[Cake] [PATCH] net/sch_generic.h: use sizeof_member() and get rid of unused variable

[David Miller]

From: Antonio Quartulli <a at unstable.cc>
Date: Tue, 19 May 2020 11:13:33 +0200

> Compiling with -Wunused triggers the following warning:
> 
> ./include/net/sch_generic.h: In function ‘qdisc_cb_private_validate’:
> ./include/net/sch_generic.h:464:23: warning: unused variable ‘qcb’ [-Wunused-variable]
>   464 |  struct qdisc_skb_cb *qcb;
>       |                       ^~~
> 
> as the qcb variable is only used to compute the sizeof one of its members.

It's referenced in the code, therefore it is not "unused".

If in some configuration BUILD_BUG_ON() does not reference it's arguments,
that's the bug that needs to be fixed.