/Zc:u8EscapeEncoding (numeric escape sequence encoding in u8 strings)

Keep the value of numeric escape sequences in u8 string literals without encoding them as utf-8.

Use this switch to increase cross compatibility or when a non-utf-8 character is embedded in an utf-8 string literal.

Syntax

/Zc:u8EscapeEncoding[-]

Remarks

In C++, u8 string literals are utf-8 encoded sequences of char8_t. This flag changes the way numeric escape sequences are interpreted in u8 string literals. The behavior under /Zc:u8EscapeEncoding is to encode them in the string as a single 8-bit char8_t value. The behavior under /Zc:u8EscapeEncoding- is to interpret the value as a unicode code point. When the value is a higher code point in Unicode, it's encoded as a multibyte character. The behavior of universal-character sequences is always to encode them as utf-8 independent of /Zc:u8EscapeEncoding[-].

The following example contains both a hex escape sequence \x and a universal escape sequence \u. /Zc:u8EscapeEncoding[-] affects the encoding of the hex escape sequence, but the universal escape sequence is always encoded as utf-8. The example string also includes the space character, which is encoded as 0x20 in utf-8.

#include <cstdio>
int main()
{
    const char8_t str[] = u8" \x00ff \u00ff ";
    for(char8_t c : str) {
        printf("0x%X ", c);
    }
    return 0;
}

Under /Zc:u8EscapeEncoding, the escape sequence \x00ff is encoded as 0xFF and the universal-character sequence \u00ff is encoded as the utf-8 sequence 0xC3 0xBF. The code example outputs:

0x20 0xFF 0x20 0xC3 0xBF 0x20 0x0

Under /Zc:u8EscapeEncoding-, the values of both \x00ff and \u00ff are re-encoded as the utf-8 sequence 0xC3 0xBF. The code example outputs:

0x20 0xC3 0xBF 0x20 0xC3 0xBF 0x20 0x0

See also

/Zc (Conformance)