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       setjmp, sigsetjmp - save stack context for nonlocal goto


       #include <setjmp.h>

       int setjmp(jmp_buf env);

       int sigsetjmp(sigjmp_buf env, int savesigs);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       setjmp(): see NOTES.
       sigsetjmp(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_C_SOURCE


       setjmp()  and  longjmp(3)  are  useful  for  dealing  with  errors  and
       interrupts  encountered  in  a  low-level  subroutine  of  a   program.
       setjmp()  saves  the  stack context/environment in env for later use by
       longjmp(3).  The stack context will  be  invalidated  if  the  function
       which called setjmp() returns.

       sigsetjmp()  is  similar  to  setjmp().   If,  and only if, savesigs is
       nonzero, the process's current signal mask is saved in env and will  be
       restored if a siglongjmp(3) is later performed with this env.


       setjmp()  and  sigsetjmp()  return 0 if returning directly, and nonzero
       when  returning  from  longjmp(3)  or  siglongjmp(3)  using  the  saved


       For   an   explanation   of   the  terms  used  in  this  section,  see

       │InterfaceAttributeValue   │
       │setjmp(), sigsetjmp() │ Thread safety │ MT-Safe │


       setjmp(): POSIX.1-2001, POSIX.1-2008, C89, C99.

       sigsetjmp(): POSIX.1-2001, POSIX.1-2008.


       POSIX does not specify whether setjmp() will save the signal  mask  (to
       be  later  restored  during  longjmp(3)).  In System V it will not.  In
       4.3BSD it will, and there is a function  _setjmp  that  will  not.   On
       Linux  with  glibc  versions before 2.19, setjmp() follows the System V
       behavior  by  default,  but  the  BSD  behavior  is  provided  if   the
       _BSD_SOURCE  feature  test  macro is defined and none of _POSIX_SOURCE,
       _SVID_SOURCE is defined.  Since glibc 2.19, <setjmp.h> exposes only the
       System V version of setjmp().  Programs that  need  the  BSD  semantics
       should  replace  calls  to  setjmp()  with  calls to sigsetjmp() with a
       nonzero savesigs argument.

       If you want to portably save and restore signal masks, use  sigsetjmp()
       and siglongjmp(3).

       setjmp() and sigsetjmp() make programs hard to understand and maintain.
       If possible, an alternative should be used.


       longjmp(3), siglongjmp(3)


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                                  2015-08-08                         SETJMP(3)