/*
  This is a version (aka dlmalloc) of malloc/free/realloc written by
  Doug Lea and released to the public domain, as explained at
  http://creativecommons.org/publicdomain/zero/1.0/ Send questions,
  comments, complaints, performance data, etc to dl@cs.oswego.edu
*/

/*
  C++ version by Gregory Popovitch (greg7mdp@gmail.com) and released 
  to the public domain as well, as explained at
  http://creativecommons.org/publicdomain/zero/1.0/.

  based on Version 2.8.6 Wed Aug 29 06:57:58 2012  Doug Lea
           (ftp://gee.cs.oswego.edu/pub/misc/malloc.c)
*/

/*
  ========================================================================
  To make a fully customizable malloc.h header file, cut everything
  above this line, put into file malloc.h, edit to suit, and #include it
  on the next line, as well as in programs that use this malloc.
  ========================================================================
*/
#include <stdint.h>
#include <platform.h>
#include <log.h>

#include "../Heap.h"
#include "dlmalloc.h"

/*------------------------------ internal #includes ---------------------- */

#ifdef DEBUG
    #if ABORT_ON_ASSERT_FAILURE
        #undef assert
        #define assert(x) if(!(x)) ABORT
    #else /* ABORT_ON_ASSERT_FAILURE */
        #include <assert.h>
    #endif /* ABORT_ON_ASSERT_FAILURE */
#else  /* DEBUG */
    #ifndef assert
        #define assert(x)
    #endif
    #define DEBUG 0
#endif /* DEBUG */

#include <string.h>      /* for memset etc */


#ifndef LOCK_AT_FORK
    #define LOCK_AT_FORK 0
#endif


/* ------------------- size_t and alignment properties -------------------- */

/* The byte and bit size of a size_t */
#define SIZE_T_BITSIZE      (sizeof(size_t) << 3)

/* Some constants coerced to size_t */
/* Annoying but necessary to avoid errors on some platforms */
#define HALF_MAX_SIZE_T     (MAX_SIZE_T / 2U)

// The bit mask value corresponding to MALLOC_ALIGNMENT
#define CHUNK_ALIGN_MASK    (MALLOC_ALIGNMENT - 1)

// True if address a has acceptable alignment
bool is_aligned(void *p) { return ((size_t)p & CHUNK_ALIGN_MASK) == 0; }

// the number of bytes to offset an address to align it
size_t align_offset(void *p)
{
    return (((size_t)p & CHUNK_ALIGN_MASK) == 0) ? 0 :
        ((MALLOC_ALIGNMENT - ((size_t)p & CHUNK_ALIGN_MASK)) & CHUNK_ALIGN_MASK);
}

/* -------------------------- MMAP preliminaries ------------------------- */

/*
   If HAVE_MORECORE or HAVE_MMAP are false, we just define calls and
   checks to fail so compiler optimizer can delete code rather than
   using so many "#if"s.
*/


/* MORECORE and MMAP must return MFAIL on failure */
#define MFAIL                ((void*)(MAX_SIZE_T))
#define CMFAIL               ((char*)(MFAIL)) /* defined for convenience */

#if HAVE_MMAP

#define MUNMAP_DEFAULT(a, s)  mem::Heap::fakeMunmap((a), (s))
#define MMAP_DEFAULT(s)       mem::Heap::fakeMmap((s))

#define DIRECT_MMAP_DEFAULT(s) MMAP_DEFAULT(s)

#endif /* HAVE_MMAP */

#if HAVE_MREMAP
#define MREMAP_DEFAULT(addr, osz, nsz, mv) mremap((addr), (osz), (nsz), (mv))
#endif /* HAVE_MREMAP */

/**
 * Define CALL_MORECORE
 */
#if HAVE_MORECORE
    #ifdef MORECORE
        #define CALL_MORECORE(S)    MORECORE(S)
    #else  /* MORECORE */
        #define CALL_MORECORE(S)    MORECORE_DEFAULT(S)
    #endif /* MORECORE */
#else  /* HAVE_MORECORE */
    #define CALL_MORECORE(S)        MFAIL
#endif /* HAVE_MORECORE */

/**
 * Define CALL_MMAP/CALL_MUNMAP/CALL_DIRECT_MMAP
 */
#if HAVE_MMAP
    #define USE_MMAP_BIT            1

    #ifdef MMAP
        #define CALL_MMAP(s)        MMAP(s)
    #else /* MMAP */
        #define CALL_MMAP(s)        MMAP_DEFAULT(s)
    #endif /* MMAP */
    #ifdef MUNMAP
        #define CALL_MUNMAP(a, s)   MUNMAP((a), (s))
    #else /* MUNMAP */
        #define CALL_MUNMAP(a, s)   MUNMAP_DEFAULT((a), (s))
    #endif /* MUNMAP */
    #ifdef DIRECT_MMAP
        #define CALL_DIRECT_MMAP(s) DIRECT_MMAP(s)
    #else /* DIRECT_MMAP */
        #define CALL_DIRECT_MMAP(s) DIRECT_MMAP_DEFAULT(s)
    #endif /* DIRECT_MMAP */
#else  /* HAVE_MMAP */
    #define USE_MMAP_BIT            0

    #define MMAP(s)                 MFAIL
    #define MUNMAP(a, s)            (-1)
    #define DIRECT_MMAP(s)          MFAIL
    #define CALL_DIRECT_MMAP(s)     DIRECT_MMAP(s)
    #define CALL_MMAP(s)            MMAP(s)
    #define CALL_MUNMAP(a, s)       MUNMAP((a), (s))
#endif /* HAVE_MMAP */

/**
 * Define CALL_MREMAP
 */
#if HAVE_MMAP && HAVE_MREMAP
    #ifdef MREMAP
        #define CALL_MREMAP(addr, osz, nsz, mv) MREMAP((addr), (osz), (nsz), (mv))
    #else /* MREMAP */
        #define CALL_MREMAP(addr, osz, nsz, mv) MREMAP_DEFAULT((addr), (osz), (nsz), (mv))
    #endif /* MREMAP */
#else  /* HAVE_MMAP && HAVE_MREMAP */
    #define CALL_MREMAP(addr, osz, nsz, mv)     MFAIL
#endif /* HAVE_MMAP && HAVE_MREMAP */

/* mstate bit set if continguous morecore disabled or failed */
#define USE_NONCONTIGUOUS_BIT (4U)

/* segment bit set in create_mspace_with_base */
#define EXTERN_BIT            (8U)


/* --------------------------- Lock preliminaries ------------------------ */

/*
  When locks are defined, there is one global lock, plus
  one per-mspace lock.

  The global lock_ensures that mparams.magic and other unique
  mparams values are initialized only once. It also protects
  sequences of calls to MORECORE.  In many cases sys_alloc requires
  two calls, that should not be interleaved with calls by other
  threads.  This does not protect against direct calls to MORECORE
  by other threads not using this lock, so there is still code to
  cope the best we can on interference.

  Per-mspace locks surround calls to malloc, free, etc.
  By default, locks are simple non-reentrant mutexes.

  Because lock-protected regions generally have bounded times, it is
  OK to use the supplied simple spinlocks. Spinlocks are likely to
  improve performance for lightly contended applications, but worsen
  performance under heavy contention.

  If USE_LOCKS is > 1, the definitions of lock routines here are
  bypassed, in which case you will need to define the type MLOCK_T,
  and at least INITIAL_LOCK, DESTROY_LOCK, ACQUIRE_LOCK, RELEASE_LOCK
  and TRY_LOCK.  You must also declare a
    static MLOCK_T malloc_global_mutex = { initialization values };.

*/

#if !USE_LOCKS
#define USE_LOCK_BIT               (0U)
#define INITIAL_LOCK(l)            (0)
#define DESTROY_LOCK(l)            (0)
#define ACQUIRE_MALLOC_GLOBAL_LOCK()
#define RELEASE_MALLOC_GLOBAL_LOCK()

#else
#if USE_LOCKS > 1
/* -----------------------  User-defined locks ------------------------ */
/* Define your own lock implementation here */
/* #define INITIAL_LOCK(lk)  ... */
/* #define DESTROY_LOCK(lk)  ... */
/* #define ACQUIRE_LOCK(lk)  ... */
/* #define RELEASE_LOCK(lk)  ... */
/* #define TRY_LOCK(lk) ... */
/* static MLOCK_T malloc_global_mutex = ... */

#elif USE_SPIN_LOCKS

/* First, define CAS_LOCK and CLEAR_LOCK on ints */
/* Note CAS_LOCK defined to return 0 on success */

#if defined(__GNUC__)&& (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 1))
#define CAS_LOCK(sl)     __sync_lock_test_and_set(sl, 1)
#define CLEAR_LOCK(sl)   __sync_lock_release(sl)

#elif (defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__)))
/* Custom spin locks for older gcc on x86 */
static FORCEINLINE int x86_cas_lock(int *sl) {
  int ret;
  int val = 1;
  int cmp = 0;
  __asm__ __volatile__  ("lock; cmpxchgl %1, %2"
                         : "=a" (ret)
                         : "r" (val), "m" (*(sl)), "0"(cmp)
                         : "memory", "cc");
  return ret;
}

static FORCEINLINE void x86_clear_lock(int* sl) {
  assert(*sl != 0);
  int prev = 0;
  int ret;
  __asm__ __volatile__ ("lock; xchgl %0, %1"
                        : "=r" (ret)
                        : "m" (*(sl)), "0"(prev)
                        : "memory");
}

#define CAS_LOCK(sl)     x86_cas_lock(sl)
#define CLEAR_LOCK(sl)   x86_clear_lock(sl)

#else /* Win32 MSC */
#define CAS_LOCK(sl)     interlockedexchange(sl, 1)
#define CLEAR_LOCK(sl)   interlockedexchange (sl, 0)

#endif /* ... gcc spins locks ... */

/* How to yield for a spin lock */
#define SPINS_PER_YIELD       63
#if !defined(LACKS_SCHED_H)
#define SPIN_LOCK_YIELD   sched::Thread::yield();
#else
#define SPIN_LOCK_YIELD
#endif /* ... yield ... */

#if !defined(USE_RECURSIVE_LOCKS) || USE_RECURSIVE_LOCKS == 0
/* Plain spin locks use single word (embedded in malloc_states) */
static int spin_acquire_lock(unsigned *sl) {
    int spins = 0;
    while (*(volatile unsigned *)sl != 0 || CAS_LOCK(sl)) {
        if ((++spins & SPINS_PER_YIELD) == 0) {
            SPIN_LOCK_YIELD;
        }
    }
    return 0;
}

#define MLOCK_T               unsigned
#define TRY_LOCK(sl)          !CAS_LOCK(sl)
#define RELEASE_LOCK(sl)      CLEAR_LOCK(sl)
#define ACQUIRE_LOCK(sl)      (CAS_LOCK(sl)? spin_acquire_lock(sl) : 0)
#define INITIAL_LOCK(sl)      (*sl = 0)
#define DESTROY_LOCK(sl)      (0)
static MLOCK_T malloc_global_mutex = 0;

#else /* USE_RECURSIVE_LOCKS */
/* types for lock owners */
#ifdef WIN32
#define THREAD_ID_T           DWORD
#define CURRENT_THREAD        GetCurrentThreadId()
#define EQ_OWNER(X,Y)         ((X) == (Y))
#else
/*
  Note: the following assume that pthread_t is a type that can be
  initialized to (casted) zero. If this is not the case, you will need to
  somehow redefine these or not use spin locks.
*/
#define THREAD_ID_T           pthread_t
#define CURRENT_THREAD        pthread_self()
#define EQ_OWNER(X,Y)         pthread_equal(X, Y)
#endif

struct malloc_recursive_lock {
    int sl;
    unsigned int c;
    THREAD_ID_T threadid;
};

#define MLOCK_T  struct malloc_recursive_lock
static MLOCK_T malloc_global_mutex = { 0, 0, (THREAD_ID_T)0};

static FORCEINLINE void recursive_release_lock(MLOCK_T *lk) {
    assert(lk->sl != 0);
    if (--lk->c == 0) {
        CLEAR_LOCK(&lk->sl);
    }
}

static FORCEINLINE int recursive_acquire_lock(MLOCK_T *lk) {
    THREAD_ID_T mythreadid = CURRENT_THREAD;
    int spins = 0;
    for (;;) {
        if (*((volatile int *)(&lk->sl)) == 0) {
            if (!CAS_LOCK(&lk->sl)) {
                lk->threadid = mythreadid;
                lk->c = 1;
                return 0;
            }
        }
        else if (EQ_OWNER(lk->threadid, mythreadid)) {
            ++lk->c;
            return 0;
        }
        if ((++spins & SPINS_PER_YIELD) == 0) {
            SPIN_LOCK_YIELD;
        }
    }
}

static FORCEINLINE int recursive_try_lock(MLOCK_T *lk) {
    THREAD_ID_T mythreadid = CURRENT_THREAD;
    if (*((volatile int *)(&lk->sl)) == 0) {
        if (!CAS_LOCK(&lk->sl)) {
            lk->threadid = mythreadid;
            lk->c = 1;
            return 1;
        }
    }
    else if (EQ_OWNER(lk->threadid, mythreadid)) {
        ++lk->c;
        return 1;
    }
    return 0;
}

#define RELEASE_LOCK(lk)      recursive_release_lock(lk)
#define TRY_LOCK(lk)          recursive_try_lock(lk)
#define ACQUIRE_LOCK(lk)      recursive_acquire_lock(lk)
#define INITIAL_LOCK(lk)      ((lk)->threadid = (THREAD_ID_T)0, (lk)->sl = 0, (lk)->c = 0)
#define DESTROY_LOCK(lk)      (0)
#endif /* USE_RECURSIVE_LOCKS */

#elif defined(WIN32) /* Win32 critical sections */
#define MLOCK_T               CRITICAL_SECTION
#define ACQUIRE_LOCK(lk)      (EnterCriticalSection(lk), 0)
#define RELEASE_LOCK(lk)      LeaveCriticalSection(lk)
#define TRY_LOCK(lk)          TryEnterCriticalSection(lk)
#define INITIAL_LOCK(lk)      (!InitializeCriticalSectionAndSpinCount((lk), 0x80000000 | 4000))
#define DESTROY_LOCK(lk)      (DeleteCriticalSection(lk), 0)
#define NEED_GLOBAL_LOCK_INIT

static MLOCK_T malloc_global_mutex;
static volatile LONG malloc_global_mutex_status;

/* Use spin loop to initialize global lock */
static void init_malloc_global_mutex() {
  for (;;) {
    long stat = malloc_global_mutex_status;
    if (stat > 0)
      return;
    /* transition to < 0 while initializing, then to > 0) */
    if (stat == 0 &&
        interlockedcompareexchange(&malloc_global_mutex_status, (LONG)-1, (LONG)0) == 0) {
      InitializeCriticalSection(&malloc_global_mutex);
      interlockedexchange(&malloc_global_mutex_status, (LONG)1);
      return;
    }
    SleepEx(0, FALSE);
  }
}

#else /* pthreads-based locks */
#define MLOCK_T               pthread_mutex_t
#define ACQUIRE_LOCK(lk)      pthread_mutex_lock(lk)
#define RELEASE_LOCK(lk)      pthread_mutex_unlock(lk)
#define TRY_LOCK(lk)          (!pthread_mutex_trylock(lk))
#define INITIAL_LOCK(lk)      pthread_init_lock(lk)
#define DESTROY_LOCK(lk)      pthread_mutex_destroy(lk)

#if defined(USE_RECURSIVE_LOCKS) && USE_RECURSIVE_LOCKS != 0 && defined(linux) && !defined(PTHREAD_MUTEX_RECURSIVE)
/* Cope with old-style linux recursive lock initialization by adding */
/* skipped internal declaration from pthread.h */
extern int pthread_mutexattr_setkind_np __P ((pthread_mutexattr_t *__attr,
                                              int __kind));
#define PTHREAD_MUTEX_RECURSIVE PTHREAD_MUTEX_RECURSIVE_NP
#define pthread_mutexattr_settype(x,y) pthread_mutexattr_setkind_np(x,y)
#endif /* USE_RECURSIVE_LOCKS ... */

static MLOCK_T malloc_global_mutex = PTHREAD_MUTEX_INITIALIZER;

static int pthread_init_lock (MLOCK_T *lk) {
  pthread_mutexattr_t attr;
  if (pthread_mutexattr_init(&attr)) return 1;
#if defined(USE_RECURSIVE_LOCKS) && USE_RECURSIVE_LOCKS != 0
  if (pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE)) return 1;
#endif
  if (pthread_mutex_init(lk, &attr)) return 1;
  if (pthread_mutexattr_destroy(&attr)) return 1;
  return 0;
}

#endif /* ... lock types ... */

/* Common code for all lock types */
#define USE_LOCK_BIT               (2U)

#ifndef ACQUIRE_MALLOC_GLOBAL_LOCK
#define ACQUIRE_MALLOC_GLOBAL_LOCK()  ACQUIRE_LOCK(&malloc_global_mutex);
#endif

#ifndef RELEASE_MALLOC_GLOBAL_LOCK
#define RELEASE_MALLOC_GLOBAL_LOCK()  RELEASE_LOCK(&malloc_global_mutex);
#endif

#endif /* USE_LOCKS */

/* -----------------------  Chunk representations ------------------------ */

/*
  (The following includes lightly edited explanations by Colin Plumb.)

  The malloc_chunk declaration below is misleading (but accurate and
  necessary).  It declares a "view" into memory allowing access to
  necessary fields at known offsets from a given base.

  Chunks of memory are maintained using a `boundary tag' method as
  originally described by Knuth.  (See the paper by Paul Wilson
  ftp://ftp.cs.utexas.edu/pub/garbage/allocsrv.ps for a survey of such
  techniques.)  Sizes of free chunks are stored both in the front of
  each chunk and at the end.  This makes consolidating fragmented
  chunks into bigger chunks fast.  The head fields also hold bits
  representing whether chunks are free or in use.

  Here are some pictures to make it clearer.  They are "exploded" to
  show that the state of a chunk can be thought of as extending from
  the high 31 bits of the head field of its header through the
  prev_foot and PINUSE_BIT bit of the following chunk header.

  A chunk that's in use looks like:

   chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           | Size of previous chunk (if P = 0)                             |
           +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |P|
         | Size of this chunk                                         1| +-+
   mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |                                                               |
         +-                                                             -+
         |                                                               |
         +-                                                             -+
         |                                                               :
         +-      size - sizeof(size_t) available payload bytes          -+
         :                                                               |
 chunk-> +-                                                             -+
         |                                                               |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1|
       | Size of next chunk (may or may not be in use)               | +-+
 mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    And if it's free, it looks like this:

   chunk-> +-                                                             -+
           | User payload (must be in use, or we would have merged!)       |
           +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |P|
         | Size of this chunk                                         0| +-+
   mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         | Next pointer                                                  |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         | Prev pointer                                                  |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         |                                                               :
         +-      size - sizeof(struct chunk) unused bytes               -+
         :                                                               |
 chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         | Size of this chunk                                            |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0|
       | Size of next chunk (must be in use, or we would have merged)| +-+
 mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               :
       +- User payload                                                -+
       :                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                                                     |0|
                                                                     +-+
  Note that since we always merge adjacent free chunks, the chunks
  adjacent to a free chunk must be in use.

  Given a pointer to a chunk (which can be derived trivially from the
  payload pointer) we can, in O(1) time, find out whether the adjacent
  chunks are free, and if so, unlink them from the lists that they
  are on and merge them with the current chunk.

  Chunks always begin on even word boundaries, so the mem portion
  (which is returned to the user) is also on an even word boundary, and
  thus at least double-word aligned.

  The P (PINUSE_BIT) bit, stored in the unused low-order bit of the
  chunk size (which is always a multiple of two words), is an in-use
  bit for the *previous* chunk.  If that bit is *clear*, then the
  word before the current chunk size contains the previous chunk
  size, and can be used to find the front of the previous chunk.
  The very first chunk allocated always has this bit set, preventing
  access to non-existent (or non-owned) memory. If pinuse is set for
  any given chunk, then you CANNOT determine the size of the
  previous chunk, and might even get a memory addressing fault when
  trying to do so.

  The C (CINUSE_BIT) bit, stored in the unused second-lowest bit of
  the chunk size redundantly records whether the current chunk is
  inuse (unless the chunk is mmapped). This redundancy enables usage
  checks within free and realloc, and reduces indirection when freeing
  and consolidating chunks.

  Each freshly allocated chunk must have both cinuse and pinuse set.
  That is, each allocated chunk borders either a previously allocated
  and still in-use chunk, or the base of its memory arena. This is
  ensured by making all allocations from the `lowest' part of any
  found chunk.  Further, no free chunk physically borders another one,
  so each free chunk is known to be preceded and followed by either
  inuse chunks or the ends of memory.

  Note that the `foot' of the current chunk is actually represented
  as the prev_foot of the NEXT chunk. This makes it easier to
  deal with alignments etc but can be very confusing when trying
  to extend or adapt this code.

  The exceptions to all this are

     1. The special chunk `top' is the top-most available chunk (i.e.,
        the one bordering the end of available memory). It is treated
        specially.  Top is never included in any bin, is used only if
        no other chunk is available, and is released back to the
        system if it is very large (see M_TRIM_THRESHOLD).  In effect,
        the top chunk is treated as larger (and thus less well
        fitting) than any other available chunk.  The top chunk
        doesn't update its trailing size field since there is no next
        contiguous chunk that would have to index off it. However,
        space is still allocated for it (TOP_FOOT_SIZE) to enable
        separation or merging when space is extended.

     3. Chunks allocated via mmap, have both cinuse and pinuse bits
        cleared in their head fields.  Because they are allocated
        one-by-one, each must carry its own prev_foot field, which is
        also used to hold the offset this chunk has within its mmapped
        region, which is needed to preserve alignment. Each mmapped
        chunk is trailed by the first two fields of a fake next-chunk
        for sake of usage checks.

*/

#define PINUSE_BIT          1
#define CINUSE_BIT          2
#define FLAG4_BIT           4
#define INUSE_BITS          (PINUSE_BIT | CINUSE_BIT)
#define FLAG_BITS           (PINUSE_BIT | CINUSE_BIT | FLAG4_BIT)

/* ------------------- Chunks sizes and alignments ----------------------- */

#define MCHUNK_SIZE         (sizeof(mchunk))

#if FOOTERS
    #define CHUNK_OVERHEAD      (2 * sizeof(size_t))
#else // FOOTERS
    #define CHUNK_OVERHEAD      (sizeof(size_t))
#endif // FOOTERS

/* MMapped chunks need a second word of overhead ... */
#define MMAP_CHUNK_OVERHEAD (2 * sizeof(size_t))
/* ... and additional padding for fake next-chunk at foot */
#define MMAP_FOOT_PAD       (4 * sizeof(size_t))

/* The smallest size we can malloc is an aligned minimal chunk */
#define MIN_CHUNK_SIZE  ((MCHUNK_SIZE + CHUNK_ALIGN_MASK) & ~CHUNK_ALIGN_MASK)

// ===============================================================================
struct malloc_chunk_header {
    void set_size_and_pinuse_of_free_chunk(size_t s) {
        _head = s | PINUSE_BIT;
        set_foot(s);
    }

    void set_foot(size_t s)  { 
        ((malloc_chunk_header *)((char*)this + s))->_prev_foot = s; 
    }

    // extraction of fields from head words
    bool cinuse() const        { return !!(_head & CINUSE_BIT); }
    bool pinuse() const        { return !!(_head & PINUSE_BIT); }
    bool flag4inuse() const    { return !!(_head & FLAG4_BIT); }
    bool is_inuse() const      { return (_head & INUSE_BITS) != PINUSE_BIT; }
    bool is_mmapped() const    { return (_head & INUSE_BITS) == 0; }

    size_t chunksize() const   { return _head & ~(FLAG_BITS); }

    void clear_pinuse()        { _head &= ~PINUSE_BIT; }
    void set_flag4()           { _head |= FLAG4_BIT; }
    void clear_flag4()         { _head &= ~FLAG4_BIT; }

    // Treat space at ptr +/- offset as a chunk
    malloc_chunk_header * chunk_plus_offset(size_t s)  {
        return (malloc_chunk_header *)((char*)this + s);
    }
    malloc_chunk_header * chunk_minus_offset(size_t s) { 
        return (malloc_chunk_header *)((char*)this - s); 
    }

    // Ptr to next or previous physical malloc_chunk.
    malloc_chunk_header * next_chunk() { 
        return (malloc_chunk_header *)((char*)this + (_head & ~FLAG_BITS)); 
    }
    malloc_chunk_header * prev_chunk() { 
        return (malloc_chunk_header *)((char*)this - (_prev_foot));
    }

    // extract next chunk's pinuse bit
    size_t next_pinuse()  { return next_chunk()->_head & PINUSE_BIT; }

    size_t   _prev_foot;  // Size of previous chunk (if free). 
    size_t   _head;       // Size and inuse bits.
};

// ===============================================================================
struct malloc_chunk : public malloc_chunk_header {
    // Set size, pinuse bit, foot, and clear next pinuse
    void set_free_with_pinuse(size_t s, malloc_chunk* n)
    {
        n->clear_pinuse();
        set_size_and_pinuse_of_free_chunk(s);
    }

    // Get the internal overhead associated with chunk p
    size_t overhead_for() { return is_mmapped() ? MMAP_CHUNK_OVERHEAD : CHUNK_OVERHEAD; }

    // Return true if malloced space is not necessarily cleared
    bool calloc_must_clear()
    {
#if MMAP_CLEARS
        return !is_mmapped();
#else 
        return true;
#endif 
    }
    
    struct malloc_chunk* _fd;         // double links -- used only if free.
    struct malloc_chunk* _bk;
};

typedef malloc_chunk  mchunk;
typedef malloc_chunk* mchunkptr;
typedef malloc_chunk_header *hchunkptr;
typedef malloc_chunk* sbinptr;         // The type of bins of chunks
typedef unsigned int bindex_t;         // Described below
typedef unsigned int binmap_t;         // Described below
typedef unsigned int flag_t;           // The type of various bit flag sets

// conversion from malloc headers to user pointers, and back 
static FORCEINLINE void *chunk2mem(void * const p) {
    return (void *)((char *)p + 2 * sizeof(size_t));
}
static FORCEINLINE mchunkptr mem2chunk(void * const mem) {
    return (mchunkptr)((char *)mem - 2 * sizeof(size_t));
}

// chunk associated with aligned address A
static FORCEINLINE mchunkptr align_as_chunk(char *A) {
    return (mchunkptr)(A + align_offset(chunk2mem(A)));
}

// Bounds on request (not chunk) sizes.
#define MAX_REQUEST         ((-MIN_CHUNK_SIZE) << 2)
#define MIN_REQUEST         (MIN_CHUNK_SIZE - CHUNK_OVERHEAD - 1)

// pad request bytes into a usable size
static FORCEINLINE size_t pad_request(size_t req) 
{
    return (req + CHUNK_OVERHEAD + CHUNK_ALIGN_MASK) & ~CHUNK_ALIGN_MASK;
}

// pad request, checking for minimum (but not maximum)
static FORCEINLINE size_t request2size(size_t req) 
{
    return req < MIN_REQUEST ? MIN_CHUNK_SIZE : pad_request(req);
}


/* ------------------ Operations on head and foot fields ----------------- */

/*
  The head field of a chunk is or'ed with PINUSE_BIT when previous
  adjacent chunk in use, and or'ed with CINUSE_BIT if this chunk is in
  use, unless mmapped, in which case both bits are cleared.

  FLAG4_BIT is not used by this malloc, but might be useful in extensions.
*/

// Head value for fenceposts
#define FENCEPOST_HEAD  (INUSE_BITS | sizeof(size_t))


/* ---------------------- Overlaid data structures ----------------------- */

/*
  When chunks are not in use, they are treated as nodes of either
  lists or trees.

  "Small"  chunks are stored in circular doubly-linked lists, and look
  like this:

    chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |             Size of previous chunk                            |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    `head:' |             Size of chunk, in bytes                         |P|
      mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |             Forward pointer to next chunk in list             |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |             Back pointer to previous chunk in list            |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |             Unused space (may be 0 bytes long)                .
            .                                                               .
            .                                                               |
nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    `foot:' |             Size of chunk, in bytes                           |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Larger chunks are kept in a form of bitwise digital trees (aka
  tries) keyed on chunksizes.  Because malloc_tree_chunks are only for
  free chunks greater than 256 bytes, their size doesn't impose any
  constraints on user chunk sizes.  Each node looks like:

    chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |             Size of previous chunk                            |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    `head:' |             Size of chunk, in bytes                         |P|
      mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |             Forward pointer to next chunk of same size        |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |             Back pointer to previous chunk of same size       |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |             Pointer to left child (child[0])                  |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |             Pointer to right child (child[1])                 |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |             Pointer to parent                                 |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |             bin index of this chunk                           |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            |             Unused space                                      .
            .                                                               |
nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    `foot:' |             Size of chunk, in bytes                           |
            +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  Each tree holding treenodes is a tree of unique chunk sizes.  Chunks
  of the same size are arranged in a circularly-linked list, with only
  the oldest chunk (the next to be used, in our FIFO ordering)
  actually in the tree.  (Tree members are distinguished by a non-null
  parent pointer.)  If a chunk with the same size an an existing node
  is inserted, it is linked off the existing node using pointers that
  work in the same way as fd/bk pointers of small chunks.

  Each tree contains a power of 2 sized range of chunk sizes (the
  smallest is 0x100 <= x < 0x180), which is is divided in half at each
  tree level, with the chunks in the smaller half of the range (0x100
  <= x < 0x140 for the top nose) in the left subtree and the larger
  half (0x140 <= x < 0x180) in the right subtree.  This is, of course,
  done by inspecting individual bits.

  Using these rules, each node's left subtree contains all smaller
  sizes than its right subtree.  However, the node at the root of each
  subtree has no particular ordering relationship to either.  (The
  dividing line between the subtree sizes is based on trie relation.)
  If we remove the last chunk of a given size from the interior of the
  tree, we need to replace it with a leaf node.  The tree ordering
  rules permit a node to be replaced by any leaf below it.

  The smallest chunk in a tree (a common operation in a best-fit
  allocator) can be found by walking a path to the leftmost leaf in
  the tree.  Unlike a usual binary tree, where we follow left child
  pointers until we reach a null, here we follow the right child
  pointer any time the left one is null, until we reach a leaf with
  both child pointers null. The smallest chunk in the tree will be
  somewhere along that path.

  The worst case number of steps to add, find, or remove a node is
  bounded by the number of bits differentiating chunks within
  bins. Under current bin calculations, this ranges from 6 up to 21
  (for 32 bit sizes) or up to 53 (for 64 bit sizes). The typical case
  is of course much better.
*/

// ===============================================================================
struct malloc_tree_chunk : public malloc_chunk_header {
    malloc_tree_chunk *leftmost_child() {
        return _child[0] ? _child[0] : _child[1]; 
    }


    malloc_tree_chunk* _fd;
    malloc_tree_chunk* _bk;

    malloc_tree_chunk* _child[2];
    malloc_tree_chunk* _parent;
    bindex_t           _index;
};

typedef malloc_tree_chunk  tchunk;
typedef malloc_tree_chunk* tchunkptr;
typedef malloc_tree_chunk* tbinptr; // The type of bins of trees

/* ----------------------------- Segments -------------------------------- */

/*
  Each malloc space may include non-contiguous segments, held in a
  list headed by an embedded malloc_segment record representing the
  top-most space. Segments also include flags holding properties of
  the space. Large chunks that are directly allocated by mmap are not
  included in this list. They are instead independently created and
  destroyed without otherwise keeping track of them.

  Segment management mainly comes into play for spaces allocated by
  MMAP.  Any call to MMAP might or might not return memory that is
  adjacent to an existing segment.  MORECORE normally contiguously
  extends the current space, so this space is almost always adjacent,
  which is simpler and faster to deal with. (This is why MORECORE is
  used preferentially to MMAP when both are available -- see
  sys_alloc.)  When allocating using MMAP, we don't use any of the
  hinting mechanisms (inconsistently) supported in various
  implementations of unix mmap, or distinguish reserving from
  committing memory. Instead, we just ask for space, and exploit
  contiguity when we get it.  It is probably possible to do
  better than this on some systems, but no general scheme seems
  to be significantly better.

  Management entails a simpler variant of the consolidation scheme
  used for chunks to reduce fragmentation -- new adjacent memory is
  normally prepended or appended to an existing segment. However,
  there are limitations compared to chunk consolidation that mostly
  reflect the fact that segment processing is relatively infrequent
  (occurring only when getting memory from system) and that we
  don't expect to have huge numbers of segments:

  * Segments are not indexed, so traversal requires linear scans.  (It
    would be possible to index these, but is not worth the extra
    overhead and complexity for most programs on most platforms.)
  * New segments are only appended to old ones when holding top-most
    memory; if they cannot be prepended to others, they are held in
    different segments.

  Except for the top-most segment of an mstate, each segment record
  is kept at the tail of its segment. Segments are added by pushing
  segment records onto the list headed by &mstate.seg for the
  containing mstate.

  Segment flags control allocation/merge/deallocation policies:
  * If EXTERN_BIT set, then we did not allocate this segment,
    and so should not try to deallocate or merge with others.
    (This currently holds only for the initial segment passed
    into create_mspace_with_base.)
  * If USE_MMAP_BIT set, the segment may be merged with
    other surrounding mmapped segments and trimmed/de-allocated
    using munmap.
  * If neither bit is set, then the segment was obtained using
    MORECORE so can be merged with surrounding MORECORE'd segments
    and deallocated/trimmed using MORECORE with negative arguments.
*/

// ===============================================================================
struct malloc_segment {
    bool is_mmapped_segment()  { return !!(_sflags & USE_MMAP_BIT); }
    bool is_extern_segment()   { return !!(_sflags & EXTERN_BIT); }

    char*           _base;          // base address
    size_t          _size;          // allocated size
    malloc_segment* _next;          // ptr to next segment
    flag_t          _sflags;        // mmap and extern flag
};

typedef malloc_segment  msegment;
typedef malloc_segment* msegmentptr;

/* ------------- Malloc_params ------------------- */

/*
  malloc_params holds global properties, including those that can be
  dynamically set using mallopt. There is a single instance, mparams,
  initialized in init_mparams. Note that the non-zeroness of "magic"
  also serves as an initialization flag.
*/

// ===============================================================================
struct malloc_params {
    malloc_params() : _magic(0) {}

    void ensure_initialization()
    {
        if (!_magic)
            _init();
    }
    int change(int param_number, int value);

    size_t page_align(size_t sz) {
        return (sz + (_page_size - 1)) & ~(_page_size - 1);
    }

    size_t granularity_align(size_t sz) {
        return (sz + (_granularity - 1)) & ~(_granularity - 1);
    }

    bool is_page_aligned(char *S) {
        return ((size_t)S & (_page_size - 1)) == 0;
    }

    int _init();

    size_t _magic;
    size_t _page_size;
    size_t _granularity;
    size_t _mmap_threshold;
    size_t _trim_threshold;
    flag_t _default_mflags;
};

static malloc_params mparams;

/* ---------------------------- malloc_state ----------------------------- */

/*
   A malloc_state holds all of the bookkeeping for a space.
   The main fields are:

  Top
    The topmost chunk of the currently active segment. Its size is
    cached in topsize.  The actual size of topmost space is
    topsize+TOP_FOOT_SIZE, which includes space reserved for adding
    fenceposts and segment records if necessary when getting more
    space from the system.  The size at which to autotrim top is
    cached from mparams in trim_check, except that it is disabled if
    an autotrim fails.

  Designated victim (dv)
    This is the preferred chunk for servicing small requests that
    don't have exact fits.  It is normally the chunk split off most
    recently to service another small request.  Its size is cached in
    dvsize. The link fields of this chunk are not maintained since it
    is not kept in a bin.

  SmallBins
    An array of bin headers for free chunks.  These bins hold chunks
    with sizes less than MIN_LARGE_SIZE bytes. Each bin contains
    chunks of all the same size, spaced 8 bytes apart.  To simplify
    use in double-linked lists, each bin header acts as a malloc_chunk
    pointing to the real first node, if it exists (else pointing to
    itself).  This avoids special-casing for headers.  But to avoid
    waste, we allocate only the fd/bk pointers of bins, and then use
    repositioning tricks to treat these as the fields of a chunk.

  TreeBins
    Treebins are pointers to the roots of trees holding a range of
    sizes. There are 2 equally spaced treebins for each power of two
    from TREE_SHIFT to TREE_SHIFT+16. The last bin holds anything
    larger.

  Bin maps
    There is one bit map for small bins ("smallmap") and one for
    treebins ("treemap).  Each bin sets its bit when non-empty, and
    clears the bit when empty.  Bit operations are then used to avoid
    bin-by-bin searching -- nearly all "search" is done without ever
    looking at bins that won't be selected.  The bit maps
    conservatively use 32 bits per map word, even if on 64bit system.
    For a good description of some of the bit-based techniques used
    here, see Henry S. Warren Jr's book "Hacker's Delight" (and
    supplement at http://hackersdelight.org/). Many of these are
    intended to reduce the branchiness of paths through malloc etc, as
    well as to reduce the number of memory locations read or written.

  Segments
    A list of segments headed by an embedded malloc_segment record
    representing the initial space.

  Address check support
    The least_addr field is the least address ever obtained from
    MORECORE or MMAP. Attempted frees and reallocs of any address less
    than this are trapped (unless INSECURE is defined).

  Magic tag
    A cross-check field that should always hold same value as mparams._magic.

  Max allowed footprint
    The maximum allowed bytes to allocate from system (zero means no limit)

  Flags
    Bits recording whether to use MMAP, locks, or contiguous MORECORE

  Statistics
    Each space keeps track of current and maximum system memory
    obtained via MORECORE or MMAP.

  Trim support
    Fields holding the amount of unused topmost memory that should trigger
    trimming, and a counter to force periodic scanning to release unused
    non-topmost segments.

  Locking
    If USE_LOCKS is defined, the "mutex" lock is acquired and released
    around every public call using this mspace.

  Extension support
    A void* pointer and a size_t field that can be used to help implement
    extensions to this malloc.
*/


// ================================================================================
class malloc_state 
{
public:
    /* ----------------------- _malloc, _free, etc... --- */
    FORCEINLINE void* _malloc(size_t bytes);
    FORCEINLINE void  _free(mchunkptr p);


    /* ------------------------ Relays to internal calls to malloc/free from realloc, memalign etc */
#if ONLY_MSPACES
    void *internal_malloc(size_t b) { return mspace_malloc(this, b); }
    void internal_free(void *mem)   { mspace_free(this,mem); }
#else 
    #if MSPACES
        FORCEINLINE void *internal_malloc(size_t b); 
        FORCEINLINE void internal_free(void *mem);
    #else
        void *internal_malloc(size_t b) { return dlmalloc(b); }
        void  internal_free(void *mem)  { dlfree(mem); }
    #endif
#endif

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

    struct mallinfo internal_mallinfo();
    void      internal_malloc_stats();

    void      init_top(mchunkptr p, size_t psize);
    void      init_bins();
    void      init(char* tbase, size_t tsize);

    /* ------------------------ System alloc/dealloc -------------------------- */
    void*     sys_alloc(size_t nb);
    size_t    release_unused_segments();
    int       sys_trim(size_t pad);
    void      dispose_chunk(mchunkptr p, size_t psize);

    /* ----------------------- Internal support for realloc, memalign, etc --- */
    mchunkptr try_realloc_chunk(mchunkptr p, size_t nb, int can_move);
    void*     internal_memalign(size_t alignment, size_t bytes);
    void**    ialloc(size_t n_elements, size_t* sizes, int opts, void* chunks[]);
    size_t    internal_bulk_free(void* array[], size_t nelem);
    void      internal_inspect_all(void(*handler)(void *start, void *end,
                                                  size_t used_bytes, void* callback_arg),
                                   void* arg);

    /* -------------------------- system alloc setup (Operations on mflags) ----- */
    bool      use_lock() const { return !!(_mflags & USE_LOCK_BIT); }
    void      enable_lock()    { _mflags |=  USE_LOCK_BIT; }
    void      set_lock(int l)  {
        _mflags = l ? _mflags | USE_LOCK_BIT : _mflags & ~USE_LOCK_BIT;
    }

#if USE_LOCKS
    void      disable_lock()   { _mflags &= ~USE_LOCK_BIT; }
    MLOCK_T&  get_mutex()      { return _mutex; }
#else
    void      disable_lock()   {}
#endif

    bool      use_mmap() const { return !!(_mflags & USE_MMAP_BIT); }
    void      enable_mmap()    { _mflags |=  USE_MMAP_BIT; }

#if HAVE_MMAP
    void      disable_mmap()   { _mflags &= ~USE_MMAP_BIT; }
#else
    void      disable_mmap()   {}
#endif

    /* ----------------------- Runtime Check Support ------------------------- */

    /*
      For security, the main invariant is that malloc/free/etc never
      writes to a static address other than malloc_state, unless static
      malloc_state itself has been corrupted, which cannot occur via
      malloc (because of these checks). In essence this means that we
      believe all pointers, sizes, maps etc held in malloc_state, but
      check all of those linked or offsetted from other embedded data
      structures.  These checks are interspersed with main code in a way
      that tends to minimize their run-time cost.

      When FOOTERS is defined, in addition to range checking, we also
      verify footer fields of inuse chunks, which can be used guarantee
      that the mstate controlling malloc/free is intact.  This is a
      streamlined version of the approach described by William Robertson
      et al in "Run-time Detection of Heap-based Overflows" LISA'03
      http://www.usenix.org/events/lisa03/tech/robertson.html The footer
      of an inuse chunk holds the xor of its mstate and a random seed,
      that is checked upon calls to free() and realloc().  This is
      (probabalistically) unguessable from outside the program, but can be
      computed by any code successfully malloc'ing any chunk, so does not
      itself provide protection against code that has already broken
      security through some other means.  Unlike Robertson et al, we
      always dynamically check addresses of all offset chunks (previous,
      next, etc). This turns out to be cheaper than relying on hashes.
    */


#if !INSECURE
    // Check if address a is at least as high as any from MORECORE or MMAP
    bool        ok_address(void *a) const { return (char *)a >= _least_addr; }

    // Check if address of next chunk n is higher than base chunk p
    static bool ok_next(void *p, void *n) { return p < n; }

    // Check if p has inuse status
    static bool ok_inuse(mchunkptr p)     { return p->is_inuse(); }
 
    // Check if p has its pinuse bit on
    static bool ok_pinuse(mchunkptr p)    { return p->pinuse(); }

    // Check if (alleged) mstate m has expected magic field
    bool        ok_magic() const          { return _magic == mparams._magic; }
    
    // In gcc, use __builtin_expect to minimize impact of checks
    #if defined(__GNUC__) && __GNUC__ >= 3
        static bool rtcheck(bool e)       { return __builtin_expect(e, 1); }
    #else
        static bool rtcheck(bool e)       { return e; }
    #endif
#else
    static bool ok_address(void *a)       { return true; }
    static bool ok_next(void *p, void *n) { return true; }
    static bool ok_inuse(mchunkptr p)     { return true; }
    static bool ok_pinuse(mchunkptr p)    { return true; }
    static bool ok_magic()                { return true; }
    static bool rtcheck(bool e)           { return true; }
#endif

    bool is_initialized() const           { return _top != 0; }

    bool use_noncontiguous()  const       { return !!(_mflags & USE_NONCONTIGUOUS_BIT); }
    void disable_contiguous()             { _mflags |=  USE_NONCONTIGUOUS_BIT; }

    // Return segment holding given address
    msegmentptr segment_holding(char* addr) {
        msegmentptr sp = (msegmentptr)&_seg;
        for (;;) {
            if (addr >= sp->_base && addr < sp->_base + sp->_size)
                return sp;
            if ((sp = sp->_next) == 0)
                return 0;
        }
    }

    // Return true if segment contains a segment link
    int has_segment_link(msegmentptr ss) {
        msegmentptr sp = (msegmentptr)&_seg;
        for (;;) {
            if ((char*)sp >= ss->_base && (char*)sp < ss->_base + ss->_size)
                return 1;
            if ((sp = sp->_next) == 0)
                return 0;
        }
    }
    
#ifndef MORECORE_CANNOT_TRIM
    bool should_trim(size_t s) const { return s > _trim_check; }
#else 
    bool should_trim(size_t s) const { return false; }
#endif 


    /* -------------------------- Debugging setup ---------------------------- */

#if ! DEBUG
    void check_free_chunk(mchunkptr) {}
    void check_inuse_chunk(mchunkptr) {}
    void check_malloced_chunk(void* , size_t) {}
    void check_mmapped_chunk(mchunkptr) {}
    void check_malloc_state() {}
    void check_top_chunk(mchunkptr) {}
#else /* DEBUG */
    void check_free_chunk(mchunkptr p)       { do_check_free_chunk(p); }
    void check_inuse_chunk(mchunkptr p)      { do_check_inuse_chunk(p); }
    void check_malloced_chunk(void* p, size_t s) { do_check_malloced_chunk(p, s); }
    void check_mmapped_chunk(mchunkptr p)    { do_check_mmapped_chunk(p); }
    void check_malloc_state()                { do_check_malloc_state(); }
    void check_top_chunk(mchunkptr p)        { do_check_top_chunk(p); }

    void do_check_any_chunk(mchunkptr p) const;
    void do_check_top_chunk(mchunkptr p) const;
    void do_check_mmapped_chunk(mchunkptr p) const;
    void do_check_inuse_chunk(mchunkptr p) const;
    void do_check_free_chunk(mchunkptr p) const;
    void do_check_malloced_chunk(void* mem, size_t s) const;
    void do_check_tree(tchunkptr t);
    void do_check_treebin(bindex_t i);
    void do_check_smallbin(bindex_t i);
    void do_check_malloc_state();
    int  bin_find(mchunkptr x);
    size_t traverse_and_check();
#endif // DEBUG

private:

    /* ---------------------------- Indexing Bins ---------------------------- */

    static bool  is_small(size_t s)          { return (s >> SMALLBIN_SHIFT) < NSMALLBINS; }
    static bindex_t  small_index(size_t s)   { return (bindex_t)(s  >> SMALLBIN_SHIFT); }
    static size_t small_index2size(size_t i) { return i << SMALLBIN_SHIFT; }
    static bindex_t  MIN_SMALL_INDEX()       { return small_index(MIN_CHUNK_SIZE); }

    // assign tree index for size S to variable I. Use x86 asm if possible 
#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
    FORCEINLINE static bindex_t compute_tree_index(size_t S)
    {
        unsigned int X = S >> TREEBIN_SHIFT;
        if (X == 0)
            return 0;
        else if (X > 0xFFFF)
            return NTREEBINS - 1;

        unsigned int K = (unsigned) sizeof(X)*__CHAR_BIT__ - 1 - (unsigned) __builtin_clz(X); 
        return (bindex_t)((K << 1) + ((S >> (K + (TREEBIN_SHIFT - 1)) & 1)));
    }

#elif defined (__INTEL_COMPILER)
    FORCEINLINE static bindex_t compute_tree_index(size_t S)
    {
        size_t X = S >> TREEBIN_SHIFT;
        if (X == 0)
            return 0;
        else if (X > 0xFFFF)
            return NTREEBINS - 1;

        unsigned int K = _bit_scan_reverse (X); 
        return (bindex_t)((K << 1) + ((S >> (K + (TREEBIN_SHIFT - 1)) & 1)));
    }

#elif defined(_MSC_VER) && _MSC_VER>=1300
    FORCEINLINE static bindex_t compute_tree_index(size_t S)
    {
        size_t X = S >> TREEBIN_SHIFT;
        if (X == 0)
            return 0;
        else if (X > 0xFFFF)
            return NTREEBINS - 1;

        unsigned int K;
        _BitScanReverse((DWORD *) &K, (DWORD) X);
        return (bindex_t)((K << 1) + ((S >> (K + (TREEBIN_SHIFT - 1)) & 1)));
    }

#else // GNUC
    FORCEINLINE static bindex_t compute_tree_index(size_t S)
    {
        size_t X = S >> TREEBIN_SHIFT;
        if (X == 0)
            return 0;
        else if (X > 0xFFFF)
            return NTREEBINS - 1;

        unsigned int Y = (unsigned int)X;
        unsigned int N = ((Y - 0x100) >> 16) & 8;
        unsigned int K = (((Y <<= N) - 0x1000) >> 16) & 4;
        N += K;
        N += K = (((Y <<= K) - 0x4000) >> 16) & 2;
        K = 14 - N + ((Y <<= K) >> 15);
        return (K << 1) + ((S >> (K + (TREEBIN_SHIFT - 1)) & 1));
    }
#endif // GNUC

    // Shift placing maximum resolved bit in a treebin at i as sign bit
    static bindex_t leftshift_for_tree_index(bindex_t i) 
    {
        return (i == NTREEBINS - 1) ? 0 :
            ((SIZE_T_BITSIZE - 1) - ((i >> 1) + TREEBIN_SHIFT - 2));
    }

    // The size of the smallest chunk held in bin with index i
    static bindex_t minsize_for_tree_index(bindex_t i)
    {
        return ((size_t)1 << ((i >> 1) + TREEBIN_SHIFT)) | 
            (((size_t)(i & 1)) << ((i >> 1) + TREEBIN_SHIFT - 1));
    }


    // ----------- isolate the least set bit of a bitmap
    static binmap_t least_bit(binmap_t x) { return x & -x; }

    // ----------- mask with all bits to left of least bit of x on
    static binmap_t left_bits(binmap_t x) { return (x<<1) | -(x<<1); }

    // index corresponding to given bit. Use x86 asm if possible
#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
    static bindex_t compute_bit2idx(binmap_t X)
    {
        unsigned int J;
        J = __builtin_ctz(X); 
        return (bindex_t)J;
    }

#elif defined (__INTEL_COMPILER)
    static bindex_t compute_bit2idx(binmap_t X)
    {
        unsigned int J;
        J = _bit_scan_forward (X); 
        return (bindex_t)J;
    }

#elif defined(_MSC_VER) && _MSC_VER>=1300
    static bindex_t compute_bit2idx(binmap_t X)
    {
        unsigned int J;
        _BitScanForward((DWORD *) &J, X);
        return (bindex_t)J;
    }

#elif USE_BUILTIN_FFS
    static bindex_t compute_bit2idx(binmap_t X) { return ffs(X) - 1; }

#else
    static bindex_t compute_bit2idx(binmap_t X)
    {
        unsigned int Y = X - 1;
        unsigned int K = Y >> (16-4) & 16;
        unsigned int N = K;        Y >>= K;
        N += K = Y >> (8-3) &  8;  Y >>= K;
        N += K = Y >> (4-2) &  4;  Y >>= K;
        N += K = Y >> (2-1) &  2;  Y >>= K;
        N += K = Y >> (1-0) &  1;  Y >>= K;
        return (bindex_t)(N + Y);
    }
#endif // GNUC

    /* ------------------------ Set up inuse chunks with or without footers ---*/
#if !FOOTERS
    void mark_inuse_foot(malloc_chunk_header *, size_t) {}
#else 
    //Set foot of inuse chunk to be xor of mstate and seed 
    void  mark_inuse_foot(malloc_chunk_header *p, size_t s) {
        (((mchunkptr)((char*)p + s))->_prev_foot = (size_t)this ^ mparams._magic); }
#endif

    void set_inuse(malloc_chunk_header *p, size_t s) {
        p->_head = (p->_head & PINUSE_BIT) | s | CINUSE_BIT;
        ((mchunkptr)(((char*)p) + s))->_head |= PINUSE_BIT;
        mark_inuse_foot(p,s);
    }

    void set_inuse_and_pinuse(malloc_chunk_header *p, size_t s) {
        p->_head = s | PINUSE_BIT | CINUSE_BIT;
        ((mchunkptr)(((char*)p) + s))->_head |= PINUSE_BIT;
        mark_inuse_foot(p,s);
    }

    void set_size_and_pinuse_of_inuse_chunk(malloc_chunk_header *p, size_t s) {
        p->_head = s | PINUSE_BIT | CINUSE_BIT;
        mark_inuse_foot(p, s);
    }
    
    /* ------------------------ Addressing by index. See  about smallbin repositioning --- */
    sbinptr  smallbin_at(bindex_t i) { return (sbinptr)((char*)&_smallbins[i << 1]); }
    tbinptr* treebin_at(bindex_t i)  { return &_treebins[i]; }

    /* ----------------------- bit corresponding to given index ---------*/
    static binmap_t idx2bit(bindex_t i) { return ((binmap_t)1 << i); }

    // --------------- Mark/Clear bits with given index
    void     mark_smallmap(bindex_t i)      { _smallmap |=  idx2bit(i); }
    void     clear_smallmap(bindex_t i)     { _smallmap &= ~idx2bit(i); }
    binmap_t smallmap_is_marked(bindex_t i) const { return _smallmap & idx2bit(i); }

    void     mark_treemap(bindex_t i)       { _treemap  |=  idx2bit(i); }
    void     clear_treemap(bindex_t i)      { _treemap  &= ~idx2bit(i); }
    binmap_t treemap_is_marked(bindex_t i)  const { return _treemap & idx2bit(i); }

    /* ------------------------ ----------------------- */
    FORCEINLINE void insert_small_chunk(mchunkptr P, size_t S);
    FORCEINLINE void unlink_small_chunk(mchunkptr P, size_t S);
    FORCEINLINE void unlink_first_small_chunk(mchunkptr B, mchunkptr P, bindex_t I);
    FORCEINLINE void replace_dv(mchunkptr P, size_t S);

    /* ------------------------- Operations on trees ------------------------- */
    FORCEINLINE void insert_large_chunk(tchunkptr X, size_t S);
    FORCEINLINE void unlink_large_chunk(tchunkptr X);

    /* ------------------------ Relays to large vs small bin operations */
    FORCEINLINE void insert_chunk(mchunkptr P, size_t S);
    FORCEINLINE void unlink_chunk(mchunkptr P, size_t S);

    /* -----------------------  Direct-mmapping chunks ----------------------- */
    void*     mmap_alloc(size_t nb);
    mchunkptr mmap_resize(mchunkptr oldp, size_t nb, int flags);

    void      reset_on_error();
    void*     prepend_alloc(char* newbase, char* oldbase, size_t nb);
    void      add_segment(char* tbase, size_t tsize, flag_t mmapped);

    /* ------------------------ malloc --------------------------- */
    void*     tmalloc_large(size_t nb);
    void*     tmalloc_small(size_t nb);

    /* ------------------------Bin types, widths and sizes -------- */
    static const size_t NSMALLBINS      = 32;
    static const size_t NTREEBINS       = 32;
    static const size_t SMALLBIN_SHIFT  = 3;
    static const size_t SMALLBIN_WIDTH  = 1 << SMALLBIN_SHIFT;
    static const size_t TREEBIN_SHIFT   = 8;
    static const size_t MIN_LARGE_SIZE  = 1 << TREEBIN_SHIFT;
    static const size_t MAX_SMALL_SIZE  =  (MIN_LARGE_SIZE - 1);
    static const size_t MAX_SMALL_REQUEST = (MAX_SMALL_SIZE - CHUNK_ALIGN_MASK - CHUNK_OVERHEAD);

    /* ------------------------ data members --------------------------- */
    binmap_t   _smallmap;
    binmap_t   _treemap;
    size_t     _dvsize;
    size_t     _topsize;
    char*      _least_addr;
    mchunkptr  _dv;
    mchunkptr  _top;
    size_t     _trim_check;
    size_t     _release_checks;
    size_t     _magic;
    mchunkptr  _smallbins[(NSMALLBINS+1)*2];
    tbinptr    _treebins[NTREEBINS];
public:
    size_t     _footprint;
    size_t     _max_footprint;
    size_t     _footprint_limit; // zero means no limit
    flag_t     _mflags;

#if USE_LOCKS
    MLOCK_T    _mutex;     // locate lock among fields that rarely change
#endif // USE_LOCKS
    msegment   _seg;

private:
    void*      _extp;      // Unused but available for extensions
    size_t     _exts;
};

typedef malloc_state*    mstate;

/* ------------- end malloc_state ------------------- */

#if FOOTERS
    malloc_state* get_mstate_for(malloc_chunk_header *p) {
        return (malloc_state*)(((mchunkptr)((char*)(p) +
                                     (p->chunksize())))->_prev_foot ^ mparams._magic);
    }
#endif

/* ------------- Global malloc_state ------------------- */

#if !ONLY_MSPACES

// The global malloc_state used for all non-"mspace" calls
static malloc_state _gm_;
#define gm                 (&_gm_)
#define is_global(M)       ((M) == &_gm_)

#endif // !ONLY_MSPACES

/* -------------------------- system alloc setup ------------------------- */



// For mmap, use granularity alignment on windows, else page-align
#ifdef WIN32
    #define mmap_align(S) mparams.granularity_align(S)
#else
    #define mmap_align(S) mparams.page_align(S)
#endif

// For sys_alloc, enough padding to ensure can malloc request on success
#define SYS_ALLOC_PADDING (TOP_FOOT_SIZE + MALLOC_ALIGNMENT)


//  True if segment S holds address A
bool segment_holds(msegmentptr S, mchunkptr A) {
    return (char*)A >= S->_base && (char*)A < S->_base + S->_size;
}

/*
  TOP_FOOT_SIZE is padding at the end of a segmentr including space
  that may be needed to place segment records and fenceposts when new
  noncontiguous segments are added.
*/
#define TOP_FOOT_SIZE \
    (align_offset(chunk2mem((void *)0))+pad_request(sizeof(struct malloc_segment))+MIN_CHUNK_SIZE)


/* -------------------------------  Hooks -------------------------------- */

/*
  PREACTION should be defined to return 0 on success, and nonzero on
  failure. If you are not using locking, you can redefine these to do
  anything you like.
*/

#if USE_LOCKS
    #define PREACTION(M)  ((M->use_lock())? ACQUIRE_LOCK(&(M)->get_mutex()) : 0)
    #define POSTACTION(M) { if (M->use_lock()) RELEASE_LOCK(&(M)->get_mutex()); }
#else // USE_LOCKS
    #ifndef PREACTION
        #define PREACTION(M) (0)
    #endif 

    #ifndef POSTACTION
        #define POSTACTION(M)
    #endif 
#endif // USE_LOCKS

/*
  CORRUPTION_ERROR_ACTION is triggered upon detected bad addresses.
  USAGE_ERROR_ACTION is triggered on detected bad frees and
  reallocs. The argument p is an address that might have triggered the
  fault. It is ignored by the two predefined actions, but might be
  useful in custom actions that try to help diagnose errors.
*/

#if PROCEED_ON_ERROR
    
    // A count of the number of corruption errors causing resets
    int malloc_corruption_error_count;
    
    #define CORRUPTION_ERROR_ACTION(m)  m->reset_on_error()
    #define USAGE_ERROR_ACTION(m, p)

#else // PROCEED_ON_ERROR
    
    #ifndef CORRUPTION_ERROR_ACTION
        #define CORRUPTION_ERROR_ACTION(m) ABORT
    #endif // CORRUPTION_ERROR_ACTION
    
    #ifndef USAGE_ERROR_ACTION
        #define USAGE_ERROR_ACTION(m,p) ABORT
    #endif // USAGE_ERROR_ACTION

#endif // PROCEED_ON_ERROR

/* ---------------------------- setting mparams -------------------------- */

#if LOCK_AT_FORK
    static void pre_fork(void)         { ACQUIRE_LOCK(&(gm)->get_mutex()); }
    static void post_fork_parent(void) { RELEASE_LOCK(&(gm)->get_mutex()); }
    static void post_fork_child(void)  { INITIAL_LOCK(&(gm)->get_mutex()); }
#endif // LOCK_AT_FORK

// Initialize mparams
int malloc_params::_init() {
#ifdef NEED_GLOBAL_LOCK_INIT
    if (malloc_global_mutex_status <= 0)
        init_malloc_global_mutex();
#endif

    ACQUIRE_MALLOC_GLOBAL_LOCK();
    if (_magic == 0) {
        size_t magic;
        size_t psize;
        size_t gsize;

        psize = malloc_getpagesize;
        gsize = ((DEFAULT_GRANULARITY != 0)? DEFAULT_GRANULARITY : psize);

        /* Sanity-check configuration:
           size_t must be unsigned and as wide as pointer type.
           ints must be at least 4 bytes.
           alignment must be at least 8.
           Alignment, min chunk size, and page size must all be powers of 2.
        */
        if ((sizeof(size_t) != sizeof(char*)) ||
            (MAX_SIZE_T < MIN_CHUNK_SIZE)  ||
            (sizeof(int) < 4)  ||
            (MALLOC_ALIGNMENT < (size_t)8U) ||
            ((MALLOC_ALIGNMENT & (MALLOC_ALIGNMENT-1)) != 0) ||
            ((MCHUNK_SIZE      & (MCHUNK_SIZE-1))      != 0) ||
            ((gsize            & (gsize-1))            != 0) ||
            ((psize            & (psize-1))            != 0))
            ABORT;
        _granularity = gsize;
        _page_size = psize;
        _mmap_threshold = DEFAULT_MMAP_THRESHOLD;
        _trim_threshold = DEFAULT_TRIM_THRESHOLD;
#if MORECORE_CONTIGUOUS
        _default_mflags = USE_LOCK_BIT | USE_MMAP_BIT;
#else  // MORECORE_CONTIGUOUS
        _default_mflags = USE_LOCK_BIT | USE_MMAP_BIT | USE_NONCONTIGUOUS_BIT;
#endif // MORECORE_CONTIGUOUS

#if !ONLY_MSPACES
        // Set up lock for main malloc area
        gm->_mflags = _default_mflags;
        (void)INITIAL_LOCK(&gm->get_mutex());
#endif
#if LOCK_AT_FORK
        pthread_atfork(&pre_fork, &post_fork_parent, &post_fork_child);
#endif

        {
            magic = (size_t)(platform_timer_now() ^ (size_t)0x55555555U);
            magic |= (size_t)8U;    // ensure nonzero
            magic &= ~(size_t)7U;   // improve chances of fault for bad values
            // Until memory modes commonly available, use volatile-write
            (*(volatile size_t *)(&(_magic))) = magic;
        }
    }

    RELEASE_MALLOC_GLOBAL_LOCK();
    return 1;
}

// support for mallopt
int malloc_params::change(int param_number, int value) {
    size_t val;
    ensure_initialization();
    val = (value == -1)? MAX_SIZE_T : (size_t)value;

    switch(param_number) {
    case M_TRIM_THRESHOLD:
        _trim_threshold = val;
        return 1;

    case M_GRANULARITY:
        if (val >= _page_size && ((val & (val - 1)) == 0)) {
            _granularity = val;
            return 1;
        }
        else
            return 0;

    case M_MMAP_THRESHOLD:
        _mmap_threshold = val;
        return 1;

    default:
        return 0;
    }
}

#if DEBUG
/* ------------------------- Debugging Support --------------------------- */

// Check properties of any chunk, whether free, inuse, mmapped etc 
void malloc_state::do_check_any_chunk(mchunkptr p)  const {
    assert((is_aligned(chunk2mem(p))) || (p->_head == FENCEPOST_HEAD));
    assert(ok_address(p));
}

// Check properties of top chunk
void malloc_state::do_check_top_chunk(mchunkptr p) const {
    msegmentptr sp = segment_holding((char*)p);
    size_t  sz = p->_head & ~INUSE_BITS; // third-lowest bit can be set!
    assert(sp != 0);
    assert((is_aligned(chunk2mem(p))) || (p->_head == FENCEPOST_HEAD));
    assert(ok_address(p));
    assert(sz == _topsize);
    assert(sz > 0);
    assert(sz == ((sp->_base + sp->_size) - (char*)p) - TOP_FOOT_SIZE);
    assert(p->pinuse());
    assert(!p->chunk_plus_offset(sz)->pinuse());
}

// Check properties of (inuse) mmapped chunks
void malloc_state::do_check_mmapped_chunk(mchunkptr p) const {
    size_t  sz = p->chunksize();
    size_t len = (sz + (p->_prev_foot) + MMAP_FOOT_PAD);
    assert(p->is_mmapped());
    assert(use_mmap());
    assert((is_aligned(chunk2mem(p))) || (p->_head == FENCEPOST_HEAD));
    assert(ok_address(p));
    assert(!is_small(sz));
    assert((len & (mparams._page_size - 1)) == 0);
    assert(p->chunk_plus_offset(sz)->_head == FENCEPOST_HEAD);
    assert(p->chunk_plus_offset(sz+sizeof(size_t))->_head == 0);
}

// Check properties of inuse chunks
void malloc_state::do_check_inuse_chunk(mchunkptr p) const {
    do_check_any_chunk(p);
    assert(p->is_inuse());
    assert(p->next_pinuse());
    // If not pinuse and not mmapped, previous chunk has OK offset
    assert(p->is_mmapped() || p->pinuse() || (mchunkptr)p->prev_chunk()->next_chunk() == p);
    if (p->is_mmapped())
        do_check_mmapped_chunk(p);
}

// Check properties of free chunks
void malloc_state::do_check_free_chunk(mchunkptr p) const {
    size_t sz = p->chunksize();
    mchunkptr next = (mchunkptr)p->chunk_plus_offset(sz);
    do_check_any_chunk(p);
    assert(!p->is_inuse());
    assert(!p->next_pinuse());
    assert (!p->is_mmapped());
    if (p != _dv && p != _top) {
        if (sz >= MIN_CHUNK_SIZE) {
            assert((sz & CHUNK_ALIGN_MASK) == 0);
            assert(is_aligned(chunk2mem(p)));
            assert(next->_prev_foot == sz);
            assert(p->pinuse());
            assert (next == _top || next->is_inuse());
            assert(p->_fd->_bk == p);
            assert(p->_bk->_fd == p);
        }
        else  // markers are always of size sizeof(size_t)
            assert(sz == sizeof(size_t));
    }
}

// Check properties of malloced chunks at the point they are malloced
void malloc_state::do_check_malloced_chunk(void* mem, size_t s) const {
    if (mem != 0) {
        mchunkptr p = mem2chunk(mem);
        size_t sz = p->_head & ~INUSE_BITS;
        do_check_inuse_chunk(p);
        assert((sz & CHUNK_ALIGN_MASK) == 0);
        assert(sz >= MIN_CHUNK_SIZE);
        assert(sz >= s);
        // unless mmapped, size is less than MIN_CHUNK_SIZE more than request
        assert(p->is_mmapped() || sz < (s + MIN_CHUNK_SIZE));
    }
}

// Check a tree and its subtrees. 
void malloc_state::do_check_tree(tchunkptr t) {
    tchunkptr head = 0;
    tchunkptr u = t;
    bindex_t tindex = t->_index;
    size_t tsize = t->chunksize();
    bindex_t idx = compute_tree_index(tsize);
    assert(tindex == idx);
    assert(tsize >= MIN_LARGE_SIZE);
    assert(tsize >= minsize_for_tree_index(idx));
    assert((idx == NTREEBINS - 1) || (tsize < minsize_for_tree_index((idx+1))));

    do {
        // traverse through chain of same-sized nodes
        do_check_any_chunk((mchunkptr)u);
        assert(u->_index == tindex);
        assert(u->chunksize() == tsize);
        assert(!u->is_inuse());
        assert(!u->next_pinuse());
        assert(u->_fd->_bk == u);
        assert(u->_bk->_fd == u);
        if (u->_parent == 0) {
            assert(u->_child[0] == 0);
            assert(u->_child[1] == 0);
        }
        else {
            assert(head == 0); // only one node on chain has parent
            head = u;
            assert(u->_parent != u);
            assert (u->_parent->_child[0] == u ||
                    u->_parent->_child[1] == u ||
                    *((tbinptr*)(u->_parent)) == u);
            if (u->_child[0] != 0) {
                assert(u->_child[0]->_parent == u);
                assert(u->_child[0] != u);
                do_check_tree(u->_child[0]);
            }
            if (u->_child[1] != 0) {
                assert(u->_child[1]->_parent == u);
                assert(u->_child[1] != u);
                do_check_tree(u->_child[1]);
            }
            if (u->_child[0] != 0 && u->_child[1] != 0) {
                assert(u->_child[0]->chunksize() < u->_child[1]->chunksize());
            }
        }
        u = u->_fd;
    } while (u != t);
    assert(head != 0);
}

//  Check all the chunks in a treebin. 
void malloc_state::do_check_treebin(bindex_t i) {
    tbinptr* tb = (tbinptr*)treebin_at(i);
    tchunkptr t = *tb;
    int empty = (_treemap & (1U << i)) == 0;
    if (t == 0)
        assert(empty);
    if (!empty)
        do_check_tree(t);
}

//  Check all the chunks in a smallbin. 
void malloc_state::do_check_smallbin(bindex_t i) {
    sbinptr b = smallbin_at(i);
    mchunkptr p = b->_bk;
    unsigned int empty = (_smallmap & (1U << i)) == 0;
    if (p == b)
        assert(empty);
    if (!empty) {
        for (; p != b; p = p->_bk) {
            size_t size = p->chunksize();
            mchunkptr q;
            // each chunk claims to be free
            do_check_free_chunk(p);
            // chunk belongs in bin
            assert(small_index(size) == i);
            assert(p->_bk == b || p->_bk->chunksize() == p->chunksize());
            // chunk is followed by an inuse chunk
            q = (mchunkptr)p->next_chunk();
            if (q->_head != FENCEPOST_HEAD)
                do_check_inuse_chunk(q);
        }
    }
}

// Find x in a bin. Used in other check functions.
int malloc_state::bin_find(mchunkptr x) {
    size_t size = x->chunksize();
    if (is_small(size)) {
        bindex_t sidx = small_index(size);
        sbinptr b = smallbin_at(sidx);
        if (smallmap_is_marked(sidx)) {
            mchunkptr p = b;
            do {
                if (p == x)
                    return 1;
            } while ((p = p->_fd) != b);
        }
    }
    else {
        bindex_t tidx = compute_tree_index(size);
        if (treemap_is_marked(tidx)) {
            tchunkptr t = *treebin_at(tidx);
            size_t sizebits = size << leftshift_for_tree_index(tidx);
            while (t != 0 && t->chunksize() != size) {
                t = t->_child[(sizebits >> (SIZE_T_BITSIZE - 1)) & 1];
                sizebits <<= 1;
            }
            if (t != 0) {
                tchunkptr u = t;
                do {
                    if (u == (tchunkptr)x)
                        return 1;
                } while ((u = u->_fd) != t);
            }
        }
    }
    return 0;
}

// Traverse each chunk and check it; return total
size_t malloc_state::traverse_and_check() {
    size_t sum = 0;
    if (is_initialized()) {
        msegmentptr s = (msegmentptr)&_seg;
        sum += _topsize + TOP_FOOT_SIZE;
        while (s != 0) {
            mchunkptr q = align_as_chunk(s->_base);
            mchunkptr lastq = 0;
            assert(q->pinuse());
            while (segment_holds(s, q) &&
                   q != _top && q->_head != FENCEPOST_HEAD) {
                sum += q->chunksize();
                if (q->is_inuse()) {
                    assert(!bin_find(q));
                    do_check_inuse_chunk(q);
                }
                else {
                    assert(q == _dv || bin_find(q));
                    assert(lastq == 0 || lastq->is_inuse()); // Not 2 consecutive free
                    do_check_free_chunk(q);
                }
                lastq = q;
                q = (mchunkptr)q->next_chunk();
            }
            s = s->_next;
        }
    }
    return sum;
}


// Check all properties of malloc_state.
void malloc_state::do_check_malloc_state() {
    bindex_t i;
    size_t total;
    // check bins
    for (i = 0; i < NSMALLBINS; ++i)
        do_check_smallbin(i);
    for (i = 0; i < NTREEBINS; ++i)
        do_check_treebin(i);

    if (_dvsize != 0) { 
        // check dv chunk
        do_check_any_chunk(_dv);
        assert(_dvsize == _dv->chunksize());
        assert(_dvsize >= MIN_CHUNK_SIZE);
        assert(bin_find(_dv) == 0);
    }

    if (_top != 0) {
        // check top chunk
        do_check_top_chunk(_top);
        //assert(topsize == top->chunksize()); redundant
        assert(_topsize > 0);
        assert(bin_find(_top) == 0);
    }

    total = traverse_and_check();
    assert(total <= _footprint);
    assert(_footprint <= _max_footprint);
}
#endif // DEBUG

/* ----------------------------- statistics ------------------------------ */

#if !NO_MALLINFO
// ===============================================================================
struct mallinfo malloc_state::internal_mallinfo() {
    struct mallinfo nm = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
    mparams.ensure_initialization();
    if (!PREACTION(this)) {
        check_malloc_state();
        if (is_initialized()) {
            size_t nfree = 1; // top always free
            size_t mfree = _topsize + TOP_FOOT_SIZE;
            size_t sum = mfree;
            msegmentptr s = &_seg;
            while (s != 0) {
                mchunkptr q = align_as_chunk(s->_base);
                while (segment_holds(s, q) &&
                       q != _top && q->_head != FENCEPOST_HEAD) {
                    size_t sz = q->chunksize();
                    sum += sz;
                    if (!q->is_inuse()) {
                        mfree += sz;
                        ++nfree;
                    }
                    q = (mchunkptr)q->next_chunk();
                }
                s = s->_next;
            }

            nm.arena    = sum;
            nm.ordblks  = nfree;
            nm.hblkhd   = _footprint - sum;
            nm.usmblks  = _max_footprint;
            nm.uordblks = _footprint - mfree;
            nm.fordblks = mfree;
            nm.keepcost = _topsize;
        }

        POSTACTION(this);
    }
    return nm;
}
#endif // !NO_MALLINFO

#if !NO_MALLOC_STATS
void malloc_state::internal_malloc_stats() {
    mparams.ensure_initialization();
    if (!PREACTION(this)) {
        size_t maxfp = 0;
        size_t fp = 0;
        size_t used = 0;
        check_malloc_state();
        if (is_initialized()) {
            msegmentptr s = &_seg;
            maxfp = _max_footprint;
            fp = _footprint;
            used = fp - (_topsize + TOP_FOOT_SIZE);

            while (s != 0) {
                mchunkptr q = align_as_chunk(s->_base);
                while (segment_holds(s, q) &&
                       q != _top && q->_head != FENCEPOST_HEAD) {
                    if (!q->is_inuse())
                        used -= q->chunksize();
                    q = (mchunkptr)q->next_chunk();
                }
                s = s->_next;
            }
        }
        POSTACTION(this); // drop lock
        fprintf(stderr, "max system bytes = %10lu\n", (unsigned long)(maxfp));
        fprintf(stderr, "system bytes     = %10lu\n", (unsigned long)(fp));
        fprintf(stderr, "in use bytes     = %10lu\n", (unsigned long)(used));
    }
}
#endif // NO_MALLOC_STATS

/* ----------------------- Operations on smallbins ----------------------- */

/*
  Various forms of linking and unlinking are defined as macros.  Even
  the ones for trees, which are very long but have very short typical
  paths.  This is ugly but reduces reliance on inlining support of
  compilers.
*/

// Link a free chunk into a smallbin 
void malloc_state::insert_small_chunk(mchunkptr p, size_t s) {
    bindex_t I  = small_index(s);
    mchunkptr B = smallbin_at(I);
    mchunkptr F = B;
    assert(s >= MIN_CHUNK_SIZE);
    if (!smallmap_is_marked(I))
        mark_smallmap(I);
    else if (rtcheck(ok_address(B->_fd)))
        F = B->_fd;
    else {
        CORRUPTION_ERROR_ACTION(this);
    }
    B->_fd = p;
    F->_bk = p;
    p->_fd = F;
    p->_bk = B;
}

// Unlink a chunk from a smallbin 
void malloc_state::unlink_small_chunk(mchunkptr p, size_t s) {
    mchunkptr F = p->_fd;
    mchunkptr B = p->_bk;
    bindex_t I = small_index(s);
    assert(p != B);
    assert(p != F);
    assert(p->chunksize() == small_index2size(I));
    if (rtcheck(F == smallbin_at(I) || (ok_address(F) && F->_bk == p))) { 
        if (B == F) {
            clear_smallmap(I);
        }
        else if (rtcheck(B == smallbin_at(I) ||
                         (ok_address(B) && B->_fd == p))) {
            F->_bk = B;
            B->_fd = F;
        }
        else {
            CORRUPTION_ERROR_ACTION(this);
        }
    }
    else {
        CORRUPTION_ERROR_ACTION(this);
    }
}

// Unlink the first chunk from a smallbin
void malloc_state::unlink_first_small_chunk(mchunkptr B, mchunkptr p, bindex_t I) {
    mchunkptr F = p->_fd;
    assert(p != B);
    assert(p != F);
    assert(p->chunksize() == small_index2size(I));
    if (B == F) {
        clear_smallmap(I);
    }
    else if (rtcheck(ok_address(F) && F->_bk == p)) {
        F->_bk = B;
        B->_fd = F;
    }
    else {
        CORRUPTION_ERROR_ACTION(this);
    }
}

// Replace dv node, binning the old one
// Used only when dvsize known to be small
void malloc_state::replace_dv(mchunkptr p, size_t s) {
    size_t DVS = _dvsize;
    assert(is_small(DVS));
    if (DVS != 0) {
        mchunkptr DV = _dv;
        insert_small_chunk(DV, DVS);
    }
    _dvsize = s;
    _dv = p;
}

/* ------------------------- Operations on trees ------------------------- */

// Insert chunk into tree
void malloc_state::insert_large_chunk(tchunkptr X, size_t s) {
    tbinptr* H;
    bindex_t I = compute_tree_index(s);
    H = treebin_at(I);
    X->_index = I;
    X->_child[0] = X->_child[1] = 0;
    if (!treemap_is_marked(I)) {
        mark_treemap(I);
        *H = X;
        X->_parent = (tchunkptr)H;
        X->_fd = X->_bk = X;
    }
    else {
        tchunkptr T = *H;
        size_t K = s << leftshift_for_tree_index(I);
        for (;;) {
            if (T->chunksize() != s) {
                tchunkptr* C = &(T->_child[(K >> (SIZE_T_BITSIZE - 1)) & 1]);
                K <<= 1;
                if (*C != 0)
                    T = *C;
                else if (rtcheck(ok_address(C))) {
                    *C = X;
                    X->_parent = T;
                    X->_fd = X->_bk = X;
                    break;
                }
                else {
                    CORRUPTION_ERROR_ACTION(this);
                    break;
                }
            }
            else {
                tchunkptr F = T->_fd;
                if (rtcheck(ok_address(T) && ok_address(F))) {
                    T->_fd = F->_bk = X;
                    X->_fd = F;
                    X->_bk = T;
                    X->_parent = 0;
                    break;
                }
                else {
                    CORRUPTION_ERROR_ACTION(this);
                    break;
                }
            }
        }
    }
}

/*
  Unlink steps:

  1. If x is a chained node, unlink it from its same-sized fd/bk links
     and choose its bk node as its replacement.
  2. If x was the last node of its size, but not a leaf node, it must
     be replaced with a leaf node (not merely one with an open left or
     right), to make sure that lefts and rights of descendents
     correspond properly to bit masks.  We use the rightmost descendent
     of x.  We could use any other leaf, but this is easy to locate and
     tends to counteract removal of leftmosts elsewhere, and so keeps
     paths shorter than minimally guaranteed.  This doesn't loop much
     because on average a node in a tree is near the bottom.
  3. If x is the base of a chain (i.e., has parent links) relink
     x's parent and children to x's replacement (or null if none).
*/

void malloc_state::unlink_large_chunk(tchunkptr X) {
    tchunkptr XP = X->_parent;
    tchunkptr R;
    if (X->_bk != X) {
        tchunkptr F = X->_fd;
        R = X->_bk;
        if (rtcheck(ok_address(F) && F->_bk == X && R->_fd == X)) {
            F->_bk = R;
            R->_fd = F;
        }
        else {
            CORRUPTION_ERROR_ACTION(this);
        }
    }
    else {
        tchunkptr* RP;
        if (((R = *(RP = &(X->_child[1]))) != 0) ||
            ((R = *(RP = &(X->_child[0]))) != 0)) {
            tchunkptr* CP;
            while ((*(CP = &(R->_child[1])) != 0) ||
                   (*(CP = &(R->_child[0])) != 0)) {
                R = *(RP = CP);
            }
            if (rtcheck(ok_address(RP)))
                *RP = 0;
            else {
                CORRUPTION_ERROR_ACTION(this);
            }
        }
    }
    if (XP != 0) {
        tbinptr* H = treebin_at(X->_index);
        if (X == *H) {
            if ((*H = R) == 0) 
                clear_treemap(X->_index);
        }
        else if (rtcheck(ok_address(XP))) {
            if (XP->_child[0] == X) 
                XP->_child[0] = R;
            else 
                XP->_child[1] = R;
        }
        else
            CORRUPTION_ERROR_ACTION(this);
        if (R != 0) {
            if (rtcheck(ok_address(R))) {
                tchunkptr C0, C1;
                R->_parent = XP;
                if ((C0 = X->_child[0]) != 0) {
                    if (rtcheck(ok_address(C0))) {
                        R->_child[0] = C0;
                        C0->_parent = R;
                    }
                    else
                        CORRUPTION_ERROR_ACTION(this);
                }
                if ((C1 = X->_child[1]) != 0) {
                    if (rtcheck(ok_address(C1))) {
                        R->_child[1] = C1;
                        C1->_parent = R;
                    }
                    else
                        CORRUPTION_ERROR_ACTION(this);
                }
            }
            else
                CORRUPTION_ERROR_ACTION(this);
        }
    }
}

// Relays to large vs small bin operations

void malloc_state::insert_chunk(mchunkptr p, size_t s)
{
    if (is_small(s)) 
        insert_small_chunk(p, s);
    else 
    { 
        tchunkptr tp = (tchunkptr)(p); 
        insert_large_chunk(tp, s); 
    }
}

void malloc_state::unlink_chunk(mchunkptr p, size_t s)
{
    if (is_small(s)) 
        unlink_small_chunk(p, s);
    else 
    {
        tchunkptr tp = (tchunkptr)(p); 
        unlink_large_chunk(tp); 
    }
}


// Relays to internal calls to malloc/free from realloc, memalign etc

#if !ONLY_MSPACES && MSPACES
    void *malloc_state::internal_malloc(size_t b) {
        return ((this == gm)? dlmalloc(b) : mspace_malloc(this, b)); 
    }
    void malloc_state::internal_free(void *mem) {
        if (this == gm) dlfree(mem); else mspace_free(this,mem);
    }
#endif

/* -----------------------  Direct-mmapping chunks ----------------------- */

/*
  Directly mmapped chunks are set up with an offset to the start of
  the mmapped region stored in the prev_foot field of the chunk. This
  allows reconstruction of the required argument to MUNMAP when freed,
  and also allows adjustment of the returned chunk to meet alignment
  requirements (especially in memalign).
*/

// Malloc using mmap
void* malloc_state::mmap_alloc(size_t nb) {
    size_t mmsize = mmap_align(nb + 6 * sizeof(size_t) + CHUNK_ALIGN_MASK);
    if (_footprint_limit != 0) {
        size_t fp = _footprint + mmsize;
        if (fp <= _footprint || fp > _footprint_limit)
            return 0;
    }
    if (mmsize > nb) {
        // Check for wrap around 0
        char* mm = (char*)(CALL_DIRECT_MMAP(mmsize));
        if (mm != CMFAIL) {
            size_t offset = align_offset(chunk2mem(mm));
            size_t psize = mmsize - offset - MMAP_FOOT_PAD;
            mchunkptr p = (mchunkptr)(mm + offset);
            p->_prev_foot = offset;
            p->_head = psize;
            mark_inuse_foot(p, psize);
            p->chunk_plus_offset(psize)->_head = FENCEPOST_HEAD;
            p->chunk_plus_offset(psize+sizeof(size_t))->_head = 0;

            if (_least_addr == 0 || mm < _least_addr)
                _least_addr = mm;
            if ((_footprint += mmsize) > _max_footprint)
                _max_footprint = _footprint;
            assert(is_aligned(chunk2mem(p)));
            check_mmapped_chunk(p);
            return chunk2mem(p);
        }
    }
    return 0;
}

// Realloc using mmap
mchunkptr malloc_state::mmap_resize(mchunkptr oldp, size_t nb, int flags) {
    size_t oldsize = oldp->chunksize();
    (void)flags;      // placate people compiling -Wunused
    if (is_small(nb)) // Can't shrink mmap regions below small size
        return 0;

    // Keep old chunk if big enough but not too big
    if (oldsize >= nb + sizeof(size_t) &&
        (oldsize - nb) <= (mparams._granularity << 1))
        return oldp;
    else {
        size_t offset = oldp->_prev_foot;
        size_t oldmmsize = oldsize + offset + MMAP_FOOT_PAD;
        size_t newmmsize = mmap_align(nb + 6 * sizeof(size_t) + CHUNK_ALIGN_MASK);
        char* cp = (char*)CALL_MREMAP((char*)oldp - offset,
                                      oldmmsize, newmmsize, flags);
        if (cp != CMFAIL) {
            mchunkptr newp = (mchunkptr)(cp + offset);
            size_t psize = newmmsize - offset - MMAP_FOOT_PAD;
            newp->_head = psize;
            mark_inuse_foot(newp, psize);
            newp->chunk_plus_offset(psize)->_head = FENCEPOST_HEAD;
            newp->chunk_plus_offset(psize+sizeof(size_t))->_head = 0;

            if (cp < _least_addr)
                _least_addr = cp;
            if ((_footprint += newmmsize - oldmmsize) > _max_footprint)
                _max_footprint = _footprint;
            check_mmapped_chunk(newp);
            return newp;
        }
    }
    return 0;
}


/* -------------------------- mspace management -------------------------- */

// Initialize top chunk and its size
void malloc_state::init_top(mchunkptr p, size_t psize) {
    // Ensure alignment
    size_t offset = align_offset(chunk2mem(p));
    p = (mchunkptr)((char*)p + offset);
    psize -= offset;

    _top = p;
    _topsize = psize;
    p->_head = psize | PINUSE_BIT;
    // set size of fake trailing chunk holding overhead space only once
    p->chunk_plus_offset(psize)->_head = TOP_FOOT_SIZE;
    _trim_check = mparams._trim_threshold; // reset on each update
}

// Initialize bins for a new mstate that is otherwise zeroed out
void malloc_state::init_bins() {
    // Establish circular links for smallbins
    bindex_t i;
    for (i = 0; i < NSMALLBINS; ++i) {
        sbinptr bin = smallbin_at(i);
        bin->_fd = bin->_bk = bin;
    }
}

#if PROCEED_ON_ERROR

// default corruption action
void malloc_state::reset_on_error() {
    int i;
    ++malloc_corruption_error_count;
    // Reinitialize fields to forget about all memory
    _smallmap = _treemap = 0;
    _dvsize = _topsize = 0;
    _seg._base = 0;
    _seg._size = 0;
    _seg._next = 0;
    _top = _dv = 0;
    for (i = 0; i < NTREEBINS; ++i)
        *treebin_at(i) = 0;
    init_bins();
}
#endif // PROCEED_ON_ERROR

/* Allocate chunk and prepend remainder with chunk in successor base. */
void* malloc_state::prepend_alloc(char* newbase, char* oldbase, size_t nb) {
    mchunkptr p = align_as_chunk(newbase);
    mchunkptr oldfirst = align_as_chunk(oldbase);
    size_t psize = (char*)oldfirst - (char*)p;
    mchunkptr q = (mchunkptr)p->chunk_plus_offset(nb);
    size_t qsize = psize - nb;
    set_size_and_pinuse_of_inuse_chunk(p, nb);

    assert((char*)oldfirst > (char*)q);
    assert(oldfirst->pinuse());
    assert(qsize >= MIN_CHUNK_SIZE);

    // consolidate remainder with first chunk of old base
    if (oldfirst == _top) {
        size_t tsize = _topsize += qsize;
        _top = q;
        q->_head = tsize | PINUSE_BIT;
        check_top_chunk(q);
    }
    else if (oldfirst == _dv) {
        size_t dsize = _dvsize += qsize;
        _dv = q;
        q->set_size_and_pinuse_of_free_chunk(dsize);
    }
    else {
        if (!oldfirst->is_inuse()) {
            size_t nsize = oldfirst->chunksize();
            unlink_chunk(oldfirst, nsize);
            oldfirst = (mchunkptr)oldfirst->chunk_plus_offset(nsize);
            qsize += nsize;
        }
        q->set_free_with_pinuse(qsize, oldfirst);
        insert_chunk(q, qsize);
        check_free_chunk(q);
    }

    check_malloced_chunk(chunk2mem(p), nb);
    return chunk2mem(p);
}

// Add a segment to hold a new noncontiguous region
void malloc_state::add_segment(char* tbase, size_t tsize, flag_t mmapped) {
    // Determine locations and sizes of segment, fenceposts, old top
    char* old_top = (char*)_top;
    msegmentptr oldsp = segment_holding(old_top);
    char* old_end = oldsp->_base + oldsp->_size;
    size_t ssize = pad_request(sizeof(struct malloc_segment));
    char* rawsp = old_end - (ssize + 4 * sizeof(size_t) + CHUNK_ALIGN_MASK);
    size_t offset = align_offset(chunk2mem(rawsp));
    char* asp = rawsp + offset;
    char* csp = (asp < (old_top + MIN_CHUNK_SIZE))? old_top : asp;
    mchunkptr sp = (mchunkptr)csp;
    msegmentptr ss = (msegmentptr)(chunk2mem(sp));
    mchunkptr tnext = (mchunkptr)sp->chunk_plus_offset(ssize);
    mchunkptr p = tnext;
    int nfences = 0;

    // reset top to new space
    init_top((mchunkptr)tbase, tsize - TOP_FOOT_SIZE);

    // Set up segment record
    assert(is_aligned(ss));
    set_size_and_pinuse_of_inuse_chunk(sp, ssize);
    *ss = _seg; // Push current record
    _seg._base = tbase;
    _seg._size = tsize;
    _seg._sflags = mmapped;
    _seg._next = ss;

    // Insert trailing fenceposts
    for (;;) {
        mchunkptr nextp = (mchunkptr)p->chunk_plus_offset(sizeof(size_t));
        p->_head = FENCEPOST_HEAD;
        ++nfences;
        if ((char*)(&(nextp->_head)) < old_end)
            p = nextp;
        else
            break;
    }
    assert(nfences >= 2);

    // Insert the rest of old top into a bin as an ordinary free chunk
    if (csp != old_top) {
        mchunkptr q = (mchunkptr)old_top;
        size_t psize = csp - old_top;
        mchunkptr tn = (mchunkptr)q->chunk_plus_offset(psize);
        q->set_free_with_pinuse(psize, tn);
        insert_chunk(q, psize);
    }

    check_top_chunk(_top);
}

/* -------------------------- System allocation -------------------------- */

// Get memory from system using MORECORE or MMAP
void* malloc_state::sys_alloc(size_t nb) {
    char* tbase = CMFAIL;
    size_t tsize = 0;
    flag_t mmap_flag = 0;
    size_t asize; // allocation size

    mparams.ensure_initialization();

    // Directly map large chunks, but only if already initialized
    if (use_mmap() && nb >= mparams._mmap_threshold && _topsize != 0) {
        void* mem = mmap_alloc(nb);
        if (mem != 0)
            return mem;
    }

    asize = mparams.granularity_align(nb + SYS_ALLOC_PADDING);
    if (asize <= nb)
        return 0; // wraparound
    if (_footprint_limit != 0) {
        size_t fp = _footprint + asize;
        if (fp <= _footprint || fp > _footprint_limit)
            return 0;
    }

    /*
      Try getting memory in any of three ways (in most-preferred to
      least-preferred order):
      1. A call to MORECORE that can normally contiguously extend memory.
      (disabled if not MORECORE_CONTIGUOUS or not HAVE_MORECORE or
      or main space is mmapped or a previous contiguous call failed)
      2. A call to MMAP new space (disabled if not HAVE_MMAP).
      Note that under the default settings, if MORECORE is unable to
      fulfill a request, and HAVE_MMAP is true, then mmap is
      used as a noncontiguous system allocator. This is a useful backup
      strategy for systems with holes in address spaces -- in this case
      sbrk cannot contiguously expand the heap, but mmap may be able to
      find space.
      3. A call to MORECORE that cannot usually contiguously extend memory.
      (disabled if not HAVE_MORECORE)

      In all cases, we need to request enough bytes from system to ensure
      we can malloc nb bytes upon success, so pad with enough space for
      top_foot, plus alignment-pad to make sure we don't lose bytes if
      not on boundary, and round this up to a granularity unit.
    */

    if (MORECORE_CONTIGUOUS && !use_noncontiguous()) {
        char* br = CMFAIL;
        size_t ssize = asize; // sbrk call size
        msegmentptr ss = (_top == 0)? 0 : segment_holding((char*)_top);
        ACQUIRE_MALLOC_GLOBAL_LOCK();

        if (ss == 0) {
            // First time through or recovery
            char* base = (char*)CALL_MORECORE(0);
            if (base != CMFAIL) {
                size_t fp;
                // Adjust to end on a page boundary
                if (!mparams.is_page_aligned(base))
                    ssize += (mparams.page_align((size_t)base) - (size_t)base);
                fp = _footprint + ssize; // recheck limits
                if (ssize > nb && ssize < HALF_MAX_SIZE_T &&
                    (_footprint_limit == 0 ||
                     (fp > _footprint && fp <= _footprint_limit)) &&
                    (br = (char*)(CALL_MORECORE(ssize))) == base) {
                    tbase = base;
                    tsize = ssize;
                }
            }
        }
        else {
            // Subtract out existing available top space from MORECORE request.
            ssize = mparams.granularity_align(nb - _topsize + SYS_ALLOC_PADDING);
            // Use mem here only if it did continuously extend old space
            if (ssize < HALF_MAX_SIZE_T &&
                (br = (char*)(CALL_MORECORE(ssize))) == ss->_base+ss->_size) {
                tbase = br;
                tsize = ssize;
            }
        }

        if (tbase == CMFAIL) {
            // Cope with partial failure
            if (br != CMFAIL) {
                // Try to use/extend the space we did get
                if (ssize < HALF_MAX_SIZE_T &&
                    ssize < nb + SYS_ALLOC_PADDING) {
                    size_t esize = mparams.granularity_align(nb + SYS_ALLOC_PADDING - ssize);
                    if (esize < HALF_MAX_SIZE_T) {
                        char* end = (char*)CALL_MORECORE(esize);
                        if (end != CMFAIL)
                            ssize += esize;
                        else {
                            // Can't use; try to release
                            (void) CALL_MORECORE(-ssize);
                            br = CMFAIL;
                        }
                    }
                }
            }
            if (br != CMFAIL) {
                // Use the space we did get
                tbase = br;
                tsize = ssize;
            }
            else
                disable_contiguous(); // Don't try contiguous path in the future
        }

        RELEASE_MALLOC_GLOBAL_LOCK();
    }

    if (HAVE_MMAP && tbase == CMFAIL) {
        // Try MMAP
        char* mp = (char*)(CALL_MMAP(asize));
        if (mp != CMFAIL) {
            tbase = mp;
            tsize = asize;
            mmap_flag = USE_MMAP_BIT;
        }
    }

    if (HAVE_MORECORE && tbase == CMFAIL) {
        // Try noncontiguous MORECORE
        if (asize < HALF_MAX_SIZE_T) {
            char* br = CMFAIL;
            char* end = CMFAIL;
            ACQUIRE_MALLOC_GLOBAL_LOCK();
            br = (char*)(CALL_MORECORE(asize));
            end = (char*)(CALL_MORECORE(0));
            RELEASE_MALLOC_GLOBAL_LOCK();
            if (br != CMFAIL && end != CMFAIL && br < end) {
                size_t ssize = end - br;
                if (ssize > nb + TOP_FOOT_SIZE) {
                    tbase = br;
                    tsize = ssize;
                }
            }
        }
    }

    if (tbase != CMFAIL) {

        if ((_footprint += tsize) > _max_footprint)
            _max_footprint = _footprint;

        if (!is_initialized()) {
            // first-time initialization
            if (_least_addr == 0 || tbase < _least_addr)
                _least_addr = tbase;
            _seg._base = tbase;
            _seg._size = tsize;
            _seg._sflags = mmap_flag;
            _magic = mparams._magic;
            _release_checks = MAX_RELEASE_CHECK_RATE;
            init_bins();
#if !ONLY_MSPACES
            if (is_global(this))
                init_top((mchunkptr)tbase, tsize - TOP_FOOT_SIZE);
            else
#endif
            {
                // Offset top by embedded malloc_state
                mchunkptr mn = (mchunkptr)mem2chunk(this)->next_chunk();
                init_top(mn, (size_t)((tbase + tsize) - (char*)mn) -TOP_FOOT_SIZE);
            }
        }

        else {
            // Try to merge with an existing segment
            msegmentptr sp = &_seg;
            // Only consider most recent segment if traversal suppressed
            while (sp != 0 && tbase != sp->_base + sp->_size)
                sp = (NO_SEGMENT_TRAVERSAL) ? 0 : sp->_next;
            if (sp != 0 &&
                !sp->is_extern_segment() &&
                (sp->_sflags & USE_MMAP_BIT) == mmap_flag &&
                segment_holds(sp, _top)) {
                // append
                sp->_size += tsize;
                init_top(_top, _topsize + tsize);
            }
            else {
                if (tbase < _least_addr)
                    _least_addr = tbase;
                sp = &_seg;
                while (sp != 0 && sp->_base != tbase + tsize)
                    sp = (NO_SEGMENT_TRAVERSAL) ? 0 : sp->_next;
                if (sp != 0 &&
                    !sp->is_extern_segment() &&
                    (sp->_sflags & USE_MMAP_BIT) == mmap_flag) {
                    char* oldbase = sp->_base;
                    sp->_base = tbase;
                    sp->_size += tsize;
                    return prepend_alloc(tbase, oldbase, nb);
                }
                else
                    add_segment(tbase, tsize, mmap_flag);
            }
        }

        if (nb < _topsize) {
            // Allocate from new or extended top space
            size_t rsize = _topsize -= nb;
            mchunkptr p = _top;
            mchunkptr r = _top = (mchunkptr)p->chunk_plus_offset(nb);
            r->_head = rsize | PINUSE_BIT;
            set_size_and_pinuse_of_inuse_chunk(p, nb);
            check_top_chunk(_top);
            check_malloced_chunk(chunk2mem(p), nb);
            return chunk2mem(p);
        }
    }

    MALLOC_FAILURE_ACTION;
    return 0;
}

/* -----------------------  system deallocation -------------------------- */

// Unmap and unlink any mmapped segments that don't contain used chunks
size_t malloc_state::release_unused_segments() {
    size_t released = 0;
    int nsegs = 0;
    msegmentptr pred = &_seg;
    msegmentptr sp = pred->_next;
    while (sp != 0) {
        char* base = sp->_base;
        size_t size = sp->_size;
        msegmentptr next = sp->_next;
        ++nsegs;
        if (sp->is_mmapped_segment() && !sp->is_extern_segment()) {
            mchunkptr p = align_as_chunk(base);
            size_t psize = p->chunksize();
            // Can unmap if first chunk holds entire segment and not pinned
            if (!p->is_inuse() && (char*)p + psize >= base + size - TOP_FOOT_SIZE) {
                tchunkptr tp = (tchunkptr)p;
                assert(segment_holds(sp, p));
                if (p == _dv) {
                    _dv = 0;
                    _dvsize = 0;
                }
                else {
                    unlink_large_chunk(tp);
                }
                if (CALL_MUNMAP(base, size) == 0) {
                    released += size;
                    _footprint -= size;
                    // unlink obsoleted record
                    sp = pred;
                    sp->_next = next;
                }
                else {
                    // back out if cannot unmap
                    insert_large_chunk(tp, psize);
                }
            }
        }
        if (NO_SEGMENT_TRAVERSAL) // scan only first segment
            break;
        pred = sp;
        sp = next;
    }
    // Reset check counter
    _release_checks = (((size_t) nsegs > (size_t) MAX_RELEASE_CHECK_RATE)?
                         (size_t) nsegs : (size_t) MAX_RELEASE_CHECK_RATE);
    return released;
}

int malloc_state::sys_trim(size_t pad) {
    size_t released = 0;
    mparams.ensure_initialization();
    if (pad < MAX_REQUEST && is_initialized()) {
        pad += TOP_FOOT_SIZE; // ensure enough room for segment overhead

        if (_topsize > pad) {
            // Shrink top space in _granularity - size units, keeping at least one
            size_t unit = mparams._granularity;
            size_t extra = ((_topsize - pad + (unit - 1)) / unit -
                            1) * unit;
            msegmentptr sp = segment_holding((char*)_top);

            if (!sp->is_extern_segment()) {
                if (sp->is_mmapped_segment()) {
                    if (HAVE_MMAP &&
                        sp->_size >= extra &&
                        !has_segment_link(sp)) {
                        // can't shrink if pinned
                        size_t newsize = sp->_size - extra;
                        (void)newsize; // placate people compiling -Wunused-variable
                        // Prefer mremap, fall back to munmap
                        if ((CALL_MREMAP(sp->_base, sp->_size, newsize, 0) != MFAIL) ||
                            (CALL_MUNMAP(sp->_base + newsize, extra) == 0)) {
                            released = extra;
                        }
                    }
                }
                else if (HAVE_MORECORE) {
                    if (extra >= HALF_MAX_SIZE_T) // Avoid wrapping negative
                        extra = (HALF_MAX_SIZE_T) + 1 - unit;
                    ACQUIRE_MALLOC_GLOBAL_LOCK();
                    {
                        // Make sure end of memory is where we last set it.
                        char* old_br = (char*)(CALL_MORECORE(0));
                        if (old_br == sp->_base + sp->_size) {
                            char* rel_br = (char*)(CALL_MORECORE(-extra));
                            char* new_br = (char*)(CALL_MORECORE(0));
                            if (rel_br != CMFAIL && new_br < old_br)
                                released = old_br - new_br;
                        }
                    }
                    RELEASE_MALLOC_GLOBAL_LOCK();
                }
            }

            if (released != 0) {
                sp->_size -= released;
                _footprint -= released;
                init_top(_top, _topsize - released);
                check_top_chunk(_top);
            }
        }

        // Unmap any unused mmapped segments
        if (HAVE_MMAP)
            released += release_unused_segments();

        // On failure, disable autotrim to avoid repeated failed future calls
        if (released == 0 && _topsize > _trim_check)
            _trim_check = MAX_SIZE_T;
    }

    return (released != 0)? 1 : 0;
}

/* Consolidate and bin a chunk. Differs from exported versions
   of free mainly in that the chunk need not be marked as inuse.
*/
void malloc_state::dispose_chunk(mchunkptr p, size_t psize) {
    mchunkptr next = (mchunkptr)p->chunk_plus_offset(psize);
    if (!p->pinuse()) {
        mchunkptr prev;
        size_t prevsize = p->_prev_foot;
        if (p->is_mmapped()) {
            psize += prevsize + MMAP_FOOT_PAD;
            if (CALL_MUNMAP((char*)p - prevsize, psize) == 0)
                _footprint -= psize;
            return;
        }
        prev = (mchunkptr)p->chunk_minus_offset(prevsize);
        psize += prevsize;
        p = prev;
        if (rtcheck(ok_address(prev))) {
            // consolidate backward
            if (p != _dv) {
                unlink_chunk(p, prevsize);
            }
            else if ((next->_head & INUSE_BITS) == INUSE_BITS) {
                _dvsize = psize;
                p->set_free_with_pinuse(psize, next);
                return;
            }
        }
        else {
            CORRUPTION_ERROR_ACTION(this);
            return;
        }
    }
    if (rtcheck(ok_address(next))) {
        if (!next->cinuse()) {
            // consolidate forward
            if (next == _top) {
                size_t tsize = _topsize += psize;
                _top = p;
                p->_head = tsize | PINUSE_BIT;
                if (p == _dv) {
                    _dv = 0;
                    _dvsize = 0;
                }
                return;
            }
            else if (next == _dv) {
                size_t dsize = _dvsize += psize;
                _dv = p;
                p->set_size_and_pinuse_of_free_chunk(dsize);
                return;
            }
            else {
                size_t nsize = next->chunksize();
                psize += nsize;
                unlink_chunk(next, nsize);
                p->set_size_and_pinuse_of_free_chunk(psize);
                if (p == _dv) {
                    _dvsize = psize;
                    return;
                }
            }
        }
        else {
            p->set_free_with_pinuse(psize, next);
        }
        insert_chunk(p, psize);
    }
    else {
        CORRUPTION_ERROR_ACTION(this);
    }
}

/* ---------------------------- malloc --------------------------- */

// allocate a large request from the best fitting chunk in a treebin
void* malloc_state::tmalloc_large(size_t nb) {
    tchunkptr v = 0;
    size_t rsize = -nb; // Unsigned negation
    tchunkptr t;
    bindex_t idx = compute_tree_index(nb);
    if ((t = *treebin_at(idx)) != 0) {
        // Traverse tree for this bin looking for node with size == nb
        size_t sizebits = nb << leftshift_for_tree_index(idx);
        tchunkptr rst = 0;  // The deepest untaken right subtree
        for (;;) {
            tchunkptr rt;
            size_t trem = t->chunksize() - nb;
            if (trem < rsize) {
                v = t;
                if ((rsize = trem) == 0)
                    break;
            }
            rt = t->_child[1];
            t = t->_child[(sizebits >> (SIZE_T_BITSIZE - 1)) & 1];
            if (rt != 0 && rt != t)
                rst = rt;
            if (t == 0) {
                t = rst; // set t to least subtree holding sizes > nb
                break;
            }
            sizebits <<= 1;
        }
    }
    if (t == 0 && v == 0) {
        // set t to root of next non-empty treebin
        binmap_t leftbits = left_bits(idx2bit(idx)) & _treemap;
        if (leftbits != 0) {
            binmap_t leastbit = least_bit(leftbits);
            bindex_t i = compute_bit2idx(leastbit);
            t = *treebin_at(i);
        }
    }

    while (t != 0) {
        // find smallest of tree or subtree
        size_t trem = t->chunksize() - nb;
        if (trem < rsize) {
            rsize = trem;
            v = t;
        }
        t = t->leftmost_child();
    }

    //  If dv is a better fit, return 0 so malloc will use it
    if (v != 0 && rsize < (size_t)(_dvsize - nb)) {
        if (rtcheck(ok_address(v))) {
            // split
            mchunkptr r = (mchunkptr)v->chunk_plus_offset(nb);
            assert(v->chunksize() == rsize + nb);
            if (rtcheck(ok_next(v, r))) {
                unlink_large_chunk(v);
                if (rsize < MIN_CHUNK_SIZE)
                    set_inuse_and_pinuse(v, (rsize + nb));
                else {
                    set_size_and_pinuse_of_inuse_chunk(v, nb);
                    r->set_size_and_pinuse_of_free_chunk(rsize);
                    insert_chunk(r, rsize);
                }
                return chunk2mem(v);
            }
        }
        CORRUPTION_ERROR_ACTION(this);
    }
    return 0;
}

// allocate a small request from the best fitting chunk in a treebin
void* malloc_state::tmalloc_small(size_t nb) {
    tchunkptr t, v;
    size_t rsize;
    binmap_t leastbit = least_bit(_treemap);
    bindex_t i = compute_bit2idx(leastbit);
    v = t = *treebin_at(i);
    rsize = t->chunksize() - nb;

    while ((t = t->leftmost_child()) != 0) {
        size_t trem = t->chunksize() - nb;
        if (trem < rsize) {
            rsize = trem;
            v = t;
        }
    }

    if (rtcheck(ok_address(v))) {
        mchunkptr r = (mchunkptr)v->chunk_plus_offset(nb);
        assert(v->chunksize() == rsize + nb);
        if (rtcheck(ok_next(v, r))) {
            unlink_large_chunk(v);
            if (rsize < MIN_CHUNK_SIZE)
                set_inuse_and_pinuse(v, (rsize + nb));
            else {
                set_size_and_pinuse_of_inuse_chunk(v, nb);
                r->set_size_and_pinuse_of_free_chunk(rsize);
                replace_dv(r, rsize);
            }
            return chunk2mem(v);
        }
    }

    CORRUPTION_ERROR_ACTION(this);
    return 0;
}

#if !ONLY_MSPACES

void* dlmalloc(size_t bytes) DLTHROW {
    /*
      Basic algorithm:
      If a small request (< 256 bytes minus per-chunk overhead):
      1. If one exists, use a remainderless chunk in associated smallbin.
      (Remainderless means that there are too few excess bytes to
      represent as a chunk.)
      2. If it is big enough, use the dv chunk, which is normally the
      chunk adjacent to the one used for the most recent small request.
      3. If one exists, split the smallest available chunk in a bin,
      saving remainder in dv.
      4. If it is big enough, use the top chunk.
      5. If available, get memory from system and use it
      Otherwise, for a large request:
      1. Find the smallest available binned chunk that fits, and use it
      if it is better fitting than dv chunk, splitting if necessary.
      2. If better fitting than any binned chunk, use the dv chunk.
      3. If it is big enough, use the top chunk.
      4. If request size >= mmap threshold, try to directly mmap this chunk.
      5. If available, get memory from system and use it

      The ugly goto's here ensure that postaction occurs along all paths.
    */

#if USE_LOCKS
    mparams.ensure_initialization(); // initialize in sys_alloc if not using locks
#endif
    return gm->_malloc(bytes);
}

void dlfree(void* mem) DLTHROW {
    /*
      Consolidate freed chunks with preceeding or succeeding bordering
      free chunks, if they exist, and then place in a bin.  Intermixed
      with special cases for top, dv, mmapped chunks, and usage errors.
    */

    if (mem != 0) {
        mchunkptr p  = mem2chunk(mem);
#if FOOTERS
        mstate fm = get_mstate_for(p);
        if (!fm->ok_magic()) {
            USAGE_ERROR_ACTION(fm, p);
            return;
        }
        fm->_free(p);
#else // FOOTERS
        gm->_free(p);
#endif // FOOTERS
    }
}

void* dlcalloc(size_t n_elements, size_t elem_size) DLTHROW {
    void* mem;
    size_t req = 0;
    if (n_elements != 0) {
        req = n_elements * elem_size;
        if (((n_elements | elem_size) & ~(size_t)0xffff) &&
            (req / n_elements != elem_size))
            req = MAX_SIZE_T; // force downstream failure on overflow
    }
    mem = dlmalloc(req);
    if (mem != 0 && mem2chunk(mem)->calloc_must_clear())
        memset(mem, 0, req);
    return mem;
}

#endif // !ONLY_MSPACES

/* ---------------------------- malloc --------------------------- */

void* malloc_state::_malloc(size_t bytes) {
    if (!PREACTION(this)) {
        void* mem;
        size_t nb;
        if (bytes <= MAX_SMALL_REQUEST) {
            bindex_t idx;
            binmap_t smallbits;
            nb = (bytes < MIN_REQUEST)? MIN_CHUNK_SIZE : pad_request(bytes);
            idx = small_index(nb);
            smallbits = _smallmap >> idx;

            if ((smallbits & 0x3U) != 0) {
                // Remainderless fit to a smallbin.
                mchunkptr b, p;
                idx += ~smallbits & 1;       // Uses next bin if idx empty
                b = smallbin_at(idx);
                p = b->_fd;
                assert(p->chunksize() == small_index2size(idx));
                unlink_first_small_chunk(b, p, idx);
                set_inuse_and_pinuse(p, small_index2size(idx));
                mem = chunk2mem(p);
                check_malloced_chunk(mem, nb);
                goto postaction;
            }

            else if (nb > _dvsize) {
                if (smallbits != 0) {
                    // Use chunk in next nonempty smallbin
                    mchunkptr b, p, r;
                    size_t rsize;
                    binmap_t leftbits = (smallbits << idx) & left_bits(malloc_state::idx2bit(idx));
                    binmap_t leastbit = least_bit(leftbits);
                    bindex_t i = compute_bit2idx(leastbit);
                    b = smallbin_at(i);
                    p = b->_fd;
                    assert(p->chunksize() == small_index2size(i));
                    unlink_first_small_chunk(b, p, i);
                    rsize = small_index2size(i) - nb;
                    // Fit here cannot be remainderless if 4byte sizes
                    if (sizeof(size_t) != 4 && rsize < MIN_CHUNK_SIZE)
                        set_inuse_and_pinuse(p, small_index2size(i));
                    else {
                        set_size_and_pinuse_of_inuse_chunk(p, nb);
                        r = (mchunkptr)p->chunk_plus_offset(nb);
                        r->set_size_and_pinuse_of_free_chunk(rsize);
                        replace_dv(r, rsize);
                    }
                    mem = chunk2mem(p);
                    check_malloced_chunk(mem, nb);
                    goto postaction;
                }

                else if (_treemap != 0 && (mem = tmalloc_small(nb)) != 0) {
                    check_malloced_chunk(mem, nb);
                    goto postaction;
                }
            }
        }
        else if (bytes >= MAX_REQUEST)
            nb = MAX_SIZE_T; // Too big to allocate. Force failure (in sys alloc)
        else {
            nb = pad_request(bytes);
            if (_treemap != 0 && (mem = tmalloc_large(nb)) != 0) {
                check_malloced_chunk(mem, nb);
                goto postaction;
            }
        }

        if (nb <= _dvsize) {
            size_t rsize = _dvsize - nb;
            mchunkptr p = _dv;
            if (rsize >= MIN_CHUNK_SIZE) {
                // split dv
                mchunkptr r = _dv = (mchunkptr)p->chunk_plus_offset(nb);
                _dvsize = rsize;
                r->set_size_and_pinuse_of_free_chunk(rsize);
                set_size_and_pinuse_of_inuse_chunk(p, nb);
            }
            else { // exhaust dv
                size_t dvs = _dvsize;
                _dvsize = 0;
                _dv = 0;
                set_inuse_and_pinuse(p, dvs);
            }
            mem = chunk2mem(p);
            check_malloced_chunk(mem, nb);
            goto postaction;
        }

        else if (nb < _topsize) {
            // Split top
            size_t rsize = _topsize -= nb;
            mchunkptr p = _top;
            mchunkptr r = _top = (mchunkptr)p->chunk_plus_offset(nb);
            r->_head = rsize | PINUSE_BIT;
            set_size_and_pinuse_of_inuse_chunk(p, nb);
            mem = chunk2mem(p);
            check_top_chunk(_top);
            check_malloced_chunk(mem, nb);
            goto postaction;
        }

        mem = sys_alloc(nb);

    postaction:
        POSTACTION(this);
        return mem;
    }

    return 0;
}

/* ---------------------------- free --------------------------- */

void malloc_state::_free(mchunkptr p) {
    if (!PREACTION(this)) {
        check_inuse_chunk(p);
        if (rtcheck(ok_address(p) && ok_inuse(p))) {
            size_t psize = p->chunksize();
            mchunkptr next = (mchunkptr)p->chunk_plus_offset(psize);
            if (!p->pinuse()) {
                size_t prevsize = p->_prev_foot;
                if (p->is_mmapped()) {
                    psize += prevsize + MMAP_FOOT_PAD;
                    if (CALL_MUNMAP((char*)p - prevsize, psize) == 0)
                        _footprint -= psize;
                    goto postaction;
                }
                else {
                    mchunkptr prev = (mchunkptr)p->chunk_minus_offset(prevsize);
                    psize += prevsize;
                    p = prev;
                    if (rtcheck(ok_address(prev))) {
                        // consolidate backward
                        if (p != _dv) {
                            unlink_chunk(p, prevsize);
                        }
                        else if ((next->_head & INUSE_BITS) == INUSE_BITS) {
                            _dvsize = psize;
                            p->set_free_with_pinuse(psize, next);
                            goto postaction;
                        }
                    }
                    else
                        goto erroraction;
                }
            }

            if (rtcheck(ok_next(p, next) && ok_pinuse(next))) {
                if (!next->cinuse()) {
                    // consolidate forward
                    if (next == _top) {
                        size_t tsize = _topsize += psize;
                        _top = p;
                        p->_head = tsize | PINUSE_BIT;
                        if (p == _dv) {
                            _dv = 0;
                            _dvsize = 0;
                        }
                        if (should_trim(tsize))
                            sys_trim(0);
                        goto postaction;
                    }
                    else if (next == _dv) {
                        size_t dsize = _dvsize += psize;
                        _dv = p;
                        p->set_size_and_pinuse_of_free_chunk(dsize);
                        goto postaction;
                    }
                    else {
                        size_t nsize = next->chunksize();
                        psize += nsize;
                        unlink_chunk(next, nsize);
                        p->set_size_and_pinuse_of_free_chunk(psize);
                        if (p == _dv) {
                            _dvsize = psize;
                            goto postaction;
                        }
                    }
                }
                else
                    p->set_free_with_pinuse(psize, next);

                if (is_small(psize)) {
                    insert_small_chunk(p, psize);
                    check_free_chunk(p);
                }
                else {
                    tchunkptr tp = (tchunkptr)p;
                    insert_large_chunk(tp, psize);
                    check_free_chunk(p);
                    if (--_release_checks == 0)
                        release_unused_segments();
                }
                goto postaction;
            }
        }
    erroraction:
        USAGE_ERROR_ACTION(this, p);
    postaction:
        POSTACTION(this);
    }
}

/* ------------ Internal support for realloc, memalign, etc -------------- */

// Try to realloc; only in-place unless can_move true
mchunkptr malloc_state::try_realloc_chunk(mchunkptr p, size_t nb, int can_move) {
    mchunkptr newp = 0;
    size_t oldsize = p->chunksize();
    mchunkptr next = (mchunkptr)p->chunk_plus_offset(oldsize);
    if (rtcheck(ok_address(p) && ok_inuse(p) &&
                ok_next(p, next) && ok_pinuse(next))) {
        if (p->is_mmapped()) {
            newp = mmap_resize(p, nb, can_move);
        }
        else if (oldsize >= nb) {
            // already big enough
            size_t rsize = oldsize - nb;
            if (rsize >= MIN_CHUNK_SIZE) {
                // split off remainder
                mchunkptr r = (mchunkptr)p->chunk_plus_offset(nb);
                set_inuse(p, nb);
                set_inuse(r, rsize);
                dispose_chunk(r, rsize);
            }
            newp = p;
        }
        else if (next == _top) {
            // extend into top
            if (oldsize + _topsize > nb) {
                size_t newsize = oldsize + _topsize;
                size_t newtopsize = newsize - nb;
                mchunkptr newtop = (mchunkptr)p->chunk_plus_offset(nb);
                set_inuse(p, nb);
                newtop->_head = newtopsize | PINUSE_BIT;
                _top = newtop;
                _topsize = newtopsize;
                newp = p;
            }
        }
        else if (next == _dv) {
            // extend into dv
            size_t dvs = _dvsize;
            if (oldsize + dvs >= nb) {
                size_t dsize = oldsize + dvs - nb;
                if (dsize >= MIN_CHUNK_SIZE) {
                    mchunkptr r = (mchunkptr)p->chunk_plus_offset(nb);
                    mchunkptr n = (mchunkptr)r->chunk_plus_offset(dsize);
                    set_inuse(p, nb);
                    r->set_size_and_pinuse_of_free_chunk(dsize);
                    n->clear_pinuse();
                    _dvsize = dsize;
                    _dv = r;
                }
                else {
                    // exhaust dv
                    size_t newsize = oldsize + dvs;
                    set_inuse(p, newsize);
                    _dvsize = 0;
                    _dv = 0;
                }
                newp = p;
            }
        }
        else if (!next->cinuse()) {
            // extend into next free chunk
            size_t nextsize = next->chunksize();
            if (oldsize + nextsize >= nb) {
                size_t rsize = oldsize + nextsize - nb;
                unlink_chunk(next, nextsize);
                if (rsize < MIN_CHUNK_SIZE) {
                    size_t newsize = oldsize + nextsize;
                    set_inuse(p, newsize);
                }
                else {
                    mchunkptr r = (mchunkptr)p->chunk_plus_offset(nb);
                    set_inuse(p, nb);
                    set_inuse(r, rsize);
                    dispose_chunk(r, rsize);
                }
                newp = p;
            }
        }
    }
    else {
        USAGE_ERROR_ACTION(m, chunk2mem(p));
    }
    return newp;
}

void* malloc_state::internal_memalign(size_t alignment, size_t bytes) {
    void* mem = 0;
    if (alignment < MIN_CHUNK_SIZE) // must be at least a minimum chunk size
        alignment = MIN_CHUNK_SIZE;
    if ((alignment & (alignment - 1)) != 0) {
        // Ensure a power of 2
        size_t a = MALLOC_ALIGNMENT << 1;
        while (a < alignment) a <<= 1;
        alignment = a;
    }
    if (bytes >= MAX_REQUEST - alignment) {
        MALLOC_FAILURE_ACTION;
    }
    else {
        size_t nb = request2size(bytes);
        size_t req = nb + alignment + MIN_CHUNK_SIZE - CHUNK_OVERHEAD;
        mem = internal_malloc(req);
        if (mem != 0) {
            mchunkptr p = mem2chunk(mem);
            if (PREACTION(this))
                return 0;
            if ((((size_t)(mem)) & (alignment - 1)) != 0) {
                // misaligned
                /*
                  Find an aligned spot inside chunk.  Since we need to give
                  back leading space in a chunk of at least MIN_CHUNK_SIZE, if
                  the first calculation places us at a spot with less than
                  MIN_CHUNK_SIZE leader, we can move to the next aligned spot.
                  We've allocated enough total room so that this is always
                  possible.
                */
                char* br = (char*)mem2chunk((void *)(((size_t)((char*)mem + alignment - 1)) &
                                                     -alignment));
                char* pos = ((size_t)(br - (char*)(p)) >= MIN_CHUNK_SIZE)?
                    br : br+alignment;
                mchunkptr newp = (mchunkptr)pos;
                size_t leadsize = pos - (char*)(p);
                size_t newsize = p->chunksize() - leadsize;

                if (p->is_mmapped()) {
                    // For mmapped chunks, just adjust offset
                    newp->_prev_foot = p->_prev_foot + leadsize;
                    newp->_head = newsize;
                }
                else {
                    // Otherwise, give back leader, use the rest
                    set_inuse(newp, newsize);
                    set_inuse(p, leadsize);
                    dispose_chunk(p, leadsize);
                }
                p = newp;
            }

            // Give back spare room at the end
            if (!p->is_mmapped()) {
                size_t size = p->chunksize();
                if (size > nb + MIN_CHUNK_SIZE) {
                    size_t remainder_size = size - nb;
                    mchunkptr remainder = (mchunkptr)p->chunk_plus_offset(nb);
                    set_inuse(p, nb);
                    set_inuse(remainder, remainder_size);
                    dispose_chunk(remainder, remainder_size);
                }
            }

            mem = chunk2mem(p);
            assert (p->chunksize() >= nb);
            assert(((size_t)mem & (alignment - 1)) == 0);
            check_inuse_chunk(p);
            POSTACTION(this);
        }
    }
    return mem;
}

/*
  Common support for independent_X routines, handling
    all of the combinations that can result.
  The opts arg has:
    bit 0 set if all elements are same size (using sizes[0])
    bit 1 set if elements should be zeroed
*/
void** malloc_state::ialloc(size_t n_elements, size_t* sizes, int opts,
                            void* chunks[]) {

    size_t    element_size;   // chunksize of each element, if all same 
    size_t    contents_size;  // total size of elements 
    size_t    array_size;     // request size of pointer array 
    void*     mem;            // malloced aggregate space 
    mchunkptr p;              // corresponding chunk 
    size_t    remainder_size; // remaining bytes while splitting 
    void**    marray;         // either "chunks" or malloced ptr array 
    mchunkptr array_chunk;    // chunk for malloced ptr array 
    flag_t    was_enabled;    // to disable mmap 
    size_t    size;
    size_t    i;

    mparams.ensure_initialization();
    // compute array length, if needed 
    if (chunks != 0) {
        if (n_elements == 0)
            return chunks; // nothing to do 
        marray = chunks;
        array_size = 0;
    }
    else {
        // if empty req, must still return chunk representing empty array 
        if (n_elements == 0)
            return (void**)internal_malloc(0);
        marray = 0;
        array_size = request2size(n_elements * (sizeof(void*)));
    }

    // compute total element size 
    if (opts & 0x1) {
        // all-same-size 
        element_size = request2size(*sizes);
        contents_size = n_elements * element_size;
    }
    else {
        // add up all the sizes 
        element_size = 0;
        contents_size = 0;
        for (i = 0; i != n_elements; ++i)
            contents_size += request2size(sizes[i]);
    }

    size = contents_size + array_size;

    /*
      Allocate the aggregate chunk.  First disable direct-mmapping so
      malloc won't use it, since we would not be able to later
      free/realloc space internal to a segregated mmap region.
    */
    was_enabled = use_mmap();
    disable_mmap();
    mem = internal_malloc(size - CHUNK_OVERHEAD);
    if (was_enabled)
        enable_mmap();
    if (mem == 0)
        return 0;

    if (PREACTION(this)) return 0;
    p = mem2chunk(mem);
    remainder_size = p->chunksize();

    assert(!p->is_mmapped());

    if (opts & 0x2) {
        // optionally clear the elements 
        memset((size_t*)mem, 0, remainder_size - sizeof(size_t) - array_size);
    }

    // If not provided, allocate the pointer array as final part of chunk 
    if (marray == 0) {
        size_t  array_chunk_size;
        array_chunk = (mchunkptr)p->chunk_plus_offset(contents_size);
        array_chunk_size = remainder_size - contents_size;
        marray = (void**) (chunk2mem(array_chunk));
        set_size_and_pinuse_of_inuse_chunk(array_chunk, array_chunk_size);
        remainder_size = contents_size;
    }

    // split out elements 
    for (i = 0; ; ++i) {
        marray[i] = chunk2mem(p);
        if (i != n_elements - 1) {
            if (element_size != 0)
                size = element_size;
            else
                size = request2size(sizes[i]);
            remainder_size -= size;
            set_size_and_pinuse_of_inuse_chunk(p, size);
            p = (mchunkptr)p->chunk_plus_offset(size);
        }
        else { 
            // the final element absorbs any overallocation slop 
            set_size_and_pinuse_of_inuse_chunk(p, remainder_size);
            break;
        }
    }

#if DEBUG
    if (marray != chunks) {
        // final element must have exactly exhausted chunk 
        if (element_size != 0) {
            assert(remainder_size == element_size);
        }
        else {
            assert(remainder_size == request2size(sizes[i]));
        }
        check_inuse_chunk(mem2chunk(marray));
    }
    for (i = 0; i != n_elements; ++i)
        check_inuse_chunk(mem2chunk(marray[i]));

#endif

    POSTACTION(this);
    return marray;
}

/* Try to free all pointers in the given array.
   Note: this could be made faster, by delaying consolidation,
   at the price of disabling some user integrity checks, We
   still optimize some consolidations by combining adjacent
   chunks before freeing, which will occur often if allocated
   with ialloc or the array is sorted.
*/
size_t malloc_state::internal_bulk_free(void* array[], size_t nelem) {
    size_t unfreed = 0;
    if (!PREACTION(this)) {
        void** a;
        void** fence = &(array[nelem]);
        for (a = array; a != fence; ++a) {
            void* mem = *a;
            if (mem != 0) {
                mchunkptr p = mem2chunk(mem);
                size_t psize = p->chunksize();
#if FOOTERS && 0 // TODO: figure out this
                if (get_mstate_for(p) != m) {
                    ++unfreed;
                    continue;
                }
#endif
                check_inuse_chunk(p);
                *a = 0;
                if (rtcheck(ok_address(p) && ok_inuse(p))) {
                    void ** b = a + 1; // try to merge with next chunk
                    mchunkptr next = (mchunkptr)p->next_chunk();
                    if (b != fence && *b == chunk2mem(next)) {
                        size_t newsize = next->chunksize() + psize;
                        set_inuse(p, newsize);
                        *b = chunk2mem(p);
                    }
                    else
                        dispose_chunk(p, psize);
                }
                else {
                    CORRUPTION_ERROR_ACTION(this);
                    break;
                }
            }
        }
        if (should_trim(_topsize))
            sys_trim(0);
        POSTACTION(this);
    }
    return unfreed;
}

void malloc_state::init(char* tbase, size_t tsize) {
    _seg._base = _least_addr = tbase;
    _seg._size = _footprint = _max_footprint = tsize;
    _magic    = mparams._magic;
    _release_checks = MAX_RELEASE_CHECK_RATE;
    _mflags   = mparams._default_mflags;
    _extp     = 0;
    _exts     = 0;
    disable_contiguous();
    init_bins();
    mchunkptr mn = (mchunkptr)mem2chunk(this)->next_chunk();
    init_top(mn, (size_t)((tbase + tsize) - (char*)mn) - TOP_FOOT_SIZE);
    check_top_chunk(_top);
}

/* Traversal */
#if MALLOC_INSPECT_ALL
void malloc_state::internal_inspect_all(void(*handler)(void *start, void *end,
                                                       size_t used_bytes,
                                                       void* callback_arg),
                                        void* arg) {
    if (is_initialized()) {
        mchunkptr top = top;
        msegmentptr s;
        for (s = &seg; s != 0; s = s->next) {
            mchunkptr q = align_as_chunk(s->base);
            while (segment_holds(s, q) && q->head != FENCEPOST_HEAD) {
                mchunkptr next = (mchunkptr)q->next_chunk();
                size_t sz = q->chunksize();
                size_t used;
                void* start;
                if (q->is_inuse()) {
                    used = sz - CHUNK_OVERHEAD; // must not be mmapped
                    start = chunk2mem(q);
                }
                else {
                    used = 0;
                    if (is_small(sz)) {
                        // offset by possible bookkeeping
                        start = (void*)((char*)q + sizeof(struct malloc_chunk));
                    }
                    else {
                        start = (void*)((char*)q + sizeof(struct malloc_tree_chunk));
                    }
                }
                if (start < (void*)next)  // skip if all space is bookkeeping
                    handler(start, next, used, arg);
                if (q == top)
                    break;
                q = next;
            }
        }
    }
}
#endif // MALLOC_INSPECT_ALL

/* ------------------ Exported realloc, memalign, etc -------------------- */

#if !ONLY_MSPACES

void* dlrealloc(void* oldmem, size_t bytes) DLTHROW {
    void* mem = 0;
    if (oldmem == 0) {
        mem = dlmalloc(bytes);
    }
    else if (bytes >= MAX_REQUEST) {
        MALLOC_FAILURE_ACTION;
    }
#ifdef REALLOC_ZERO_BYTES_FREES
    else if (bytes == 0) {
        dlfree(oldmem);
    }
#endif // REALLOC_ZERO_BYTES_FREES
    else {
        size_t nb = request2size(bytes);
        mchunkptr oldp = mem2chunk(oldmem);
#if ! FOOTERS
        mstate m = gm;
#else 
        mstate m = get_mstate_for(oldp);
        if (!m->ok_magic()) {
            USAGE_ERROR_ACTION(m, oldmem);
            return 0;
        }
#endif
        if (!PREACTION(m)) {
            mchunkptr newp = m->try_realloc_chunk(oldp, nb, 1);
            POSTACTION(m);
            if (newp != 0) {
                m->check_inuse_chunk(newp);
                mem = chunk2mem(newp);
            }
            else {
                mem = m->internal_malloc(bytes);
                if (mem != 0) {
                    size_t oc = oldp->chunksize() - oldp->overhead_for();
                    memcpy(mem, oldmem, (oc < bytes)? oc : bytes);
                    m->internal_free(oldmem);
                }
            }
        }
    }
    return mem;
}

void* dlrealloc_in_place(void* oldmem, size_t bytes) {
    void* mem = 0;
    if (oldmem != 0) {
        if (bytes >= MAX_REQUEST) {
            MALLOC_FAILURE_ACTION;
        }
        else {
            size_t nb = request2size(bytes);
            mchunkptr oldp = mem2chunk(oldmem);
#if ! FOOTERS
            mstate m = gm;
#else 
            mstate m = get_mstate_for(oldp);
            if (!m->ok_magic()) {
                USAGE_ERROR_ACTION(m, oldmem);
                return 0;
            }
#endif
            if (!PREACTION(m)) {
                mchunkptr newp = m->try_realloc_chunk(oldp, nb, 0);
                POSTACTION(m);
                if (newp == oldp) {
                    m->check_inuse_chunk(newp);
                    mem = oldmem;
                }
            }
        }
    }
    return mem;
}

void* dlmemalign(size_t alignment, size_t bytes) {
    if (alignment <= MALLOC_ALIGNMENT) {
        return dlmalloc(bytes);
    }
    return gm->internal_memalign(alignment, bytes);
}

int dlposix_memalign(void** pp, size_t alignment, size_t bytes) DLTHROW {
    void* mem = 0;
    if (alignment == MALLOC_ALIGNMENT)
        mem = dlmalloc(bytes);
    else {
        size_t d = alignment / sizeof(void*);
        size_t r = alignment % sizeof(void*);
        if (r != 0 || d == 0 || (d & (d - 1)) != 0)
            return -1; // EINVAL
        else if (bytes <= MAX_REQUEST - alignment) {
            if (alignment <  MIN_CHUNK_SIZE)
                alignment = MIN_CHUNK_SIZE;
            mem = gm->internal_memalign(alignment, bytes);
        }
    }
    if (mem == 0)
        return -1; // ENOMEM
    else {
        *pp = mem;
        return 0;
    }
}

void* dlvalloc(size_t bytes) DLTHROW {
    size_t pagesz;
    mparams.ensure_initialization();
    pagesz = mparams._page_size;
    return dlmemalign(pagesz, bytes);
}

void* dlpvalloc(size_t bytes) {
    size_t pagesz;
    mparams.ensure_initialization();
    pagesz = mparams._page_size;
    return dlmemalign(pagesz, (bytes + pagesz - 1) & ~(pagesz - 1));
}

void** dlindependent_calloc(size_t n_elements, size_t elem_size,
                            void* chunks[]) {
    size_t sz = elem_size; // serves as 1-element array
    return gm->ialloc(n_elements, &sz, 3, chunks);
}

void** dlindependent_comalloc(size_t n_elements, size_t sizes[],
                              void* chunks[]) {
    return gm->ialloc(n_elements, sizes, 0, chunks);
}

size_t dlbulk_free(void* array[], size_t nelem) {
    return gm->internal_bulk_free(array, nelem);
}

#if MALLOC_INSPECT_ALL
void dlmalloc_inspect_all(void(*handler)(void *start,
                                         void *end,
                                         size_t used_bytes,
                                         void* callback_arg),
                          void* arg) {
    mparams.ensure_initialization();
    if (!PREACTION(gm)) {
        internal_inspect_all(gm, handler, arg);
        POSTACTION(gm);
    }
}
#endif 

int dlmalloc_trim(size_t pad) {
    int result = 0;
    mparams.ensure_initialization();
    if (!PREACTION(gm)) {
        result = gm->sys_trim(pad);
        POSTACTION(gm);
    }
    return result;
}

size_t dlmalloc_footprint(void) {
    return gm->_footprint;
}

size_t dlmalloc_max_footprint(void) {
    return gm->_max_footprint;
}

size_t dlmalloc_footprint_limit(void) {
    size_t maf = gm->_footprint_limit;
    return maf == 0 ? MAX_SIZE_T : maf;
}

size_t dlmalloc_set_footprint_limit(size_t bytes) {
    size_t result;  // invert sense of 0
    if (bytes == 0)
        result = mparams.granularity_align(1); // Use minimal size
    if (bytes == MAX_SIZE_T)
        result = 0;                    // disable
    else
        result = mparams.granularity_align(bytes);
    return gm->_footprint_limit = result;
}

#if !NO_MALLINFO
struct mallinfo dlmallinfo(void) {
    return gm->internal_mallinfo();
}
#endif

#if !NO_MALLOC_STATS
void dlmalloc_stats() {
    gm->internal_malloc_stats();
}
#endif 

int dlmallopt(int param_number, int value) {
    return mparams.change(param_number, value);
}

size_t dlmalloc_usable_size(void* mem) {
    if (mem != 0) {
        mchunkptr p = mem2chunk(mem);
        if (p->is_inuse())
            return p->chunksize() - p->overhead_for();
    }
    return 0;
}

#endif /* !ONLY_MSPACES */


/* ----------------------------- user mspaces ---------------------------- */

#if MSPACES

static mstate init_user_mstate(char* tbase, size_t tsize) {
    size_t msize = pad_request(sizeof(malloc_state));
    mchunkptr msp = align_as_chunk(tbase);
    mstate m = (mstate)(chunk2mem(msp));
    memset(m, 0, msize);
    (void)INITIAL_LOCK(&m->get_mutex());
    msp->_head = (msize | INUSE_BITS);
    m->init(tbase, tsize);
    return m;
}

mspace create_mspace(size_t capacity, int locked) {
    mstate m = 0;
    size_t msize;
    mparams.ensure_initialization();
    msize = pad_request(sizeof(malloc_state));
    if (capacity < (size_t) -(msize + TOP_FOOT_SIZE + mparams._page_size)) {
        size_t rs = ((capacity == 0)? mparams._granularity :
                     (capacity + TOP_FOOT_SIZE + msize));
        size_t tsize = mparams.granularity_align(rs);
        char* tbase = (char*)(CALL_MMAP(tsize));
        if (tbase != CMFAIL) {
            m = init_user_mstate(tbase, tsize);
            m->_seg._sflags = USE_MMAP_BIT;
            m->set_lock(locked);
        }
    }
    return (mspace)m;
}

mspace create_mspace_with_base(void* base, size_t capacity, int locked) {
    mstate m = 0;
    size_t msize;
    mparams.ensure_initialization();
    msize = pad_request(sizeof(malloc_state));
    if (capacity > msize + TOP_FOOT_SIZE &&
        capacity < (size_t) -(msize + TOP_FOOT_SIZE + mparams._page_size)) {
        m = init_user_mstate((char*)base, capacity);
        m->_seg._sflags = EXTERN_BIT;
        m->set_lock(locked);
    }
    return (mspace)m;
}

int mspace_track_large_chunks(mspace msp, int enable) {
    int ret = 0;
    mstate ms = (mstate)msp;
    if (!PREACTION(ms)) {
        if (!ms->use_mmap()) {
            ret = 1;
        }
        if (!enable) {
            ms->enable_mmap();
        } else {
            ms->disable_mmap();
        }
        POSTACTION(ms);
    }
    return ret;
}

size_t destroy_mspace(mspace msp) {
    size_t freed = 0;
    mstate ms = (mstate)msp;
    if (ms->ok_magic()) {
        msegmentptr sp = &ms->_seg;
        (void)DESTROY_LOCK(&ms->get_mutex()); // destroy before unmapped
        while (sp != 0) {
            char* base = sp->_base;
            size_t size = sp->_size;
            flag_t flag = sp->_sflags;
            (void)base; // placate people compiling -Wunused-variable
            sp = sp->_next;
            if ((flag & USE_MMAP_BIT) && !(flag & EXTERN_BIT) &&
                CALL_MUNMAP(base, size) == 0)
                freed += size;
        }
    }
    else {
        USAGE_ERROR_ACTION(ms,ms);
    }
    return freed;
}

/* ----------------------------  mspace versions of malloc/calloc/free routines -------------------- */
void* mspace_malloc(mspace msp, size_t bytes) {
    mstate ms = (mstate)msp;
    if (!ms->ok_magic()) {
        USAGE_ERROR_ACTION(ms,ms);
        return 0;
    }
    return ms->_malloc(bytes);
}

void mspace_free(mspace msp, void* mem) {
    if (mem != 0) {
        mchunkptr p  = mem2chunk(mem);
#if FOOTERS
        mstate fm = get_mstate_for(p);
        (void)msp; // placate people compiling -Wunused
#else 
        mstate fm = (mstate)msp;
#endif
        if (!fm->ok_magic()) {
            USAGE_ERROR_ACTION(fm, p);
            return;
        }
        fm->_free(p);
    }
}

void* mspace_calloc(mspace msp, size_t n_elements, size_t elem_size) {
    void* mem;
    size_t req = 0;
    mstate ms = (mstate)msp;
    if (!ms->ok_magic()) {
        USAGE_ERROR_ACTION(ms,ms);
        return 0;
    }
    if (n_elements != 0) {
        req = n_elements * elem_size;
        if (((n_elements | elem_size) & ~(size_t)0xffff) &&
            (req / n_elements != elem_size))
            req = MAX_SIZE_T; // force downstream failure on overflow
    }
    mem = ms->internal_malloc(req);
    if (mem != 0 && mem2chunk(mem)->calloc_must_clear())
        memset(mem, 0, req);
    return mem;
}

void* mspace_realloc(mspace msp, void* oldmem, size_t bytes) {
    void* mem = 0;
    if (oldmem == 0) {
        mem = mspace_malloc(msp, bytes);
    }
    else if (bytes >= MAX_REQUEST) {
        MALLOC_FAILURE_ACTION;
    }
#ifdef REALLOC_ZERO_BYTES_FREES
    else if (bytes == 0) {
        mspace_free(msp, oldmem);
    }
#endif
    else {
        size_t nb = request2size(bytes);
        mchunkptr oldp = mem2chunk(oldmem);
#if ! FOOTERS
        mstate m = (mstate)msp;
#else 
        mstate m = get_mstate_for(oldp);
        if (!m->ok_magic()) {
            USAGE_ERROR_ACTION(m, oldmem);
            return 0;
        }
#endif
        if (!PREACTION(m)) {
            mchunkptr newp = m->try_realloc_chunk(oldp, nb, 1);
            POSTACTION(m);
            if (newp != 0) {
                m->check_inuse_chunk(newp);
                mem = chunk2mem(newp);
            }
            else {
                mem = mspace_malloc(m, bytes);
                if (mem != 0) {
                    size_t oc = oldp->chunksize() - oldp->overhead_for();
                    memcpy(mem, oldmem, (oc < bytes)? oc : bytes);
                    mspace_free(m, oldmem);
                }
            }
        }
    }
    return mem;
}

void* mspace_realloc_in_place(mspace msp, void* oldmem, size_t bytes) {
    void* mem = 0;
    if (oldmem != 0) {
        if (bytes >= MAX_REQUEST) {
            MALLOC_FAILURE_ACTION;
        }
        else {
            size_t nb = request2size(bytes);
            mchunkptr oldp = mem2chunk(oldmem);
#if ! FOOTERS
            mstate m = (mstate)msp;
#else
            mstate m = get_mstate_for(oldp);
            (void)msp; // placate people compiling -Wunused
            if (!m->ok_magic()) {
                USAGE_ERROR_ACTION(m, oldmem);
                return 0;
            }
#endif
            if (!PREACTION(m)) {
                mchunkptr newp = m->try_realloc_chunk(oldp, nb, 0);
                POSTACTION(m);
                if (newp == oldp) {
                    m->check_inuse_chunk(newp);
                    mem = oldmem;
                }
            }
        }
    }
    return mem;
}

void* mspace_memalign(mspace msp, size_t alignment, size_t bytes) {
    mstate ms = (mstate)msp;
    if (!ms->ok_magic()) {
        USAGE_ERROR_ACTION(ms,ms);
        return 0;
    }
    if (alignment <= MALLOC_ALIGNMENT)
        return mspace_malloc(msp, bytes);
    return ms->internal_memalign(alignment, bytes);
}

void** mspace_independent_calloc(mspace msp, size_t n_elements,
                                 size_t elem_size, void* chunks[]) {
    size_t sz = elem_size; // serves as 1-element array
    mstate ms = (mstate)msp;
    if (!ms->ok_magic()) {
        USAGE_ERROR_ACTION(ms,ms);
        return 0;
    }
    return ms->ialloc(n_elements, &sz, 3, chunks);
}

void** mspace_independent_comalloc(mspace msp, size_t n_elements,
                                   size_t sizes[], void* chunks[]) {
    mstate ms = (mstate)msp;
    if (!ms->ok_magic()) {
        USAGE_ERROR_ACTION(ms,ms);
        return 0;
    }
    return ms->ialloc(n_elements, sizes, 0, chunks);
}

size_t mspace_bulk_free(mspace msp, void* array[], size_t nelem) {
    return ((mstate)msp)->internal_bulk_free(array, nelem);
}

#if MALLOC_INSPECT_ALL
void mspace_inspect_all(mspace msp,
                        void(*handler)(void *start,
                                       void *end,
                                       size_t used_bytes,
                                       void* callback_arg),
                        void* arg) {
    mstate ms = (mstate)msp;
    if (ms->ok_magic()) {
        if (!PREACTION(ms)) {
            internal_inspect_all(ms, handler, arg);
            POSTACTION(ms);
        }
    }
    else {
        USAGE_ERROR_ACTION(ms,ms);
    }
}
#endif // MALLOC_INSPECT_ALL

int mspace_trim(mspace msp, size_t pad) {
    int result = 0;
    mstate ms = (mstate)msp;
    if (ms->ok_magic()) {
        if (!PREACTION(ms)) {
            result = ms->sys_trim(pad);
            POSTACTION(ms);
        }
    }
    else {
        USAGE_ERROR_ACTION(ms,ms);
    }
    return result;
}

#if !NO_MALLOC_STATS
void mspace_malloc_stats(mspace msp) {
    mstate ms = (mstate)msp;
    if (ms->ok_magic()) {
        ms->internal_malloc_stats();
    }
    else {
        USAGE_ERROR_ACTION(ms,ms);
    }
}
#endif // NO_MALLOC_STATS

size_t mspace_footprint(mspace msp) {
    size_t result = 0;
    mstate ms = (mstate)msp;
    if (ms->ok_magic()) {
        result = ms->_footprint;
    }
    else {
        USAGE_ERROR_ACTION(ms,ms);
    }
    return result;
}

size_t mspace_max_footprint(mspace msp) {
    size_t result = 0;
    mstate ms = (mstate)msp;
    if (ms->ok_magic()) {
        result = ms->_max_footprint;
    }
    else {
        USAGE_ERROR_ACTION(ms,ms);
    }
    return result;
}

size_t mspace_footprint_limit(mspace msp) {
    size_t result = 0;
    mstate ms = (mstate)msp;
    if (ms->ok_magic()) {
        size_t maf = ms->_footprint_limit;
        result = (maf == 0) ? MAX_SIZE_T : maf;
    }
    else {
        USAGE_ERROR_ACTION(ms,ms);
    }
    return result;
}

size_t mspace_set_footprint_limit(mspace msp, size_t bytes) {
    size_t result = 0;
    mstate ms = (mstate)msp;
    if (ms->ok_magic()) {
        if (bytes == 0)
            result = mparams.granularity_align(1); // Use minimal size
        if (bytes == MAX_SIZE_T)
            result = 0;                    // disable
        else
            result = mparams.granularity_align(bytes);
        ms->_footprint_limit = result;
    }
    else {
        USAGE_ERROR_ACTION(ms,ms);
    }
    return result;
}

#if !NO_MALLINFO
struct mallinfo mspace_mallinfo(mspace msp) {
    mstate ms = (mstate)msp;
    if (!ms->ok_magic()) {
        USAGE_ERROR_ACTION(ms,ms);
    }
    return ms->internal_mallinfo();
}
#endif // NO_MALLINFO

size_t mspace_usable_size(const void* mem) {
    if (mem != 0) {
        mchunkptr p = mem2chunk(mem);
        if (p->is_inuse())
            return p->chunksize() - p->overhead_for();
    }
    return 0;
}

int mspace_mallopt(int param_number, int value) {
    return mparams.change(param_number, value);
}

#endif // MSPACES


/* -------------------- Alternative MORECORE functions ------------------- */

/*
  Guidelines for creating a custom version of MORECORE:

  * For best performance, MORECORE should allocate in multiples of pagesize.
  * MORECORE may allocate more memory than requested. (Or even less,
      but this will usually result in a malloc failure.)
  * MORECORE must not allocate memory when given argument zero, but
      instead return one past the end address of memory from previous
      nonzero call.
  * For best performance, consecutive calls to MORECORE with positive
      arguments should return increasing addresses, indicating that
      space has been contiguously extended.
  * Even though consecutive calls to MORECORE need not return contiguous
      addresses, it must be OK for malloc'ed chunks to span multiple
      regions in those cases where they do happen to be contiguous.
  * MORECORE need not handle negative arguments -- it may instead
      just return MFAIL when given negative arguments.
      Negative arguments are always multiples of pagesize. MORECORE
      must not misinterpret negative args as large positive unsigned
      args. You can suppress all such calls from even occurring by defining
      MORECORE_CANNOT_TRIM,

  As an example alternative MORECORE, here is a custom allocator
  kindly contributed for pre-OSX macOS.  It uses virtually but not
  necessarily physically contiguous non-paged memory (locked in,
  present and won't get swapped out).  You can use it by uncommenting
  this section, adding some #includes, and setting up the appropriate
  defines above:

      #define MORECORE osMoreCore

  There is also a shutdown routine that should somehow be called for
  cleanup upon program exit.

  #define MAX_POOL_ENTRIES 100
  #define MINIMUM_MORECORE_SIZE  (64 * 1024U)
  static int next_os_pool;
  void *our_os_pools[MAX_POOL_ENTRIES];

  void *osMoreCore(int size)
  {
    void *ptr = 0;
    static void *sbrk_top = 0;

    if (size > 0)
    {
      if (size < MINIMUM_MORECORE_SIZE)
         size = MINIMUM_MORECORE_SIZE;
      if (CurrentExecutionLevel() == kTaskLevel)
         ptr = PoolAllocateResident(size + RM_PAGE_SIZE, 0);
      if (ptr == 0)
      {
        return (void *) MFAIL;
      }
      // save ptrs so they can be freed during cleanup
      our_os_pools[next_os_pool] = ptr;
      next_os_pool++;
      ptr = (void *) ((((size_t) ptr) + RM_PAGE_MASK) & ~RM_PAGE_MASK);
      sbrk_top = (char *) ptr + size;
      return ptr;
    }
    else if (size < 0)
    {
      // we don't currently support shrink behavior
      return (void *) MFAIL;
    }
    else
    {
      return sbrk_top;
    }
  }

  // cleanup any allocated memory pools
  // called as last thing before shutting down driver

  void osCleanupMem(void)
  {
    void **ptr;

    for (ptr = our_os_pools; ptr < &our_os_pools[MAX_POOL_ENTRIES]; ptr++)
      if (*ptr)
      {
         PoolDeallocate(*ptr);
         *ptr = 0;
      }
  }

*/


/* -----------------------------------------------------------------------
History:
    v2.8.6 Wed Aug 29 06:57:58 2012  Doug Lea
      * fix bad comparison in dlposix_memalign
      * don't reuse adjusted asize in sys_alloc
      * add LOCK_AT_FORK -- thanks to Kirill Artamonov for the suggestion
      * reduce compiler warnings -- thanks to all who reported/suggested these

    v2.8.5 Sun May 22 10:26:02 2011  Doug Lea  (dl at gee)
      * Always perform unlink checks unless INSECURE
      * Add posix_memalign.
      * Improve realloc to expand in more cases; expose realloc_in_place.
        Thanks to Peter Buhr for the suggestion.
      * Add footprint_limit, inspect_all, bulk_free. Thanks
        to Barry Hayes and others for the suggestions.
      * Internal refactorings to avoid calls while holding locks
      * Use non-reentrant locks by default. Thanks to Roland McGrath
        for the suggestion.
      * Small fixes to mspace_destroy, reset_on_error.
      * Various configuration extensions/changes. Thanks
         to all who contributed these.

    V2.8.4a Thu Apr 28 14:39:43 2011 (dl at gee.cs.oswego.edu)
      * Update Creative Commons URL

    V2.8.4 Wed May 27 09:56:23 2009  Doug Lea  (dl at gee)
      * Use zeros instead of prev foot for is_mmapped
      * Add mspace_track_large_chunks; thanks to Jean Brouwers
      * Fix set_inuse in internal_realloc; thanks to Jean Brouwers
      * Fix insufficient sys_alloc padding when using 16byte alignment
      * Fix bad error check in mspace_footprint
      * Adaptations for ptmalloc; thanks to Wolfram Gloger.
      * Reentrant spin locks; thanks to Earl Chew and others
      * Win32 improvements; thanks to Niall Douglas and Earl Chew
      * Add NO_SEGMENT_TRAVERSAL and MAX_RELEASE_CHECK_RATE options
      * Extension hook in malloc_state
      * Various small adjustments to reduce warnings on some compilers
      * Various configuration extensions/changes for more platforms. Thanks
         to all who contributed these.

    V2.8.3 Thu Sep 22 11:16:32 2005  Doug Lea  (dl at gee)
      * Add max_footprint functions
      * Ensure all appropriate literals are size_t
      * Fix conditional compilation problem for some #define settings
      * Avoid concatenating segments with the one provided
        in create_mspace_with_base
      * Rename some variables to avoid compiler shadowing warnings
      * Use explicit lock initialization.
      * Better handling of sbrk interference.
      * Simplify and fix segment insertion, trimming and mspace_destroy
      * Reinstate REALLOC_ZERO_BYTES_FREES option from 2.7.x
      * Thanks especially to Dennis Flanagan for help on these.

    V2.8.2 Sun Jun 12 16:01:10 2005  Doug Lea  (dl at gee)
      * Fix memalign brace error.

    V2.8.1 Wed Jun  8 16:11:46 2005  Doug Lea  (dl at gee)
      * Fix improper #endif nesting in C++
      * Add explicit casts needed for C++

    V2.8.0 Mon May 30 14:09:02 2005  Doug Lea  (dl at gee)
      * Use trees for large bins
      * Support mspaces
      * Use segments to unify sbrk-based and mmap-based system allocation,
        removing need for emulation on most platforms without sbrk.
      * Default safety checks
      * Optional footer checks. Thanks to William Robertson for the idea.
      * Internal code refactoring
      * Incorporate suggestions and platform-specific changes.
        Thanks to Dennis Flanagan, Colin Plumb, Niall Douglas,
        Aaron Bachmann,  Emery Berger, and others.
      * Speed up non-fastbin processing enough to remove fastbins.
      * Remove useless cfree() to avoid conflicts with other apps.
      * Remove internal memcpy, memset. Compilers handle builtins better.
      * Remove some options that no one ever used and rename others.

    V2.7.2 Sat Aug 17 09:07:30 2002  Doug Lea  (dl at gee)
      * Fix malloc_state bitmap array misdeclaration

    V2.7.1 Thu Jul 25 10:58:03 2002  Doug Lea  (dl at gee)
      * Allow tuning of FIRST_SORTED_BIN_SIZE
      * Use PTR_UINT as type for all ptr->int casts. Thanks to John Belmonte.
      * Better detection and support for non-contiguousness of MORECORE.
        Thanks to Andreas Mueller, Conal Walsh, and Wolfram Gloger
      * Bypass most of malloc if no frees. Thanks To Emery Berger.
      * Fix freeing of old top non-contiguous chunk im sysmalloc.
      * Raised default trim and map thresholds to 256K.
      * Fix mmap-related #defines. Thanks to Lubos Lunak.
      * Fix copy macros; added LACKS_FCNTL_H. Thanks to Neal Walfield.
      * Branch-free bin calculation
      * Default trim and mmap thresholds now 256K.

    V2.7.0 Sun Mar 11 14:14:06 2001  Doug Lea  (dl at gee)
      * Introduce independent_comalloc and independent_calloc.
        Thanks to Michael Pachos for motivation and help.
      * Make optional .h file available
      * Allow > 2GB requests on 32bit systems.
      * new WIN32 sbrk, mmap, munmap, lock code from <Walter@GeNeSys-e.de>.
        Thanks also to Andreas Mueller <a.mueller at paradatec.de>,
        and Anonymous.
      * Allow override of MALLOC_ALIGNMENT (Thanks to Ruud Waij for
        helping test this.)
      * memalign: check alignment arg
      * realloc: don't try to shift chunks backwards, since this
        leads to  more fragmentation in some programs and doesn't
        seem to help in any others.
      * Collect all cases in malloc requiring system memory into sysmalloc
      * Use mmap as backup to sbrk
      * Place all internal state in malloc_state
      * Introduce fastbins (although similar to 2.5.1)
      * Many minor tunings and cosmetic improvements
      * Introduce USE_PUBLIC_MALLOC_WRAPPERS, USE_MALLOC_LOCK
      * Introduce MALLOC_FAILURE_ACTION, MORECORE_CONTIGUOUS
        Thanks to Tony E. Bennett <tbennett@nvidia.com> and others.
      * Include errno.h to support default failure action.

    V2.6.6 Sun Dec  5 07:42:19 1999  Doug Lea  (dl at gee)
      * return null for negative arguments
      * Added Several WIN32 cleanups from Martin C. Fong <mcfong at yahoo.com>
         * Add 'LACKS_SYS_PARAM_H' for those systems without 'sys/param.h'
          (e.g. WIN32 platforms)
         * Cleanup header file inclusion for WIN32 platforms
         * Cleanup code to avoid Microsoft Visual C++ compiler complaints
         * Add 'USE_DL_PREFIX' to quickly allow co-existence with existing
           memory allocation routines
         * Set 'malloc_getpagesize' for WIN32 platforms (needs more work)
         * Use 'assert' rather than 'ASSERT' in WIN32 code to conform to
           usage of 'assert' in non-WIN32 code
         * Improve WIN32 'sbrk()' emulation's 'findRegion()' routine to
           avoid infinite loop
      * Always call 'fREe()' rather than 'free()'

    V2.6.5 Wed Jun 17 15:57:31 1998  Doug Lea  (dl at gee)
      * Fixed ordering problem with boundary-stamping

    V2.6.3 Sun May 19 08:17:58 1996  Doug Lea  (dl at gee)
      * Added pvalloc, as recommended by H.J. Liu
      * Added 64bit pointer support mainly from Wolfram Gloger
      * Added anonymously donated WIN32 sbrk emulation
      * Malloc, calloc, getpagesize: add optimizations from Raymond Nijssen
      * malloc_extend_top: fix mask error that caused wastage after
        foreign sbrks
      * Add linux mremap support code from HJ Liu

    V2.6.2 Tue Dec  5 06:52:55 1995  Doug Lea  (dl at gee)
      * Integrated most documentation with the code.
      * Add support for mmap, with help from
        Wolfram Gloger (Gloger@lrz.uni-muenchen.de).
      * Use last_remainder in more cases.
      * Pack bins using idea from  colin@nyx10.cs.du.edu
      * Use ordered bins instead of best-fit threshhold
      * Eliminate block-local decls to simplify tracing and debugging.
      * Support another case of realloc via move into top
      * Fix error occuring when initial sbrk_base not word-aligned.
      * Rely on page size for units instead of SBRK_UNIT to
        avoid surprises about sbrk alignment conventions.
      * Add mallinfo, mallopt. Thanks to Raymond Nijssen
        (raymond@es.ele.tue.nl) for the suggestion.
      * Add `pad' argument to malloc_trim and top_pad mallopt parameter.
      * More precautions for cases where other routines call sbrk,
        courtesy of Wolfram Gloger (Gloger@lrz.uni-muenchen.de).
      * Added macros etc., allowing use in linux libc from
        H.J. Lu (hjl@gnu.ai.mit.edu)
      * Inverted this history list

    V2.6.1 Sat Dec  2 14:10:57 1995  Doug Lea  (dl at gee)
      * Re-tuned and fixed to behave more nicely with V2.6.0 changes.
      * Removed all preallocation code since under current scheme
        the work required to undo bad preallocations exceeds
        the work saved in good cases for most test programs.
      * No longer use return list or unconsolidated bins since
        no scheme using them consistently outperforms those that don't
        given above changes.
      * Use best fit for very large chunks to prevent some worst-cases.
      * Added some support for debugging

    V2.6.0 Sat Nov  4 07:05:23 1995  Doug Lea  (dl at gee)
      * Removed footers when chunks are in use. Thanks to
        Paul Wilson (wilson@cs.texas.edu) for the suggestion.

    V2.5.4 Wed Nov  1 07:54:51 1995  Doug Lea  (dl at gee)
      * Added malloc_trim, with help from Wolfram Gloger
        (wmglo@Dent.MED.Uni-Muenchen.DE).

    V2.5.3 Tue Apr 26 10:16:01 1994  Doug Lea  (dl at g)

    V2.5.2 Tue Apr  5 16:20:40 1994  Doug Lea  (dl at g)
      * realloc: try to expand in both directions
      * malloc: swap order of clean-bin strategy;
      * realloc: only conditionally expand backwards
      * Try not to scavenge used bins
      * Use bin counts as a guide to preallocation
      * Occasionally bin return list chunks in first scan
      * Add a few optimizations from colin@nyx10.cs.du.edu

    V2.5.1 Sat Aug 14 15:40:43 1993  Doug Lea  (dl at g)
      * faster bin computation & slightly different binning
      * merged all consolidations to one part of malloc proper
         (eliminating old malloc_find_space & malloc_clean_bin)
      * Scan 2 returns chunks (not just 1)
      * Propagate failure in realloc if malloc returns 0
      * Add stuff to allow compilation on non-ANSI compilers
          from kpv@research.att.com

    V2.5 Sat Aug  7 07:41:59 1993  Doug Lea  (dl at g.oswego.edu)
      * removed potential for odd address access in prev_chunk
      * removed dependency on getpagesize.h
      * misc cosmetics and a bit more internal documentation
      * anticosmetics: mangled names in macros to evade debugger strangeness
      * tested on sparc, hp-700, dec-mips, rs6000
          with gcc & native cc (hp, dec only) allowing
          Detlefs & Zorn comparison study (in SIGPLAN Notices.)

    Trial version Fri Aug 28 13:14:29 1992  Doug Lea  (dl at g.oswego.edu)
      * Based loosely on libg++-1.2X malloc. (It retains some of the overall
         structure of old version,  but most details differ.)

*/
