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

[Thomas Huth]

On 16/09/2020 19.19, 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;
>      assert(strlen(state) < sizeof(global_state.runstate));
> -    strncpy((char *)global_state.runstate,
> -           state, sizeof(global_state.runstate));
> +    strncpy(dest, state, sizeof(global_state.runstate));
>  }

Darn, I was sending too fast here, sorry, but seems like this does *not*
fix the issue with GCC 9.3:

 https://travis-ci.com/github/huth/qemu/jobs/385871010#L2930

... so maybe we should simply switch to strpadcpy() instead?

 Thomas