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 08:56:10 +0100 [thread overview]
Message-ID: <57b5d1c9-72c1-6fff-a242-90f5f24f0972@web.de> (raw)
In-Reply-To: <fc56b970-4ca1-7734-c4bb-f57cae7a273f@web.de>
>> @@
>> expression dst, src, n, E;
>> @@
>> memcpy(dst, src, sizeof(
>> + *(
>> E
>> - [...]
>> + )
>> ) * n
>> )
>
> That's longer and looks more complicated to me
I point another possibility out to express a change specification
by the means of the semantic patch language.
How would you think about such SmPL code if the indentation
will be reduced?
> than what we currently have:
> @@
> expression dst, src, n, E;
> @@
> memcpy(dst, src, n * sizeof(
> - E[...]
> + *(E)
> ))
>
> Avoiding to duplicate E doesn't seem to be worth it.
I show other development preferences occasionally.
> I can see that indenting the sizeof parameter and parentheses could
> improve readability, though.
Thanks that you can follow such coding style aspects.
>> @@
>> 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?
But this transformation rule can probably be omitted if the usage
of SmPL disjunctions will be increased in a subsequent rule, can't it?
>> @@
>> type T;
>> T* dst_ptr, src_ptr;
>> T[] dst_arr, src_arr;
>> expression n, x;
>> @@
>> -memcpy
>> +COPY_ARRAY
>> (
>> ( dst_ptr
>> | dst_arr
>> )
>> ,
>> ( src_ptr
>> | src_arr
>> )
>> - , (n) * \( sizeof(T) \| sizeof(*(x)) \)
>> + , n
>> )
>
> That x could be anything -- it's not tied to the element size of source
> or destination. Such a transformation might change the meaning of the
> code, as COPY_ARRAY will use the element size of the destination behind
> the scenes. So that doesn't look safe to me.
Would you like to use the SmPL code “*( \( src_ptr \| src_arr \) )” instead?
>> @@
>> type T;
>> T* dst, src, ptr;
>> expression n;
>> @@
>> (
>> -memmove
>> +MOVE_ARRAY
>> (dst, src
>> - , (n) * \( sizeof(* \( dst \| src \) ) \| sizeof(T) \)
>> + , n
>> )
>> |
>> -ptr = xmalloc((n) * \( sizeof(*ptr) \| sizeof(T) \))
>> +ALLOC_ARRAY(ptr, n)
>> );
>
> memmove/MOVE_ARRAY and xmalloc/ALLOC_ARRAY are quite different;
These functions provide another programming interface.
> why would we want to jam transformations for them into the same rule
> like this?
Possible nicer run time characteristics by the Coccinelle software.
> The only overlap seems to be n.
These case distinctions can share also the metavariable “T” for the
desired source code deletion.
> Handling memmove/MOVE_ARRAY and memcpy/COPY_ARRAY together would make
> more sense, as they take the same kinds of parameters.
Would you like to adjust the SmPL code in such a design direction?
> I didn't know that disjunctions can be specified inline using \(, \|
> and \), though. Rules can be much more compact that way.
I hope that more corresponding software improvements can be achieved.
> Mixing languages like that can also be quite confusing.
I agree to this development concern.
>> Now I observe that the placement of space characters can be a coding style
>> concern at four places for adjusted lines by the generated patch.
>> Would you like to clarify remaining issues for pretty-printing
>> in such use cases?
>
> Ideally, generated code should adhere to Documentation/CodingGuidelines,
> so that it can be accepted without requiring hand-editing.
But how does the software situation look like if the original source code
would contain coding style issues?
It seems to be possible to specify SmPL code in a way so that even questionable
code layout would be preserved by an automatic transformation.
Regards,
Markus
next prev parent reply other threads:[~2019-11-17 7:59 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 [this message]
2019-11-17 13:40 ` René Scharfe
2019-11-17 18:19 ` Markus Elfring
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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