Pointers - Is it safe to point to invalid memory?

[monkyyy]

On Saturday, 16 August 2025 at 21:26:55 UTC, Brother Bill wrote:
> On Saturday, 16 August 2025 at 15:44:45 UTC, Richard (Rikki) 
> Andrew Cattermole wrote:
>> On 17/08/2025 3:44 AM, Brother Bill wrote:
>>> On Saturday, 16 August 2025 at 15:30:43 UTC, H. S. Teoh wrote:
>>>> On Sat, Aug 16, 2025 at 03:24:55PM +0000, Brother Bill via 
>>>> Digitalmars-d-learn wrote: [...]
>>>>> So a good D developer should not store an invalid pointer 
>>>>> address into a pointer, with the single exception of 
>>>>> storing a pointer address just past a slice or array.
>>>>
>>>> Where does it say this in the spec?  Because this is wrong.
>>>>
>>>> D arrays carry length with them; they do not rely on 
>>>> pointers pointing past the allocated memory region.
>>>>
>>>>
>>>> T
>>> 
>>> Source: Programming in D book, page 432, chapter 68.8
>>> Quote: It is valid to point at the imaginary element one past 
>>> the end of an array.
>>
>> That is not the spec, the book is wrong.
>
>
> Please provide link to the current spec?

Its irrelivent https://dlang.org/spec/type.html#pointers
Its defined on deference not on existence.

Its over in the gc that has any relivence:

https://dlang.org/spec/garbage.html#pointers_and_gc

> Do not xor pointers with other values, like the xor pointer 
> linked list trick used in C.

But this is just whake-a-mole docs, they are just describing how 
the current gc works without thoery or usecase clarity

Rikki will be wrong, an exclusive bounded would *have to* be 
defined by an off by 1 pointer, but no one does that not even me.