**Circular references with static libraries**

Some linkers are one-pass only so to handle circular references between
static libraries, the following feature can be used:

``RESCAN``
  The specified static libraries are searched repeatedly until no
  new undefined references are created. Normally, an static library is searched
  only once in the order that it is specified on the command line. If a symbol
  in that library is needed to resolve an undefined symbol referred to by an
  object in an library that appears later on the command line, the linker would
  not be able to resolve that reference. By grouping the static libraries, they
  all be searched repeatedly until all possible references are resolved (use
  linker options ``--start-group`` and ``--end-group`` or, on ``SunOS``,
  ``-z rescan-start`` and ``-z rescan-end``).

  Using this feature has a significant performance cost. It is best to use it
  only when there are unavoidable circular references between two or more
  static libraries.

  This feature is available on ``Linux``, ``BSD``, and ``SunOS`` target
  platforms as well as ``Windows`` when ``GNU`` toolchain is used.
