Re: [PATCH][next] perf/x86: Avoid multiple -Wflex-array-member-not-at-end warnings

[Peter Zijlstra <peterz@infradead.org>]

On Wed, Apr 29, 2026 at 01:29:18PM -0600, Gustavo A. R. Silva wrote:

> +	/*
> +	 * Intel LBR bits
> +	 */
> +	int				lbr_users;
> +	int				lbr_pebs_users;
> +	union {
> +		struct er_account		*lbr_sel;
> +		struct er_account		*lbr_ctl;
> +	};
> +	u64				br_sel;
> +	void				*last_task_ctx;
> +	int				last_log_id;
> +	int				lbr_select;
> +	void				*lbr_xsave;
> +
> +	/* Must be last as it ends in a flexible-array member. */
> +	TRAILING_OVERLAP(struct perf_branch_stack, lbr_stack, entries,
> +		struct perf_branch_entry	lbr_entries[MAX_LBR_ENTRIES];
> +		u64				lbr_counters[MAX_LBR_ENTRIES]; /* branch stack extra */
> +	);

FWIW, this thing is horrible crap. Per construction this thing does not
need to be last at all, you can have multiple such constructs in a
single structure and things would be perfectly fine.

Also, your TRAILING_OVERLAP() thing should probably have
__no_randomize_layout in ATTRS, rather than empty (and I'm assuming
__packed implies __no_randomized_layout, otherwise 'fun' things can
happen).

>  };