Re: if (a & X || b & ~Y) in dasd.c

From: Stevie O (stevie@qrpff.net)
Date: Wed Nov 21 2001 - 01:57:13 EST

At 08:38 PM 11/19/2001 +0100, Peter T. Breuer wrote:

>"bill davidsen wrote:"
> > If the code does what I think it does, it works as written. However, I
> > usually would throw in parenthesis on something like this to be sure
> > that the next person reading the code won't waste time thinking about
>
>Which is WHY you do not put in parentheses.

<snip snip>

So instead of using extra parentheses, we should include a copy of your
response in every potentially ambiguous location instead?

Two C constructs that have bitten me in the glutinous maximus on more than
one occasion:

mem_address = mem_base + page_index << 12; // Wrong!

if ( bit_mask & BIT_FLAG == 0) { flag_not_set(); } // Wrong!

Of course C has precedence. It's not always obvious. And the difference
between this

x = y + z << 2;

and

x = (y + z) << 2;

is that the 2nd doesn't make me have to remember the relative precedences
of + and <<. 

--
Stevie-O

REAL kernel hackers use
# cat > /vmlinuz
and
# insmod /dev/stdin

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This archive was generated by hypermail 2b29 : Fri Nov 23 2001 - 21:00:26 EST