OpenEuphoria

Re: cross platform GUI suggestions for Euphoria

• Posted by David Cuny <dcuny at LANSET.COM> Oct 02, 2000
• 400 views

mic wrote:

>> I know about the C++ Object Oriented part being
>> hard to wrap up properly.
>
> I wouldn't say it's hard, I'd say it's freaking impossible
> (just about).

When you write  a wrapper, you need to use a C++ compiler. You define the
interface something like this:

   extern "C" __declspec(dllexport) blah_do_something( blah self ) {
      self->do_something()
   }

Here's the rundown:

[ extern "C" ]

This prevents that C++ compiler from mangling the routine name, so it's
visible in the DLL. Otherwise, you have no guarantee what the routine name
will look like once the C++ compiler gets done with it.

[ __declspec(dllexport) ]

Only needed on the Windows platform. This tells the compiler and linker that
this routine is going to be exported (visible) in the DLL.

[ blah_do_something ]

The class name is prefixed to the function, to make it unique from all those
other 'do_something' routines in the other classes. Actually, you probably
want to name it something like 'wrap_blah_do_something' out of sheer
paranoia.

[ (blah this) ]

In C++, you can just call the routine like this:

   someBlah.my_routine()

and the object is implicitly passed. We have to make this explicit in our
interface.

[ self->do_something() ]

This is the actual call. We take the object that we passed, and call the
routine.

It's actually a pretty mechanical process, once you've done it a couple of
times. There's actually a program called SWIG that is designed to process
C/C++ libraries, and generate this sort of wrapper automatically. I've
written a fairly simple module to SWIG that will generate the source code
for DLLs as well as the Euphoria code to link to the compiled DLL.

Unfortunately, I can no longer get my code to work properly - calls to stdio
cause the program to choke. I blame the Borland compiler, and after
struggling with it for a while, gave up and have rewritten the SWIG code in
Euphoria. It doesn't handle as large a class of C/C++ code, but it's decent.
It was going well, but I got sidetracked into writing a yacc-like front end
to a LL1 grammar parser...

I hope this clarifies things.

-- David Cuny