Re: Struct default constructor - need some kind of solution for C++ interop

[Walter Bright via Digitalmars-d]

On 9/7/2016 2:08 PM, deadalnix wrote:
It is clear at this point that structures with obligatory initialization are
necessary. For C++ but not only.

If not interfacing to C++, why?

Right now, all dtors need to make sure that the
.init state is valid, which can be a performance problem (you need to add
runtime checks to know if you actually need to destroy a resource).

Is:

    if (resource != null)
        resource.destroy();

v.s.:

    resource.destroy();

so onerous? It's one TST/JNE pair for a value loaded into a register anyway. And 
with a default constructor, there's all that code added to deal with the 
constructor failing and throwing.

Besides, you can still write:

    struct S {
        Resource resource;

        Resource builder() {
            S s;
            s.resource = new Resource();
            return s;
        }

        ~this() {
            assert(resource);  // ensure user used builder()
            resource.destroy();
        }
    }