Bjarne Stroustrup on C++20's significance

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The following are notes from Bjarne Stroustrup, regarding the completion of C++20 on Saturday and summarizing his comments to the committee in the room:

After the 79-0 vote deeming C++20 done on February 15, 2020 in Prague, I made a few comments to emphasize the significance of the event. I got to the lectern just after Herb Sutter had shown photos of the C++ standards committee members at the first meeting and the meetings that voted for the C++11, C++14, C++17, and C++20 standards. I was in all of those, so was Mike Miller from EDG and chair of the Core Working Group. We were the only ones in all photos. This is roughly what I said:

This is a historical event:

  • 30 years of C++ standardization.
  • 40 years of C++.
  • C++20 is the 6th standard, the 3rd major standard; by “major” I mean “changes the way people think.”
  • This is something like the 75th meeting; I have been at about 70 of those.

I’d like to add a personal note. For me, C++20 is special because it has essentially all from “The Design and Evolution” (1994). In particular, it has concepts, modules, and coroutines:

  • Concepts were not in D&E, but there were three pages of apologies for not having them. Then, neither I nor anyone else know how to design and implement them sufficiently well.
  • Modules were just a dream then, but they were specifically mentioned – I dreamed of a day where we could finally eliminate the preprocessor.
  • Coroutines were the  bread and butter for C++ during the first 10 years; they were missing in most other languages. I was sore having lost them to implementation problems on SPARC architecture.

In addition, we get improved concurrency and a library with ranges, dates, and span.

We (the C++ standards committee members) must be careful and responsible; we serve a huge community:

  • Serve the community at large, rather than just experts – “keep simple things simple.”
  • Be careful, the world changes; what seems essential or fashionable today may not be good in the longer term.
  • Be pragmatic, not doctrinaire; pragmatic and principled.

This has guided the development of C++ so far. No, that’s not easy. We must balance many concerns. I suggest we:

  • Pursue the goal of a completely resource-safe and type-safe C++.
  • Support a wide variety of hardware well.
  • Maintain C++’s record of stability (compatibility) – “stability is a feature” – as much as makes sense.

These aims have served C++ well throughout.

I wonder who’ll be here in 30 years? That’ll be 2050.

Thanks for listening. See you in Varna! (Varna is the location of the next ISO C++ Standards meeting).

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