[Bug c++/43947] New: [C++0x] constexpr should allow declaration without a definition

[public at alisdairm dot net]

GCC 4.5 has early support for constexpr, which syntax checks code but does not
support use in a constant expression.

The following code should be allowed, but fails as GCC currently requires the
in initial declaration also be a definition:

constexpr auto five() -> int;
inline constexpr auto five() -> int { return 5; }


Similarly, member functions should be allowed:

struct host {
 static constexpr auto five() -> int;
}

inline constexpr auto host::five() -> int { return 5; }


and finally constructors:

struct test_type {
  int data;
  constexpr test_type(int x);
};

inline constexpr test_type::test_type(int x )
  : data{x}
  {
}


Note that the constexpr keyword is required on *every* declaration and
definition.


-- 
           Summary: [C++0x] constexpr should allow declaration without a
                    definition
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: public at alisdairm dot net


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43947