Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> writes:
> Oh yes it can. People look at that, and it's so uncommon that they
> literally believe it is a mis-indent.
People learn, or should, through the life :-)
I'm not sure being common or less common does matter here much.
OTOH I think it's pretty common. Approx as common as while (x) y is,
isn't it?
Except in macros: do-while(0) is commonly used in macros because it
"eats" the semicolon.
(do { xxx; yyy; zzz } while (0) is also quite common instead of "goto"
to add multiple exits from a long block).
> Your example with nested if-statements are totally pointless, because you
> didn't even apparently understand my comment about "while()" having two
> totally different meanings (which is not true of "if()"), nor realize the
> importance of how common something is.
Only apparently. If there is no ambiguity, there is no problem, the
double meaning does not seem relevant.
You tell me that
do
expr;
while (condition);
(with precisely this formatting) can be unclear?
Or you say
do {
expr;
} while (condition);
is better? If it is, then certainly not for me.
Now: are we going to write {} because you say so, even if it makes the
code worse? Or should we rather aim at improving the code, even if
only a bit? (I admit that, IMO, the second example is worse = less
readable, but only a small bit).
> Sorry, you're wrong. It's not changed to silence some tool.
Come on, you have it plain in the subject - "fix sparse warnings".
If it was "improve obscure notation" I wouldn't say a word.
> And I agree with you. "sizeof i" doesn't look good. It's uncommon, and
> doesn't match peoples expectations.
But it doesn't matter if it's common or not. It doesn't look good and
THIS IS WHY it's uncommon/nonexistent. Not the other way around.
There are many uncommon things in a project like a Linux kernel. There
are some macros which take me a while :-) to understand and they
thankfully don't spew warnings.
> Another example of "common vs non-common" is this:
>
> if (0 <= x)
> do something..
>
> is something that crazy people do (sadly, one of the crazy people taught
> the git maintainer C programming, so now even sane people do it). It's
> crazy because it's uncommon, which means that most people have to think
> about it A LOT MORE than about
>
> if (x >= 0)
> do something..
No. It's crazy not because it's uncommon, but because this is how we
have been taught in school.
I don't know reasons for "0 >= x" but I know one for
if (0 == x)
do something..
It's because people sometimes write "=" instead of "==" and "0 = x"
doesn't make sense to gcc. I think it's not a valid reason, and
(unless you use (()) which is IMHO also crazy) gcc will warn about
if (x = 0) (though I think the warning is stupid and "if (a = b)"
is a valid usage if a and b are short).
It's simple: one has to see the difference between if (x = 0) vs
if (x == 0), there is no way around it. if (0 >= x), I don't know.
> Can you see the argument? Doing things the common way is important,
> because it allows people to see what they mean without having to think
> about it. They just scan it, and the meaning is clear.
Then I must be different. Things are clear to me if they are clear,
even if they are uncommon. And common things aren't necessarily clear.
Hmm, I should have expected something like that.
> And that's why "do while" without braces is bad. If you scan it quickly on
> its own, you may well end up just seeing the
>
> while (x);
>
> part, and get confused ("oh, a delay loop").
Nope.
It raises a red flag in my head immediately. We don't do such busy
loops generally, and if we do, I would write it as:
while (x)
;
> But if you see
>
> } while (x);
>
> you aren't confused, because the latter one is clearly an ending condition
> of a do-while loop, IN A WAY THAT THE FIRST ONE IS NOT!
>
> See?
No. I must be different.
> do-while is very special, because as mentioned, "while" is a really magic
> C keyword that has two TOTALLY DIFFERENT meanings.
Probably. I just don't see it.
For me, every code fragment is different, and a program like sparse
can't even come close to know what's clear for me and what is not.
I use sparse as a great help - but only that, a help.
--
Krzysztof Halasa
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