On Tuesday, 31 March 2015 at 15:12:54 UTC, ref2401 wrote:
Could anyone describe me what this initialization does, please?
It skips the initialization entirely, leaving the memory random
instead of making it zeroes (or NaN or whatever the .init is of
the actual type, typically zero though).
The struct members will thus be random when made with =void.
However, it does tell the compiler that you thought about
initializing it - you tell it you specifically want it
uniniitalized and didn't just forget to write something.
When do I need to use the void initialization?
Very rarely, don't use it unless you can answer this yourself.
But some possible answers would be:
1) the initialization wasted program runtime; it can be an
optimization. Only use it in this case if you are sure it matters
(the speed was actually a problem) and if you do initialize it
yourself immediately afterward. Otherwise, you might be
introducing bugs.
2) you want some kind of random data, like if you are using it to
seed a random number. There's often better ways of doing this,
but =void might work in some cases.
3) You are initializing a private member with default
construction turned off. Here, "Struct s;" wouldn't compile
because of the disabled default constructor, but you need to set
it up anyway. So you do "Struct s = void; s.values = something;"
- void to tell the compiler you know what you're doing, then you
quickly initialize it to what it needs to be. I say in a private
member because you'd be bypassing the object's requirements this
way, so you are responsibile for making sure the values are
indeed valid before using the object.
