constexpr:

constexpr:
  The recent support for potential constant expressions exposed a bug in the
  implementation of libstdc++4.6, where numeric_limits<int>::min() is defined
  as (int)1 << 31, which isn't a constant expression. Disable the 'constexpr
  function never produces a constant expression' error inside system headers
  to compensate.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@149729 91177308-0d34-0410-b5e6-96231b3b80d8