Message ID | 20200319224326.GA25390@embeddedor.com |
---|---|
State | Accepted |
Delegated to: | Ambarus Tudor |
Headers | show |
Series | [next] mtd: spi-nor: controllers: aspeed-smc: Replace zero-length array with flexible-array member | expand |
On Friday, March 20, 2020 12:43:26 AM EET Gustavo A. R. Silva wrote: > EXTERNAL EMAIL: Do not click links or open attachments unless you know the > content is safe > > 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/mtd/spi-nor/controllers/aspeed-smc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Applied, thanks. ta
diff --git a/drivers/mtd/spi-nor/controllers/aspeed-smc.c b/drivers/mtd/spi-nor/controllers/aspeed-smc.c index 395127349aa8..e26a1897db0e 100644 --- a/drivers/mtd/spi-nor/controllers/aspeed-smc.c +++ b/drivers/mtd/spi-nor/controllers/aspeed-smc.c @@ -109,7 +109,7 @@ struct aspeed_smc_controller { void __iomem *ahb_base; /* per-chip windows resource */ u32 ahb_window_size; /* full mapping window size */ - struct aspeed_smc_chip *chips[0]; /* pointers to attached chips */ + struct aspeed_smc_chip *chips[]; /* pointers to attached chips */ }; /*
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/mtd/spi-nor/controllers/aspeed-smc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)