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Subject: Re: [PATCH] coccinelle: misc: add swap script
To:     Julia Lawall <julia.lawall@inria.fr>
Cc:     cocci@systeme.lip6.fr, linux-kernel@vger.kernel.org
References: <20210216080133.455456-1-efremov@linux.com>
 <alpine.DEB.2.22.394.2102172224570.3081@hadrien>
From:   Denis Efremov <efremov@linux.com>
Message-ID: <c2b60288-3e46-14e3-9be2-3f75366a4b47@linux.com>
Date:   Thu, 18 Feb 2021 09:13:34 +0300
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On 2/18/21 12:31 AM, Julia Lawall wrote:
>> +@depends on patch@
>> +identifier tmp;
>> +expression a, b;
>> +type T;
>> +@@
>> +
>> +(
>> +- T tmp;
>> +|
>> +- T tmp = 0;
>> +|
>> +- T *tmp = NULL;
>> +)
>> +... when != tmp
>> +- tmp = a;
>> +- a = b;
>> +- b = tmp;
>> ++ swap(a, b);
>> +... when != tmp
> 
> In this rule and the next one, if you remove the final ; from the b = tmp
> line and from the swap line, and put it into context code afterwards, them
> the generated code looks better on cases like fs/xfs/xfs_inode.c in the
> function xfs_lock_two_inodes where two successive swap calls are
> generated.
> 
> There are also some cases such as drivers/net/wireless/ath/ath5k/phy.c in
> the function ath5k_hw_get_median_noise_floor where the swap code makes up
> a whole if branch. 

> In this cases it would be good to remove the {}.

How this can be handled?

If I use this pattern:
@depends on patch@
identifier tmp;
expression a, b;
@@

(
  if (...)
- {
-       tmp = a;
-       a = b;
-       b = tmp
+       swap(a, b)
        ;
- }
|
-       tmp = a;
-       a = b;
-       b = tmp
+       swap(a, b)
        ;
)

The tool fails with error:

EXN: Failure("rule starting on line 58: already tagged token:\nC code context\nFile \"drivers/net/wireless/ath/ath5k/phy.c\", line 1574, column 4, charpos = 41650\n  around = 'sort',\n  whole content = \t\t\t\tsort[j - 1] = tmp;") in drivers/net/wireless/ath/ath5k/phy.c

Thanks,
Denis