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| author | Gustavo A. R. Silva <gustavoars@kernel.org> | 2020-05-07 22:22:10 +0300 |
|---|---|---|
| committer | Song Liu <songliubraving@fb.com> | 2020-05-13 22:02:23 +0300 |
| commit | 358369f03ac94637c9fd9d8f94a2dfde86b9f25f (patch) | |
| tree | aad637516aada9aff42bad4332d9b442d54394df /drivers/md/raid1.h | |
| parent | 3f99980c8f70bc56584450c0a69973eef7b65913 (diff) | |
| download | linux-358369f03ac94637c9fd9d8f94a2dfde86b9f25f.tar.xz | |
md/raid1: 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>
Signed-off-by: Song Liu <songliubraving@fb.com>
Diffstat (limited to 'drivers/md/raid1.h')
| -rw-r--r-- | drivers/md/raid1.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/md/raid1.h b/drivers/md/raid1.h index e7ccad898736..b7eb09e8c025 100644 --- a/drivers/md/raid1.h +++ b/drivers/md/raid1.h @@ -180,7 +180,7 @@ struct r1bio { * if the IO is in WRITE direction, then multiple bios are used. * We choose the number when they are allocated. */ - struct bio *bios[0]; + struct bio *bios[]; /* DO NOT PUT ANY NEW FIELDS HERE - bios array is contiguously alloced*/ }; |