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@kaizen_nagoya(Dr. Kiyoshi Ogawa)

C++ N4606(109)9.1 Class names [class.name] p241

Last updated at Posted at 2018-04-18

#はじめに
N4606 Working Draft, Standard for Programming Language C++
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/#mailing2016-11
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/n4606.pdf

n4606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。

##作業方針
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。

list

N4606 Working Draft 2016, ISO/IEC 14882, C++ standard(1) coding list
https://qiita.com/kaizen_nagoya/items/df5d62c35bd6ed1c3d43/

Compiler

###clang++ --version
clang version 6.0.0 (tags/RELEASE_600/final)

###g++-7 --version
g++-7 (Homebrew GCC 7.3.0_1) 7.3.0
Copyright (C) 2017 Free Software Foundation, Inc.

#(109)9.1 Class names [class.name]
p241

p241.cpp
// N4606 Committee Draft, Standard for Programming Language C++
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/n4606.pdf 
#define msg "p241.cpp(109)9.1 Class names [class.name]"

#include <iostream>


struct X { int a; };
struct Y { int a; };
X a1;
Y a2;
int a3;

a1 = a2; // error: Y assigned to X
a1 = a3; // error: int assigned to X

int f(X);
int f(Y);

struct S { int a; };
struct S { int a; }; // error, double definition

struct stat {
// ...
};
stat gstat; // use plain stat to
// define variable
int stat(struct stat*); // redeclare stat as function
void f() {
struct stat* ps; // struct prefix needed
// to name struct stat
stat(ps); // call stat()
}

struct s { int a; };
void g() {
struct s; // hide global struct s

// with a block-scope declaration
s* p; // refer to local struct s
struct s { char* p; }; // define local struct s
struct s; // redeclaration, has no effect
}

class Vector;
class Matrix {
// ...
friend Vector operator*(const Matrix&, const Vector&);
};
class Vector {
// ...
friend Vector operator*(const Matrix&, const Vector&);
};

struct s { int a; };
void g(int s) {
struct s* p = new struct s; // global s
p->a = s; // parameter s
}

class A * A;

struct X { int a; };
struct Y { int a; };
X a1;
Y a2;
int a3;

a1 = a2; // error: Y assigned to X
a1 = a3; // error: int assigned to X

int f(X);
int f(Y);

struct S { int a; };
struct S { int a; }; // error, double definition

struct stat {
// ...
};
stat gstat; // use plain stat to
// define variable
int stat(struct stat*); // redeclare stat as function
void f() {
struct stat* ps; // struct prefix needed
// to name struct stat
stat(ps); // call stat()
}

struct s { int a; };
void g() {
struct s; // hide global struct s

// with a block-scope declaration
s* p; // refer to local struct s
struct s { char* p; }; // define local struct s
struct s; // redeclaration, has no effect
}

class Vector;
class Matrix {
// ...
friend Vector operator*(const Matrix&, const Vector&);
};
class Vector {
// ...
friend Vector operator*(const Matrix&, const Vector&);
};

struct s { int a; };
void g(int s) {
struct s* p = new struct s; // global s
p->a = s; // parameter s
}

class A * A;

int main(){

  std::cout<< msg << std::endl;
  return EXIT_SUCCESS;
}

$ ./cppgl17.sh p241
$ clang++ p241.cpp
p241.cpp:14:1: error: C++ requires a type specifier for all declarations
a1 = a2; // error: Y assigned to X
^
p241.cpp:15:1: error: C++ requires a type specifier for all declarations
a1 = a3; // error: int assigned to X
^
p241.cpp:63:8: error: redefinition of 'X'
struct X { int a; };
       ^
p241.cpp:8:8: note: previous definition is here
struct X { int a; };
       ^
p241.cpp:64:8: error: redefinition of 'Y'
struct Y { int a; };
       ^
p241.cpp:9:8: note: previous definition is here
struct Y { int a; };
       ^
p241.cpp:65:3: error: redefinition of 'a1'
X a1;
  ^
p241.cpp:10:3: note: previous definition is here
X a1;
  ^
p241.cpp:66:3: error: redefinition of 'a2'
Y a2;
  ^
p241.cpp:11:3: note: previous definition is here
Y a2;
  ^
p241.cpp:67:5: error: redefinition of 'a3'
int a3;
    ^
p241.cpp:12:5: note: previous definition is here
int a3;
    ^
p241.cpp:69:1: error: C++ requires a type specifier for all declarations
a1 = a2; // error: Y assigned to X
^
p241.cpp:70:1: error: C++ requires a type specifier for all declarations
a1 = a3; // error: int assigned to X
^
p241.cpp:78:8: error: redefinition of 'stat'
struct stat {
       ^
p241.cpp:23:8: note: previous definition is here
struct stat {
       ^
p241.cpp:81:1: error: must use 'struct' tag to refer to type 'stat' in this scope
stat gstat; // use plain stat to
^
struct 
p241.cpp:28:5: note: struct 'stat' is hidden by a non-type declaration of 'stat' here
int stat(struct stat*); // redeclare stat as function
    ^
p241.cpp:81:6: error: redefinition of 'gstat'
stat gstat; // use plain stat to
     ^
p241.cpp:26:6: note: previous definition is here
stat gstat; // use plain stat to
     ^
p241.cpp:84:6: error: redefinition of 'f'
void f() {
     ^
p241.cpp:29:6: note: previous definition is here
void f() {
     ^
p241.cpp:90:8: error: redefinition of 's'
struct s { int a; };
       ^
p241.cpp:35:8: note: previous definition is here
struct s { int a; };
       ^
p241.cpp:91:6: error: redefinition of 'g'
void g() {
     ^
p241.cpp:36:6: note: previous definition is here
void g() {
     ^
p241.cpp:101:7: error: redefinition of 'Matrix'
class Matrix {
      ^
p241.cpp:46:7: note: previous definition is here
class Matrix {
      ^
p241.cpp:105:7: error: redefinition of 'Vector'
class Vector {
      ^
p241.cpp:50:7: note: previous definition is here
class Vector {
      ^
p241.cpp:110:8: error: redefinition of 's'
struct s { int a; };
       ^
p241.cpp:35:8: note: previous definition is here
struct s { int a; };
       ^
p241.cpp:111:6: error: redefinition of 'g'
void g(int s) {
     ^
p241.cpp:56:6: note: previous definition is here
void g(int s3) {
     ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.

$ g++-7 p241.cpp
p241.cpp:14:1: error: 'a1' does not name a type
 a1 = a2; // error: Y assigned to X
 ^~
p241.cpp:15:1: error: 'a1' does not name a type
 a1 = a3; // error: int assigned to X
 ^~
p241.cpp:63:8: error: redefinition of 'struct X'
 struct X { int a; };
        ^
p241.cpp:8:8: note: previous definition of 'struct X'
 struct X { int a; };
        ^
p241.cpp:64:8: error: redefinition of 'struct Y'
 struct Y { int a; };
        ^
p241.cpp:9:8: note: previous definition of 'struct Y'
 struct Y { int a; };
        ^
p241.cpp:65:3: error: redefinition of 'X a1'
 X a1;
   ^~
p241.cpp:10:3: note: 'X a1' previously declared here
 X a1;
   ^~
p241.cpp:66:3: error: redefinition of 'Y a2'
 Y a2;
   ^~
p241.cpp:11:3: note: 'Y a2' previously declared here
 Y a2;
   ^~
p241.cpp:67:5: error: redefinition of 'int a3'
 int a3;
     ^~
p241.cpp:12:5: note: 'int a3' previously declared here
 int a3;
     ^~
p241.cpp:69:1: error: 'a1' does not name a type
 a1 = a2; // error: Y assigned to X
 ^~
p241.cpp:70:1: error: 'a1' does not name a type
 a1 = a3; // error: int assigned to X
 ^~
p241.cpp:78:8: error: redefinition of 'struct stat'
 struct stat {
        ^~~~
p241.cpp:23:8: note: previous definition of 'struct stat'
 struct stat {
        ^~~~
p241.cpp:81:1: error: 'stat' does not name a type
 stat gstat; // use plain stat to
 ^~~~
p241.cpp: In function 'void f()':
p241.cpp:84:6: error: redefinition of 'void f()'
 void f() {
      ^
p241.cpp:29:6: note: 'void f()' previously defined here
 void f() {
      ^
p241.cpp: At global scope:
p241.cpp:90:8: error: redefinition of 'struct s'
 struct s { int a; };
        ^
p241.cpp:35:8: note: previous definition of 'struct s'
 struct s { int a; };
        ^
p241.cpp: In function 'void g()':
p241.cpp:91:6: error: redefinition of 'void g()'
 void g() {
      ^
p241.cpp:36:6: note: 'void g()' previously defined here
 void g() {
      ^
p241.cpp: At global scope:
p241.cpp:101:7: error: redefinition of 'class Matrix'
 class Matrix {
       ^~~~~~
p241.cpp:46:7: note: previous definition of 'class Matrix'
 class Matrix {
       ^~~~~~
p241.cpp:105:7: error: redefinition of 'class Vector'
 class Vector {
       ^~~~~~
p241.cpp:50:7: note: previous definition of 'class Vector'
 class Vector {
       ^~~~~~
p241.cpp:110:8: error: redefinition of 'struct s'
 struct s { int a; };
        ^
p241.cpp:35:8: note: previous definition of 'struct s'
 struct s { int a; };
        ^
p241.cpp: In function 'void g(int)':
p241.cpp:111:6: error: redefinition of 'void g(int)'
 void g(int s) {
      ^
p241.cpp:56:6: note: 'void g(int)' previously defined here
 void g(int s3) {
      ^
p241.cpp: At global scope:
p241.cpp:116:11: error: redefinition of 'A* A'
 class A * A;
           ^
p241.cpp:61:11: note: 'A* A' previously declared here
 class A * A;
           ^

#検討事項
コンパイルエラーをなくす修正。

#参考資料

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

Qiitaに投稿するCのStyle例(暫定)
https://qiita.com/kaizen_nagoya/items/946df1528a6a1ef2bc0d

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

#文書履歴
0.10 初稿 2080418

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