Hi group,

I've been reading up on D for the past few days--something I'd been
planning to do for quite a while--and find much to like and little to
dislike; as such, I am considering using it for my next project, which
would run on Linux (and possibly some other POSIX systems) and would
need to load plugins.

Now I've done such things in C in the past, and it's not too difficult:
you create a .so file, have it call some initial function right after
the dlopen(), and then have that initial function register the new
functionality available.

After looking at the documentation for a few days, I've come to the
conclusion that with Object.factory and interfaces, I believe I can
abstract things enough so that all a plugin would need to do is register
a new class, which could then be instantiated if needs be. However, what
I don't find is the answer to the two following questions:

- Does D support dlopen(), or some similar mechanism, to allow me to
 load plugins at runtime?
- If it does, does Object.factory() still work for new classes loaded in
 through dlopen() (or its functional equivalence)?

Thanks,

-- 
The volume of a pizza of thickness a and radius z can be described by
the following formula:

pi zz a

On 2012-06-18 16:56, Wouter Verhelst wrote:
> Hi group,
>
> I've been reading up on D for the past few days--something I'd been
> planning to do for quite a while--and find much to like and little to
> dislike; as such, I am considering using it for my next project, which
> would run on Linux (and possibly some other POSIX systems) and would
> need to load plugins.
>
> Now I've done such things in C in the past, and it's not too difficult:
> you create a .so file, have it call some initial function right after
> the dlopen(), and then have that initial function register the new
> functionality available.
>
> After looking at the documentation for a few days, I've come to the
> conclusion that with Object.factory and interfaces, I believe I can
> abstract things enough so that all a plugin would need to do is register
> a new class, which could then be instantiated if needs be.

Yes, in theory.

> However, what
> I don't find is the answer to the two following questions:
>
> - Does D support dlopen(), or some similar mechanism, to allow me to
>    load plugins at runtime?

Yes. You can compile D code to a standard dynamic library, just as you 
would using C.

> - If it does, does Object.factory() still work for new classes loaded in
>    through dlopen() (or its functional equivalence)?

No.

Dynamic libraries are currently not working properly in D. The runtime 
needs to be updated to handle it. There are some problem with module 
info, exception handling tables and TLS. There might be some problem 
left with PIC as well.

This is worked on and hopefully we will have a solution not too far in 
the future.

-- 
/Jacob Carlborg

Jacob Carlborg <doob@me.com> writes:

> On 2012-06-18 16:56, Wouter Verhelst wrote:
>> However, what
>> I don't find is the answer to the two following questions:
>>
>> - Does D support dlopen(), or some similar mechanism, to allow me to
>>    load plugins at runtime?
>
> Yes. You can compile D code to a standard dynamic library, just as you
> would using C.

Cool.

>> - If it does, does Object.factory() still work for new classes loaded in
>>    through dlopen() (or its functional equivalence)?
>
> No.
>
> Dynamic libraries are currently not working properly in D. The runtime
> needs to be updated to handle it. There are some problem with module
> info, exception handling tables and TLS. There might be some problem
> left with PIC as well.
>
> This is worked on and hopefully we will have a solution not too far in
> the future.

Ah, too bad.

Do you have a pointer to some more detailed information on this? Just so
I can get a feel for how fast things are moving, and/or whether it's
worth for me to wait for that -- I can get started on the other parts;
while the plugin architecture would be crucial eventually, it's not
something I'll need from the very beginning.

Thanks,

-- 
The volume of a pizza of thickness a and radius z can be described by
the following formula:

pi zz a

On Monday, 18 June 2012 at 15:22:19 UTC, Wouter Verhelst wrote:

> Ah, too bad.
>
> Do you have a pointer to some more detailed information on 
> this? Just so
> I can get a feel for how fast things are moving, and/or whether 
> it's
> worth for me to wait for that -- I can get started on the other 
> parts;
> while the plugin architecture would be crucial eventually, it's 
> not
> something I'll need from the very beginning.
>
> Thanks,

Martin Nowak is working on this: 
https://github.com/dawgfoto/druntime/tree/SharedRuntime

--
/Jacob Carlborg

I'm not too experienced with Github - am I right in thinking that
the SharedRuntime repository has been idle for six months? If so,
does this indicate that Martin has likely abandoned the project?

Like Wouter, I'm looking into developing a project with D that
would eventually require plugins, and I could really do with a
definite answer whether or not this functionality is expected to
be available within, say, twelve months. Is there anybody I could
contact who's likely to know the answer?

One last question - when you say that the runtime can't yet
properly handle dynamic library loading, does this apply equally
to both DMD and GDC? I know that both projects share a fair
amount of common code.

On 2012-06-20 09:50, R. Grocott wrote:
> I'm not too experienced with Github - am I right in thinking that
> the SharedRuntime repository has been idle for six months? If so,
> does this indicate that Martin has likely abandoned the project?

The last commit was three months ago, Mars 20, 2012:

https://github.com/dawgfoto/druntime/commits/SharedRuntime

> Like Wouter, I'm looking into developing a project with D that
> would eventually require plugins, and I could really do with a
> definite answer whether or not this functionality is expected to
> be available within, say, twelve months. Is there anybody I could
> contact who's likely to know the answer?

Yes, I think it will be available within twelve months.

> One last question - when you say that the runtime can't yet
> properly handle dynamic library loading, does this apply equally
> to both DMD and GDC? I know that both projects share a fair
> amount of common code.

I think it applies to GDC as well. Unless GDC uses its own fork of the 
runtime and have fixes for this.

Note that you can load dynamic libraries wirtten in C. It probably works 
with D as well, just not all features.

What probably will not work are:

* Module constructors
* Module info
* Exceptions (not sure about this, might just be limited to crossing 
dynamic library boundaries)
* TLS
* Probably some other stuff I've forgotten

-- 
/Jacob Carlborg