From e0db7c42b05f7b9d76174db56d683f0ec4f206c1 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Fri, 20 Mar 2020 18:16:34 -0500 Subject: [PATCH] platform/chrome: wilco_ec: event: 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: Enric Balletbo i Serra --- drivers/platform/chrome/wilco_ec/event.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/platform/chrome/wilco_ec/event.c b/drivers/platform/chrome/wilco_ec/event.c index dba3d445623f..814518509739 100644 --- a/drivers/platform/chrome/wilco_ec/event.c +++ b/drivers/platform/chrome/wilco_ec/event.c @@ -79,7 +79,7 @@ static DEFINE_IDA(event_ida); struct ec_event { u16 size; u16 type; - u16 event[0]; + u16 event[]; } __packed; #define ec_event_num_words(ev) (ev->size - 1) @@ -96,7 +96,7 @@ struct ec_event_queue { int capacity; int head; int tail; - struct ec_event *entries[0]; + struct ec_event *entries[]; }; /* Maximum number of events to store in ec_event_queue */