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/* Malloc implementation for multiple threads without lock contention.

   Copyright (C) 1996-2001, 2002 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Wolfram Gloger <wmglo@dent.med.uni-muenchen.de>

   and Doug Lea <dl@cs.oswego.edu>, 1996.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, write to the Free

   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA

   02111-1307 USA.  */

/* $Id: malloc.c 148 2010-06-30 19:21:22Z jeremybennett $

  This work is mainly derived from malloc-2.6.4 by Doug Lea

  <dl@cs.oswego.edu>, which is available from:

                 ftp://g.oswego.edu/pub/misc/malloc.c

  Most of the original comments are reproduced in the code below.

* 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

  On many systems, the standard malloc implementation is by itself not

  thread-safe, and therefore wrapped with a single global lock around

  all malloc-related functions.  In some applications, especially with

  multiple available processors, this can lead to contention problems

  and bad performance.  This malloc version was designed with the goal

  to avoid waiting for locks as much as possible.  Statistics indicate

  that this goal is achieved in many cases.

* Synopsis of public routines

  (Much fuller descriptions are contained in the program documentation below.)

  ptmalloc_init();

     Initialize global configuration.  When compiled for multiple threads,

     this function must be called once before any other function in the

     package.  It is not required otherwise.  It is called automatically

     in the Linux/GNU C libray or when compiling with MALLOC_HOOKS.

  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

       Alignment 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 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. 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.

  MALLOC_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.

  MALLOC_HOOKS             (default: NOT defined)

     Define to enable support run-time replacement of the allocation

     functions through user-defined `hooks'.

  REALLOC_ZERO_BYTES_FREES (default: defined)

     Define this if you think that realloc(p, 0) should be equivalent

     to free(p).  (The C standard requires this behaviour, therefore

     it is the default.)  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.

  USE_ARENAS                (default: the same as HAVE_MMAP)

     Enable support for multiple arenas, allocated using mmap().

  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.

  _LIBC                     (default: NOT defined)

     Defined only when compiled as part of the Linux libc/glibc.

     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.

  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)

     The degree to which the routine mapped to MORECORE zeroes out

     memory: never (0), only for newly allocated space (1) or always

     (2).  The distinction between (1) and (2) is necessary because on

     some systems, if the application first decrements and then

     increments the break value, the contents of the reallocated space

     are unspecified.

  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.

  DEFAULT_CHECK_ACTION

     When the standard debugging hooks are in place, and a pointer is

     detected as corrupt, do nothing (0), print an error message (1),

     or call abort() (2).

*/

/*

* Compile-time options for multiple threads:

  USE_PTHREADS, USE_THR, USE_SPROC

     Define one of these as 1 to select the thread interface:

     POSIX threads, Solaris threads or SGI sproc's, respectively.

     If none of these is defined as non-zero, you get a `normal'

     malloc implementation which is not thread-safe.  Support for

     multiple threads requires HAVE_MMAP=1.  As an exception, when

     compiling for GNU libc, i.e. when _LIBC is defined, then none of

     the USE_... symbols have to be defined.

  HEAP_MIN_SIZE

  HEAP_MAX_SIZE

     When thread support is enabled, additional `heap's are created

     with mmap calls.  These are limited in size; HEAP_MIN_SIZE should

     be a multiple of the page size, while HEAP_MAX_SIZE must be a power

     of two for alignment reasons.  HEAP_MAX_SIZE should be at least

     twice as large as the mmap threshold.

  THREAD_STATS

     When this is defined as non-zero, some statistics on mutex locking

     are computed.

*/

/* Preliminaries */

#ifndef __STD_C

#if defined (__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*/

#define _GNU_SOURCE

#include <features.h>

#define _LIBC 1

#define NOT_IN_libc 1

#if __STD_C

# include <stddef.h>   /* for size_t */

# if defined _LIBC || defined MALLOC_HOOKS

#  include <stdlib.h>  /* for getenv(), abort() */

# endif

#else

# include <sys/types.h>

# if defined _LIBC || defined MALLOC_HOOKS

extern char* getenv();

# endif

#endif

/* newlib modifications */

#include <libc-symbols.h>

#include <sys/types.h>

extern void __pthread_initialize (void) __attribute__((weak));

extern void *__mmap (void *__addr, size_t __len, int __prot,

                     int __flags, int __fd, off_t __offset);

extern int __munmap (void *__addr, size_t __len);

extern void *__mremap (void *__addr, size_t __old_len, size_t __new_len,

                       int __may_move);

extern int __getpagesize (void);

#define __libc_enable_secure 1

/* Macros for handling mutexes and thread-specific data.  This is

   included early, because some thread-related header files (such as

   pthread.h) should be included before any others. */

#include <bits/libc-lock.h>

#include "thread-m.h"

void *(*__malloc_internal_tsd_get) (enum __libc_tsd_key_t) = NULL;

int (*__malloc_internal_tsd_set) (enum __libc_tsd_key_t,

                                       __const void *) = NULL;

weak_alias(__malloc_internal_tsd_get, __libc_internal_tsd_get)

weak_alias(__malloc_internal_tsd_set, __libc_internal_tsd_set)

#ifdef __cplusplus

extern "C" {

#endif

#include <errno.h>

#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 -DMALLOC_DEBUG, 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 MALLOC_DEBUG set will

    attempt to check every non-mmapped allocated and free chunk in the

    course of computing the summaries. (By nature, mmapped regions

    cannot be checked very much automatically.)

    Setting MALLOC_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 MALLOC_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.  The C standard

  requires this. 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 1

#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);

void* memmove(void*, const void*, size_t);

#else

Void_t* memset();

Void_t* memcpy();

Void_t* memmove();

#endif

#endif

/* 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.  If the regions to be

   copied do overlap, the destination lies always _below_ the source.  */

#if USE_MEMCPY

#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)

/* If the regions overlap, dest is always _below_ src.  */

#define MALLOC_COPY(dest,src,nbytes,overlap)                                  \

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 if(overlap)                                                          \

    memmove(dest, src, mcsz);                                                 \

  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)

/* If the regions overlap, dest is always _below_ src.  */

#define MALLOC_COPY(dest,src,nbytes,overlap)                                  \

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

#ifndef LACKS_UNISTD_H

#  include <unistd.h>

#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().  HAVE_MMAP is also a prerequisite to

  support multiple `arenas' (see USE_ARENAS below).

*/

#ifndef HAVE_MMAP

# ifdef _POSIX_MAPPED_FILES

#  define HAVE_MMAP 1

# endif

#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

#define HAVE_MREMAP defined(__linux__)

#endif

/* Define USE_ARENAS to enable support for multiple `arenas'.  These

   are allocated using mmap(), are necessary for threads and

   occasionally useful to overcome address space limitations affecting

   sbrk(). */

#ifndef USE_ARENAS

#define USE_ARENAS HAVE_MMAP

#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

#if !defined(MAP_FAILED)

#define MAP_FAILED ((char*)-1)

#endif

#ifndef MAP_NORESERVE

# ifdef MAP_AUTORESRV

#  define MAP_NORESERVE MAP_AUTORESRV

# else

#  define MAP_NORESERVE 0

# endif

#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 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

/*

  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

# ifdef _LIBC

#  include "malloc.h"

# else

#  include "ptmalloc.h"

# endif

#endif

#include <bp-checks.h>

#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 than 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.

*/