* [PATCH] lib: objagg: Replace zero-length arrays with flexible-array member
@ 2020-02-11 20:53 Gustavo A. R. Silva
2020-02-12 7:24 ` Jiri Pirko
2020-02-17 2:33 ` David Miller
0 siblings, 2 replies; 3+ messages in thread
From: Gustavo A. R. Silva @ 2020-02-11 20:53 UTC (permalink / raw)
To: Jiri Pirko, Andrew Morton; +Cc: netdev, linux-kernel, Gustavo A. R. Silva
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
inadvertenly introduced[3] to the codebase from now on.
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>
---
lib/objagg.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/lib/objagg.c b/lib/objagg.c
index 576be22e86de..668a2c0a88ac 100644
--- a/lib/objagg.c
+++ b/lib/objagg.c
@@ -28,7 +28,7 @@ struct objagg_hints_node {
struct objagg_hints_node *parent;
unsigned int root_id;
struct objagg_obj_stats_info stats_info;
- unsigned long obj[0];
+ unsigned long obj[];
};
static struct objagg_hints_node *
@@ -66,7 +66,7 @@ struct objagg_obj {
* including nested objects
*/
struct objagg_obj_stats stats;
- unsigned long obj[0];
+ unsigned long obj[];
};
static unsigned int objagg_obj_ref_inc(struct objagg_obj *objagg_obj)
--
2.25.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] lib: objagg: Replace zero-length arrays with flexible-array member
2020-02-11 20:53 [PATCH] lib: objagg: Replace zero-length arrays with flexible-array member Gustavo A. R. Silva
@ 2020-02-12 7:24 ` Jiri Pirko
2020-02-17 2:33 ` David Miller
1 sibling, 0 replies; 3+ messages in thread
From: Jiri Pirko @ 2020-02-12 7:24 UTC (permalink / raw)
To: Gustavo A. R. Silva; +Cc: Jiri Pirko, Andrew Morton, netdev, linux-kernel
Tue, Feb 11, 2020 at 09:53:56PM CET, gustavo@embeddedor.com wrote:
>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
>inadvertenly introduced[3] to the codebase from now on.
>
>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>
Acked-by: Jiri Pirko <jiri@mellanox.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] lib: objagg: Replace zero-length arrays with flexible-array member
2020-02-11 20:53 [PATCH] lib: objagg: Replace zero-length arrays with flexible-array member Gustavo A. R. Silva
2020-02-12 7:24 ` Jiri Pirko
@ 2020-02-17 2:33 ` David Miller
1 sibling, 0 replies; 3+ messages in thread
From: David Miller @ 2020-02-17 2:33 UTC (permalink / raw)
To: gustavo; +Cc: jiri, akpm, netdev, linux-kernel
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Tue, 11 Feb 2020 14:53:56 -0600
> 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
> inadvertenly introduced[3] to the codebase from now on.
>
> 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>
Applied to net-next.
^ permalink raw reply [flat|nested] 3+ messages in thread
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