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draft
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C++23: The Next C++ Standard
I should have said the "latest standard", not "spec", if we're being technical. But EVERY bit of official material is very clear about asserting that C++23 is still a preview/in-progress, not a standard. Saying otherwise is, strictly speaking, incorrect.
https://isocpp.org/std/the-standard
https://www.iso.org/standard/79358.html
https://github.com/cplusplus/draft/blob/main/papers/n4951.md
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Never trust a programmer who says they know C++
[3] https://github.com/cplusplus/draft/releases/tag/n4917
*This is a joke, but only barely so.
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How to become a C++ Chad ?
pdf
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Can sanitizers find the two bugs I wrote in C++?
> I don't have a copy of the standard at hand, can anyone quote the relevant section?
The C++ (draft) standard is on GitHub! [0] Compiling it needs Perl and some LaTeX packages, but is reasonably straightforwards otherwise. In addition, links to specific draft standards can be found on cppreference [1].
But anyways, in the first C++20 post-publication draft (N4868), the wording you're interested in is in multiple sections. Section 22.2.3 Sequence Containers [sequence.reqmts] has Table 78: Optional sequence container operations [tab:container.seq.opt] (starting on page 815), which states that a precondition of pop_back() is that empty() returns false. Section 16.3.2.4 Detailed Specifications [structure.specifications] (page 481) states:
> Preconditions: the conditions that the function assumes to hold whenever it is called; violation of any preconditions results in undefined behavior.
Therefore, calling pop_back() on an empty vector results in undefined behavior.
> Is this something that in practice is implemented in different (exception-throwing) ways?
Based on a quick glance at the major implementations (libc++ 15.0.7 at [2], MSVC at [3], libstdc++ at [4]), it looks like asserts are used. Whether those result in exceptions probably depends on whether the asserts are compiled in in the first place and how they are implemented, but it's definitely not a guaranteed exception.
[0]: https://github.com/cplusplus/draft
[1]: https://en.cppreference.com/w/cpp/links
[2]: https://github.com/llvm/llvm-project/blob/llvmorg-15.0.7/lib...
[3]: https://github.com/llvm/llvm-project/blob/8dfdcc7b7bf66834a7...
[4]: https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=libstdc%2B%2B-v3...
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Rust and C++
https://github.com/cplusplus/draft/releases/download/n4917/n4917.pdf (page 1, chapter 1 scope):
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My programming language history
C/C++
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WG21, aka C++ Standard Committee, May 2022 Mailing
Yes, its actually the "individual papers" link there: https://www.open-std.org/jtc1/sc22/wg21/
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Exactly how expensive is <vector> to include in an embedded environment?
It used to be undefined behaviour for all types, even trivial builtin types like int, until some change in 2020, because it wouldn't start their lifetime, but they have fixed this now, afaik even retroactively for C++17: https://github.com/cplusplus/draft/pull/3765
- Is it possible to buy a physical print copy of the C++20 standard?
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The one and only..
It is written in TeX.
papers
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Learn Modern C++
What's fun is, because everything is decided in papers, we can find out why! https://github.com/cplusplus/papers/issues/884
Accepted paper here: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p20...
> The proposed std::print function improves usability, avoids allocating a temporary std::string object and calling operator<< which performs formatted I/O on text that is already formatted. The number of function calls is reduced to one which, together with std::vformat-like type erasure, results in much smaller binary code (see § 13 Binary code).
Additionally,
> Another problem is formatting of Unicode text:
> std::cout << "Привет, κόσμος!";
> If the source and execution encoding is UTF-8 this will produce the expected output on most GNU/Linux and macOS systems. Unfortunately on Windows it is almost guaranteed to produce mojibake despite the fact that the system is fully capable of printing Unicode
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The insanity of compile time programming
You will be happy to learn that indexing a parameter pack is on track for C++26: https://github.com/cplusplus/papers/issues/1329
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C++ Papercuts
Bringing editions to C++ failed, and I am not aware of anyone trying to tackle the issues https://github.com/cplusplus/papers/issues/631
(I could be wrong though! I follow the committee more than you may guess, but not as much as to think I know everything about what's going on.)
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Argonne National Lab is attempting to replicate LK-99
GitHub would not be relevant in this respect because:
* It's owned by a (single) commercial corporation, Microsoft.
* There is censorship both by content and in some respects by country of origin.
* The code is closed.
but otherwise it's an interesting idea.
The C++ standardization committee uses GitHub to track papers submitted to them, see:
- What C++ library do you wish existed but hasn’t been created yet?
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2023-06 Varna ISO C++ Committee Trip Report — First Official C++26 meeting!
For more details on what we did at the 2023-06 Varna meeting, the [GitHub issue](https://github.com/cplusplus/papers/issues/328) associated with the paper has a summary.
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Trip Summer ISO C++ standards meeting (Varna, Bulgaria)
You subscribe to the Github issue of the proposal: https://github.com/cplusplus/papers/issues
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Is there any ongoing work to introduce Rust-like safety guarantees into C++?
Yes, plenty of proposals; you can search through the papers at: https://github.com/cplusplus/papers/issues
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What is the status of the monadic operations for std::expected? It seems like they made it into the standard for C++23, but they don't actually seem to be available in the std::expected implementation (in MSVC's STL)
Regardless, I am so glad that the monadic functions actually made it into the standard for this year and that we can expect to see them in the MSVC STL soon. Would have been unfortunate to have to wait until C++26, and it appears that that was very nearly the case: https://github.com/cplusplus/papers/issues/1161
What are some alternatives?
circle - The compiler is available for download. Get it!
compiler-explorer - Run compilers interactively from your web browser and interact with the assembly
C++ Format - A modern formatting library
LEWG - Project planning for the C++ Library Evolution Working Group
FastAD - FastAD is a C++ implementation of automatic differentiation both forward and reverse mode.
CPM.cmake - 📦 CMake's missing package manager. A small CMake script for setup-free, cross-platform, reproducible dependency management.
tinyformat - Minimal, type safe printf replacement library for C++
rangesnext - ranges features for c+23 ported to C++20
mp11 - C++11 metaprogramming library
team - Rust teams structure
LLVMSharp - LLVM bindings for .NET Standard written in C# using ClangSharp
foundation.rust-lang.org - website for Rust Foundation