A symbol that was not defined was used with a preprocessordirective.
未定义的符号与预处理器指令一起使用。
2
That is, a variable name should not be passed to a preprocessordirective and a symbol can only be evaluated by a preprocessordirective.
即,不应将变量名传递到预处理器指令,并且只能用预处理器指令计算符号。
3
This point in the source file is usually marked by a lexeme that is not consumed as a token by the preprocessor, meaning one that is not a preprocessordirective.