Discussion Thread: DIP 1035-- at system Variables--Community Review Round 2

[Atila Neves]

On Tuesday, 2 March 2021 at 21:41:40 UTC, Paul Backus wrote:
> On Tuesday, 2 March 2021 at 20:46:17 UTC, Atila Neves wrote:
>> Pointer types *can* be unsafe, if the values came from @system 
>> code. Otherwise they're perfectly safe. Slices (dynamic 
>> arrays) are slightly different because of the necessity of 
>> bounds checks. But deferencing a pointer is fine in @safe code 
>> - the possibilities are:
>>
>> * it came from the GC.
>> * is the address of a module-level variable.
>> * is a scoped address on the stack.
>> * is null.
>>
>> Am I missing a case?
>
> You are conflating types and values. Pointer *values* can be 
> either safe or unsafe, depending on what they point to. Pointer 
> *types* are always unsafe, because they include both safe and 
> unsafe values.

I don't think I am, but I think I understand where you're coming 
from. Let me restate my point and maybe then it will be clearer: 
if all the code in a program is @safe, then pointers are memory 
safe (with DIP1000).

I guess I'd argue that pointer types are safe unless the value 
was obtained from @system code. But throw @system code into the 
mix...

Anyway, the wording confused me.