Re: how to allocate class without gc?

[Basile B. via Digitalmars-d-learn]

On Wednesday, 27 January 2016 at 22:39:54 UTC, Igor wrote:
But doesn't this ultimately defeat the purpose of having manual 
memory management if one has to add it to the GC to be scanned?


You can make the LOC related to the GC optional with an 
additional bool template parameter and a static if, but as said 
previously it can introduce bugs.


AddRange() is used to make the GC scan pointers inside the range 
(build-in array for example)) but the range is itself well 
manually managed.

Re: how to allocate class without gc?

[Kagamin via Digitalmars-d-learn]

On Wednesday, 27 January 2016 at 22:39:54 UTC, Igor wrote:
Ultimately I want no GC dependency. Is there an article that 
shows how this can be done?


You can link with gcstub 
https://github.com/D-Programming-Language/druntime/blob/master/src/gcstub/gc.d it will replace GC completely.

Re: how to allocate class without gc?

[Igor via Digitalmars-d-learn]

On Wednesday, 27 January 2016 at 06:40:00 UTC, Basile B. wrote:

On Tuesday, 26 January 2016 at 01:09:50 UTC, Igor wrote:
Is there any examples that shows how to properly allocate an 
object of a class type with the new allocators and then 
release it when desired?


This is more or less the same answer as you've get previously 
except that I don't use emplace but rather a copy of what's 
done in _d_new_class() from the D runtime:


CT construct(CT, A...)(A a) @trusted @nogc
if (is(CT == class))
{
import std.experimental.allocator.mallocator;
auto size = typeid(CT).init.length;
auto memory = Mallocator.instance.allocate(size); // D 
runtime use GC here

memory[0 .. size] = typeid(CT).init[];
static if (__traits(hasMember, CT, "__ctor"))
(cast(CT) (memory.ptr)).__ctor(a);
import core.memory: GC;
GC.addRange(memory.ptr, size, typeid(CT));
return cast(CT) memory.ptr;
}

the GC stuff could look superfluous but without this and if 
there's a GC allocated members in your class (even a simple 
dynamic array) then you'll encounter random errors at run-time.


Thanks.

But doesn't this ultimately defeat the purpose of having manual 
memory management if one has to add it to the GC to be scanned? 
Seems like it is just an extra step. The whole point is to 
prevent the GC from having to mess with the object in the first 
place. I understand if it uses GC based objects then the GC needs 
to be informed but this really feels like it defeats the purpose.


Ultimately I want no GC dependency. Is there an article that 
shows how this can be done?

Re: how to allocate class without gc?

[Mike via Digitalmars-d-learn]

On Tuesday, 26 January 2016 at 01:09:50 UTC, Igor wrote:
Is there any examples that shows how to properly allocate an 
object of a class type with the new allocators and then release 
it when desired?


There are a number of different patterns discussed and 
illustrated with examples at 
http://wiki.dlang.org/Memory_Management.  These don't use 
std.experimental.allocator, but should serve as a pretty good 
foundation for doing so.


Mike

Re: how to allocate class without gc?

[Adrian Matoga via Digitalmars-d-learn]

On Tuesday, 26 January 2016 at 01:09:50 UTC, Igor wrote:
Is there any examples that shows how to properly allocate an 
object of a class type with the new allocators and then release 
it when desired?


There's an example of class object allocation in the 
std.experimental.allocator docs:


// Dynamically allocate a class object
static class Customer
{
uint id = uint.max;
this() {}
this(uint id) { this.id = id; }
// ...
}
Customer cust = theAllocator.make!Customer;
assert(cust.id == uint.max); // default initialized
cust = theAllocator.make!Customer(42);
assert(cust.id == 42);

To release the object (call the destructor and free the memory), 
call dispose():

theAllocator.dispose(cust);

You'll need to replace "theAllocator" with the allocator you want.

Re: how to allocate class without gc?

[Daniel Kozak via Digitalmars-d-learn]

V Tue, 26 Jan 2016 05:47:42 +
Igor via Digitalmars-d-learn 
napsáno:

> On Tuesday, 26 January 2016 at 05:11:54 UTC, Mike Parker wrote:
> > On Tuesday, 26 January 2016 at 01:09:50 UTC, Igor wrote:  
> >> Is there any examples that shows how to properly allocate an 
> >> object of a class type with the new allocators and then 
> >> release it when desired?  
> >
> > Allocate a block of memory big enough to hold an instance of 
> > your class using whichever allocator you need, then instantiate 
> > a class instance with std.conv.emplace.
> >
> > http://p0nce.github.io/d-idioms/#Placement-new-with-emplace  
> 
> I created a class using this example. But my code is now failing. 
> It seems one can't just replace new with this and expect it to 
> work?
> 
> What is happening is some fields(strings) are not retaining their 
> value.
> 
> ubyte[__traits(classInstanceSize, App)] buffer;
> auto app = cast(App)emplace!App(buffer[]);
> //auto app = new App();
> 
> Basically the comment is the original. When I finally call 
> createWindow, it fails because the string representing the name 
> inside App is null... Which doesn't happen when I use new.
> 
> Should it work as expected(which it isn't) or do I have to also 
> emplace all the fields and such so they are not for some reason 
> released?
> 
Can you try it with GC.disable()?

Re: how to allocate class without gc?

[Basile B. via Digitalmars-d-learn]

On Tuesday, 26 January 2016 at 01:09:50 UTC, Igor wrote:
Is there any examples that shows how to properly allocate an 
object of a class type with the new allocators and then release 
it when desired?


This is more or less the same answer as you've get previously 
except that I don't use emplace but rather a copy of what's done 
in _d_new_class() from the D runtime:


CT construct(CT, A...)(A a) @trusted @nogc
if (is(CT == class))
{
import std.experimental.allocator.mallocator;
auto size = typeid(CT).init.length;
auto memory = Mallocator.instance.allocate(size); // D 
runtime use GC here

memory[0 .. size] = typeid(CT).init[];
static if (__traits(hasMember, CT, "__ctor"))
(cast(CT) (memory.ptr)).__ctor(a);
import core.memory: GC;
GC.addRange(memory.ptr, size, typeid(CT));
return cast(CT) memory.ptr;
}

the GC stuff could look superfluous but without this and if 
there's a GC allocated members in your class (even a simple 
dynamic array) then you'll encounter random errors at run-time.

Re: how to allocate class without gc?

[Igor via Digitalmars-d-learn]

On Tuesday, 26 January 2016 at 09:32:06 UTC, Daniel Kozak wrote:

V Tue, 26 Jan 2016 05:47:42 +
Igor via Digitalmars-d-learn 
napsáno:


[...]

Can you try it with GC.disable()?



Didn't change anything.

Re: how to allocate class without gc?

[Igor via Digitalmars-d-learn]

On Tuesday, 26 January 2016 at 09:32:06 UTC, Daniel Kozak wrote:

V Tue, 26 Jan 2016 05:47:42 +
Igor via Digitalmars-d-learn 
napsáno:


On Tuesday, 26 January 2016 at 05:11:54 UTC, Mike Parker wrote:
> [...]


Can you try it with GC.disable()?


//ubyte[__traits(classInstanceSize, App)] buffer;
auto buffer = core.stdc.stdlib.malloc(__traits(classInstanceSize, 
App))[0..__traits(classInstanceSize, App)];


works, so it is the ubyte line.

Re: how to allocate class without gc?

[Daniel Kozak via Digitalmars-d-learn]

V Tue, 26 Jan 2016 13:56:39 +
Igor via Digitalmars-d-learn 
napsáno:

> On Tuesday, 26 January 2016 at 09:32:06 UTC, Daniel Kozak wrote:
> > V Tue, 26 Jan 2016 05:47:42 +
> > Igor via Digitalmars-d-learn 
> > napsáno:
> >  
> >> On Tuesday, 26 January 2016 at 05:11:54 UTC, Mike Parker wrote:  
> >> > [...]  
> >>   
> > Can you try it with GC.disable()?  
> 
> //ubyte[__traits(classInstanceSize, App)] buffer;
> auto buffer = core.stdc.stdlib.malloc(__traits(classInstanceSize, 
> App))[0..__traits(classInstanceSize, App)];
> 
> works, so it is the ubyte line.
>   

What about:

auto buffer = new ubyte[__traits(classInstanceSize, App)];

Re: how to allocate class without gc?

[Marc Schütz via Digitalmars-d-learn]

On Tuesday, 26 January 2016 at 13:56:39 UTC, Igor wrote:

//ubyte[__traits(classInstanceSize, App)] buffer;
auto buffer = 
core.stdc.stdlib.malloc(__traits(classInstanceSize, 
App))[0..__traits(classInstanceSize, App)];


works, so it is the ubyte line.



Can you please post the full code? From your description, it 
looks like the stack frame might get invalidated...

Re: how to allocate class without gc?

[Guillaume Piolat via Digitalmars-d-learn]

On Tuesday, 26 January 2016 at 13:56:39 UTC, Igor wrote:


//ubyte[__traits(classInstanceSize, App)] buffer;
auto buffer = 
core.stdc.stdlib.malloc(__traits(classInstanceSize, 
App))[0..__traits(classInstanceSize, App)];


works, so it is the ubyte line.



Make sure the buffer outlives the class instance.
If you emplace on the stack, then at the end of the scope your 
instance is gone.

Re: how to allocate class without gc?

[Mike Parker via Digitalmars-d-learn]

On Tuesday, 26 January 2016 at 01:09:50 UTC, Igor wrote:
Is there any examples that shows how to properly allocate an 
object of a class type with the new allocators and then release 
it when desired?


Allocate a block of memory big enough to hold an instance of your 
class using whichever allocator you need, then instantiate a 
class instance with std.conv.emplace.


http://p0nce.github.io/d-idioms/#Placement-new-with-emplace

Re: how to allocate class without gc?

[Ali Çehreli via Digitalmars-d-learn]

On 01/25/2016 09:47 PM, Igor wrote:

> it fails because the string representing the name inside App is null...
> Which doesn't happen when I use new.

There must be something else going on. Do you see it with a simpler type?

> Should it work as expected(which it isn't)

new allocates and constructs, emplace does not allocate and construct. 
That shold be the only difference.


> or do I have to also emplace all the fields and such so they are not for
> some reason released?

Not at all.

Ali

Re: how to allocate class without gc?

[Igor via Digitalmars-d-learn]

On Tuesday, 26 January 2016 at 05:11:54 UTC, Mike Parker wrote:

On Tuesday, 26 January 2016 at 01:09:50 UTC, Igor wrote:
Is there any examples that shows how to properly allocate an 
object of a class type with the new allocators and then 
release it when desired?


Allocate a block of memory big enough to hold an instance of 
your class using whichever allocator you need, then instantiate 
a class instance with std.conv.emplace.


http://p0nce.github.io/d-idioms/#Placement-new-with-emplace


I created a class using this example. But my code is now failing. 
It seems one can't just replace new with this and expect it to 
work?


What is happening is some fields(strings) are not retaining their 
value.


ubyte[__traits(classInstanceSize, App)] buffer;
auto app = cast(App)emplace!App(buffer[]);
//auto app = new App();

Basically the comment is the original. When I finally call 
createWindow, it fails because the string representing the name 
inside App is null... Which doesn't happen when I use new.


Should it work as expected(which it isn't) or do I have to also 
emplace all the fields and such so they are not for some reason 
released?

how to allocate class without gc?

[Igor via Digitalmars-d-learn]

Is there any examples that shows how to properly allocate an 
object of a class type with the new allocators and then release 
it when desired?