DMD OSX / Segfault 11

[anonymous via Digitalmars-d-learn]

On 02.02.2016 19:06, Robert M. Münch wrote:
> I have a very strange effect, I'm not sure what it is about:
>
> Value: {}
>
> WordV: Value {
>      Value* get() {}
> }
>
> BaseOperator: Value : {
> }

This isn't valid D code at all, which makes it unnecessarily hard to 
understand what you mean.

> Now comes the code using this:
>
> auto op = cast(BaseOperator)(Word.get());
> if (op !is null) {...
>
>
> If get() returns "Value*" it segfaults, if I change it to "Value" it
> works. How can this be?

A Value* is a pointer to a class reference. Unless you're doing 
something really funky with the pointer, casting it to a class type 
doesn't make sense.

Casting between class types that have an inheritance relation, like 
Value and BaseOperator, does make sense (upcat/downcast).

If anything, you should be casting between Value* and BaseOperator* 
(both pointer types) if you want to do something with pointers.

But you very seldom need pointers to class references. Just return Value 
from get, and cast to BaseOperator.