Re: [PATCH 3/5][next] uapi: wireless: Avoid -Wflex-array-member-not-at-end warnings

[Johannes Berg]

On Tue, 2024-10-15 at 18:31 -0600, Gustavo A. R. Silva wrote:
> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
> 
> Address the following warnings by changing the type of the middle struct
> members in various composite structs, which are currently causing trouble,
> from `struct sockaddr` to `struct sockaddr_legacy`. Note that the latter
> struct doesn't contain a flexible-array member.
> 
> include/uapi/linux/wireless.h:751:33: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> include/uapi/linux/wireless.h:776:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> include/uapi/linux/wireless.h:833:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> include/uapi/linux/wireless.h:857:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> include/uapi/linux/wireless.h:864:25: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> 
> No binary differences are present after these changes.

I don't see how this works if you introduce "struct sockaddr_legacy" in
a non-UAPI header, but then use it in UAPI?!

Also, userspace might have pointers to it or whatnot, and warn/break if
you change the type?

johannes