From: Gustavo A. R. Silva Date: Thu, 19 Mar 2020 22:42:00 +0000 (-0500) Subject: mtd: maps: sa1100-flash: Replace zero-length array with flexible-array member X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=f1ffdbfad00a3c424cadfd307b5bb9c466638532;p=linux.git mtd: maps: sa1100-flash: Replace zero-length array with flexible-array member 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 Signed-off-by: Miquel Raynal Link: https://lore.kernel.org/linux-mtd/20200319224200.GA25162@embeddedor.com --- diff --git a/drivers/mtd/maps/sa1100-flash.c b/drivers/mtd/maps/sa1100-flash.c index 47602af4ee349..bb1ef650ffd20 100644 --- a/drivers/mtd/maps/sa1100-flash.c +++ b/drivers/mtd/maps/sa1100-flash.c @@ -34,7 +34,7 @@ struct sa_subdev_info { struct sa_info { struct mtd_info *mtd; int num_subdev; - struct sa_subdev_info subdev[0]; + struct sa_subdev_info subdev[]; }; static DEFINE_SPINLOCK(sa1100_vpp_lock);