Re: [Cocci] Matching variable declarations

[Valentin Schneider <valentin.schneider@arm.com>]

On 05/09/2019 13:03, Julia Lawall wrote:
>> I tried to write it as
>> ---
>> - T
>> + int
>> var
>> ? = E
>> ;
>> ---
>> but that doesn't seem to be a valid syntax.
> 
> No.  ? is restricted to complete statements.
> 

Makes sense now that I'm looking at other snippets, thanks.

>>
>>
>> Now, I'd like to match declarations of several variables in a single
>> statement as well.
>>
>> Say I want to get something like
>>
>> - long a, b = 2, c, d = 42, e;
>> + long a, b = 2, c, e;
>> + int d = 42;
>>
>>  (match on longs initialized to 42)
>>
>> My current attempt is
>> ---
>> @@
>> identifier var;
>> type T = long;
>> expression L, R;
>> @@
>>
>> T L,
>> - var = 42
>> R;
>> + int var;
>> ---
>> But that isn't valid either. How should I go about writing this sort of
>> rule?
> 
> Declaartions with multiple variables are tricky.  By the following may
> work:
> 
> - long
> + int
>   x;
> 
> Since you are leaving the variables alone in this case, I think this will
> match thing that declare multiple variables as well.
> 

I can't get it to match on something like

	long a, b = 42;

Perhaps a roundabout way of getting there - would it be possible to
specify a rule where an identifier has to be a variable? That way I could
at least print their use and cross-check the output diff (I don't expect
multiple variables declaration to be common for this, but would like to
have some way of raising a flag when it does occur).

>>
>> If you're curious, there's more context about what I'm trying to achieve
>> at:
>>
>> https://lore.kernel.org/lkml/20190902210558.GA23013@avx2/
> 
> I guess your next question will be about converting %ld to %d, etc.
> 
> It may be helpful to look at coccinelle/demos/format.cocci
> 

Thanks for the pointers & swift reply! Much appreciated.
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