G1CollectedHeap::safe_object_iterate uses ContiguousSpace::object_iterate_from which does not avoid dead objects that can still be on the heap when using G1 and no fullgc has happened.

[VM_Operation (0x00007f6dcfd3ae00): G1IncCollectionPause, mode: safepoint, requested by thread 0x00007f6dc800b800]
[VM_Operation (0x00007f6dcfd3b620): G1IncCollectionPause, mode: safepoint, requested by thread 0x00007f6dc800b800]
[VM_Operation (0x00007f6dc4b8ec00): CGC_Operation, mode: safepoint, requested by thread 0x00007f6dc803e800]
[VM_Operation (0x00007f6dc4b8ec00): CGC_Operation, mode: safepoint, requested by thread 0x00007f6dc803e800]
[VM_Operation (0x00007f6dcfd3ae50): G1IncCollectionPause, mode: safepoint, requested by thread 0x00007f6dc800b800]
[VM_Operation (0x00007f6dcfd3b650): G1IncCollectionPause, mode: safepoint, requested by thread 0x00007f6dc800b800]
[VM_Operation (0x00007f6dc4b8ec00): CGC_Operation, mode: safepoint, requested by thread 0x00007f6dc803e800]
[VM_Operation (0x00007f6dc4b8ec00): CGC_Operation, mode: safepoint, requested by thread 0x00007f6dc803e800]
[VM_Operation (0x00007f6dcfd39ae0): HeapDumper, mode: safepoint, requested by thread 0x00007f6dc800b800#
# A fatal error has been detected by the Java Runtime Environment:
#
# SIGSEGV (0xb) at pc=0x00007f6dce0f02fc, pid=3437, tid=140108642043648
#
# JRE version: Java(TM) SE Runtime Environment (7.0_65-b06) (build 1.7.0_65-ea-fastdebug-b06)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (24.65-b01-fastdebug mixed mode linux-amd64 compressed oops)
# Problematic frame:
# V [libjvm.so+0x40d2fc] oopDesc::is_klass() const+0x1c
#
# Core dump written. Default location: /home/aeriksso/cce/bug18490360/core or core.3437
#
# An error report file with more information is saved as:
# /home/aeriksso/cce/bug18490360/hs_err_pid3437.log