Re: [PATCH] migration: Silence compiler warning in global_state_store_running()

[Eric Blake]

On 9/16/20 12:19 PM, Thomas Huth wrote:
> GCC 9.3.0 on Ubuntu complains:
>
> In file included from /usr/include/string.h:495,
>                   from /home/travis/build/huth/qemu/include/qemu/osdep.h:87,
>                   from ../migration/global_state.c:13:
> In function ‘strncpy’,
>      inlined from ‘global_state_store_running’ at 
> ../migration/global_state.c:47:5:
> /usr/include/x86_64-linux-gnu/bits/string_fortified.h:106:10: error: 
> ‘__builtin_strncpy’ specified bound 100 equals destination size 
> [-Werror=stringop-truncation]
>    106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos 
> (__dest));
>        |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> ... but we apparently really want to do the strncpy here. Silence the
> warning with QEMU_NONSTRING.
>
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>   migration/global_state.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/migration/global_state.c b/migration/global_state.c
> index 25311479a4..f1355d7d97 100644
> --- a/migration/global_state.c
> +++ b/migration/global_state.c
> @@ -43,9 +43,9 @@ int global_state_store(void)
>   void global_state_store_running(void)
>   {
>       const char *state = RunState_str(RUN_STATE_RUNNING);
> +    QEMU_NONSTRING char *dest = (char *)global_state.runstate;

Do we still need the cast to char*?

>       assert(strlen(state) < sizeof(global_state.runstate));
> -    strncpy((char *)global_state.runstate,
> -           state, sizeof(global_state.runstate));
> +    strncpy(dest, state, sizeof(global_state.runstate));
>   }
>   

Otherwise,
Reviewed-by: Eric Blake <eblake@redhat.com>

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org