/* ----------------------------------------------------------------------------

Copyright (c) 2018-2024, Microsoft Research, Daan Leijen

This is free software; you can redistribute it and/or modify it under the

terms of the MIT license. A copy of the license can be found in the file

"LICENSE" at the root of this distribution.

-----------------------------------------------------------------------------*/

#if !defined(MI_IN_ALLOC_C)

#error "this file should be included from 'alloc.c' (so aliases can work from alloc-override)"

// add includes help an IDE

#include "mimalloc.h"

#include "mimalloc/internal.h"

#include "mimalloc/prim.h"   // _mi_prim_thread_id()

#endif

// forward declarations

static void   mi_check_padding(const mi_page_t* page, const mi_block_t* block);

static bool   mi_check_is_double_free(const mi_page_t* page, const mi_block_t* block);

static size_t mi_page_usable_size_of(const mi_page_t* page, const mi_block_t* block, bool was_guarded);

static void   mi_stat_free(const mi_page_t* page, const mi_block_t* block);

// ------------------------------------------------------

// Free

// ------------------------------------------------------

// forward declaration of multi-threaded free (`_mt`) (or free in huge block if compiled with MI_HUGE_PAGE_ABANDON)

static mi_decl_noinline void mi_free_block_mt(mi_page_t* page, mi_segment_t* segment, mi_block_t* block, void* p, bool was_guarded);

// regular free of a (thread local) block pointer

// fast path written carefully to prevent spilling on the stack

static inline void mi_free_block_local(mi_page_t* page, mi_block_t* block, bool was_guarded, bool track_stats, bool check_full)

{

  MI_UNUSED(was_guarded);

  // checks

  if mi_unlikely(mi_check_is_double_free(page, block)) return;

  if (!was_guarded) { mi_check_padding(page, block); }

  if (track_stats) { mi_stat_free(page, block); }

  #if (MI_DEBUG>0) && !MI_TRACK_ENABLED  && !MI_TSAN

  if (!mi_page_is_huge(page)) {   // huge page content may be already decommitted

    size_t dbgsize = mi_page_block_size(page); if (dbgsize > 1*MI_MiB) { dbgsize = 1*MI_MiB; }

    mi_debug_fill(page, block, MI_DEBUG_FREED, dbgsize);

  }

  #endif

  if (track_stats) { mi_track_free_size(block, mi_page_usable_size_of(page, block, was_guarded)); } // faster then mi_usable_size as we already know the page and that p is unaligned

  // actual free: push on the local free list

  mi_block_set_next(page, block, page->local_free);

  page->local_free = block;

  if mi_unlikely(--page->used == 0) {

    _mi_page_retire(page);

  }

  else if mi_unlikely(check_full && mi_page_is_in_full(page)) {

    _mi_page_unfull(page);

  }

}

// Adjust a block that was allocated aligned, to the actual start of the block in the page.

// note: this can be called from `mi_free_generic_mt` where a non-owning thread accesses the

// `page_start` and `block_size` fields; however these are constant and the page won't be

// deallocated (as the block we are freeing keeps it alive) and thus safe to read concurrently.

mi_block_t* _mi_page_ptr_unalign(const mi_page_t* page, const void* p) {

  mi_assert_internal(page!=NULL && p!=NULL);

  size_t diff = (uint8_t*)p - page->page_start;

  size_t adjust = 0;

  if mi_likely(page->block_size_shift != 0) {

    adjust = diff & (((size_t)1 << page->block_size_shift) - 1);

  }

  else {

    const size_t block_size = page->block_size;

    if mi_likely(block_size != 0) {

      adjust = diff % block_size;

    }

    else {

      _mi_error_message(EFAULT, "reading from invalid page, possibly corrupted meta-data (address=%p, page=%p)\n", p, page);

    }

  }

  return (mi_block_t*)((uintptr_t)p - adjust);

}

static inline mi_block_t* mi_validate_block_from_ptr( const mi_page_t* page, const void* p ) {

  mi_assert(_mi_page_ptr_unalign(page,p) == (mi_block_t*)p); // should never be an interior pointer

  #if MI_SECURE > 0

  // in secure mode we always unalign to guard against free-ing interior pointers

  return _mi_page_ptr_unalign(page,p);

  #else

  MI_UNUSED(page);

  return (mi_block_t*)p;

  #endif

}

// forward declaration for a MI_GUARDED build

#if MI_GUARDED

static void mi_block_unguard(mi_page_t* page, mi_block_t* block, void* p); // forward declaration

static inline bool mi_block_check_unguard(mi_page_t* page, mi_block_t* block, void* p) {

  if (mi_block_ptr_is_guarded(block, p)) {

    mi_block_unguard(page, block, p);

    return true;

  }

  else {

    return false;

  }

}

#else

static inline bool mi_block_check_unguard(mi_page_t* page, mi_block_t* block, void* p) {

  MI_UNUSED(page); MI_UNUSED(block); MI_UNUSED(p);

  return false;

}

#endif

// free a local pointer  (page parameter comes first for better codegen)

static void mi_decl_noinline mi_free_generic_local(mi_page_t* page, mi_segment_t* segment, void* p) mi_attr_noexcept {

  MI_UNUSED(segment);

  mi_block_t* const block = (mi_page_has_aligned(page) ? _mi_page_ptr_unalign(page, p) : mi_validate_block_from_ptr(page,p));

  const bool was_guarded = mi_block_check_unguard(page, block, p);

  mi_free_block_local(page, block, was_guarded, true /* track stats */, true /* check for a full page */);

}

// free a pointer owned by another thread (page parameter comes first for better codegen)

static void mi_decl_noinline mi_free_generic_mt(mi_page_t* page, mi_segment_t* segment, void* p) mi_attr_noexcept {

  mi_block_t* const block = _mi_page_ptr_unalign(page, p); // don't check `has_aligned` flag to avoid a race (issue #865)

  const bool was_guarded = mi_block_check_unguard(page, block, p);

  mi_free_block_mt(page, segment, block, p, was_guarded);

}

// generic free (for runtime integration)

void mi_decl_noinline _mi_free_generic(mi_segment_t* segment, mi_page_t* page, bool is_local, void* p) mi_attr_noexcept {

  if (is_local) mi_free_generic_local(page,segment,p);

           else mi_free_generic_mt(page,segment,p);

}

// Get the segment data belonging to a pointer

// This is just a single `and` in release mode but does further checks in debug mode

// (and secure mode) to see if this was a valid pointer.

static inline mi_segment_t* mi_checked_ptr_segment(const void* p, const char* msg)

{

  MI_UNUSED(msg);

  #if (MI_DEBUG>0)

  if mi_unlikely(((uintptr_t)p & (MI_INTPTR_SIZE - 1)) != 0 && !mi_option_is_enabled(mi_option_guarded_precise)) {

    _mi_error_message(EINVAL, "%s: invalid (unaligned) pointer: %p\n", msg, p);

    return NULL;

  }

  #endif

  mi_segment_t* const segment = _mi_ptr_segment(p);

  if mi_unlikely(segment==NULL) return segment;

  #if 0 && (MI_DEBUG>0)  // CPython: disabled, the warning is noisy and not actionable for Python allocations

  if mi_unlikely(!mi_is_in_heap_region(p)) {

  #if (MI_INTPTR_SIZE == 8 && defined(__linux__))

    if (((uintptr_t)p >> 40) != 0x7F) { // linux tends to align large blocks above 0x7F000000000 (issue #640)

  #else

    {

  #endif

      _mi_warning_message("%s: pointer might not point to a valid heap region: %p\n"

        "(this may still be a valid very large allocation (over 64MiB))\n", msg, p);

      if mi_likely(_mi_ptr_cookie(segment) == segment->cookie) {

        _mi_warning_message("(yes, the previous pointer %p was valid after all)\n", p);

      }

    }

  }

  #endif

  #if (MI_DEBUG>0 || MI_SECURE>=3)

  if mi_unlikely(_mi_ptr_cookie(segment) != segment->cookie) {

    _mi_error_message(EINVAL, "%s: pointer does not point to a valid heap space: %p\n", msg, p);

    return NULL;

  }

  #endif

  return segment;

}

// Free a block

// Fast path written carefully to prevent register spilling on the stack

static inline void mi_free_ex(void* p, size_t* pblock_size) mi_attr_noexcept

{

  mi_segment_t* const segment = mi_checked_ptr_segment(p,"mi_free");

  if mi_unlikely(segment==NULL) {

    if (pblock_size!=NULL) { *pblock_size = 0; }

    return;

  }

  const bool is_local = (_mi_prim_thread_id() == mi_atomic_load_relaxed(&segment->thread_id));

  mi_page_t* const page = _mi_segment_page_of(segment, p);

  if (pblock_size!=NULL) { *pblock_size = mi_page_block_size(page); }

  if mi_likely(is_local) {                        // thread-local free?

    if mi_likely(page->flags.full_aligned == 0) { // and it is not a full page (full pages need to move from the full bin), nor has aligned blocks (aligned blocks need to be unaligned)

      // thread-local, aligned, and not a full page

      mi_block_t* const block = mi_validate_block_from_ptr(page,p);

      mi_free_block_local(page, block, false /* is guarded */, true /* track stats */, false /* no need to check if the page is full */);

    }

    else {

      // page is full or contains (inner) aligned blocks; use generic path

      mi_free_generic_local(page, segment, p);

    }

  }

  else {

    // not thread-local; use generic path

    mi_free_generic_mt(page, segment, p);

  }

}

void mi_free(void* p) mi_attr_noexcept {

  mi_free_ex(p,NULL);

}

void mi_ufree(void* p, size_t* pblock_size) mi_attr_noexcept {

  mi_free_ex(p,pblock_size);

}

void mi_free_small(void* p) mi_attr_noexcept {

  mi_free(p);

}

// return true if successful

bool _mi_free_delayed_block(mi_block_t* block) {

  // get segment and page

  mi_assert_internal(block!=NULL);

  const mi_segment_t* const segment = _mi_ptr_segment(block);

  mi_assert_internal(_mi_ptr_cookie(segment) == segment->cookie);

#ifndef Py_GIL_DISABLED

  // CPython: the GC traverses heaps of other threads, which can trigger this assert.

  mi_assert_internal(_mi_thread_id() == segment->thread_id);

#endif

  mi_page_t* const page = _mi_segment_page_of(segment, block);

  // Clear the no-delayed flag so delayed freeing is used again for this page.

  // This must be done before collecting the free lists on this page -- otherwise

  // some blocks may end up in the page `thread_free` list with no blocks in the

  // heap `thread_delayed_free` list which may cause the page to be never freed!

  // (it would only be freed if we happen to scan it in `mi_page_queue_find_free_ex`)

  if (!_mi_page_try_use_delayed_free(page, MI_USE_DELAYED_FREE, false /* dont overwrite never delayed */)) {

    return false;

  }

  // collect all other non-local frees (move from `thread_free` to `free`) to ensure up-to-date `used` count

  _mi_page_free_collect(page, false);

  // and free the block (possibly freeing the page as well since `used` is updated)

  mi_free_block_local(page, block, false /* is guarded */, false /* stats have already been adjusted */, true /* check for a full page */);

  return true;

}

// ------------------------------------------------------

// Multi-threaded Free (`_mt`)

// ------------------------------------------------------

// Push a block that is owned by another thread on its page-local thread free

// list or it's heap delayed free list. Such blocks are later collected by

// the owning thread in `_mi_free_delayed_block`.

static void mi_decl_noinline mi_free_block_delayed_mt( mi_page_t* page, mi_block_t* block )

{

  // Try to put the block on either the page-local thread free list,

  // or the heap delayed free list (if this is the first non-local free in that page)

  mi_thread_free_t tfreex;

  bool use_delayed;

  mi_thread_free_t tfree = mi_atomic_load_relaxed(&page->xthread_free);

  do {

    use_delayed = (mi_tf_delayed(tfree) == MI_USE_DELAYED_FREE);

    if mi_unlikely(use_delayed) {

      // unlikely: this only happens on the first concurrent free in a page that is in the full list

      tfreex = mi_tf_set_delayed(tfree,MI_DELAYED_FREEING);

    }

    else {

      // usual: directly add to page thread_free list

      mi_block_set_next(page, block, mi_tf_block(tfree));

      tfreex = mi_tf_set_block(tfree,block);

    }

  } while (!mi_atomic_cas_weak_release(&page->xthread_free, &tfree, tfreex));

  // If this was the first non-local free, we need to push it on the heap delayed free list instead

  if mi_unlikely(use_delayed) {

    // racy read on `heap`, but ok because MI_DELAYED_FREEING is set (see `mi_heap_delete` and `mi_heap_collect_abandon`)

    mi_heap_t* const heap = (mi_heap_t*)(mi_atomic_load_acquire(&page->xheap)); //mi_page_heap(page);

    mi_assert_internal(heap != NULL);

    if (heap != NULL) {

      // add to the delayed free list of this heap. (do this atomically as the lock only protects heap memory validity)

      mi_block_t* dfree = mi_atomic_load_ptr_relaxed(mi_block_t, &heap->thread_delayed_free);

      do {

        mi_block_set_nextx(heap,block,dfree, heap->keys);

      } while (!mi_atomic_cas_ptr_weak_release(mi_block_t,&heap->thread_delayed_free, &dfree, block));

    }

    // and reset the MI_DELAYED_FREEING flag

    tfree = mi_atomic_load_relaxed(&page->xthread_free);

    do {

      tfreex = tfree;

      mi_assert_internal(mi_tf_delayed(tfree) == MI_DELAYED_FREEING);

      tfreex = mi_tf_set_delayed(tfree,MI_NO_DELAYED_FREE);

    } while (!mi_atomic_cas_weak_release(&page->xthread_free, &tfree, tfreex));

  }

}

// Multi-threaded free (`_mt`) (or free in huge block if compiled with MI_HUGE_PAGE_ABANDON)

static void mi_decl_noinline mi_free_block_mt(mi_page_t* page, mi_segment_t* segment, mi_block_t* block, void* p, bool was_guarded)

{

  MI_UNUSED(was_guarded);

  // first see if the segment was abandoned and if we can reclaim it into our thread

  if (_mi_option_get_fast(mi_option_abandoned_reclaim_on_free) != 0 &&

      #if MI_HUGE_PAGE_ABANDON

      segment->page_kind != MI_PAGE_HUGE &&

      #endif

      mi_atomic_load_relaxed(&segment->thread_id) == 0 &&  // segment is abandoned?

      mi_prim_get_default_heap() != (mi_heap_t*)&_mi_heap_empty) // and we did not already exit this thread (without this check, a fresh heap will be initalized (issue #944))

  {

    // the segment is abandoned, try to reclaim it into our heap

    if (_mi_segment_attempt_reclaim(mi_heap_get_default(), segment)) {

      mi_assert_internal(_mi_thread_id() == mi_atomic_load_relaxed(&segment->thread_id));

      mi_assert_internal(mi_heap_get_default()->tld->segments.subproc == segment->subproc);

      mi_free(p);  // recursively free as now it will be a local free in our heap

      return;

    }

  }

  // The padding check may access the non-thread-owned page for the key values.

  // that is safe as these are constant and the page won't be freed (as the block is not freed yet).

  if (!was_guarded) { mi_check_padding(page, block); }

  // adjust stats (after padding check and potentially recursive `mi_free` above)

  mi_stat_free(page, block);    // stat_free may access the padding

  mi_track_free_size(block, mi_page_usable_size_of(page,block,was_guarded));

  // for small size, ensure we can fit the delayed thread pointers without triggering overflow detection

  _mi_padding_shrink(page, block, sizeof(mi_block_t));

  if (segment->kind == MI_SEGMENT_HUGE) {

    #if MI_HUGE_PAGE_ABANDON

    // huge page segments are always abandoned and can be freed immediately

    _mi_segment_huge_page_free(segment, page, block);

    return;

    #else

    // huge pages are special as they occupy the entire segment

    // as these are large we reset the memory occupied by the page so it is available to other threads

    // (as the owning thread needs to actually free the memory later).

    _mi_segment_huge_page_reset(segment, page, block);

    #endif

  }

  else {

    #if (MI_DEBUG>0) && !MI_TRACK_ENABLED  && !MI_TSAN       // note: when tracking, cannot use mi_usable_size with multi-threading

    size_t dbgsize = mi_usable_size(block); if (dbgsize > 1*MI_MiB) { dbgsize = 1*MI_MiB; }

    mi_debug_fill(page, block, MI_DEBUG_FREED, dbgsize);

    #endif

  }

  // and finally free the actual block by pushing it on the owning heap

  // thread_delayed free list (or heap delayed free list)

  mi_free_block_delayed_mt(page,block);

}

// ------------------------------------------------------

// Usable size

// ------------------------------------------------------

// Bytes available in a block

static size_t mi_decl_noinline mi_page_usable_aligned_size_of(const mi_page_t* page, const void* p) mi_attr_noexcept {

  const mi_block_t* block = _mi_page_ptr_unalign(page, p);

  const bool is_guarded = mi_block_ptr_is_guarded(block,p);

  const size_t size = mi_page_usable_size_of(page, block, is_guarded);

  mi_assert_internal((void*)p >= (void*)block);

  const size_t adjust = (uint8_t*)p - (uint8_t*)block;

  mi_assert_internal(adjust <= size);

  const size_t aligned_size = (adjust <= size ? size - adjust : 0);  // size can be zero if the padding is corrupted

  return aligned_size;

}

static inline mi_page_t* mi_validate_ptr_page(const void* p, const char* msg) {

  const mi_segment_t* const segment = mi_checked_ptr_segment(p, msg);

  if mi_unlikely(segment==NULL) return NULL;

  mi_page_t* const page = _mi_segment_page_of(segment, p);

  return page;

}

size_t _mi_page_usable_size(const mi_page_t* page, const void* p) mi_attr_noexcept {

  if mi_unlikely(page==NULL) return 0;

  mi_assert_internal(mi_validate_ptr_page(p,"_mi_page_usable_size") == page);

  if mi_likely(!mi_page_has_aligned(page)) {

    const mi_block_t* block = mi_validate_block_from_ptr(page,p);

    return mi_page_usable_size_of(page, block, false /* is guarded */);

  }

  else {

    // split out to separate routine for improved code generation

    return mi_page_usable_aligned_size_of(page, p);

  }

}

mi_decl_nodiscard size_t mi_usable_size(const void* p) mi_attr_noexcept {

  const mi_page_t* const page = mi_validate_ptr_page(p,"mi_usable_size");

  return _mi_page_usable_size(page,p);

}

// ------------------------------------------------------

// Free variants

// ------------------------------------------------------

void mi_free_size(void* p, size_t size) mi_attr_noexcept {

  MI_UNUSED_RELEASE(size);

  #if MI_DEBUG

  const mi_page_t* const page = mi_validate_ptr_page(p,"mi_free_size");

  const size_t available = _mi_page_usable_size(page,p);

  mi_assert(p == NULL || size <= available || available == 0 /* invalid pointer */ );

  #endif

  mi_free(p);

}

void mi_free_size_aligned(void* p, size_t size, size_t alignment) mi_attr_noexcept {

  MI_UNUSED_RELEASE(alignment);

  mi_assert(((uintptr_t)p % alignment) == 0);

  mi_free_size(p,size);

}

void mi_free_aligned(void* p, size_t alignment) mi_attr_noexcept {

  MI_UNUSED_RELEASE(alignment);

  mi_assert(((uintptr_t)p % alignment) == 0);

  mi_free(p);

}

// ------------------------------------------------------

// Check for double free in secure and debug mode

// This is somewhat expensive so only enabled for secure mode 4

// ------------------------------------------------------

#if MI_CHECK_DOUBLE_FREE

// linear check if the free list contains a specific element

static bool mi_list_contains(const mi_page_t* page, const mi_block_t* list, const mi_block_t* elem, const char* list_kind) {

  const size_t max_count = page->capacity;      // can never hold more blocks than the capacity

  size_t count = 0;

  while (list != NULL && count <= max_count) {  // double-free can create cycles so we limit the number of iterations

    if (elem==list) return true;

    list = mi_block_next(page, list);

    count++;

  }

  if mi_unlikely(count > max_count) {

    _mi_error_message(EFAULT, "corrupted %s list (possibly due to a double free)\n", list_kind);

  }

  return false;

}

static mi_decl_noinline bool mi_check_is_double_freex(const mi_page_t* page, const mi_block_t* block) {

  // The decoded value is in the same page (or NULL).

  // Walk the free lists to verify positively if it is already freed

  if (mi_list_contains(page, page->free, block, "free") ||

      mi_list_contains(page, page->local_free, block, "local free") ||

      mi_list_contains(page, mi_page_thread_free(page), block, "thread free"))

  {

    _mi_error_message(EAGAIN, "double free detected of block %p with size %zu\n", block, mi_page_block_size(page));

    return true;

  }

  return false;

}

#define mi_track_page(page,access)  { size_t psize; void* pstart = _mi_page_start(_mi_page_segment(page),page,&psize); mi_track_mem_##access( pstart, psize); }

// Used for double free checking to avoid checking free lists too frequently

static inline bool mi_block_could_be_double_free(const mi_page_t* page, const mi_block_t* block) {

  mi_block_t* n = mi_block_nextx(page,block,page->keys);

  return (((uintptr_t)n & (MI_INTPTR_SIZE-1))==0 &&  // quick check: aligned pointer?

          (n==NULL || mi_is_in_same_page(block,n))); // quick check: in the same page or NULL?

}

static inline bool mi_check_is_double_free(const mi_page_t* page, const mi_block_t* block) {

  if mi_unlikely(mi_block_could_be_double_free(page,block))  // quick check: next field is aligned in the same page or NULL?

  {

    // Suspicious: decoded value a in block is in the same page (or NULL) -- maybe a double free?

    // (continue in separate function to improve code generation)

    return mi_check_is_double_freex(page, block);

  }

  else return false;

}

#else

static inline bool mi_check_is_double_free(const mi_page_t* page, const mi_block_t* block) {

  MI_UNUSED(page);

  MI_UNUSED(block);

  return false;

}

#endif

// ---------------------------------------------------------------------------

// Check for heap block overflow by setting up padding at the end of the block

// ---------------------------------------------------------------------------

#if MI_PADDING // && !MI_TRACK_ENABLED

static bool mi_page_decode_padding(const mi_page_t* page, const mi_block_t* block, size_t* delta, size_t* bsize) {

  *bsize = mi_page_usable_block_size(page);

  const mi_padding_t* const padding = (mi_padding_t*)((uint8_t*)block + *bsize);

  mi_track_mem_defined(padding,sizeof(mi_padding_t));

  *delta = padding->delta;

  uint32_t canary = padding->canary;

  uintptr_t keys[2];

  keys[0] = page->keys[0];

  keys[1] = page->keys[1];

  bool ok = (mi_ptr_encode_canary(page,block,keys) == canary && *delta <= *bsize);

  mi_track_mem_noaccess(padding,sizeof(mi_padding_t));

  return ok;

}

// Return the exact usable size of a block.

static size_t mi_page_usable_size_of(const mi_page_t* page, const mi_block_t* block, bool is_guarded) {

  if (is_guarded) {

    const size_t bsize = mi_page_block_size(page);

    return (bsize - _mi_os_page_size());

  }

  else {

    size_t bsize;

    size_t delta;

    bool ok = mi_page_decode_padding(page, block, &delta, &bsize);

    mi_assert_internal(ok); mi_assert_internal(delta <= bsize);

    return (ok ? bsize - delta : 0);

  }

}

// When a non-thread-local block is freed, it becomes part of the thread delayed free

// list that is freed later by the owning heap. If the exact usable size is too small to

// contain the pointer for the delayed list, then shrink the padding (by decreasing delta)

// so it will later not trigger an overflow error in `mi_free_block`.

void _mi_padding_shrink(const mi_page_t* page, const mi_block_t* block, const size_t min_size) {

  size_t bsize;

  size_t delta;

  bool ok = mi_page_decode_padding(page, block, &delta, &bsize);

  mi_assert_internal(ok);

  if (!ok || (bsize - delta) >= min_size) return;  // usually already enough space

  mi_assert_internal(bsize >= min_size);

  if (bsize < min_size) return;  // should never happen

  size_t new_delta = (bsize - min_size);

  mi_assert_internal(new_delta < bsize);

  mi_padding_t* padding = (mi_padding_t*)((uint8_t*)block + bsize);

  mi_track_mem_defined(padding,sizeof(mi_padding_t));

  padding->delta = (uint32_t)new_delta;

  mi_track_mem_noaccess(padding,sizeof(mi_padding_t));

}

#else

static size_t mi_page_usable_size_of(const mi_page_t* page, const mi_block_t* block, bool is_guarded) {

  MI_UNUSED(block);

  if (is_guarded) {

    const size_t bsize = mi_page_block_size(page);

    return (bsize - _mi_os_page_size());

  }

  else {

    return mi_page_usable_block_size(page);

  }

}

void _mi_padding_shrink(const mi_page_t* page, const mi_block_t* block, const size_t min_size) {

  MI_UNUSED(page); MI_UNUSED(block); MI_UNUSED(min_size);

}

#endif

#if MI_PADDING && MI_PADDING_CHECK

static bool mi_verify_padding(const mi_page_t* page, const mi_block_t* block, size_t* size, size_t* wrong) {

  size_t bsize;

  size_t delta;

  bool ok = mi_page_decode_padding(page, block, &delta, &bsize);

  *size = *wrong = bsize;

  if (!ok) return false;

  mi_assert_internal(bsize >= delta);

  *size = bsize - delta;

  if (!mi_page_is_huge(page)) {

    uint8_t* fill = (uint8_t*)block + bsize - delta;

    const size_t maxpad = (delta > MI_MAX_ALIGN_SIZE ? MI_MAX_ALIGN_SIZE : delta); // check at most the first N padding bytes

    mi_track_mem_defined(fill, maxpad);

    for (size_t i = 0; i < maxpad; i++) {

      if (fill[i] != MI_DEBUG_PADDING) {

        *wrong = bsize - delta + i;

        ok = false;

        break;

      }

    }

    mi_track_mem_noaccess(fill, maxpad);

  }

  return ok;

}

static void mi_check_padding(const mi_page_t* page, const mi_block_t* block) {

  size_t size;

  size_t wrong;

  if (!mi_verify_padding(page,block,&size,&wrong)) {

    _mi_error_message(EFAULT, "buffer overflow in heap block %p of size %zu: write after %zu bytes\n", block, size, wrong );

  }

}

#else

static void mi_check_padding(const mi_page_t* page, const mi_block_t* block) {

  MI_UNUSED(page);

  MI_UNUSED(block);

}

#endif

// 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) {

  MI_UNUSED(block);

  mi_heap_t* const heap = mi_heap_get_default();

  const size_t bsize = mi_page_usable_block_size(page);

  // #if (MI_STAT>1)

  // const size_t usize = mi_page_usable_size_of(page, block);

  // mi_heap_stat_decrease(heap, malloc_requested, usize);

  // #endif

  if (bsize <= MI_MEDIUM_OBJ_SIZE_MAX) {

    mi_heap_stat_decrease(heap, malloc_normal, bsize);

    #if (MI_STAT > 1)

    mi_heap_stat_decrease(heap, malloc_bins[_mi_bin(bsize)], 1);

    #endif

  }

  //else if (bsize <= MI_LARGE_OBJ_SIZE_MAX) {

  //  mi_heap_stat_decrease(heap, malloc_large, bsize);

  //}

  else {

    mi_heap_stat_decrease(heap, malloc_huge, bsize);

  }

}

#else

static void mi_stat_free(const mi_page_t* page, const mi_block_t* block) {

  MI_UNUSED(page); MI_UNUSED(block);

}

#endif

// Remove guard page when building with MI_GUARDED

#if MI_GUARDED

static void mi_block_unguard(mi_page_t* page, mi_block_t* block, void* p) {

  MI_UNUSED(p);

  mi_assert_internal(mi_block_ptr_is_guarded(block, p));

  mi_assert_internal(mi_page_has_aligned(page));

  mi_assert_internal((uint8_t*)p - (uint8_t*)block >= (ptrdiff_t)sizeof(mi_block_t));

  mi_assert_internal(block->next == MI_BLOCK_TAG_GUARDED);

  const size_t bsize = mi_page_block_size(page);

  const size_t psize = _mi_os_page_size();

  mi_assert_internal(bsize > psize);

  mi_assert_internal(_mi_page_segment(page)->allow_decommit);

  void* gpage = (uint8_t*)block + bsize - psize;

  mi_assert_internal(_mi_is_aligned(gpage, psize));

  _mi_os_unprotect(gpage, psize);

}

#endif