[TUHS] Re: A fuzzy awk.

On Tue, May 21, 2024 at 12:09 AM Serissa <stewart(a)serissa.com> wrote: In the mid-late 1980s Bill Mckeeman worked with DEC's compiler product teams to introduce fuzz testing into our testing process. As with the C compiler work at DEC Cambridge, fuzz testing for other compilers (Fortran, PL/I) also found large numbers of bugs. The pushback from the compiler folks was mainly a matter of priorities. Fuzz testing is very adept at finding edge conditions, but most failing fuzz tests have syntax that no human programmer would ever write. As a compiler engineer you have limited time to devote to bug testing. Do you spend that time addressing real customer issues that have been reported or do you spend it fixing problems with code that no human being would ever write? To take an example that really happened, a fuzz test consisting of 100 nested parentheses caused an overflow in a parser table (it could only handle 50 nested parens). Is that worth fixing? As you pointed out, fuzz test failures tend to occur in clusters and many of the failures eventually are traced to the same underlying bug. Which leads to the counter-argument to the pushback. The fuzz tests are finding real underlying bugs. Why not fix them before a customer runs into them? That very thing did happen several times. A customer-reported bug was fixed and suddenly several of the fuzz test problems that had been reported went away. Another consideration is that, even back in the 1980s, humans weren't the only ones writing programs. There were programs writing programs and they sometimes produced bizarre (but syntactically correct) code. -Paul W.