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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 >= 1 || _XOPEN_SOURCE || _POSIX_C_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,  and  only  if, the sigsetjmp(3) call that set this env
       used a non-zero savesigs flag, siglongjmp() also  restores  the  signal
       mask that was saved by sigsetjmp(3).

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 (see setjmp(3) for some more details).  If you want to portably
       save and restore signal masks, use sigsetjmp() and 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

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                                  2009-01-13                        LONGJMP(3)