[Issue 6581] Yet another dtor/postblit problem?

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=6581



--- Comment #4 from Dmitry Olshansky <dmitry.olsh at gmail.com> 2011-09-20 07:37:10 PDT ---
> Please note this line:
> >         a = A(dummy); // a(dummy) was a typo, thought it changes nothing
> 
> This is "assignment", not initializing.
> The assignment of an object that has postblit (like A) is implemented *swap and
> destroy*. 

Note this line was in constructor. No way to initialize member of a struct?
That's something I'd call unacceptable.

I should point out that move == swap & destroy, iff left side of assigment
_was_ initialized. A constructor may be called on chunk of uninitialized memory
e.g. in Phobos std.typecons.emplace.

> For this purpose, D compiler implements opAssign implicitly, like
> follows:
> 
> struct A {
>   ...
>   ref A opAssign(A rhs) {  // rhs is copyed from original value

why do we copying the original value in the first place? 
It should be moved with e.g. memmov

>     std.algorithm.swap(this, rhs);  // bitwise swapping
>     return rhs;
>     // rhs is equals to original 'this', and it is destroyed here.
>   }
> }


> 
> Therefore, the assignment of an object of A always increment A.dtor.

Thanks, that clarifies it in part, but still how about initialization in
constructor?

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------