[Cocci] Remove entire multidecl

[Cocci] Remove entire multidecl

[Christoph Böhmwalder]

So I've looked around in the demos/ and tests/ as well as the documentation,
but I can't seem to figure out what I'm doing wrong:

test.c
------
int x, y;


test.cocci
----------
@@
identifier x, y;
@@
- int x, y;


Should be pretty straightforward, but the rule does not match. Is there
another syntax to use here? In my real use case, I'm trying the same thing
within a function, and that doesn't match either.

Also, while playing around with it, I found this weird behaviour:

@@
identifier x, y;
@@
- int x;

Yields:

--- test.c
+++ /tmp/cocci-output-6916-8bc8e1-test.c
@@ -1 +1 @@
-int x, y;
+


Not exactly what I expected...

Thanks,
--
Christoph Böhmwalder
LINBIT | Keeping the Digital World Running
DRBD HA —  Disaster Recovery — Software defined Storage
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Re: [Cocci] Remove entire multidecl

[Julia Lawall]

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On Thu, 8 Aug 2019, Christoph Böhmwalder wrote:

> So I've looked around in the demos/ and tests/ as well as the documentation,
> but I can't seem to figure out what I'm doing wrong:
>
> test.c
> ------
> int x, y;
>
>
> test.cocci
> ----------
> @@
> identifier x, y;
> @@
> - int x, y;
>
>
> Should be pretty straightforward, but the rule does not match. Is there
> another syntax to use here? In my real use case, I'm trying the same thing
> within a function, and that doesn't match either.
>
> Also, while playing around with it, I found this weird behaviour:
>
> @@
> identifier x, y;
> @@
> - int x;
>
> Yields:
>
> --- test.c
> +++ /tmp/cocci-output-6916-8bc8e1-test.c
> @@ -1 +1 @@
> -int x, y;
> +
>
>
> Not exactly what I expected...

SmPL doesn't support patterns with multiple variable declarations, because
there is really no way to tell whether they will be on one line or
multiple lines.

I'm not sure why the latter is not what you expected.  If you only
expected to remove the int x, then x should not have been an identifier
metavariable.

Basically, it is matching the pattern multiple times on the same code,
once for each variable.  If these matches cause all of the variables to go
away, the type and the ; are removed as well.

It seems that this resulted in adding a blank line.  That is indeed not
really ideal.

julia

>
> Thanks,
> --
> Christoph Böhmwalder
> LINBIT | Keeping the Digital World Running
> DRBD HA —  Disaster Recovery — Software defined Storage
> _______________________________________________
> Cocci mailing list
> Cocci@systeme.lip6.fr
> https://systeme.lip6.fr/mailman/listinfo/cocci
>

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Re: [Cocci] Remove entire multidecl

[Markus Elfring]

> > Not exactly what I expected...


>
> SmPL doesn't support patterns with multiple variable declarations,

How are the chances to adjust this software limitation?


> because
 there is really no way to tell whether they will be on one line
> or
 multiple lines.


Will it become more interesting to make such a case distinction possible?


> Basically, it is matching the pattern multiple times on the same code,
> once for each variable.

Would you like to achieve that metavariables of the same type (or kind)
can refer to different source code?


> It seems that this resulted in adding a blank line.  That is indeed not
> really ideal.

Was just a blank line left over after the deletion of declarations
(which looks like an addition in the diff format)?

Would you occasionally prefer to omit it (because of pretty-printing)?

Regards,
Markus
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