svn commit: r298933 - in head: share/man/man9 sys/amd64/include sys/dev/acpica sys/dev/drm2 sys/dev/drm2/i915 sys/kern sys/sys sys/x86/acpica sys/x86/x86

[Bruce Evans]

On Thu, 5 May 2016, Konstantin Belousov wrote:

> On Wed, May 04, 2016 at 09:17:50PM -0700, John Baldwin wrote:
>> ...
>> How about this:
>> ...
>> diff --git a/sys/sys/_bitset.h b/sys/sys/_bitset.h
>> index 26a8848..89dd7b6 100644
>> --- a/sys/sys/_bitset.h
>> +++ b/sys/sys/_bitset.h
>> @@ -36,26 +36,15 @@
>>   * Macros addressing word and bit within it, tuned to make compiler
>>   * optimize cases when SETSIZE fits into single machine word.
>>   */
>> -#define	_BITSET_BITS		(sizeof(long) * NBBY)
>> +#define	_BITSET_BITS		(sizeof(long) * 8)
>>
>> -#define	__bitset_words(_s)	(howmany(_s, _BITSET_BITS))
>> +#define	_howmany(x, y)	(((x) + ((y) - 1)) / (y))
> The _howmany symbol is still in the user namespace.  Implementation-reserved
> names are __.* and _[A-Z].* .

The names _.* also are reserved at file scope.

sys/select.h also uses _howmany(), and that is correct there since it is
only used in inner scopes that the application cannot conflict with
(except possibly via -Wshadow warnings).  I haven't checked this in the
patch yet, but it is probably the same.  In select.h, the inner scopes
are one inside a struct declaration and one inside a compound statement
in a statement-like macro.

I like to use minimal underscores since 2 underscores are uglier.  select.h
does this perfectly or almost perfectly.  An example of this is the
__fd_mask typedef.  This is used in non-inner scopes so it needs 2
underscores.

The above fixes the bogus underscore on _s.  1 underscore is also ugly,
and this one shows lack of understanding of namespaces.  Underscores
are never needed for macro parameters since they create their their
own namespace.

Bruce