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authorGustavo A. R. Silva <gustavoars@kernel.org>2020-05-07 14:21:41 -0500
committerPeter Zijlstra <peterz@infradead.org>2020-05-19 20:34:14 +0200
commit04f5c362ec6d3ff0e14f1c05230b550da7f528a4 (patch)
treed21f39df3f6ae8d34991697ab8aad138ccd75812 /kernel/sched/fair.c
parent95d685935a2edf209fc68f52494ede4a382a6c2b (diff)
downloadlinux-04f5c362ec6d3ff0e14f1c05230b550da7f528a4.tar.gz
sched/fair: 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: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200507192141.GA16183@embeddedor
Diffstat (limited to 'kernel/sched/fair.c')
-rw-r--r--kernel/sched/fair.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 44b0c8edc260..01f94cf52783 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1094,7 +1094,7 @@ struct numa_group {
* more by CPU use than by memory faults.
*/
unsigned long *faults_cpu;
- unsigned long faults[0];
+ unsigned long faults[];
};
/*