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authorGustavo A. R. Silva <gustavoars@kernel.org>2020-05-07 13:53:42 -0500
committerJason Gunthorpe <jgg@mellanox.com>2020-05-13 12:01:56 -0300
commit0cb9e4f9e98af4b969b9140e964c646ad6ed7d40 (patch)
tree55748f433869763cbdcb88b1f3092c1864dbcd19 /include/rdma/rdmavt_qp.h
parenta0e46db4e764f56c61f85c235c50bf4578c51a47 (diff)
IB/rdmavt: Replace zero-length array with flexible-array
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] sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues. 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") Link: https://lore.kernel.org/r/20200507185342.GA14476@embeddedor Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Diffstat (limited to 'include/rdma/rdmavt_qp.h')
-rw-r--r--include/rdma/rdmavt_qp.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/rdma/rdmavt_qp.h b/include/rdma/rdmavt_qp.h
index 5fc10108703a..982bf2340840 100644
--- a/include/rdma/rdmavt_qp.h
+++ b/include/rdma/rdmavt_qp.h
@@ -440,7 +440,7 @@ struct rvt_qp {
/*
* This sge list MUST be last. Do not add anything below here.
*/
- struct rvt_sge r_sg_list[0] /* verified SGEs */
+ struct rvt_sge r_sg_list[] /* verified SGEs */
____cacheline_aligned_in_smp;
};