Hi David, On 20/05/2020 00:40, David Miller wrote: > From: Antonio Quartulli <a...@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".
True. > > If in some configuration BUILD_BUG_ON() does not reference it's arguments, > that's the bug that needs to be fixed. > I don't think it's BUILD_BUG_ON()'s fault, because qcb->data is passed to sizeof() first. My best guess is that gcc is somewhat optimizing the sizeof(gcb->data) and thus leaving the gcb variable unused. This said, I think it's better for the code style (and for the compiler) if we used sizeof_member(). Should I resend the patch with a commit message that does not mention the "unused" warning? Thanks a lot. Best Regards, -- Antonio Quartulli
