Re: C++ vs C for PicoGUI 2

Lalo and I have been discussing this more on IRC.

The main sticking point seems to be exceptions- It would be great to use C++ as
a C-with-exceptions, but the problem with that comes in interfacing between libOm
and other components that may be in C, C++, Python, or any other language. If you
call a C++ function from C (or from a C interface generated for another language)
the exception wouldn't be handled correctly.

There are a few solutions to this:

  - Give up on real C compatibility, and use something C++-friendly like SWIG
    for interfacing to other languages

  - Allow users of libOm to produce either C++ exceptions or something C-friendly.
    This would be a lot of unnecessary pain.

  - Make Om more like pg1's protocol- a protocol definition with completely 
    separate implementations in each language.

  - Give up on using C++ in libOm, and stick to some C-compatible exceptions.
    The two workable ways to do this that we've come up with so far:

       - Use calling macros similar to what pg1 uses, but with real objects instead
         of just integers for exceptions. The objects could be tagged as the stack
         unwinds, for providing backtraces.

       - Use setjmp/longjmp and a separate stack. There's an implementation of this
         in Kazlib: http://users.footprints.net/~kaz/kazlib.html

--Micah


On Mon, Mar 31, 2003 at 01:22:37PM -0700, Micah Dowty wrote:
> Hi Everybody,
> 
> It will still be a few months yet until we're really coding Om and
> PicoGUI 2.0, but this is a decision worth a discussion:
> Should the core components of Om and PicoGUI 2.0 be written in C or C++?
> 
> Here are a few arguments each way:
> 
> - In favor of C:
> 
>   - smaller binary size
>   - C++'s class-based object model won't help much in implementing Om's
>     python-like object model.
>   - possibly more compatibility with older systems that don't support C++
>   - C code is natively compatible with many other languages, while C++ must
>     use 'extern "C"' functions for compatibility, not allowing the other
>     language access to C++'s class-based object model.
> 
> - In favor of C++:
> 
>   - C++'s classes won't help implement Om, but they do provide a more standard
>     way to organize the source code.
>   - C++ code can be compiled without libstdc++ to produce binaries not much
>     larger than C. (http://fresco.org/~njs/c++-without-stdc++)
>   - C++ includes exceptions and constructors/destructors, two features we would
>     definitely need to implement by hand if we used C.
> 
> --Micah
> 
> -- 
> Only you can prevent creeping featurism!
> 
> 
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