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@kaizen_nagoya(Dr. Kiyoshi Ogawa)

10.6 Instantiation context [module.context] C++N4910:2022 (135) p255.cpp

Posted at

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.

10.6 Instantiation context [module.context] C++N4910:2022 (135) p255.cpp

算譜(source code)

p255.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 = "10.6 Instantiation context  [module.context] C++N4910:2022 (135) p255.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>

using namespace std;

// Example 1  
Translation unit #1:
     export module stuff;
     export template<typename T, typename U> void foo(T, U u) { auto v = u; }
     export template<typename T, typename U> void bar(T, U u) { auto v = *u; }
Translation unit #2:
export module M1;
import "defn.h"; // provides struct X {}; import stuff;
export template<typename T> void f(T t) {
X x;
foo(t, x); }
Translation unit #3:
     export module M2;
     import "decl.h";
     import stuff;
     export template<typename T> void g(T t) {
X *x;
bar(t, x); }
// provides struct X; (not a definition)
// Translation unit #4:
  import M1;
  import M2;
  void test() {
f(0);
g(0); }
//— the point at the end of translation unit #1,
//— the point at the end of translation unit #3, and — the point of the call to g(0),
//so the definition of X need not be reachable, as described in 10.7. 
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  p255
rm: cannot remove 'p255l': No such file or directory
rm: cannot remove 'p255g': No such file or directory
$ clang++ p255.cpp -std=03 -o p255l -I. -Wall
In file included from p255.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 \
 ^
p255.cpp:26:13: error: expected template
     export module stuff;
            ^
p255.cpp:26:13: error: unknown type name 'module'
p255.cpp:27:6: warning: exported templates are unsupported
     export template<typename T, typename U> void foo(T, U u) { auto v = u; }
     ^
p255.cpp:27:65: warning: 'auto' type specifier is a C++11 extension [-Wc++11-extensions]
     export template<typename T, typename U> void foo(T, U u) { auto v = u; }
                                                                ^
p255.cpp:28:6: warning: exported templates are unsupported
     export template<typename T, typename U> void bar(T, U u) { auto v = *u; }
     ^
p255.cpp:28:65: warning: 'auto' type specifier is a C++11 extension [-Wc++11-extensions]
     export template<typename T, typename U> void bar(T, U u) { auto v = *u; }
                                                                ^
p255.cpp:30:8: error: expected template
export module M1;
       ^
p255.cpp:30:8: error: unknown type name 'module'
p255.cpp:31:1: error: unknown type name 'import'
import "defn.h"; // provides struct X {}; import stuff;
^
p255.cpp:31:8: error: expected unqualified-id
import "defn.h"; // provides struct X {}; import stuff;
       ^
p255.cpp:32:1: warning: exported templates are unsupported
export template<typename T> void f(T t) {
^
p255.cpp:33:1: error: unknown type name 'X'
X x;
^
p255.cpp:36:13: error: expected template
     export module M2;
            ^
p255.cpp:36:13: error: unknown type name 'module'
p255.cpp:37:6: error: unknown type name 'import'
     import "decl.h";
     ^
p255.cpp:37:13: error: expected unqualified-id
     import "decl.h";
            ^
p255.cpp:38:6: error: unknown type name 'import'
     import stuff;
     ^
p255.cpp:39:6: warning: exported templates are unsupported
     export template<typename T> void g(T t) {
     ^
p255.cpp:40:1: error: unknown type name 'X'
X *x;
^
p255.cpp:44:3: error: unknown type name 'import'
  import M1;
  ^
p255.cpp:45:3: error: unknown type name 'import'
  import M2;
  ^
6 warnings and 16 errors generated.
rm: cannot remove 'p255l': No such file or directory
$ clang++ p255.cpp -std=2b -o p255l -I. -Wall
p255.cpp:26:13: error: module declaration must occur at the start of the translation unit
     export module stuff;
            ^
p255.cpp:1:1: note: add 'module;' to the start of the file to introduce a global module fragment
// C++N4910 Committee Draft, Standard for Programming Language C++
^
p255.cpp:30:8: error: translation unit contains multiple module declarations
export module M1;
       ^
p255.cpp:26:13: note: previous module declaration is here
     export module stuff;
            ^
p255.cpp:31:8: fatal error: 'defn.h' file not found
import "defn.h"; // provides struct X {}; import stuff;
       ^~~~~~~~
3 errors generated.

$ g++ p255.cpp -std=03 -o p255g -I. -Wall
In file included from /usr/local/include/c++/12.1.0/atomic:38,
                 from p255.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 \
      |  ^~~~~
p255.cpp:26:6: warning: keyword 'export' not implemented, and will be ignored
   26 |      export module stuff;
      |      ^~~~~~
p255.cpp:26:13: error: 'module' does not name a type
   26 |      export module stuff;
      |             ^~~~~~
p255.cpp:26:13: note: C++20 'module' only available with '-fmodules-ts'
p255.cpp:27:6: warning: keyword 'export' not implemented, and will be ignored
   27 |      export template<typename T, typename U> void foo(T, U u) { auto v = u; }
      |      ^~~~~~
p255.cpp: In function 'void foo(T, U)':
p255.cpp:27:65: warning: 'auto' changes meaning in C++11; please remove it [-Wc++11-compat]
   27 |      export template<typename T, typename U> void foo(T, U u) { auto v = u; }
      |                                                                 ^~~~
      |                                                                 ----
p255.cpp:27:70: error: 'v' does not name a type
   27 |      export template<typename T, typename U> void foo(T, U u) { auto v = u; }
      |                                                                      ^
p255.cpp: At global scope:
p255.cpp:28:6: warning: keyword 'export' not implemented, and will be ignored
   28 |      export template<typename T, typename U> void bar(T, U u) { auto v = *u; }
      |      ^~~~~~
p255.cpp: In function 'void bar(T, U)':
p255.cpp:28:65: warning: 'auto' changes meaning in C++11; please remove it [-Wc++11-compat]
   28 |      export template<typename T, typename U> void bar(T, U u) { auto v = *u; }
      |                                                                 ^~~~
      |                                                                 ----
p255.cpp:28:70: error: 'v' does not name a type
   28 |      export template<typename T, typename U> void bar(T, U u) { auto v = *u; }
      |                                                                      ^
p255.cpp: At global scope:
p255.cpp:30:1: warning: keyword 'export' not implemented, and will be ignored
   30 | export module M1;
      | ^~~~~~
p255.cpp:30:8: error: 'module' does not name a type
   30 | export module M1;
      |        ^~~~~~
p255.cpp:30:8: note: C++20 'module' only available with '-fmodules-ts'
p255.cpp:31:1: error: 'import' does not name a type
   31 | import "defn.h"; // provides struct X {}; import stuff;
      | ^~~~~~
p255.cpp:31:1: note: C++20 'import' only available with '-fmodules-ts'
p255.cpp:32:1: warning: keyword 'export' not implemented, and will be ignored
   32 | export template<typename T> void f(T t) {
      | ^~~~~~
p255.cpp: In function 'void f(T)':
p255.cpp:33:1: error: 'X' was not declared in this scope
   33 | X x;
      | ^
p255.cpp:34:8: error: 'x' was not declared in this scope
   34 | foo(t, x); }
      |        ^
p255.cpp: At global scope:
p255.cpp:36:6: warning: keyword 'export' not implemented, and will be ignored
   36 |      export module M2;
      |      ^~~~~~
p255.cpp:36:13: error: 'module' does not name a type
   36 |      export module M2;
      |             ^~~~~~
p255.cpp:36:13: note: C++20 'module' only available with '-fmodules-ts'
p255.cpp:37:6: error: 'import' does not name a type
   37 |      import "decl.h";
      |      ^~~~~~
p255.cpp:37:6: note: C++20 'import' only available with '-fmodules-ts'
p255.cpp:38:6: error: 'import' does not name a type
   38 |      import stuff;
      |      ^~~~~~
p255.cpp:38:6: note: C++20 'import' only available with '-fmodules-ts'
p255.cpp:39:6: warning: keyword 'export' not implemented, and will be ignored
   39 |      export template<typename T> void g(T t) {
      |      ^~~~~~
p255.cpp: In function 'void g(T)':
p255.cpp:40:1: error: 'X' was not declared in this scope
   40 | X *x;
      | ^
p255.cpp:40:4: error: 'x' was not declared in this scope
   40 | X *x;
      |    ^
p255.cpp: At global scope:
p255.cpp:44:3: error: 'import' does not name a type
   44 |   import M1;
      |   ^~~~~~
p255.cpp:44:3: note: C++20 'import' only available with '-fmodules-ts'
p255.cpp:45:3: error: 'import' does not name a type
   45 |   import M2;
      |   ^~~~~~
p255.cpp:45:3: note: C++20 'import' only available with '-fmodules-ts'
rm: cannot remove 'p255g': No such file or directory

$ g++ p255.cpp -std=2b -o p255g -I. -Wall
p255.cpp:26:6: warning: keyword 'export' is enabled with '-fmodules-ts'
   26 |      export module stuff;
      |      ^~~~~~
p255.cpp:26:13: error: 'module' does not name a type
   26 |      export module stuff;
      |             ^~~~~~
p255.cpp:26:13: note: C++20 'module' only available with '-fmodules-ts', which is not yet enabled with '-std=c++20'
p255.cpp:27:6: warning: keyword 'export' is enabled with '-fmodules-ts'
   27 |      export template<typename T, typename U> void foo(T, U u) { auto v = u; }
      |      ^~~~~~
p255.cpp:28:6: warning: keyword 'export' is enabled with '-fmodules-ts'
   28 |      export template<typename T, typename U> void bar(T, U u) { auto v = *u; }
      |      ^~~~~~
p255.cpp:30:1: warning: keyword 'export' is enabled with '-fmodules-ts'
   30 | export module M1;
      | ^~~~~~
p255.cpp:30:8: error: 'module' does not name a type
   30 | export module M1;
      |        ^~~~~~
p255.cpp:30:8: note: C++20 'module' only available with '-fmodules-ts', which is not yet enabled with '-std=c++20'
p255.cpp:31:1: error: 'import' does not name a type
   31 | import "defn.h"; // provides struct X {}; import stuff;
      | ^~~~~~
p255.cpp:31:1: note: C++20 'import' only available with '-fmodules-ts', which is not yet enabled with '-std=c++20'
p255.cpp:32:1: warning: keyword 'export' is enabled with '-fmodules-ts'
   32 | export template<typename T> void f(T t) {
      | ^~~~~~
p255.cpp: In function 'void f(T)':
p255.cpp:33:1: error: 'X' was not declared in this scope
   33 | X x;
      | ^
p255.cpp:34:8: error: 'x' was not declared in this scope
   34 | foo(t, x); }
      |        ^
p255.cpp: At global scope:
p255.cpp:36:6: warning: keyword 'export' is enabled with '-fmodules-ts'
   36 |      export module M2;
      |      ^~~~~~
p255.cpp:36:13: error: 'module' does not name a type
   36 |      export module M2;
      |             ^~~~~~
p255.cpp:36:13: note: C++20 'module' only available with '-fmodules-ts', which is not yet enabled with '-std=c++20'
p255.cpp:37:6: error: 'import' does not name a type
   37 |      import "decl.h";
      |      ^~~~~~
p255.cpp:37:6: note: C++20 'import' only available with '-fmodules-ts', which is not yet enabled with '-std=c++20'
p255.cpp:38:6: error: 'import' does not name a type
   38 |      import stuff;
      |      ^~~~~~
p255.cpp:38:6: note: C++20 'import' only available with '-fmodules-ts', which is not yet enabled with '-std=c++20'
p255.cpp:39:6: warning: keyword 'export' is enabled with '-fmodules-ts'
   39 |      export template<typename T> void g(T t) {
      |      ^~~~~~
p255.cpp: In function 'void g(T)':
p255.cpp:40:1: error: 'X' was not declared in this scope
   40 | X *x;
      | ^
p255.cpp:40:4: error: 'x' was not declared in this scope
   40 | X *x;
      |    ^
p255.cpp: At global scope:
p255.cpp:44:3: error: 'import' does not name a type
   44 |   import M1;
      |   ^~~~~~
p255.cpp:44:3: note: C++20 'import' only available with '-fmodules-ts', which is not yet enabled with '-std=c++20'
p255.cpp:45:3: error: 'import' does not name a type
   45 |   import M2;
      |   ^~~~~~
p255.cpp:45:3: note: C++20 'import' only available with '-fmodules-ts', which is not yet enabled with '-std=c++20'

検討事項(agenda)

コンパイルエラーの理由を解説する。

<|--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)

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
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
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 　20220628

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