GCC is getting smarter and detects that we're not copying the NUL
terminator over.

There are two approaches to fixing the warning:

  - where code is already a bit more complicated, just use `std::string`
    instead of C-style string manipulations; and
  - where we were doing `strncpy(dest, src, strlen(src))`, just use
    `strcpy` instead since the destination sizes are made based on the
    size of `src` anyways.