It looks better than Delta

[PenelopeFudd]

Hi; I've been using 'Delta', from http://delta.tigris.org/using_delta.html , and I was wondering if perl-reduce is better. I guess it must be, since perl-reduce at least knows something about the language! Does perl-reduce do a binary search?

[wumpus]

It's probably fair to say that Delta does better than perl-reduce some of the time, and vice versa. I am depending on B::Deparse for deformatting, but some of the original formatting sneaks through it. Sounds like Delta is less sensitive to that, but, since it doesn't know perl syntax it probably screws up some of the time. I should probably try stealing Delta's parser thingie to run after B::Deparse... B::Deparse at least makes all of the strings a lot more normalized.

perl-reduce does a line-at-a-time search right now, so it's not very fast.

What I really really really need is more real examples of crash-inducing code. Can you provide some?

[PenelopeFudd]

Well, I've broadened my definition of crash-inducing to just 'has a bug', and I use delta to minimize for that. It's true that delta doesn't know anything about perl constructs, and wastes time testing things that couldn't possibly run. My solution was to write a minimal version of the c preprocessor CPP that only understands un-nested ifdefs and ifndefs, which is what diff -D generates, and the test script accepts a list of ifdef targets, uses my CPP to create a modified input file, checks it for syntax with perl -c, then runs it to see if it still exhibits the bug or other interesting behaviour. The ifdef targets have to be unique, or else they all get turned on or off at the same time, but I've got a gawk script to renumber them.

So, instead of crash-inducing code, it could look for code that runs differently before and after B::deparse, for instance. Of course, that would be tricky if B::deparse is the first step! :-). I used delta to minimize a program that decrypted a file and printed it to stdout, among many other things; the resulting program was simple and did only that which I tested for (grep for the decrypted plaintext from stdout).

What about modifying codesmith to emit perl instead?

Greg Lindahl notifications@github.com wrote:

It's probably fair to say that Delta does better than perl-reduce some of the time, and vice versa. I am depending on B::Deparse for deformatting, but some of the original formatting sneaks through it. Sounds like Delta is less sensitive to that, but, since it doesn't know perl syntax it probably screws up some of the time. I should probably try stealing Delta's parser thingie to run after B::Deparse... B::Deparse at least makes all of the strings a lot more normalized.

perl-reduce does a line-at-a-time search right now, so it's not very fast.

What I really really really need is more real examples of crash-inducing code. Can you provide some?

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