Loading DLLs

[Jarrett Billingsley]

On Tue, Apr 7, 2009 at 5:13 AM, Georg Wrede <georg.wrede at iki.fi> wrote:
> Any large application benefits from being able to load DLLs, sooner or
> later. Some applicatons seem to do it effortlessly, even in very disparate
> environments. For example, the Lua interpreter appears to consider it a
> trivial excercise.
>
> An excerpt from the manual:
>
>
> For instance, if the C path is the string
>
>     "./?.so;./?.dll;/usr/local/?/init.so"
>
> the searcher for module foo will try to open the files ./foo.so, ./foo.dll,
> and /usr/local/foo/init.so, in that order. Once it finds a C library, this
> searcher first uses a dynamic link facility to link the application with the
> library. Then it tries to find a C function inside the library [...].
>
>
> This is useful even when you are simply using the Lua interpreter, when you
> want to use C libraries. But it becomes extremely useful when using Lua as a
> scripting language within your own application. (In that case, of course, D
> would not even have to do the loading.)
>
> But, for D-only applications, such DLL loading would be just as useful. To
> fix this simply cannot be as difficult as it might seem from the persistent
> lack of a final solution.
>
> If I understand correctly, the Lua licence does allow it to be used,
> modified, even sold, freely.
>
> My question: would it be worthwhile to take a peek at the library loading
> code in Lua sources, to see if we can implement it (possibly as such, since
> much of the loading is non-Lua specific) into D?
>
> (In case there is rampant paranoia about licences, I think a simple e-mail
> to Roberto, (home page: www.inf.puc-rio.br/~roberto/) would dissolve any
> doubts.)

There's no difficulty in _loading_ DLLs or shared libraries on any
system with D.  Both Phobos and Tango have had shared library loader
modules for years.

In fact, there's no difficulty at all on Posix-based systems.

The only difficulty arises on Windows, because DLLs suck.  They cannot
load symbols out of the host app that loads them, and because of that,
things like typeinfo and classinfo are duplicated.  Then things break.

As Tim already pointed out, DDL has been around for quite some time too.