Enforce.h

#pragma once

// Author: Torarin Hals Bakke (2012)

// Boost Software License - Version 1.0 - August 17th, 2003

// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:

// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

#include <boost/config.hpp>
#include <string>
#include <utility>
#include <type_traits>
#include <exception>

class Enforce_error : public std::exception {
  std::string what_;
  std::string user_friendly_what_;
public:
  template<typename T, typename U>
  explicit Enforce_error(T&& what_arg, U&& user_friendly_what_arg)
  : what_(std::forward<T>(what_arg)),
    user_friendly_what_(std::forward<U>(user_friendly_what_arg))
  {}

#if __GNUC__ == 4 && __GNUC_MINOR__  == 6
  ~Enforce_error() throw() {}
#endif

  const char* what() const BOOST_NOEXCEPT {
    return what_.c_str();
  }

  const std::string& user_friendly_what() const BOOST_NOEXCEPT {
    return user_friendly_what_;
  }
};

template <typename T, typename U>
void enforce(bool condition, T&& msg, U&& user_friendly_msg) {
  static_assert(std::is_convertible<T, std::string>::value,
                "msg must be convertible to std::string");
  static_assert(std::is_convertible<U, std::string>::value,
                "user_friendly_msg must be convertible to std::string");
  if (!condition)
    throw Enforce_error(std::forward<T>(msg), std::forward<U>(user_friendly_msg));
}

#define ENFORCE_MESSAGE "Enforcement failed in " __FILE__ "(" BOOST_STRINGIZE(__LINE__) ")"

#define ENFORCE(condition) enforce(condition, ENFORCE_MESSAGE, "")
#define ENFORCE2(condition, user_friendly_msg) enforce(condition, ENFORCE_MESSAGE, user_friendly_msg)