first question: WHAT COMPILER?
as far as I know, none of the currently available C compilers are cross-compatible because they don't all conform to a standard specification, ie - ANSI C.
Therefore, without knowing what compiler you plan to use it's hard to give very useful example code.
I use BoostC, and have attached the header file that I usually use to run LCD's in 4-bit interface mode. All the I/O pins required need to be defined before the header file is included. The only built-in (proprietary) compiler functions that I make use of are the delay routines. I would expect most compilers have similar functions built-in, if not you would have to write your own. Also note that this header file is for a 2-line display. It should not take much work to modify it for a 4-line.
I would highly recommend you do some google searching and find some good info on the HD44780 LCD interfacing protocol so you actually understand what's involved in driving one. In my experience, 90% of the work in implementing an LCD interface is in getting the initialization routine working, since it requires your instruction routine works, and also requires proper data and timing between steps. After you get it initialized, the rest is easy.