[prev in list] [next in list] [prev in thread] [next in thread] 

List:       cfe-commits
Subject:    Re: [cfe-commits] [libcxx] r157764 - in /libcxx/trunk: include/__config src/iostream.cpp
From:       Howard Hinnant <hhinnant () apple ! com>
Date:       2012-05-31 20:16:03
Message-ID: 80094D6B-04CE-4615-89CF-75B944461EB8 () apple ! com
[Download RAW message or body]

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

> On Thu, May 31, 2012 at 1:02 PM, Howard Hinnant <hhinnant@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@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

_______________________________________________
cfe-commits mailing list
cfe-commits@cs.uiuc.edu
http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits


[prev in list] [next in list] [prev in thread] [next in thread]