Disallow destroy(structPtr)?

Steven Schveighoffer via Digitalmars-d-learn digitalmars-d-learn at puremagic.com
Fri Feb 20 12:30:04 PST 2015


On 2/20/15 1:05 PM, Nick Treleaven wrote:
> Hi,
>
> The following code is supposed to destroy the struct instance:
>
>      import std.stdio;
>      struct S{
>          ~this(){"destruct".writeln;}
>          }
>      auto p = new S;
>      destroy(p);
>      "end".writeln;
>
> It works correctly if I use destroy(*p), but the above code could
> perhaps be statically rejected by object.destroy to help prevent bugs.
> Currently, the pointer p is set to null without calling the destructor
> (with recent dmd the destructor is called, but only after "end" is
> printed).
>
> Here is the destroy overload:
>
> void destroy(T)(ref T obj)
>      if (!is(T == struct) && !is(T == interface) && !is(T == class) &&
> !_isStaticArray!T)
> {
>      obj = T.init;
> }

I'm beginning to think this is the right thing to do. It confuses so 
many people, and setting a pointer/class reference/array to null is easy 
enough without needing a special function to do it. In other words, if 
you are using destroy, you aren't just trying to nullify a pointer. You 
want to destroy what the pointer represents.

The only problem is, how does this affect existing code?

-Steve


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