[Cocci] Deleting unused declarations for variables with SmPL?

[Cocci] Deleting unused declarations for variables with SmPL?

[SF Markus Elfring]

Hello,

I have tried another simple script out for the semantic patch language.

@deletion@
identifier x;
type t;
@@
-t x;
 ... when != x


elfring@Sonne:~/Projekte/Linux/next-patched> spatch ~/Projekte/Coccinelle/Probe/delete_unused_variable1.cocci init/main.c
…
@@ -101,22 +101,6 @@
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/initcall.h>
-
-static int kernel_init(void *);
-
-extern void init_IRQ(void);
…


Now I wonder about the generated change suggestions.
Does such a transformation approach need any extensions for the safe handling
of function declarations?

Regards,
Markus
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Re: [Cocci] Deleting unused declarations for variables with SmPL?

[Julia Lawall]

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On Tue, 25 Dec 2018, SF Markus Elfring wrote:

> Hello,
>
> I have tried another simple script out for the semantic patch language.
>
> @deletion@
> identifier x;
> type t;
> @@
> -t x;
>  ... when != x

f(...) {
   ... when any
   t x;
   ... when != x
}

julia


>
>
> elfring@Sonne:~/Projekte/Linux/next-patched> spatch ~/Projekte/Coccinelle/Probe/delete_unused_variable1.cocci init/main.c
> …
> @@ -101,22 +101,6 @@
>
>  #define CREATE_TRACE_POINTS
>  #include <trace/events/initcall.h>
> -
> -static int kernel_init(void *);
> -
> -extern void init_IRQ(void);
> …
>
>
> Now I wonder about the generated change suggestions.
> Does such a transformation approach need any extensions for the safe handling
> of function declarations?
>
> Regards,
> Markus
> _______________________________________________
> Cocci mailing list
> Cocci@systeme.lip6.fr
> https://systeme.lip6.fr/mailman/listinfo/cocci
>

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Re: [Cocci] Deleting unused declarations for variables with SmPL?

[Julia Lawall]

On Tue, 25 Dec 2018, SF Markus Elfring wrote:

> > f(...) {
> >    ... when any
> >    t x;
> >    ... when != x
> > }
>
> I wonder about the need to wrap a bit of SmPL code by a function skeleton.
> Should the Coccinelle software handle the shown source code search
> also without such an addition?

Apprently not, as shown by your experiment.  Declarations can appear at
top level and in functions, and Coccinelle doesn't know which you want.

julia
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Re: [Cocci] Deleting unused declarations for variables with SmPL?

[Julia Lawall]

On Thu, 27 Dec 2018, SF Markus Elfring wrote:

> > If you have a problem, provide a complete example.
>
> Do you find software development difficulties easier
> to clarify based on source code analysis by a SmPL script
> like the following?
>
> @find@
> identifier f, x;
> type ft, xt;
> @@
>  ft f(...)
>  {
>  ... when any
>  xt x;
>  ... when != x
>  }
>
> @show@
> identifier find.f, find.x;
> type find.ft, find.xt;
> @@
>  ft f(...)
>  {
>  ... when any
>  xt x;
>  ...
> *x
>  ...
>  }

I don't know what you expect the second rule to do, but it will only match
when there exists a control-flow path through the function where x is
referenced exactly once.

julia
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Re: [Cocci] Deleting unused declarations for variables with SmPL?

[Julia Lawall]

> @find@
> identifier f, x;
> type ft, xt;
> @@
>  ft f(...)
>  {
>  ... when any
>  xt x;
>  ... when != x
>  }

If you put when strict additionally on the second ..., then everything
should be fine.  Without when strict, it will skip over error handling
code (an if with only a then branch that ends with some kind of jump) if
doing so is necessary to get a match.

julia
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