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)