Re: [PATCH] migration: fix stringop-truncation warning

[Paolo Bonzini <pbonzini@redhat.com>]

On 12/12/19 01:55, Richard Henderson wrote:
> On 12/11/19 6:23 AM, Paolo Bonzini wrote:
>> @@ -44,8 +44,7 @@ void global_state_store_running(void)
>>  {
>>      const char *state = RunState_str(RUN_STATE_RUNNING);
>>      assert(strlen(state) < sizeof(global_state.runstate));
>> -    strncpy((char *)global_state.runstate,
>> -           state, sizeof(global_state.runstate));
>> +    memcpy(global_state.runstate, state, strlen(state) + 1);
> 
> We should assign the strlen result to a local variable rather than compute it
> twice.

We could even strcpy since the assertion ensures it's valid, but perhaps
it's better to do nothing, since the best alternative would be
memset+strcpy, i.e. back to strncpy.

We generally are quite mindful about our uses of strncpy, but maybe we
could fold the assertion and strncpy into a qemu_strncpy function,
and/or qemu_strncpy_nonul for when you're copying into an array that
does _not_ need to be nul-terminated (so the assertion can become <=
rather than <).  I'll add it to BiteSizedTasks.

Paolo