* [PATCH] platform/x86: i2c-multi-instantiate: Replace zero-length array with flexible-array member
@ 2020-02-13 0:55 Gustavo A. R. Silva
2020-02-27 19:03 ` Gustavo A. R. Silva
0 siblings, 1 reply; 4+ messages in thread
From: Gustavo A. R. Silva @ 2020-02-13 0:55 UTC (permalink / raw)
To: Hans de Goede, Darren Hart, Andy Shevchenko
Cc: platform-driver-x86, 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/platform/x86/i2c-multi-instantiate.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/platform/x86/i2c-multi-instantiate.c b/drivers/platform/x86/i2c-multi-instantiate.c
index ffb8d5d1eb5f..6acc8457866e 100644
--- a/drivers/platform/x86/i2c-multi-instantiate.c
+++ b/drivers/platform/x86/i2c-multi-instantiate.c
@@ -28,7 +28,7 @@ struct i2c_inst_data {
struct i2c_multi_inst_data {
int num_clients;
- struct i2c_client *clients[0];
+ struct i2c_client *clients[];
};
static int i2c_multi_inst_count(struct acpi_resource *ares, void *data)
--
2.23.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] platform/x86: i2c-multi-instantiate: Replace zero-length array with flexible-array member
2020-02-27 19:03 ` Gustavo A. R. Silva
@ 2020-02-27 19:01 ` Hans de Goede
2020-02-27 19:40 ` Gustavo A. R. Silva
0 siblings, 1 reply; 4+ messages in thread
From: Hans de Goede @ 2020-02-27 19:01 UTC (permalink / raw)
To: Gustavo A. R. Silva, Darren Hart, Andy Shevchenko
Cc: platform-driver-x86, linux-kernel
Hi,
On 2/27/20 8:03 PM, Gustavo A. R. Silva wrote:
> Hi all,
>
> Friendly ping: who can take this?
FWIW, the patch looks good to me:
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Regards,
Hans
> On 2/12/20 18:55, 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/platform/x86/i2c-multi-instantiate.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/platform/x86/i2c-multi-instantiate.c b/drivers/platform/x86/i2c-multi-instantiate.c
>> index ffb8d5d1eb5f..6acc8457866e 100644
>> --- a/drivers/platform/x86/i2c-multi-instantiate.c
>> +++ b/drivers/platform/x86/i2c-multi-instantiate.c
>> @@ -28,7 +28,7 @@ struct i2c_inst_data {
>>
>> struct i2c_multi_inst_data {
>> int num_clients;
>> - struct i2c_client *clients[0];
>> + struct i2c_client *clients[];
>> };
>>
>> static int i2c_multi_inst_count(struct acpi_resource *ares, void *data)
>>
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] platform/x86: i2c-multi-instantiate: Replace zero-length array with flexible-array member
2020-02-13 0:55 [PATCH] platform/x86: i2c-multi-instantiate: Replace zero-length array with flexible-array member Gustavo A. R. Silva
@ 2020-02-27 19:03 ` Gustavo A. R. Silva
2020-02-27 19:01 ` Hans de Goede
0 siblings, 1 reply; 4+ messages in thread
From: Gustavo A. R. Silva @ 2020-02-27 19:03 UTC (permalink / raw)
To: Hans de Goede, Darren Hart, Andy Shevchenko
Cc: platform-driver-x86, linux-kernel
Hi all,
Friendly ping: who can take this?
Thanks
--
Gustavo
On 2/12/20 18:55, 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/platform/x86/i2c-multi-instantiate.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/platform/x86/i2c-multi-instantiate.c b/drivers/platform/x86/i2c-multi-instantiate.c
> index ffb8d5d1eb5f..6acc8457866e 100644
> --- a/drivers/platform/x86/i2c-multi-instantiate.c
> +++ b/drivers/platform/x86/i2c-multi-instantiate.c
> @@ -28,7 +28,7 @@ struct i2c_inst_data {
>
> struct i2c_multi_inst_data {
> int num_clients;
> - struct i2c_client *clients[0];
> + struct i2c_client *clients[];
> };
>
> static int i2c_multi_inst_count(struct acpi_resource *ares, void *data)
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] platform/x86: i2c-multi-instantiate: Replace zero-length array with flexible-array member
2020-02-27 19:01 ` Hans de Goede
@ 2020-02-27 19:40 ` Gustavo A. R. Silva
0 siblings, 0 replies; 4+ messages in thread
From: Gustavo A. R. Silva @ 2020-02-27 19:40 UTC (permalink / raw)
To: Hans de Goede, Darren Hart, Andy Shevchenko
Cc: platform-driver-x86, linux-kernel
On 2/27/20 13:01, Hans de Goede wrote:
> Hi,
>
>
> On 2/27/20 8:03 PM, Gustavo A. R. Silva wrote:
>> Hi all,
>>
>> Friendly ping: who can take this?
>
> FWIW, the patch looks good to me:
>
> Reviewed-by: Hans de Goede <hdegoede@redhat.com>
>
Thanks, Hans.
--
Gustavo
> Regards,
>
> Hans
>
>
>
>> On 2/12/20 18:55, 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/platform/x86/i2c-multi-instantiate.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/platform/x86/i2c-multi-instantiate.c b/drivers/platform/x86/i2c-multi-instantiate.c
>>> index ffb8d5d1eb5f..6acc8457866e 100644
>>> --- a/drivers/platform/x86/i2c-multi-instantiate.c
>>> +++ b/drivers/platform/x86/i2c-multi-instantiate.c
>>> @@ -28,7 +28,7 @@ struct i2c_inst_data {
>>> struct i2c_multi_inst_data {
>>> int num_clients;
>>> - struct i2c_client *clients[0];
>>> + struct i2c_client *clients[];
>>> };
>>> static int i2c_multi_inst_count(struct acpi_resource *ares, void *data)
>>>
>>
>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2020-02-13 0:55 [PATCH] platform/x86: i2c-multi-instantiate: Replace zero-length array with flexible-array member Gustavo A. R. Silva
2020-02-27 19:03 ` Gustavo A. R. Silva
2020-02-27 19:01 ` Hans de Goede
2020-02-27 19:40 ` Gustavo A. R. Silva
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