[Intel-wired-lan] [PATCH][next] intel: Replace zero-length array with flexible-array member

David Miller davem at davemloft.net
Mon Feb 24 23:26:59 UTC 2020

From: "Gustavo A. R. Silva" <gustavo at embeddedor.com>
Date: Mon, 24 Feb 2020 10:41:06 -0600

> 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
> inadvertently introduced[3] to the codebase from now on.
> Also, notice that, dynamic memory allocations won't be affected by
> this change:
> "Flexible array members have incomplete type, and so the sizeof operator
> may not be applied. As a quirk of the original implementation of
> zero-length arrays, sizeof evaluates to zero."[1]
> This issue was found with the help of Coccinelle.
> [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")
> Signed-off-by: Gustavo A. R. Silva <gustavo at embeddedor.com>


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