Class system_error

3rd/asio-1.24.0/include/asio/system_error.hpp:42–123

The system_error class is used to represent system conditions that prevent the library from operating correctly.

/// The system_error class is used to represent system conditions that
/// prevent the library from operating correctly.
class system_error
  : public std::exception
{
public:
  /// Construct with an error code.
  system_error(const error_code& ec)
    : code_(ec),
      context_()
  {
  }

  /// Construct with an error code and context.
  system_error(const error_code& ec, const std::string& context)
    : code_(ec),
      context_(context)
  {
  }

  /// Copy constructor.
  system_error(const system_error& other)
    : std::exception(other),
      code_(other.code_),
      context_(other.context_),
      what_()
  {
  }

  /// Destructor.
  virtual ~system_error() throw ()
  {
  }

  /// Assignment operator.
  system_error& operator=(const system_error& e)
  {
    context_ = e.context_;
    code_ = e.code_;
    what_.reset();
    return *this;
  }

  /// Get a string representation of the exception.
  virtual const char* what() const throw ()
  {
#if !defined(ASIO_NO_EXCEPTIONS)
    try
#endif // !defined(ASIO_NO_EXCEPTIONS)
    {
      if (!what_.get())
      {
        std::string tmp(context_);
        if (tmp.length())
          tmp += ": ";
        tmp += code_.message();
        what_.reset(new std::string(tmp));
      }
      return what_->c_str();
    }