[Issue 14078] Call DTor for stack allocated objects

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=14078

--- Comment #3 from Ketmar Dark <ketmar at ketmar.no-ip.org> ---
(In reply to rswhite4 from comment #2)
> (In reply to Ketmar Dark from comment #1)
> > `emplace` is not a built-in. one can write alot of emplace-like functions
> > that allocates any memory for the object. even the function named `emplace`,
> > that will sometimes allocates on stack and sometimes uses `malloc()`.
> > 
> > what you actually asking is compiler that is able to use some AI to see what
> > programmer *means* by writing the code. this is not possible.
> 
> No. The compiler should be able to detect that a2 is stack allocated (the
> compiler should be able to see the type of a2 -> A and also that the memory
> is on the stack).
compiler doesn't know what `emplace` does. to determine that it have to switch
on secret AI button somehow. can you please show a sample code that is able to
determine such things in all cases? 'cause if some cases are missed, then there
will be no way for programmer to determine when destructor will be called and
when not.

> But your example with malloc could be true, but I'm sure that the DTor of a2
> should be called at least at the end of the programm. The compiler should be
> able to do that, even without any AI. ;)
class dtors are not guaranteed to be called at all. if someone will change GC
so it will stop calling dtors, it will break nothing by the specs. and this is
not an oversight.

> > if you want stack-allocated classes with automatic dtors, why don't use
> > `std.typecons.scoped`?
> 
> It is IMO not well implemented.
please, can you show the cases where it's not working, so we can fill
bugreports and somebody will fix it?

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