Understanding RefCounted

[JG]

On Wednesday, 12 May 2021 at 13:38:10 UTC, Steven Schveighoffer 
wrote:
> On 5/12/21 3:28 AM, JG wrote:
>> Reading the documentation on RefCounted I get the impression 
>> that the following can lead to memory errors. Could someone 
>> explain exactly how that could happen? I suppose that problem 
>> would be the call something to do with front?
>> 
>> 
>> ```
>> private struct RefCountedRangeReturnType(R)
>> {
>>      import std.typecons : RefCounted;
>>      private RefCounted!R r;
>>      auto empty() { return r.refCountedPayload.empty; }
>>      auto front() { return r.refCountedPayload.front; }
>>      void popFront() { r.refCountedPayload.popFront; }
>>      auto save() { return 
>> typeof(this)(RefCounted!R(r.refCountedPayload.save)); }
>> }
>> 
>> auto refCountedRange(R)(R r)
>> {
>>      import std.typecons : RefCounted;
>>      return  RefCountedRangeReturnType!R(RefCounted!R(r));
>> }
>> ```
>
> You don't need to access refCountedPayload. RefCounted is 
> supposed to be like a transparent reference type, and should 
> forward all calls to the referenced item.
>
> I don't see how you will get memory errors from your code. 
> Maybe you can elaborate why you think that is?
>
> -Steve

To be honest I can't see the problem. But the following from the 
documentation made me wonder if I was doing something that could 
lead to memory problems:

"RefCounted is unsafe and should be used with care. No references 
to the payload should be escaped outside the RefCounted object."

In particular I wondered if in some special case holding a 
reference to front might cause a problem, but perhaps that is 
incorrect.