Re: BUG-lockdep and freeze (was: Arrr! Linux 2.6.18)

Linus Torvalds
2006-09-30T20:44:03Z

On Sat, 30 Sep 2006, Linus Torvalds wrote:
>
> It's not just unreadable and obviously buggy, it's so scarily that it's
> hard to even talk about it. Lookie here:
>
> #define HANDLE_STACK(cond) \
> do while (cond) { \
> unsigned long addr = *stack++; \
>
> What the F*CK! "do while(cond) {" ????

Btw, it took me quite a while to realize how something like that can
even compile. Seriously. Don't write code like that. Maybe some humans
parse it as

do {
while (cond) {
..
}
} while(0)

(which is the technically correct parsing and explains why it compiles
and wors), but I suspect I'm not the only one who went "What the F*CK"
when shown it without the "extraneous" braces.

For similar reasons, we write

#define dummy(x) do { } while (0)

rather than the shorter

#define dummy(x) do ; while (0)

(which some people _do_ seem to use. Aarggh!)

Or at least indent it. Or something.

I'll see if I can make git warn about "do <non-blockstatement> while ()",
if only because I at least personally seem to have trouble parsing it.

Linus