sequence containing the longjmp() is	started,
	  declare them as volatile.


     RETURN VALUES
	  The setjmp() function	returns	a value	of 0 (zero), unless
	  the return is	from a call to the longjmp() function, in
	  which	case setjmp() returns a	nonzero	value.

	  The longjmp()	function cannot	return 0 (zero)	to the previ-
	  ous context. The value 0 is reserved to indicate the actual
	  return from the setjmp() function when first called by the
	  program. If the longjmp() function is	passed a value parame-
	  ter of 0, then execution continues as	if the corresponding
	  call to the setjmp() function	had returned a value of	1. All
	  accessible data have values as of the	time the longjmp()
	  function is called.

     RELATED INFORMATION
	  Functions: siglongjmp(3), sigsetjmp(3)