I had only a quick look at your stuff, and found this problem:
You should initialize the strings correctly. You have three empty string-pointer with the length of zero, so you can't store any chars in this strings. (Take a look at the manual)

This are ways to initialize strings:
Code:
STRING* debug_string1 = "#99"; //length of 99 chars
STRING* debug_string2;
STRING* debug_string3;

void init_str_startup() {
debug_string2 = str_create("#99");
debug_string3 = str_create("This would be correct!");
}


Hope this helps! wink