What type of exception should I throw?

Question

After going through some links on exception handling (1, 2, and 3), I know that C++ programs can throw pretty much anything as exceptions (int, char*

Answer 1

I thought it might be interesting to post some real code for a change. This is the exception class my own utility library uses:

//---------------------------------------------------------------------------
// a_except.h
//
// alib exception handling stuff
//
// Copyright (C) 2008 Neil Butterworth
//---------------------------------------------------------------------------

#ifndef INC_A_EXCEPT_H
#define INC_A_EXCEPT_H

#include "a_base.h"
#include 
#include 

namespace ALib {

//------------------------------------------------------------------------
// The only exception thrown directly by alib
//------------------------------------------------------------------------

class Exception : public std::exception {

    public:

        Exception( const std::string & msg = "" );
        Exception( const std::string & msg, int line,
                        const std::string & file );

        ~Exception() throw();

        const char *what() const throw();
        const std::string & Msg() const;

        int Line() const;
        const std::string & File() const;

    private:

        std::string mMsg, mFile;
        int mLine;
};

//------------------------------------------------------------------------
// Macro to throw an alib exception with message formatting.
// Remember macro is not in ALib namespace!
//------------------------------------------------------------------------

#define ATHROW( msg )                                               \
{                                                                   \
    std::ostringstream os;                                          \
    os << msg;                                                      \
    throw ALib::Exception( os.str(), __LINE__, __FILE__ );          \
}                                                                   \


}  // namespace

#endif

And this is the .cpp file:

//---------------------------------------------------------------------------
// a_except.h
//
// alib exception handling stuff
//
// Copyright (C) 2008 Neil Butterworth
//---------------------------------------------------------------------------

#include "a_except.h"
using std::string;

namespace ALib {

//---------------------------------------------------------------------------
// exception with optional message, filename & line number
//------------------------------------------------------------------------

Exception :: Exception( const string & msg ) 
    : mMsg( msg ),  mFile( "" ), mLine(0) {
}

Exception :: Exception( const string & msg, int line, const string & file ) 
    : mMsg( msg ), mFile( file ), mLine( line ) {
}

//---------------------------------------------------------------------------
// Do nothing
//---------------------------------------------------------------------------

Exception :: ~Exception() throw() {
}

//------------------------------------------------------------------------
// message as C string via standard what() function
//------------------------------------------------------------------------

const char * Exception :: what() const throw() {
    return mMsg.c_str();
}

//------------------------------------------------------------------------
// as above, but as C++ string
//------------------------------------------------------------------------

const string & Exception :: Msg() const {
    return mMsg;
}

//---------------------------------------------------------------------------
// File name & line number
//---------------------------------------------------------------------------

int Exception :: Line() const {
    return mLine;
}

const string & Exception :: File() const {
    return mFile;
}

}  // namespace

// end