From patchwork Fri Feb 21 16:00:05 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Gustavo A. R. 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R. Silva" To: Bartlomiej Zolnierkiewicz Subject: [PATCH] video: Replace zero-length array with flexible-array member Message-ID: <20200221160005.GA13552@embeddedor> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - lists.freedesktop.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 200.68.140.54 X-Source-L: No X-Exim-ID: 1j5Ag4-003vD4-K4 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [200.68.140.54]:6638 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 30 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, "Gustavo A. R. Silva" Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" 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/video/fbdev/mmp/hw/mmp_ctrl.h | 2 +- drivers/video/fbdev/ssd1307fb.c | 2 +- include/video/mmp_disp.h | 2 +- 3 files changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/video/fbdev/mmp/hw/mmp_ctrl.h b/drivers/video/fbdev/mmp/hw/mmp_ctrl.h index 335d4983dc52..167585a889d3 100644 --- a/drivers/video/fbdev/mmp/hw/mmp_ctrl.h +++ b/drivers/video/fbdev/mmp/hw/mmp_ctrl.h @@ -1406,7 +1406,7 @@ struct mmphw_ctrl { /*pathes*/ int path_num; - struct mmphw_path_plat path_plats[0]; + struct mmphw_path_plat path_plats[]; }; static inline int overlay_is_vid(struct mmp_overlay *overlay) diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c index 142535267fec..fb2640fe575a 100644 --- a/drivers/video/fbdev/ssd1307fb.c +++ b/drivers/video/fbdev/ssd1307fb.c @@ -89,7 +89,7 @@ struct ssd1307fb_par { struct ssd1307fb_array { u8 type; - u8 data[0]; + u8 data[]; }; static const struct fb_fix_screeninfo ssd1307fb_fix = { diff --git a/include/video/mmp_disp.h b/include/video/mmp_disp.h index 1f9bc133e230..77252cb46361 100644 --- a/include/video/mmp_disp.h +++ b/include/video/mmp_disp.h @@ -231,7 +231,7 @@ struct mmp_path { /* layers */ int overlay_num; - struct mmp_overlay overlays[0]; + struct mmp_overlay overlays[]; }; extern struct mmp_path *mmp_get_path(const char *name);