c - Why does wcwidth return -1 with a sign that I can print on the terminal?

Question

Why does here wcwidth return "-1" (not a printable wide character) width "Ԥ" (0x0524)?

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

int wcwidth(wchar_t wc);

int main()
{
    setlocale(LC_CTYPE, "");

    wchar_t wc1 = L'合'; // 0x5408
    int width1 = wcwidth(wc1);
    printf("%lc - print width: %i\n", wc1, width1);

    wchar_t wc2 = L'Ԥ'; // 0x0524
    int width2 = wcwidth(wc2);
    printf("%lc - print width: %i\n", wc2, width2);

    return 0;
}

Output:

合 - print width: 2
Ԥ - print width: -1

Answer 1

创建 libc 字符数据库时，很可能 U+0524 不是有效字符。它是在 Unicode 5.2 中添加的。您的字体可能已经包含该字符，但wcwidth不会查看使用的是哪种字体。