The case for integer overflow checks?

Neia Neutuladh via Digitalmars-d digitalmars-d at
Fri Sep 15 16:04:08 UTC 2017

On Friday, 15 September 2017 at 12:33:56 UTC, Adam D. Ruppe wrote:
> On Friday, 15 September 2017 at 12:04:27 UTC, Kagamin wrote:
>> Since width can't be negative, C programmer would use unsigned 
>> integer for it
> That's often a big mistake. Lots of people do it... but you 
> shouldn't, exactly because of the wraparound behavior.

Signed integers have the same issue, no? Using int32s:

2147483635 * 400000000 * 4 = 674836480

It's just that you're more likely to be able to detect it, since 
a lot of inputs result in negative numbers.

One solution is to switch to the next larger integer size. That 
works up to 32-bit numbers. When you hit 64-bit, you've got to 
switch to BigInt.

Another solution is to check the overflow bit as appropriate. The 
checkedint package automates that.

The last solution that I can think of, specific to this type of 
thing, is to use the result to allocate a bounds-checked array, 
where the allocation function yields the appropriately sized 
array. You'll get an array bounds error that may be inscrutable.

More information about the Digitalmars-d mailing list