Linker error 2001?

[v0idy]

Hello, facepunch.
I have recently began coding Garry's Mod C++ modules with SourceSDK and the lua headers.
But when I use function declared in SourceSDK files (convar.h, icvar.h) like Warning, DevMsg, Msg and the cvar pointer it will throw these linker errors:

1>Atlas.obj : error LNK2001: unresolved external symbol __imp__Msg
error LNK2001: unresolved external symbol __imp__Warning
error LNK2001: unresolved external symbol "class ILuaInterface * g_Lua" (?g_Lua@@3PAVILuaInterface@@A)
error LNK2001: unresolved external symbol _cvar

bool ChangeCvar(const char * GFCvar, int CVal)
{
	try
	{
		ConVar *CCvar  = cvar->FindVar(GFCvar);
		CCvar->AddFlags(0);
		CCvar->SetValue(CVal);
		return true;
	}
	catch(char * str)
	{
		Warning("Edit CVAR Error: %s", str);
		return false;
	}
}

Sorry if this is a low quality post I just couldn't find anything searching.