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@kaizen_nagoya(Dr. Kiyoshi Ogawa)

17.3.5.2 numeric_limits members [numeric.limits.members] C++N4910:2022 (275) p505.cpp

Last updated at Posted at 2022-07-09

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.

17.3.5.2 numeric_limits members [numeric.limits.members] C++N4910:2022 (275) p505.cpp

算譜(source code)

p505.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 = "17.3.5.2 numeric_limits members [numeric.limits.members] C++N4910:2022 (275) p505.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
static constexpr T min() noexcept;
static constexpr T max() noexcept;
// Maximum finite value.175
// Meaningful for all specializations in which is_bounded != false.
static constexpr T lowest() noexcept;
// A finite value x such that there is no other finite value y where y < x.176 // Meaningful for all specializations in which is_bounded != false.
static constexpr int digits;
// Number of radix digits that can be represented without change.
// For integer types, the number of non-sign bits in the representation. For floating-point types, the number of radix digits in the mantissa.177
static constexpr int digits10;
// Number of base 10 digits that can be represented without change.178 Meaningful for all specializations in which is_bounded != false.
static constexpr int max_digits10;
// Number of base 10 digits required to ensure that values which differ are always differentiated. Meaningful for all floating-point types.
static constexpr bool is_signed;
// true if the type is signed. Meaningful for all specializations.
static constexpr bool is_integer;
// true if the type is integer. Meaningful for all specializations.
static constexpr bool is_exact;
// true if the type uses an exact representation. All integer types are exact, but not all exact types are integer. For example, rational and fixed-exponent representations are exact but not integer.
// Meaningful for all specializations.
static constexpr int radix;
// For floating-point types, specifies the base or radix of the exponent representation (often 2).179 For integer types, specifies the base of the representation.180
// Meaningful for all specializations.
static constexpr T epsilon() noexcept;
// Machine epsilon: the difference between 1 and the least value greater than 1 that is representable.181 Meaningful for all floating-point types.
static constexpr T round_error() noexcept;
// Measure of the maximum rounding error.182 static constexpr int min_exponent;
// Minimum negative integer such that radix raised to the power of one less than that integer is a normalized floating-point number.183
// Meaningful for all floating-point types.
static constexpr int  min_exponent10;
// Minimum negative integer such that 10 raised to that power is in the range of normalized floating-point numbers.184
// Meaningful for all floating-point types.
static constexpr int  max_exponent;
// Maximum positive integer such that radix raised to the power one less than that integer is a representable finite floating-point number.185
// Meaningful for all floating-point types.
static constexpr int  max_exponent10;
// Maximum positive integer such that 10 raised to that power is in the range of representable finite floating-point numbers.186
// Meaningful for all floating-point types.
static constexpr bool has_infinity;
// true if the type has a representation for positive infinity.
// Meaningful for all floating-point types.
// Shall be true for all specializations in which is_iec559 != false.
static constexpr bool has_quiet_NaN;
// true if the type has a representation for a quiet (non-signaling) “Not a Number”.187 Meaningful for all floating-point types.
// Shall be true for all specializations in which is_iec559 != false.
static constexpr bool has_signaling_NaN;
// true if the type has a representation for a signaling “Not a Number”.188 Meaningful for all floating-point types.
// Shall be true for all specializations in which is_iec559 != false.
static constexpr float_denorm_style has_denorm;
// denorm_present if the type allows subnormal values (variable number of exponent bits),189 denorm_- absent if the type does not allow subnormal values, and denorm_indeterminate if it is indeterminate at compile time whether the type allows subnormal values.
// Meaningful for all floating-point types.
static constexpr bool has_denorm_loss;
// true if loss of accuracy is detected as a denormalization loss, rather than as an inexact result.190
static constexpr T infinity() noexcept;
// Representation of positive infinity, if available.191
// Meaningful for all specializations for which has_infinity != false. Required in specializations for which is_iec559 != false.
static constexpr T quiet_NaN() noexcept;
// Representation of a quiet “Not a Number”, if available.192
// Meaningful for all specializations for which has_quiet_NaN != false. Required in specializations for which is_iec559 != false.
static constexpr T signaling_NaN() noexcept;
// Representation of a signaling “Not a Number”, if available.193
// Meaningful for all specializations for which has_signaling_NaN != false. Required in specializations for which is_iec559 != false.
static constexpr T denorm_min() noexcept;
// Minimum positive subnormal value.194. Meaningful for all floating-point types. In specializations for which has_denorm == false, returns the minimum positive normalized value.
static constexpr bool is_iec559;
// true if and only if the type adheres to ISO/IEC/IEEE 60559.195 Meaningful for all floating-point types.
static constexpr bool is_bounded;
// true if the set of values representable by the type is finite.196 [Note 1: All fundamental types (6.8.2) are bounded. This member would be false for arbitrary precision types. —end note] Meaningful for all specializations.
static constexpr bool is_modulo;
// true if the type is modulo.197 A type is modulo if, for any operation involving +, -, or * on values of that type whose result would fall outside the range [min(), max()], the value returned differs from the true value by an integer multiple of max() - min() + 1. [Example 1: is_modulo is false for signed integer types (6.8.2) unless an implementation, as an extension to this document, defines signed integer overflow to wrap. —end example] Meaningful for all specializations.
static constexpr bool traps;
// true if, at the start of the program, there exists a value of the type that would cause an arithmetic operation using that value to trap.198. Meaningful for all specializations.
static constexpr bool tinyness_before;
// true if tinyness is detected before rounding.199. Meaningful for all floating-point types.
static constexpr float_round_style round_style;
// The rounding style for the type.200. Meaningful for all floating-point types. Specializations for integer types shall return round_toward_-zero.
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
# clang++ p505.cpp -std=c++2b -o p505g -I. -Wall -fpermissive
p505.cpp:26:18: error: unknown type name 'T'
static constexpr T min() noexcept;
                 ^
p505.cpp:27:18: error: unknown type name 'T'
static constexpr T max() noexcept;
                 ^
p505.cpp:30:18: error: unknown type name 'T'
static constexpr T lowest() noexcept;
                 ^
p505.cpp:32:22: error: default initialization of an object of const type 'const int'
static constexpr int digits;
                     ^
                            = 0
p505.cpp:35:22: error: default initialization of an object of const type 'const int'
static constexpr int digits10;
                     ^
                              = 0
p505.cpp:37:22: error: default initialization of an object of const type 'const int'
static constexpr int max_digits10;
                     ^
                                  = 0
p505.cpp:39:26: error: default initialization of an object of const type 'const bool'
   static constexpr bool is_signed;
                         ^
                                   = false
p505.cpp:41:23: error: default initialization of an object of const type 'const bool'
static constexpr bool is_integer;
                      ^
                                 = false
p505.cpp:43:23: error: default initialization of an object of const type 'const bool'
static constexpr bool is_exact;
                      ^
                               = false
p505.cpp:46:22: error: default initialization of an object of const type 'const int'
static constexpr int radix;
                     ^
                           = 0
p505.cpp:49:18: error: unknown type name 'T'
static constexpr T epsilon() noexcept;
                 ^
p505.cpp:51:18: error: unknown type name 'T'
static constexpr T round_error() noexcept;
                 ^
p505.cpp:55:23: error: default initialization of an object of const type 'const int'
static constexpr int  min_exponent10;
                      ^
                                     = 0
p505.cpp:58:23: error: default initialization of an object of const type 'const int'
static constexpr int  max_exponent;
                      ^
                                   = 0
p505.cpp:61:23: error: default initialization of an object of const type 'const int'
static constexpr int  max_exponent10;
                      ^
                                     = 0
p505.cpp:64:23: error: default initialization of an object of const type 'const bool'
static constexpr bool has_infinity;
                      ^
                                   = false
p505.cpp:68:23: error: default initialization of an object of const type 'const bool'
static constexpr bool has_quiet_NaN;
                      ^
                                    = false
p505.cpp:71:23: error: default initialization of an object of const type 'const bool'
static constexpr bool has_signaling_NaN;
                      ^
                                        = false
p505.cpp:74:37: error: default initialization of an object of const type 'const std::float_denorm_style'
static constexpr float_denorm_style has_denorm;
                                    ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.
# g++ p505.cpp -std=c++2b -o p505g -I. -Wall -fpermissive
p505.cpp:26:18: error: 'T' does not name a type
   26 | static constexpr T min() noexcept;
      |                  ^
p505.cpp:27:18: error: 'T' does not name a type
   27 | static constexpr T max() noexcept;
      |                  ^
p505.cpp:30:18: error: 'T' does not name a type
   30 | static constexpr T lowest() noexcept;
      |                  ^
p505.cpp:32:22: warning: uninitialized 'const digits' [-fpermissive]
   32 | static constexpr int digits;
      |                      ^~~~~~
p505.cpp:35:22: warning: uninitialized 'const digits10' [-fpermissive]
   35 | static constexpr int digits10;
      |                      ^~~~~~~~
p505.cpp:37:22: warning: uninitialized 'const max_digits10' [-fpermissive]
   37 | static constexpr int max_digits10;
      |                      ^~~~~~~~~~~~
p505.cpp:39:26: warning: uninitialized 'const is_signed' [-fpermissive]
   39 |    static constexpr bool is_signed;
      |                          ^~~~~~~~~
p505.cpp:41:23: warning: uninitialized 'const is_integer' [-fpermissive]
   41 | static constexpr bool is_integer;
      |                       ^~~~~~~~~~
p505.cpp:43:23: warning: uninitialized 'const is_exact' [-fpermissive]
   43 | static constexpr bool is_exact;
      |                       ^~~~~~~~
p505.cpp:46:22: warning: uninitialized 'const radix' [-fpermissive]
   46 | static constexpr int radix;
      |                      ^~~~~
p505.cpp:49:18: error: 'T' does not name a type
   49 | static constexpr T epsilon() noexcept;
      |                  ^
p505.cpp:51:18: error: 'T' does not name a type
   51 | static constexpr T round_error() noexcept;
      |                  ^
p505.cpp:55:23: warning: uninitialized 'const min_exponent10' [-fpermissive]
   55 | static constexpr int  min_exponent10;
      |                       ^~~~~~~~~~~~~~
p505.cpp:58:23: warning: uninitialized 'const max_exponent' [-fpermissive]
   58 | static constexpr int  max_exponent;
      |                       ^~~~~~~~~~~~
p505.cpp:61:23: warning: uninitialized 'const max_exponent10' [-fpermissive]
   61 | static constexpr int  max_exponent10;
      |                       ^~~~~~~~~~~~~~
p505.cpp:64:23: warning: uninitialized 'const has_infinity' [-fpermissive]
   64 | static constexpr bool has_infinity;
      |                       ^~~~~~~~~~~~
p505.cpp:68:23: warning: uninitialized 'const has_quiet_NaN' [-fpermissive]
   68 | static constexpr bool has_quiet_NaN;
      |                       ^~~~~~~~~~~~~
p505.cpp:71:23: warning: uninitialized 'const has_signaling_NaN' [-fpermissive]
   71 | static constexpr bool has_signaling_NaN;
      |                       ^~~~~~~~~~~~~~~~~
p505.cpp:74:37: warning: uninitialized 'const has_denorm' [-fpermissive]
   74 | static constexpr float_denorm_style has_denorm;
      |                                     ^~~~~~~~~~
p505.cpp:77:23: warning: uninitialized 'const has_denorm_loss' [-fpermissive]
   77 | static constexpr bool has_denorm_loss;
      |                       ^~~~~~~~~~~~~~~
p505.cpp:79:18: error: 'T' does not name a type
   79 | static constexpr T infinity() noexcept;
      |                  ^
p505.cpp:82:18: error: 'T' does not name a type
   82 | static constexpr T quiet_NaN() noexcept;
      |                  ^
p505.cpp:85:18: error: 'T' does not name a type
   85 | static constexpr T signaling_NaN() noexcept;
      |                  ^
p505.cpp:88:18: error: 'T' does not name a type
   88 | static constexpr T denorm_min() noexcept;
      |                  ^
p505.cpp:90:23: warning: uninitialized 'const is_iec559' [-fpermissive]
   90 | static constexpr bool is_iec559;
      |                       ^~~~~~~~~
p505.cpp:92:23: warning: uninitialized 'const is_bounded' [-fpermissive]
   92 | static constexpr bool is_bounded;
      |                       ^~~~~~~~~~
p505.cpp:94:23: warning: uninitialized 'const is_modulo' [-fpermissive]
   94 | static constexpr bool is_modulo;
      |                       ^~~~~~~~~
p505.cpp:96:23: warning: uninitialized 'const traps' [-fpermissive]
   96 | static constexpr bool traps;
      |                       ^~~~~
p505.cpp:98:23: warning: uninitialized 'const tinyness_before' [-fpermissive]
   98 | static constexpr bool tinyness_before;
      |                       ^~~~~~~~~~~~~~~
p505.cpp:100:36: warning: uninitialized 'const round_style' [-fpermissive]
  100 | static constexpr float_round_style round_style;

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。＞

文書履歴(document history)

ver. 0.01 初稿 　20220709

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