Re: [TUHS] DEC Compilers (was: Re: SDB debugger

[Dan Cross <crossd@gmail.com>]

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On Tue, May 5, 2020 at 1:37 PM Paul Winalski <paul.winalski@gmail.com>
wrote:

> On 5/4/20, Win Treese <treese@acm.org> wrote:
> >
> > Andy Payne, a recent hire at the lab, had been an intern in DEC’s
> > semiconductor group, where he had worked on randomized testing for
> hardware
> > verification. With all the compilers available, he decided to hack up a
> > program to generate random small C programs with computable expected
> > outputs. His program then compiled the random code with each compiler and
> > tested the result. After finding a number of bugs this way, he got tired
> of
> > submitting the bug reports, and changed his program to write and submit
> the
> > bug reports automatically.
> >
> > This caused a little bit of consternation with some of the compiler
> teams at
> > first.
>
> I remember that very well.  IIRC it was called fuzz testing, and
> indeed it was controversial, for the reasons Bill McKeeman discusses
> in his paper. [1]  On the one hand, compiler developers said, "nobody
> would ever write something like that--we can't waste our time on these
> issues when there are real bugs waiting to be fixed."  On the other
> hand, some of the bugs that fuzz testing turned up provoked reactions
> such as, "OMG!  THAT caused the compiler to crash?"  I think the
> turning point was when fixing one of the fuzz testing bugs also fixed
> an obscure and hard-to-debug customer problem.  Intel's C and Fortran
> compiler team has also used random testing technology.
>

Ah, very cool. The same approach has come into favor again recently. I've
dealt personally with https://github.com/google/syzkaller, which is a
kernel fuzzer that generates random inputs to system calls and detects e.g.
panics. It's a neat approach.

        - Dan C.

> [1] https://www.hpl.hp.com/hpjournal/dtj/vol10num1/vol10num1art9.pdf
>
> -Paul W.
>

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