13.10.2 Explicit template argument specification [temp.arg.explicit] C++N4910:2022 (238) p420.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.

# 13.10.2 Explicit template argument specification [temp.arg.explicit] C++N4910:2022 (238) p420.cpp

## 算譜(source code)

```c++:p420.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 = "13.10.2 Explicit template argument specification [temp.arg.explicit] C++N4910:2022 (238) p420.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> void sort(Array<T>& v);
void f(Array<dcomplex>& cv, Array<int>& ci) {
sort<dcomplex>(cv); // sort(Array<dcomplex>&) sort<int>(ci); // sort(Array<int>&)
}
// and
     template<class U, class V> U convert(V v);
void g(double d) {
int i = convert<int,double>(d); // int convert(double) char c = convert<char,double>(d); // char convert(double)
}
// [Example 2:
     template<class X, class Y> X f(Y);
     template<class X, class Y, class ... Z> X g(Y);
     void h() {
    int i = f<int>(5.6);
    int j = f(5.6);
    f<void>(f<int, bool>);
    f<void>(f<int>);
    int k = g<int>(5.6);
    f<void>(g<int, bool>);
// Y deduced as double
// error: X cannot be deduced
// Y for outer f deduced as int (*)(bool)
// error: f<int> does not denote a single function template specialization // Y deduced as double; Z deduced as an empty sequence
// Y for outer f deduced as int (*)(bool),
// Z deduced as an empty sequence
}
//  [Note 2: An empty template argument list can be used to indicate that a given use refers to a specialization of a function template even when a non-template function (9.3.4.6) is visible that would otherwise be used. For example:
  template <class T> int f(T);
  int f(int);
  int k = f(1);
  int l = f<>(1);
// #1
// #2
// uses #2 // uses #1
// [Example 3:
template<class X, class Y, class Z> X f(Y,Z);
     template<class ... Args> void f2();
void g() {
f<int,const char*,double>("aa",3.0);
f<int,const char*>("aa",3.0); // Z deduced as double
f<int>("aa",3.0); // Y deduced as const char*; Z deduced as double f("aa",3.0); // error: X cannot be deduced
f2<char, short, int, long>(); // OK
}
// [Note 3: Template parameters do not participate in template argument deduction if they are explicitly specified. For example,
     template<class T> void f(T);
  class Complex {
    Complex(double);
};
  void g() {
    f<Complex>(1);
}
// OK, means f<Complex>(Complex(1))
// [Example 4:
template<class ... Types> void f(Types ... values);
void g() {
f<int*, float*>(0, 0, 0); // Types deduced as the sequence int*, float*, int
}
int main(){
  cout  <<  n4910 << endl;
  return EXIT_SUCCESS;
}
```

## Script

```bash:clgc.sh
#!/bin/sh
rm $1l
rm $1g
echo "$ clang++ $1.cpp -std=03 -o $1l -I. -Wall" 
clang++ $1.cpp -std=c++03 -o $1l -I. -Wall
if [  -e $1l ]; then
./$1l 
fi
rm $1l
echo "$ clang++ $1.cpp -std=2b -o $1l -I. -Wall"
clang++ $1.cpp -std=c++2b -o $1l -I. -Wall
if [  -e $1l ]; then
./$1l
fi
echo "\r"
echo "$ g++ $1.cpp -std=03 -o $1g -I. -Wall"
g++ $1.cpp -std=c++03 -o $1g -I. -Wall
if [ -e $1g ]; then
./$1g
fi
rm $1g
echo "\r"
echo "$ g++ $1.cpp -std=2b -o $1g -I. -Wall"
g++ $1.cpp -std=c++2b -o $1g -I. -Wall
if [ -e $1g ]; then
./$1g 
fi
```
## 編纂・実行結果(compile and go)

```ubuntu:bash
# ./clgc.sh p420
rm: cannot remove 'p420l': No such file or directory
rm: cannot remove 'p420g': No such file or directory
$ clang++ p420.cpp -std=c++03 -o p420l -I. -Wall
In file included from p420.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 \
 ^
p420.cpp:26:29: error: no template named 'Array'
template<class T> void sort(Array<T>& v);
                            ^
p420.cpp:27:14: error: use of undeclared identifier 'dcomplex'; did you mean 'complex'?
void f(Array<dcomplex>& cv, Array<int>& ci) {
             ^~~~~~~~
             complex
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/complex:127:12: note: 'complex' declared here
    struct complex
           ^
p420.cpp:27:14: error: use of undeclared identifier 'dcomplex'; did you mean 'complex'?
void f(Array<dcomplex>& cv, Array<int>& ci) {
             ^~~~~~~~
             complex
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/complex:127:12: note: 'complex' declared here
    struct complex
           ^
p420.cpp:27:14: error: use of undeclared identifier 'dcomplex'
void f(Array<dcomplex>& cv, Array<int>& ci) {
             ^
p420.cpp:27:29: error: no template named 'Array'
void f(Array<dcomplex>& cv, Array<int>& ci) {
                            ^
p420.cpp:28:6: error: use of undeclared identifier 'dcomplex'; did you mean 'complex'?
sort<dcomplex>(cv); // sort(Array<dcomplex>&) sort<int>(ci); // sort(Array<int>&)
     ^~~~~~~~
     complex
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/complex:127:12: note: 'complex' declared here
    struct complex
           ^
p420.cpp:28:6: error: use of undeclared identifier 'dcomplex'
sort<dcomplex>(cv); // sort(Array<dcomplex>&) sort<int>(ci); // sort(Array<int>&)
     ^
p420.cpp:33:5: warning: unused variable 'i' [-Wunused-variable]
int i = convert<int,double>(d); // int convert(double) char c = convert<char,double>(d); // char convert(double)
    ^
p420.cpp:37:39: warning: variadic templates are a C++11 extension [-Wc++11-extensions]
     template<class X, class Y, class ... Z> X g(Y);
                                      ^
p420.cpp:40:13: error: no matching function for call to 'f'
    int j = f(5.6);
            ^
p420.cpp:36:35: note: candidate template ignored: couldn't infer template argument 'X'
     template<class X, class Y> X f(Y);
                                  ^
p420.cpp:42:5: error: no matching function for call to 'f'
    f<void>(f<int>);
    ^~~~~~~
p420.cpp:36:35: note: candidate template ignored: couldn't infer template argument 'Y'
     template<class X, class Y> X f(Y);
                                  ^
p420.cpp:62:21: warning: variadic templates are a C++11 extension [-Wc++11-extensions]
     template<class ... Args> void f2();
                    ^
p420.cpp:74:8: error: redefinition of 'g'
  void g() {
       ^
p420.cpp:63:6: note: previous definition is here
void g() {
     ^
p420.cpp:79:16: warning: variadic templates are a C++11 extension [-Wc++11-extensions]
template<class ... Types> void f(Types ... values);
               ^
4 warnings and 11 errors generated.
rm: cannot remove 'p420l': No such file or directory
$ clang++ p420.cpp -std=c++2b -o p420l -I. -Wall
p420.cpp:26:29: error: no template named 'Array'; did you mean 'array'?
template<class T> void sort(Array<T>& v);
                            ^~~~~
                            array
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/array:94:12: note: 'array' declared here
    struct array
           ^
p420.cpp:26:29: error: too few template arguments for class template 'array'
template<class T> void sort(Array<T>& v);
                            ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/array:94:12: note: template is declared here
    struct array
           ^
p420.cpp:27:14: error: use of undeclared identifier 'dcomplex'; did you mean 'complex'?
void f(Array<dcomplex>& cv, Array<int>& ci) {
             ^~~~~~~~
             complex
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/complex:127:12: note: 'complex' declared here
    struct complex
           ^
p420.cpp:27:14: error: use of undeclared identifier 'dcomplex'; did you mean 'complex'?
void f(Array<dcomplex>& cv, Array<int>& ci) {
             ^~~~~~~~
             complex
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/complex:127:12: note: 'complex' declared here
    struct complex
           ^
p420.cpp:27:14: error: use of undeclared identifier 'dcomplex'
void f(Array<dcomplex>& cv, Array<int>& ci) {
             ^
p420.cpp:27:29: error: no template named 'Array'; did you mean 'array'?
void f(Array<dcomplex>& cv, Array<int>& ci) {
                            ^~~~~
                            array
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/array:94:12: note: 'array' declared here
    struct array
           ^
p420.cpp:27:29: error: too few template arguments for class template 'array'
void f(Array<dcomplex>& cv, Array<int>& ci) {
                            ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/array:94:12: note: template is declared here
    struct array
           ^
p420.cpp:28:6: error: use of undeclared identifier 'dcomplex'; did you mean 'complex'?
sort<dcomplex>(cv); // sort(Array<dcomplex>&) sort<int>(ci); // sort(Array<int>&)
     ^~~~~~~~
     complex
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/complex:127:12: note: 'complex' declared here
    struct complex
           ^
p420.cpp:28:6: error: use of undeclared identifier 'dcomplex'
sort<dcomplex>(cv); // sort(Array<dcomplex>&) sort<int>(ci); // sort(Array<int>&)
     ^
p420.cpp:33:5: warning: unused variable 'i' [-Wunused-variable]
int i = convert<int,double>(d); // int convert(double) char c = convert<char,double>(d); // char convert(double)
    ^
p420.cpp:40:13: error: no matching function for call to 'f'
    int j = f(5.6);
            ^
p420.cpp:36:35: note: candidate template ignored: couldn't infer template argument 'X'
     template<class X, class Y> X f(Y);
                                  ^
p420.cpp:42:5: error: no matching function for call to 'f'
    f<void>(f<int>);
    ^~~~~~~
p420.cpp:36:35: note: candidate template ignored: couldn't infer template argument 'Y'
     template<class X, class Y> X f(Y);
                                  ^
p420.cpp:74:8: error: redefinition of 'g'
  void g() {
       ^
p420.cpp:63:6: note: previous definition is here
void g() {
     ^
1 warning and 12 errors generated.

$ g++ p420.cpp -std=c++03 -o p420g -I. -Wall
In file included from /usr/local/include/c++/12.1.0/atomic:38,
                 from p420.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 \
      |  ^~~~~
p420.cpp:26:24: error: variable or field 'sort' declared void
   26 | template<class T> void sort(Array<T>& v);
      |                        ^~~~
p420.cpp:26:29: error: 'Array' was not declared in this scope
   26 | template<class T> void sort(Array<T>& v);
      |                             ^~~~~
p420.cpp:26:36: error: expected primary-expression before '>' token
   26 | template<class T> void sort(Array<T>& v);
      |                                    ^
p420.cpp:26:39: error: 'v' was not declared in this scope
   26 | template<class T> void sort(Array<T>& v);
      |                                       ^
p420.cpp:27:6: error: variable or field 'f' declared void
   27 | void f(Array<dcomplex>& cv, Array<int>& ci) {
      |      ^
p420.cpp:27:8: error: 'Array' was not declared in this scope
   27 | void f(Array<dcomplex>& cv, Array<int>& ci) {
      |        ^~~~~
p420.cpp:27:14: error: 'dcomplex' was not declared in this scope
   27 | void f(Array<dcomplex>& cv, Array<int>& ci) {
      |              ^~~~~~~~
p420.cpp:27:25: error: 'cv' was not declared in this scope
   27 | void f(Array<dcomplex>& cv, Array<int>& ci) {
      |                         ^~
p420.cpp:27:29: error: 'Array' was not declared in this scope
   27 | void f(Array<dcomplex>& cv, Array<int>& ci) {
      |                             ^~~~~
p420.cpp:27:35: error: expected primary-expression before 'int'
   27 | void f(Array<dcomplex>& cv, Array<int>& ci) {
      |                                   ^~~
p420.cpp: In function 'void g(double)':
p420.cpp:33:5: warning: unused variable 'i' [-Wunused-variable]
   33 | int i = convert<int,double>(d); // int convert(double) char c = convert<char,double>(d); // char convert(double)
      |     ^
p420.cpp: At global scope:
p420.cpp:37:39: warning: variadic templates only available with '-std=c++11' or '-std=gnu++11' [-Wc++11-extensions]
   37 |      template<class X, class Y, class ... Z> X g(Y);
      |                                       ^~~
p420.cpp: In function 'void h()':
p420.cpp:40:14: error: no matching function for call to 'f(double)'
   40 |     int j = f(5.6);
      |             ~^~~~~
p420.cpp:36:35: note: candidate: 'template<class X, class Y> X f(Y)'
   36 |      template<class X, class Y> X f(Y);
      |                                   ^
p420.cpp:36:35: note:   template argument deduction/substitution failed:
p420.cpp:40:14: note:   couldn't deduce template parameter 'X'
   40 |     int j = f(5.6);
      |             ~^~~~~
p420.cpp:42:12: error: no matching function for call to 'f<void>(<unresolved overloaded function type>)'
   42 |     f<void>(f<int>);
      |     ~~~~~~~^~~~~~~~
p420.cpp:36:35: note: candidate: 'template<class X, class Y> X f(Y)'
   36 |      template<class X, class Y> X f(Y);
      |                                   ^
p420.cpp:36:35: note:   template argument deduction/substitution failed:
p420.cpp:42:12: note:   couldn't deduce template parameter 'Y'
   42 |     f<void>(f<int>);
      |     ~~~~~~~^~~~~~~~
p420.cpp:39:9: warning: unused variable 'i' [-Wunused-variable]
   39 |     int i = f<int>(5.6);
      |         ^
p420.cpp:40:9: warning: unused variable 'j' [-Wunused-variable]
   40 |     int j = f(5.6);
      |         ^
p420.cpp:43:9: warning: unused variable 'k' [-Wunused-variable]
   43 |     int k = g<int>(5.6);
      |         ^
p420.cpp: At global scope:
p420.cpp:62:21: warning: variadic templates only available with '-std=c++11' or '-std=gnu++11' [-Wc++11-extensions]
   62 |      template<class ... Args> void f2();
      |                     ^~~
p420.cpp:74:8: error: redefinition of 'void g()'
   74 |   void g() {
      |        ^
p420.cpp:63:6: note: 'void g()' previously defined here
   63 | void g() {
      |      ^
p420.cpp:79:16: warning: variadic templates only available with '-std=c++11' or '-std=gnu++11' [-Wc++11-extensions]
   79 | template<class ... Types> void f(Types ... values);
      |                ^~~
p420.cpp:79:44: warning: variadic templates only available with '-std=c++11' or '-std=gnu++11' [-Wc++11-extensions]
   79 | template<class ... Types> void f(Types ... values);
      |                                            ^~~~~~
p420.cpp:80:6: error: redefinition of 'void g()'
   80 | void g() {
      |      ^
p420.cpp:63:6: note: 'void g()' previously defined here
   63 | void g() {
      |      ^
rm: cannot remove 'p420g': No such file or directory

$ g++ p420.cpp -std=c++2b -o p420g -I. -Wall
p420.cpp:26:24: error: variable or field 'sort' declared void
   26 | template<class T> void sort(Array<T>& v);
      |                        ^~~~
p420.cpp:26:29: error: 'Array' was not declared in this scope
   26 | template<class T> void sort(Array<T>& v);
      |                             ^~~~~
p420.cpp:26:36: error: expected primary-expression before '>' token
   26 | template<class T> void sort(Array<T>& v);
      |                                    ^
p420.cpp:26:39: error: 'v' was not declared in this scope
   26 | template<class T> void sort(Array<T>& v);
      |                                       ^
p420.cpp:27:14: error: 'dcomplex' was not declared in this scope
   27 | void f(Array<dcomplex>& cv, Array<int>& ci) {
      |              ^~~~~~~~
p420.cpp:27:14: error: 'dcomplex' was not declared in this scope
p420.cpp:27:14: error: 'dcomplex' was not declared in this scope
p420.cpp:27:14: error: 'dcomplex' was not declared in this scope
p420.cpp:27:6: error: variable or field 'f' declared void
   27 | void f(Array<dcomplex>& cv, Array<int>& ci) {
      |      ^
p420.cpp:27:14: error: 'dcomplex' was not declared in this scope
   27 | void f(Array<dcomplex>& cv, Array<int>& ci) {
      |              ^~~~~~~~
p420.cpp:27:14: error: 'dcomplex' was not declared in this scope
p420.cpp:27:14: error: 'dcomplex' was not declared in this scope
p420.cpp:27:14: error: 'dcomplex' was not declared in this scope
p420.cpp:27:14: error: 'dcomplex' was not declared in this scope
p420.cpp:27:8: error: 'Array' was not declared in this scope
   27 | void f(Array<dcomplex>& cv, Array<int>& ci) {
      |        ^~~~~
p420.cpp:27:14: error: 'dcomplex' was not declared in this scope
   27 | void f(Array<dcomplex>& cv, Array<int>& ci) {
      |              ^~~~~~~~
p420.cpp:27:25: error: 'cv' was not declared in this scope
   27 | void f(Array<dcomplex>& cv, Array<int>& ci) {
      |                         ^~
p420.cpp:27:29: error: 'Array' was not declared in this scope
   27 | void f(Array<dcomplex>& cv, Array<int>& ci) {
      |                             ^~~~~
p420.cpp:27:35: error: expected primary-expression before 'int'
   27 | void f(Array<dcomplex>& cv, Array<int>& ci) {
      |                                   ^~~
p420.cpp: In function 'void g(double)':
p420.cpp:33:5: warning: unused variable 'i' [-Wunused-variable]
   33 | int i = convert<int,double>(d); // int convert(double) char c = convert<char,double>(d); // char convert(double)
      |     ^
p420.cpp: In function 'void h()':
p420.cpp:40:14: error: no matching function for call to 'f(double)'
   40 |     int j = f(5.6);
      |             ~^~~~~
p420.cpp:36:35: note: candidate: 'template<class X, class Y> X f(Y)'
   36 |      template<class X, class Y> X f(Y);
      |                                   ^
p420.cpp:36:35: note:   template argument deduction/substitution failed:
p420.cpp:40:14: note:   couldn't deduce template parameter 'X'
   40 |     int j = f(5.6);
      |             ~^~~~~
p420.cpp:42:12: error: no matching function for call to 'f<void>(<unresolved overloaded function type>)'
   42 |     f<void>(f<int>);
      |     ~~~~~~~^~~~~~~~
p420.cpp:36:35: note: candidate: 'template<class X, class Y> X f(Y)'
   36 |      template<class X, class Y> X f(Y);
      |                                   ^
p420.cpp:36:35: note:   template argument deduction/substitution failed:
p420.cpp:42:12: note:   couldn't deduce template parameter 'Y'
   42 |     f<void>(f<int>);
      |     ~~~~~~~^~~~~~~~
p420.cpp:39:9: warning: unused variable 'i' [-Wunused-variable]
   39 |     int i = f<int>(5.6);
      |         ^
p420.cpp:40:9: warning: unused variable 'j' [-Wunused-variable]
   40 |     int j = f(5.6);
      |         ^
p420.cpp:43:9: warning: unused variable 'k' [-Wunused-variable]
   43 |     int k = g<int>(5.6);
      |         ^
p420.cpp: At global scope:
p420.cpp:74:8: error: redefinition of 'void g()'
   74 |   void g() {
      |        ^
p420.cpp:63:6: note: 'void g()' previously defined here
   63 | void g() {
      |      ^
p420.cpp:80:6: error: redefinition of 'void g()'
   80 | void g() {
      |      ^
p420.cpp:63:6: note: 'void g()' previously defined here
   63 | void g() {
      |      ^
```

## 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 　20220706