Porblem with an error() function

**pibo99** · 01-19-2015

Hello, I'm studying C++ by two months using the book : programming principles and practice using C++, I'm on chapter 5 now studying error reporting. The author in this chapter uses this example to show to the readers the run time errors.

Code:

 #include "std_lib_facilities"

    int area(int length, int width)
    {

    return length*width;

    }

    int framed_area(int x, int y)
    {

    return area(x - 2, y - 2);

    }

    int main()
    {

    int x = -1;
    int y = 2;
    int z = 4;

    
    int area1 = area(x, y);

    int area2 = framed_area(1, z); 
    int area3 = framed_area(y, z); 

    }

this code produces a run-time error due to the division of area1 with 0.
Subsequently, the author introduces a facilitation contained in the header file which he wrote called error (). My problem is that when this function call should produces a system error over a string literal that we passed as an argument to the function, instead my program code at runtime produces a screen that reports:

>> Microsoft visual C++ runtime library

>> debug error!
>> program:..dio
>> 2013\Projects\learnprogramming\Debug\learnprogramm ing.exe
>> abort() has been called

What could be happened ? is this a problem of the function implementation ?

I thought that there was something wrong with this program so I decided to write a simple selection program using error() but it produced the same errors.

for example :

Code:

int main ()
{

int n = 0; 

cout << "Enter a positive value "; 
cin >> n; 

if(n >0)
cout << "Ok\n"; 
else error ("not a positive value"); 
}

I am

just wondering if the message I get is normal ?

**grumpy** · 01-19-2015

There is no division, let alone a division by zero, in the first sample of code you have shown.

The second sample of code has no relationship to the first. Without knowing what error() does, nobody has a hope of guessing whether it is normal for it to call abort().

If you are going to post, the onus on you is to provide information - including code samples - that is actually representative of your problem. You have not done that, so you have effectively eliminated the chance of any forum member providing you useful advice.

**pibo99** · 01-20-2015

Originally Posted by grumpy

There is no division, let alone a division by zero, in the first sample of code you have shown.

The second sample of code has no relationship to the first. Without knowing what error() does, nobody has a hope of guessing whether it is normal for it to call abort().

If you are going to post, the onus on you is to provide information - including code samples - that is actually representative of your problem. You have not done that, so you have effectively eliminated the chance of any forum member providing you useful advice.

Sorry I forgot to post the link with the descritption of error
here is : http://www.stroustrup.com/Programmin...b_facilities.h

For the code I have shown, there is no division because I'm a mess, sorry, I forgot to write just one line after the definition of area 3 : double ratio = double(area1) / area3;

**grumpy** · 01-20-2015

The error() function provided by that sample (from Stroustrup) throws an exception. If an exception is not caught, std::terminate() is called. std::terminate(), by default, calls abort(). Your code does not catch any exceptions.

So, yes, when calling that error() function, it is normal for abort() to be called. No, that is not a problem with the function implementation - throwing an exception is certainly one logical way of handling an error. The problem is that your code is not catching and handling exceptions - which it needs to do in order to respond to them.

Since area3 will have a value of zero in your code, dividing by area3 will divide by zero. That is, strictly speaking, undefined behaviour. One common behaviour, however, is to terminate due to division by zero.

**Elysia** · 01-20-2015

This is normal because you let an exception propagate out of scope in main. You need to catch it with a try-catch block.
I would also suggest you run the program using the debugger to catch where these exceptions are thrown if you need to debug your program.

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