[Boost-bugs] [Boost C++ Libraries] #9971: Use constexpr for boost::mpl::c_str::value when possible.

Subject: [Boost-bugs] [Boost C++ Libraries] #9971: Use constexpr for boost::mpl::c_str::value when possible.
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2014-05-01 11:23:47

#9971: Use constexpr for boost::mpl::c_str::value when possible.
-------------------------------------+-----------------------
 Reporter:  ytj000@…                 |      Owner:  agurtovoy
     Type:  Patches                  |     Status:  new
Milestone:  To Be Determined         |  Component:  mpl
  Version:  Boost Development Trunk  |   Severity:  Problem
 Keywords:                           |
-------------------------------------+-----------------------
 Right now boost::mpl::c_str::value is a static const member variable.
 I think it is a decent idea to add the constexpr keyword here.

 I have a patch for this issue. Here is an example why it is useful:

 {{{
 #include<boost/mpl/string.hpp>
 int main() {
     using H = boost::mpl::string<'h'>;
     static_assert(boost::mpl::c_str<H>::value[0] == 'h', "");
 }
 }}}

 Without my patch, compiler will complain we could not use c_str::value in
 constant expression. With my patch, compiler will accept this code.

 Tested in clang++ 3.4, CentOS 6.3, but I think GCC should works as well.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/9971>
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