SYNOPSIS
       #include <setjmp.h>

       void _longjmp(jmp_buf env, int val);
       int _setjmp(jmp_buf env);


DESCRIPTION
       The _longjmp() and _setjmp() functions shall be equivalent to longjmp()
       and  setjmp(),  respectively,  with  the  additional  restriction  that
       _longjmp() and _setjmp() shall not manipulate the signal mask.

       If _longjmp() is called even though env was never initialized by a call
       to _setjmp(), or when the last such call was in  a  function  that  has
       since returned, the results are undefined.

RETURN VALUE
       Refer to longjmp() and setjmp() .

ERRORS
       No errors are defined.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       If  _longjmp()  is  executed and the environment in which _setjmp() was
       executed no longer exists, errors  can  occur.   The  conditions  under
       which the environment of the _setjmp() no longer exists include exiting
       the function that contains the _setjmp() call,  and  exiting  an  inner
       block  with temporary storage.  This condition might not be detectable,
       in which case the _longjmp() occurs and, if the environment  no  longer
       exists,  the  contents  of  the temporary storage of an inner block are
       unpredictable. This condition might also cause unexpected process  ter-
       mination. If the function has returned, the results are undefined.

       Passing  longjmp() a pointer to a buffer not created by setjmp(), pass-
       ing _longjmp() a pointer to a buffer not created by _setjmp(),  passing
       siglongjmp() a pointer to a buffer not created by sigsetjmp(), or pass-
       ing any of these three functions a buffer that has been modified by the
       user can cause all the problems listed above, and more.

       The _longjmp() and _setjmp() functions are included to support programs
       written to historical system interfaces.  New applications  should  use
       siglongjmp() and sigsetjmp() respectively.

RATIONALE
       None.

FUTURE DIRECTIONS
       The _longjmp() and _setjmp() functions may be marked LEGACY in a future
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .