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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 (consult 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 correspond-
       ing jmp_buf argument. If there is no such invocation, or if  the  func-
       tion  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 speci-
       fied  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(3P)