Re: [Cocci] Problem writing simple patch

[David Frey <dpfrey@gmail.com>]

On 11/25/2019 1:10 PM, Julia Lawall wrote:
> On Mon, 25 Nov 2019, David Frey wrote:
> 
>> Hi,
>>
>> I'm trying to write a .cocci file to transform all calls to a function
>> "f(ex)" to something like this:
>>
>> #ifdef USE_F
>> f(ex)
>> #else
>> g(ex)
>> #endif
>>
>> The function has this signature:
>> bool f(int x);
>>
>> This is the patch that I tried to use:
>> @@
>> expression ex;
>> @@
>> +#ifdef USE_F
>>  f(ex)
>> +#else
>> +g(ex)
>> +#endif
>>
>>
>> This is the result of running it:
>> $ spatch --show-c --sp-file test.cocci test.c
>> init_defs_builtins: /usr/bin/../lib/coccinelle/standard.h
>> plus: parse error:
>>   File "test.cocci", line 7, column 1, charpos = 50
>>   around = 'g',
>>   whole content = +g(ex)
>>
>> What is wrong with the patch above?
> 
> Coccinelle doesn't currently support adding ifdefs on expressions, only on
> statements.
> 
> You could try for some typical usage contexts, like
> 
> +ifdef...
> x = f(ex);
> +#else
> +x = g(ex);
> +#endif
> 
> julia
> 


Hi Julia,

Thanks for your explanation and your suggestion.  I ended up creating a
new header that was like this:

#ifdef SOMETHING
#define foo_backport_x(_arg) bar_x(_arg)
#define foo_backport_y(_arg) bar_y(_arg)
#else
#define foo_backport_x(_arg) foo_x(_arg)
#define foo_backport_y(_arg) foo_y(_arg)
#endif

and then I defined coccinelle rules to change:
foo_x -> foo_backport_x
foo_y -> foo_backport_y

It's not the most elegant solution, but it works.

David
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