From: Markus Elfring <Markus.Elfring@web.de>
To: "René Scharfe" <l.s.r@web.de>
Cc: git@vger.kernel.org
Subject: Re: coccinelle: adjustments for array.cocci?
Date: Sun, 17 Nov 2019 19:19:40 +0100 [thread overview]
Message-ID: <eff19da9-3f9f-0cf0-1e88-64d2acdbabcd@web.de> (raw)
In-Reply-To: <37c84512-ba83-51ce-4253-ea0f7bd41de0@web.de>
> Whitespace is not what makes the above example more complicated than the
> equivalent rule below;
A different code layout might help in a better understanding for such
change specifications.
> separating the pieces of simple expressions does.
Will there occasionally be a need to change only the required source code parts?
>>> than what we currently have:
>>> @@
>>> expression dst, src, n, E;
>>> @@
>>> memcpy(dst, src, n * sizeof(
>>> - E[...]
>>> + *(E)
>>> ))
Are any circumstances to consider where only the essential implementation details
should be touched by an automatic software transformation?
>>>> @@
>>>> type T;
>>>> T *ptr;
>>>> T[] arr;
>>>> expression E, n;
>>>> @@
>>>> memcpy(
>>>> ( ptr, E, sizeof(
>>>> - *(ptr)
>>>> + T
>>>> ) * n
>>>> | arr, E, sizeof(
>>>> - *(arr)
>>>> + T
>>>> ) * n
>>>> | E, ptr, sizeof(
>>>> - *(ptr)
>>>> + T
>>>> ) * n
>>>> | E, arr, sizeof(
>>>> - *(arr)
>>>> + T
>>>> ) * n
>>>> )
>>>> )
>>>
>>> This still fails to regenerate two of the changes from 921d49be86
>>> (use COPY_ARRAY for copying arrays, 2019-06-15), at least with for me
>>> (and Coccinelle 1.0.4).
>>
>> Would you become keen to find the reasons out for unexpected data processing
>> results (also by the software combination “Coccinelle 1.0.8-00004-g842075f7”)
>> at this place?
>
> It looks like a bug in Coccinelle to me
We might stumble also on just another (temporary) software limitation.
> and I'd like to see it fixed
Would you like to support corresponding development anyhow?
> if that's confirmed, of course.
I am curious if further feedback will evolve for affected software areas.
> And I'd like to see Debian pick up a newer version, preferably containing that fix.
I assume that you can wait a long time for progress in the software
distribution direction.
> But at least until then our semantic patches need to work around it.
Would another concrete fix for the currently discussed SmPL script
be better than a “workaround”?
>> But this transformation rule can probably be omitted if the usage
>> of SmPL disjunctions will be increased in a subsequent rule, can't it?
>
> Perhaps, but I don't see how. Do you?
Obviously, yes (in principle according to my proposal from yesterday).
https://public-inbox.org/git/05ab1110-2115-7886-f890-9983caabc52c@web.de/
>> Would you like to use the SmPL code “*( \( src_ptr \| src_arr \) )” instead?
>
> That leaves out dst_ptr and dst_arr.
How many items should finally be filtered in the discussed SmPL disjunction?
> And what would it mean to match e.g. this ?
>
> memcpy(dst_ptr, src_ptr, n * sizeof(*src_arr))
The Coccinelle software takes care for commutativity by isomorphisms.
https://github.com/coccinelle/coccinelle/blob/19ee1697bf152d37a78a20cefe148775bf4b0e0d/standard.iso#L241
> At least the element size would be the same, but I'd rather shy away from
> transforming weird cases like this automatically.
Do you mean to specify additional restrictions by SmPL code?
> void *memmove(void *dest, const void *src, size_t n);
> void *memcpy(void *dest, const void *src, size_t n);
>
> COPY_ARRAY(dst, src, n)
> MOVE_ARRAY(dst, src, n)
Can the replacement of these functions by macro calls be combined further
by improved SmPL code?
>> Possible nicer run time characteristics by the Coccinelle software.
>
> How much faster is it exactly?
The answer will depend on efforts which you would like to invest
in corresponding (representative) measurements.
> Speedups are good, but I think readability of rules is more important
> than coccicheck duration.
I hope that a more pleasing balance can be found for the involved
usability factors.
>> But how does the software situation look like if the original source code
>> would contain coding style issues?
>
> The same: Generated code should not add coding style issues.
Such an expectation is generally nice. - But target conflicts can occur there.
> We can still use results that need to be polished, but that's a manual step
> which reduces the benefits of automation.
I am curious how the software development practice will evolve further.
Regards,
Markus
next prev parent reply other threads:[~2019-11-17 18:19 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-12 15:08 coccinelle: adjustments for array.cocci? Markus Elfring
2019-11-12 18:37 ` René Scharfe
2019-11-13 2:11 ` Junio C Hamano
2019-11-13 8:49 ` Markus Elfring
2019-11-14 2:03 ` Junio C Hamano
2019-11-14 13:15 ` Markus Elfring
2019-11-14 16:41 ` René Scharfe
2019-11-14 17:14 ` Markus Elfring
2019-11-14 17:46 ` René Scharfe
2019-11-15 11:11 ` git-coccinelle: " Markus Elfring
2019-11-15 14:20 ` Markus Elfring
2019-11-15 18:50 ` Markus Elfring
2019-11-16 1:00 ` [Cocci] " Julia Lawall
2019-11-16 6:57 ` Markus Elfring
2019-11-16 8:29 ` Markus Elfring
2019-11-16 17:57 ` Julia Lawall
2019-11-16 18:29 ` Markus Elfring
2019-11-15 20:37 ` coccinelle: " Markus Elfring
2019-11-16 21:13 ` René Scharfe
2019-11-17 7:56 ` Markus Elfring
2019-11-17 13:40 ` René Scharfe
2019-11-17 18:19 ` Markus Elfring [this message]
2019-11-19 19:14 ` René Scharfe
2019-11-19 20:21 ` Markus Elfring
2019-11-21 19:01 ` René Scharfe
2019-11-16 16:33 ` Markus Elfring
2019-11-16 21:38 ` René Scharfe
2019-11-17 8:19 ` Markus Elfring
2019-11-17 13:40 ` René Scharfe
2019-11-17 18:36 ` Markus Elfring
2019-11-19 19:15 ` René Scharfe
2019-11-18 16:10 ` [PATCH] coccinelle: improve array.cocci Markus Elfring
2019-11-19 19:15 ` René Scharfe
2019-11-20 9:01 ` Markus Elfring
2019-11-21 19:02 ` René Scharfe
2019-11-21 19:44 ` Markus Elfring
2019-11-22 15:29 ` SZEDER Gábor
2019-11-22 16:17 ` Markus Elfring
2019-11-22 5:54 ` [PATCH] " Junio C Hamano
2019-11-22 7:34 ` Markus Elfring
2020-01-25 8:23 ` Markus Elfring
-- strict thread matches above, loose matches on Subject: below --
2019-11-12 15:08 coccinelle: adjustments for array.cocci? Markus Elfring
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