vhdl-mode-hook is a variable defined in `vhdl-mode.el'.
Its value is
(align-set-vhdl-rules)
This variable may be risky if used as a file-local variable.
Documentation:
Hook run after entering (quote (VHDL (vhdl-electric-mode / (vhdl-stutter-mode /)) (vhdl-electric-mode e) (vhdl-stutter-mode s))) mode.
No problems result if this variable is not bound.
`add-hook' automatically binds it. (This is true for all hook variables.)