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@embeddedor.com --- drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c | 2 +- drivers/gpu/drm/vmwgfx/vmwgfx_surface.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c b/drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c index f07aa857587c..60cfbfadd3f2 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 3ce630aa4fde..ec893cd17b50 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);