Integer overflow and underflow semantics
Era Scarecrow
rtcvb32 at yahoo.com
Fri May 4 22:32:08 PDT 2012
On Saturday, 5 May 2012 at 04:57:48 UTC, Alex Rønne Petersen
wrote:
> Hi,
>
> I don't think the language really makes it clear whether
> overflows and underflows are well-defined. Do we guarantee that
> for any integral type T, T.max + 1 == T.min and T.min - 1 ==
> T.max?
>
> This is relevant in particular for GDC and LDC since they
> target a lot of weird architectures.
Any systems that implement a carry flag likely works exactly
like that. Carry flag is set or cleared after a math operation,
allowing you to extend the size of your integer any level you
want, like in oh the 6502?
Might look something like this: Been a while but you should get
the idea
clc ;clear carry
loop_here:
mov ax, [bx]
adc [dx], ax
inc bx
inc dx
dec cx
cmp cx, 0
jne loop_here
;if carry after this point then...
jc overflow_warning
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