[Info-vax] DCL Integer Overflow

[Arne Vajhøj]

On 7/3/2017 1:31 PM, Bob Koehler wrote:
> In article <5ae4986d-0da2-4457-b02d-057beff36d2b at googlegroups.com>, GerMarsh <marsh.family at tirhir.com> writes:
>> 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
>> $
> 
> 
>     I don't see any intger overflow, I see perfectly reasonable
>     behaviour for a 32 bit integer.

It is very reasonable and as expected.

But it is an integer overflow.

To quote from the VAX Architecture Reference Manual:

"Integer overflow occurs if the input operands to the add have
the same sign and the results has the opposite sign."

Arne