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So by using a dynamic language, you trade the cost of a long build time with possible runtime errors that would have easily been caught by the build system? Instead of paying the cost once per build you are now inflicting runtime errors on your customers.

Is there a strong, real world correlation between heavy use of dynamic languages, and a poor user experience (versus competitors, for example)?

The theory that it would makes sense to me, but I suspect other factors outshadow any effect it might have.

For example, I haven't heard that Facebook, Instacart, Booking.com, WordPress.com, etc, have stability or experience issues worse than their competitors.

Well, the costs are once per every build, which can take many hours, as the author describes it, even be only available on the next day. Static typechecking is a valuable tool, but it shouldn't be as the solution for all correctness problems. Testing is another. And when the build times become too large, testing suffers. Finally, it is absoultely possible to have dynamic languages with type declarations which can be automatically checked.

So now you trade reduced build times for increase in the amount of developer time for creating extra tests that check for type correctness and you increase the “build” time by having your build system run more tests?

And once you have type declaration that can “automatically” be checked - something has to run against the same code base to check the correctness of your code and you’re back to increasing your build time?

No. With dynamic languages, one gets not only "reduced" build times, they are instant. Testing for correctness needs to be done with any kind of language. Type checking is not a replacement for that. But you can add the necessary type declarations to dynamic language to facilitate static type checking if desired. These checks don't influence the build time significantly.

As written in my first post, using dynamic languages is only one way of improving development times. The other of course is, use languages which allow for fast compilation.

> But you can add the necessary type declarations to dynamic language to facilitate static type checking if desired. These checks don't influence the build time significantly.

Indeed, type checking is rarely the slowest compilation stage for most languages.

No. In every large system I've ever seen, there's large dynamic components. Avoiding existing dynamic languages entirely simply means building your own ad-hoc one, which is neither more robust nor more efficient (at development time or at run time). You're trading "known, working dynamic system" for "unknown, homemade dynamic system". (In other words, Greenspun's Law holds true.) There isn't a third choice where users simply stop wanting features which are easily implemented in dynamic fashion.

Every web browser today includes lots of modules written in JavaScript. Every web browser today also has lots of bugs. But nobody believes that rewriting all their JS in C++ would improve the situation. For all the complaints I've ever had about Firefox/Safari/Chrome, "I got a JS TypeError" has somehow never once come up.

And how many ignored JS errors do you see when you look on the web console? Don’t you want a little more robustness on the backend?

I’ve never in 30 years of development needed to make an adhoc dynamic language for a large system. I use Python for simple scripts and JS because you have to for the browser.

I wrote physics simulation code some time ago. The build was fast, but since the simulation speed was about 10ns/day the tests would take several hours to run. And the only way to know if your change fixed something is if the tests passed.

So it took several hours to get feedback for a change. But it also took about that long to come up with a new idea to try. Eventually I had a pipeline running where I could fire off a few ideas throughout the day, keep track of the change in the build, and iterate that way.

You're going to lose that gained time as soon as your "build" includes running tests. And you'll need more tests because in dynamic langueses generally nothing works until you check it with a test.

Mixing lanuages is a waste. It makes everything harder operationally, technically and business wise.

The solution to long builds is projects structure that supports caching and parallelism. No one ever changes more than couple thousands lines even in a multi million line project, so why would everything had to get rebuilt?

I've seen ci pipelines building millions of lines in under a minute, no sweat.

Have you ever tried to build Chromium or Firefox yourself? If you have a slow machine, the build can take even 10 hours or more

No, I have not. But wouldn't be those code bases which compile very slow because of being written in C++? C++ seems to baloon in building time for large code bases. On the other side, the big Threadripper manages to compile the Linux Kernel in 40s. I don't think those web browsers are that much bigger than Linux than the compile times differ.

Firefox is further slowed down by using more and more Rust based code - Rust is known to compile slowly. However I would say this is a good tradeoff, since Rust brings much more safety to one of the most safety-critical applications on a typical desktop.

the general issue is that the feature rich web browser contains libraries wrapped around basically every leaf and stem of windows, mac and *nix desktop interface family forests.

(if your building on say, a completely fresh stage3 gentoo system, that equals some pretty good linker load. cairo comes to mind as a huge culprit, whether its webkit or mozilla.)

It is extremely easy to let your C++ code get into long build times. People get fond of putting code into the header, for example. This adds that compile time to every file that includes that file. And it prevents you from using forward declaration, which then requires including those definitions in your header.

With discipline and tracking the build time, and tools that record how long each build step takes, you can keep people from doing things like declaring a Boost multimap in a header file. They can go ahead and use it but hide it in a cpp source file behind a pointer or a virtual interface.

I've noticed that some people fall in love with C++11 move constructors, and they are pretty cool, but unlike a reference or pointer they require full type definitions in order to pass "by value." So that's annoying.

C code is definitely faster to build, unless you've got some crazy programmer who reimplemented C++ templates using five level deep nested macros.

Then maybe they don't have proper dependencies set. Inclusing too many things, too many acessible stuff, globals, no libraries?

Doesn't Firefox use -flto? That might be why.

Fast builds for C++ require unending diligence from day 1. Part of my team’s CI is a build time check. Our code base runs to 10mm lines of code; clean uncached builds are 3m; cached builds are 30s; incremental builds are in the 100s of ms range. The entire system is a single, short Makefile combined with ccache. There’s no fine-grain dependency tracking, so our builds never go wrong.