[DiscoBBQ]

Alright, so I am a little confused as to what functions/classes I can access.

My current compile dependencies are "common;public;public\tier0;public\tier1;game \server;game\shared;"
Linking with "lib\common & lib\public"

Does that mean I can reference anything within those header files?

For instance, In my current code, anytime I try to pull a function from util.h, I always receive an 'unresolved external error' (which occurs when there is no implementation in the linked libraries, right?).

For example:

void CASW_Plugin::FireGameEvent( KeyValues * event )
{

 const char * eventName = event->GetName();

 if(strcmp("marine_hurt", eventName) == 0)
 {

		int index = event->GetInt("entindex");
		edict_t *pEntity = PEntityOfEntIndex(index);
		Vector org = pEntity->GetCollideable()->GetCollisionOrigin();

		//UNRESOLVED EXTERNAL ERROR:
		UTIL_BloodSpray( org, org, 0, 10, 12 );
 }
)

[pRED*]

As a general rule you should stick to files within public/.

The current example doesn't compile because the definition of UTIL_BloodSpray is inside a .cpp file someone in the sdk, and isn't being compiled into your project. You really don't want to add this cpp file to the project as the code within it probably won't match the current game.

The 3 main solutions for this are (in order of preference):

1) Find the definition and reimplement it using code you can access.
2) Lookup the compiled definition of the code inside the valve binary at runtime, known as signature scanning. Lots of information on this around the forums/wiki.
3) Linux only, add the server/engine binaries to your link path and let the loader do the equivalent of signature scanning for you.

[DiscoBBQ]

That was very informative and answered my question completely,
Thank you Pred.