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 <[email protected]>
---
drivers/regulator/da9063-regulator.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/regulator/da9063-regulator.c b/drivers/regulator/da9063-regulator.c
index 2b0c7a85306a..368f8ad2a9f9 100644
--- a/drivers/regulator/da9063-regulator.c
+++ b/drivers/regulator/da9063-regulator.c
@@ -119,7 +119,7 @@ struct da9063_regulator {
struct da9063_regulators {
unsigned n_regulators;
/* Array size to be defined during init. Keep at end. */
- struct da9063_regulator regulator[0];
+ struct da9063_regulator regulator[];
};
/* BUCK modes for DA9063 */
--
2.25.0
On 11 February 2020 23:47, 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
> 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 <[email protected]>
> ---
> drivers/regulator/da9063-regulator.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/regulator/da9063-regulator.c b/drivers/regulator/da9063-
> regulator.c
> index 2b0c7a85306a..368f8ad2a9f9 100644
> --- a/drivers/regulator/da9063-regulator.c
> +++ b/drivers/regulator/da9063-regulator.c
> @@ -119,7 +119,7 @@ struct da9063_regulator {
> struct da9063_regulators {
> unsigned n_regulators;
> /* Array size to be defined during init. Keep at end. */
> - struct da9063_regulator regulator[0];
> + struct da9063_regulator regulator[];
Same comment as for da9062. The probe uses malloc and does not statically
initialise for this struct so this will break the probe.
> };
>
> /* BUCK modes for DA9063 */
> --
> 2.25.0
On 2/12/20 05:14, Adam Thomson wrote:
> On 11 February 2020 23:47, 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
>> 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 <[email protected]>
>> ---
>> drivers/regulator/da9063-regulator.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/regulator/da9063-regulator.c b/drivers/regulator/da9063-
>> regulator.c
>> index 2b0c7a85306a..368f8ad2a9f9 100644
>> --- a/drivers/regulator/da9063-regulator.c
>> +++ b/drivers/regulator/da9063-regulator.c
>> @@ -119,7 +119,7 @@ struct da9063_regulator {
>> struct da9063_regulators {
>> unsigned n_regulators;
>> /* Array size to be defined during init. Keep at end. */
>> - struct da9063_regulator regulator[0];
>> + struct da9063_regulator regulator[];
>
> Same comment as for da9062. The probe uses malloc and does not statically
> initialise for this struct so this will break the probe.
>
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]
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
Thanks
--
Gustavo
On 12 February 2020 14:29, Gustavo A. R. Silva wrote:
> On 2/12/20 05:14, Adam Thomson wrote:
> > On 11 February 2020 23:47, 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
> >> 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 <[email protected]>
> >> ---
> >> drivers/regulator/da9063-regulator.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/regulator/da9063-regulator.c b/drivers/regulator/da9063-
> >> regulator.c
> >> index 2b0c7a85306a..368f8ad2a9f9 100644
> >> --- a/drivers/regulator/da9063-regulator.c
> >> +++ b/drivers/regulator/da9063-regulator.c
> >> @@ -119,7 +119,7 @@ struct da9063_regulator {
> >> struct da9063_regulators {
> >> unsigned n_regulators;
> >> /* Array size to be defined during init. Keep at end. */
> >> - struct da9063_regulator regulator[0];
> >> + struct da9063_regulator regulator[];
> >
> > Same comment as for da9062. The probe uses malloc and does not statically
> > initialise for this struct so this will break the probe.
> >
>
> 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]
>
> [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
As for da9062:
Acked-by: Adam Thomson <[email protected]>
>
> Thanks
> --
> Gustavo