Correct compilation errors reported by GCC 10/11

[szubersk]

Motivation and Context

#12167

Description

New zfs_type_t value ZFS_TYPE_INVALID is introduced.
Variable initialization is now possible to make GCC happy.

Close #12167.

How Has This Been Tested?

$ make

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

[behlendorf]

This breaks the build on FreeBSD,

  CC       os/freebsd/libzfs_zmount.lo
os/freebsd/libzfs_compat.c:295:10: error: enumeration value 'ZFS_TYPE_INVALID' not handled in switch [-Werror,-Wswitch]
        switch (zhp->zfs_type) {

[szubersk]

This breaks the build on FreeBSD,

Thanks for spotting this! Corrected and rebased. As a bonus, I got rid of shadowed errbuf stack variable in lib/libzfs/os/freebsd/libzfs_compat.c (cppcheck complained).

[behlendorf]

Looks good, thanks for sorting this out.

[behlendorf]

@szubersk we're going to need one more rebase. I've just merged #13110 which has a conflict.

[szubersk]

@behlendorf, rebased.

[szubersk]

@behlendorf I found 2 more issues: one from Debian bullseye ASan+UBSan, the other one from Debian Bookworm. Most likely other would hit them soon.