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

[Laurent Vivier]

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>
> ---
>  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.

>        (dest)[__NEW_UTS_LEN] = '\0'; \
>    } while (0)
>  
>