From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Gustavo A. R. Silva" Subject: [PATCH] mfd: omap-usb-tll: Replace zero-length array with flexible-array member Date: Wed, 12 Feb 2020 17:56:42 -0600 Message-ID: <20200212235642.GA19206@embeddedor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from gateway30.websitewelcome.com ([50.116.127.1]:24100 "EHLO gateway30.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729256AbgBMARA (ORCPT ); Wed, 12 Feb 2020 19:17:00 -0500 Received: from cm14.websitewelcome.com (cm14.websitewelcome.com [100.42.49.7]) by gateway30.websitewelcome.com (Postfix) with ESMTP id 32FF67279C for ; Wed, 12 Feb 2020 17:56:46 -0600 (CST) Content-Disposition: inline Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Tony Lindgren , Lee Jones Cc: linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" 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 --- drivers/mfd/omap-usb-tll.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/mfd/omap-usb-tll.c b/drivers/mfd/omap-usb-tll.c index 265f5e350e1c..1cf259a48966 100644 --- a/drivers/mfd/omap-usb-tll.c +++ b/drivers/mfd/omap-usb-tll.c @@ -99,7 +99,7 @@ struct usbtll_omap { void __iomem *base; int nch; /* num. of channels */ - struct clk *ch_clk[0]; /* must be the last member */ + struct clk *ch_clk[]; /* must be the last member */ }; /*-------------------------------------------------------------------------*/ -- 2.23.0