The "small string optimization" makes the strings harder to manipulate with `unsafe` code. However, being easy to manipulate with `unsafe` code is in fact a pri

The "small string optimization" makes the strings harder to manipulate with `unsafe` code. However, being easy to manipulate with `unsafe` code is in fact a priority for most std types, so that they are easily understood, extended, rearranged, passed over FFI and then later reconstituted, etc. You can tear apart these types and reassemble them very easily. For many C++ std types, you cannot do this.