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From: gert@nikhefh.UUCP
Newsgroups: comp.sys.atari.st
Subject: Megamax WON'T compile .... structures passed to functions
Message-ID: <280@nikhefh.UUCP>
Date: Wed, 20-May-87 06:43:06 EDT
Article-I.D.: nikhefh.280
Posted: Wed May 20 06:43:06 1987
Date-Received: Thu, 21-May-87 07:15:37 EDT
Organization: Nikhef-H, Amsterdam (the Netherlands).
Lines: 73
Keywords: megamax


In response to the denial of a few persons that Megamax won't accept 
passing of structures to functions: The Megamax compiler will accept the C
code. It will not issue any warning, but the code it generates it 
totally wrong!


This is the test program:


typedef struct {
	int	t1;
	int	t2;
} test;

main ()
{
	test test;

	ftest ( test );
}

ftest ( t )
test t;
{
	t.t1 = 1;
	t.t2 = 2;
}




Megamax disassembler V1.0, Copyright (C) 1986 by Megamax Inc.

CODE SEG "main"
main:/* global */
	LINK	A6,L$0
	PEA	-4(A6)				!!! here main pushes the  ADDRESS of the structure
								test, when it should push the contents of it.
	JSR	ftest(PC)
	ADDQ.L	#4,A7
L1:
	UNLK	A6
	RTS
L$0:	.EQU	#-4
_initargcv:/* global */
	RTS
ftest:/* global */
	LINK	A6,L$2
	MOVE	#1,8(A6)		!!! this would be t.t1 = 1, the ftest function
								apparantly expects the structure to be on
								stack, unfortunately only the address of the
								structure is on the stack. (Bomb!!)
	MOVE	#2,10(A6)
L3:
	UNLK	A6
	RTS
L$2:	.EQU	#0



This example was compiled with version 1.1 of the Megamax compiler.
I hope this makes clear that Megamax does not 'allow' structure passing.

In one of my previous message I said that Megamax would also not allow 
declaration of variables somewhere in a function (not neccesarily at the
top). In that case I was wrong, sorry. I still think I remember reading
something to that extend in one of the manuals, but it may very well have
been for another C compiler.



Gert Poletiek.