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NAME

       longjmp, siglongjmp - non-local jump to a saved stack context

SYNOPSIS

       #include <setjmp.h>

       void longjmp(jmp_buf env, int val);

       void siglongjmp(sigjmp_buf env, int val);

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

       siglongjmp(): _POSIX_C_SOURCE || _XOPEN_SOURCE

DESCRIPTION

       longjmp()  and  setjmp(3)  are  useful  for  dealing  with  errors  and
       interrupts  encountered  in  a  low-level  subroutine  of  a   program.
       longjmp()  restores the environment saved by the last call of setjmp(3)
       with the corresponding env argument.   After  longjmp()  is  completed,
       program  execution  continues as if the corresponding call of setjmp(3)
       had just returned the value  val.   longjmp()  cannot  cause  0  to  be
       returned.   If longjmp() is invoked with a second argument of 0, 1 will
       be returned instead.

       siglongjmp() is similar to longjmp() except for the  type  of  its  env
       argument.   If  the  sigsetjmp(3) call that set this env used a nonzero
       savesigs flag, siglongjmp() also restores the set of blocked signals.

RETURN VALUE

       These functions never return.

CONFORMING TO

       C89, C99, and POSIX.1-2001 specify longjmp().   POSIX.1-2001  specifies
       siglongjmp().

NOTES

       POSIX  does  not  specify  whether  longjmp()  will  restore the signal
       context.   If  you  want  to  save  and  restore  signal   masks,   use
       siglongjmp().

       The  values  of  automatic  variables  are  unspecified after a call to
       longjmp() if they meet all the following criteria:

       ·  they are local to the function that made the corresponding setjmp(3)
          call;

       ·  their  values  are  changed  between  the  calls  to  setjmp(3)  and
          longjmp(); and

       ·  they are not declared as volatile.

       Analogous remarks apply for siglongjmp().

       longjmp()  and  siglongjmp()  make  programs  hard  to  understand  and
       maintain.  If possible an alternative should be used.

SEE ALSO

       setjmp(3), sigsetjmp(3)

COLOPHON

       This  page  is  part of release 2.77 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

                                  2007-09-06                        LONGJMP(3)