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@kaizen_nagoya(Dr. Kiyoshi Ogawa)

13.5.2.3 Atomic constraints [temp.constr.atomic] C++N4910:2022 (205) p368.cpp

Posted at

はじめに(Introduction)

N4910 Working Draft, Standard for Programming Language C++

n4910は、ISO/IEC JTC1 SC22 WG21の作業原案(Working Draft)です。
公式のISO/IEC 14882原本ではありません。
ISO/IEC JTC1 SC22 WG21では、可能な限り作業文書を公開し、幅広い意見を求めています。
一連の記事はコード断片をコンパイルできる形にする方法を検討してコンパイル、リンク、実行して、規格案の原文と処理系(g++, Clang++)との違いを確認し、技術内容を検討し、ISO/IEC JTC1 SC22 WG21にフィードバックするために用います。
また、CERT C++, MISRA C++等のコーディング標準のコード断片をコンパイルする際の参考にさせていただこうと考えています。CERT C++, MISRA C++が標準化の動きとの時間的なずれがあれば確認できれば幸いです。また、boostライブラリとの関連、Linux OS, TOPPERSカーネル、g++(GCC), clang++(LLVM）との関係も調査中です。
何か、抜け漏れ、耳より情報がありましたらおしらせくださると幸いです。

<この項は書きかけです。順次追記します。>

背景(back ground)

C/C++でコンパイルエラーが出ると、途方にくれることがしばしばあります。
何回かに１回は、該当するエラーが検索できます。
ただ、条件が違っていて、そこでの修正方法では目的を達成しないこともしばしばです。いろいろな条件のコンパイルエラーとその対応方法について、広く記録することによって、いつか同じエラーに遭遇した時にやくに立つことを目指しています。

この半年の間で、三度、自分のネットでの記録に助けられたことがあります。
また過去に解決できなかった記録を１０種類以上、最近になって解決できたことがあります。それは、主に次の３つの情報に基づいています。

https://stackoverflow.com
https://cpprefjp.github.io
http://ja.cppreference.com/

また
https://researchmap.jp/joub9b3my-1797580/#_1797580
に記載したサイトのお世話になっています。

作業方針(sequence)

Clang++では-std=c++03, C++2bの2種類
g++では-std=c++03, c++2bの２種類
でコンパイルし、

１）コンパイルエラーを収集する。
２）コンパイルエラーをなくす方法を検討する。
コンパイルエラーになる例を示すだけが目的のコードは、コンパイルエラーをなくすのではなく、コンパイルエラーの種類を収集するだけにする。
文法を示すのが目的のコード場合に、コンパイルエラーをなくすのに手間がかかる場合は、順次作業します。
３）リンクエラーをなくす方法を検討する。
文法を示すのが目的のコード場合に、リンクエラーをなくすのに手間がかかる場合は、順次作業します。
４）意味のある出力を作る。
コンパイル、リンクが通っても、意味のある出力を示そうとすると、コンパイル・リンクエラーが出て収拾できそうにない場合がある。順次作業します。

１）だけのものから４）まで進んだものと色々ある状態です。一歩でも前に進むご助言をお待ちしています。「検討事項」の欄に現状を記録するようにしています。

C++N4910:2022 Standard Working Draft on ISO/IEC 14882(0) sample code compile list

C++N4741, 2018 Standard Working Draft on ISO/IEC 14882 sample code compile list

C++N4606, 2016符号断片編纂一覧(example code compile list)

C++N4606, 2016 Working Draft 2016, ISO/IEC 14882, C++ standard(1) Example code compile list
https://qiita.com/kaizen_nagoya/items/df5d62c35bd6ed1c3d43/

C++N3242, 2011 sample code compile list on clang++ and g++

編纂器(Compiler)

clang++ --version

Debian clang version 14.0.5-++20220610033153+c12386ae247c-1~exp1~20220610153237.151
Target: x86_64-pc-linux-gnu, Thread model: posix, InstalledDir: /usr/bin

g++- --version

g++ (GCC) 12.1.0 Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

13.5.2.3 Atomic constraints [temp.constr.atomic] C++N4910:2022 (205) p368.cpp

算譜(source code)

p368.cpp
// C++N4910 Committee Draft, Standard for Programming Language C++
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/n4910.pdf
const char * n4910 = "13.5.2.3 Atomic constraints [temp.constr.atomic] C++N4910:2022 (205) p368.cpp";
// Debian clang version 14.0.5-++20220610033153+c12386ae247c-
// g++ (GCC) 12.1.0 Copyright (C) 2022 Free Software Foundation, Inc.
// Edited by Dr. Ogawa Kiyoshi. Compile procedure and results record.
// C++N4910:2022 Standard Working Draft on ISO/IEC 14882(0) sample code compile list
// https://qiita.com/kaizen_nagoya/items/fc957ddddd402004bb91

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cassert>
#include <coroutine>
#include <vector>
#include <complex>
#include <map>
#include <atomic>
#include <unordered_map>
#include <typeinfo>

using namespace std;

// Example 1
template <unsigned N> constexpr bool Atomic = true;
template <unsigned N> concept C = Atomic<N>;
template <unsigned N> concept Add1 = C<N + 1>;
template <unsigned N> concept AddOne = C<N + 1>;
template <unsigned M> void f()
requires Add1<2 * M>;
template <unsigned M> int f()
requires AddOne<2 * M> && true;
int x = f<0>(); // OK, the atomic constraints from concept C in both fs are Atomic<N>
// with mapping similar to N􏰀→2 * M + 1
template <unsigned N> struct WrapN;
template <unsigned N> using Add1Ty = WrapN<N + 1>;
template <unsigned N> using AddOneTy = WrapN<N + 1>;
template <unsigned M> void g(Add1Ty<2 * M> *);
template <unsigned M> void g(AddOneTy<2 * M> *);
void h() {
    g<0>(nullptr); // OK, there is only one g
}
// [Example 2:
template <unsigned N2> void f2()
requires Add1<2 * N2>;
template <unsigned N2> int f2()
requires Add1<N2 * 2> && true;
void h2() {
    f2<0>();
}
// il l-formed, no diagnostic required:
// requires determination of subsumption between atomic constraints that are
// functionally equivalent but not equivalent
// [Example 3:
template<typename T> concept C3 =
    sizeof(T) == 4 && !true; // requires atomic constraints sizeof(T) == 4 and !true
template<typename T> struct S {
    constexpr operator bool() const {
        return true;
    }
};
template<typename T> requires (S<T> {})
void f3(T);
void f3(int);
void g3() {
    f3(0);
}
// #1
// #2
// error: expression S<int>{} does not have type bool
// while checking satisfaction of deduced arguments of #1;
// call is ill-formed even though #2 is a better match
int main() {
    cout  <<  n4910 << endl;
    return EXIT_SUCCESS;
}

Script

clgc.sh
#!/bin/sh
rm $1l
rm $1g
echo "$ clang++ $1.cpp -std=03 -o $1l -I. -Wall" 
clang++ $1.cpp -std=c++03 -o $1l -I. -Wall
if [  -e $1l ]; then
./$1l 
fi
rm $1l
echo "$ clang++ $1.cpp -std=2b -o $1l -I. -Wall"
clang++ $1.cpp -std=c++2b -o $1l -I. -Wall
if [  -e $1l ]; then
./$1l
fi
echo "\r"
echo "$ g++ $1.cpp -std=03 -o $1g -I. -Wall"
g++ $1.cpp -std=c++03 -o $1g -I. -Wall
if [ -e $1g ]; then
./$1g
fi
rm $1g
echo "\r"
echo "$ g++ $1.cpp -std=2b -o $1g -I. -Wall"
g++ $1.cpp -std=c++2b -o $1g -I. -Wall
if [ -e $1g ]; then
./$1g 
fi

編纂・実行結果(compile and go)

bash
# ./clgc.sh p368
rm: cannot remove 'p368l': No such file or directory
rm: cannot remove 'p368g': No such file or directory
$ clang++ p368.cpp -std=c++03 -o p368l -I. -Wall
In file included from p368.cpp:19:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/atomic:38:
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/c++0x_warning.h:32:2: error: This file requires compiler and library support for the ISO C++ 2011 standard. This support must be enabled with the -std=c++11 or -std=gnu++11 compiler options.
#error This file requires compiler and library support \
 ^
p368.cpp:26:23: error: unknown type name 'constexpr'
template <unsigned N> constexpr bool Atomic = true;
                      ^
p368.cpp:26:38: warning: variable templates are a C++14 extension [-Wc++14-extensions]
template <unsigned N> constexpr bool Atomic = true;
                                     ^
p368.cpp:27:28: error: unknown type name 'concept'
     template <unsigned N> concept C = Atomic<N>;
                           ^
p368.cpp:27:36: warning: variable templates are a C++14 extension [-Wc++14-extensions]
     template <unsigned N> concept C = Atomic<N>;
                                   ^
p368.cpp:28:28: error: unknown type name 'concept'
     template <unsigned N> concept Add1 = C<N + 1>;
                           ^
p368.cpp:28:36: warning: variable templates are a C++14 extension [-Wc++14-extensions]
     template <unsigned N> concept Add1 = C<N + 1>;
                                   ^
p368.cpp:29:28: error: unknown type name 'concept'
     template <unsigned N> concept AddOne = C<N + 1>;
                           ^
p368.cpp:29:36: warning: variable templates are a C++14 extension [-Wc++14-extensions]
     template <unsigned N> concept AddOne = C<N + 1>;
                                   ^
p368.cpp:30:36: error: expected ';' at end of declaration
     template <unsigned M> void f()
                                   ^
                                   ;
p368.cpp:31:8: error: unknown type name 'requires'
       requires Add1<2 * M>;
       ^
p368.cpp:31:26: error: use of undeclared identifier 'M'
       requires Add1<2 * M>;
                         ^
p368.cpp:32:35: error: expected ';' at end of declaration
     template <unsigned M> int f()
                                  ^
                                  ;
p368.cpp:33:1: error: unknown type name 'requires'
requires AddOne<2 * M> && true;
^
p368.cpp:33:21: error: use of undeclared identifier 'M'
requires AddOne<2 * M> && true;
                    ^
p368.cpp:34:9: error: call to 'f' is ambiguous
int x = f<0>(); // OK, the atomic constraints from concept C in both fs are Atomic<N>
        ^~~~
p368.cpp:30:33: note: candidate function [with M = 0]
     template <unsigned M> void f()
                                ^
p368.cpp:32:32: note: candidate function [with M = 0]
     template <unsigned M> int f()
                               ^
p368.cpp:37:43: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
     template <unsigned N> using Add1Ty = WrapN<N + 1>;
                                          ^
p368.cpp:38:45: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
     template <unsigned N> using AddOneTy = WrapN<N + 1>;
                                            ^
p368.cpp:42:6: error: use of undeclared identifier 'nullptr'
g<0>(nullptr); // OK, there is only one g
     ^
p368.cpp:45:38: error: expected ';' at end of declaration
     template <unsigned N2> void f2()
                                     ^
                                     ;
p368.cpp:46:8: error: unknown type name 'requires'
       requires Add1<2 * N2>;
       ^
p368.cpp:46:26: error: use of undeclared identifier 'N2'
       requires Add1<2 * N2>;
                         ^
p368.cpp:47:37: error: expected ';' at end of declaration
     template <unsigned N2> int f2()
                                    ^
                                    ;
p368.cpp:48:8: error: unknown type name 'requires'
       requires Add1<N2 * 2> && true;
       ^
p368.cpp:48:22: error: use of undeclared identifier 'N2'
       requires Add1<N2 * 2> && true;
                     ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
6 warnings and 20 errors generated.
rm: cannot remove 'p368l': No such file or directory
$ clang++ p368.cpp -std=c++2b -o p368l -I. -Wall
p368.cpp:50:5: error: call to 'f2' is ambiguous
    f2<0>();
    ^~~~~
p368.cpp:45:34: note: candidate function [with N2 = 0]
     template <unsigned N2> void f2()
                                 ^
p368.cpp:47:33: note: candidate function [with N2 = 0]
     template <unsigned N2> int f2()
                                ^
1 error generated.

$ g++ p368.cpp -std=c++03 -o p368g -I. -Wall
In file included from /usr/local/include/c++/12.1.0/atomic:38,
                 from p368.cpp:19:
/usr/local/include/c++/12.1.0/bits/c++0x_warning.h:32:2: error: #error This file requires compiler and library support for the ISO C++ 2011 standard. This support must be enabled with the -std=c++11 or -std=gnu++11 compiler options.
   32 | #error This file requires compiler and library support \
      |  ^~~~~
p368.cpp:26:23: warning: identifier 'constexpr' is a keyword in C++11 [-Wc++11-compat]
   26 | template <unsigned N> constexpr bool Atomic = true;
      |                       ^~~~~~~~~
p368.cpp:42:6: warning: identifier 'nullptr' is a keyword in C++11 [-Wc++11-compat]
   42 | g<0>(nullptr); // OK, there is only one g
      |      ^~~~~~~
p368.cpp:26:23: error: 'constexpr' does not name a type
   26 | template <unsigned N> constexpr bool Atomic = true;
      |                       ^~~~~~~~~
p368.cpp:26:23: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p368.cpp:27:28: error: 'concept' does not name a type; did you mean 'const'?
   27 |      template <unsigned N> concept C = Atomic<N>;
      |                            ^~~~~~~
      |                            const
p368.cpp:27:28: note: 'concept' only available with '-std=c++20' or '-fconcepts'
p368.cpp:28:28: error: 'concept' does not name a type; did you mean 'const'?
   28 |      template <unsigned N> concept Add1 = C<N + 1>;
      |                            ^~~~~~~
      |                            const
p368.cpp:28:28: note: 'concept' only available with '-std=c++20' or '-fconcepts'
p368.cpp:29:28: error: 'concept' does not name a type; did you mean 'const'?
   29 |      template <unsigned N> concept AddOne = C<N + 1>;
      |                            ^~~~~~~
      |                            const
p368.cpp:29:28: note: 'concept' only available with '-std=c++20' or '-fconcepts'
p368.cpp:31:8: error: 'requires' only available with '-std=c++20' or '-fconcepts'
   31 |        requires Add1<2 * M>;
      |        ^~~~~~~~
p368.cpp:31:17: error: 'Add1' was not declared in this scope
   31 |        requires Add1<2 * M>;
      |                 ^~~~
p368.cpp:31:28: error: expected primary-expression before ';' token
   31 |        requires Add1<2 * M>;
      |                            ^
p368.cpp:33:1: error: 'requires' only available with '-std=c++20' or '-fconcepts'
   33 | requires AddOne<2 * M> && true;
      | ^~~~~~~~
p368.cpp:33:10: error: 'AddOne' was not declared in this scope
   33 | requires AddOne<2 * M> && true;
      |          ^~~~~~
p368.cpp:33:27: error: expected identifier before 'true'
   33 | requires AddOne<2 * M> && true;
      |                           ^~~~
p368.cpp:33:27: error: expected initializer before 'true'
p368.cpp:34:13: error: void value not ignored as it ought to be
   34 | int x = f<0>(); // OK, the atomic constraints from concept C in both fs are Atomic<N>
      |         ~~~~^~
p368.cpp:37:28: error: expected unqualified-id before 'using'
   37 |      template <unsigned N> using Add1Ty = WrapN<N + 1>;
      |                            ^~~~~
p368.cpp:38:28: error: expected unqualified-id before 'using'
   38 |      template <unsigned N> using AddOneTy = WrapN<N + 1>;
      |                            ^~~~~
p368.cpp:39:33: error: variable or field 'g' declared void
   39 |      template <unsigned M> void g(Add1Ty<2 * M> *);
      |                                 ^
p368.cpp:39:35: error: 'Add1Ty' was not declared in this scope
   39 |      template <unsigned M> void g(Add1Ty<2 * M> *);
      |                                   ^~~~~~
p368.cpp:39:50: error: expected primary-expression before ')' token
   39 |      template <unsigned M> void g(Add1Ty<2 * M> *);
      |                                                  ^
p368.cpp:40:33: error: variable or field 'g' declared void
   40 |      template <unsigned M> void g(AddOneTy<2 * M> *);
      |                                 ^
p368.cpp:40:35: error: 'AddOneTy' was not declared in this scope
   40 |      template <unsigned M> void g(AddOneTy<2 * M> *);
      |                                   ^~~~~~~~
p368.cpp:40:52: error: expected primary-expression before ')' token
   40 |      template <unsigned M> void g(AddOneTy<2 * M> *);
      |                                                    ^
p368.cpp: In function 'void h()':
p368.cpp:42:1: error: 'g' was not declared in this scope
   42 | g<0>(nullptr); // OK, there is only one g
      | ^
p368.cpp:42:6: error: 'nullptr' was not declared in this scope
   42 | g<0>(nullptr); // OK, there is only one g
      |      ^~~~~~~
p368.cpp: At global scope:
p368.cpp:46:8: error: 'requires' only available with '-std=c++20' or '-fconcepts'
   46 |        requires Add1<2 * N2>;
      |        ^~~~~~~~
p368.cpp:46:17: error: 'Add1' was not declared in this scope
   46 |        requires Add1<2 * N2>;
      |                 ^~~~
p368.cpp:46:29: error: expected primary-expression before ';' token
   46 |        requires Add1<2 * N2>;
      |                             ^
p368.cpp:48:8: error: 'requires' only available with '-std=c++20' or '-fconcepts'
   48 |        requires Add1<N2 * 2> && true;
      |        ^~~~~~~~
p368.cpp:48:17: error: 'Add1' was not declared in this scope
   48 |        requires Add1<N2 * 2> && true;
      |                 ^~~~
p368.cpp:48:33: error: expected identifier before 'true'
   48 |        requires Add1<N2 * 2> && true;
      |                                 ^~~~
p368.cpp:48:33: error: expected initializer before 'true'
p368.cpp:56:22: error: 'concept' does not name a type; did you mean 'const'?
   56 | template<typename T> concept C3 =
      |                      ^~~~~~~
      |                      const
p368.cpp:56:22: note: 'concept' only available with '-std=c++20' or '-fconcepts'
p368.cpp:59:3: error: 'constexpr' does not name a type
   59 |   constexpr operator bool() const { return true; }
      |   ^~~~~~~~~
p368.cpp:59:3: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p368.cpp:61:31: error: expected constructor, destructor, or type conversion before '(' token
   61 | template<typename T> requires (S<T>{})
      |                               ^
p368.cpp:61:38: error: expected unqualified-id before ')' token
   61 | template<typename T> requires (S<T>{})
      |                                      ^
rm: cannot remove 'p368g': No such file or directory

$ g++ p368.cpp -std=c++2b -o p368g -I. -Wall
p368.cpp: In function 'void h2()':
p368.cpp:50:10: error: call of overloaded 'f2<0>()' is ambiguous
   50 |     f2<0>();
      |     ~~~~~^~
p368.cpp:45:34: note: candidate: 'void f2() requires  Add1<2 * N2> [with unsigned int N2 = 0]'
   45 |      template <unsigned N2> void f2()
      |                                  ^~
p368.cpp:47:33: note: candidate: 'int f2() requires (Add1<N2 * 2>) && true [with unsigned int N2 = 0]'
   47 |      template <unsigned N2> int f2()
      |                                 ^~
p368.cpp: At global scope:
p368.cpp:61:32: error: constraint expression does not have type 'bool'
   61 | template<typename T> requires (S<T>{})
      |                               ~^~~~~~~

検討事項(agenda)

コンパイルエラーを取るか、コンパイルエラーの理由を解説する。

参考資料(reference)

cpprefjp - C++日本語リファレンス

コンパイラの実装状況

typedef は C++11 ではオワコン

C99からC++14を駆け抜けるC++講座

自己参照(self reference)

コピペコンパイルエラーあるある

C++ Error Message Collection(1)does not name a type, 11 articles

dockerにclang

docker gnu(gcc/g++) and llvm(clang/clang++)

コンパイル用shell script C版(clangとgcc)とC++版(clang++とg++)

Compare the contents of C++N4910:2022, C++N4741:2018 and C++N4606:2015

C++ sample list

clang++, g++コンパイルエラー方針の違いの例

astyle 使ってみた

C++N4606 Working Draft 2016, ISO/IEC 14882, C++ standardのコード断片をコンパイルするためにしていること
https://qiita.com/kaizen_nagoya/items/a8d7ee2f2e29e76c19c1

コンパイル用shell script C版(clangとgcc)とC++版(clang++とg++)
https://qiita.com/kaizen_nagoya/items/74220c0577a512c2d7da

Clang/Clang++(LLVM) gcc/g++(GNU) コンパイラ警告等比較
https://qiita.com/kaizen_nagoya/items/9a82b958cc3aeef0403f

C++2003とC++2017でコンパイルエラーになるならない事例集
https://qiita.com/kaizen_nagoya/items/a13ea3823441c430edff

Qiitaに投稿するCのStyle例(暫定)
https://qiita.com/kaizen_nagoya/items/946df1528a6a1ef2bc0d

cpprefjpのdecltypeをコンパイル試験
https://qiita.com/kaizen_nagoya/items/090909af702f0d5d8a67

MISRA C++ 5-0-16
https://qiita.com/kaizen_nagoya/items/7df2d4e05db724752a74

C++ Templates Part1 BASICS Chapter 3. Class Templates 3.2 Use of Class Template Stack stack1test.cpp
https://qiita.com/kaizen_nagoya/items/cd5fc49106fad5a4e9ed

ISO/IEC TS 17961:2013 C Secure Coding Rules(1) All list(to be confirmed)
https://qiita.com/kaizen_nagoya/items/54e056195c4f11b850a1

C言語（C++)に対する誤解、曲解、無理解、爽快。
https://qiita.com/kaizen_nagoya/items/3f3992c9722c1cee2e3a

C Puzzle Bookの有り難み5つ、C言語規格及びCコンパイラの特性を認識
https://qiita.com/kaizen_nagoya/items/d89a48c1536a02ecdec9

'wchar.h' file not found で困った clang++ macOS
https://qiita.com/kaizen_nagoya/items/de15cd46d657517fac11

Open POSIX Test Suiteの使い方を調べはじめました
https://qiita.com/kaizen_nagoya/items/644d5e407f5faf96e6dc

MISRA-C 2012 Referenceに掲載している文献の入手可能性を確認
https://qiita.com/kaizen_nagoya/items/96dc8b125e462d5575bb

どうやって MISRA Example Suiteをコンパイルするか
https://qiita.com/kaizen_nagoya/items/fbdbff5ff696e2ca7f00

MISRA C まとめ #include
https://qiita.com/kaizen_nagoya/items/f1a79a7cbd281607c7c9

「C++完全理解ガイド」の同意できること上位10
https://qiita.com/kaizen_nagoya/items/aa5744e0c4a8618c7671

＜この記事は個人の過去の経験に基づく個人の感想です。現在所属する組織、業務とは関係がありません。＞

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ver. 0.01 初稿 　20220703

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