Sonar complains there is define/undefine of a global macro WALK_FORWARD_IN_BLOCK_START.

After JDK-8358735, we have this:

#ifdef ASSERT
#define WALK_FORWARD_IN_BLOCK_START true
#else
#define WALK_FORWARD_IN_BLOCK_START false
#endif // ASSERT
  while (WALK_FORWARD_IN_BLOCK_START && p + obj->size() < left) {
    p += obj->size();
    obj = cast_to_oop(p);
    assert(oopDesc::is_oop(obj), "Should be an object");
    assert(Klass::is_valid(obj->klass()), "Not a valid klass ptr");
    // Check assumptions in previous block comment if this assert fires
    guarantee(false, "Should never need forward walk in block start");
  }
#undef WALK_FORWARD_IN_BLOCK_START

But it makes no sense, since we can just wrap the entire while loop with #ifdef ASSERT.