Re: [Qemu-trivial] [Qemu-devel] [PATCH v2 4/5] linux-user/uname: Fix GCC 9 build warnings

[Alistair Francis]

On Wed, May 1, 2019 at 5:00 AM Eric Blake <address@hidden> wrote:
>
> On 5/1/19 4:40 AM, Laurent Vivier wrote:
> > On 01/05/2019 01:28, Alistair Francis wrote:
> >> Fix this warning when building with GCC9 on Fedora 30:
> >> In function ‘strncpy’,
> >>     inlined from ‘sys_uname’ at 
> >> /home/alistair/qemu/linux-user/uname.c:94:3:
> >> /usr/include/bits/string_fortified.h:106:10: error: ‘__builtin_strncpy’ 
> >> output may be truncated copying 64 bytes from a string of length 64 
> >> [-Werror=stringop-truncation]
> >>   106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos 
> >> (__dest));
> >>       |          
> >> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >>
> >> Signed-off-by: Alistair Francis <address@hidden>

I'm dropping this patch in favour of the other one.

Alistair

> >> ---
> >>  linux-user/uname.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/linux-user/uname.c b/linux-user/uname.c
> >> index 313b79dbad..2fc6096a5b 100644
> >> --- a/linux-user/uname.c
> >> +++ b/linux-user/uname.c
> >> @@ -73,7 +73,7 @@ const char *cpu_to_uname_machine(void *cpu_env)
> >>  #define COPY_UTSNAME_FIELD(dest, src) \
> >>    do { \
> >>        /* __NEW_UTS_LEN doesn't include terminating null */ \
> >> -      (void) strncpy((dest), (src), __NEW_UTS_LEN); \
> >> +      (void) memcpy((dest), (src), MIN(strlen(src), __NEW_UTS_LEN)); \
> >
> > You should use MIN(strlen(src) + 1, __NEW_UTS_LEN) to copy the NUL
> > character if it is present and fit in __NEW_UTS_LEN.
>
> No, the NUL character is already present, due to the memset() prior to
> any use of COPY_UTSNAME_FIELD().  However, the commit message should
> call that out, as it is not part of the default 3-line diff.
>
> --
> Eric Blake, Principal Software Engineer
> Red Hat, Inc.           +1-919-301-3226
> Virtualization:  qemu.org | libvirt.org
>