🚀 go-pugleaf

In article <HALLETT.90Sep6142725@enterprise.positron.gemed.ge.com> hallettJ@geme
d.ge.com writes:
>
>I'm interested in doing something funky.  I have a shell running that
>basically interprets user commands and then calls a procedure to
>handle the command.  Each command is self-contained.  Now, I want to
>allow a user to add commands.  The mechanism I would like to try is to
>have the user create a .o file with the compiled code in it, then,
>when he enters his command into the shell, have the shell load the .o
>file and execute the code in it.  The only problem is that I don't
>have a clue where to look to figure out how to do this.
>

Look up the "-A" option in the ld(1) man page. This option lets
you take a .o file, and link it to an existing a.out format file
(executable). The result is a code file that you can load into
memory, and jump into. I have some example code (not well commented)
that does this, if you are interested.

Beware : some unix systems DO NOT have this feature. I am sure it
works in BSD and SunOS, but I have checked DG/UX on an Aviion
(as an example), and it has no -A option to ld.

BTW : This ld -A option is called "incremental" loading. "Dynamic"
loading is a term used concerning run-time and shared library loads.
(At least that's the BSD and SunOS terminology).

Hope this helps,

Gil.
--
--------------------------------------------------------------------
| Gil Tene                      "Some days it just doesn't pay     |
| devil@techunix.technion.ac.il   to go to sleep in the morning."  |
--------------------------------------------------------------------

In article <9769@discus.technion.ac.il> 
	devil%techunix.bitnet@lilac.berkeley.edu (Gil Tene) writes:
- In article <HALLETT.90Sep6142725@enterprise.positron.gemed.ge.com> 
-		hallettJ@gemed.ge.com writes:
- >
- >	[Wants to link in objects on the fly]
- 
- Look up the "-A" option in the ld(1) man page.  [...]
- 
- Beware : some unix systems DO NOT have this feature. I am sure it
- works in BSD and SunOS, but I have checked DG/UX on an Aviion
- (as an example), and it has no -A option to ld.

        And some systems use the -A flag for something completely
different.  An example is the ConvexOS loader, which uses -A for a
compiler only type of switch.  ConvexOS is nominally BSD, but the object
format is now a COFF like thing, as opposed the original BSD a.out
format.

        From my other experiences, System V (at least releases 2 and 3+)
don't support ld -A at all.

-- 
Eric Schnoebelen		eric@cirr.com		schnoebe@convex.com
    "This is an important announcement.  This is flight 121 to Los Angeles.
    If your travel plans today do not include Los Angeles, now would be a
    perfect time to disembark." - _So_Long_And_Thanks_For_All_The_Fish_

>        From my other experiences, System V (at least releases 2 and 3+)
>don't support ld -A at all.

I doubt S5R4 does, either, but then it has "dlopen()"/"dlsym()"/etc.
which gives you a built-in dynamic linking mechanism (which "ld -A" does
NOT - you have to write the "load the file" code yourself, or pick up
one of the already-written versions floating around).

In the recently announced release 1.2 of the Elk Scheme implementation
you find a function that dynamically loads object files by means of
incremental linking (see file src/load.c in the distribution).
It works under 4.3BSD, Ultrix on the DECStation 3100 (ECOFF format),
NEWS-OS (Sony RISC), HP-UX on the HP9000/3xx, SunOS, and probably others
(but not under System V).

Regards,
--
Oliver Laumann     net@TUB.BITNET     net@tub.cs.tu-berlin.de     net@tub.UUCP