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")
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| @@ -4162,7 +4162,7 @@ struct skb_ext { · 4161 unmodified lines | ||
| 4162 | 4162 | refcount_t refcnt; |
| 4163 | 4163 | u8 offset[SKB_EXT_NUM]; /* in chunks of 8 bytes */ |
| 4164 | 4164 | u8 chunks; /* same */ |
| 4165 | − char data[0] __aligned(8); | |
| 4165 | + char data[] __aligned(8); | |
| 4166 | 4166 | }; |
| 4167 | 4167 | |
| 4168 | 4168 | struct skb_ext *__skb_ext_alloc(void); |