Error Condition Testing

This topic applies to:

Edition	Visual Basic	C#	C++	Web Developer
Express			Native only
Standard			Native only
Pro and Team			Native only

Table legend:

	Applies
	Does not apply
	Command or commands hidden by default.

You can use assertions to test for error conditions at a point in your code where any errors should have been handled. In the following example, a graphic routine returns an error code or zero for success.

myErr = myGraphRoutine(a, b);

/* Code to handle errors and
   reset myErr if successful */

ASSERT(!myErr); -- MFC version
_ASSERT(!myErr); -- CRT version

If the error-handling code works properly, the error should be handled and myErr reset to zero before the assertion is reached. If myErr has another value, the assertion fails, the program halts, and the Assertion Failed Dialog Box appears.

Assertion statements are not a substitute for error-handling code, however. The following example shows an assertion statement that can lead to problems in the final release code:

myErr = myGraphRoutine(a, b);

/* No Code to handle errors */

ASSERT(!myErr); // Don't do this!
_ASSERT(!myErr); // Don't do this, either!

This code relies on the assertion statement to handle the error condition. As a result, any error code returned by myGraphRoutine will be unhandled in the final release code.

See Also

Concepts

Result Checking

Logic Error Catching

Assertions