src/hotspot/share/gc/shenandoah/shenandoahObjArrayAllocator.cpp

@@ -69,11 +69,14 @@
    region->record_pin();
  
    // Always initialize the mem with primitive array first so GC won't look into the elements in the array.
    // For obj array, the header will be corrected to object array after clearing the memory.
    Klass* filling_klass = _klass;
-   const bool is_ref_type = is_reference_type(element_type);
+ 
+   // Flat arrays containing oops are not supported and only contain primitives
+   // from here on out.
+   const bool is_ref_type = (element_type != T_FLAT_ELEMENT) && is_reference_type(element_type);
  
    if (is_ref_type) {
      filling_klass = LP64_ONLY(UseCompressedOops ? Universe::intArrayKlass() : Universe::longArrayKlass()) NOT_LP64(Universe::intArrayKlass());
      assert(type2aelembytes(ArrayKlass::cast(filling_klass)->element_type()) == type2aelembytes(element_type), "filling element size must match ref size");
    }