Re: [Outreachy kernel] Coccinelle Constification

[Eva Rachel Retuya <eraretuya@gmail.com>]

Hello Liz,

I'm a fellow applicant so I might be wrong on some things but let me
share my experience so far with coccinelle usage.

On Sat, Oct 15, 2016 at 07:21:46PM -0700, Elizabeth Ferdman wrote:
> I'd like to try doing constification using Coccinelle but I'm having
> trouble starting on this task. Bhumika Goyal has submitted lots of these
> and I've looked at the scripts she uses but I'm very confused about the
> process.
> 
> Do you identify the structs that
> need to be const first, then write the cocci script? If not, then what
> is a basic script to use to find structs that need to be const? I can't
> find any specific documentation that pertains to constification and
> coccinelle.
> 

It depends on your approach. Sure you can manually identify by code
tracing if the struct qualifies to be made const then make a script to
write the changes esp. if there are lots of places to be changed.

You can also define a set of properties/situations where declaring the
structure const is justified like this:
https://git.kernel.org/cgit/linux/kernel/git/gregkh/staging.git/commit/drivers/staging?h=staging-testing&id=1c099ed63f8363228a0b075a25511c9feb90e03f

and from there write your script so that it'll detect instances where
the criteria you previously defined is met. Now that covers detection,
for making the changes I suggest you write another one to cater
specifically to a specific driver and also include the transformation
that needs to be done.

About the basic script, I suggest you try to match any struct
declaration first using the disable optional_qualifier isomorphism
stated on the project's small task 1. Start small then build your way
up.

Once you get your basic script running, coordinate the rest with Julia.
Bhumika's patches are great reference, just observe the 'criteria' at
which structures can be deemed 'const'.

I hope I clear some of your confusion,
Eva

> Thanks,
> Liz
> 
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