Hi Lucas,
On 3/5/20 05:17, Lucas Stach wrote:
Hi Gustavo,
I've adjusted the subject a bit to match the style of the other etnaviv driver commits and applied this to the etnaviv/next branch.
Great. Thanks a lot for that. :) -- Gustavo
Regards, Lucas
On Do, 2020-03-05 at 04:51 -0600, 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@embeddedor.com
drivers/gpu/drm/etnaviv/etnaviv_gem.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.h b/drivers/gpu/drm/etnaviv/etnaviv_gem.h index 6b68fe16041b..98e60df882b6 100644 --- a/drivers/gpu/drm/etnaviv/etnaviv_gem.h +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.h @@ -105,7 +105,7 @@ struct etnaviv_gem_submit { unsigned int nr_pmrs; struct etnaviv_perfmon_request *pmrs; unsigned int nr_bos;
- struct etnaviv_gem_submit_bo bos[0];
- struct etnaviv_gem_submit_bo bos[]; /* No new members here, the previous one is variable-length! */
};