Re: [Boost-users] Re: Guidelines for effective exception usage

From: Stephen torri (storri_at_[hidden])
Date: 2004-08-22 23:40:57

On Sun, 2004-08-22 at 23:41, Jonathan Turkanis wrote:
> "Stephen torri" <storri_at_[hidden]> wrote in message
> news:1093230456.8377.44.camel_at_base.torri.org...
> > Are there any guidelines on where and when to use exceptions?
> 
> See http://www.boost.org/more/error_handling.html

Thanks for the link. I had already found this link but was confused on
some of advice it gave. The question below are some of my confusion
about using exceptions wisely. What I am seeking for each of them is an
example explaining how it implements a solution.

1)  Use virutal inheritance. I see the example and can understand why
its wrong I just do not understand how to fix it. 
 
2) Don't embed a std::string ... How can I use the data I have at the
point of the error safely? I want to provide a debug message to the user
that will lead them to the answer. This affects 6) Expose relevant
information about the cause of the error. 

In my project I have a base class called BaseException that inherits
from std::exception.

class BaseException : public std::exception
{
        // virtual functions?
        virtual const char* what() const throw() = 0;
};

I want exceptions in the code to be obvious to what is wrong but use the
what() message to say why:

class DataTypeException : public BaseException
{
        DataTypeException (std::string msg)
        : Base_Exception(),
          m_msg(msg)
        {}

        // Specify virtual functions?
        virtual const char* what() const throw()
        {
             try
               {
                std::stringstream output;
                output << m_exception_name << ": " << m_message.c_str()
                               << std::endl;
                 return (output.str()).c_str();
         }
         catch(std::exception &)
                {
                return m_exception_name;
                }
        }
  private:

        std::string m_msg;
};

Stephen
-- 
Email: storri_at_[hidden]