Path: utzoo!mnetor!uunet!husc6!purdue!i.cc.purdue.edu!j.cc.purdue.edu!ray
From: ray@j.cc.purdue.edu (Ray Moody)
Newsgroups: comp.sys.ibm.pc
Subject: Bug in TurboC version 1.0
Message-ID: <6374@j.cc.purdue.edu>
Date: 7 Feb 88 05:21:58 GMT
Reply-To: ray@j.cc.purdue.edu (Ray Moody)
Organization: Purdue University
Lines: 94
Keywords: inportb


    This is a posting for a friend.  Please reply to c13@s.cc.purdue.edu, not
me.

								Ray
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Well, after spending at least 5 hours in a nightmare debugging session, I have
found what I am sure is a bug in TurboC V1.0.  The problem is that in between
doing two inportb's (macro version) the compiler did a push dx and then never
popped it off!!  If I delete the push dx, it works fine. Is this a known bug
in the compiler?!?  If so, has this been fixed in the new version of TurboC ??
I would appreciate any help on this subject!
                                                  Roy C Riggs
                                                  c13@s.cc.purdue.edu 

Just in case it is relevant:
   AT clone, 12Mhz
   Hercules graphics
   30M hard drive
   360K drive
   512K base 1024K expansion
   DAS-8 a/d convertor
   DOS 3.2
   TurboC V1.0
 
The source and the asm follow:
 
/* test program that crashes due to bug in TurboC V1.0 */
/* WARNING: you will have to reboot after running this */
 
#include <dos.h>
 
main()
{
   printf("test %d\n", inportb(768) + inportb(769));
}
 
 
/* test.asm created by tcc -S test.c */
/* it has not been edited in ANY way, the bug is 4 lines after ;Line 8 */
 
	name	test
_text	segment	byte public 'code'
dgroup	group	_data,_bss
	assume	cs:_text,ds:dgroup,ss:dgroup
_text	ends
_data	segment word public 'data'
_d@	label	byte
_data	ends
_bss	segment word public 'bss'
_b@	label	byte
_bss	ends
_text	segment	byte public 'code'
; Line 7
_main	proc	near
; Line 8
	mov	dx,768
	in	al,dx
	mov	ah,0
	push	dx
	mov	dx,769
	push	ax
	in	al,dx
	mov	ah,0
	pop	bx
	add	bx,ax
	push	bx
	mov	ax,offset _s@
	push	ax
	call	near ptr _printf
	pop	cx
	pop	cx
; Line 9
@1:
	ret	
_main	endp
_text	ends
_data	segment word public 'data'
_s@	label	byte
	db	116
	db	101
	db	115
	db	116
	db	32
	db	37
	db	100
	db	10
	db	0
_data	ends
_text	segment	byte public 'code'
	extrn	_printf:near
	public	_main
_text	ends
	end