May 6, 2012

Website Mania

By the 1840s, a "Railroad Mania" was raging, with stocks selling on multiples of passenger miles, a precursor for multiples of page views that Yahoo stock would trade on 150 years later. An inventor named Charles Babbage complained that "the railroad mania withdrew from other pursuits the most intellectual and skillful draftsmen." [...] Investors made money, investors lost money, but in the best and worst of times, the railroads got built, and people and goods were shuffled about.

How We Got Here, A Slightly Irreverent History of Technology and Markets

I think that, these days, Babbage would be looking for the systems programmers.

Using C89 in 2012 isn't crazy

The first group I worked with in industry wrote the compiler in C and made fun of C++ on a regular basis. The second group I worked with in industry wrote the compiler in C++ and made fun of C on occasion. Like most systems programmers I've met, they were a loveable, but snarky bunch!

In any case, I've seen life on both sides of the fence, and there's really simple reasoning that dictates what you choose from C89, GNU C, C99, C++98, or C++11 in the year 2012 AD:

If this sounds simple, you're lucky!

Life gets a little bit more interesting when the match is fuzzy: you could make a strategic gamble and (at least initially) ignore parts of your "maximal" target market to gain some productivity. If you're under the gun, that may be the right way to go.

But then again, keeping your options open is also important. The wider the target market the more people you can give an immediate "yes" to. I have to imagine that phone calls like this can be important:

[A sunny afternoon in a South Bay office park. Just outside, a white Prius merges three lanes without activating a blinker. Suddenly, the phone rings.]

Nice to hear from you, Bigbucks McWindfall! What's that? You say you want my code to run as an exokernel on an in-house embedded platform with an in-house C89 toolchain? No problem! We'll send a guy to your office to compile our product and run tests tomorrow morning.

Suffice it to say that there are legitimate considerations. Consider that GCC isn't everywhere (though I love how prevalent it is these days!) and it certainly doesn't generate the best code on every platform for every workload. Consider that MSVC can only compile C89 as "real" C (as opposed to a C++ subset). Consider that the folks out there who have custom toolchains probably have them because they can afford them.

There are benefits to taking a dependency on a lowest common denominator.

Paradox of the generalist

Classic management advice is to build a republic: each team member specializes in what they're good at. It just makes sense.

You nurture existing talents in attempt to ensure personal growth; simultaneously, you fill niches that need filling, constructively combine strengths, and orchestrate sufficient overlap in order to wind up with a functioning, durable, kick-ass machine of a team. A place for everyone, everyone in their place, and badassery ensues! (So the old saying goes...)

But what if, instead, you could simultaneously fork off N teams — one for every team member — and make that team member simultaneously responsible for everything? What would happen to the personal knowledge, growth rate, and impact of each member?

Let's take it one step farther: imagine you're that team member. All of a sudden it sounds terrifying, right? If you don't know it, nobody does. If you don't do it, nobody will. If you don't research it, you'll have no idea what it's about. If you don't network, no contacts are made. If you don't ship it, you know it will never change the firm/industry/world.

So, you think like you've been trained to think: you disambiguate the possible results. What could happen? Maybe you'd crumble under the pressure. Maybe you wouldn't be able to find your calling because you're glossing over the details that make you an artisan. Maybe you'd look like a fool. Maybe you would ship totally uninteresting crap that's all been done before.

But, then again, maybe you would grow like you've never grown before, learn things that you never had the rational imperative to learn, talk to interesting people you would have never talked to, ship a product that moves an industry, and blow the fucking lid off of a whole can of worms.

And so we arrive at one tautological cliché that I actually agree with: you never know until you try. And, if you choose wisely, you'll probably have a damn good time doing it.

At the least, by definition, you'll learn something you couldn't have learned by specializing.

Accomplish your new year's resolution of being more badass

I know what you're going through — I've done it all before.

The market is teeming with products that purport to help you meet your badassery quota.

First you do the shakes. Then, you go with the bars that say they're infused with the good stuff, but just seem to leave a slightly corrugated taste in your mouth. Finally, you're droppin' hard-earned dinero on a facility that you don't need or a professional badassery trainer whose appointments you desperately wish you could cancel.

But I'm here to tell you don't need to shell out cash-money to become more badass, my friends. Not anymore, thanks to the beauty of open source, the ES6 plans wiki page, and our delightful SpiderMonkey technical staff who are standing by to receive your calls for mentorship.

Allow me to explain.

Badass begets badass

You may have seen Badass JavaScript: self described as, "A showcase of awesome JavaScript code that pushes the boundaries of what's possible on the web." Check out their badass year in review if you haven't. (Some of the stuff that the interwebs has done with JavaScript even has @NeckbeardHacker envious.)

It probably won't surprise you, but do you know what those folks love? JavaScript evolution. There's nothing quite so refreshing as a fresh-squeezed JS language feature that removes that irritating itching-burning sensation. Sets that do what you mean! String repetition that you can use without copy/pasting from your last project! Inverse hyperbolic sine that you can use for... your... math! (Again, all of this is in the ES6 plans.)

I, for example, have wanted String.prototype.startsWith very badly, to the point that I've started washing people's window panes against their will as they exit highway 101. Around here, odds are that a programmer sees my sign and implements the thing just to stop me from bothering them again. (A little tactic that I call SpiderGuerilla warfare.)

Me, holding my SpiderGuerilla sign.

So what are you waiting for?

I know, you're probably already quite beefcake, but here's my three step plan:

  1. Watch the SpiderMonkey hacking intro.

  2. Pick out a bug from the ES6 plans.

  3. Come talk to great people on in channel #jsapi (for example, cdleary, jorendorff, luke, or whoever else is in there) or comment in the bug — tell them that you're on a quest to become even more badass, describe a bug that you're interested in taking, and give a quick note on what you've done with the engine so far — for example, walking through the video in step 1! We'll find you a mentor who will get you started on the right track.

Don't miss out on this exclusive offer — SpiderMonkey contribution is not sold in stores.

In fact, if you act now, we'll throw in an IonMonkey shirt (or another Firefox shirt of equivalent awesomeness) and publish a blurb about your feature in Mozilla hacks. Of course, you can also have yourself added to about:credits, providing that's what you are into.

IonMonkey shirt.

This one-of-a-kind offer is too ridonk to pass up. Just listen to this testimonial from one of our badass contributors:

I started contributing to SpiderMonkey and now I can write a JIT compiler from scratch in a matter of days. BEEFCAKE!

@evilpies [Liberally paraphrased]

See you in the tubes!

C++, generic wrappers, and CRTP, oh MI!

Reading some of the original traits papers, I got to the part where they mention the conceptual difficulties inherent in multiple inheritance (MI), one of which is "factoring out generic wrappers". [*]

There's a footnote clarifying that, in practice, languages with MI actually do have other ways of accomplishing the factoring, and in reading that I remembered that the first time I actually understood CRTP (Curiously Recurring Template Pattern) was because I needed some generic wrappers.

Some folks were asking about CRTP on our IRC channel this past week, so I figured I'd share a quick walk-though.

Sometimes you want to be able to shove a method implementation onto a class, given that it has a few buiding blocks for you to work with. Let's say that there's some generic and formulaic way of making a delicious cake.

class CakeMaker
    Cake makeCake() {
        Ingredients ingredients = fetchIngredients();
        if (ingredients.spoiled())
            return Cake::Fail;

        BatterAndWhatnot batter = mixAndStuff(ingredients);
        Cake result = bake(batter);
        if (cake.burned())
            return Cake::Fail;

        return cake;

This is supposed to be a reusable component for shoving a makeCake method onto another class that already has the necessary methods, fetchIngredients, mixAndStuff, and bake.

Great. So now let's say that we have two different cake makers, CakeFactory and PersonalChef — we want to just implement the necessary methods for CakeMaker in those and somehow shove the makeCake method onto their class definition as well. Maybe we can inherit from CakeMaker or something?

But here's the rub: CakeMaker can't exist. It is an invalid class definition that will not compile, because it refers to methods that it does not have.

cdleary@stretch:~$ g++ -c crtp.cpp
crtp.cpp: In member function ‘Cake CakeMaker::makeCake()’:
crtp.cpp:17:56: error: ‘fetchIngredients’ was not declared in this scope
crtp.cpp:21:62: error: ‘mixAndStuff’ was not declared in this scope
crtp.cpp:22:38: error: ‘bake’ was not declared in this scope

Luckily, C++ templates have this nice lazy instantiation property, where the code goes mostly unchecked by the compiler until you actually try to use it. So, if we just change our definition to:

template <typename T>
class CakeMaker
    // ...

GCC will accept it if we ask it to shut up a little bit (with -fpermissive), because we're thinking.

So now we take a look at our close friend, PersonalChef:

class PersonalChef
    Ingredients fetchIngredients();
    BatterAndWhatnot mixAndStuff(Ingredients);
    Cake bake(BatterAndWhatnot);

We want to shove the CakeMaker method onto his/her class definition. We could inherit from the CakeMaker and just pass it an arbitrary type T, like so:

class PersonalChef : public CakeMaker<int>
    // ...

But we need a way to wire up the methods that CakeMaker needs to the methods that PersonalChef actually has. And this is where we take the final step — via a stroke of intuition, let's pass in the type that actually has the methods on it, and use that type to refer to the method implementations within CakeMaker:

template <class Wrapped>
class CakeMaker
    Cake makeCake() {
        Wrapped *self = static_cast<Wrapped *>(this);
        Ingredients ingredients = self->fetchIngredients();
        if (ingredients.spoiled())
            return Cake::Fail;

        BatterAndWhatnot batter = self->mixAndStuff(ingredients);
        Cake result = self->bake(batter);
        if (result.burned())
            return Cake::Fail;

        return result;

class PersonalChef : public CakeMaker<PersonalChef>
    Ingredients fetchIngredients();
    BatterAndWhatnot mixAndStuff(Ingredients);
    Cake bake(BatterAndWhatnot);

    friend class CakeMaker;

int main()
    PersonalChef chef;
    return 0;

Bam! Now it compiles normally. The CakeMaker is given PersonalChef as the template type argument, and the CakeMaker converts its this pointer for use as the PersonalChef type (which is valid in this case, since PersonalChef is a CakeMaker), which does implement the required methods!

This can also be used to enforce minimum interface requirements at compile time (as in the cross-platform macro assembler) without the use of virtual functions, which have a tendency to thwart inlining optimization.

Fun fact: it looks like we have about 90 virtual function declarations in the 190k lines of engine-related C/C++ code that cloc tells me are in the js/src directory.



Fun concept from the papers: the conceptual issue with MI is that classes are overloaded in their purpose: they are intended to serve both as units of code (implementation) reuse and for instantiation of actual objects.