[racket] C++ Extensions and Classes

Hmmm, I haven't had to wrap anything using extern C because all the
function prototypes are in C already I believe (the three I mentioned
above). The main idea here is that I want to reuse my extensions in the
same way that my classes are constructed. I want to write extensions
separately for each class that I have already written in C++. I have
already successfully written my extension for Foo. I can load Foo_ext.rkt
in my racket script and execute all the functions that I need. The issue is
that I have *another *class, Bar, that inherits from Foo. So as it stands
now, I can't figure out how to write my Bar extension such that I don't
have to rewrite (or copy and paste) all the code from my Foo extension. I'd
like to leverage the fact that I already wrote the extension for Foo and
Bar is just a few extra variables and functions. I hope this clearly
illustrates my goal.

Thanks :-)


On Thu, Feb 6, 2014 at 12:17 PM, Jon Zeppieri <zeppieri at gmail.com> wrote:

> I'm not entirely sure that I follow, but if you're writing these
> extension functions in C++, I believe you'll need to wrap their
> prototypes in an extern(C) { ... } block so that they'll be given
> un-mangled names for the linker to use.
>
> On Thu, Feb 6, 2014 at 4:56 PM, Cody Eilar <cody.eilar at gmail.com> wrote:
> > I understand that, the issue is that I have to provide three functions
> that
> > are not static so that I can make my c++ code known to scheme. Those
> > functions are:
> >
> > scheme_reload(Scheme_Env *env)
> > scheme_initialize(Scheme_Env *env)
> > scheme_module_name()
> >
> > Each one of these functions are known to the linker. Inside the
> Foo_ext.cpp
> > file, I have these three functions implemented. But in order to use
> > Bar_ext.cpp I have to implement them as well, which means I have multiple
> > declarations to the same function. So my Bar_ext.cpp file would Ideally
> look
> > something like this:
> >
> > Bar_ext.cpp
> > scheme_reload(Scheme_Env *env)
> > {
> >  /* Bar _ext reload stuff */
> >     Foo_ext.scheme_reload(env)
> > }
> >
> > Currently, the only way I see to solve this is to use a bunch of ifdefs,
> but
> > I was curious if there was a more elegant solution.
> >
> > Thanks!
> >
> > On Thu, Feb 6, 2014 at 2:48 AM, David T. Pierson <dtp at mindstory.com>
> wrote:
> >>
> >> On Wed, Feb 05, 2014 at 02:16:54PM -1000, Cody Eilar wrote:
> >> > > But what I really want is:
> >> > >
> >> > > Foo_ext.h:
> >> > >
> >> > > func1_racket_ext() { /*... do racket stuff and run func1() */}
> >> > >
> >> > > /* Scheme initializes etc... */
> >> > >
> >> > >
> >> > > Bar_ext.cpp:
> >> > > #include "Foo_ext.h"
> >> > >
> >> > > func2_racket_ext() {/* ... do more racket stuff and run func2() /*}
> >>
> >> Disclaimer: I know nothing about Racket extensions.
> >>
> >> In C++, if you want to be able to call a function from multiple .cpp
> >> files, you typically put the *declaration* in a header:
> >>
> >>   void func1_ext(void);
> >>
> >> The definition would still go in a .cpp file:
> >>
> >>   void func1_ext(void)
> >>   {
> >>     /*...*/
> >>   }
> >>
> >> You typically only put the definition in a header if you want to make an
> >> inline function.  It doesn't seem like you want an inline function here.
> >>
> >> Does that help?
> >>
> >> David
> >
> >
> >
> > ____________________
> >   Racket Users list:
> >   http://lists.racket-lang.org/users
> >
>
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