linux-kernel - Re: [PATCH][RESEND] do not redefine userspace's NULL #define

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Message-ID: <CA+55aFzWiaXYSwO7eGt_V6oUZGWkp_v1hv9xc6KAiFnrzumxXA@mail.gmail.com>
Date:	Fri, 13 Apr 2012 17:44:37 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Lubos Lunak <l.lunak@...e.cz>
Cc:	Peter Seebach <peter.seebach@...driver.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH][RESEND] do not redefine userspace's NULL #define

On Fri, Apr 13, 2012 at 4:18 PM, Lubos Lunak <l.lunak@...e.cz> wrote:
>> imagine replacing the kernel ((void *)0) with __null.
>
>  __null apparently exists only with g++, C does not have the stronger type
> safety that prevents ((void*)0) from being usable in C++

Please don't continue to spread this total bogosity.

The reason C++ cannot use "(void *)0" has nothing to do with "stronger
type safety". That's a total idiotic lie by C++ apologists, and I hate
hearing it repeated over and over again.

And it really *is* a lie. The C++ type system isn't even "stronger",
it's just different, and it's actively *broken* wrt NULL. Always has
been.

The sane thing to do for C++ would always have been to recognize that
"(void *)0" is not a "void pointer" - it's just NULL. INSTEAD, the
morons involved said "no, it's a void pointer, and instead we'll make
'0' be NULL".

Which is clearly insane, but is also technically simply *wrong*.

0 is an integer, it's not NULL _either_, and it's just a more stupid
version of NULL.

So the C++ people then completely made up the argument that "C++ has a
stronger type system, we can't use 'void *', so the C style ((void
*)0) is wrong for C++".

Which is utter and complete bullshit, and any amount of brains would
have realized that (since C++ at the same time happily continued to
special case the *integer* zero).

I don't hate __null, but I absolutely despise the crazy C++ apologists
who try to claim that C++ was somehow "right" in not accepting (void
*)0, and that it was somehow about "type safety". No, it was not. It
has always been just nothing but a moronic hang-up, and it has always
been *wrong*.

So don't spread that lie. It was wrong. The fact is, the *constant* 0
is the special one, and C++ could have (and should have) just accepted
that that constant should have been cast to (void *) and that is what
NULL is defined to. Instead, C++ used the *weaker* type system of
saying that the *integer* constant 0 is NULL, which is pure and utter
garbage.

And then they lie, and claim that their *weaker* type system NULL is
"stronger". Pure idiocy.

                 Linus
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