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")
Showing the changes to include/linux (1 of 1 file). Show all
Unified · Split
| @@ -38,7 +38,7 @@ struct ip_sf_socklist { · 37 unmodified lines | |||
| 38 | unsigned int sl_max; | 38 | unsigned int sl_max; |
| 39 | unsigned int sl_count; | 39 | unsigned int sl_count; |
| 40 | struct rcu_head rcu; | 40 | struct rcu_head rcu; |
| 41 | __be32 sl_addr[0]; | 41 | __be32 sl_addr[]; |
| 42 | }; | 42 | }; |
| 43 | 43 | ||
| 44 | #define IP_SFLSIZE(count) (sizeof(struct ip_sf_socklist) + \ | 44 | #define IP_SFLSIZE(count) (sizeof(struct ip_sf_socklist) + \ |