[cfe-commits] [libcxx] r157764 - in /libcxx/trunk: include/__config src/iostream.cpp

[Howard Hinnant]

On May 31, 2012, at 4:11 PM, Eli Friedman wrote:

> On Thu, May 31, 2012 at 1:02 PM, Howard Hinnant <hhinnant at apple.com> wrote:
>> On May 31, 2012, at 3:58 PM, Chandler Carruth wrote:
>> 
>>> On Thu, May 31, 2012 at 12:31 PM, Howard Hinnant <hhinnant at apple.com> wrote:
>>> Author: hhinnant
>>> Date: Thu May 31 14:31:14 2012
>>> New Revision: 157764
>>> 
>>> URL: http://llvm.org/viewvc/llvm-project?rev=157764&view=rev
>>> Log:
>>> Protect use of alignas against older versions of clang
>>> 
>>> Modified:
>>>    libcxx/trunk/include/__config
>>>    libcxx/trunk/src/iostream.cpp
>>> 
>>> Modified: libcxx/trunk/include/__config
>>> URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/__config?rev=157764&r1=157763&r2=157764&view=diff
>>> ==============================================================================
>>> --- libcxx/trunk/include/__config (original)
>>> +++ libcxx/trunk/include/__config Thu May 31 14:31:14 2012
>>> @@ -145,8 +145,10 @@
>>>  #if defined(__clang__)
>>> 
>>>  #if __has_feature(cxx_alignas)
>>> +#  define _ALIGNAS_TYPE(x) alignas(x)
>>>  #  define _ALIGNAS(x) alignas(x)
>>>  #else
>>> +#  define _ALIGNAS_TYPE(x) __attribute__((__aligned__))
>>> 
>>> Should this be __aligned__(x) as it is here:
>>> 
>>>  #  define _ALIGNAS(x) __attribute__((__aligned__(x)))
>>> 
>>> Or are you intentionally shooting for the 'maximally aligned' thing? If the latter, maybe comment that this is intentional and not a typo?
>> 
>> It's intentional.  My first try was using _ALIGNAS, and the compiler really didn't like it:
>> 
>> ../src/iostream.cpp:16:21: error: expected ')'
>> _ALIGNAS (__stdinbuf<char> ) static char __cin [sizeof(__stdinbuf <char>)];
>>                    ^
>> ../include/__config:149:50: note: expanded from macro '_ALIGNAS'
>> #  define _ALIGNAS(x) __attribute__((__aligned__(x)))
>>                                                 ^
>> 
>> And so I punted by introducing _ALIGNAS_TYPE.
>> 
>> I can add a comment, but I'd really like to hold trunk stable for just a couple more hours.
> 
> The correct definition for _ALIGNAS_TYPE is something like the following:
> 
> #define _ALIGNAS_TYPE(x) __attribute__((__aligned__(__alignof(x)))

Done!  Thanks Eli!

Howard