| Message ID | 20200305105451.GA18973@embeddedor |
|---|---|
| State | New |
| Headers | show |
| Series | [next] drm/msm/msm_gem.h: Replace zero-length array with flexible-array member | expand |
diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h index 9e0953c2b7ce..37aa556c5f92 100644 --- a/drivers/gpu/drm/msm/msm_gem.h +++ b/drivers/gpu/drm/msm/msm_gem.h @@ -157,7 +157,7 @@ struct msm_gem_submit { uint32_t handle; }; uint64_t iova; - } bos[0]; + } bos[]; }; #endif /* __MSM_GEM_H__ */
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/msm/msm_gem.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)