Re: Coccinelle Constification

[Bhumika Goyal <bhumirks@gmail.com>]

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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.

I hope this helps :)

Thanks,
Bhumika

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