Hi,
On 3/6/20 11:41 AM, Daniel Vetter wrote:
On Thu, Mar 05, 2020 at 03:22:38PM +0100, Hans de Goede wrote:
Hi,
On 3/5/20 11:55 AM, Gustavo A. R. Silva wrote:
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@xxxxxxxxxxxxxx>
Patch looks good to me:
Reviewed-by: Hans de Goede <hdegoede@xxxxxxxxxx>
You're also going to push this? r-b by maintainers without any hint to
what's going to happen is always rather confusing.
I've pushed this now, sorry for the confusion I will be more
clear about my intentions next time.
Regards,
Hans
---
drivers/gpu/drm/vboxvideo/vboxvideo.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
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)
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