Memory safe in D

[Richard (Rikki) Andrew Cattermole]

On 12/03/2024 4:31 AM, bachmeier wrote:
> On Monday, 11 March 2024 at 08:48:47 UTC, Richard (Rikki) Andrew 
> Cattermole wrote:
>> On 11/03/2024 9:16 PM, Alex wrote:
>>> So I don't see any errors or warnings from compiler when I use 
>>> uninitialized variable |a| and don't see any exception with backtrace 
>>> in runtime (application is build in debug mode).
>>>
>>> Is it expected behavior? Looks like it is not very safe approach and 
>>> can lead to very unpleasant memory errors...
>>
>> This is expected behavior.
>>
>> The variable a was default initialized to null.
>>
>> D has not got type state analysis as part of it, so it cannot detect 
>> this situation and cause an error.
>>
>> It is at the top of my todo list for memory safety research for D, as 
>> the IR it requires enables other analysis and provides a framework for 
>> it to exist in.
> 
> Rather than doing that, couldn't the compiler say `A a;` is not valid 
> inside `@safe`?

One of the improvements for type state analysis I want to make is for 
methods:

```d
class Foo {
	void func(this'nonnull);
}
```

Instead of:

```d
class Foo {
	void func(this'reachable);
}
```

That'll catch it when you try to call something.

However I'm not sure if disallowing null entering is a great idea, its 
going to enter through other methods so you might as well embrace 
catching that as well.