• Zachary Lund <admin computerquip.com> Jan 31 2012
• Nicolas Silva <nical.silva gmail.com> Jan 31 2012
• Trass3r <un known.com> Jan 31 2012
• "Zachary Lund" <admin computerquip.com> Jan 31 2012
• =?utf-8?Q?Simen_Kj=C3=A6r=C3=A5s?= <simen.kjaras gmail.com> Jan 31 2012

Zachary Lund <admin computerquip.com> writes:

I've been looking into (basic) memory management within D. Through IRC 
conversation and reading the article on memory management on dlang.org 
(which seems to be a bit out-of-date), I've concluded that using a 
global (or static member) function and emplace() in std.conv is a simple 
solution for providing alternative allocation methods. However, I 
cannot, by default, scope my custom allocations. Take this for instance:

void main() {
	MyClass inst = alloc!(MyClass)();
	inst.do_something();
	dealloc(inst);
}

Now, I want my dealloc function to be called automagically. One safe 
measure is:

void main() {
	MyClass inst = alloc!(MyClass)();
	scope(exit) dealloc(inst);
	inst.do_something();
}

But I'm lazy and I'm looking for shorter methods.

void main() {
	mixin AutoRef(MyClass, "inst");
	inst.do_something();
}

Any ideas?

Nicolas Silva <nical.silva gmail.com> writes:

You can use structs for this kind of problems, somethin like

struct Scoped(T)
{
    ~this()
    {
        //handle deallocation here
    }
    T inst;
}

if you create a Scoped!MyClass in a scope, the struct's destructor
will be invoked whenever the program leaves the scope, even if it is
because of an exception.

On Tue, Jan 31, 2012 at 2:40 PM, Zachary Lund <admin computerquip.com> wrot=
e:
 I've been looking into (basic) memory management within D. Through IRC
 conversation and reading the article on memory management on dlang.org
 (which seems to be a bit out-of-date), I've concluded that using a global
 (or static member) function and emplace() in std.conv is a simple solutio=


 for providing alternative allocation methods. However, I cannot, by defau=


 scope my custom allocations. Take this for instance:

 void main() {
 =A0 =A0 =A0 =A0MyClass inst =3D alloc!(MyClass)();
 =A0 =A0 =A0 =A0inst.do_something();
 =A0 =A0 =A0 =A0dealloc(inst);
 }

 Now, I want my dealloc function to be called automagically. One safe meas=


 is:

 void main() {
 =A0 =A0 =A0 =A0MyClass inst =3D alloc!(MyClass)();
 =A0 =A0 =A0 =A0scope(exit) dealloc(inst);
 =A0 =A0 =A0 =A0inst.do_something();
 }

 But I'm lazy and I'm looking for shorter methods.

 void main() {
 =A0 =A0 =A0 =A0mixin AutoRef(MyClass, "inst");
 =A0 =A0 =A0 =A0inst.do_something();
 }

 Any ideas?

Trass3r <un known.com> writes:

 However, I cannot, by default, scope my custom allocations.
 Any ideas?


std.typecons.scoped

"Zachary Lund" <admin computerquip.com> writes:

On Tuesday, 31 January 2012 at 15:19:00 UTC, Trass3r wrote:
 However, I cannot, by default, scope my custom allocations.
 Any ideas?


 std.typecons.scoped


I looked into this and I'm unsure of its exact use. It says, 
"Allocates a class object right inside the current scope" which 
doesn't really define how it's allocated nor does it explain how 
this would work with custom de/allocators. Also, it claims it 
"avoids" the overhead of new of which I'm not entirely sure of 
what it means. Could some clarification be made?

=?utf-8?Q?Simen_Kj=C3=A6r=C3=A5s?= <simen.kjaras gmail.com> writes:

On Tue, 31 Jan 2012 16:42:52 +0100, Zachary Lund <admin computerquip.com=
  =


wrote:

 On Tuesday, 31 January 2012 at 15:19:00 UTC, Trass3r wrote:
 However, I cannot, by default, scope my custom allocations.
 Any ideas?


 std.typecons.scoped


 I looked into this and I'm unsure of its exact use. It says, "Allocate=



 a class object right inside the current scope" which doesn't really  =


 define how it's allocated nor does it explain how this would work with=



 custom de/allocators. Also, it claims it "avoids" the overhead of new =



 which I'm not entirely sure of what it means. Could some clarification=



 be made?


If scoped is used inside a struct or class, it allocates the space withi=
n
that struct or class. If used inside a function, the space is allocated
on the stack. The size of the allocated buffer must be known at compile
time, so you may not put an instance of a subclass into a scoped variabl=
e.

Because the class may be allocated on the stack, returning it from a
function is a Bad Idea=E2=84=A2, unless it's part of a struct or class y=
ou know
will survive for a while longer.

The reason it avoids the overhead of new is it does not allocate using
new. Basically, Scoped does this:

class A {}

A scoped =3D cast(A)alloca(sizeof(A));
A.__ctor(args);