Re: GNU diff and git diff - difference on myers algorithm?

From: Jacob Keller <jacob.keller-re5jqeeqqe8avxtiumwx3w@public.gmane.org>
Date: Jul 17, 2015, 04:22 UTC
Message-ID: <CA+P7+xrOPS6NeQhte-ATdm2Nqo0PpmUAxS+XYzWDvZGtwPtWMw@mail.gmail.com>
In-Reply-To: <CAB=NE6UFMv0qu8fJ1P2-pJCF0tSGKoW+uKhfwt0jV5fj2wZGSQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

On Thu, Jul 16, 2015 at 12:07 PM, Luis R. Rodriguez <mcgrof-3uybbJdB1yH774rrrx3eTA@public.gmane.org> wrote:

Show 31 quoted lines

> On Fri, Jun 12, 2015 at 11:52 AM, Luis R. Rodriguez
> <mcgrof-3uybbJdB1yH774rrrx3eTA@public.gmane.org> wrote:
>> OK wells I'm curious about more research / effort when trying to
>> evaluate a diff with two seprate but adjoining preprocessor directives
>> and if anyone has implemented an optimizaiton option to let the diff
>> generator join them.
>>
>> For example, to let it infer that:
>>
>> --- a/test.c
>> +++ b/test.c
>> @@ -10,8 +10,6 @@ int main(int argc, char *argv[])
>>
>>  #ifdef FOO
>>         a = 4;
>> -#endif /* FOO */
>> -#ifdef FOO
>>         a = 5;
>>  #endif /* FOO */
>>
>> is possible.
>
> Anyone familiar if any tool exists today that would optimize this? Is
> anyone working on it? Would git be a good place for such a thing? I'd
> consider it as an option to optimize a diff. This for example is
> extremely useful for us working with Coccinelle where we have a tool
> writing code for us, while such an optimization might be useful to
> Coccinelle it would seem like a rather generic feature, its just not
> clear to me where to give such a tool a proper home.
>
>  Luis

I do not understand exactly what would be optimized in this case?

In any regards, that's not a diff transformation, that is a code transformation, and I would suggest starting with Coccinelle and seeing if you can get that to do what you want. http://coccinelle.lip6.fr/

Regards, Jake