| Message ID | 20230315010110.GD11376@frogsfrogsfrogs (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | xfs_db: fix complaints about unsigned char casting | expand |
On Tue, Mar 14, 2023 at 06:01:10PM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong <djwong@kernel.org> > > 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@kernel.org> Looks good, will test. Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com> > --- > 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;
Is there any reason keep these definition with different types? Question from a newbie... Thanks, Alan > 2023年3月17日 下午6:25，Carlos Maiolino <cem@kernel.org> 写道： > > On Tue, Mar 14, 2023 at 06:01:10PM -0700, Darrick J. Wong wrote: >> From: Darrick J. Wong <djwong@kernel.org> >> >> 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@kernel.org> > > Looks good, will test. > > Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com> > >> --- >> 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
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@kernel.org> 写道： > > > > On Tue, Mar 14, 2023 at 06:01:10PM -0700, Darrick J. Wong wrote: > >> From: Darrick J. Wong <djwong@kernel.org> > >> > >> 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@kernel.org> > > > > Looks good, will test. > > > > Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com> > > > >> --- > >> 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 >
Thank you for your detailed explanation! Thanks, Alan > 2023年3月18日 上午4:29，Darrick J. Wong <djwong@kernel.org> 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@kernel.org> 写道： >>> >>> On Tue, Mar 14, 2023 at 06:01:10PM -0700, Darrick J. Wong wrote: >>>> From: Darrick J. Wong <djwong@kernel.org> >>>> >>>> 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@kernel.org> >>> >>> Looks good, will test. >>> >>> Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com> >>> >>>> --- >>>> 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 >>
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;