Why can't throw/catch a const string

Hi friends,
I found the following codes and the catch
block couldn't get the string correctly. Could you please help to see it. Thanks.

Code:

---

#include <iostream>
using namespace std;
void test(void)
{
        try
        {
                cout<<"This is try block!\n";
                throw "String";
//                char str[]="String";
//                throw str;
                cout<<"This is hidden block!\n";
        }
        catch(char *str)
        {
                cout<<"This is catch block!"<<endl;
                cout<<"The caught string is "<<str<<endl;
        }
}
int main(void)
{
        cout<<"Start"<<endl;
        test();
        cout<<"End"<<endl;
}

---

What happens when you attempt to catch a const char* (which is what "String" is)?

The line

Code:

---

throw "String";

---

should occur some errors.
I got a debug error when running the code:
Project XX raised exception class const char * with message 'Exception Object Address:0x8F444E' in CB2007.

If your debugger is set to pop up a message when any exception occurs, then you will get that message even if it will be caught. The question is whether the catch block is entered. Can you continue when the message comes up? Or run it but not through the debugger.

I also tried the following code to catch the exception but I found the exception type is unkonwn
and not be "char *"

Code:

---

#include <iostream>
using namespace std;
void test(void)
{
        try
        {
                cout<<"This is try block!\n";
                throw "String";
//                char str[]="String";
//                throw str;
                cout<<"This is hidden block!\n";
        }
        catch(char *str)
        {
                cout<<"This is catch block!"<<endl;
                cout<<"The caught string is "<<str<<endl;
        }
        catch(...)
        {
                cout<<"This is public catch block!"<<endl;
        }
}
int main(void)
{
        cout<<"Start"<<endl;
        test();
        cout<<"End"<<endl;
}

---

/*output
Start
This is try block!
This is public catch block!
End
*/

I run the program in windows console and the "Debug error" pops up.

If touch on "Ignore" the following is the output:
/*output
Start
This is try block!

This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.
*/

Quote:

---

Originally Posted by chenayang

I also tried the following code to catch the exception but I found the exception type is unkonwn

---

The exception type is not unknown. Daved just told you what it is.

Hi Daved and brewbuck,
Thank you very much.
Got it.

Code:

---

catch(const char *str)

---

.
But I'm still confused about when I need to add the "const".
Could you please show me more about how to use the "const" especially when it is needed?

For example if

Code:

---

throw 'C';

---

for catch block the const is not necessarily need.

Code:

---

        catch(char str)
//          catch(const char str) is also OK

---

A string literal such as "My string" is const. Simply because it is treated as such by the language and is typically stored in some read-only memory.
You can't catch long with int, either, so type matters.

Why on earth would anyone want to throw a literal string instead of an object anyways?