Re: [Outreachy kernel] Re: Coccinelle Constification

[Elizabeth Ferdman <gnudevliz@gmail.com>]

On Sat, Oct 15, 2016 at 10:33:11PM -0700, Bhumika Goyal wrote:
> 
> Hey Liz,
> 
> Eva has already explained the process well but I would like to
> share my approach :
> 
> 1. Firstly, I find all structures of the form static struct s i ={...};
> by using the script:
> @r disable optional_qualifier@
> identifier s,i;
> @@
> * static struct s i ={...};
> disable optional_qualifier is used here as we want to look only for
> the non-const structures.
> 
> 2. Now pick a structure instance from a file and look how it is used
> in that file.
> If the structure's fields are not getting modified => it can be
> declared as const.
> You will have to analyze the usage carefully so that nothing is missed.
> Also, you can do a grep to be sure that all the referenced are covered.
> 
> 3. After this you can write a Coccinelle script to constify all the
> instances that follows this particular pattern of usage.
> 
> Make a rule in the script which matches the structure's reference that 
> is justified for const declaration and stores the reference position.
> Look for the @ok@ rule in my scripts.
> Now make another rule which looks for any other reference other 
> than the above one and stores this position as well.
> Look for @bad@ rule for this step.
> Next, add another rule @depends on !bad disable optional_qualifier@
> that declares the structure as const.
> 
> 4. After doing the changes compile the affected drivers and run
> size <affected_file_name> to get the size details of the affected
> file.
> 
Hey Bhumika,
Thanks for your reply and all the advice. I understand a little
bit more about what's going on in those scripts now and I will give it a
try...

Liz

> I hope this helps :)
> 
> Thanks,
> Bhumika
> 
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