Memory safe in D

[Quirin Schroll]

On Tuesday, 12 March 2024 at 03:00:24 UTC, Walter Bright wrote:
> On 3/11/2024 3:20 AM, Alex wrote:
>> Oh... looks like null is also used for refs in D. It's sad :)
>> I thought it used only for pointers in unsafe mode.
>> I think, the null safety feature is very important in modern 
>> world (maybe "must have" :) ). Very nice to have such feature 
>> in D like in Kotlin for example.
>> So, as I understand, D team have the task in TODO list about 
>> implementation something like "null safety"?
>
> Null is actually not a memory safety issue. What happens when 
> null is read or written to is a seg fault. The seg fault is the 
> hardware saying "you cannot do that", so there is nothing 
> unsafe about it.

I guess what people want instead of segmentation faults is not 
UB, but compile errors. Segmentation faults are better than UB, 
but a type system that tells you where your code might segfault 
because of a null dereference is even better: Not only gives it 
peace of mind, it works on platforms that don’t segfault, and 
it’s likewise free of any runtime cost.

It’s a whole different discussion how to add those compile-time 
checks to D’s type system.