[CMake] unusual strings

[Micha Renner]

Hello,

what is wrong with this command:

SET(INVALID_PATH_CHAR "\001\002\003\004\005\006\007\010\011\012\013\014
\015\016\017\020\021\022\023\024\025\026\027\030\031\032\033\034\035\036
\037 \177/")

Resulting error: 
syntax error, unexpected cal_ERROR, expecting $end (127), when parsing
string "\001\002\003\004\005\006\007\010\011\012\013\014\015\016\017\020
\021\022\023\024\025\026\027\030\031\032\033\034\035\036\037 \177/"

I do not understand the message.

Michael