destroy(someStruct)

[monarch_dodra via Digitalmars-d-learn]

On Saturday, 20 September 2014 at 22:46:10 UTC, John Colvin wrote:
> import core.stdc.stdio;
> struct S
> {
> 	~this()
> 	{
> 		printf("%x\n".ptr, &this);
> 	}
> }
> void main()
> {
> 	S* sp = new S;
> 	destroy(*sp);
>
> 	S s;
> 	destroy(s);
>
> 	auto sa = new S[2];
> 	foreach(ref s_; sa)
> 		destroy(s_);
> }
>
> output:
>
> 4002dff0
> bfa89a70
> 4002dfe0
> 4002dfe1
> bfa89a70
>
> Note the double destruction of s
>
> Its seems that calling destroy on a stack-allocated struct is a 
> no-no (unless you have a re-entrant destructor). The other two 
> examples seem OK though.
>
> Am I in dangerous territory? Will I see unexpected 
> double-destructions in some cases?

Destroy leaves your struct in its T.init state, and T.init should 
always be destroyable. So even though the destroyer gets called 
twice, you should be perfectly safe.

FYI, "move" relies on this mechanism: it sets object state to 
T.init, to make sure the later stack destruction has no side 
effect.