Creating and loading D plugins in D app

[aberba via Digitalmars-d-learn]

On Friday, 2 June 2017 at 16:36:34 UTC, H. S. Teoh wrote:
> On Fri, Jun 02, 2017 at 12:19:48PM +0000, Adam D. Ruppe via 
> Digitalmars-d-learn wrote:
>> On Friday, 2 June 2017 at 11:09:05 UTC, aberba wrote:
>> > 1. Get shared libs to work in D (the best approach for all D 
>> > code)
>> 
>> I have done very little with this myself but other people have 
>> so it is doable.
> [...]
>
> This is not directly related to the OP's question, but recently 
> I wrote a program that, given a user-specified string, 
> transforms it into D code using a code template, invokes dmd to 
> compile it into a shared object, loads the shared object using 
> dlopen(), and looks up the generated function with dlsym() to 
> obtain a function pointer that can be used for calling the 
> function. The shared object is unloaded after it's done.

Will be of much use to me to see the brief instructions for this. 
I saw the C style on Wikipedia.

Seems the functions loaded needs to be casted from void* to a 
type... before calling. Didn't quite understand that part.

>
> So it's definitely doable, in the sense that I've successfully 
> generated D code, compiled it into a shared library, loaded it 
> into the running executable, and can call the code.  Of course, 
> in my case, the code template is relatively simple so I don't 
> have to worry about things like module ctors, shared data, 
> non-TLS globals, or GC use.  If you're planning to support 
> those features, you might need to do a bit more work after 
> calling dlopen(). At the very least you'd have to use dlsym() 
> to look up module ctor symbols and run them before calling any 
> other functions in the shared object, and you may have to 
> initialize druntime in the shared object too, if it's 
> statically linked.

That seem like D with its features will be lot of work if I'm 
using loaded code that way.

How about exposing standard interface/apis for loaded object's 
code to query info about the main app at runtime, similar to COM 
(if that's how if even works)

> I'm not sure what happens if it's dynamically linked, or if it 
> uses its own copy of the GC.
>
Does D work different from C in that regard?

> In any case, this is all possible, it just takes someone to dig 
> into the details and write the code to make it all work.  Then 
> publish it on github or dub, and the rest of us can reap the 
> benefits too. ;-)
>
>
> T