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| author | Gustavo A. R. Silva <gustavo@embeddedor.com> | 2020-03-09 10:56:08 -0500 |
|---|---|---|
| committer | David Teigland <teigland@redhat.com> | 2020-05-12 14:06:14 -0500 |
| commit | a4e439a6f628a52f7074c9d73ec7eb4f6c1a4dfc (patch) | |
| tree | 7545882bd15e3a31f12ac1359d973ed892bb99af | |
| parent | 1d2cc5ac6f6668cc15216d51051103c61467d7e8 (diff) | |
| download | linux-a4e439a6f628a52f7074c9d73ec7eb4f6c1a4dfc.tar.gz linux-a4e439a6f628a52f7074c9d73ec7eb4f6c1a4dfc.tar.bz2 linux-a4e439a6f628a52f7074c9d73ec7eb4f6c1a4dfc.zip | |
dlm: dlm_internal: Replace zero-length array with flexible-array member
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>
Signed-off-by: David Teigland <teigland@redhat.com>
| -rw-r--r-- | fs/dlm/dlm_internal.h | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/fs/dlm/dlm_internal.h b/fs/dlm/dlm_internal.h index 416d9de35679..d231ae5d2c65 100644 --- a/fs/dlm/dlm_internal.h +++ b/fs/dlm/dlm_internal.h @@ -421,7 +421,7 @@ struct dlm_message { int m_bastmode; int m_asts; int m_result; /* 0 or -EXXX */ - char m_extra[0]; /* name or lvb */ + char m_extra[]; /* name or lvb */ }; @@ -450,7 +450,7 @@ struct dlm_rcom { uint64_t rc_id; /* match reply with request */ uint64_t rc_seq; /* sender's ls_recover_seq */ uint64_t rc_seq_reply; /* remote ls_recover_seq */ - char rc_buf[0]; + char rc_buf[]; }; union dlm_packet { @@ -506,7 +506,7 @@ struct rcom_lock { __le16 rl_wait_type; __le16 rl_namelen; char rl_name[DLM_RESNAME_MAXLEN]; - char rl_lvb[0]; + char rl_lvb[]; }; /* |