Discussion: Rvalue refs and a Move construtor for D

kinke noone at nowhere.com
Wed Sep 4 21:59:46 UTC 2019

On Wednesday, 4 September 2019 at 21:09:27 UTC, Exil wrote:
> So you change the ABI to pass by a pointer to the object on the 
> stack. In cases where we use some "move" intrinsic, a pointer 
> to a lvalue (passed in to the move()) is passed in place of the 
> pointer to the object on the stack?


> Because of this, even though the function doesn't use a 
> reference. It could unknowingly change state outside of the 
> scope of the function. That'll entirely depend on the use if 
> they mistakenly use `move()` where they didn't mean to.

Yes, the assumption being that people do use `move` when they 
mean to (it's explicit after all) and are fine with not being 
able to make any assumptions about its state after the move. 
Re-assigning would still be possible.

But as stated further up, the crux is probably the lifetime for 
moved lvalues, i.e., the by-value parameter not being destroyed 
right before/after returning, but when the moved-from lvalue goes 
out of scope.
Maybe we could destruct the moved-from lvalue after the call and 
reset it to `T.init`. It would be destroyed a 2nd time when going 
out of scope.

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