Re: Errors in TCPStream

[David Sugar]

The older mailing list is at address@hidden  A
std::exception based exception class hierarchy is actually in development.

David

On Thu, 25 Oct 2001, Tommi [ISO-8859-1] M?kitalo wrote:

> Hi,
>
> I am working on a FTP-class and use CommonC++ as a base. But I
> discovered difficulties catching errors. Here is a example-code:
>
>   TCPStream* socket;
>   try
>   {
>     cout << "connecting" << endl;
>     socket = new TCPStream(InetHostAddress("localhost"), 4711);
>
>     cout << "delete" << endl;
>     delete socket;
>     cout << "OK" << endl;
>   }
>   catch(Socket* s)
>   {
>     cerr << "socket error " << s->getErrorNumber() << endl
>          << s->getErrorString() << endl;
>   }
>
> If there is no server listening I should get a SOCKET_CONNECT_FAILED.
> But the problem is, that you use the this-pointer in socket-class to
> throw the exception. But it isn't valid in the catch-block, because the
> constructor isn't fully executed. It makes no difference when I declare
> my socket on the stack like this:
>
>   try
>   {
>     cout << "connecting" << endl;
>     TCPStream socket(InetHostAddress("localhost"), 4711);
>     cout << "OK" << endl;
>   }
>   catch(Socket* s)
>   {
>     cerr << "socket error " << s->getErrorNumber() << endl
>          << s->getErrorString() << endl;
>   }
>
> It is better to create a exception-class and throw that. Maybe you can
> derive from std::exception.
>
> Like this:
>
> class SocketException : public std::exception
> {
>     sockerror_t errid;
>     std::string errstr;
>   public:
>     SocketException(sockerror_t err, const char* errs)
>       : errid(err),
>         errstr(errs)
>         { }
>     virtual const char* what() const
>     { return errstr.c_str(); }
>     sockerror_t getErrorNumber() const  { return errid; }
>     std::string getErrorString() const  { return errstr; }
> };
>
> Now this should work:
>
>   try
>   {
>     cout << "connecting" << endl;
>     TCPStream socket(InetHostAddress("localhost"), 4711);
>     cout << "OK" << endl;
>   }
>   catch(SocketException s)
>   {
>     cerr << "socket error " << s->getErrorNumber() << endl
>          << s->getErrorString() << endl;
>   }
>
> Or even:
>
>   try
>   {
>     cout << "connecting" << endl;
>     TCPStream socket(InetHostAddress("localhost"), 4711);
>     cout << "OK" << endl;
>   }
>   catch(exception e)
>   {
>     cerr << "exception occured: " << e.what() << endl;
>   }
>
> By the way, is there a mailing-list for CommonC++ users, where I can
> subscribe?
>
> Tommi M?kitalo
>
>
> _______________________________________________
> Bug-commoncpp mailing list
> address@hidden
> http://mail.gnu.org/mailman/listinfo/bug-commoncpp
>