1. A method performed by a diagnostic tool process executing on a computer, the method comprising: receiving an expression to be evaluated based on a state of a target program process, the expression including a call to a first function that is included in the target program process, evaluation of the first function being dependent upon evaluation of a second function that is not included in the target program process; and evaluating the expression by at least emulating the execution of the first function and the second function within a process other than the target program process.