| Message ID | 20200213002430.GA31056@embeddedor.com (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | cfb8d7811f815d17babadd87436300261fd54de7 |
| Headers | show |
| Series | Input: goldfish_events - Replace zero-length array with flexible-array member | expand |
On Wed, Feb 12, 2020 at 06:24:30PM -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/goldfish_events.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/input/keyboard/goldfish_events.c b/drivers/input/keyboard/goldfish_events.c > index bc8c85a52a10..57d435fc5c73 100644 > --- a/drivers/input/keyboard/goldfish_events.c > +++ b/drivers/input/keyboard/goldfish_events.c > @@ -30,7 +30,7 @@ struct event_dev { > struct input_dev *input; > int irq; > void __iomem *addr; > - char name[0]; > + char name[]; > }; > > static irqreturn_t events_interrupt(int irq, void *dev_id) > -- > 2.23.0 >
diff --git a/drivers/input/keyboard/goldfish_events.c b/drivers/input/keyboard/goldfish_events.c index bc8c85a52a10..57d435fc5c73 100644 --- a/drivers/input/keyboard/goldfish_events.c +++ b/drivers/input/keyboard/goldfish_events.c @@ -30,7 +30,7 @@ struct event_dev { struct input_dev *input; int irq; void __iomem *addr; - char name[0]; + char name[]; }; static irqreturn_t events_interrupt(int irq, void *dev_id)
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/goldfish_events.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)