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この記事誰得？ 私しか得しないニッチな技術で記事投稿！
@kaizen_nagoya(Dr. Kiyoshi Ogawa)

N4606 Working Draft 2016, ISO/IEC 14882, C++ standard(66)7.1.1 Storage class specifiers [dcl.stc] p156

Last updated at Posted at 2018-04-17

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。

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.

#(66)7.1.1 Storage class specifiers [dcl.stc]
p156

p156.cpp
// N4606 Committee Draft, Standard for Programming Language C++
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/n4606.pdf 
#define msg "p156.cpp(66)7.1.1 Storage class specifiers [dcl.stc]"

#include <iostream>

static char* f(); // f() has internal linkage
char* f() // f() still has internal linkage
{ /* ... */ }
char g(); // g() has external linkage
//static char* g() // error: inconsistent linkage
//{ /* ... */ }
//$ clang++ p156.cpp
//p156.cpp:11:14: error: static declaration of 'g' follows non-static declaration
//static char* g() // error: inconsistent linkage
//             ^
// $ g++-7 p156.cpp
// p156.cpp: In function 'char* g()':
// p156.cpp:11:14: error: ambiguating new declaration of 'char* g()'
//  static char* g() // error: inconsistent linkage
//               ^
// p156.cpp:10:6: note: old declaration 'char g()'
//  char g(); // g() has external linkage
//       ^


void h();
inline void h(); // external linkage
inline void l();
void l(); // external linkage
inline void m();
extern void m(); // external linkage
static void n();
inline void n(); // internal linkage
static int a; // a has internal linkage
//int a; // error: two definitions
//p156.cpp:22:5: error: non-static declaration of 'a' follows static declaration
//int a; // error: two definitions
//    ^
//p156.cpp:21:12: note: previous definition is here
//static int a; // a has internal linkage
//           ^

static int b; // b has internal linkage
extern int b; // b still has internal linkage
int c; // c has external linkage
//static int c; // error: inconsistent linkage
//p156.cpp:26:12: error: static declaration of 'c' follows non-static declaration
//static int c; // error: inconsistent linkage
//           ^
//p156.cpp:25:5: note: previous definition is here
//int c; // c has external linkage
//    ^

extern int d; // d has external linkage
//static int d; // error: inconsistent linkage
//p156.cpp:28:12: error: static declaration of 'd' follows non-static declaration
//static int d; // error: inconsistent linkage
//           ^
//p156.cpp:27:12: note: previous declaration is here
//extern int d; // d has external linkage
//           ^
struct S;
extern S a;
extern S f();
extern void g(S);
void h() {
//  g(a); // error: S is incomplete
//p156.cpp:34:3: error: no matching function for call to 'g'
//  g(a); // error: S is incomplete
//  ^
//p156.cpp:32:13: note: candidate function not viable: no known conversion from 'int' to 'S' for 1st argument
//extern void g(S);
//            ^
//p156.cpp:10:6: note: candidate function not viable: requires 0 arguments, but 1 was provided
//char g(); // g() has external linkage
//     ^

  f(); // error: S is incomplete
}
class X {
mutable const int* p; // OK
//mutable int* const q; // ill-formed
//p156.cpp:39:1: error: 'mutable' and 'const' cannot be mixed
//mutable int* const q; // ill-formed
//^
//p156.cpp:39:20: error: const 'q' cannot be declared 'mutable'
// mutable int* const q; // ill-formed
//                    ^


};

int main(){
  h();
  std::cout<< msg << std::endl;
  return EXIT_SUCCESS;
}

$ ./cppgl17.sh p156
$ clang++ p156.cpp
p156.cpp:9:13: warning: control reaches end of non-void function [-Wreturn-type]
{ /* ... */ }
            ^
p156.cpp:30:10: error: redeclaration of 'a' with a different type: 'S' vs 'int'
extern S a;
         ^
p156.cpp:21:12: note: previous definition is here
static int a; // a has internal linkage
           ^
p156.cpp:31:10: error: functions that differ only in their return type cannot be overloaded
extern S f();
       ~ ^
p156.cpp:8:7: note: previous definition is here
char* f() // f() still has internal linkage
~~~~~ ^
1 warning and 2 errors generated.

$ g++-7 p156.cpp
p156.cpp:30:10: error: conflicting declaration 'S a'
 extern S a;
          ^
p156.cpp:21:12: note: previous declaration as 'int a'
 static int a; // a has internal linkage
            ^
p156.cpp:31:10: error: ambiguating new declaration of 'S f()'
 extern S f();
          ^
p156.cpp:8:7: note: old declaration 'char* f()'
 char* f() // f() still has internal linkage
       ^

#検討事項
コンパイルエラーをなくす修正方法

#参考資料

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

文書履歴

0.10 初稿 2080417

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