[Issue 9335] Dtors are not called for dynamic arrays initialized by literals

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=9335



--- Comment #9 from yebblies <yebblies at gmail.com> 2013-06-29 00:55:21 EST ---
(In reply to comment #8)
> (In reply to comment #4)
> >
> > There is no need to call the destructor or postblit when moving the stack
> > allocated structs to the heap, it is legal to move them with memcpy.
> 
> Issue here is not in non-calling destructor when object is moved from stack to
> heap by pointer but is in non-calling destructor for temporary. This
> contradicts to policy in issue 9334 (which is itself not stable). 
> 

The temporary you are talking about is the struct that is being moved to the
heap.  D allows a struct to be moved with a memcpy.  9334 aside, what is
happening here is valid.

1. Structs are constructed on the stack
2. Heap array space is allocated
3. Structs are bit-copied into the heap memory
4. The original stack structs are abandoned

Because only one copy of the structs exists at the end, there is no copy, only
a move.

> General problem here is that dmd (unexpectedly) sometimes initializes > variables
> with temporaries and sometimes not. When it does initialize objects with a
temporary, sometimes it calls destructors on it and sometimes not. Such game
> with temporaries and destructors causes bugs.

dmd is free to choose either making a copy (which means calling the postblit,
then the destructor of the temporary) or to do a move (bitcopy) like it is
doing here.  The main difference is that a move has better performance.  Both
are valid.

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