On Thu, Nov 09, 2017 at 07:21:04PM -0800, Darrick J. Wong wrote: > On Thu, Nov 09, 2017 at 07:43:59PM -0600, Eric Sandeen wrote: > > On 11/9/17 7:39 PM, Dave Chinner wrote: > > > From: Dave Chinner <dchinner@xxxxxxxxxx> > > > > > > New compiler, new checks, new warnings. > > > > > > Fix the new [-Wformat-truncation=] warnings that io/fsmap.c is > > > throwing w/ gcc-7.2 because "%lld..%lld" requires a buffer 40 > > > characters long, not 32. > > > > > > Signed-Off-By: Dave Chinner <dchinner@xxxxxxxxxx> > > > > 2^63 is 19 chars, yup. > > > > Reviewed-by: Eric Sandeen <sandeen@xxxxxxxxxxx> > > > > > --- > > > io/fsmap.c | 4 ++-- > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/io/fsmap.c b/io/fsmap.c > > > index 448fb5356466..e46fdbaa148c 100644 > > > --- a/io/fsmap.c > > > +++ b/io/fsmap.c > > > @@ -184,8 +184,8 @@ dump_map_verbose( > > > off64_t agoff, bperag; > > > int foff_w, boff_w, aoff_w, tot_w, agno_w, own_w; > > > int nr_w, dev_w; > > > - char rbuf[32], bbuf[32], abuf[32], obuf[32]; > > > - char nbuf[32], dbuf[32], gbuf[32]; > > > + char rbuf[40], bbuf[40], abuf[40], obuf[40]; > > > + char nbuf[40], dbuf[40], gbuf[40]; > > Waitaminute. The longest format string is bbuf, which gets > "[%lld..%lld]:". The longest number %lld can print is > "-9223372036854775807" which requires 20 bytes. Therefore, bbuf needs > 1 + 20 + 2 + 20 + 2 + 1 == 46 bytes, not 40. rbuf and abuf have similar > problems, though I guess a 48-byte string will work for all. > > Granted, it's snprintf so it'll just truncate the second number if it > has to, but seeing as this came from a gcc warning: > > "fsmap.c:228:3: note: ‘snprintf’ output between 8 and 40 bytes into a > destination of size 32" > > So am I just bad at math, or is gcc wrong here? Ah, dchinner points out on irc that gcc knows we (>> 9) the numbers before printing them so the maximum value is 36028797018963967, so 40 bytes works. gcc: 1, maintainer: 0 Looks ok, Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> --D > --D > > > > char owner[OWNER_BUF_SZ]; > > > int sunit, swidth; > > > int flg = 0; > > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
