[character set 8] char8_ t、char16_ t、char32_ t、wchar、char

One 、vs How the compiler supports C++20 standard

Reference resources ：

Two 、 brief introduction

• char :
  c++ Keywords in , Occupy 1 Bytes .

• wchar_t
  https://www.educba.com/c-plus-plus-wchar_t/

• char16_t、char32_t
  https://en.cppreference.com/w/c/string/multibyte/char16_t

• char8_t：c++20 New keywords added to the standard .
  https://open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0482r6.html

3、 ... and 、demo

#include <iostream>
using namespace std;
int main()
{
    
    //char* loc = setlocale(LC_ALL,".65001");

    char ch[] = " I ";
    char8_t ch8[] = u8" I ";
    wchar_t wch[] = L" I ";
    char16_t ch16[] = u" I ";
    char32_t ch32[] = U" I ";

    cout << &ch<<endl;
    cout << &ch8 << endl;
    cout << &wch << endl;
    cout << &ch16 << endl;
    cout << &ch32 << endl<<endl;

    /*cout << ch << endl; wcout << wch << endl;*/
    printf("ch:%#x", ch[0]); printf("%#x", ch[1]); printf("%#x", ch[2]); printf("%#x", ch[3]);
    printf("\n");

    printf("ch8:%#x", ch[0]); printf("%#x", ch8[1]); printf("%#x", ch8[2]); printf("%#x", ch8[3]);
    printf("\n");

    printf("wch:%#x", wch[0]);
    printf("\n");

    printf("ch16:%#x", ch16[0]);
    printf("\n");

    printf("ch32:%#x", ch32[0]);
    printf("\n");
}

Output ：

00B7F83C
00B7F830
00B7F824
00B7F818
00B7F808
ch:0xffffffe60xffffff880xffffff910
ch8:0xffffffe60x880x910
wch:0x6211
ch16:0x6211
ch32:0x6211

utf-8 Is one Chinese character three bytes long ？

Four 、 analysis

• char and char8_t The number stored in is ：e6 88 91. Represents my character code of Chinese characters , Three bytes , Refer to Character set vs Character encoding . Install the calculation method in the article , After conversion, it is also equal to 62 11.
• wchar_t、char16_t、char_32t The number stored in is ：62 11. among 6211 by Unicode Chinese characters ” I " Character encoding of ; See What are the wide character codes and multi byte codes of Chinese characters

5、 ... and 、c++20 standard ：char8_t Can't output

Recap
char8_t can not hold a full range of utf-8 glyphs. utf-8 glyphs can be up to 4 bytes. char8_t holds up to 1 byte.
char8_t stream out is expressly forbidden in C++20
for utf-8 compatibility while in VStudio use char and the /utf-8 switch
in case you really want C++20 way of transforming to/from char8_t, you need to use … AFAIK not yet fully implemented in any of the 3, as required by the standard

See ：C++20 char8_t, the Boson