Re: [cocci] Adding an attribute to struct pointer in function parameter

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On Wed, 17 Jun 2026, Pierrick Philippe wrote:

> Hi everyone,
>
> I recently send some mail on this mailing list, and my goal was to use
> Coccinelle to automatically annotate some variables or parameters for
> our analyzer.
>
> Just to recall, our attribute have an optional parameter corresponding
> to a field of interest when the annotated object is a structure.
> That parameter should also be a string.
> There was some limitations due to character escaping with Coccinelle to
> apply the following patch:
>
> ```cocci
> +struct foo f = {42, 42};
> -struct foo __attribute__((myattr("x"))) f = {42, 42}
> ```
>
> A workaround was to go through a python script to build the string
> holding the whole attribute (including the optional parameter between
> quotes).
> Unfortunately, I can't find a way to apply the same logic to a
> function's parameter.
> Here is the test code:
>
> ```C
> #include <string.h>
>
> struct foo {
>     int x;
>     int kdiedexko;
>     int y;
> };
>
> int foo(struct foo *ptr, int y) {
>     int z = memcmp(&ptr->x, &y, sizeof(int));
>     return z;   
> }
> ```
>
> And here is my patch:
>
> ```cocci
> @searching_struct_param_begin@
> expression E1, E2;
> identifier F, X;
> type T, T1;
> identifier S;
> parameter list[n = { 0 ... 7 }] p;
> @@
> T1 F(T *S, p)
> {
> ...
> (
> memcmp(&F->X, E1, E2)
> |
> memcmp(E1, &F->X, E2)

These are supposed to be S not F.  F is the name of the function.

> )
> ...
> }
>
> @script:python generation_struct_param_begin@
> s << searching_struct_param_begin.S;
> x << searching_struct_param_begin.X;
> content;
> @@
> coccinelle.content = cocci.make_ident("__attribute__((myattr(\"" + x +
> "\"))) *" + s)
>
> @replacement_struct_param_begin@
> expression searching_struct_param_begin.E1, searching_struct_param_begin.E2;
> identifier searching_struct_param_begin.F,
> searching_struct_param_begin.X, generation_struct_param_begin.content;
> parameter list[n = { 0 ... 7 }] searching_struct_param_begin.p;
> type searching_struct_param_begin.T, searching_struct_param_begin.T1;

The metavariable S is not declared here.  You should have gotten a warning
about this?

julia

> @@
> T1 F(
> -T *S,
> +T content,
> p)
> {
> ...
> (
> memcmp(&F->X, E1, E2)
> |
> memcmp(E1, &F->X, E2)
> )
> ...
> }
> ```
>
> The semantic patch is valid, but for some reason, no patch is generated
> by Coccinelle and I can't figure out why.
> Anyway, thank you for reading me again.
>
> Have a good day,
>
> Pierrick
>
>
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