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Comment by gwervc | Hacker News Reader

Which percentage of Firefox is now written in Rust? If the project it was started for still isn't totally migrated, it makes sense for others to remain skeptical. There's value in simplicity, like having to use a single language for a projet instead of two.

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I don't see why this is a reason to be skeptical. Firefox is a huge codebase. Substantial chunks of it have been rewritten using Rust while maintaining the entire app and adding features. This is entirely the plan: You can slowly, as you touch parts, migrate the codebase.

Firefox (and many other projects) was already a mix of multiple languages - it uses C, C++, Javascript, ... and now Rust. And while there is value in having less languages to deal with, there is equally value to use multiple languages and apply them where you see major benefit. For example, replacing exposed and high-risk components (image/file parsers for example) with a language that de-risks those implementations. Like all of the things in software engineering, this is a tradeoff. It may not make sense for your application, but it can make sense for others.

Of the 32,373,275 lines in Firefox that tokei reports, 3,439,065 is Rust. 5,740,010 is in C (C + C Headers). And 5,643,721 is C++ (C++ + C++ Headers). 7,343,459 is JS.

Using the "Code" column to ignore comments and blanks.

This is based on the mozilla-central-78a5d30a370f bundle.

(Also, holy crap it took tokei 10m to run this analysis).

I don’t think the relative % of rust has changed a lot in the past few years though, has it? After they got the obvious low lying fruit it slowed down dramatically didn’t it?

It's a good question but I have no plans to write a script that walks mercurial history and plots the relative percentages of the code based on language.

If you find the time and urge I'd be interested to know the results.

1 line of rust != 1 line of C

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