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

[Chandler Carruth]

On Thu, May 31, 2012 at 1:11 PM, Eli Friedman <eli.friedman at gmail.com>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)))
>

*that* was the incantation I couldn't dredge up from memory! =D
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