Adding upstream version 0.0~git20221206.8b7148f.upstream/0.0_git20221206.8b7148f

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1535 insertions, 0 deletions

diff --git a/emmalloc/emmalloc.c b/emmalloc/emmalloc.c
new file mode 100644
index 0000000..c98e42e
--- /dev/null
+++ b/emmalloc/emmalloc.c
@@ -0,0 +1,1535 @@
+/*
+ * Copyright 2018 The Emscripten Authors.  All rights reserved.
+ * Emscripten is available under two separate licenses, the MIT license and the
+ * University of Illinois/NCSA Open Source License.  Both these licenses can be
+ * found in the LICENSE file.
+ *
+ * Simple minimalistic but efficient sbrk()-based malloc/free that works in
+ * singlethreaded and multithreaded builds.
+ *
+ * Assumptions:
+ *
+ *  - sbrk() is used to claim new memory (sbrk handles geometric/linear
+ *  - overallocation growth)
+ *  - sbrk() can be used by other code outside emmalloc.
+ *  - sbrk() is very fast in most cases (internal wasm call).
+ *  - sbrk() returns pointers with an alignment of alignof(max_align_t)
+ *
+ * Invariants:
+ *
+ *  - Per-allocation header overhead is 8 bytes, smallest allocated payload
+ *    amount is 8 bytes, and a multiple of 4 bytes.
+ *  - Acquired memory blocks are subdivided into disjoint regions that lie
+ *    next to each other.
+ *  - A region is either in used or free.
+ *    Used regions may be adjacent, and a used and unused region
+ *    may be adjacent, but not two unused ones - they would be
+ *    merged.
+ *  - Memory allocation takes constant time, unless the alloc needs to sbrk()
+ *    or memory is very close to being exhausted.
+ *
+ * Debugging:
+ *
+ *  - If not NDEBUG, runtime assert()s are in use.
+ *  - If EMMALLOC_MEMVALIDATE is defined, a large amount of extra checks are done.
+ *  - If EMMALLOC_VERBOSE is defined, a lot of operations are logged
+ *    out, in addition to EMMALLOC_MEMVALIDATE.
+ *  - Debugging and logging directly uses console.log via uses EM_ASM, not
+ *    printf etc., to minimize any risk of debugging or logging depending on
+ *    malloc.
+ */
+
+#include <stdalign.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <memory.h>
+#include <assert.h>
+#include <malloc.h>
+#include <limits.h>
+#include <stdlib.h>
+
+#ifdef __EMSCRIPTEN_TRACING__
+#include <emscripten/trace.h>
+#endif
+
+// Defind by the linker to have the address of the start of the heap.
+extern unsigned char __heap_base;
+
+// Behavior of right shifting a signed integer is compiler implementation defined.
+static_assert((((int32_t)0x80000000U) >> 31) == -1, "This malloc implementation requires that right-shifting a signed integer produces a sign-extending (arithmetic) shift!");
+
+// Configuration: specifies the minimum alignment that malloc()ed memory outputs. Allocation requests with smaller alignment
+// than this will yield an allocation with this much alignment.
+#define MALLOC_ALIGNMENT alignof(max_align_t)
+static_assert(alignof(max_align_t) == 16, "max_align_t must be correct");
+
+#define EMMALLOC_EXPORT __attribute__((weak))
+
+#define MIN(x, y) ((x) < (y) ? (x) : (y))
+#define MAX(x, y) ((x) > (y) ? (x) : (y))
+
+#define NUM_FREE_BUCKETS 64
+#define BUCKET_BITMASK_T uint64_t
+
+// Dynamic memory is subdivided into regions, in the format
+
+// <size:uint32_t> ..... <size:uint32_t> | <size:uint32_t> ..... <size:uint32_t> | <size:uint32_t> ..... <size:uint32_t> | .....
+
+// That is, at the bottom and top end of each memory region, the size of that region is stored. That allows traversing the
+// memory regions backwards and forwards. Because each allocation must be at least a multiple of 4 bytes, the lowest two bits of
+// each size field is unused. Free regions are distinguished by used regions by having the FREE_REGION_FLAG bit present
+// in the size field. I.e. for free regions, the size field is odd, and for used regions, the size field reads even.
+#define FREE_REGION_FLAG 0x1u
+
+// Attempts to malloc() more than this many bytes would cause an overflow when calculating the size of a region,
+// therefore allocations larger than this are short-circuited immediately on entry.
+#define MAX_ALLOC_SIZE 0xFFFFFFC7u
+
+// A free region has the following structure:
+// <size:size_t> <prevptr> <nextptr> ... <size:size_t>
+
+typedef struct Region
+{
+  size_t size;
+  // Use a circular doubly linked list to represent free region data.
+  struct Region *prev, *next;
+  // ... N bytes of free data
+  size_t _at_the_end_of_this_struct_size; // do not dereference, this is present for convenient struct sizeof() computation only
+} Region;
+
+// Each memory block starts with a RootRegion at the beginning.
+// The RootRegion specifies the size of the region block, and forms a linked
+// list of all RootRegions in the program, starting with `listOfAllRegions`
+// below.
+typedef struct RootRegion
+{
+  uint32_t size;
+  struct RootRegion *next;
+  uint8_t* endPtr;
+} RootRegion;
+
+#if defined(__EMSCRIPTEN_PTHREADS__)
+// In multithreaded builds, use a simple global spinlock strategy to acquire/release access to the memory allocator.
+static volatile uint8_t multithreadingLock = 0;
+#define MALLOC_ACQUIRE() while(__sync_lock_test_and_set(&multithreadingLock, 1)) { while(multithreadingLock) { /*nop*/ } }
+#define MALLOC_RELEASE() __sync_lock_release(&multithreadingLock)
+// Test code to ensure we have tight malloc acquire/release guards in place.
+#define ASSERT_MALLOC_IS_ACQUIRED() assert(multithreadingLock == 1)
+#else
+// In singlethreaded builds, no need for locking.
+#define MALLOC_ACQUIRE() ((void)0)
+#define MALLOC_RELEASE() ((void)0)
+#define ASSERT_MALLOC_IS_ACQUIRED() ((void)0)
+#endif
+
+#define IS_POWER_OF_2(val) (((val) & ((val)-1)) == 0)
+#define ALIGN_UP(ptr, alignment) ((uint8_t*)((((uintptr_t)(ptr)) + ((alignment)-1)) & ~((alignment)-1)))
+#define HAS_ALIGNMENT(ptr, alignment) ((((uintptr_t)(ptr)) & ((alignment)-1)) == 0)
+
+static_assert(IS_POWER_OF_2(MALLOC_ALIGNMENT), "MALLOC_ALIGNMENT must be a power of two value!");
+static_assert(MALLOC_ALIGNMENT >= 4, "Smallest possible MALLOC_ALIGNMENT if 4!");
+
+// A region that contains as payload a single forward linked list of pointers to
+// root regions of each disjoint region blocks.
+static RootRegion *listOfAllRegions = NULL;
+
+// For each of the buckets, maintain a linked list head node. The head node for each
+// free region is a sentinel node that does not actually represent any free space, but
+// the sentinel is used to avoid awkward testing against (if node == freeRegionHeadNode)
+// when adding and removing elements from the linked list, i.e. we are guaranteed that
+// the sentinel node is always fixed and there, and the actual free region list elements
+// start at freeRegionBuckets[i].next each.
+static Region freeRegionBuckets[NUM_FREE_BUCKETS] = {
+	{ .prev = &freeRegionBuckets[0], .next = &freeRegionBuckets[0] },
+	{ .prev = &freeRegionBuckets[1], .next = &freeRegionBuckets[1] },
+	{ .prev = &freeRegionBuckets[2], .next = &freeRegionBuckets[2] },
+	{ .prev = &freeRegionBuckets[3], .next = &freeRegionBuckets[3] },
+	{ .prev = &freeRegionBuckets[4], .next = &freeRegionBuckets[4] },
+	{ .prev = &freeRegionBuckets[5], .next = &freeRegionBuckets[5] },
+	{ .prev = &freeRegionBuckets[6], .next = &freeRegionBuckets[6] },
+	{ .prev = &freeRegionBuckets[7], .next = &freeRegionBuckets[7] },
+	{ .prev = &freeRegionBuckets[8], .next = &freeRegionBuckets[8] },
+	{ .prev = &freeRegionBuckets[9], .next = &freeRegionBuckets[9] },
+	{ .prev = &freeRegionBuckets[10], .next = &freeRegionBuckets[10] },
+	{ .prev = &freeRegionBuckets[11], .next = &freeRegionBuckets[11] },
+	{ .prev = &freeRegionBuckets[12], .next = &freeRegionBuckets[12] },
+	{ .prev = &freeRegionBuckets[13], .next = &freeRegionBuckets[13] },
+	{ .prev = &freeRegionBuckets[14], .next = &freeRegionBuckets[14] },
+	{ .prev = &freeRegionBuckets[15], .next = &freeRegionBuckets[15] },
+	{ .prev = &freeRegionBuckets[16], .next = &freeRegionBuckets[16] },
+	{ .prev = &freeRegionBuckets[17], .next = &freeRegionBuckets[17] },
+	{ .prev = &freeRegionBuckets[18], .next = &freeRegionBuckets[18] },
+	{ .prev = &freeRegionBuckets[19], .next = &freeRegionBuckets[19] },
+	{ .prev = &freeRegionBuckets[20], .next = &freeRegionBuckets[20] },
+	{ .prev = &freeRegionBuckets[21], .next = &freeRegionBuckets[21] },
+	{ .prev = &freeRegionBuckets[22], .next = &freeRegionBuckets[22] },
+	{ .prev = &freeRegionBuckets[23], .next = &freeRegionBuckets[23] },
+	{ .prev = &freeRegionBuckets[24], .next = &freeRegionBuckets[24] },
+	{ .prev = &freeRegionBuckets[25], .next = &freeRegionBuckets[25] },
+	{ .prev = &freeRegionBuckets[26], .next = &freeRegionBuckets[26] },
+	{ .prev = &freeRegionBuckets[27], .next = &freeRegionBuckets[27] },
+	{ .prev = &freeRegionBuckets[28], .next = &freeRegionBuckets[28] },
+	{ .prev = &freeRegionBuckets[29], .next = &freeRegionBuckets[29] },
+	{ .prev = &freeRegionBuckets[30], .next = &freeRegionBuckets[30] },
+	{ .prev = &freeRegionBuckets[31], .next = &freeRegionBuckets[31] },
+	{ .prev = &freeRegionBuckets[32], .next = &freeRegionBuckets[32] },
+	{ .prev = &freeRegionBuckets[33], .next = &freeRegionBuckets[33] },
+	{ .prev = &freeRegionBuckets[34], .next = &freeRegionBuckets[34] },
+	{ .prev = &freeRegionBuckets[35], .next = &freeRegionBuckets[35] },
+	{ .prev = &freeRegionBuckets[36], .next = &freeRegionBuckets[36] },
+	{ .prev = &freeRegionBuckets[37], .next = &freeRegionBuckets[37] },
+	{ .prev = &freeRegionBuckets[38], .next = &freeRegionBuckets[38] },
+	{ .prev = &freeRegionBuckets[39], .next = &freeRegionBuckets[39] },
+	{ .prev = &freeRegionBuckets[40], .next = &freeRegionBuckets[40] },
+	{ .prev = &freeRegionBuckets[41], .next = &freeRegionBuckets[41] },
+	{ .prev = &freeRegionBuckets[42], .next = &freeRegionBuckets[42] },
+	{ .prev = &freeRegionBuckets[43], .next = &freeRegionBuckets[43] },
+	{ .prev = &freeRegionBuckets[44], .next = &freeRegionBuckets[44] },
+	{ .prev = &freeRegionBuckets[45], .next = &freeRegionBuckets[45] },
+	{ .prev = &freeRegionBuckets[46], .next = &freeRegionBuckets[46] },
+	{ .prev = &freeRegionBuckets[47], .next = &freeRegionBuckets[47] },
+	{ .prev = &freeRegionBuckets[48], .next = &freeRegionBuckets[48] },
+	{ .prev = &freeRegionBuckets[49], .next = &freeRegionBuckets[49] },
+	{ .prev = &freeRegionBuckets[50], .next = &freeRegionBuckets[50] },
+	{ .prev = &freeRegionBuckets[51], .next = &freeRegionBuckets[51] },
+	{ .prev = &freeRegionBuckets[52], .next = &freeRegionBuckets[52] },
+	{ .prev = &freeRegionBuckets[53], .next = &freeRegionBuckets[53] },
+	{ .prev = &freeRegionBuckets[54], .next = &freeRegionBuckets[54] },
+	{ .prev = &freeRegionBuckets[55], .next = &freeRegionBuckets[55] },
+	{ .prev = &freeRegionBuckets[56], .next = &freeRegionBuckets[56] },
+	{ .prev = &freeRegionBuckets[57], .next = &freeRegionBuckets[57] },
+	{ .prev = &freeRegionBuckets[58], .next = &freeRegionBuckets[58] },
+	{ .prev = &freeRegionBuckets[59], .next = &freeRegionBuckets[59] },
+	{ .prev = &freeRegionBuckets[60], .next = &freeRegionBuckets[60] },
+	{ .prev = &freeRegionBuckets[61], .next = &freeRegionBuckets[61] },
+	{ .prev = &freeRegionBuckets[62], .next = &freeRegionBuckets[62] },
+	{ .prev = &freeRegionBuckets[63], .next = &freeRegionBuckets[63] },
+};
+
+// A bitmask that tracks the population status for each of the 64 distinct memory regions:
+// a zero at bit position i means that the free list bucket i is empty. This bitmask is
+// used to avoid redundant scanning of the 64 different free region buckets: instead by
+// looking at the bitmask we can find in constant time an index to a free region bucket
+// that contains free memory of desired size.
+static BUCKET_BITMASK_T freeRegionBucketsUsed = 0;
+
+// Amount of bytes taken up by allocation header data
+#define REGION_HEADER_SIZE (2*sizeof(size_t))
+
+// Smallest allocation size that is possible is 2*pointer size, since payload of each region must at least contain space
+// to store the free region linked list prev and next pointers. An allocation size smaller than this will be rounded up
+// to this size.
+#define SMALLEST_ALLOCATION_SIZE (2*sizeof(void*))
+
+/* Subdivide regions of free space into distinct circular doubly linked lists, where each linked list
+represents a range of free space blocks. The following function compute_free_list_bucket() converts
+an allocation size to the bucket index that should be looked at. The buckets are grouped as follows:
+
+  Bucket 0: [8, 15], range size=8
+  Bucket 1: [16, 23], range size=8
+  Bucket 2: [24, 31], range size=8
+  Bucket 3: [32, 39], range size=8
+  Bucket 4: [40, 47], range size=8
+  Bucket 5: [48, 55], range size=8
+  Bucket 6: [56, 63], range size=8
+  Bucket 7: [64, 71], range size=8
+  Bucket 8: [72, 79], range size=8
+  Bucket 9: [80, 87], range size=8
+  Bucket 10: [88, 95], range size=8
+  Bucket 11: [96, 103], range size=8
+  Bucket 12: [104, 111], range size=8
+  Bucket 13: [112, 119], range size=8
+  Bucket 14: [120, 159], range size=40
+  Bucket 15: [160, 191], range size=32
+  Bucket 16: [192, 223], range size=32
+  Bucket 17: [224, 255], range size=32
+  Bucket 18: [256, 319], range size=64
+  Bucket 19: [320, 383], range size=64
+  Bucket 20: [384, 447], range size=64
+  Bucket 21: [448, 511], range size=64
+  Bucket 22: [512, 639], range size=128
+  Bucket 23: [640, 767], range size=128
+  Bucket 24: [768, 895], range size=128
+  Bucket 25: [896, 1023], range size=128
+  Bucket 26: [1024, 1279], range size=256
+  Bucket 27: [1280, 1535], range size=256
+  Bucket 28: [1536, 1791], range size=256
+  Bucket 29: [1792, 2047], range size=256
+  Bucket 30: [2048, 2559], range size=512
+  Bucket 31: [2560, 3071], range size=512
+  Bucket 32: [3072, 3583], range size=512
+  Bucket 33: [3584, 6143], range size=2560
+  Bucket 34: [6144, 8191], range size=2048
+  Bucket 35: [8192, 12287], range size=4096
+  Bucket 36: [12288, 16383], range size=4096
+  Bucket 37: [16384, 24575], range size=8192
+  Bucket 38: [24576, 32767], range size=8192
+  Bucket 39: [32768, 49151], range size=16384
+  Bucket 40: [49152, 65535], range size=16384
+  Bucket 41: [65536, 98303], range size=32768
+  Bucket 42: [98304, 131071], range size=32768
+  Bucket 43: [131072, 196607], range size=65536
+  Bucket 44: [196608, 262143], range size=65536
+  Bucket 45: [262144, 393215], range size=131072
+  Bucket 46: [393216, 524287], range size=131072
+  Bucket 47: [524288, 786431], range size=262144
+  Bucket 48: [786432, 1048575], range size=262144
+  Bucket 49: [1048576, 1572863], range size=524288
+  Bucket 50: [1572864, 2097151], range size=524288
+  Bucket 51: [2097152, 3145727], range size=1048576
+  Bucket 52: [3145728, 4194303], range size=1048576
+  Bucket 53: [4194304, 6291455], range size=2097152
+  Bucket 54: [6291456, 8388607], range size=2097152
+  Bucket 55: [8388608, 12582911], range size=4194304
+  Bucket 56: [12582912, 16777215], range size=4194304
+  Bucket 57: [16777216, 25165823], range size=8388608
+  Bucket 58: [25165824, 33554431], range size=8388608
+  Bucket 59: [33554432, 50331647], range size=16777216
+  Bucket 60: [50331648, 67108863], range size=16777216
+  Bucket 61: [67108864, 100663295], range size=33554432
+  Bucket 62: [100663296, 134217727], range size=33554432
+  Bucket 63: 134217728 bytes and larger. */
+static_assert(NUM_FREE_BUCKETS == 64, "Following function is tailored specifically for NUM_FREE_BUCKETS == 64 case");
+static int compute_free_list_bucket(size_t allocSize)
+{
+  if (allocSize < 128) return (allocSize >> 3) - 1;
+  int clz = __builtin_clz(allocSize);
+  int bucketIndex = (clz > 19) ? 110 - (clz<<2) + ((allocSize >> (29-clz)) ^ 4) : MIN(71 - (clz<<1) + ((allocSize >> (30-clz)) ^ 2), NUM_FREE_BUCKETS-1);
+  assert(bucketIndex >= 0);
+  assert(bucketIndex < NUM_FREE_BUCKETS);
+  return bucketIndex;
+}
+
+#define DECODE_CEILING_SIZE(size) ((size_t)((size) & ~FREE_REGION_FLAG))
+
+static Region *prev_region(Region *region)
+{
+  size_t prevRegionSize = ((size_t*)region)[-1];
+  prevRegionSize = DECODE_CEILING_SIZE(prevRegionSize);
+  return (Region*)((uint8_t*)region - prevRegionSize);
+}
+
+static Region *next_region(Region *region)
+{
+  return (Region*)((uint8_t*)region + region->size);
+}
+
+static size_t region_ceiling_size(Region *region)
+{
+  return ((size_t*)((uint8_t*)region + region->size))[-1];
+}
+
+static bool region_is_free(Region *r)
+{
+  return region_ceiling_size(r) & FREE_REGION_FLAG;
+}
+
+static bool region_is_in_use(Region *r)
+{
+  return r->size == region_ceiling_size(r);
+}
+
+static size_t size_of_region_from_ceiling(Region *r)
+{
+  size_t size = region_ceiling_size(r);
+  return DECODE_CEILING_SIZE(size);
+}
+
+static bool debug_region_is_consistent(Region *r)
+{
+  assert(r);
+  size_t sizeAtBottom = r->size;
+  size_t sizeAtCeiling = size_of_region_from_ceiling(r);
+  return sizeAtBottom == sizeAtCeiling;
+}
+
+static uint8_t *region_payload_start_ptr(Region *region)
+{
+  return (uint8_t*)region + sizeof(size_t);
+}
+
+static uint8_t *region_payload_end_ptr(Region *region)
+{
+  return (uint8_t*)region + region->size - sizeof(size_t);
+}
+
+static void create_used_region(void *ptr, size_t size)
+{
+  assert(ptr);
+  assert(HAS_ALIGNMENT(ptr, sizeof(size_t)));
+  assert(HAS_ALIGNMENT(size, sizeof(size_t)));
+  assert(size >= sizeof(Region));
+  *(size_t*)ptr = size;
+  ((size_t*)ptr)[(size/sizeof(size_t))-1] = size;
+}
+
+static void create_free_region(void *ptr, size_t size)
+{
+  assert(ptr);
+  assert(HAS_ALIGNMENT(ptr, sizeof(size_t)));
+  assert(HAS_ALIGNMENT(size, sizeof(size_t)));
+  assert(size >= sizeof(Region));
+  Region *freeRegion = (Region*)ptr;
+  freeRegion->size = size;
+  ((size_t*)ptr)[(size/sizeof(size_t))-1] = size | FREE_REGION_FLAG;
+}
+
+static void prepend_to_free_list(Region *region, Region *prependTo)
+{
+  assert(region);
+  assert(prependTo);
+  // N.b. the region we are prepending to is always the sentinel node,
+  // which represents a dummy node that is technically not a free node, so
+  // region_is_free(prependTo) does not hold.
+  assert(region_is_free((Region*)region));
+  region->next = prependTo;
+  region->prev = prependTo->prev;
+  assert(region->prev);
+  prependTo->prev = region;
+  region->prev->next = region;
+}
+
+static void unlink_from_free_list(Region *region)
+{
+  assert(region);
+  assert(region_is_free((Region*)region));
+  assert(region->prev);
+  assert(region->next);
+  region->prev->next = region->next;
+  region->next->prev = region->prev;
+}
+
+static void link_to_free_list(Region *freeRegion)
+{
+  assert(freeRegion);
+  assert(freeRegion->size >= sizeof(Region));
+  int bucketIndex = compute_free_list_bucket(freeRegion->size-REGION_HEADER_SIZE);
+  Region *freeListHead = freeRegionBuckets + bucketIndex;
+  freeRegion->prev = freeListHead;
+  freeRegion->next = freeListHead->next;
+  assert(freeRegion->next);
+  freeListHead->next = freeRegion;
+  freeRegion->next->prev = freeRegion;
+  freeRegionBucketsUsed |= ((BUCKET_BITMASK_T)1) << bucketIndex;
+}
+
+#if 0
+static void dump_memory_regions()
+{
+  ASSERT_MALLOC_IS_ACQUIRED();
+  RootRegion *root = listOfAllRegions;
+  MAIN_THREAD_ASYNC_EM_ASM(console.log('All memory regions:'));
+  while(root)
+  {
+    Region *r = (Region*)root;
+    assert(debug_region_is_consistent(r));
+    uint8_t *lastRegionEnd = root->endPtr;
+    MAIN_THREAD_ASYNC_EM_ASM(console.log('Region block 0x'+($0>>>0).toString(16)+' - 0x'+($1>>>0).toString(16)+ ' ('+($2>>>0)+' bytes):'),
+      r, lastRegionEnd, lastRegionEnd-(uint8_t*)r);
+    while((uint8_t*)r < lastRegionEnd)
+    {
+      MAIN_THREAD_ASYNC_EM_ASM(console.log('Region 0x'+($0>>>0).toString(16)+', size: '+($1>>>0)+' ('+($2?"used":"--FREE--")+')'),
+        r, r->size, region_ceiling_size(r) == r->size);
+
+      assert(debug_region_is_consistent(r));
+      size_t sizeFromCeiling = size_of_region_from_ceiling(r);
+      if (sizeFromCeiling != r->size)
+        MAIN_THREAD_ASYNC_EM_ASM(console.log('Corrupt region! Size marker at the end of the region does not match: '+($0>>>0)), sizeFromCeiling);
+      if (r->size == 0)
+        break;
+      r = next_region(r);
+    }
+    root = root->next;
+    MAIN_THREAD_ASYNC_EM_ASM(console.log(""));
+  }
+  MAIN_THREAD_ASYNC_EM_ASM(console.log('Free regions:'));
+  for(int i = 0; i < NUM_FREE_BUCKETS; ++i)
+  {
+    Region *prev = &freeRegionBuckets[i];
+    Region *fr = freeRegionBuckets[i].next;
+    while(fr != &freeRegionBuckets[i])
+    {
+      MAIN_THREAD_ASYNC_EM_ASM(console.log('In bucket '+$0+', free region 0x'+($1>>>0).toString(16)+', size: ' + ($2>>>0) + ' (size at ceiling: '+($3>>>0)+'), prev: 0x' + ($4>>>0).toString(16) + ', next: 0x' + ($5>>>0).toString(16)),
+        i, fr, fr->size, size_of_region_from_ceiling(fr), fr->prev, fr->next);
+      assert(debug_region_is_consistent(fr));
+      assert(region_is_free(fr));
+      assert(fr->prev == prev);
+      prev = fr;
+      assert(fr->next != fr);
+      assert(fr->prev != fr);
+      fr = fr->next;
+    }
+  }
+  MAIN_THREAD_ASYNC_EM_ASM(console.log('Free bucket index map: ' + ($0>>>0).toString(2) + ' ' + ($1>>>0).toString(2)), (uint32_t)(freeRegionBucketsUsed >> 32), (uint32_t)freeRegionBucketsUsed);
+  MAIN_THREAD_ASYNC_EM_ASM(console.log(""));
+}
+
+void emmalloc_dump_memory_regions()
+{
+  MALLOC_ACQUIRE();
+  dump_memory_regions();
+  MALLOC_RELEASE();
+}
+
+static int validate_memory_regions()
+{
+  ASSERT_MALLOC_IS_ACQUIRED();
+  RootRegion *root = listOfAllRegions;
+  while(root)
+  {
+    Region *r = (Region*)root;
+    if (!debug_region_is_consistent(r))
+    {
+      MAIN_THREAD_ASYNC_EM_ASM(console.error('Used region 0x'+($0>>>0).toString(16)+', size: '+($1>>>0)+' ('+($2?"used":"--FREE--")+') is corrupt (size markers in the beginning and at the end of the region do not match!)'),
+        r, r->size, region_ceiling_size(r) == r->size);
+      return 1;
+    }
+    uint8_t *lastRegionEnd = root->endPtr;
+    while((uint8_t*)r < lastRegionEnd)
+    {
+      if (!debug_region_is_consistent(r))
+      {
+        MAIN_THREAD_ASYNC_EM_ASM(console.error('Used region 0x'+($0>>>0).toString(16)+', size: '+($1>>>0)+' ('+($2?"used":"--FREE--")+') is corrupt (size markers in the beginning and at the end of the region do not match!)'),
+          r, r->size, region_ceiling_size(r) == r->size);
+        return 1;
+      }
+      if (r->size == 0)
+        break;
+      r = next_region(r);
+    }
+    root = root->next;
+  }
+  for(int i = 0; i < NUM_FREE_BUCKETS; ++i)
+  {
+    Region *prev = &freeRegionBuckets[i];
+    Region *fr = freeRegionBuckets[i].next;
+    while(fr != &freeRegionBuckets[i])
+    {
+      if (!debug_region_is_consistent(fr) || !region_is_free(fr) || fr->prev != prev || fr->next == fr || fr->prev == fr)
+      {
+        MAIN_THREAD_ASYNC_EM_ASM(console.log('In bucket '+$0+', free region 0x'+($1>>>0).toString(16)+', size: ' + ($2>>>0) + ' (size at ceiling: '+($3>>>0)+'), prev: 0x' + ($4>>>0).toString(16) + ', next: 0x' + ($5>>>0).toString(16) + ' is corrupt!'),
+          i, fr, fr->size, size_of_region_from_ceiling(fr), fr->prev, fr->next);
+        return 1;
+      }
+      prev = fr;
+      fr = fr->next;
+    }
+  }
+  return 0;
+}
+
+int emmalloc_validate_memory_regions()
+{
+  MALLOC_ACQUIRE();
+  int memoryError = validate_memory_regions();
+  MALLOC_RELEASE();
+  return memoryError;
+}
+#endif
+
+static bool claim_more_memory(size_t numBytes)
+{
+#ifdef EMMALLOC_VERBOSE
+  MAIN_THREAD_ASYNC_EM_ASM(console.log('claim_more_memory(numBytes='+($0>>>0)+ ')'), numBytes);
+#endif
+
+#ifdef EMMALLOC_MEMVALIDATE
+  validate_memory_regions();
+#endif
+
+  uint8_t *startPtr;
+  uint8_t *endPtr;
+  do {
+    // If this is the first time we're called, see if we can use
+    // the initial heap memory set up by wasm-ld.
+    if (!listOfAllRegions) {
+      unsigned char *heap_end = sbrk(0);
+      if (numBytes <= (size_t)(heap_end - &__heap_base)) {
+        startPtr = &__heap_base;
+        endPtr = heap_end;
+	break;
+      }
+    }
+
+    // Round numBytes up to the nearest page size.
+    numBytes = (numBytes + (PAGE_SIZE-1)) & -PAGE_SIZE;
+
+    // Claim memory via sbrk
+    startPtr = (uint8_t*)sbrk(numBytes);
+    if ((intptr_t)startPtr == -1)
+    {
+#ifdef EMMALLOC_VERBOSE
+      MAIN_THREAD_ASYNC_EM_ASM(console.error('claim_more_memory: sbrk failed!'));
+#endif
+      return false;
+    }
+#ifdef EMMALLOC_VERBOSE
+    MAIN_THREAD_ASYNC_EM_ASM(console.log('claim_more_memory: claimed 0x' + ($0>>>0).toString(16) + ' - 0x' + ($1>>>0).toString(16) + ' (' + ($2>>>0) + ' bytes) via sbrk()'), startPtr, startPtr + numBytes, numBytes);
+#endif
+    assert(HAS_ALIGNMENT(startPtr, alignof(size_t)));
+    endPtr = startPtr + numBytes;
+  } while (0);
+
+  // Create a sentinel region at the end of the new heap block
+  Region *endSentinelRegion = (Region*)(endPtr - sizeof(Region));
+  create_used_region(endSentinelRegion, sizeof(Region));
+
+  // If we are the sole user of sbrk(), it will feed us continuous/consecutive memory addresses - take advantage
+  // of that if so: instead of creating two disjoint memory regions blocks, expand the previous one to a larger size.
+  uint8_t *previousSbrkEndAddress = listOfAllRegions ? listOfAllRegions->endPtr : 0;
+  if (startPtr == previousSbrkEndAddress)
+  {
+    Region *prevEndSentinel = prev_region((Region*)startPtr);
+    assert(debug_region_is_consistent(prevEndSentinel));
+    assert(region_is_in_use(prevEndSentinel));
+    Region *prevRegion = prev_region(prevEndSentinel);
+    assert(debug_region_is_consistent(prevRegion));
+
+    listOfAllRegions->endPtr = endPtr;
+
+    // Two scenarios, either the last region of the previous block was in use, in which case we need to create
+    // a new free region in the newly allocated space; or it was free, in which case we can extend that region
+    // to cover a larger size.
+    if (region_is_free(prevRegion))
+    {
+      size_t newFreeRegionSize = (uint8_t*)endSentinelRegion - (uint8_t*)prevRegion;
+      unlink_from_free_list(prevRegion);
+      create_free_region(prevRegion, newFreeRegionSize);
+      link_to_free_list(prevRegion);
+      return true;
+    }
+    // else: last region of the previous block was in use. Since we are joining two consecutive sbrk() blocks,
+    // we can swallow the end sentinel of the previous block away.
+    startPtr -= sizeof(Region);
+  }
+  else
+  {
+    // Create a root region at the start of the heap block
+    create_used_region(startPtr, sizeof(Region));
+
+    // Dynamic heap start region:
+    RootRegion *newRegionBlock = (RootRegion*)startPtr;
+    newRegionBlock->next = listOfAllRegions; // Pointer to next region block head
+    newRegionBlock->endPtr = endPtr; // Pointer to the end address of this region block
+    listOfAllRegions = newRegionBlock;
+    startPtr += sizeof(Region);
+  }
+
+  // Create a new memory region for the new claimed free space.
+  create_free_region(startPtr, (uint8_t*)endSentinelRegion - startPtr);
+  link_to_free_list((Region*)startPtr);
+  return true;
+}
+
+#if 0
+// Initialize emmalloc during static initialization.
+// See system/lib/README.md for static constructor ordering.
+__attribute__((constructor(47)))
+static void initialize_emmalloc_heap()
+{
+  // Initialize circular doubly linked lists representing free space
+  // Never useful to unroll this for loop, just takes up code size.
+#pragma clang loop unroll(disable)
+  for(int i = 0; i < NUM_FREE_BUCKETS; ++i)
+    freeRegionBuckets[i].prev = freeRegionBuckets[i].next = &freeRegionBuckets[i];
+
+#ifdef EMMALLOC_VERBOSE
+  MAIN_THREAD_ASYNC_EM_ASM(console.log('initialize_emmalloc_heap()'));
+#endif
+
+  // Start with a tiny dynamic region.
+  claim_more_memory(3*sizeof(Region));
+}
+
+void emmalloc_blank_slate_from_orbit()
+{
+  MALLOC_ACQUIRE();
+  listOfAllRegions = NULL;
+  freeRegionBucketsUsed = 0;
+  initialize_emmalloc_heap();
+  MALLOC_RELEASE();
+}
+#endif
+
+static void *attempt_allocate(Region *freeRegion, size_t alignment, size_t size)
+{
+  ASSERT_MALLOC_IS_ACQUIRED();
+  assert(freeRegion);
+  // Look at the next potential free region to allocate into.
+  // First, we should check if the free region has enough of payload bytes contained
+  // in it to accommodate the new allocation. This check needs to take account the
+  // requested allocation alignment, so the payload memory area needs to be rounded
+  // upwards to the desired alignment.
+  uint8_t *payloadStartPtr = region_payload_start_ptr(freeRegion);
+  uint8_t *payloadStartPtrAligned = ALIGN_UP(payloadStartPtr, alignment);
+  uint8_t *payloadEndPtr = region_payload_end_ptr(freeRegion);
+
+  // Do we have enough free space, taking into account alignment?
+  if (payloadStartPtrAligned + size > payloadEndPtr)
+    return NULL;
+
+  // We have enough free space, so the memory allocation will be made into this region. Remove this free region
+  // from the list of free regions: whatever slop remains will be later added back to the free region pool.
+  unlink_from_free_list(freeRegion);
+
+  // Before we proceed further, fix up the boundary of this region and the region that precedes this one,
+  // so that the boundary between the two regions happens at a right spot for the payload to be aligned.
+  if (payloadStartPtr != payloadStartPtrAligned)
+  {
+    Region *prevRegion = prev_region((Region*)freeRegion);
+    // We never have two free regions adjacent to each other, so the region before this free
+    // region should be in use.
+    assert(region_is_in_use(prevRegion));
+    size_t regionBoundaryBumpAmount = payloadStartPtrAligned - payloadStartPtr;
+    size_t newThisRegionSize = freeRegion->size - regionBoundaryBumpAmount;
+    create_used_region(prevRegion, prevRegion->size + regionBoundaryBumpAmount);
+    freeRegion = (Region *)((uint8_t*)freeRegion + regionBoundaryBumpAmount);
+    freeRegion->size = newThisRegionSize;
+  }
+  // Next, we need to decide whether this region is so large that it should be split into two regions,
+  // one representing the newly used memory area, and at the high end a remaining leftover free area.
+  // This splitting to two is done always if there is enough space for the high end to fit a region.
+  // Carve 'size' bytes of payload off this region. So,
+  // [sz prev next sz]
+  // becomes
+  // [sz payload sz] [sz prev next sz]
+  if (sizeof(Region) + REGION_HEADER_SIZE + size <= freeRegion->size)
+  {
+    // There is enough space to keep a free region at the end of the carved out block
+    // -> construct the new block
+    Region *newFreeRegion = (Region *)((uint8_t*)freeRegion + REGION_HEADER_SIZE + size);
+    create_free_region(newFreeRegion, freeRegion->size - size - REGION_HEADER_SIZE);
+    link_to_free_list(newFreeRegion);
+
+    // Recreate the resized Region under its new size.
+    create_used_region(freeRegion, size + REGION_HEADER_SIZE);
+  }
+  else
+  {
+    // There is not enough space to split the free memory region into used+free parts, so consume the whole
+    // region as used memory, not leaving a free memory region behind.
+    // Initialize the free region as used by resetting the ceiling size to the same value as the size at bottom.
+    ((size_t*)((uint8_t*)freeRegion + freeRegion->size))[-1] = freeRegion->size;
+  }
+
+#ifdef __EMSCRIPTEN_TRACING__
+  emscripten_trace_record_allocation(freeRegion, freeRegion->size);
+#endif
+
+#ifdef EMMALLOC_VERBOSE
+  MAIN_THREAD_ASYNC_EM_ASM(console.log('attempt_allocate - succeeded allocating memory, region ptr=0x' + ($0>>>0).toString(16) + ', align=' + $1 + ', payload size=' + ($2>>>0) + ' bytes)'), freeRegion, alignment, size);
+#endif
+
+  return (uint8_t*)freeRegion + sizeof(size_t);
+}
+
+static size_t validate_alloc_alignment(size_t alignment)
+{
+  // Cannot perform allocations that are less than 4 byte aligned, because the Region
+  // control structures need to be aligned. Also round up to minimum outputted alignment.
+  alignment = MAX(alignment, MALLOC_ALIGNMENT);
+  // Arbitrary upper limit on alignment - very likely a programming bug if alignment is higher than this.
+  assert(alignment <= 1024*1024);
+  return alignment;
+}
+
+static size_t validate_alloc_size(size_t size)
+{
+  assert(size + REGION_HEADER_SIZE > size);
+
+  // Allocation sizes must be a multiple of pointer sizes, and at least 2*sizeof(pointer).
+  size_t validatedSize = size > SMALLEST_ALLOCATION_SIZE ? (size_t)ALIGN_UP(size, sizeof(Region*)) : SMALLEST_ALLOCATION_SIZE;
+  assert(validatedSize >= size); // 32-bit wraparound should not occur, too large sizes should be stopped before
+
+  return validatedSize;
+}
+
+static void *allocate_memory(size_t alignment, size_t size)
+{
+  ASSERT_MALLOC_IS_ACQUIRED();
+
+#ifdef EMMALLOC_VERBOSE
+  MAIN_THREAD_ASYNC_EM_ASM(console.log('allocate_memory(align=' + $0 + ', size=' + ($1>>>0) + ' bytes)'), alignment, size);
+#endif
+
+#ifdef EMMALLOC_MEMVALIDATE
+  validate_memory_regions();
+#endif
+
+  if (!IS_POWER_OF_2(alignment))
+  {
+#ifdef EMMALLOC_VERBOSE
+    MAIN_THREAD_ASYNC_EM_ASM(console.log('Allocation failed: alignment not power of 2!'));
+#endif
+    return 0;
+  }
+
+  if (size > MAX_ALLOC_SIZE)
+  {
+#ifdef EMMALLOC_VERBOSE
+    MAIN_THREAD_ASYNC_EM_ASM(console.log('Allocation failed: attempted allocation size is too large: ' + ($0 >>> 0) + 'bytes! (negative integer wraparound?)'), size);
+#endif
+    return 0;
+  }
+
+  alignment = validate_alloc_alignment(alignment);
+  size = validate_alloc_size(size);
+
+  // Attempt to allocate memory starting from smallest bucket that can contain the required amount of memory.
+  // Under normal alignment conditions this should always be the first or second bucket we look at, but if
+  // performing an allocation with complex alignment, we may need to look at multiple buckets.
+  int bucketIndex = compute_free_list_bucket(size);
+  BUCKET_BITMASK_T bucketMask = freeRegionBucketsUsed >> bucketIndex;
+
+  // Loop through each bucket that has free regions in it, based on bits set in freeRegionBucketsUsed bitmap.
+  while(bucketMask)
+  {
+    BUCKET_BITMASK_T indexAdd = __builtin_ctzll(bucketMask);
+    bucketIndex += indexAdd;
+    bucketMask >>= indexAdd;
+    assert(bucketIndex >= 0);
+    assert(bucketIndex <= NUM_FREE_BUCKETS-1);
+    assert(freeRegionBucketsUsed & (((BUCKET_BITMASK_T)1) << bucketIndex));
+
+    Region *freeRegion = freeRegionBuckets[bucketIndex].next;
+    assert(freeRegion);
+    if (freeRegion != &freeRegionBuckets[bucketIndex])
+    {
+      void *ptr = attempt_allocate(freeRegion, alignment, size);
+      if (ptr)
+        return ptr;
+
+      // We were not able to allocate from the first region found in this bucket, so penalize
+      // the region by cycling it to the end of the doubly circular linked list. (constant time)
+      // This provides a randomized guarantee that when performing allocations of size k to a
+      // bucket of [k-something, k+something] range, we will not always attempt to satisfy the
+      // allocation from the same available region at the front of the list, but we try each
+      // region in turn.
+      unlink_from_free_list(freeRegion);
+      prepend_to_free_list(freeRegion, &freeRegionBuckets[bucketIndex]);
+      // But do not stick around to attempt to look at other regions in this bucket - move
+      // to search the next populated bucket index if this did not fit. This gives a practical
+      // "allocation in constant time" guarantee, since the next higher bucket will only have
+      // regions that are all of strictly larger size than the requested allocation. Only if
+      // there is a difficult alignment requirement we may fail to perform the allocation from
+      // a region in the next bucket, and if so, we keep trying higher buckets until one of them
+      // works.
+      ++bucketIndex;
+      bucketMask >>= 1;
+    }
+    else
+    {
+      // This bucket was not populated after all with any regions,
+      // but we just had a stale bit set to mark a populated bucket.
+      // Reset the bit to update latest status so that we do not
+      // redundantly look at this bucket again.
+      freeRegionBucketsUsed &= ~(((BUCKET_BITMASK_T)1) << bucketIndex);
+      bucketMask ^= 1;
+    }
+    // Instead of recomputing bucketMask from scratch at the end of each loop, it is updated as we go,
+    // to avoid undefined behavior with (x >> 32)/(x >> 64) when bucketIndex reaches 32/64, (the shift would comes out as a no-op instead of 0).
+
+    assert((bucketIndex == NUM_FREE_BUCKETS && bucketMask == 0) || (bucketMask == freeRegionBucketsUsed >> bucketIndex));
+  }
+
+  // None of the buckets were able to accommodate an allocation. If this happens we are almost out of memory.
+  // The largest bucket might contain some suitable regions, but we only looked at one region in that bucket, so
+  // as a last resort, loop through more free regions in the bucket that represents the largest allocations available.
+  // But only if the bucket representing largest allocations available is not any of the first thirty buckets,
+  // these represent allocatable areas less than <1024 bytes - which could be a lot of scrap.
+  // In such case, prefer to sbrk() in more memory right away.
+  int largestBucketIndex = NUM_FREE_BUCKETS - 1 - __builtin_clzll(freeRegionBucketsUsed);
+  // freeRegion will be null if there is absolutely no memory left. (all buckets are 100% used)
+  Region *freeRegion = freeRegionBucketsUsed ? freeRegionBuckets[largestBucketIndex].next : 0;
+  if (freeRegionBucketsUsed >> 30)
+  {
+    // Look only at a constant number of regions in this bucket max, to avoid bad worst case behavior.
+    // If this many regions cannot find free space, we give up and prefer to sbrk() more instead.
+    const int maxRegionsToTryBeforeGivingUp = 99;
+    int numTriesLeft = maxRegionsToTryBeforeGivingUp;
+    while(freeRegion != &freeRegionBuckets[largestBucketIndex] && numTriesLeft-- > 0)
+    {
+      void *ptr = attempt_allocate(freeRegion, alignment, size);
+      if (ptr)
+        return ptr;
+      freeRegion = freeRegion->next;
+    }
+  }
+
+  // We were unable to find a free memory region. Must sbrk() in more memory!
+  size_t numBytesToClaim = size+sizeof(Region)*3;
+  assert(numBytesToClaim > size); // 32-bit wraparound should not happen here, allocation size has been validated above!
+  bool success = claim_more_memory(numBytesToClaim);
+  if (success)
+    return allocate_memory(alignment, size); // Recurse back to itself to try again
+
+  // also sbrk() failed, we are really really constrained :( As a last resort, go back to looking at the
+  // bucket we already looked at above, continuing where the above search left off - perhaps there are
+  // regions we overlooked the first time that might be able to satisfy the allocation.
+  if (freeRegion)
+  {
+    while(freeRegion != &freeRegionBuckets[largestBucketIndex])
+    {
+      void *ptr = attempt_allocate(freeRegion, alignment, size);
+      if (ptr)
+        return ptr;
+      freeRegion = freeRegion->next;
+    }
+  }
+
+#ifdef EMMALLOC_VERBOSE
+  MAIN_THREAD_ASYNC_EM_ASM(console.log('Could not find a free memory block!'));
+#endif
+
+  return 0;
+}
+
+static
+void *emmalloc_memalign(size_t alignment, size_t size)
+{
+  MALLOC_ACQUIRE();
+  void *ptr = allocate_memory(alignment, size);
+  MALLOC_RELEASE();
+  return ptr;
+}
+
+#if 0
+void * EMMALLOC_EXPORT memalign(size_t alignment, size_t size)
+{
+  return emmalloc_memalign(alignment, size);
+}
+#endif
+
+void * EMMALLOC_EXPORT aligned_alloc(size_t alignment, size_t size)
+{
+  if ((alignment % sizeof(void *) != 0) || (size % alignment) != 0)
+    return 0;
+  return emmalloc_memalign(alignment, size);
+}
+
+static
+void *emmalloc_malloc(size_t size)
+{
+  return emmalloc_memalign(MALLOC_ALIGNMENT, size);
+}
+
+void * EMMALLOC_EXPORT malloc(size_t size)
+{
+  return emmalloc_malloc(size);
+}
+
+static
+size_t emmalloc_usable_size(void *ptr)
+{
+  if (!ptr)
+    return 0;
+
+  uint8_t *regionStartPtr = (uint8_t*)ptr - sizeof(size_t);
+  Region *region = (Region*)(regionStartPtr);
+  assert(HAS_ALIGNMENT(region, sizeof(size_t)));
+
+  MALLOC_ACQUIRE();
+
+  size_t size = region->size;
+  assert(size >= sizeof(Region));
+  assert(region_is_in_use(region));
+
+  MALLOC_RELEASE();
+
+  return size - REGION_HEADER_SIZE;
+}
+
+size_t EMMALLOC_EXPORT malloc_usable_size(void *ptr)
+{
+  return emmalloc_usable_size(ptr);
+}
+
+static
+void emmalloc_free(void *ptr)
+{
+#ifdef EMMALLOC_MEMVALIDATE
+  emmalloc_validate_memory_regions();
+#endif
+
+  if (!ptr)
+    return;
+
+#ifdef EMMALLOC_VERBOSE
+  MAIN_THREAD_ASYNC_EM_ASM(console.log('free(ptr=0x'+($0>>>0).toString(16)+')'), ptr);
+#endif
+
+  uint8_t *regionStartPtr = (uint8_t*)ptr - sizeof(size_t);
+  Region *region = (Region*)(regionStartPtr);
+  assert(HAS_ALIGNMENT(region, sizeof(size_t)));
+
+  MALLOC_ACQUIRE();
+
+  size_t size = region->size;
+#ifdef EMMALLOC_VERBOSE
+  if (size < sizeof(Region) || !region_is_in_use(region))
+  {
+    if (debug_region_is_consistent(region))
+      // LLVM wasm backend bug: cannot use MAIN_THREAD_ASYNC_EM_ASM() here, that generates internal compiler error
+      // Reproducible by running e.g. other.test_alloc_3GB
+      EM_ASM(console.error('Double free at region ptr 0x' + ($0>>>0).toString(16) + ', region->size: 0x' + ($1>>>0).toString(16) + ', region->sizeAtCeiling: 0x' + ($2>>>0).toString(16) + ')'), region, size, region_ceiling_size(region));
+    else
+      MAIN_THREAD_ASYNC_EM_ASM(console.error('Corrupt region at region ptr 0x' + ($0>>>0).toString(16) + ' region->size: 0x' + ($1>>>0).toString(16) + ', region->sizeAtCeiling: 0x' + ($2>>>0).toString(16) + ')'), region, size, region_ceiling_size(region));
+  }
+#endif
+  assert(size >= sizeof(Region));
+  assert(region_is_in_use(region));
+
+#ifdef __EMSCRIPTEN_TRACING__
+  emscripten_trace_record_free(region);
+#endif
+
+  // Check merging with left side
+  size_t prevRegionSizeField = ((size_t*)region)[-1];
+  size_t prevRegionSize = prevRegionSizeField & ~FREE_REGION_FLAG;
+  if (prevRegionSizeField != prevRegionSize) // Previous region is free?
+  {
+    Region *prevRegion = (Region*)((uint8_t*)region - prevRegionSize);
+    assert(debug_region_is_consistent(prevRegion));
+    unlink_from_free_list(prevRegion);
+    regionStartPtr = (uint8_t*)prevRegion;
+    size += prevRegionSize;
+  }
+
+  // Check merging with right side
+  Region *nextRegion = next_region(region);
+  assert(debug_region_is_consistent(nextRegion));
+  size_t sizeAtEnd = *(size_t*)region_payload_end_ptr(nextRegion);
+  if (nextRegion->size != sizeAtEnd)
+  {
+    unlink_from_free_list(nextRegion);
+    size += nextRegion->size;
+  }
+
+  create_free_region(regionStartPtr, size);
+  link_to_free_list((Region*)regionStartPtr);
+
+  MALLOC_RELEASE();
+
+#ifdef EMMALLOC_MEMVALIDATE
+  emmalloc_validate_memory_regions();
+#endif
+}
+
+void EMMALLOC_EXPORT free(void *ptr)
+{
+  emmalloc_free(ptr);
+}
+
+// Can be called to attempt to increase or decrease the size of the given region
+// to a new size (in-place). Returns 1 if resize succeeds, and 0 on failure.
+static int attempt_region_resize(Region *region, size_t size)
+{
+  ASSERT_MALLOC_IS_ACQUIRED();
+  assert(size > 0);
+  assert(HAS_ALIGNMENT(size, sizeof(size_t)));
+
+#ifdef EMMALLOC_VERBOSE
+  MAIN_THREAD_ASYNC_EM_ASM(console.log('attempt_region_resize(region=0x' + ($0>>>0).toString(16) + ', size=' + ($1>>>0) + ' bytes)'), region, size);
+#endif
+
+  // First attempt to resize this region, if the next region that follows this one
+  // is a free region.
+  Region *nextRegion = next_region(region);
+  uint8_t *nextRegionEndPtr = (uint8_t*)nextRegion + nextRegion->size;
+  size_t sizeAtCeiling = ((size_t*)nextRegionEndPtr)[-1];
+  if (nextRegion->size != sizeAtCeiling) // Next region is free?
+  {
+    assert(region_is_free(nextRegion));
+    uint8_t *newNextRegionStartPtr = (uint8_t*)region + size;
+    assert(HAS_ALIGNMENT(newNextRegionStartPtr, sizeof(size_t)));
+    // Next region does not shrink to too small size?
+    if (newNextRegionStartPtr + sizeof(Region) <= nextRegionEndPtr)
+    {
+      unlink_from_free_list(nextRegion);
+      create_free_region(newNextRegionStartPtr, nextRegionEndPtr - newNextRegionStartPtr);
+      link_to_free_list((Region*)newNextRegionStartPtr);
+      create_used_region(region, newNextRegionStartPtr - (uint8_t*)region);
+      return 1;
+    }
+    // If we remove the next region altogether, allocation is satisfied?
+    if (newNextRegionStartPtr <= nextRegionEndPtr)
+    {
+      unlink_from_free_list(nextRegion);
+      create_used_region(region, region->size + nextRegion->size);
+      return 1;
+    }
+  }
+  else
+  {
+    // Next region is an used region - we cannot change its starting address. However if we are shrinking the
+    // size of this region, we can create a new free region between this and the next used region.
+    if (size + sizeof(Region) <= region->size)
+    {
+      size_t freeRegionSize = region->size - size;
+      create_used_region(region, size);
+      Region *freeRegion = (Region *)((uint8_t*)region + size);
+      create_free_region(freeRegion, freeRegionSize);
+      link_to_free_list(freeRegion);
+      return 1;
+    }
+    else if (size <= region->size)
+    {
+      // Caller was asking to shrink the size, but due to not being able to fit a full Region in the shrunk
+      // area, we cannot actually do anything. This occurs if the shrink amount is really small. In such case,
+      // just call it success without doing any work.
+      return 1;
+    }
+  }
+#ifdef EMMALLOC_VERBOSE
+  MAIN_THREAD_ASYNC_EM_ASM(console.log('attempt_region_resize failed.'));
+#endif
+  return 0;
+}
+
+static int acquire_and_attempt_region_resize(Region *region, size_t size)
+{
+  MALLOC_ACQUIRE();
+  int success = attempt_region_resize(region, size);
+  MALLOC_RELEASE();
+  return success;
+}
+
+static
+void *emmalloc_aligned_realloc(void *ptr, size_t alignment, size_t size)
+{
+#ifdef EMMALLOC_VERBOSE
+  MAIN_THREAD_ASYNC_EM_ASM(console.log('aligned_realloc(ptr=0x' + ($0>>>0).toString(16) + ', alignment=' + $1 + ', size=' + ($2>>>0)), ptr, alignment, size);
+#endif
+
+  if (!ptr)
+    return emmalloc_memalign(alignment, size);
+
+  if (size == 0)
+  {
+    free(ptr);
+    return 0;
+  }
+
+  if (size > MAX_ALLOC_SIZE)
+  {
+#ifdef EMMALLOC_VERBOSE
+    MAIN_THREAD_ASYNC_EM_ASM(console.log('Allocation failed: attempted allocation size is too large: ' + ($0 >>> 0) + 'bytes! (negative integer wraparound?)'), size);
+#endif
+    return 0;
+  }
+
+  assert(IS_POWER_OF_2(alignment));
+  // aligned_realloc() cannot be used to ask to change the alignment of a pointer.
+  assert(HAS_ALIGNMENT(ptr, alignment));
+  size = validate_alloc_size(size);
+
+  // Calculate the region start address of the original allocation
+  Region *region = (Region*)((uint8_t*)ptr - sizeof(size_t));
+
+  // First attempt to resize the given region to avoid having to copy memory around
+  if (acquire_and_attempt_region_resize(region, size + REGION_HEADER_SIZE))
+  {
+#ifdef __EMSCRIPTEN_TRACING__
+    emscripten_trace_record_reallocation(ptr, ptr, size);
+#endif
+    return ptr;
+  }
+
+  // If resize failed, we must allocate a new region, copy the data over, and then
+  // free the old region.
+  void *newptr = emmalloc_memalign(alignment, size);
+  if (newptr)
+  {
+    memcpy(newptr, ptr, MIN(size, region->size - REGION_HEADER_SIZE));
+    free(ptr);
+  }
+  // N.B. If there is not enough memory, the old memory block should not be freed and
+  // null pointer is returned.
+  return newptr;
+}
+
+#if 0
+void * EMMALLOC_EXPORT aligned_realloc(void *ptr, size_t alignment, size_t size)
+{
+  return emmalloc_aligned_realloc(ptr, alignment, size);
+}
+#endif
+
+#if 0
+// realloc_try() is like realloc(), but only attempts to try to resize the existing memory
+// area. If resizing the existing memory area fails, then realloc_try() will return 0
+// (the original memory block is not freed or modified). If resizing succeeds, previous
+// memory contents will be valid up to min(old length, new length) bytes.
+void *emmalloc_realloc_try(void *ptr, size_t size)
+{
+  if (!ptr)
+    return 0;
+
+  if (size == 0)
+  {
+    free(ptr);
+    return 0;
+  }
+
+  if (size > MAX_ALLOC_SIZE)
+  {
+#ifdef EMMALLOC_VERBOSE
+    MAIN_THREAD_ASYNC_EM_ASM(console.log('Allocation failed: attempted allocation size is too large: ' + ($0 >>> 0) + 'bytes! (negative integer wraparound?)'), size);
+#endif
+    return 0;
+  }
+
+  size = validate_alloc_size(size);
+
+  // Calculate the region start address of the original allocation
+  Region *region = (Region*)((uint8_t*)ptr - sizeof(size_t));
+
+  // Attempt to resize the given region to avoid having to copy memory around
+  int success = acquire_and_attempt_region_resize(region, size + REGION_HEADER_SIZE);
+#ifdef __EMSCRIPTEN_TRACING__
+  if (success)
+    emscripten_trace_record_reallocation(ptr, ptr, size);
+#endif
+  return success ? ptr : 0;
+}
+
+// emmalloc_aligned_realloc_uninitialized() is like aligned_realloc(), but old memory contents
+// will be undefined after reallocation. (old memory is not preserved in any case)
+void *emmalloc_aligned_realloc_uninitialized(void *ptr, size_t alignment, size_t size)
+{
+  if (!ptr)
+    return emmalloc_memalign(alignment, size);
+
+  if (size == 0)
+  {
+    free(ptr);
+    return 0;
+  }
+
+  if (size > MAX_ALLOC_SIZE)
+  {
+#ifdef EMMALLOC_VERBOSE
+    MAIN_THREAD_ASYNC_EM_ASM(console.log('Allocation failed: attempted allocation size is too large: ' + ($0 >>> 0) + 'bytes! (negative integer wraparound?)'), size);
+#endif
+    return 0;
+  }
+
+  size = validate_alloc_size(size);
+
+  // Calculate the region start address of the original allocation
+  Region *region = (Region*)((uint8_t*)ptr - sizeof(size_t));
+
+  // First attempt to resize the given region to avoid having to copy memory around
+  if (acquire_and_attempt_region_resize(region, size + REGION_HEADER_SIZE))
+  {
+#ifdef __EMSCRIPTEN_TRACING__
+    emscripten_trace_record_reallocation(ptr, ptr, size);
+#endif
+    return ptr;
+  }
+
+  // If resize failed, drop the old region and allocate a new region. Memory is not
+  // copied over
+  free(ptr);
+  return emmalloc_memalign(alignment, size);
+}
+#endif
+
+static
+void *emmalloc_realloc(void *ptr, size_t size)
+{
+  return emmalloc_aligned_realloc(ptr, MALLOC_ALIGNMENT, size);
+}
+
+void * EMMALLOC_EXPORT realloc(void *ptr, size_t size)
+{
+  return emmalloc_realloc(ptr, size);
+}
+
+#if 0
+// realloc_uninitialized() is like realloc(), but old memory contents
+// will be undefined after reallocation. (old memory is not preserved in any case)
+void *emmalloc_realloc_uninitialized(void *ptr, size_t size)
+{
+  return emmalloc_aligned_realloc_uninitialized(ptr, MALLOC_ALIGNMENT, size);
+}
+#endif
+
+static
+int emmalloc_posix_memalign(void **memptr, size_t alignment, size_t size)
+{
+  assert(memptr);
+  if (alignment % sizeof(void *) != 0)
+    return 22/* EINVAL*/;
+  *memptr = emmalloc_memalign(alignment, size);
+  return *memptr ?  0 : 12/*ENOMEM*/;
+}
+
+int EMMALLOC_EXPORT posix_memalign(void **memptr, size_t alignment, size_t size)
+{
+  return emmalloc_posix_memalign(memptr, alignment, size);
+}
+
+static
+void *emmalloc_calloc(size_t num, size_t size)
+{
+  size_t bytes = num*size;
+  void *ptr = emmalloc_memalign(MALLOC_ALIGNMENT, bytes);
+  if (ptr)
+    memset(ptr, 0, bytes);
+  return ptr;
+}
+
+void * EMMALLOC_EXPORT calloc(size_t num, size_t size)
+{
+  return emmalloc_calloc(num, size);
+}
+
+#if 0
+static int count_linked_list_size(Region *list)
+{
+  int size = 1;
+  for(Region *i = list->next; i != list; list = list->next)
+    ++size;
+  return size;
+}
+
+static size_t count_linked_list_space(Region *list)
+{
+  size_t space = 0;
+  for(Region *i = list->next; i != list; list = list->next)
+    space += region_payload_end_ptr(i) - region_payload_start_ptr(i);
+  return space;
+}
+
+struct mallinfo emmalloc_mallinfo()
+{
+  MALLOC_ACQUIRE();
+
+  struct mallinfo info;
+  // Non-mmapped space allocated (bytes): For emmalloc,
+  // let's define this as the difference between heap size and dynamic top end.
+  info.arena = emscripten_get_heap_size() - (size_t)sbrk(0);
+  // Number of "ordinary" blocks. Let's define this as the number of highest
+  // size blocks. (subtract one from each, since there is a sentinel node in each list)
+  info.ordblks = count_linked_list_size(&freeRegionBuckets[NUM_FREE_BUCKETS-1])-1;
+  // Number of free "fastbin" blocks. For emmalloc, define this as the number
+  // of blocks that are not in the largest pristine block.
+  info.smblks = 0;
+  // The total number of bytes in free "fastbin" blocks.
+  info.fsmblks = 0;
+  for(int i = 0; i < NUM_FREE_BUCKETS-1; ++i)
+  {
+    info.smblks += count_linked_list_size(&freeRegionBuckets[i])-1;
+    info.fsmblks += count_linked_list_space(&freeRegionBuckets[i]);
+  }
+
+  info.hblks = 0; // Number of mmapped regions: always 0. (no mmap support)
+  info.hblkhd = 0; // Amount of bytes in mmapped regions: always 0. (no mmap support)
+
+  // Walk through all the heap blocks to report the following data:
+  // The "highwater mark" for allocated space—that is, the maximum amount of
+  // space that was ever allocated. Emmalloc does not want to pay code to
+  // track this, so this is only reported from current allocation data, and
+  // may not be accurate.
+  info.usmblks = 0;
+  info.uordblks = 0; // The total number of bytes used by in-use allocations.
+  info.fordblks = 0; // The total number of bytes in free blocks.
+  // The total amount of releasable free space at the top of the heap.
+  // This is the maximum number of bytes that could ideally be released by malloc_trim(3).
+  Region *lastActualRegion = prev_region((Region*)(listOfAllRegions->endPtr - sizeof(Region)));
+  info.keepcost = region_is_free(lastActualRegion) ? lastActualRegion->size : 0;
+
+  RootRegion *root = listOfAllRegions;
+  while(root)
+  {
+    Region *r = (Region*)root;
+    assert(debug_region_is_consistent(r));
+    uint8_t *lastRegionEnd = root->endPtr;
+    while((uint8_t*)r < lastRegionEnd)
+    {
+      assert(debug_region_is_consistent(r));
+
+      if (region_is_free(r))
+      {
+        // Count only the payload of the free block towards free memory.
+        info.fordblks += region_payload_end_ptr(r) - region_payload_start_ptr(r);
+        // But the header data of the free block goes towards used memory.
+        info.uordblks += REGION_HEADER_SIZE;
+      }
+      else
+      {
+        info.uordblks += r->size;
+      }
+      // Update approximate watermark data
+      info.usmblks = MAX(info.usmblks, (intptr_t)r + r->size);
+
+      if (r->size == 0)
+        break;
+      r = next_region(r);
+    }
+    root = root->next;
+  }
+
+  MALLOC_RELEASE();
+  return info;
+}
+
+struct mallinfo EMMALLOC_EXPORT mallinfo()
+{
+  return emmalloc_mallinfo();
+}
+
+// Note! This function is not fully multithreadin safe: while this function is running, other threads should not be
+// allowed to call sbrk()!
+static int trim_dynamic_heap_reservation(size_t pad)
+{
+  ASSERT_MALLOC_IS_ACQUIRED();
+
+  if (!listOfAllRegions)
+    return 0; // emmalloc is not controlling any dynamic memory at all - cannot release memory.
+  uint8_t *previousSbrkEndAddress = listOfAllRegions->endPtr;
+  assert(sbrk(0) == previousSbrkEndAddress);
+  size_t lastMemoryRegionSize = ((size_t*)previousSbrkEndAddress)[-1];
+  assert(lastMemoryRegionSize == 16); // // The last memory region should be a sentinel node of exactly 16 bytes in size.
+  Region *endSentinelRegion = (Region*)(previousSbrkEndAddress - sizeof(Region));
+  Region *lastActualRegion = prev_region(endSentinelRegion);
+
+  // Round padding up to multiple of 4 bytes to keep sbrk() and memory region alignment intact.
+  // Also have at least 8 bytes of payload so that we can form a full free region.
+  size_t newRegionSize = (size_t)ALIGN_UP(pad, 4);
+  if (pad > 0)
+    newRegionSize += sizeof(Region) - (newRegionSize - pad);
+
+  if (!region_is_free(lastActualRegion) || lastActualRegion->size <= newRegionSize)
+    return 0; // Last actual region is in use, or caller desired to leave more free memory intact than there is.
+
+  // This many bytes will be shrunk away.
+  size_t shrinkAmount = lastActualRegion->size - newRegionSize;
+  assert(HAS_ALIGNMENT(shrinkAmount, 4));
+
+  unlink_from_free_list(lastActualRegion);
+  // If pad == 0, we should delete the last free region altogether. If pad > 0,
+  // shrink the last free region to the desired size.
+  if (newRegionSize > 0)
+  {
+    create_free_region(lastActualRegion, newRegionSize);
+    link_to_free_list(lastActualRegion);
+  }
+
+  // Recreate the sentinel region at the end of the last free region
+  endSentinelRegion = (Region*)((uint8_t*)lastActualRegion + newRegionSize);
+  create_used_region(endSentinelRegion, sizeof(Region));
+
+  // And update the size field of the whole region block.
+  listOfAllRegions->endPtr = (uint8_t*)endSentinelRegion + sizeof(Region);
+
+  // Finally call sbrk() to shrink the memory area.
+  void *oldSbrk = sbrk(-(intptr_t)shrinkAmount);
+  assert((intptr_t)oldSbrk != -1); // Shrinking with sbrk() should never fail.
+  assert(oldSbrk == previousSbrkEndAddress); // Another thread should not have raced to increase sbrk() on us!
+
+  // All successful, and we actually trimmed memory!
+  return 1;
+}
+
+int emmalloc_trim(size_t pad)
+{
+  MALLOC_ACQUIRE();
+  int success = trim_dynamic_heap_reservation(pad);
+  MALLOC_RELEASE();
+  return success;
+}
+
+int EMMALLOC_EXPORT malloc_trim(size_t pad)
+{
+  return emmalloc_trim(pad);
+}
+
+size_t emmalloc_dynamic_heap_size()
+{
+  size_t dynamicHeapSize = 0;
+
+  MALLOC_ACQUIRE();
+  RootRegion *root = listOfAllRegions;
+  while(root)
+  {
+    dynamicHeapSize += root->endPtr - (uint8_t*)root;
+    root = root->next;
+  }
+  MALLOC_RELEASE();
+  return dynamicHeapSize;
+}
+
+size_t emmalloc_free_dynamic_memory()
+{
+  size_t freeDynamicMemory = 0;
+
+  int bucketIndex = 0;
+
+  MALLOC_ACQUIRE();
+  BUCKET_BITMASK_T bucketMask = freeRegionBucketsUsed;
+
+  // Loop through each bucket that has free regions in it, based on bits set in freeRegionBucketsUsed bitmap.
+  while(bucketMask)
+  {
+    BUCKET_BITMASK_T indexAdd = __builtin_ctzll(bucketMask);
+    bucketIndex += indexAdd;
+    bucketMask >>= indexAdd;
+    for(Region *freeRegion = freeRegionBuckets[bucketIndex].next;
+      freeRegion != &freeRegionBuckets[bucketIndex];
+      freeRegion = freeRegion->next)
+    {
+      freeDynamicMemory += freeRegion->size - REGION_HEADER_SIZE;
+    }
+    ++bucketIndex;
+    bucketMask >>= 1;
+  }
+  MALLOC_RELEASE();
+  return freeDynamicMemory;
+}
+
+size_t emmalloc_compute_free_dynamic_memory_fragmentation_map(size_t freeMemorySizeMap[32])
+{
+  memset((void*)freeMemorySizeMap, 0, sizeof(freeMemorySizeMap[0])*32);
+
+  size_t numFreeMemoryRegions = 0;
+  int bucketIndex = 0;
+  MALLOC_ACQUIRE();
+  BUCKET_BITMASK_T bucketMask = freeRegionBucketsUsed;
+
+  // Loop through each bucket that has free regions in it, based on bits set in freeRegionBucketsUsed bitmap.
+  while(bucketMask)
+  {
+    BUCKET_BITMASK_T indexAdd = __builtin_ctzll(bucketMask);
+    bucketIndex += indexAdd;
+    bucketMask >>= indexAdd;
+    for(Region *freeRegion = freeRegionBuckets[bucketIndex].next;
+      freeRegion != &freeRegionBuckets[bucketIndex];
+      freeRegion = freeRegion->next)
+    {
+      ++numFreeMemoryRegions;
+      size_t freeDynamicMemory = freeRegion->size - REGION_HEADER_SIZE;
+      if (freeDynamicMemory > 0)
+        ++freeMemorySizeMap[31-__builtin_clz(freeDynamicMemory)];
+      else
+        ++freeMemorySizeMap[0];
+    }
+    ++bucketIndex;
+    bucketMask >>= 1;
+  }
+  MALLOC_RELEASE();
+  return numFreeMemoryRegions;
+}
+
+size_t emmalloc_unclaimed_heap_memory(void) {
+  return emscripten_get_heap_max() - (size_t)sbrk(0);
+}
+#endif
+
+// Define these to satisfy musl references.
+void *__libc_malloc(size_t) __attribute__((alias("malloc")));
+void __libc_free(void *) __attribute__((alias("free")));
+void *__libc_calloc(size_t nmemb, size_t size) __attribute__((alias("calloc")));