Le 01/09/2017 à 11:35, Leon Romanovsky a écrit :
> On Fri, Sep 01, 2017 at 09:00:01AM +0200, Nicolas Morey-Chaisemartin wrote:
>>
>> Le 01/09/2017 à 06:56, Leon Romanovsky a écrit :
>>> On Thu, Aug 31, 2017 at 02:50:56PM -0600, Jason Gunthorpe wrote:
>>>> To avoid clashing with user variables.
>>>>
>>>> Signed-off-by: Jason Gunthorpe <jgunthorpe@xxxxxxxxxxxxxxxxxxxx>
>>>> ---
>>>> util/util.h | 4 ++--
>>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/util/util.h b/util/util.h
>>>> index cbf0deca2dde7b..30d32ee6b51e24 100644
>>>> --- a/util/util.h
>>>> +++ b/util/util.h
>>>> @@ -8,8 +8,8 @@
>>>> * error */
>>>> #define check_snprintf(buf, len, fmt, ...) \
>>>> ({ \
>>>> - int rc = snprintf(buf, len, fmt, ##__VA_ARGS__); \
>>>> - (rc < len && rc >= 0); \
>>>> + int __rc__ = snprintf(buf, len, fmt, ##__VA_ARGS__); \
>>> It can't clash, because it is declared in the scope {..} of that define and
>>> it is local to check_snprintf macro.
>> It does if any of the va-args is called rc.
>> This is "valid" C although not sure what printfs does print here (probably random stack value)
>> {
>> int i = printf("i = %d\n", i);
>> }
> So how does this rename solve the issue?
> Now, we can clash with __rc__ variable.
>
> Thanks
There is no safe way to handle that. It can be detected with -Wshadow though.
But rc is quite a common name (39 definitions in the code base), __rc__ much less (unused... yet)
If you want some real fun, try writing macros with local variables that can be called recursively ;)
Nicolas
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