Inconsistent behavior shared struct vs non-shared storage - bug?

[LesleyRobinson]

On Wednesday, 2 June 2021 at 16:25:27 UTC, Iain Buclaw wrote:
> On Wednesday, 2 June 2021 at 12:25:54 UTC, apz28 wrote:
>>
>>     struct S
>>     {
>>         C c;
>>         this(C c)
>>         {
>>             counter++; writeln("this(): ", counter);
>>             this.c = c is null ? new C() : c;
>>         }
>
> I suspect this is a topic better suited to d.learn, but you are 
> missing a shared constructor.
>
> ```
> shared this(shared C c)
> {
>     counter++; writeln("this(): ", counter);
>     this.c = c is null ? new shared C() : c;
> }
> ```
>
>>     shared static this()
>>     {
>>         writeln("shared static this(1): ", counter);
>>         static if (sharedit) s = cast(shared)S(null);
>>         else s = S(null);
>>         writeln("shared static this(2): ", counter);
>>     }
>
> The `sharedit` path constructs a non-shared object, which you 
> cast to a shared one.  This causes a copy to occur, so what 
> you're seeing is the destruction of the temporary.
>
> Instead, construct a shared object.
> ```
> static if (sharedit) s = shared(S)(null);
> else s = S(null);
> ```

Using possibly undefined storage or returning storage that is not 
properly  Inside a function body, no error is reported when the 
field of a partial structure is used. Splint will report warnings 
when numabstract types are used inconsistently, but  calls (e.g., 
strcpy) have undefined behavior if parameters share storage.

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