Anyone has any information about the ABI of delegates?

In particular how to call them with a particular "this"/frame pointer?

To solve a hairy problem I need a delegate with a synthesized frame pointer.
https://dpaste.dzfl.pl/cf44417c98f9

The problem is that delegate forwarding seems to require GC closures. I want manually-managed closures.

On Sunday, 16 September 2018 at 14:12:27 UTC, Guillaume Piolat wrote:
> In particular how to call them with a particular "this"/frame pointer?
>


Related thread: https://forum.dlang.org/post/wjbhpztovxratexaobpp@forum.dlang.org

On Sunday, 16 September 2018 at 14:12:27 UTC, Guillaume Piolat wrote:
> Anyone has any information about the ABI of delegates?
>
> In particular how to call them with a particular "this"/frame pointer?
>
> To solve a hairy problem I need a delegate with a synthesized frame pointer.
> https://dpaste.dzfl.pl/cf44417c98f9
>
> The problem is that delegate forwarding seems to require GC closures. I want manually-managed closures.

Have a look at the implementation of toDelegate, which does exactly this:

https://github.com/dlang/phobos/blob/v2.082.0/std/functional.d#L1463

On Sunday, 16 September 2018 at 14:45:08 UTC, Vladimir Panteleev wrote:
> On Sunday, 16 September 2018 at 14:12:27 UTC, Guillaume Piolat wrote:
>> Anyone has any information about the ABI of delegates?
>>
>> In particular how to call them with a particular "this"/frame pointer?
>>
>> To solve a hairy problem I need a delegate with a synthesized frame pointer.
>> https://dpaste.dzfl.pl/cf44417c98f9
>>
>> The problem is that delegate forwarding seems to require GC closures. I want manually-managed closures.
>
> Have a look at the implementation of toDelegate, which does exactly this:
>
> https://github.com/dlang/phobos/blob/v2.082.0/std/functional.d#L1463

Thanks.

I ended up using toDelegate internally, and enclosing the resulting delegate with code returning a struct with `opCall`.

The conclusion is that "struct with `opCall`" is much easier to implement that faking delegate ABI, this is less brittle ; and doesn't add a lifetime of a trampoline context to extend the input delegate.

On 2018-09-16 16:12, Guillaume Piolat wrote:
> Anyone has any information about the ABI of delegates?
> 
> In particular how to call them with a particular "this"/frame pointer?

You can explicitly set the context pointer of a delegate using the ".ptr" property:

class Foo
{
    void bar() { }
}

void main()
{
    auto a = new Foo;
    void delegate () dg;
    dg.ptr = cast(void*) a;
    dg.funcptr = &Foo.bar;
    dg();
}

> To solve a hairy problem I need a delegate with a synthesized frame pointer.
> https://dpaste.dzfl.pl/cf44417c98f9
> 
> The problem is that delegate forwarding seems to require GC closures. I want manually-managed closures.


-- 
/Jacob Carlborg