| Message ID | 20200507192550.GA16683@embeddedor (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | ec38c0adc0a149496b6b0e0bfcff9bc7d80db2c4 |
| Headers | show |
| Series | scsi: ufs: Replace zero-length array with flexible-array | expand |
On Thu, 7 May 2020 14:25:50 -0500, 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[]; > }; > > [...] Applied to 5.8/scsi-queue, thanks! [1/1] scsi: ufs: Replace zero-length array with flexible-array https://git.kernel.org/mkp/scsi/c/ec38c0adc0a1
On Tue, May 12, 2020 at 03:28:31AM +0000, Martin K. Petersen wrote: > On Thu, 7 May 2020 14:25:50 -0500, Gustavo A. R. Silva wrote: > > Applied to 5.8/scsi-queue, thanks! > > [1/1] scsi: ufs: Replace zero-length array with flexible-array > https://git.kernel.org/mkp/scsi/c/ec38c0adc0a1 > Thanks, Martin. -- Gustavo
diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index 698e8d20b4ba..cd34a7873623 100644 --- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c @@ -3223,7 +3223,7 @@ static inline int ufshcd_read_desc(struct ufs_hba *hba, struct uc_string_id { u8 len; u8 type; - wchar_t uc[0]; + wchar_t uc[]; } __packed; /* replace non-printable or non-ASCII characters with spaces */
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] sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues. 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 <gustavoars@kernel.org> --- drivers/scsi/ufs/ufshcd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)