_longjmp, _setjmp — non-local goto

       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 termination. If the function has returned, the results are undefined.

       Passing longjmp() a pointer to a buffer not created by setjmp(), passing _longjmp() a pointer to a buffer
       not created by _setjmp(), passing siglongjmp() a pointer to a  buffer  not  created  by  sigsetjmp(),  or
       passing  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.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical  and  Electronics
       Engineers, Inc and The Open Group.  In the 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 .

       Any typographical or formatting errors that appear in this page are most likely to have  been  introduced
       during   the   conversion  of  the  source  files  to  man  page  format.  To  report  such  errors,  see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                      _LONGJMP(3POSIX)

       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.

       No errors are defined.

       Thefollowingsectionsareinformative.

       None.

       The _longjmp() and _setjmp() functions may be removed in a future version.

       _longjmp, _setjmp — non-local goto

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

       None.

       Refer to longjmp() and setjmp().

longjmp(), setjmp(), siglongjmp(), sigsetjmp()

       The Base Definitions volume of POSIX.1‐2017, <setjmp.h>

       #include <setjmp.h>

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