C转义字符问题

今天遇到了一个C语言的问题，以前没注意到：

http://wordaligned.org/articles/octal-literals

Very large Hex value in a String Literal

std::string s = "ABC\x7FDEF";

Here, the "DEF" characters are valid hexadecimal and therefore become part of the number we’re embedding; so we’ve tried to put the hex number 7FDEF into a byte. If we’re lucky our compiler will warn us:

warning: hex escape sequence out of range

If we’re unlucky or if we don’t act on the warning, the result is implementation defined. In any case, it’s certainly not what we wanted. Of course, embedded octal escape sequences suffer from the exact same problem if succeeded by one of the letters "0" - "7".

The workaround is simple:

Hex 7F in a String Literal

std::string s = "ABC\x7F" "DEF";

or even:

Hex 7F in a String Literal

std::string s = "ABC" "\x7F" "DEF";

In other words, even this use of octal values is of limited practical use.

以后要用正确的方式使用8，16进制转义。