The -fstrict-flex-arrays=3 option is now available with the release
of GCC 13[1] and Clang 16[2]. This feature instructs the compiler to
treat only C99 flexible arrays as dynamically sized for the purposes of
object size calculations. In other words, the ancient practice of using
1-element arrays, or the GNU extension of using 0-sized arrays, as a
dynamically sized array is disabled. This allows CONFIG_UBSAN_BOUNDS,
CONFIG_FORTIFY_SOURCE, and other object-size aware features to behave
unambiguously in the face of trailing arrays: only C99 flexible arrays
are considered to be dynamically sized. For yet more detail, see:
https://people.kernel.org/kees/bounded-flexible-arrays-in-c
Enabling this will help track down any outstanding cases of fake
flexible arrays that need attention in kernel code.