Ceph

This is probably https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80593 so just putting it here as a placeholder.

The CXX compiler identification is GNU 7.0.1

[  3%] Building CXX object CMakeFiles/rocksdb.dir/db/builder.cc.o
In file included from /builddir/build/BUILD/ceph-12.0.1-1912-gc124b05/src/rocksdb/db/write_batch_internal.h:12:0,
                 from /builddir/build/BUILD/ceph-12.0.1-1912-gc124b05/src/rocksdb/db/column_family.h:20,
                 from /builddir/build/BUILD/ceph-12.0.1-1912-gc124b05/src/rocksdb/db/version_set.h:31,
                 from /builddir/build/BUILD/ceph-12.0.1-1912-gc124b05/src/rocksdb/db/compaction.h:11,
                 from /builddir/build/BUILD/ceph-12.0.1-1912-gc124b05/src/rocksdb/db/compaction_iterator.h:14,
                 from /builddir/build/BUILD/ceph-12.0.1-1912-gc124b05/src/rocksdb/db/builder.cc:16:
/builddir/build/BUILD/ceph-12.0.1-1912-gc124b05/src/rocksdb/db/write_thread.h: In member function 'std::mutex& rocksdb::WriteThread::Writer::StateMutex()':
/builddir/build/BUILD/ceph-12.0.1-1912-gc124b05/src/rocksdb/db/write_thread.h:192:78: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
       return *static_cast<std::mutex*>(static_cast<void*>(&state_mutex_bytes));
                                                                              ^
cc1plus: all warnings being treated as errors