boost::asio::execution::bad_executor needs an explicit BOOST_ASIO_DECL

[jcelerier]

When linking with lld (from clang-64 MinGW) on windows, with BOOST_ASIO_DYN_LINK:

 ld.lld: error: undefined symbol: vtable for boost::asio::execution::bad_executor

Every other symbol is correct, but since the type boost::asio::execution::bad_executor itself is not marked BOOST_ASIO_DECL, then the implicit dtor won't be marked as exported.

[jcelerier]

hmm.. actually I'm still getting the same link error despite marking everything:

class BOOST_ASIO_DECL bad_executor : public std::exception
{
public:
  /// Constructor.
  BOOST_ASIO_DECL bad_executor() noexcept;
  BOOST_ASIO_DECL virtual ~bad_executor() noexcept;

  /// Obtain message associated with exception.
  BOOST_ASIO_DECL virtual const char* what() const noexcept;
};

BOOST_ASIO_DECL bad_executor::bad_executor() noexcept { }
BOOST_ASIO_DECL bad_executor::~bad_executor() noexcept { }

BOOST_ASIO_DECL const char* bad_executor::what() const noexcept
{
  return "bad executor";
}