Probably there is a header missing and to find it, just search the headers in the original project for "Unsafe_sprintf" and the others. Then you can either use the header as-is or make another version of the header for your use that only contains the parts you need.
Another possibility, if possible, is to replace all occurences of symbols that begin with Unsafe_ with a safe equivalent. I assume, but I cannot be sure, that the reason the prefix Unsafe_ is used is so that occurences of unsafe code can be easily found. It is highly likely that there was/is an intent to replace the unsafe code, so your reuse of the code (depending on how it is reused) is a productive time to do that in the code you are reusing.