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I think a large reason of why Clang lags behind in C++ standards is that Google and Apple don't really use modern C++ at all. Google has strict guidelines that

I think a large reason of why Clang lags behind in C++ standards is that Google and Apple don't really use modern C++ at all. Google has strict guidelines that prevent people to use half of the language (look at exceptions, for instance, without which most of the STL is crippled) and they use Abseil anyway, so they don't really care about the STL in the first place. Apple on the other hand mostly uses C++ in very restricted scopes such as DeviceKit which are very limited and can't safely use the entire language anyway. Xcode-shipped Clang and libcxx are often pretty old, too. They don't really need C++ that much above what C++03 already had, so it's clearly an afterthought for them.

_0w8t 4y ago
Chromium finally switched to C++17 this year. The switch to C++20 will happen much sooner given that PNaCL support will be finally removed this summer.
gpderetta 4y ago
That alone doesn't explain why clang conformance was very good till c++17 and then suddenly fell behind. The major clang contributors decided to focus their attention elsewhere, One guess is because they didn't get what they wanted within the committee.
- pjmlp 4y ago
  Google basically withdraw from clang after they lost the ABI vote, and Intel is now taking care of what used to be mostly Google stuff. If I remember correctly some discussions on /r/cpp. As for Apple, OP is right, Metal Shaders are based on C++14 dialect, IOKit/DriverKit use an Embedded C++ dialect, and for everything else there is Objective-C/Swift, and they only need enough C++ to use LLVM to develop them.
  - 3836293648 4y ago
    Was google pushing for breaking the ABI?
    - codys 4y ago
      - a WG paper by a google employee regarding breaking the C++ ABI: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p1863r1.pdf http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p186... - A post about a C++ ABI break being voted against: https://cor3ntin.github.io/posts/abi/ https://cor3ntin.github.io/posts/abi/ I would not be surprised if google (or others in favor of breaking the ABI for the c++ standard library) would refocus on their alternate non-std std-replacement-ish library implementations (like abseil) instead given the lack of willingness to fix things in std proper from the committee.
      - 3836293648 4y ago
        Yeah, I've seen both of those before, but was unsure if it was just the position of a single Google employee or the position of google as a whole, as you made it sound like Google the company had actually taken such a stand
  - lenkite 4y ago
    The permanent-ABI compatibility decision was effectively the death-knell for C++. Can't improve the standard library performance, making it effectively useless for the real world. Can't correct mistakes - the language and library warts grow and grow as the years pass by, making it impossible for beginners to pick up and learn the language. Frankly, Google should fork C++ and create a new language without the warts and a new standard library.
    - ok123456 4y ago
      > Frankly, Google should fork C++ and create a new language without the warts and a new standard library. That's how we got golang.
      - qalmakka 4y ago
        Golang isn't really a C++ replacement, the performance metrics just aren't comparable. It's more of a Python replacement, for those applications where it would be just too slow, forcing you to write C or C++ because that's still the #1 way to accelerate your Python. Sure there are compilers such as Cython or Nuitka, but they just do not suffice when you _really_ need to speed up your code.
        zarzavat 4y ago
        In C++‘s heyday there were things such as OKWS[0] web application server. Yes externally C++ was no so popular in such situations, but at Google they had/have many such C++ services and that was the motivation behind Go - a safe language to build mostly-IO-bound-but-a-little-bit-CPU-bound services. Another example of this shift would be that Bitcoin’s reference impl (2009) is written in C++, whereas Ethereum’s reference impl (2015) is written in Go. [0] https://okws.org/ https://okws.org/
        pjmlp 4y ago
        They still mostly do, that is where Abseil is used. Go has more mindshare outside Google than on Google's critical infrastructure.
  - jeffbee 4y ago
    I still see a lot of google contributions to llvm recently. For example the mem* functions.
- tialaramex 4y ago
  Yes. For example (there are a lot more) Vittorio's Epochs proposal P1881R1: https://www.youtube.com/watch?v=PFdKFoQxRqM https://www.youtube.com/watch?v=PFdKFoQxRqM Now, one of the things which you may have noticed really annoys C++ proponents here on HN is when people say "What Rust does..." and well, maybe Vittorio should not have done that in his talk. But the reason he's saying it is that although Rust has very few new ideas it popularises lots of existing ideas from PL theory that were not seen in the kind of languages C++ developers had experience with before. A few slides in, Vittorio explains that he's not offering language fragmentation or dialects, an ABI break, or yet more stuff every programmer needs to learn. Nevertheless, criticisms of Epochs generally say that this is language fragmentation, it introduces dialects, it's an ABI break, and every programmer will have to learn all this extra stuff so it's hopeless...
mrpippy 4y ago
Apple’s public/external-facing uses of C++ are restricted and odd (MSL, IOKit), but internally it seems pretty common in the OSes. Dyld, font rendering, and lower-level event handling (the remains of Carbon/HIToolbox) are all things I’ve seen in stack traces. And of course there’s also WebKit and LLVM.
- pjmlp 4y ago
  WebKit standard requires C++17, while LLVM still on C++14, so no pressure from Apple side to move forward, https://webkit.org/languages-staged-08192020 https://webkit.org/languages-staged-08192020 https://llvm.org/docs/CodingStandards.html#c-standard-versions https://llvm.org/docs/CodingStandards.html#c-standard-versio...
erwincoumans 4y ago
C++ is great to have as much control over memory and performance as possible, while still providing more convenience than C. The C++ Standard Library and exceptions don't improve this control generally. Possibly an unpopular opinion, but personally I wish the C++ Standard Library was kept separate from the C++ language and have the C++ committee focus on the language features instead.
- codeflo 4y ago
  My impression is that this is an opinion about the stdlib that many programmers concerned with performance share.
- aninteger 4y ago
  > Possibly an unpopular opinion, but personally I wish the C++ Standard Library was kept separate from the C++ language and have the C++ committee focus on the language features instead. This is not an unpopular opinion.
kccqzy 4y ago
The Google style guide is public: https://google.github.io/styleguide/cppguide.html https://google.github.io/styleguide/cppguide.html I think reading it would convince you that the statement Google doesn't use modern C++ at all is false. It talks about modern features like CTAD.

_0w8t 4y ago

Chromium finally switched to C++17 this year. The switch to C++20 will happen much sooner given that PNaCL support will be finally removed this summer.

gpderetta 4y ago

That alone doesn't explain why clang conformance was very good till c++17 and then suddenly fell behind. The major clang contributors decided to focus their attention elsewhere, One guess is because they didn't get what they wanted within the committee.

pjmlp 4y ago
Google basically withdraw from clang after they lost the ABI vote, and Intel is now taking care of what used to be mostly Google stuff. If I remember correctly some discussions on /r/cpp. As for Apple, OP is right, Metal Shaders are based on C++14 dialect, IOKit/DriverKit use an Embedded C++ dialect, and for everything else there is Objective-C/Swift, and they only need enough C++ to use LLVM to develop them.
- 3836293648 4y ago
  Was google pushing for breaking the ABI?
  - codys 4y ago
    - a WG paper by a google employee regarding breaking the C++ ABI: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p1863r1.pdf http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p186... - A post about a C++ ABI break being voted against: https://cor3ntin.github.io/posts/abi/ https://cor3ntin.github.io/posts/abi/ I would not be surprised if google (or others in favor of breaking the ABI for the c++ standard library) would refocus on their alternate non-std std-replacement-ish library implementations (like abseil) instead given the lack of willingness to fix things in std proper from the committee.
    - 3836293648 4y ago
      Yeah, I've seen both of those before, but was unsure if it was just the position of a single Google employee or the position of google as a whole, as you made it sound like Google the company had actually taken such a stand
- lenkite 4y ago
  The permanent-ABI compatibility decision was effectively the death-knell for C++. Can't improve the standard library performance, making it effectively useless for the real world. Can't correct mistakes - the language and library warts grow and grow as the years pass by, making it impossible for beginners to pick up and learn the language. Frankly, Google should fork C++ and create a new language without the warts and a new standard library.
  - ok123456 4y ago
    > Frankly, Google should fork C++ and create a new language without the warts and a new standard library. That's how we got golang.
    - qalmakka 4y ago
      Golang isn't really a C++ replacement, the performance metrics just aren't comparable. It's more of a Python replacement, for those applications where it would be just too slow, forcing you to write C or C++ because that's still the #1 way to accelerate your Python. Sure there are compilers such as Cython or Nuitka, but they just do not suffice when you _really_ need to speed up your code.
      - zarzavat 4y ago
        In C++‘s heyday there were things such as OKWS[0] web application server. Yes externally C++ was no so popular in such situations, but at Google they had/have many such C++ services and that was the motivation behind Go - a safe language to build mostly-IO-bound-but-a-little-bit-CPU-bound services. Another example of this shift would be that Bitcoin’s reference impl (2009) is written in C++, whereas Ethereum’s reference impl (2015) is written in Go. [0] https://okws.org/ https://okws.org/
        pjmlp 4y ago
        They still mostly do, that is where Abseil is used. Go has more mindshare outside Google than on Google's critical infrastructure.
- jeffbee 4y ago
  I still see a lot of google contributions to llvm recently. For example the mem* functions.
tialaramex 4y ago
Yes. For example (there are a lot more) Vittorio's Epochs proposal P1881R1: https://www.youtube.com/watch?v=PFdKFoQxRqM https://www.youtube.com/watch?v=PFdKFoQxRqM Now, one of the things which you may have noticed really annoys C++ proponents here on HN is when people say "What Rust does..." and well, maybe Vittorio should not have done that in his talk. But the reason he's saying it is that although Rust has very few new ideas it popularises lots of existing ideas from PL theory that were not seen in the kind of languages C++ developers had experience with before. A few slides in, Vittorio explains that he's not offering language fragmentation or dialects, an ABI break, or yet more stuff every programmer needs to learn. Nevertheless, criticisms of Epochs generally say that this is language fragmentation, it introduces dialects, it's an ABI break, and every programmer will have to learn all this extra stuff so it's hopeless...

mrpippy 4y ago

Apple’s public/external-facing uses of C++ are restricted and odd (MSL, IOKit), but internally it seems pretty common in the OSes. Dyld, font rendering, and lower-level event handling (the remains of Carbon/HIToolbox) are all things I’ve seen in stack traces. And of course there’s also WebKit and LLVM.

pjmlp 4y ago
WebKit standard requires C++17, while LLVM still on C++14, so no pressure from Apple side to move forward, https://webkit.org/languages-staged-08192020 https://webkit.org/languages-staged-08192020 https://llvm.org/docs/CodingStandards.html#c-standard-versions https://llvm.org/docs/CodingStandards.html#c-standard-versio...

erwincoumans 4y ago

C++ is great to have as much control over memory and performance as possible, while still providing more convenience than C. The C++ Standard Library and exceptions don't improve this control generally. Possibly an unpopular opinion, but personally I wish the C++ Standard Library was kept separate from the C++ language and have the C++ committee focus on the language features instead.

codeflo 4y ago
My impression is that this is an opinion about the stdlib that many programmers concerned with performance share.
aninteger 4y ago
> Possibly an unpopular opinion, but personally I wish the C++ Standard Library was kept separate from the C++ language and have the C++ committee focus on the language features instead. This is not an unpopular opinion.

kccqzy 4y ago

The Google style guide is public: https://google.github.io/styleguide/cppguide.html https://google.github.io/styleguide/cppguide.html I think reading it would convince you that the statement Google doesn't use modern C++ at all is false. It talks about modern features like CTAD.