On Thu, Mar 05, 2020 at 04:53:06AM -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 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@embeddedor.com

Applied to drm-misc-next, thanks for your patch. -Daniel

---

drivers/gpu/drm/gma500/intel_bios.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/gma500/intel_bios.h b/drivers/gpu/drm/gma500/intel_bios.h index a1f9ce9465a5..0e6facf21e33 100644 --- a/drivers/gpu/drm/gma500/intel_bios.h +++ b/drivers/gpu/drm/gma500/intel_bios.h @@ -227,7 +227,7 @@ struct bdb_general_definitions { * number = (block_size - sizeof(bdb_general_definitions))/ * sizeof(child_device_config); */

• struct child_device_config devices[0];

• struct child_device_config devices[];

};

struct bdb_lvds_options {

2.25.0