• Carl Sturtivant (9/9) Mar 30 2014 Context: struct values that are (non-ref) parameters & local
• Benjamin Thaut (12/19) Mar 30 2014 D's structs don't have identity. That means, they can be moved without
• Carl Sturtivant (5/15) Mar 30 2014 Thanks for that discussion. As you might have guessed, adding
• monarch_dodra (9/12) Mar 30 2014 AFAIK, a destructor is always called when an object goes out of
• Benjamin Thaut (9/15) Mar 31 2014 The destructor is always called. There is never a instance that gets

"Carl Sturtivant" <sturtivant gmail.com> writes:

Context: struct values that are (non-ref) parameters & local 
variables.

Is there a way to arrange that a particular struct's special 
constructors (postblit,destructor) should always be called even 
on move, or on destruction of a default initialized value, 
temporary or not, etcetera, i.e. ensure they should always be 
called?

Is a struct's destructor always called when it goes out of scope, 
even if it is default initialized?

Benjamin Thaut <code benjamin-thaut.de> writes:

Am 30.03.2014 21:35, schrieb Carl Sturtivant:
 Context: struct values that are (non-ref) parameters & local variables.

 Is there a way to arrange that a particular struct's special
 constructors (postblit,destructor) should always be called even on move,
 or on destruction of a default initialized value, temporary or not,
 etcetera, i.e. ensure they should always be called?

 Is a struct's destructor always called when it goes out of scope, even
 if it is default initialized?

D's structs don't have identity. That means, they can be moved without 
notice at any point in the program. AFAIK the compiler even does that 
when handling exceptions in a few cases (e.g. with structs on the 
stack). Having moveable value types allows for a lot of optimizations, 
both on the compiler side as well as when implementing e.g. containers 
in user code. So no there is no way to always get notified. I also 
proposed a move constructor in the past, but the idea was not well 
recieved. When I needed a move constructor, usually adding another level 
of indirection solved the problem.

Kind Regards
Benjamin Thaut

"Carl Sturtivant" <sturtivant gmail.com> writes:

 D's structs don't have identity. That means, they can be moved 
 without notice at any point in the program. AFAIK the compiler 
 even does that when handling exceptions in a few cases (e.g. 
 with structs on the stack). Having moveable value types allows 
 for a lot of optimizations, both on the compiler side as well 
 as when implementing e.g. containers in user code. So no there 
 is no way to always get notified. I also proposed a move 
 constructor in the past, but the idea was not well recieved. 
 When I needed a move constructor, usually adding another level 
 of indirection solved the problem.

Thanks for that discussion. As you might have guessed, adding 
another level of indirection is what I was trying to avoid. A 
move constructor would have taken care of my problem.

What about destructors, are they always called, or is this 
another optimization if the struct is in it's default .init state?

"monarch_dodra" <monarchdodra gmail.com> writes:

On Monday, 31 March 2014 at 01:03:22 UTC, Carl Sturtivant wrote:
 What about destructors, are they always called, or is this 
 another optimization if the struct is in it's default .init 
 state?

AFAIK, a destructor is always called when an object goes out of 
scope... unless, it's being moved out of scope. As a matter of 
fact, spec RVO *will* get triggered. This is what allows witting 
factory functions for types without postblit.

In any case, there should be 1 destructor call for every object 
you declared.

Except for thing on the heap. Those are just collected, not 
destroyed :/

Benjamin Thaut <code benjamin-thaut.de> writes:

Am 31.03.2014 08:06, schrieb monarch_dodra:
 On Monday, 31 March 2014 at 01:03:22 UTC, Carl Sturtivant wrote:
 What about destructors, are they always called, or is this another
 optimization if the struct is in it's default .init state?

 In any case, there should be 1 destructor call for every object you
 declared.

 Except for thing on the heap. Those are just collected, not destroyed :/

The destructor is always called. There is never a instance that gets 
destroyed without the destructor beeing called. It can happen however 
that the destructor gets called on a .init state. This happens for 
example if you use "std.algorithm.move". To be fully correct your struct 
should handle the .init state in the destructor (or assert at least so 
you can find and fix those occurences).

Kind Regards
Benjamin Thaut