October 10, 2017

My Little Pony And The Downfall Of Western Civilization

Our current political climate is best described as a bunch of chimpanzees angrily throwing feces at each other. Many people recognize that there are many problems with modern politics, but few agree on what those problems actually are. Liberals, republicans, Trump, millenials, capitalism, communism, too many regulations, too few regulations, gerrymandering, illegal immigrants, rich people, poor people, schools, governments, religion, secularism, the list goes on and on and on. These, however, are not problems, they are excuses. They are scapegoats we have conjured up from our mental list of things we don't like so we can ignore the ugly truth.

At some point, Americans are going to have to admit that the entire problem with this country has been summed up in a TV show for six-year-old girls designed to sell toys. My Little Pony was released seven years ago, and as the series has progressed, it has focused more and more on reforming villains instead of defeating them. Time and time again, ponies refuse to give up on those who seem lost to darkness and try to figure out what is causing them to lash out. A central theme of the show is that almost no one is truly a "villain", only misguided, misunderstood, or pushed towards lashing out after a traumatic experience. While a select few villains have been show to be truly irredeemable, this is rare, which is in line with reality. Only a very small percentage of the human population is deliberately evil as opposed to simply lashing out, being stupid, or being tragically misinformed.

It is no longer possible to argue with anyone anymore. This is not because everyone suddenly became incapable of critical thought, but because no one can agree on any facts. When we built the internet, we thought having access to the sum of all human knowledge would bring infinite prosperity, but instead it brought us infinite misinformation. Russians have been making this worse, feeding false narratives to both sides to make us hate each other. It worked. When scientists themselves have been manipulated by corporations without anyone bothering to attempt to reproduce experiments, there simply isn't any good way to verify the truth of anything. The entire point of the scientific method is to make sure something is reproducible, but a staggering number of retractions in recent years has demonstrated that barely anyone actually checks anyone else's work. This has fostered a general distrust in science, even for results that have been reproduced thousands of times, like the thoroughly debunked "Vaccines cause autism!" claim.

This kind of political polarization is untenable. We no longer live in a world where we can get into a fight, stab someone else with a sword and call it good. If our political polarization goes unchecked, it will result in nothing less than the total collapse of western civilization. Humanity will have proven itself too dumb and tribalist to wield a tool as powerful as the internet. Whatever civilization comes after us will struggle to reclaim the technological progress we enjoy, now that we've stripped the planet of resources. If we fail now, humanity will never again be capable of reaching for the stars. We will have sentenced ourselves to live on this small rock until the sun boils the oceans away, doomed by our own stupidity.

There was an episode of My Little Pony that explained the origin of their country, Equestria. The three races, Pegasi, Earth ponies, and Unicorns, hated each other. Evil forces fed on their hatred, smothering the land in snow and threatening to freeze them all to death. So, each race set out to find a new land to colonize, only to suddenly realize that each of them had wound up on the exact same new continent. The leaders of each race immediately started yelling at each other, and the blizzard returned, until each of them was encased in ice. Only when the assistants of each leader realized they didn't actually hate each other were they able to dispel the evil forces by starving them of hatred and talking sense into their leaders. The moral of this story is very clear: either we figure out how to get along, or we're all going to die. I really, honestly don't know how to explain this better than a saturday morning cartoon show about magical ponies.

The problem is that I don't know if humanity is capable of moving past this. I've seen one of my friends rapidly devolve into insane conspiracy theory nonsense, and I simply don't have the mental willpower to engage with them. I eventually had to block them, and accomplished two things at once: reinforcing their echo chamber and reinforcing my echo chamber. I tried to hold on to them as a window into conservative nonsense so my twitter wasn't a complete echo chamber, but when the other side is saying truly horrible things about you, this becomes more and more difficult. It also make it more likely for me to say truly horrible things about the other side, in a vicious, endless cycle, and I simply have too many other things to worry about to be capable of dealing with that level of toxicity. At this stage, I'm not sure humanity has the strength to actually reconcile with itself. I think there is a real possibility that our worries about AI were misplaced - the technology that might ultimately destroy us could be the internet, simply because our tribalist brains are too desperate to find someone to hate. We may be fundamentally incapable of sustaining a global, interconnected society with instantaneous communication.

At least then we'll have a very definitive answer to the Fermi Paradox.

September 5, 2017

I Used To Want To Work For Google

A long time ago I thought Google was this magical company that truly cared about engineering and solving problems instead of maximizing shareholder value. Then Larry Page became CEO and I realized they were not a magical unicorn and lamented the fact that they had been transformed into "just another large company". Several important things happened between that post and now: Microsoft got a new CEO, so I decided to give them a shot and got hired there. I quit right before Windows 10 came out because I knew it was going to be a disaster. More recently, it's become apparent that Google had gone far past simply being a behemoth unconcerned with the cries of the helpless and transformed into something outright malevolent. It's silenced multiple reporters, blocked windows phone from accessing youtube out of spite, and successfully gotten an entire group of researchers fired by threatening to pull funding (but that didn't stop them).

This is evil. This is horrifying. This is the kind of stuff Microsoft did in the 90s that made everyone hate it so much they still have to fight against the repercussions of decisions made two decades ago because of the sheer amount of damage they did and lives they ruined. I'm at the point where I'd rather go back to Microsoft, whose primary sin at this point is mostly just being incompetent instead of outright evil, rather than Google, who is actually doing things that are fundamentally morally wrong. These are the kinds of decisions that are bald-faced abuses of power, without any possible "good intention" driving them. It's vile. There is no excuse.

As an ex-Microsoft employee, I can assure you that at no point did I think Microsoft was doing something evil while I was there. I haven't seen Microsoft do anything outright evil since I left, either. The few times they came close they backed off and apologized later. Microsoft didn't piss people off by being evil, it pissed people off by being dumb. I was approached by a Google recruiter shortly after I left and I briefly considered going to Google because I considered them vastly more competent, and I still do. However, no amount of engineering competency can make me want to work for a company that actively does things I consider morally reprehensible. This is the same reason I will never work for Facebook. I've drawn a line in the sand, and I find myself in the surprising situation of being on the opposite side of Google, and discovering that Microsoft, of all companies, isn't with them.

I always thought I'd be able to mostly disregard the questionable things that Google and Microsoft were doing and compare them purely on the competency of their engineers. However, it seems that Google has every intention of driving me away by doing things so utterly disgusting I could never work there and still be able to sleep at night. This worries me deeply, because as these companies get larger and larger, they eat up all the other sources of employment. Working at a startup that isn't one of the big 5 won't help if it gets bought out next month. One friend of mine with whom I shared many horror stories with worked at LinkedIn. He was not happy when he woke up one day to discover he now worked for the very company he had heard me complaining about. Even now, he's thinking of quitting, and not because Microsoft is evil - they're just so goddamn dumb.

The problem is that there aren't many other options, short of starting your own company. Google is evil, Facebook is evil, Apple is evil if you care about open hardware, Microsoft is too stupid to be evil but might at some point become evil again, and Amazon is probably evil and may or may not treat it's employees like shit depending on who you ask. Even if you don't work directly for them, you're probably using their products or services. At some point, you have to put food on the table. This is why I generally refuse to blame someone for working for an evil company because the economy punishes you for trying to stand up for your morals. It's not the workers fault, here, it's Wall Street incentivizing rotten behavior by rewarding short-term profits instead of long-term growth. A free market optimizes to a monopoly. Monopolies are bad. I don't know what people don't get about this. We're fighting over stupid shit like transgender troops or gay rights instead of just treating other human beings with decency, all the while letting rich people rob us blind as they decimate the economy. This is stupid. I would daresay it's almost more stupid than the guy at Microsoft who decided to fire all the testers.

But I guess I'll take unrelenting stupidity over retaliating against researchers for criticizing you. At least until Microsoft remembers how to be evil. Then I don't know what I'll do.

I don't know what anyone will do.

August 6, 2017

Sexist Programmers Are Awful Engineers

Men and women are fundamentally different. So are white people and black people and autistic people and gay people and transgender people and conservatives and liberals and every other human being along every imaginable axis of discrimination. Some of these differences are cultural. Others are genetic. Others depend on environmental factors. These differences mean that some of us are inherently better at certain tasks than others. On average, men are better at spatial temporal reasoning, women are better at reading comprehension and writing ability, and psychopaths can sometimes be excellent CEOs.

Whenever I meet a programmer who insists on doing everything a certain way, the chances I'll hire them drop off a cliff. Just as object-oriented programming didn't fix everything, neither will functional programming, or data-oriented programming or array-based programming or any other language. They are different tools that allow you to attack a problem from different directions, much like we have different classes of algorithms to attack certain classes of problems. Greedy algorithms, lazy evaluation, dynamic programming, recursive-descent, maximum flow, all of these are different ways to approach a problem. They represent looking at a problem from different perspectives. A problem that is difficult from one angle might be trivial when examined from a different angle.

When I stumbled upon this anti-diversity memo written by a Google employee, I wonder just how dysfunctional of an engineer that person is. Problems are never solved by being closed-minded. They are solved by opening ourselves to new possibilities and exploring the problem space as an infinitely-dimensional fabric of possible configurations. You do not find possible edge-cases by being closed-minded. You find them by probing the outer edges of your solution, trying to find singularities and inflection points that hint at unusual behavior.

You cannot build a great company by hiring people who are good at the same things you are. Attempting to maximize diversity only comes at a perceived cost of aptitude if you are measuring the wrong things. If your concept of what makes a "good programmer" is an extremely narrow set of skills, then you will inevitably select towards a specific ethnicity, culture, or sex, because the tiny statistical differences will be grossly magnified by the extremely narrow job requirements. Demand that all your programmers invert a binary tree on a whiteboard and you'll filter out the guy who wrote the software 90% of your company uses.

If you think the field of computer science is really this narrow, you're a terrible programmer. Turing completeness is a fundamental property of the universe, and we are only just beginning to explore the full implications of information theory, the foundations of type theory, NP-completeness, and the nature of computation itself. Disregarding other people because they can't do something without ever considering what they can do will only hurt your team, and your company. Diversity inclusion programs shouldn't try to hire more women and ethnic groups because they're the same, they should be trying to hire them because they are different.

When hiring someone to complete a job, you should hire whoever is the best fit for the job. In a vacuum where there is a single task that needs to be completed, gender and ethnicity should be ignored in favor of a purely meritocratic assessment. However, if you have a company that must respond to a changing world, diversity can reveal solutions you never even knew existed. An established company like Google must actively seek to increase diversity so that it can explore new perspectives that may give it an edge over its rivals. They cannot select on a purely meritocratic basis, because all measures of merit would be based on what the company is already good at, not what it could be good at. You cannot explore new opportunities by hiring the same people.

Intelligent people value feedback from people who think differently than them. This is why many executives will deliberately hire people they disagree with so they can have someone challenge their views. This helps avoid creating an echo-chamber, which is the ultimate irony of a memo that's called "Google’s Ideological Echo Chamber", because scrapping the diversity inclusion programs as the memo suggests would itself create a new echo-chamber. You can't remove an echo-chamber by removing diversity - the author's premise is self-defeating. If they had stuck with only claiming that conservative ideologies should not be discriminated against, they would have been correct. Unfortunately, telling everyone they shouldn't discriminate against your perspective, which itself involves discriminating against other perspectives, is by definition a contradiction.

We aren't going to write better programs by doing the same thing we've been doing for the past 10 years. To improve is to change, and those who seek to become better software engineers must themselves embrace change, or they will be left behind to rot in the sewers of forgotten programs, maintaining rancid enterprise code for the rest of their lives. If we are unwilling to change who is writing the programs, we'll be stuck making the same thing over and over again. A business that thinks nothing needs to change is one ripe for disruption. If you really think only hiring white males who correctly answer all your questions about graph theory and B-trees will help your business in the long-term, you're an idiot.

July 30, 2017

Why I Never Built My SoundCloud Killer

While the news of SoundCloud imploding are fairly recent, musicians and producers have had a beef with the music uploading site's direction for years. I still remember when SoundCloud only gave you a paltry 2 hours worth of free upload time and managed to convert my high quality lossless WAV files to the shittiest 128 kbps MP3 I've ever heard in my life. What really pissed me off was that they demanded a ridiculous $7 a month just to double your upload time. This is in contrast to Newgrounds, a tiny website run by a dozen people with an audio portal built almost as an afterthought that still manages to be superior to every single other offering. It gives you unlimited space, for free, and lets you upload your own MP3, which allows me to upload properly encoded joint-stereo 128 kbps MP3 files, or much higher quality MP3s for songs I'm giving out for free.

Obviously, Newgrounds is only able to offer unlimited free uploads because the audio portal just piggybacks on the rest of the site. However, I was so pissed off at SoundCloud's disgusting subscription offering that I actually ran the numbers in terms of what it would cost to store lossless FLAC encodings of songs using Amazon S3. These calculations are now out of date, so I've redone them for the purposes of this blog.

The average size of an FLAC encoded song is around 60 MB, but we'll assume it's 80 MB as an upper-bound, and to include the cost of storing the joint-stereo 128 kbps streaming MP3, which is usually less than 10% the size (using OPUS would reduce this even more, but it is not supported on all browsers yet). Amazon offers the first 50 TB of storage at $0.023 per gigabyte, per month. This comes down to about $0.00184 per month, per song, in order to store the full uncompressed version. Now, obviously, we must also stream the song, but we're only streaming the low-quality version, which is 10% the size, which is about 7 MB in our example (7 MB + 70 MB is about 80 MB for storage). The vast majority of music producers on the website have almost no following, and most will be lucky to get a single viral hit. As an example, after being on SoundCloud for over 7 years, I have managed to amass a mere 100000 views total. If I somehow got 20000 views of my songs every single month, the total cost of streaming 140 GB from Amazon S3 at $0.05 per GB would be $7 per month. That's how much SoundCloud is charging just to double my storage space!

This makes even less sense when you calculate that 6 hours of FLAC would be 4.7 GB, or about 5 GB including the 128 kbps streaming MP3s. 5 GB of storage space costs a pathetic $0.12 cents a month to store on Amazon S3! All of the costs come down to bandwidth, which is relatively fixed by how many people are listening to songs, not how many songs there are. This means, if I'm paying any music service for the right to store music on their servers, I should get near unlimited storage space (maybe put in a sanity check of 10 GB max per month to limit abuse). I will point out that Clyp.it actually does this properly, giving you 6 hours of storage space for free and unlimited storage space if you pay them $6 a month.

Unfortunately, Clyp.it does not try to be SoundCloud as it has no comments, no reshares, and well, not much of anything, really. It's like a giant pastebin for sounds where you can follow people or favorite things. It's also probably screwed.

Even though I had a name and a website design, I never launched it because even if I could find a way to identify a copyrighted song via some sort of ContentID system, I couldn't make it work without the record industry's cooperation. The problem is that the system has to know what songs are illegal in order to block them in the first place. Otherwise, people could upload Justin Bieber songs with impunity and I'd still get sued out of existence. The hard part about making a site like SoundCloud isn't actually making the website, it's dealing with the insane, litigation-happy oligarchs that own the entire music industry.

SoundCloud's ordeal is mentioned in this article. Surprisingly, it took until 2012 for them to realize they had to start making deals with the major music labels. It took until 2014 for many of those deals to actually happen, and they were not in SoundCloud's favor. A deal with Warner Music Group, closed in 2014, gave Warner a 3-5% stake in the company and an undisclosed cut of ad-revenue, just so SoundCloud could have the privilege of not being sued out of existence. This wasn't even an investment round, it was just so SoundCloud could have Warner Music Group's catalog on the site and not get sued!

At this point, you have to be either very naive or very rich to go up against an industry that can and will send an army of lawyers after you. The legal system is not in your favor. It will be used to crush you like a bug and there is nothing you can do about it, because of one fundamental problem: You can't detect copyright infringement without access to the original copy.

Because of this, the music industry holds the entire world hostage with a kind of Catch-22: They demand you take down all copyright infringing material, but in order to figure out if something is copyright infringement, you need access to their songs, which they only give out on their terms, which are never in your favor.

July 24, 2017

Integrating LuaJIT and Autogenerating C Bindings In Visual Studio

Lua is a popular scripting language due to its tight integration with C. LuaJIT is an extremely fast JIT compiler for Lua that can be integrated into your game, which also provides an FFI Library that directly interfaces with C functions, eliminating most overhead. However, the FFI library only accepts a subset of the C standard. Specifically, "C declarations are not passed through a C pre-processor, yet. No pre-processor tokens are allowed, except for #pragma pack." The website suggests running the header file through a preprocesser stage, but I have yet to find a LuaJIT tutorial that actually explains how to do this. Instead, all the examples simply copy+paste the function prototype into the Lua file itself. Doing this with makefiles and GCC is trivial, because you just have to add a compile step using the -E option, but integrating this with Visual Studio is more difficult. In addition, I'll show you how to properly load scripts and modify the PATH lookup variable so your game can have a proper scripts folder instead of dumping everything in bin.

Compilation

To begin, we need to download LuaJIT and get it to actually compile. Doing this manually isn't too difficult, simply open an x64 Native Tools Command Prompt (or x86 Native Tools if you want 32-bit), navigate to src/msvcbuild.bat and run msvcbuild.bat. The default options will build an x64 or x86 dll with dynamic linking to the CRT. If you want a static lib file, you need to run it with the static option. If you want static linking to the CRT so you don't have to deal with that annoying Visual Studio Runtime Library crap, you'll have to modify the .bat file directly. Specifically, you need to find %LJCOMPILE% /MD and change it to %LJCOMPILE% /MT. This will then compile the static lib or dll with static CRT linking to match your other projects.

This is a bit of a pain, and recently I've been trying to automate my build process and dependencies using vcpkg to act as a C++ package manager. A port of LuaJIT is included in the latest update of vcpkg, but if you want one that always statically links to the CRT, you can get it here.

An important note: the build instructions for LuaJIT state that you should copy the lua scripts contained in src/jit to your application folder. What it doesn't mention is that this is optional - those scripts contain debugging instructions for the JIT engine, which you probably don't need. It will work just fine without them.

Once you have LuaJIT built, you should add it's library file to your project. This library file is called lua51.lib (and the dll is lua51.dll), because LuaJIT is designed as a drop-in replacement for the default Lua runtime. Now we need to actually load Lua in our program and integrate it with our code. To do this, use lua_open(), which returns a lua_State* pointer. You will need that lua_State* pointer for everything else you do, so store it somewhere easy to get to. If you are building a game using an Entity Component System, it makes sense to build a LuaSystem that stores your lua_State* pointer.

Initialization

The next step is to load in all the standard Lua libraries using luaL_openlibs(L). Normally, you shouldn't do this if you need script sandboxing for player-created scripts. However, LuaJIT's FFI library is inherently unsafe. Any script with access to the FFI library can call any kernel API it wants, so you should be extremely careful about using LuaJIT if this is a use-case for your game. We can also register any C functions we want to the old-fashioned way via lua_register, but this is only useful for functions that don't have C analogues (due to having multiple return values, etc).

There is one function in particular that you probably want to overload, and that is the print() function. By default, Lua will simply print to standard out, but if you aren't redirecting standard out to your in-game console, you probably have your own std::ostream (or even a custom stream class) that is sent all log messages. By overloading print(), we can have our Lua scripts automatically write to both our log file and our in-game console, which is extremely useful. Here is a complete re-implementation of print that outputs to an arbitrary std::ostream& object:
int PrintOut(lua_State *L, std::ostream& out)
{
  int n = lua_gettop(L);  /* number of arguments */
  if(!n)
    return 0;
  int i;
  lua_getglobal(L, "tostring");
  for(i = 1; i <= n; i++)
  {
    const char *s;
    lua_pushvalue(L, -1);  /* function to be called */
    lua_pushvalue(L, i);   /* value to print */
    lua_call(L, 1, 1);
    s = lua_tostring(L, -1);  /* get result */
    if(s == NULL)
      return luaL_error(L, LUA_QL("tostring") " must return a string to "
        LUA_QL("print"));
    if(i > 1) out << "\t";
    out << s;
    lua_pop(L, 1);  /* pop result */
  }
  out << std::endl;
  return 0;
}
To overwrite the existing print function, we need to first define a Lua compatible shim function. In this example, I pass std::cout as the target stream:

int lua_Print(lua_State *L)
{
  return PrintOut(L, std::cout);
}
Now we simply register our lua_Print function using lua_register(L, "print", &lua_Print). If we were doing this in a LuaSystem object, our constructor would look like this:

LuaSystem::LuaSystem()
{
  L = lua_open();
  luaL_openlibs(L);
  lua_register(L, "print", &lua_Print);
}
To clean up our Lua instance, we need to both trigger a final GC iteration to clean up any dangling memory, and then we call lua_close(L), so our destructor would look like this:
LuaSystem::~LuaSystem()
{
  lua_gc(L, LUA_GCCOLLECT, 0);
  lua_close(L);
  L = 0;
}

Loadings Scripts via Require

At this point most tutorials skip to the part where you load a Lua script and write "Hello World", but we aren't done yet. Integrating Lua into your game means loading scripts and/or arbitrary strings as Lua code while properly resolving dependencies. If you don't do this, any one of your scripts that relies on another script will have to do require("full/path/to/script.lua"). We also face another problem - if we want to have a scripts folder where we simply automatically load every single script into our workspace, simply loading them all can cause duplicated code, because luaL_loadfile does not have any knowledge of require. You can solve this by simply loading a single bootstrap.lua script which then loads all your game's scripts via require, but we're going to build a much more robust solution.

First, we need to modify Lua's PATH variable, or the variable that controls where it looks up scripts relative to our current directory. This function will append a path (which should be of the form "path/to/scripts/?.lua") to the beginning of the PATH variable, giving it highest priority, which you can then use to add as many script directories as you want in your game, and any lua script from any of those folders will then be able to require() a script from any other folder in PATH without a problem. Obviously, you should probably only add one or two folders, because you don't want to deal with potential name conflicts in your script files.
int AppendPath(lua_State *L, const char* path)
{
  lua_getglobal(L, "package");
  lua_getfield(L, -1, "path"); // get field "path" from table at top of stack (-1)
  std::string npath = path;
  npath.append(";");
  npath.append(lua_tostring(L, -1)); // grab path string from top of stack
  lua_pop(L, 1);
  lua_pushstring(L, npath.c_str());
  lua_setfield(L, -2, "path"); // set the field "path" in table at -2 with value at top of stack
  lua_pop(L, 1); // get rid of package table from top of stack
  return 0;
}
Next, we need a way to load all of our scripts using require() so that Lua properly resolves the dependencies. To do this, we create a function in C that literally calls the require() function for us:
int Require(lua_State *L,const char *name)
{
  lua_getglobal(L, "require");
  lua_pushstring(L, name);
  int r = lua_pcall(L, 1, 1, 0);
  if(!r)
    lua_pop(L, 1);
  WriteError(L, r, std::cout);
  return r;
}
By using this to load all our scripts, we don't have to worry about loading them in any particular order - require will ensure everything gets loaded correctly. An important note here is WriteError(), which is a generic error handling function that processes Lua errors and writes them to a log. All errors in lua will return a nonzero error code, and will usually push a string containing the error message to the stack, which must then be popped off, or it'll mess things up later.
void WriteError(lua_State *L, int r, std::ostream& out)
{
  if(!r)
    return;
  if(!lua_isnil(L, -1)) // Check if a string was pushed
  {
    const char* m = lua_tostring(L, -1);
    out << "Error " << r << ": " << m << std::endl;
    lua_pop(L, 1);
  }
  else
    out << "Error " << r << std::endl;
}

Automatic C Binding Generation

Fantastic, now we're all set to load up our scripts, but we still need to somehow define a header file and also load that header file into LuaJIT's FFI library so our scripts have direct access to our program's exposed C functions. One way to do this is to just copy+paste your C function definitions into a Lua file in your scripts folder that is then automatically loaded. This, however, is a pain in the butt and is error-prone. We want to have a single source of truth for our function definitions, which means defining our entire LuaJIT C API in a single header file, which is then loaded directly into LuaJIT. Predictably, we will accomplish this by abusing the C preprocessor:

#ifndef __LUA_API_H__
#define __LUA_API_H__

#ifndef LUA_EXPORTS
#define LUAFUNC(ret, name, ...) ffi.cdef[[ ret lua_##name(__VA_ARGS__); ]]; name = ffi.C.lua_##name
local ffi = require("ffi")
ffi.cdef[[ // Initial struct definitions
#else
#define LUAFUNC(ret, name, ...) ret __declspec(dllexport) lua_##name(__VA_ARGS__)
extern "C" { // Ensure C linkage is being used
#endif

struct GameInfo
{
  uint64_t DashTail;
  uint64_t MaxDash;
};

typedef const char* CSTRING; // VC++ complains about having const char* in macros, so we typedef it here

#ifndef LUA_EXPORTS
]] // End struct definitions
#endif

  LUAFUNC(CSTRING, GetGameName);
  LUAFUNC(CSTRING, IntToString, int);
  LUAFUNC(void, setdeadzone, float);

#ifdef Everglade_EXPORTS
}
#endif

#endif
The key idea here is to use macros such that, when we pass this through the preprocessor without any predefined constants, it will magically turn into a valid Lua script. However, when we compile it in our C++ project, our project defines LUA_EXPORTS, and the result is a valid C header. Our C LUAFUNC is set up so that we're using C linkage for our structs and functions, and that we're exporting the function via __declspec(dllexport). This obviously only works for Visual Studio so you'll want to set up a macro for the GCC version, but I will warn you that VC++ got really cranky when i tried to use a macro for that in my code, so you may end up having to redefine the entire LUAFUNC macro for each compiler.

At this point, we have a bit of a choice to make. It's more convenient to have the C functions available in the global namespace, which is what this script does, because this simplifies calling them from an interactive console. However, using ffi.C.FunctionName is significantly faster. Technically the fastest way is declaring local C = ffi.C at the top of a file and then calling the functions via C.FunctionName. Luckily, importing the functions into the global namespace does not preclude us from using the "fast" way of calling them, so our script here imports them into the global namespace for ease of use, but in our scripts we can use the C.FunctionName method instead. Thus, when outputting our Lua script, our LUAFUNC macro wraps our function definition in a LuaJIT ffi.cdef block, and then runs a second Lua statement that brings the function into the global namespace. This is why we have an initial ffi.cdef code block for the structs up top, so we can include that second lua statement after each function definition.

Now we need to set up our compilation so that Visual Studio generates this file without any predefined constants and outputs the resulting lua script to our scripts folder, where our other in-game scripts can automatically load it from. We can accomplish this using a Post-Build Event (under Configuration Properties -> Build Events -> Post-Build Event), which then runs the following code:
CL LuaAPI.h /P /EP /u
COPY "LuaAPI.i" "../bin/your/script/folder/LuaAPI.lua" /Y
Visual Studio can sometimes be finicky about that newline, but if you put in two statements on two separate lines, it should run both commands sequentially. You may have to edit the project file directly to convince it to actually do this. The key line here is CL LuaAPI.h /P /EP /u, which tells the compiler to preprocess the file and output it to a *.i file. There is no option to configure the output file, it will always be the exact same file but with a .i extension, so we have to copy and rename it ourselves to our scripts folder using the COPY command.

Loading and Calling Lua Code

We are now set to load all our lua scripts in our script folder via Require, but what if we want an interactive Lua console? There are lua functions that read strings, but to make this simpler, I will provide a function that loads a lua script from an arbitrary std::istream and outputs to an arbitrary std::ostream:
const char* _luaStreamReader(lua_State *L, void *data, size_t *size)
{
  static char buf[CHUNKSIZE];
  reinterpret_cast(data)->read(buf, CHUNKSIZE);
  *size = reinterpret_cast(data)->gcount();
  return buf;
}

int Load(lua_State *L, std::istream& s, std::ostream& out)
{
  int r = lua_load(L, &_luaStreamReader, &s, 0);

  if(!r)
  {
    r = lua_pcall(L, 0, LUA_MULTRET, 0);
    if(!r)
      PrintOut(L, out);
  }

  WriteError(L, r, out);
  return r;
}

Of course, the other question is how to call Lua functions from our C++ code directly. There are many, many different implementations of this available, of varying amounts of safety and completeness, but to get you started, here is a very simple implementation in C++ using templates. Note that this does not handle errors - you can change it to use lua_pcall and check the return code, but handling arbitrary Lua errors is nontrivial.
template<class T, int N>
struct LuaStack;

template<class T> // Integers
struct LuaStack<T, 1>
{
  static inline void Push(lua_State *L, T i) { lua_pushinteger(L, static_cast<lua_Integer>(i)); }
  static inline T Pop(lua_State *L) { T r = (T)lua_tointeger(L, -1); lua_pop(L, 1); return r; }
};
template<class T> // Pointers
struct LuaStack<T, 2>
{
  static inline void Push(lua_State *L, T p) { lua_pushlightuserdata(L, (void*)p); }
  static inline T Pop(lua_State *L) { T r = (T)lua_touserdata(L, -1); lua_pop(L, 1); return r; }
};
template<class T> // Floats
struct LuaStack<T, 3>
{
  static inline void Push(lua_State *L, T n) { lua_pushnumber(L, static_cast<lua_Number>(n)); }
  static inline T Pop(lua_State *L) { T r = static_cast<T>(lua_touserdata(L, -1)); lua_pop(L, 1); return r; }
};
template<> // Strings
struct LuaStack<std::string, 0>
{
  static inline void Push(lua_State *L, std::string s) { lua_pushlstring(L, s.c_str(), s.size()); }
  static inline std::string Pop(lua_State *L) { size_t sz; const char* s = lua_tolstring(L, -1, &sz); std::string r(s, sz); lua_pop(L, 1); return r; }
};
template<> // Boolean
struct LuaStack<bool, 1>
{
  static inline void Push(lua_State *L, bool b) { lua_pushboolean(L, b); }
  static inline bool Pop(lua_State *L) { bool r = lua_toboolean(L, -1); lua_pop(L, 1); return r; }
};
template<> // Void return type
struct LuaStack<void, 0> { static inline void Pop(lua_State *L) { } };

template<typename T>
struct LS : std::integral_constant<int, 
  std::is_integral<T>::value + 
  (std::is_pointer<T>::value * 2) + 
  (std::is_floating_point<T>::value * 3)>
{};

template<typename R, int N, typename Arg, typename... Args>
inline R _callLua(const char* function, Arg arg, Args... args)
{
  LuaStack<Arg, LS<Arg>::value>::Push(_l, arg);
  return _callLua<R, N, Args...>(function, args...);
}
template<typename R, int N>
inline R _callLua(const char* function)
{
  lua_call(_l, N, std::is_void<R>::value ? 0 : 1);
  return LuaStack<R, LS<R>::value>::Pop(_l);
}

template<typename R, typename... Args>
inline R CallLua(lua_State *L, const char* function, Args... args)
{
  lua_getglobal(L, function);
  return _callLua<R, sizeof...(Args), Args...>(L, function, args...);
}
Now you have everything you need for an extensible Lua scripting implementation for your game engine, and even an interactive Lua console, all using LuaJIT. Good Luck!