A difference between 'struct utmp' and 'struct utmpx' is that
the former uses UT_LINESIZE for the size of its array members,
while the latter doesn't have a standard variable to get its
size. Therefore, we need to get the number of elements in
the array with NITEMS().
Reviewed-by: Iker Pedrosa <ipedrosa@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Cc: Firas Khalil Khana <firasuke@gmail.com>
Cc: "A. Wilfox" <https://github.com/awilfox>
Cherry-picked-from: 5ff6edf9f2 ("lib/utmp.c: Replace UT_LINESIZE by a NITEMS() calculation")
Signed-off-by: Alejandro Colomar <alx@kernel.org>
utmpx is specified by POSIX as an XSI extension. That's more portable
than utmp, which is unavailable for example in musl libc. The manual
page specifies that in Linux (but it probably means in glibc), utmp and
utmpx (and the functions that use them) are identical, so this commit
shouldn't affect glibc systems.
Assume utmpx is always present.
Also, if utmpx is present, POSIX guarantees that some members exist:
- ut_user
- ut_id
- ut_line
- ut_pid
- ut_type
- ut_tv
So, rely on them unconditionally.
Fixes: 170b76cdd1 ("Disable utmpx permanently")
Closes: <https://github.com/shadow-maint/shadow/issues/945>
Reported-by: Firas Khalil Khana <firasuke@gmail.com>
Reported-by: "A. Wilfox" <https://github.com/awilfox>
Tested-by: Firas Khalil Khana <firasuke@gmail.com>
Reviewed-by: Iker Pedrosa <ipedrosa@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Cherry-picked-from: 64bcb54fa9 ("lib/, src/, configure.ac: Use utmpx instead of utmp")
Signed-off-by: Alejandro Colomar <alx@kernel.org>
