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 .