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authorGustavo A. R. Silva <gustavoars@kernel.org>2020-05-07 22:22:10 +0300
committerSong Liu <songliubraving@fb.com>2020-05-13 22:02:23 +0300
commit358369f03ac94637c9fd9d8f94a2dfde86b9f25f (patch)
treeaad637516aada9aff42bad4332d9b442d54394df /drivers/md/raid1.h
parent3f99980c8f70bc56584450c0a69973eef7b65913 (diff)
downloadlinux-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.h2
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*/
};