On 19/07/2023 7:44 PM, Sergey wrote:
> Forking GC was introduced some time ago. But I don't think it is quite different from regular (https://forum.dlang.org/post/tf8mbo$1jvp$1@digitalmars.com)

It is a modification of the conservative GC. Rather than a unique GC implementation and is upstreamed.

> There are some posts about it GCs, but I don't think anything was released.
> https://forum.dlang.org/thread/jquklsqxtfgvsezrcuzu@forum.dlang.org?page=1
> https://forum.dlang.org/post/yonbmhifafbyjhwpcixp@forum.dlang.org

The only GC design I know of that is semi-interesting is Rainer's concurrent GC for Windows.

http://rainers.github.io/visuald/druntime/concurrentgc.html

This has not been upstreamed.

Its not as simple as porting to the API unfortunately.

We don't have barriers of any kind, so that removes most GC designs you would want to use today. We are very close to maxing out what we can do as a result.

A whole pile of logic is hidden in rt, so you have no choice but to either do the work to fix that, or recompile druntime with your GC.

On Wednesday, 19 July 2023 at 08:27:18 UTC, Richard (Rikki) Andrew Cattermole wrote:
> Its not as simple as porting to the API unfortunately.
>
> We don't have barriers of any kind, so that removes most GC designs you would want to use today. We are very close to maxing out what we can do as a result.
>
> A whole pile of logic is hidden in rt, so you have no choice but to either do the work to fix that, or recompile druntime with your GC.

I'm mostly a frontend person, but is what would need doing there? Is there any existing discussion about that?

On 19/07/2023 9:02 PM, IchorDev wrote:
> On Wednesday, 19 July 2023 at 08:27:18 UTC, Richard (Rikki) Andrew Cattermole wrote:
>> Its not as simple as porting to the API unfortunately.
>>
>> We don't have barriers of any kind, so that removes most GC designs you would want to use today. We are very close to maxing out what we can do as a result.
>>
>> A whole pile of logic is hidden in rt, so you have no choice but to either do the work to fix that, or recompile druntime with your GC.
> 
> I'm mostly a frontend person, but is what would need doing there? Is there any existing discussion about that?

Not really, last time I tried, I didn't document what was hidden.

Copying out the conservative GC, register it under a different name and getting that to compile and link without recompiling druntime would be a good place to begin without having to understand how GC's work.

On Wednesday, 19 July 2023 at 10:50:07 UTC, Richard (Rikki) Andrew Cattermole wrote:
>
> Copying out the conservative GC, register it under a different name and getting that to compile and link without recompiling druntime would be a good place to begin without having to understand how GC's work.

That sounds pretty easy, but I don't really see how would that be particularly helpful to allowing a different style of GC to be registered?

On 19/07/2023 11:13 PM, IchorDev wrote:
> On Wednesday, 19 July 2023 at 10:50:07 UTC, Richard (Rikki) Andrew Cattermole wrote:
>>
>> Copying out the conservative GC, register it under a different name and getting that to compile and link without recompiling druntime would be a good place to begin without having to understand how GC's work.
> 
> That sounds pretty easy, but I don't really see how would that be particularly helpful to allowing a different style of GC to be registered?

druntime supports registering of GC's not compiled with druntime.

But because some of the machinery isn't available to you, you would have to recreate it.

So in practice you cannot find a GC on the dub-registry to try it out. Even if one were to exist, you would have to do a new build of druntime/phobos special which isn't the easiest thing to do.

https://github.com/dlang/dmd/blob/master/druntime/src/core/gc/registry.d#L39

Regardless, its a barrier to anyone wanting to try writing a GC to experiment with (or port one).