openblt

malloc.c (96959B)

---

 /* $Id: //depot/blt/lib/malloc.c#2 $ */
 
 /* ---------- To make a malloc.h, start cutting here ------------ */
 
 /* 
   A version of malloc/free/realloc written by Doug Lea and released to the 
   public domain.  Send questions/comments/complaints/performance data
   to dl@cs.oswego.edu
 
 * VERSION 2.6.5  Wed Jun 17 15:55:16 1998  Doug Lea  (dl at gee)
 
    Note: There may be an updated version of this malloc obtainable at
            ftp://g.oswego.edu/pub/misc/malloc.c
          Check before installing!
 
    Note: This version differs from 2.6.4 only by correcting a
          statement ordering error that could cause failures only
          when calls to this malloc are interposed with calls to
          other memory allocators.
 
 * Why use this malloc?
 
   This is not the fastest, most space-conserving, most portable, or
   most tunable malloc ever written. However it is among the fastest
   while also being among the most space-conserving, portable and tunable.
   Consistent balance across these factors results in a good general-purpose 
   allocator. For a high-level description, see 
      http://g.oswego.edu/dl/html/malloc.html
 
 * Synopsis of public routines
 
   (Much fuller descriptions are contained in the program documentation below.)
 
   malloc(size_t n);
      Return a pointer to a newly allocated chunk of at least n bytes, or null
      if no space is available.
   free(Void_t* p);
      Release the chunk of memory pointed to by p, or no effect if p is null.
   realloc(Void_t* p, size_t n);
      Return a pointer to a chunk of size n that contains the same data
      as does chunk p up to the minimum of (n, p's size) bytes, or null
      if no space is available. The returned pointer may or may not be
      the same as p. If p is null, equivalent to malloc.  Unless the
      #define REALLOC_ZERO_BYTES_FREES below is set, realloc with a
      size argument of zero (re)allocates a minimum-sized chunk.
   memalign(size_t alignment, size_t n);
      Return a pointer to a newly allocated chunk of n bytes, aligned
      in accord with the alignment argument, which must be a power of
      two.
   valloc(size_t n);
      Equivalent to memalign(pagesize, n), where pagesize is the page
      size of the system (or as near to this as can be figured out from
      all the includes/defines below.)
   pvalloc(size_t n);
      Equivalent to valloc(minimum-page-that-holds(n)), that is,
      round up n to nearest pagesize.
   calloc(size_t unit, size_t quantity);
      Returns a pointer to quantity * unit bytes, with all locations
      set to zero.
   cfree(Void_t* p);
      Equivalent to free(p).
   malloc_trim(size_t pad);
      Release all but pad bytes of freed top-most memory back 
      to the system. Return 1 if successful, else 0.
   malloc_usable_size(Void_t* p);
      Report the number usable allocated bytes associated with allocated
      chunk p. This may or may not report more bytes than were requested,
      due to alignment and minimum size constraints.
   malloc_stats();
      Prints brief summary statistics on stderr.
   mallinfo()
      Returns (by copy) a struct containing various summary statistics.
   mallopt(int parameter_number, int parameter_value)
      Changes one of the tunable parameters described below. Returns
      1 if successful in changing the parameter, else 0.
 
 * Vital statistics:
 
   Alignment:                            8-byte
        8 byte alignment is currently hardwired into the design.  This
        seems to suffice for all current machines and C compilers.
 
   Assumed pointer representation:       4 or 8 bytes
        Code for 8-byte pointers is untested by me but has worked
        reliably by Wolfram Gloger, who contributed most of the
        changes supporting this.
 
   Assumed size_t  representation:       4 or 8 bytes
        Note that size_t is allowed to be 4 bytes even if pointers are 8.        
 
   Minimum overhead per allocated chunk: 4 or 8 bytes
        Each malloced chunk has a hidden overhead of 4 bytes holding size
        and status information.  
 
   Minimum allocated size: 4-byte ptrs:  16 bytes    (including 4 overhead)
                           8-byte ptrs:  24/32 bytes (including, 4/8 overhead)
                                      
        When a chunk is freed, 12 (for 4byte ptrs) or 20 (for 8 byte
        ptrs but 4 byte size) or 24 (for 8/8) additional bytes are 
        needed; 4 (8) for a trailing size field
        and 8 (16) bytes for free list pointers. Thus, the minimum
        allocatable size is 16/24/32 bytes.
 
        Even a request for zero bytes (i.e., malloc(0)) returns a
        pointer to something of the minimum allocatable size.
 
   Maximum allocated size: 4-byte size_t: 2^31 -  8 bytes
                           8-byte size_t: 2^63 - 16 bytes
 
        It is assumed that (possibly signed) size_t bit values suffice to
        represent chunk sizes. `Possibly signed' is due to the fact
        that `size_t' may be defined on a system as either a signed or
        an unsigned type. To be conservative, values that would appear
        as negative numbers are avoided.  
        Requests for sizes with a negative sign bit will return a
        minimum-sized chunk.
 
   Maximum overhead wastage per allocated chunk: normally 15 bytes
 
        Alignnment demands, plus the minimum allocatable size restriction
        make the normal worst-case wastage 15 bytes (i.e., up to 15
        more bytes will be allocated than were requested in malloc), with 
        two exceptions:
          1. Because requests for zero bytes allocate non-zero space,
             the worst case wastage for a request of zero bytes is 24 bytes.
          2. For requests >= mmap_threshold that are serviced via
             mmap(), the worst case wastage is 8 bytes plus the remainder
             from a system page (the minimal mmap unit); typically 4096 bytes.
 
 * Limitations
 
     Here are some features that are NOT currently supported
 
     * No user-definable hooks for callbacks and the like.
     * No automated mechanism for fully checking that all accesses
       to malloced memory stay within their bounds.
     * No support for compaction.
 
 * Synopsis of compile-time options:
 
     People have reported using previous versions of this malloc on all
     versions of Unix, sometimes by tweaking some of the defines
     below. It has been tested most extensively on Solaris and
     Linux. It is also reported to work on WIN32 platforms.
     People have also reported adapting this malloc for use in
     stand-alone embedded systems.
 
     The implementation is in straight, hand-tuned ANSI C.  Among other
     consequences, it uses a lot of macros.  Because of this, to be at
     all usable, this code should be compiled using an optimizing compiler
     (for example gcc -O2) that can simplify expressions and control
     paths.
 
   __STD_C                  (default: derived from C compiler defines)
      Nonzero if using ANSI-standard C compiler, a C++ compiler, or
      a C compiler sufficiently close to ANSI to get away with it.
   DEBUG                    (default: NOT defined)
      Define to enable debugging. Adds fairly extensive assertion-based 
      checking to help track down memory errors, but noticeably slows down
      execution.
   REALLOC_ZERO_BYTES_FREES (default: NOT defined) 
      Define this if you think that realloc(p, 0) should be equivalent
      to free(p). Otherwise, since malloc returns a unique pointer for
      malloc(0), so does realloc(p, 0).
   HAVE_MEMCPY               (default: defined)
      Define if you are not otherwise using ANSI STD C, but still 
      have memcpy and memset in your C library and want to use them.
      Otherwise, simple internal versions are supplied.
   USE_MEMCPY               (default: 1 if HAVE_MEMCPY is defined, 0 otherwise)
      Define as 1 if you want the C library versions of memset and
      memcpy called in realloc and calloc (otherwise macro versions are used). 
      At least on some platforms, the simple macro versions usually
      outperform libc versions.
   HAVE_MMAP                 (default: defined as 1)
      Define to non-zero to optionally make malloc() use mmap() to
      allocate very large blocks.  
   HAVE_MREMAP                 (default: defined as 0 unless Linux libc set)
      Define to non-zero to optionally make realloc() use mremap() to
      reallocate very large blocks.  
   malloc_getpagesize        (default: derived from system #includes)
      Either a constant or routine call returning the system page size.
   HAVE_USR_INCLUDE_MALLOC_H (default: NOT defined) 
      Optionally define if you are on a system with a /usr/include/malloc.h
      that declares struct mallinfo. It is not at all necessary to
      define this even if you do, but will ensure consistency.
   INTERNAL_SIZE_T           (default: size_t)
      Define to a 32-bit type (probably `unsigned int') if you are on a 
      64-bit machine, yet do not want or need to allow malloc requests of 
      greater than 2^31 to be handled. This saves space, especially for
      very small chunks.
   INTERNAL_LINUX_C_LIB      (default: NOT defined)
      Defined only when compiled as part of Linux libc.
      Also note that there is some odd internal name-mangling via defines
      (for example, internally, `malloc' is named `mALLOc') needed
      when compiling in this case. These look funny but don't otherwise
      affect anything.
   WIN32                     (default: undefined)
      Define this on MS win (95, nt) platforms to compile in sbrk emulation.
   LACKS_UNISTD_H            (default: undefined)
      Define this if your system does not have a <unistd.h>.
   MORECORE                  (default: sbrk)
      The name of the routine to call to obtain more memory from the system.
   MORECORE_FAILURE          (default: -1)
      The value returned upon failure of MORECORE.
   MORECORE_CLEARS           (default 1)
      True (1) if the routine mapped to MORECORE zeroes out memory (which
      holds for sbrk).
   DEFAULT_TRIM_THRESHOLD
   DEFAULT_TOP_PAD       
   DEFAULT_MMAP_THRESHOLD
   DEFAULT_MMAP_MAX      
      Default values of tunable parameters (described in detail below)
      controlling interaction with host system routines (sbrk, mmap, etc).
      These values may also be changed dynamically via mallopt(). The
      preset defaults are those that give best performance for typical
      programs/systems.
 
 
 */
 
 /* Preliminaries */
 
 #ifndef __STD_C
 #ifdef __STDC__
 #define __STD_C     1
 #else
 #if __cplusplus
 #define __STD_C     1
 #else
 #define __STD_C     0
 #endif /*__cplusplus*/
 #endif /*__STDC__*/
 #endif /*__STD_C*/
 
 #ifndef Void_t
 #if __STD_C
 #define Void_t      void
 #else
 #define Void_t      char
 #endif
 #endif /*Void_t*/
 
 #if __STD_C
 #include <stddef.h>   /* for size_t */
 #else
 #include <sys/types.h>
 #endif
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 #include <stdio.h>    /* needed for malloc_stats */
 
 /*
   Compile-time options
 */
 
 /*
     Debugging:
 
     Because freed chunks may be overwritten with link fields, this
     malloc will often die when freed memory is overwritten by user
     programs.  This can be very effective (albeit in an annoying way)
     in helping track down dangling pointers.
 
     If you compile with -DDEBUG, a number of assertion checks are
     enabled that will catch more memory errors. You probably won't be
     able to make much sense of the actual assertion errors, but they
     should help you locate incorrectly overwritten memory.  The
     checking is fairly extensive, and will slow down execution
     noticeably. Calling malloc_stats or mallinfo with DEBUG set will
     attempt to check every non-mmapped allocated and free chunk in the
     course of computing the summmaries. (By nature, mmapped regions
     cannot be checked very much automatically.)
 
     Setting DEBUG may also be helpful if you are trying to modify 
     this code. The assertions in the check routines spell out in more 
     detail the assumptions and invariants underlying the algorithms.
 
 */
 
 #if DEBUG 
 #include <assert.h>
 #else
 #define assert(x) ((void)0)
 #endif
 
 /*
   INTERNAL_SIZE_T is the word-size used for internal bookkeeping
   of chunk sizes. On a 64-bit machine, you can reduce malloc
   overhead by defining INTERNAL_SIZE_T to be a 32 bit `unsigned int'
   at the expense of not being able to handle requests greater than
   2^31. This limitation is hardly ever a concern; you are encouraged
   to set this. However, the default version is the same as size_t.
 */
 
 #ifndef INTERNAL_SIZE_T
 #define INTERNAL_SIZE_T size_t
 #endif
 
 /*
   REALLOC_ZERO_BYTES_FREES should be set if a call to
   realloc with zero bytes should be the same as a call to free.
   Some people think it should. Otherwise, since this malloc
   returns a unique pointer for malloc(0), so does realloc(p, 0). 
 */
 
 
 /*   #define REALLOC_ZERO_BYTES_FREES */
 
 /*
   HAVE_MEMCPY should be defined if you are not otherwise using
   ANSI STD C, but still have memcpy and memset in your C library
   and want to use them in calloc and realloc. Otherwise simple
   macro versions are defined here.
 
   USE_MEMCPY should be defined as 1 if you actually want to
   have memset and memcpy called. People report that the macro
   versions are often enough faster than libc versions on many
   systems that it is better to use them. 
 
 */
 
 #define HAVE_MEMCPY 
 
 #ifndef USE_MEMCPY
 #ifdef HAVE_MEMCPY
 #define USE_MEMCPY 1
 #else
 #define USE_MEMCPY 0
 #endif
 #endif
 
 #if (__STD_C || defined(HAVE_MEMCPY)) 
 
 #if __STD_C
 void* memset(void*, int, size_t);
 void* memcpy(void*, const void*, size_t);
 #else
 Void_t* memset();
 Void_t* memcpy();
 #endif
 #endif
 
 #if USE_MEMCPY
 
 /* The following macros are only invoked with (2n+1)-multiples of
    INTERNAL_SIZE_T units, with a positive integer n. This is exploited
    for fast inline execution when n is small. */
 
 #define MALLOC_ZERO(charp, nbytes)                                            \
 do {                                                                          \
   INTERNAL_SIZE_T mzsz = (nbytes);                                            \
   if(mzsz <= 9*sizeof(mzsz)) {                                                \
     INTERNAL_SIZE_T* mz = (INTERNAL_SIZE_T*) (charp);                         \
     if(mzsz >= 5*sizeof(mzsz)) {     *mz++ = 0;                               \
                                      *mz++ = 0;                               \
       if(mzsz >= 7*sizeof(mzsz)) {   *mz++ = 0;                               \
                                      *mz++ = 0;                               \
         if(mzsz >= 9*sizeof(mzsz)) { *mz++ = 0;                               \
                                      *mz++ = 0; }}}                           \
                                      *mz++ = 0;                               \
                                      *mz++ = 0;                               \
                                      *mz   = 0;                               \
   } else memset((charp), 0, mzsz);                                            \
 } while(0)
 
 #define MALLOC_COPY(dest,src,nbytes)                                          \
 do {                                                                          \
   INTERNAL_SIZE_T mcsz = (nbytes);                                            \
   if(mcsz <= 9*sizeof(mcsz)) {                                                \
     INTERNAL_SIZE_T* mcsrc = (INTERNAL_SIZE_T*) (src);                        \
     INTERNAL_SIZE_T* mcdst = (INTERNAL_SIZE_T*) (dest);                       \
     if(mcsz >= 5*sizeof(mcsz)) {     *mcdst++ = *mcsrc++;                     \
                                      *mcdst++ = *mcsrc++;                     \
       if(mcsz >= 7*sizeof(mcsz)) {   *mcdst++ = *mcsrc++;                     \
                                      *mcdst++ = *mcsrc++;                     \
         if(mcsz >= 9*sizeof(mcsz)) { *mcdst++ = *mcsrc++;                     \
                                      *mcdst++ = *mcsrc++; }}}                 \
                                      *mcdst++ = *mcsrc++;                     \
                                      *mcdst++ = *mcsrc++;                     \
                                      *mcdst   = *mcsrc  ;                     \
   } else memcpy(dest, src, mcsz);                                             \
 } while(0)
 
 #else /* !USE_MEMCPY */
 
 /* Use Duff's device for good zeroing/copying performance. */
 
 #define MALLOC_ZERO(charp, nbytes)                                            \
 do {                                                                          \
   INTERNAL_SIZE_T* mzp = (INTERNAL_SIZE_T*)(charp);                           \
   long mctmp = (nbytes)/sizeof(INTERNAL_SIZE_T), mcn;                         \
   if (mctmp < 8) mcn = 0; else { mcn = (mctmp-1)/8; mctmp %= 8; }             \
   switch (mctmp) {                                                            \
     case 0: for(;;) { *mzp++ = 0;                                             \
     case 7:           *mzp++ = 0;                                             \
     case 6:           *mzp++ = 0;                                             \
     case 5:           *mzp++ = 0;                                             \
     case 4:           *mzp++ = 0;                                             \
     case 3:           *mzp++ = 0;                                             \
     case 2:           *mzp++ = 0;                                             \
     case 1:           *mzp++ = 0; if(mcn <= 0) break; mcn--; }                \
   }                                                                           \
 } while(0)
 
 #define MALLOC_COPY(dest,src,nbytes)                                          \
 do {                                                                          \
   INTERNAL_SIZE_T* mcsrc = (INTERNAL_SIZE_T*) src;                            \
   INTERNAL_SIZE_T* mcdst = (INTERNAL_SIZE_T*) dest;                           \
   long mctmp = (nbytes)/sizeof(INTERNAL_SIZE_T), mcn;                         \
   if (mctmp < 8) mcn = 0; else { mcn = (mctmp-1)/8; mctmp %= 8; }             \
   switch (mctmp) {                                                            \
     case 0: for(;;) { *mcdst++ = *mcsrc++;                                    \
     case 7:           *mcdst++ = *mcsrc++;                                    \
     case 6:           *mcdst++ = *mcsrc++;                                    \
     case 5:           *mcdst++ = *mcsrc++;                                    \
     case 4:           *mcdst++ = *mcsrc++;                                    \
     case 3:           *mcdst++ = *mcsrc++;                                    \
     case 2:           *mcdst++ = *mcsrc++;                                    \
     case 1:           *mcdst++ = *mcsrc++; if(mcn <= 0) break; mcn--; }       \
   }                                                                           \
 } while(0)
 
 #endif
 
 /*
   Define HAVE_MMAP to optionally make malloc() use mmap() to
   allocate very large blocks.  These will be returned to the
   operating system immediately after a free().
 */
 
 #ifndef HAVE_MMAP
 #define HAVE_MMAP 0
 #endif
 
 /*
   Define HAVE_MREMAP to make realloc() use mremap() to re-allocate
   large blocks.  This is currently only possible on Linux with
   kernel versions newer than 1.3.77.
 */
 
 #ifndef HAVE_MREMAP
 #ifdef INTERNAL_LINUX_C_LIB
 #define HAVE_MREMAP 1
 #else
 #define HAVE_MREMAP 0
 #endif
 #endif
 
 #if HAVE_MMAP
 
 #include <unistd.h>
 #include <fcntl.h>
 #include <sys/mman.h>
 
 #if !defined(MAP_ANONYMOUS) && defined(MAP_ANON)
 #define MAP_ANONYMOUS MAP_ANON
 #endif
 
 #endif /* HAVE_MMAP */
 
 /*
   Access to system page size. To the extent possible, this malloc
   manages memory from the system in page-size units.
   
   The following mechanics for getpagesize were adapted from 
   bsd/gnu getpagesize.h 
 */
 
 #ifndef LACKS_UNISTD_H
 #  include <unistd.h>
 #endif
 
 #if 0
 #ifndef malloc_getpagesize
 #  ifdef _SC_PAGESIZE         /* some SVR4 systems omit an underscore */
 #    ifndef _SC_PAGE_SIZE
 #      define _SC_PAGE_SIZE _SC_PAGESIZE
 #    endif
 #  endif
 #  ifdef _SC_PAGE_SIZE
 #    define malloc_getpagesize sysconf(_SC_PAGE_SIZE)
 #  else
 #    if defined(BSD) || defined(DGUX) || defined(HAVE_GETPAGESIZE)
        extern size_t getpagesize();
 #      define malloc_getpagesize getpagesize()
 #    else
 #      include <sys/param.h>
 #      ifdef EXEC_PAGESIZE
 #        define malloc_getpagesize EXEC_PAGESIZE
 #      else
 #        ifdef NBPG
 #          ifndef CLSIZE
 #            define malloc_getpagesize NBPG
 #          else
 #            define malloc_getpagesize (NBPG * CLSIZE)
 #          endif
 #        else 
 #          ifdef NBPC
 #            define malloc_getpagesize NBPC
 #          else
 #            ifdef PAGESIZE
 #              define malloc_getpagesize PAGESIZE
 #            else
 #              define malloc_getpagesize (4096) /* just guess */
 #            endif
 #          endif
 #        endif 
 #      endif
 #    endif 
 #  endif
 #endif
 #endif
 
 #define malloc_getpagesize (0x1000)
 
 /*
 
   This version of malloc supports the standard SVID/XPG mallinfo
   routine that returns a struct containing the same kind of
   information you can get from malloc_stats. It should work on
   any SVID/XPG compliant system that has a /usr/include/malloc.h
   defining struct mallinfo. (If you'd like to install such a thing
   yourself, cut out the preliminary declarations as described above
   and below and save them in a malloc.h file. But there's no
   compelling reason to bother to do this.)
 
   The main declaration needed is the mallinfo struct that is returned
   (by-copy) by mallinfo().  The SVID/XPG malloinfo struct contains a
   bunch of fields, most of which are not even meaningful in this
   version of malloc. Some of these fields are are instead filled by
   mallinfo() with other numbers that might possibly be of interest.
 
   HAVE_USR_INCLUDE_MALLOC_H should be set if you have a
   /usr/include/malloc.h file that includes a declaration of struct
   mallinfo.  If so, it is included; else an SVID2/XPG2 compliant
   version is declared below.  These must be precisely the same for
   mallinfo() to work.
 
 */
 
 /* #define HAVE_USR_INCLUDE_MALLOC_H */
 
 #if HAVE_USR_INCLUDE_MALLOC_H
 #include "/usr/include/malloc.h"
 #else
 
 /* SVID2/XPG mallinfo structure */
 
 struct mallinfo {
   int arena;    /* total space allocated from system */
   int ordblks;  /* number of non-inuse chunks */
   int smblks;   /* unused -- always zero */
   int hblks;    /* number of mmapped regions */
   int hblkhd;   /* total space in mmapped regions */
   int usmblks;  /* unused -- always zero */
   int fsmblks;  /* unused -- always zero */
   int uordblks; /* total allocated space */
   int fordblks; /* total non-inuse space */
   int keepcost; /* top-most, releasable (via malloc_trim) space */
 };	
 
 /* SVID2/XPG mallopt options */
 
 #define M_MXFAST  1    /* UNUSED in this malloc */
 #define M_NLBLKS  2    /* UNUSED in this malloc */
 #define M_GRAIN   3    /* UNUSED in this malloc */
 #define M_KEEP    4    /* UNUSED in this malloc */
 
 #endif
 
 /* mallopt options that actually do something */
 
 #define M_TRIM_THRESHOLD    -1
 #define M_TOP_PAD           -2
 #define M_MMAP_THRESHOLD    -3
 #define M_MMAP_MAX          -4
 
 #ifndef DEFAULT_TRIM_THRESHOLD
 #define DEFAULT_TRIM_THRESHOLD (128 * 1024)
 #endif
 
 /*
     M_TRIM_THRESHOLD is the maximum amount of unused top-most memory 
       to keep before releasing via malloc_trim in free().
 
       Automatic trimming is mainly useful in long-lived programs.
       Because trimming via sbrk can be slow on some systems, and can
       sometimes be wasteful (in cases where programs immediately
       afterward allocate more large chunks) the value should be high
       enough so that your overall system performance would improve by
       releasing.  
 
       The trim threshold and the mmap control parameters (see below)
       can be traded off with one another. Trimming and mmapping are
       two different ways of releasing unused memory back to the
       system. Between these two, it is often possible to keep
       system-level demands of a long-lived program down to a bare
       minimum. For example, in one test suite of sessions measuring
       the XF86 X server on Linux, using a trim threshold of 128K and a
       mmap threshold of 192K led to near-minimal long term resource
       consumption.  
 
       If you are using this malloc in a long-lived program, it should
       pay to experiment with these values.  As a rough guide, you
       might set to a value close to the average size of a process
       (program) running on your system.  Releasing this much memory
       would allow such a process to run in memory.  Generally, it's
       worth it to tune for trimming rather tham memory mapping when a
       program undergoes phases where several large chunks are
       allocated and released in ways that can reuse each other's
       storage, perhaps mixed with phases where there are no such
       chunks at all.  And in well-behaved long-lived programs,
       controlling release of large blocks via trimming versus mapping
       is usually faster.
 
       However, in most programs, these parameters serve mainly as
       protection against the system-level effects of carrying around
       massive amounts of unneeded memory. Since frequent calls to
       sbrk, mmap, and munmap otherwise degrade performance, the default
       parameters are set to relatively high values that serve only as
       safeguards.
 
       The default trim value is high enough to cause trimming only in
       fairly extreme (by current memory consumption standards) cases.
       It must be greater than page size to have any useful effect.  To
       disable trimming completely, you can set to (unsigned long)(-1);
 */
 
 #ifndef DEFAULT_TOP_PAD
 #define DEFAULT_TOP_PAD        (0)
 #endif
 
 /*
     M_TOP_PAD is the amount of extra `padding' space to allocate or 
       retain whenever sbrk is called. It is used in two ways internally:
 
       * When sbrk is called to extend the top of the arena to satisfy
         a new malloc request, this much padding is added to the sbrk
         request.
 
       * When malloc_trim is called automatically from free(),
         it is used as the `pad' argument.
 
       In both cases, the actual amount of padding is rounded 
       so that the end of the arena is always a system page boundary.
 
       The main reason for using padding is to avoid calling sbrk so
       often. Having even a small pad greatly reduces the likelihood
       that nearly every malloc request during program start-up (or
       after trimming) will invoke sbrk, which needlessly wastes
       time. 
 
       Automatic rounding-up to page-size units is normally sufficient
       to avoid measurable overhead, so the default is 0.  However, in
       systems where sbrk is relatively slow, it can pay to increase
       this value, at the expense of carrying around more memory than 
       the program needs.
 
 */
 
 #ifndef DEFAULT_MMAP_THRESHOLD
 #define DEFAULT_MMAP_THRESHOLD (128 * 1024)
 #endif
 
 /*
     M_MMAP_THRESHOLD is the request size threshold for using mmap() 
       to service a request. Requests of at least this size that cannot 
       be allocated using already-existing space will be serviced via mmap.  
       (If enough normal freed space already exists it is used instead.)
 
       Using mmap segregates relatively large chunks of memory so that
       they can be individually obtained and released from the host
       system. A request serviced through mmap is never reused by any
       other request (at least not directly; the system may just so
       happen to remap successive requests to the same locations).
 
       Segregating space in this way has the benefit that mmapped space
       can ALWAYS be individually released back to the system, which
       helps keep the system level memory demands of a long-lived
       program low. Mapped memory can never become `locked' between
       other chunks, as can happen with normally allocated chunks, which
       menas that even trimming via malloc_trim would not release them.
 
       However, it has the disadvantages that:
 
          1. The space cannot be reclaimed, consolidated, and then
             used to service later requests, as happens with normal chunks. 
          2. It can lead to more wastage because of mmap page alignment
             requirements
          3. It causes malloc performance to be more dependent on host
             system memory management support routines which may vary in
             implementation quality and may impose arbitrary
             limitations. Generally, servicing a request via normal
             malloc steps is faster than going through a system's mmap.
 
       All together, these considerations should lead you to use mmap
       only for relatively large requests.  
 */
 
 #ifndef DEFAULT_MMAP_MAX
 #if HAVE_MMAP
 #define DEFAULT_MMAP_MAX       (64)
 #else
 #define DEFAULT_MMAP_MAX       (0)
 #endif
 #endif
 
 /*
     M_MMAP_MAX is the maximum number of requests to simultaneously 
       service using mmap. This parameter exists because:
 
          1. Some systems have a limited number of internal tables for
             use by mmap.
          2. In most systems, overreliance on mmap can degrade overall
             performance.
          3. If a program allocates many large regions, it is probably
             better off using normal sbrk-based allocation routines that
             can reclaim and reallocate normal heap memory. Using a
             small value allows transition into this mode after the
             first few allocations.
 
       Setting to 0 disables all use of mmap.  If HAVE_MMAP is not set,
       the default value is 0, and attempts to set it to non-zero values
       in mallopt will fail.
 */
 
 /* 
 
   Special defines for linux libc
 
   Except when compiled using these special defines for Linux libc
   using weak aliases, this malloc is NOT designed to work in
   multithreaded applications.  No semaphores or other concurrency
   control are provided to ensure that multiple malloc or free calls
   don't run at the same time, which could be disasterous. A single
   semaphore could be used across malloc, realloc, and free (which is
   essentially the effect of the linux weak alias approach). It would
   be hard to obtain finer granularity.
 */
 
 #ifdef INTERNAL_LINUX_C_LIB
 
 #if __STD_C
 
 Void_t * __default_morecore_init (ptrdiff_t);
 Void_t *(*__morecore)(ptrdiff_t) = __default_morecore_init;
 
 #else
 
 Void_t * __default_morecore_init ();
 Void_t *(*__morecore)() = __default_morecore_init;
 
 #endif
 
 #define MORECORE (*__morecore)
 #define MORECORE_FAILURE 0
 #define MORECORE_CLEARS 1 
 
 #else /* INTERNAL_LINUX_C_LIB */
 
 #if __STD_C
 extern Void_t*     sbrk(int ptrdiff_t);
 #else
 extern Void_t*     sbrk();
 #endif
 
 #ifndef MORECORE
 #define MORECORE sbrk
 #endif
 
 #ifndef MORECORE_FAILURE
 #define MORECORE_FAILURE -1
 #endif
 
 #ifndef MORECORE_CLEARS
 #define MORECORE_CLEARS 1
 #endif
 
 #endif /* INTERNAL_LINUX_C_LIB */
 
 #if defined(INTERNAL_LINUX_C_LIB) && defined(__ELF__)
 
 #define cALLOc		__libc_calloc
 #define fREe		__libc_free
 #define mALLOc		__libc_malloc
 #define mEMALIGn	__libc_memalign
 #define rEALLOc		__libc_realloc
 #define vALLOc		__libc_valloc
 #define pvALLOc		__libc_pvalloc
 #define mALLINFo	__libc_mallinfo
 #define mALLOPt		__libc_mallopt
 
 #pragma weak calloc = __libc_calloc
 #pragma weak free = __libc_free
 #pragma weak cfree = __libc_free
 #pragma weak malloc = __libc_malloc
 #pragma weak memalign = __libc_memalign
 #pragma weak realloc = __libc_realloc
 #pragma weak valloc = __libc_valloc
 #pragma weak pvalloc = __libc_pvalloc
 #pragma weak mallinfo = __libc_mallinfo
 #pragma weak mallopt = __libc_mallopt
 
 #else
 
 
 #define cALLOc		__calloc
 #define fREe		  __free
 #define mALLOc		__malloc
 #define mEMALIGn	__memalign
 #define rEALLOc		__realloc
 #define vALLOc		__valloc
 #define pvALLOc		__pvalloc
 #define mALLINFo	__mallinfo
 #define mALLOPt		__mallopt
 
 #endif
 
 /* Public routines */
 
 #if __STD_C
 
 Void_t* mALLOc(size_t);
 void    fREe(Void_t*);
 Void_t* rEALLOc(Void_t*, size_t);
 Void_t* mEMALIGn(size_t, size_t);
 Void_t* vALLOc(size_t);
 Void_t* pvALLOc(size_t);
 Void_t* cALLOc(size_t, size_t);
 void    cfree(Void_t*);
 int     malloc_trim(size_t);
 size_t  malloc_usable_size(Void_t*);
 void    malloc_stats();
 int     mALLOPt(int, int);
 struct mallinfo mALLINFo(void);
 #else
 Void_t* mALLOc();
 void    fREe();
 Void_t* rEALLOc();
 Void_t* mEMALIGn();
 Void_t* vALLOc();
 Void_t* pvALLOc();
 Void_t* cALLOc();
 void    cfree();
 int     malloc_trim();
 size_t  malloc_usable_size();
 void    malloc_stats();
 int     mALLOPt();
 struct mallinfo mALLINFo();
 #endif
 
 #ifdef __cplusplus
 };  /* end of extern "C" */
 #endif
 
 /* ---------- To make a malloc.h, end cutting here ------------ */
 
 /*
   Type declarations
 */
 
 struct malloc_chunk
 {
   INTERNAL_SIZE_T prev_size; /* Size of previous chunk (if free). */
   INTERNAL_SIZE_T size;      /* Size in bytes, including overhead. */
   struct malloc_chunk* fd;   /* double links -- used only if free. */
   struct malloc_chunk* bk;
 };
 
 typedef struct malloc_chunk* mchunkptr;
 
 /*
    malloc_chunk details:
 
     (The following includes lightly edited explanations by Colin Plumb.)
 
     Chunks of memory are maintained using a `boundary tag' method as
     described in e.g., Knuth or Standish.  (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 very fast.  The
     size fields also hold bits representing whether chunks are free or
     in use.
 
     An allocated chunk looks like this:  
 
 
     chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             |             Size of previous chunk, if allocated            | |
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             |             Size of chunk, in bytes                         |P|
       mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             |             User data starts here...                          .
             .                                                               .
             .             (malloc_usable_space() bytes)                     .
             .                                                               |
 nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             |             Size of chunk                                     |
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 
 
     Where "chunk" is the front of the chunk for the purpose of most of
     the malloc code, but "mem" is the pointer that is returned to the
     user.  "Nextchunk" is the beginning of the next contiguous chunk.
 
     Chunks always begin on even word boundries, so the mem portion
     (which is returned to the user) is also on an even word boundary, and
     thus double-word aligned.
 
     Free 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                           |
             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 
     The P (PREV_INUSE) 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.)
 
     Note that the `foot' of the current chunk is actually represented
     as the prev_size of the NEXT chunk. (This makes it easier to
     deal with alignments etc).
 
     The two exceptions to all this are 
 
      1. The special chunk `top', which doesn't bother using the 
         trailing size field since there is no
         next contiguous chunk that would have to index off it. (After
         initialization, `top' is forced to always exist.  If it would
         become less than MINSIZE bytes long, it is replenished via
         malloc_extend_top.)
 
      2. Chunks allocated via mmap, which have the second-lowest-order
         bit (IS_MMAPPED) set in their size fields.  Because they are
         never merged or traversed from any other chunk, they have no
         foot size or inuse information.
 
     Available chunks are kept in any of several places (all declared below):
 
     * `av': An array of chunks serving as bin headers for consolidated
        chunks. Each bin is doubly linked.  The bins are approximately
        proportionally (log) spaced.  There are a lot of these bins
        (128). This may look excessive, but works very well in
        practice.  All procedures maintain the invariant that no
        consolidated chunk physically borders another one. Chunks in
        bins are kept in size order, with ties going to the
        approximately least recently used chunk.
 
        The chunks in each bin are maintained in decreasing sorted order by
        size.  This is irrelevant for the small bins, which all contain
        the same-sized chunks, but facilitates best-fit allocation for
        larger chunks. (These lists are just sequential. Keeping them in
        order almost never requires enough traversal to warrant using
        fancier ordered data structures.)  Chunks of the same size are
        linked with the most recently freed at the front, and allocations
        are taken from the back.  This results in LRU or FIFO allocation
        order, which tends to give each chunk an equal opportunity to be
        consolidated with adjacent freed chunks, resulting in larger free
        chunks and less fragmentation. 
 
     * `top': The top-most available chunk (i.e., the one bordering the
        end of available memory) is treated specially. It 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).
 
     * `last_remainder': A bin holding only the remainder of the
        most recently split (non-top) chunk. This bin is checked
        before other non-fitting chunks, so as to provide better
        locality for runs of sequentially allocated chunks. 
 
     *  Implicitly, through the host system's memory mapping tables.
        If supported, requests greater than a threshold are usually 
        serviced via calls to mmap, and then later released via munmap.
 
 */
 
 /*  sizes, alignments */
 
 #define SIZE_SZ                (sizeof(INTERNAL_SIZE_T))
 #define MALLOC_ALIGNMENT       (SIZE_SZ + SIZE_SZ)
 #define MALLOC_ALIGN_MASK      (MALLOC_ALIGNMENT - 1)
 #define MINSIZE                (sizeof(struct malloc_chunk))
 
 /* conversion from malloc headers to user pointers, and back */
 
 #define chunk2mem(p)   ((Void_t*)((char*)(p) + 2*SIZE_SZ))
 #define mem2chunk(mem) ((mchunkptr)((char*)(mem) - 2*SIZE_SZ))
 
 /* pad request bytes into a usable size */
 
 #define request2size(req) \
  (((long)((req) + (SIZE_SZ + MALLOC_ALIGN_MASK)) < \
   (long)(MINSIZE + MALLOC_ALIGN_MASK)) ? MINSIZE : \
    (((req) + (SIZE_SZ + MALLOC_ALIGN_MASK)) & ~(MALLOC_ALIGN_MASK)))
 
 /* Check if m has acceptable alignment */
 
 #define aligned_OK(m)    (((unsigned long)((m)) & (MALLOC_ALIGN_MASK)) == 0)
 
 /* 
   Physical chunk operations  
 */
 
 /* size field is or'ed with PREV_INUSE when previous adjacent chunk in use */
 
 #define PREV_INUSE 0x1 
 
 /* size field is or'ed with IS_MMAPPED if the chunk was obtained with mmap() */
 
 #define IS_MMAPPED 0x2
 
 /* Bits to mask off when extracting size */
 
 #define SIZE_BITS (PREV_INUSE|IS_MMAPPED)
 
 /* Ptr to next physical malloc_chunk. */
 
 #define next_chunk(p) ((mchunkptr)( ((char*)(p)) + ((p)->size & ~PREV_INUSE) ))
 
 /* Ptr to previous physical malloc_chunk */
 
 #define prev_chunk(p)\
    ((mchunkptr)( ((char*)(p)) - ((p)->prev_size) ))
 
 /* Treat space at ptr + offset as a chunk */
 
 #define chunk_at_offset(p, s)  ((mchunkptr)(((char*)(p)) + (s)))
 
 /* 
   Dealing with use bits 
 */
 
 /* extract p's inuse bit */
 
 #define inuse(p)\
 ((((mchunkptr)(((char*)(p))+((p)->size & ~PREV_INUSE)))->size) & PREV_INUSE)
 
 /* extract inuse bit of previous chunk */
 
 #define prev_inuse(p)  ((p)->size & PREV_INUSE)
 
 /* check for mmap()'ed chunk */
 
 #define chunk_is_mmapped(p) ((p)->size & IS_MMAPPED)
 
 /* set/clear chunk as in use without otherwise disturbing */
 
 #define set_inuse(p)\
 ((mchunkptr)(((char*)(p)) + ((p)->size & ~PREV_INUSE)))->size |= PREV_INUSE
 
 #define clear_inuse(p)\
 ((mchunkptr)(((char*)(p)) + ((p)->size & ~PREV_INUSE)))->size &= ~(PREV_INUSE)
 
 /* check/set/clear inuse bits in known places */
 
 #define inuse_bit_at_offset(p, s)\
  (((mchunkptr)(((char*)(p)) + (s)))->size & PREV_INUSE)
 
 #define set_inuse_bit_at_offset(p, s)\
  (((mchunkptr)(((char*)(p)) + (s)))->size |= PREV_INUSE)
 
 #define clear_inuse_bit_at_offset(p, s)\
  (((mchunkptr)(((char*)(p)) + (s)))->size &= ~(PREV_INUSE))
 
 /* 
   Dealing with size fields 
 */
 
 /* Get size, ignoring use bits */
 
 #define chunksize(p)          ((p)->size & ~(SIZE_BITS))
 
 /* Set size at head, without disturbing its use bit */
 
 #define set_head_size(p, s)   ((p)->size = (((p)->size & PREV_INUSE) | (s)))
 
 /* Set size/use ignoring previous bits in header */
 
 #define set_head(p, s)        ((p)->size = (s))
 
 /* Set size at footer (only when chunk is not in use) */
 
 #define set_foot(p, s)   (((mchunkptr)((char*)(p) + (s)))->prev_size = (s))
 
 /*
    Bins
 
     The bins, `av_' are an array of pairs of pointers serving as the
     heads of (initially empty) doubly-linked lists of chunks, laid out
     in a way so that each pair can be treated as if it were in a
     malloc_chunk. (This way, the fd/bk offsets for linking bin heads
     and chunks are the same).
 
     Bins for sizes < 512 bytes contain chunks of all the same size, spaced
     8 bytes apart. Larger bins are approximately logarithmically
     spaced. (See the table below.) The `av_' array is never mentioned
     directly in the code, but instead via bin access macros.
 
     Bin layout:
 
     64 bins of size       8
     32 bins of size      64
     16 bins of size     512
      8 bins of size    4096
      4 bins of size   32768
      2 bins of size  262144
      1 bin  of size what's left
 
     There is actually a little bit of slop in the numbers in bin_index
     for the sake of speed. This makes no difference elsewhere.
 
     The special chunks `top' and `last_remainder' get their own bins,
     (this is implemented via yet more trickery with the av_ array),
     although `top' is never properly linked to its bin since it is
     always handled specially.
 
 */
 
 #define NAV             128   /* number of bins */
 
 typedef struct malloc_chunk* mbinptr;
 
 /* access macros */
 
 #define bin_at(i)      ((mbinptr)((char*)&(av_[2*(i) + 2]) - 2*SIZE_SZ))
 #define next_bin(b)    ((mbinptr)((char*)(b) + 2 * sizeof(mbinptr)))
 #define prev_bin(b)    ((mbinptr)((char*)(b) - 2 * sizeof(mbinptr)))
 
 /*
    The first 2 bins are never indexed. The corresponding av_ cells are instead
    used for bookkeeping. This is not to save space, but to simplify
    indexing, maintain locality, and avoid some initialization tests.
 */
 
 #define top            (bin_at(0)->fd)   /* The topmost chunk */
 #define last_remainder (bin_at(1))       /* remainder from last split */
 
 /*
    Because top initially points to its own bin with initial
    zero size, thus forcing extension on the first malloc request, 
    we avoid having any special code in malloc to check whether 
    it even exists yet. But we still need to in malloc_extend_top.
 */
 
 #define initial_top    ((mchunkptr)(bin_at(0)))
 
 /* Helper macro to initialize bins */
 
 #define IAV(i)  bin_at(i), bin_at(i)
 
 static mbinptr av_[NAV * 2 + 2] = {
  0, 0,
  IAV(0),   IAV(1),   IAV(2),   IAV(3),   IAV(4),   IAV(5),   IAV(6),   IAV(7),
  IAV(8),   IAV(9),   IAV(10),  IAV(11),  IAV(12),  IAV(13),  IAV(14),  IAV(15),
  IAV(16),  IAV(17),  IAV(18),  IAV(19),  IAV(20),  IAV(21),  IAV(22),  IAV(23),
  IAV(24),  IAV(25),  IAV(26),  IAV(27),  IAV(28),  IAV(29),  IAV(30),  IAV(31),
  IAV(32),  IAV(33),  IAV(34),  IAV(35),  IAV(36),  IAV(37),  IAV(38),  IAV(39),
  IAV(40),  IAV(41),  IAV(42),  IAV(43),  IAV(44),  IAV(45),  IAV(46),  IAV(47),
  IAV(48),  IAV(49),  IAV(50),  IAV(51),  IAV(52),  IAV(53),  IAV(54),  IAV(55),
  IAV(56),  IAV(57),  IAV(58),  IAV(59),  IAV(60),  IAV(61),  IAV(62),  IAV(63),
  IAV(64),  IAV(65),  IAV(66),  IAV(67),  IAV(68),  IAV(69),  IAV(70),  IAV(71),
  IAV(72),  IAV(73),  IAV(74),  IAV(75),  IAV(76),  IAV(77),  IAV(78),  IAV(79),
  IAV(80),  IAV(81),  IAV(82),  IAV(83),  IAV(84),  IAV(85),  IAV(86),  IAV(87),
  IAV(88),  IAV(89),  IAV(90),  IAV(91),  IAV(92),  IAV(93),  IAV(94),  IAV(95),
  IAV(96),  IAV(97),  IAV(98),  IAV(99),  IAV(100), IAV(101), IAV(102), IAV(103),
  IAV(104), IAV(105), IAV(106), IAV(107), IAV(108), IAV(109), IAV(110), IAV(111),
  IAV(112), IAV(113), IAV(114), IAV(115), IAV(116), IAV(117), IAV(118), IAV(119),
  IAV(120), IAV(121), IAV(122), IAV(123), IAV(124), IAV(125), IAV(126), IAV(127)
 };
 
 /* field-extraction macros */
 
 #define first(b) ((b)->fd)
 #define last(b)  ((b)->bk)
 
 /* 
   Indexing into bins
 */
 
 #define bin_index(sz)                                                          \
 (((((unsigned long)(sz)) >> 9) ==    0) ?       (((unsigned long)(sz)) >>  3): \
  ((((unsigned long)(sz)) >> 9) <=    4) ?  56 + (((unsigned long)(sz)) >>  6): \
  ((((unsigned long)(sz)) >> 9) <=   20) ?  91 + (((unsigned long)(sz)) >>  9): \
  ((((unsigned long)(sz)) >> 9) <=   84) ? 110 + (((unsigned long)(sz)) >> 12): \
  ((((unsigned long)(sz)) >> 9) <=  340) ? 119 + (((unsigned long)(sz)) >> 15): \
  ((((unsigned long)(sz)) >> 9) <= 1364) ? 124 + (((unsigned long)(sz)) >> 18): \
                                           126)                     
 /* 
   bins for chunks < 512 are all spaced 8 bytes apart, and hold
   identically sized chunks. This is exploited in malloc.
 */
 
 #define MAX_SMALLBIN         63
 #define MAX_SMALLBIN_SIZE   512
 #define SMALLBIN_WIDTH        8
 
 #define smallbin_index(sz)  (((unsigned long)(sz)) >> 3)
 
 /* 
    Requests are `small' if both the corresponding and the next bin are small
 */
 
 #define is_small_request(nb) (nb < MAX_SMALLBIN_SIZE - SMALLBIN_WIDTH)
 
 /*
     To help compensate for the large number of bins, a one-level index
     structure is used for bin-by-bin searching.  `binblocks' is a
     one-word bitvector recording whether groups of BINBLOCKWIDTH bins
     have any (possibly) non-empty bins, so they can be skipped over
     all at once during during traversals. The bits are NOT always
     cleared as soon as all bins in a block are empty, but instead only
     when all are noticed to be empty during traversal in malloc.
 */
 
 #define BINBLOCKWIDTH     4   /* bins per block */
 
 #define binblocks      (bin_at(0)->size) /* bitvector of nonempty blocks */
 
 /* bin<->block macros */
 
 #define idx2binblock(ix)    ((unsigned)1 << (ix / BINBLOCKWIDTH))
 #define mark_binblock(ii)   (binblocks |= idx2binblock(ii))
 #define clear_binblock(ii)  (binblocks &= ~(idx2binblock(ii)))
 
 /*  Other static bookkeeping data */
 
 /* variables holding tunable values */
 
 static unsigned long trim_threshold   = DEFAULT_TRIM_THRESHOLD;
 static unsigned long top_pad          = DEFAULT_TOP_PAD;
 static unsigned int  n_mmaps_max      = DEFAULT_MMAP_MAX;
 static unsigned long mmap_threshold   = DEFAULT_MMAP_THRESHOLD;
 
 /* The first value returned from sbrk */
 static char* sbrk_base = (char*)(-1);
 
 /* The maximum memory obtained from system via sbrk */
 static unsigned long max_sbrked_mem = 0; 
 
 /* The maximum via either sbrk or mmap */
 static unsigned long max_total_mem = 0; 
 
 /* internal working copy of mallinfo */
 static struct mallinfo current_mallinfo = {  0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
 
 /* The total memory obtained from system via sbrk */
 #define sbrked_mem  (current_mallinfo.arena)
 
 /* Tracking mmaps */
 
 static unsigned int n_mmaps = 0;
 static unsigned long mmapped_mem = 0;
 
 /* 
   Debugging support 
 */
 
 #if DEBUG
 
 /*
   These routines make a number of assertions about the states
   of data structures that should be true at all times. If any
   are not true, it's very likely that a user program has somehow
   trashed memory. (It's also possible that there is a coding error
   in malloc. In which case, please report it!)
 */
 
 #if __STD_C
 static void do_check_chunk(mchunkptr p) 
 #else
 static void do_check_chunk(p) mchunkptr p;
 #endif
 { 
   INTERNAL_SIZE_T sz = p->size & ~PREV_INUSE;
 
   /* No checkable chunk is mmapped */
   assert(!chunk_is_mmapped(p));
 
   /* Check for legal address ... */
   assert((char*)p >= sbrk_base);
   if (p != top) 
     assert((char*)p + sz <= (char*)top);
   else
     assert((char*)p + sz <= sbrk_base + sbrked_mem);
 }
 
 #if __STD_C
 static void do_check_free_chunk(mchunkptr p) 
 #else
 static void do_check_free_chunk(p) mchunkptr p;
 #endif
 { 
   INTERNAL_SIZE_T sz = p->size & ~PREV_INUSE;
   mchunkptr next = chunk_at_offset(p, sz);
 
   do_check_chunk(p);
 
   /* Check whether it claims to be free ... */
   assert(!inuse(p));
 
   /* Unless a special marker, must have OK fields */
   if ((long)sz >= (long)MINSIZE)
   {
     assert((sz & MALLOC_ALIGN_MASK) == 0);
     assert(aligned_OK(chunk2mem(p)));
     /* ... matching footer field */
     assert(next->prev_size == sz);
     /* ... and is fully consolidated */
     assert(prev_inuse(p));
     assert (next == top || inuse(next));
     
     /* ... and has minimally sane links */
     assert(p->fd->bk == p);
     assert(p->bk->fd == p);
   }
   else /* markers are always of size SIZE_SZ */
     assert(sz == SIZE_SZ); 
 }
 
 #if __STD_C
 static void do_check_inuse_chunk(mchunkptr p) 
 #else
 static void do_check_inuse_chunk(p) mchunkptr p;
 #endif
 { 
   mchunkptr next = next_chunk(p);
   do_check_chunk(p);
 
   /* Check whether it claims to be in use ... */
   assert(inuse(p));
 
   /* ... and is surrounded by OK chunks.
     Since more things can be checked with free chunks than inuse ones,
     if an inuse chunk borders them and debug is on, it's worth doing them.
   */
   if (!prev_inuse(p)) 
   {
     mchunkptr prv = prev_chunk(p);
     assert(next_chunk(prv) == p);
     do_check_free_chunk(prv);
   }
   if (next == top)
   {
     assert(prev_inuse(next));
     assert(chunksize(next) >= MINSIZE);
   }
   else if (!inuse(next))
     do_check_free_chunk(next);
 }
 
 #if __STD_C
 static void do_check_malloced_chunk(mchunkptr p, INTERNAL_SIZE_T s) 
 #else
 static void do_check_malloced_chunk(p, s) mchunkptr p; INTERNAL_SIZE_T s;
 #endif
 {
   INTERNAL_SIZE_T sz = p->size & ~PREV_INUSE;
   long room = sz - s;
 
   do_check_inuse_chunk(p);
 
   /* Legal size ... */
   assert((long)sz >= (long)MINSIZE);
   assert((sz & MALLOC_ALIGN_MASK) == 0);
   assert(room >= 0);
   assert(room < (long)MINSIZE);
 
   /* ... and alignment */
   assert(aligned_OK(chunk2mem(p)));
 
   /* ... and was allocated at front of an available chunk */
   assert(prev_inuse(p));
 }
 
 #define check_free_chunk(P)  do_check_free_chunk(P)
 #define check_inuse_chunk(P) do_check_inuse_chunk(P)
 #define check_chunk(P) do_check_chunk(P)
 #define check_malloced_chunk(P,N) do_check_malloced_chunk(P,N)
 #else
 #define check_free_chunk(P) 
 #define check_inuse_chunk(P)
 #define check_chunk(P)
 #define check_malloced_chunk(P,N)
 #endif
 
 /* 
   Macro-based internal utilities
 */
 
 /*  
   Linking chunks in bin lists.
   Call these only with variables, not arbitrary expressions, as arguments.
 */
 
 /* 
   Place chunk p of size s in its bin, in size order,
   putting it ahead of others of same size.
 */
 
 #define frontlink(P, S, IDX, BK, FD)                                          \
 {                                                                             \
   if (S < MAX_SMALLBIN_SIZE)                                                  \
   {                                                                           \
     IDX = smallbin_index(S);                                                  \
     mark_binblock(IDX);                                                       \
     BK = bin_at(IDX);                                                         \
     FD = BK->fd;                                                              \
     P->bk = BK;                                                               \
     P->fd = FD;                                                               \
     FD->bk = BK->fd = P;                                                      \
   }                                                                           \
   else                                                                        \
   {                                                                           \
     IDX = bin_index(S);                                                       \
     BK = bin_at(IDX);                                                         \
     FD = BK->fd;                                                              \
     if (FD == BK) mark_binblock(IDX);                                         \
     else                                                                      \
     {                                                                         \
       while (FD != BK && S < chunksize(FD)) FD = FD->fd;                      \
       BK = FD->bk;                                                            \
     }                                                                         \
     P->bk = BK;                                                               \
     P->fd = FD;                                                               \
     FD->bk = BK->fd = P;                                                      \
   }                                                                           \
 }
 
 /* take a chunk off a list */
 
 #define unlink(P, BK, FD)                                                     \
 {                                                                             \
   BK = P->bk;                                                                 \
   FD = P->fd;                                                                 \
   FD->bk = BK;                                                                \
   BK->fd = FD;                                                                \
 }                                                                             \
 
 /* Place p as the last remainder */
 
 #define link_last_remainder(P)                                                \
 {                                                                             \
   last_remainder->fd = last_remainder->bk =  P;                               \
   P->fd = P->bk = last_remainder;                                             \
 }
 
 /* Clear the last_remainder bin */
 
 #define clear_last_remainder \
   (last_remainder->fd = last_remainder->bk = last_remainder)
 
 /* Routines dealing with mmap(). */
 
 #if HAVE_MMAP
 
 #if __STD_C
 static mchunkptr mmap_chunk(size_t size)
 #else
 static mchunkptr mmap_chunk(size) size_t size;
 #endif
 {
   size_t page_mask = malloc_getpagesize - 1;
   mchunkptr p;
 
 #ifndef MAP_ANONYMOUS
   static int fd = -1;
 #endif
 
   if(n_mmaps >= n_mmaps_max) return 0; /* too many regions */
 
   /* For mmapped chunks, the overhead is one SIZE_SZ unit larger, because
    * there is no following chunk whose prev_size field could be used.
    */
   size = (size + SIZE_SZ + page_mask) & ~page_mask;
 
 #ifdef MAP_ANONYMOUS
   p = (mchunkptr)mmap(0, size, PROT_READ|PROT_WRITE,
 		      MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
 #else /* !MAP_ANONYMOUS */
   if (fd < 0) 
   {
     fd = open("/dev/zero", O_RDWR);
     if(fd < 0) return 0;
   }
   p = (mchunkptr)mmap(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
 #endif
 
   if(p == (mchunkptr)-1) return 0;
 
   n_mmaps++;
   if (n_mmaps > max_n_mmaps) max_n_mmaps = n_mmaps;
   
   /* We demand that eight bytes into a page must be 8-byte aligned. */
   assert(aligned_OK(chunk2mem(p)));
 
   /* The offset to the start of the mmapped region is stored
    * in the prev_size field of the chunk; normally it is zero,
    * but that can be changed in memalign().
    */
   p->prev_size = 0;
   set_head(p, size|IS_MMAPPED);
   
   mmapped_mem += size;
   if ((unsigned long)mmapped_mem > (unsigned long)max_mmapped_mem) 
     max_mmapped_mem = mmapped_mem;
   if ((unsigned long)(mmapped_mem + sbrked_mem) > (unsigned long)max_total_mem) 
     max_total_mem = mmapped_mem + sbrked_mem;
   return p;
 }
 
 #if __STD_C
 static void munmap_chunk(mchunkptr p)
 #else
 static void munmap_chunk(p) mchunkptr p;
 #endif
 {
   INTERNAL_SIZE_T size = chunksize(p);
   int ret;
 
   assert (chunk_is_mmapped(p));
   assert(! ((char*)p >= sbrk_base && (char*)p < sbrk_base + sbrked_mem));
   assert((n_mmaps > 0));
   assert(((p->prev_size + size) & (malloc_getpagesize-1)) == 0);
 
   n_mmaps--;
   mmapped_mem -= (size + p->prev_size);
 
   ret = munmap((char *)p - p->prev_size, size + p->prev_size);
 
   /* munmap returns non-zero on failure */
   assert(ret == 0);
 }
 
 #if HAVE_MREMAP
 
 #if __STD_C
 static mchunkptr mremap_chunk(mchunkptr p, size_t new_size)
 #else
 static mchunkptr mremap_chunk(p, new_size) mchunkptr p; size_t new_size;
 #endif
 {
   size_t page_mask = malloc_getpagesize - 1;
   INTERNAL_SIZE_T offset = p->prev_size;
   INTERNAL_SIZE_T size = chunksize(p);
   char *cp;
 
   assert (chunk_is_mmapped(p));
   assert(! ((char*)p >= sbrk_base && (char*)p < sbrk_base + sbrked_mem));
   assert((n_mmaps > 0));
   assert(((size + offset) & (malloc_getpagesize-1)) == 0);
 
   /* Note the extra SIZE_SZ overhead as in mmap_chunk(). */
   new_size = (new_size + offset + SIZE_SZ + page_mask) & ~page_mask;
 
   cp = (char *)mremap((char *)p - offset, size + offset, new_size, 1);
 
   if (cp == (char *)-1) return 0;
 
   p = (mchunkptr)(cp + offset);
 
   assert(aligned_OK(chunk2mem(p)));
 
   assert((p->prev_size == offset));
   set_head(p, (new_size - offset)|IS_MMAPPED);
 
   mmapped_mem -= size + offset;
   mmapped_mem += new_size;
   if ((unsigned long)mmapped_mem > (unsigned long)max_mmapped_mem) 
     max_mmapped_mem = mmapped_mem;
   if ((unsigned long)(mmapped_mem + sbrked_mem) > (unsigned long)max_total_mem)
     max_total_mem = mmapped_mem + sbrked_mem;
   return p;
 }
 
 #endif /* HAVE_MREMAP */
 
 #endif /* HAVE_MMAP */
 
 /* 
   Extend the top-most chunk by obtaining memory from system.
   Main interface to sbrk (but see also malloc_trim).
 */
 
 #if __STD_C
 static void malloc_extend_top(INTERNAL_SIZE_T nb)
 #else
 static void malloc_extend_top(nb) INTERNAL_SIZE_T nb;
 #endif
 {
   char*     brk;                  /* return value from sbrk */
   INTERNAL_SIZE_T front_misalign; /* unusable bytes at front of sbrked space */
   INTERNAL_SIZE_T correction;     /* bytes for 2nd sbrk call */
   char*     new_brk;              /* return of 2nd sbrk call */
   INTERNAL_SIZE_T top_size;       /* new size of top chunk */
 
   mchunkptr old_top     = top;  /* Record state of old top */
   INTERNAL_SIZE_T old_top_size = chunksize(old_top);
   char*     old_end      = (char*)(chunk_at_offset(old_top, old_top_size));
 
   /* Pad request with top_pad plus minimal overhead */
   
   INTERNAL_SIZE_T    sbrk_size     = nb + top_pad + MINSIZE;
   unsigned long pagesz    = malloc_getpagesize;
 
   /* If not the first time through, round to preserve page boundary */
   /* Otherwise, we need to correct to a page size below anyway. */
   /* (We also correct below if an intervening foreign sbrk call.) */
 
   if (sbrk_base != (char*)(-1))
     sbrk_size = (sbrk_size + (pagesz - 1)) & ~(pagesz - 1);
 
   brk = (char*)(MORECORE (sbrk_size));
 
   /* Fail if sbrk failed or if a foreign sbrk call killed our space */
   if (brk == (char*)(MORECORE_FAILURE) || 
       (brk < old_end && old_top != initial_top))
     return;     
 
   sbrked_mem += sbrk_size;
 
   if (brk == old_end) /* can just add bytes to current top */
   {
     top_size = sbrk_size + old_top_size;
     set_head(top, top_size | PREV_INUSE);
   }
   else
   {
     if (sbrk_base == (char*)(-1))  /* First time through. Record base */
       sbrk_base = brk;
     else  /* Someone else called sbrk().  Count those bytes as sbrked_mem. */
       sbrked_mem += brk - (char*)old_end;
 
     /* Guarantee alignment of first new chunk made from this space */
     front_misalign = (unsigned long)chunk2mem(brk) & MALLOC_ALIGN_MASK;
     if (front_misalign > 0) 
     {
       correction = (MALLOC_ALIGNMENT) - front_misalign;
       brk += correction;
     }
     else
       correction = 0;
 
     /* Guarantee the next brk will be at a page boundary */
     correction += pagesz - ((unsigned long)(brk + sbrk_size) & (pagesz - 1));
 
     /* Allocate correction */
     new_brk = (char*)(MORECORE (correction));
     if (new_brk == (char*)(MORECORE_FAILURE)) return; 
 
     sbrked_mem += correction;
 
     top = (mchunkptr)brk;
     top_size = new_brk - brk + correction;
     set_head(top, top_size | PREV_INUSE);
 
     if (old_top != initial_top)
     {
       /* There must have been an intervening foreign sbrk call. */
       /* A double fencepost is necessary to prevent consolidation */
 
       /* If not enough space to do this, then user did something very wrong */
       if (old_top_size < MINSIZE) 
       {
         set_head(top, PREV_INUSE); /* will force null return from malloc */
         return;
       }
 
       /* Also keep size a multiple of MALLOC_ALIGNMENT */
       old_top_size = (old_top_size - 3*SIZE_SZ) & ~MALLOC_ALIGN_MASK;
       set_head_size(old_top, old_top_size);
       chunk_at_offset(old_top, old_top_size          )->size =
         SIZE_SZ|PREV_INUSE;
       chunk_at_offset(old_top, old_top_size + SIZE_SZ)->size =
         SIZE_SZ|PREV_INUSE;
       /* If possible, release the rest. */
       if (old_top_size >= MINSIZE) 
         fREe(chunk2mem(old_top));
     }
   }
 
   if ((unsigned long)sbrked_mem > (unsigned long)max_sbrked_mem) 
     max_sbrked_mem = sbrked_mem;
   if ((unsigned long)(mmapped_mem + sbrked_mem) > (unsigned long)max_total_mem) 
     max_total_mem = mmapped_mem + sbrked_mem;
 
   /* We always land on a page boundary */
   assert(((unsigned long)((char*)top + top_size) & (pagesz - 1)) == 0);
 }
 
 /* Main public routines */
 
 /*
   Malloc Algorthim:
 
     The requested size is first converted into a usable form, `nb'.
     This currently means to add 4 bytes overhead plus possibly more to
     obtain 8-byte alignment and/or to obtain a size of at least
     MINSIZE (currently 16 bytes), the smallest allocatable size.
     (All fits are considered `exact' if they are within MINSIZE bytes.)
 
     From there, the first successful of the following steps is taken:
 
       1. The bin corresponding to the request size is scanned, and if
          a chunk of exactly the right size is found, it is taken.
 
       2. The most recently remaindered chunk is used if it is big
          enough.  This is a form of (roving) first fit, used only in
          the absence of exact fits. Runs of consecutive requests use
          the remainder of the chunk used for the previous such request
          whenever possible. This limited use of a first-fit style
          allocation strategy tends to give contiguous chunks
          coextensive lifetimes, which improves locality and can reduce
          fragmentation in the long run.
 
       3. Other bins are scanned in increasing size order, using a
          chunk big enough to fulfill the request, and splitting off
          any remainder.  This search is strictly by best-fit; i.e.,
          the smallest (with ties going to approximately the least
          recently used) chunk that fits is selected.
 
       4. If large enough, the chunk bordering the end of memory
          (`top') is split off. (This use of `top' is in accord with
          the best-fit search rule.  In effect, `top' is treated as
          larger (and thus less well fitting) than any other available
          chunk since it can be extended to be as large as necessary
          (up to system limitations).
 
       5. If the request size meets the mmap threshold and the
          system supports mmap, and there are few enough currently
          allocated mmapped regions, and a call to mmap succeeds,
          the request is allocated via direct memory mapping.
 
       6. Otherwise, the top of memory is extended by
          obtaining more space from the system (normally using sbrk,
          but definable to anything else via the MORECORE macro).
          Memory is gathered from the system (in system page-sized
          units) in a way that allows chunks obtained across different
          sbrk calls to be consolidated, but does not require
          contiguous memory. Thus, it should be safe to intersperse
          mallocs with other sbrk calls.
 
 
       All allocations are made from the the `lowest' part of any found
       chunk. (The implementation invariant is that prev_inuse is
       always true of any allocated chunk; i.e., that each allocated
       chunk borders either a previously allocated and still in-use chunk,
       or the base of its memory arena.)
 */
 
 #if __STD_C
 Void_t* mALLOc(size_t bytes)
 #else
 Void_t* mALLOc(bytes) size_t bytes;
 #endif
 {
   mchunkptr victim;                  /* inspected/selected chunk */
   INTERNAL_SIZE_T victim_size;       /* its size */
   int       idx;                     /* index for bin traversal */
   mbinptr   bin;                     /* associated bin */
   mchunkptr remainder;               /* remainder from a split */
   long      remainder_size;          /* its size */
   int       remainder_index;         /* its bin index */
   unsigned long block;               /* block traverser bit */
   int       startidx;                /* first bin of a traversed block */
   mchunkptr fwd;                     /* misc temp for linking */
   mchunkptr bck;                     /* misc temp for linking */
   mbinptr q;                         /* misc temp */
 
   INTERNAL_SIZE_T nb  = request2size(bytes);  /* padded request size; */
 
   /* Check for exact match in a bin */
 
   if (is_small_request(nb))  /* Faster version for small requests */
   {
     idx = smallbin_index(nb); 
 
     /* No traversal or size check necessary for small bins.  */
 
     q = bin_at(idx);
     victim = last(q);
 
     /* Also scan the next one, since it would have a remainder < MINSIZE */
     if (victim == q)
     {
       q = next_bin(q);
       victim = last(q);
     }
     if (victim != q)
     {
       victim_size = chunksize(victim);
       unlink(victim, bck, fwd);
       set_inuse_bit_at_offset(victim, victim_size);
       check_malloced_chunk(victim, nb);
       return chunk2mem(victim);
     }
 
     idx += 2; /* Set for bin scan below. We've already scanned 2 bins. */
 
   }
   else
   {
     idx = bin_index(nb);
     bin = bin_at(idx);
 
     for (victim = last(bin); victim != bin; victim = victim->bk)
     {
       victim_size = chunksize(victim);
       remainder_size = victim_size - nb;
       
       if (remainder_size >= (long)MINSIZE) /* too big */
       {
         --idx; /* adjust to rescan below after checking last remainder */
         break;   
       }
 
       else if (remainder_size >= 0) /* exact fit */
       {
         unlink(victim, bck, fwd);
         set_inuse_bit_at_offset(victim, victim_size);
         check_malloced_chunk(victim, nb);
         return chunk2mem(victim);
       }
     }
     ++idx; 
   }
 
   /* Try to use the last split-off remainder */
 
   if ( (victim = last_remainder->fd) != last_remainder)
   {
     victim_size = chunksize(victim);
     remainder_size = victim_size - nb;
 
     if (remainder_size >= (long)MINSIZE) /* re-split */
     {
       remainder = chunk_at_offset(victim, nb);
       set_head(victim, nb | PREV_INUSE);
       link_last_remainder(remainder);
       set_head(remainder, remainder_size | PREV_INUSE);
       set_foot(remainder, remainder_size);
       check_malloced_chunk(victim, nb);
       return chunk2mem(victim);
     }
 
     clear_last_remainder;
 
     if (remainder_size >= 0)  /* exhaust */
     {
       set_inuse_bit_at_offset(victim, victim_size);
       check_malloced_chunk(victim, nb);
       return chunk2mem(victim);
     }
 
     /* Else place in bin */
 
     frontlink(victim, victim_size, remainder_index, bck, fwd);
   }
 
   /* 
      If there are any possibly nonempty big-enough blocks, 
      search for best fitting chunk by scanning bins in blockwidth units.
   */
 
   if ( (block = idx2binblock(idx)) <= binblocks)  
   {
 
     /* Get to the first marked block */
 
     if ( (block & binblocks) == 0) 
     {
       /* force to an even block boundary */
       idx = (idx & ~(BINBLOCKWIDTH - 1)) + BINBLOCKWIDTH;
       block <<= 1;
       while ((block & binblocks) == 0)
       {
         idx += BINBLOCKWIDTH;
         block <<= 1;
       }
     }
       
     /* For each possibly nonempty block ... */
     for (;;)  
     {
       startidx = idx;          /* (track incomplete blocks) */
       q = bin = bin_at(idx);
 
       /* For each bin in this block ... */
       do
       {
         /* Find and use first big enough chunk ... */
 
         for (victim = last(bin); victim != bin; victim = victim->bk)
         {
           victim_size = chunksize(victim);
           remainder_size = victim_size - nb;
 
           if (remainder_size >= (long)MINSIZE) /* split */
           {
             remainder = chunk_at_offset(victim, nb);
             set_head(victim, nb | PREV_INUSE);
             unlink(victim, bck, fwd);
             link_last_remainder(remainder);
             set_head(remainder, remainder_size | PREV_INUSE);
             set_foot(remainder, remainder_size);
             check_malloced_chunk(victim, nb);
             return chunk2mem(victim);
           }
 
           else if (remainder_size >= 0)  /* take */
           {
             set_inuse_bit_at_offset(victim, victim_size);
             unlink(victim, bck, fwd);
             check_malloced_chunk(victim, nb);
             return chunk2mem(victim);
           }
 
         }
 
        bin = next_bin(bin);
 
       } while ((++idx & (BINBLOCKWIDTH - 1)) != 0);
 
       /* Clear out the block bit. */
 
       do   /* Possibly backtrack to try to clear a partial block */
       {
         if ((startidx & (BINBLOCKWIDTH - 1)) == 0)
         {
           binblocks &= ~block;
           break;
         }
         --startidx;
        q = prev_bin(q);
       } while (first(q) == q);
 
       /* Get to the next possibly nonempty block */
 
       if ( (block <<= 1) <= binblocks && (block != 0) ) 
       {
         while ((block & binblocks) == 0)
         {
           idx += BINBLOCKWIDTH;
           block <<= 1;
         }
       }
       else
         break;
     }
   }
 
 
   /* Try to use top chunk */
 
   /* Require that there be a remainder, ensuring top always exists  */
   if ( (remainder_size = chunksize(top) - nb) < (long)MINSIZE)
   {
 
 #if HAVE_MMAP
     /* If big and would otherwise need to extend, try to use mmap instead */
     if ((unsigned long)nb >= (unsigned long)mmap_threshold &&
         (victim = mmap_chunk(nb)) != 0)
       return chunk2mem(victim);
 #endif
 
     /* Try to extend */
     malloc_extend_top(nb);
     if ( (remainder_size = chunksize(top) - nb) < (long)MINSIZE)
 			{
       return 0; /* propagate failure */
 			}
   }
 
   victim = top;
   set_head(victim, nb | PREV_INUSE);
   top = chunk_at_offset(victim, nb);
   set_head(top, remainder_size | PREV_INUSE);
   check_malloced_chunk(victim, nb);
 
   return chunk2mem(victim);
 }
 
 /*
 
   free() algorithm :
 
     cases:
 
        1. free(0) has no effect.  
 
        2. If the chunk was allocated via mmap, it is release via munmap().
 
        3. If a returned chunk borders the current high end of memory,
           it is consolidated into the top, and if the total unused
           topmost memory exceeds the trim threshold, malloc_trim is
           called.
 
        4. Other chunks are consolidated as they arrive, and
           placed in corresponding bins. (This includes the case of
           consolidating with the current `last_remainder').
 
 */
 
 
 #if __STD_C
 void fREe(Void_t* mem)
 #else
 void fREe(mem) Void_t* mem;
 #endif
 {
   mchunkptr p;         /* chunk corresponding to mem */
   INTERNAL_SIZE_T hd;  /* its head field */
   INTERNAL_SIZE_T sz;  /* its size */
   int       idx;       /* its bin index */
   mchunkptr next;      /* next contiguous chunk */
   INTERNAL_SIZE_T nextsz; /* its size */
   INTERNAL_SIZE_T prevsz; /* size of previous contiguous chunk */
   mchunkptr bck;       /* misc temp for linking */
   mchunkptr fwd;       /* misc temp for linking */
   int       islr;      /* track whether merging with last_remainder */
 
   if (mem == 0)                              /* free(0) has no effect */
     return;
 
   p = mem2chunk(mem);
   hd = p->size;
 
 #if HAVE_MMAP
   if (hd & IS_MMAPPED)                       /* release mmapped memory. */
   {
     munmap_chunk(p);
     return;
   }
 #endif
   
   check_inuse_chunk(p);
   
   sz = hd & ~PREV_INUSE;
   next = chunk_at_offset(p, sz);
   nextsz = chunksize(next);
   
   if (next == top)                            /* merge with top */
   {
     sz += nextsz;
 
     if (!(hd & PREV_INUSE))                    /* consolidate backward */
     {
       prevsz = p->prev_size;
       p = chunk_at_offset(p, -prevsz);
       sz += prevsz;
       unlink(p, bck, fwd);
     }
 
     set_head(p, sz | PREV_INUSE);
     top = p;
     if ((unsigned long)(sz) >= (unsigned long)trim_threshold) 
       malloc_trim(top_pad); 
     return;
   }
 
   set_head(next, nextsz);                    /* clear inuse bit */
 
   islr = 0;
 
   if (!(hd & PREV_INUSE))                    /* consolidate backward */
   {
     prevsz = p->prev_size;
     p = chunk_at_offset(p, -prevsz);
     sz += prevsz;
     
     if (p->fd == last_remainder)             /* keep as last_remainder */
       islr = 1;
     else
       unlink(p, bck, fwd);
   }
   
   if (!(inuse_bit_at_offset(next, nextsz)))   /* consolidate forward */
   {
     sz += nextsz;
     
     if (!islr && next->fd == last_remainder)  /* re-insert last_remainder */
     {
       islr = 1;
       link_last_remainder(p);   
     }
     else
       unlink(next, bck, fwd);
   }
 
 
   set_head(p, sz | PREV_INUSE);
   set_foot(p, sz);
   if (!islr)
     frontlink(p, sz, idx, bck, fwd);  
 }
 
 /*
 
   Realloc algorithm:
 
     Chunks that were obtained via mmap cannot be extended or shrunk
     unless HAVE_MREMAP is defined, in which case mremap is used.
     Otherwise, if their reallocation is for additional space, they are
     copied.  If for less, they are just left alone.
 
     Otherwise, if the reallocation is for additional space, and the
     chunk can be extended, it is, else a malloc-copy-free sequence is
     taken.  There are several different ways that a chunk could be
     extended. All are tried:
 
        * Extending forward into following adjacent free chunk.
        * Shifting backwards, joining preceding adjacent space
        * Both shifting backwards and extending forward.
        * Extending into newly sbrked space
 
     Unless the #define REALLOC_ZERO_BYTES_FREES is set, realloc with a
     size argument of zero (re)allocates a minimum-sized chunk.
 
     If the reallocation is for less space, and the new request is for
     a `small' (<512 bytes) size, then the newly unused space is lopped
     off and freed.
 
     The old unix realloc convention of allowing the last-free'd chunk
     to be used as an argument to realloc is no longer supported.
     I don't know of any programs still relying on this feature,
     and allowing it would also allow too many other incorrect 
     usages of realloc to be sensible.
 
 
 */
 
 
 #if __STD_C
 Void_t* rEALLOc(Void_t* oldmem, size_t bytes)
 #else
 Void_t* rEALLOc(oldmem, bytes) Void_t* oldmem; size_t bytes;
 #endif
 {
   INTERNAL_SIZE_T    nb;      /* padded request size */
 
   mchunkptr oldp;             /* chunk corresponding to oldmem */
   INTERNAL_SIZE_T    oldsize; /* its size */
 
   mchunkptr newp;             /* chunk to return */
   INTERNAL_SIZE_T    newsize; /* its size */
   Void_t*   newmem;           /* corresponding user mem */
 
   mchunkptr next;             /* next contiguous chunk after oldp */
   INTERNAL_SIZE_T  nextsize;  /* its size */
 
   mchunkptr prev;             /* previous contiguous chunk before oldp */
   INTERNAL_SIZE_T  prevsize;  /* its size */
 
   mchunkptr remainder;        /* holds split off extra space from newp */
   INTERNAL_SIZE_T  remainder_size;   /* its size */
 
   mchunkptr bck;              /* misc temp for linking */
   mchunkptr fwd;              /* misc temp for linking */
 
 #ifdef REALLOC_ZERO_BYTES_FREES
   if (bytes == 0) { fREe(oldmem); return 0; }
 #endif
 
 
   /* realloc of null is supposed to be same as malloc */
   if (oldmem == 0) return mALLOc(bytes);
 
   newp    = oldp    = mem2chunk(oldmem);
   newsize = oldsize = chunksize(oldp);
 
 
   nb = request2size(bytes);
 
 #if HAVE_MMAP
   if (chunk_is_mmapped(oldp)) 
   {
 #if HAVE_MREMAP
     newp = mremap_chunk(oldp, nb);
     if(newp) return chunk2mem(newp);
 #endif
     /* Note the extra SIZE_SZ overhead. */
     if(oldsize - SIZE_SZ >= nb) return oldmem; /* do nothing */
     /* Must alloc, copy, free. */
     newmem = mALLOc(bytes);
     if (newmem == 0) return 0; /* propagate failure */
     MALLOC_COPY(newmem, oldmem, oldsize - 2*SIZE_SZ);
     munmap_chunk(oldp);
     return newmem;
   }
 #endif
 
   check_inuse_chunk(oldp);
 
   if ((long)(oldsize) < (long)(nb))  
   {
 
     /* Try expanding forward */
 
     next = chunk_at_offset(oldp, oldsize);
     if (next == top || !inuse(next)) 
     {
       nextsize = chunksize(next);
 
       /* Forward into top only if a remainder */
       if (next == top)
       {
         if ((long)(nextsize + newsize) >= (long)(nb + MINSIZE))
         {
           newsize += nextsize;
           top = chunk_at_offset(oldp, nb);
           set_head(top, (newsize - nb) | PREV_INUSE);
           set_head_size(oldp, nb);
           return chunk2mem(oldp);
         }
       }
 
       /* Forward into next chunk */
       else if (((long)(nextsize + newsize) >= (long)(nb)))
       { 
         unlink(next, bck, fwd);
         newsize  += nextsize;
         goto split;
       }
     }
     else
     {
       next = 0;
       nextsize = 0;
     }
 
     /* Try shifting backwards. */
 
     if (!prev_inuse(oldp))
     {
       prev = prev_chunk(oldp);
       prevsize = chunksize(prev);
 
       /* try forward + backward first to save a later consolidation */
 
       if (next != 0)
       {
         /* into top */
         if (next == top)
         {
           if ((long)(nextsize + prevsize + newsize) >= (long)(nb + MINSIZE))
           {
             unlink(prev, bck, fwd);
             newp = prev;
             newsize += prevsize + nextsize;
             newmem = chunk2mem(newp);
             MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ);
             top = chunk_at_offset(newp, nb);
             set_head(top, (newsize - nb) | PREV_INUSE);
             set_head_size(newp, nb);
             return newmem;
           }
         }
 
         /* into next chunk */
         else if (((long)(nextsize + prevsize + newsize) >= (long)(nb)))
         {
           unlink(next, bck, fwd);
           unlink(prev, bck, fwd);
           newp = prev;
           newsize += nextsize + prevsize;
           newmem = chunk2mem(newp);
           MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ);
           goto split;
         }
       }
       
       /* backward only */
       if (prev != 0 && (long)(prevsize + newsize) >= (long)nb)  
       {
         unlink(prev, bck, fwd);
         newp = prev;
         newsize += prevsize;
         newmem = chunk2mem(newp);
         MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ);
         goto split;
       }
     }
 
     /* Must allocate */
 
     newmem = mALLOc (bytes);
 
     if (newmem == 0)  /* propagate failure */
       return 0; 
 
     /* Avoid copy if newp is next chunk after oldp. */
     /* (This can only happen when new chunk is sbrk'ed.) */
 
     if ( (newp = mem2chunk(newmem)) == next_chunk(oldp)) 
     {
       newsize += chunksize(newp);
       newp = oldp;
       goto split;
     }
 
     /* Otherwise copy, free, and exit */
     MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ);
     fREe(oldmem);
     return newmem;
   }
 
 
  split:  /* split off extra room in old or expanded chunk */
 
   if (newsize - nb >= MINSIZE) /* split off remainder */
   {
     remainder = chunk_at_offset(newp, nb);
     remainder_size = newsize - nb;
     set_head_size(newp, nb);
     set_head(remainder, remainder_size | PREV_INUSE);
     set_inuse_bit_at_offset(remainder, remainder_size);
     fREe(chunk2mem(remainder)); /* let free() deal with it */
   }
   else
   {
     set_head_size(newp, newsize);
     set_inuse_bit_at_offset(newp, newsize);
   }
 
   check_inuse_chunk(newp);
   return chunk2mem(newp);
 }
 
 /*
   memalign algorithm:
 
     memalign requests more than enough space from malloc, finds a spot
     within that chunk that meets the alignment request, and then
     possibly frees the leading and trailing space. 
 
     The alignment argument must be a power of two. This property is not
     checked by memalign, so misuse may result in random runtime errors.
 
     8-byte alignment is guaranteed by normal malloc calls, so don't
     bother calling memalign with an argument of 8 or less.
 
     Overreliance on memalign is a sure way to fragment space.
 */
 
 
 #if __STD_C
 Void_t* mEMALIGn(size_t alignment, size_t bytes)
 #else
 Void_t* mEMALIGn(alignment, bytes) size_t alignment; size_t bytes;
 #endif
 {
   INTERNAL_SIZE_T    nb;      /* padded  request size */
   char*     m;                /* memory returned by malloc call */
   mchunkptr p;                /* corresponding chunk */
   char*     brk;              /* alignment point within p */
   mchunkptr newp;             /* chunk to return */
   INTERNAL_SIZE_T  newsize;   /* its size */
   INTERNAL_SIZE_T  leadsize;  /* leading space befor alignment point */
   mchunkptr remainder;        /* spare room at end to split off */
   long      remainder_size;   /* its size */
 
   /* If need less alignment than we give anyway, just relay to malloc */
 
   if (alignment <= MALLOC_ALIGNMENT) return mALLOc(bytes);
 
   /* Otherwise, ensure that it is at least a minimum chunk size */
   
   if (alignment <  MINSIZE) alignment = MINSIZE;
 
   /* Call malloc with worst case padding to hit alignment. */
 
   nb = request2size(bytes);
   m  = (char*)(mALLOc(nb + alignment + MINSIZE));
 
   if (m == 0) return 0; /* propagate failure */
 
   p = mem2chunk(m);
 
   if ((((unsigned long)(m)) % alignment) == 0) /* aligned */
   {
 #if HAVE_MMAP
     if(chunk_is_mmapped(p))
       return chunk2mem(p); /* nothing more to do */
 #endif
   }
   else /* misaligned */
   {
     /* 
       Find an aligned spot inside chunk.
       Since we need to give back leading space in a chunk of at 
       least MINSIZE, if the first calculation places us at
       a spot with less than MINSIZE leader, we can move to the
       next aligned spot -- we've allocated enough total room so that
       this is always possible.
     */
 
     brk = (char*)mem2chunk(((unsigned long)(m + alignment - 1)) & -alignment);
     if ((long)(brk - (char*)(p)) < MINSIZE) brk = brk + alignment;
 
     newp = (mchunkptr)brk;
     leadsize = brk - (char*)(p);
     newsize = chunksize(p) - leadsize;
 
 #if HAVE_MMAP
     if(chunk_is_mmapped(p)) 
     {
       newp->prev_size = p->prev_size + leadsize;
       set_head(newp, newsize|IS_MMAPPED);
       return chunk2mem(newp);
     }
 #endif
 
     /* give back leader, use the rest */
 
     set_head(newp, newsize | PREV_INUSE);
     set_inuse_bit_at_offset(newp, newsize);
     set_head_size(p, leadsize);
     fREe(chunk2mem(p));
     p = newp;
 
     assert (newsize >= nb && (((unsigned long)(chunk2mem(p))) % alignment) == 0);
   }
 
   /* Also give back spare room at the end */
 
   remainder_size = chunksize(p) - nb;
 
   if (remainder_size >= (long)MINSIZE)
   {
     remainder = chunk_at_offset(p, nb);
     set_head(remainder, remainder_size | PREV_INUSE);
     set_head_size(p, nb);
     fREe(chunk2mem(remainder));
   }
 
   check_inuse_chunk(p);
   return chunk2mem(p);
 
 }
 
 /*
     valloc just invokes memalign with alignment argument equal
     to the page size of the system (or as near to this as can
     be figured out from all the includes/defines above.)
 */
 
 #if __STD_C
 Void_t* vALLOc(size_t bytes)
 #else
 Void_t* vALLOc(bytes) size_t bytes;
 #endif
 {
   return mEMALIGn (malloc_getpagesize, bytes);
 }
 
 /* 
   pvalloc just invokes valloc for the nearest pagesize
   that will accommodate request
 */
 
 #if __STD_C
 Void_t* pvALLOc(size_t bytes)
 #else
 Void_t* pvALLOc(bytes) size_t bytes;
 #endif
 {
   size_t pagesize = malloc_getpagesize;
   return mEMALIGn (pagesize, (bytes + pagesize - 1) & ~(pagesize - 1));
 }
 
 /*
   calloc calls malloc, then zeroes out the allocated chunk.
 */
 
 #if __STD_C
 Void_t* cALLOc(size_t n, size_t elem_size)
 #else
 Void_t* cALLOc(n, elem_size) size_t n; size_t elem_size;
 #endif
 {
   mchunkptr p;
   INTERNAL_SIZE_T csz;
 
   INTERNAL_SIZE_T sz = n * elem_size;
 
   /* check if expand_top called, in which case don't need to clear */
 #if MORECORE_CLEARS
   mchunkptr oldtop = top;
   INTERNAL_SIZE_T oldtopsize = chunksize(top);
 #endif
   Void_t* mem = mALLOc (sz);
 
   if (mem == 0) 
     return 0;
   else
   {
     p = mem2chunk(mem);
 
     /* Two optional cases in which clearing not necessary */
 
 #if HAVE_MMAP
     if (chunk_is_mmapped(p)) return mem;
 #endif
 
     csz = chunksize(p);
 
 #if MORECORE_CLEARS
     if (p == oldtop && csz > oldtopsize) 
     {
       /* clear only the bytes from non-freshly-sbrked memory */
       csz = oldtopsize;
     }
 #endif
 
     MALLOC_ZERO(mem, csz - SIZE_SZ);
     return mem;
   }
 }
 
 /*
   cfree just calls free. It is needed/defined on some systems
   that pair it with calloc, presumably for odd historical reasons.
 */
 
 #if !defined(INTERNAL_LINUX_C_LIB) || !defined(__ELF__)
 #if __STD_C
 void cfree(Void_t *mem)
 #else
 void cfree(mem) Void_t *mem;
 #endif
 {
   fREe(mem);
 }
 #endif
 
 /*
     Malloc_trim gives memory back to the system (via negative
     arguments to sbrk) if there is unused memory at the `high' end of
     the malloc pool. You can call this after freeing large blocks of
     memory to potentially reduce the system-level memory requirements
     of a program. However, it cannot guarantee to reduce memory. Under
     some allocation patterns, some large free blocks of memory will be
     locked between two used chunks, so they cannot be given back to
     the system.
 
     The `pad' argument to malloc_trim represents the amount of free
     trailing space to leave untrimmed. If this argument is zero,
     only the minimum amount of memory to maintain internal data
     structures will be left (one page or less). Non-zero arguments
     can be supplied to maintain enough trailing space to service
     future expected allocations without having to re-obtain memory
     from the system.
 
     Malloc_trim returns 1 if it actually released any memory, else 0.
 */
 
 #if __STD_C
 int malloc_trim(size_t pad)
 #else
 int malloc_trim(pad) size_t pad;
 #endif
 {
   long  top_size;        /* Amount of top-most memory */
   long  extra;           /* Amount to release */
   char* current_brk;     /* address returned by pre-check sbrk call */
   char* new_brk;         /* address returned by negative sbrk call */
 
   unsigned long pagesz = malloc_getpagesize;
 
   top_size = chunksize(top);
   extra = ((top_size - pad - MINSIZE + (pagesz-1)) / pagesz - 1) * pagesz;
 
   if (extra < (long)pagesz)  /* Not enough memory to release */
     return 0;
 
   else
   {
     /* Test to make sure no one else called sbrk */
     current_brk = (char*)(MORECORE (0));
     if (current_brk != (char*)(top) + top_size)
       return 0;     /* Apparently we don't own memory; must fail */
 
     else
     {
       new_brk = (char*)(MORECORE (-extra));
       
       if (new_brk == (char*)(MORECORE_FAILURE)) /* sbrk failed? */
       {
         /* Try to figure out what we have */
         current_brk = (char*)(MORECORE (0));
         top_size = current_brk - (char*)top;
         if (top_size >= (long)MINSIZE) /* if not, we are very very dead! */
         {
           sbrked_mem = current_brk - sbrk_base;
           set_head(top, top_size | PREV_INUSE);
         }
         check_chunk(top);
         return 0; 
       }
 
       else
       {
         /* Success. Adjust top accordingly. */
         set_head(top, (top_size - extra) | PREV_INUSE);
         sbrked_mem -= extra;
         check_chunk(top);
         return 1;
       }
     }
   }
 }
 
 /*
   malloc_usable_size:
 
     This routine tells you how many bytes you can actually use in an
     allocated chunk, which may be more than you requested (although
     often not). You can use this many bytes without worrying about
     overwriting other allocated objects. Not a particularly great
     programming practice, but still sometimes useful.
 */
 
 #if __STD_C
 size_t malloc_usable_size(Void_t* mem)
 #else
 size_t malloc_usable_size(mem) Void_t* mem;
 #endif
 {
   mchunkptr p;
   if (mem == 0)
     return 0;
   else
   {
     p = mem2chunk(mem);
     if(!chunk_is_mmapped(p))
     {
       if (!inuse(p)) return 0;
       check_inuse_chunk(p);
       return chunksize(p) - SIZE_SZ;
     }
     return chunksize(p) - 2*SIZE_SZ;
   }
 }
 
 /* Utility to update current_mallinfo for malloc_stats and mallinfo() */
 
 static void malloc_update_mallinfo() 
 {
   int i;
   mbinptr b;
   mchunkptr p;
 #if DEBUG
   mchunkptr q;
 #endif
 
   INTERNAL_SIZE_T avail = chunksize(top);
   int   navail = ((long)(avail) >= (long)MINSIZE)? 1 : 0;
 
   for (i = 1; i < NAV; ++i)
   {
     b = bin_at(i);
     for (p = last(b); p != b; p = p->bk) 
     {
 #if DEBUG
       check_free_chunk(p);
       for (q = next_chunk(p); 
            q < top && inuse(q) && (long)(chunksize(q)) >= (long)MINSIZE; 
            q = next_chunk(q))
         check_inuse_chunk(q);
 #endif
       avail += chunksize(p);
       navail++;
     }
   }
 
   current_mallinfo.ordblks = navail;
   current_mallinfo.uordblks = sbrked_mem - avail;
   current_mallinfo.fordblks = avail;
   current_mallinfo.hblks = n_mmaps;
   current_mallinfo.hblkhd = mmapped_mem;
   current_mallinfo.keepcost = chunksize(top);
 
 }
 
 /*
 
   malloc_stats:
 
     Prints on stderr the amount of space obtain from the system (both
     via sbrk and mmap), the maximum amount (which may be more than
     current if malloc_trim and/or munmap got called), the maximum
     number of simultaneous mmap regions used, and the current number
     of bytes allocated via malloc (or realloc, etc) but not yet
     freed. (Note that this is the number of bytes allocated, not the
     number requested. It will be larger than the number requested
     because of alignment and bookkeeping overhead.)
 
 */
 
 void malloc_stats()
 {
   malloc_update_mallinfo();
 /*
 	This commented out since we don't have a printf(1) in userspace yet
 
   printf("max system bytes = %10u\n", 
           (unsigned int)(max_total_mem));
   printf("system bytes     = %10u\n", 
           (unsigned int)(sbrked_mem + mmapped_mem));
   printf("in use bytes     = %10u\n", 
           (unsigned int)(current_mallinfo.uordblks + mmapped_mem));
 #if HAVE_MMAP
   printf("max mmap regions = %10u\n", 
           (unsigned int)max_n_mmaps);
 #endif
 */
 }
 
 /*
   mallinfo returns a copy of updated current mallinfo.
 */
 
 struct mallinfo mALLINFo()
 {
   malloc_update_mallinfo();
   return current_mallinfo;
 }
 
 /*
   mallopt:
 
     mallopt is the general SVID/XPG interface to tunable parameters.
     The format is to provide a (parameter-number, parameter-value) pair.
     mallopt then sets the corresponding parameter to the argument
     value if it can (i.e., so long as the value is meaningful),
     and returns 1 if successful else 0.
 
     See descriptions of tunable parameters above.
 
 */
 
 #if __STD_C
 int mALLOPt(int param_number, int value)
 #else
 int mALLOPt(param_number, value) int param_number; int value;
 #endif
 {
   switch(param_number) 
   {
     case M_TRIM_THRESHOLD:
       trim_threshold = value; return 1; 
     case M_TOP_PAD:
       top_pad = value; return 1; 
     case M_MMAP_THRESHOLD:
       mmap_threshold = value; return 1;
     case M_MMAP_MAX:
 #if HAVE_MMAP
       n_mmaps_max = value; return 1;
 #else
       if (value != 0) return 0; else  n_mmaps_max = value; return 1;
 #endif
 
     default:
       return 0;
   }
 }
 
 /*
 
 History:
 
     V2.6.5 Wed Jun 17 15:57:31 1998  Doug Lea  (dl at gee)
       * Fixed ordering problem with boundary-stamping
 
     V2.6.3 Sun May 19 08:17:58 1996  Doug Lea  (dl at gee)
       * Added pvalloc, as recommended by H.J. Liu
       * Added 64bit pointer support mainly from Wolfram Gloger
       * Added anonymously donated WIN32 sbrk emulation
       * Malloc, calloc, getpagesize: add optimizations from Raymond Nijssen
       * malloc_extend_top: fix mask error that caused wastage after
         foreign sbrks
       * Add linux mremap support code from HJ Liu
    
     V2.6.2 Tue Dec  5 06:52:55 1995  Doug Lea  (dl at gee)
       * Integrated most documentation with the code.
       * Add support for mmap, with help from 
         Wolfram Gloger (Gloger@lrz.uni-muenchen.de).
       * Use last_remainder in more cases.
       * Pack bins using idea from  colin@nyx10.cs.du.edu
       * Use ordered bins instead of best-fit threshhold
       * Eliminate block-local decls to simplify tracing and debugging.
       * Support another case of realloc via move into top
       * Fix error occuring when initial sbrk_base not word-aligned.  
       * Rely on page size for units instead of SBRK_UNIT to
         avoid surprises about sbrk alignment conventions.
       * Add mallinfo, mallopt. Thanks to Raymond Nijssen
         (raymond@es.ele.tue.nl) for the suggestion. 
       * Add `pad' argument to malloc_trim and top_pad mallopt parameter.
       * More precautions for cases where other routines call sbrk,
         courtesy of Wolfram Gloger (Gloger@lrz.uni-muenchen.de).
       * Added macros etc., allowing use in linux libc from
         H.J. Lu (hjl@gnu.ai.mit.edu)
       * Inverted this history list
 
     V2.6.1 Sat Dec  2 14:10:57 1995  Doug Lea  (dl at gee)
       * Re-tuned and fixed to behave more nicely with V2.6.0 changes.
       * Removed all preallocation code since under current scheme
         the work required to undo bad preallocations exceeds
         the work saved in good cases for most test programs.
       * No longer use return list or unconsolidated bins since
         no scheme using them consistently outperforms those that don't
         given above changes.
       * Use best fit for very large chunks to prevent some worst-cases.
       * Added some support for debugging
 
     V2.6.0 Sat Nov  4 07:05:23 1995  Doug Lea  (dl at gee)
       * Removed footers when chunks are in use. Thanks to
         Paul Wilson (wilson@cs.texas.edu) for the suggestion.
 
     V2.5.4 Wed Nov  1 07:54:51 1995  Doug Lea  (dl at gee)
       * Added malloc_trim, with help from Wolfram Gloger 
         (wmglo@Dent.MED.Uni-Muenchen.DE).
 
     V2.5.3 Tue Apr 26 10:16:01 1994  Doug Lea  (dl at g)
 
     V2.5.2 Tue Apr  5 16:20:40 1994  Doug Lea  (dl at g)
       * realloc: try to expand in both directions
       * malloc: swap order of clean-bin strategy;
       * realloc: only conditionally expand backwards
       * Try not to scavenge used bins
       * Use bin counts as a guide to preallocation
       * Occasionally bin return list chunks in first scan
       * Add a few optimizations from colin@nyx10.cs.du.edu
 
     V2.5.1 Sat Aug 14 15:40:43 1993  Doug Lea  (dl at g)
       * faster bin computation & slightly different binning
       * merged all consolidations to one part of malloc proper
          (eliminating old malloc_find_space & malloc_clean_bin)
       * Scan 2 returns chunks (not just 1)
       * Propagate failure in realloc if malloc returns 0
       * Add stuff to allow compilation on non-ANSI compilers 
           from kpv@research.att.com
      
     V2.5 Sat Aug  7 07:41:59 1993  Doug Lea  (dl at g.oswego.edu)
       * removed potential for odd address access in prev_chunk
       * removed dependency on getpagesize.h
       * misc cosmetics and a bit more internal documentation
       * anticosmetics: mangled names in macros to evade debugger strangeness
       * tested on sparc, hp-700, dec-mips, rs6000 
           with gcc & native cc (hp, dec only) allowing
           Detlefs & Zorn comparison study (in SIGPLAN Notices.)
 
     Trial version Fri Aug 28 13:14:29 1992  Doug Lea  (dl at g.oswego.edu)
       * Based loosely on libg++-1.2X malloc. (It retains some of the overall 
          structure of old version,  but most details differ.)
 
 */