Subject: Re: [PATCH net-next 0/6] sctp: fix a plenty of flexible-array-nested warnings

From: Jakub Kicinski <[email-masked]>
Date: Wed, 19 Apr 2023 18:18:24 -0700

On Wed, 19 Apr 2023 11:16:27 -0400 Xin Long wrote:
> Paolo noticed a compile warning in SCTP,
> 
> ../net/sctp/stream_sched_fc.c: note: in included file (through ../include/net/sctp/sctp.h):
> ../include/net/sctp/structs.h:335:41: warning: array of flexible structures
> 
> But not only this, there are actually quite a lot of such warnings in
> some SCTP structs. This patchset fixes most of warnings by deleting
> these nested flexible array members.
> 
> After this patchset, there are still some warnings left:
> 
>   # make C=2 CF="-Wflexible-array-nested" M=./net/sctp/
>   ./include/net/sctp/structs.h:1145:41: warning: nested flexible array
>   ./include/uapi/linux/sctp.h:641:34: warning: nested flexible array
>   ./include/uapi/linux/sctp.h:643:34: warning: nested flexible array
>   ./include/uapi/linux/sctp.h:644:33: warning: nested flexible array
>   ./include/uapi/linux/sctp.h:650:40: warning: nested flexible array
>   ./include/uapi/linux/sctp.h:653:39: warning: nested flexible array
> 
> the 1st is caused by __data[] in struct ip_options, not in SCTP;
> the others are in uapi, and we should not touch them.
> 
> Note that instead of completely deleting it, we just leave it as a
> comment in the struct, signalling to the reader that we do expect
> such variable parameters over there, as Marcelo suggested.

Hi Kees, is there no workaround for nested flexible arrays within 
the kernel?  Any recommendations?

https://lore.kernel.org/all/[email-masked]/