Re: C++ in kernel (was Re: exception in a device driver)

Chip Salzenberg (chip@perlsupport.com)
Sat, 16 Jan 1999 01:21:57 -0500

According to Alexander Viro:
> On Sat, 16 Jan 1999, Chip Salzenberg wrote:
> > Stroupstrup's design rule: "Constructors acquite resources;
> > destructors release them."
>
> So, you are going to allocate an object in stack for each
> semaphore you are holding?

Yup.

> shitload of overhead even if we'll do it in assembler

I doubt that very strongly. Consider that the object need not be
polymorphic; all it needs is a pointer member. And if you use a
template class, you don't even need the pointer, so it'll be 100% as
efficient as the C version (except one byte for the object itself
(zero-length objects are not allowed (yet))).

Given:

template <semaphore_t *SEM>
class hold {
public:
hold() { down(SEM); }
~hold() { up(SEM); }
};

The code would look like:

void random_function()
{
hold<&one_semaphore> hold1;
hold<&other_semaphore> hold2;
// ...
}

-- 
Chip Salzenberg      - a.k.a. -      <chip@perlsupport.com>
      "When do you work?"   "Whenever I'm not busy."


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/