Re: C++ pushback

J.A. Magallon
2006-04-25T20:20:28Z

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On Tue, 25 Apr 2006 11:22:32 +0200, Xavier Bestel <xavier.bestel@free.fr> wrote:

>
> Yes, "if". With straight C, it's immediatly obvious the kmalloc() is the
> only function with side-effects and special requirements - an
> experienced hacker won't even look it up. With C++ those may be hidden
> behind each object or object member, that's the philosophy of the
> language.
> The problem is that in kernel mode you must know precisely when and how
> you allocate memory.
>

Don't mix allocation with initialization.
Well, lets see:

struct xxx {
struct yyy* y;
int z;
}

xxx_init(struct xxx* x)
{
z = 0;
y = kmalloc(GPF_KERNEL,sizeof(struct yyy));
yyy_init(y);
}

Now, if on other source file you read:
...
struct xxx* x;
x = kmallloc(GPF_KERNEL,sizeof(struct xxx));
xxx_init(x);
..
struct xxx x2;
xxx_init(&x2);

How do you know what xxx_init() does without looking at it ?
Cay you have just the allocation without init ? What happens if you forget it ?
What happens if you cut'n'paste from other driver and let something like

struct xxx* x;
x = kmallloc(GPF_KERNEL,sizeof(struct qqqqq));
xxx_init(x);

The only difference it that
x = new(GPF_KERNEL) XXX;

always does what it has to do correctly. What does XXX() constructor ?
You have to look at it, same as xxx_init().

As I said in other answer: I'm not advocating to include C++ support in
current kernel. I just say that the only valid argument is that
'KERNEL IS C', and interfacing C with C++ just would add bloat and errors.
There is no technical argument to reject to write an OS kernel in C++.
It would not be slower nor more complicated, and it will be probably safer
because it leaves less things (from thost you always _must_ do) to
programmers memories.

--
J.A. Magallon <jamagallon()able!es> \ Software is like sex:
werewolf!able!es \ It's better when it's free
Mandriva Linux release 2006.1 (Cooker) for i586
Linux 2.6.16-jam9 (gcc 4.1.1 20060330 (prerelease)) #1 SMP PREEMPT Tue

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