From: zhuguangqing <zhuguangq...@xiaomi.com> In commit 04f5c362ec6, a zero-length array cpumask[0] has been replaced with cpumask[]. But there is still a cpumask[0] in struct sched_group_capacity{} which maybe missed.
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: zhuguangqing <zhuguangq...@xiaomi.com> --- kernel/sched/sched.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 28709f6b0975..648f02363ff9 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1471,7 +1471,7 @@ struct sched_group_capacity { int id; #endif - unsigned long cpumask[0]; /* Balance mask */ + unsigned long cpumask[]; /* Balance mask */ }; struct sched_group { -- 2.17.1