Re: Kernel Development & Objective-C

J.A. Magallón
2007-12-04T21:24:58Z

On Tue, 4 Dec 2007 12:54:13 -0500, lsorense@csclub.uwaterloo.ca (Lennart Sorensen) wrote:

> On Sat, Dec 01, 2007 at 12:19:50AM +0100, J.A. Magall??n wrote:
> > I think BeOS was C++ and OSX is C+ObjectiveC (and runs on an iPhone).
> > Original MacOS (fron 6 to 9) was Pascal (and a mac SE was very near
> > to embedded hardware :) ).
> >
> > I do not advocate to rewrite Linux in C++, but don't say a kernel written
> > in C++ can not be efficient.
>
> Well I am pretty sure the micro kernel of OS X is in C, and certainly
> the BSD layer is as well. So the only ObjC part would be the nextstep
> framework and other parts of the Mac GUI and other Mac APIs they
> provide, which all at some point probably end up calling down into the C
> stuff below.
>

Yup, thanks.

> > C++ (and for what I read on other answer, nor ObjectiveC) has no garbage
> > collection. It does not anything you did not it to do. It just allows
> > you to change this
> >
> > struct buffer *x;
> > x = kmalloc(...)
> > x->sz = 128
> > x->buff = kmalloc(...)
> > ...
> > kfree(x->buff)
> > kfree(x)
> >
> > to
> > struct buffer *x;
> > x = new buffer(128); (that does itself allocates x->buff,
> > because _you_ programmed it,
> > so you poor programmer don't forget)
> > ...
> > delete x; (that also was programmed to deallocate
> > x->buff itself, sou you have one less
> > memory leak to worry about)
>
> But kmalloc is implemented by the kernel. Who implements 'new'?
>

Help yourself... as kmalloc() is a replacement for userspace glibc's
malloc, you can write your replacements for functions/operators in
libstdc++ (operators are just cosmetic, as many other features in C++)
In fact, for someone who dared to write a kernel C++ framework, the
very first function he has to write could be something like:

void* operator new(size_t sz)
{
return kmalloc(sz,GPF_KERNEL);
}

And could write alternatives like

operator new(size_t sz,int flags) -> x = new(GPF_ATOMIC) X;

operator new(size_t sz,MemPool& pl) -> x = new(pool) X;

If you are curious, this page http://www.osdev.org/wiki/C_PlusPlus
has some clues about what should you implement to get rid of
libstdc++.

--
J.A. Magallon <jamagallon()ono!com> \ Software is like sex:
\ It's better when it's free
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