On Thursday, 1 September 2022 at 09:13:56 UTC, Redwan wrote:
> Hi all
> I'm new to D from c, cpp and Rust.
>
> this language made me surprised because of its features and syntax and etc.
>
> but I shocked when I found that classes must be created only on stack! Is this nightmare real? why???
> I want declare classes and create instance of them on stack and nicely use them. why I must put them on heap??
> structs does not support inheritance and I don't want to use them. please tell me that is not true or give me some other ways. I don't want define objects always on heap. don't let me go back on cpp :( tnx!

I think something like std.typecons.scoped (https://dlang.org/phobos/std_typecons.html#scoped) does something like this, I think.

On Thursday, 1 September 2022 at 12:50:44 UTC, Commander Zot wrote:
> On Thursday, 1 September 2022 at 11:17:20 UTC, Redwan wrote:
>> On Thursday, 1 September 2022 at 11:06:31 UTC, bauss wrote:
>>> On Thursday, 1 September 2022 at 10:51:44 UTC, Redwan wrote:
>>>> [...]
>>>
>>> I already gave you the solution one message above; betterC (A subset of D) is what you want.
>>
>> yes sorry, I saw and I was reading about it, thank you.
>>
>> as I found, I can't use some important features in betterC. like classes. but I need them.
>
> as an alternative to betterC, you could write your own runtime.

How???

On 02/09/2022 12:53 AM, Redwan wrote:
>> as an alternative to betterC, you could write your own runtime.
> 
> How???

May be a good starting point:

https://github.com/hmmdyl/LWDR

On 9/1/22 03:51, Redwan wrote:

> it's uses alot of heap and I don't like it.

> all of heap usages needs to be done by me

As a fellow ex-C++ programmer (actually, I am still exposed to C++ and I don't like what I see), I know my old feelings of "I don't like it", "I need", and "I want" were remnants of what C++ had convinced me in its way of thinking.

Now I know that what matters is one correct and super efficient program written while having fun.

I use the GC wherever it makes sense and I use classes where they make sense. By one count, I had 95 structs, 2 classes, and 1 interface in my family of programs. "Everything is a class" has always been wrong. It took me a long time to see through some experts.

By the way, I haven't started to use @nogc yet.

The only time I had a memory leak in D was due to integral values being mistaken for pointers for a 32-bit build when I was loading files into huge buffers. I don't use 32 bits anymore, I don't do that anymore, and D runtime has been improved since then to have some information where actual pointers are.

Ali

On Thursday, 1 September 2022 at 17:24:41 UTC, Ali Çehreli wrote:
> The only time I had a memory leak in D was due to integral values being mistaken for pointers for a 32-bit build when I was loading files into huge buffers. I don't use 32 bits anymore, I don't do that anymore, and D runtime has been improved since then to have some information where actual pointers are.

Recently, we had someone in the community Discord ask for help tracking down a memory leak in their D project, which used the GC.

After a bit of investigation, it turned out that the leak was coming from a C library holding onto manually-allocated data longer than expected. In order to free it, the user had to call an additional library function to indicate that the data was no longer needed.

Moral of the story: if you are worried about memory leaks, the GC is your friend, not your enemy. :)

On 9/1/22 10:59, Redwan wrote:
> On Thursday, 1 September 2022 at 13:53:06 UTC, IGotD- wrote:

>> If you have any classes in the class you allocate on the stack, the constructor of the class will allocate them on the heap. Basically only the top level class will be on stack.
> 
> Can you give an example?
> 

Sorry to jump in but the following program demonstrates this by pointer values:

import std.stdio;

class A {
  int i;
}

class B {
  A a;
  int i;

  this() {
    this.a = new A();
  }
}

void main() {
  scope b = new B();
  int i;

  writeln("on stack: ", &i);
  writeln("on stack: ", &b.i);
  writeln("on heap : ", &b.a.i);
}

Ali

On Thursday, 1 September 2022 at 18:26:12 UTC, Ali Çehreli wrote:
> On 9/1/22 10:59, Redwan wrote:
>> On Thursday, 1 September 2022 at 13:53:06 UTC, IGotD- wrote:
>
>>> If you have any classes in the class you allocate on the stack, the constructor of the class will allocate them on the heap. Basically only the top level class will be on stack.
>> 
>> Can you give an example?
>> 
>
> Sorry to jump in but the following program demonstrates this by pointer values:
>
> import std.stdio;
>
> class A {
>   int i;
> }
>
> class B {
>   A a;
>   int i;
>
>   this() {
>     this.a = new A();
>   }
> }
>
> void main() {
>   scope b = new B();
>   int i;
>
>   writeln("on stack: ", &i);
>   writeln("on stack: ", &b.i);
>   writeln("on heap : ", &b.a.i);
> }
>
> Ali

how about `scope this.a = new A();`?