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R. Silva" Cc: Jan Kara , Amir Goldstein , Alexander Viro , Christian Brauner , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH][next] fsnotify: Avoid -Wflex-array-member-not-at-end warning Message-ID: <202403051548.045B16BF@keescook> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Mar 05, 2024 at 04:18:46PM -0600, Gustavo A. R. Silva wrote: > -Wflex-array-member-not-at-end is coming in GCC-14, and we are getting > ready to enable it globally. > > There is currently a local structure `f` that is using a flexible > `struct file_handle` as header for an on-stack place-holder for the > flexible-array member `unsigned char f_handle[];`. > > struct { > struct file_handle handle; > u8 pad[MAX_HANDLE_SZ]; > } f; This code pattern is "put a flex array struct on the stack", but we have a macro for this now: DEFINE_FLEX(struct file_handle, handle, f_handle, MAX_HANDLE_SZ); And you can even include the initializer: _DEFINE_FLEX(struct file_handle, handle, f_handle, MAX_HANDLE_SZ, = { .handle_bytes = MAX_HANDLE_SZ }); I think this would be a simpler conversion. Also, this could use a __counted_by tag... I need to improve the DEFINE_FLEX macro a bit, though, to take advantage of __counted_by. -- Kees Cook