#if & #error giving C322 Error - enum not defined?

Hi

Here is the code I have problems with
I an just starting to use this C compiler
Have used many others, mainly closer to C99

#define Num_LANGUAGEs 6


enum _LANGUAGE {
	eUSING_LAN_START = -1,	// This is always the First item
	eUSING_ENGLISH,
	eUSING_ITALIAN,
	eUSING_FRENCH_Can,
	eUSING_LAST_LANG	// This is always the Last item
};

#if Num_LANGUAGEs != eUSING_LAST_LANG
#error "Warning Not enough Lang defined"
#endif

Where is a list of C Compiler error defs(Not in manual)?

Manual poor on #if conditionals, where can I find more info?

Where is "cosf" function, for faster math?
Where is source for Libraries?