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Date: Mon, 2 Mar 2020 16:48:51 -0600 From: "Gustavo A. R. Silva" <gustavo@...eddedor.com> To: Peter Oberparleiter <oberpar@...ux.ibm.com>, Andrew Morton <akpm@...ux-foundation.org> Cc: linux-kernel@...r.kernel.org, "Gustavo A. R. Silva" <gustavo@...eddedor.com> Subject: [PATCH] gcov: fs: 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 <gustavo@...eddedor.com> --- kernel/gcov/fs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/gcov/fs.c b/kernel/gcov/fs.c index cc4ee482d3fb..82babf5aa077 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; -- 2.25.0
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