diff --git a/include/mimalloc/atomic.h b/include/mimalloc/atomic.h
index f4bde7f43..dc72c5105 100644
--- a/include/mimalloc/atomic.h
+++ b/include/mimalloc/atomic.h
@@ -304,7 +304,7 @@ typedef _Atomic(uintptr_t) mi_atomic_once_t;
 
 // Returns true only on the first invocation
 static inline bool mi_atomic_once( mi_atomic_once_t* once ) {
-  if (mi_atomic_load_relaxed(once) != 0) return false;     // quick test 
+  if (mi_atomic_load_relaxed(once) != 0) return false;     // quick test
   uintptr_t expected = 0;
   return mi_atomic_cas_strong_acq_rel(once, &expected, (uintptr_t)1); // try to set to 1
 }
@@ -373,7 +373,7 @@ static inline void mi_atomic_yield(void) {
 static inline void mi_atomic_yield(void) {
   smt_pause();
 }
-#elif defined(__wasi__)
+#elif defined(__wasm__)
 #include <sched.h>
 static inline void mi_atomic_yield(void) {
   sched_yield();
diff --git a/include/mimalloc/internal.h b/include/mimalloc/internal.h
index f98a46494..9e8c5f3d1 100644
--- a/include/mimalloc/internal.h
+++ b/include/mimalloc/internal.h
@@ -40,10 +40,6 @@ terms of the MIT license. A copy of the license can be found in the file
 #define mi_decl_cache_align
 #endif
 
-#if defined(__EMSCRIPTEN__) && !defined(__wasi__)
-#define __wasi__
-#endif
-
 #if defined(__cplusplus)
 #define mi_decl_externc       extern "C"
 #else
@@ -51,7 +47,7 @@ terms of the MIT license. A copy of the license can be found in the file
 #endif
 
 // pthreads
-#if !defined(_WIN32) && !defined(__wasi__)
+#if !defined(_WIN32) && !defined(__wasm__)
 #define  MI_USE_PTHREADS
 #include <pthread.h>
 #endif
@@ -88,7 +84,7 @@ void       _mi_thread_data_collect(void);
 
 // os.c
 void       _mi_os_init(void);                                            // called from process init
-void*      _mi_os_alloc(size_t size, mi_memid_t* memid, mi_stats_t* stats);  
+void*      _mi_os_alloc(size_t size, mi_memid_t* memid, mi_stats_t* stats);
 void       _mi_os_free(void* p, size_t size, mi_memid_t memid, mi_stats_t* stats);
 void       _mi_os_free_ex(void* p, size_t size, bool still_committed, mi_memid_t memid, mi_stats_t* stats);
 
@@ -311,6 +307,14 @@ static inline uintptr_t _mi_align_down(uintptr_t sz, size_t alignment) {
   }
 }
 
+ __attribute__((__unused__)) static void* mi_align_up_ptr(void* p, size_t alignment) {
+  return (void*)_mi_align_up((uintptr_t)p, alignment);
+}
+
+ __attribute__((__unused__)) static void* mi_align_down_ptr(void* p, size_t alignment) {
+  return (void*)_mi_align_down((uintptr_t)p, alignment);
+}
+
 // Divide upwards: `s <= _mi_divide_up(s,d)*d < s+d`.
 static inline uintptr_t _mi_divide_up(uintptr_t size, size_t divider) {
   mi_assert_internal(divider != 0);
@@ -427,7 +431,7 @@ static inline mi_slice_t* mi_page_to_slice(mi_page_t* p) {
 
 // Segment belonging to a page
 static inline mi_segment_t* _mi_page_segment(const mi_page_t* page) {
-  mi_segment_t* segment = _mi_ptr_segment(page); 
+  mi_segment_t* segment = _mi_ptr_segment(page);
   mi_assert_internal(segment == NULL || ((mi_slice_t*)page >= segment->slices && (mi_slice_t*)page < segment->slices + segment->slice_entries));
   return segment;
 }
@@ -729,12 +733,12 @@ size_t _mi_commit_mask_next_run(const mi_commit_mask_t* cm, size_t* idx);
 
 #define mi_commit_mask_foreach(cm,idx,count) \
   idx = 0; \
-  while ((count = _mi_commit_mask_next_run(cm,&idx)) > 0) { 
-        
+  while ((count = _mi_commit_mask_next_run(cm,&idx)) > 0) {
+
 #define mi_commit_mask_foreach_end() \
     idx += count; \
   }
-      
+
 
 
 /* -----------------------------------------------------------
diff --git a/include/mimalloc/prim.h b/include/mimalloc/prim.h
index 9e560696f..38475c83e 100644
--- a/include/mimalloc/prim.h
+++ b/include/mimalloc/prim.h
@@ -12,7 +12,7 @@ terms of the MIT license. A copy of the license can be found in the file
 // --------------------------------------------------------------------------
 // This file specifies the primitive portability API.
 // Each OS/host needs to implement these primitives, see `src/prim`
-// for implementations on Window, macOS, WASI, and Linux/Unix.
+// for implementations on Window, macOS, wasm, and Linux/Unix.
 //
 // note: on all primitive functions, we always have result parameters != NUL, and:
 //  addr != NULL and page aligned
@@ -35,10 +35,10 @@ void _mi_prim_mem_init( mi_os_mem_config_t* config );
 
 // Free OS memory
 int _mi_prim_free(void* addr, size_t size );
-  
+
 // Allocate OS memory. Return NULL on error.
 // The `try_alignment` is just a hint and the returned pointer does not have to be aligned.
-// If `commit` is false, the virtual memory range only needs to be reserved (with no access) 
+// If `commit` is false, the virtual memory range only needs to be reserved (with no access)
 // which will later be committed explicitly using `_mi_prim_commit`.
 // `is_zero` is set to true if the memory was zero initialized (as on most OS's)
 // pre: !commit => !allow_large
@@ -82,11 +82,11 @@ mi_msecs_t _mi_prim_clock_now(void);
 typedef struct mi_process_info_s {
   mi_msecs_t  elapsed;
   mi_msecs_t  utime;
-  mi_msecs_t  stime; 
-  size_t      current_rss; 
-  size_t      peak_rss;  
+  mi_msecs_t  stime;
+  size_t      current_rss;
+  size_t      peak_rss;
   size_t      current_commit;
-  size_t      peak_commit; 
+  size_t      peak_commit;
   size_t      page_faults;
 } mi_process_info_t;
 
@@ -117,7 +117,7 @@ void _mi_prim_thread_associate_default_heap(mi_heap_t* heap);
 
 //-------------------------------------------------------------------
 // Thread id: `_mi_prim_thread_id()`
-// 
+//
 // Getting the thread id should be performant as it is called in the
 // fast path of `_mi_free` and we specialize for various platforms as
 // inlined definitions. Regular code should call `init.c:_mi_thread_id()`.
diff --git a/src/alloc-override.c b/src/alloc-override.c
index 873065dc6..04b92ddea 100644
--- a/src/alloc-override.c
+++ b/src/alloc-override.c
@@ -264,7 +264,7 @@ int   reallocarr(void* p, size_t count, size_t size)    { return mi_reallocarr(p
 void* memalign(size_t alignment, size_t size)           { return mi_memalign(alignment, size); }
 void* _aligned_malloc(size_t alignment, size_t size)    { return mi_aligned_alloc(alignment, size); }
 
-#if defined(__wasi__)
+#if defined(__wasm__)
   // forward __libc interface (see PR #667)
   void* __libc_malloc(size_t size)                      MI_FORWARD1(mi_malloc, size)
   void* __libc_calloc(size_t count, size_t size)        MI_FORWARD2(mi_calloc, count, size)
diff --git a/src/alloc.c b/src/alloc.c
index ffc1747d5..ea1d3d6ee 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -58,7 +58,7 @@ extern inline void* _mi_page_malloc(mi_heap_t* heap, mi_page_t* page, size_t siz
     }
     else {
       _mi_memzero_aligned(block, page->xblock_size - MI_PADDING_SIZE);
-    }    
+    }
   }
 
 #if (MI_DEBUG>0) && !MI_TRACK_ENABLED && !MI_TSAN
@@ -113,7 +113,7 @@ static inline mi_decl_restrict void* mi_heap_malloc_small_zero(mi_heap_t* heap,
   if (size == 0) { size = sizeof(void*); }
   #endif
   mi_page_t* page = _mi_heap_get_free_small_page(heap, size + MI_PADDING_SIZE);
-  void* const p = _mi_page_malloc(heap, page, size + MI_PADDING_SIZE, zero);  
+  void* const p = _mi_page_malloc(heap, page, size + MI_PADDING_SIZE, zero);
   mi_track_malloc(p,size,zero);
   #if MI_STAT>1
   if (p != NULL) {
@@ -346,7 +346,7 @@ static void mi_check_padding(const mi_page_t* page, const mi_block_t* block) {
 // only maintain stats for smaller objects if requested
 #if (MI_STAT>0)
 static void mi_stat_free(const mi_page_t* page, const mi_block_t* block) {
-  #if (MI_STAT < 2)  
+  #if (MI_STAT < 2)
   MI_UNUSED(block);
   #endif
   mi_heap_t* const heap = mi_heap_get_default();
@@ -354,7 +354,7 @@ static void mi_stat_free(const mi_page_t* page, const mi_block_t* block) {
   #if (MI_STAT>1)
   const size_t usize = mi_page_usable_size_of(page, block);
   mi_heap_stat_decrease(heap, malloc, usize);
-  #endif  
+  #endif
   if (bsize <= MI_MEDIUM_OBJ_SIZE_MAX) {
     mi_heap_stat_decrease(heap, normal, bsize);
     #if (MI_STAT > 1)
@@ -366,7 +366,7 @@ static void mi_stat_free(const mi_page_t* page, const mi_block_t* block) {
   }
   else {
     mi_heap_stat_decrease(heap, huge, bsize);
-  }  
+  }
 }
 #else
 static void mi_stat_free(const mi_page_t* page, const mi_block_t* block) {
@@ -405,7 +405,7 @@ static mi_decl_noinline void _mi_free_block_mt(mi_page_t* page, mi_block_t* bloc
   // that is safe as these are constant and the page won't be freed (as the block is not freed yet).
   mi_check_padding(page, block);
   _mi_padding_shrink(page, block, sizeof(mi_block_t));       // for small size, ensure we can fit the delayed thread pointers without triggering overflow detection
-  
+
   // huge page segments are always abandoned and can be freed immediately
   mi_segment_t* segment = _mi_page_segment(page);
   if (segment->kind == MI_SEGMENT_HUGE) {
@@ -421,7 +421,7 @@ static mi_decl_noinline void _mi_free_block_mt(mi_page_t* page, mi_block_t* bloc
     _mi_segment_huge_page_reset(segment, page, block);
     #endif
   }
-  
+
   #if (MI_DEBUG>0) && !MI_TRACK_ENABLED && !MI_TSAN        // note: when tracking, cannot use mi_usable_size with multi-threading
   if (segment->kind != MI_SEGMENT_HUGE) {                  // not for huge segments as we just reset the content
     memset(block, MI_DEBUG_FREED, mi_usable_size(block));
@@ -823,7 +823,7 @@ mi_decl_nodiscard mi_decl_restrict char* mi_strndup(const char* s, size_t n) mi_
   return mi_heap_strndup(mi_prim_get_default_heap(),s,n);
 }
 
-#ifndef __wasi__
+#ifndef __wasm__
 // `realpath` using mi_malloc
 #ifdef _WIN32
 #ifndef PATH_MAX
diff --git a/src/arena.c b/src/arena.c
index 4e34b12f0..58336e281 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -13,7 +13,7 @@ threads and need to be accessed using atomic operations.
 
 Arenas are used to for huge OS page (1GiB) reservations or for reserving
 OS memory upfront which can be improve performance or is sometimes needed
-on embedded devices. We can also employ this with WASI or `sbrk` systems 
+on embedded devices. We can also employ this with wasm or `sbrk` systems
 to reserve large arenas upfront and be able to reuse the memory more effectively.
 
 The arena allocation needs to be thread safe and we use an atomic bitmap to allocate.
@@ -48,13 +48,13 @@ typedef struct mi_arena_s {
   size_t   meta_size;                     // size of the arena structure itself (including its bitmaps)
   mi_memid_t meta_memid;                  // memid of the arena structure itself (OS or static allocation)
   int      numa_node;                     // associated NUMA node
-  bool     exclusive;                     // only allow allocations if specifically for this arena  
+  bool     exclusive;                     // only allow allocations if specifically for this arena
   bool     is_large;                      // memory area consists of large- or huge OS pages (always committed)
   _Atomic(size_t) search_idx;             // optimization to start the search for free blocks
-  _Atomic(mi_msecs_t) purge_expire;       // expiration time when blocks should be decommitted from `blocks_decommit`.  
+  _Atomic(mi_msecs_t) purge_expire;       // expiration time when blocks should be decommitted from `blocks_decommit`.
   mi_bitmap_field_t* blocks_dirty;        // are the blocks potentially non-zero?
   mi_bitmap_field_t* blocks_committed;    // are the blocks committed? (can be NULL for memory that cannot be decommitted)
-  mi_bitmap_field_t* blocks_purge;        // blocks that can be (reset) decommitted. (can be NULL for memory that cannot be (reset) decommitted)  
+  mi_bitmap_field_t* blocks_purge;        // blocks that can be (reset) decommitted. (can be NULL for memory that cannot be (reset) decommitted)
   mi_bitmap_field_t  blocks_inuse[1];     // in-place bitmap of in-use blocks (of size `field_count`)
 } mi_arena_t;
 
@@ -103,7 +103,7 @@ bool _mi_arena_memid_is_os_allocated(mi_memid_t memid) {
 }
 
 /* -----------------------------------------------------------
-  Arena allocations get a (currently) 16-bit memory id where the 
+  Arena allocations get a (currently) 16-bit memory id where the
   lower 8 bits are the arena id, and the upper bits the block index.
 ----------------------------------------------------------- */
 
@@ -211,7 +211,7 @@ static bool mi_arena_try_claim(mi_arena_t* arena, size_t blocks, mi_bitmap_index
 {
   size_t idx = 0; // mi_atomic_load_relaxed(&arena->search_idx);  // start from last search; ok to be relaxed as the exact start does not matter
   if (_mi_bitmap_try_find_from_claim_across(arena->blocks_inuse, arena->field_count, idx, blocks, bitmap_idx)) {
-    mi_atomic_store_relaxed(&arena->search_idx, mi_bitmap_index_field(*bitmap_idx));  // start search from found location next time around    
+    mi_atomic_store_relaxed(&arena->search_idx, mi_bitmap_index_field(*bitmap_idx));  // start search from found location next time around
     return true;
   };
   return false;
@@ -231,7 +231,7 @@ static mi_decl_noinline void* mi_arena_try_alloc_at(mi_arena_t* arena, size_t ar
   mi_bitmap_index_t bitmap_index;
   if (!mi_arena_try_claim(arena, needed_bcount, &bitmap_index)) return NULL;
 
-  // claimed it! 
+  // claimed it!
   void* p = mi_arena_block_start(arena, bitmap_index);
   *memid = mi_memid_create_arena(arena->id, arena->exclusive, bitmap_index);
   memid->is_pinned = arena->memid.is_pinned;
@@ -271,21 +271,21 @@ static mi_decl_noinline void* mi_arena_try_alloc_at(mi_arena_t* arena, size_t ar
     // no need to commit, but check if already fully committed
     memid->initially_committed = _mi_bitmap_is_claimed_across(arena->blocks_committed, arena->field_count, needed_bcount, bitmap_index);
   }
-  
+
   return p;
 }
 
 // allocate in a speficic arena
-static void* mi_arena_try_alloc_at_id(mi_arena_id_t arena_id, bool match_numa_node, int numa_node, size_t size, size_t alignment, 
-                                       bool commit, bool allow_large, mi_arena_id_t req_arena_id, mi_memid_t* memid, mi_os_tld_t* tld ) 
+static void* mi_arena_try_alloc_at_id(mi_arena_id_t arena_id, bool match_numa_node, int numa_node, size_t size, size_t alignment,
+                                       bool commit, bool allow_large, mi_arena_id_t req_arena_id, mi_memid_t* memid, mi_os_tld_t* tld )
 {
   MI_UNUSED_RELEASE(alignment);
   mi_assert_internal(alignment <= MI_SEGMENT_ALIGN);
-  const size_t bcount = mi_block_count_of_size(size);  
+  const size_t bcount = mi_block_count_of_size(size);
   const size_t arena_index = mi_arena_id_index(arena_id);
   mi_assert_internal(arena_index < mi_atomic_load_relaxed(&mi_arena_count));
   mi_assert_internal(size <= mi_arena_block_size(bcount));
-  
+
   // Check arena suitability
   mi_arena_t* arena = mi_atomic_load_ptr_acquire(mi_arena_t, &mi_arenas[arena_index]);
   if (arena == NULL) return NULL;
@@ -305,7 +305,7 @@ static void* mi_arena_try_alloc_at_id(mi_arena_id_t arena_id, bool match_numa_no
 
 
 // allocate from an arena with fallback to the OS
-static mi_decl_noinline void* mi_arena_try_alloc(int numa_node, size_t size, size_t alignment, 
+static mi_decl_noinline void* mi_arena_try_alloc(int numa_node, size_t size, size_t alignment,
                                                   bool commit, bool allow_large,
                                                   mi_arena_id_t req_arena_id, mi_memid_t* memid, mi_os_tld_t* tld )
 {
@@ -313,9 +313,9 @@ static mi_decl_noinline void* mi_arena_try_alloc(int numa_node, size_t size, siz
   mi_assert_internal(alignment <= MI_SEGMENT_ALIGN);
   const size_t max_arena = mi_atomic_load_relaxed(&mi_arena_count);
   if mi_likely(max_arena == 0) return NULL;
-  
+
   if (req_arena_id != _mi_arena_id_none()) {
-    // try a specific arena if requested 
+    // try a specific arena if requested
     if (mi_arena_id_index(req_arena_id) < max_arena) {
       void* p = mi_arena_try_alloc_at_id(req_arena_id, true, numa_node, size, alignment, commit, allow_large, req_arena_id, memid, tld);
       if (p != NULL) return p;
@@ -323,7 +323,7 @@ static mi_decl_noinline void* mi_arena_try_alloc(int numa_node, size_t size, siz
   }
   else {
     // try numa affine allocation
-    for (size_t i = 0; i < max_arena; i++) {    
+    for (size_t i = 0; i < max_arena; i++) {
       void* p = mi_arena_try_alloc_at_id(mi_arena_id_create(i), true, numa_node, size, alignment, commit, allow_large, req_arena_id, memid, tld);
       if (p != NULL) return p;
     }
@@ -351,22 +351,22 @@ static bool mi_arena_reserve(size_t req_size, bool allow_large, mi_arena_id_t re
   size_t arena_reserve = mi_option_get_size(mi_option_arena_reserve);
   if (arena_reserve == 0) return false;
 
-  if (!_mi_os_has_virtual_reserve()) { 
+  if (!_mi_os_has_virtual_reserve()) {
     arena_reserve = arena_reserve/4;  // be conservative if virtual reserve is not supported (for some embedded systems for example)
   }
   arena_reserve = _mi_align_up(arena_reserve, MI_ARENA_BLOCK_SIZE);
   if (arena_count >= 8 && arena_count <= 128) {
     arena_reserve = ((size_t)1<<(arena_count/8)) * arena_reserve;  // scale up the arena sizes exponentially
-  }    
+  }
   if (arena_reserve < req_size) return false;  // should be able to at least handle the current allocation size
-      
+
   // commit eagerly?
   bool arena_commit = false;
   if (mi_option_get(mi_option_arena_eager_commit) == 2)      { arena_commit = _mi_os_has_overcommit(); }
   else if (mi_option_get(mi_option_arena_eager_commit) == 1) { arena_commit = true; }
 
   return (mi_reserve_os_memory_ex(arena_reserve, arena_commit, allow_large, false /* exclusive */, arena_id) == 0);
-}    
+}
 
 
 void* _mi_arena_alloc_aligned(size_t size, size_t alignment, size_t align_offset, bool commit, bool allow_large,
@@ -381,9 +381,9 @@ void* _mi_arena_alloc_aligned(size_t size, size_t alignment, size_t align_offset
   // try to allocate in an arena if the alignment is small enough and the object is not too small (as for heap meta data)
   if (size >= MI_ARENA_MIN_OBJ_SIZE && alignment <= MI_SEGMENT_ALIGN && align_offset == 0) {
     void* p = mi_arena_try_alloc(numa_node, size, alignment, commit, allow_large, req_arena_id, memid, tld);
-    if (p != NULL) return p;    
+    if (p != NULL) return p;
 
-    // otherwise, try to first eagerly reserve a new arena 
+    // otherwise, try to first eagerly reserve a new arena
     if (req_arena_id == _mi_arena_id_none()) {
       mi_arena_id_t arena_id = 0;
       if (mi_arena_reserve(size, allow_large, req_arena_id, &arena_id)) {
@@ -400,14 +400,14 @@ void* _mi_arena_alloc_aligned(size_t size, size_t alignment, size_t align_offset
     errno = ENOMEM;
     return NULL;
   }
-   
+
   // finally, fall back to the OS
   if (align_offset > 0) {
     return _mi_os_alloc_aligned_at_offset(size, alignment, align_offset, commit, allow_large, memid, tld->stats);
   }
   else {
     return _mi_os_alloc_aligned(size, alignment, commit, allow_large, memid, tld->stats);
-  }  
+  }
 }
 
 void* _mi_arena_alloc(size_t size, bool commit, bool allow_large, mi_arena_id_t req_arena_id, mi_memid_t* memid, mi_os_tld_t* tld)
@@ -443,22 +443,22 @@ static void mi_arena_purge(mi_arena_t* arena, size_t bitmap_idx, size_t blocks,
   mi_assert_internal(arena->blocks_purge != NULL);
   mi_assert_internal(!arena->memid.is_pinned);
   const size_t size = mi_arena_block_size(blocks);
-  void* const p = mi_arena_block_start(arena, bitmap_idx); 
+  void* const p = mi_arena_block_start(arena, bitmap_idx);
   bool needs_recommit;
   if (_mi_bitmap_is_claimed_across(arena->blocks_committed, arena->field_count, blocks, bitmap_idx)) {
     // all blocks are committed, we can purge freely
     needs_recommit = _mi_os_purge(p, size, stats);
   }
   else {
-    // some blocks are not committed -- this can happen when a partially committed block is freed 
+    // some blocks are not committed -- this can happen when a partially committed block is freed
     // in `_mi_arena_free` and it is conservatively marked as uncommitted but still scheduled for a purge
-    // we need to ensure we do not try to reset (as that may be invalid for uncommitted memory), 
+    // we need to ensure we do not try to reset (as that may be invalid for uncommitted memory),
     // and also undo the decommit stats (as it was already adjusted)
     mi_assert_internal(mi_option_is_enabled(mi_option_purge_decommits));
     needs_recommit = _mi_os_purge_ex(p, size, false /* allow reset? */, stats);
     _mi_stat_increase(&stats->committed, size);
   }
-  
+
   // clear the purged blocks
   _mi_bitmap_unclaim_across(arena->blocks_purge, arena->field_count, blocks, bitmap_idx);
   // update committed bitmap
@@ -476,7 +476,7 @@ static void mi_arena_schedule_purge(mi_arena_t* arena, size_t bitmap_idx, size_t
 
   if (_mi_preloading() || delay == 0) {
     // decommit directly
-    mi_arena_purge(arena, bitmap_idx, blocks, stats);    
+    mi_arena_purge(arena, bitmap_idx, blocks, stats);
   }
   else {
     // schedule decommit
@@ -518,7 +518,7 @@ static bool mi_arena_purge_range(mi_arena_t* arena, size_t idx, size_t startidx,
 }
 
 // returns true if anything was purged
-static bool mi_arena_try_purge(mi_arena_t* arena, mi_msecs_t now, bool force, mi_stats_t* stats) 
+static bool mi_arena_try_purge(mi_arena_t* arena, mi_msecs_t now, bool force, mi_stats_t* stats)
 {
   if (arena->memid.is_pinned || arena->blocks_purge == NULL) return false;
   mi_msecs_t expire = mi_atomic_loadi64_relaxed(&arena->purge_expire);
@@ -527,10 +527,10 @@ static bool mi_arena_try_purge(mi_arena_t* arena, mi_msecs_t now, bool force, mi
 
   // reset expire (if not already set concurrently)
   mi_atomic_casi64_strong_acq_rel(&arena->purge_expire, &expire, 0);
-  
+
   // potential purges scheduled, walk through the bitmap
   bool any_purged = false;
-  bool full_purge = true;  
+  bool full_purge = true;
   for (size_t i = 0; i < arena->field_count; i++) {
     size_t purge = mi_atomic_load_relaxed(&arena->blocks_purge[i]);
     if (purge != 0) {
@@ -581,7 +581,7 @@ static void mi_arenas_try_purge( bool force, bool visit_all, mi_stats_t* stats )
 
   // allow only one thread to purge at a time
   static mi_atomic_guard_t purge_guard;
-  mi_atomic_guard(&purge_guard) 
+  mi_atomic_guard(&purge_guard)
   {
     mi_msecs_t now = _mi_clock_now();
     size_t max_purge_count = (visit_all ? max_arena : 1);
@@ -594,7 +594,7 @@ static void mi_arenas_try_purge( bool force, bool visit_all, mi_stats_t* stats )
         }
       }
     }
-  }  
+  }
 }
 
 
@@ -608,7 +608,7 @@ void _mi_arena_free(void* p, size_t size, size_t committed_size, mi_memid_t memi
   if (p==NULL) return;
   if (size==0) return;
   const bool all_committed = (committed_size == size);
-  
+
   if (mi_memkind_is_os(memid.memkind)) {
     // was a direct OS allocation, pass through
     if (!all_committed && committed_size > 0) {
@@ -626,7 +626,7 @@ void _mi_arena_free(void* p, size_t size, size_t committed_size, mi_memid_t memi
     mi_arena_t* arena = mi_atomic_load_ptr_acquire(mi_arena_t,&mi_arenas[arena_idx]);
     mi_assert_internal(arena != NULL);
     const size_t blocks = mi_block_count_of_size(size);
-    
+
     // checks
     if (arena == NULL) {
       _mi_error_message(EINVAL, "trying to free from non-existent arena: %p, size %zu, memid: 0x%zx\n", p, size, memid);
@@ -648,7 +648,7 @@ void _mi_arena_free(void* p, size_t size, size_t committed_size, mi_memid_t memi
     else {
       mi_assert_internal(arena->blocks_committed != NULL);
       mi_assert_internal(arena->blocks_purge != NULL);
-      
+
       if (!all_committed) {
         // mark the entire range as no longer committed (so we recommit the full range when re-using)
         _mi_bitmap_unclaim_across(arena->blocks_committed, arena->field_count, blocks, bitmap_idx);
@@ -663,9 +663,9 @@ void _mi_arena_free(void* p, size_t size, size_t committed_size, mi_memid_t memi
         // works (as we should never reset decommitted parts).
       }
       // (delay) purge the entire range
-      mi_arena_schedule_purge(arena, bitmap_idx, blocks, stats);      
+      mi_arena_schedule_purge(arena, bitmap_idx, blocks, stats);
     }
-    
+
     // and make it available to others again
     bool all_inuse = _mi_bitmap_unclaim_across(arena->blocks_inuse, arena->field_count, blocks, bitmap_idx);
     if (!all_inuse) {
@@ -690,9 +690,9 @@ static void mi_arenas_unsafe_destroy(void) {
   for (size_t i = 0; i < max_arena; i++) {
     mi_arena_t* arena = mi_atomic_load_ptr_acquire(mi_arena_t, &mi_arenas[i]);
     if (arena != NULL) {
-      if (arena->start != NULL && mi_memkind_is_os(arena->memid.memkind)) {      
+      if (arena->start != NULL && mi_memkind_is_os(arena->memid.memkind)) {
         mi_atomic_store_ptr_release(mi_arena_t, &mi_arenas[i], NULL);
-        _mi_os_free(arena->start, mi_arena_size(arena), arena->memid, &_mi_stats_main); 
+        _mi_os_free(arena->start, mi_arena_size(arena), arena->memid, &_mi_stats_main);
       }
       else {
         new_max_arena = i;
@@ -715,7 +715,7 @@ void _mi_arena_collect(bool force_purge, mi_stats_t* stats) {
 // for dynamic libraries that are unloaded and need to release all their allocated memory.
 void _mi_arena_unsafe_destroy_all(mi_stats_t* stats) {
   mi_arenas_unsafe_destroy();
-  _mi_arena_collect(true /* force purge */, stats);  // purge non-owned arenas  
+  _mi_arena_collect(true /* force purge */, stats);  // purge non-owned arenas
 }
 
 // Is a pointer inside any of our arenas?
@@ -723,8 +723,8 @@ bool _mi_arena_contains(const void* p) {
   const size_t max_arena = mi_atomic_load_relaxed(&mi_arena_count);
   for (size_t i = 0; i < max_arena; i++) {
     mi_arena_t* arena = mi_atomic_load_ptr_acquire(mi_arena_t, &mi_arenas[i]);
-    if (arena != NULL && arena->start <= (const uint8_t*)p && arena->start + mi_arena_block_size(arena->block_count) > (const uint8_t*)p) { 
-      return true;      
+    if (arena != NULL && arena->start <= (const uint8_t*)p && arena->start + mi_arena_block_size(arena->block_count) > (const uint8_t*)p) {
+      return true;
     }
   }
   return false;
@@ -768,7 +768,7 @@ static bool mi_manage_os_memory_ex2(void* start, size_t size, bool is_large, int
   mi_memid_t meta_memid;
   mi_arena_t* arena   = (mi_arena_t*)mi_arena_meta_zalloc(asize, &meta_memid, &_mi_stats_main); // TODO: can we avoid allocating from the OS?
   if (arena == NULL) return false;
-  
+
   // already zero'd due to os_alloc
   // _mi_memzero(arena, asize);
   arena->id = _mi_arena_id_none();
@@ -785,12 +785,12 @@ static bool mi_manage_os_memory_ex2(void* start, size_t size, bool is_large, int
   arena->search_idx   = 0;
   arena->blocks_dirty = &arena->blocks_inuse[fields]; // just after inuse bitmap
   arena->blocks_committed = (arena->memid.is_pinned ? NULL : &arena->blocks_inuse[2*fields]); // just after dirty bitmap
-  arena->blocks_purge  = (arena->memid.is_pinned ? NULL : &arena->blocks_inuse[3*fields]); // just after committed bitmap  
+  arena->blocks_purge  = (arena->memid.is_pinned ? NULL : &arena->blocks_inuse[3*fields]); // just after committed bitmap
   // initialize committed bitmap?
   if (arena->blocks_committed != NULL && arena->memid.initially_committed) {
     memset((void*)arena->blocks_committed, 0xFF, fields*sizeof(mi_bitmap_field_t)); // cast to void* to avoid atomic warning
   }
-  
+
   // and claim leftover blocks if needed (so we never allocate there)
   ptrdiff_t post = (fields * MI_BITMAP_FIELD_BITS) - bcount;
   mi_assert_internal(post >= 0);
@@ -939,4 +939,3 @@ int mi_reserve_huge_os_pages(size_t pages, double max_secs, size_t* pages_reserv
   if (err==0 && pages_reserved!=NULL) *pages_reserved = pages;
   return err;
 }
-
diff --git a/src/os.c b/src/os.c
index b4f02ba37..d1fbf5092 100644
--- a/src/os.c
+++ b/src/os.c
@@ -29,7 +29,7 @@ bool _mi_os_has_overcommit(void) {
   return mi_os_mem_config.has_overcommit;
 }
 
-bool _mi_os_has_virtual_reserve(void) { 
+bool _mi_os_has_virtual_reserve(void) {
   return mi_os_mem_config.has_virtual_reserve;
 }
 
@@ -73,14 +73,6 @@ void _mi_os_init(void) {
 bool _mi_os_decommit(void* addr, size_t size, mi_stats_t* stats);
 bool _mi_os_commit(void* addr, size_t size, bool* is_zero, mi_stats_t* tld_stats);
 
-static void* mi_align_up_ptr(void* p, size_t alignment) {
-  return (void*)_mi_align_up((uintptr_t)p, alignment);
-}
-
-static void* mi_align_down_ptr(void* p, size_t alignment) {
-  return (void*)_mi_align_down((uintptr_t)p, alignment);
-}
-
 
 /* -----------------------------------------------------------
   aligned hinting
@@ -173,7 +165,7 @@ void _mi_os_free_ex(void* addr, size_t size, bool still_committed, mi_memid_t me
     }
   }
   else {
-    // nothing to do 
+    // nothing to do
     mi_assert(memid.memkind < MI_MEM_OS);
   }
 }
@@ -197,7 +189,7 @@ static void* mi_os_prim_alloc(size_t size, size_t try_alignment, bool commit, bo
   if (try_alignment == 0) { try_alignment = 1; } // avoid 0 to ensure there will be no divide by zero when aligning
 
   *is_zero = false;
-  void* p = NULL; 
+  void* p = NULL;
   int err = _mi_prim_alloc(size, try_alignment, commit, allow_large, is_large, is_zero, &p);
   if (err != 0) {
     _mi_warning_message("unable to allocate OS memory (error: %d (0x%x), size: 0x%zx bytes, align: 0x%zx, commit: %d, allow large: %d)\n", err, err, size, try_alignment, commit, allow_large);
@@ -205,14 +197,14 @@ static void* mi_os_prim_alloc(size_t size, size_t try_alignment, bool commit, bo
   mi_stat_counter_increase(stats->mmap_calls, 1);
   if (p != NULL) {
     _mi_stat_increase(&stats->reserved, size);
-    if (commit) { 
-      _mi_stat_increase(&stats->committed, size); 
+    if (commit) {
+      _mi_stat_increase(&stats->committed, size);
       // seems needed for asan (or `mimalloc-test-api` fails)
       #ifdef MI_TRACK_ASAN
       if (*is_zero) { mi_track_mem_defined(p,size); }
                else { mi_track_mem_undefined(p,size); }
       #endif
-    }    
+    }
   }
   return p;
 }
@@ -249,7 +241,7 @@ static void* mi_os_prim_alloc_aligned(size_t size, size_t alignment, bool commit
       // over-allocate uncommitted (virtual) memory
       p = mi_os_prim_alloc(over_size, 1 /*alignment*/, false /* commit? */, false /* allow_large */, is_large, is_zero, stats);
       if (p == NULL) return NULL;
-      
+
       // set p to the aligned part in the full region
       // note: this is dangerous on Windows as VirtualFree needs the actual base pointer
       // this is handled though by having the `base` field in the memid's
@@ -265,7 +257,7 @@ static void* mi_os_prim_alloc_aligned(size_t size, size_t alignment, bool commit
       // overallocate...
       p = mi_os_prim_alloc(over_size, 1, commit, false, is_large, is_zero, stats);
       if (p == NULL) return NULL;
-      
+
       // and selectively unmap parts around the over-allocated area. (noop on sbrk)
       void* aligned_p = mi_align_up_ptr(p, alignment);
       size_t pre_size = (uint8_t*)aligned_p - (uint8_t*)p;
@@ -276,7 +268,7 @@ static void* mi_os_prim_alloc_aligned(size_t size, size_t alignment, bool commit
       if (post_size > 0) { mi_os_prim_free((uint8_t*)aligned_p + mid_size, post_size, commit, stats); }
       // we can return the aligned pointer on `mmap` (and sbrk) systems
       p = aligned_p;
-      *base = aligned_p; // since we freed the pre part, `*base == p`.      
+      *base = aligned_p; // since we freed the pre part, `*base == p`.
     }
   }
 
@@ -300,7 +292,7 @@ void* _mi_os_alloc(size_t size, mi_memid_t* memid, mi_stats_t* tld_stats) {
   void* p = mi_os_prim_alloc(size, 0, true, false, &os_is_large, &os_is_zero, stats);
   if (p != NULL) {
     *memid = _mi_memid_create_os(true, os_is_zero, os_is_large);
-  }  
+  }
   return p;
 }
 
@@ -312,7 +304,7 @@ void* _mi_os_alloc_aligned(size_t size, size_t alignment, bool commit, bool allo
   if (size == 0) return NULL;
   size = _mi_os_good_alloc_size(size);
   alignment = _mi_align_up(alignment, _mi_os_page_size());
-  
+
   bool os_is_large = false;
   bool os_is_zero  = false;
   void* os_base = NULL;
@@ -390,7 +382,7 @@ static void* mi_os_page_align_area_conservative(void* addr, size_t size, size_t*
 
 bool _mi_os_commit(void* addr, size_t size, bool* is_zero, mi_stats_t* tld_stats) {
   MI_UNUSED(tld_stats);
-  mi_stats_t* stats = &_mi_stats_main;  
+  mi_stats_t* stats = &_mi_stats_main;
   if (is_zero != NULL) { *is_zero = false; }
   _mi_stat_increase(&stats->committed, size);  // use size for precise commit vs. decommit
   _mi_stat_counter_increase(&stats->commit_calls, 1);
@@ -400,21 +392,21 @@ bool _mi_os_commit(void* addr, size_t size, bool* is_zero, mi_stats_t* tld_stats
   void* start = mi_os_page_align_areax(false /* conservative? */, addr, size, &csize);
   if (csize == 0) return true;
 
-  // commit  
+  // commit
   bool os_is_zero = false;
-  int err = _mi_prim_commit(start, csize, &os_is_zero); 
+  int err = _mi_prim_commit(start, csize, &os_is_zero);
   if (err != 0) {
     _mi_warning_message("cannot commit OS memory (error: %d (0x%x), address: %p, size: 0x%zx bytes)\n", err, err, start, csize);
     return false;
   }
-  if (os_is_zero && is_zero != NULL) { 
+  if (os_is_zero && is_zero != NULL) {
     *is_zero = true;
     mi_assert_expensive(mi_mem_is_zero(start, csize));
   }
   // note: the following seems required for asan (otherwise `mimalloc-test-stress` fails)
   #ifdef MI_TRACK_ASAN
   if (os_is_zero) { mi_track_mem_defined(start,csize); }
-             else { mi_track_mem_undefined(start,csize); } 
+             else { mi_track_mem_undefined(start,csize); }
   #endif
   return true;
 }
@@ -428,11 +420,11 @@ static bool mi_os_decommit_ex(void* addr, size_t size, bool* needs_recommit, mi_
   // page align
   size_t csize;
   void* start = mi_os_page_align_area_conservative(addr, size, &csize);
-  if (csize == 0) return true; 
+  if (csize == 0) return true;
 
   // decommit
   *needs_recommit = true;
-  int err = _mi_prim_decommit(start,csize,needs_recommit);  
+  int err = _mi_prim_decommit(start,csize,needs_recommit);
   if (err != 0) {
     _mi_warning_message("cannot decommit OS memory (error: %d (0x%x), address: %p, size: 0x%zx bytes)\n", err, err, start, csize);
   }
@@ -450,7 +442,7 @@ bool _mi_os_decommit(void* addr, size_t size, mi_stats_t* tld_stats) {
 // but may be used later again. This will release physical memory
 // pages and reduce swapping while keeping the memory committed.
 // We page align to a conservative area inside the range to reset.
-bool _mi_os_reset(void* addr, size_t size, mi_stats_t* stats) { 
+bool _mi_os_reset(void* addr, size_t size, mi_stats_t* stats) {
   // page align conservatively within the range
   size_t csize;
   void* start = mi_os_page_align_area_conservative(addr, size, &csize);
@@ -470,7 +462,7 @@ bool _mi_os_reset(void* addr, size_t size, mi_stats_t* stats) {
 }
 
 
-// either resets or decommits memory, returns true if the memory needs 
+// either resets or decommits memory, returns true if the memory needs
 // to be recommitted if it is to be re-used later on.
 bool _mi_os_purge_ex(void* p, size_t size, bool allow_reset, mi_stats_t* stats)
 {
@@ -483,7 +475,7 @@ bool _mi_os_purge_ex(void* p, size_t size, bool allow_reset, mi_stats_t* stats)
   {
     bool needs_recommit = true;
     mi_os_decommit_ex(p, size, &needs_recommit, stats);
-    return needs_recommit;   
+    return needs_recommit;
   }
   else {
     if (allow_reset) {  // this can sometimes be not allowed if the range is not fully committed
@@ -493,7 +485,7 @@ bool _mi_os_purge_ex(void* p, size_t size, bool allow_reset, mi_stats_t* stats)
   }
 }
 
-// either resets or decommits memory, returns true if the memory needs 
+// either resets or decommits memory, returns true if the memory needs
 // to be recommitted if it is to be re-used later on.
 bool _mi_os_purge(void* p, size_t size, mi_stats_t * stats) {
   return _mi_os_purge_ex(p, size, true, stats);
diff --git a/src/prim/prim.c b/src/prim/prim.c
index 9a597d8eb..bf072e0f5 100644
--- a/src/prim/prim.c
+++ b/src/prim/prim.c
@@ -14,9 +14,9 @@ terms of the MIT license. A copy of the license can be found in the file
 #elif defined(__APPLE__)
 #include "osx/prim.c"      // macOSX (actually defers to mmap in unix/prim.c)
 
-#elif defined(__wasi__)
+#elif defined(__wasm__)
 #define MI_USE_SBRK
-#include "wasi/prim.c"     // memory-grow or sbrk (Wasm)
+#include "wasm/prim.c"     // memory-grow or sbrk (Wasm)
 
 #else
 #include "unix/prim.c"     // mmap() (Linux, macOSX, BSD, Illumnos, Haiku, DragonFly, etc.)
diff --git a/src/prim/readme.md b/src/prim/readme.md
index 380dd3a71..df41642b5 100644
--- a/src/prim/readme.md
+++ b/src/prim/readme.md
@@ -3,7 +3,7 @@
 This is the portability layer where all primitives needed from the OS are defined.
 
 - `include/mimalloc/prim.h`: primitive portability API definition.
-- `prim.c`: Selects one of `unix/prim.c`, `wasi/prim.c`, or `windows/prim.c` depending on the host platform
+- `prim.c`: Selects one of `unix/prim.c`, `wasm/prim.c`, or `windows/prim.c` depending on the host platform
             (and on macOS, `osx/prim.c` defers to `unix/prim.c`).
 
-Note: still work in progress, there may still be places in the sources that still depend on OS ifdef's.
\ No newline at end of file
+Note: still work in progress, there may still be places in the sources that still depend on OS ifdef's.
diff --git a/src/prim/unix/prim.c b/src/prim/unix/prim.c
index 4ed8bd925..2bb5f7b29 100644
--- a/src/prim/unix/prim.c
+++ b/src/prim/unix/prim.c
@@ -57,7 +57,7 @@ terms of the MIT license. A copy of the license can be found in the file
 
 //------------------------------------------------------------------------------------
 // Use syscalls for some primitives to allow for libraries that override open/read/close etc.
-// and do allocation themselves; using syscalls prevents recursion when mimalloc is 
+// and do allocation themselves; using syscalls prevents recursion when mimalloc is
 // still initializing (issue #713)
 //------------------------------------------------------------------------------------
 
@@ -120,7 +120,7 @@ static bool unix_detect_overcommit(void) {
     os_overcommit = (val != 0);
   }
 #else
-  // default: overcommit is true  
+  // default: overcommit is true
 #endif
   return os_overcommit;
 }
@@ -168,12 +168,12 @@ static void* unix_mmap_prim(void* addr, size_t size, size_t try_alignment, int p
     size_t n = mi_bsr(try_alignment);
     if (((size_t)1 << n) == try_alignment && n >= 12 && n <= 30) {  // alignment is a power of 2 and 4096 <= alignment <= 1GiB
       p = mmap(addr, size, protect_flags, flags | MAP_ALIGNED(n), fd, 0);
-      if (p==MAP_FAILED || !_mi_is_aligned(p,try_alignment)) { 
+      if (p==MAP_FAILED || !_mi_is_aligned(p,try_alignment)) {
         int err = errno;
         _mi_warning_message("unable to directly request aligned OS memory (error: %d (0x%x), size: 0x%zx bytes, alignment: 0x%zx, hint address: %p)\n", err, err, size, try_alignment, addr);
       }
       if (p!=MAP_FAILED) return p;
-      // fall back to regular mmap      
+      // fall back to regular mmap
     }
   }
   #elif defined(MAP_ALIGN)  // Solaris
@@ -189,7 +189,7 @@ static void* unix_mmap_prim(void* addr, size_t size, size_t try_alignment, int p
     void* hint = _mi_os_get_aligned_hint(try_alignment, size);
     if (hint != NULL) {
       p = mmap(hint, size, protect_flags, flags, fd, 0);
-      if (p==MAP_FAILED || !_mi_is_aligned(p,try_alignment)) { 
+      if (p==MAP_FAILED || !_mi_is_aligned(p,try_alignment)) {
         #if MI_TRACK_ENABLED  // asan sometimes does not instrument errno correctly?
         int err = 0;
         #else
@@ -198,7 +198,7 @@ static void* unix_mmap_prim(void* addr, size_t size, size_t try_alignment, int p
         _mi_warning_message("unable to directly request hinted aligned OS memory (error: %d (0x%x), size: 0x%zx bytes, alignment: 0x%zx, hint address: %p)\n", err, err, size, try_alignment, hint);
       }
       if (p!=MAP_FAILED) return p;
-      // fall back to regular mmap      
+      // fall back to regular mmap
     }
   }
   #endif
@@ -327,9 +327,9 @@ int _mi_prim_alloc(size_t size, size_t try_alignment, bool commit, bool allow_la
   mi_assert_internal(size > 0 && (size % _mi_os_page_size()) == 0);
   mi_assert_internal(commit || !allow_large);
   mi_assert_internal(try_alignment > 0);
-  
+
   *is_zero = true;
-  int protect_flags = (commit ? (PROT_WRITE | PROT_READ) : PROT_NONE);  
+  int protect_flags = (commit ? (PROT_WRITE | PROT_READ) : PROT_NONE);
   *addr = unix_mmap(NULL, size, try_alignment, protect_flags, false, allow_large, is_large);
   return (*addr != NULL ? 0 : errno);
 }
@@ -357,19 +357,19 @@ int _mi_prim_commit(void* start, size_t size, bool* is_zero) {
   // was either from mmap PROT_NONE, or from decommit MADV_DONTNEED, but
   // we sometimes call commit on a range with still partially committed
   // memory and `mprotect` does not zero the range.
-  *is_zero = false;  
+  *is_zero = false;
   int err = mprotect(start, size, (PROT_READ | PROT_WRITE));
-  if (err != 0) { 
-    err = errno; 
+  if (err != 0) {
+    err = errno;
     unix_mprotect_hint(err);
   }
   return err;
 }
 
 int _mi_prim_decommit(void* start, size_t size, bool* needs_recommit) {
-  int err = 0;  
+  int err = 0;
   // decommit: use MADV_DONTNEED as it decreases rss immediately (unlike MADV_FREE)
-  err = unix_madvise(start, size, MADV_DONTNEED);    
+  err = unix_madvise(start, size, MADV_DONTNEED);
   #if !MI_DEBUG && !MI_SECURE
     *needs_recommit = false;
   #else
@@ -381,15 +381,15 @@ int _mi_prim_decommit(void* start, size_t size, bool* needs_recommit) {
   *needs_recommit = true;
   const int fd = unix_mmap_fd();
   void* p = mmap(start, size, PROT_NONE, (MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE), fd, 0);
-  if (p != start) { err = errno; }    
+  if (p != start) { err = errno; }
   */
   return err;
 }
 
 int _mi_prim_reset(void* start, size_t size) {
-  // We try to use `MADV_FREE` as that is the fastest. A drawback though is that it 
+  // We try to use `MADV_FREE` as that is the fastest. A drawback though is that it
   // will not reduce the `rss` stats in tools like `top` even though the memory is available
-  // to other processes. With the default `MIMALLOC_PURGE_DECOMMITS=1` we ensure that by 
+  // to other processes. With the default `MIMALLOC_PURGE_DECOMMITS=1` we ensure that by
   // default `MADV_DONTNEED` is used though.
   #if defined(MADV_FREE)
   static _Atomic(size_t) advice = MI_ATOMIC_VAR_INIT(MADV_FREE);
@@ -409,7 +409,7 @@ int _mi_prim_reset(void* start, size_t size) {
 
 int _mi_prim_protect(void* start, size_t size, bool protect) {
   int err = mprotect(start, size, protect ? PROT_NONE : (PROT_READ | PROT_WRITE));
-  if (err != 0) { err = errno; }  
+  if (err != 0) { err = errno; }
   unix_mprotect_hint(err);
   return err;
 }
@@ -450,7 +450,7 @@ int _mi_prim_alloc_huge_os_pages(void* hint_addr, size_t size, int numa_node, bo
     if (err != 0) {
       err = errno;
       _mi_warning_message("failed to bind huge (1GiB) pages to numa node %d (error: %d (0x%x))\n", numa_node, err, err);
-    }    
+    }
   }
   return (*addr != NULL ? 0 : errno);
 }
@@ -565,9 +565,9 @@ mi_msecs_t _mi_prim_clock_now(void) {
 // low resolution timer
 mi_msecs_t _mi_prim_clock_now(void) {
   #if !defined(CLOCKS_PER_SEC) || (CLOCKS_PER_SEC == 1000) || (CLOCKS_PER_SEC == 0)
-  return (mi_msecs_t)clock();  
+  return (mi_msecs_t)clock();
   #elif (CLOCKS_PER_SEC < 1000)
-  return (mi_msecs_t)clock() * (1000 / (mi_msecs_t)CLOCKS_PER_SEC);  
+  return (mi_msecs_t)clock() * (1000 / (mi_msecs_t)CLOCKS_PER_SEC);
   #else
   return (mi_msecs_t)clock() / ((mi_msecs_t)CLOCKS_PER_SEC / 1000);
   #endif
@@ -607,7 +607,7 @@ void _mi_prim_process_info(mi_process_info_t* pinfo)
   pinfo->stime = timeval_secs(&rusage.ru_stime);
 #if !defined(__HAIKU__)
   pinfo->page_faults = rusage.ru_majflt;
-#endif  
+#endif
 #if defined(__HAIKU__)
   // Haiku does not have (yet?) a way to
   // get these stats per process
@@ -642,7 +642,7 @@ void _mi_prim_process_info(mi_process_info_t* pinfo)
 
 #else
 
-#ifndef __wasi__
+#ifndef __wasm__
 // WebAssembly instances are not processes
 #pragma message("define a way to get process info")
 #endif
@@ -748,7 +748,7 @@ bool _mi_prim_random_buf(void* buf, size_t buf_len) {
 
 #elif defined(__ANDROID__) || defined(__DragonFly__) || \
       defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) || \
-      defined(__sun) 
+      defined(__sun)
 
 #include <stdlib.h>
 bool _mi_prim_random_buf(void* buf, size_t buf_len) {
@@ -840,7 +840,7 @@ void _mi_prim_thread_associate_default_heap(mi_heap_t* heap) {
   }
 }
 
-#else 
+#else
 
 void _mi_prim_thread_init_auto_done(void) {
   // nothing
diff --git a/src/prim/wasi/prim.c b/src/prim/wasm/prim.c
similarity index 86%
rename from src/prim/wasi/prim.c
rename to src/prim/wasm/prim.c
index 50511f0b5..8b159cce2 100644
--- a/src/prim/wasi/prim.c
+++ b/src/prim/wasm/prim.c
@@ -7,6 +7,10 @@ terms of the MIT license. A copy of the license can be found in the file
 
 // This file is included in `src/prim/prim.c`
 
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
 #include "mimalloc.h"
 #include "mimalloc/internal.h"
 #include "mimalloc/atomic.h"
@@ -19,7 +23,7 @@ terms of the MIT license. A copy of the license can be found in the file
 void _mi_prim_mem_init( mi_os_mem_config_t* config ) {
   config->page_size = 64*MI_KiB; // WebAssembly has a fixed page size: 64KiB
   config->alloc_granularity = 16;
-  config->has_overcommit = false;  
+  config->has_overcommit = false;
   config->must_free_whole = true;
   config->has_virtual_reserve = false;
 }
@@ -30,32 +34,23 @@ void _mi_prim_mem_init( mi_os_mem_config_t* config ) {
 
 int _mi_prim_free(void* addr, size_t size ) {
   MI_UNUSED(addr); MI_UNUSED(size);
-  // wasi heap cannot be shrunk
+  // wasm linear memory cannot be shrunk
   return 0;
 }
 
 
 //---------------------------------------------
-// Allocation: sbrk or memory_grow
+// Allocation: sbrk
 //---------------------------------------------
 
-#if defined(MI_USE_SBRK)
-  static void* mi_memory_grow( size_t size ) {
-    void* p = sbrk(size);
-    if (p == (void*)(-1)) return NULL;
-    #if !defined(__wasi__) // on wasi this is always zero initialized already (?)
-    memset(p,0,size);
-    #endif
-    return p;
-  }
-#elif defined(__wasi__)
-  static void* mi_memory_grow( size_t size ) {
-    size_t base = (size > 0 ? __builtin_wasm_memory_grow(0,_mi_divide_up(size, _mi_os_page_size()))
-                            : __builtin_wasm_memory_size(0));
-    if (base == SIZE_MAX) return NULL;
-    return (void*)(base * _mi_os_page_size());
-  }
+static void* mi_memory_grow( size_t size ) {
+  void* p = sbrk(size);
+  if (p == (void*)(-1)) return NULL;
+#if !defined(__wasm__) // on wasm this is always zero initialized already.
+  memset(p,0,size);
 #endif
+  return p;
+}
 
 #if defined(MI_USE_PTHREADS)
 static pthread_mutex_t mi_heap_grow_mutex = PTHREAD_MUTEX_INITIALIZER;
@@ -96,7 +91,7 @@ static void* mi_prim_mem_grow(size_t size, size_t try_alignment) {
     if (base != NULL) {
       p = mi_align_up_ptr(base, try_alignment);
       if ((uint8_t*)p + size > (uint8_t*)base + alloc_size) {
-        // another thread used wasm_memory_grow/sbrk in-between and we do not have enough
+        // another thread used sbrk in-between and we do not have enough
         // space after alignment. Give up (and waste the space as we cannot shrink :-( )
         // (in `mi_os_mem_alloc_aligned` this will fall back to overallocation to align)
         p = NULL;
@@ -105,7 +100,7 @@ static void* mi_prim_mem_grow(size_t size, size_t try_alignment) {
   }
   /*
   if (p == NULL) {
-    _mi_warning_message("unable to allocate sbrk/wasm_memory_grow OS memory (%zu bytes, %zu alignment)\n", size, try_alignment);
+    _mi_warning_message("unable to allocate sbrk OS memory (%zu bytes, %zu alignment)\n", size, try_alignment);
     errno = ENOMEM;
     return NULL;
   }
@@ -114,7 +109,7 @@ static void* mi_prim_mem_grow(size_t size, size_t try_alignment) {
   return p;
 }
 
-// Note: the `try_alignment` is just a hint and the returned pointer is not guaranteed to be aligned.
+// Note: the `try_alignment` argument is respected by over-allocating.
 int _mi_prim_alloc(size_t size, size_t try_alignment, bool commit, bool allow_large, bool* is_large, bool* is_zero, void** addr) {
   MI_UNUSED(allow_large); MI_UNUSED(commit);
   *is_large = false;
@@ -129,7 +124,7 @@ int _mi_prim_alloc(size_t size, size_t try_alignment, bool commit, bool allow_la
 //---------------------------------------------
 
 int _mi_prim_commit(void* addr, size_t size, bool* is_zero) {
-  MI_UNUSED(addr); MI_UNUSED(size); 
+  MI_UNUSED(addr); MI_UNUSED(size);
   *is_zero = false;
   return 0;
 }
@@ -194,9 +189,9 @@ mi_msecs_t _mi_prim_clock_now(void) {
 // low resolution timer
 mi_msecs_t _mi_prim_clock_now(void) {
   #if !defined(CLOCKS_PER_SEC) || (CLOCKS_PER_SEC == 1000) || (CLOCKS_PER_SEC == 0)
-  return (mi_msecs_t)clock();  
+  return (mi_msecs_t)clock();
   #elif (CLOCKS_PER_SEC < 1000)
-  return (mi_msecs_t)clock() * (1000 / (mi_msecs_t)CLOCKS_PER_SEC);  
+  return (mi_msecs_t)clock() * (1000 / (mi_msecs_t)CLOCKS_PER_SEC);
   #else
   return (mi_msecs_t)clock() / ((mi_msecs_t)CLOCKS_PER_SEC / 1000);
   #endif
@@ -254,7 +249,8 @@ bool _mi_prim_getenv(const char* name, char* result, size_t result_size) {
 //----------------------------------------------------------------
 
 bool _mi_prim_random_buf(void* buf, size_t buf_len) {
-  return false;
+  int r = getentropy(buf, buf_len);
+  return r == 0;
 }
 
 
diff --git a/src/random.c b/src/random.c
index 4fc8b2f8f..d9a430af4 100644
--- a/src/random.c
+++ b/src/random.c
@@ -160,7 +160,7 @@ If we cannot get good randomness, we fall back to weak randomness based on a tim
 
 uintptr_t _mi_os_random_weak(uintptr_t extra_seed) {
   uintptr_t x = (uintptr_t)&_mi_os_random_weak ^ extra_seed; // ASLR makes the address random
-  x ^= _mi_prim_clock_now();  
+  x ^= _mi_prim_clock_now();
   // and do a few randomization steps
   uintptr_t max = ((x ^ (x >> 17)) & 0x0F) + 1;
   for (uintptr_t i = 0; i < max; i++) {
@@ -175,7 +175,7 @@ static void mi_random_init_ex(mi_random_ctx_t* ctx, bool use_weak) {
   if (use_weak || !_mi_prim_random_buf(key, sizeof(key))) {
     // if we fail to get random data from the OS, we fall back to a
     // weak random source based on the current time
-    #if !defined(__wasi__)
+    #if !defined(__wasm__)
     if (!use_weak) { _mi_warning_message("unable to use secure randomness\n"); }
     #endif
     uintptr_t x = _mi_os_random_weak(0);