Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!iuvax!pur-ee!ea.ecn.purdue.edu!housel
From: housel@ea.ecn.purdue.edu (Peter S. Housel)
Newsgroups: comp.os.minix
Subject: alloca() for Minix (was: GNU c and c++ under MINIX)
Message-ID: <5396@ea.ecn.purdue.edu>
Date: 17 Sep 88 00:10:23 GMT
References: <4073@louie.udel.EDU>
Reply-To: housel@ea.ecn.purdue.edu.UUCP (Peter S. Housel)
Organization: Purdue University Engineering Computer Network
Lines: 64

In article <4073@louie.udel.EDU> Leisner.Henr@xerox.com (marty) writes:
>I think the gnu tools would be a welcome addition to Minix -- I haven't filtered
>through the source code, but the only think I know of which is missing from
>Minix would be alloca().  Also the gnu distribution has a plethora of tools.
>
>I've had terrible luck with the Minix C compiler (everything I port to it has
>problems).  I quickly recompiled some of my favorite programs on gnu on the
>Vaxstation (John Gilmore's tar, Ian Darwin's file) and had no problems.
>

	Funny you should mention alloca()... I'd just been thinking about
posting it. It's at the end of this article.

	I've gotten GNU's bison (yacc replacement) working under Minix
with the help of shortc, a program which allows you to compile programs
that contain identifiers longer than seven characters. alloca() was
required, of course, as well as some tweaking of table sizes. Right now
I'm trying gawk, but that's not done yet.

	Most of the other GNU tools, however, are really such memory hogs
that they wouldn't work out. The GCC preprocessor, for instance,
malloc()'s a buffer big enough for each input file and modifies it in place.

	I haven't had such bad luck with the Minix C compiler. You just
have to be patient and hack at the program until it compiles. Some nifty
things I've got running include:
	- bison
	- shortc (available from comp.sources.unix archives)
	- Allen Holub's NR nroff clone, as published by Dr. Dobbs/M&T
	  (this took about six hours, and it had to be done twice. The
	  result was a halfway decent nroff.)
	- smail, the uucp mail router. This is still a novelty at the moment.
	- pathalias, the uucp path router. Ditto.
	- the public-domain dial(3) modem capability library
	- SVC, the Shell Version Control system (of course)

-Peter S. Housel-	housel@ei.ecn.purdue.edu	...!pur-ee!housel
-----------------cut here------------------------------------------------
.define _alloca
|
| alloca() for Minix
| by Peter S. Housel 8/15/88 - in the public domain
|
| Stack frame:
|    on entry			on return
|    |	...	 |		| ...	    |
|    |-----------| <=caller sp	|-----------|
|    | size arg  |		|	    |
|    |-----------|		|alloca data|
|    | ret addr  |		| ...	    |
|    |-----------| <=sp		|-----------| <= return value in ax
|				| dummy word|
|				|-----------| <= sp
|    
	.globl _alloca
_alloca:
	mov	bx,sp		| bx = sp (for indexing)
	mov	ax,sp
	add	ax,#4		| ax = sp from calling routine
	sub	ax,2(bx)	| ax = beginning of alloca block
	mov	bx,0(bx)	| save return address
	mov	sp,ax		| set new sp
	push	bx		| push a random value for caller to remove
	jmp	(bx)		| jump back to caller