rdlmalloc.cpp

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#ifdef _RAKNET_SUPPORT_DL_MALLOC

#include "rdlmalloc.h"

/* --------------------------- 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.  To enable use
in layered extensions, per-mspace locks are reentrant.

Because lock-protected regions generally have bounded times, it is
OK to use the supplied simple spinlocks in the custom versions for
x86. 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, ACQUIRE_LOCK, RELEASE_LOCK and possibly
TRY_LOCK (which is not used in this malloc, but commonly needed in
extensions.)  You must also declare a
static MLOCK_T malloc_global_mutex = { initialization values };.

*/

#if USE_LOCKS == 1

#if USE_SPIN_LOCKS && SPIN_LOCKS_AVAILABLE
#if defined(_XBOX) || defined(X360)
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
#elif !defined(DL_PLATFORM_WIN32)

/* Custom pthread-style spin locks on x86 and x64 for gcc */
struct pthread_mlock_t {
        volatile unsigned int l;
        unsigned int c;
        pthread_t threadid;
};
#define MLOCK_T               struct pthread_mlock_t
#define CURRENT_THREAD        pthread_self()
#define INITIAL_LOCK(sl)      ((sl)->threadid = 0, (sl)->l = (sl)->c = 0, 0)
#define ACQUIRE_LOCK(sl)      pthread_acquire_lock(sl)
#define RELEASE_LOCK(sl)      pthread_release_lock(sl)
#define TRY_LOCK(sl)          pthread_try_lock(sl)
#define SPINS_PER_YIELD       63

static MLOCK_T malloc_global_mutex = { 0, 0, 0};

static FORCEINLINE int pthread_acquire_lock (MLOCK_T *sl) {
        int spins = 0;
        volatile unsigned int* lp = &sl->l;
        for (;;) {
                if (*lp != 0) {
                        if (sl->threadid == CURRENT_THREAD) {
                                ++sl->c;
                                return 0;
                        }
                }
                else {
                        /* place args to cmpxchgl in locals to evade oddities in some gccs */
                        int cmp = 0;
                        int val = 1;
                        int ret;
                        __asm__ __volatile__  ("lock; cmpxchgl %1, %2"
                                : "=a" (ret)
                                : "r" (val), "m" (*(lp)), "0"(cmp)
                                : "memory", "cc");
                        if (!ret) {
                                assert(!sl->threadid);
                                sl->threadid = CURRENT_THREAD;
                                sl->c = 1;
                                return 0;
                        }
                }
                if ((++spins & SPINS_PER_YIELD) == 0) {
#if defined (__SVR4) && defined (__sun) /* solaris */
                        thr_yield();
#else
#if defined(__linux__) || defined(__FreeBSD__) || defined(__APPLE__)
                        sched_yield();
#else  /* no-op yield on unknown systems */
                        ;
#endif /* __linux__ || __FreeBSD__ || __APPLE__ */
#endif /* solaris */
                }
        }
}

static FORCEINLINE void pthread_release_lock (MLOCK_T *sl) {
        volatile unsigned int* lp = &sl->l;
        assert(*lp != 0);
        assert(sl->threadid == CURRENT_THREAD);
        if (--sl->c == 0) {
                sl->threadid = 0;
                int prev = 0;
                int ret;
                __asm__ __volatile__ ("lock; xchgl %0, %1"
                        : "=r" (ret)
                        : "m" (*(lp)), "0"(prev)
                        : "memory");
        }
}

static FORCEINLINE int pthread_try_lock (MLOCK_T *sl) {
        volatile unsigned int* lp = &sl->l;
        if (*lp != 0) {
                if (sl->threadid == CURRENT_THREAD) {
                        ++sl->c;
                        return 1;
                }
        }
        else {
                int cmp = 0;
                int val = 1;
                int ret;
                __asm__ __volatile__  ("lock; cmpxchgl %1, %2"
                        : "=a" (ret)
                        : "r" (val), "m" (*(lp)), "0"(cmp)
                        : "memory", "cc");
                if (!ret) {
                        assert(!sl->threadid);
                        sl->threadid = CURRENT_THREAD;
                        sl->c = 1;
                        return 1;
                }
        }
        return 0;
}


#else /* DL_PLATFORM_WIN32 */
/* Custom win32-style spin locks on x86 and x64 for MSC */
struct win32_mlock_t {
        volatile long l;
        unsigned int c;
        long threadid;
};

#define MLOCK_T               struct win32_mlock_t
#define CURRENT_THREAD        GetCurrentThreadId()
#define INITIAL_LOCK(sl)      ((sl)->threadid = 0, (sl)->l = (sl)->c = 0, 0)
#define ACQUIRE_LOCK(sl)      win32_acquire_lock(sl)
#define RELEASE_LOCK(sl)      win32_release_lock(sl)
#define TRY_LOCK(sl)          win32_try_lock(sl)
#define SPINS_PER_YIELD       63

static MLOCK_T malloc_global_mutex = { 0, 0, 0};

static FORCEINLINE int win32_acquire_lock (MLOCK_T *sl) {
        int spins = 0;
        for (;;) {
                if (sl->l != 0) {
                        if (sl->threadid == CURRENT_THREAD) {
                                ++sl->c;
                                return 0;
                        }
                }
                else {
                        if (!interlockedexchange(&sl->l, 1)) {
                                assert(!sl->threadid);
                                sl->threadid = CURRENT_THREAD;
                                sl->c = 1;
                                return 0;
                        }
                }
                if ((++spins & SPINS_PER_YIELD) == 0)
                        SleepEx(0, FALSE);
        }
}

static FORCEINLINE void win32_release_lock (MLOCK_T *sl) {
        assert(sl->threadid == CURRENT_THREAD);
        assert(sl->l != 0);
        if (--sl->c == 0) {
                sl->threadid = 0;
                interlockedexchange (&sl->l, 0);
        }
}

static FORCEINLINE int win32_try_lock (MLOCK_T *sl) {
        if (sl->l != 0) {
                if (sl->threadid == CURRENT_THREAD) {
                        ++sl->c;
                        return 1;
                }
        }
        else {
                if (!interlockedexchange(&sl->l, 1)){
                        assert(!sl->threadid);
                        sl->threadid = CURRENT_THREAD;
                        sl->c = 1;
                        return 1;
                }
        }
        return 0;
}

#endif /* DL_PLATFORM_WIN32 */
#else /* USE_SPIN_LOCKS */

#ifndef DL_PLATFORM_WIN32
/* pthreads-based locks */

#define MLOCK_T               pthread_mutex_t
#define CURRENT_THREAD        pthread_self()
#define INITIAL_LOCK(sl)      pthread_init_lock(sl)
#define ACQUIRE_LOCK(sl)      pthread_mutex_lock(sl)
#define RELEASE_LOCK(sl)      pthread_mutex_unlock(sl)
#define TRY_LOCK(sl)          (!pthread_mutex_trylock(sl))

static MLOCK_T malloc_global_mutex = PTHREAD_MUTEX_INITIALIZER;

/* Cope with old-style linux recursive lock initialization by adding */
/* skipped internal declaration from pthread.h */
#ifdef linux
#ifndef PTHREAD_MUTEX_RECURSIVE
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
#endif

static int pthread_init_lock (MLOCK_T *sl) {
        pthread_mutexattr_t attr;
        if (pthread_mutexattr_init(&attr)) return 1;
        if (pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE)) return 1;
        if (pthread_mutex_init(sl, &attr)) return 1;
        if (pthread_mutexattr_destroy(&attr)) return 1;
        return 0;
}

#else /* DL_PLATFORM_WIN32 */
/* Win32 critical sections */
#define MLOCK_T               CRITICAL_SECTION
#define CURRENT_THREAD        GetCurrentThreadId()
#define INITIAL_LOCK(s)       (!InitializeCriticalSectionAndSpinCount((s), 0x80000000|4000))
#define ACQUIRE_LOCK(s)       (EnterCriticalSection(sl), 0)
#define RELEASE_LOCK(s)       LeaveCriticalSection(sl)
#define TRY_LOCK(s)           TryEnterCriticalSection(sl)
#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, -1, 0) == 0) {
                                InitializeCriticalSection(&malloc_global_mutex);
                                interlockedexchange(&malloc_global_mutex_status,1);
                                return;
                }
                SleepEx(0, FALSE);
        }
}

#endif /* DL_PLATFORM_WIN32 */
#endif /* USE_SPIN_LOCKS */
#endif /* USE_LOCKS == 1 */

/* -----------------------  User-defined locks ------------------------ */

#if USE_LOCKS > 1
/* Define your own lock implementation here */
/* #define INITIAL_LOCK(sl)  ... */
/* #define ACQUIRE_LOCK(sl)  ... */
/* #define RELEASE_LOCK(sl)  ... */
/* #define TRY_LOCK(sl) ... */
/* static MLOCK_T malloc_global_mutex = ... */
#endif /* USE_LOCKS > 1 */

/* -----------------------  Lock-based state ------------------------ */

#if USE_LOCKS
#define USE_LOCK_BIT               (2U)
#else  /* USE_LOCKS */
#define USE_LOCK_BIT               (0U)
#define INITIAL_LOCK(l)
#endif /* USE_LOCKS */

#if USE_LOCKS
#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
#else  /* USE_LOCKS */
#define ACQUIRE_MALLOC_GLOBAL_LOCK()
#define RELEASE_MALLOC_GLOBAL_LOCK()
#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 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.

*/

struct malloc_chunk {
        size_t               prev_foot;  /* Size of previous chunk (if free).  */
        size_t               head;       /* Size and inuse bits. */
        struct malloc_chunk* fd;         /* double links -- used only if free. */
        struct malloc_chunk* bk;
};

typedef struct malloc_chunk  mchunk;
typedef struct malloc_chunk* mchunkptr;
typedef struct 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 */

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

#define MCHUNK_SIZE         (sizeof(mchunk))

#if FOOTERS
#define CHUNK_OVERHEAD      (TWO_SIZE_T_SIZES)
#else /* FOOTERS */
#define CHUNK_OVERHEAD      (SIZE_T_SIZE)
#endif /* FOOTERS */

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

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

/* conversion from malloc headers to user pointers, and back */
#define chunk2mem(p)        ((void*)((char*)(p)       + TWO_SIZE_T_SIZES))
#define mem2chunk(mem)      ((mchunkptr)((char*)(mem) - TWO_SIZE_T_SIZES))
/* chunk associated with aligned address A */
#define align_as_chunk(A)   (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 - SIZE_T_ONE)

/* pad request bytes into a usable size */
#define pad_request(req) \
        (((req) + CHUNK_OVERHEAD + CHUNK_ALIGN_MASK) & ~CHUNK_ALIGN_MASK)

/* pad request, checking for minimum (but not maximum) */
#define request2size(req) \
        (((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.
*/

#define PINUSE_BIT          (SIZE_T_ONE)
#define CINUSE_BIT          (SIZE_T_TWO)
#define FLAG4_BIT           (SIZE_T_FOUR)
#define INUSE_BITS          (PINUSE_BIT|CINUSE_BIT)
#define FLAG_BITS           (PINUSE_BIT|CINUSE_BIT|FLAG4_BIT)

/* Head value for fenceposts */
#define FENCEPOST_HEAD      (INUSE_BITS|SIZE_T_SIZE)

/* extraction of fields from head words */
#define cinuse(p)           ((p)->head & CINUSE_BIT)
#define pinuse(p)           ((p)->head & PINUSE_BIT)
#define is_inuse(p)         (((p)->head & INUSE_BITS) != PINUSE_BIT)
#define is_mmapped(p)       (((p)->head & INUSE_BITS) == 0)

#define chunksize(p)        ((p)->head & ~(FLAG_BITS))

#define clear_pinuse(p)     ((p)->head &= ~PINUSE_BIT)

/* Treat space at ptr +/- offset as a chunk */
#define chunk_plus_offset(p, s)  ((mchunkptr)(((char*)(p)) + (s)))
#define chunk_minus_offset(p, s) ((mchunkptr)(((char*)(p)) - (s)))

/* Ptr to next or previous physical malloc_chunk. */
#define next_chunk(p) ((mchunkptr)( ((char*)(p)) + ((p)->head & ~FLAG_BITS)))
#define prev_chunk(p) ((mchunkptr)( ((char*)(p)) - ((p)->prev_foot) ))

/* extract next chunk's pinuse bit */
#define next_pinuse(p)  ((next_chunk(p)->head) & PINUSE_BIT)

/* Get/set size at footer */
#define get_foot(p, s)  (((mchunkptr)((char*)(p) + (s)))->prev_foot)
#define set_foot(p, s)  (((mchunkptr)((char*)(p) + (s)))->prev_foot = (s))

/* Set size, pinuse bit, and foot */
#define set_size_and_pinuse_of_free_chunk(p, s)\
        ((p)->head = (s|PINUSE_BIT), set_foot(p, s))

/* Set size, pinuse bit, foot, and clear next pinuse */
#define set_free_with_pinuse(p, s, n)\
        (clear_pinuse(n), set_size_and_pinuse_of_free_chunk(p, s))

/* Get the internal overhead associated with chunk p */
#define overhead_for(p)\
        (is_mmapped(p)? MMAP_CHUNK_OVERHEAD : CHUNK_OVERHEAD)

/* Return true if malloced space is not necessarily cleared */
#if MMAP_CLEARS
#define calloc_must_clear(p) (!is_mmapped(p))
#else /* MMAP_CLEARS */
#define calloc_must_clear(p) (1)
#endif /* MMAP_CLEARS */

/* ---------------------- 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 {
        /* The first four fields must be compatible with malloc_chunk */
        size_t                    prev_foot;
        size_t                    head;
        struct malloc_tree_chunk* fd;
        struct malloc_tree_chunk* bk;

        struct malloc_tree_chunk* child[2];
        struct malloc_tree_chunk* parent;
        bindex_t                  index;
};

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

/* A little helper macro for trees */
#define leftmost_child(t) ((t)->child[0] != 0? (t)->child[0] : (t)->child[1])

/* ----------------------------- 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 rak_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 {
        char*        base;             /* base address */
        size_t       size;             /* allocated size */
        struct malloc_segment* next;   /* ptr to next segment */
        flag_t       sflags;           /* mmap and extern flag */
};

#define is_mmapped_segment(S)  ((S)->sflags & USE_MMAP_BIT)
#define is_extern_segment(S)   ((S)->sflags & EXTERN_BIT)

typedef struct malloc_segment  msegment;
typedef struct malloc_segment* msegmentptr;

/* ---------------------------- 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.

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
timming, 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.
*/

/* Bin types, widths and sizes */
#define NSMALLBINS        (32U)
#define NTREEBINS         (32U)
#define SMALLBIN_SHIFT    (3U)
#define SMALLBIN_WIDTH    (SIZE_T_ONE << SMALLBIN_SHIFT)
#define TREEBIN_SHIFT     (8U)
#define MIN_LARGE_SIZE    (SIZE_T_ONE << TREEBIN_SHIFT)
#define MAX_SMALL_SIZE    (MIN_LARGE_SIZE - SIZE_T_ONE)
#define MAX_SMALL_REQUEST (MAX_SMALL_SIZE - CHUNK_ALIGN_MASK - CHUNK_OVERHEAD)

struct malloc_state {
        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];
        size_t     footprint;
        size_t     max_footprint;
        flag_t     mflags;
#if USE_LOCKS
        MLOCK_T    mutex;     /* locate lock among fields that rarely change */
#endif /* USE_LOCKS */
        msegment   seg;
        void*      extp;      /* Unused but available for extensions */
        size_t     exts;
};

typedef struct malloc_state*    mstate;

/* ------------- Global malloc_state and 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 {
        volatile size_t magic;
        size_t page_size;
        size_t granularity;
        size_t mmap_threshold;
        size_t trim_threshold;
        flag_t default_mflags;
};

static struct malloc_params mparams;

/* Ensure mparams initialized */
#define ensure_initialization() (void)(mparams.magic != 0 || init_mparams())

#if !ONLY_MSPACES

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

#endif /* !ONLY_MSPACES */

#define is_initialized(M)  ((M)->top != 0)

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

/* Operations on mflags */

#define use_lock(M)           ((M)->mflags &   USE_LOCK_BIT)
#define enable_lock(M)        ((M)->mflags |=  USE_LOCK_BIT)
#define disable_lock(M)       ((M)->mflags &= ~USE_LOCK_BIT)

#define use_mmap(M)           ((M)->mflags &   USE_MMAP_BIT)
#define enable_mmap(M)        ((M)->mflags |=  USE_MMAP_BIT)
#define disable_mmap(M)       ((M)->mflags &= ~USE_MMAP_BIT)

#define use_noncontiguous(M)  ((M)->mflags &   USE_NONCONTIGUOUS_BIT)
#define disable_contiguous(M) ((M)->mflags |=  USE_NONCONTIGUOUS_BIT)

#define set_lock(M,L)\
        ((M)->mflags = (L)?\
        ((M)->mflags | USE_LOCK_BIT) :\
        ((M)->mflags & ~USE_LOCK_BIT))

/* page-align a size */
#define page_align(S)\
        (((S) + (mparams.page_size - SIZE_T_ONE)) & ~(mparams.page_size - SIZE_T_ONE))

/* granularity-align a size */
#define granularity_align(S)\
        (((S) + (mparams.granularity - SIZE_T_ONE))\
        & ~(mparams.granularity - SIZE_T_ONE))


/* For mmap, use granularity alignment on windows, else page-align */
#ifdef DL_PLATFORM_WIN32
#define mmap_align(S) granularity_align(S)
#else
#define mmap_align(S) 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)

#define is_page_aligned(S)\
        (((size_t)(S) & (mparams.page_size - SIZE_T_ONE)) == 0)
#define is_granularity_aligned(S)\
        (((size_t)(S) & (mparams.granularity - SIZE_T_ONE)) == 0)

/*  True if segment S holds address A */
#define segment_holds(S, A)\
        ((char*)(A) >= S->base && (char*)(A) < S->base + S->size)

/* Return segment holding given address */
static msegmentptr segment_holding(mstate m, char* addr) {
        msegmentptr sp = &m->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 */
static int has_segment_link(mstate m, msegmentptr ss) {
        msegmentptr sp = &m->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
#define should_trim(M,s)  ((s) > (M)->trim_check)
#else  /* MORECORE_CANNOT_TRIM */
#define should_trim(M,s)  (0)
#endif /* MORECORE_CANNOT_TRIM */

/*
TOP_FOOT_SIZE is padding at the end of a segment, 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(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)  ((use_lock(M))? ACQUIRE_LOCK(&(M)->mutex) : 0)
#define POSTACTION(M) { if (use_lock(M)) RELEASE_LOCK(&(M)->mutex); }
#else /* USE_LOCKS */

#ifndef PREACTION
#define PREACTION(M) (0)
#endif  /* PREACTION */

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

#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;

/* default corruption action */
static void reset_on_error(mstate m);

#define CORRUPTION_ERROR_ACTION(m)  reset_on_error(m)
#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 */

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

#if ! DEBUG

#define check_free_chunk(M,P)
#define check_inuse_chunk(M,P)
#define check_malloced_chunk(M,P,N)
#define check_mmapped_chunk(M,P)
#define check_malloc_state(M)
#define check_top_chunk(M,P)

#else /* DEBUG */
#define check_free_chunk(M,P)       do_check_free_chunk(M,P)
#define check_inuse_chunk(M,P)      do_check_inuse_chunk(M,P)
#define check_top_chunk(M,P)        do_check_top_chunk(M,P)
#define check_malloced_chunk(M,P,N) do_check_malloced_chunk(M,P,N)
#define check_mmapped_chunk(M,P)    do_check_mmapped_chunk(M,P)
#define check_malloc_state(M)       do_check_malloc_state(M)

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

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

#define is_small(s)         (((s) >> SMALLBIN_SHIFT) < NSMALLBINS)
#define small_index(s)      ((s)  >> SMALLBIN_SHIFT)
#define small_index2size(i) ((i)  << SMALLBIN_SHIFT)
#define MIN_SMALL_INDEX     (small_index(MIN_CHUNK_SIZE))

/* addressing by index. See above about smallbin repositioning */
#define smallbin_at(M, i)   ((sbinptr)((char*)&((M)->smallbins[(i)<<1])))
#define treebin_at(M,i)     (&((M)->treebins[i]))

/* assign tree index for size S to variable I. Use x86 asm if possible  */
#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
#define compute_tree_index(S, I)\
{\
        unsigned int X = S >> TREEBIN_SHIFT;\
        if (X == 0)\
        I = 0;\
  else if (X > 0xFFFF)\
  I = NTREEBINS-1;\
  else {\
  unsigned int K;\
  __asm__("bsrl\t%1, %0\n\t" : "=r" (K) : "g"  (X));\
  I =  (bindex_t)((K << 1) + ((S >> (K + (TREEBIN_SHIFT-1)) & 1)));\
}\
}

#elif defined (__INTEL_COMPILER)
#define compute_tree_index(S, I)\
{\
        size_t X = S >> TREEBIN_SHIFT;\
        if (X == 0)\
        I = 0;\
  else if (X > 0xFFFF)\
  I = NTREEBINS-1;\
  else {\
  unsigned int K = _bit_scan_reverse (X); \
  I =  (bindex_t)((K << 1) + ((S >> (K + (TREEBIN_SHIFT-1)) & 1)));\
}\
}

#elif defined(_MSC_VER) && _MSC_VER>=1300 && defined(DL_PLATFORM_WIN32)
#define compute_tree_index(S, I)\
{\
        size_t X = S >> TREEBIN_SHIFT;\
        if (X == 0)\
        I = 0;\
  else if (X > 0xFFFF)\
  I = NTREEBINS-1;\
  else {\
  unsigned int K;\
  _BitScanReverse((DWORD *) &K, X);\
  I =  (bindex_t)((K << 1) + ((S >> (K + (TREEBIN_SHIFT-1)) & 1)));\
}\
}

#else /* GNUC */
#define compute_tree_index(S, I)\
{\
        size_t X = S >> TREEBIN_SHIFT;\
        if (X == 0)\
        I = 0;\
  else if (X > 0xFFFF)\
  I = NTREEBINS-1;\
  else {\
  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);\
  I = (K << 1) + ((S >> (K + (TREEBIN_SHIFT-1)) & 1));\
}\
}
#endif /* GNUC */

/* Bit representing maximum resolved size in a treebin at i */
#define bit_for_tree_index(i) \
        (i == NTREEBINS-1)? (SIZE_T_BITSIZE-1) : (((i) >> 1) + TREEBIN_SHIFT - 2)

/* Shift placing maximum resolved bit in a treebin at i as sign bit */
#define leftshift_for_tree_index(i) \
        ((i == NTREEBINS-1)? 0 : \
        ((SIZE_T_BITSIZE-SIZE_T_ONE) - (((i) >> 1) + TREEBIN_SHIFT - 2)))

/* The size of the smallest chunk held in bin with index i */
#define minsize_for_tree_index(i) \
        ((SIZE_T_ONE << (((i) >> 1) + TREEBIN_SHIFT)) |  \
        (((size_t)((i) & SIZE_T_ONE)) << (((i) >> 1) + TREEBIN_SHIFT - 1)))


/* ------------------------ Operations on bin maps ----------------------- */

/* bit corresponding to given index */
#define idx2bit(i)              ((binmap_t)(1) << (i))

/* Mark/Clear bits with given index */
#define mark_smallmap(M,i)      ((M)->smallmap |=  idx2bit(i))
#define clear_smallmap(M,i)     ((M)->smallmap &= ~idx2bit(i))
#define smallmap_is_marked(M,i) ((M)->smallmap &   idx2bit(i))

#define mark_treemap(M,i)       ((M)->treemap  |=  idx2bit(i))
#define clear_treemap(M,i)      ((M)->treemap  &= ~idx2bit(i))
#define treemap_is_marked(M,i)  ((M)->treemap  &   idx2bit(i))

/* isolate the least set bit of a bitmap */
#define least_bit(x)         ((x) & -(x))

/* mask with all bits to left of least bit of x on */
#define left_bits(x)         ((x<<1) | -(x<<1))

/* mask with all bits to left of or equal to least bit of x on */
#define same_or_left_bits(x) ((x) | -(x))

/* index corresponding to given bit. Use x86 asm if possible */

#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
#define compute_bit2idx(X, I)\
{\
        unsigned int J;\
        __asm__("bsfl\t%1, %0\n\t" : "=r" (J) : "g" (X));\
        I = (bindex_t)J;\
}

#elif defined (__INTEL_COMPILER)
#define compute_bit2idx(X, I)\
{\
        unsigned int J;\
        J = _bit_scan_forward (X); \
        I = (bindex_t)J;\
}

#elif defined(_MSC_VER) && _MSC_VER>=1300 && defined(DL_PLATFORM_WIN32)
#define compute_bit2idx(X, I)\
{\
        unsigned int J;\
        _BitScanForward((DWORD *) &J, X);\
        I = (bindex_t)J;\
}

#elif USE_BUILTIN_FFS
#define compute_bit2idx(X, I) I = ffs(X)-1

#else
#define compute_bit2idx(X, I)\
{\
        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;\
        I = (bindex_t)(N + Y);\
}
#endif /* GNUC */


/* ----------------------- 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
(probablistically) 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 */
#define ok_address(M, a) ((char*)(a) >= (M)->least_addr)
/* Check if address of next chunk n is higher than base chunk p */
#define ok_next(p, n)    ((char*)(p) < (char*)(n))
/* Check if p has inuse status */
#define ok_inuse(p)     is_inuse(p)
/* Check if p has its pinuse bit on */
#define ok_pinuse(p)     pinuse(p)

#else /* !INSECURE */
#define ok_address(M, a) (1)
#define ok_next(b, n)    (1)
#define ok_inuse(p)      (1)
#define ok_pinuse(p)     (1)
#endif /* !INSECURE */

#if (FOOTERS && !INSECURE)
/* Check if (alleged) mstate m has expected magic field */
#define ok_magic(M)      ((M)->magic == mparams.magic)
#else  /* (FOOTERS && !INSECURE) */
#define ok_magic(M)      (1)
#endif /* (FOOTERS && !INSECURE) */


/* In gcc, use __builtin_expect to minimize impact of checks */
#if !INSECURE
#if defined(__GNUC__) && __GNUC__ >= 3
#define RTCHECK(e)  __builtin_expect(e, 1)
#else /* GNUC */
#define RTCHECK(e)  (e)
#endif /* GNUC */
#else /* !INSECURE */
#define RTCHECK(e)  (1)
#endif /* !INSECURE */

/* macros to set up inuse chunks with or without footers */

#if !FOOTERS

#define mark_inuse_foot(M,p,s)

/* Macros for setting head/foot of non-mmapped chunks */

/* Set cinuse bit and pinuse bit of next chunk */
#define set_inuse(M,p,s)\
        ((p)->head = (((p)->head & PINUSE_BIT)|s|CINUSE_BIT),\
        ((mchunkptr)(((char*)(p)) + (s)))->head |= PINUSE_BIT)

/* Set cinuse and pinuse of this chunk and pinuse of next chunk */
#define set_inuse_and_pinuse(M,p,s)\
        ((p)->head = (s|PINUSE_BIT|CINUSE_BIT),\
        ((mchunkptr)(((char*)(p)) + (s)))->head |= PINUSE_BIT)

/* Set size, cinuse and pinuse bit of this chunk */
#define set_size_and_pinuse_of_inuse_chunk(M, p, s)\
        ((p)->head = (s|PINUSE_BIT|CINUSE_BIT))

#else /* FOOTERS */

/* Set foot of inuse chunk to be xor of mstate and seed */
#define mark_inuse_foot(M,p,s)\
        (((mchunkptr)((char*)(p) + (s)))->prev_foot = ((size_t)(M) ^ mparams.magic))

#define get_mstate_for(p)\
        ((mstate)(((mchunkptr)((char*)(p) +\
        (chunksize(p))))->prev_foot ^ mparams.magic))

#define set_inuse(M,p,s)\
        ((p)->head = (((p)->head & PINUSE_BIT)|s|CINUSE_BIT),\
        (((mchunkptr)(((char*)(p)) + (s)))->head |= PINUSE_BIT), \
        mark_inuse_foot(M,p,s))

#define set_inuse_and_pinuse(M,p,s)\
        ((p)->head = (s|PINUSE_BIT|CINUSE_BIT),\
        (((mchunkptr)(((char*)(p)) + (s)))->head |= PINUSE_BIT),\
        mark_inuse_foot(M,p,s))

#define set_size_and_pinuse_of_inuse_chunk(M, p, s)\
        ((p)->head = (s|PINUSE_BIT|CINUSE_BIT),\
        mark_inuse_foot(M, p, s))

#endif /* !FOOTERS */

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

/* Initialize mparams */
static int init_mparams(void) {
#ifdef NEED_GLOBAL_LOCK_INIT
        if (malloc_global_mutex_status <= 0)
                init_malloc_global_mutex();
#endif

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

#ifndef DL_PLATFORM_WIN32
                psize = malloc_getpagesize;
                gsize = ((DEFAULT_GRANULARITY != 0)? DEFAULT_GRANULARITY : psize);
#else /* DL_PLATFORM_WIN32 */
                {
                        SYSTEM_INFO system_info;
                        GetSystemInfo(&system_info);
                        psize = system_info.dwPageSize;
                        gsize = ((DEFAULT_GRANULARITY != 0)?
DEFAULT_GRANULARITY : system_info.dwAllocationGranularity);
                }
#endif /* DL_PLATFORM_WIN32 */

                /* 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-SIZE_T_ONE)) != 0) ||
                        ((MCHUNK_SIZE      & (MCHUNK_SIZE-SIZE_T_ONE))      != 0) ||
                        ((gsize            & (gsize-SIZE_T_ONE))            != 0) ||
                        ((psize            & (psize-SIZE_T_ONE))            != 0))
                        ABORT;

                mparams.granularity = gsize;
                mparams.page_size = psize;
                mparams.mmap_threshold = DEFAULT_MMAP_THRESHOLD;
                mparams.trim_threshold = DEFAULT_TRIM_THRESHOLD;
#if MORECORE_CONTIGUOUS
                mparams.default_mflags = USE_LOCK_BIT|USE_MMAP_BIT;
#else  /* MORECORE_CONTIGUOUS */
                mparams.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 = mparams.default_mflags;
                INITIAL_LOCK(&gm->mutex);
#endif

                {
#if USE_DEV_RANDOM
                        int fd;
                        unsigned char buf[sizeof(size_t)];
                        /* Try to use /dev/urandom, else fall back on using time */
                        if ((fd = open("/dev/urandom", O_RDONLY)) >= 0 &&
                                read(fd, buf, sizeof(buf)) == sizeof(buf)) {
                                        magic = *((size_t *) buf);
                                        close(fd);
                        }
                        else
#endif /* USE_DEV_RANDOM */

#if defined(_XBOX) || defined(X360)
                                                           
#elif defined(DL_PLATFORM_WIN32)
                                magic = (size_t)(GetTickCount() ^ (size_t)0x55555555U);
#else
                                magic = (size_t)(time(0) ^ (size_t)0x55555555U);
#endif
                        magic |= (size_t)8U;    /* ensure nonzero */
                        magic &= ~(size_t)7U;   /* improve chances of fault for bad values */
                        mparams.magic = magic;
                }
        }

        RELEASE_MALLOC_GLOBAL_LOCK();
        return 1;
}

/* support for mallopt */
static int change_mparam(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:
          mparams.trim_threshold = val;
          return 1;
  case M_GRANULARITY:
          if (val >= mparams.page_size && ((val & (val-1)) == 0)) {
                  mparams.granularity = val;
                  return 1;
          }
          else
                  return 0;
  case M_MMAP_THRESHOLD:
          mparams.mmap_threshold = val;
          return 1;
  default:
          return 0;
        }
}

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

/* Check properties of any chunk, whether free, inuse, mmapped etc  */
static void do_check_any_chunk(mstate m, mchunkptr p) {
        assert((is_aligned(chunk2mem(p))) || (p->head == FENCEPOST_HEAD));
        assert(ok_address(m, p));
}

/* Check properties of top chunk */
static void do_check_top_chunk(mstate m, mchunkptr p) {
        msegmentptr sp = segment_holding(m, (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(m, p));
        assert(sz == m->topsize);
        assert(sz > 0);
        assert(sz == ((sp->base + sp->size) - (char*)p) - TOP_FOOT_SIZE);
        assert(pinuse(p));
        assert(!pinuse(chunk_plus_offset(p, sz)));
}

/* Check properties of (inuse) mmapped chunks */
static void do_check_mmapped_chunk(mstate m, mchunkptr p) {
        size_t  sz = chunksize(p);
        size_t len = (sz + (p->prev_foot) + MMAP_FOOT_PAD);
        assert(is_mmapped(p));
        assert(use_mmap(m));
        assert((is_aligned(chunk2mem(p))) || (p->head == FENCEPOST_HEAD));
        assert(ok_address(m, p));
        assert(!is_small(sz));
        assert((len & (mparams.page_size-SIZE_T_ONE)) == 0);
        assert(chunk_plus_offset(p, sz)->head == FENCEPOST_HEAD);
        assert(chunk_plus_offset(p, sz+SIZE_T_SIZE)->head == 0);
}

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

/* Check properties of free chunks */
static void do_check_free_chunk(mstate m, mchunkptr p) {
        size_t sz = chunksize(p);
        mchunkptr next = chunk_plus_offset(p, sz);
        do_check_any_chunk(m, p);
        assert(!is_inuse(p));
        assert(!next_pinuse(p));
        assert (!is_mmapped(p));
        if (p != m->dv && p != m->top) {
                if (sz >= MIN_CHUNK_SIZE) {
                        assert((sz & CHUNK_ALIGN_MASK) == 0);
                        assert(is_aligned(chunk2mem(p)));
                        assert(next->prev_foot == sz);
                        assert(pinuse(p));
                        assert (next == m->top || is_inuse(next));
                        assert(p->fd->bk == p);
                        assert(p->bk->fd == p);
                }
                else  /* markers are always of size SIZE_T_SIZE */
                        assert(sz == SIZE_T_SIZE);
        }
}

/* Check properties of malloced chunks at the point they are malloced */
static void do_check_malloced_chunk(mstate m, void* mem, size_t s) {
        if (mem != 0) {
                mchunkptr p = mem2chunk(mem);
                size_t sz = p->head & ~INUSE_BITS;
                do_check_inuse_chunk(m, 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(is_mmapped(p) || sz < (s + MIN_CHUNK_SIZE));
        }
}

/* Check a tree and its subtrees.  */
static void do_check_tree(mstate m, tchunkptr t) {
        tchunkptr head = 0;
        tchunkptr u = t;
        bindex_t tindex = t->index;
        size_t tsize = chunksize(t);
        bindex_t idx;
        compute_tree_index(tsize, idx);
        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(m, ((mchunkptr)u));
                assert(u->index == tindex);
                assert(chunksize(u) == tsize);
                assert(!is_inuse(u));
                assert(!next_pinuse(u));
                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(m, u->child[0]);
                        }
                        if (u->child[1] != 0) {
                                assert(u->child[1]->parent == u);
                                assert(u->child[1] != u);
                                do_check_tree(m, u->child[1]);
                        }
                        if (u->child[0] != 0 && u->child[1] != 0) {
                                assert(chunksize(u->child[0]) < chunksize(u->child[1]));
                        }
                }
                u = u->fd;
        } while (u != t);
        assert(head != 0);
}

/*  Check all the chunks in a treebin.  */
static void do_check_treebin(mstate m, bindex_t i) {
        tbinptr* tb = treebin_at(m, i);
        tchunkptr t = *tb;
        int empty = (m->treemap & (1U << i)) == 0;
        if (t == 0)
                assert(empty);
        if (!empty)
                do_check_tree(m, t);
}

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

/* Find x in a bin. Used in other check functions. */
static int bin_find(mstate m, mchunkptr x) {
        size_t size = chunksize(x);
        if (is_small(size)) {
                bindex_t sidx = small_index(size);
                sbinptr b = smallbin_at(m, sidx);
                if (smallmap_is_marked(m, sidx)) {
                        mchunkptr p = b;
                        do {
                                if (p == x)
                                        return 1;
                        } while ((p = p->fd) != b);
                }
        }
        else {
                bindex_t tidx;
                compute_tree_index(size, tidx);
                if (treemap_is_marked(m, tidx)) {
                        tchunkptr t = *treebin_at(m, tidx);
                        size_t sizebits = size << leftshift_for_tree_index(tidx);
                        while (t != 0 && chunksize(t) != size) {
                                t = t->child[(sizebits >> (SIZE_T_BITSIZE-SIZE_T_ONE)) & 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 */
static size_t traverse_and_check(mstate m) {
        size_t sum = 0;
        if (is_initialized(m)) {
                msegmentptr s = &m->seg;
                sum += m->topsize + TOP_FOOT_SIZE;
                while (s != 0) {
                        mchunkptr q = align_as_chunk(s->base);
                        mchunkptr lastq = 0;
                        assert(pinuse(q));
                        while (segment_holds(s, q) &&
                                q != m->top && q->head != FENCEPOST_HEAD) {
                                        sum += chunksize(q);
                                        if (is_inuse(q)) {
                                                assert(!bin_find(m, q));
                                                do_check_inuse_chunk(m, q);
                                        }
                                        else {
                                                assert(q == m->dv || bin_find(m, q));
                                                assert(lastq == 0 || is_inuse(lastq)); /* Not 2 consecutive free */
                                                do_check_free_chunk(m, q);
                                        }
                                        lastq = q;
                                        q = next_chunk(q);
                        }
                        s = s->next;
                }
        }
        return sum;
}

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

        if (m->dvsize != 0) { /* check dv chunk */
                do_check_any_chunk(m, m->dv);
                assert(m->dvsize == chunksize(m->dv));
                assert(m->dvsize >= MIN_CHUNK_SIZE);
                assert(bin_find(m, m->dv) == 0);
        }

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

        total = traverse_and_check(m);
        assert(total <= m->footprint);
        assert(m->footprint <= m->max_footprint);
}
#endif /* DEBUG */

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

#if !NO_MALLINFO
static struct mallinfo internal_mallinfo(mstate m) {
        struct mallinfo nm = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        ensure_initialization();
        if (!PREACTION(m)) {
                check_malloc_state(m);
                if (is_initialized(m)) {
                        size_t nfree = SIZE_T_ONE; /* top always free */
                        size_t mfree = m->topsize + TOP_FOOT_SIZE;
                        size_t sum = mfree;
                        msegmentptr s = &m->seg;
                        while (s != 0) {
                                mchunkptr q = align_as_chunk(s->base);
                                while (segment_holds(s, q) &&
                                        q != m->top && q->head != FENCEPOST_HEAD) {
                                                size_t sz = chunksize(q);
                                                sum += sz;
                                                if (!is_inuse(q)) {
                                                        mfree += sz;
                                                        ++nfree;
                                                }
                                                q = next_chunk(q);
                                }
                                s = s->next;
                        }

                        nm.arena    = sum;
                        nm.ordblks  = nfree;
                        nm.hblkhd   = m->footprint - sum;
                        nm.usmblks  = m->max_footprint;
                        nm.uordblks = m->footprint - mfree;
                        nm.fordblks = mfree;
                        nm.keepcost = m->topsize;
                }

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

static void internal_malloc_stats(mstate m) {
        ensure_initialization();
        if (!PREACTION(m)) {
                size_t maxfp = 0;
                size_t fp = 0;
                size_t used = 0;
                check_malloc_state(m);
                if (is_initialized(m)) {
                        msegmentptr s = &m->seg;
                        maxfp = m->max_footprint;
                        fp = m->footprint;
                        used = fp - (m->topsize + TOP_FOOT_SIZE);

                        while (s != 0) {
                                mchunkptr q = align_as_chunk(s->base);
                                while (segment_holds(s, q) &&
                                        q != m->top && q->head != FENCEPOST_HEAD) {
                                                if (!is_inuse(q))
                                                        used -= chunksize(q);
                                                q = next_chunk(q);
                                }
                                s = s->next;
                        }
                }

                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));

                POSTACTION(m);
        }
}

/* ----------------------- 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  */
#define insert_small_chunk(M, P, S) {\
        bindex_t I  = small_index(S);\
        mchunkptr B = smallbin_at(M, I);\
        mchunkptr F = B;\
        assert(S >= MIN_CHUNK_SIZE);\
        if (!smallmap_is_marked(M, I))\
        mark_smallmap(M, I);\
  else if (RTCHECK(ok_address(M, B->fd)))\
  F = B->fd;\
  else {\
  CORRUPTION_ERROR_ACTION(M);\
}\
        B->fd = P;\
        F->bk = P;\
        P->fd = F;\
        P->bk = B;\
}

/* Unlink a chunk from a smallbin  */
#define unlink_small_chunk(M, P, S) {\
        mchunkptr F = P->fd;\
        mchunkptr B = P->bk;\
        bindex_t I = small_index(S);\
        assert(P != B);\
        assert(P != F);\
        assert(chunksize(P) == small_index2size(I));\
        if (F == B)\
        clear_smallmap(M, I);\
  else if (RTCHECK((F == smallbin_at(M,I) || ok_address(M, F)) &&\
  (B == smallbin_at(M,I) || ok_address(M, B)))) {\
  F->bk = B;\
  B->fd = F;\
}\
  else {\
  CORRUPTION_ERROR_ACTION(M);\
}\
}

/* Unlink the first chunk from a smallbin */
#define unlink_first_small_chunk(M, B, P, I) {\
        mchunkptr F = P->fd;\
        assert(P != B);\
        assert(P != F);\
        assert(chunksize(P) == small_index2size(I));\
        if (B == F)\
        clear_smallmap(M, I);\
  else if (RTCHECK(ok_address(M, F))) {\
  B->fd = F;\
  F->bk = B;\
}\
  else {\
  CORRUPTION_ERROR_ACTION(M);\
}\
}



/* Replace dv node, binning the old one */
/* Used only when dvsize known to be small */
#define replace_dv(M, P, S) {\
        size_t DVS = M->dvsize;\
        if (DVS != 0) {\
        mchunkptr DV = M->dv;\
        assert(is_small(DVS));\
        insert_small_chunk(M, DV, DVS);\
        }\
        M->dvsize = S;\
        M->dv = P;\
}

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

/* Insert chunk into tree */
#define insert_large_chunk(M, X, S) {\
        tbinptr* H;\
        bindex_t I;\
        compute_tree_index(S, I);\
        H = treebin_at(M, I);\
        X->index = I;\
        X->child[0] = X->child[1] = 0;\
        if (!treemap_is_marked(M, I)) {\
        mark_treemap(M, 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 (chunksize(T) != S) {\
  tchunkptr* C = &(T->child[(K >> (SIZE_T_BITSIZE-SIZE_T_ONE)) & 1]);\
  K <<= 1;\
  if (*C != 0)\
  T = *C;\
                else if (RTCHECK(ok_address(M, C))) {\
                *C = X;\
                X->parent = T;\
                X->fd = X->bk = X;\
                break;\
}\
                else {\
                CORRUPTION_ERROR_ACTION(M);\
                break;\
}\
  }\
          else {\
          tchunkptr F = T->fd;\
          if (RTCHECK(ok_address(M, T) && ok_address(M, F))) {\
          T->fd = F->bk = X;\
          X->fd = F;\
          X->bk = T;\
          X->parent = 0;\
          break;\
          }\
                else {\
                CORRUPTION_ERROR_ACTION(M);\
                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).
*/

#define unlink_large_chunk(M, X) {\
        tchunkptr XP = X->parent;\
        tchunkptr R;\
        if (X->bk != X) {\
        tchunkptr F = X->fd;\
        R = X->bk;\
        if (RTCHECK(ok_address(M, F))) {\
        F->bk = R;\
        R->fd = F;\
        }\
        else {\
        CORRUPTION_ERROR_ACTION(M);\
}\
        }\
  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(M, RP)))\
        *RP = 0;\
          else {\
          CORRUPTION_ERROR_ACTION(M);\
}\
}\
}\
        if (XP != 0) {\
        tbinptr* H = treebin_at(M, X->index);\
        if (X == *H) {\
        if ((*H = R) == 0) \
        clear_treemap(M, X->index);\
        }\
        else if (RTCHECK(ok_address(M, XP))) {\
        if (XP->child[0] == X) \
        XP->child[0] = R;\
          else \
          XP->child[1] = R;\
}\
        else\
        CORRUPTION_ERROR_ACTION(M);\
        if (R != 0) {\
        if (RTCHECK(ok_address(M, R))) {\
        tchunkptr C0, C1;\
        R->parent = XP;\
        if ((C0 = X->child[0]) != 0) {\
        if (RTCHECK(ok_address(M, C0))) {\
        R->child[0] = C0;\
        C0->parent = R;\
        }\
                  else\
                  CORRUPTION_ERROR_ACTION(M);\
        }\
        if ((C1 = X->child[1]) != 0) {\
        if (RTCHECK(ok_address(M, C1))) {\
        R->child[1] = C1;\
        C1->parent = R;\
        }\
                  else\
                  CORRUPTION_ERROR_ACTION(M);\
        }\
        }\
          else\
          CORRUPTION_ERROR_ACTION(M);\
        }\
        }\
}

/* Relays to large vs small bin operations */

#define insert_chunk(M, P, S)\
        if (is_small(S)) insert_small_chunk(M, P, S)\
  else { tchunkptr TP = (tchunkptr)(P); insert_large_chunk(M, TP, S); }

#define unlink_chunk(M, P, S)\
        if (is_small(S)) unlink_small_chunk(M, P, S)\
  else { tchunkptr TP = (tchunkptr)(P); unlink_large_chunk(M, TP); }


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

#if ONLY_MSPACES
#define internal_malloc(m, b) rak_mspace_malloc(m, b)
#define internal_free(m, mem) rak_mspace_free(m,mem);
#else /* ONLY_MSPACES */
#if MSPACES
#define internal_malloc(m, b)\
        (m == gm)? rdlmalloc(b) : rak_mspace_malloc(m, b)
#define internal_free(m, mem)\
        if (m == gm) rdlfree(mem); else rak_mspace_free(m,mem);
#else /* MSPACES */
#define internal_malloc(m, b) rdlmalloc(b)
#define internal_free(m, mem) rdlfree(mem)
#endif /* MSPACES */
#endif /* ONLY_MSPACES */

/* -----------------------  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 */
static void* mmap_alloc(mstate m, size_t nb) {
        size_t mmsize = mmap_align(nb + SIX_SIZE_T_SIZES + CHUNK_ALIGN_MASK);
        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(m, p, psize);
                        chunk_plus_offset(p, psize)->head = FENCEPOST_HEAD;
                        chunk_plus_offset(p, psize+SIZE_T_SIZE)->head = 0;

                        if (m->least_addr == 0 || mm < m->least_addr)
                                m->least_addr = mm;
                        if ((m->footprint += mmsize) > m->max_footprint)
                                m->max_footprint = m->footprint;
                        assert(is_aligned(chunk2mem(p)));
                        check_mmapped_chunk(m, p);
                        return chunk2mem(p);
                }
        }
        return 0;
}

/* Realloc using mmap */
static mchunkptr mmap_resize(mstate m, mchunkptr oldp, size_t nb) {
        size_t oldsize = chunksize(oldp);
        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 + SIZE_T_SIZE &&
                (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 + SIX_SIZE_T_SIZES + CHUNK_ALIGN_MASK);
                char* cp = (char*)CALL_MREMAP((char*)oldp - offset,
                        oldmmsize, newmmsize, 1);
                if (cp != CMFAIL) {
                        mchunkptr newp = (mchunkptr)(cp + offset);
                        size_t psize = newmmsize - offset - MMAP_FOOT_PAD;
                        newp->head = psize;
                        mark_inuse_foot(m, newp, psize);
                        chunk_plus_offset(newp, psize)->head = FENCEPOST_HEAD;
                        chunk_plus_offset(newp, psize+SIZE_T_SIZE)->head = 0;

                        if (cp < m->least_addr)
                                m->least_addr = cp;
                        if ((m->footprint += newmmsize - oldmmsize) > m->max_footprint)
                                m->max_footprint = m->footprint;
                        check_mmapped_chunk(m, newp);
                        return newp;
                }
        }
        return 0;
}

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

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

        m->top = p;
        m->topsize = psize;
        p->head = psize | PINUSE_BIT;
        /* set size of fake trailing chunk holding overhead space only once */
        chunk_plus_offset(p, psize)->head = TOP_FOOT_SIZE;
        m->trim_check = mparams.trim_threshold; /* reset on each update */
}

/* Initialize bins for a new mstate that is otherwise zeroed out */
static void init_bins(mstate m) {
        /* Establish circular links for smallbins */
        bindex_t i;
        for (i = 0; i < NSMALLBINS; ++i) {
                sbinptr bin = smallbin_at(m,i);
                bin->fd = bin->bk = bin;
        }
}

#if PROCEED_ON_ERROR

/* default corruption action */
static void reset_on_error(mstate m) {
        int i;
        ++malloc_corruption_error_count;
        /* Reinitialize fields to forget about all memory */
        m->smallbins = m->treebins = 0;
        m->dvsize = m->topsize = 0;
        m->seg.base = 0;
        m->seg.size = 0;
        m->seg.next = 0;
        m->top = m->dv = 0;
        for (i = 0; i < NTREEBINS; ++i)
                *treebin_at(m, i) = 0;
        init_bins(m);
}
#endif /* PROCEED_ON_ERROR */

/* Allocate chunk and prepend remainder with chunk in successor base. */
static void* prepend_alloc(mstate m, 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 = chunk_plus_offset(p, nb);
                                                           size_t qsize = psize - nb;
                                                           set_size_and_pinuse_of_inuse_chunk(m, p, nb);

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

                                                           /* consolidate remainder with first chunk of old base */
                                                           if (oldfirst == m->top) {
                                                                   size_t tsize = m->topsize += qsize;
                                                                   m->top = q;
                                                                   q->head = tsize | PINUSE_BIT;
                                                                   check_top_chunk(m, q);
                                                           }
                                                           else if (oldfirst == m->dv) {
                                                                   size_t dsize = m->dvsize += qsize;
                                                                   m->dv = q;
                                                                   set_size_and_pinuse_of_free_chunk(q, dsize);
                                                           }
                                                           else {
                                                                   if (!is_inuse(oldfirst)) {
                                                                           size_t nsize = chunksize(oldfirst);
                                                                           unlink_chunk(m, oldfirst, nsize);
                                                                           oldfirst = chunk_plus_offset(oldfirst, nsize);
                                                                           qsize += nsize;
                                                                   }
                                                                   set_free_with_pinuse(q, qsize, oldfirst);
                                                                   insert_chunk(m, q, qsize);
                                                                   check_free_chunk(m, q);
                                                           }

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

/* Add a segment to hold a new noncontiguous region */
static void add_segment(mstate m, char* tbase, size_t tsize, flag_t mmapped) {
        /* Determine locations and sizes of segment, fenceposts, old top */
        char* old_top = (char*)m->top;
        msegmentptr oldsp = segment_holding(m, old_top);
        char* old_end = oldsp->base + oldsp->size;
        size_t ssize = pad_request(sizeof(struct malloc_segment));
        char* rawsp = old_end - (ssize + FOUR_SIZE_T_SIZES + 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 = chunk_plus_offset(sp, ssize);
        mchunkptr p = tnext;
        int nfences = 0;

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

        /* Set up segment record */
        assert(is_aligned(ss));
        set_size_and_pinuse_of_inuse_chunk(m, sp, ssize);
        *ss = m->seg; /* Push current record */
        m->seg.base = tbase;
        m->seg.size = tsize;
        m->seg.sflags = mmapped;
        m->seg.next = ss;

        /* Insert trailing fenceposts */
        for (;;) {
                mchunkptr nextp = chunk_plus_offset(p, SIZE_T_SIZE);
                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 = chunk_plus_offset(q, psize);
                set_free_with_pinuse(q, psize, tn);
                insert_chunk(m, q, psize);
        }

        check_top_chunk(m, m->top);
}

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

/* Get memory from system using MORECORE or MMAP */
static void* sys_alloc(mstate m, size_t nb) {
        char* tbase = CMFAIL;
        size_t tsize = 0;
        flag_t mmap_flag = 0;

        ensure_initialization();

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

        /*
        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(m)) {
                char* br = CMFAIL;
                msegmentptr ss = (m->top == 0)? 0 : segment_holding(m, (char*)m->top);
                size_t asize = 0;
                ACQUIRE_MALLOC_GLOBAL_LOCK();

                if (ss == 0) {  /* First time through or recovery */
                        char* base = (char*)CALL_MORECORE(0);
                        if (base != CMFAIL) {
                                asize = granularity_align(nb + SYS_ALLOC_PADDING);
                                /* Adjust to end on a page boundary */
                                if (!is_page_aligned(base))
                                        asize += (page_align((size_t)base) - (size_t)base);
                                /* Can't call MORECORE if size is negative when treated as signed */
                                if (asize < HALF_MAX_SIZE_T &&
                                        (br = (char*)(CALL_MORECORE(asize))) == base) {
                                                tbase = base;
                                                tsize = asize;
                                }
                        }
                }
                else {
                        /* Subtract out existing available top space from MORECORE request. */
                        asize = granularity_align(nb - m->topsize + SYS_ALLOC_PADDING);
                        /* Use mem here only if it did continuously extend old space */
                        if (asize < HALF_MAX_SIZE_T &&
                                (br = (char*)(CALL_MORECORE(asize))) == ss->base+ss->size) {
                                        tbase = br;
                                        tsize = asize;
                        }
                }

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

                RELEASE_MALLOC_GLOBAL_LOCK();
        }

        if (HAVE_MMAP && tbase == CMFAIL) {  /* Try MMAP */
                size_t rsize = granularity_align(nb + SYS_ALLOC_PADDING);
                if (rsize > nb) { /* Fail if wraps around zero */
                        char* mp = (char*)(CALL_MMAP(rsize));
                        if (mp != CMFAIL) {
                                tbase = mp;
                                tsize = rsize;
                                mmap_flag = USE_MMAP_BIT;
                        }
                }
        }

        if (HAVE_MORECORE && tbase == CMFAIL) { /* Try noncontiguous MORECORE */
                size_t asize = granularity_align(nb + SYS_ALLOC_PADDING);
                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 ((m->footprint += tsize) > m->max_footprint)
                        m->max_footprint = m->footprint;

                if (!is_initialized(m)) { /* first-time initialization */
                        if (m->least_addr == 0 || tbase < m->least_addr)
                                m->least_addr = tbase;
                        m->seg.base = tbase;
                        m->seg.size = tsize;
                        m->seg.sflags = mmap_flag;
                        m->magic = mparams.magic;
                        m->release_checks = MAX_RELEASE_CHECK_RATE;
                        init_bins(m);
#if !ONLY_MSPACES
                        if (is_global(m))
                                init_top(m, (mchunkptr)tbase, tsize - TOP_FOOT_SIZE);
                        else
#endif
                        {
                                /* Offset top by embedded malloc_state */
                                mchunkptr mn = next_chunk(mem2chunk(m));
                                init_top(m, mn, (size_t)((tbase + tsize) - (char*)mn) -TOP_FOOT_SIZE);
                        }
                }

                else {
                        /* Try to merge with an existing segment */
                        msegmentptr sp = &m->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 &&
                                !is_extern_segment(sp) &&
                                (sp->sflags & USE_MMAP_BIT) == mmap_flag &&
                                segment_holds(sp, m->top)) { /* append */
                                        sp->size += tsize;
                                        init_top(m, m->top, m->topsize + tsize);
                        }
                        else {
                                if (tbase < m->least_addr)
                                        m->least_addr = tbase;
                                sp = &m->seg;
                                while (sp != 0 && sp->base != tbase + tsize)
                                        sp = (NO_SEGMENT_TRAVERSAL) ? 0 : sp->next;
                                if (sp != 0 &&
                                        !is_extern_segment(sp) &&
                                        (sp->sflags & USE_MMAP_BIT) == mmap_flag) {
                                                char* oldbase = sp->base;
                                                sp->base = tbase;
                                                sp->size += tsize;
                                                return prepend_alloc(m, tbase, oldbase, nb);
                                }
                                else
                                        add_segment(m, tbase, tsize, mmap_flag);
                        }
                }

                if (nb < m->topsize) { /* Allocate from new or extended top space */
                        size_t rsize = m->topsize -= nb;
                        mchunkptr p = m->top;
                        mchunkptr r = m->top = chunk_plus_offset(p, nb);
                        r->head = rsize | PINUSE_BIT;
                        set_size_and_pinuse_of_inuse_chunk(m, p, nb);
                        check_top_chunk(m, m->top);
                        check_malloced_chunk(m, 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 */
static size_t release_unused_segments(mstate m) {
        size_t released = 0;
        int nsegs = 0;
        msegmentptr pred = &m->seg;
        msegmentptr sp = pred->next;
        while (sp != 0) {
                char* base = sp->base;
                size_t size = sp->size;
                msegmentptr next = sp->next;
                ++nsegs;
                if (is_mmapped_segment(sp) && !is_extern_segment(sp)) {
                        mchunkptr p = align_as_chunk(base);
                        size_t psize = chunksize(p);
                        /* Can unmap if first chunk holds entire segment and not pinned */
                        if (!is_inuse(p) && (char*)p + psize >= base + size - TOP_FOOT_SIZE) {
                                tchunkptr tp = (tchunkptr)p;
                                assert(segment_holds(sp, (char*)sp));
                                if (p == m->dv) {
                                        m->dv = 0;
                                        m->dvsize = 0;
                                }
                                else {
                                        unlink_large_chunk(m, tp);
                                }
                                if (CALL_MUNMAP(base, size) == 0) {
                                        released += size;
                                        m->footprint -= size;
                                        /* unlink obsoleted record */
                                        sp = pred;
                                        sp->next = next;
                                }
                                else { /* back out if cannot unmap */
                                        insert_large_chunk(m, tp, psize);
                                }
                        }
                }
                if (NO_SEGMENT_TRAVERSAL) /* scan only first segment */
                        break;
                pred = sp;
                sp = next;
        }
        /* Reset check counter */
        m->release_checks = ((nsegs > MAX_RELEASE_CHECK_RATE)?
nsegs : MAX_RELEASE_CHECK_RATE);
        return released;
}

static int sys_trim(mstate m, size_t pad) {
        size_t released = 0;
        ensure_initialization();
        if (pad < MAX_REQUEST && is_initialized(m)) {
                pad += TOP_FOOT_SIZE; /* ensure enough room for segment overhead */

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

                        if (!is_extern_segment(sp)) {
                                if (is_mmapped_segment(sp)) {
                                        if (HAVE_MMAP &&
                                                sp->size >= extra &&
                                                !has_segment_link(m, sp)) { /* can't shrink if pinned */
                                                        size_t newsize = sp->size - extra;
                                                        /* 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) + SIZE_T_ONE - 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;
                                m->footprint -= released;
                                init_top(m, m->top, m->topsize - released);
                                check_top_chunk(m, m->top);
                        }
                }

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

                /* On failure, disable autotrim to avoid repeated failed future calls */
                if (released == 0 && m->topsize > m->trim_check)
                        m->trim_check = MAX_SIZE_T;
        }

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


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

/* allocate a large request from the best fitting chunk in a treebin */
static void* tmalloc_large(mstate m, size_t nb) {
        tchunkptr v = 0;
        size_t rsize = -nb; /* Unsigned negation */
        tchunkptr t;
        bindex_t idx;
        compute_tree_index(nb, idx);
        if ((t = *treebin_at(m, 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 = chunksize(t) - nb;
                        if (trem < rsize) {
                                v = t;
                                if ((rsize = trem) == 0)
                                        break;
                        }
                        rt = t->child[1];
                        t = t->child[(sizebits >> (SIZE_T_BITSIZE-SIZE_T_ONE)) & 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)) & m->treemap;
                if (leftbits != 0) {
                        bindex_t i;
                        binmap_t leastbit = least_bit(leftbits);
                        compute_bit2idx(leastbit, i);
                        t = *treebin_at(m, i);
                }
        }

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

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

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

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

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

        CORRUPTION_ERROR_ACTION(m);
        return 0;
}

/* --------------------------- realloc support --------------------------- */

static void* internal_realloc(mstate m, void* oldmem, size_t bytes) {
        if (bytes >= MAX_REQUEST) {
                MALLOC_FAILURE_ACTION;
                return 0;
        }
        if (!PREACTION(m)) {
                mchunkptr oldp = mem2chunk(oldmem);
                size_t oldsize = chunksize(oldp);
                mchunkptr next = chunk_plus_offset(oldp, oldsize);
                mchunkptr newp = 0;
                void* extra = 0;

                /* Try to either shrink or extend into top. Else malloc-copy-free */

                if (RTCHECK(ok_address(m, oldp) && ok_inuse(oldp) &&
                        ok_next(oldp, next) && ok_pinuse(next))) {
                                size_t nb = request2size(bytes);
                                if (is_mmapped(oldp))
                                        newp = mmap_resize(m, oldp, nb);
                                else if (oldsize >= nb) { /* already big enough */
                                        size_t rsize = oldsize - nb;
                                        newp = oldp;
                                        if (rsize >= MIN_CHUNK_SIZE) {
                                                mchunkptr remainder = chunk_plus_offset(newp, nb);
                                                set_inuse(m, newp, nb);
                                                set_inuse_and_pinuse(m, remainder, rsize);
                                                extra = chunk2mem(remainder);
                                        }
                                }
                                else if (next == m->top && oldsize + m->topsize > nb) {
                                        /* Expand into top */
                                        size_t newsize = oldsize + m->topsize;
                                        size_t newtopsize = newsize - nb;
                                        mchunkptr newtop = chunk_plus_offset(oldp, nb);
                                        set_inuse(m, oldp, nb);
                                        newtop->head = newtopsize |PINUSE_BIT;
                                        m->top = newtop;
                                        m->topsize = newtopsize;
                                        newp = oldp;
                                }
                }
                else {
                        USAGE_ERROR_ACTION(m, oldmem);
                        POSTACTION(m);
                        return 0;
                }
#if DEBUG
                if (newp != 0) {
                        check_inuse_chunk(m, newp); /* Check requires lock */
                }
#endif

                POSTACTION(m);

                if (newp != 0) {
                        if (extra != 0) {
                                internal_free(m, extra);
                        }
                        return chunk2mem(newp);
                }
                else {
                        void* newmem = internal_malloc(m, bytes);
                        if (newmem != 0) {
                                size_t oc = oldsize - overhead_for(oldp);
                                memcpy(newmem, oldmem, (oc < bytes)? oc : bytes);
                                internal_free(m, oldmem);
                        }
                        return newmem;
                }
        }
        return 0;
}

/* --------------------------- memalign support -------------------------- */

static void* internal_memalign(mstate m, size_t alignment, size_t bytes) {
        if (alignment <= MALLOC_ALIGNMENT)    /* Can just use malloc */
                return internal_malloc(m, bytes);
        if (alignment <  MIN_CHUNK_SIZE) /* must be at least a minimum chunk size */
                alignment = MIN_CHUNK_SIZE;
        if ((alignment & (alignment-SIZE_T_ONE)) != 0) {/* Ensure a power of 2 */
                size_t a = MALLOC_ALIGNMENT << 1;
                while (a < alignment) a <<= 1;
                alignment = a;
        }

        if (bytes >= MAX_REQUEST - alignment) {
                if (m != 0)  { /* Test isn't needed but avoids compiler warning */
                        MALLOC_FAILURE_ACTION;
                }
        }
        else {
                size_t nb = request2size(bytes);
                size_t req = nb + alignment + MIN_CHUNK_SIZE - CHUNK_OVERHEAD;
                char* mem = (char*)internal_malloc(m, req);
                if (mem != 0) {
                        void* leader = 0;
                        void* trailer = 0;
                        mchunkptr p = mem2chunk(mem);

                        if (PREACTION(m)) return 0;
                        if ((((size_t)(mem)) % alignment) != 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((size_t)(((size_t)(mem +
                                        alignment -
                                        SIZE_T_ONE)) &
                                        -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 = chunksize(p) - leadsize;

                                if (is_mmapped(p)) { /* 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(m, newp, newsize);
                                        set_inuse(m, p, leadsize);
                                        leader = chunk2mem(p);
                                }
                                p = newp;
                        }

                        /* Give back spare room at the end */
                        if (!is_mmapped(p)) {
                                size_t size = chunksize(p);
                                if (size > nb + MIN_CHUNK_SIZE) {
                                        size_t remainder_size = size - nb;
                                        mchunkptr remainder = chunk_plus_offset(p, nb);
                                        set_inuse(m, p, nb);
                                        set_inuse(m, remainder, remainder_size);
                                        trailer = chunk2mem(remainder);
                                }
                        }

                        assert (chunksize(p) >= nb);
                        assert((((size_t)(chunk2mem(p))) % alignment) == 0);
                        check_inuse_chunk(m, p);
                        POSTACTION(m);
                        if (leader != 0) {
                                internal_free(m, leader);
                        }
                        if (trailer != 0) {
                                internal_free(m, trailer);
                        }
                        return chunk2mem(p);
                }
        }
        return 0;
}

/* ------------------------ comalloc/coalloc support --------------------- */

static void** ialloc(mstate m,
                                         size_t n_elements,
                                         size_t* sizes,
                                         int opts,
                                         void* chunks[]) {
                                                 /*
                                                 This provides 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
                                                 */

                                                 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;

                                                 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(m, 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(m);
                                                 disable_mmap(m);
                                                 mem = internal_malloc(m, size - CHUNK_OVERHEAD);
                                                 if (was_enabled)
                                                         enable_mmap(m);
                                                 if (mem == 0)
                                                         return 0;

                                                 if (PREACTION(m)) return 0;
                                                 p = mem2chunk(mem);
                                                 remainder_size = chunksize(p);

                                                 assert(!is_mmapped(p));

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

                                                 /* If not provided, allocate the pointer array as final part of chunk */
                                                 if (marray == 0) {
                                                         size_t  array_chunk_size;
                                                         array_chunk = chunk_plus_offset(p, contents_size);
                                                         array_chunk_size = remainder_size - contents_size;
                                                         marray = (void**) (chunk2mem(array_chunk));
                                                         set_size_and_pinuse_of_inuse_chunk(m, 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(m, p, size);
                                                                 p = chunk_plus_offset(p, size);
                                                         }
                                                         else { /* the final element absorbs any overallocation slop */
                                                                 set_size_and_pinuse_of_inuse_chunk(m, 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(m, mem2chunk(marray));
                                                 }
                                                 for (i = 0; i != n_elements; ++i)
                                                         check_inuse_chunk(m, mem2chunk(marray[i]));

#endif /* DEBUG */

                                                 POSTACTION(m);
                                                 return marray;
}


/* -------------------------- public routines ---------------------------- */

#if !ONLY_MSPACES

void* rdlmalloc(size_t bytes) {
        /*
        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
        ensure_initialization(); /* initialize in sys_alloc if not using locks */
#endif

        if (!PREACTION(gm)) {
                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 = gm->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(gm, idx);
                                p = b->fd;
                                assert(chunksize(p) == small_index2size(idx));
                                unlink_first_small_chunk(gm, b, p, idx);
                                set_inuse_and_pinuse(gm, p, small_index2size(idx));
                                mem = chunk2mem(p);
                                check_malloced_chunk(gm, mem, nb);
                                goto postaction;
                        }

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

                                else if (gm->treemap != 0 && (mem = tmalloc_small(gm, nb)) != 0) {
                                        check_malloced_chunk(gm, 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 (gm->treemap != 0 && (mem = tmalloc_large(gm, nb)) != 0) {
                                check_malloced_chunk(gm, mem, nb);
                                goto postaction;
                        }
                }

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

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

                mem = sys_alloc(gm, nb);

postaction:
                POSTACTION(gm);
                return mem;
        }

        return 0;
}

void rdlfree(void* mem) {
        /*
        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 (!ok_magic(fm)) {
                        USAGE_ERROR_ACTION(fm, p);
                        return;
                }
#else /* FOOTERS */
#define fm gm
#endif /* FOOTERS */
                if (!PREACTION(fm)) {
                        check_inuse_chunk(fm, p);
                        if (RTCHECK(ok_address(fm, p) && ok_inuse(p))) {
                                size_t psize = chunksize(p);
                                mchunkptr next = chunk_plus_offset(p, psize);
                                if (!pinuse(p)) {
                                        size_t prevsize = p->prev_foot;
                                        if (is_mmapped(p)) {
                                                psize += prevsize + MMAP_FOOT_PAD;
                                                if (CALL_MUNMAP((char*)p - prevsize, psize) == 0)
                                                        fm->footprint -= psize;
                                                goto postaction;
                                        }
                                        else {
                                                mchunkptr prev = chunk_minus_offset(p, prevsize);
                                                psize += prevsize;
                                                p = prev;
                                                if (RTCHECK(ok_address(fm, prev))) { /* consolidate backward */
                                                        if (p != fm->dv) {
                                                                unlink_chunk(fm, p, prevsize);
                                                        }
                                                        else if ((next->head & INUSE_BITS) == INUSE_BITS) {
                                                                fm->dvsize = psize;
                                                                set_free_with_pinuse(p, psize, next);
                                                                goto postaction;
                                                        }
                                                }
                                                else
                                                        goto erroraction;
                                        }
                                }

                                if (RTCHECK(ok_next(p, next) && ok_pinuse(next))) {
                                        if (!cinuse(next)) {  /* consolidate forward */
                                                if (next == fm->top) {
                                                        size_t tsize = fm->topsize += psize;
                                                        fm->top = p;
                                                        p->head = tsize | PINUSE_BIT;
                                                        if (p == fm->dv) {
                                                                fm->dv = 0;
                                                                fm->dvsize = 0;
                                                        }
                                                        if (should_trim(fm, tsize))
                                                                sys_trim(fm, 0);
                                                        goto postaction;
                                                }
                                                else if (next == fm->dv) {
                                                        size_t dsize = fm->dvsize += psize;
                                                        fm->dv = p;
                                                        set_size_and_pinuse_of_free_chunk(p, dsize);
                                                        goto postaction;
                                                }
                                                else {
                                                        size_t nsize = chunksize(next);
                                                        psize += nsize;
                                                        unlink_chunk(fm, next, nsize);
                                                        set_size_and_pinuse_of_free_chunk(p, psize);
                                                        if (p == fm->dv) {
                                                                fm->dvsize = psize;
                                                                goto postaction;
                                                        }
                                                }
                                        }
                                        else
                                                set_free_with_pinuse(p, psize, next);

                                        if (is_small(psize)) {
                                                insert_small_chunk(fm, p, psize);
                                                check_free_chunk(fm, p);
                                        }
                                        else {
                                                tchunkptr tp = (tchunkptr)p;
                                                insert_large_chunk(fm, tp, psize);
                                                check_free_chunk(fm, p);
                                                if (--fm->release_checks == 0)
                                                        release_unused_segments(fm);
                                        }
                                        goto postaction;
                                }
                        }
erroraction:
                        USAGE_ERROR_ACTION(fm, p);
postaction:
                        POSTACTION(fm);
                }
        }
#if !FOOTERS
#undef fm
#endif /* FOOTERS */
}

void* rdlcalloc(size_t n_elements, size_t elem_size) {
        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 = rdlmalloc(req);
        if (mem != 0 && calloc_must_clear(mem2chunk(mem)))
                memset(mem, 0, req);
        return mem;
}

void* rdlrealloc(void* oldmem, size_t bytes) {
        if (oldmem == 0)
                return rdlmalloc(bytes);
#ifdef REALLOC_ZERO_BYTES_FREES
        if (bytes == 0) {
                rdlfree(oldmem);
                return 0;
        }
#endif /* REALLOC_ZERO_BYTES_FREES */
        else {
#if ! FOOTERS
                mstate m = gm;
#else /* FOOTERS */
                mstate m = get_mstate_for(mem2chunk(oldmem));
                if (!ok_magic(m)) {
                        USAGE_ERROR_ACTION(m, oldmem);
                        return 0;
                }
#endif /* FOOTERS */
                return internal_realloc(m, oldmem, bytes);
        }
}

void* rdlmemalign(size_t alignment, size_t bytes) {
        return internal_memalign(gm, alignment, bytes);
}

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

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

void* rdlvalloc(size_t bytes) {
        size_t pagesz;
        ensure_initialization();
        pagesz = mparams.page_size;
        return rdlmemalign(pagesz, bytes);
}

void* rdlpvalloc(size_t bytes) {
        size_t pagesz;
        ensure_initialization();
        pagesz = mparams.page_size;
        return rdlmemalign(pagesz, (bytes + pagesz - SIZE_T_ONE) & ~(pagesz - SIZE_T_ONE));
}

int rdlmalloc_trim(size_t pad) {
        int result = 0;
        ensure_initialization();
        if (!PREACTION(gm)) {
                result = sys_trim(gm, pad);
                POSTACTION(gm);
        }
        return result;
}

size_t rdlmalloc_footprint(void) {
        return gm->footprint;
}

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

#if !NO_MALLINFO
struct mallinfo rdlmallinfo(void) {
        return internal_mallinfo(gm);
}
#endif /* NO_MALLINFO */

void rdlmalloc_stats() {
        internal_malloc_stats(gm);
}

int rdlmallopt(int param_number, int value) {
        return change_mparam(param_number, value);
}

#endif /* !ONLY_MSPACES */

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

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

#if MSPACES

static mstate init_user_mstate(char* tbase, size_t tsize) {
        size_t msize = pad_request(sizeof(struct malloc_state));
        mchunkptr mn;
        mchunkptr msp = align_as_chunk(tbase);
        mstate m = (mstate)(chunk2mem(msp));
        memset(m, 0, msize);
        INITIAL_LOCK(&m->mutex);
        msp->head = (msize|INUSE_BITS);
        m->seg.base = m->least_addr = tbase;
        m->seg.size = m->footprint = m->max_footprint = tsize;
        m->magic = mparams.magic;
        m->release_checks = MAX_RELEASE_CHECK_RATE;
        m->mflags = mparams.default_mflags;
        m->extp = 0;
        m->exts = 0;
        disable_contiguous(m);
        init_bins(m);
        mn = next_chunk(mem2chunk(m));
        init_top(m, mn, (size_t)((tbase + tsize) - (char*)mn) - TOP_FOOT_SIZE);
        check_top_chunk(m, m->top);
        return m;
}

mspace rak_create_mspace(size_t capacity, int locked) {
        mstate m = 0;
        size_t msize;
        ensure_initialization();
        msize = pad_request(sizeof(struct 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 = granularity_align(rs);
        char* tbase = (char*)(CALL_MMAP(tsize));
        if (tbase != CMFAIL) {
                m = init_user_mstate(tbase, tsize);
                m->seg.sflags = USE_MMAP_BIT;
                set_lock(m, locked);
        }
        }
        return (mspace)m;
}

mspace rak_create_mspace_with_base(void* base, size_t capacity, int locked) {
        mstate m = 0;
        size_t msize;
        ensure_initialization();
        msize = pad_request(sizeof(struct 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;
                        set_lock(m, locked);
        }
        return (mspace)m;
}

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

size_t rak_destroy_mspace(mspace msp) {
        size_t freed = 0;
        mstate ms = (mstate)msp;
        if (ok_magic(ms)) {
                msegmentptr sp = &ms->seg;
                while (sp != 0) {
                        char* base = sp->base;
                        size_t size = sp->size;
                        flag_t flag = sp->sflags;
                        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 routines are near-clones of the global
versions. This is not so nice but better than the alternatives.
*/


void* rak_mspace_malloc(mspace msp, size_t bytes) {
        mstate ms = (mstate)msp;
        if (!ok_magic(ms)) {
                USAGE_ERROR_ACTION(ms,ms);
                return 0;
        }
        if (!PREACTION(ms)) {
                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 = ms->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(ms, idx);
                                p = b->fd;
                                assert(chunksize(p) == small_index2size(idx));
                                unlink_first_small_chunk(ms, b, p, idx);
                                set_inuse_and_pinuse(ms, p, small_index2size(idx));
                                mem = chunk2mem(p);
                                check_malloced_chunk(ms, mem, nb);
                                goto postaction;
                        }

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

                                else if (ms->treemap != 0 && (mem = tmalloc_small(ms, nb)) != 0) {
                                        check_malloced_chunk(ms, 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 (ms->treemap != 0 && (mem = tmalloc_large(ms, nb)) != 0) {
                                check_malloced_chunk(ms, mem, nb);
                                goto postaction;
                        }
                }

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

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

                mem = sys_alloc(ms, nb);

postaction:
                POSTACTION(ms);
                return mem;
        }

        return 0;
}

void rak_mspace_free(mspace msp, void* mem) {
        if (mem != 0) {
                mchunkptr p  = mem2chunk(mem);
#if FOOTERS
                mstate fm = get_mstate_for(p);
                msp = msp; /* placate people compiling -Wunused */
#else /* FOOTERS */
                mstate fm = (mstate)msp;
#endif /* FOOTERS */
                if (!ok_magic(fm)) {
                        USAGE_ERROR_ACTION(fm, p);
                        return;
                }
                if (!PREACTION(fm)) {
                        check_inuse_chunk(fm, p);
                        if (RTCHECK(ok_address(fm, p) && ok_inuse(p))) {
                                size_t psize = chunksize(p);
                                mchunkptr next = chunk_plus_offset(p, psize);
                                if (!pinuse(p)) {
                                        size_t prevsize = p->prev_foot;
                                        if (is_mmapped(p)) {
                                                psize += prevsize + MMAP_FOOT_PAD;
                                                if (CALL_MUNMAP((char*)p - prevsize, psize) == 0)
                                                        fm->footprint -= psize;
                                                goto postaction;
                                        }
                                        else {
                                                mchunkptr prev = chunk_minus_offset(p, prevsize);
                                                psize += prevsize;
                                                p = prev;
                                                if (RTCHECK(ok_address(fm, prev))) { /* consolidate backward */
                                                        if (p != fm->dv) {
                                                                unlink_chunk(fm, p, prevsize);
                                                        }
                                                        else if ((next->head & INUSE_BITS) == INUSE_BITS) {
                                                                fm->dvsize = psize;
                                                                set_free_with_pinuse(p, psize, next);
                                                                goto postaction;
                                                        }
                                                }
                                                else
                                                        goto erroraction;
                                        }
                                }

                                if (RTCHECK(ok_next(p, next) && ok_pinuse(next))) {
                                        if (!cinuse(next)) {  /* consolidate forward */
                                                if (next == fm->top) {
                                                        size_t tsize = fm->topsize += psize;
                                                        fm->top = p;
                                                        p->head = tsize | PINUSE_BIT;
                                                        if (p == fm->dv) {
                                                                fm->dv = 0;
                                                                fm->dvsize = 0;
                                                        }
                                                        if (should_trim(fm, tsize))
                                                                sys_trim(fm, 0);
                                                        goto postaction;
                                                }
                                                else if (next == fm->dv) {
                                                        size_t dsize = fm->dvsize += psize;
                                                        fm->dv = p;
                                                        set_size_and_pinuse_of_free_chunk(p, dsize);
                                                        goto postaction;
                                                }
                                                else {
                                                        size_t nsize = chunksize(next);
                                                        psize += nsize;
                                                        unlink_chunk(fm, next, nsize);
                                                        set_size_and_pinuse_of_free_chunk(p, psize);
                                                        if (p == fm->dv) {
                                                                fm->dvsize = psize;
                                                                goto postaction;
                                                        }
                                                }
                                        }
                                        else
                                                set_free_with_pinuse(p, psize, next);

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

void* rak_mspace_calloc(mspace msp, size_t n_elements, size_t elem_size) {
        void* mem;
        size_t req = 0;
        mstate ms = (mstate)msp;
        if (!ok_magic(ms)) {
                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 = internal_malloc(ms, req);
        if (mem != 0 && calloc_must_clear(mem2chunk(mem)))
                memset(mem, 0, req);
        return mem;
}

void* rak_mspace_realloc(mspace msp, void* oldmem, size_t bytes) {
        if (oldmem == 0)
                return rak_mspace_malloc(msp, bytes);
#ifdef REALLOC_ZERO_BYTES_FREES
        if (bytes == 0) {
                rak_mspace_free(msp, oldmem);
                return 0;
        }
#endif /* REALLOC_ZERO_BYTES_FREES */
        else {
#if FOOTERS
                mchunkptr p  = mem2chunk(oldmem);
                mstate ms = get_mstate_for(p);
#else /* FOOTERS */
                mstate ms = (mstate)msp;
#endif /* FOOTERS */
                if (!ok_magic(ms)) {
                        USAGE_ERROR_ACTION(ms,ms);
                        return 0;
                }
                return internal_realloc(ms, oldmem, bytes);
        }
}

void* rak_mspace_memalign(mspace msp, size_t alignment, size_t bytes) {
        mstate ms = (mstate)msp;
        if (!ok_magic(ms)) {
                USAGE_ERROR_ACTION(ms,ms);
                return 0;
        }
        return internal_memalign(ms, alignment, bytes);
}

void** rak_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 (!ok_magic(ms)) {
                                                                                 USAGE_ERROR_ACTION(ms,ms);
                                                                                 return 0;
                                                                         }
                                                                         return ialloc(ms, n_elements, &sz, 3, chunks);
}

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

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

void rak_mspace_malloc_stats(mspace msp) {
        mstate ms = (mstate)msp;
        if (ok_magic(ms)) {
                internal_malloc_stats(ms);
        }
        else {
                USAGE_ERROR_ACTION(ms,ms);
        }
}

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


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

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

int rak_mspace_mallopt(int param_number, int value) {
        return change_mparam(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:
V2.8.4 Wed May 27 09:56:23 2009  Doug Lea  (dl at gee)
* Use zeros instead of prev foot for is_mmapped
* Add rak_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 rak_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 rak_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 DL_PLATFORM_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 DL_PLATFORM_WIN32 cleanups from Martin C. Fong <mcfong at yahoo.com>
* Add 'LACKS_SYS_PARAM_H' for those systems without 'sys/param.h'
(e.g. DL_PLATFORM_WIN32 platforms)
* Cleanup header file inclusion for DL_PLATFORM_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 DL_PLATFORM_WIN32 platforms (needs more work)
* Use 'assert' rather than 'ASSERT' in DL_PLATFORM_WIN32 code to conform to
usage of 'assert' in non-DL_PLATFORM_WIN32 code
* Improve DL_PLATFORM_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 DL_PLATFORM_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.)

*/

#endif // _RAKNET_SUPPORT_DL_MALLOC