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@kaizen_nagoya(Dr. Kiyoshi Ogawa)

13.8.3.2 Dependent types [temp.dep.type] C++N4910:2022 (231) p399.cpp

Last updated at Posted at 2022-07-06

はじめに(Introduction)

N4910 Working Draft, Standard for Programming Language C++

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

C++N4741, 2018 Standard Working Draft on ISO/IEC 14882 sample code compile list

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++

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.

13.8.3.2 Dependent types [temp.dep.type] C++N4910:2022 (231) p398.cpp

算譜(source code)

p399.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 = "13.8.3.2 Dependent types [temp.dep.type]  C++N4910:2022 (231) p399.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> class A {
    A* p1; // A is the current instantiation
    A<T>* p2;
    A<T*> p3;
    ::A<T>* p4;
    class B {
        B* p1;
        A<T>::B* p2;
        typename A<T*>::B* p3;
// A<T> is the current instantiation
// A<T*> is not the current instantiation // ::A<T> is the current instantiation
// B is the current instantiation
// A<T>::B is the current instantiation
// A<T*>::B is not the current instantiation
    };
};
template <class T> class A<T*> {
    A<T*>* p1; // A<T*> is the current instantiation A<T>* p2; // A<T> is not the current instantiation
};
template <class T1, class T2, int I> struct B {
    B<T1, T2, I>* b1; // refers to the current instantiation B<T2, T1, I>* b2; // not the current instantiation typedef T1 my_T1;
    static const int my_I = I;
    static const int my_I2 = I+0;
    static const int my_I3 = my_I;
    static const long my_I4 = I;
    static const int my_I5 = (I);
    B<my_T1, T2, my_I>* b3;
    B<my_T1, T2, my_I2>* b4;
    B<my_T1, T2, my_I3>* b5;
    B<my_T1, T2, my_I4>* b6;
    B<my_T1, T2, my_I5>* b7;
};
// [Example 2:
template<class T> struct A2 {
    typedef int M;
    struct B2 {
        typedef void M;
        struct C2;
    };
};
template<class T> struct A2<T>::B2::C : A2<T> {
    M m; // OK, A<T>::M
};
// [Example 3:
template <class T> class A3 {
    static const int i = 5;
    int n1[i];
    int n2[A::i];
    int n3[A<T>::i];
    int f3();
};
// i refers to a member of the current instantiation
// A::i refers to a member of the current instantiation
// A<T>::i refers to a member of the current instantiation
// refers to the current instantiation // not the current instantiation
// refers to the current instantiation
// not the current instantiation
// not the current instantiation
template <class T> int A3<T>::f3() {
    return i; // i refers to a member of the current instantiation
}
// [Example 4:
struct A4 {
    using B4 = int;
    A4 f4();
};
struct C4 : A4 {};
template<class T>
void g4(T t) {
    decltype(t.A4::f4())::B4 i;
}
template void g4(C4);
// error: typename needed to interpret B as a type // ...even though A is ::A here
// [Example 5:
struct A5 {
    int m5;
};
struct B5 {
    int m5;
};
template<typename T>
struct C5 : A5, T {
    int f5() {
        return this->m5;
    }
    int g5() {
        return m5;
    }
};
template int C5<B5>::f5();
template int C5<B5>::g5();
// finds A::m in the template definition context // finds A::m in the template definition context
// error: finds both A::m and B::m
// OK, transformation to class member access syntax
// does not occur in the template definition context; see 11.4.3
int main() {
    cout  <<  n4910 << endl;
    return EXIT_SUCCESS;
}

Script

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)

bash
# ./clgc.sh p399
$ clang++ p399.cpp -std=c++03 -o p399l -I. -Wall
In file included from p399.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 \
 ^
p399.cpp:51:3: error: use of undeclared identifier 'my_T1'
B<my_T1, T2, my_I>* b3;
  ^
p399.cpp:52:3: error: use of undeclared identifier 'my_T1'
B<my_T1, T2, my_I2>* b4;
  ^
p399.cpp:53:3: error: use of undeclared identifier 'my_T1'
B<my_T1, T2, my_I3>* b5;
  ^
p399.cpp:54:3: error: use of undeclared identifier 'my_T1'
B<my_T1, T2, my_I4>* b6;
  ^
p399.cpp:55:3: error: use of undeclared identifier 'my_T1'
B<my_T1, T2, my_I5>* b7;
  ^
p399.cpp:64:37: error: no struct named 'C' in 'A2::B2'
template<class T> struct A2<T>::B2::C : A2<T> {
                         ~~~~~~~~~~~^
p399.cpp:71:12: error: 'A' is not a class, namespace, or enumeration
    int n2[A::i];
           ^
p399.cpp:26:26: note: 'A' declared here
template <class T> class A {
                         ^
p399.cpp:86:16: warning: alias declarations are a C++11 extension [-Wc++11-extensions]
    using B4 = int;
               ^
p399.cpp:92:25: error: expected ';' after expression
    decltype(t.A4::f4())::B4 i;
                        ^
                        ;
p399.cpp:92:25: error: no type named 'B4' in the global namespace; did you mean 'A4::B4'?
    decltype(t.A4::f4())::B4 i;
                        ^~~~
                        A4::B4
p399.cpp:86:11: note: 'A4::B4' declared here
    using B4 = int;
          ^
p399.cpp:92:5: error: use of undeclared identifier 'decltype'
    decltype(t.A4::f4())::B4 i;
    ^
p399.cpp:94:17: note: in instantiation of function template specialization 'g4<C4>' requested here
  template void g4(C4);
                ^
p399.cpp:105:32: error: member 'm5' found in multiple base classes of different types
       int f5() { return this->m5; }
                               ^
p399.cpp:108:27: note: in instantiation of member function 'C5<B5>::f5' requested here
     template int C5<B5>::f5();
                          ^
p399.cpp:98:12: note: member found by ambiguous name lookup
       int m5;
           ^
p399.cpp:101:12: note: member found by ambiguous name lookup
       int m5;
           ^
1 warning and 12 errors generated.
rm: cannot remove 'p399l': No such file or directory
$ clang++ p399.cpp -std=c++2b -o p399l -I. -Wall
p399.cpp:51:3: error: use of undeclared identifier 'my_T1'
B<my_T1, T2, my_I>* b3;
  ^
p399.cpp:52:3: error: use of undeclared identifier 'my_T1'
B<my_T1, T2, my_I2>* b4;
  ^
p399.cpp:53:3: error: use of undeclared identifier 'my_T1'
B<my_T1, T2, my_I3>* b5;
  ^
p399.cpp:54:3: error: use of undeclared identifier 'my_T1'
B<my_T1, T2, my_I4>* b6;
  ^
p399.cpp:55:3: error: use of undeclared identifier 'my_T1'
B<my_T1, T2, my_I5>* b7;
  ^
p399.cpp:64:37: error: no struct named 'C' in 'A2::B2'
template<class T> struct A2<T>::B2::C : A2<T> {
                         ~~~~~~~~~~~^
p399.cpp:71:12: error: 'A' is not a class, namespace, or enumeration
    int n2[A::i];
           ^
p399.cpp:26:26: note: 'A' declared here
template <class T> class A {
                         ^
p399.cpp:92:5: error: missing 'typename' prior to dependent type name 'decltype(t.A4::f4())::B4'
    decltype(t.A4::f4())::B4 i;
    ^~~~~~~~~~~~~~~~~~~~~~~~
    typename 
p399.cpp:92:30: warning: unused variable 'i' [-Wunused-variable]
    decltype(t.A4::f4())::B4 i;
                             ^
p399.cpp:94:17: note: in instantiation of function template specialization 'g4<C4>' requested here
  template void g4(C4);
                ^
p399.cpp:105:32: error: member 'm5' found in multiple base classes of different types
       int f5() { return this->m5; }
                               ^
p399.cpp:108:27: note: in instantiation of member function 'C5<B5>::f5' requested here
     template int C5<B5>::f5();
                          ^
p399.cpp:98:12: note: member found by ambiguous name lookup
       int m5;
           ^
p399.cpp:101:12: note: member found by ambiguous name lookup
       int m5;
           ^
1 warning and 9 errors generated.

$ g++ p399.cpp -std=c++03 -o p399g -I. -Wall
In file included from /usr/local/include/c++/12.1.0/atomic:38,
                 from p399.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 \
      |  ^~~~~
p399.cpp:92:5: warning: identifier 'decltype' is a keyword in C++11 [-Wc++11-compat]
   92 |     decltype(t.A4::f4())::B4 i;
      |     ^~~~~~~~
p399.cpp:51:3: error: 'my_T1' was not declared in this scope
   51 | B<my_T1, T2, my_I>* b3;
      |   ^~~~~
p399.cpp:51:18: error: template argument 1 is invalid
   51 | B<my_T1, T2, my_I>* b3;
      |                  ^
p399.cpp:52:3: error: 'my_T1' was not declared in this scope
   52 | B<my_T1, T2, my_I2>* b4;
      |   ^~~~~
p399.cpp:52:19: error: template argument 1 is invalid
   52 | B<my_T1, T2, my_I2>* b4;
      |                   ^
p399.cpp:53:3: error: 'my_T1' was not declared in this scope
   53 | B<my_T1, T2, my_I3>* b5;
      |   ^~~~~
p399.cpp:53:19: error: template argument 1 is invalid
   53 | B<my_T1, T2, my_I3>* b5;
      |                   ^
p399.cpp:54:3: error: 'my_T1' was not declared in this scope
   54 | B<my_T1, T2, my_I4>* b6;
      |   ^~~~~
p399.cpp:54:19: error: template argument 1 is invalid
   54 | B<my_T1, T2, my_I4>* b6;
      |                   ^
p399.cpp:55:3: error: 'my_T1' was not declared in this scope
   55 | B<my_T1, T2, my_I5>* b7;
      |   ^~~~~
p399.cpp:55:19: error: template argument 1 is invalid
   55 | B<my_T1, T2, my_I5>* b7;
      |                   ^
p399.cpp:64:37: error: invalid class name in declaration of 'class A2<T>::B2::C'
   64 | template<class T> struct A2<T>::B2::C : A2<T> {
      |                                     ^
p399.cpp:71:12: error: 'template<class T> class A' used without template arguments
   71 |     int n2[A::i];
      |            ^
p399.cpp:86:11: error: expected nested-name-specifier before 'B4'
   86 |     using B4 = int;
      |           ^~
p399.cpp: In function 'void g4(T)':
p399.cpp:92:25: error: expected ';' before '::' token
   92 |     decltype(t.A4::f4())::B4 i;
      |                         ^~
      |                         ;
p399.cpp: In instantiation of 'void g4(T) [with T = C4]':
p399.cpp:94:22:   required from here
p399.cpp:92:13: error: 'decltype' was not declared in this scope; did you mean 'wctype'?
   92 |     decltype(t.A4::f4())::B4 i;
      |     ~~~~~~~~^~~~~~~~~~~~
      |     wctype
p399.cpp: In instantiation of 'int C5<T>::f5() [with T = B5]':
p399.cpp:108:30:   required from here
p399.cpp:105:32: error: request for member 'm5' is ambiguous
  105 |        int f5() { return this->m5; }
      |                          ~~~~~~^~
p399.cpp:101:12: note: candidates are: 'int B5::m5'
  101 |        int m5;
      |            ^~
p399.cpp:98:12: note:                 'int A5::m5'
   98 |        int m5;
      |            ^~
rm: cannot remove 'p399g': No such file or directory

$ g++ p399.cpp -std=c++2b -o p399g -I. -Wall
p399.cpp:51:3: error: 'my_T1' was not declared in this scope
   51 | B<my_T1, T2, my_I>* b3;
      |   ^~~~~
p399.cpp:51:18: error: template argument 1 is invalid
   51 | B<my_T1, T2, my_I>* b3;
      |                  ^
p399.cpp:52:3: error: 'my_T1' was not declared in this scope
   52 | B<my_T1, T2, my_I2>* b4;
      |   ^~~~~
p399.cpp:52:19: error: template argument 1 is invalid
   52 | B<my_T1, T2, my_I2>* b4;
      |                   ^
p399.cpp:53:3: error: 'my_T1' was not declared in this scope
   53 | B<my_T1, T2, my_I3>* b5;
      |   ^~~~~
p399.cpp:53:19: error: template argument 1 is invalid
   53 | B<my_T1, T2, my_I3>* b5;
      |                   ^
p399.cpp:54:3: error: 'my_T1' was not declared in this scope
   54 | B<my_T1, T2, my_I4>* b6;
      |   ^~~~~
p399.cpp:54:19: error: template argument 1 is invalid
   54 | B<my_T1, T2, my_I4>* b6;
      |                   ^
p399.cpp:55:3: error: 'my_T1' was not declared in this scope
   55 | B<my_T1, T2, my_I5>* b7;
      |   ^~~~~
p399.cpp:55:19: error: template argument 1 is invalid
   55 | B<my_T1, T2, my_I5>* b7;
      |                   ^
p399.cpp:64:37: error: invalid class name in declaration of 'class A2<T>::B2::C'
   64 | template<class T> struct A2<T>::B2::C : A2<T> {
      |                                     ^
p399.cpp:71:12: error: 'template<class T> class A' used without template arguments
   71 |     int n2[A::i];
      |            ^
p399.cpp: In function 'void g4(T)':
p399.cpp:92:5: error: need 'typename' before 'decltype (t.A4::f4())::B4' because 'decltype (t.A4::f4())' is a dependent scope
   92 |     decltype(t.A4::f4())::B4 i;
      |     ^~~~~~~~~~~~~~~~~~~~
p399.cpp:92:29: error: expected ';' before 'i'
   92 |     decltype(t.A4::f4())::B4 i;
      |                             ^~
      |                             ;
p399.cpp: In instantiation of 'void g4(T) [with T = C4]':
p399.cpp:94:22:   required from here
p399.cpp:92:27: error: dependent-name 'decltype (t.A4::f4())::B4' is parsed as a non-type, but instantiation yields a type
   92 |     decltype(t.A4::f4())::B4 i;
      |                           ^~
p399.cpp:92:27: note: say 'typename decltype (t.A4::f4())::B4' if a type is meant
p399.cpp: In instantiation of 'int C5<T>::f5() [with T = B5]':
p399.cpp:108:30:   required from here
p399.cpp:105:32: error: request for member 'm5' is ambiguous
  105 |        int f5() { return this->m5; }
      |                          ~~~~~~^~
p399.cpp:101:12: note: candidates are: 'int B5::m5'
  101 |        int m5;
      |            ^~
p399.cpp:98:12: note:                 'int A5::m5'
   98 |        int m5;
      |            ^~

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。

参考資料(reference)

cpprefjp - C++日本語リファレンス

コンパイラの実装状況

typedef は C++11 ではオワコン

C99からC++14を駆け抜けるC++講座

自己参照(self reference)

コピペコンパイルエラーあるある

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

dockerにclang

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

コンパイル用shell script C版(clangとgcc)とC++版(clang++とg++)

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

C++ sample list

clang++, g++コンパイルエラー方針の違いの例

astyle 使ってみた

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
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https://qiita.com/kaizen_nagoya/items/090909af702f0d5d8a67

MISRA C++ 5-0-16
https://qiita.com/kaizen_nagoya/items/7df2d4e05db724752a74

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https://qiita.com/kaizen_nagoya/items/3f3992c9722c1cee2e3a

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https://qiita.com/kaizen_nagoya/items/644d5e407f5faf96e6dc

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https://qiita.com/kaizen_nagoya/items/96dc8b125e462d5575bb

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https://qiita.com/kaizen_nagoya/items/fbdbff5ff696e2ca7f00

MISRA C まとめ #include
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。＞

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ver. 0.01 初稿 　20220706

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