a little bit of c++ in kernel [module]

[Bruce Cran]

On Wed, 11 Feb 2009 22:51:02 +0100
Christoph Mallon <christoph.mallon at gmx.de> wrote:

> Aniruddha Bohra schrieb:
> > On Wed, Feb 11, 2009 at 8:25 AM, Andriy Gapon <avg at icyb.net.ua>
> > wrote:
> >> on 10/02/2009 22:43 Aniruddha Bohra said the following:
> >>> You can see Click: http://read.cs.ucla.edu/click/
> >>> It does not  run on FreeBSD >4.
> >>> I have an old diff which builds on the work by Marko Zec and Bruce
> >>> Simpson, that allows me to load the click module.
> >>> http://www.cs.rutgers.edu/~bohra/click-1.5.0.diff
> >> 1. options -fpermissive -fno-exceptions -fno-rtti are passed to
> >> c++ compiler 2. there are new/delete implementations that use
> >> kernel malloc
> >>
> >> I think that #1 means that there are no exceptions, (non-trivial)
> >> dynamic_cast and typeid for kernel c++ code.
> > 
> > Correct.
> 
> That's a pity. Lack of exceptions negates some major benefits of C++.
> 
> >> 1. do you use any global/static objects with constructors? did you
> >> have to write any code to call on those constructors when the
> >> module is loaded?
> > 
> > Not sure about this one. But AFAIK, there are no global static
> > objects with constructors in Click code.
> > There is one router object that is always initialized and it is
> > updated by writing to the clickfs file system.
> > The other objects are created with new.
> > 
> >> 2. did you have to write any other run-time support code or
> >> platform glue code (besides new/delete)?
> > 
> >  Apart from the new and delete, I think the other things were the
> > pseudofs code to initialize the file system,
> > the locks in include/click/sync.hh, the glue code in atomic.hh.
> > 
> > 
> >> 3. I assume virtual inheritance can be used in kernel code? do you
> >> use it?
> 
> Virtual inheritence needs no support from the "outside", so it is
> available.
> 
> > Yes. For example, all objects inherit from "Element" and that
> > defines virtual functions. (include/click/element.hh)
> 
> Virtual inheritance is something completely different than virtual
> methods. 

Microsoft has an overview of using C++ in kernel drivers at
http://www.microsoft.com/whdc/driver/kernel/KMcode.mspx .  It sounds
like the situation on FreeBSD may be somewhat similar.

-- 
Bruce Cran