NAME

       longjmp - non-local goto

SYNOPSIS

       #include <setjmp.h>

       void longjmp(jmp_buf env, int val);

DESCRIPTION

       The  longjmp()  function shall restore the environment saved by the most recent invocation of setjmp() in
       the same thread, with the corresponding jmp_buf argument. If there is  no  such  invocation,  or  if  the
       function  containing  the  invocation  of  setjmp()  has  terminated  execution in the interim, or if the
       invocation of setjmp() was within the scope of an identifier with variably modified  type  and  execution
       has  left  that  scope  in  the interim, the behavior is undefined.   It is unspecified whether longjmp()
       restores the signal mask, leaves the signal mask unchanged, or restores it  to  its  value  at  the  time
       setjmp() was called.

       All  accessible  objects  have  values,  and all other components of the abstract machine have state (for
       example, floating-point status flags and open files), as of the time longjmp() was  called,  except  that
       the  values  of  objects  of  automatic  storage  duration are unspecified if they meet all the following
       conditions:

        * They are local to the function containing the corresponding setjmp() invocation.

        * They do not have volatile-qualified type.

        * They are changed between the setjmp() invocation and longjmp() call.

       As it bypasses the usual function call and  return  mechanisms,  longjmp()  shall  execute  correctly  in
       contexts  of interrupts, signals, and any of their associated functions. However, if longjmp() is invoked
       from a nested signal handler (that is, from a function invoked as a result of a signal raised during  the
       handling of another signal), the behavior is undefined.

       The  effect of a call to longjmp() where initialization of the jmp_buf structure was not performed in the
       calling thread is undefined.

RETURN VALUE

       After longjmp() is completed, program execution continues as if the corresponding invocation of  setjmp()
       had  just  returned the value specified by val. The longjmp() function shall not cause setjmp() to return
       0; if val is 0, setjmp() shall return 1.

ERRORS

       No errors are defined.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       Applications whose behavior depends on the value  of  the  signal  mask  should  not  use  longjmp()  and
       setjmp(),  since  their effect on the signal mask is unspecified, but should instead use the siglongjmp()
       and sigsetjmp() functions (which can save and restore the signal mask under application control).

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       setjmp()  ,  sigaction()  ,   siglongjmp()   ,   sigsetjmp()   ,   the   Base   Definitions   volume   of
       IEEE Std 1003.1-2001, <setjmp.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003 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 .

IEEE/The Open Group                                   2003                                            LONGJMP(P)