Question

I’m writing a NON-GUI app which I want to be cross platform between OS X and Windows. I’m looking at the following architecture, but I don’t know if it will work on the windows side:

(Platform specific entry point) -> ANSI C main loop => ANSI C model code doing data processing / logic => (Platform specific helpers)

So the core stuff I’m planning to write in regular ANSI C, because A) it should be platform independent, B) I’m extremely comfortable with C, C) It can do the job and do it well

(Platform specific entry point) can be written in whatever necessary to get the job done, this is a small amount of code, doesn’t matter to me.

(Platform specific helpers) is the sticky thing. This is stuff like parsing XML, accessing databases, graphics toolkit stuff, whatever. Things that aren’t easy in C. Things that modern languages/frameworks will give for free. On OS X this code will be written in Objective-C interfacing with Cocoa. On Windows I’m thinking my best bet is to use C#

So on Windows my architecture (simplified) looks like

(C# or C?) -> ANSI C -> C#

Is this possible? Some thoughts/suggestions so far..

1) Compile my C core as a .dll — this is fine, but seems there’s no way to call my C# helpers unless I can somehow get function pointers and pass them to my core, but that seems unlikely

2) Compile a C .exe and a C# .exe and have them talk via shared memory or some kind of IPC. I’m not entirely opposed to this but it obviously introduces a lot of complexity so it doesn’t seem ideal

3) Instead of C# use C++, it gets me some nice data management stuff and nice helper code. And I can mix it pretty easily. And the work I do could probably easily port to Linux. But I really don’t like C++, and I don’t want this to turn in to a 3rd-party-library-fest. Not that it’s a huge deal, but it’s 2010.. anything for basic data management should be built in. And targetting Linux is really not a priority.

Note that no “total” alternatives are OK as suggested in other similar questions on SO I’ve seen; java, RealBasic, mono.. this is an extremely performance intensive application doing soft realtime for game/simulation purposes, I need C & friends here to do it right (maybe you don’t, but I do)

Answer 1

First of all, to answer one specific worry: you can marshal delegates as function pointers to your native C code – in fact, it “just works”, and P/Invoke will take care of all the wrapping:

// C#
class ManagedEntryPoint {

    [DllImport("core", CallingConvention=CallingConvention.Cdecl)]
    static extern void NativeEntryPoint(Func<int, int, float> helper);

    static float Helper(int, int) { ... }

    static void Main() {
        NativeEntryPoint(Helper);
    }
}

// C
void NativeEntryPoint(float (*helper)(int, int)) {
    float x = helper(1, 2);
    ...
}

However, I don’t see much point in this – it’s easier to use C++/CLI compiler. Note that this doesn’t mean that you actually have to use C++ – you can stick to the subset of C which is C++-compatible, which is 95% of it (I’d expect about the only thing you’ll need to do differently in practice is explicitly casting the return of malloc). You compile your native C functions as a native .lib, and then link that to an executable compiled with /clr. C++/CLI will take care of all the marshaling itself, and you won’t need to write P/Invoke declarations and such.