[Info-vax] QIO Writes to a mailbox

[Richard B. Gilbert]

On 11/4/2011 5:48 PM, Steve Bainbridge wrote:
> On Nov 4, 9:09 pm, "Richard B. Gilbert"<rgilber... at comcast.net>
> wrote:
>> On 11/4/2011 12:52 PM, Steve Bainbridge wrote:
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>>> On Nov 4, 2:46 pm, Steven Schweda<sms.antin... at gmail.com>    wrote:
>>>> On Nov 4, 5:04 am, Steve Bainbridge<stephen_bainbri... at yahoo.co.uk>
>>>> wrote:
>>
>>>>> I have a very simple question, but when looking at the Alpha internals
>>>>> manual and talking to colleagues the answer does not seem so obvious.
>>>>> [...]
>>>>> Unfortunately the writer does not check or report what value the IOSB
>>>>> returns [...]
>>
>>>>      I'm confused.  You _know_ that you're ignoring the IOSB
>>>> status, and, rather than fixing that, you're looking at "the
>>>> Alpha internals manual"?  Really?
>>
>>>>> Is it QIO or QIOW? [...]
>>
>>>>      Another fair question.
>>
>>>>      Why not start by fixing the obvious problems, and then
>>>> move on to the obscure stuff (if necessary)?
>>
>>> Hi,
>>
>>> This code was written several years ago and I've been dumped on to
>>> investigate and correct the issue we now very occasionally see. I'm
>>> aware of the obvious missing check on the IOSB, but I can't say with
>>> any certainty that this is causing the problem.
>>
>> The missing check on the IOSB is almost certainly NOT causing the problem!
>>
>> The missing check is making diagnosis more difficult!
>>
>> I'd suggest designating one of the systems involved as the guinea pig
>> and add that missing error check.
>>
>> If the check tells you that there is an error and it correlates with
>> your problem, you know what to do!  If the error does not correlate, fix
>> it at your convenience and keep looking.
>>
>> If there are more instances of this sort of "lazy coding", fix them too.
>>
>> Good luck.  And if you have a few hundred thousand lines of code of this
>> quality, you have my sympathy.
>>
>> <snip>
>
> Richard,
>
> If it was just a couple of hundred thousand lines of code I would
> laugh my rocks off, alas it's circa 2-2.5 million lines of code,
> written over many years by developers of variable quality...some good,
> some certainly bad and some very ugly code.
>
> I realise that I'm going to have make changes and release it in the
> hope that it will work - it's just difficult to justify the changes
> and it's likely success.
>

You have my sympathy!  I've overhauled a LOT of code that would have had
me hysterical with laughter if SOMEONE ELSE had to fix it.

When I got out of the Army in late 1969 I got a job with Princeton 
University as a "Junior Programmer".  In effect, I was teaching graduate 
students the art of computer programming.  These students had mostly 
NEVER seen a computer, much less USED one!  The IBM PC was just a rumor 
that became reality a year or so later

The student written code was full of variables declared but never used, 
and variables that somehow were NEVER INITIALIZED.  This meant that they 
got the garbage left behind by the last program to run in that part of 
memory.

Comments were just TOO MUCH WORK!

I learned a lot!  I hope the students did also.

If your compilers offer a "CROSS_REFERENCE" option, use it.  This may 
help you find some of the garbage.

If you need help, I'm available.