Messages in this thread Patch in this message | | | Date | Thu, 19 Mar 2020 18:09:37 -0500 | From | "Gustavo A. R. Silva" <> | Subject | [PATCH][next] nvdimm: nd.h: Replace zero-length array with flexible-array member |
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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/nvdimm/nd.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h index c4d69c1cce55..85dbb2a322b9 100644 --- a/drivers/nvdimm/nd.h +++ b/drivers/nvdimm/nd.h @@ -39,7 +39,7 @@ struct nd_region_data { int ns_count; int ns_active; unsigned int hints_shift; - void __iomem *flush_wpq[0]; + void __iomem *flush_wpq[]; }; static inline void __iomem *ndrd_get_flush_wpq(struct nd_region_data *ndrd, @@ -157,7 +157,7 @@ struct nd_region { struct nd_interleave_set *nd_set; struct nd_percpu_lane __percpu *lane; int (*flush)(struct nd_region *nd_region, struct bio *bio); - struct nd_mapping mapping[0]; + struct nd_mapping mapping[]; }; struct nd_blk_region { -- 2.23.0
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