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

[Howard Hinnant]

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.

Howard