[Fwd: Re: [ooc-compiler] PROPOSAL: Interface to C++ objects and methods]

[Frank C. <fj...@th...>]

-------- Original Message --------
Subject: Re: [ooc-compiler] PROPOSAL: Interface to C++ objects and methods
Date: Tue, 17 Jan 2006 21:31:08 +1100
From: Frank Copeland <fj...@th...>
To: Stewart Greenhill <sgr...@ii...>
References: <43C...@ii...>

Stewart Greenhill wrote:

> I'm interested in being able to use existing C++ APIs from Oberon-2.

It would certainly broaden the options available. There are some C++ APIs I
have an interest in.

> Currently, oo2c has a limited ability to call methods of C++ objects. 
> When one declares a record with the VTABLE flag, oo2c builds a C++-style 
> virtual method table for all instantiated objects, and calls methods of 
> that object via VTABLE dispatch. This means (for example) that you can 
> call methods of COM interfaces, and even implement your own COM objects.
> 
> This is fine if one follows a design methodology like COM, which ensures 
> that there is a language-independent binary interface to your API. COM 
> uses abstract interfaces and VTABLE method dispatch. It also has a 
> language-independent type mechanism (ie. IUnknown::QueryInterface). 
> Unfortunately, most C++ coders seem completely uninterested in language 
> interoperability. The biggest obstacle with existing C++ APIs is the use 
> of static (ie. non-virtual) methods. Its only really possible to call 
> these methods from a C++ compiler, since the symbol names are mangled to 
> include type information.
> 
> The approach that I'm proposing is to:
> 
> 1) Introduce a [STATIC] method flag. This causes calls to methods to be 
> dispatched statically, rather than using type-descriptor lookup.
> 
> 2) Write (by hand, or automatically) a FOREIGN implementation that can 
> be processed by the C++ compiler. This dispatches method calls to the 
> C++ objects.

Would it not be simpler to have OOC mangle the symbol names the same way as
the C++ compiler? I realise that is compiler-dependant and I believe g++
broke ABI recently by changing the mangling algorithm. Even so the
algorithms should be reasonably easy to discover (especially for g++). There
would remain the issue of telling OOC which algorithm to use.

-- 

This sentence contradicts itself -- no actually it doesn't.
		-- Douglas Hofstadter

-- 

Politics are almost as exciting as war, and quite as dangerous.  In war,
you can only be killed once.
		-- Winston Churchill