15.6.2 Argument substitution [cpp.subst] C++N4910:2022 (254) p456.cpp

# はじめに(Introduction)

N4910  Working Draft, Standard for Programming Language C++

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/n4910.pdf

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  

https://qiita.com/kaizen_nagoya/items/fc957ddddd402004bb91

### C++N4741, 2018 Standard Working Draft on ISO/IEC 14882 sample code compile list
https://qiita.com/kaizen_nagoya/items/3294c014044550896010

### 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++
https://qiita.com/kaizen_nagoya/items/685b5c1a2c17c1bf1318

## 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.

# 15.6.2 Argument substitution [cpp.subst] C++N4910:2022 (254) p456.cpp

## 算譜(source code)

```c++:p456.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 = "15.6.2 Argument substitution [cpp.subst] C++N4910:2022 (254) p456.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
#define LPAREN() (
#define G(Q) 42
#define F(R, X, ...) __VA_OPT__(G R X) )
int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
// [Example 2:
#define debug(...) fprintf(stderr, __VA_ARGS__)
#define showlist(...) puts(#__VA_ARGS__)
#define report(test, ...) ((test) ? puts(#test) : printf(__VA_ARGS__)) debug("Flag");
debug("X = %d\n", x);
showlist(The first, second, and third items.);
report(x>y, "x is %d but y is %d", x, y);
// results in
fprintf(stderr, "Flag");
fprintf(stderr, "X = %d\n", x);
puts("The first, second, and third items.");
((x>y) ? puts("x>y") : printf("x is %d but y is %d", x, y));
// [Example 3:
#define F(...)           f(0 __VA_OPT__(,) __VA_ARGS__)
#define G(X, ...)        f(0, X __VA_OPT__(,) __VA_ARGS__)
#define SDEF(sname, ...) S sname __VA_OPT__(= { __VA_ARGS__ })
#define EMP
int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
F(a, b, c)
F()
F(EMP)
G(a, b, c)
G(a, )
G(a)
SDEF(foo);
SDEF(bar, 1, 2);
// replaced by f(0, // replaced by f(0) // replaced by f(0)
// replaced by f(0,
// replaced by f(0, a) // replaced by f(0, a)
// replaced by S foo; // replaced by S bar =
#define H1(X, ...) X __VA_OPT__(##) __VA_ARGS__ // error: ## may not appear at
// the beginning of a replacement list (15.6.4)
#define H2(X, Y, ...) __VA_OPT__(X ## Y,) __VA_ARGS__ H2(a, b, c, d) // replaced by ab, c, d
#define H3(X, ...) #__VA_OPT__(X##X X##X) H3(, 0) // replaced by ""
#define H4(X, ...) __VA_OPT__(a X ## X) ## b H4(, 1) // replaced by a b
#define H5A(...) __VA_OPT__()/**/__VA_OPT__()
#define H5B(X) a ## X ## b
#define H5C(X) H5B(X)
H5C(H5A()) // replaced by ab
int main() {
    cout  <<  n4910 << endl;
    return EXIT_SUCCESS;
}
```

## Script

```bash: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)

```ubuntu:bash
# ./clgc.sh p456
$ clang++ p456.cpp -std=c++03 -o p456l -I. -Wall
In file included from p456.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 \
 ^
p456.cpp:34:1: error: C++ requires a type specifier for all declarations
debug("X = %d\n", x);
^
p456.cpp:31:20: note: expanded from macro 'debug'
#define debug(...) fprintf(stderr, __VA_ARGS__)
                   ^
p456.cpp:35:1: error: C++ requires a type specifier for all declarations
showlist(The first, second, and third items.);
^
p456.cpp:32:23: note: expanded from macro 'showlist'
#define showlist(...) puts(#__VA_ARGS__)
                      ^
p456.cpp:36:9: error: expected ')'
report(x>y, "x is %d but y is %d", x, y);
        ^
p456.cpp:36:1: note: to match this '('
report(x>y, "x is %d but y is %d", x, y);
^
p456.cpp:33:28: note: expanded from macro 'report'
#define report(test, ...) ((test) ? puts(#test) : printf(__VA_ARGS__)) debug("Flag");
                           ^
p456.cpp:36:1: error: expected ')'
report(x>y, "x is %d but y is %d", x, y);
^
p456.cpp:33:35: note: expanded from macro 'report'
#define report(test, ...) ((test) ? puts(#test) : printf(__VA_ARGS__)) debug("Flag");
                                  ^
p456.cpp:36:1: note: to match this '('
p456.cpp:33:27: note: expanded from macro 'report'
#define report(test, ...) ((test) ? puts(#test) : printf(__VA_ARGS__)) debug("Flag");
                          ^
p456.cpp:36:8: error: C++ requires a type specifier for all declarations
report(x>y, "x is %d but y is %d", x, y);
       ^
p456.cpp:36:1: error: expected ';' after top level declarator
report(x>y, "x is %d but y is %d", x, y);
^
p456.cpp:33:72: note: expanded from macro 'report'
#define report(test, ...) ((test) ? puts(#test) : printf(__VA_ARGS__)) debug("Flag");
                                                                       ^
p456.cpp:31:20: note: expanded from macro 'debug'
#define debug(...) fprintf(stderr, __VA_ARGS__)
                   ^
p456.cpp:38:8: error: C++ requires a type specifier for all declarations
       fprintf(stderr, "Flag");
       ^
p456.cpp:39:8: error: C++ requires a type specifier for all declarations
       fprintf(stderr, "X = %d\n", x);
       ^
p456.cpp:40:8: error: C++ requires a type specifier for all declarations
       puts("The first, second, and third items.");
       ^
p456.cpp:41:11: error: expected ')'
       ((x>y) ? puts("x>y") : printf("x is %d but y is %d", x, y));
          ^
p456.cpp:41:9: note: to match this '('
       ((x>y) ? puts("x>y") : printf("x is %d but y is %d", x, y));
        ^
p456.cpp:41:15: error: expected ')'
       ((x>y) ? puts("x>y") : printf("x is %d but y is %d", x, y));
              ^
p456.cpp:41:8: note: to match this '('
       ((x>y) ? puts("x>y") : printf("x is %d but y is %d", x, y));
       ^
p456.cpp:41:10: error: C++ requires a type specifier for all declarations
       ((x>y) ? puts("x>y") : printf("x is %d but y is %d", x, y));
         ^
p456.cpp:43:16: warning: 'F' macro redefined [-Wmacro-redefined]
       #define F(...)           f(0 __VA_OPT__(,) __VA_ARGS__)
               ^
p456.cpp:28:9: note: previous definition is here
#define F(R, X, ...) __VA_OPT__(G R X) )
        ^
p456.cpp:44:16: warning: 'G' macro redefined [-Wmacro-redefined]
       #define G(X, ...)        f(0, X __VA_OPT__(,) __VA_ARGS__)
               ^
p456.cpp:27:9: note: previous definition is here
#define G(Q) 42
        ^
p456.cpp:47:5: error: redefinition of 'x'
int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
    ^
p456.cpp:29:5: note: previous definition is here
int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
    ^
p456.cpp:47:19: error: expected expression
int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
                  ^
p456.cpp:47:24: error: expected expression
int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
                       ^
p456.cpp:60:33: error: '##' cannot appear at start of __VA_OPT__ argument
#define H1(X, ...) X __VA_OPT__(##) __VA_ARGS__ // error: ## may not appear at
                                ^
p456.cpp:72:2: error: expected ';' after top level declarator
}
 ^
 ;
2 warnings and 18 errors generated.
rm: cannot remove 'p456l': No such file or directory
$ clang++ p456.cpp -std=c++2b -o p456l -I. -Wall
p456.cpp:34:1: error: C++ requires a type specifier for all declarations
debug("X = %d\n", x);
^
p456.cpp:31:20: note: expanded from macro 'debug'
#define debug(...) fprintf(stderr, __VA_ARGS__)
                   ^
p456.cpp:35:1: error: C++ requires a type specifier for all declarations
showlist(The first, second, and third items.);
^
p456.cpp:32:23: note: expanded from macro 'showlist'
#define showlist(...) puts(#__VA_ARGS__)
                      ^
p456.cpp:36:9: error: expected ')'
report(x>y, "x is %d but y is %d", x, y);
        ^
p456.cpp:36:1: note: to match this '('
report(x>y, "x is %d but y is %d", x, y);
^
p456.cpp:33:28: note: expanded from macro 'report'
#define report(test, ...) ((test) ? puts(#test) : printf(__VA_ARGS__)) debug("Flag");
                           ^
p456.cpp:36:1: error: expected ')'
report(x>y, "x is %d but y is %d", x, y);
^
p456.cpp:33:35: note: expanded from macro 'report'
#define report(test, ...) ((test) ? puts(#test) : printf(__VA_ARGS__)) debug("Flag");
                                  ^
p456.cpp:36:1: note: to match this '('
p456.cpp:33:27: note: expanded from macro 'report'
#define report(test, ...) ((test) ? puts(#test) : printf(__VA_ARGS__)) debug("Flag");
                          ^
p456.cpp:36:8: error: C++ requires a type specifier for all declarations
report(x>y, "x is %d but y is %d", x, y);
       ^
p456.cpp:36:1: error: expected ';' after top level declarator
report(x>y, "x is %d but y is %d", x, y);
^
p456.cpp:33:72: note: expanded from macro 'report'
#define report(test, ...) ((test) ? puts(#test) : printf(__VA_ARGS__)) debug("Flag");
                                                                       ^
p456.cpp:31:20: note: expanded from macro 'debug'
#define debug(...) fprintf(stderr, __VA_ARGS__)
                   ^
p456.cpp:38:8: error: C++ requires a type specifier for all declarations
       fprintf(stderr, "Flag");
       ^
p456.cpp:39:8: error: C++ requires a type specifier for all declarations
       fprintf(stderr, "X = %d\n", x);
       ^
p456.cpp:40:8: error: C++ requires a type specifier for all declarations
       puts("The first, second, and third items.");
       ^
p456.cpp:41:11: error: expected ')'
       ((x>y) ? puts("x>y") : printf("x is %d but y is %d", x, y));
          ^
p456.cpp:41:9: note: to match this '('
       ((x>y) ? puts("x>y") : printf("x is %d but y is %d", x, y));
        ^
p456.cpp:41:15: error: expected ')'
       ((x>y) ? puts("x>y") : printf("x is %d but y is %d", x, y));
              ^
p456.cpp:41:8: note: to match this '('
       ((x>y) ? puts("x>y") : printf("x is %d but y is %d", x, y));
       ^
p456.cpp:41:10: error: C++ requires a type specifier for all declarations
       ((x>y) ? puts("x>y") : printf("x is %d but y is %d", x, y));
         ^
p456.cpp:43:16: warning: 'F' macro redefined [-Wmacro-redefined]
       #define F(...)           f(0 __VA_OPT__(,) __VA_ARGS__)
               ^
p456.cpp:28:9: note: previous definition is here
#define F(R, X, ...) __VA_OPT__(G R X) )
        ^
p456.cpp:44:16: warning: 'G' macro redefined [-Wmacro-redefined]
       #define G(X, ...)        f(0, X __VA_OPT__(,) __VA_ARGS__)
               ^
p456.cpp:27:9: note: previous definition is here
#define G(Q) 42
        ^
p456.cpp:47:5: error: redefinition of 'x'
int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
    ^
p456.cpp:29:5: note: previous definition is here
int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
    ^
p456.cpp:47:19: error: expected expression
int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
                  ^
p456.cpp:47:26: error: expected variable name or 'this' in lambda capture list
int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
                         ^
p456.cpp:60:33: error: '##' cannot appear at start of __VA_OPT__ argument
#define H1(X, ...) X __VA_OPT__(##) __VA_ARGS__ // error: ## may not appear at
                                ^
p456.cpp:72:2: error: expected ';' after top level declarator
}
 ^
 ;
2 warnings and 17 errors generated.

$ g++ p456.cpp -std=c++03 -o p456g -I. -Wall
In file included from /usr/local/include/c++/12.1.0/atomic:38,
                 from p456.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 \
      |  ^~~~~
p456.cpp:43: warning: "F" redefined
   43 |        #define F(...)           f(0 __VA_OPT__(,) __VA_ARGS__)
      | 
p456.cpp:28: note: this is the location of the previous definition
   28 | #define F(R, X, ...) __VA_OPT__(G R X) )
      | 
p456.cpp:44: warning: "G" redefined
   44 |        #define G(X, ...)        f(0, X __VA_OPT__(,) __VA_ARGS__)
      | 
p456.cpp:27: note: this is the location of the previous definition
   27 | #define G(Q) 42
      | 
p456.cpp:60:33: error: '##' cannot appear at either end of __VA_OPT__
   60 | #define H1(X, ...) X __VA_OPT__(##) __VA_ARGS__ // error: ## may not appear at
      |                                 ^~
p456.cpp:60:37: warning: __VA_ARGS__ can only appear in the expansion of a C++11 variadic macro
   60 | #define H1(X, ...) X __VA_OPT__(##) __VA_ARGS__ // error: ## may not appear at
      |                                     ^
p456.cpp:31:27: error: expected constructor, destructor, or type conversion before '(' token
   31 | #define debug(...) fprintf(stderr, __VA_ARGS__)
      |                           ^
p456.cpp:34:1: note: in expansion of macro 'debug'
   34 | debug("X = %d\n", x);
      | ^~~~~
p456.cpp:32:27: error: expected constructor, destructor, or type conversion before '(' token
   32 | #define showlist(...) puts(#__VA_ARGS__)
      |                           ^
p456.cpp:35:1: note: in expansion of macro 'showlist'
   35 | showlist(The first, second, and third items.);
      | ^~~~~~~~
p456.cpp:36:9: error: expected ')' before '>' token
   36 | report(x>y, "x is %d but y is %d", x, y);
      |         ^
p456.cpp:33:29: note: in definition of macro 'report'
   33 | #define report(test, ...) ((test) ? puts(#test) : printf(__VA_ARGS__)) debug("Flag");
      |                             ^~~~
p456.cpp:33:28: note: to match this '('
   33 | #define report(test, ...) ((test) ? puts(#test) : printf(__VA_ARGS__)) debug("Flag");
      |                            ^
p456.cpp:36:1: note: in expansion of macro 'report'
   36 | report(x>y, "x is %d but y is %d", x, y);
      | ^~~~~~
p456.cpp:36:9: error: expected ')' before '>' token
   36 | report(x>y, "x is %d but y is %d", x, y);
      |         ^
p456.cpp:33:29: note: in definition of macro 'report'
   33 | #define report(test, ...) ((test) ? puts(#test) : printf(__VA_ARGS__)) debug("Flag");
      |                             ^~~~
p456.cpp:33:27: note: to match this '('
   33 | #define report(test, ...) ((test) ? puts(#test) : printf(__VA_ARGS__)) debug("Flag");
      |                           ^
p456.cpp:36:1: note: in expansion of macro 'report'
   36 | report(x>y, "x is %d but y is %d", x, y);
      | ^~~~~~
p456.cpp:38:15: error: expected constructor, destructor, or type conversion before '(' token
   38 |        fprintf(stderr, "Flag");
      |               ^
p456.cpp:39:15: error: expected constructor, destructor, or type conversion before '(' token
   39 |        fprintf(stderr, "X = %d\n", x);
      |               ^
p456.cpp:40:12: error: expected constructor, destructor, or type conversion before '(' token
   40 |        puts("The first, second, and third items.");
      |            ^
p456.cpp:41:11: error: expected ')' before '>' token
   41 |        ((x>y) ? puts("x>y") : printf("x is %d but y is %d", x, y));
      |         ~ ^
      |           )
p456.cpp:41:11: error: expected ')' before '>' token
   41 |        ((x>y) ? puts("x>y") : printf("x is %d but y is %d", x, y));
      |        ~  ^
      |           )
p456.cpp:47:5: error: redefinition of 'int x'
   47 | int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
      |     ^
p456.cpp:29:5: note: 'int x' previously defined here
   29 | int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
      |     ^
p456.cpp:47:19: error: expected primary-expression before ',' token
   47 | int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
      |                   ^
p456.cpp:43:51: note: in definition of macro 'F'
   43 |        #define F(...)           f(0 __VA_OPT__(,) __VA_ARGS__)
      |                                                   ^~~~~~~~~~~
p456.cpp:47:26: error: expected identifier before '-' token
   47 | int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
      |                          ^
p456.cpp:43:51: note: in definition of macro 'F'
   43 |        #define F(...)           f(0 __VA_OPT__(,) __VA_ARGS__)
      |                                                   ^~~~~~~~~~~
p456.cpp:47:28: error: expected ']' before ';' token
   47 | int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
      |                            ^
p456.cpp: In lambda function:
p456.cpp:47:28: error: expected '{' before ';' token
p456.cpp: At global scope:
p456.cpp:47:28: warning: lambda expressions only available with '-std=c++11' or '-std=gnu++11' [-Wc++11-extensions]
p456.cpp:47:28: error: expected ')' before ';' token
p456.cpp:26:18: note: to match this '('
   26 | #define LPAREN() (
      |                  ^
p456.cpp:43:51: note: in definition of macro 'F'
   43 |        #define F(...)           f(0 __VA_OPT__(,) __VA_ARGS__)
      |                                                   ^~~~~~~~~~~
p456.cpp:47:11: note: in expansion of macro 'LPAREN'
   47 | int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
      |           ^~~~~~
p456.cpp:43:34: error: expected constructor, destructor, or type conversion before '(' token
   43 |        #define F(...)           f(0 __VA_OPT__(,) __VA_ARGS__)
      |                                  ^
p456.cpp:48:1: note: in expansion of macro 'F'
   48 | F(a, b, c)
      | ^
p456.cpp:45:33: error: 'S' does not name a type
   45 |        #define SDEF(sname, ...) S sname __VA_OPT__(= { __VA_ARGS__ })
      |                                 ^
p456.cpp:55:1: note: in expansion of macro 'SDEF'
   55 | SDEF(bar, 1, 2);
      | ^~~~
p456.cpp:66:16: error: 'ab' does not name a type
   66 | #define H5B(X) a ## X ## b
      |                ^
p456.cpp:67:16: note: in expansion of macro 'H5B'
   67 | #define H5C(X) H5B(X)
      |                ^~~
p456.cpp:68:1: note: in expansion of macro 'H5C'
   68 | H5C(H5A()) // replaced by ab
      | ^~~
rm: cannot remove 'p456g': No such file or directory

$ g++ p456.cpp -std=c++2b -o p456g -I. -Wall
p456.cpp:43: warning: "F" redefined
   43 |        #define F(...)           f(0 __VA_OPT__(,) __VA_ARGS__)
      | 
p456.cpp:28: note: this is the location of the previous definition
   28 | #define F(R, X, ...) __VA_OPT__(G R X) )
      | 
p456.cpp:44: warning: "G" redefined
   44 |        #define G(X, ...)        f(0, X __VA_OPT__(,) __VA_ARGS__)
      | 
p456.cpp:27: note: this is the location of the previous definition
   27 | #define G(Q) 42
      | 
p456.cpp:60:33: error: '##' cannot appear at either end of __VA_OPT__
   60 | #define H1(X, ...) X __VA_OPT__(##) __VA_ARGS__ // error: ## may not appear at
      |                                 ^~
p456.cpp:60:37: warning: __VA_ARGS__ can only appear in the expansion of a C++11 variadic macro
   60 | #define H1(X, ...) X __VA_OPT__(##) __VA_ARGS__ // error: ## may not appear at
      |                                     ^
p456.cpp:31:27: error: expected constructor, destructor, or type conversion before '(' token
   31 | #define debug(...) fprintf(stderr, __VA_ARGS__)
      |                           ^
p456.cpp:34:1: note: in expansion of macro 'debug'
   34 | debug("X = %d\n", x);
      | ^~~~~
p456.cpp:32:27: error: expected constructor, destructor, or type conversion before '(' token
   32 | #define showlist(...) puts(#__VA_ARGS__)
      |                           ^
p456.cpp:35:1: note: in expansion of macro 'showlist'
   35 | showlist(The first, second, and third items.);
      | ^~~~~~~~
p456.cpp:36:9: error: expected ')' before '>' token
   36 | report(x>y, "x is %d but y is %d", x, y);
      |         ^
p456.cpp:33:29: note: in definition of macro 'report'
   33 | #define report(test, ...) ((test) ? puts(#test) : printf(__VA_ARGS__)) debug("Flag");
      |                             ^~~~
p456.cpp:33:28: note: to match this '('
   33 | #define report(test, ...) ((test) ? puts(#test) : printf(__VA_ARGS__)) debug("Flag");
      |                            ^
p456.cpp:36:1: note: in expansion of macro 'report'
   36 | report(x>y, "x is %d but y is %d", x, y);
      | ^~~~~~
p456.cpp:36:9: error: expected ')' before '>' token
   36 | report(x>y, "x is %d but y is %d", x, y);
      |         ^
p456.cpp:33:29: note: in definition of macro 'report'
   33 | #define report(test, ...) ((test) ? puts(#test) : printf(__VA_ARGS__)) debug("Flag");
      |                             ^~~~
p456.cpp:33:27: note: to match this '('
   33 | #define report(test, ...) ((test) ? puts(#test) : printf(__VA_ARGS__)) debug("Flag");
      |                           ^
p456.cpp:36:1: note: in expansion of macro 'report'
   36 | report(x>y, "x is %d but y is %d", x, y);
      | ^~~~~~
p456.cpp:38:15: error: expected constructor, destructor, or type conversion before '(' token
   38 |        fprintf(stderr, "Flag");
      |               ^
p456.cpp:39:15: error: expected constructor, destructor, or type conversion before '(' token
   39 |        fprintf(stderr, "X = %d\n", x);
      |               ^
p456.cpp:40:12: error: expected constructor, destructor, or type conversion before '(' token
   40 |        puts("The first, second, and third items.");
      |            ^
p456.cpp:41:11: error: expected ')' before '>' token
   41 |        ((x>y) ? puts("x>y") : printf("x is %d but y is %d", x, y));
      |         ~ ^
      |           )
p456.cpp:41:11: error: expected ')' before '>' token
   41 |        ((x>y) ? puts("x>y") : printf("x is %d but y is %d", x, y));
      |        ~  ^
      |           )
p456.cpp:47:5: error: redefinition of 'int x'
   47 | int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
      |     ^
p456.cpp:29:5: note: 'int x' previously defined here
   29 | int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
      |     ^
p456.cpp:47:19: error: expected primary-expression before ',' token
   47 | int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
      |                   ^
p456.cpp:43:51: note: in definition of macro 'F'
   43 |        #define F(...)           f(0 __VA_OPT__(,) __VA_ARGS__)
      |                                                   ^~~~~~~~~~~
p456.cpp:47:26: error: expected identifier before '-' token
   47 | int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
      |                          ^
p456.cpp:43:51: note: in definition of macro 'F'
   43 |        #define F(...)           f(0 __VA_OPT__(,) __VA_ARGS__)
      |                                                   ^~~~~~~~~~~
p456.cpp:47:28: error: expected ']' before ';' token
   47 | int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
      |                            ^
p456.cpp: In lambda function:
p456.cpp:47:28: error: expected '{' before ';' token
p456.cpp: At global scope:
p456.cpp:47:28: error: expected ')' before ';' token
p456.cpp:26:18: note: to match this '('
   26 | #define LPAREN() (
      |                  ^
p456.cpp:43:51: note: in definition of macro 'F'
   43 |        #define F(...)           f(0 __VA_OPT__(,) __VA_ARGS__)
      |                                                   ^~~~~~~~~~~
p456.cpp:47:11: note: in expansion of macro 'LPAREN'
   47 | int x = F(LPAREN(), 0, <:-); // replaced by int x = 42;
      |           ^~~~~~
p456.cpp:43:34: error: expected constructor, destructor, or type conversion before '(' token
   43 |        #define F(...)           f(0 __VA_OPT__(,) __VA_ARGS__)
      |                                  ^
p456.cpp:48:1: note: in expansion of macro 'F'
   48 | F(a, b, c)
      | ^
p456.cpp:45:33: error: 'S' does not name a type
   45 |        #define SDEF(sname, ...) S sname __VA_OPT__(= { __VA_ARGS__ })
      |                                 ^
p456.cpp:55:1: note: in expansion of macro 'SDEF'
   55 | SDEF(bar, 1, 2);
      | ^~~~
p456.cpp:66:16: error: 'ab' does not name a type
   66 | #define H5B(X) a ## X ## b
      |                ^
p456.cpp:67:16: note: in expansion of macro 'H5B'
   67 | #define H5C(X) H5B(X)
      |                ^~~
p456.cpp:68:1: note: in expansion of macro 'H5C'
   68 | H5C(H5A()) // replaced by ab
      | ^~~

```

## 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。

<!-- リンクエラーの解説をする。clang++とg++の比較。意味のある出力。
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

https://cpprefjp.github.io/

コンパイラの実装状況

https://cpprefjp.github.io/implementation-status.html


typedef は C++11 ではオワコン

https://qiita.com/Linda_pp/items/44a67c64c14cba00eef1

C99からC++14を駆け抜けるC++講座

https://qiita.com/yumetodo/items/e49a673afd9a3ecb81a8

## 自己参照(self reference)

コピペコンパイルエラーあるある

https://qiita.com/kaizen_nagoya/items/29c832de9d762aed2761

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

https://qiita.com/kaizen_nagoya/items/acb9f1a9b5aad6df06bd

dockerにclang

https://qiita.com/kaizen_nagoya/items/8829ffeee397eda50e80

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

https://qiita.com/drafts/059874ea39c4de64c0f7

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

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

https://qiita.com/kaizen_nagoya/items/483246d40f98abff7ded

C++ sample list

https://qiita.com/kaizen_nagoya/items/54ad75b73825b7c04f86


clang++, g++コンパイルエラー方針の違いの例

https://qiita.com/kaizen_nagoya/items/ea6e5009fe126d270a82

astyle 使ってみた

https://qiita.com/kaizen_nagoya/items/3c9a87a781d53a1a23f3

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 <misra_c.h>
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 　20220707