Man Page longjmp.3f

NAME

     longjmp, isetjmp - longjmp returns to the  location  set  by
     isetjmp

SYNOPSIS

     Usage:  isetjmp:

         integer*4  env(12)
         common /jmpblk/ env
         j = isetjmp( env )

     Usage:  longjmp:

         integer*4  env(12)
         common /jmpblk/ env
         call longjmp(env,ival)

     When compiling for 64-bit environments, the 12-element array
     env used by these routines must be declared INTEGER*8.

DESCRIPTION

     The isetjmp and longjmp  routines  are  used  to  deal  with
     errors  and interrupts encountered in a low-level routine of
     a program.  These routines should be used  only  as  a  last
     resort,  as  they  require  discipline and are not portable.
     Read the man page setjmp(3c) for bugs and other details.

     isetjmp saves the stack environment in env.  It  also  saves
     the register environment.

     longjmp restores the environment saved by the last  call  to
     isetjmp,  and returns in such a way that execution continues
     as if the call to isetjmp had just returned the value ival.

     The integer expression ival returned from isetjmp is zero if
     longjmp is not called, and nonzero if longjmp is called.

     Example: Code fragment using isetjmp and longjmp:
          integer*4  env(12)
          common /jmpblk/ env
          j = isetjmp( env )                   !      <-- isetjmp
          if ( j .eq. 0 ) then
               call  sbrtnA
          else
               call error_processor
          end if
          end
          subroutine sbrtnA
          integer*4  env(12)
          common /jmpblk/ env
          call longjmp( env, ival )            !      <-- longjmp
          return
          end

NOTE

     You must invoke isetjmp before calling longjmp().

     The argument to isetjmp must be a 12-integer array.

     You must pass the env variable from the routine  that  calls
     isetjmp  to the routine that calls longjmp, either by common
     or as an argument.

     longjmp() attempts to clean up the stack.

     longjmp() must  be  called  from  a  lower  call-level  than
     isetjmp().

     Passing isetjmp as an argument that is a procedure name does
     not work.

BUGS

     See setjmp(3c).

FILES

     libC.a

SEE ALSO

     setjmp(3C).