17.11.2.3 Class weak_ordering [cmp.weakord] C++N4910:2022 (317) p530.cpp

# はじめに(Introduction)

N4910  Working Draft, Standard for Programming Language C++

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/n4910.pdf

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  

https://qiita.com/kaizen_nagoya/items/fc957ddddd402004bb91

### C++N4741, 2018 Standard Working Draft on ISO/IEC 14882 sample code compile list
https://qiita.com/kaizen_nagoya/items/3294c014044550896010

### 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++
https://qiita.com/kaizen_nagoya/items/685b5c1a2c17c1bf1318

## 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.

# 17.11.2.3 Class weak_ordering [cmp.weakord] C++N4910:2022 (317) p530.cpp

## 算譜(source code)

```c++:p530.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 = "17.11.2.3 Class weak_ordering [cmp.weakord] C++N4910:2022 (317) p530.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
namespace std {
class weak_ordering {
    int value; // exposition only // exposition-only constructors
    constexpr explicit weak_ordering(ord v) noexcept : value(int(v)) {} // exposition only
public:
// valid values
    static const weak_ordering less;
    static const weak_ordering equivalent;
    static const weak_ordering greater;
// conversions
    constexpr operator partial_ordering() const noexcept;
// comparisons
}
friend constexpr bool operator==(weak_ordering v, unspecified) noexcept;
friend constexpr bool operator==(weak_ordering v, weak_ordering w) noexcept = default;
friend constexpr bool operator< (weak_ordering v, unspecified) noexcept;
friend constexpr bool operator> (weak_ordering v, unspecified) noexcept;
friend constexpr bool operator<=(weak_ordering v, unspecified) noexcept;
friend constexpr bool operator>=(weak_ordering v, unspecified) noexcept;
friend constexpr bool operator< (unspecified, weak_ordering v) noexcept;
friend constexpr bool operator> (unspecified, weak_ordering v) noexcept;
friend constexpr bool operator<=(unspecified, weak_ordering v) noexcept;
friend constexpr bool operator>=(unspecified, weak_ordering v) noexcept;
friend constexpr weak_ordering operator<=>(weak_ordering v, unspecified) noexcept;
friend constexpr weak_ordering operator<=>(unspecified, weak_ordering v)
// valid values’ definitions
};
inline constexpr weak_ordering weak_ordering::less(ord::less);
inline constexpr weak_ordering weak_ordering::equivalent(ord::equivalent);
inline constexpr weak_ordering weak_ordering::greater(ord::greater);
constexpr operator partial_ordering() const noexcept;
// Returns:
value == 0 ? partial_ordering::equivalent :
value < 0  ? partial_ordering::less :
partial_ordering::greater
constexpr bool operator==(weak_ordering v, unspecified) noexcept;
constexpr bool operator< (weak_ordering v, unspecified) noexcept;
constexpr bool operator> (weak_ordering v, unspecified) noexcept;
constexpr bool operator<=(weak_ordering v, unspecified) noexcept;
constexpr bool operator>=(weak_ordering v, unspecified) noexcept;
// Returns: v.value @ 0 for operator@.
constexpr bool operator< (unspecified, weak_ordering v) noexcept;
constexpr bool operator> (unspecified, weak_ordering v) noexcept;
constexpr bool operator<=(unspecified, weak_ordering v) noexcept;
constexpr bool operator>=(unspecified, weak_ordering v) noexcept;
// Returns: 0 @ v.value for operator@.
constexpr weak_ordering operator<=>(weak_ordering v, unspecified) noexcept;
// Returns: v.
constexpr weak_ordering operator<=>(unspecified, weak_ordering v) noexcept;
// Returns: v < 0 ? weak_ordering::greater : v > 0 ? weak_ordering::less : v.
int main() {
    cout  <<  n4910 << endl;
    return EXIT_SUCCESS;
}
```

## Script

```bash: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)

```ubuntu:bash
# ./clgc.sh p530
$ clang++ p530.cpp -std=c++03 -o p530l -I. -Wall
In file included from p530.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 \
 ^
p530.cpp:29:1: error: unknown type name 'constexpr'
constexpr explicit weak_ordering(ord v) noexcept : value(int(v)) {} // exposition only
^
p530.cpp:29:34: error: unknown type name 'ord'
constexpr explicit weak_ordering(ord v) noexcept : value(int(v)) {} // exposition only
                                 ^
p530.cpp:29:20: error: constructor cannot have a return type
constexpr explicit weak_ordering(ord v) noexcept : value(int(v)) {} // exposition only
                   ^~~~~~~~~~~~~
p530.cpp:29:40: error: expected ';' at end of declaration list
constexpr explicit weak_ordering(ord v) noexcept : value(int(v)) {} // exposition only
                                       ^
                                       ;
p530.cpp:36:7: error: unknown type name 'constexpr'
      constexpr operator partial_ordering() const noexcept;
      ^
p530.cpp:36:26: error: unknown type name 'partial_ordering'
      constexpr operator partial_ordering() const noexcept;
                         ^
p530.cpp:39:1: error: 'friend' used outside of class
friend constexpr bool operator==(weak_ordering v, unspecified) noexcept;
^
p530.cpp:39:17: error: expected ';' after top level declarator
friend constexpr bool operator==(weak_ordering v, unspecified) noexcept;
                ^
                ;
p530.cpp:39:51: error: unknown type name 'unspecified'
friend constexpr bool operator==(weak_ordering v, unspecified) noexcept;
                                                  ^
p530.cpp:39:64: error: expected function body after function declarator
friend constexpr bool operator==(weak_ordering v, unspecified) noexcept;
                                                               ^
p530.cpp:40:1: error: 'friend' used outside of class
friend constexpr bool operator==(weak_ordering v, weak_ordering w) noexcept = default; 
^
p530.cpp:40:8: error: unknown type name 'constexpr'
friend constexpr bool operator==(weak_ordering v, weak_ordering w) noexcept = default; 
       ^
p530.cpp:40:68: error: expected function body after function declarator
friend constexpr bool operator==(weak_ordering v, weak_ordering w) noexcept = default; 
                                                                   ^
p530.cpp:41:1: error: 'friend' used outside of class
friend constexpr bool operator< (weak_ordering v, unspecified) noexcept;
^
p530.cpp:41:8: error: unknown type name 'constexpr'
friend constexpr bool operator< (weak_ordering v, unspecified) noexcept;
       ^
p530.cpp:41:51: error: unknown type name 'unspecified'
friend constexpr bool operator< (weak_ordering v, unspecified) noexcept;
                                                  ^
p530.cpp:41:64: error: expected function body after function declarator
friend constexpr bool operator< (weak_ordering v, unspecified) noexcept;
                                                               ^
p530.cpp:42:1: error: 'friend' used outside of class
friend constexpr bool operator> (weak_ordering v, unspecified) noexcept;
^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.
rm: cannot remove 'p530l': No such file or directory
$ clang++ p530.cpp -std=c++2b -o p530l -I. -Wall
p530.cpp:27:11: error: redefinition of 'weak_ordering'
    class weak_ordering {
          ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/compare:155:9: note: previous definition is here
  class weak_ordering
        ^
p530.cpp:39:1: error: 'friend' used outside of class
friend constexpr bool operator==(weak_ordering v, unspecified) noexcept;
^
p530.cpp:39:18: error: cannot combine with previous 'class' declaration specifier
friend constexpr bool operator==(weak_ordering v, unspecified) noexcept;
                 ^
p530.cpp:39:51: error: unknown type name 'unspecified'
friend constexpr bool operator==(weak_ordering v, unspecified) noexcept;
                                                  ^
p530.cpp:40:1: error: 'friend' used outside of class
friend constexpr bool operator==(weak_ordering v, weak_ordering w) noexcept = default; 
^
p530.cpp:40:23: error: redefinition of 'operator=='
friend constexpr bool operator==(weak_ordering v, weak_ordering w) noexcept = default; 
                      ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/compare:180:5: note: previous definition is here
    operator==(weak_ordering, weak_ordering) noexcept = default;
    ^
p530.cpp:41:1: error: 'friend' used outside of class
friend constexpr bool operator< (weak_ordering v, unspecified) noexcept;
^
p530.cpp:41:51: error: unknown type name 'unspecified'
friend constexpr bool operator< (weak_ordering v, unspecified) noexcept;
                                                  ^
p530.cpp:42:1: error: 'friend' used outside of class
friend constexpr bool operator> (weak_ordering v, unspecified) noexcept;
^
p530.cpp:42:51: error: unknown type name 'unspecified'
friend constexpr bool operator> (weak_ordering v, unspecified) noexcept;
                                                  ^
p530.cpp:43:1: error: 'friend' used outside of class
friend constexpr bool operator<=(weak_ordering v, unspecified) noexcept;
^
p530.cpp:43:51: error: unknown type name 'unspecified'
friend constexpr bool operator<=(weak_ordering v, unspecified) noexcept;
                                                  ^
p530.cpp:44:1: error: 'friend' used outside of class
friend constexpr bool operator>=(weak_ordering v, unspecified) noexcept;
^
p530.cpp:44:51: error: unknown type name 'unspecified'
friend constexpr bool operator>=(weak_ordering v, unspecified) noexcept;
                                                  ^
p530.cpp:45:1: error: 'friend' used outside of class
friend constexpr bool operator< (unspecified, weak_ordering v) noexcept;
^
p530.cpp:45:34: error: unknown type name 'unspecified'
friend constexpr bool operator< (unspecified, weak_ordering v) noexcept;
                                 ^
p530.cpp:46:1: error: 'friend' used outside of class
friend constexpr bool operator> (unspecified, weak_ordering v) noexcept;
^
p530.cpp:46:34: error: unknown type name 'unspecified'
friend constexpr bool operator> (unspecified, weak_ordering v) noexcept;
                                 ^
p530.cpp:47:1: error: 'friend' used outside of class
friend constexpr bool operator<=(unspecified, weak_ordering v) noexcept;
^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.

$ g++ p530.cpp -std=c++03 -o p530g -I. -Wall
In file included from /usr/local/include/c++/12.1.0/atomic:38,
                 from p530.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 \
      |  ^~~~~
p530.cpp:29:1: warning: identifier 'constexpr' is a keyword in C++11 [-Wc++11-compat]
   29 | constexpr explicit weak_ordering(ord v) noexcept : value(int(v)) {} // exposition only
      | ^~~~~~~~~
p530.cpp:29:41: warning: identifier 'noexcept' is a keyword in C++11 [-Wc++11-compat]
   29 | constexpr explicit weak_ordering(ord v) noexcept : value(int(v)) {} // exposition only
      |                                         ^~~~~~~~
p530.cpp:29:1: error: 'constexpr' does not name a type
   29 | constexpr explicit weak_ordering(ord v) noexcept : value(int(v)) {} // exposition only
      | ^~~~~~~~~
p530.cpp:29:1: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:36:7: error: 'constexpr' does not name a type
   36 |       constexpr operator partial_ordering() const noexcept;
      |       ^~~~~~~~~
p530.cpp:36:7: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:39:1: error: 'friend' used outside of class
   39 | friend constexpr bool operator==(weak_ordering v, unspecified) noexcept;
      | ^~~~~~
      | ------
p530.cpp:39:18: error: expected initializer before 'bool'
   39 | friend constexpr bool operator==(weak_ordering v, unspecified) noexcept;
      |                  ^~~~
p530.cpp:40:1: error: 'friend' used outside of class
   40 | friend constexpr bool operator==(weak_ordering v, weak_ordering w) noexcept = default;
      | ^~~~~~
      | ------
p530.cpp:40:8: error: 'constexpr' does not name a type
   40 | friend constexpr bool operator==(weak_ordering v, weak_ordering w) noexcept = default;
      |        ^~~~~~~~~
p530.cpp:40:8: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:41:1: error: 'friend' used outside of class
   41 | friend constexpr bool operator< (weak_ordering v, unspecified) noexcept;
      | ^~~~~~
      | ------
p530.cpp:41:8: error: 'constexpr' does not name a type
   41 | friend constexpr bool operator< (weak_ordering v, unspecified) noexcept;
      |        ^~~~~~~~~
p530.cpp:41:8: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:42:1: error: 'friend' used outside of class
   42 | friend constexpr bool operator> (weak_ordering v, unspecified) noexcept;
      | ^~~~~~
      | ------
p530.cpp:42:8: error: 'constexpr' does not name a type
   42 | friend constexpr bool operator> (weak_ordering v, unspecified) noexcept;
      |        ^~~~~~~~~
p530.cpp:42:8: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:43:1: error: 'friend' used outside of class
   43 | friend constexpr bool operator<=(weak_ordering v, unspecified) noexcept;
      | ^~~~~~
      | ------
p530.cpp:43:8: error: 'constexpr' does not name a type
   43 | friend constexpr bool operator<=(weak_ordering v, unspecified) noexcept;
      |        ^~~~~~~~~
p530.cpp:43:8: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:44:1: error: 'friend' used outside of class
   44 | friend constexpr bool operator>=(weak_ordering v, unspecified) noexcept;
      | ^~~~~~
      | ------
p530.cpp:44:8: error: 'constexpr' does not name a type
   44 | friend constexpr bool operator>=(weak_ordering v, unspecified) noexcept;
      |        ^~~~~~~~~
p530.cpp:44:8: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:45:1: error: 'friend' used outside of class
   45 | friend constexpr bool operator< (unspecified, weak_ordering v) noexcept;
      | ^~~~~~
      | ------
p530.cpp:45:8: error: 'constexpr' does not name a type
   45 | friend constexpr bool operator< (unspecified, weak_ordering v) noexcept;
      |        ^~~~~~~~~
p530.cpp:45:8: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:46:1: error: 'friend' used outside of class
   46 | friend constexpr bool operator> (unspecified, weak_ordering v) noexcept;
      | ^~~~~~
      | ------
p530.cpp:46:8: error: 'constexpr' does not name a type
   46 | friend constexpr bool operator> (unspecified, weak_ordering v) noexcept;
      |        ^~~~~~~~~
p530.cpp:46:8: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:47:1: error: 'friend' used outside of class
   47 | friend constexpr bool operator<=(unspecified, weak_ordering v) noexcept;
      | ^~~~~~
      | ------
p530.cpp:47:8: error: 'constexpr' does not name a type
   47 | friend constexpr bool operator<=(unspecified, weak_ordering v) noexcept;
      |        ^~~~~~~~~
p530.cpp:47:8: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:48:1: error: 'friend' used outside of class
   48 | friend constexpr bool operator>=(unspecified, weak_ordering v) noexcept;
      | ^~~~~~
      | ------
p530.cpp:48:8: error: 'constexpr' does not name a type
   48 | friend constexpr bool operator>=(unspecified, weak_ordering v) noexcept;
      |        ^~~~~~~~~
p530.cpp:48:8: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:49:1: error: 'friend' used outside of class
   49 | friend constexpr weak_ordering operator<=>(weak_ordering v, unspecified) noexcept;
      | ^~~~~~
      | ------
p530.cpp:49:8: error: 'constexpr' does not name a type
   49 | friend constexpr weak_ordering operator<=>(weak_ordering v, unspecified) noexcept;
      |        ^~~~~~~~~
p530.cpp:49:8: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:50:1: error: 'friend' used outside of class
   50 | friend constexpr weak_ordering operator<=>(unspecified, weak_ordering v)
      | ^~~~~~
      | ------
p530.cpp:50:8: error: 'constexpr' does not name a type
   50 | friend constexpr weak_ordering operator<=>(unspecified, weak_ordering v)
      |        ^~~~~~~~~
p530.cpp:50:8: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:53:8: error: 'constexpr' does not name a type
   53 | inline constexpr weak_ordering weak_ordering::less(ord::less);
      |        ^~~~~~~~~
p530.cpp:53:8: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:54:8: error: 'constexpr' does not name a type
   54 | inline constexpr weak_ordering weak_ordering::equivalent(ord::equivalent);
      |        ^~~~~~~~~
p530.cpp:54:8: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:55:8: error: 'constexpr' does not name a type
   55 | inline constexpr weak_ordering weak_ordering::greater(ord::greater);
      |        ^~~~~~~~~
p530.cpp:55:8: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:56:1: error: 'constexpr' does not name a type
   56 | constexpr operator partial_ordering() const noexcept;
      | ^~~~~~~~~
p530.cpp:56:1: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:58:8: error: 'value' does not name a type
   58 |        value == 0 ? partial_ordering::equivalent :
      |        ^~~~~
p530.cpp:62:1: error: 'constexpr' does not name a type
   62 | constexpr bool operator< (weak_ordering v, unspecified) noexcept;
      | ^~~~~~~~~
p530.cpp:62:1: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:63:1: error: 'constexpr' does not name a type
   63 | constexpr bool operator> (weak_ordering v, unspecified) noexcept;
      | ^~~~~~~~~
p530.cpp:63:1: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:64:1: error: 'constexpr' does not name a type
   64 | constexpr bool operator<=(weak_ordering v, unspecified) noexcept;
      | ^~~~~~~~~
p530.cpp:64:1: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:65:1: error: 'constexpr' does not name a type
   65 | constexpr bool operator>=(weak_ordering v, unspecified) noexcept;
      | ^~~~~~~~~
p530.cpp:65:1: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:67:1: error: 'constexpr' does not name a type
   67 | constexpr bool operator< (unspecified, weak_ordering v) noexcept;
      | ^~~~~~~~~
p530.cpp:67:1: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:68:1: error: 'constexpr' does not name a type
   68 | constexpr bool operator> (unspecified, weak_ordering v) noexcept;
      | ^~~~~~~~~
p530.cpp:68:1: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:69:1: error: 'constexpr' does not name a type
   69 | constexpr bool operator<=(unspecified, weak_ordering v) noexcept;
      | ^~~~~~~~~
p530.cpp:69:1: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:70:1: error: 'constexpr' does not name a type
   70 | constexpr bool operator>=(unspecified, weak_ordering v) noexcept;
      | ^~~~~~~~~
p530.cpp:70:1: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:72:1: error: 'constexpr' does not name a type
   72 | constexpr weak_ordering operator<=>(weak_ordering v, unspecified) noexcept;
      | ^~~~~~~~~
p530.cpp:72:1: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p530.cpp:74:1: error: 'constexpr' does not name a type
   74 | constexpr weak_ordering operator<=>(unspecified, weak_ordering v) noexcept;
      | ^~~~~~~~~
p530.cpp:74:1: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
rm: cannot remove 'p530g': No such file or directory

$ g++ p530.cpp -std=c++2b -o p530g -I. -Wall
p530.cpp:27:11: error: redefinition of 'class std::weak_ordering'
   27 |     class weak_ordering {
      |           ^~~~~~~~~~~~~
In file included from /usr/local/include/c++/12.1.0/bits/char_traits.h:45,
                 from /usr/local/include/c++/12.1.0/ios:40,
                 from /usr/local/include/c++/12.1.0/ostream:38,
                 from /usr/local/include/c++/12.1.0/iostream:39,
                 from p530.cpp:10:
/usr/local/include/c++/12.1.0/compare:167:9: note: previous definition of 'class std::weak_ordering'
  167 |   class weak_ordering
      |         ^~~~~~~~~~~~~
p530.cpp:39:1: error: 'friend' used outside of class
   39 | friend constexpr bool operator==(weak_ordering v, unspecified) noexcept;
      | ^~~~~~
      | ------
p530.cpp:39:51: error: 'unspecified' has not been declared
   39 | friend constexpr bool operator==(weak_ordering v, unspecified) noexcept;
      |                                                   ^~~~~~~~~~~
p530.cpp:27:5: error: new types may not be defined in a return type
   27 |     class weak_ordering {
      |     ^~~~~
p530.cpp:27:5: note: (perhaps a semicolon is missing after the definition of '<type error>')
p530.cpp:27:5: error: two or more data types in declaration of 'operator=='
p530.cpp:40:1: error: 'friend' used outside of class
   40 | friend constexpr bool operator==(weak_ordering v, weak_ordering w) noexcept = default;
      | ^~~~~~
      | ------
p530.cpp:41:1: error: 'friend' used outside of class
   41 | friend constexpr bool operator< (weak_ordering v, unspecified) noexcept;
      | ^~~~~~
      | ------
p530.cpp:41:51: error: 'unspecified' has not been declared
   41 | friend constexpr bool operator< (weak_ordering v, unspecified) noexcept;
      |                                                   ^~~~~~~~~~~
p530.cpp:42:1: error: 'friend' used outside of class
   42 | friend constexpr bool operator> (weak_ordering v, unspecified) noexcept;
      | ^~~~~~
      | ------
p530.cpp:42:51: error: 'unspecified' has not been declared
   42 | friend constexpr bool operator> (weak_ordering v, unspecified) noexcept;
      |                                                   ^~~~~~~~~~~
p530.cpp:43:1: error: 'friend' used outside of class
   43 | friend constexpr bool operator<=(weak_ordering v, unspecified) noexcept;
      | ^~~~~~
      | ------
p530.cpp:43:51: error: 'unspecified' has not been declared
   43 | friend constexpr bool operator<=(weak_ordering v, unspecified) noexcept;
      |                                                   ^~~~~~~~~~~
p530.cpp:44:1: error: 'friend' used outside of class
   44 | friend constexpr bool operator>=(weak_ordering v, unspecified) noexcept;
      | ^~~~~~
      | ------
p530.cpp:44:51: error: 'unspecified' has not been declared
   44 | friend constexpr bool operator>=(weak_ordering v, unspecified) noexcept;
      |                                                   ^~~~~~~~~~~
p530.cpp:45:1: error: 'friend' used outside of class
   45 | friend constexpr bool operator< (unspecified, weak_ordering v) noexcept;
      | ^~~~~~
      | ------
p530.cpp:45:23: error: declaration of 'operator<' as non-function
   45 | friend constexpr bool operator< (unspecified, weak_ordering v) noexcept;
      |                       ^~~~~~~~
p530.cpp:45:34: error: 'unspecified' was not declared in this scope
   45 | friend constexpr bool operator< (unspecified, weak_ordering v) noexcept;
      |                                  ^~~~~~~~~~~
p530.cpp:45:61: error: expected primary-expression before 'v'
   45 | friend constexpr bool operator< (unspecified, weak_ordering v) noexcept;
      |                                                             ^
p530.cpp:46:1: error: 'friend' used outside of class
   46 | friend constexpr bool operator> (unspecified, weak_ordering v) noexcept;
      | ^~~~~~
      | ------
p530.cpp:46:23: error: declaration of 'operator>' as non-function
   46 | friend constexpr bool operator> (unspecified, weak_ordering v) noexcept;
      |                       ^~~~~~~~
p530.cpp:46:34: error: 'unspecified' was not declared in this scope
   46 | friend constexpr bool operator> (unspecified, weak_ordering v) noexcept;
      |                                  ^~~~~~~~~~~
p530.cpp:46:61: error: expected primary-expression before 'v'
   46 | friend constexpr bool operator> (unspecified, weak_ordering v) noexcept;
      |                                                             ^
p530.cpp:47:1: error: 'friend' used outside of class
   47 | friend constexpr bool operator<=(unspecified, weak_ordering v) noexcept;
      | ^~~~~~
      | ------
p530.cpp:47:23: error: declaration of 'operator<=' as non-function
   47 | friend constexpr bool operator<=(unspecified, weak_ordering v) noexcept;
      |                       ^~~~~~~~
p530.cpp:47:34: error: 'unspecified' was not declared in this scope
   47 | friend constexpr bool operator<=(unspecified, weak_ordering v) noexcept;
      |                                  ^~~~~~~~~~~
p530.cpp:47:61: error: expected primary-expression before 'v'
   47 | friend constexpr bool operator<=(unspecified, weak_ordering v) noexcept;
      |                                                             ^
p530.cpp:48:1: error: 'friend' used outside of class
   48 | friend constexpr bool operator>=(unspecified, weak_ordering v) noexcept;
      | ^~~~~~
      | ------
p530.cpp:48:23: error: declaration of 'operator>=' as non-function
   48 | friend constexpr bool operator>=(unspecified, weak_ordering v) noexcept;
      |                       ^~~~~~~~
p530.cpp:48:34: error: 'unspecified' was not declared in this scope
   48 | friend constexpr bool operator>=(unspecified, weak_ordering v) noexcept;
      |                                  ^~~~~~~~~~~
p530.cpp:48:61: error: expected primary-expression before 'v'
   48 | friend constexpr bool operator>=(unspecified, weak_ordering v) noexcept;
      |                                                             ^
p530.cpp:49:1: error: 'friend' used outside of class
   49 | friend constexpr weak_ordering operator<=>(weak_ordering v, unspecified) noexcept;
      | ^~~~~~
      | ------
p530.cpp:49:61: error: 'unspecified' has not been declared
   49 | friend constexpr weak_ordering operator<=>(weak_ordering v, unspecified) noexcept;
      |                                                             ^~~~~~~~~~~
p530.cpp:50:1: error: 'friend' used outside of class
   50 | friend constexpr weak_ordering operator<=>(unspecified, weak_ordering v)
      | ^~~~~~
      | ------
p530.cpp:50:32: error: declaration of 'operator<=>' as non-function
   50 | friend constexpr weak_ordering operator<=>(unspecified, weak_ordering v)
      |                                ^~~~~~~~
p530.cpp:50:44: error: 'unspecified' was not declared in this scope
   50 | friend constexpr weak_ordering operator<=>(unspecified, weak_ordering v)
      |                                            ^~~~~~~~~~~
p530.cpp:50:71: error: expected primary-expression before 'v'
   50 | friend constexpr weak_ordering operator<=>(unspecified, weak_ordering v)
      |                                                                       ^
p530.cpp:53:52: error: 'ord' has not been declared
   53 | inline constexpr weak_ordering weak_ordering::less(ord::less);
      |                                                    ^~~
p530.cpp:54:58: error: 'ord' has not been declared
   54 | inline constexpr weak_ordering weak_ordering::equivalent(ord::equivalent);
      |                                                          ^~~
p530.cpp:55:55: error: 'ord' has not been declared
   55 | inline constexpr weak_ordering weak_ordering::greater(ord::greater);
      |                                                       ^~~
p530.cpp:56:45: error: non-member function 'constexpr operator std::partial_ordering()' cannot have cv-qualifier
   56 | constexpr operator partial_ordering() const noexcept;
      |                                             ^~~~~~~~
p530.cpp:56:11: error: 'constexpr operator std::partial_ordering()' must be a non-static member function
   56 | constexpr operator partial_ordering() const noexcept;
      |           ^~~~~~~~
p530.cpp:58:8: error: 'value' does not name a type
   58 |        value == 0 ? partial_ordering::equivalent :
      |        ^~~~~
p530.cpp:62:44: error: 'unspecified' has not been declared
   62 | constexpr bool operator< (weak_ordering v, unspecified) noexcept;
      |                                            ^~~~~~~~~~~
p530.cpp:63:44: error: 'unspecified' has not been declared
   63 | constexpr bool operator> (weak_ordering v, unspecified) noexcept;
      |                                            ^~~~~~~~~~~
p530.cpp:64:44: error: 'unspecified' has not been declared
   64 | constexpr bool operator<=(weak_ordering v, unspecified) noexcept;
      |                                            ^~~~~~~~~~~
p530.cpp:65:44: error: 'unspecified' has not been declared
   65 | constexpr bool operator>=(weak_ordering v, unspecified) noexcept;
      |                                            ^~~~~~~~~~~
p530.cpp:67:16: error: declaration of 'operator<' as non-function
   67 | constexpr bool operator< (unspecified, weak_ordering v) noexcept;
      |                ^~~~~~~~
p530.cpp:67:27: error: 'unspecified' was not declared in this scope
   67 | constexpr bool operator< (unspecified, weak_ordering v) noexcept;
      |                           ^~~~~~~~~~~
p530.cpp:67:54: error: expected primary-expression before 'v'
   67 | constexpr bool operator< (unspecified, weak_ordering v) noexcept;
      |                                                      ^
p530.cpp:68:16: error: declaration of 'operator>' as non-function
   68 | constexpr bool operator> (unspecified, weak_ordering v) noexcept;
      |                ^~~~~~~~
p530.cpp:68:27: error: 'unspecified' was not declared in this scope
   68 | constexpr bool operator> (unspecified, weak_ordering v) noexcept;
      |                           ^~~~~~~~~~~
p530.cpp:68:54: error: expected primary-expression before 'v'
   68 | constexpr bool operator> (unspecified, weak_ordering v) noexcept;
      |                                                      ^
p530.cpp:69:16: error: declaration of 'operator<=' as non-function
   69 | constexpr bool operator<=(unspecified, weak_ordering v) noexcept;
      |                ^~~~~~~~
p530.cpp:69:27: error: 'unspecified' was not declared in this scope
   69 | constexpr bool operator<=(unspecified, weak_ordering v) noexcept;
      |                           ^~~~~~~~~~~
p530.cpp:69:54: error: expected primary-expression before 'v'
   69 | constexpr bool operator<=(unspecified, weak_ordering v) noexcept;
      |                                                      ^
p530.cpp:70:16: error: declaration of 'operator>=' as non-function
   70 | constexpr bool operator>=(unspecified, weak_ordering v) noexcept;
      |                ^~~~~~~~
p530.cpp:70:27: error: 'unspecified' was not declared in this scope
   70 | constexpr bool operator>=(unspecified, weak_ordering v) noexcept;
      |                           ^~~~~~~~~~~
p530.cpp:70:54: error: expected primary-expression before 'v'
   70 | constexpr bool operator>=(unspecified, weak_ordering v) noexcept;
      |                                                      ^
p530.cpp:72:54: error: 'unspecified' has not been declared
   72 | constexpr weak_ordering operator<=>(weak_ordering v, unspecified) noexcept;
      |                                                      ^~~~~~~~~~~
p530.cpp:74:25: error: declaration of 'operator<=>' as non-function
   74 | constexpr weak_ordering operator<=>(unspecified, weak_ordering v) noexcept;
      |                         ^~~~~~~~
p530.cpp:74:37: error: 'unspecified' was not declared in this scope
   74 | constexpr weak_ordering operator<=>(unspecified, weak_ordering v) noexcept;
      |                                     ^~~~~~~~~~~
p530.cpp:74:64: error: expected primary-expression before 'v'
   74 | constexpr weak_ordering operator<=>(unspecified, weak_ordering v) noexcept;
      |                                                                ^

```

## 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。

<!-- リンクエラーの解説をする。clang++とg++の比較。意味のある出力。
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

https://cpprefjp.github.io/

コンパイラの実装状況

https://cpprefjp.github.io/implementation-status.html


typedef は C++11 ではオワコン

https://qiita.com/Linda_pp/items/44a67c64c14cba00eef1

C99からC++14を駆け抜けるC++講座

https://qiita.com/yumetodo/items/e49a673afd9a3ecb81a8

## 自己参照(self reference)

コピペコンパイルエラーあるある

https://qiita.com/kaizen_nagoya/items/29c832de9d762aed2761

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

https://qiita.com/kaizen_nagoya/items/acb9f1a9b5aad6df06bd

dockerにclang

https://qiita.com/kaizen_nagoya/items/8829ffeee397eda50e80

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

https://qiita.com/drafts/059874ea39c4de64c0f7

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

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

https://qiita.com/kaizen_nagoya/items/483246d40f98abff7ded

C++ sample list

https://qiita.com/kaizen_nagoya/items/54ad75b73825b7c04f86


clang++, g++コンパイルエラー方針の違いの例

https://qiita.com/kaizen_nagoya/items/ea6e5009fe126d270a82

astyle 使ってみた

https://qiita.com/kaizen_nagoya/items/3c9a87a781d53a1a23f3

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 <misra_c.h>
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。＞

# 文書履歴(document history)
ver. 0.01 初稿 　20220710