Compiler Warning (level 1) C4539
'char': a universal-character-name specifies an invalid character
A character was specified out of Unicode range.
The character must be in the Unicode range, or be a valid surropate pair.
Example
The following sample generates C4539
// C4539.cpp
// compile with: /W1
int main() {
char \U12345678 = 'x'; // C4539
char \u2134 = 'x'; // OK 16-bit Unicode char
char \UD808DF45 = 'x'; // OK 32-bit Unicode value
}