libcxx patch for N3655

Howard Hinnant hhinnant at
Wed Jul 3 14:31:29 PDT 2013

On Jul 3, 2013, at 2:44 PM, Marshall Clow <mclow.lists at> wrote:

> On Jul 3, 2013, at 9:37 AM, Howard Hinnant <howard.hinnant at> wrote:
>> On Jul 2, 2013, at 2:43 PM, Marshall Clow <mclow.lists at> wrote:
>>> In N3655 (the first half of which was incorporated into C++14), Walter added a bunch of template aliases to simplify template metaprogramming.
>>> Lots of stuff like this:
>>> 	template <class T> using remove_const_t    = typename remove_const<T>::type;
>>> This patch adds all those aliases into libc++, and tests.
>>> Also some drive-by cleanups of existing tests.
>> Thanks Marshall.  I think you did your svn diff from the wrong subdirectory.  The patch doesn't include an updated <type_traits>.
> D'oh!
> Here's a better patch.

Looks pretty good to me.  I've enclosed a few differences:

1.  I tried to verify that those traits that do work in C++03 mode still worked.  But I've let the '03 test suite deteriorate to the point that I was getting too many errors in '03 mode to see what had changed.  So I took this opportunity to first make meta test cleanly in '03 mode.

2.  To get your patch to test cleanly in C++03 mode I had to wrap static_assert in some irritating '()', and emulate variadics in a couple of tests.

3.  I removed 'const' from the size_t in both aligned_storage and aligned_storage_t.  That was just a latent bug and this was a good opportunity to clean that up.

4.  I removed typename from several of the new tests.  The typename didn't hurt, but it was nice to see that it is no longer needed with these new aliases.

You did a nice job with the updated comments, the macro protection and the c++1y protection.  I couldn't find anything else to whine about. :-)  Oh, I did remove section numbers from the comment section.  They get outdated really quickly and become impossible to keep correct.

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