Messages in this thread Patch in this message | | | Date | Thu, 13 Feb 2020 10:40:22 -0600 | From | "Gustavo A. R. Silva" <> | Subject | [PATCH] rapidio: Replace zero-length array with flexible-array member |
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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> --- drivers/rapidio/rio-scan.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/rapidio/rio-scan.c b/drivers/rapidio/rio-scan.c index 0e90c5d4bb2b..eb8ed28533f8 100644 --- a/drivers/rapidio/rio-scan.c +++ b/drivers/rapidio/rio-scan.c @@ -39,7 +39,7 @@ struct rio_id_table { u16 start; /* logical minimal id */ u32 max; /* max number of IDs in table */ spinlock_t lock; - unsigned long table[0]; + unsigned long table[]; }; static int next_destid = 0; -- 2.25.0
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