From mboxrd@z Thu Jan 1 00:00:00 1970 From: Randy Dunlap Subject: Re: New bcache compiler warning (was: Re: bcache: Minor fixes from kbuild robot) Date: Mon, 17 Feb 2014 14:44:47 -0800 Message-ID: <530290DF.1060008@infradead.org> References: <530279EC.5010605@infradead.org> <20140217214553.GB11655@kmo> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from merlin.infradead.org ([205.233.59.134]:56906 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751254AbaBQWox (ORCPT ); Mon, 17 Feb 2014 17:44:53 -0500 In-Reply-To: <20140217214553.GB11655@kmo> Sender: linux-bcache-owner@vger.kernel.org List-Id: linux-bcache@vger.kernel.org To: Kent Overstreet , Geert Uytterhoeven Cc: Linux Kernel Mailing List , linux-bcache@vger.kernel.org On 02/17/2014 01:45 PM, Kent Overstreet wrote: > On Mon, Feb 17, 2014 at 10:11:51PM +0100, Geert Uytterhoeven wrote: >> On Mon, Feb 17, 2014 at 10:06 PM, Randy Dunlap wrote: >>> On 02/17/2014 01:00 PM, Geert Uytterhoeven wrote: >>>> On Fri, Feb 14, 2014 at 8:04 PM, Linux Kernel Mailing List >>>> wrote: >>>>> bcache: Minor fixes from kbuild robot >>>> >>>>> diff --git a/drivers/md/bcache/bset.c b/drivers/md/bcache/bset.c >>>>> index 4f6b594..3f74b4b 100644 >>>>> --- a/drivers/md/bcache/bset.c >>>>> +++ b/drivers/md/bcache/bset.c >>>>> @@ -23,7 +23,7 @@ void bch_dump_bset(struct btree_keys *b, struct= bset *i, unsigned set) >>>>> for (k =3D i->start; k < bset_bkey_last(i); k =3D next) { >>>>> next =3D bkey_next(k); >>>>> >>>>> - printk(KERN_ERR "block %u key %zi/%u: ", set, >>>>> + printk(KERN_ERR "block %u key %li/%u: ", set, >>>>> (uint64_t *) k - i->d, i->keys); >>>>> >>>>> if (b->ops->key_dump) >>>> >>>> On 32-bit (m68k): >>>> drivers/md/bcache/bset.c: In function =91bch_dump_bset=92: >>>> drivers/md/bcache/bset.c:27: warning: format =91%li=92 expects typ= e =91long >>>> int=92, but argument 3 has type =91int=92 >>>> >>>> What are you trying to print here? It looks a bit strange to me. >>>> Technically, the difference between two pointers is of type ptrdif= f_. >>>> The kernel had >>>> >>>> typedef __kernel_ptrdiff_t ptrdiff_t; >>>> >>>> and >>>> >>>> #if __BITS_PER_LONG !=3D 64 >>>> typedef unsigned int __kernel_size_t; >>>> typedef int __kernel_ssize_t; >>>> typedef int __kernel_ptrdiff_t; >>>> #else >>>> typedef __kernel_ulong_t __kernel_size_t; >>>> typedef __kernel_long_t __kernel_ssize_t; >>>> typedef __kernel_long_t __kernel_ptrdiff_t; >>>> #endif >>>> >>>> So I'd expect "%zi" to be the right way, and a quick test compile = on >>>> 32-bit (m68k) >>>> and 64-bit (amd64) comfirms that. What was wrong with it? >>> >>> The kernel supports 't' (%t) for ptrdiff_t (same as glibc), >>> so %ti should work (or %tu). >> >> Yes, that compiles without warnings, too. >> >> And after more decyphering, "(uint64_t *) k - i->d" seems to be posi= tive, >> so "%tu" should be OK. >=20 > *swears* Actually, I'm just going to cast this to unsigned (that's de= finitely > safe here): >=20 >=20 > commit 70bc49d421c793f73a772ae1f50622a39c6136d9 > Author: Kent Overstreet > Date: Mon Feb 17 13:44:06 2014 -0800 >=20 > bcache: Fix another compiler warning on m68k > =20 > Use a bigger hammer this time > =20 > Signed-off-by: Kent Overstreet >=20 > diff --git a/drivers/md/bcache/bset.c b/drivers/md/bcache/bset.c > index 3f74b4b074..5454164153 100644 > --- a/drivers/md/bcache/bset.c > +++ b/drivers/md/bcache/bset.c > @@ -23,8 +23,8 @@ void bch_dump_bset(struct btree_keys *b, struct bse= t *i, unsigned set) > for (k =3D i->start; k < bset_bkey_last(i); k =3D next) { > next =3D bkey_next(k); > =20 > - printk(KERN_ERR "block %u key %li/%u: ", set, > - (uint64_t *) k - i->d, i->keys); > + printk(KERN_ERR "block %u key %u/%u: ", set, > + (unsigned) ((u64 *) k - i->d), i->keys); > =20 > if (b->ops->key_dump) > b->ops->key_dump(b, k); >=20 Could that cause a truncation? unsigned means unsigned int. Can unsigned int be smaller (fewer bits) than the k pointer? If so, is that OK or a problem? --=20 ~Randy