Details on how aggregates are constructed with `new` and later destroyed by the GC

[Nicholas Wilson]

On Monday, 8 October 2018 at 11:19:40 UTC, Per Nordlöw wrote:
> I want to understand how calls to `new` for classes

see _d_newclass

> and structs are lowered by the compiler and druntime to a 
> GC-allocation (specifically how the `ba`-argument bits are 
> determined) followed by an initialization using default 
> constructor or via a user-defined constructor called using 
> arguments to `new`. And how this is related to the trait 
> `hasElaborateConstructor` for both `classes` and `structs`.

Memory is allocated, .init (for classes this comes from 
typeid(T).initializer)
  is copied over the memory and then the constructor is run.

> I also want to understand how manually defined constructors and 
> destructors affect the setting of the GC finalizer for a given 
> aggregate type. And how this is related to the trait 
> `hasElaborateDestructor` for both `classes` and `structs`

For classes the typeid(T).destructor is called on the class, for 
structs I'm not sure.

> Where's the dmd and druntime code that handles these steps?

should be src/rt/lifetime.d IIRC