You shouldn't really assign numeric values - that kills much of the advantages with enumerators.

If the compiler will warn or not depends on used compiler, and what warning levels you have turned on.

Another question is - will your compiler warn about:

switch (my_enum_var) {
    case actionEmpty: break;
    case actionOn: break;
    case actionOff: break;
    //actionRegulate, <= case not handled
    case actionPulse: break;
}

With #define, the missing rule for actionRegulate can not be detected. Many compilers will inform that actionRegulate doesn't have an explicit match and that there isn't any garbage collect using a default case.

The difference between enum and #define is that good use of enum always gives more information to the programmer. And use of enum will allow better compiler to produce additional type checking. The #define search/replace does not give any information to programmer or compiler about what set of values that are intended for a variable.