Path: utzoo!utgpu!watmath!watdragon!rose!ehoogerbeets
From: ehoogerbeets@rose.waterloo.edu (Edwin Hoogerbeets)
Newsgroups: comp.sys.amiga.tech
Subject: Another Manx v3.6 bug
Keywords: Gnu --> quality compiler stress tests at low prices!
Message-ID: <14395@watdragon.waterloo.edu>
Date: 9 Jun 89 20:17:36 GMT
References: <14328@watdragon.waterloo.edu>
Sender: daemon@watdragon.waterloo.edu
Reply-To: ehoogerbeets@rose.waterloo.edu (Edwin Hoogerbeets)
Organization: U. of Waterloo, Ontario
Lines: 53

In article <14328@watdragon.waterloo.edu> ehoogerbeets@rose.waterloo.edu (Edwin Hoogerbeets) writes:
% I know it is pretty gross
% C code, but it occurs in GnuGrep (fish 204), and probably other Gnu
% code.

Speaking of Gnu code, here is another Manx bug:

main()
{
  char *list;
  char c;

  c = '8';

  list = &c;

  c = ( list , *list );
}

Causes guru 0x00000003, unaligned word or address error.
(It is valid, albeit strange, C code isn't it?)

Looking at the assembler:

[...etc...]
;  c = '8';
	move.b	#56,-5(a5)
;
;  list = &c;
	lea	-5(a5),a0         ; load the effective address of c into a0
	move.l	a0,-4(a5)     ; save that address in list
;
;  c = ( list , *list );
	move.l	-4(a5),a0     ; [redundantly] get the address again
	move.b	(a0),d0       ; move c into d0
	ext.w	d0              ; sign extend it to a word  [?????]
	move.w	d0,-5(a5)     ; Whoops! This is a no no!
;}

The assembler produced by compiling with +L is the same, except the
offensive lines are:

;  c = ( list , *list );
	move.l	-4(a5),a0     ; [redundantly] get the address again
	move.b	(a0),d0       ; move c into d0
	ext.w	d0              ; sign extend it to a word  [?????]
	ext.l	d0              ; sign extend it to a long  [2*?????]
	move.l	d0,-5(a5)     ; Even better...

Perhaps gnucc should be ported to the Amiga, since presumably it
compiles all the gnu stuff.

Edwin