[Cocci] Replacing one (specific!) type with another

[Nikolaus@rath.org (Nikolaus Rath)]

On Oct 05 2016, Julia Lawall <julia.lawall@lip6.fr> wrote:
>> 1. What would I need to do if I don't want to replace a struct but
>>    something typedef'd? (my_type *ptr --> new_type *ptr).
>
> Coccinelle needs to know that the thing is a typedef.  So this time, you
> can start your rule with
>
> @@
> typedef my_type;
> typedef new_type;
> @@

Makes sense, thanks!

>> 2. ..and how would I go about if instead of the type, I want to replace
>>    a variable name? (my_type *ptr --> my_type *pointer).
>
> I'm not completely sure what the issue is here.  Do you specifically want
> to convert ptr to pointer?  Is the type important?  To make exactly what
> you have written, you could put:
>
> @@
> typedef my_type;
> idexpression mytype * p1;
> @@
>
> - ptr at p1
> + pointer
>
> This checks for the word ptr, and also checks that it is an identifier of
> the right type.  I haven't tested it, so let me know if there is any
> problem.

Well, I don't have an actual use-case anymore. My problem is solved, I'm
just curious what else I could do with Coccinelle to do :-).

Somehow I'm having a really hard time grasping the fundamentals. The
first two examples make sense - I could adapt them for similar
situations. But then, I still have absolutely no idea how I would come
up with the third example, or how to adapt it. What does "idexpression"
mean? What does "ptr at p1" mean? Is this documented anywhere? 

I'd hate to waste your time asking tons of such trivial questions on the
mailing list, but I just can't find any helpful documentation at all...


Best,
-Nikolaus
-- 
GPG encrypted emails preferred. Key id: 0xD113FCAC3C4E599F
Fingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F

             ?Time flies like an arrow, fruit flies like a Banana.?