Re: [lwip-devel] [bug #35875] #define ⇒ enum?

[David Empson]

One argument against using enums (admittedly weak): some compilers, 
including one we are using, implement enums as unsigned instead of 
signed integers, in violation of C standards. Attempting to declare a 
negative enum value produces an error. I generally prefer to use enums 
for named constants, but with this compiler I've had to use #define for 
negative values.

If LWIP switches from #define to enum for declaring constants, and some 
of the values are negative, our port will have to partly undo these 
changes and keep using #define for the constants with negative values. 
From a quick glance, this may only affect err.h and the PPPERR 
constants in ppp.h so it should be pretty minor.