From: Gustavo A. R. Silva Date: Thu, 5 Mar 2020 10:58:42 +0000 (-0600) Subject: drm/vmwgfx: Replace zero-length array with flexible-array member X-Git-Tag: v5.15~4077^2~19^2 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=6b656755428dc0c96d21d7af697dc2a10c7ff175;p=platform%2Fkernel%2Flinux-starfive.git drm/vmwgfx: 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 Reviewed-by: Thomas Hellstrom Signed-off-by: Thomas Hellstrom --- diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c b/drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c index f07aa85..60cfbfa 100644 --- a/drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c @@ -69,7 +69,7 @@ struct vmw_bo_dirty { unsigned int ref_count; unsigned long bitmap_size; size_t size; - unsigned long bitmap[0]; + unsigned long bitmap[]; }; /** diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c index 3ce630a..ec893cd 100644 --- a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c @@ -79,7 +79,7 @@ struct vmw_surface_dirty { struct svga3dsurface_cache cache; size_t size; u32 num_subres; - SVGA3dBox boxes[0]; + SVGA3dBox boxes[]; }; static void vmw_user_surface_free(struct vmw_resource *res);