Go to Qiita Advent Calendar 2024 Top
LoginSignup
0
0

Delete article

Deleted articles cannot be recovered.

Draft of this article would be also deleted.

Are you sure you want to delete this article?

More than 1 year has passed since last update.

@kaizen_nagoya(Dr. Kiyoshi Ogawa)

9.8.4 Using namespace directive [namespace.udir] C++N4910:2022 (117) p230.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.

9.8.4 Using namespace directive [namespace.udir] C++N4910:2022 (117) p230.cpp

算譜(source code)

p230.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 = "9.8.4 Using namespace directive [namespace.udir]  C++N4910:2022 (117) p230.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>

using namespace std;

// Example 1
namespace A {
int i;
namespace B {
namespace C {
int i;
}
using namespace A::B::C;
void f1() {
    i = 5; // OK, C::i visible in B and hides A::i
}
}
namespace D {
using namespace B;
using namespace C;
void f2() {
    i = 5; // ambiguous, B::C::i or A::i?
}
}
void f3() {
    i = 5; // uses A::i
}
}
void f4() {
    i = 5; // error: neither i is visible
}
// [Example 2 :
namespace M {
int i2;
}
namespace N {
int i2;
using namespace M;
}
void f() {
    using namespace N;
    i2 = 7; // error: both M::i and N::i are visible
}
// For another example,
namespace A {
int i2;
}
namespace B {
int i2;
int j2;
namespace C {
namespace D {
using namespace A;
int j2;
int k2;
int a2 = i2; // B::i hides A::i
}
using namespace D;
int k2 = 89; // no problem yet
int l2 = k2; // ambiguous: C::k or D::k
int m2 = i2; // B::i hides A::i
int n2 = j2; // D::j hides B::j
}
}
// [Note 6 : If name lookup finds a declaration for a name in two different namespaces, and the declarations do not declare the same entity and do not declare functions or function templates, the use of the name is ill-formed (6.5). In particular, the name of a variable, function or enumerator does not hide the name of a class or enumeration declared in a different namespace. For example,
namespace A6 {
class X6 { };
extern "C" int g6();
extern "C++" int h6();
}
namespace B6 {
void X6(int);
extern "C" int g6();
extern "C++" int h6(int);
}
using namespace A6;
using namespace B6;
void f6() {
    X6(1); // error: name X found in two namespaces
    g6(); // OK, name g refers to the same entity
    h6(); // OK, overload resolution selects A::h
}
// [Example 3 :
namespace D3 {
int d1;
void f3(char);
}
using namespace D3;
int d1; // OK, no conflict with D::d1
namespace E3 {
int e3;
void f3(int);
}
namespace D3 { // namespace extension
int d2;
using namespace E3;
void f3(int);
}
void f3() {
    d1++; // error: ambiguous ::d1 or D::d1?
    ::d1++; // OK
    D3::d1++; // OK
    d2++; // OK, D::d2
    e3++; // OK, E::e
    f3(1); // error: ambiguous: D::f(int) or E::f(int)?
    f3('a'); // OK, D::f(char)
}
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  p230
rm: cannot remove 'p230l': No such file or directory
rm: cannot remove 'p230g': No such file or directory
$ clang++ p230.cpp -std=03 -o p230l -I. -Wall
p230.cpp:38:1: error: reference to 'i' is ambiguous
i = 5; // ambiguous, B::C::i or A::i?
^
p230.cpp:24:5: note: candidate found by name lookup is 'A::i'
int i;
    ^
p230.cpp:27:5: note: candidate found by name lookup is 'A::B::C::i'
int i;
    ^
p230.cpp:46:1: error: use of undeclared identifier 'i'; did you mean 'A::i'?
i = 5; // error: neither i is visible
^
A::i
p230.cpp:24:5: note: 'A::i' declared here
int i;
    ^
p230.cpp:58:1: error: reference to 'i2' is ambiguous
i2 = 7; // error: both M::i and N::i are visible
^
p230.cpp:53:5: note: candidate found by name lookup is 'N::i2'
int i2;
    ^
p230.cpp:50:5: note: candidate found by name lookup is 'M::i2'
int i2;
    ^
p230.cpp:76:10: error: reference to 'k2' is ambiguous
int l2 = k2; // ambiguous: C::k or D::k
         ^
p230.cpp:75:5: note: candidate found by name lookup is 'B::C::k2'
int k2 = 89; // no problem yet
    ^
p230.cpp:71:5: note: candidate found by name lookup is 'B::C::D::k2'
int k2;
    ^
p230.cpp:95:1: error: reference to 'X6' is ambiguous
X6(1); // error: name X found in two namespaces
^
p230.cpp:83:7: note: candidate found by name lookup is 'A6::X6'
class X6 { };
      ^
p230.cpp:88:6: note: candidate found by name lookup is 'B6::X6'
void X6(int);
     ^
p230.cpp:116:1: error: reference to 'd1' is ambiguous
d1++; // error: ambiguous ::d1 or D::d1?
^
p230.cpp:105:5: note: candidate found by name lookup is 'd1'
int d1; // OK, no conflict with D::d1
    ^
p230.cpp:101:5: note: candidate found by name lookup is 'D3::d1'
int d1;
    ^
p230.cpp:121:1: error: call to 'f3' is ambiguous
f3(1); // error: ambiguous: D::f(int) or E::f(int)?
^~
p230.cpp:108:6: note: candidate function
void f3(int);
     ^
p230.cpp:113:6: note: candidate function
void f3(int);
     ^
7 errors generated.
rm: cannot remove 'p230l': No such file or directory
$ clang++ p230.cpp -std=2b -o p230l -I. -Wall
p230.cpp:38:1: error: reference to 'i' is ambiguous
i = 5; // ambiguous, B::C::i or A::i?
^
p230.cpp:24:5: note: candidate found by name lookup is 'A::i'
int i;
    ^
p230.cpp:27:5: note: candidate found by name lookup is 'A::B::C::i'
int i;
    ^
p230.cpp:46:1: error: use of undeclared identifier 'i'; did you mean 'A::i'?
i = 5; // error: neither i is visible
^
A::i
p230.cpp:24:5: note: 'A::i' declared here
int i;
    ^
p230.cpp:58:1: error: reference to 'i2' is ambiguous
i2 = 7; // error: both M::i and N::i are visible
^
p230.cpp:53:5: note: candidate found by name lookup is 'N::i2'
int i2;
    ^
p230.cpp:50:5: note: candidate found by name lookup is 'M::i2'
int i2;
    ^
p230.cpp:76:10: error: reference to 'k2' is ambiguous
int l2 = k2; // ambiguous: C::k or D::k
         ^
p230.cpp:75:5: note: candidate found by name lookup is 'B::C::k2'
int k2 = 89; // no problem yet
    ^
p230.cpp:71:5: note: candidate found by name lookup is 'B::C::D::k2'
int k2;
    ^
p230.cpp:95:1: error: reference to 'X6' is ambiguous
X6(1); // error: name X found in two namespaces
^
p230.cpp:83:7: note: candidate found by name lookup is 'A6::X6'
class X6 { };
      ^
p230.cpp:88:6: note: candidate found by name lookup is 'B6::X6'
void X6(int);
     ^
p230.cpp:116:1: error: reference to 'd1' is ambiguous
d1++; // error: ambiguous ::d1 or D::d1?
^
p230.cpp:105:5: note: candidate found by name lookup is 'd1'
int d1; // OK, no conflict with D::d1
    ^
p230.cpp:101:5: note: candidate found by name lookup is 'D3::d1'
int d1;
    ^
p230.cpp:121:1: error: call to 'f3' is ambiguous
f3(1); // error: ambiguous: D::f(int) or E::f(int)?
^~
p230.cpp:108:6: note: candidate function
void f3(int);
     ^
p230.cpp:113:6: note: candidate function
void f3(int);
     ^
7 errors generated.

$ g++ p230.cpp -std=03 -o p230g -I. -Wall
p230.cpp: In function 'void A::D::f2()':
p230.cpp:38:1: error: reference to 'i' is ambiguous
   38 | i = 5; // ambiguous, B::C::i or A::i?
      | ^
p230.cpp:27:5: note: candidates are: 'int A::B::C::i'
   27 | int i;
      |     ^
p230.cpp:24:5: note:                 'int A::i'
   24 | int i;
      |     ^
p230.cpp: In function 'void f4()':
p230.cpp:46:1: error: 'i' was not declared in this scope
   46 | i = 5; // error: neither i is visible
      | ^
p230.cpp:46:1: note: suggested alternatives:
p230.cpp:24:5: note:   'A::i'
   24 | int i;
      |     ^
p230.cpp:27:5: note:   'A::B::C::i'
   27 | int i;
      |     ^
p230.cpp: In function 'void f()':
p230.cpp:58:1: error: reference to 'i2' is ambiguous
   58 | i2 = 7; // error: both M::i and N::i are visible
      | ^~
p230.cpp:50:5: note: candidates are: 'int M::i2'
   50 | int i2;
      |     ^~
p230.cpp:53:5: note:                 'int N::i2'
   53 | int i2;
      |     ^~
p230.cpp: At global scope:
p230.cpp:76:10: error: reference to 'k2' is ambiguous
   76 | int l2 = k2; // ambiguous: C::k or D::k
      |          ^~
p230.cpp:71:5: note: candidates are: 'int B::C::D::k2'
   71 | int k2;
      |     ^~
p230.cpp:75:5: note:                 'int B::C::k2'
   75 | int k2 = 89; // no problem yet
      |     ^~
p230.cpp: In function 'void f6()':
p230.cpp:95:1: error: reference to 'X6' is ambiguous
   95 | X6(1); // error: name X found in two namespaces
      | ^~
p230.cpp:88:6: note: candidates are: 'void B6::X6(int)'
   88 | void X6(int);
      |      ^~
p230.cpp:83:7: note:                 'class A6::X6'
   83 | class X6 { };
      |       ^~
p230.cpp: In function 'void f3()':
p230.cpp:116:1: error: reference to 'd1' is ambiguous
  116 | d1++; // error: ambiguous ::d1 or D::d1?
      | ^~
p230.cpp:101:5: note: candidates are: 'int D3::d1'
  101 | int d1;
      |     ^~
p230.cpp:105:5: note:                 'int d1'
  105 | int d1; // OK, no conflict with D::d1
      |     ^~
p230.cpp:121:3: error: call of overloaded 'f3(int)' is ambiguous
  121 | f3(1); // error: ambiguous: D::f(int) or E::f(int)?
      | ~~^~~
p230.cpp:108:6: note: candidate: 'void E3::f3(int)'
  108 | void f3(int);
      |      ^~
p230.cpp:102:6: note: candidate: 'void D3::f3(char)'
  102 | void f3(char);
      |      ^~
p230.cpp:113:6: note: candidate: 'void D3::f3(int)'
  113 | void f3(int);
      |      ^~
rm: cannot remove 'p230g': No such file or directory

$ g++ p230.cpp -std=2b -o p230g -I. -Wall
p230.cpp: In function 'void A::D::f2()':
p230.cpp:38:1: error: reference to 'i' is ambiguous
   38 | i = 5; // ambiguous, B::C::i or A::i?
      | ^
p230.cpp:27:5: note: candidates are: 'int A::B::C::i'
   27 | int i;
      |     ^
p230.cpp:24:5: note:                 'int A::i'
   24 | int i;
      |     ^
p230.cpp: In function 'void f4()':
p230.cpp:46:1: error: 'i' was not declared in this scope
   46 | i = 5; // error: neither i is visible
      | ^
p230.cpp:46:1: note: suggested alternatives:
p230.cpp:24:5: note:   'A::i'
   24 | int i;
      |     ^
p230.cpp:27:5: note:   'A::B::C::i'
   27 | int i;
      |     ^
p230.cpp: In function 'void f()':
p230.cpp:58:1: error: reference to 'i2' is ambiguous
   58 | i2 = 7; // error: both M::i and N::i are visible
      | ^~
p230.cpp:50:5: note: candidates are: 'int M::i2'
   50 | int i2;
      |     ^~
p230.cpp:53:5: note:                 'int N::i2'
   53 | int i2;
      |     ^~
p230.cpp: At global scope:
p230.cpp:76:10: error: reference to 'k2' is ambiguous
   76 | int l2 = k2; // ambiguous: C::k or D::k
      |          ^~
p230.cpp:71:5: note: candidates are: 'int B::C::D::k2'
   71 | int k2;
      |     ^~
p230.cpp:75:5: note:                 'int B::C::k2'
   75 | int k2 = 89; // no problem yet
      |     ^~
p230.cpp: In function 'void f6()':
p230.cpp:95:1: error: reference to 'X6' is ambiguous
   95 | X6(1); // error: name X found in two namespaces
      | ^~
p230.cpp:88:6: note: candidates are: 'void B6::X6(int)'
   88 | void X6(int);
      |      ^~
p230.cpp:83:7: note:                 'class A6::X6'
   83 | class X6 { };
      |       ^~
p230.cpp: In function 'void f3()':
p230.cpp:116:1: error: reference to 'd1' is ambiguous
  116 | d1++; // error: ambiguous ::d1 or D::d1?
      | ^~
p230.cpp:101:5: note: candidates are: 'int D3::d1'
  101 | int d1;
      |     ^~
p230.cpp:105:5: note:                 'int d1'
  105 | int d1; // OK, no conflict with D::d1
      |     ^~
p230.cpp:121:3: error: call of overloaded 'f3(int)' is ambiguous
  121 | f3(1); // error: ambiguous: D::f(int) or E::f(int)?
      | ~~^~~
p230.cpp:108:6: note: candidate: 'void E3::f3(int)'
  108 | void f3(int);
      |      ^~
p230.cpp:102:6: note: candidate: 'void D3::f3(char)'
  102 | void f3(char);
      |      ^~
p230.cpp:113:6: note: candidate: 'void D3::f3(int)'
  113 | void f3(int);
      |      ^~

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)

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

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 　20220626

0
0
0

Register as a new user and use Qiita more conveniently

  1. You get articles that match your needs
  2. You can efficiently read back useful information
  3. You can use dark theme
What you can do with signing up
Sign upLogin
0
0

Delete article

Deleted articles cannot be recovered.

Draft of this article would be also deleted.

Are you sure you want to delete this article?