| Message ID | 20200213005525.GA11420@embeddedor.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Delegated to: | Andy Shevchenko |
| Headers | show |
| Series | platform/x86: i2c-multi-instantiate: Replace zero-length array with flexible-array member | expand |
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) >> >
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) >
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) >>> >> >
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)
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(-)