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authorGustavo A. R. Silva <gustavoars@kernel.org>2020-05-07 13:51:38 -0500
committerIlya Dryomov <idryomov@gmail.com>2020-06-01 13:22:53 +0200
commit53ab8e7cd2d47594e68951994ac083d30f82fce4 (patch)
treede8a33ef708a79bf5f92a24d51918cac763e34a8 /include/linux
parentdffdcd71458e699e839f0bf47c3d42d64210b939 (diff)
libceph, rbd: 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") Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> Reviewed-by: Ilya Dryomov <idryomov@gmail.com> Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/ceph/mon_client.h2
-rw-r--r--include/linux/crush/crush.h2
2 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/ceph/mon_client.h b/include/linux/ceph/mon_client.h
index dbb8a6959a73..ce4ffeb384d7 100644
--- a/include/linux/ceph/mon_client.h
+++ b/include/linux/ceph/mon_client.h
@@ -19,7 +19,7 @@ struct ceph_monmap {
struct ceph_fsid fsid;
u32 epoch;
u32 num_mon;
- struct ceph_entity_inst mon_inst[0];
+ struct ceph_entity_inst mon_inst[];
};
struct ceph_mon_client;
diff --git a/include/linux/crush/crush.h b/include/linux/crush/crush.h
index 54741295c70b..38b0e4d50ed9 100644
--- a/include/linux/crush/crush.h
+++ b/include/linux/crush/crush.h
@@ -87,7 +87,7 @@ struct crush_rule_mask {
struct crush_rule {
__u32 len;
struct crush_rule_mask mask;
- struct crush_rule_step steps[0];
+ struct crush_rule_step steps[];
};
#define crush_rule_size(len) (sizeof(struct crush_rule) + \