> On Dec 26, 2023, at 11:29 AM, Zhenlei Huang <z...@freebsd.org> wrote:
>
>
>
>> On Dec 26, 2023, at 9:36 AM, Konstantin Belousov <k...@freebsd.org
>> <mailto:k...@freebsd.org>> wrote:
>>
>> The branch main has been updated by kib:
>>
>> URL:
>> https://cgit.FreeBSD.org/src/commit/?id=2a1d50fc12f6e604da834fbaea961d412aae6e85
>>
>> <https://cgit.freebsd.org/src/commit/?id=2a1d50fc12f6e604da834fbaea961d412aae6e85>
>>
>> commit 2a1d50fc12f6e604da834fbaea961d412aae6e85
>> Author: Andrew Gierth <and...@tao146.riddles.org.uk
>> <mailto:and...@tao146.riddles.org.uk>>
>> AuthorDate: 2023-12-24 12:04:21 +0000
>> Commit: Konstantin Belousov <k...@freebsd.org <mailto:k...@freebsd.org>>
>> CommitDate: 2023-12-26 01:35:46 +0000
>>
>> vfs_domount_update(): correct fsidcmp() usage
>>
>> MFC after: 3 days
>> ---
>> sys/kern/vfs_mount.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c
>> index 8e54c832e9f1..331e4887c200 100644
>> --- a/sys/kern/vfs_mount.c
>> +++ b/sys/kern/vfs_mount.c
>> @@ -1388,7 +1388,7 @@ vfs_domount_update(
>> error = EINVAL;
>> goto end;
>> }
>> - if (fsidcmp(&fsid_up, &mp->mnt_stat.f_fsid) != 0) {
>> + if (fsidcmp(fsid_up, &mp->mnt_stat.f_fsid) != 0) {
>> error = ENOENT;
>> goto end;
>> }
>
>
The fsidcmp is currently defined as
```
#define fsidcmp(a, b) memcmp((a), (b), sizeof(fsid_t))
```
>
> I guess we want to ensure ` typeof(a) == typeof(b) == fsid_t `, to prevent
> such kind of error in future.
>
> I see both gcc [1] and clang [2] have __builtin_types_compatible_p , so
> probably a good definition of fsidcmp should be
>
> ```
> #define TYPEASSERT(v, t) \
> _Static_assert(__builtin_types_compatible_p(typeof(v), t), "Requires
> type '" #t "'")
>
> #define fsidcmp(a, b) ({ \
> TYPEASSERT((a), fsid_t *); \
> TYPEASSERT((b), fsid_t *); \
> memcmp((a), (b), sizeof(fsid_t)); \
> })
> ```
>
> 1. https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html
> <https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html>
> 2. https://clang.llvm.org/docs/LanguageExtensions.html
> <https://clang.llvm.org/docs/LanguageExtensions.html>
> Best regards,
> Zhenlei
>
