Re: Forth for Mac OS X Leopard (Intel) - what are the options?

In article <vjrLj.662$Ms6.496@[EMAIL PROTECTED]
>,
Josh Grams  <josh@[EMAIL PROTECTED]
> wrote:
<SNIP>
>
>But the linker only looks for the normal sections, so if you want to use
>different section names, you have to write a linker script.  These can

In my experience the gnu linkers just put my out-of-the-ordinary
sections in a reasonable place. The only crucial point is to have
a _start global symbol somewhere. The linker script has a default
place for extra sections.

>be very simple: basically you have to set the base address, then tell it
>how to combine sections into segments.  I have a minimal example of how
>to create your own ELF headers using the GNU assembler and linker (on
>PPC Linux) at http://qualdan.com/examples/linking/
but it's not
>commented at all.  The info page for ld does describe linker scripts,
>and I can go into detail about it if you're interested.  The following
>might work for the original lina (replacing ??? with the actual base
>address).  Probably won't work on BSD though; IIRC .text and .data
>segments.
>
>SECTIONS
>{
>       . = ??? + SIZEOF_HEADERS;
>       .text : { *(forth) }
>       /DISCARD/ : { *(*) }
>}
>
>Usually executables have the same structure in memory as in the file
>(though often there is a gap between code and data).  And usually the
>headers are also mapped into memory.  So to SAVE-SYSTEM, you just have
>to know where the headers are, store the new (larger) sizes, and then
>write everything out to a file.

This is almost exactly how the SAVE-SYSTEM in lina works. The elf headers
contain references to things that are not important. Specify that there
are zero of those, and nobody will try to read them.
There is little value or portability in lina's SAVE-SYSTEM so it is
not worthwhile to try to use elf on OSX just to use it.
The same tricks are applicable to OSX executable headers.

A very effective dirty trick to analyse the header is adding
a $1000 buffer in the kernel somewhere. Now the numbers
that shift by $1000 are what you need to adapt.
(This is inspired by FYSForth's "relocation" mechanism.
It was just a matter of two assembly's at different absolute
addresses, then compare them.)

>
>--Josh


--
-- 
Albert van der Horst, UTRECHT,THE NETHERLANDS
Economic growth -- like all pyramid schemes -- ultimately falters.
albert@[EMAIL PROTECTED]
 &=n http://home.hccnet.nl/a.w.m.van.der.horst