Trying to build pam_mount 2.8 (or 2.7) against libHX-3.10.1 fails with
mtencfs13.c:48:2: error: size of unnamed array is negative
I will try to find out whether libHX or pam_mount is "to blame", but I hope you can decide that more quickly.
Attached is a full build log (from paludis running on exherbo).
Compiles fine on the exact same system with libHX-3.9.1.