* [PATCH] stm class: Replace zero-length array with flexible-array member
@ 2020-02-12 23:54 ` Gustavo A. R. Silva
0 siblings, 0 replies; 4+ messages in thread
From: Gustavo A. R. Silva @ 2020-02-12 23:54 UTC (permalink / raw)
To: Alexander Shishkin, Maxime Coquelin, Alexandre Torgue
Cc: Gustavo A. R. Silva, linux-stm32, linux-arm-kernel, linux-kernel
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/hwtracing/stm/policy.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/hwtracing/stm/policy.c b/drivers/hwtracing/stm/policy.c
index 4f932a419752..603b4a9969d3 100644
--- a/drivers/hwtracing/stm/policy.c
+++ b/drivers/hwtracing/stm/policy.c
@@ -34,7 +34,7 @@ struct stp_policy_node {
unsigned int first_channel;
unsigned int last_channel;
/* this is the one that's exposed to the attributes */
- unsigned char priv[0];
+ unsigned char priv[];
};
void *stp_policy_node_priv(struct stp_policy_node *pn)
--
2.23.0
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH] stm class: Replace zero-length array with flexible-array member
@ 2020-02-12 23:54 ` Gustavo A. R. Silva
0 siblings, 0 replies; 4+ messages in thread
From: Gustavo A. R. Silva @ 2020-02-12 23:54 UTC (permalink / raw)
To: Alexander Shishkin, Maxime Coquelin, Alexandre Torgue
Cc: linux-stm32, linux-arm-kernel, 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
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/hwtracing/stm/policy.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/hwtracing/stm/policy.c b/drivers/hwtracing/stm/policy.c
index 4f932a419752..603b4a9969d3 100644
--- a/drivers/hwtracing/stm/policy.c
+++ b/drivers/hwtracing/stm/policy.c
@@ -34,7 +34,7 @@ struct stp_policy_node {
unsigned int first_channel;
unsigned int last_channel;
/* this is the one that's exposed to the attributes */
- unsigned char priv[0];
+ unsigned char priv[];
};
void *stp_policy_node_priv(struct stp_policy_node *pn)
--
2.23.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] stm class: Replace zero-length array with flexible-array member
2020-02-12 23:54 ` Gustavo A. R. Silva
@ 2020-02-27 13:15 ` Gustavo A. R. Silva
-1 siblings, 0 replies; 4+ messages in thread
From: Gustavo A. R. Silva @ 2020-02-27 13:15 UTC (permalink / raw)
To: Alexander Shishkin, Maxime Coquelin, Alexandre Torgue
Cc: linux-stm32, linux-arm-kernel, linux-kernel
Hi all,
Friendly ping: Who can take this?
Thanks
--
Gustavo
On 2/12/20 17:54, Gustavo A. R. Silva 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
> 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/hwtracing/stm/policy.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/hwtracing/stm/policy.c b/drivers/hwtracing/stm/policy.c
> index 4f932a419752..603b4a9969d3 100644
> --- a/drivers/hwtracing/stm/policy.c
> +++ b/drivers/hwtracing/stm/policy.c
> @@ -34,7 +34,7 @@ struct stp_policy_node {
> unsigned int first_channel;
> unsigned int last_channel;
> /* this is the one that's exposed to the attributes */
> - unsigned char priv[0];
> + unsigned char priv[];
> };
>
> void *stp_policy_node_priv(struct stp_policy_node *pn)
>
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] stm class: Replace zero-length array with flexible-array member
@ 2020-02-27 13:15 ` Gustavo A. R. Silva
0 siblings, 0 replies; 4+ messages in thread
From: Gustavo A. R. Silva @ 2020-02-27 13:15 UTC (permalink / raw)
To: Alexander Shishkin, Maxime Coquelin, Alexandre Torgue
Cc: linux-stm32, linux-arm-kernel, linux-kernel
Hi all,
Friendly ping: Who can take this?
Thanks
--
Gustavo
On 2/12/20 17:54, Gustavo A. R. Silva 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
> 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/hwtracing/stm/policy.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/hwtracing/stm/policy.c b/drivers/hwtracing/stm/policy.c
> index 4f932a419752..603b4a9969d3 100644
> --- a/drivers/hwtracing/stm/policy.c
> +++ b/drivers/hwtracing/stm/policy.c
> @@ -34,7 +34,7 @@ struct stp_policy_node {
> unsigned int first_channel;
> unsigned int last_channel;
> /* this is the one that's exposed to the attributes */
> - unsigned char priv[0];
> + unsigned char priv[];
> };
>
> void *stp_policy_node_priv(struct stp_policy_node *pn)
>
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-02-27 13:37 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2020-02-12 23:54 [PATCH] stm class: Replace zero-length array with flexible-array member Gustavo A. R. Silva
2020-02-12 23:54 ` Gustavo A. R. Silva
2020-02-27 13:15 ` Gustavo A. R. Silva
2020-02-27 13:15 ` Gustavo A. R. Silva
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.