[HALtheWise]

It sounds like one function in libmodem accepts a pointer to a configuration struct, then stores that pointer (or an interior pointer from within it), which is then later used by another libmodem function later. If all of libmodem were written in Rust, this could be done without any use of unsafe, but it would require the lifetime on the original "reference" to provably outlive the second function getting called, probably by being static.