From: Gustavo A. R. Silva Date: Thu, 5 Mar 2020 10:55:58 +0000 (-0600) Subject: drm/vboxvideo/vboxvideo.h: Replace zero-length array with flexible-array member X-Git-Tag: libata-5.7-2020-04-09~30^2~15^2~4 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=afdd597940f386eeb03175c98744bdbe622fad7a;p=linux-2.6-block.git drm/vboxvideo/vboxvideo.h: 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: Hans de Goede Signed-off-by: Hans de Goede Link: https://patchwork.freedesktop.org/patch/msgid/20200305105558.GA19124@embeddedor --- diff --git a/drivers/gpu/drm/vboxvideo/vboxvideo.h b/drivers/gpu/drm/vboxvideo/vboxvideo.h index 0592004f71aa..a5de40fe1a76 100644 --- a/drivers/gpu/drm/vboxvideo/vboxvideo.h +++ b/drivers/gpu/drm/vboxvideo/vboxvideo.h @@ -138,7 +138,7 @@ struct vbva_buffer { u32 data_len; /* variable size for the rest of the vbva_buffer area in VRAM. */ - u8 data[0]; + u8 data[]; } __packed; #define VBVA_MAX_RECORD_SIZE (128 * 1024 * 1024)