| Message ID | 20200214172022.GA27490@embeddedor (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | 94bef5d57992f9e987a9b7e8fa736ee204ac4f7a |
| Headers | show |
| Series | Input: tca6416-keypad - replace zero-length array with flexible-array member | expand |
On Fri, Feb 14, 2020 at 11:20:22AM -0600, 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> Applied, thank you. > --- > drivers/input/keyboard/tca6416-keypad.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/input/keyboard/tca6416-keypad.c b/drivers/input/keyboard/tca6416-keypad.c > index 2a14769de637..21758767ccf0 100644 > --- a/drivers/input/keyboard/tca6416-keypad.c > +++ b/drivers/input/keyboard/tca6416-keypad.c > @@ -33,7 +33,7 @@ MODULE_DEVICE_TABLE(i2c, tca6416_id); > > struct tca6416_drv_data { > struct input_dev *input; > - struct tca6416_button data[0]; > + struct tca6416_button data[]; > }; > > struct tca6416_keypad_chip { > @@ -48,7 +48,7 @@ struct tca6416_keypad_chip { > int irqnum; > u16 pinmask; > bool use_polling; > - struct tca6416_button buttons[0]; > + struct tca6416_button buttons[]; > }; > > static int tca6416_write_reg(struct tca6416_keypad_chip *chip, int reg, u16 val) > -- > 2.25.0 >
diff --git a/drivers/input/keyboard/tca6416-keypad.c b/drivers/input/keyboard/tca6416-keypad.c index 2a14769de637..21758767ccf0 100644 --- a/drivers/input/keyboard/tca6416-keypad.c +++ b/drivers/input/keyboard/tca6416-keypad.c @@ -33,7 +33,7 @@ MODULE_DEVICE_TABLE(i2c, tca6416_id); struct tca6416_drv_data { struct input_dev *input; - struct tca6416_button data[0]; + struct tca6416_button data[]; }; struct tca6416_keypad_chip { @@ -48,7 +48,7 @@ struct tca6416_keypad_chip { int irqnum; u16 pinmask; bool use_polling; - struct tca6416_button buttons[0]; + struct tca6416_button buttons[]; }; static int tca6416_write_reg(struct tca6416_keypad_chip *chip, int reg, u16 val)
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/input/keyboard/tca6416-keypad.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)