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.

All these instances of code were found with the help of the following
Coccinelle script:

@@
identifier S, member, array;
type T1, T2;
@@

struct S {
  ...
  T1 member;
  T2 array[
- 0
  ];
};

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

NOTE: I'll carry this in my -next tree for the v5.6 merge window.

Why not carve this up into per-subsystem patches so that we can apply
them to our 5.7-rc1 trees and then you submit the "remaining" that don't
somehow get merged at that timeframe for 5.7-rc2?

thanks,

greg k-h