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Exception handling not performing?

kilrothy (9)
This is just a section of the code as the program runs as expected before I started adding exception handling. Still a new subject for me and I reviewed the tutorial here and can't seem to figure out why my catch statement can catch about as well as a no-armed man.

I run the code and input 8, the debugger hangs at the correct throw statement. or full on crashes the program. I tried defining the catch statement to catch an int as well as the throw statement and the program still hangs at the throw statement. I am sure I am missing something simple but I am going bald from scratching my head. Anyone able to help me out?

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         cin >> choice1;
       do{ //loop until exceptioncheck=true
            try{
                if (cin.fail()) //exceptioncheck for non int input
                {
                    cin.clear();
                    cin.ignore();
                    throw;
                }
                else if (choice1>7||choice1<1)
                    throw;
                    exceptioncheck=true;
                }
                catch(...)
                {
                     cout<<"Choice must be a number from 1-7\n";
                     cout << "Your choice: ";
                     cin >> choice1;
                }Put the code you need help with here.

salem c (3700)
Your catch is inside the try.

It should be
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try {
}
catch ( ) {
}


mbozzi (3933)
An exception is an object - like an int or a std::string or a std::runtime_error. The throw keyword causes an exception object to propagate, but we need to say which object we want to throw.

For example, you've got to throw something:
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try 
{
  throw 24; // throw 24, an int
} 
catch(int const& e) // note: catch exceptions by const reference
{ // this catch block matches ints.
  std::cerr << "caught an int\n";

  // inside this catch block, there is a current exception object:
  // if we cannot handle the exception here, we can cause the current 
  // exception to be re-thrown

  std::cerr << "couldn't handle current exception " << e << '\n';
  throw;
} // later on in the program, we might encounter another catch block:
catch (...) // this catch block matches everything
{
  std::cerr << "caught something\n";
}


If the statement throw; appears without a current exception, std::terminate() is called.
Last edited on
kilrothy (9)
Thanks, I ended up going with :
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    do{ //loop until exceptioncheck=true
        try{
            if (cin.fail()) //exception check for non int input
            {
                cin.clear();
                cin.ignore();
                throw "Choice must be a number!\n";
            }
            else if (choice3>100||choice3<1) // exception check for int range
                throw "Choice must be a number from 1-100";
            exceptioncheck=true;
        }
        catch(const char* msg)
        {
            cerr << msg << endl;
            cout << "Your choice: ";
            cin >> choice3;
        }
    }


I must have missed the fine print about throw; terminates the program instead of throwing a generic exception that can be caught by catch(...) In my implementation I would be satisfied with a single error message after catch. This will come in handy for some of the more complex exception handling I have on the horizon.
mbozzi (3933)
The Core Guidelines has good information about using exceptions effectively:
https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#e-error-handling
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