Why Programs Fail, 2nd Edition

CHAPTER 7 Deducing Errors

In this chapter, we begin exploring the techniques for creating hypotheses introduced in Chapter 6. We start with deduction techniques—reasoning from the abstract program code to the concrete program run. In particular, we present program slicing, an automated means of determing possible origins of a variable value. Using program slicing, one can effectively narrow down the number of possible infection sites.

7.1 ISOLATING VALUE ORIGINS

Oops! We have observed something that should not happen—the program has reached some state it never should have reached. How did it get into this state? Kernighan and Pike (1999) give a hint:

Something impossible occurred, and the only solid information is that it really did occur. ...