[Info-vax] DCL Integer Overflow

[Stephen Hoffman]

On 2017-07-01 18:07:01 +0000, Scott Dorsey said:

> On 6/30/2017 5:06 AM, GerMarsh wrote:
>> I know that there have been a few discussions about enhancing/replacing 
>> DCL, but I wonder if someone will fix the old integer overflow which 
>> has been there since the year dot...
>> 
>> $ int=%x7fffffff
>> $ sho sym int
>> INT = 2147483647   Hex = 7FFFFFFF  Octal = 17777777777
>> $ int=int+1
>> $ sho sym int
>> INT = -2147483648   Hex = 80000000  Octal = 20000000000
> 
> This is not a bug, it's a feature.

Or as this particular case can also be known, "broken as designed."

> If you don't want it to roll over, what DO you want it to do?

In most contexts, overflows are considered bad.   Yes, some programmers 
do use overflows, and this particular DCL mess is completely expected 
and normal.

> Halt with an error?

Usually trigger a warning.  In classic OpenVMS, it'd be another option 
on the ON statement.    Even better, detect and flag that the error can 
even arise as far ahead of run-time as possible.    Less surprises that 
way.   Alas, DCL is not good at that sort of thing, though.

...Even C is starting to deal decently with these cases, too.


-- 
Pure Personal Opinion | HoffmanLabs LLC