LONGJMP(3P)                                         POSIX Programmer's Manual                                        LONGJMP(3P)



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

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 unspeci-
       fied  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  inter-
       rupts,  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, Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                   LONGJMP(3P)