Allocator-aware @safe reference counting is still not possible

[jmh530]

On Monday, 30 January 2023 at 01:07:32 UTC, Timon Gehr wrote:
> On 1/28/23 16:56, Nick Treleaven wrote:
>> [snip]
>> Isolated could go in std.typecons.
>
> Isolated is not sufficient, you also have to guarantee the 
> pointer was allocated with `malloc`.

Could you explain in a bit more detail why this is the case? 
Thanks.