[xproto] _X_NONNULL and C++ 11

[walter harms]

Am 27.05.2017 14:10, schrieb Mark Kettenis:
>> Date: Sat, 27 May 2017 13:33:25 +0200
>> From: walter harms <wharms at bfs.de>
>>
>> Am 27.05.2017 11:02, schrieb Matthieu Herrb:
>>> Hi,
>>>
>>> Marc Espie recently found out that the X_NONNULL macro in Xfuncproto.h
>>> is generating spurious warnings when included in C++ code build with
>>> clang++ -std=c++11.
>>>
>>> Other OpenBSD developper tried to find uses of the macro in the wild
>>> and didn't find any, even in the X.Org lib app or xserver tree.
>>>
>>> So, should this macro definition be removed alltogether (acking that
>>> no-one cares to use it) or just apply the patch below ?
>>>
>>> From 6ae956660879d70e078025c3d8f1ac3fd438cad2 Mon Sep 17 00:00:00 2001
>>> From: Marc Espie <espie at nerim.net>
>>> Date: Sat, 27 May 2017 10:55:04 +0200
>>> Subject: [PATCH] Fix compiling any C++ code including Xfuncproto.h with
>>>  clang++ -std=c++11
>>>
>>> It shouldn't warn, bu it will use the "legacy" varargs macros and whine.
>>> ---
>>>  Xfuncproto.h.in | 3 ++-
>>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/Xfuncproto.h.in b/Xfuncproto.h.in
>>> index b88493d..1be3f55 100644
>>> --- a/Xfuncproto.h.in
>>> +++ b/Xfuncproto.h.in
>>> @@ -166,7 +166,8 @@ in this Software without prior written authorization from The Open Group.
>>>     argument macros, must be only used inside #ifdef _X_NONNULL guards, as
>>>     many legacy X clients are compiled in C89 mode still. */
>>>  #if __has_attribute(nonnull) \
>>> -    && defined(__STDC_VERSION__) && (__STDC_VERSION__ - 0 >= 199901L) /* C99 */
>>> +    && (defined(__STDC_VERSION__) && (__STDC_VERSION__ - 0 >= 199901L) \
>>> +    || (defined(__cplusplus) && (__cplusplus - 0 >= 201103L))) /* C99 C++11 */
>>>  #define _X_NONNULL(...)  __attribute__((nonnull(__VA_ARGS__)))
>>>  #elif __has_attribute(nonnull) \
>>>      || defined(__GNUC__) &&  ((__GNUC__ * 100 + __GNUC_MINOR__) >= 303)
>>>
>>>
>>>
>>
>> So far i understand this is a problem with clang++. "spurious
>> warning" sounds for me more like a compiler bug (assuming that gcc
>> has no problems with that). So why not make that a NOOP until fixed
>> in clang ?
> 
> GCC 4.9.4 warns as well:
> 
> $ g++ -pedantic -std=c++11 -I/usr/X11R6/include xfunc.cc
> In file included from xfunc.cc:1:0:
> /usr/X11R6/include/X11/Xfuncproto.h:173:24: warning: ISO C does not permit named variadic macros [-Wvariadic-macros]
>  #define _X_NONNULL(args...)  __attribute__((nonnull(args)))
> 

i have checked my version and can confirm the problem also with gcc (and -pedantic).

i guess it is more simple the remove the macro completely. It is only for optimization,
it is never used, ... lets remove it.

re,
 wh