Re: random debugging, What should I prepare for a PL PhD program

gah4 <gah4@u.washington.edu> schrieb:
> On Friday, October 21, 2022 at 4:46:28 PM UTC-7, Thomas Koenig wrote:
>
> (snip)
>
>> Traditionally, internal compiler errors on invalid code have been
>> considered relatively easy. But you may always find a hard one...
>
> Reminds me of the story (I never saw anyone do it) that in the early days
> of compilers, they would feed cards from the card recycle bin to them.
>
> That is, as you note, a test of (most likely) invalid code.
>
> But now that we don't have card recycle bins, where do you get a good
> selection of invalid code to test them with?


There appears to be an art to it. At least one frequent submitter
of bug reports to gfortran has mastered, but I don't know how he
does it (and haven't asked).


An automated code generator which generates valid programs according
to the syntax and semantics rules of a langauge and then systematically
violates the rules (especially those prescribed outside the formal
grammar) one by one might be possible. Alternatively, it might
also be feasible to parse an existing code base and systematically
insert violations there.


I am not sure that research has been one on that, but it would
be interesting.
[I believe I have seen both random program generators and "fuzzers"
that make random changes to programs. This isn't just for compilers,
it's for anything that is supposed to interpret its input. -John]

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