13.7.8 Alias templates [temp.alias] C++N4910:2022 (226) p391.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.

# 13.7.8 Alias templates [temp.alias] C++N4910:2022 (226) p391.cpp

## 算譜(source code)

```c++:p391.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 = "13.7.8 Alias templates [temp.alias] C++N4910:2022 (226) p391.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<class T> struct Alloc { /* ... */
};
template<class T> using Vec = vector<T, Alloc<T>>;
Vec<int> v; // same as vector<int, Alloc<int>> v;
template<class T>  void process(Vec<T>& v)       { /* ... */ }
template<class T> void process(vector<T, Alloc<T>>& w) { /* ... */ } // error: redefinition
template<template<class> class TT>       void f(TT<int>);
f(v); // error: Vec not deduced
template<template<class,class> class TT> void g(TT<int, Alloc<int>>);
g(v); // OK, TT = vector
// [Example 2:
template<typename...> using void_t = void;
template<typename T> void_t<typename T::foo> f2();
f2<int>(); // error: int does not have a nested type foo
// [Example 3:
template <class T> struct A;
template <class T> using B = typename A<T>::U;
template <class T> struct A {
    typedef B<T> U;
};
B<short> b; // error: instantiation of B<short> uses own type via A<short>::U
// [Example 4:
template <class T>
using A4 = decltype([] { }); // A<int> and A<char> refer to different closure types
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
0# ./clgc.sh p391
rm: cannot remove 'p391l': No such file or directory
rm: cannot remove 'p391g': No such file or directory
$ clang++ p391.cpp -std=c++03 -o p391l -I. -Wall
In file included from p391.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 \
 ^
p391.cpp:27:31: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
template<class T> using Vec = vector<T, Alloc<T>>; Vec<int> v; // same as vector<int, Alloc<int>> v;
                              ^
p391.cpp:27:48: error: a space is required between consecutive right angle brackets (use '> >')
template<class T> using Vec = vector<T, Alloc<T>>; Vec<int> v; // same as vector<int, Alloc<int>> v;
                                               ^~
                                               > >
In file included from p391.cpp:10:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/iostream:39:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ostream:38:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ios:42:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/ios_base.h:41:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/locale_classes.h:40:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/string:55:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/basic_string.h:40:
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ext/alloc_traits.h:47:55: error: no type named 'value_type' in 'Alloc<int>'
template<typename _Alloc, typename = typename _Alloc::value_type>
                                     ~~~~~~~~~~~~~~~~~^~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:86:35: note: in instantiation of default argument for '__alloc_traits<Alloc<int> >' required here
      typedef typename __gnu_cxx::__alloc_traits<_Alloc>::template
                                  ^~~~~~~~~~~~~~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:389:30: note: in instantiation of template class 'std::_Vector_base<int, Alloc<int> >' requested here
    class vector : protected _Vector_base<_Tp, _Alloc>
                             ^
p391.cpp:27:61: note: in instantiation of template class 'std::vector<int, Alloc<int> >' requested here
template<class T> using Vec = vector<T, Alloc<T>>; Vec<int> v; // same as vector<int, Alloc<int>> v;
                                                            ^
In file included from p391.cpp:10:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/iostream:39:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ostream:38:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ios:42:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/ios_base.h:41:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/locale_classes.h:40:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/string:55:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/basic_string.h:40:
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ext/alloc_traits.h:47:47: error: type 'int' cannot be used prior to '::' because it has no members
template<typename _Alloc, typename = typename _Alloc::value_type>
                                              ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:88:35: note: in instantiation of default argument for '__alloc_traits<int>' required here
      typedef typename __gnu_cxx::__alloc_traits<_Tp_alloc_type>::pointer
                                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:389:30: note: in instantiation of template class 'std::_Vector_base<int, Alloc<int> >' requested here
    class vector : protected _Vector_base<_Tp, _Alloc>
                             ^
p391.cpp:27:61: note: in instantiation of template class 'std::vector<int, Alloc<int> >' requested here
template<class T> using Vec = vector<T, Alloc<T>>; Vec<int> v; // same as vector<int, Alloc<int>> v;
                                                            ^
In file included from p391.cpp:16:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/vector:67:
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:129:11: error: base specifier must name a class
        : public _Tp_alloc_type, public _Vector_impl_data
          ~~~~~~~^~~~~~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:340:20: note: in instantiation of member class 'std::_Vector_base<int, Alloc<int> >::_Vector_impl' requested here
      _Vector_impl _M_impl;
                   ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:389:30: note: in instantiation of template class 'std::_Vector_base<int, Alloc<int> >' requested here
    class vector : protected _Vector_base<_Tp, _Alloc>
                             ^
p391.cpp:27:61: note: in instantiation of template class 'std::vector<int, Alloc<int> >' requested here
template<class T> using Vec = vector<T, Alloc<T>>; Vec<int> v; // same as vector<int, Alloc<int>> v;
                                                            ^
In file included from p391.cpp:10:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/iostream:39:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ostream:38:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ios:42:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/ios_base.h:41:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/locale_classes.h:40:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/string:55:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/basic_string.h:40:
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ext/alloc_traits.h:47:47: error: type 'int' cannot be used prior to '::' because it has no members
template<typename _Alloc, typename = typename _Alloc::value_type>
                                              ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:411:26: note: in instantiation of default argument for '__alloc_traits<int>' required here
      typedef __gnu_cxx::__alloc_traits<_Tp_alloc_type> _Alloc_traits;
                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
p391.cpp:27:61: note: in instantiation of template class 'std::vector<int, Alloc<int> >' requested here
template<class T> using Vec = vector<T, Alloc<T>>; Vec<int> v; // same as vector<int, Alloc<int>> v;
                                                            ^
In file included from p391.cpp:16:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/vector:67:
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:474:13: error: using declaration refers into '_Base::', which is not a base class of 'vector<int, Alloc<int> >'
      using _Base::_M_allocate;
            ^~~~~~~
p391.cpp:27:61: note: in instantiation of template class 'std::vector<int, Alloc<int> >' requested here
template<class T> using Vec = vector<T, Alloc<T>>; Vec<int> v; // same as vector<int, Alloc<int>> v;
                                                            ^
In file included from p391.cpp:16:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/vector:67:
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:475:13: error: using declaration refers into '_Base::', which is not a base class of 'vector<int, Alloc<int> >'
      using _Base::_M_deallocate;
            ^~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:476:13: error: using declaration refers into '_Base::', which is not a base class of 'vector<int, Alloc<int> >'
      using _Base::_M_impl;
            ^~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:477:13: error: using declaration refers into '_Base::', which is not a base class of 'vector<int, Alloc<int> >'
      using _Base::_M_get_Tp_allocator;
            ^~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:802:13: error: using declaration refers into '_Base::', which is not a base class of 'vector<int, Alloc<int> >'
      using _Base::get_allocator;
            ^~~~~~~
p391.cpp:29:49: error: a space is required between consecutive right angle brackets (use '> >')
template<class T> void process(vector<T, Alloc<T>>& w) { /* ... */ } // error: redefinition
                                                ^~
                                                > >
p391.cpp:29:24: error: redefinition of 'process'
template<class T> void process(vector<T, Alloc<T>>& w) { /* ... */ } // error: redefinition
                       ^
p391.cpp:28:25: note: previous definition is here
template<class T>  void process(Vec<T>& v)       { /* ... */ }
                        ^
p391.cpp:31:1: error: unknown type name 'f'
f(v); // error: Vec not deduced
^
p391.cpp:32:66: error: a space is required between consecutive right angle brackets (use '> >')
template<template<class,class> class TT> void g(TT<int, Alloc<int>>);
                                                                 ^~
                                                                 > >
p391.cpp:33:1: error: unknown type name 'g'
g(v); // OK, TT = vector 
^
p391.cpp:35:18: warning: variadic templates are a C++11 extension [-Wc++11-extensions]
template<typename...> using void_t = void;
                 ^
p391.cpp:35:38: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
template<typename...> using void_t = void;
                                     ^
p391.cpp:37:1: error: C++ requires a type specifier for all declarations
f2<int>(); // error: int does not have a nested type foo
^
p391.cpp:37:1: error: template specialization requires 'template<>'
f2<int>(); // error: int does not have a nested type foo
^ ~~~~~
template<> 
p391.cpp:40:35: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
     template <class T> using B = typename A<T>::U;
                                  ^
p391.cpp:40:25: error: no type named 'U' in 'A<T>'
     template <class T> using B = typename A<T>::U;
                        ^~~~~
p391.cpp:42:16: note: in instantiation of template type alias 'B' requested here
       typedef B<T> U;
               ^
p391.cpp:47:12: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
using A4 = decltype([] { }); // A<int> and A<char> refer to different closure types 
           ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
5 warnings and 20 errors generated.
rm: cannot remove 'p391l': No such file or directory
$ clang++ p391.cpp -std=c++2b -o p391l -I. -Wall
In file included from p391.cpp:10:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/iostream:39:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ostream:38:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ios:42:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/ios_base.h:41:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/locale_classes.h:40:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/string:55:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/basic_string.h:40:
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ext/alloc_traits.h:47:55: error: no type named 'value_type' in 'Alloc<int>'
template<typename _Alloc, typename = typename _Alloc::value_type>
                                     ~~~~~~~~~~~~~~~~~^~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:86:35: note: in instantiation of default argument for '__alloc_traits<Alloc<int>>' required here
      typedef typename __gnu_cxx::__alloc_traits<_Alloc>::template
                                  ^~~~~~~~~~~~~~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:389:30: note: in instantiation of template class 'std::_Vector_base<int, Alloc<int>>' requested here
    class vector : protected _Vector_base<_Tp, _Alloc>
                             ^
p391.cpp:27:61: note: in instantiation of template class 'std::vector<int, Alloc<int>>' requested here
template<class T> using Vec = vector<T, Alloc<T>>; Vec<int> v; // same as vector<int, Alloc<int>> v;
                                                            ^
In file included from p391.cpp:10:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/iostream:39:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ostream:38:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ios:42:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/ios_base.h:41:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/locale_classes.h:40:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/string:55:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/basic_string.h:40:
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ext/alloc_traits.h:47:47: error: type 'int' cannot be used prior to '::' because it has no members
template<typename _Alloc, typename = typename _Alloc::value_type>
                                              ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:88:35: note: in instantiation of default argument for '__alloc_traits<int>' required here
      typedef typename __gnu_cxx::__alloc_traits<_Tp_alloc_type>::pointer
                                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:389:30: note: in instantiation of template class 'std::_Vector_base<int, Alloc<int>>' requested here
    class vector : protected _Vector_base<_Tp, _Alloc>
                             ^
p391.cpp:27:61: note: in instantiation of template class 'std::vector<int, Alloc<int>>' requested here
template<class T> using Vec = vector<T, Alloc<T>>; Vec<int> v; // same as vector<int, Alloc<int>> v;
                                                            ^
In file included from p391.cpp:16:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/vector:67:
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:129:11: error: base specifier must name a class
        : public _Tp_alloc_type, public _Vector_impl_data
          ~~~~~~~^~~~~~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:340:20: note: in instantiation of member class 'std::_Vector_base<int, Alloc<int>>::_Vector_impl' requested here
      _Vector_impl _M_impl;
                   ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:389:30: note: in instantiation of template class 'std::_Vector_base<int, Alloc<int>>' requested here
    class vector : protected _Vector_base<_Tp, _Alloc>
                             ^
p391.cpp:27:61: note: in instantiation of template class 'std::vector<int, Alloc<int>>' requested here
template<class T> using Vec = vector<T, Alloc<T>>; Vec<int> v; // same as vector<int, Alloc<int>> v;
                                                            ^
In file included from p391.cpp:16:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/vector:67:
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:404:46: error: no type named 'value_type' in 'Alloc<int>'
      static_assert(is_same<typename _Alloc::value_type, _Tp>::value,
                            ~~~~~~~~~~~~~~~~~^~~~~~~~~~
p391.cpp:27:61: note: in instantiation of template class 'std::vector<int, Alloc<int>>' requested here
template<class T> using Vec = vector<T, Alloc<T>>; Vec<int> v; // same as vector<int, Alloc<int>> v;
                                                            ^
In file included from p391.cpp:10:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/iostream:39:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ostream:38:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ios:42:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/ios_base.h:41:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/locale_classes.h:40:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/string:55:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/basic_string.h:40:
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/ext/alloc_traits.h:47:47: error: type 'int' cannot be used prior to '::' because it has no members
template<typename _Alloc, typename = typename _Alloc::value_type>
                                              ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_vector.h:411:26: note: in instantiation of default argument for '__alloc_traits<int>' required here
      typedef __gnu_cxx::__alloc_traits<_Tp_alloc_type> _Alloc_traits;
                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
p391.cpp:27:61: note: in instantiation of template class 'std::vector<int, Alloc<int>>' requested here
template<class T> using Vec = vector<T, Alloc<T>>; Vec<int> v; // same as vector<int, Alloc<int>> v;
                                                            ^
p391.cpp:29:24: error: redefinition of 'process'
template<class T> void process(vector<T, Alloc<T>>& w) { /* ... */ } // error: redefinition
                       ^
p391.cpp:28:25: note: previous definition is here
template<class T>  void process(Vec<T>& v)       { /* ... */ }
                        ^
p391.cpp:31:1: error: unknown type name 'f'
f(v); // error: Vec not deduced
^
p391.cpp:33:1: error: unknown type name 'g'
g(v); // OK, TT = vector 
^
p391.cpp:36:22: error: reference to 'void_t' is ambiguous
template<typename T> void_t<typename T::foo> f2();
                     ^
p391.cpp:35:23: note: candidate found by name lookup is 'void_t'
template<typename...> using void_t = void;
                      ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/type_traits:2576:25: note: candidate found by name lookup is 'std::void_t'
  template<typename...> using void_t = void;
                        ^
p391.cpp:37:1: error: C++ requires a type specifier for all declarations
f2<int>(); // error: int does not have a nested type foo
^
p391.cpp:37:1: error: template specialization requires 'template<>'
f2<int>(); // error: int does not have a nested type foo
^ ~~~~~
template<> 
p391.cpp:40:25: error: no type named 'U' in 'A<T>'
     template <class T> using B = typename A<T>::U;
                        ^~~~~
p391.cpp:42:16: note: in instantiation of template type alias 'B' requested here
       typedef B<T> U;
               ^
12 errors generated.

$ g++ p391.cpp -std=c++03 -o p391g -I. -Wall
In file included from /usr/local/include/c++/12.1.0/atomic:38,
                 from p391.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 \
      |  ^~~~~
p391.cpp:47:12: warning: identifier 'decltype' is a keyword in C++11 [-Wc++11-compat]
   47 | using A4 = decltype([] { }); // A<int> and A<char> refer to different closure types
      |            ^~~~~~~~
p391.cpp:27:19: error: expected unqualified-id before 'using'
   27 | template<class T> using Vec = vector<T, Alloc<T>>; Vec<int> v; // same as vector<int, Alloc<int>> v;
      |                   ^~~~~
p391.cpp:27:52: error: 'Vec' does not name a type
   27 | template<class T> using Vec = vector<T, Alloc<T>>; Vec<int> v; // same as vector<int, Alloc<int>> v;
      |                                                    ^~~
p391.cpp:28:25: error: variable or field 'process' declared void
   28 | template<class T>  void process(Vec<T>& v)       { /* ... */ }
      |                         ^~~~~~~
p391.cpp:28:33: error: 'Vec' was not declared in this scope
   28 | template<class T>  void process(Vec<T>& v)       { /* ... */ }
      |                                 ^~~
p391.cpp:28:38: error: expected primary-expression before '>' token
   28 | template<class T>  void process(Vec<T>& v)       { /* ... */ }
      |                                      ^
p391.cpp:28:41: error: 'v' was not declared in this scope
   28 | template<class T>  void process(Vec<T>& v)       { /* ... */ }
      |                                         ^
p391.cpp:29:49: error: '>>' should be '> >' within a nested template argument list
   29 | template<class T> void process(vector<T, Alloc<T>>& w) { /* ... */ } // error: redefinition
      |                                                 ^~
      |                                                 > >
p391.cpp:31:2: error: expected constructor, destructor, or type conversion before '(' token
   31 | f(v); // error: Vec not deduced
      |  ^
p391.cpp:32:66: error: '>>' should be '> >' within a nested template argument list
   32 | template<template<class,class> class TT> void g(TT<int, Alloc<int>>);
      |                                                                  ^~
      |                                                                  > >
p391.cpp:33:2: error: expected constructor, destructor, or type conversion before '(' token
   33 | g(v); // OK, TT = vector
      |  ^
p391.cpp:35:18: warning: variadic templates only available with '-std=c++11' or '-std=gnu++11' [-Wc++11-extensions]
   35 | template<typename...> using void_t = void;
      |                  ^~~
p391.cpp:35:23: error: expected unqualified-id before 'using'
   35 | template<typename...> using void_t = void;
      |                       ^~~~~
p391.cpp:36:22: error: 'void_t' does not name a type; did you mean 'void'?
   36 | template<typename T> void_t<typename T::foo> f2();
      |                      ^~~~~~
      |                      void
p391.cpp:37:1: error: 'f2' does not name a type
   37 | f2<int>(); // error: int does not have a nested type foo
      | ^~
p391.cpp:40:25: error: expected unqualified-id before 'using'
   40 |      template <class T> using B = typename A<T>::U;
      |                         ^~~~~
p391.cpp:42:16: error: 'B' does not name a type
   42 |        typedef B<T> U;
      |                ^
p391.cpp:44:1: error: 'B' does not name a type
   44 | B<short> b; // error: instantiation of B<short> uses own type via A<short>::U
      | ^
p391.cpp:47:1: error: expected unqualified-id before 'using'
   47 | using A4 = decltype([] { }); // A<int> and A<char> refer to different closure types
      | ^~~~~
p391.cpp:47:27: error: expected unqualified-id before ')' token
   47 | using A4 = decltype([] { }); // A<int> and A<char> refer to different closure types
      |                           ^
rm: cannot remove 'p391g': No such file or directory

$ g++ p391.cpp -std=c++2b -o p391g -I. -Wall
In file included from /usr/local/include/c++/12.1.0/vector:64,
                 from p391.cpp:16:
/usr/local/include/c++/12.1.0/bits/stl_vector.h: In instantiation of 'struct std::_Vector_base<int, Alloc<int> >':
/usr/local/include/c++/12.1.0/bits/stl_vector.h:423:11:   required from 'class std::vector<int, Alloc<int> >'
p391.cpp:27:61:   required from here
/usr/local/include/c++/12.1.0/bits/stl_vector.h:88:28: error: no type named 'value_type' in 'struct Alloc<int>'
   88 |         rebind<_Tp>::other _Tp_alloc_type;
      |                            ^~~~~~~~~~~~~~
/usr/local/include/c++/12.1.0/bits/stl_vector.h:90:9: error: no type named 'value_type' in 'struct Alloc<int>'
   90 |         pointer;
      |         ^~~~~~~
/usr/local/include/c++/12.1.0/bits/stl_vector.h: In instantiation of 'class std::vector<int, Alloc<int> >':
p391.cpp:27:61:   required from here
/usr/local/include/c++/12.1.0/bits/stl_vector.h:438:64: error: no type named 'value_type' in 'struct Alloc<int>'
  438 |       static_assert(is_same<typename _Alloc::value_type, _Tp>::value,
      |                                                                ^~~~~
/usr/local/include/c++/12.1.0/bits/stl_vector.h:513:20: error: '_M_allocate' has not been declared in 'std::vector<int, Alloc<int> >::_Base'
  513 |       using _Base::_M_allocate;
      |                    ^~~~~~~~~~~
/usr/local/include/c++/12.1.0/bits/stl_vector.h:514:20: error: '_M_deallocate' has not been declared in 'std::vector<int, Alloc<int> >::_Base'
  514 |       using _Base::_M_deallocate;
      |                    ^~~~~~~~~~~~~
/usr/local/include/c++/12.1.0/bits/stl_vector.h:516:20: error: '_M_get_Tp_allocator' has not been declared in 'std::vector<int, Alloc<int> >::_Base'
  516 |       using _Base::_M_get_Tp_allocator;
      |                    ^~~~~~~~~~~~~~~~~~~
In file included from /usr/local/include/c++/12.1.0/iostream:38,
                 from p391.cpp:10:
/usr/local/include/c++/12.1.0/bits/stl_vector.h: In instantiation of 'constexpr std::_Vector_base<_Tp, _Alloc>::_Vector_impl::_Vector_impl() [with _Tp = int; _Alloc = Alloc<int>]':
p391.cpp:27:61:   required from here
/usr/local/include/c++/12.1.0/bits/stl_vector.h:137:24: error: no type named 'value_type' in 'struct Alloc<int>'
  137 |         _Vector_impl() _GLIBCXX_NOEXCEPT_IF(
      |                        ^~~~~~~~~~~~~~~~~~~~
/usr/local/include/c++/12.1.0/bits/stl_vector.h: In instantiation of 'constexpr std::_Vector_base<_Tp, _Alloc>::_Vector_impl::_Vector_impl() [with _Tp = int; _Alloc = Alloc<int>]':
/usr/local/include/c++/12.1.0/bits/stl_vector.h:312:7:   required from here
p391.cpp:27:61:   in 'constexpr' expansion of 'v.std::vector<int, Alloc<int> >::vector()'
/usr/local/include/c++/12.1.0/bits/stl_vector.h:526:7:   in 'constexpr' expansion of '((std::vector<int, Alloc<int> >*)this)->std::vector<int, Alloc<int> >::<anonymous>.std::_Vector_base<int, Alloc<int> >::_Vector_base()'
/usr/local/include/c++/12.1.0/bits/stl_vector.h:139:26: error: no type named 'value_type' in 'struct Alloc<int>'
  139 |         : _Tp_alloc_type()
      |                          ^
/usr/local/include/c++/12.1.0/bits/stl_vector.h: In instantiation of 'constexpr std::_Vector_base<_Tp, _Alloc>::_Vector_impl_data::_Vector_impl_data() [with _Tp = int; _Alloc = Alloc<int>]':
/usr/local/include/c++/12.1.0/bits/stl_vector.h:139:19:   required from here
p391.cpp:27:61:   in 'constexpr' expansion of 'v.std::vector<int, Alloc<int> >::vector()'
/usr/local/include/c++/12.1.0/bits/stl_vector.h:526:7:   in 'constexpr' expansion of '((std::vector<int, Alloc<int> >*)this)->std::vector<int, Alloc<int> >::<anonymous>.std::_Vector_base<int, Alloc<int> >::_Vector_base()'
/usr/local/include/c++/12.1.0/bits/stl_vector.h:312:7:   in 'constexpr' expansion of '((std::_Vector_base<int, Alloc<int> >*)this)->std::_Vector_base<int, Alloc<int> >::_M_impl.std::_Vector_base<int, Alloc<int> >::_Vector_impl::_Vector_impl()'
/usr/local/include/c++/12.1.0/bits/stl_vector.h:100:54: error: using invalid field 'std::_Vector_base<_Tp, _Alloc>::_Vector_impl_data::_M_start'
  100 |         : _M_start(), _M_finish(), _M_end_of_storage()
      |                                                      ^
/usr/local/include/c++/12.1.0/bits/stl_vector.h:100:54: error: using invalid field 'std::_Vector_base<_Tp, _Alloc>::_Vector_impl_data::_M_finish'
/usr/local/include/c++/12.1.0/bits/stl_vector.h:100:54: error: using invalid field 'std::_Vector_base<_Tp, _Alloc>::_Vector_impl_data::_M_end_of_storage'
p391.cpp:29:24: error: redefinition of 'template<class T> void process(std::vector<T, Alloc<T> >&)'
   29 | template<class T> void process(vector<T, Alloc<T>>& w) { /* ... */ } // error: redefinition
      |                        ^~~~~~~
p391.cpp:28:25: note: 'template<class T> void process(Vec<T>&)' previously declared here
   28 | template<class T>  void process(Vec<T>& v)       { /* ... */ }
      |                         ^~~~~~~
p391.cpp:31:2: error: expected constructor, destructor, or type conversion before '(' token
   31 | f(v); // error: Vec not deduced
      |  ^
p391.cpp:33:2: error: expected constructor, destructor, or type conversion before '(' token
   33 | g(v); // OK, TT = vector
      |  ^
p391.cpp:36:22: error: reference to 'void_t' is ambiguous
   36 | template<typename T> void_t<typename T::foo> f2();
      |                      ^~~~~~
In file included from /usr/local/include/c++/12.1.0/bits/move.h:57,
                 from /usr/local/include/c++/12.1.0/bits/exception_ptr.h:43,
                 from /usr/local/include/c++/12.1.0/exception:168,
                 from /usr/local/include/c++/12.1.0/ios:39,
                 from /usr/local/include/c++/12.1.0/ostream:38,
                 from /usr/local/include/c++/12.1.0/iostream:39:
/usr/local/include/c++/12.1.0/type_traits:2636:31: note: candidates are: 'template<class ...> using void_t = void'
 2636 |   template<typename...> using void_t = void;
      |                               ^~~~~~
p391.cpp:35:29: note:                 'template<class ...> using void_t = void'
   35 | template<typename...> using void_t = void;
      |                             ^~~~~~
p391.cpp:37:1: error: specializing member '::f2<int>' requires 'template<>' syntax
   37 | f2<int>(); // error: int does not have a nested type foo
      | ^~~~~~~
p391.cpp: In substitution of 'template<class T> using B = typename A::U [with T = short int]':
p391.cpp:42:21:   required from 'struct A<short int>'
p391.cpp:40:31:   required by substitution of 'template<class T> using B = typename A::U [with T = short int]'
p391.cpp:44:8:   required from here
p391.cpp:40:31: error: invalid use of incomplete type 'struct A<short int>'
   40 |      template <class T> using B = typename A<T>::U;
      |                               ^
p391.cpp:41:32: note: declaration of 'struct A<short int>'
   41 |      template <class T> struct A {
      |                                ^
```

## 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 　20220705