The following code causes the tclsh to crash (8.6.0 and 8.6.1)

interp create ip; # Need slave because crash only occurs when interp is deleted
set script {
    oo::class create C {method m {} {}}
    C create c
    c m
    oo::define C {deletemethod m}
    c m
}

catch { interp eval ip $script }
interp delete ip

If method m is not deleted or not called after deletion,or interp is not deleted, crash does not occur.

/Ashok