Interview on CppCast

A few days ago I recorded CppCast episode 357. Thanks to Timur Doumler and Phil Nash for inviting me on their show – and for continuing CppCast, which was so wonderfully founded by Rob Irving and Jason Turner!

This time, we chatted about news in the C++ world, and then about my Cpp2 and cppfront experimental work.

The podcast doesn’t seem to have chapters, but here are a few of my own notes about sections of interest:

• 00:00 Intro
• 04:30 News: LLVM 16.0.0, “C++ Initialisation” book, new user groups
• 15:45 Start of interview
• 16:08 Why I don’t view Cpp2 as a “successor language”
• 16:25 A transpiler is a compiler (see also: cfront, PyPy, TypeScript, …)
• 17:20 Origins of the Cpp2 project, 2015/16
• 19:00 100% compatibility as a primary goal and design constraint
• 22:00 Avoid divergence, continue in same path C++ is already going
• 22:50 What compatibility means: 100% link compat always on, 100% source compat always available but pay only if you need it
• 24:14 Making the syntax unique in a simple way, start with “name :”
• 28:10 Avoid divergence and still make a major simplification, by letting programmers directly declare their intent
• 30:30 Bringing the pieces to ISO and the community for feedback
• 31:55 What about “epochs”/“editions”? tl;dr: It’s exactly the right question, but I think the right answer is “epoch” (singular)
• 35:42 C++ is popular and will endure no matter what we do; question is can we make it nicer
• 37:05 My personal experiment, and others are now helping
• 38:20 What “safeties” I’m targeting, and what degree of safety, and why formally provable guarantees are nice but neither necessary nor sufficient (I expect this view to be controversial)
• 44:00 The issue is making things 50x (98%) safer, vs. 100% safer, because what does requiring that last 2% actually cost the design in incompatibility / difficulty of use
• 47:05 The zero-overhead principle is non-negotiable, and so is always being able to “open the hood” to take control, otherwise it’s not C++ anymore
• 48:20 Examples: dynamic bounds/null checking is opt-out, now the default but still pay for it only if you use it
• 50:20 Will cppfront support all major compilers and platforms? It already does, any reasonably conforming C++20 compiler (any gcc/clang/msvc since about 2020), and that will continue
• 52:15 Keeping the generated source code very close to the original is a priority
• 53:25 “TypeScript for C++” plan vs. “Dart for C++” plan
• 55:20 TypeScript did what Bjarne’s cfront did: Transpiler that let you always keep your generated JavaScript/C code, so you could drop using the new language anytime if you want with #NoRegrets, risk-free
• 57:20 Shout out to Anders Hejlsberg, IIRC the only human to produce a million-user programming language more than once, and his approach to TypeScript vs. C#
• 59:20 Why generating C++ code isn’t in tension with the goal of compatibility (it’s actually synergistic), and the targeted subset is C++20 (with a workaround only when modules are not yet available on a given compiler)
• 1:00:40 Why C++20 is super important (if constexpr, requires-expressions)
• 1:01:40 Why any C++ evolution/successor language attempt that for now only tries to be compatible with C++17 faces a big hill/disadvantage
• 1:02:40 What’s next for Cpp2 and cppfront
• 1:05:35 Where can people learn more: cppfront repo, CppCon 2022 talk, C++Now talk coming up in a month, then CppCon 2023 in October
• 1:07:28 C++ world is alive and well and thriving, now embracing challenges like safety to keep C++ working well for all of us

In at least one place I said “cppfront” where I meant “cfront”… I think the intent should be clear from context. Read More