Nut upsdev - Dec 2009 - drivers/bcmxcp.c portability issue

I ran into a portability issue with drivers/bcmxcp.c in nut-2.4.1 on
my UnixWare 7.1.4 machine. The error I get is
.....
UX:acomp: ERROR: "/opt/src/utils/nut-2.4.1/drivers/bcmxcp.c", line
835: integral constant expression expected
.....

Looking at the code we see
.....
int init_outlet(unsigned char len)
{
        unsigned char answer[len];
.....

Although gcc can handle it, it's not portable C code.

What size should the answer array be?

Thanks.

-- 
Tim Rice				Multitalents	(707) 887-1469
tim at multitalents.net

Hi Tim,
> I ran into a portability issue with drivers/bcmxcp.c in nut-2.4.1 on
> my UnixWare 7.1.4 machine. The error I get is
> .....
> UX:acomp: ERROR: "/opt/src/utils/nut-2.4.1/drivers/bcmxcp.c",
line 835:
>  integral constant expression expected .....
> 
> Looking at the code we see
> .....
> int init_outlet(unsigned char len)
> {
>         unsigned char answer[len];
> .....
> 
> Although gcc can handle it, it's not portable C code.
> 
> What size should the answer array be?
> 
It depends on the ups.
In the upsdrv_initinfo parsing the ID Block you get the length of the
outlet_block.
---------------------------------
	/* Size of outlet monitoring block */
	outlet_block_len = get_word(answer+iIndex);
	upsdebugx(2, "Length of outlet_block: %d\n", outlet_block_len);
	iIndex += 2;
---------------------------------
If this block is larger that 8 this indicate more than one outlet. So we go to
setup and read the outlet. Also add the commands.
---------------------------------
	/* Due to a bug in PW5115 firmware, we need to use blocklength > 8.
	The protocol state that outlet block is only implemented if there is
	at least 2 outlet block. 5115 has only one outlet, but has outlet block! */ 
	if (outlet_block_len > 8) {
		len = init_outlet(outlet_block_len);

		for(res = 1 ; res <= len ; res++) {
			snprintf(outlet_name, sizeof(outlet_name)-1,
"outlet.%d.shutdown.return", res);
			dstate_addcmd(outlet_name);
		}
	}
---------------------------

So setting the length of the answer from the ID_block. So from 0 - 20 at the
moment.
It would be possible to hardcode this len, and leave some space for 4 outlet.

Would be 2+6+6+6+6 = 26

Regards
Kjell

On Tue, Dec 15, 2009 at 2:27 AM, Kjell Claesson
<kjell.claesson at epost.tidanet.se> wrote:
> So setting the length of the answer from the ID_block. So from 0 - 20 at
the moment.
> It would be possible to hardcode this len, and leave some space for 4
outlet.
>
> Would be 2+6+6+6+6 = 26
If you do hardcode it, be sure to use something like fatalx() to
indicate whether there are more outlets than the code can handle. This
sounds unlikely, but it could happen if there is an error parsing
something earlier on.

Otherwise, as Arjen suggested, you could allocate it dynamically. The
xmalloc() function in common/common.c does out-of-memory checking for
you.

-- 
- Charles Lepple