All of lore.kernel.org
 help / color / mirror / Atom feed
* [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

end of thread, other threads:[~2020-02-27 19:37 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
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

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.