Re: [PATCH 3/6] migration: Silence compiler warning in global_state_store_running()

[Thomas Huth]

On 21/09/2020 22.39, Cleber Rosa wrote:
> On Fri, Sep 18, 2020 at 12:34:27PM +0200, 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.
>>
>> Suggested-by: Philippe Mathieu-Daudé <philmd@redhat.com> (two years ago)
>> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>> 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..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');
>>  }
>>  
>>  bool global_state_received(void)
>> -- 
>> 2.18.2
>>
>>
> 
> Hi Thomas,
> 
> FIY, I couldn't reproduce the complaint from GCC.  I've tested it on focal,
> "gcc (Ubuntu 9.3.0-10ubuntu2) 9.3.0", with QEMU 5df6c87e8.

 Hi Cleber,

I've hit the error here:

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

It seems to use the very same compiler version as you did, so that's
kind of weird... Maybe it's related to the other compiler flags, either
--enable-gprof, --enable-gcov or --disable-pie ?

 Thomas

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