With JDK-8198445, the hotspot no longer builds with GCC 7.3.0. Oracle was just about to make the switch when this was discovered.

Here are the errors:

In file included from /localhome/hg/jdk-switchgcc/open/src/hotspot/share/oops/access.inline.hpp:35:0,
                 from /localhome/hg/jdk-switchgcc/open/src/hotspot/share/oops/oop.inline.hpp:32,
                 from /localhome/hg/jdk-switchgcc/open/src/hotspot/share/oops/markOop.inline.hpp:30,
                 from /localhome/hg/jdk-switchgcc/open/src/hotspot/share/precompiled/precompiled.hpp:153:
/localhome/hg/jdk-switchgcc/open/src/hotspot/share/oops/accessBackend.inline.hpp: In static member function 'static bool RawAccessBarrier<decorators>::oop_arraycopy(arrayOop, arrayOop, HeapWord*, HeapWord*, size_t)':
/localhome/hg/jdk-switchgcc/open/src/hotspot/share/oops/accessBackend.inline.hpp:129:98: error: no matching function for call to 'RawAccessBarrier<decorators>::arraycopy(narrowOop*, narrowOop*, size_t&)'
     return arraycopy(reinterpret_cast<narrowOop*>(src), reinterpret_cast<narrowOop*>(dst), length);
                                                                                                  ^
In file included from /localhome/hg/jdk-switchgcc/open/src/hotspot/share/gc/shared/barrierSet.hpp:31:0,
                 from /localhome/hg/jdk-switchgcc/open/src/hotspot/share/gc/shared/collectorPolicy.hpp:28,
                 from /localhome/hg/jdk-switchgcc/open/src/hotspot/share/gc/shared/genCollectedHeap.hpp:29,
                 from /localhome/hg/jdk-switchgcc/open/src/hotspot/share/gc/shared/gcLocker.hpp:29,
   ... (rest of output omitted)
* For target hotspot_variant-server_libjvm_objs_precompiled_precompiled.hpp.gch:
In file included from /localhome/hg/jdk-switchgcc/open/src/hotspot/share/oops/access.inline.hpp:35:0,
                 from /localhome/hg/jdk-switchgcc/open/src/hotspot/share/oops/oop.inline.hpp:32,
                 from /localhome/hg/jdk-switchgcc/open/src/hotspot/share/oops/markOop.inline.hpp:30,
                 from /localhome/hg/jdk-switchgcc/open/src/hotspot/share/precompiled/precompiled.hpp:153:
/localhome/hg/jdk-switchgcc/open/src/hotspot/share/oops/accessBackend.inline.hpp: In static member function 'static bool RawAccessBarrier<decorators>::oop_arraycopy(arrayOop, arrayOop, HeapWord*, HeapWord*, size_t)':
/localhome/hg/jdk-switchgcc/open/src/hotspot/share/oops/accessBackend.inline.hpp:129:98: error: no matching function for call to 'RawAccessBarrier<decorators>::arraycopy(narrowOop*, narrowOop*, size_t&)'
     return arraycopy(reinterpret_cast<narrowOop*>(src), reinterpret_cast<narrowOop*>(dst), length);
                                                                                                  ^
In file included from /localhome/hg/jdk-switchgcc/open/src/hotspot/share/gc/shared/barrierSet.hpp:31:0,
                 from /localhome/hg/jdk-switchgcc/open/src/hotspot/share/gc/shared/collectorPolicy.hpp:28,
                 from /localhome/hg/jdk-switchgcc/open/src/hotspot/share/gc/shared/genCollectedHeap.hpp:29,
                 from /localhome/hg/jdk-switchgcc/open/src/hotspot/share/gc/shared/gcLocker.hpp:29,
   ... (rest of output omitted)