Thread: Problems with exceptions

I have a problem with handling exceptions. It is as below:

I have a class lets say ABC (in ABC.h):

Code:

class ABC {
              public:
                    ABC(const char *name="ME";
                          ) throw (Ex,Exfile);
               ABC(const ABC& Y)
                       throw();
               virtual ~ABC();
              };

Next I have the constructors defined as:

Code:

ABC::ABC(const char* _name)
             throw(Ex,Exfile);

ABC::ABC(const ABC& Y):name()
              {
             try {Init();
                    Copy(Y);
                   }
           catch(Ex &)
                            {  }

}

Further I have Ex structure as:

Code:

struct Ex{ int errornu;
                 Ex(int erronu);
              virtual  ~Ex();
            };

}


upon compilation of the program I get the following error:

Code:

declaration of `ABC::ABC(const ABC &)' throws different exception.
ABC.h:19: previous declaration here

Can any one help in resoving this error?

Code:

throw();

throw() re-throws the current exception and is usually used only in catch blocks. You need to actually throw a type.

Code:

class aclass {};

void fuunction(void) {
    throw aclass();
}

try {
    function();
}
catch(aclass e) {
    // error
}

Code:

ABC(const ABC& Y) throw();

In this case, I believe throw specifies that the function cannot throw an exception, while throw(type) specifies an exception of type can be thrown (correct me if I'm wrong)

Edit: This looks like a mistake to me:

Code:

   ABC(const char *name="ME";) throw (Ex,Exfile);

Originally Posted by dwks

Code:

throw();

throw() re-throws the current exception and is usually used only in catch blocks. You need to actually throw a type.

Code:

class aclass {};

void fuunction(void) {
    throw aclass();
}

try {
    function();
}
catch(aclass e) {
    // error
}

This line:

Code:

ABC(const ABC& Y)
         throw();

is a function prototype--not a function definition, and it can be rewritten like this:

Code:

ABC(const ABC& Y) throw();

throw() is an exception specification which enforces which exceptions a function is allowed to throw(). A function can only throw the exceptions listed between the parentheses, and if you don't specify any then the function is not allowed to throw any exceptions. Here are some examples:

Code:

#include<iostream>
using namespace std;

void someFunc() throw(const char*)
{
	throw("hello exception");
}

int main()
{
	try
	{
		someFunc();
	}
	catch(const char* message)
	{
		cout<<message<<endl;
	}

	return 0;
}

Code:

#include<iostream>
using namespace std;

void someFunc() throw()
{
	try
	{
		throw("hello exception");
	}
	catch(...)
	{
		cout<<"exceptions that can't be thrown."<<endl;
	}
}

int main()
{
	try
	{
		someFunc();
	}
	
	catch(const char* message)
	{
		cout<<message<<endl;
	}

	return 0;
}