NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/comp/lang/fortran/4415

Text File | 1992-11-23 | 1.7 KB | 39 lines

Newsgroups: comp.lang.fortran
Path: sparky!uunet!pgroup!lfm
From: [e-mail] (Larry Meadows)
Subject: Re: ENTRY in main (was re: Jumping from nested subroutine)
Message-ID: <[e-mail]>
Date: Mon, 23 Nov 1992 14:26:53 GMT
References: <[e-mail]%mailhost.ecn.uoknor.edu> <[e-mail]>
Organization: The Portland Group, Portland, OR
Lines: 28

Well, I can't resist...

What the original poster wants is called non-local GOTO in pascal, and
setjmp/longjmp in C.  In either case, the return stack is unwound to
the invocation record of the function to which control is being returned.
In pascal this is the function containing the label to which control
is being transferred; in C, it is the function that called setjmp.

Ordinarily, unwinding the stack consists of restoring the stack pointer,
possibly the frame pointer; then, control transfer is performed by loading
the program counter (i.e., performing an indirect branch).  Machines
with register windows are more complicated; I'm sure someone can tell us
exactly how it is done on the Sparc.

So, anyway, it should be possible to call setjmp and longjmp from fortran,
assuming they exist on the original poster's system.  Problem is, they
would need fortran entry points, since wrapping a C function around
the original setjmp/longjmp won't work (setjmp must be called from the
function to which control is to return, then that function must not return
before longjmp is called).  If fortran entry point's don't exist, I'd
be inclined to hack the object to create them.

Of course, the ability to do all this is entirely system dependent.

Good luck.
--
Larry Meadows        The Portland Group
[e-mail]