On Tue, Feb 11, 2020 at 11:41:26AM -0600, Gustavo A. R. Silva wrote:

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
unadvertenly introduced[3] to the codebase from now on.

Is there a compiler warning we can enable to avoid new 0-byte arrays
from entering the kernel source tree? I can only find "-pedantic" which
enables way too many other checks.

-- 
Kees Cook