# V6118. The original exception object was swallowed. Cause of original exception could be lost.

The analyzer has detected that the original exception data was lost during rethrowing from a 'catch' block. The issue makes errors hard to debug.

Look at the example of the incorrect code:

    try {
      sb.append((char) Integer.parseInt(someString));
      ....
    } catch (NumberFormatException e) {
      throw new IllegalArgumentException();
    }

In this case, developers want to rethrow the caught exception but do not pass the necessary data in the form of a message and stack trace.

Here is the fixed code:

    try {
      sb.append((char) Integer.parseInt(someString));
      ....
    } catch (NumberFormatException e) {
      throw new IllegalArgumentException(e);
    }

The original exception is passed as an internal exception. It saves all data about the original error.

As another option to fix the issue, we can throw an exception with a message.

    try {
      sb.append((char) Integer.parseInt(someString));
      ....
    } catch (NumberFormatException e) {
      throw new IllegalArgumentException(
        "String " + someString + " is not number"
      );
    }

The original error stack has been lost, but the new exception data helps debug the code.

If we expect to lose exception data, we can replace the 'catch' parameter names with 'ignore' or 'expected'. In this case, the exception is not thrown.

This diagnostic is classified as:

CWE-390