C has only positive constants: -1 is really an expression, the unary '-' operator applied to the constant 1. '-1' as a constant value only exists after the expansion of constant expressions. This is rather unfortunate since it inhibits easy testing of such constants in the evaluation phase, like here for restricted_value(). So, expand expressions like +CTE, -CTE or ~CTE before calling restricted_value(). Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>