Re: [PATCH] fds/drm.c: Increase buffer size.

[Vinson Lee <vlee@freedesktop.org>]

On Tue, Feb 28, 2017 at 4:08 PM, Dave Jones <davej@codemonkey.org.uk> wrote:
> On Tue, Feb 28, 2017 at 07:49:16PM +0000, Vinson Lee wrote:
>  > Fix GCC format-truncation error.
>  >
>  >   CC fds/drm.o
>  > fds/drm.c: In function ‘open_drm_fds’:
>  > fds/drm.c:106:40: error: ‘%s’ directive output may be truncated writing up to 255 bytes into a region of size 119 [-Werror=format-truncation=]
>  >    snprintf(buf, sizeof(buf), "/dev/dri/%s", entry->d_name);
>  >                                         ^~
>  > In file included from /usr/include/stdio.h:939:0,
>  >                  from include/list.h:3,
>  >                  from include/fd.h:3,
>  >                  from fds/drm.c:4:
>  > /usr/include/bits/stdio2.h:64:10: note: ‘__builtin___snprintf_chk’ output between 10 and 265 bytes into a destination of size 128
>  >    return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
>  >           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>  >         __bos (__s), __fmt, __va_arg_pack ());
>  >         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>  >
>  > Signed-off-by: Vinson Lee <vlee@freedesktop.org>
>  > ---
>  >  fds/drm.c | 2 +-
>  >  1 file changed, 1 insertion(+), 1 deletion(-)
>  >
>  > diff --git a/fds/drm.c b/fds/drm.c
>  > index 1f7b95f1eb34..b094183d8d0d 100644
>  > --- a/fds/drm.c
>  > +++ b/fds/drm.c
>  > @@ -83,7 +83,7 @@ static int open_drm_fds(void)
>  >      int fd, dfd;
>  >      DIR *dir;
>  >      struct dirent *entry;
>  > -    char buf[128];
>  > +    char buf[512];
>
> d_name is only 256. Does 256+10 make the error go away ?
>
> I don't think this is ever a problem in real life, because no-one is
> insane enough to name a device node in that dir that long, but we should
> shut the warning up.
>
> Is this a gcc7 thing ?
>
>         Dave
>

Yes, buf[256+10] also fixes the build error.

Yes, this build error occurs with 7.0.

Vinson