Coccinelle Archive on lore.kernel.org
 help / color / Atom feed
From: Denis Efremov <efremov@linux.com>
To: Julia Lawall <julia.lawall@inria.fr>
Cc: cocci@systeme.lip6.fr, linux-kernel@vger.kernel.org
Subject: Re: [Cocci] [PATCH] coccinelle: misc: add swap script
Date: Thu, 18 Feb 2021 14:34:04 +0300
Message-ID: <afd7f80a-90c9-9d05-cc78-aacc5495174b@linux.com> (raw)
In-Reply-To: <alpine.DEB.2.22.394.2102181227230.2748@hadrien>



On 2/18/21 2:29 PM, Julia Lawall wrote:
> 
> 
> On Thu, 18 Feb 2021, Denis Efremov wrote:
> 
>>
>>
>> On 2/18/21 1:17 PM, Julia Lawall wrote:
>>>
>>>
>>> On Thu, 18 Feb 2021, Denis Efremov wrote:
>>>
>>>>
>>>>
>>>> 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
>>>
>>> A disjunction basically says "at this node in the cfg, can I match the
>>> first patter, or can I match the second pattern, etc."  Unfortunately in
>>> this case the two branches start matching at different nodes, so the short
>>> circuit aspect of a disjunction isn't used, and it matches both patterns.
>>>
>>> The solution is to just make two rules.  The first for the if case and the
>>> second for everything else.
>>>
>>
>>   if (...)
>> - {
>> -       tmp = a;
>> -       a = b;
>> -       b = tmp
>> +       swap(a, b)
>>         ;
>> - }
>>
>>
>> This produces "single-line ifs".
>> Maybe generated patches can be improved somehow?
>> Moving -+; doesn't help in this case.
> 
> There is clearly some problem with the management of newlines...
> 
> The other alternative is to just have one rule for introducing swap and
> another for removing the braces around a swap, ie
> 
> if (...)
> - {
>   swap(...);
> - }
> 
> I don't think it would be motivated to remove the newline in that case.

Yes, this works. I'll send v2.

Thanks
_______________________________________________
Cocci mailing list
Cocci@systeme.lip6.fr
https://systeme.lip6.fr/mailman/listinfo/cocci

  reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-16  8:01 Denis Efremov
2021-02-16 18:05 ` Markus Elfring
2021-02-17 21:31 ` Julia Lawall
2021-02-18  6:13   ` Denis Efremov
2021-02-18 10:17     ` Julia Lawall
2021-02-18 11:03       ` Denis Efremov
2021-02-18 11:29         ` Julia Lawall
2021-02-18 11:34           ` Denis Efremov [this message]
     [not found]       ` <50eb8319-a552-c749-6143-7e24a8778a04@web.de>
2021-02-18 20:03         ` Julia Lawall
2021-02-19  9:05 ` [Cocci] [PATCH v2] coccinelle: misc: add minmax script Denis Efremov
2021-02-19  9:07   ` Denis Efremov
2021-02-19  9:24 ` [Cocci] [PATCH v2] coccinelle: misc: add swap script Denis Efremov
2021-03-03 16:37   ` Julia Lawall
2021-03-05 10:09 ` [Cocci] [PATCH v3] " Denis Efremov
     [not found]   ` <afb06bbc-5c28-8a92-f205-c9a1c87c707c@linux.com>
2021-04-04 12:33     ` Julia Lawall

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=afd7f80a-90c9-9d05-cc78-aacc5495174b@linux.com \
    --to=efremov@linux.com \
    --cc=cocci@systeme.lip6.fr \
    --cc=julia.lawall@inria.fr \
    --cc=linux-kernel@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Coccinelle Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/cocci/0 cocci/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 cocci cocci/ https://lore.kernel.org/cocci \
		cocci@systeme.lip6.fr
	public-inbox-index cocci

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/fr.lip6.systeme.cocci


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git