On Wed, Jan 9, 2013 at 3:04 PM, Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > So, it seems there's some concensus building here, and it seems that > I've become the chosen victi^wvolunteer for this. So, here's a patch. > It's missing a Guns-supplied-by: tag though. > > From: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx> > Subject: Mark IS_ERR_OR_NULL() deprecated > > IS_ERR_OR_NULL() attracts a lot of abuse: people use it without much > thought about it's effects. Common errors include: > 1. checking the returned pointer for functions defined as only > returning errno-pointer values, rather than using IS_ERR(). > This leads to: ptr = foo(); if (IS_ERR_OR_NULL(ptr)) return > PTR_ERR(ptr); > 2. using it to check functions which only ever return NULL on error, > thereby leading to another zero-error value return. > In the case of debugfs functions, these return errno-pointer values when > debugfs is configured out, which means code which blindly checks using > IS_ERR_OR_NULL() ends up returning errors, which is rather perverse for > something that's not implemented. > > Therefore, let's schedule it for removal in a few releases. > > Nicolas Pitre comments: >> I do agree with Russell here. Despite the original intentions behind >> IS_ERR_OR_NULL() which were certainly legitimate, the end result in >> practice is less reliable code with increased maintenance costs. >> Unlike other convenience macros in the kernel, this one is giving a >> false sense of correctness with too many people falling in the trap >> of using it just because it is available. >> >> I strongly think this macro should simply be removed from the source >> tree entirely and the code reverted to explicit tests against NULL >> when appropriate. > > Suggested-by: David Howells <dhowells@xxxxxxxxxx> > Tape-measuring-service-offered-by: Will Deacon <will.deacon@xxxxxxx> > Victim-for-firing-sqad: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx> > Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx> Acked-by: Grant Likely <grant.likely@xxxxxxxxxxxx> I fully agree with doing this. While I'm not a fan of the PTR_ERR pattern, this does (hopefully) make users think just a little bit more about it. > --- > Ok, so I'm in the firing line for suggesting this, but it appears > several people wish this to happen. > > I'm not intending to push this patch forwards _just_ yet: we need to > sort out the existing users _first_ to prevent the kernel turning into > one hell of a mess of warnings. I currently see 355 users. That's a lot, but not inconceivable for an auditing effort for pulling them out instead of scheduling for future removal. g. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
