On Sat Jul 4 18:12:16 EDT 2009, [email protected] wrote:
> Thanks for the answer Erik.
>
> [...]
> > the extra () around tor->sha1list are confusing.
>
> Noted, thanks, they're gone. I suck at remembering operators precedence
> so I usually add a few parentheses to be on the safe side.
i think it's important to learn operator precedence.
why guess when you can know? you can steal
the cheet sheet i stole from bwc:
#! /bin/rc
label prec
cat <<!
left to right () [] -> .
right to left ! ~ ++ -- - (type) * & sizeof
left to right * / %
left to right + -
left to right << >>
left to right < <= > >=
left to right == !=
left to right &
left to right ^
left to right |
left to right &&
left to right ||
right to left ?:
right to left = += -= etc.
left to right ,
!
> > the three most common errors that cause this are
> > (a) not allocating enough memory by, e.g.
> > malloc(sizeof tor) not malloc(sizeof *tor). or
> > (b) pointing to a non-static on the stack,
> > or (c) mistyping of tor->sha1list so that sizeof
> > tor->sha1list[0][0] != 1.
>
> Could you elaborate on (b), or point me to an example please? I don't
> really understand what it means or how it could happen...
generally, it's not so obvious, but a variation of this
would do it:
uchar*
badfn(char *txt, uint len)
{
uchar buf[SHA1dlen];
sha1(txt, len, sha, nil);
return buf;
}
- erik
