Displaying wide chars with printf

Question

I'm trying to understand how does printf work with wide characters (wchar_t).

I've made the following code samples :

Sample 1 :

#include <stdio.h>
#include <stdlib.h>

int     main(void)
{
    wchar_t     *s;

    s = (wchar_t *)malloc(sizeof(wchar_t) * 2);
    s[0] = 42;
    s[1] = 0;
    printf("%ls\n", s);
    free(s);
    return (0);
}

output :

*

Everything is fine here : my character (*) is correctly displayed.

Sample 2 :

I wanted to display an other kind of character. On my system, wchar_t seem encoded on 4 bytes. So I tried to display the following character : É

#include <stdio.h>
#include <stdlib.h>

int     main(void)
{
    wchar_t     *s;

    s = (wchar_t *)malloc(sizeof(wchar_t) * 2);
    s[0] = 0xC389;
    s[1] = 0;
    printf("%ls\n", s);
    free(s);
    return (0);
}

But there is no output this time, I tried with many values from the "encoding" section (cf. previous link) for s[0] (0xC389, 201, 0xC9)... But I never get the É character displayed. I also tried with %S instead of %ls.

If I try to call printf like this : printf("<%ls>\n", s) the only character printed is '<', the display is truncated.

Why do I have this problem? How should I do?

Answer 1

I found a simple way to print wide chars. One key point is setlocale()

#include <stdio.h>
#include <wchar.h>
#include <locale.h>

int main(int argc, char *argv[])
{
    setlocale(LC_ALL, "");
    // setlocale(LC_ALL, "C.UTF-8"); // this also works

    wchar_t hello_eng[] = L"Hello World!";
    wchar_t hello_china[] = L"世界, 你好!";
    wchar_t *hello_japan = L"こんにちは日本!";
    printf("%ls\n", hello_eng);
    printf("%ls\n", hello_china);
    printf("%ls\n", hello_japan);

    return 0;
}