Re: [PATCH][next] fsnotify: Avoid -Wflex-array-member-not-at-end warning

[Gustavo A. R. Silva]

On 3/5/24 17:52, Kees Cook wrote:

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.

Yep, I like it.

I'll go and hunt down all those on-stack -Wflex-array-member-not-at-end
issues with this helper. :)

Thanks
--
Gustavo