[RFC] Throwing an exception with null pointers

[Richard (Rikki) Andrew Cattermole]

On 14/04/2025 9:49 PM, a11e99z wrote:
> On Saturday, 12 April 2025 at 23:11:41 UTC, Richard (Rikki) Andrew 
> Cattermole wrote:
>> I've been looking once again at having an exception being thrown on 
>> null pointer dereferencing.
> 
> null pointer in x86 is any pointer less than 0x00010000

The null page right, and how exactly did you get access to a value that 
isn't 0 or a valid pointer?

Program corruption. Which should only be possible in non- at safe code.

> also what about successful dereferencing 0x23a7b63c41704h827? its 
> depends: reserved this memory by process, committed, mmaped etc

How did you get this value? Program corruption.

> failure for any "wrong" pointer should be same as for 0x0000....000 
> (pure NULL)

Null (0) is a special value in D, these other values are simply assumed 
to be valid. Of course its not possible to get these other values 
without calling out of @safe code where program corruption can occur.

> imo need to dig into .net source and grab their option

.net is an application VM, and for all intents and purposes they will be 
injecting read barriers before each null dereference.

They also have strong guarantees that you cannot have a invalid to a 
pointer, pointer. It must be null or point to a valid object.

It isn't as simple as copying them.

Plus they have the type state analysis as part of the language to handle 
nullability!