[Bug c++/59013] New: alignas rejects valid constant expressions

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59013

            Bug ID: 59013
           Summary: alignas rejects valid constant expressions
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
            Blocks: 58601

template<int N>
struct foo
{
  static const unsigned value = 8;
};

template<unsigned N>
struct aligned_union
{
  alignas(foo<N>::value) char data[N];
};

int main()
{
  aligned_union<8> a;
}

aa.cc: In instantiation of ‘struct aligned_union<8u>’:
aa.cc:15:22:   required from here
aa.cc:10:39: error: requested alignment is not an integer constant
     alignas(foo<N>::value) char data[N];
                                       ^

This is wrong, foo<N>::value is an integer constant. The code is valid.