I always wondered how Rust at Mozilla was sustainable. Maintaining an ecosystem like that and bringing it into an already complex project like a browser is a huge undertaking that probably has eaten up significant amount of manhours. At a Microsoft sized company I'd get it because they can basically blow billions on that sort of thing but I always wondered if it actually took time away from improving Firefox or other…
https://www.amazon.com/Coders-Work-Reflections-Craft-Program...
The Brendan Eich interview was really interesting, because it talked about bridging research and software engineering, specifically with regard to memory safety in C++ and debugging tools.
I think he was talking about manual annotations on C++. It seems clear that this interest morphed into sponsoring of Rust. I think Rust was a side project since 2006 and it was "announced" around 2010 (?).
And Mozilla also sponsored the "rr" reversible Debugger, which is also some very impressive engineering. (Sadly it seems to get less attention than Rust!)
Anyway, for PL nerds, I recommend reading this interview.
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I think this work on software engineering tools is great, but as a Firefox user of 15+ years, it would be hard for me to argue that Firefox received sufficient attention. It does feel like the situation where the engineers work on the tools for too long and then management cancels both projects (which I've seen happen in my career).