On Wed, Mar 28, 2007 at 01:14:54PM -0700, Andrew Morton wrote:
> On Wed, 28 Mar 2007 19:23:32 +0200 (CEST)
> Jiri Kosina <[EMAIL PROTECTED]> wrote:
>
> > blockdev: bd_claim_by_kobject() could check value of unititalized pointer
[..]
> > @@ -950,7 +950,7 @@ static int bd_claim_by_kobject(struct block_device
> > *bdev, void *holder,
> > struct kobject *kobj)
> > {
> > int res;
> > - struct bd_holder *bo, *found;
> > + struct bd_holder *bo, *found = NULL;
>
> that generates extra code and people get upset.
I, for one, not upset. On the contrary.
IMHO gcc should be smart enough to optimize that code properly with that
"= NULL" added.
BTW with gcc 4.1.2 on x86_64 that warning doesn't get emitted, and it
generates the same exact code with or without " = NULL". One could aruge,
if people are upset about more code being generated because they use an
older stable branch of gcc, it's _their_ problem.
> struct bd_holder *found;
>
> squash_bogus_uninit_warning(found); /* useful comment goes here */
>
> which is also unpleasant, but not as unpleasant as a screenful of warnings
> which hide real problems, IMO.
If there was such 'squash_bogus_uninit_warning' macro exist and in use,
then this could have been a possible scenario:
A) There's some 200-lines long function.
B) It has a squash_bogus_uninit_warning() somewhere in the beginning.
C) Someone commits a patch that uses an uninitialized variable on _some_
cases and it doesn't generate a warning.
D) You get an 'heisenbug', since that pointer might point to something
that is dereferencable without a fault, etc.
I think that warnings of these kind (assuming that they are not generated
as a result of deficiencies in the latest stable version of gcc) exist
for a damn good reason - the code should be fixed and that warning
shouldn't be bypassed in semi-nasty ways.
--
Dan Aloni
XIV LTD, http://www.xivstorage.com
da-x (at) monatomic.org, dan (at) xiv.co.il
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
