Thank you for your detailed explanation!
Thanks,
Alan
> 2023年3月18日 上午4:29，Darrick J. Wong <djwong@xxxxxxxxxx> 写道：
>
> On Fri, Mar 17, 2023 at 06:43:40PM +0800, Alan Huang wrote:
>> Is there any reason keep these definition with different types? Question from a newbie...
>
> Probably not, but char* handling in C is a mess if you don't specify
> signedness -- on some arches gcc interprets "char" as "signed char", and
> on others it uses "unsigned char". The C library string functions all
> operate on "char *", so if you start changing types you quickly end up
> in compiler warning hell over that.
>
> libxfs seems to use "unsigned char*" and "uint8_t *". I don't know if
> that was just an SGI thing, or merely a quirk of the codebase? The
> Linux VFS code all take "char *", though as of 6.2 the makefiles force
> those to unsigned everywhere. As far as directory entry and extended
> attribute names go, all eight bits are allowed.
>
> UTF8 encoding uses the upper bit of a char, which means that we really
> want unsigned to avoid problems with sign extension when computing
> hashes and things like that, because emoji and kanji characters are in
> use around the world.
>
> IOWS: it's a giant auditing headache to research what parts use the type
> declarations they do, figure out what subtleties go with them, and
> decide on appropriate fixes. And in the end... the system still behaves
> the same way it did.
>
> --D
>
>> Thanks,
>> Alan
>>
>>> 2023年3月17日 下午6:25，Carlos Maiolino <cem@xxxxxxxxxx> 写道：
>>>
>>> On Tue, Mar 14, 2023 at 06:01:10PM -0700, Darrick J. Wong wrote:
>>>> From: Darrick J. Wong <djwong@xxxxxxxxxx>
>>>>
>>>> Make the warnings about signed/unsigned char pointer casting go away.
>>>> For printing dirent names it doesn't matter at all.
>>>>
>>>> Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
>>>
>>> Looks good, will test.
>>>
>>> Reviewed-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
>>>
>>>> ---
>>>> db/namei.c | 4 ++--
>>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/db/namei.c b/db/namei.c
>>>> index 00e8c8dc6d5..063721ca98f 100644
>>>> --- a/db/namei.c
>>>> +++ b/db/namei.c
>>>> @@ -98,7 +98,7 @@ path_navigate(
>>>>
>>>> for (i = 0; i < dirpath->depth; i++) {
>>>> struct xfs_name xname = {
>>>> - .name = dirpath->path[i],
>>>> + .name = (unsigned char *)dirpath->path[i],
>>>> .len = strlen(dirpath->path[i]),
>>>> };
>>>>
>>>> @@ -250,7 +250,7 @@ dir_emit(
>>>> uint8_t dtype)
>>>> {
>>>> char *display_name;
>>>> - struct xfs_name xname = { .name = name };
>>>> + struct xfs_name xname = { .name = (unsigned char *)name };
>>>> const char *dstr = get_dstr(mp, dtype);
>>>> xfs_dahash_t hash;
>>>> bool good;
>>>
>>> --
>>> Carlos Maiolino
>>
