* [PATCH] xfs_io: fix gcc-7 related printf warnings
@ 2017-11-10 1:39 Dave Chinner
2017-11-10 1:43 ` Eric Sandeen
0 siblings, 1 reply; 4+ messages in thread
From: Dave Chinner @ 2017-11-10 1:39 UTC (permalink / raw)
To: linux-xfs
From: Dave Chinner <dchinner@redhat.com>
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@redhat.com>
---
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];
char owner[OWNER_BUF_SZ];
int sunit, swidth;
int flg = 0;
--
2.15.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] xfs_io: fix gcc-7 related printf warnings
2017-11-10 1:39 [PATCH] xfs_io: fix gcc-7 related printf warnings Dave Chinner
@ 2017-11-10 1:43 ` Eric Sandeen
2017-11-10 3:21 ` Darrick J. Wong
0 siblings, 1 reply; 4+ messages in thread
From: Eric Sandeen @ 2017-11-10 1:43 UTC (permalink / raw)
To: Dave Chinner, linux-xfs
On 11/9/17 7:39 PM, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> 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@redhat.com>
2^63 is 19 chars, yup.
Reviewed-by: Eric Sandeen <sandeen@sandeen.net>
> ---
> 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];
> char owner[OWNER_BUF_SZ];
> int sunit, swidth;
> int flg = 0;
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] xfs_io: fix gcc-7 related printf warnings
2017-11-10 1:43 ` Eric Sandeen
@ 2017-11-10 3:21 ` Darrick J. Wong
2017-11-10 3:27 ` Darrick J. Wong
0 siblings, 1 reply; 4+ messages in thread
From: Darrick J. Wong @ 2017-11-10 3:21 UTC (permalink / raw)
To: Eric Sandeen; +Cc: Dave Chinner, linux-xfs
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@redhat.com>
> >
> > 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@redhat.com>
>
> 2^63 is 19 chars, yup.
>
> Reviewed-by: Eric Sandeen <sandeen@sandeen.net>
>
> > ---
> > 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?
--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@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] xfs_io: fix gcc-7 related printf warnings
2017-11-10 3:21 ` Darrick J. Wong
@ 2017-11-10 3:27 ` Darrick J. Wong
0 siblings, 0 replies; 4+ messages in thread
From: Darrick J. Wong @ 2017-11-10 3:27 UTC (permalink / raw)
To: Eric Sandeen; +Cc: Dave Chinner, linux-xfs
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@redhat.com>
> > >
> > > 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@redhat.com>
> >
> > 2^63 is 19 chars, yup.
> >
> > Reviewed-by: Eric Sandeen <sandeen@sandeen.net>
> >
> > > ---
> > > 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@oracle.com>
--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@vger.kernel.org
> > 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@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
^ permalink raw reply [flat|nested] 4+ messages in thread
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2017-11-10 1:39 [PATCH] xfs_io: fix gcc-7 related printf warnings Dave Chinner
2017-11-10 1:43 ` Eric Sandeen
2017-11-10 3:21 ` Darrick J. Wong
2017-11-10 3:27 ` Darrick J. Wong
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