Destructor called while object is still alive

[Steven Schveighoffer]

On 10/23/20 2:57 AM, Ola Fosheim Grøstad wrote:
> On Friday, 23 October 2020 at 06:37:43 UTC, Daniel Kozak wrote:
>> On Fri, Oct 23, 2020 at 8:20 AM frame via Digitalmars-d < 
>> digitalmars-d at puremagic.com> wrote:
>>
>>>  Even this is a "intelligent"
>>> feature by the compiler for non reachable code like that loop,
>>> it's still confusing. There are maybe situations while the object
>>> should stay in background, eg. socket related/event stuff. If
>>> there is a valid pointer, there is no excuse to reap it.
>>>
>>>
>> There is no use of foo anywhere so there is no reason to not collect it.
> 
> It is in use until the end of main. Think locking. Seems like the 
> pointer is optimized away and then the GC collects. Makes RAII useless 
> with GC.

But you don't get RAII with classes or pointers. Only with structs.

> 
> Basically a consequence of the optimizer assuming that there is no GC. A 
> rather serious correctness issue.
> 
> 

I don't think so. A class reference itself doesn't have a destructor. 
The compiler is free to elide storage just like it was a pointer. One 
cannot expect any specific behavior from the GC in this case, as the 
correctness of the program doesn't depend on the object staying in place 
for the duration of the function. Here there is just a disconnect in how 
the OP expects the compiler to implement the machine code.

Use a type that *does* support RAII (i.e. struct with dtor), and it will 
be allocated and properly destroyed.

-Steve