From: Gustavo A. R. Silva Date: Tue, 7 Apr 2020 03:11:58 +0000 (-0700) Subject: kernel/gcov/fs.c: replace zero-length array with flexible-array member X-Git-Tag: v5.15~4112^2~10 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=6524d79413f4ffd28480f541ef68f9ea199b2e0c;p=mirror_ubuntu-kernels.git kernel/gcov/fs.c: 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: Andrew Morton Cc: Peter Oberparleiter Link: http://lkml.kernel.org/r/20200302224851.GA26467@embeddedor Signed-off-by: Linus Torvalds --- diff --git a/kernel/gcov/fs.c b/kernel/gcov/fs.c index e5eb5ea7ea59..5e891c3c2d93 100644 --- a/kernel/gcov/fs.c +++ b/kernel/gcov/fs.c @@ -58,7 +58,7 @@ struct gcov_node { struct dentry *dentry; struct dentry **links; int num_loaded; - char name[0]; + char name[]; }; static const char objtree[] = OBJTREE;