C++N4910:2022 (387) p563.cpp 19.5.2 Header <system_error> synopsis [system.error.syn] error(29)

# 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.

# 19.5.2 Header <system_error> synopsis [system.error.syn] C++N4910:2022 (387) p563.c

## 算譜(source code)

```c++:p563.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 = "19.5.2 Header <system_error> synopsis [system.error.syn] C++N4910:2022 (387) p563.c";
// 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  
#include <compare> // see 17.11.1
     namespace std {
       class error_category;
       const error_category& generic_category() noexcept;
       const error_category& system_category() noexcept;
       class error_code;
       class error_condition;
       class system_error;
       template<class T>
         struct is_error_code_enum : public false_type {};
       template<class T>
         struct is_error_condition_enum : public false_type {};
enum class errc {
  address_family_not_supported,
  address_in_use,
  address_not_available,
  already_connected,
  argument_list_too_long,
  argument_out_of_domain,
  bad_address,
  bad_file_descriptor,
  bad_message,
  broken_pipe,
  connection_aborted,
  connection_already_in_progress,
  connection_refused,
  connection_reset,
  cross_device_link,
  destination_address_required,
  device_or_resource_busy,
  directory_not_empty,
// EAFNOSUPPORT // EADDRINUSE
// EADDRNOTAVAIL // EISCONN
// E2BIG
// EDOM
// EFAULT
// EBADF
// EBADMSG
// EPIPE
// ECONNABORTED // EALREADY
// ECONNREFUSED // ECONNRESET // EXDEV
// EDESTADDRREQ // EBUSY
// ENOTEMPTY
executable_format_error,
file_exists,
file_too_large,
filename_too_long,
function_not_supported,
host_unreachable,
identifier_removed,
illegal_byte_sequence,
inappropriate_io_control_operation,
interrupted,
invalid_argument,
invalid_seek,
io_error,
is_a_directory,
message_size,
network_down,
network_reset,
network_unreachable,
no_buffer_space,
no_child_process,
no_link,
no_lock_available,
no_message_available,
no_message,
no_protocol_option,
no_space_on_device,
no_stream_resources,
no_such_device_or_address,
no_such_device,
no_such_file_or_directory,
no_such_process,
not_a_directory,
not_a_socket,
not_a_stream,
not_connected,
not_enough_memory,
not_supported,
operation_canceled,
operation_in_progress,
operation_not_permitted,
operation_not_supported,
operation_would_block,
owner_dead,
permission_denied,
protocol_error,
protocol_not_supported,
read_only_file_system,
resource_deadlock_would_occur,
resource_unavailable_try_again,
result_out_of_range,
state_not_recoverable,
stream_timeout,
text_file_busy,
timed_out,
too_many_files_open_in_system,
too_many_files_open,
too_many_links,
too_many_symbolic_link_levels,
value_too_large,
wrong_protocol_type,
// ENOEXEC
// EEXIST
// EFBIG
// ENAMETOOLONG // ENOSYS
// EHOSTUNREACH // EIDRM
// EILSEQ
// ENOTTY
// EINTR // EINVAL // ESPIPE // EIO
// EISDIR
// EMSGSIZE
// ENETDOWN
// ENETRESET
// ENETUNREACH
// ENOBUFS
// ECHILD
// ENOLINK
// ENOLCK
// ENODATA
// ENOMSG
// ENOPROTOOPT
// ENOSPC
// ENOSR
// ENXIO
// ENODEV
// ENOENT
// ESRCH
// ENOTDIR
// ENOTSOCK
// ENOSTR
// ENOTCONN
// ENOMEM
// ENOTSUP
// ECANCELED
// EINPROGRESS
// EPERM
// EOPNOTSUPP
// EWOULDBLOCK
// EOWNERDEAD
// EACCES
// EPROTO
// EPROTONOSUPPORT // EROFS
// EDEADLK
// EAGAIN
// ERANGE
// ENOTRECOVERABLE // ETIME
// ETXTBSY
// ETIMEDOUT
// ENFILE
// EMFILE
// EMLINK
// ELOOP
// EOVERFLOW
// EPROTOTYPE
};
template<> struct is_error_condition_enum<errc> : true_type {};
// 19.5.4.5, non-member functions
error_code make_error_code(errc e) noexcept;
       template<class charT, class traits>
         basic_ostream<charT, traits>&
           operator<<(basic_ostream<charT, traits>& os, const error_code& ec);
// 19.5.5.5, non-member functions
error_condition make_error_condition(errc e) noexcept;
// 19.5.6, comparison operator functions
bool operator==(const error_code& lhs, const error_code& rhs) noexcept;
bool operator==(const error_code& lhs, const error_condition& rhs) noexcept;
bool operator==(const error_condition& lhs, const error_condition& rhs) noexcept; strong_ordering operator<=>(const error_code& lhs, const error_code& rhs) noexcept; strong_ordering operator<=>(const error_condition& lhs, const error_condition& rhs) noexcept;
// 19.5.7, hash support
template<class T> struct hash; template<> struct hash<error_code>; template<> struct hash<error_condition>;
// 19.5, system error support template<class T>
         inline constexpr bool is_error_code_enum_v = is_error_code_enum<T>::value;
       template<class T>
         inline constexpr bool is_error_condition_enum_v = is_error_condition_enum<T>::value;
     }
int main(){
  cout  <<  n4910 << endl;
  return EXIT_SUCCESS;
}
```

## 編纂・実行結果(compile and go)

```ubuntu:bash
$ clang++ p563.cpp -std=c++03 -o p563l -I. -Wall
In file included from p563.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 \
 ^
p563.cpp:29:49: error: expected function body after function declarator
       const error_category& generic_category() noexcept;
                                                ^
p563.cpp:30:48: error: expected function body after function declarator
       const error_category& system_category() noexcept;
                                               ^
p563.cpp:35:45: error: unknown class name 'false_type'; did you mean '__false_type'?
         struct is_error_code_enum : public false_type {};
                                            ^~~~~~~~~~
                                            __false_type
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/cpp_type_traits.h:74:10: note: '__false_type' declared here
  struct __false_type { };
         ^
p563.cpp:37:50: error: unknown class name 'false_type'; did you mean '__false_type'?
         struct is_error_condition_enum : public false_type {};
                                                 ^~~~~~~~~~
                                                 __false_type
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/cpp_type_traits.h:74:10: note: '__false_type' declared here
  struct __false_type { };
         ^
p563.cpp:38:6: warning: scoped enumerations are a C++11 extension [-Wc++11-extensions]
enum class errc {
     ^
p563.cpp:183:51: error: unknown class name 'true_type'; did you mean '__true_type'?
template<> struct is_error_condition_enum<errc> : true_type {};
                                                  ^~~~~~~~~
                                                  __true_type
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/cpp_type_traits.h:73:10: note: '__true_type' declared here
  struct __true_type { };
         ^
p563.cpp:185:36: error: expected function body after function declarator
error_code make_error_code(errc e) noexcept;
                                   ^
p563.cpp:190:46: error: expected function body after function declarator
error_condition make_error_condition(errc e) noexcept;
                                             ^
p563.cpp:192:63: error: expected function body after function declarator
bool operator==(const error_code& lhs, const error_code& rhs) noexcept;
                                                              ^
p563.cpp:193:68: error: expected function body after function declarator
bool operator==(const error_code& lhs, const error_condition& rhs) noexcept;
                                                                   ^
p563.cpp:194:73: error: expected function body after function declarator
bool operator==(const error_condition& lhs, const error_condition& rhs) noexcept; strong_ordering operator<=>(const error_code& lhs, const error_code& rhs) noexcept; strong_ordering operator<=>(const error_condition& lhs, const error_condition& rhs) noexcept;
                                                                        ^
p563.cpp:194:83: error: unknown type name 'strong_ordering'
bool operator==(const error_condition& lhs, const error_condition& rhs) noexcept; strong_ordering operator<=>(const error_code& lhs, const error_code& rhs) noexcept; strong_ordering operator<=>(const error_condition& lhs, const error_condition& rhs) noexcept;
                                                                                  ^
p563.cpp:194:107: warning: '<=>' is a single token in C++20; add a space to avoid a change in behavior [-Wc++20-compat]
bool operator==(const error_condition& lhs, const error_condition& rhs) noexcept; strong_ordering operator<=>(const error_code& lhs, const error_code& rhs) noexcept; strong_ordering operator<=>(const error_condition& lhs, const error_condition& rhs) noexcept;
                                                                                                          ^
                                                                                                             
p563.cpp:194:99: error: 'operator<=' cannot be the name of a variable or data member
bool operator==(const error_condition& lhs, const error_condition& rhs) noexcept; strong_ordering operator<=>(const error_code& lhs, const error_code& rhs) noexcept; strong_ordering operator<=>(const error_condition& lhs, const error_condition& rhs) noexcept;
                                                                                                  ^
p563.cpp:194:109: error: expected ';' after top level declarator
bool operator==(const error_condition& lhs, const error_condition& rhs) noexcept; strong_ordering operator<=>(const error_code& lhs, const error_code& rhs) noexcept; strong_ordering operator<=>(const error_condition& lhs, const error_condition& rhs) noexcept;
                                                                                                            ^
                                                                                                            ;
p563.cpp:194:167: error: unknown type name 'strong_ordering'
bool operator==(const error_condition& lhs, const error_condition& rhs) noexcept; strong_ordering operator<=>(const error_code& lhs, const error_code& rhs) noexcept; strong_ordering operator<=>(const error_condition& lhs, const error_condition& rhs) noexcept;
                                                                                                                                                                      ^
p563.cpp:194:191: warning: '<=>' is a single token in C++20; add a space to avoid a change in behavior [-Wc++20-compat]
bool operator==(const error_condition& lhs, const error_condition& rhs) noexcept; strong_ordering operator<=>(const error_code& lhs, const error_code& rhs) noexcept; strong_ordering operator<=>(const error_condition& lhs, const error_condition& rhs) noexcept;
                                                                                                                                                                                              ^
                                                                                                                                                                                                 
p563.cpp:194:183: error: 'operator<=' cannot be the name of a variable or data member
bool operator==(const error_condition& lhs, const error_condition& rhs) noexcept; strong_ordering operator<=>(const error_code& lhs, const error_code& rhs) noexcept; strong_ordering operator<=>(const error_condition& lhs, const error_condition& rhs) noexcept;
                                                                                                                                                                                      ^
p563.cpp:194:193: error: expected ';' after top level declarator
bool operator==(const error_condition& lhs, const error_condition& rhs) noexcept; strong_ordering operator<=>(const error_code& lhs, const error_code& rhs) noexcept; strong_ordering operator<=>(const error_condition& lhs, const error_condition& rhs) noexcept;
                                                                                                                                                                                                ^
                                                                                                                                                                                                ;
p563.cpp:198:17: error: unknown type name 'constexpr'
         inline constexpr bool is_error_code_enum_v = is_error_code_enum<T>::value;
                ^
p563.cpp:198:10: warning: inline variables are a C++17 extension [-Wc++17-extensions]
         inline constexpr bool is_error_code_enum_v = is_error_code_enum<T>::value;
         ^
p563.cpp:198:74: error: use of undeclared identifier 'T'
         inline constexpr bool is_error_code_enum_v = is_error_code_enum<T>::value;
                                                                         ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
4 warnings and 20 errors generated.
rm: cannot remove 'p563l': No such file or directory
$ clang++ p563.cpp -std=c++2b -o p563l -I. -Wall
p563.cpp:29:14: error: reference to 'error_category' is ambiguous
       const error_category& generic_category() noexcept;
             ^
p563.cpp:28:14: note: candidate found by name lookup is 'std::error_category'
       class error_category;
             ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/system_error:89:9: note: candidate found by name lookup is 'std::_V2::error_category'
  class error_category
        ^
p563.cpp:30:14: error: reference to 'error_category' is ambiguous
       const error_category& system_category() noexcept;
             ^
p563.cpp:28:14: note: candidate found by name lookup is 'std::error_category'
       class error_category;
             ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/system_error:89:9: note: candidate found by name lookup is 'std::_V2::error_category'
  class error_category
        ^
p563.cpp:35:17: error: redefinition of 'is_error_code_enum'
         struct is_error_code_enum : public false_type {};
                ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/system_error:60:12: note: previous definition is here
    struct is_error_code_enum : public false_type { };
           ^
p563.cpp:37:17: error: redefinition of 'is_error_condition_enum'
         struct is_error_condition_enum : public false_type {};
                ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/system_error:64:12: note: previous definition is here
    struct is_error_condition_enum : public false_type { };
           ^
p563.cpp:38:12: error: redefinition of 'errc'
enum class errc {
           ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/x86_64-linux-gnu/c++/10/bits/error_constants.h:40:14: note: previous definition is here
  enum class errc
             ^
p563.cpp:183:19: error: redefinition of 'is_error_condition_enum<std::errc>'
template<> struct is_error_condition_enum<errc> : true_type {};
                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/system_error:67:12: note: previous definition is here
    struct is_error_condition_enum<errc>
           ^
p563.cpp:198:32: error: redefinition of 'is_error_code_enum_v' as different kind of symbol
         inline constexpr bool is_error_code_enum_v = is_error_code_enum<T>::value;
                               ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/system_error:72:27: note: previous definition is here
    inline constexpr bool is_error_code_enum_v =
                          ^
p563.cpp:198:74: error: use of undeclared identifier 'T'
         inline constexpr bool is_error_code_enum_v = is_error_code_enum<T>::value;
                                                                         ^
p563.cpp:200:32: error: redefinition of 'is_error_condition_enum_v'
         inline constexpr bool is_error_condition_enum_v = is_error_condition_enum<T>::value;
                               ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/system_error:75:27: note: previous definition is here
    inline constexpr bool is_error_condition_enum_v =
                          ^
9 errors generated.

$ g++ p563.cpp -std=c++03 -o p563g -I. -Wall
In file included from /usr/local/include/c++/12.1.0/atomic:38,
                 from p563.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 \
      |  ^~~~~
p563.cpp:29:49: warning: identifier 'noexcept' is a keyword in C++11 [-Wc++11-compat]
   29 |        const error_category& generic_category() noexcept;
      |                                                 ^~~~~~~~
p563.cpp:198:17: warning: identifier 'constexpr' is a keyword in C++11 [-Wc++11-compat]
  198 |          inline constexpr bool is_error_code_enum_v = is_error_code_enum<T>::value;
      |                 ^~~~~~~~~
p563.cpp:29:49: error: expected initializer before 'noexcept'
   29 |        const error_category& generic_category() noexcept;
      |                                                 ^~~~~~~~
p563.cpp:30:48: error: expected initializer before 'noexcept'
   30 |        const error_category& system_category() noexcept;
      |                                                ^~~~~~~~
p563.cpp:35:56: error: expected class-name before '{' token
   35 |          struct is_error_code_enum : public false_type {};
      |                                                        ^
p563.cpp:37:61: error: expected class-name before '{' token
   37 |          struct is_error_condition_enum : public false_type {};
      |                                                             ^
p563.cpp:38:1: warning: scoped enums only available with '-std=c++11' or '-std=gnu++11' [-Wc++11-extensions]
   38 | enum class errc {
      | ^~~~
p563.cpp:183:61: error: expected class-name before '{' token
  183 | template<> struct is_error_condition_enum<errc> : true_type {};
      |                                                             ^
p563.cpp:185:36: error: expected initializer before 'noexcept'
  185 | error_code make_error_code(errc e) noexcept;
      |                                    ^~~~~~~~
p563.cpp:190:46: error: expected initializer before 'noexcept'
  190 | error_condition make_error_condition(errc e) noexcept;
      |                                              ^~~~~~~~
p563.cpp:192:63: error: expected initializer before 'noexcept'
  192 | bool operator==(const error_code& lhs, const error_code& rhs) noexcept;
      |                                                               ^~~~~~~~
p563.cpp:193:68: error: expected initializer before 'noexcept'
  193 | bool operator==(const error_code& lhs, const error_condition& rhs) noexcept;
      |                                                                    ^~~~~~~~
p563.cpp:194:73: error: expected initializer before 'noexcept'
  194 | bool operator==(const error_condition& lhs, const error_condition& rhs) noexcept; strong_ordering operator<=>(const error_code& lhs, const error_code& rhs) noexcept; strong_ordering operator<=>(const error_condition& lhs, const error_condition& rhs) noexcept;
      |                                                                         ^~~~~~~~
p563.cpp:194:83: error: 'strong_ordering' does not name a type
  194 | bool operator==(const error_condition& lhs, const error_condition& rhs) noexcept; strong_ordering operator<=>(const error_code& lhs, const error_code& rhs) noexcept; strong_ordering operator<=>(const error_condition& lhs, const error_condition& rhs) noexcept;
      |                                                                                   ^~~~~~~~~~~~~~~
p563.cpp:194:167: error: 'strong_ordering' does not name a type
  194 | noexcept; strong_ordering operator<=>(const error_code& lhs, const error_code& rhs) noexcept; strong_ordering operator<=>(const error_condition& lhs, const error_condition& rhs) noexcept;
      |                                                                                               ^~~~~~~~~~~~~~~

p563.cpp:198:17: error: 'constexpr' does not name a type
  198 |          inline constexpr bool is_error_code_enum_v = is_error_code_enum<T>::value;
      |                 ^~~~~~~~~
p563.cpp:198:17: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
p563.cpp:200:17: error: 'constexpr' does not name a type
  200 |          inline constexpr bool is_error_condition_enum_v = is_error_condition_enum<T>::value;
      |                 ^~~~~~~~~
p563.cpp:200:17: note: C++11 'constexpr' only available with '-std=c++11' or '-std=gnu++11'
rm: cannot remove 'p563g': No such file or directory

$ g++ p563.cpp -std=c++2b -o p563g -I. -Wall
p563.cpp:29:14: error: reference to 'error_category' is ambiguous
   29 |        const error_category& generic_category() noexcept;
      |              ^~~~~~~~~~~~~~
In file included from /usr/local/include/c++/12.1.0/bits/ios_base.h:46,
                 from /usr/local/include/c++/12.1.0/ios:42,
                 from /usr/local/include/c++/12.1.0/ostream:38,
                 from /usr/local/include/c++/12.1.0/iostream:39,
                 from p563.cpp:10:
/usr/local/include/c++/12.1.0/system_error:97:9: note: candidates are: 'class std::_V2::error_category'
   97 |   class error_category
      |         ^~~~~~~~~~~~~~
p563.cpp:28:14: note:                 'class std::error_category'
   28 |        class error_category;
      |              ^~~~~~~~~~~~~~
p563.cpp:30:14: error: reference to 'error_category' is ambiguous
   30 |        const error_category& system_category() noexcept;
      |              ^~~~~~~~~~~~~~
/usr/local/include/c++/12.1.0/system_error:97:9: note: candidates are: 'class std::_V2::error_category'
   97 |   class error_category
      |         ^~~~~~~~~~~~~~
p563.cpp:28:14: note:                 'class std::error_category'
   28 |        class error_category;
      |              ^~~~~~~~~~~~~~
p563.cpp:35:17: error: redefinition of 'struct std::is_error_code_enum<_Tp>'
   35 |          struct is_error_code_enum : public false_type {};
      |                 ^~~~~~~~~~~~~~~~~~
/usr/local/include/c++/12.1.0/system_error:60:12: note: previous definition of 'struct std::is_error_code_enum<_Tp>'
   60 |     struct is_error_code_enum : public false_type { };
      |            ^~~~~~~~~~~~~~~~~~
p563.cpp:37:17: error: redefinition of 'struct std::is_error_condition_enum<_Tp>'
   37 |          struct is_error_condition_enum : public false_type {};
      |                 ^~~~~~~~~~~~~~~~~~~~~~~
/usr/local/include/c++/12.1.0/system_error:64:12: note: previous definition of 'struct std::is_error_condition_enum<_Tp>'
   64 |     struct is_error_condition_enum : public false_type { };
      |            ^~~~~~~~~~~~~~~~~~~~~~~
p563.cpp:38:12: error: multiple definition of 'enum class std::errc'
   38 | enum class errc {
      |            ^~~~
In file included from /usr/local/include/c++/12.1.0/system_error:39:
/usr/local/include/c++/12.1.0/x86_64-linux-gnu/bits/error_constants.h:40:14: note: previous definition here
   40 |   enum class errc
      |              ^~~~
p563.cpp:183:19: error: redefinition of 'struct std::is_error_condition_enum<std::errc>'
  183 | template<> struct is_error_condition_enum<errc> : true_type {};
      |                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/local/include/c++/12.1.0/system_error:67:12: note: previous definition of 'struct std::is_error_condition_enum<std::errc>'
   67 |     struct is_error_condition_enum<errc>
      |            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
p563.cpp:198:32: error: 'constexpr const bool std::is_error_code_enum_v' redeclared as different kind of entity
  198 |          inline constexpr bool is_error_code_enum_v = is_error_code_enum<T>::value;
      |                                ^~~~~~~~~~~~~~~~~~~~
/usr/local/include/c++/12.1.0/system_error:72:27: note: previous declaration 'template<class _Tp> constexpr const bool std::is_error_code_enum_v<_Tp>'
   72 |     inline constexpr bool is_error_code_enum_v =
      |                           ^~~~~~~~~~~~~~~~~~~~
p563.cpp:198:74: error: 'T' was not declared in this scope
  198 |          inline constexpr bool is_error_code_enum_v = is_error_code_enum<T>::value;
      |                                                                          ^
p563.cpp:198:75: error: template argument 1 is invalid
  198 |          inline constexpr bool is_error_code_enum_v = is_error_code_enum<T>::value;
      |                                                                           ^
p563.cpp:200:32: error: redefinition of 'template<class T> constexpr const bool std::is_error_condition_enum_v'
  200 |          inline constexpr bool is_error_condition_enum_v = is_error_condition_enum<T>::value;
      |                                ^~~~~~~~~~~~~~~~~~~~~~~~~
/usr/local/include/c++/12.1.0/system_error:75:27: note: 'template<class _Tp> constexpr const bool std::is_error_condition_enum_v<_Tp>' previously declared here
   75 |     inline constexpr bool is_error_condition_enum_v =
      |                           ^~~~~~~~~~~~~~~~~~~~~~~~~
```

## 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。-->

## 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
```

# 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

@kazuo_reve 私が効果を確認した「小川メソッド」
https://qiita.com/kazuo_reve/items/a3ea1d9171deeccc04da

## 自己参照(self reference)
DoCAP（ドゥーキャップ）って何ですか？
https://qiita.com/kaizen_nagoya/items/47e0e6509ab792c43327

小川メソッド　覚え（書きかけ）
https://qiita.com/kaizen_nagoya/items/3593d72eca551742df68

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

Error一覧 error(0)
https://qiita.com/kaizen_nagoya/items/48b6cbc8d68eae2c42b8

＜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。＞
This article is an individual impression based on the individual's experience. It has nothing to do with the organization or business to which I currently belong.
# 文書履歴(document history)
ver. 0.01 初稿 　20220715
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