From 89f60a5d9bf5a6b9b16dfdd56a91c4a2d7b8830d Mon Sep 17 00:00:00 2001 From: Gustavo A. R. Silva Date: Mon, 23 Mar 2020 17:43:59 -0500 Subject: genalloc.h: 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 --- include/linux/genalloc.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/genalloc.h b/include/linux/genalloc.h index 5b14a0f38124..0bd581003cd5 100644 --- a/include/linux/genalloc.h +++ b/include/linux/genalloc.h @@ -76,7 +76,7 @@ struct gen_pool_chunk { void *owner; /* private data to retrieve at alloc time */ unsigned long start_addr; /* start address of memory chunk */ unsigned long end_addr; /* end address of memory chunk (inclusive) */ - unsigned long bits[0]; /* bitmap for allocating memory chunk */ + unsigned long bits[]; /* bitmap for allocating memory chunk */ }; /* -- cgit v1.2.3