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src/magazine_medium.c libmalloc-521.100.59 /dev/null
--- libmalloc/libmalloc-521.100.59/src/magazine_medium.c
+++ /dev/null
@@ -1,2933 +0,0 @@
-/*
- * Copyright (c) 2018 Apple Inc. All rights reserved.
- *
- * @APPLE_LICENSE_HEADER_START@
- *
- * This file contains Original Code and/or Modifications of Original Code
- * as defined in and that are subject to the Apple Public Source License
- * Version 2.0 (the 'License'). You may not use this file except in
- * compliance with the License. Please obtain a copy of the License at
- * http://www.opensource.apple.com/apsl/ and read it before using this
- * file.
- *
- * The Original Code and all software distributed under the License are
- * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
- * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
- * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
- * Please see the License for the specific language governing rights and
- * limitations under the License.
- *
- * @APPLE_LICENSE_HEADER_END@
- */
-
-#include "internal.h"
-
-#if CONFIG_MEDIUM_ALLOCATOR
-
-/*********************	MEDIUM FREE LIST UTILITIES	************************/
-
-#pragma mark meta header helpers
-
-static MALLOC_INLINE uint64_t
-medium_sliding_madvise_granularity(magazine_t *magazine)
-{
-	uint64_t granularity = MEDIUM_MADVISE_MIN;
-	// Use a sliding madvise granularity based on how many bytes the region
-	// currently has allocated. This way we will advise at a finer granularity
-	// as the region becomes more and more empty.
-	// region_trailer_t *t = REGION_TRAILER_FOR_MEDIUM_REGION(region);
-	if (magazine->mag_num_bytes_in_objects > 0) {
-		if (magazine_medium_madvise_window_scale_factor == 1) {
-			// NB: This code has a bug causing undefined behavior whenever the result of clzl is > 32
-			// because it's shifting a signed integer. It should be 1ULL << (64 - ...) but
-			// fixing this bug will introduce memory regressions, so for now we've only fixed it on very
-			// large memory configs that are scaling up their window anyways.
-			// See rdar://82128925 for details
-			granularity = MAX(granularity, 1 << (64 -
-					__builtin_clzl(magazine->mag_num_bytes_in_objects >> MEDIUM_MADVISE_SHIFT)));
-		} else {
-			granularity = MAX(granularity, 1ULL << (64 -
-					__builtin_clzl(magazine->mag_num_bytes_in_objects >> MEDIUM_MADVISE_SHIFT)));
-			if (os_mul_overflow(granularity, magazine_medium_madvise_window_scale_factor, &granularity)) {
-				return UINT64_MAX;
-			}
-		}
-	}
-	return granularity;
-}
-
-static MALLOC_INLINE void
-medium_madvise_header_mark_dirty(msize_t *headers, msize_t index,
-		msize_t msize)
-{
-	// MALLOC_ASSERT(index < NUM_MEDIUM_BLOCKS);
-	// MALLOC_ASSERT(index + msize <= NUM_MEDIUM_BLOCKS);
-	headers[index] = msize;
-	headers[index + msize - 1] = msize;
-}
-
-static MALLOC_INLINE void
-medium_madvise_header_mark_clean(msize_t *headers, msize_t index,
-		msize_t msize)
-{
-	// MALLOC_ASSERT(index < NUM_MEDIUM_BLOCKS);
-	// MALLOC_ASSERT(index + msize <= NUM_MEDIUM_BLOCKS);
-	headers[index] = msize | MEDIUM_IS_ADVISED;
-	headers[index + msize - 1] = msize | MEDIUM_IS_ADVISED;
-}
-
-static MALLOC_INLINE void
-medium_madvise_header_mark_middle(msize_t *headers, msize_t index)
-{
-	// MALLOC_ASSERT(index < NUM_MEDIUM_BLOCKS);
-	headers[index] = 0;
-}
-
-static MALLOC_INLINE msize_t
-medium_madvise_header_dirty_len(msize_t *headers, msize_t index)
-{
-	// MALLOC_ASSERT(index < NUM_MEDIUM_BLOCKS);
-	if (headers[index] & MEDIUM_IS_ADVISED) {
-		return 0;
-	}
-	return headers[index] & ~MEDIUM_IS_ADVISED;
-}
-
-/*
- * Mark a block as free.  Only the first quantum of a block is marked thusly,
- * the remainder are marked "middle".
- */
-static MALLOC_INLINE void
-medium_meta_header_set_is_free(msize_t *meta_headers, msize_t index, msize_t msize)
-{
-	meta_headers[index] = msize | MEDIUM_IS_FREE;
-}
-
-/*
- * Mark a block as not free, preserving its size.
- */
-static MALLOC_INLINE void
-medium_meta_header_set_not_free(msize_t *meta_headers, msize_t index)
-{
-	meta_headers[index] &= ~MEDIUM_IS_FREE;
-}
-
-/*
- * Mark a block as in use.  Only the first quantum of a block is marked thusly,
- * the remainder are marked "middle".
- */
-static MALLOC_INLINE void
-medium_meta_header_set_in_use(msize_t *meta_headers, msize_t index, msize_t msize)
-{
-	meta_headers[index] = msize;
-}
-
-/*
- * Mark a quantum as being the second or later in a block.
- */
-static MALLOC_INLINE void
-medium_meta_header_set_middle(msize_t *meta_headers, msize_t index)
-{
-	meta_headers[index] = 0;
-}
-
-#pragma mark in-place free list
-
-static MALLOC_INLINE void
-medium_inplace_checksum_ptr(rack_t *rack, inplace_linkage_s *linkage, void *ptr)
-{
-	uintptr_t checksum = free_list_gen_checksum((uintptr_t)ptr ^ rack->cookie ^ (uintptr_t)rack);
-	linkage->checksum = checksum;
-	linkage->ptr = ptr;
-}
-
-static MALLOC_INLINE free_list_t
-medium_inplace_unchecksum_ptr(rack_t *rack, inplace_linkage_s *linkage)
-{
-	if (linkage->checksum != (uint8_t)free_list_gen_checksum((uintptr_t)linkage->ptr ^ rack->cookie ^ (uintptr_t)rack)) {
-		free_list_checksum_botch(rack, linkage, linkage->ptr);
-		__builtin_trap();
-	}
-
-	return (free_list_t){ .p = linkage->ptr };
-}
-
-static MALLOC_INLINE free_list_t
-medium_inplace_unchecksum_ptr_task(task_t task, memory_reader_t reader,
-		print_task_printer_t printer, rack_t *rack, inplace_linkage_s *linkage)
-{
-	inplace_linkage_s *mapped_linkage;
-	rack_t *mapped_rack;
-	if (reader(task, (vm_address_t)linkage, sizeof(*linkage),
-			(void **)&mapped_linkage)) {
-		printer("Unable to map medium linkage pointer %p\n", linkage);
-		return (free_list_t){ .p = NULL };
-	}
-
-	if (reader(task, (vm_address_t)rack,
-			sizeof(struct rack_s), (void **)&mapped_rack)) {
-		printer("Failed to map medium rack\n");
-		return (free_list_t){ .p = NULL };
-	}
-
-	if (mapped_linkage->checksum != (uint8_t)free_list_gen_checksum(
-			(uintptr_t)mapped_linkage->ptr ^ mapped_rack->cookie ^ (uintptr_t)rack)) {
-		free_list_checksum_botch(rack, linkage, mapped_linkage->ptr);
-		__builtin_trap();
-	}
-
-	return (free_list_t){ .p = mapped_linkage->ptr };
-}
-
-static MALLOC_INLINE free_list_t
-medium_inplace_free_entry_get_previous(rack_t *rack, medium_inplace_free_entry_t ptr)
-{
-	return medium_inplace_unchecksum_ptr(rack, &ptr->previous);
-}
-
-static MALLOC_INLINE void
-medium_inplace_free_entry_set_previous(rack_t *rack, medium_inplace_free_entry_t entry, free_list_t previous)
-{
-	medium_inplace_checksum_ptr(rack, &entry->previous, previous.p);
-}
-
-static MALLOC_INLINE free_list_t
-medium_inplace_free_entry_get_next(rack_t *rack, medium_inplace_free_entry_t ptr)
-{
-	return medium_inplace_unchecksum_ptr(rack, &ptr->next);
-}
-
-static MALLOC_INLINE free_list_t
-medium_inplace_free_entry_get_next_task(task_t task, memory_reader_t reader,
-		print_task_printer_t printer, rack_t *rack,
-		medium_inplace_free_entry_t ptr)
-{
-	return medium_inplace_unchecksum_ptr_task(task, reader, printer, rack,
-			&ptr->next);
-}
-
-static MALLOC_INLINE void
-medium_inplace_free_entry_set_next(rack_t *rack, medium_inplace_free_entry_t entry, free_list_t next)
-{
-	medium_inplace_checksum_ptr(rack, &entry->next, next.p);
-}
-
-#pragma mark OOB free list
-
-// Returns true if the address and size of the free list entry would result
-// in the free entry being the only data on a given page.
-static MALLOC_INLINE boolean_t
-medium_needs_oob_free_entry(void *ptr, msize_t msize)
-{
-	return ((trunc_page_quanta((uintptr_t)ptr) == (uintptr_t)ptr) &&
-			(MEDIUM_BYTES_FOR_MSIZE(msize) >= vm_kernel_page_size));
-}
-
-// Returns true if the address given lies within the region's OOB free
-// list entries, rather than a free_list_t in the region's heap space.
-static MALLOC_INLINE boolean_t
-medium_is_oob_free_entry(free_list_t ptr)
-{
-	medium_region_t region = MEDIUM_REGION_FOR_PTR(ptr.p);
-	return (((uintptr_t)ptr.p >= (uintptr_t)&region->medium_oob_free_entries[0]) &&
-			((uintptr_t)ptr.p < (uintptr_t)&region->medium_oob_free_entries[MEDIUM_OOB_COUNT]));
-}
-
-static MALLOC_INLINE void
-medium_oob_free_entry_set_previous(oob_free_entry_t oobe, free_list_t previous)
-{
-	// MALLOC_ASSERT(medium_is_oob_free_entry(previous) || !((uintptr_t)previous.p & 0x1fffffff));
-	oobe->prev = (uintptr_t)previous.p;
-}
-
-static MALLOC_INLINE free_list_t
-medium_oob_free_entry_get_previous(oob_free_entry_t oobe)
-{
-	return (free_list_t){ .p = (void *)oobe->prev };
-}
-
-static MALLOC_INLINE void
-medium_oob_free_entry_set_next(oob_free_entry_t oobe, free_list_t next)
-{
-	// MALLOC_ASSERT(medium_is_oob_free_entry(next) || !((uintptr_t)next.p & 0x1fffffff));
-	oobe->next = (uintptr_t)next.p;
-}
-
-static MALLOC_INLINE free_list_t
-medium_oob_free_entry_get_next(oob_free_entry_t oobe)
-{
-	return (free_list_t){ .p = (void *)oobe->next };
-}
-
-static MALLOC_INLINE free_list_t
-medium_oob_free_entry_get_next_task(task_t task, memory_reader_t reader,
-		print_task_printer_t printer, oob_free_entry_t oobe)
-{
-	oob_free_entry_t mapped_oobe;
-	if (reader(task, (vm_address_t)oobe, sizeof(*oobe),
-			(void **)&mapped_oobe)) {
-		printer("Failed to map medium oobe pointer\n");
-		return (free_list_t){ .p = NULL };
-	}
-	return (free_list_t){ .p = (void *)mapped_oobe->next };
-}
-
-static MALLOC_INLINE void *
-medium_oob_free_entry_get_ptr(oob_free_entry_t oobe)
-{
-	medium_region_t region = MEDIUM_REGION_FOR_PTR(oobe);
-	uint16_t block = oobe->ptr & ~MEDIUM_IS_OOB;
-	return (void *)((uintptr_t)region + (block << SHIFT_MEDIUM_QUANTUM));
-}
-
-static MALLOC_INLINE void *
-medium_oob_free_entry_get_ptr_task(task_t task, memory_reader_t reader,
-		print_task_printer_t printer, oob_free_entry_t oobe)
-{
-	// We need to map the oob_free_entry_t to read the pointer value.
-	oob_free_entry_t mapped_oobe;
-	if (reader(task, (vm_address_t)oobe, sizeof(*oobe),
-			(void **)&mapped_oobe)) {
-		printer("Failed to map medium oobe pointer\n");
-		return NULL;
-	}
-
-	if (!(mapped_oobe->ptr & MEDIUM_IS_OOB)) {
-		return NULL;
-	}
-
-	// The rest of this code works with target process addresses and returns an
-	// address in the target process.
-	medium_region_t region = MEDIUM_REGION_FOR_PTR(oobe);
-	uint16_t block = mapped_oobe->ptr & ~MEDIUM_IS_OOB;
-	return (void *)((uintptr_t)region + (block << SHIFT_MEDIUM_QUANTUM));
-}
-
-static MALLOC_INLINE void
-medium_oob_free_entry_set_ptr(oob_free_entry_t oobe, void *ptr)
-{
-	oobe->ptr = MEDIUM_IS_OOB | (MEDIUM_REGION_OFFSET_FOR_PTR(ptr) >> SHIFT_MEDIUM_QUANTUM);
-}
-
-static MALLOC_INLINE void
-medium_oob_free_entry_set_free(oob_free_entry_t oobe)
-{
-	oobe->prev = ~0;
-	oobe->next = ~0;
-	oobe->ptr = 0;
-}
-
-// Finds the first unused OOB free list entry in the pointer's region.
-// Returns NULL if all of the OOB entries are used.
-static MALLOC_INLINE oob_free_entry_t
-medium_oob_free_find_empty(void *ptr, msize_t msize)
-{
-	medium_region_t region = MEDIUM_REGION_FOR_PTR(ptr);
-
-	// There are 61 of these entries at the end of a medium region.
-	// If this changes, then a linear search through the list may
-	// become an unsuitable choice.
-	for (int i=0; i < MEDIUM_OOB_COUNT; i++) {
-		if (region->medium_oob_free_entries[i].ptr == 0) {
-			return &region->medium_oob_free_entries[i];
-		}
-	}
-
-#if DEBUG_MALLOC
-	malloc_report(ASL_LEVEL_INFO, "used all slots of OOB entries\n");
-#endif
-	return NULL;
-}
-
-static MALLOC_INLINE oob_free_entry_t
-medium_oob_free_find_ptr(void *ptr, msize_t msize)
-{
-	medium_region_t region = MEDIUM_REGION_FOR_PTR(ptr);
-
-	// There are 61 of these entries at the end of a medium region.
-	// If this changes, then a linear search through the list may
-	// become an unsuitable choice.
-	for (int i=0; i < MEDIUM_OOB_COUNT; i++) {
-		oob_free_entry_t oob = &region->medium_oob_free_entries[i];
-		if (medium_oob_free_entry_get_ptr(oob) == ptr &&
-				oob->ptr & MEDIUM_IS_OOB) {
-			return &region->medium_oob_free_entries[i];
-		}
-	}
-
-	return NULL;
-}
-
-#pragma mark generic free list
-
-static MALLOC_INLINE void
-medium_free_list_set_previous(rack_t *rack, free_list_t entry, free_list_t previous)
-{
-	if (medium_is_oob_free_entry(entry)) {
-		medium_oob_free_entry_set_previous(entry.oob, previous);
-	} else {
-		medium_inplace_free_entry_set_previous(rack, entry.medium_inplace, previous);
-	}
-}
-
-static MALLOC_INLINE free_list_t
-medium_free_list_get_previous(rack_t *rack, free_list_t ptr)
-{
-	MALLOC_ASSERT(ptr.p);
-	if (medium_is_oob_free_entry(ptr)) {
-		return medium_oob_free_entry_get_previous(ptr.oob);
-	} else {
-		return medium_inplace_free_entry_get_previous(rack, ptr.medium_inplace);
-	}
-}
-
-static MALLOC_INLINE void
-medium_free_list_set_next(rack_t *rack, free_list_t entry, free_list_t next)
-{
-	if (medium_is_oob_free_entry(entry)) {
-		medium_oob_free_entry_set_next(entry.oob, next);
-	} else {
-		medium_inplace_free_entry_set_next(rack, entry.medium_inplace, next);
-	}
-}
-
-static MALLOC_INLINE free_list_t
-medium_free_list_get_next(rack_t *rack, free_list_t ptr)
-{
-	MALLOC_ASSERT(ptr.p);
-	if (medium_is_oob_free_entry(ptr)) {
-		return medium_oob_free_entry_get_next(ptr.oob);
-	} else {
-		return medium_inplace_free_entry_get_next(rack, ptr.medium_inplace);
-	}
-}
-
-static MALLOC_INLINE free_list_t
-medium_free_list_get_next_task(task_t task, memory_reader_t reader,
-		print_task_printer_t printer, rack_t *rack, free_list_t ptr)
-{
-	MALLOC_ASSERT(ptr.p);
-	if (medium_is_oob_free_entry(ptr)) {
-		return medium_oob_free_entry_get_next_task(task, reader, printer, ptr.oob);
-	} else {
-		return medium_inplace_free_entry_get_next_task(task, reader, printer,
-				rack, ptr.medium_inplace);
-	}
-}
-
-static MALLOC_INLINE void *
-medium_free_list_get_ptr(rack_t *rack, free_list_t ptr)
-{
-	if (!ptr.p) {
-		return NULL;
-	} else if (medium_is_oob_free_entry(ptr)) {
-		return medium_oob_free_entry_get_ptr(ptr.oob);
-	} else {
-		return (void *)ptr.p;
-	}
-}
-
-static MALLOC_INLINE void *
-medium_free_list_get_ptr_task(task_t task, memory_reader_t reader,
-		print_task_printer_t printer, free_list_t ptr)
-{
-	if (!ptr.p) {
-		return NULL;
-	} else if (medium_is_oob_free_entry(ptr)) {
-		return medium_oob_free_entry_get_ptr_task(task, reader, printer, ptr.oob);
-	} else {
-		return (void *)ptr.p;
-	}
-}
-
-// Returns a free_list_t that is either inline or not based on the
-// pointer and msize.
-static MALLOC_INLINE free_list_t
-medium_free_list_from_ptr(rack_t *rack, void *ptr, msize_t msize)
-{
-	MALLOC_ASSERT(msize);
-
-	// The default is to put the free_list_t in the memory that
-	// the pointer leads to.
-	free_list_t entry;
-	entry.p = ptr;
-
-	// If the pointer is page aligned, and the msize is greater
-	// than a whole page, then we try and put the entry in
-	// the out-of-band area instead.
-	if (medium_needs_oob_free_entry(ptr, msize)) {
-		oob_free_entry_t oobe = medium_oob_free_find_empty(ptr, msize);
-		if (oobe) {
-			medium_oob_free_entry_set_ptr(oobe, ptr);
-			entry.oob = oobe;
-		}
-	}
-
-	return entry;
-}
-
-static MALLOC_INLINE void
-medium_free_mark_free(rack_t *rack, free_list_t entry, msize_t msize)
-{
-	// Marks both the start and end block of a free-list entry as free.
-	void *ptr = medium_free_list_get_ptr(rack, entry);
-	msize_t *meta_headers = MEDIUM_META_HEADER_FOR_PTR(ptr);
-	uintptr_t start_index = MEDIUM_META_INDEX_FOR_PTR(ptr);
-	uintptr_t end_index = MEDIUM_META_INDEX_FOR_PTR(ptr + MEDIUM_BYTES_FOR_MSIZE(msize) - 1);
-	MALLOC_ASSERT(start_index <= end_index);
-
-	medium_meta_header_set_is_free(meta_headers, start_index, msize);
-	medium_meta_header_set_is_free(meta_headers, end_index, msize);
-}
-
-static MALLOC_INLINE void
-medium_free_mark_middle(rack_t *rack, free_list_t entry, msize_t msize)
-{
-	// Marks both the start and end block of a free-list entry as "middle" (unfree).
-	void *ptr = medium_free_list_get_ptr(rack, entry);
-	msize_t *meta_headers = MEDIUM_META_HEADER_FOR_PTR(ptr);
-	uintptr_t start_index = MEDIUM_META_INDEX_FOR_PTR(ptr);
-	uintptr_t end_index = MEDIUM_META_INDEX_FOR_PTR(ptr + MEDIUM_BYTES_FOR_MSIZE(msize) - 1);
-	MALLOC_ASSERT(start_index <= end_index);
-	MALLOC_ASSERT((meta_headers[start_index] & ~MEDIUM_IS_FREE) == msize);
-
-	medium_meta_header_set_middle(meta_headers, start_index);
-	medium_meta_header_set_middle(meta_headers, end_index);
-}
-
-static MALLOC_INLINE void
-medium_free_mark_unfree(rack_t *rack, free_list_t entry, msize_t msize)
-{
-	// Marks both the start and end block of a free-list entry as not free.
-	void *ptr = medium_free_list_get_ptr(rack, entry);
-	msize_t *meta_headers = MEDIUM_META_HEADER_FOR_PTR(ptr);
-	uintptr_t start_index = MEDIUM_META_INDEX_FOR_PTR(ptr);
-	uintptr_t end_index = MEDIUM_META_INDEX_FOR_PTR(ptr +
-			MEDIUM_BYTES_FOR_MSIZE(msize) - 1);
-	MALLOC_ASSERT(start_index <= end_index);
-
-	medium_meta_header_set_not_free(meta_headers, start_index);
-	medium_meta_header_set_not_free(meta_headers, end_index);
-}
-
-static MALLOC_INLINE unsigned int
-medium_free_list_count(task_t task, memory_reader_t reader,
-		print_task_printer_t printer, rack_t *rack, free_list_t ptr)
-{
-	unsigned int count = 0;
-	while (ptr.p) {
-		count++;
-		ptr = medium_free_list_get_next_task(task, reader, printer, rack, ptr);
-	}
-	return count;
-}
-
-/*
- * Adds an item to the proper free list, and also marks the meta-header of the
- * block properly.
- * Assumes szone has been locked
- */
-static free_list_t
-medium_free_list_add_ptr(rack_t *rack, magazine_t *medium_mag_ptr, void *ptr, msize_t msize)
-{
-	grain_t slot = MEDIUM_FREE_SLOT_FOR_MSIZE(rack, msize);
-	free_list_t free_head = medium_mag_ptr->mag_free_list[slot];
-
-	// This will either return the free_list_t for the current pointer, or attempt
-	// to reserve an OOB entry for us.
-	free_list_t free_ptr = medium_free_list_from_ptr(rack, ptr, msize);
-
-#if DEBUG_MALLOC
-	if (LOG(szone, ptr)) {
-		malloc_report(ASL_LEVEL_INFO, "in %s, ptr=%p, msize=%d\n", __FUNCTION__, ptr, msize);
-	}
-	if (((uintptr_t)ptr) & (MEDIUM_QUANTUM - 1)) {
-		malloc_zone_error(rack->debug_flags, true, "medium_free_list_add_ptr: Unaligned ptr %p\n", ptr);
-	}
-	if (!msize) {
-		malloc_zone_error(rack->debug_flags, true, "medium_free_list_add_ptr: msize=0, %p\n", ptr);
-	}
-#endif
-
-	medium_free_list_set_previous(rack, free_ptr, (free_list_t){ .p = NULL });
-	medium_free_list_set_next(rack, free_ptr, free_head);
-
-	// Set the start and end blocks of the meta header as "free". Marking the last block
-	// allows coalescing the regions when we free adjacent regions.
-	medium_free_mark_free(rack, free_ptr, msize);
-
-	if (medium_free_list_get_ptr(rack, free_head)) {
-#if DEBUG_MALLOC
-		if (medium_free_list_get_previous(szone, free_head)) {
-			malloc_zone_error(rack->debug_flags, true, "medium_free_list_add_ptr: Internal invariant broken (free_head->previous != NULL)\n"
-						"ptr=%p slot=%d free_head=%p previous=%p\n", ptr, slot, (void *)free_head, free_head->previous.p);
-		}
-		if (!MEDIUM_PTR_IS_FREE(medium_free_list_get_ptr(szone, free_head))) {
-			malloc_zone_error(rack->debug_flags, true, "medium_free_list_add_ptr: Internal invariant broken (free_head is not a free pointer)\n"
-						"ptr=%p slot=%d free_head=%p\n", ptr, slot, (void *)medium_free_list_get_ptr(szone, free_head));
-		}
-#endif
-		medium_free_list_set_previous(rack, free_head, free_ptr);
-	} else {
-		BITMAPN_SET(medium_mag_ptr->mag_bitmap, slot);
-	}
-
-	medium_mag_ptr->mag_free_list[slot] = free_ptr;
-	return free_ptr;
-}
-
-/*
- * Removes the item pointed to by ptr in the proper free list.
- * Assumes szone has been locked
- */
-static void
-medium_free_list_remove_ptr_no_clear(rack_t *rack, magazine_t *medium_mag_ptr, free_list_t entry, msize_t msize)
-{
-	grain_t slot = MEDIUM_FREE_SLOT_FOR_MSIZE(rack, msize);
-	free_list_t next, previous;
-
-#if DEBUG_MALLOC
-	if (LOG(szone, ptr)) {
-		malloc_report(ASL_LEVEL_INFO, "In %s, ptr=%p, msize=%d\n", __FUNCTION__, ptr, msize);
-	}
-#endif
-
-	previous = medium_free_list_get_previous(rack, entry);
-	next = medium_free_list_get_next(rack, entry);
-
-	if (!medium_free_list_get_ptr(rack, previous)) {
-		// The block to remove is the head of the free list
-#if DEBUG_MALLOC
-		if (medium_mag_ptr->mag_free_list[slot] != ptr) {
-			malloc_zone_error(rack->debug_flags, true,
-					"medium_free_list_remove_ptr_no_clear: Internal invariant broken (medium_mag_ptr->mag_free_list[slot])\n"
-					"ptr=%p slot=%d msize=%d medium_mag_ptr->mag_free_list[slot]=%p\n", ptr, slot, msize,
-					(void *)medium_mag_ptr->mag_free_list[slot]);
-			return;
-		}
-#endif
-		medium_mag_ptr->mag_free_list[slot] = next;
-		if (!medium_free_list_get_ptr(rack, next)) {
-			BITMAPN_CLR(medium_mag_ptr->mag_bitmap, slot);
-		}
-	} else {
-		// Check that the next pointer of "previous" points to "entry".
-		free_list_t prev_next = medium_free_list_get_next(rack, previous);
-		if (medium_free_list_get_ptr(rack, prev_next) != medium_free_list_get_ptr(rack, entry)) {
-			malloc_zone_error(rack->debug_flags, true,
-					"medium_free_list_remove_ptr_no_clear: Internal invariant broken (next ptr of prev) for %p, prev_next=%p\n",
-					medium_free_list_get_ptr(rack, entry), medium_free_list_get_ptr(rack, prev_next));
-			__builtin_unreachable(); // Always crashes in malloc_zone_error().
-		}
-		medium_free_list_set_next(rack, previous, next);
-	}
-
-	if (medium_free_list_get_ptr(rack, next)) {
-		// Check that the previous pointer of "next" points to "entry".
-		free_list_t next_prev = medium_free_list_get_previous(rack, next);
-		if (medium_free_list_get_ptr(rack, next_prev) != medium_free_list_get_ptr(rack, entry)) {
-			malloc_zone_error(rack->debug_flags, true,
-					"medium_free_list_remove_ptr_no_clear: Internal invariant broken (prev ptr of next) for %p, next_prev=%p\n",
-					medium_free_list_get_ptr(rack, entry), medium_free_list_get_ptr(rack, next_prev));
-			__builtin_unreachable(); // Always crashes in malloc_zone_error().
-		}
-		medium_free_list_set_previous(rack, next, previous);
-	}
-
-	if (medium_is_oob_free_entry(entry)) {
-		medium_oob_free_entry_set_free(entry.oob);
-	}
-}
-
-static void
-medium_free_list_remove_ptr(rack_t *rack, magazine_t *medium_mag_ptr, free_list_t entry, msize_t msize)
-{
-	// In the general case we want to ensure we marked these entries as "middle"
-	// while we are in this function. However, when we're moving free list entries
-	// from/to the recirc depot we rely on the metadata bits being intact to
-	// reconstruct the free list. In that case we have to be able to skip this
-	// metadata manipulation.
-	medium_free_mark_middle(rack, entry, msize);
-	medium_free_list_remove_ptr_no_clear(rack, medium_mag_ptr, entry, msize);
-}
-
-// Find a free list entry by its pointer address. This should only really be used
-// by medium_finalize_region, or similar, where the free_list_t entry of a known
-// pointer is desired. Otherwise it is cheaper to always pull off the free lists.
-static free_list_t
-medium_free_list_find_by_ptr(rack_t *rack, magazine_t *medium_mag_ptr, void *ptr, msize_t msize)
-{
-	if (*MEDIUM_METADATA_FOR_PTR(ptr) == (MEDIUM_IS_FREE | msize)) {
-		// If the block is marked free, and of size `msize`, then we first must check
-		// if the alignment+size is such that we could have use an OOB-entry.
-		if (medium_needs_oob_free_entry(ptr, msize)) {
-			// Scan the OOB entries looking for this address.
-			medium_region_t region = MEDIUM_REGION_FOR_PTR(ptr);
-			for (int i=0; i<MEDIUM_OOB_COUNT; i++) {
-				if (!region->medium_oob_free_entries[i].ptr) {
-					continue;
-				}
-				if (medium_oob_free_entry_get_ptr(&region->medium_oob_free_entries[i]) == ptr) {
-					return (free_list_t){ .oob = &region->medium_oob_free_entries[i] };
-				}
-			}
-		}
-
-		// Otherwise, the freed pointer will be in place.
-		return (free_list_t){ .p = ptr };
-	}
-
-	malloc_zone_error(rack->debug_flags, true,
-			"medium_free_list_find_by_ptr: ptr is not free (ptr metadata !MEDIUM_IS_FREE), "
-			"ptr=%p msize=%d metadata=0x%x\n", ptr, msize, *MEDIUM_METADATA_FOR_PTR(ptr));
-	__builtin_trap();
-}
-
-void
-medium_finalize_region(rack_t *rack, magazine_t *medium_mag_ptr)
-{
-	void *last_block, *previous_block;
-	msize_t last_msize, previous_msize, last_index;
-	free_list_t previous;
-
-	// It is possible that the block prior to the last block in the region has
-	// been free'd, but was not coalesced with the free bytes at the end of the
-	// block, since we treat the bytes at the end of the region as "in use" in
-	// the meta headers. Attempt to coalesce the last block with the previous
-	// block, so we don't violate the "no consecutive free blocks" invariant.
-	//
-	// FIXME: If we could calculate the previous medium free size in the same
-	//        manner as tiny_previous_preceding_free, it would eliminate the
-	//        index & previous msize checks, which are a guard against reading
-	//        bogus data out of in-use or written-on-freed memory.
-	//
-	// FIXME: Need to investigate how much work would be required to increase
-	//        'mag_bytes_free_at_end' when freeing the preceding block, rather
-	//        than performing this workaround.
-	//
-	if (medium_mag_ptr->mag_bytes_free_at_end) {
-		last_block = MEDIUM_REGION_HEAP_END(medium_mag_ptr->mag_last_region) - medium_mag_ptr->mag_bytes_free_at_end;
-		last_msize = MEDIUM_MSIZE_FOR_BYTES(medium_mag_ptr->mag_bytes_free_at_end);
-
-		last_index = MEDIUM_META_INDEX_FOR_PTR(last_block);
-		previous_msize = MEDIUM_PREVIOUS_MSIZE(last_block);
-
-		if (last_index && (previous_msize <= last_index)) {
-			previous_block = (void *)((uintptr_t)last_block - MEDIUM_BYTES_FOR_MSIZE(previous_msize));
-
-			if (MEDIUM_PTR_IS_FREE(previous_block)) {
-				previous = medium_free_list_find_by_ptr(rack, medium_mag_ptr, previous_block, previous_msize);
-				medium_free_list_remove_ptr(rack, medium_mag_ptr, previous, previous_msize);
-				last_block = previous_block;
-				last_msize += previous_msize;
-			}
-		}
-
-		// splice last_block into the free list
-		medium_free_list_add_ptr(rack, medium_mag_ptr, last_block, last_msize);
-		medium_mag_ptr->mag_bytes_free_at_end = 0;
-	}
-
-#if CONFIG_ASLR_INTERNAL
-	free_list_t next;
-
-	if (medium_mag_ptr->mag_bytes_free_at_start) {
-		last_block = MEDIUM_REGION_ADDRESS(medium_mag_ptr->mag_last_region);
-		last_msize = MEDIUM_MSIZE_FOR_BYTES(medium_mag_ptr->mag_bytes_free_at_start);
-
-		void *next_block = (void *)((uintptr_t)last_block + medium_mag_ptr->mag_bytes_free_at_start);
-		if (MEDIUM_PTR_IS_FREE(next_block)) {
-			msize_t next_msize = MEDIUM_PTR_SIZE(next_block);
-			next = medium_free_list_find_by_ptr(rack, medium_mag_ptr, next_block, next_msize);
-			medium_free_list_remove_ptr(rack, medium_mag_ptr, next, next_msize);
-			last_msize += next_msize;
-		}
-
-		// splice last_block into the free list
-		medium_free_list_add_ptr(rack, medium_mag_ptr, last_block, last_msize);
-		medium_mag_ptr->mag_bytes_free_at_start = 0;
-	}
-#endif
-
-	// TODO: Will we ever need to coalesce the blocks at the beginning and end when we finalize?
-	medium_mag_ptr->mag_last_region = NULL;
-}
-
-int
-medium_free_detach_region(rack_t *rack, magazine_t *medium_mag_ptr, region_t r)
-{
-	uintptr_t start = (uintptr_t)MEDIUM_REGION_HEAP_BASE(r);
-	uintptr_t current = start;
-	uintptr_t limit = (uintptr_t)MEDIUM_REGION_HEAP_END(r);
-	int total_alloc = 0;
-	msize_t *meta_headers = MEDIUM_META_HEADER_FOR_PTR(start);
-
-	while (current < limit) {
-		unsigned index = MEDIUM_META_INDEX_FOR_PTR(current);
-		msize_t msize_and_free = meta_headers[index];
-		boolean_t is_free = msize_and_free & MEDIUM_IS_FREE;
-		msize_t msize = msize_and_free & ~MEDIUM_IS_FREE;
-
-		if (!msize) {
-#if DEBUG_MALLOC
-			boolean_t is_free = msize_and_free & MEDIUM_IS_FREE;
-			malloc_report(ASL_LEVEL_ERR, "*** medium_free_detach_region error with %p: msize=%d is_free=%d\n", (void *)current, msize, is_free);
-#endif
-			break;
-		}
-
-		if (is_free) {
-			free_list_t entry = medium_free_list_find_by_ptr(rack, medium_mag_ptr, (void *)current, msize);
-			medium_free_list_remove_ptr_no_clear(rack, medium_mag_ptr, entry, msize);
-		} else {
-			total_alloc++;
-		}
-		current += MEDIUM_BYTES_FOR_MSIZE(msize);
-	}
-	return total_alloc;
-}
-
-size_t
-medium_free_reattach_region(rack_t *rack, magazine_t *medium_mag_ptr, region_t r)
-{
-	uintptr_t start = (uintptr_t)MEDIUM_REGION_HEAP_BASE(r);
-	uintptr_t current = start;
-	uintptr_t limit = (uintptr_t)MEDIUM_REGION_HEAP_END(r);
-	size_t total_alloc = 0;
-	msize_t *meta_headers = MEDIUM_META_HEADER_FOR_PTR(start);
-
-	while (current < limit) {
-		unsigned index = MEDIUM_META_INDEX_FOR_PTR(current);
-		msize_t msize_and_free = meta_headers[index];
-		boolean_t is_free = msize_and_free & MEDIUM_IS_FREE;
-		msize_t msize = msize_and_free & ~MEDIUM_IS_FREE;
-
-		if (!msize) {
-#if DEBUG_MALLOC
-			malloc_report(ASL_LEVEL_ERR, "*** medium_free_reattach_region error with %p: msize=%d is_free=%d\n", (void *)current, msize, is_free);
-#endif
-			break;
-		}
-		if (is_free) {
-			medium_free_list_add_ptr(rack, medium_mag_ptr, (void *)current, msize);
-		} else {
-			total_alloc += MEDIUM_BYTES_FOR_MSIZE(msize);
-		}
-		current += MEDIUM_BYTES_FOR_MSIZE(msize);
-	}
-	return total_alloc;
-}
-
-typedef struct _medium_advisory_s {
-	struct _medium_advisory_s *next;
-	size_t size;
-} medium_advisory_s, *medium_advisory_t;
-
-void
-medium_free_scan_madvise_free(rack_t *rack, magazine_t *depot_ptr, region_t r)
-{
-	uintptr_t start = (uintptr_t)MEDIUM_REGION_HEAP_BASE(r);
-	uintptr_t current = start;
-	uintptr_t limit = (uintptr_t)MEDIUM_REGION_HEAP_END(r);
-	msize_t *meta_headers = MEDIUM_META_HEADER_FOR_PTR(start);
-	msize_t *madv_headers = MEDIUM_MADVISE_HEADER_FOR_PTR(start);
-
-	medium_advisory_t advisories = NULL;
-
-	// Scan the metadata identifying blocks which span one or more pages. Mark
-	// the pages MADV_FREE taking care to preserve free list management data.
-	while (current < limit) {
-		unsigned index = MEDIUM_META_INDEX_FOR_PTR(current);
-
-		msize_t alloc_msize = meta_headers[index] & ~MEDIUM_IS_FREE;
-		bool alloc_is_free = meta_headers[index] & MEDIUM_IS_FREE;
-
-		if (alloc_is_free && alloc_msize == MEDIUM_MAX_MSIZE) {
-			// The first allocation is both free and covers the entire of the
-			// zone.
-#if DEBUG_MALLOC
-			// first block is all free
-			malloc_report(ASL_LEVEL_ERR, "*** medium_free_scan_madvise_free "
-					"first block is all free! %p: msize=%d is_free=%d\n",
-					(void *)current, alloc_msize, alloc_is_free);
-#endif
-			uintptr_t pgLo = round_page_kernel(start + sizeof(medium_inplace_free_entry_s) +
-					sizeof(msize_t));
-			uintptr_t pgHi = trunc_page_kernel(start - sizeof(msize_t) +
-					(NUM_MEDIUM_BLOCKS << SHIFT_MEDIUM_QUANTUM));
-
-			if (pgLo < pgHi) {
-				medium_advisory_t mat = (medium_advisory_t)pgLo;
-				mat->next = advisories;
-				mat->size = pgHi - pgLo;
-				advisories = mat;
-			}
-			break;
-		}
-		if (!alloc_msize) {
-#if DEBUG_MALLOC
-			malloc_report(ASL_LEVEL_ERR, "*** medium_free_scan_madvise_free "
-					"error with %p: msize=%d is_free=%d\n", (void *)current,
-					msize, is_free);
-#endif
-			break;
-		}
-		if (alloc_is_free) {
-			msize_t advise_msize = madv_headers[index]
-				& ~MEDIUM_IS_ADVISED;
-			bool run_is_advised = madv_headers[index]
-				& MEDIUM_IS_ADVISED;
-
-			if (advise_msize != alloc_msize || !run_is_advised) {
-				uintptr_t pgLo = round_page_kernel(current + 
-						sizeof(medium_inplace_free_entry_s) + sizeof(msize_t));
-				uintptr_t pgHi = trunc_page_kernel(current - sizeof(msize_t) +
-						MEDIUM_BYTES_FOR_MSIZE(alloc_msize));
-
-				if (pgLo < pgHi) {
-					medium_advisory_t mat = (medium_advisory_t)pgLo;
-					mat->next = advisories;
-					mat->size = pgHi - pgLo;
-					advisories = mat;
-				}
-
-				memset(&madv_headers[index], 0, sizeof(uint16_t) * alloc_msize);
-				medium_madvise_header_mark_clean(madv_headers, index,
-						alloc_msize);
-			}
-		}
-		current += MEDIUM_BYTES_FOR_MSIZE(alloc_msize);
-	}
-
-	if (advisories) {
-		OSAtomicIncrement32Barrier(
-				&(REGION_TRAILER_FOR_MEDIUM_REGION(r)->pinned_to_depot));
-		SZONE_MAGAZINE_PTR_UNLOCK(depot_ptr);
-		while (advisories) {
-			uintptr_t addr = (uintptr_t)advisories;
-			size_t size = advisories->size;
-			advisories = advisories->next;
-
-			mvm_madvise_free(rack, r, addr, addr + size, NULL,
-					rack->debug_flags & MALLOC_DO_SCRIBBLE);
-		}
-		SZONE_MAGAZINE_PTR_LOCK(depot_ptr);
-		OSAtomicDecrement32Barrier(
-				&(REGION_TRAILER_FOR_MEDIUM_REGION(r)->pinned_to_depot));
-	}
-}
-
-static region_t
-medium_find_msize_region(rack_t *rack, magazine_t *medium_mag_ptr, mag_index_t mag_index, msize_t msize)
-{
-	void *ptr;
-	grain_t slot = MEDIUM_FREE_SLOT_FOR_MSIZE(rack, msize);
-	free_list_t *free_list = medium_mag_ptr->mag_free_list;
-	free_list_t *the_slot = free_list + slot;
-	free_list_t *limit;
-	unsigned bitmap;
-
-	// Assumes we've locked the magazine
-	CHECK_MAGAZINE_PTR_LOCKED(szone, medium_mag_ptr, __PRETTY_FUNCTION__);
-
-	// Look for an exact match by checking the freelist for this msize.
-	ptr = medium_free_list_get_ptr(rack, *the_slot);
-	if (ptr) {
-		return MEDIUM_REGION_FOR_PTR(ptr);
-	}
-
-	// Mask off the bits representing slots holding free blocks smaller than
-	// the size we need.
-	//
-	// BITMAPN_CTZ implementation
-	unsigned idx = slot >> 5;
-	bitmap = 0;
-	unsigned mask = ~((1 << (slot & 31)) - 1);
-	for (; idx < MEDIUM_FREELIST_BITMAP_WORDS(rack); ++idx) {
-		bitmap = medium_mag_ptr->mag_bitmap[idx] & mask;
-		if (bitmap != 0) {
-			break;
-		}
-		mask = ~0U;
-	}
-	// Check for fallthrough: No bits set in bitmap
-	if ((bitmap == 0) && (idx == MEDIUM_FREELIST_BITMAP_WORDS(rack))) {
-		return NULL;
-	}
-
-	// Start looking at the first set bit, plus 32 bits for every word of
-	// zeroes or entries that were too medium.
-	slot = BITMAP32_CTZ((&bitmap)) + (idx * 32);
-
-	limit = free_list + MEDIUM_FREE_SLOT_COUNT(rack) - 1;
-	free_list += slot;
-
-	if (free_list < limit) {
-		ptr = medium_free_list_get_ptr(rack, *free_list);
-		if (ptr) {
-			return MEDIUM_REGION_FOR_PTR(ptr);
-		} else {
-			/* Shouldn't happen. Fall through to look at last slot. */
-#if DEBUG_MALLOC
-			malloc_report(ASL_LEVEL_ERR, "in medium_malloc_from_free_list(), mag_bitmap out of sync, slot=%d\n", slot);
-#endif
-		}
-	}
-
-	// We are now looking at the last slot, which contains blocks equal to, or
-	// due to coalescing of free blocks, larger than (num_medium_slots - 1) * (medium quantum size).
-	ptr = medium_free_list_get_ptr(rack, *limit);
-	if (ptr) {
-		return MEDIUM_REGION_FOR_PTR(ptr);
-	}
-
-	return NULL;
-}
-
-static boolean_t
-medium_get_region_from_depot(rack_t *rack, magazine_t *medium_mag_ptr, mag_index_t mag_index, msize_t msize)
-{
-	magazine_t *depot_ptr = &(rack->magazines[DEPOT_MAGAZINE_INDEX]);
-
-#if DEBUG_MALLOC
-	if (DEPOT_MAGAZINE_INDEX == mag_index) {
-		malloc_zone_error(rack->debug_flags, true, "medium_get_region_from_depot called for magazine index -1\n", NULL, NULL);
-		return 0;
-	}
-#endif
-
-	SZONE_MAGAZINE_PTR_LOCK(depot_ptr);
-
-	// Appropriate a Depot'd region that can satisfy requested msize.
-	region_trailer_t *node;
-	region_t sparse_region;
-	msize_t try_msize = msize;
-
-	while (1) {
-		sparse_region = medium_find_msize_region(rack, depot_ptr, DEPOT_MAGAZINE_INDEX, try_msize);
-		if (NULL == sparse_region) { // Depot empty?
-			SZONE_MAGAZINE_PTR_UNLOCK(depot_ptr);
-			return 0;
-		}
-
-		node = REGION_TRAILER_FOR_MEDIUM_REGION(sparse_region);
-		if (0 == node->pinned_to_depot) {
-			// Found one!
-			break;
-		}
-
-		// Try the next msize up - maybe the head of its free list will be in
-		// a region we can use. Once we get the region we'll still allocate the
-		// original msize.
-		try_msize++;
-
-		if (try_msize > NUM_MEDIUM_SLOTS) {
-			// Tried all the msizes but couldn't get a usable region. Let's
-			// give up for now and we'll allocate a new region from the kernel.
-			SZONE_MAGAZINE_PTR_UNLOCK(depot_ptr);
-			return 0;
-		}
-	}
-
-	// disconnect node from Depot
-	recirc_list_extract(rack, depot_ptr, node);
-
-	// Iterate the region pulling its free entries off the (locked) Depot's free list
-	int objects_in_use = medium_free_detach_region(rack, depot_ptr, sparse_region);
-
-	// Transfer ownership of the region
-	MAGAZINE_INDEX_FOR_MEDIUM_REGION(sparse_region) = mag_index;
-	MALLOC_ASSERT(node->pinned_to_depot == 0);
-
-	// Iterate the region putting its free entries on its new (locked) magazine's free list
-	size_t bytes_inplay = medium_free_reattach_region(rack, medium_mag_ptr, sparse_region);
-
-	depot_ptr->mag_num_bytes_in_objects -= bytes_inplay;
-	depot_ptr->num_bytes_in_magazine -= MEDIUM_REGION_PAYLOAD_BYTES;
-	depot_ptr->mag_num_objects -= objects_in_use;
-
-	medium_mag_ptr->mag_num_bytes_in_objects += bytes_inplay;
-	medium_mag_ptr->num_bytes_in_magazine += MEDIUM_REGION_PAYLOAD_BYTES;
-	medium_mag_ptr->mag_num_objects += objects_in_use;
-
-	// connect to magazine as first node
-	recirc_list_splice_first(rack, medium_mag_ptr, node);
-
-	SZONE_MAGAZINE_PTR_UNLOCK(depot_ptr);
-
-	MAGMALLOC_DEPOTREGION(MEDIUM_SZONE_FROM_RACK(rack), (int)mag_index, (void *)sparse_region, MEDIUM_REGION_SIZE,
-						  (int)BYTES_USED_FOR_MEDIUM_REGION(sparse_region)); // DTrace USDT Probe
-
-	return 1;
-}
-
-#if CONFIG_MADVISE_PRESSURE_RELIEF
-void
-medium_madvise_pressure_relief(rack_t *rack)
-{
-	mag_index_t mag_index;
-	magazine_t *medium_depot_ptr = &rack->magazines[DEPOT_MAGAZINE_INDEX];
-
-	for (mag_index = 0; mag_index < rack->num_magazines; mag_index++) {
-		size_t index;
-		for (index = 0; index < rack->region_generation->num_regions_allocated; ++index) {
-			rack_region_lock(rack);
-
-			region_t medium = rack->region_generation->hashed_regions[index];
-			if (!medium || medium == HASHRING_REGION_DEALLOCATED) {
-				rack_region_unlock(rack);
-				continue;
-			}
-
-			region_trailer_t *trailer =
-					REGION_TRAILER_FOR_MEDIUM_REGION(medium);
-			// Make sure that the owning magazine doesn't try and take this out
-			// from under our feet.
-			trailer->dispose_flags |= RACK_DISPOSE_DELAY;
-			rack_region_unlock(rack);
-
-			magazine_t *mag_ptr = mag_lock_zine_for_region_trailer(rack->magazines,
-					trailer, MAGAZINE_INDEX_FOR_MEDIUM_REGION(medium));
-
-			// If acquiring the region lock was enough to prevent the owning
-			// magazine from deallocating the region, free it now so we don't
-			// do wasted work.
-			if (rack_region_maybe_dispose(rack, medium, MEDIUM_REGION_SIZE, trailer)) {
-				SZONE_MAGAZINE_PTR_UNLOCK(mag_ptr);
-				continue;
-			}
-
-			/* Ordering is important here, the magazine of a region may potentially change
-			 * during mag_lock_zine_for_region_trailer, so src_mag_index must be taken
-			 * after we've obtained the lock.
-			 */
-			mag_index_t src_mag_index = MAGAZINE_INDEX_FOR_MEDIUM_REGION(medium);
-
-			/* We can (and must) ignore magazines that are already in the recirc depot. */
-			if (src_mag_index == DEPOT_MAGAZINE_INDEX) {
-				SZONE_MAGAZINE_PTR_UNLOCK(mag_ptr);
-				continue;
-			}
-
-			if (REGION_TRAILER_FOR_MEDIUM_REGION(medium)->pinned_to_depot > 0) {
-				SZONE_MAGAZINE_PTR_UNLOCK(mag_ptr);
-				continue;
-			}
-
-			if (medium == mag_ptr->mag_last_region && (mag_ptr->mag_bytes_free_at_end || mag_ptr->mag_bytes_free_at_start)) {
-				medium_finalize_region(rack, mag_ptr);
-			}
-
-			/* Because this region is currently in use, we can't safely madvise it while
-			 * it's attached to the magazine. For this operation we have to remove it from
-			 * the current mag, attach it to the depot and then madvise.
-			 */
-
-			recirc_list_extract(rack, mag_ptr, REGION_TRAILER_FOR_MEDIUM_REGION(medium));
-			int objects_in_use = medium_free_detach_region(rack, mag_ptr, medium);
-
-			SZONE_MAGAZINE_PTR_LOCK(medium_depot_ptr);
-			MAGAZINE_INDEX_FOR_MEDIUM_REGION(medium) = DEPOT_MAGAZINE_INDEX;
-			MALLOC_ASSERT(REGION_TRAILER_FOR_MEDIUM_REGION(medium)->pinned_to_depot == 0);
-
-			size_t bytes_inplay = medium_free_reattach_region(rack, medium_depot_ptr, medium);
-
-			/* Fix up the metadata of the target magazine while the region is in the depot. */
-			mag_ptr->mag_num_bytes_in_objects -= bytes_inplay;
-			mag_ptr->num_bytes_in_magazine -= MEDIUM_REGION_PAYLOAD_BYTES;
-			mag_ptr->mag_num_objects -= objects_in_use;
-
-			/* Now we can drop the magazine lock of the source mag. */
-			SZONE_MAGAZINE_PTR_UNLOCK(mag_ptr);
-
-			medium_depot_ptr->mag_num_bytes_in_objects += bytes_inplay;
-			medium_depot_ptr->num_bytes_in_magazine += MEDIUM_REGION_PAYLOAD_BYTES;
-			medium_depot_ptr->mag_num_objects -= objects_in_use;
-
-			recirc_list_splice_last(rack, medium_depot_ptr, REGION_TRAILER_FOR_MEDIUM_REGION(medium));
-
-			/* Actually do the scan, done holding the depot lock, the call will drop the lock
-			 * around the actual madvise syscalls.
-			 */
-			medium_free_scan_madvise_free(rack, medium_depot_ptr, medium);
-
-			/* Now the region is in the recirc depot, the next allocations to require more
-			 * blocks will come along and take one of these regions back out of the depot.
-			 * As OS X madvise's reuse on an per-region basis, we leave as many of these
-			 * regions in the depot as possible after memory pressure.
-			 */
-			SZONE_MAGAZINE_PTR_UNLOCK(medium_depot_ptr);
-		}
-	}
-}
-#endif // CONFIG_MADVISE_PRESSURE_RELIEF
-
-static MALLOC_INLINE void
-medium_madvise_free_range_conditional_no_lock(rack_t *rack, magazine_t *mag_ptr,
-		size_t trigger_level, region_t region, free_list_t *fl, msize_t flmsz,
-		void *ptr, size_t sz)
-{
-	region_trailer_t *node = REGION_TRAILER_FOR_MEDIUM_REGION(region);
-	msize_t *madvh = MEDIUM_MADVISE_HEADER_FOR_PTR(ptr);
-	msize_t trigger_msize = trigger_level >> SHIFT_MEDIUM_QUANTUM;
-
-	size_t free_header_size = sizeof(medium_inplace_free_entry_s) + sizeof(msize_t);
-	size_t free_trailer_size = sizeof(msize_t);
-	// We have to avoid the free_list header at the start of the allocation
-	// unless the entry is out in the OOB area, in which case, we can madvise
-	// the whole region.
-	if (medium_is_oob_free_entry(*fl)) {
-		free_header_size = 0;
-		free_trailer_size = 0;
-	}
-
-	uintptr_t rangep = (uintptr_t)medium_free_list_get_ptr(rack, *fl);
-	msize_t range_idx = MEDIUM_META_INDEX_FOR_PTR(rangep);
-	msize_t range_msz = flmsz;
-
-	msize_t src_idx = MEDIUM_META_INDEX_FOR_PTR(ptr);
-	msize_t src_msz = MEDIUM_MSIZE_FOR_BYTES(sz);
-	msize_t src_end_idx = src_idx + src_msz - 1;
-	medium_madvise_header_mark_middle(madvh, src_idx);
-	medium_madvise_header_mark_middle(madvh, src_idx + src_msz - 1);
-
-	msize_t left_end_idx = src_idx - 1;
-	msize_t left_msz = src_idx - range_idx;
-	msize_t right_start_idx = src_idx + src_msz;
-	msize_t right_end_idx = range_idx + range_msz - 1;
-	msize_t right_msz = right_end_idx - right_start_idx + 1;
-
-	msize_t dirty_msz = src_msz;
-
-	size_t vote_force = 0;
-	msize_t left_dirty_msz = 0;
-	if (range_idx < src_idx) {
-		// Peek back one block and see if the range directly in front of this
-		// one had any blocks that had not been madvised.
-		left_dirty_msz = medium_madvise_header_dirty_len(madvh, left_end_idx);
-		if (left_dirty_msz) {
-			dirty_msz += left_dirty_msz;
-		} else if (src_idx - range_idx > src_msz) {
-			// The left-hand region was actually clean, so only choose to
-			// madvise if the center region is enclosured by clean data.
-			vote_force++;
-		}
-		medium_madvise_header_mark_middle(madvh, range_idx);
-		medium_madvise_header_mark_middle(madvh, left_end_idx);
-	}
-
-	msize_t right_dirty_msz = 0;
-	if (right_end_idx > src_end_idx) {
-		// Same as above, if we had trailing data coalesced with this entry
-		// and that was not madvised, consider it, too.
-		right_dirty_msz = medium_madvise_header_dirty_len(madvh, right_start_idx);
-		if (right_dirty_msz) {
-			dirty_msz += right_dirty_msz;
-		} else if (right_end_idx - right_start_idx > src_msz) {
-			vote_force++;
-		}
-		medium_madvise_header_mark_middle(madvh, right_start_idx);
-		medium_madvise_header_mark_middle(madvh, right_end_idx);
-	}
-
-	// We absolutely can't madvise lower than the free-list entry pointer plus
-	// the header size. When the entry is OOB, there's no header or footer to
-	// store in memory.
-	uintptr_t safe_start_ptr = round_page_kernel(rangep + free_header_size);
-	uintptr_t safe_end_ptr = trunc_page_kernel(rangep +
-			MEDIUM_BYTES_FOR_MSIZE(range_msz) - free_trailer_size);
-
-	// If the target region is madvisable, then madvise whatever we can but
-	// bound it by the safe_start/end pointers to make sure we don't clobber
-	// the free-list.
-	bool should_madvise = (vote_force == 2) || (dirty_msz >= trigger_msize);
-	if (magazine_medium_madvise_window_scale_factor > 1) {
-		// trigger_msize is an unsigned short, but it's possible that trigger level was larger than UINT16_MAX
-		// even after we shifted it. In this case the window rolls around to 0. This is even more likely
-		// if we're scaling the window up. We should fix the truncation bug above, but doing so
-		// will cause a memory regression. For now, we avoid using trigger_msize iff we're scaling
-		// the window up since truncating to 0 would be self-defeating in this case.
-		// See rdar://82128639 for details
-		should_madvise = (vote_force == 2) || (MEDIUM_BYTES_FOR_MSIZE(dirty_msz) >= trigger_level);
-	}
-	if (should_madvise) {
-		uintptr_t lo = MAX((uintptr_t)MEDIUM_PTR_FOR_META_INDEX(region, range_idx),
-				safe_start_ptr);
-		uintptr_t hi = MIN((uintptr_t)MEDIUM_PTR_FOR_META_INDEX(region, range_idx) +
-				MEDIUM_BYTES_FOR_MSIZE(range_msz), safe_end_ptr);
-
-		// The page that contains the freelist entry needs to be marked as not
-		// having been madvised. Note that the quantum is larger than the kernel page size
-		// so if safe_start_ptr and rangep are on different pages, we just mark
-		// the whole block as clean.
-		if (range_idx < MEDIUM_META_INDEX_FOR_PTR(safe_start_ptr)) {
-			medium_madvise_header_mark_dirty(madvh, range_idx,
-					MEDIUM_META_INDEX_FOR_PTR(safe_start_ptr) - range_idx);
-		}
-		if (range_idx + range_msz > MEDIUM_META_INDEX_FOR_PTR(safe_end_ptr)) {
-			medium_madvise_header_mark_dirty(madvh,
-					MEDIUM_META_INDEX_FOR_PTR(safe_end_ptr), range_idx +
-					range_msz - MEDIUM_META_INDEX_FOR_PTR(safe_end_ptr));
-		}
-
-		medium_madvise_header_mark_clean(madvh,
-				MEDIUM_META_INDEX_FOR_PTR(lo),
-				MEDIUM_META_INDEX_FOR_PTR(hi) - MEDIUM_META_INDEX_FOR_PTR(lo));
-
-		// Mark the whole region as off-limits for the allocator while we drop
-		// the lock and go to the kernel.
-		medium_free_mark_unfree(rack, *fl, flmsz);
-		medium_free_list_remove_ptr_no_clear(rack, mag_ptr, *fl, flmsz);
-		OSAtomicIncrement32Barrier(&node->pinned_to_depot);
-		SZONE_MAGAZINE_PTR_UNLOCK(mag_ptr);
-
-		mvm_madvise_free(rack, region, lo, hi,
-				&rack->last_madvise, rack->debug_flags & MALLOC_DO_SCRIBBLE);
-
-		SZONE_MAGAZINE_PTR_LOCK(mag_ptr);
-		OSAtomicDecrement32Barrier(&node->pinned_to_depot);
-		*fl = medium_free_list_add_ptr(rack, mag_ptr, (void *)rangep, flmsz);
-	} else {
-		// We chose not to madvise, we need to re-mark the region as dirty
-		// for when we come back to it later.
-		if (left_dirty_msz < left_msz) {
-			/* The preceding block was clean. */
-			medium_madvise_header_mark_clean(madvh, range_idx,
-					left_msz - left_dirty_msz);
-		}
-		if (right_dirty_msz < right_msz) {
-			/* The trailing block was clean. */
-			medium_madvise_header_mark_clean(madvh, right_start_idx +
-					right_dirty_msz, right_msz - right_dirty_msz);
-		}
-		medium_madvise_header_mark_dirty(madvh, src_idx - left_dirty_msz,
-				src_msz + right_dirty_msz + left_dirty_msz);
-	}
-}
-
-#if CONFIG_AGGRESSIVE_MADVISE || CONFIG_RECIRC_DEPOT
-static MALLOC_INLINE void
-medium_madvise_free_range_no_lock(rack_t *rack,
-								 magazine_t *medium_mag_ptr,
-								 size_t trigger_level,
-								 region_t region,
-								 free_list_t freee,
-								 msize_t fmsize,
-								 void *headptr,
-								 size_t headsize)
-{
-	void *ptr = medium_free_list_get_ptr(rack, freee);
-	region_trailer_t *node = REGION_TRAILER_FOR_MEDIUM_REGION(region);
-
-	// Lock on medium_magazines[mag_index] is already held here.
-	// Calculate the first page in the coalesced block that would be safe to mark MADV_FREE
-	size_t free_header_size = sizeof(medium_inplace_free_entry_s) + sizeof(msize_t);
-
-	// If the free_list_t entry is out-of-line then we don't need to reserve any space
-	// at the start of the region.
-	if (medium_is_oob_free_entry(freee)) {
-		free_header_size = 0;
-	}
-
-	uintptr_t safe_ptr = (uintptr_t)ptr + free_header_size;
-	uintptr_t round_safe = round_page_kernel(safe_ptr);
-
-	// Calculate the last page in the coalesced block that would be safe to mark MADV_FREE
-	uintptr_t safe_extent = (uintptr_t)ptr + MEDIUM_BYTES_FOR_MSIZE(fmsize);
-	uintptr_t trunc_extent = trunc_page_kernel(safe_extent);
-
-	// If the region spans more than the madvise trigger level, then mark the
-	// pages as advise-freed.
-	if (round_safe + trigger_level < trunc_extent) {
-		// Extend the freed block by the free region header and tail sizes to include pages
-		// we may have coalesced that no longer host free region tails and headers.
-		// This may extend over in-use ranges, but the MIN/MAX clamping below will fix that up.
-		uintptr_t lo = trunc_page_kernel((uintptr_t)headptr);
-		uintptr_t hi = round_page_kernel((uintptr_t)headptr + headsize + free_header_size);
-
-		uintptr_t free_lo = MAX(round_safe, lo);
-		uintptr_t free_hi = MIN(trunc_extent, hi);
-
-		if (free_lo < free_hi) {
-			// Before unlocking, ensure that the metadata for the freed region
-			// makes it look not free but includes the length. This ensures that
-			// any code that inspects the metadata while we are unlocked sees
-			// a valid state and will not try to use or coalesce freed memory
-			// into it.
-			medium_free_mark_unfree(rack, freee, fmsize);
-			medium_free_list_remove_ptr_no_clear(rack, medium_mag_ptr, freee, fmsize);
-			OSAtomicIncrement32Barrier(&(node->pinned_to_depot));
-			SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-			mvm_madvise_free(rack, region, free_lo, free_hi, &rack->last_madvise, rack->debug_flags & MALLOC_DO_SCRIBBLE);
-			SZONE_MAGAZINE_PTR_LOCK(medium_mag_ptr);
-			OSAtomicDecrement32Barrier(&(node->pinned_to_depot));
-			medium_free_list_add_ptr(rack, medium_mag_ptr, ptr, fmsize);
-		}
-	}
-}
-#endif // CONFIG_AGGRESSIVE_MADVISE || CONFIG_RECIRC_DEPOT
-
-#if CONFIG_RECIRC_DEPOT
-static region_t
-medium_free_try_depot_unmap_no_lock(rack_t *rack, magazine_t *depot_ptr, region_trailer_t *node)
-{
-	if (0 < node->bytes_used || 0 < node->pinned_to_depot || depot_ptr->recirculation_entries < recirc_retained_regions) {
-		return NULL;
-	}
-
-	// disconnect first node from Depot
-	recirc_list_extract(rack, depot_ptr, node);
-
-	// Iterate the region pulling its free entries off the (locked) Depot's free list
-	region_t sparse_region = MEDIUM_REGION_FOR_PTR(node);
-	int objects_in_use = medium_free_detach_region(rack, depot_ptr, sparse_region);
-
-	if (0 == objects_in_use) {
-		if (!rack_region_remove(rack, sparse_region, node)) {
-			return NULL;
-		}
-		depot_ptr->num_bytes_in_magazine -= MEDIUM_REGION_PAYLOAD_BYTES;
-
-		// Caller will transfer ownership of the region back to the OS with no locks held
-		MAGMALLOC_DEALLOCREGION(MEDIUM_SZONE_FROM_RACK(rack), (void *)sparse_region, (int)MEDIUM_REGION_SIZE); // DTrace USDT Probe
-		return sparse_region;
-
-	} else {
-		malloc_zone_error(rack->debug_flags, true, "medium_free_try_depot_unmap_no_lock objects_in_use not zero: %d\n", objects_in_use);
-		return NULL;
-	}
-}
-
-static boolean_t
-medium_free_do_recirc_to_depot(rack_t *rack, magazine_t *medium_mag_ptr, mag_index_t mag_index)
-{
-	// The entire magazine crossed the "emptiness threshold". Transfer a region
-	// from this magazine to the Depot. Choose a region that itself has crossed the emptiness threshold (i.e
-	// is at least fraction "f" empty.) Such a region will be marked "suitable" on the recirculation list.
-	region_trailer_t *node = medium_mag_ptr->firstNode;
-
-	while (node && (!node->recirc_suitable || node->pinned_to_depot)) {
-		node = node->next;
-	}
-
-	if (NULL == node) {
-#if DEBUG_MALLOC
-		malloc_report(ASL_LEVEL_ERR, "*** medium_free_do_recirc_to_depot end of list\n");
-#endif
-		return TRUE; // Caller must SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-	}
-
-	region_t sparse_region = MEDIUM_REGION_FOR_PTR(node);
-
-	// Deal with unclaimed memory -- mag_bytes_free_at_end or mag_bytes_free_at start
-	if (sparse_region == medium_mag_ptr->mag_last_region &&
-		(medium_mag_ptr->mag_bytes_free_at_end || medium_mag_ptr->mag_bytes_free_at_start)) {
-		medium_finalize_region(rack, medium_mag_ptr);
-	}
-
-	// disconnect "suitable" node from magazine
-	recirc_list_extract(rack, medium_mag_ptr, node);
-
-	// Iterate the region pulling its free entries off its (locked) magazine's free list
-	int objects_in_use = medium_free_detach_region(rack, medium_mag_ptr, sparse_region);
-	magazine_t *depot_ptr = &(rack->magazines[DEPOT_MAGAZINE_INDEX]);
-
-	// hand over the region to the (locked) Depot
-	SZONE_MAGAZINE_PTR_LOCK(depot_ptr);
-	// this will cause medium_free_list_add_ptr called by medium_free_reattach_region to use
-	// the depot as its target magazine, rather than magazine formerly associated with sparse_region
-	MAGAZINE_INDEX_FOR_MEDIUM_REGION(sparse_region) = DEPOT_MAGAZINE_INDEX;
-	node->pinned_to_depot = 0;
-
-	// Iterate the region putting its free entries on Depot's free list
-	size_t bytes_inplay = medium_free_reattach_region(rack, depot_ptr, sparse_region);
-
-	medium_mag_ptr->mag_num_bytes_in_objects -= bytes_inplay;
-	medium_mag_ptr->num_bytes_in_magazine -= MEDIUM_REGION_PAYLOAD_BYTES;
-	medium_mag_ptr->mag_num_objects -= objects_in_use;
-
-	SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr); // Unlock the originating magazine
-
-	depot_ptr->mag_num_bytes_in_objects += bytes_inplay;
-	depot_ptr->num_bytes_in_magazine += MEDIUM_REGION_PAYLOAD_BYTES;
-	depot_ptr->mag_num_objects += objects_in_use;
-
-	// connect to Depot as last node
-	recirc_list_splice_last(rack, depot_ptr, node);
-
-	MAGMALLOC_RECIRCREGION(MEDIUM_SZONE_FROM_RACK(rack), (int)mag_index, (void *)sparse_region, MEDIUM_REGION_SIZE,
-						   (int)BYTES_USED_FOR_MEDIUM_REGION(sparse_region)); // DTrace USDT Probe
-
-#if CONFIG_AGGRESSIVE_MADVISE
-	if (!aggressive_madvise_enabled)
-#endif
-	{
-		// Mark free'd dirty pages with MADV_FREE to reduce memory pressure
-		medium_free_scan_madvise_free(rack, depot_ptr, sparse_region);
-	}
-
-	// If the region is entirely empty vm_deallocate() it outside the depot lock
-	region_t r_dealloc = medium_free_try_depot_unmap_no_lock(rack, depot_ptr, node);
-	SZONE_MAGAZINE_PTR_UNLOCK(depot_ptr);
-	if (r_dealloc) {
-		mvm_deallocate_pages(r_dealloc, MEDIUM_REGION_SIZE,
-				MALLOC_FIX_GUARD_PAGE_FLAGS(rack->debug_flags));
-	}
-	return FALSE; // Caller need not unlock the originating magazine
-}
-
-static MALLOC_INLINE boolean_t
-medium_free_try_recirc_to_depot(rack_t *rack,
-							   magazine_t *medium_mag_ptr,
-							   mag_index_t mag_index,
-							   region_t region,
-							   free_list_t freee,
-							   msize_t msize,
-							   void *headptr,
-							   size_t headsize)
-{
-	region_trailer_t *node = REGION_TRAILER_FOR_MEDIUM_REGION(region);
-	size_t bytes_used = node->bytes_used;
-
-	if (DEPOT_MAGAZINE_INDEX != mag_index) {
-		// Emptiness discriminant
-		if (bytes_used < DENSITY_THRESHOLD(MEDIUM_REGION_PAYLOAD_BYTES)) {
-			/* Region has crossed threshold from density to sparsity. Mark it "suitable" on the
-			 * recirculation candidates list. */
-			node->recirc_suitable = TRUE;
-		} else {
-			/* After this free, we've found the region is still dense, so it must have been even more so before
-			 * the free. That implies the region is already correctly marked. Do nothing. */
-		}
-
-		// Has the entire magazine crossed the "emptiness threshold"? If so, transfer a region
-		// from this magazine to the Depot. Choose a region that itself has crossed the emptiness threshold (i.e
-		// is at least fraction "f" empty.) Such a region will be marked "suitable" on the recirculation list.
-
-		size_t a = medium_mag_ptr->num_bytes_in_magazine;	// Total bytes allocated to this magazine
-		size_t u = medium_mag_ptr->mag_num_bytes_in_objects; // In use (malloc'd) from this magaqzine
-
-		if (a - u > ((3 * MEDIUM_REGION_PAYLOAD_BYTES) / 2) && u < DENSITY_THRESHOLD(a)) {
-			return medium_free_do_recirc_to_depot(rack, medium_mag_ptr, mag_index);
-		}
-
-	} else {
-#if CONFIG_AGGRESSIVE_MADVISE
-		if (!aggressive_madvise_enabled)
-#endif
-		{
-			// We are free'ing into the depot, so madvise as we do so unless we were madvising every incoming
-			// allocation anyway.
-			medium_madvise_free_range_no_lock(rack, medium_mag_ptr,
-					vm_kernel_page_size, region, freee, msize, headptr, headsize);
-		}
-
-		if (0 < bytes_used || 0 < node->pinned_to_depot) {
-			/* Depot'd region is still live. Leave it in place on the Depot's recirculation list
-			 * so as to avoid thrashing between the Depot's free list and a magazines's free list
-			 * with detach_region/reattach_region */
-		} else {
-			/* Depot'd region is just now empty. Consider return to OS. */
-			region_t r_dealloc = medium_free_try_depot_unmap_no_lock(rack, medium_mag_ptr, node);
-			SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-			if (r_dealloc) {
-				mvm_deallocate_pages(r_dealloc, MEDIUM_REGION_SIZE, MALLOC_FIX_GUARD_PAGE_FLAGS(rack->debug_flags));
-			}
-			return FALSE; // Caller need not unlock
-		}
-	}
-	return TRUE; // Caller must do SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr)
-}
-#endif // CONFIG_RECIRC_DEPOT
-
-static MALLOC_INLINE boolean_t
-medium_free_no_lock(rack_t *rack, magazine_t *medium_mag_ptr, mag_index_t mag_index, region_t region, void *ptr, msize_t msize)
-{
-	msize_t *meta_headers = MEDIUM_META_HEADER_FOR_PTR(ptr);
-	unsigned index = MEDIUM_META_INDEX_FOR_PTR(ptr);
-	size_t original_size = MEDIUM_BYTES_FOR_MSIZE(msize);
-	void *next_block = ptr + original_size;
-	msize_t next_index = index + msize;
-
-	MALLOC_TRACE(TRACE_medium_free, (uintptr_t)rack, (uintptr_t)medium_mag_ptr, (uintptr_t)ptr, MEDIUM_BYTES_FOR_MSIZE(msize));
-
-	void *original_ptr = ptr;
-
-#if DEBUG_MALLOC
-	if (!msize) {
-		malloc_zone_error(rack->debug_flags, true, "trying to free medium block "
-				"that is too small in medium_free_no_lock(), ptr=%p, msize=%d\n",
-				ptr, msize);
-	}
-	if (medium_madvise_header_dirty_len(MEDIUM_MADVISE_HEADER_FOR_PTR(ptr), index) == 0) {
-		malloc_zone_error(rack->debug_flags, true, "incoming freed block is not "
-				"marked as dirty in madvise metadata, ptr=%p, msize=%d\n",
-				ptr, msize);
-	}
-#endif
-
-	// Check that the region cookie is intact.
-	region_check_cookie(region, &REGION_COOKIE_FOR_MEDIUM_REGION(region));
-
-	// We try to coalesce this block with the preceeding one
-	if (index > 0 && (meta_headers[index - 1] & MEDIUM_IS_FREE)) {
-		msize_t previous_msize = meta_headers[index - 1] & ~MEDIUM_IS_FREE;
-		grain_t previous_index = index - previous_msize;
-
-		// Check if the metadata for the start of the block is also free.
-		if (meta_headers[previous_index] == (previous_msize | MEDIUM_IS_FREE)) {
-			void *previous_ptr = (void *)((uintptr_t)ptr - MEDIUM_BYTES_FOR_MSIZE(previous_msize));
-			free_list_t previous = medium_free_list_find_by_ptr(rack, medium_mag_ptr, previous_ptr, previous_msize);
-			medium_free_list_remove_ptr(rack, medium_mag_ptr, previous, previous_msize);
-			ptr = previous_ptr;
-			medium_meta_header_set_middle(meta_headers, index); // This block is now a middle block.
-			msize += previous_msize;
-			index -= previous_msize;
-		} else {
-			_os_set_crash_log_message("medium free list metadata inconsistency (headers[previous] != previous size)");
-			__builtin_trap();
-		}
-	}
-
-	// Try to coalesce with this block with the next block
-	if ((next_block < MEDIUM_REGION_HEAP_END(region)) && (meta_headers[next_index] & MEDIUM_IS_FREE)) {
-		msize_t next_msize = meta_headers[next_index] & ~MEDIUM_IS_FREE;
-		free_list_t next = medium_free_list_find_by_ptr(rack, medium_mag_ptr, next_block, next_msize);
-		medium_free_list_remove_ptr(rack, medium_mag_ptr, next, next_msize);
-		msize += next_msize;
-	}
-
-	if (rack->debug_flags & MALLOC_DO_SCRIBBLE) {
-		if (!msize) {
-			malloc_zone_error(rack->debug_flags, true, "incorrect size information for %p - block header was damaged\n", ptr);
-		} else {
-			memset(ptr, SCRABBLE_BYTE, MEDIUM_BYTES_FOR_MSIZE(msize));
-		}
-	}
-
-	free_list_t freee = medium_free_list_add_ptr(rack, medium_mag_ptr, ptr, msize);
-
-	// use original_size and not msize to avoid double counting the coalesced blocks
-	medium_mag_ptr->mag_num_bytes_in_objects -= original_size;
-	medium_mag_ptr->mag_num_objects--;
-
-	// Update this region's bytes in use count
-	region_trailer_t *trailer = REGION_TRAILER_FOR_MEDIUM_REGION(region);
-	size_t bytes_used = trailer->bytes_used - original_size;
-	trailer->bytes_used = (unsigned int)bytes_used;
-
-#if CONFIG_AGGRESSIVE_MADVISE
-	if (aggressive_madvise_enabled) {
-		medium_madvise_free_range_no_lock(rack, medium_mag_ptr,
-				vm_kernel_page_size, region, freee, msize, original_ptr, original_size);
-	}
-	else
-#endif
-	{
-		// Always attempt to madvise free regions that exceed the conditional
-		// madvise limit size.
-		medium_madvise_free_range_conditional_no_lock(rack, medium_mag_ptr,
-				medium_sliding_madvise_granularity(medium_mag_ptr), region, &freee,
-				msize, original_ptr, original_size);
-	}
-
-	// Caller must do SZONE_MAGAZINE_PTR_UNLOCK(tiny_mag_ptr) if this function
-	// returns TRUE.
-	boolean_t needs_unlock = TRUE;
-
-#if CONFIG_RECIRC_DEPOT
-	needs_unlock = medium_free_try_recirc_to_depot(rack, medium_mag_ptr, mag_index, region, freee, msize, original_ptr, original_size);
-#endif
-	return needs_unlock;
-}
-
-// Allocates from the last region or a freshly allocated region
-static void *
-medium_malloc_from_region_no_lock(rack_t *rack,
-								 magazine_t *medium_mag_ptr,
-								 mag_index_t mag_index,
-								 msize_t msize,
-								 void *aligned_address)
-{
-	void *ptr;
-
-	// Before anything we transform the mag_bytes_free_at_end or mag_bytes_free_at_start - if any - to a regular free block
-	/* FIXME: last_block needs to be coalesced with previous entry if free, <rdar://5462322> */
-	if (medium_mag_ptr->mag_bytes_free_at_end || medium_mag_ptr->mag_bytes_free_at_start) {
-		medium_finalize_region(rack, medium_mag_ptr);
-	}
-
-	medium_region_t region = (medium_region_t)aligned_address;
-
-	// Tag the region at "aligned_address" as belonging to us,
-	// and so put it under the protection of the magazine lock we are holding.
-	// Do this before advertising "aligned_address" on the hash ring(!)
-	MAGAZINE_INDEX_FOR_MEDIUM_REGION(region) = mag_index;
-
-	// Insert the new region into the hash ring
-	rack_region_insert(rack, region);
-
-	medium_mag_ptr->mag_last_region = region;
-	BYTES_USED_FOR_MEDIUM_REGION(region) = MEDIUM_BYTES_FOR_MSIZE(msize);
-
-#if CONFIG_ASLR_INTERNAL
-	int offset_msize = malloc_entropy[1] & MEDIUM_ENTROPY_MASK;
-#if DEBUG_MALLOC
-	if (getenv("MallocASLRForce")) {
-		offset_msize = strtol(getenv("MallocASLRForce"), NULL, 0) & MEDIUM_ENTROPY_MASK;
-	}
-	if (getenv("MallocASLRPrint")) {
-		malloc_report(ASL_LEVEL_INFO, "Region: %p offset: %d\n", region, offset_msize);
-	}
-#endif
-#else
-	int offset_msize = 0;
-#endif
-	ptr = (void *)(MEDIUM_REGION_HEAP_BASE(region) +
-			MEDIUM_BYTES_FOR_MSIZE(offset_msize));
-	medium_meta_header_set_in_use(MEDIUM_META_HEADER_FOR_PTR(ptr),
-			offset_msize, msize);
-	medium_madvise_header_mark_dirty(MEDIUM_MADVISE_HEADER_FOR_PTR(ptr),
-			offset_msize, msize);
-	medium_mag_ptr->mag_num_objects++;
-	medium_mag_ptr->mag_num_bytes_in_objects += MEDIUM_BYTES_FOR_MSIZE(msize);
-	medium_mag_ptr->num_bytes_in_magazine += MEDIUM_REGION_PAYLOAD_BYTES;
-
-	// add a big free block at the end, mark as already advised clean
-	// because we haven't touched it.
-	msize_t trailing_offset = offset_msize + msize;
-	msize_t trailing_msize = NUM_MEDIUM_BLOCKS - msize - offset_msize;
-	medium_meta_header_set_in_use(MEDIUM_META_HEADER_FOR_PTR(ptr),
-			trailing_offset, trailing_msize);
-	medium_madvise_header_mark_clean(MEDIUM_MADVISE_HEADER_FOR_PTR(ptr),
-			trailing_offset, trailing_msize);
-	medium_mag_ptr->mag_bytes_free_at_end = 
-		MEDIUM_BYTES_FOR_MSIZE(NUM_MEDIUM_BLOCKS - msize - offset_msize);
-
-#if CONFIG_ASLR_INTERNAL
-	// add a big free block at the start
-	medium_mag_ptr->mag_bytes_free_at_start = MEDIUM_BYTES_FOR_MSIZE(offset_msize);
-	if (offset_msize) {
-		medium_meta_header_set_in_use(MEDIUM_META_HEADER_FOR_PTR(ptr), 0,
-				offset_msize);
-		medium_madvise_header_mark_clean(MEDIUM_MADVISE_HEADER_FOR_PTR(ptr), 0,
-				offset_msize);
-	}
-#else
-	medium_mag_ptr->mag_bytes_free_at_start = 0;
-#endif
-
-	// connect to magazine as last node
-	recirc_list_splice_last(rack, medium_mag_ptr,
-			REGION_TRAILER_FOR_MEDIUM_REGION(region));
-
-	return ptr;
-}
-
-void *
-medium_memalign(szone_t *szone, size_t alignment, size_t size, size_t span)
-{
-	msize_t mspan = MEDIUM_MSIZE_FOR_BYTES(span + MEDIUM_QUANTUM - 1);
-	void *p = medium_malloc_should_clear(&szone->medium_rack, mspan, 0);
-
-	if (NULL == p) {
-		return NULL;
-	}
-
-	size_t offset = ((uintptr_t)p) & (alignment - 1);	// p % alignment
-	size_t pad = (0 == offset) ? 0 : alignment - offset; // p + pad achieves desired alignment
-
-	msize_t msize = MEDIUM_MSIZE_FOR_BYTES(size + MEDIUM_QUANTUM - 1);
-	msize_t mpad = MEDIUM_MSIZE_FOR_BYTES(pad + MEDIUM_QUANTUM - 1);
-	msize_t mwaste = mspan - msize - mpad; // excess blocks
-
-	if (mpad > 0) {
-		void *q = (void *)(((uintptr_t)p) + pad);
-
-		// Mark q as block header and in-use, thus creating two blocks.
-		magazine_t *medium_mag_ptr = mag_lock_zine_for_region_trailer(
-				szone->medium_rack.magazines,
-				REGION_TRAILER_FOR_MEDIUM_REGION(MEDIUM_REGION_FOR_PTR(p)),
-				MAGAZINE_INDEX_FOR_MEDIUM_REGION(MEDIUM_REGION_FOR_PTR(p)));
-		medium_meta_header_set_in_use(MEDIUM_META_HEADER_FOR_PTR(p), MEDIUM_META_INDEX_FOR_PTR(p), mpad);
-		medium_madvise_header_mark_dirty(MEDIUM_MADVISE_HEADER_FOR_PTR(p), MEDIUM_META_INDEX_FOR_PTR(p), mpad);
-		medium_meta_header_set_in_use(MEDIUM_META_HEADER_FOR_PTR(q), MEDIUM_META_INDEX_FOR_PTR(q), msize + mwaste);
-		medium_madvise_header_mark_dirty(MEDIUM_MADVISE_HEADER_FOR_PTR(q), MEDIUM_META_INDEX_FOR_PTR(q), msize + mwaste);
-		medium_mag_ptr->mag_num_objects++;
-		SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-
-		// Give up mpad blocks beginning at p to the medium free list
-		free_medium(&szone->medium_rack, p, MEDIUM_REGION_FOR_PTR(p), MEDIUM_BYTES_FOR_MSIZE(mpad));
-
-		p = q; // advance p to the desired alignment
-	}
-	if (mwaste > 0) {
-		void *q = (void *)(((uintptr_t)p) + MEDIUM_BYTES_FOR_MSIZE(msize));
-		// Mark q as block header and in-use, thus creating two blocks.
-		magazine_t *medium_mag_ptr = mag_lock_zine_for_region_trailer(szone->medium_rack.magazines,
-				REGION_TRAILER_FOR_MEDIUM_REGION(MEDIUM_REGION_FOR_PTR(p)),
-				MAGAZINE_INDEX_FOR_MEDIUM_REGION(MEDIUM_REGION_FOR_PTR(p)));
-		medium_meta_header_set_in_use(MEDIUM_META_HEADER_FOR_PTR(p), MEDIUM_META_INDEX_FOR_PTR(p), msize);
-		medium_madvise_header_mark_dirty(MEDIUM_MADVISE_HEADER_FOR_PTR(p), MEDIUM_META_INDEX_FOR_PTR(p), msize);
-		medium_meta_header_set_in_use(MEDIUM_META_HEADER_FOR_PTR(q), MEDIUM_META_INDEX_FOR_PTR(q), mwaste);
-		medium_madvise_header_mark_dirty(MEDIUM_MADVISE_HEADER_FOR_PTR(q), MEDIUM_META_INDEX_FOR_PTR(q), mwaste);
-		medium_mag_ptr->mag_num_objects++;
-		SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-
-		// Give up mwaste blocks beginning at q to the medium free list
-		free_medium(&szone->medium_rack, q, MEDIUM_REGION_FOR_PTR(q), MEDIUM_BYTES_FOR_MSIZE(mwaste));
-	}
-
-	return p; // p has the desired size and alignment, and can later be free()'d
-}
-
-boolean_t
-medium_claimed_address(rack_t *rack, void *ptr)
-{
-	region_t r = medium_region_for_ptr_no_lock(rack, ptr);
-	return r && ptr >= MEDIUM_REGION_HEAP_BASE(r)
-			&& ptr < MEDIUM_REGION_HEAP_END(r);
-}
-
-void *
-medium_try_shrink_in_place(rack_t *rack, void *ptr, size_t old_size, size_t new_good_size)
-{
-	msize_t new_msize = MEDIUM_MSIZE_FOR_BYTES(new_good_size);
-	msize_t mshrinkage = MEDIUM_MSIZE_FOR_BYTES(old_size) - new_msize;
-
-	if (mshrinkage) {
-		void *q = (void *)((uintptr_t)ptr + MEDIUM_BYTES_FOR_MSIZE(new_msize));
-		magazine_t *medium_mag_ptr = mag_lock_zine_for_region_trailer(rack->magazines,
-				REGION_TRAILER_FOR_MEDIUM_REGION(MEDIUM_REGION_FOR_PTR(ptr)),
-				MAGAZINE_INDEX_FOR_MEDIUM_REGION(MEDIUM_REGION_FOR_PTR(ptr)));
-
-		// Mark q as block header and in-use, thus creating two blocks.
-		medium_meta_header_set_in_use(MEDIUM_META_HEADER_FOR_PTR(ptr), MEDIUM_META_INDEX_FOR_PTR(ptr), new_msize);
-		medium_madvise_header_mark_dirty(MEDIUM_MADVISE_HEADER_FOR_PTR(ptr), MEDIUM_META_INDEX_FOR_PTR(ptr), new_msize);
-		medium_meta_header_set_in_use(MEDIUM_META_HEADER_FOR_PTR(q), MEDIUM_META_INDEX_FOR_PTR(q), mshrinkage);
-		medium_madvise_header_mark_dirty(MEDIUM_MADVISE_HEADER_FOR_PTR(q), MEDIUM_META_INDEX_FOR_PTR(q), mshrinkage);
-		medium_mag_ptr->mag_num_objects++;
-
-		SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-		free_medium(rack, q, MEDIUM_REGION_FOR_PTR(q), 0);
-	}
-
-	return ptr;
-}
-
-boolean_t
-medium_try_realloc_in_place(rack_t *rack, void *ptr, size_t old_size, size_t new_size)
-{
-	// returns 1 on success
-	msize_t *meta_headers = MEDIUM_META_HEADER_FOR_PTR(ptr);
-	msize_t *madv_headers = MEDIUM_MADVISE_HEADER_FOR_PTR(ptr);
-	unsigned index;
-	msize_t old_msize, new_msize;
-	unsigned next_index;
-	void *next_block;
-	msize_t next_msize_and_free;
-	boolean_t is_free;
-	msize_t next_msize, leftover_msize;
-	void *leftover;
-
-	index = MEDIUM_META_INDEX_FOR_PTR(ptr);
-	old_msize = MEDIUM_MSIZE_FOR_BYTES(old_size);
-	new_msize = MEDIUM_MSIZE_FOR_BYTES(new_size + MEDIUM_QUANTUM - 1);
-	next_index = index + old_msize;
-
-	if (next_index >= NUM_MEDIUM_BLOCKS) {
-		return 0;
-	}
-	next_block = (char *)ptr + old_size;
-
-#if DEBUG_MALLOC
-	if ((uintptr_t)next_block & (MEDIUM_QUANTUM - 1)) {
-		malloc_zone_error(rack->debug_flags, true, "internal invariant broken in realloc(next_block) for %p\n", next_block);
-	}
-	if (meta_headers[index] != old_msize) {
-		malloc_report(ASL_LEVEL_ERR, "*** medium_try_realloc_in_place incorrect old %d %d\n", meta_headers[index], old_msize);
-	}
-#endif
-
-	magazine_t *medium_mag_ptr = mag_lock_zine_for_region_trailer(rack->magazines,
-			REGION_TRAILER_FOR_MEDIUM_REGION(MEDIUM_REGION_FOR_PTR(ptr)),
-			MAGAZINE_INDEX_FOR_MEDIUM_REGION(MEDIUM_REGION_FOR_PTR(ptr)));
-	if (DEPOT_MAGAZINE_INDEX == MAGAZINE_INDEX_FOR_MEDIUM_REGION(MEDIUM_REGION_FOR_PTR(ptr))) {
-		SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-		return 0;
-	}
-
-	msize_t coalesced_msize = new_msize - old_msize;
-#if CONFIG_MEDIUM_CACHE
-	void *last_free_ptr = medium_mag_ptr->mag_last_free;
-	msize_t last_free_msize = medium_mag_ptr->mag_last_free_msize;
-	if (last_free_ptr == next_block && old_msize + last_free_msize >= new_msize) {
-		/*
-		 * There is a block in mag_last_free and it's immediately after
-		 * this block and it's large enough. We can use some or all of it.
-		 */
-		leftover_msize = last_free_msize - coalesced_msize;
-		if (leftover_msize) {
-			medium_mag_ptr->mag_last_free_msize -= coalesced_msize;
-			medium_mag_ptr->mag_last_free += new_size - old_size;
-			// The block in mag_last_free is still marked as header and in-use, so copy that
-			// state to the block that remains. The state for the block that we're going to
-			// use is adjusted by the medium_meta_header_set_middle() call below.
-			medium_meta_header_set_in_use(meta_headers, index + new_msize, leftover_msize);
-
-			/* Propagate the madvise information from the block we're using to the leftover block. */
-			if (madv_headers[next_index] & MEDIUM_IS_ADVISED) {
-				medium_madvise_header_mark_clean(madv_headers, index + new_msize, leftover_msize);
-			} else {
-				medium_madvise_header_mark_dirty(madv_headers, index + new_msize, leftover_msize);
-			}
-		} else {
-			// Using the whole block.
-			medium_mag_ptr->mag_last_free = NULL;
-			medium_mag_ptr->mag_last_free_msize = 0;
-			medium_mag_ptr->mag_last_free_rgn = NULL;
-		}
-		medium_meta_header_set_in_use(meta_headers, index, new_msize);
-		medium_madvise_header_mark_dirty(madv_headers, index, new_msize);
-		medium_meta_header_set_middle(meta_headers, next_index);
-		medium_madvise_header_mark_middle(madv_headers, next_index);
-	} else {
-#endif // CONFIG_MEDIUM_CACHE
-		/*
-		 * Try to expand into unused space immediately after this block.
-		 */
-		msize_t unused_msize = MEDIUM_MSIZE_FOR_BYTES(medium_mag_ptr->mag_bytes_free_at_end);
-		void *unused_start = MEDIUM_REGION_HEAP_END(MEDIUM_REGION_FOR_PTR(ptr)) - medium_mag_ptr->mag_bytes_free_at_end;
-		if (medium_mag_ptr->mag_last_region == MEDIUM_REGION_FOR_PTR(ptr)
-				&& coalesced_msize < unused_msize && unused_start == ptr + old_size) {
-			// Extend the in-use for this block to the new size
-			medium_meta_header_set_in_use(meta_headers, index, new_msize);
-			medium_madvise_header_mark_dirty(madv_headers, index, new_msize);
-
-			// Clear the in-use size for the start of the area we extended into
-			medium_meta_header_set_middle(meta_headers, next_index);
-			medium_madvise_header_mark_middle(madv_headers, next_index);
-
-			// Reduce mag_bytes_free_at_end and update its in-use size.
-			medium_mag_ptr->mag_bytes_free_at_end -= MEDIUM_BYTES_FOR_MSIZE(coalesced_msize);
-			medium_meta_header_set_in_use(meta_headers, index + new_msize,
-					MEDIUM_MSIZE_FOR_BYTES(medium_mag_ptr->mag_bytes_free_at_end));
-			medium_madvise_header_mark_clean(madv_headers, index + new_msize,
-					MEDIUM_MSIZE_FOR_BYTES(medium_mag_ptr->mag_bytes_free_at_end));
-		} else {
-			/*
-			 * Look for a free block immediately afterwards.  If it's large enough, we can consume (part of)
-			 * it.
-			 */
-			next_msize_and_free = meta_headers[next_index];
-			is_free = next_msize_and_free & MEDIUM_IS_FREE;
-			if (!is_free) {
-				SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-				return 0; // next_block is in use;
-			}
-
-			next_msize = next_msize_and_free & ~MEDIUM_IS_FREE;
-			if (old_msize + next_msize < new_msize) {
-				SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-				return 0; // even with next block, not enough
-			}
-
-			// The following block is big enough; pull it from its freelist and chop off enough to satisfy
-			// our needs.
-			free_list_t freee = medium_free_list_find_by_ptr(rack, medium_mag_ptr, next_block, next_msize);
-			medium_free_list_remove_ptr(rack, medium_mag_ptr, freee, next_msize);
-			medium_meta_header_set_middle(meta_headers, next_index);
-			medium_madvise_header_mark_middle(madv_headers, next_index);
-			leftover_msize = old_msize + next_msize - new_msize;
-			if (leftover_msize) {
-				/* there's some left, so put the remainder back */
-				leftover = (unsigned char *)ptr + MEDIUM_BYTES_FOR_MSIZE(new_msize);
-				medium_free_list_add_ptr(rack, medium_mag_ptr, leftover, leftover_msize);
-				msize_t leftover_index = MEDIUM_META_INDEX_FOR_PTR(leftover);
-				if (madv_headers[leftover_index] & MEDIUM_IS_ADVISED) {
-					medium_madvise_header_mark_clean(madv_headers, leftover_index, leftover_msize);
-				} else {
-					medium_madvise_header_mark_dirty(madv_headers, leftover_index, leftover_msize);
-				}
-			}
-			medium_meta_header_set_in_use(meta_headers, index, new_msize);
-			medium_madvise_header_mark_dirty(madv_headers, index, new_msize);
-		}
-#if CONFIG_MEDIUM_CACHE
-	}
-#endif // CONFIG_MEDIUM_CACHE
-#if DEBUG_MALLOC
-	if (MEDIUM_BYTES_FOR_MSIZE(new_msize) > szone->large_threshold) {
-		malloc_report(ASL_LEVEL_ERR, "*** realloc in place for %p exceeded msize=%d\n", new_msize);
-	}
-
-	if (LOG(szone, ptr)) {
-		malloc_report(ASL_LEVEL_INFO, "in medium_try_realloc_in_place(), ptr=%p, msize=%d\n", ptr, *MEDIUM_METADATA_FOR_PTR(ptr));
-	}
-#endif
-	medium_mag_ptr->mag_num_bytes_in_objects += MEDIUM_BYTES_FOR_MSIZE(new_msize - old_msize);
-
-	// Update this region's bytes in use count
-	region_trailer_t *node = REGION_TRAILER_FOR_MEDIUM_REGION(MEDIUM_REGION_FOR_PTR(ptr));
-	size_t bytes_used = node->bytes_used + MEDIUM_BYTES_FOR_MSIZE(new_msize - old_msize);
-	node->bytes_used = (unsigned int)bytes_used;
-
-	// Emptiness discriminant
-	if (bytes_used < DENSITY_THRESHOLD(MEDIUM_REGION_PAYLOAD_BYTES)) {
-		/* After this reallocation the region is still sparse, so it must have been even more so before
-		 * the reallocation. That implies the region is already correctly marked. Do nothing. */
-	} else {
-		/* Region has crossed threshold from sparsity to density. Mark it not "suitable" on the
-		 * recirculation candidates list. */
-		node->recirc_suitable = FALSE;
-	}
-
-	SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-	CHECK(szone, __PRETTY_FUNCTION__);
-	return 1;
-}
-
-static char *medium_check_fail_msg = "check: incorrect medium region ";
-
-#define MEDIUM_CHECK_FAIL(fmt, ...) \
-	malloc_zone_check_fail(medium_check_fail_msg, \
-			"%ld, counter=%d\n" fmt,  region_index, counter, __VA_ARGS__);
-
-boolean_t
-medium_check_region(rack_t *rack, region_t region, size_t region_index,
-		unsigned counter)
-{
-	void *ptr = MEDIUM_REGION_HEAP_BASE(region);
-	msize_t *meta_headers = MEDIUM_META_HEADER_FOR_PTR(ptr);
-	void *region_end = MEDIUM_REGION_HEAP_END(region);
-	msize_t prev_free = 0;
-	unsigned index;
-	msize_t msize_and_free;
-	msize_t msize;
-	free_list_t free_head, previous, next;
-	msize_t *follower;
-	mag_index_t mag_index = MAGAZINE_INDEX_FOR_MEDIUM_REGION(MEDIUM_REGION_FOR_PTR(ptr));
-	magazine_t *medium_mag_ptr = &(rack->magazines[mag_index]);
-
-	// Assumes locked
-	CHECK_MAGAZINE_PTR_LOCKED(szone, medium_mag_ptr, __PRETTY_FUNCTION__);
-
-	if (region == medium_mag_ptr->mag_last_region) {
-		ptr += medium_mag_ptr->mag_bytes_free_at_start;
-		region_end -= medium_mag_ptr->mag_bytes_free_at_end;
-	}
-
-	while (ptr < region_end) {
-		index = MEDIUM_META_INDEX_FOR_PTR(ptr);
-		msize_and_free = meta_headers[index];
-		if (!(msize_and_free & MEDIUM_IS_FREE)) {
-			// block is in use
-			msize = msize_and_free;
-			if (!msize) {
-				MEDIUM_CHECK_FAIL("*** invariant broken: null msize ptr=%p num_medium_regions=%d end=%p\n", ptr,
-							  (int)rack->num_regions, region_end);
-				return 0;
-			}
-#if !CONFIG_RELAXED_INVARIANT_CHECKS
-			if (MEDIUM_BYTES_FOR_MSIZE(msize) > szone->large_threshold) {
-				MEDIUM_CHECK_FAIL("*** invariant broken for %p this medium msize=%d - size is too large\n", ptr, msize_and_free);
-				return 0;
-			}
-#endif // CONFIG_RELAXED_INVARIANT_CHECKS
-			ptr += MEDIUM_BYTES_FOR_MSIZE(msize);
-			prev_free = 0;
-		} else {
-			// free pointer
-			msize = msize_and_free & ~MEDIUM_IS_FREE;
-			free_head = (free_list_t){ .p = ptr };
-			follower = (msize_t *)FOLLOWING_MEDIUM_PTR(ptr, msize);
-			if (!msize) {
-				MEDIUM_CHECK_FAIL("*** invariant broken for free block %p this msize=%d\n", ptr, msize);
-				return 0;
-			}
-#if !CONFIG_RELAXED_INVARIANT_CHECKS
-			if (prev_free) {
-				MEDIUM_CHECK_FAIL("*** invariant broken for %p (2 free in a row)\n", ptr);
-				return 0;
-			}
-#endif
-
-			// <rdar://problem/24680189> check for possible OOB entry if needed
-			if (medium_needs_oob_free_entry(ptr, msize)) {
-				oob_free_entry_t oob = medium_oob_free_find_ptr(ptr, msize);
-				if (oob) {
-					free_head.oob = oob;
-				}
-			}
-
-			previous = medium_free_list_get_previous(rack, free_head);
-			next = medium_free_list_get_next(rack, free_head);
-			if (previous.p && !MEDIUM_PTR_IS_FREE(medium_free_list_get_ptr(rack, previous))) {
-				MEDIUM_CHECK_FAIL("*** invariant broken for %p (previous %p is not a free pointer)\n", ptr, medium_free_list_get_ptr(rack, previous));
-				return 0;
-			}
-			if (next.p && !MEDIUM_PTR_IS_FREE(medium_free_list_get_ptr(rack, next))) {
-				MEDIUM_CHECK_FAIL("*** invariant broken for %p (next %p is not a free pointer)\n", ptr, medium_free_list_get_ptr(rack, next));
-				return 0;
-			}
-			if (MEDIUM_PREVIOUS_MSIZE(follower) != msize) {
-				MEDIUM_CHECK_FAIL("*** invariant broken for medium free %p followed by %p in region %p [%p-%p] "
-						"(end marker incorrect) should be %d; in fact %d\n",
-						ptr, follower, region, MEDIUM_REGION_HEAP_BASE(region),
-						region_end, msize, MEDIUM_PREVIOUS_MSIZE(follower));
-				return 0;
-			}
-			ptr = (unsigned char *)follower;
-			prev_free = MEDIUM_IS_FREE;
-		}
-	}
-	return 1;
-}
-
-kern_return_t
-medium_in_use_enumerator(task_t task,
-						void *context,
-						unsigned type_mask,
-						szone_t *szone,
-						memory_reader_t reader,
-						vm_range_recorder_t recorder)
-{
-	size_t num_regions;
-	size_t index;
-	region_t *regions;
-	vm_range_t buffer[MAX_RECORDER_BUFFER];
-	unsigned count = 0;
-	kern_return_t err;
-	region_t region;
-	vm_range_t range;
-	vm_range_t admin_range;
-	vm_range_t ptr_range;
-	unsigned char *mapped_region;
-	msize_t *block_header;
-	unsigned block_index;
-	unsigned block_limit;
-	msize_t msize_and_free;
-	msize_t msize;
-	magazine_t *medium_mag_base = NULL;
-
-	region_hash_generation_t *srg_ptr;
-	err = reader(task, (vm_address_t)szone->medium_rack.region_generation, sizeof(region_hash_generation_t), (void **)&srg_ptr);
-	if (err) {
-		return err;
-	}
-
-	num_regions = srg_ptr->num_regions_allocated;
-	err = reader(task, (vm_address_t)srg_ptr->hashed_regions, sizeof(region_t) * num_regions, (void **)&regions);
-	if (err) {
-		return err;
-	}
-
-	if (type_mask & MALLOC_PTR_IN_USE_RANGE_TYPE) {
-		// Map in all active magazines. Do this outside the iteration over regions.
-		err = reader(task, (vm_address_t)(szone->medium_rack.magazines), szone->medium_rack.num_magazines * sizeof(magazine_t),
-					 (void **)&medium_mag_base);
-		if (err) {
-			return err;
-		}
-	}
-
-	for (index = 0; index < num_regions; ++index) {
-		region = regions[index];
-		if (HASHRING_OPEN_ENTRY != region && HASHRING_REGION_DEALLOCATED != region) {
-			range.address = (vm_address_t)MEDIUM_REGION_HEAP_BASE(region);
-			range.size = MEDIUM_HEAP_SIZE;
-			if (type_mask & MALLOC_ADMIN_REGION_RANGE_TYPE) {
-				admin_range.address = MEDIUM_REGION_METADATA(region);
-				admin_range.size = MEDIUM_METADATA_SIZE;
-				recorder(task, context, MALLOC_ADMIN_REGION_RANGE_TYPE, &admin_range, 1);
-			}
-			if (type_mask & (MALLOC_PTR_REGION_RANGE_TYPE | MALLOC_ADMIN_REGION_RANGE_TYPE)) {
-				ptr_range.address = range.address;
-				ptr_range.size = MEDIUM_HEAP_SIZE;
-				recorder(task, context, MALLOC_PTR_REGION_RANGE_TYPE, &ptr_range, 1);
-			}
-			if (type_mask & MALLOC_PTR_IN_USE_RANGE_TYPE) {
-				err = reader(task, (vm_address_t)region,
-						(vm_size_t)MEDIUM_REGION_SIZE, (void **)&mapped_region);
-				if (err) {
-					return err;
-				}
-
-				mag_index_t mag_index = MAGAZINE_INDEX_FOR_MEDIUM_REGION(mapped_region);
-				magazine_t *medium_mag_ptr = medium_mag_base + mag_index;
-
-				int cached_free_blocks = 0;
-#if CONFIG_MEDIUM_CACHE
-				// Each magazine could have a pointer to a cached free block from
-				// this region. Count the regions that have such a pointer.
-				for (mag_index = 0; mag_index < szone->medium_rack.num_magazines; mag_index++) {
-					if (region == (medium_mag_base + mag_index)->mag_last_free_rgn) {
-						cached_free_blocks++;
-					}
-				}
-#endif // CONFIG_MEDIUM_CACHE
-
-				block_header = MEDIUM_META_HEADER_FOR_REGION(mapped_region);
-				block_index = 0;
-				block_limit = NUM_MEDIUM_BLOCKS;
-				if (region == medium_mag_ptr->mag_last_region) {
-					block_index += MEDIUM_MSIZE_FOR_BYTES(medium_mag_ptr->mag_bytes_free_at_start);
-					block_limit -= MEDIUM_MSIZE_FOR_BYTES(medium_mag_ptr->mag_bytes_free_at_end);
-				}
-				for (;block_index < block_limit; block_index += msize) {
-					msize_and_free = block_header[block_index];
-					msize = msize_and_free & ~MEDIUM_IS_FREE;
-					if (!msize) {
-						return KERN_FAILURE; // Somethings amiss. Avoid looping at this block_index.
-					}
-					if (!(msize_and_free & MEDIUM_IS_FREE)) {
-						void *ptr = MEDIUM_REGION_HEAP_BASE(region) + MEDIUM_BYTES_FOR_MSIZE(block_index);
-#if CONFIG_MEDIUM_CACHE
-						// If there are still magazines that have cached free
-						// blocks in this region, check whether this is one of
-						// them and don't return the block pointer if it is.
-						boolean_t block_cached = false;
-						if (cached_free_blocks) {
-							for (mag_index = 0; mag_index < szone->medium_rack.num_magazines; mag_index++) {
-								if (ptr == (medium_mag_base + mag_index)->mag_last_free) {
-									block_cached = true;
-									cached_free_blocks--;
-									break;
-								}
-							}
-						}
-						if (block_cached) {
-							continue;
-						}
-#endif // CONFIG_MEDIUM_CACHE
-						// Block in use
-						buffer[count].address = (vm_address_t)ptr;
-						buffer[count].size = MEDIUM_BYTES_FOR_MSIZE(msize);
-						count++;
-						if (count >= MAX_RECORDER_BUFFER) {
-							recorder(task, context, MALLOC_PTR_IN_USE_RANGE_TYPE, buffer, count);
-							count = 0;
-						}
-					}
-				}
-				if (count) {
-					recorder(task, context, MALLOC_PTR_IN_USE_RANGE_TYPE, buffer, count);
-					count = 0;
-				}
-			}
-		}
-	}
-	return 0;
-}
-
-static void *
-medium_malloc_from_free_list(rack_t *rack, magazine_t *medium_mag_ptr, mag_index_t mag_index, msize_t msize)
-{
-	msize_t this_msize;
-	bool was_madvised;
-	grain_t slot = MEDIUM_FREE_SLOT_FOR_MSIZE(rack, msize);
-	free_list_t *free_list = medium_mag_ptr->mag_free_list;
-	free_list_t *the_slot = free_list + slot;
-	free_list_t *limit;
-	unsigned bitmap;
-	msize_t leftover_msize;
-	void *leftover_ptr;
-	void *ptr;
-
-	// Assumes we've locked the region
-	CHECK_MAGAZINE_PTR_LOCKED(szone, medium_mag_ptr, __PRETTY_FUNCTION__);
-
-	// Look for an exact match by checking the freelist for this msize.
-	if (medium_free_list_get_ptr(rack, *the_slot)) {
-		ptr = medium_free_list_get_ptr(rack, *the_slot);
-		this_msize = msize;
-		medium_free_list_remove_ptr(rack, medium_mag_ptr, *the_slot, msize);
-		goto return_medium_alloc;
-	}
-
-	// Mask off the bits representing slots holding free blocks smaller than
-	// the size we need.  If there are no larger free blocks, try allocating
-	// from the free space at the end of the medium region.
-	//
-	// BITMAPN_CTZ implementation
-	unsigned idx = slot >> 5;
-	bitmap = 0;
-	unsigned mask = ~((1 << (slot & 31)) - 1);
-	for (; idx < MEDIUM_FREELIST_BITMAP_WORDS(rack); ++idx) {
-		bitmap = medium_mag_ptr->mag_bitmap[idx] & mask;
-		if (bitmap != 0) {
-			break;
-		}
-		mask = ~0U;
-	}
-	// Check for fallthrough: No bits set in bitmap
-	if ((bitmap == 0) && (idx == MEDIUM_FREELIST_BITMAP_WORDS(rack))) {
-		goto try_medium_from_end;
-	}
-
-	// Start looking at the first set bit, plus 32 bits for every word of
-	// zeroes or entries that were too medium.
-	slot = BITMAP32_CTZ((&bitmap)) + (idx * 32);
-
-	// FIXME: Explain use of - 1 here, last slot has special meaning
-	limit = free_list + MEDIUM_FREE_SLOT_COUNT(rack) - 1;
-	free_list += slot;
-
-	// Attempt to pull off the free_list slot that we now think is full.
-	if ((ptr = medium_free_list_get_ptr(rack, *free_list))) {
-		this_msize = MEDIUM_PTR_SIZE(ptr);
-		was_madvised = (medium_madvise_header_dirty_len(
-				MEDIUM_MADVISE_HEADER_FOR_PTR(ptr), MEDIUM_META_INDEX_FOR_PTR(ptr)) == 0);
-		medium_free_list_remove_ptr(rack, medium_mag_ptr, *free_list, this_msize);
-		goto add_leftover_and_proceed;
-	}
-
-#if DEBUG_MALLOC
-	malloc_report(ASL_LEVEL_ERR, "in medium_malloc_from_free_list(), mag_bitmap out of sync, slot=%d\n", slot);
-#endif
-
-try_medium_from_end:
-	// Let's see if we can use medium_mag_ptr->mag_bytes_free_at_end
-	if (medium_mag_ptr->mag_bytes_free_at_end >= MEDIUM_BYTES_FOR_MSIZE(msize)) {
-		ptr = MEDIUM_REGION_HEAP_END(medium_mag_ptr->mag_last_region) -
-			medium_mag_ptr->mag_bytes_free_at_end;
-		medium_mag_ptr->mag_bytes_free_at_end -= MEDIUM_BYTES_FOR_MSIZE(msize);
-		if (medium_mag_ptr->mag_bytes_free_at_end) {
-			// let's mark this block as in use to serve as boundary
-			medium_meta_header_set_in_use(MEDIUM_META_HEADER_FOR_PTR(ptr),
-					MEDIUM_META_INDEX_FOR_PTR((unsigned char *)ptr + MEDIUM_BYTES_FOR_MSIZE(msize)),
-					MEDIUM_MSIZE_FOR_BYTES(medium_mag_ptr->mag_bytes_free_at_end));
-			medium_madvise_header_mark_clean(MEDIUM_MADVISE_HEADER_FOR_PTR(ptr),
-					MEDIUM_META_INDEX_FOR_PTR((unsigned char *)ptr + MEDIUM_BYTES_FOR_MSIZE(msize)),
-					MEDIUM_MSIZE_FOR_BYTES(medium_mag_ptr->mag_bytes_free_at_end));
-		}
-		this_msize = msize;
-		goto return_medium_alloc;
-	}
-#if CONFIG_ASLR_INTERNAL
-	// Try from start if nothing left at end
-	if (medium_mag_ptr->mag_bytes_free_at_start >= MEDIUM_BYTES_FOR_MSIZE(msize)) {
-		ptr = MEDIUM_REGION_ADDRESS(medium_mag_ptr->mag_last_region) +
-				medium_mag_ptr->mag_bytes_free_at_start -
-				MEDIUM_BYTES_FOR_MSIZE(msize);
-		medium_mag_ptr->mag_bytes_free_at_start -= MEDIUM_BYTES_FOR_MSIZE(msize);
-		if (medium_mag_ptr->mag_bytes_free_at_start) {
-			// let's mark this block as in use to serve as boundary
-			medium_meta_header_set_in_use(MEDIUM_META_HEADER_FOR_PTR(ptr), 0,
-					MEDIUM_MSIZE_FOR_BYTES(medium_mag_ptr->mag_bytes_free_at_start));
-			medium_madvise_header_mark_clean(MEDIUM_MADVISE_HEADER_FOR_PTR(ptr), 0,
-					MEDIUM_MSIZE_FOR_BYTES(medium_mag_ptr->mag_bytes_free_at_start));
-		}
-		this_msize = msize;
-		goto return_medium_alloc;
-	}
-#endif
-	return NULL;
-
-add_leftover_and_proceed:
-	if (this_msize > msize) {
-		leftover_msize = this_msize - msize;
-		leftover_ptr = (unsigned char *)ptr + MEDIUM_BYTES_FOR_MSIZE(msize);
-#if DEBUG_MALLOC
-		if (LOG(szone, ptr)) {
-			malloc_report(ASL_LEVEL_INFO, "in medium_malloc_from_free_list(), adding leftover ptr=%p, this_msize=%d\n", ptr, this_msize);
-		}
-#endif
-		medium_free_list_add_ptr(rack, medium_mag_ptr, leftover_ptr, leftover_msize);
-		if (was_madvised) {
-			medium_madvise_header_mark_clean(
-					MEDIUM_MADVISE_HEADER_FOR_PTR(leftover_ptr),
-					MEDIUM_META_INDEX_FOR_PTR(leftover_ptr), leftover_msize);
-		} else {
-			medium_madvise_header_mark_dirty(
-					MEDIUM_MADVISE_HEADER_FOR_PTR(leftover_ptr),
-					MEDIUM_META_INDEX_FOR_PTR(leftover_ptr), leftover_msize);
-		}
-		this_msize = msize;
-	}
-
-return_medium_alloc:
-	medium_mag_ptr->mag_num_objects++;
-	medium_mag_ptr->mag_num_bytes_in_objects += MEDIUM_BYTES_FOR_MSIZE(this_msize);
-
-	// Check that the region cookie is intact and update the region's bytes in use count
-	medium_region_t region = MEDIUM_REGION_FOR_PTR(ptr);
-	region_check_cookie(region, &REGION_COOKIE_FOR_MEDIUM_REGION(region));
-
-	region_trailer_t *trailer = REGION_TRAILER_FOR_MEDIUM_REGION(region);
-	size_t bytes_used = trailer->bytes_used + MEDIUM_BYTES_FOR_MSIZE(this_msize);
-	trailer->bytes_used = (unsigned int)bytes_used;
-
-	// Emptiness discriminant
-	if (bytes_used < DENSITY_THRESHOLD(MEDIUM_REGION_PAYLOAD_BYTES)) {
-		/* After this allocation the region is still sparse, so it must have been even more so before
-		 * the allocation. That implies the region is already correctly marked. Do nothing. */
-	} else {
-		/* Region has crossed threshold from sparsity to density. Mark in not "suitable" on the
-		 * recirculation candidates list. */
-		trailer->recirc_suitable = FALSE;
-	}
-#if DEBUG_MALLOC
-	if (LOG(szone, ptr)) {
-		malloc_report(ASL_LEVEL_INFO, "in medium_malloc_from_free_list(), ptr=%p, this_msize=%d, msize=%d\n", ptr, this_msize, msize);
-	}
-#endif
-	medium_meta_header_set_in_use(MEDIUM_META_HEADER_FOR_PTR(ptr),
-			MEDIUM_META_INDEX_FOR_PTR(ptr), this_msize);
-	medium_madvise_header_mark_dirty(MEDIUM_MADVISE_HEADER_FOR_PTR(ptr),
-			MEDIUM_META_INDEX_FOR_PTR(ptr), this_msize);
-	return ptr;
-}
-
-void *
-medium_malloc_should_clear(rack_t *rack, msize_t msize, boolean_t cleared_requested)
-{
-	void *ptr;
-	mag_index_t mag_index = rack_get_thread_index(rack) % rack->num_magazines;
-	magazine_t *medium_mag_ptr = &(rack->magazines[mag_index]);
-
-	MALLOC_TRACE(TRACE_medium_malloc, (uintptr_t)rack, MEDIUM_BYTES_FOR_MSIZE(msize), (uintptr_t)medium_mag_ptr, cleared_requested);
-
-	SZONE_MAGAZINE_PTR_LOCK(medium_mag_ptr);
-
-#if CONFIG_MEDIUM_CACHE
-	ptr = medium_mag_ptr->mag_last_free;
-
-	if (medium_mag_ptr->mag_last_free_msize == msize) {
-		// we have a winner
-		medium_mag_ptr->mag_last_free = NULL;
-		medium_mag_ptr->mag_last_free_msize = 0;
-		medium_mag_ptr->mag_last_free_rgn = NULL;
-		SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-		CHECK(szone, __PRETTY_FUNCTION__);
-		if (cleared_requested) {
-			memset(ptr, 0, MEDIUM_BYTES_FOR_MSIZE(msize));
-		}
-		return ptr;
-	}
-#endif /* CONFIG_MEDIUM_CACHE */
-
-	while (1) {
-		ptr = medium_malloc_from_free_list(rack, medium_mag_ptr, mag_index, msize);
-		if (ptr) {
-			SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-			CHECK(szone, __PRETTY_FUNCTION__);
-			if (cleared_requested) {
-				memset(ptr, 0, MEDIUM_BYTES_FOR_MSIZE(msize));
-			}
-			return ptr;
-		}
-
-		if (medium_get_region_from_depot(rack, medium_mag_ptr, mag_index, msize)) {
-			ptr = medium_malloc_from_free_list(rack, medium_mag_ptr, mag_index, msize);
-			if (ptr) {
-				SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-				CHECK(szone, __PRETTY_FUNCTION__);
-				if (cleared_requested) {
-					memset(ptr, 0, MEDIUM_BYTES_FOR_MSIZE(msize));
-				}
-				return ptr;
-			}
-		}
-
-		// The magazine is exhausted. A new region (heap) must be allocated to satisfy this call to malloc().
-		// The allocation, an mmap() system call, will be performed outside the magazine spin locks by the first
-		// thread that suffers the exhaustion. That thread sets "alloc_underway" and enters a critical section.
-		// Threads arriving here later are excluded from the critical section, yield the CPU, and then retry the
-		// allocation. After some time the magazine is resupplied, the original thread leaves with its allocation,
-		// and retry-ing threads succeed in the code just above.
-		if (!medium_mag_ptr->alloc_underway) {
-			void *fresh_region;
-
-			// time to create a new region (do this outside the magazine lock)
-			medium_mag_ptr->alloc_underway = TRUE;
-			OSMemoryBarrier();
-			SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-			fresh_region = mvm_allocate_pages(MEDIUM_REGION_SIZE,
-					MEDIUM_BLOCKS_ALIGN,
-					MALLOC_FIX_GUARD_PAGE_FLAGS(rack->debug_flags),
-					VM_MEMORY_MALLOC_MEDIUM);
-			SZONE_MAGAZINE_PTR_LOCK(medium_mag_ptr);
-
-			// DTrace USDT Probe
-			MAGMALLOC_ALLOCREGION(MEDIUM_SZONE_FROM_RACK(rack), (int)mag_index,
-					fresh_region, MEDIUM_REGION_SIZE);
-
-			if (!fresh_region) { // out of memory!
-				medium_mag_ptr->alloc_underway = FALSE;
-				OSMemoryBarrier();
-				SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-				return NULL;
-			}
-
-			region_set_cookie(&REGION_COOKIE_FOR_MEDIUM_REGION(fresh_region));
-			ptr = medium_malloc_from_region_no_lock(rack, medium_mag_ptr,
-					mag_index, msize, fresh_region);
-
-			// we don't clear because this freshly allocated space is pristine
-			medium_mag_ptr->alloc_underway = FALSE;
-			OSMemoryBarrier();
-			SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-			CHECK(szone, __PRETTY_FUNCTION__);
-			return ptr;
-		} else {
-			SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-			yield();
-			SZONE_MAGAZINE_PTR_LOCK(medium_mag_ptr);
-		}
-	}
-	/* NOTREACHED */
-}
-
-size_t
-medium_size(rack_t *rack, const void *ptr)
-{
-	if (medium_region_for_ptr_no_lock(rack, ptr)) {
-		if (MEDIUM_META_INDEX_FOR_PTR(ptr) >= NUM_MEDIUM_BLOCKS) {
-			return 0;
-		}
-		msize_t msize_and_free = *MEDIUM_METADATA_FOR_PTR(ptr);
-		if (msize_and_free & MEDIUM_IS_FREE) {
-			return 0;
-		}
-#if CONFIG_MEDIUM_CACHE
-		{
-			mag_index_t mag_index = MAGAZINE_INDEX_FOR_MEDIUM_REGION(MEDIUM_REGION_FOR_PTR(ptr));
-			if (DEPOT_MAGAZINE_INDEX != mag_index) {
-				magazine_t *medium_mag_ptr = &(rack->magazines[mag_index]);
-
-				if (ptr == medium_mag_ptr->mag_last_free) {
-					return 0;
-				}
-			} else {
-				for (mag_index = 0; mag_index < rack->num_magazines; mag_index++) {
-					magazine_t *medium_mag_ptr = &(rack->magazines[mag_index]);
-
-					if (ptr == medium_mag_ptr->mag_last_free) {
-						return 0;
-					}
-				}
-			}
-		}
-#endif
-		return MEDIUM_BYTES_FOR_MSIZE(msize_and_free);
-	}
-
-	return 0;
-}
-
-static MALLOC_NOINLINE void
-free_medium_botch(rack_t *rack, void *ptr)
-{
-	malloc_zone_error(rack->debug_flags, true, "double free for ptr %p\n", ptr);
-}
-
-void
-free_medium(rack_t *rack, void *ptr, region_t medium_region, size_t known_size)
-{
-	msize_t msize;
-	mag_index_t mag_index = MAGAZINE_INDEX_FOR_MEDIUM_REGION(MEDIUM_REGION_FOR_PTR(ptr));
-	magazine_t *medium_mag_ptr = &(rack->magazines[mag_index]);
-
-	// ptr is known to be in medium_region
-	if (known_size) {
-		msize = MEDIUM_MSIZE_FOR_BYTES(known_size + MEDIUM_QUANTUM - 1);
-	} else {
-		msize = MEDIUM_PTR_SIZE(ptr);
-		if (MEDIUM_PTR_IS_FREE(ptr)) {
-			free_medium_botch(rack, ptr);
-			return;
-		}
-	}
-
-	SZONE_MAGAZINE_PTR_LOCK(medium_mag_ptr);
-
-#if CONFIG_MEDIUM_CACHE
-	// Depot does not participate in CONFIG_MEDIUM_CACHE since it can't be directly malloc()'d
-	if (DEPOT_MAGAZINE_INDEX != mag_index) {
-		void *ptr2 = medium_mag_ptr->mag_last_free; // Might be NULL
-		msize_t msize2 = medium_mag_ptr->mag_last_free_msize;
-		region_t rgn2 = medium_mag_ptr->mag_last_free_rgn;
-
-		/* check that we don't already have this pointer in the cache */
-		if (ptr == ptr2) {
-			SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-			free_medium_botch(rack, ptr);
-			return;
-		}
-
-		if ((rack->debug_flags & MALLOC_DO_SCRIBBLE) && msize) {
-			memset(ptr, SCRABBLE_BYTE, MEDIUM_BYTES_FOR_MSIZE(msize));
-		}
-
-		uint64_t madv_window = medium_sliding_madvise_granularity(medium_mag_ptr);
-		if (MEDIUM_BYTES_FOR_MSIZE(msize) > madv_window) {
-			uintptr_t lo = round_page_kernel((uintptr_t)ptr);
-			uintptr_t hi = trunc_page_kernel((uintptr_t)ptr + MEDIUM_BYTES_FOR_MSIZE(msize));
-			SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-			mvm_madvise_free(rack, medium_region, lo, hi, NULL, false);
-			SZONE_MAGAZINE_PTR_LOCK(medium_mag_ptr);
-
-			medium_madvise_header_mark_clean(MEDIUM_MADVISE_HEADER_FOR_PTR(ptr),
-					MEDIUM_META_INDEX_FOR_PTR(ptr), msize);
-
-			ptr2 = medium_mag_ptr->mag_last_free; // Might be NULL
-			msize2 = medium_mag_ptr->mag_last_free_msize;
-			rgn2 = medium_mag_ptr->mag_last_free_rgn;
-		}
-
-
-		medium_mag_ptr->mag_last_free = ptr;
-		medium_mag_ptr->mag_last_free_msize = msize;
-		medium_mag_ptr->mag_last_free_rgn = medium_region;
-
-		if (!ptr2) {
-			SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-			CHECK(szone, __PRETTY_FUNCTION__);
-			return;
-		}
-
-		msize = msize2;
-		ptr = ptr2;
-		medium_region = rgn2;
-	}
-#endif /* CONFIG_MEDIUM_CACHE */
-
-	// Now in the time it took to acquire the lock, the region may have migrated
-	// from one magazine to another. I.e. trailer->mag_index is volatile.
-	// In which case the magazine lock we obtained (namely magazines[mag_index].mag_lock)
-	// is stale. If so, keep on tryin' ...
-	region_trailer_t *trailer = REGION_TRAILER_FOR_MEDIUM_REGION(medium_region);
-	mag_index_t refreshed_index;
-
-	while (mag_index != (refreshed_index = trailer->mag_index)) { // Note assignment
-
-		SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-
-		mag_index = refreshed_index;
-		medium_mag_ptr = &(rack->magazines[mag_index]);
-		SZONE_MAGAZINE_PTR_LOCK(medium_mag_ptr);
-	}
-
-	if (medium_free_no_lock(rack, medium_mag_ptr, mag_index, medium_region, ptr, msize)) {
-		SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-	}
-
-	CHECK(szone, __PRETTY_FUNCTION__);
-}
-
-void
-print_medium_free_list(task_t task, memory_reader_t reader,
-		print_task_printer_t printer, rack_t *rack)
-{
-	free_list_t ptr;
-	_SIMPLE_STRING b = _simple_salloc();
-	mag_index_t mag_index;
-
-	if (b) {
-		rack_t *mapped_rack;
-		magazine_t *mapped_magazines;
-		if (reader(task, (vm_address_t)rack, sizeof(struct rack_s),
-				(void **)&mapped_rack)) {
-			printer("Failed to map medium rack\n");
-			return;
-		}
-		if (reader(task, (vm_address_t)mapped_rack->magazines,
-				mapped_rack->num_magazines * sizeof(magazine_t),
-				(void **)&mapped_magazines)) {
-			printer("Failed to map medium rack magazines\n");
-			return;
-		}
-
-		_simple_sappend(b, "medium free sizes:\n");
-		grain_t free_slots = MEDIUM_FREE_SLOT_COUNT(mapped_rack);
-		for (mag_index = -1; mag_index < mapped_rack->num_magazines;
-				mag_index++) {
-			grain_t slot = 0;
-			if (mag_index == -1) {
-				_simple_sprintf(b, "\tRecirc depot: ");
-			} else {
-				_simple_sprintf(b, "\tMagazine %d: ", mag_index);
-			}
-			while (slot < free_slots) {
-				ptr = mapped_magazines[mag_index].mag_free_list[slot];
-				if (medium_free_list_get_ptr_task(task, reader, printer, ptr)) {
-					_simple_sprintf(b, "%s%y[%lld]; ", (slot == free_slots - 1) ?
-							">=" : "", (slot + 1) * MEDIUM_QUANTUM,
-							medium_free_list_count(task, reader, printer,
-									rack, ptr));
-				}
-				slot++;
-			}
-			_simple_sappend(b, "\n");
-		}
-		printer("%s\n", _simple_string(b));
-		_simple_sfree(b);
-	}
-}
-
-void
-print_medium_region(task_t task, memory_reader_t reader,
-		print_task_printer_t printer, szone_t *szone, int level,
-		region_t region, size_t bytes_at_start, size_t bytes_at_end)
-{
-	unsigned counts[1024];
-	unsigned in_use = 0;
-	uintptr_t start = (uintptr_t)MEDIUM_REGION_HEAP_BASE(region);
-	uintptr_t current = start + bytes_at_start;
-	uintptr_t limit = (uintptr_t)MEDIUM_REGION_HEAP_END(region) - bytes_at_end;
-	uintptr_t mapped_start;
-	msize_t msize_and_free;
-	msize_t msize;
-	unsigned ci;
-	_SIMPLE_STRING b;
-	uintptr_t pgTot = 0;
-	uintptr_t advTot = 0;
-
-	if (reader(task, (vm_address_t)start, MEDIUM_REGION_SIZE,
-			(void **)&mapped_start)) {
-		printer("Failed to map small region at %p\n", start);
-		return;
-	}
-	off_t start_offset = mapped_start - start;
-	region_t mapped_region = (region_t)mapped_start;
-
-	if (region == HASHRING_REGION_DEALLOCATED) {
-		if ((b = _simple_salloc()) != NULL) {
-			_simple_sprintf(b, "Medium region [unknown address] was returned to the OS\n");
-			printer("%s\n", _simple_string(b));
-			_simple_sfree(b);
-		}
-		return;
-	}
-
-	memset(counts, 0, sizeof(counts));
-	while (current < limit) {
-		msize_and_free = *(uintptr_t *)((char *)MEDIUM_METADATA_FOR_PTR(current)
-				+ start_offset);
-		msize = msize_and_free & ~MEDIUM_IS_FREE;
-		if (!msize) {
-			printer("*** error with %p: msize=%d, free: %x\n", (void *)current,
-					(unsigned)msize, msize_and_free & MEDIUM_IS_FREE);
-			break;
-		}
-		if (!(msize_and_free & MEDIUM_IS_FREE)) {
-			// block in use
-			if (msize < 1024) {
-				counts[msize]++;
-			}
-			in_use++;
-		} else {
-			uintptr_t pgLo = round_page_quanta(current + 
-					sizeof(medium_inplace_free_entry_s) + sizeof(msize_t));
-			uintptr_t pgHi = trunc_page_quanta(current + 
-					MEDIUM_BYTES_FOR_MSIZE(msize) - sizeof(msize_t));
-
-			if (pgLo < pgHi) {
-				pgTot += (pgHi - pgLo);
-			}
-
-			uintptr_t curAdv = current;
-			uintptr_t limAdv = current + MEDIUM_BYTES_FOR_MSIZE(msize);
-			while (curAdv < limAdv) {
-				msize_t adv = *(MEDIUM_MADVISE_HEADER_FOR_PTR(curAdv) + 
-					MEDIUM_META_INDEX_FOR_PTR(curAdv));
-				uintptr_t bytes = MEDIUM_BYTES_FOR_MSIZE(adv & ~MEDIUM_IS_ADVISED);
-				if (adv & MEDIUM_IS_ADVISED) {
-					advTot += bytes;
-				}
-				curAdv += bytes;
-			}
-		}
-		current += MEDIUM_BYTES_FOR_MSIZE(msize);
-	}
-	if ((b = _simple_salloc()) != NULL) {
-		mag_index_t mag_index = MAGAZINE_INDEX_FOR_MEDIUM_REGION(mapped_region);
-		_simple_sprintf(b, "Medium region %p [%p-%p, %y] \t", region,
-				(void *)start, MEDIUM_REGION_HEAP_END(region),
-				(int)MEDIUM_REGION_SIZE);
-		if (mag_index == DEPOT_MAGAZINE_INDEX) {
-			_simple_sprintf(b, "Recirc depot \t");
-		} else {
-			_simple_sprintf(b, "Magazine=%d \t", mag_index);
-		}
-		_simple_sprintf(b, "Allocations in use=%d \t Bytes in use=%ly (%d%%) \t",
-				in_use, BYTES_USED_FOR_MEDIUM_REGION(region),
-				(int)(100.0F * BYTES_USED_FOR_MEDIUM_REGION(mapped_region))/MEDIUM_REGION_SIZE);
-		if (bytes_at_end || bytes_at_start) {
-			_simple_sprintf(b, "Untouched=%ly ", bytes_at_end + bytes_at_start);
-		}
-		_simple_sprintf(b, "Advised=%ly ", advTot);
-#if CONFIG_RECIRC_DEPOT
-		_simple_sprintf(b, medium_region_below_recirc_threshold(mapped_region) ?
-				"\tEmpty enough to be moved to recirc depot" :
-				"\tNot empty enough to be moved to recirc depot");
-#endif // CONFIG_RECIRC_DEPOT
-		_simple_sprintf(b, "Dirty=%ly ", MEDIUM_REGION_PAYLOAD_BYTES - 
-				bytes_at_start - bytes_at_end -
-				BYTES_USED_FOR_MEDIUM_REGION(mapped_region) - advTot);
-		if (level >= MALLOC_VERBOSE_PRINT_LEVEL && in_use) {
-			_simple_sappend(b, "\n\tSizes in use: ");
-			for (ci = 0; ci < 1024; ci++) {
-				if (counts[ci]) {
-					_simple_sprintf(b, "%y[%d] ", MEDIUM_BYTES_FOR_MSIZE(ci),
-							counts[ci]);
-				}
-			}
-		}
-		printer("%s\n", _simple_string(b));
-		_simple_sfree(b);
-	}
-}
-
-void
-print_medium_region_vis(szone_t *szone, region_t region)
-{
-	_SIMPLE_STRING b;
-
-	if (region == HASHRING_REGION_DEALLOCATED) {
-		if ((b = _simple_salloc()) != NULL) {
-			_simple_sprintf(b, "Medium region [unknown address] was returned "
-					"to the kernel\n");
-			malloc_report(MALLOC_REPORT_NOLOG | MALLOC_REPORT_NOPREFIX,
-					"%s\n", _simple_string(b));
-			_simple_sfree(b);
-		}
-		return;
-	}
-
-	msize_t *metah = MEDIUM_META_HEADER_FOR_PTR(region);
-	msize_t *madvh = MEDIUM_MADVISE_HEADER_FOR_PTR(region);
-
-	mag_index_t mag_idx = MAGAZINE_INDEX_FOR_MEDIUM_REGION(region);
-	magazine_t *mag = &szone->medium_rack.magazines[mag_idx];
-
-	msize_t cur_msz = 0;
-	bool is_free = false;
-	msize_t cur_adv_msz = 0;
-	bool is_advised = false;
-
-	if ((b = _simple_salloc()) == NULL) {
-		abort();
-	}
-
-	malloc_report(MALLOC_REPORT_NOLOG | MALLOC_REPORT_NOPREFIX,
-			"Medium region %p  [%p-%p, %y, %y]\n", (void *)region,
-			MEDIUM_REGION_HEAP_BASE(region),
-			MEDIUM_REGION_HEAP_END(region), (int)MEDIUM_REGION_SIZE,
-			((medium_region_t)region)->trailer.bytes_used);
-
-	for (size_t x = 0; x < NUM_MEDIUM_BLOCKS; x++) {
-		bool is_last_rgn = mag->mag_last_region == region;
-		bool is_in_free_trailer = is_last_rgn && ((x << SHIFT_MEDIUM_QUANTUM) >
-				(MEDIUM_REGION_SIZE - mag->mag_bytes_free_at_end));
-		bool is_blk_start = false;
-		bool is_blk_end = cur_msz == 1;
-		bool is_adv_boundary = false;
-
-		if (cur_msz == 0) {
-			cur_msz = metah[x] & ~MEDIUM_IS_FREE;
-			is_free = metah[x] & MEDIUM_IS_FREE;
-			is_blk_start = true;
-		}
-		if (cur_adv_msz == 0 && madvh[x]) {
-			cur_adv_msz = madvh[x] & ~MEDIUM_IS_FREE;
-			is_advised = madvh[x] & MEDIUM_IS_FREE;
-			is_adv_boundary = true;
-		}
-		if (cur_adv_msz > 0) {
-			cur_adv_msz--;
-		}
-
-		const char *sigil = "?";
-		if (is_in_free_trailer) {
-			sigil = "_";
-		} else if (cur_msz > 0) {
-			if (is_free) {
-				if (is_advised) { sigil = "~";  }
-				else if (is_blk_start && cur_msz == 1) { sigil = "."; }
-				else if (is_blk_start) { sigil = "<"; }
-				else if (is_blk_end) { sigil = ">"; }
-				else if (is_adv_boundary) { sigil = "!"; }
-				else { sigil = "."; }
-			} else {
-				if (is_blk_start && cur_msz == 1) { sigil = "#"; }
-				else if (is_blk_start) { sigil = "["; }
-				else if (is_blk_end) { sigil = "]"; }
-				else { sigil = "#"; }
-			}
-			cur_msz--;
-		}
-
-		if (x > 0 && (x % 128) == 0) {
-			malloc_report(MALLOC_REPORT_NOLOG | MALLOC_REPORT_NOPREFIX, "%s\n",
-					_simple_string(b));
-			_simple_sfree(b);
-			if ((b = _simple_salloc()) == NULL) {
-				abort();
-			}
-			if (is_in_free_trailer) {
-				break;
-			}
-		}
-
-		_simple_sappend(b, sigil);
-	}
-	_simple_sfree(b);
-}
-
-static char *medium_freelist_fail_msg = "check: medium free list incorrect";
-
-#define MEDIUM_FREELIST_FAIL(fmt, ...) \
-	malloc_zone_check_fail(medium_freelist_fail_msg, \
-			" (slot=%u), counter=%d\n" fmt,  slot, counter, __VA_ARGS__);
-
-boolean_t
-medium_free_list_check(rack_t *rack, grain_t slot, unsigned counter)
-{
-	mag_index_t mag_index;
-
-	for (mag_index = -1; mag_index < rack->num_magazines; mag_index++) {
-		magazine_t *medium_mag_ptr = &(rack->magazines[mag_index]);
-		SZONE_MAGAZINE_PTR_LOCK(medium_mag_ptr);
-
-		unsigned count = 0;
-		free_list_t current = rack->magazines[mag_index].mag_free_list[slot];
-		free_list_t previous = (free_list_t){ .p = NULL };
-		msize_t msize_and_free;
-		void *ptr = NULL;
-
-		while ((ptr = medium_free_list_get_ptr(rack, current))) {
-			msize_and_free = *MEDIUM_METADATA_FOR_PTR(ptr);
-			if (!(msize_and_free & MEDIUM_IS_FREE)) {
-				MEDIUM_FREELIST_FAIL("*** in-use ptr in free list slot=%u count=%d ptr=%p\n", slot, count, ptr);
-				SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-				return 0;
-			}
-			if (((uintptr_t)ptr) & (MEDIUM_QUANTUM - 1)) {
-				MEDIUM_FREELIST_FAIL("*** unaligned ptr in free list slot=%u count=%d ptr=%p\n", slot, count, ptr);
-				SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-				return 0;
-			}
-			if (!medium_region_for_ptr_no_lock(rack, ptr)) {
-				MEDIUM_FREELIST_FAIL("*** ptr not in szone slot=%d count=%d ptr=%p\n", slot, count, ptr);
-				SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-				return 0;
-			}
-			if (medium_free_list_get_previous(rack, current).p != previous.p) {
-				MEDIUM_FREELIST_FAIL("*** previous incorrectly set slot=%u count=%d ptr=%p\n", slot, count, ptr);
-				SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-				return 0;
-			}
-			previous = current;
-			current = medium_free_list_get_next(rack, current);
-			count++;
-		}
-
-		SZONE_MAGAZINE_PTR_UNLOCK(medium_mag_ptr);
-	}
-	return 1;
-}
-
-#endif // CONFIG_MEDIUM_ALLOCATOR