Le 10/01/13 07:44, Emil Dotchevski a écrit :
On Wed, Jan 9, 2013 at 6:23 PM, Marshall Clow <mclow.lists@gmail.com> wrote:
Has anyone put any effort into making Boost.Exception (and BOOST_ASSERT) work with constexpr? I don't think assert or throw are compatible with constexpr.
I don't see a problem with throw. The problem is with throw_exception. We can add a basic_throw_exception that behaves as the old throw_exception that can be made constexpr #ifdef BOOST_NO_EXCEPTIONS BOOST_CONTEXPR void basic_throw_exception( std::exception const & e ); // user defined #else inline BOOST_CONTEXPR bool basic_throw_exception_assert_compatibility( std::exception const & ) { return true; } template<class E> BOOST_ATTRIBUTE_NORETURN inline BOOST_CONTEXPR void basic_throw_exception( E const & e ) { //All boost exceptions are required to derive from std::exception, //to ensure compatibility with BOOST_NO_EXCEPTIONS. if (basic_throw_exception_assert_compatibility(e)) throw e; else throw e; } #endif so that rangecheck is constexpr static BOOST_CONTTEXPR void rangecheck (size_type i) { if (i >= size()) basic_throw_exception( std::out_of_range e("array<>: index out of range") ); } On the other side, assert is a C macro so no way to qualify it as constexpr. The best we can do instead of asserting const_reference operator[](size_type i) const { BOOST_ASSERT_MSG( i < N, "out of range" ); return elems[i]; } is to abort without providing a message when the test fail. The following macro could help #if defined(BOOST_DISABLE_ASSERTS) || defined(NDEBUG) # define BOOST_RETURN_IF(Test, Value) return (Val) #else # define BOOST_RETURN_IF(Test, Value) \ if (Test) return (Val); \ else abort(); #endif constexpr const_reference operator[](size_type i) { return BOOST_RETURN_IF( i < N, elems[i]); } It would be reasonable to raise an issue for c++14. I would expect that the compiler could be able to manage with assert in a different way when evaluated at compile time. Best, Vicente