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From: DERMOTT@DREA-XX.ARPA (Dave Dermott)
Newsgroups: comp.os.vms
Subject: DECUS C on VMS
Message-ID: <12306036928.37.DERMOTT@DREA-XX.ARPA>
Date: Thu, 28-May-87 15:19:48 EDT
Article-I.D.: DREA-XX.12306036928.37.DERMOTT
Posted: Thu May 28 15:19:48 1987
Date-Received: Sat, 30-May-87 09:54:35 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: world
Organization: The ARPA Internet
Lines: 128


 DECUS C PROBLEMS ON VMS
   This may not be the right group for DECUS C but I don't know where
else to ask and there were several messages about it here.
1/  DECUS-C on VMS RSX emulation mode ?
      I can't run the DECUS C compiler on VMS RSX11 emulation mode.
The compiler starts but aborts with "Memory protect error". The same task
does work when I move it to a real PDP 11.
    I used the supplied command file(VMAKCC.COM)  for building it on VMS but
I used object files that had been assembled previously  on a real PDP11.
Do  I have to reassemble all the sources on VMS ?
I rebuilt the task on VMS from objects.

2/ BUG in DECUS C 
      I found this bug in the compiler . It generates a word "add"
when it should be a byte "add". This causes an address error when
an odd address is reached, the sum will also be wrong.
.11:
	mov	$_data,r4     * r4 contains address of data[0]
	add	_i,r4         * add i to address
	movb	_chksum,r0
	add	(r4),r0        * add word causes error odd address
	movb	r0,_chksum

      This code occurs in SPACK in the 
original C-KERMIT. Changing chksum to int works.
    Has this bug been fixed?

/* -------------------------------------------------- */
/* odd addressing error in DECUS C for pdp 11 */
#include <stdio.h>
char data[10];
char chksum;   /* int chksum works */
int i;
int len;
int t;
main()
{
len=5;
chksum=0;

for (i=0;i<len;i++){data[i]=i+1;} /* initialize array */
for (i=0;i<len;i++){
    chksum += data[i]; /* sum array causes error */
    }
t=chksum;
printf(" sum is %d\n",t);
}
/* ------------------------------------------------------ */

/ Decus C patch level 9, Compilation date: "Thu May 28 15:09:06 1987"
	.psect	c~data
_data:
	.blkb	12
	.even
_chksum:
	.blkb	1
	.even
_i:
	.blkb	2
	.even
_len:
	.blkb	2
	.even
_t:
	.blkb	2
	.even
	.psect	c~code
_main:
	jsr	r5,csv~
	mov	$5,_len
	clrb	_chksum
	clr	_i
	br	.4
.5:
	mov	_i,r4
	inc	r4
	mov	$_data,r0
	add	_i,r0
	movb	r4,(r0)
.3:
	inc	_i
.4:
	cmp	_i,_len
	blt	.5
.2:
	clr	_i
	br	.10
.11:
	mov	$_data,r4
	add	_i,r4
	movb	_chksum,r0
	add	(r4),r0        * add word causes error odd address
	movb	r0,_chksum
.7:
	inc	_i
.10:
	cmp	_i,_len
	blt	.11
.6:
	movb	_chksum,r0
	mov	r0,_t
	.psect	c~strn
.12:
	.byte	40,163,165,155,40,151,163,40,45,144,12,0
	.psect	c~code
	mov	_t,-(sp)
	mov	$.12,-(sp)
	jsr	pc,_printf
	cmp	(sp)+,(sp)+
.1:
	jmp	cret~
	.psect	c~data
	.even
	.globl	_chksum
	.globl	_printf
	.globl	_data
	.globl	_main
	.globl	_len
	.globl	_i
	.globl	_t
	.globl	csv~
	.globl	cret~
	.psect	c~code
	.even
	.psect	c~data
	.even
-------