Re: [PATCH v2] migration: Silence compiler warning in global_state_store_running()

[Thomas Huth]

On 17/09/2020 10.02, Thomas Huth wrote:
> On 17/09/2020 09.47, Philippe Mathieu-Daudé wrote:
>> On 9/17/20 9:43 AM, 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 a strncpy here - the size is already
>>> checked with the assert() statement right in front of it. To silence the
>>> warning, simply replace it with our strpadcpy() function.
>>>
>>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>>> ---
>>>  v2: Use strpadcpy instead of QEMU_NONSTRING (and yes, this time it seems
>>>      to really silence the compiler warning :-))
>>>
>>>  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..a33947ca32 100644
>>> --- a/migration/global_state.c
>>> +++ b/migration/global_state.c
>>> @@ -44,8 +44,8 @@ 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));
>>> +    strpadcpy((char *)global_state.runstate, sizeof(global_state.runstate),
>>> +              state, '\0');
>>
>> https://www.mail-archive.com/qemu-block@nongnu.org/msg44925.html
>> ;)
> 
> Oh, well :-) ... but why did you never pushed to get that merged?

Hmm, commit 0a5526a18b0245dfa20a9fe453b2a9af3125d175 was supposed to fix
it already ... but apparently, that does not work with GCC 9.3 ?

 Thomas