Re: [cocci] Search for the concatenation of meta variable + fixed string (similar fresh identifier)

Am 03.12.2025 22:47 schrieb Tobias Deiminger:
> Hello again :)
> 
> In Linux, the DEVICE_ATTR_RO macro works like this:
> 
> static ssize_t led_status_show(struct device *dev, struct
> device_attribute *attr, char *buf) { /* ... */ }
> 
> // The macro automatically concatenates led_status + _show for struct
> initialization.
> static DEVICE_ATTR_RO(led_status);
> 
> 
> I'd like to find the position of all functions assigned by
> DEVICE_ATTR_RO. So I thought to use a 1st rule to search for the
> identifier inside DEVICE_ATTR_RO, then use a 2nd rule to search for
> the inherited meta variable, concatenated with the fixed string
> "_show". Like:
> 
> @device_attr_ro@
> declarer name DEVICE_ATTR_RO;
> identifier attr_name;
> @@
>   DEVICE_ATTR_RO(attr_name);
> 
> @device_attr_ro_show_fn@
> identifier device_attr_ro.attr_name;
> position p_fn;
> @@
>   attr_name ## "_show" @ p_fn (...) {...}     // invalid syntax, but
> you get the point
> 
> 
> This doesn't work and I couldn't figure how to do it correctly.
> There's "fresh identifier" which looks close, but it only works for +,
> not for search context. Is such a search possible? How?
> 
> Tobias

Found a workaround using fresh identifier to add an intermediate helper 
construct:

@device_attr_ro@
declarer name DEVICE_ATTR_RO;
typedef __DEVICE_ATTR_RO_T;
identifier attr_name;
fresh identifier show_fn_name = attr_name ## "_show";
@@
   DEVICE_ATTR_RO(attr_name);
+ __DEVICE_ATTR_RO_T attr_name = show_fn_name;

/* Helper construct needed to get concatenated identifier for final 
search. */
@device_attr_ro_2@
identifier device_attr_ro.attr_name;
identifier show_fn;
@@
   __DEVICE_ATTR_RO_T attr_name = show_fn;

@device_attr_ro_show_fn@
identifier device_attr_ro_2.show_fn;
position p_fn;
@@
   show_fn@p_fn(...) {...}

Seems to work good enough. If there are cleaner ways, let me know.

Tobias