13.8.1 General [temp.res.general] C++N4910:2022 (228) p393.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.

# 13.8.1 General [temp.res.general] C++N4910:2022 (228) p393.cpp

## 算譜(source code)

```c++:p393.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 = "13.8.1 General [temp.res.general] C++N4910:2022 (228) p393.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
struct A {
    operator int();
};
template<class B, class T>
struct D : B {
    T get() {
        return operator T();
    }
};
int f(D<A, int> d) {
    return d.get();
}
// [Example 2:
void f(char);
// conversion-function-id is dependent // OK, lookup finds A::operator int
template<class T> void g(T t) {
    f(1); // f(char)
    f(T(1)); // dependent
    f(t); // dependent
    dd++; // not dependent; error: declaration for dd not found
}
enum E { e };
void f(E);
double dd;
void h() {
    g(e);
    g('a');
// [Example 3:
// will cause one call of f(char) followed by two calls of f(E) // will cause three calls of f(char)
}
struct A {
    struct B { /* ... */
    };
    int a;
    int Y;
};
int a;
template<class T> struct Y : T {
    struct B { /* ... */
    };
    B b;
    void f(int i) {
        a = i;
    }
    Y* p;
};
Y<A> ya;
//TheBdefinedinY
// ::a
// Y<T>
// The members A::B, A::a, and A::Y of the template argument A do not affect the binding of names in Y<A>.
//  [Example 4:
struct A {
    struct X { };
    int X;
};
struct B {
    struct X { };
};
template<class T> void f(T t) {
    typename T::X x;
}
void foo() {
    A a;
    B b;
    f(b); // OK, T::X refers to B::X
    f(a); // error: T::X refers to the data member A::X not the struct A::X
}
template<class T> T::R f();
template<class T> void f(T::R);
template<class T> struct S {
    using Ptr = PtrTraits<T>::Ptr;
    T::R f(T::P p) {
        return static_cast<T::R>(p);
        auto g() -> S<T*>::Ptr;
    };
    template<typename T> void f() {
        void (*pf)(T::X);
        void g(T::X);
// OK, return type of a function declaration at global scope // ill-formed, no diagnostic required: attempt to declare
// a void variable template
// OK, in a defining-type-id
// OK, class scope
// OK, type-id of a static_cast
// OK, trailing-return-type
// variable pf of type void* initialized with T::X // error: T::X at block scope does not denote a type // (attempt to declare a void variable)
    }
}
// [Example 6:
template <class T> void f(int i) {
    T::x * i;
    struct Foo {
        typedef int x;
    };
// expression, not the declaration of a variable i
}
struct Bar {
    static int const x = 5;
};
//int main() {
//f<Bar>(1); // OK
//f<Foo>(1); // error: Foo::x is a type
//}
// [Example 7:
int j;
template<class T> class X {
    void f(T t, int i, char* p) {
    }
};
t = i;
p = i;
p = j;
X<T>::g(t);
X<T>::h();

void g(T t) {
    +;
}
// diagnosed if X::f is instantiated, and the assignment to t is an error
// // may be diagnosed even if X::f is not instantiated
// may be diagnosed even if X::f is not instantiated
// OK
// may be diagnosed even if X::f is not instantiated
// // may be diagnosed even if X::g is not instantiated
template<class... T> struct A {
    void operator++(int, T... t);
};
template<class... T> union X : T... { };
template<class... T> struct A : T...,  T... { };
// error: too many parameters
// error: union with base class // error: duplicate base class

int main() {
    f<Bar>(1); // OK
    f<Foo>(1); // error: Foo::x is a type
    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 p393
rm: cannot remove 'p393l': No such file or directory
rm: cannot remove 'p393g': No such file or directory
$ clang++ p393.cpp -std=c++03 -o p393l -I. -Wall
In file included from p393.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 \
 ^
p393.cpp:39:1: error: use of undeclared identifier 'dd'
dd++; // not dependent; error: declaration for dd not found
^
p393.cpp:50:8: error: redefinition of 'A'
struct A {
       ^
p393.cpp:26:9: note: previous definition is here
 struct A { operator int(); };
        ^
p393.cpp:68:13: error: redefinition of 'A'
     struct A {
            ^
p393.cpp:26:9: note: previous definition is here
 struct A { operator int(); };
        ^
p393.cpp:83:19: error: missing 'typename' prior to dependent type name 'T::R'
template<class T> T::R f();
                  ^~~~
                  typename 
p393.cpp:84:24: warning: variable templates are a C++14 extension [-Wc++14-extensions]
template<class T> void f(T::R);
                       ^
p393.cpp:84:24: error: variable has incomplete type 'void'
p393.cpp:86:15: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
  using Ptr = PtrTraits<T>::Ptr;
              ^
p393.cpp:86:15: error: no template named 'PtrTraits'
p393.cpp:87:3: error: missing 'typename' prior to dependent type name 'T::R'
  T::R f(T::P p) {
  ^~~~
  typename 
p393.cpp:87:10: error: missing 'typename' prior to dependent type name 'T::P'
  T::R f(T::P p) {
         ^~~~
         typename 
p393.cpp:91:19: error: declaration of 'T' shadows template parameter
template<typename T> void f() {
                  ^
p393.cpp:85:16: note: template parameter is declared here
template<class T> struct S {
               ^
p393.cpp:88:24: error: missing 'typename' prior to dependent type name 'T::R'
    return static_cast<T::R>(p);
                       ^~~~
                       typename 
p393.cpp:89:3: warning: 'auto' type specifier is a C++11 extension [-Wc++11-extensions]
  auto g() -> S<T*>::Ptr;
  ^
p393.cpp:89:3: error: 'auto' not allowed in function return type
  auto g() -> S<T*>::Ptr;
  ^~~~
p393.cpp:89:11: error: expected ';' at end of declaration
  auto g() -> S<T*>::Ptr;
          ^
          ;
p393.cpp:93:8: error: variable has incomplete type 'void'
  void g(T::X);
       ^
p393.cpp:102:2: error: expected ';' after struct
}
 ^
 ;
p393.cpp:124:3: error: C++ requires a type specifier for all declarations
  t = i;
  ^
p393.cpp:124:7: error: use of undeclared identifier 'i'
  t = i;
      ^
p393.cpp:125:3: error: C++ requires a type specifier for all declarations
  p = i;
  ^
p393.cpp:125:7: error: use of undeclared identifier 'i'
  p = i;
      ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
3 warnings and 20 errors generated.
rm: cannot remove 'p393l': No such file or directory
$ clang++ p393.cpp -std=c++2b -o p393l -I. -Wall
p393.cpp:39:1: error: use of undeclared identifier 'dd'
dd++; // not dependent; error: declaration for dd not found
^
p393.cpp:50:8: error: redefinition of 'A'
struct A {
       ^
p393.cpp:26:9: note: previous definition is here
 struct A { operator int(); };
        ^
p393.cpp:68:13: error: redefinition of 'A'
     struct A {
            ^
p393.cpp:26:9: note: previous definition is here
 struct A { operator int(); };
        ^
p393.cpp:83:19: error: missing 'typename' prior to dependent type name 'T::R'
template<class T> T::R f();
                  ^~~~
                  typename 
p393.cpp:84:24: error: variable has incomplete type 'void'
template<class T> void f(T::R);
                       ^
p393.cpp:86:15: error: no template named 'PtrTraits'
  using Ptr = PtrTraits<T>::Ptr;
              ^
p393.cpp:87:3: error: missing 'typename' prior to dependent type name 'T::R'
  T::R f(T::P p) {
  ^~~~
  typename 
p393.cpp:87:10: error: missing 'typename' prior to dependent type name 'T::P'
  T::R f(T::P p) {
         ^~~~
         typename 
p393.cpp:91:19: error: declaration of 'T' shadows template parameter
template<typename T> void f() {
                  ^
p393.cpp:85:16: note: template parameter is declared here
template<class T> struct S {
               ^
p393.cpp:88:24: error: missing 'typename' prior to dependent type name 'T::R'
    return static_cast<T::R>(p);
                       ^~~~
                       typename 
p393.cpp:89:15: error: missing 'typename' prior to dependent type name 'S<T *>::Ptr'
  auto g() -> S<T*>::Ptr;
              ^~~~~~~~~~
              typename 
p393.cpp:93:8: error: variable has incomplete type 'void'
  void g(T::X);
       ^
p393.cpp:102:2: error: expected ';' after struct
}
 ^
 ;
p393.cpp:124:3: error: C++ requires a type specifier for all declarations
  t = i;
  ^
p393.cpp:124:7: error: use of undeclared identifier 'i'
  t = i;
      ^
p393.cpp:125:3: error: C++ requires a type specifier for all declarations
  p = i;
  ^
p393.cpp:125:7: error: use of undeclared identifier 'i'
  p = i;
      ^
p393.cpp:126:3: error: C++ requires a type specifier for all declarations
  p = j;
  ^
p393.cpp:127:5: error: use of undeclared identifier 'T'
  X<T>::g(t);
    ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.

$ g++ p393.cpp -std=c++03 -o p393g -I. -Wall
In file included from /usr/local/include/c++/12.1.0/atomic:38,
                 from p393.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 \
      |  ^~~~~
p393.cpp: In member function 'T D<B, T>::get()':
p393.cpp:29:34: error: there are no arguments to 'operator T' that depend on a template parameter, so a declaration of 'operator T' must be available [-fpermissive]
   29 |      T get() { return operator T(); }
      |                                  ^
p393.cpp:29:34: note: (if you use '-fpermissive', G++ will accept your code, but allowing the use of an undeclared name is deprecated)
p393.cpp: In function 'void g(T)':
p393.cpp:39:1: error: 'dd' was not declared in this scope
   39 | dd++; // not dependent; error: declaration for dd not found
      | ^~
p393.cpp: At global scope:
p393.cpp:50:8: error: redefinition of 'struct A'
   50 | struct A {
      |        ^
p393.cpp:26:9: note: previous definition of 'struct A'
   26 |  struct A { operator int(); };
      |         ^
p393.cpp:68:13: error: redefinition of 'struct A'
   68 |      struct A {
      |             ^
p393.cpp:26:9: note: previous definition of 'struct A'
   26 |  struct A { operator int(); };
      |         ^
p393.cpp:83:19: error: need 'typename' before 'T::R' because 'T' is a dependent scope
   83 | template<class T> T::R f();
      |                   ^
      |                   typename 
p393.cpp:84:24: error: variable or field 'f' declared void
   84 | template<class T> void f(T::R);
      |                        ^
p393.cpp:86:9: error: expected nested-name-specifier before 'Ptr'
   86 |   using Ptr = PtrTraits<T>::Ptr;
      |         ^~~
p393.cpp:87:3: error: need 'typename' before 'T::R' because 'T' is a dependent scope
   87 |   T::R f(T::P p) {
      |   ^
      |   typename 
p393.cpp:91:10: error: declaration of template parameter 'T' shadows template parameter
   91 | template<typename T> void f() {
      |          ^~~~~~~~
p393.cpp:85:10: note: template parameter 'T' declared here
   85 | template<class T> struct S {
      |          ^~~~~
p393.cpp:102:2: error: expected ';' after struct definition
  102 | }
      |  ^
      |  ;
p393.cpp: In member function 'void S<T>::f()':
p393.cpp:93:8: error: variable or field 'g' declared void
   93 |   void g(T::X);
      |        ^
p393.cpp: At global scope:
p393.cpp:124:3: error: 't' does not name a type; did you mean 'tm'?
  124 |   t = i;
      |   ^
      |   tm
p393.cpp:125:3: error: 'p' does not name a type
  125 |   p = i;
      |   ^
p393.cpp:126:3: error: 'p' does not name a type
  126 |   p = j;
      |   ^
p393.cpp:127:5: error: 'T' was not declared in this scope
  127 |   X<T>::g(t);
      |     ^
p393.cpp:127:6: error: template argument 1 is invalid
  127 |   X<T>::g(t);
      |      ^
p393.cpp:127:12: error: 'int g' redeclared as different kind of entity
  127 |   X<T>::g(t);
      |            ^
p393.cpp:35:24: note: previous declaration 'template<class T> void g(T)'
   35 | template<class T> void g(T t) {
      |                        ^
p393.cpp:127:11: error: 't' was not declared in this scope; did you mean 'tm'?
  127 |   X<T>::g(t);
      |           ^
      |           tm
p393.cpp:128:5: error: 'T' was not declared in this scope
  128 |   X<T>::h();
      |     ^
p393.cpp:128:6: error: template argument 1 is invalid
  128 |   X<T>::h();
      |      ^
p393.cpp:128:9: error: ambiguating new declaration of 'int h()'
  128 |   X<T>::h();
      |         ^
p393.cpp:44:8: note: old declaration 'void h()'
   44 |   void h() {
      |        ^
p393.cpp:130:6: error: variable or field 'g' declared void
  130 | void g(T t) {
      |      ^
p393.cpp:130:8: error: 'T' was not declared in this scope
  130 | void g(T t) {
      |        ^
p393.cpp:139:17: warning: variadic templates only available with '-std=c++11' or '-std=gnu++11' [-Wc++11-extensions]
  139 |   template<class... T> struct A {
      |                 ^~~
p393.cpp:139:31: error: 'A' is not a template
  139 |   template<class... T> struct A {
      |                               ^
p393.cpp:26:9: note: previous declaration here
   26 |  struct A { operator int(); };
      |         ^
p393.cpp:142:17: warning: variadic templates only available with '-std=c++11' or '-std=gnu++11' [-Wc++11-extensions]
  142 |   template<class... T> union X : T... { };
      |                 ^~~
p393.cpp:120:12: error: template parameter 'class T'
  120 |   template<class T> class X {
      |            ^~~~~
p393.cpp:142:12: note: redeclared here as 'class ... T'
  142 |   template<class... T> union X : T... { };
      |            ^~~~~
p393.cpp:143:17: warning: variadic templates only available with '-std=c++11' or '-std=gnu++11' [-Wc++11-extensions]
  143 |   template<class... T> struct A : T...,  T... { };
      |                 ^~~
p393.cpp:143:31: error: 'A' is not a template
  143 |   template<class... T> struct A : T...,  T... { };
      |                               ^
p393.cpp:26:9: note: previous declaration here
   26 |  struct A { operator int(); };
      |         ^
p393.cpp: In function 'int main()':
p393.cpp:149:3: error: 'Foo' was not declared in this scope; did you mean 'foo'?
  149 | f<Foo>(1); // error: Foo::x is a type
      |   ^~~
      |   foo
p393.cpp:149:7: error: no matching function for call to 'f<<expression error> >(int)'
  149 | f<Foo>(1); // error: Foo::x is a type
      | ~~~~~~^~~
p393.cpp:75:29: note: candidate: 'template<class T> void f(T)'
   75 |      template<class T> void f(T t) {
      |                             ^
p393.cpp:75:29: note:   template argument deduction/substitution failed:
p393.cpp:149:7: error: template argument 1 is invalid
  149 | f<Foo>(1); // error: Foo::x is a type
      | ~~~~~~^~~
p393.cpp:104:25: note: candidate: 'template<class T> void f(int)'
  104 | template <class T> void f(int i) {
      |                         ^
p393.cpp:104:25: note:   template argument deduction/substitution failed:
p393.cpp:149:7: error: template argument 1 is invalid
  149 | f<Foo>(1); // error: Foo::x is a type
      | ~~~~~~^~~
p393.cpp: In instantiation of 'void f(T) [with T = B]':
p393.cpp:80:2:   required from here
p393.cpp:76:22: warning: unused variable 'x' [-Wunused-variable]
   76 |        typename T::X x;
      |                      ^
p393.cpp: In instantiation of 'void f(T) [with T = A]':
p393.cpp:81:2:   required from here
p393.cpp:76:22: error: no type named 'X' in 'struct A'
p393.cpp: In instantiation of 'void f(int) [with T = Bar]':
p393.cpp:148:7:   required from here
p393.cpp:105:6: warning: statement has no effect [-Wunused-value]
  105 | T::x * i;
      |    ~~^~~
rm: cannot remove 'p393g': No such file or directory

$ g++ p393.cpp -std=c++2b -o p393g -I. -Wall
p393.cpp: In member function 'T D<B, T>::get()':
p393.cpp:29:34: error: there are no arguments to 'operator T' that depend on a template parameter, so a declaration of 'operator T' must be available [-fpermissive]
   29 |      T get() { return operator T(); }
      |                                  ^
p393.cpp:29:34: note: (if you use '-fpermissive', G++ will accept your code, but allowing the use of an undeclared name is deprecated)
p393.cpp: In function 'void g(T)':
p393.cpp:39:1: error: 'dd' was not declared in this scope
   39 | dd++; // not dependent; error: declaration for dd not found
      | ^~
p393.cpp: At global scope:
p393.cpp:50:8: error: redefinition of 'struct A'
   50 | struct A {
      |        ^
p393.cpp:26:9: note: previous definition of 'struct A'
   26 |  struct A { operator int(); };
      |         ^
p393.cpp:68:13: error: redefinition of 'struct A'
   68 |      struct A {
      |             ^
p393.cpp:26:9: note: previous definition of 'struct A'
   26 |  struct A { operator int(); };
      |         ^
p393.cpp:84:24: error: variable or field 'f' declared void
   84 | template<class T> void f(T::R);
      |                        ^
p393.cpp:86:15: error: 'PtrTraits' does not name a type
   86 |   using Ptr = PtrTraits<T>::Ptr;
      |               ^~~~~~~~~
p393.cpp:91:10: error: declaration of template parameter 'T' shadows template parameter
   91 | template<typename T> void f() {
      |          ^~~~~~~~
p393.cpp:85:10: note: template parameter 'T' declared here
   85 | template<class T> struct S {
      |          ^~~~~
p393.cpp:102:2: error: expected ';' after struct definition
  102 | }
      |  ^
      |  ;
p393.cpp: In member function 'typename T::R S<T>::f(typename T::P)':
p393.cpp:89:9: warning: empty parentheses were disambiguated as a function declaration [-Wvexing-parse]
   89 |   auto g() -> S<T*>::Ptr;
      |         ^~
p393.cpp:89:9: note: remove parentheses to default-initialize a variable
   89 |   auto g() -> S<T*>::Ptr;
      |         ^~
      |         --
p393.cpp:89:9: note: or replace parentheses with braces to value-initialize a variable
p393.cpp: In member function 'void S<T>::f()':
p393.cpp:93:8: error: variable or field 'g' declared void
   93 |   void g(T::X);
      |        ^
p393.cpp: At global scope:
p393.cpp:124:3: error: 't' does not name a type; did you mean 'tm'?
  124 |   t = i;
      |   ^
      |   tm
p393.cpp:125:3: error: 'p' does not name a type
  125 |   p = i;
      |   ^
p393.cpp:126:3: error: 'p' does not name a type
  126 |   p = j;
      |   ^
p393.cpp:127:5: error: 'T' was not declared in this scope
  127 |   X<T>::g(t);
      |     ^
p393.cpp:127:6: error: template argument 1 is invalid
  127 |   X<T>::g(t);
      |      ^
p393.cpp:127:12: error: 'int g' redeclared as different kind of entity
  127 |   X<T>::g(t);
      |            ^
p393.cpp:35:24: note: previous declaration 'template<class T> void g(T)'
   35 | template<class T> void g(T t) {
      |                        ^
p393.cpp:127:11: error: 't' was not declared in this scope; did you mean 'tm'?
  127 |   X<T>::g(t);
      |           ^
      |           tm
p393.cpp:128:5: error: 'T' was not declared in this scope
  128 |   X<T>::h();
      |     ^
p393.cpp:128:6: error: template argument 1 is invalid
  128 |   X<T>::h();
      |      ^
p393.cpp:128:9: error: ambiguating new declaration of 'int h()'
  128 |   X<T>::h();
      |         ^
p393.cpp:44:8: note: old declaration 'void h()'
   44 |   void h() {
      |        ^
p393.cpp:130:6: error: variable or field 'g' declared void
  130 | void g(T t) {
      |      ^
p393.cpp:130:8: error: 'T' was not declared in this scope
  130 | void g(T t) {
      |        ^
p393.cpp:139:31: error: 'A' is not a template
  139 |   template<class... T> struct A {
      |                               ^
p393.cpp:26:9: note: previous declaration here
   26 |  struct A { operator int(); };
      |         ^
p393.cpp:120:12: error: template parameter 'class T'
  120 |   template<class T> class X {
      |            ^~~~~
p393.cpp:142:12: note: redeclared here as 'class ... T'
  142 |   template<class... T> union X : T... { };
      |            ^~~~~
p393.cpp:143:31: error: 'A' is not a template
  143 |   template<class... T> struct A : T...,  T... { };
      |                               ^
p393.cpp:26:9: note: previous declaration here
   26 |  struct A { operator int(); };
      |         ^
p393.cpp: In function 'int main()':
p393.cpp:149:3: error: 'Foo' was not declared in this scope; did you mean 'foo'?
  149 | f<Foo>(1); // error: Foo::x is a type
      |   ^~~
      |   foo
p393.cpp:149:7: error: no matching function for call to 'f<<expression error> >(int)'
  149 | f<Foo>(1); // error: Foo::x is a type
      | ~~~~~~^~~
p393.cpp:75:29: note: candidate: 'template<class T> void f(T)'
   75 |      template<class T> void f(T t) {
      |                             ^
p393.cpp:75:29: note:   template argument deduction/substitution failed:
p393.cpp:149:7: error: template argument 1 is invalid
  149 | f<Foo>(1); // error: Foo::x is a type
      | ~~~~~~^~~
p393.cpp:83:24: note: candidate: 'template<class T> typename T::R f()'
   83 | template<class T> T::R f();
      |                        ^
p393.cpp:83:24: note:   candidate expects 0 arguments, 1 provided
p393.cpp:104:25: note: candidate: 'template<class T> void f(int)'
  104 | template <class T> void f(int i) {
      |                         ^
p393.cpp:104:25: note:   template argument deduction/substitution failed:
p393.cpp:149:7: error: template argument 1 is invalid
  149 | f<Foo>(1); // error: Foo::x is a type
      | ~~~~~~^~~
p393.cpp: In instantiation of 'void f(T) [with T = B]':
p393.cpp:80:2:   required from here
p393.cpp:76:22: warning: unused variable 'x' [-Wunused-variable]
   76 |        typename T::X x;
      |                      ^
p393.cpp: In instantiation of 'void f(T) [with T = A]':
p393.cpp:81:2:   required from here
p393.cpp:76:22: error: no type named 'X' in 'struct A'
p393.cpp: In instantiation of 'void f(int) [with T = Bar]':
p393.cpp:148:7:   required from here
p393.cpp:105:6: warning: statement has no effect [-Wunused-value]
  105 | T::x * i;
      |    ~~^~~

```

## 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