view src/share/vm/gc/shared/collectedHeap.cpp @ 8649:d51e38f88f9f

8129573: CollectedHeap::fill_with_objects() needs to use multiple arrays in 32 bit mode too Summary: In JDK-8042668 we introduced a custom fill threshold for G1. This leads to CollectedHeap::fill_with_objects create too large objects in G1 when using it in 32 bit mode, as the code to create multiple filler objects is IFDEF'ed out on 32 bit. Enable this code on 32 bit too. Reviewed-by: tonyp, mgerdin, tbenson
author tschatzl
date Thu, 25 Jun 2015 09:06:35 +0200
parents 678e64c3211a
children 1ca70c12a335
line wrap: on
line source
/*
 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "precompiled.hpp"
#include "classfile/systemDictionary.hpp"
#include "gc/shared/allocTracer.hpp"
#include "gc/shared/barrierSet.inline.hpp"
#include "gc/shared/collectedHeap.hpp"
#include "gc/shared/collectedHeap.inline.hpp"
#include "gc/shared/gcHeapSummary.hpp"
#include "gc/shared/gcTrace.hpp"
#include "gc/shared/gcTraceTime.hpp"
#include "gc/shared/gcWhen.hpp"
#include "gc/shared/vmGCOperations.hpp"
#include "memory/metaspace.hpp"
#include "oops/instanceMirrorKlass.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/init.hpp"
#include "runtime/thread.inline.hpp"
#include "services/heapDumper.hpp"


#ifdef ASSERT
int CollectedHeap::_fire_out_of_memory_count = 0;
#endif

size_t CollectedHeap::_filler_array_max_size = 0;

template <>
void EventLogBase<GCMessage>::print(outputStream* st, GCMessage& m) {
  st->print_cr("GC heap %s", m.is_before ? "before" : "after");
  st->print_raw(m);
}

void GCHeapLog::log_heap(bool before) {
  if (!should_log()) {
    return;
  }

  double timestamp = fetch_timestamp();
  MutexLockerEx ml(&_mutex, Mutex::_no_safepoint_check_flag);
  int index = compute_log_index();
  _records[index].thread = NULL; // Its the GC thread so it's not that interesting.
  _records[index].timestamp = timestamp;
  _records[index].data.is_before = before;
  stringStream st(_records[index].data.buffer(), _records[index].data.size());
  if (before) {
    Universe::print_heap_before_gc(&st, true);
  } else {
    Universe::print_heap_after_gc(&st, true);
  }
}

VirtualSpaceSummary CollectedHeap::create_heap_space_summary() {
  size_t capacity_in_words = capacity() / HeapWordSize;

  return VirtualSpaceSummary(
    reserved_region().start(), reserved_region().start() + capacity_in_words, reserved_region().end());
}

GCHeapSummary CollectedHeap::create_heap_summary() {
  VirtualSpaceSummary heap_space = create_heap_space_summary();
  return GCHeapSummary(heap_space, used());
}

MetaspaceSummary CollectedHeap::create_metaspace_summary() {
  const MetaspaceSizes meta_space(
      MetaspaceAux::committed_bytes(),
      MetaspaceAux::used_bytes(),
      MetaspaceAux::reserved_bytes());
  const MetaspaceSizes data_space(
      MetaspaceAux::committed_bytes(Metaspace::NonClassType),
      MetaspaceAux::used_bytes(Metaspace::NonClassType),
      MetaspaceAux::reserved_bytes(Metaspace::NonClassType));
  const MetaspaceSizes class_space(
      MetaspaceAux::committed_bytes(Metaspace::ClassType),
      MetaspaceAux::used_bytes(Metaspace::ClassType),
      MetaspaceAux::reserved_bytes(Metaspace::ClassType));

  const MetaspaceChunkFreeListSummary& ms_chunk_free_list_summary =
    MetaspaceAux::chunk_free_list_summary(Metaspace::NonClassType);
  const MetaspaceChunkFreeListSummary& class_chunk_free_list_summary =
    MetaspaceAux::chunk_free_list_summary(Metaspace::ClassType);

  return MetaspaceSummary(MetaspaceGC::capacity_until_GC(), meta_space, data_space, class_space,
                          ms_chunk_free_list_summary, class_chunk_free_list_summary);
}

void CollectedHeap::print_heap_before_gc() {
  if (PrintHeapAtGC) {
    Universe::print_heap_before_gc();
  }
  if (_gc_heap_log != NULL) {
    _gc_heap_log->log_heap_before();
  }
}

void CollectedHeap::print_heap_after_gc() {
  if (PrintHeapAtGC) {
    Universe::print_heap_after_gc();
  }
  if (_gc_heap_log != NULL) {
    _gc_heap_log->log_heap_after();
  }
}

void CollectedHeap::print_on_error(outputStream* st) const {
  st->print_cr("Heap:");
  print_extended_on(st);
  st->cr();

  _barrier_set->print_on(st);
}

void CollectedHeap::register_nmethod(nmethod* nm) {
  assert_locked_or_safepoint(CodeCache_lock);
}

void CollectedHeap::unregister_nmethod(nmethod* nm) {
  assert_locked_or_safepoint(CodeCache_lock);
}

void CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
  const GCHeapSummary& heap_summary = create_heap_summary();
  gc_tracer->report_gc_heap_summary(when, heap_summary);

  const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
  gc_tracer->report_metaspace_summary(when, metaspace_summary);
}

void CollectedHeap::trace_heap_before_gc(const GCTracer* gc_tracer) {
  trace_heap(GCWhen::BeforeGC, gc_tracer);
}

void CollectedHeap::trace_heap_after_gc(const GCTracer* gc_tracer) {
  trace_heap(GCWhen::AfterGC, gc_tracer);
}

// Memory state functions.


CollectedHeap::CollectedHeap() {
  const size_t max_len = size_t(arrayOopDesc::max_array_length(T_INT));
  const size_t elements_per_word = HeapWordSize / sizeof(jint);
  _filler_array_max_size = align_object_size(filler_array_hdr_size() +
                                             max_len / elements_per_word);

  _barrier_set = NULL;
  _is_gc_active = false;
  _total_collections = _total_full_collections = 0;
  _gc_cause = _gc_lastcause = GCCause::_no_gc;
  NOT_PRODUCT(_promotion_failure_alot_count = 0;)
  NOT_PRODUCT(_promotion_failure_alot_gc_number = 0;)

  if (UsePerfData) {
    EXCEPTION_MARK;

    // create the gc cause jvmstat counters
    _perf_gc_cause = PerfDataManager::create_string_variable(SUN_GC, "cause",
                             80, GCCause::to_string(_gc_cause), CHECK);

    _perf_gc_lastcause =
                PerfDataManager::create_string_variable(SUN_GC, "lastCause",
                             80, GCCause::to_string(_gc_lastcause), CHECK);
  }
  _defer_initial_card_mark = false; // strengthened by subclass in pre_initialize() below.
  // Create the ring log
  if (LogEvents) {
    _gc_heap_log = new GCHeapLog();
  } else {
    _gc_heap_log = NULL;
  }
}

// This interface assumes that it's being called by the
// vm thread. It collects the heap assuming that the
// heap lock is already held and that we are executing in
// the context of the vm thread.
void CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
  assert(Thread::current()->is_VM_thread(), "Precondition#1");
  assert(Heap_lock->is_locked(), "Precondition#2");
  GCCauseSetter gcs(this, cause);
  switch (cause) {
    case GCCause::_heap_inspection:
    case GCCause::_heap_dump:
    case GCCause::_metadata_GC_threshold : {
      HandleMark hm;
      do_full_collection(false);        // don't clear all soft refs
      break;
    }
    case GCCause::_last_ditch_collection: {
      HandleMark hm;
      do_full_collection(true);         // do clear all soft refs
      break;
    }
    default:
      ShouldNotReachHere(); // Unexpected use of this function
  }
}

void CollectedHeap::set_barrier_set(BarrierSet* barrier_set) {
  _barrier_set = barrier_set;
  oopDesc::set_bs(_barrier_set);
}

void CollectedHeap::pre_initialize() {
  // Used for ReduceInitialCardMarks (when COMPILER2 is used);
  // otherwise remains unused.
#ifdef COMPILER2
  _defer_initial_card_mark =    ReduceInitialCardMarks && can_elide_tlab_store_barriers()
                             && (DeferInitialCardMark || card_mark_must_follow_store());
#else
  assert(_defer_initial_card_mark == false, "Who would set it?");
#endif
}

#ifndef PRODUCT
void CollectedHeap::check_for_bad_heap_word_value(HeapWord* addr, size_t size) {
  if (CheckMemoryInitialization && ZapUnusedHeapArea) {
    for (size_t slot = 0; slot < size; slot += 1) {
      assert((*(intptr_t*) (addr + slot)) != ((intptr_t) badHeapWordVal),
             "Found badHeapWordValue in post-allocation check");
    }
  }
}

void CollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr, size_t size) {
  if (CheckMemoryInitialization && ZapUnusedHeapArea) {
    for (size_t slot = 0; slot < size; slot += 1) {
      assert((*(intptr_t*) (addr + slot)) == ((intptr_t) badHeapWordVal),
             "Found non badHeapWordValue in pre-allocation check");
    }
  }
}
#endif // PRODUCT

#ifdef ASSERT
void CollectedHeap::check_for_valid_allocation_state() {
  Thread *thread = Thread::current();
  // How to choose between a pending exception and a potential
  // OutOfMemoryError?  Don't allow pending exceptions.
  // This is a VM policy failure, so how do we exhaustively test it?
  assert(!thread->has_pending_exception(),
         "shouldn't be allocating with pending exception");
  if (StrictSafepointChecks) {
    assert(thread->allow_allocation(),
           "Allocation done by thread for which allocation is blocked "
           "by No_Allocation_Verifier!");
    // Allocation of an oop can always invoke a safepoint,
    // hence, the true argument
    thread->check_for_valid_safepoint_state(true);
  }
}
#endif

HeapWord* CollectedHeap::allocate_from_tlab_slow(KlassHandle klass, Thread* thread, size_t size) {

  // Retain tlab and allocate object in shared space if
  // the amount free in the tlab is too large to discard.
  if (thread->tlab().free() > thread->tlab().refill_waste_limit()) {
    thread->tlab().record_slow_allocation(size);
    return NULL;
  }

  // Discard tlab and allocate a new one.
  // To minimize fragmentation, the last TLAB may be smaller than the rest.
  size_t new_tlab_size = thread->tlab().compute_size(size);

  thread->tlab().clear_before_allocation();

  if (new_tlab_size == 0) {
    return NULL;
  }

  // Allocate a new TLAB...
  HeapWord* obj = Universe::heap()->allocate_new_tlab(new_tlab_size);
  if (obj == NULL) {
    return NULL;
  }

  AllocTracer::send_allocation_in_new_tlab_event(klass, new_tlab_size * HeapWordSize, size * HeapWordSize);

  if (ZeroTLAB) {
    // ..and clear it.
    Copy::zero_to_words(obj, new_tlab_size);
  } else {
    // ...and zap just allocated object.
#ifdef ASSERT
    // Skip mangling the space corresponding to the object header to
    // ensure that the returned space is not considered parsable by
    // any concurrent GC thread.
    size_t hdr_size = oopDesc::header_size();
    Copy::fill_to_words(obj + hdr_size, new_tlab_size - hdr_size, badHeapWordVal);
#endif // ASSERT
  }
  thread->tlab().fill(obj, obj + size, new_tlab_size);
  return obj;
}

void CollectedHeap::flush_deferred_store_barrier(JavaThread* thread) {
  MemRegion deferred = thread->deferred_card_mark();
  if (!deferred.is_empty()) {
    assert(_defer_initial_card_mark, "Otherwise should be empty");
    {
      // Verify that the storage points to a parsable object in heap
      DEBUG_ONLY(oop old_obj = oop(deferred.start());)
      assert(is_in(old_obj), "Not in allocated heap");
      assert(!can_elide_initializing_store_barrier(old_obj),
             "Else should have been filtered in new_store_pre_barrier()");
      assert(old_obj->is_oop(true), "Not an oop");
      assert(deferred.word_size() == (size_t)(old_obj->size()),
             "Mismatch: multiple objects?");
    }
    BarrierSet* bs = barrier_set();
    assert(bs->has_write_region_opt(), "No write_region() on BarrierSet");
    bs->write_region(deferred);
    // "Clear" the deferred_card_mark field
    thread->set_deferred_card_mark(MemRegion());
  }
  assert(thread->deferred_card_mark().is_empty(), "invariant");
}

size_t CollectedHeap::max_tlab_size() const {
  // TLABs can't be bigger than we can fill with a int[Integer.MAX_VALUE].
  // This restriction could be removed by enabling filling with multiple arrays.
  // If we compute that the reasonable way as
  //    header_size + ((sizeof(jint) * max_jint) / HeapWordSize)
  // we'll overflow on the multiply, so we do the divide first.
  // We actually lose a little by dividing first,
  // but that just makes the TLAB  somewhat smaller than the biggest array,
  // which is fine, since we'll be able to fill that.
  size_t max_int_size = typeArrayOopDesc::header_size(T_INT) +
              sizeof(jint) *
              ((juint) max_jint / (size_t) HeapWordSize);
  return align_size_down(max_int_size, MinObjAlignment);
}

// Helper for ReduceInitialCardMarks. For performance,
// compiled code may elide card-marks for initializing stores
// to a newly allocated object along the fast-path. We
// compensate for such elided card-marks as follows:
// (a) Generational, non-concurrent collectors, such as
//     GenCollectedHeap(ParNew,DefNew,Tenured) and
//     ParallelScavengeHeap(ParallelGC, ParallelOldGC)
//     need the card-mark if and only if the region is
//     in the old gen, and do not care if the card-mark
//     succeeds or precedes the initializing stores themselves,
//     so long as the card-mark is completed before the next
//     scavenge. For all these cases, we can do a card mark
//     at the point at which we do a slow path allocation
//     in the old gen, i.e. in this call.
// (b) GenCollectedHeap(ConcurrentMarkSweepGeneration) requires
//     in addition that the card-mark for an old gen allocated
//     object strictly follow any associated initializing stores.
//     In these cases, the memRegion remembered below is
//     used to card-mark the entire region either just before the next
//     slow-path allocation by this thread or just before the next scavenge or
//     CMS-associated safepoint, whichever of these events happens first.
//     (The implicit assumption is that the object has been fully
//     initialized by this point, a fact that we assert when doing the
//     card-mark.)
// (c) G1CollectedHeap(G1) uses two kinds of write barriers. When a
//     G1 concurrent marking is in progress an SATB (pre-write-)barrier is
//     is used to remember the pre-value of any store. Initializing
//     stores will not need this barrier, so we need not worry about
//     compensating for the missing pre-barrier here. Turning now
//     to the post-barrier, we note that G1 needs a RS update barrier
//     which simply enqueues a (sequence of) dirty cards which may
//     optionally be refined by the concurrent update threads. Note
//     that this barrier need only be applied to a non-young write,
//     but, like in CMS, because of the presence of concurrent refinement
//     (much like CMS' precleaning), must strictly follow the oop-store.
//     Thus, using the same protocol for maintaining the intended
//     invariants turns out, serendepitously, to be the same for both
//     G1 and CMS.
//
// For any future collector, this code should be reexamined with
// that specific collector in mind, and the documentation above suitably
// extended and updated.
oop CollectedHeap::new_store_pre_barrier(JavaThread* thread, oop new_obj) {
  // If a previous card-mark was deferred, flush it now.
  flush_deferred_store_barrier(thread);
  if (can_elide_initializing_store_barrier(new_obj)) {
    // The deferred_card_mark region should be empty
    // following the flush above.
    assert(thread->deferred_card_mark().is_empty(), "Error");
  } else {
    MemRegion mr((HeapWord*)new_obj, new_obj->size());
    assert(!mr.is_empty(), "Error");
    if (_defer_initial_card_mark) {
      // Defer the card mark
      thread->set_deferred_card_mark(mr);
    } else {
      // Do the card mark
      BarrierSet* bs = barrier_set();
      assert(bs->has_write_region_opt(), "No write_region() on BarrierSet");
      bs->write_region(mr);
    }
  }
  return new_obj;
}

size_t CollectedHeap::filler_array_hdr_size() {
  return size_t(align_object_offset(arrayOopDesc::header_size(T_INT))); // align to Long
}

size_t CollectedHeap::filler_array_min_size() {
  return align_object_size(filler_array_hdr_size()); // align to MinObjAlignment
}

#ifdef ASSERT
void CollectedHeap::fill_args_check(HeapWord* start, size_t words)
{
  assert(words >= min_fill_size(), "too small to fill");
  assert(words % MinObjAlignment == 0, "unaligned size");
  assert(Universe::heap()->is_in_reserved(start), "not in heap");
  assert(Universe::heap()->is_in_reserved(start + words - 1), "not in heap");
}

void CollectedHeap::zap_filler_array(HeapWord* start, size_t words, bool zap)
{
  if (ZapFillerObjects && zap) {
    Copy::fill_to_words(start + filler_array_hdr_size(),
                        words - filler_array_hdr_size(), 0XDEAFBABE);
  }
}
#endif // ASSERT

void
CollectedHeap::fill_with_array(HeapWord* start, size_t words, bool zap)
{
  assert(words >= filler_array_min_size(), "too small for an array");
  assert(words <= filler_array_max_size(), "too big for a single object");

  const size_t payload_size = words - filler_array_hdr_size();
  const size_t len = payload_size * HeapWordSize / sizeof(jint);
  assert((int)len >= 0, err_msg("size too large " SIZE_FORMAT " becomes %d", words, (int)len));

  // Set the length first for concurrent GC.
  ((arrayOop)start)->set_length((int)len);
  post_allocation_setup_common(Universe::intArrayKlassObj(), start);
  DEBUG_ONLY(zap_filler_array(start, words, zap);)
}

void
CollectedHeap::fill_with_object_impl(HeapWord* start, size_t words, bool zap)
{
  assert(words <= filler_array_max_size(), "too big for a single object");

  if (words >= filler_array_min_size()) {
    fill_with_array(start, words, zap);
  } else if (words > 0) {
    assert(words == min_fill_size(), "unaligned size");
    post_allocation_setup_common(SystemDictionary::Object_klass(), start);
  }
}

void CollectedHeap::fill_with_object(HeapWord* start, size_t words, bool zap)
{
  DEBUG_ONLY(fill_args_check(start, words);)
  HandleMark hm;  // Free handles before leaving.
  fill_with_object_impl(start, words, zap);
}

void CollectedHeap::fill_with_objects(HeapWord* start, size_t words, bool zap)
{
  DEBUG_ONLY(fill_args_check(start, words);)
  HandleMark hm;  // Free handles before leaving.

  // Multiple objects may be required depending on the filler array maximum size. Fill
  // the range up to that with objects that are filler_array_max_size sized. The
  // remainder is filled with a single object.
  const size_t min = min_fill_size();
  const size_t max = filler_array_max_size();
  while (words > max) {
    const size_t cur = (words - max) >= min ? max : max - min;
    fill_with_array(start, cur, zap);
    start += cur;
    words -= cur;
  }

  fill_with_object_impl(start, words, zap);
}

void CollectedHeap::post_initialize() {
  collector_policy()->post_heap_initialize();
}

HeapWord* CollectedHeap::allocate_new_tlab(size_t size) {
  guarantee(false, "thread-local allocation buffers not supported");
  return NULL;
}

void CollectedHeap::ensure_parsability(bool retire_tlabs) {
  // The second disjunct in the assertion below makes a concession
  // for the start-up verification done while the VM is being
  // created. Callers be careful that you know that mutators
  // aren't going to interfere -- for instance, this is permissible
  // if we are still single-threaded and have either not yet
  // started allocating (nothing much to verify) or we have
  // started allocating but are now a full-fledged JavaThread
  // (and have thus made our TLAB's) available for filling.
  assert(SafepointSynchronize::is_at_safepoint() ||
         !is_init_completed(),
         "Should only be called at a safepoint or at start-up"
         " otherwise concurrent mutator activity may make heap "
         " unparsable again");
  const bool use_tlab = UseTLAB;
  const bool deferred = _defer_initial_card_mark;
  // The main thread starts allocating via a TLAB even before it
  // has added itself to the threads list at vm boot-up.
  assert(!use_tlab || Threads::first() != NULL,
         "Attempt to fill tlabs before main thread has been added"
         " to threads list is doomed to failure!");
  for (JavaThread *thread = Threads::first(); thread; thread = thread->next()) {
     if (use_tlab) thread->tlab().make_parsable(retire_tlabs);
#ifdef COMPILER2
     // The deferred store barriers must all have been flushed to the
     // card-table (or other remembered set structure) before GC starts
     // processing the card-table (or other remembered set).
     if (deferred) flush_deferred_store_barrier(thread);
#else
     assert(!deferred, "Should be false");
     assert(thread->deferred_card_mark().is_empty(), "Should be empty");
#endif
  }
}

void CollectedHeap::accumulate_statistics_all_tlabs() {
  if (UseTLAB) {
    assert(SafepointSynchronize::is_at_safepoint() ||
         !is_init_completed(),
         "should only accumulate statistics on tlabs at safepoint");

    ThreadLocalAllocBuffer::accumulate_statistics_before_gc();
  }
}

void CollectedHeap::resize_all_tlabs() {
  if (UseTLAB) {
    assert(SafepointSynchronize::is_at_safepoint() ||
         !is_init_completed(),
         "should only resize tlabs at safepoint");

    ThreadLocalAllocBuffer::resize_all_tlabs();
  }
}

void CollectedHeap::pre_full_gc_dump(GCTimer* timer) {
  if (HeapDumpBeforeFullGC) {
    GCTraceTime tt("Heap Dump (before full gc): ", PrintGCDetails, false, timer, GCId::create());
    // We are doing a "major" collection and a heap dump before
    // major collection has been requested.
    HeapDumper::dump_heap();
  }
  if (PrintClassHistogramBeforeFullGC) {
    GCTraceTime tt("Class Histogram (before full gc): ", PrintGCDetails, true, timer, GCId::create());
    VM_GC_HeapInspection inspector(gclog_or_tty, false /* ! full gc */);
    inspector.doit();
  }
}

void CollectedHeap::post_full_gc_dump(GCTimer* timer) {
  if (HeapDumpAfterFullGC) {
    GCTraceTime tt("Heap Dump (after full gc): ", PrintGCDetails, false, timer, GCId::create());
    HeapDumper::dump_heap();
  }
  if (PrintClassHistogramAfterFullGC) {
    GCTraceTime tt("Class Histogram (after full gc): ", PrintGCDetails, true, timer, GCId::create());
    VM_GC_HeapInspection inspector(gclog_or_tty, false /* ! full gc */);
    inspector.doit();
  }
}

void CollectedHeap::initialize_reserved_region(HeapWord *start, HeapWord *end) {
  // It is important to do this in a way such that concurrent readers can't
  // temporarily think something is in the heap.  (Seen this happen in asserts.)
  _reserved.set_word_size(0);
  _reserved.set_start(start);
  _reserved.set_end(end);
}

/////////////// Unit tests ///////////////

#ifndef PRODUCT
void CollectedHeap::test_is_in() {
  CollectedHeap* heap = Universe::heap();

  uintptr_t epsilon    = (uintptr_t) MinObjAlignment;
  uintptr_t heap_start = (uintptr_t) heap->_reserved.start();
  uintptr_t heap_end   = (uintptr_t) heap->_reserved.end();

  // Test that NULL is not in the heap.
  assert(!heap->is_in(NULL), "NULL is unexpectedly in the heap");

  // Test that a pointer to before the heap start is reported as outside the heap.
  assert(heap_start >= ((uintptr_t)NULL + epsilon), "sanity");
  void* before_heap = (void*)(heap_start - epsilon);
  assert(!heap->is_in(before_heap),
      err_msg("before_heap: " PTR_FORMAT " is unexpectedly in the heap", p2i(before_heap)));

  // Test that a pointer to after the heap end is reported as outside the heap.
  assert(heap_end <= ((uintptr_t)-1 - epsilon), "sanity");
  void* after_heap = (void*)(heap_end + epsilon);
  assert(!heap->is_in(after_heap),
      err_msg("after_heap: " PTR_FORMAT " is unexpectedly in the heap", p2i(after_heap)));
}
#endif