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Comment by misnome | Hacker News Reader

Wait, so the words "concepts" and "requires" were newly made keywords, and this breaks code, but the words "yield" and "await" were determined too important and too common to standards members that they needed to be renamed to the horrifically ugly "co_await" and "co_yield"?

Also, last time I actually tried to use C++20 none of the standard library implementations had std::format; has this changed now?

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One day in the far away future the standard C++ hello world will use 'import std;' and 'std::print' and it will be glorious.

When I was going to university the computer science department's primary system had two compilers available, GCC 2.96[0] and TenDRA. GCC was generally more popular but it didn't have std::string and any code that threw an exception would crash, so adventurous students would use TenDRA for development.

One of the stranger behaviors of TenDRA was that it put all standard library symbols, including the C headers, into namespace std. A hello world in TenDRA looked like this:

  #include <cstdio> // no <stdio.h> available

  int main() {
    std::printf("Hello, world!\n");
    return 0;
  }

It was not glorious. If anything ... the opposite. When TenDRA deigned to compile your program it would generally work (excepting bugs in the code itself), but getting it to accept any sort of third-party code was impossible because of the std namespace thing.

I ended up writing a bunch of utilities for strings, including a unit testing library that spawned each test as a subprocess (to avoid exceptions) just so I could use GCC instead.

[0] There is no such version recorded on the GNU project website.

C symbols are supposed to be in std if you use the cstdio style headers. It’s just that for a very long time compilers put them into the global namespace too.

GCC, Clang, and MSVC all still duplicate c* header definitions into the global namespace by default as far as I'm aware.

In fact, the last time I checked, the MSVC cstdio header was implemented more or less like this:

    namespace std {
        #include <stdio.h>
    }

    using namespace std;

It's kind of crazy how major compilers have been ignoring the standard for so long that people consider a standard compliant compiler to be weird and broken.

> It's kind of crazy how major compilers have been ignoring the standard for so long that people consider a standard compliant compiler to be weird and broken.

I had absolutely no idea this wasn't even supposed to be the case (although I was aware of the duplication in std::). Guess it makes sense that the standard would shy away from global namespace pollution - I suppose one of the compilers perhaps did this for long enough that the others ended up duplicating it to increase code compatibility?

That the as actually not conforming. It was made conforming in c++11 because it was pointless to have the standard say something that all major implementations would ignore.

>There is no such version recorded on the GNU project website.

It's sort-of recorded. It's not in the version list since there wasn't a release, just distros making a mess:

https://gcc.gnu.org/gcc-2.96.html

GCC 2.96 was a development version that incorrectly got released by Redhat on Redhat 7 (and possibly other distros).

https://gcc.gnu.org/legacy-ml/gcc-announce/2000/msg00003.htm...

This was on a DEC Tru64 system, very far from any sort of Linux.

My personal suspicion is that someone (student or faculty) got their hands on a CVS snapshot and installed it system wide. That's the only explanation I can think of for it being so broken.

Fairly sure some PS2 SDKs also shipped GCC 2.96, which is why I know this tidbit of info.

2.96 exists, at least in the RedHat world.

    $ rpm -qi gcc
    Name        : gcc                          Relocations: (not relocateable)
    Version     : 2.96                              Vendor: Red Hat, Inc.
    Release     : 110                           Build Date: Fri 12 Apr 2002 10:30:47 PM UTC
    Install date: Thu 20 Jan 2011 03:34:36 AM UTC      Build Host: daffy.perf.redhat.com
    Group       : Development/Languages         Source RPM: gcc-2.96-110.src.rpm
    Size        : 8389509                          License: GPL
    Packager    : Red Hat, Inc. <http://bugzilla.redhat.com/bugzilla>
    URL         : http://gcc.gnu.org
    Summary     : The GNU cc and gcc C compilers.
    Description :
    The gcc package includes the cc and gcc GNU compilers for compiling C
    code.
    $ cat /etc/redhat-release
    Red Hat Linux release 7.3 (Valhalla)

https://en.cppreference.com/w/cpp/header/cstdio#Synopsis.

That will be in cpp2 already: https://github.com/hsutter/cppfront

Already available in C++23.

The future tense seems better here. This will (almost certainly) be available in C++ 23.

In the context of Chromium, this slide deck, that means in about 2026.

So if you're starting a three year degree next week, and you already know Google will hire you for the Chromium team straight after because you're the perfect person for that, you won't be writing std::print() calls in that codebase yet 'cos that's too early.

Well, they could convince their management to restart doing clang contributions for ISO C++ compliance, or maybe allocate 20% of their time for that.

The far away future? You mean next year?

I don't mean available as in the committee has published their final version of the standard that allows it. I mean available in production.

Oh, that'll probably be sooner, then; STL is already working on it. Also if you want to use it now, fmt has an implementation.

`std::this_thread::yield` already existed at the time, and “yield” was presumed to also be a common identifier in financial and agricultural contexts.

I’m nevertheless surprised that new noncontextual and previously-unreserved-identifier keywords were added at all. In earlier times, the approach would have been to use a reserved identifier like “_Yield” for the keyword, and to provide a standard opt-in header that would `#define yield _Yield`. Maybe they don’t want to add dependencies on the preprocessor anymore.

I’m not sure C++ has ever used the `_Yield` hack, except for C compatibility? C on the other hand uses it all the time.

It could be that I'm remembering it from C.

It's super common in C because C doesn't have namespaces and templates which means stuff C++ implements as namespaced library classes C has to implement as language keywords.

A good example is atomics. C++11 introduced `std::atomic`, C11 introduced the keyword `_Atomic`

Such a weak argument, you can fix this in your entire code base with a single call to sed. There is no reason to introduce a language feature with some weird prefix instead of changing existing code and having them prefix their variable names.

> last time I actually tried to use C++20 none of the standard library implementations had std::format; has this changed now?

MSVC is the only major implementation that has std::format for now.

It's so funny to me that MSVC has become the cutting edge of C++ standards implementation. I remember starting out when it was a joke compared to Clang - although I was a novice, so who knows how complete my knowledge was at the time.

In any case, it's a really impressive effort from STL and the rest of their library team. STL has some incredible CPPCon talks, too.

One way you could interpret this (definitely not the only way) would be that Microsoft - or some group within Microsoft - sees C++ as a possible legacy system, with an opportunity to make a lot of money by judging correctly what customers want and how much income you need to justify that support as existing offerings rust out (so to speak).

Do you have any particular CPPCon talks to recommend ?

My favourite is "Abseil's Open Source Hashtables: 2 Years In" by Matt Kulukundis, Matt's a fine speaker but what makes it so fun is that Hyrum Wright is in the audience yelling interjections as a result of Hyrum's law (this is scripted). For example Matt explains a significant size optimisation for people who only have a few things in their map, it's just smaller with no other consequences - right? Hyrum points out that now rehash happens earlier, so if you depend on it not to invalidate references during the first 15 insertions you are screwed. Guess whether any real Google code did that...

I really love this talk in particular: https://www.youtube.com/watch?v=4P_kbF0EbZM (On charconv)

But any of the ones I've seen from Stephan have been fantastic, I think, although I'm not actually sure if I've seen more. He seems to have a lot of talks on very specific subjects, which can be really fun.

> Hyrum Wright is in the audience yelling interjections as a result of Hyrum's law

This sounds absolutely hilarious, I'll have to take a look.

I'm glad you liked my charconv talk! Here's a complete list of my recorded conference talks:

BoostCon/C++Now 2012: Regex In C++11 And Boost: https://youtu.be/mUZL-PRWMeg

GoingNative 2012: STL11: Magic && Secrets: https://docs.microsoft.com/en-us/events/goingnative-2012/stl...

GoingNative 2013: Don't Help The Compiler: https://docs.microsoft.com/en-us/events/goingnative-2013/don...

GoingNative 2013: rand() Considered Harmful: https://docs.microsoft.com/en-us/events/goingnative-2013/ran...

CppCon 2014: STL Features And Implementation Techniques: https://youtu.be/dTeKf5Oek2c

CppCon 2015: functional: What's New, And Proper Usage: https://youtu.be/zt7ThwVfap0

CppCon 2016: tuple: What's New, And How It Works: https://youtu.be/JhgWFYfdIho

CppCon 2018: Class Template Argument Deduction for Everyone: https://youtu.be/-H-ut6j1BYU

CppCon 2019: Floating-Point charconv: Making Your Code 10x Faster With C++17's Final Boss: https://youtu.be/4P_kbF0EbZM

CppCon 2020: C++20 STL Features: 1 Year of Development on GitHub: https://youtu.be/8kjRx8vo6y4

Pure Virtual C++ 2022: MSVC C++20/23 Update: https://youtu.be/DAl37n2XOwk

That's a way better list than what I had! Thanks! Think I'll watch the rand() talk tomorrow, I love (to hate on) rand.

I love the idea of placing a gadfly in the crowd to provide a dialogue.

> "Abseil's Open Source Hashtables: 2 Years In"

URL seems to be https://www.youtube.com/watch?v=JZE3_0qvrMg ?

std::format is available, with all C++20 Defect Reports implemented, in VS 2019 16.11.14 (and all later 16.11.x) and VS 2022 17.2 (and all later 17.x).

The east coast fintech folks are the reason we couldn’t have yield as a keyword. Too much of their code uses the variable name yield in the trading sense of the word, and so we’re stuck with this instead. This is what someone on the standards committee told me on the cpp slack a few years ago, at least.

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