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@kaizen_nagoya(Dr. Kiyoshi Ogawa)

13.4.3 Template non-type arguments [temp.arg.nontype]C++N4910:2022 (202) p364.cpp

Last updated at Posted at 2022-07-03

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.

13.4.3 Template non-type arguments [temp.arg.nontype]C++N4910:2022 (202) p364.cpp

算譜(source code)

p364.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 = "13.4.3 Template non-type arguments [temp.arg.nontype]C++N4910:2022 (202) p364.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  
template<const int* pci> struct X { /* ... */ };
int ai[10];
X<ai> xi; // array to pointer and qualification conversions
struct Y { /* ... */ };
template<const Y& b> struct Z { /* ... */ };
Y y;
Z<y> z; // no conversion, but note extra cv-qualification
template<int (&pa)[5]> struct W { /* ... */ }; int b[5];
W<b> w; // no conversion
void f(char);
void f(int);
template<void (*pf)(int)> struct A { /* ... */ }; A<&f> a; // selects f(int) template<auto n> struct B { /* ... */ };
B<5> b1;
B<'a'> b2;
B<2.5> b3;
B<void(0)> b4;
// OK, template parameter type is int
// OK, template parameter type is char
// OK, template parameter type is double
// error: template parameter type cannot be void
// [Example 2:
     template<class T, T p> class X {
       /* ... */
};
X<const char*, "Studebaker"> x; // error: string literal object as template-argument
X<const char*, "Knope" + 1> x2; // error: subobject of string literal object as template-argument const char p[] = "Vivisectionist";
  X<const char*, p> y;
  struct A {
    constexpr A(const char*) {}
};
  X<A, "Pyrophoricity"> z;
// OK
// OK, string-literal is a constructor argument to A
// [Example 3:
template<const int& CRI> struct B { /* ... */ };
B<1> b1; // error: temporary would be required for template argument
int c = 1;
B<c> b2; // OK
struct X { int n; };
struct Y { const int &r; };
template<Y y> struct C { /* ... */ };
C<Y{X{1}.n}> c; // error: subobject of temporary object used to initialize
// reference member of template parameter
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 p364
rm: cannot remove 'p364l': No such file or directory
rm: cannot remove 'p364g': No such file or directory
$ clang++ p364.cpp -std=c++03 -o p364l -I. -Wall
In file included from p364.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 \
 ^
p364.cpp:38:1: error: no template named 'B'
B<5> b1;
^
p364.cpp:39:1: error: no template named 'B'
B<'a'> b2;
^
p364.cpp:40:1: error: no template named 'B'
B<2.5> b3;
^
p364.cpp:41:1: error: no template named 'B'
B<void(0)> b4;
^
p364.cpp:47:6: error: too many template parameters in template redeclaration
     template<class T, T p> class X {
     ^~~~~~~~~~~~~~~~~~~~~~
p364.cpp:26:1: note: previous template declaration is here
template<const int* pci> struct X { /* ... */ };
^~~~~~~~~~~~~~~~~~~~~~~~
p364.cpp:50:9: error: template argument for non-type template parameter must be an expression
X<const char*, "Studebaker"> x; // error: string literal object as template-argument
        ^~~~~
p364.cpp:26:21: note: template parameter is declared here
template<const int* pci> struct X { /* ... */ };
                    ^
p364.cpp:51:24: warning: adding 'int' to a string does not append to the string [-Wstring-plus-int]
X<const char*, "Knope" + 1> x2; // error: subobject of string literal object as template-argument const char p[] = "Vivisectionist";
               ~~~~~~~~^~~
p364.cpp:51:24: note: use array indexing to silence this warning
X<const char*, "Knope" + 1> x2; // error: subobject of string literal object as template-argument const char p[] = "Vivisectionist";
                       ^
               &       [  ]
p364.cpp:51:9: error: template argument for non-type template parameter must be an expression
X<const char*, "Knope" + 1> x2; // error: subobject of string literal object as template-argument const char p[] = "Vivisectionist";
        ^~~~~
p364.cpp:26:21: note: template parameter is declared here
template<const int* pci> struct X { /* ... */ };
                    ^
p364.cpp:52:18: error: use of undeclared identifier 'p'
  X<const char*, p> y;
                 ^
p364.cpp:53:10: error: redefinition of 'A' as different kind of symbol
  struct A {
         ^
p364.cpp:37:34: note: previous definition is here
template<void (*pf)(int)> struct A { /* ... */ }; A<&f> a; // selects f(int) template<auto n> struct B { /* ... */ };
                                 ^
p364.cpp:56:5: error: template argument for non-type template parameter must be an expression
  X<A, "Pyrophoricity"> z;
    ^
p364.cpp:26:21: note: template parameter is declared here
template<const int* pci> struct X { /* ... */ };
                    ^
p364.cpp:61:3: error: non-type template argument does not refer to any declaration
B<1> b1; // error: temporary would be required for template argument
  ^
p364.cpp:60:21: note: template parameter is declared here
template<const int& CRI> struct B { /* ... */ };
                    ^
p364.cpp:63:6: error: redefinition of 'b2'
B<c> b2; // OK
     ^
p364.cpp:39:8: note: previous definition is here
B<'a'> b2;
       ^
p364.cpp:64:8: error: redefinition of 'X' as different kind of symbol
struct X { int n; };
       ^
p364.cpp:26:33: note: previous definition is here
template<const int* pci> struct X { /* ... */ };
                                ^
p364.cpp:65:8: error: redefinition of 'Y'
struct Y { const int &r; };
       ^
p364.cpp:29:8: note: previous definition is here
struct Y { /* ... */ };
       ^
p364.cpp:66:12: error: a non-type template parameter cannot have type 'Y' before C++20
template<Y y> struct C { /* ... */ };
           ^
p364.cpp:67:4: error: expected '>'
C<Y{X{1}.n}> c; // error: subobject of temporary object used to initialize
   ^
p364.cpp:67:2: note: to match this '<'
C<Y{X{1}.n}> c; // error: subobject of temporary object used to initialize
 ^
p364.cpp:67:4: error: expected unqualified-id
C<Y{X{1}.n}> c; // error: subobject of temporary object used to initialize
   ^
p364.cpp:67:12: error: expected unqualified-id
C<Y{X{1}.n}> c; // error: subobject of temporary object used to initialize
           ^
1 warning and 19 errors generated.
rm: cannot remove 'p364l': No such file or directory
$ clang++ p364.cpp -std=c++2b -o p364l -I. -Wall
p364.cpp:38:1: error: no template named 'B'
B<5> b1;
^
p364.cpp:39:1: error: no template named 'B'
B<'a'> b2;
^
p364.cpp:40:1: error: no template named 'B'
B<2.5> b3;
^
p364.cpp:41:1: error: no template named 'B'
B<void(0)> b4;
^
p364.cpp:47:6: error: too many template parameters in template redeclaration
     template<class T, T p> class X {
     ^~~~~~~~~~~~~~~~~~~~~~
p364.cpp:26:1: note: previous template declaration is here
template<const int* pci> struct X { /* ... */ };
^~~~~~~~~~~~~~~~~~~~~~~~
p364.cpp:50:9: error: template argument for non-type template parameter must be an expression
X<const char*, "Studebaker"> x; // error: string literal object as template-argument
        ^~~~~
p364.cpp:26:21: note: template parameter is declared here
template<const int* pci> struct X { /* ... */ };
                    ^
p364.cpp:51:24: warning: adding 'int' to a string does not append to the string [-Wstring-plus-int]
X<const char*, "Knope" + 1> x2; // error: subobject of string literal object as template-argument const char p[] = "Vivisectionist";
               ~~~~~~~~^~~
p364.cpp:51:24: note: use array indexing to silence this warning
X<const char*, "Knope" + 1> x2; // error: subobject of string literal object as template-argument const char p[] = "Vivisectionist";
                       ^
               &       [  ]
p364.cpp:51:9: error: template argument for non-type template parameter must be an expression
X<const char*, "Knope" + 1> x2; // error: subobject of string literal object as template-argument const char p[] = "Vivisectionist";
        ^~~~~
p364.cpp:26:21: note: template parameter is declared here
template<const int* pci> struct X { /* ... */ };
                    ^
p364.cpp:52:18: error: use of undeclared identifier 'p'
  X<const char*, p> y;
                 ^
p364.cpp:53:10: error: redefinition of 'A' as different kind of symbol
  struct A {
         ^
p364.cpp:37:34: note: previous definition is here
template<void (*pf)(int)> struct A { /* ... */ }; A<&f> a; // selects f(int) template<auto n> struct B { /* ... */ };
                                 ^
p364.cpp:56:5: error: template argument for non-type template parameter must be an expression
  X<A, "Pyrophoricity"> z;
    ^
p364.cpp:26:21: note: template parameter is declared here
template<const int* pci> struct X { /* ... */ };
                    ^
p364.cpp:61:3: error: conversion from 'int' to 'const int &' in converted constant expression would bind reference to a temporary
B<1> b1; // error: temporary would be required for template argument
  ^
p364.cpp:63:6: error: redefinition of 'b2'
B<c> b2; // OK
     ^
p364.cpp:39:8: note: previous definition is here
B<'a'> b2;
       ^
p364.cpp:64:8: error: redefinition of 'X' as different kind of symbol
struct X { int n; };
       ^
p364.cpp:26:33: note: previous definition is here
template<const int* pci> struct X { /* ... */ };
                                ^
p364.cpp:65:8: error: redefinition of 'Y'
struct Y { const int &r; };
       ^
p364.cpp:29:8: note: previous definition is here
struct Y { /* ... */ };
       ^
p364.cpp:67:5: error: no viable constructor or deduction guide for deduction of template arguments of 'X'
C<Y{X{1}.n}> c; // error: subobject of temporary object used to initialize
    ^
p364.cpp:26:33: note: candidate template ignored: could not match 'X<pci>' against 'int'
template<const int* pci> struct X { /* ... */ };
                                ^
p364.cpp:26:33: note: candidate function template not viable: requires 0 arguments, but 1 was provided
1 warning and 15 errors generated.

$ g++ p364.cpp -std=c++03 -o p364g -I. -Wall
In file included from /usr/local/include/c++/12.1.0/atomic:38,
                 from p364.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 \
      |  ^~~~~
p364.cpp:54:5: warning: identifier 'constexpr' is a keyword in C++11 [-Wc++11-compat]
   54 |     constexpr A(const char*) {}
      |     ^~~~~~~~~
p364.cpp:38:1: error: 'B' does not name a type
   38 | B<5> b1;
      | ^
p364.cpp:39:1: error: 'B' does not name a type
   39 | B<'a'> b2;
      | ^
p364.cpp:40:1: error: 'B' does not name a type
   40 | B<2.5> b3;
      | ^
p364.cpp:41:1: error: 'B' does not name a type
   41 | B<void(0)> b4;
      | ^
p364.cpp:47:35: error: redeclared with 2 template parameters
   47 |      template<class T, T p> class X {
      |                                   ^
p364.cpp:26:33: note: previous declaration 'template<const int* pci> struct X' used 1 template parameter
   26 | template<const int* pci> struct X { /* ... */ };
      |                                 ^
p364.cpp:50:28: error: wrong number of template arguments (2, should be 1)
   50 | X<const char*, "Studebaker"> x; // error: string literal object as template-argument
      |                            ^
p364.cpp:26:33: note: provided for 'template<const int* pci> struct X'
   26 | template<const int* pci> struct X { /* ... */ };
      |                                 ^
p364.cpp:51:27: error: wrong number of template arguments (2, should be 1)
   51 | X<const char*, "Knope" + 1> x2; // error: subobject of string literal object as template-argument const char p[] = "Vivisectionist";
      |                           ^
p364.cpp:26:33: note: provided for 'template<const int* pci> struct X'
   26 | template<const int* pci> struct X { /* ... */ };
      |                                 ^
p364.cpp:52:18: error: 'p' was not declared in this scope
   52 |   X<const char*, p> y;
      |                  ^
p364.cpp:52:19: error: wrong number of template arguments (2, should be 1)
   52 |   X<const char*, p> y;
      |                   ^
p364.cpp:26:33: note: provided for 'template<const int* pci> struct X'
   26 | template<const int* pci> struct X { /* ... */ };
      |                                 ^
p364.cpp:52:21: error: conflicting declaration 'int y'
   52 |   X<const char*, p> y;
      |                     ^
p364.cpp:31:3: note: previous declaration as 'Y y'
   31 | Y y;
      |   ^
p364.cpp:53:10: error: class template 'A' redeclared as non-template
   53 |   struct A {
      |          ^
p364.cpp:37:34: note: previous declaration here
   37 | template<void (*pf)(int)> struct A { /* ... */ }; A<&f> a; // selects f(int) template<auto n> struct B { /* ... */ };
      |                                  ^
p364.cpp:56:23: error: wrong number of template arguments (2, should be 1)
   56 |   X<A, "Pyrophoricity"> z;
      |                       ^
p364.cpp:26:33: note: provided for 'template<const int* pci> struct X'
   26 | template<const int* pci> struct X { /* ... */ };
      |                                 ^
p364.cpp:56:25: error: conflicting declaration 'int z'
   56 |   X<A, "Pyrophoricity"> z;
      |                         ^
p364.cpp:32:6: note: previous declaration as 'Z<((const Y&)(& y))> z'
   32 | Z<y> z; // no conversion, but note extra cv-qualification
      |      ^
p364.cpp:61:4: error: '1' is not a valid template argument for type 'const int&' because it is not an lvalue
   61 | B<1> b1; // error: temporary would be required for template argument
      |    ^
p364.cpp:64:8: error: class template 'X' redeclared as non-template
   64 | struct X { int n; };
      |        ^
p364.cpp:26:33: note: previous declaration here
   26 | template<const int* pci> struct X { /* ... */ };
      |                                 ^
p364.cpp:65:8: error: redefinition of 'struct Y'
   65 | struct Y { const int &r; };
      |        ^
p364.cpp:29:8: note: previous definition of 'struct Y'
   29 | struct Y { /* ... */ };
      |        ^
p364.cpp:66:12: error: non-type template parameters of class type only available with '-std=c++20' or '-std=gnu++20'
   66 | template<Y y> struct C { /* ... */ };
      |            ^
p364.cpp:67:4: warning: extended initializer lists only available with '-std=c++11' or '-std=gnu++11' [-Wc++11-extensions]
   67 | C<Y{X{1}.n}> c; // error: subobject of temporary object used to initialize
      |    ^
p364.cpp:67:3: error: template argument 1 is invalid
   67 | C<Y{X{1}.n}> c; // error: subobject of temporary object used to initialize
      |   ^
p364.cpp:67:4: error: expected unqualified-id before '{' token
   67 | C<Y{X{1}.n}> c; // error: subobject of temporary object used to initialize
      |    ^
p364.cpp:67:12: error: expected unqualified-id before '>' token
   67 | C<Y{X{1}.n}> c; // error: subobject of temporary object used to initialize
      |            ^
rm: cannot remove 'p364g': No such file or directory

$ g++ p364.cpp -std=c++2b -o p364g -I. -Wall
p364.cpp:38:1: error: 'B' does not name a type
   38 | B<5> b1;
      | ^
p364.cpp:39:1: error: 'B' does not name a type
   39 | B<'a'> b2;
      | ^
p364.cpp:40:1: error: 'B' does not name a type
   40 | B<2.5> b3;
      | ^
p364.cpp:41:1: error: 'B' does not name a type
   41 | B<void(0)> b4;
      | ^
p364.cpp:47:35: error: redeclared with 2 template parameters
   47 |      template<class T, T p> class X {
      |                                   ^
p364.cpp:26:33: note: previous declaration 'template<const int* pci> struct X' used 1 template parameter
   26 | template<const int* pci> struct X { /* ... */ };
      |                                 ^
p364.cpp:50:28: error: wrong number of template arguments (2, should be 1)
   50 | X<const char*, "Studebaker"> x; // error: string literal object as template-argument
      |                            ^
p364.cpp:26:33: note: provided for 'template<const int* pci> struct X'
   26 | template<const int* pci> struct X { /* ... */ };
      |                                 ^
p364.cpp:51:27: error: wrong number of template arguments (2, should be 1)
   51 | X<const char*, "Knope" + 1> x2; // error: subobject of string literal object as template-argument const char p[] = "Vivisectionist";
      |                           ^
p364.cpp:26:33: note: provided for 'template<const int* pci> struct X'
   26 | template<const int* pci> struct X { /* ... */ };
      |                                 ^
p364.cpp:52:18: error: 'p' was not declared in this scope
   52 |   X<const char*, p> y;
      |                  ^
p364.cpp:52:19: error: wrong number of template arguments (2, should be 1)
   52 |   X<const char*, p> y;
      |                   ^
p364.cpp:26:33: note: provided for 'template<const int* pci> struct X'
   26 | template<const int* pci> struct X { /* ... */ };
      |                                 ^
p364.cpp:52:21: error: conflicting declaration 'int y'
   52 |   X<const char*, p> y;
      |                     ^
p364.cpp:31:3: note: previous declaration as 'Y y'
   31 | Y y;
      |   ^
p364.cpp:53:10: error: class template 'A' redeclared as non-template
   53 |   struct A {
      |          ^
p364.cpp:37:34: note: previous declaration here
   37 | template<void (*pf)(int)> struct A { /* ... */ }; A<&f> a; // selects f(int) template<auto n> struct B { /* ... */ };
      |                                  ^
p364.cpp:56:23: error: wrong number of template arguments (2, should be 1)
   56 |   X<A, "Pyrophoricity"> z;
      |                       ^
p364.cpp:26:33: note: provided for 'template<const int* pci> struct X'
   26 | template<const int* pci> struct X { /* ... */ };
      |                                 ^
p364.cpp:56:25: error: conflicting declaration 'int z'
   56 |   X<A, "Pyrophoricity"> z;
      |                         ^
p364.cpp:32:6: note: previous declaration as 'Z<((const Y&)(& y))> z'
   32 | Z<y> z; // no conversion, but note extra cv-qualification
      |      ^
p364.cpp:61:4: error: initializing 'const int&' with 'int' in converted constant expression does not bind directly
   61 | B<1> b1; // error: temporary would be required for template argument
      |    ^
p364.cpp:61:4: error: could not convert '1' from 'int' to 'const int&'
   61 | B<1> b1; // error: temporary would be required for template argument
      |    ^
      |    |
      |    int
p364.cpp:64:8: error: class template 'X' redeclared as non-template
   64 | struct X { int n; };
      |        ^
p364.cpp:26:33: note: previous declaration here
   26 | template<const int* pci> struct X { /* ... */ };
      |                                 ^
p364.cpp:65:8: error: redefinition of 'struct Y'
   65 | struct Y { const int &r; };
      |        ^
p364.cpp:29:8: note: previous definition of 'struct Y'
   29 | struct Y { /* ... */ };
      |        ^
p364.cpp:67:8: error: invalid use of placeholder 'X<...auto...>'
   67 | C<Y{X{1}.n}> c; // error: subobject of temporary object used to initialize
      |        ^
p364.cpp:67:12: error: template argument 1 is invalid
   67 | C<Y{X{1}.n}> c; // error: subobject of temporary object used to initialize
      |            ^
p364.cpp:67:14: error: redefinition of 'int c'
   67 | C<Y{X{1}.n}> c; // error: subobject of temporary object used to initialize
      |              ^
p364.cpp:62:5: note: 'int c' previously defined here
   62 | int c = 1;
      |     ^

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。

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)

コピペコンパイルエラーあるある

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。＞

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