GCC optionally uses the MPC library for complex numbers. As per this message, we must hard-require MPC prior to the next release: http://gcc.gnu.org/ml/gcc/2009-05/msg00346.html
-- Summary: GCC must hard-require MPC before release Product: gcc Version: 4.5.0 Status: UNCONFIRMED Severity: blocker Priority: P3 Component: other AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: ghazi at gcc dot gnu dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40302