Throw in constexpr function

Question

The following piece of code compiles under clang++ 3.7.0 but is denied by g++ 5.3.1. Both have -std=c++14 option. Which compiler is correct? Anyone knows whe

Answer 1

As shown by Shafik Yaghmour it's a gcc bug, which is fixed in v6.1

If you are still using the old gcc version you can revert to the c++11 constexpr style:

constexpr auto foo(int n) -> int
{
  return n <= 0 ? throw runtime_error("") : 1;
}

However there is a better workaround, still retaining all of the c++14 constexpr extensions:

// or maybe name it
// throw_if_zero_or_less
constexpr auto foo_check_throw(int n) -> void
{  
  n <= 0 ? throw std::runtime_error("") : 0;
}

constexpr auto foo(int n) -> int
{
  foo_check_throw(n);

  // C++14 extensions for constexpr work:
  if (n % 2)
    return 1;
  return 2;
}