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[p5sagit/p5-mst-13.2.git] / malloc.c

/*    malloc.c
 *
 */

/*
 * "'The Chamber of Records,' said Gimli. 'I guess that is where we now stand.'"
 */

/*
  Here are some notes on configuring Perl's malloc.  (For non-perl
  usage see below.)
 
  There are two macros which serve as bulk disablers of advanced
  features of this malloc: NO_FANCY_MALLOC, PLAIN_MALLOC (undef by
  default).  Look in the list of default values below to understand
  their exact effect.  Defining NO_FANCY_MALLOC returns malloc.c to the
  state of the malloc in Perl 5.004.  Additionally defining PLAIN_MALLOC
  returns it to the state as of Perl 5.000.

  Note that some of the settings below may be ignored in the code based
  on values of other macros.  The PERL_CORE symbol is only defined when
  perl itself is being compiled (so malloc can make some assumptions
  about perl's facilities being available to it).

  Each config option has a short description, followed by its name,
  default value, and a comment about the default (if applicable).  Some
  options take a precise value, while the others are just boolean.
  The boolean ones are listed first.

    # Read configuration settings from malloc_cfg.h
    HAVE_MALLOC_CFG_H		undef

    # Enable code for an emergency memory pool in $^M.  See perlvar.pod
    # for a description of $^M.
    PERL_EMERGENCY_SBRK		(!PLAIN_MALLOC && (PERL_CORE || !NO_MALLOC_DYNAMIC_CFG))

    # Enable code for printing memory statistics.
    DEBUGGING_MSTATS		(!PLAIN_MALLOC && PERL_CORE)

    # Move allocation info for small buckets into separate areas.
    # Memory optimization (especially for small allocations, of the
    # less than 64 bytes).  Since perl usually makes a large number
    # of small allocations, this is usually a win.
    PACK_MALLOC			(!PLAIN_MALLOC && !RCHECK)

    # Add one page to big powers of two when calculating bucket size.
    # This is targeted at big allocations, as are common in image
    # processing.
    TWO_POT_OPTIMIZE		!PLAIN_MALLOC
 
    # Use intermediate bucket sizes between powers-of-two.  This is
    # generally a memory optimization, and a (small) speed pessimization.
    BUCKETS_ROOT2		!NO_FANCY_MALLOC

    # Do not check small deallocations for bad free().  Memory
    # and speed optimization, error reporting pessimization.
    IGNORE_SMALL_BAD_FREE	(!NO_FANCY_MALLOC && !RCHECK)

    # Use table lookup to decide in which bucket a given allocation will go.
    SMALL_BUCKET_VIA_TABLE	!NO_FANCY_MALLOC

    # Use a perl-defined sbrk() instead of the (presumably broken or
    # missing) system-supplied sbrk().
    USE_PERL_SBRK		undef

    # Use system malloc() (or calloc() etc.) to emulate sbrk(). Normally
    # only used with broken sbrk()s.
    PERL_SBRK_VIA_MALLOC	undef

    # Which allocator to use if PERL_SBRK_VIA_MALLOC
    SYSTEM_ALLOC(a) 		malloc(a)

    # Minimal alignment (in bytes, should be a power of 2) of SYSTEM_ALLOC
    SYSTEM_ALLOC_ALIGNMENT	MEM_ALIGNBYTES

    # Disable memory overwrite checking with DEBUGGING.  Memory and speed
    # optimization, error reporting pessimization.
    NO_RCHECK			undef

    # Enable memory overwrite checking with DEBUGGING.  Memory and speed
    # pessimization, error reporting optimization
    RCHECK			(DEBUGGING && !NO_RCHECK)

    # Do not overwrite uninit areas with DEBUGGING.  Speed
    # optimization, error reporting pessimization
    NO_MFILL			undef

    # Overwrite uninit areas with DEBUGGING.  Speed
    # pessimization, error reporting optimization
    MALLOC_FILL			(DEBUGGING && !NO_RCHECK && !NO_MFILL)

    # Do not check overwritten uninit areas with DEBUGGING.  Speed
    # optimization, error reporting pessimization
    NO_FILL_CHECK		undef

    # Check overwritten uninit areas with DEBUGGING.  Speed
    # pessimization, error reporting optimization
    MALLOC_FILL_CHECK		(DEBUGGING && !NO_RCHECK && !NO_FILL_CHECK)

    # Failed allocations bigger than this size croak (if
    # PERL_EMERGENCY_SBRK is enabled) without touching $^M.  See
    # perlvar.pod for a description of $^M.
    BIG_SIZE			 (1<<16)	# 64K

    # Starting from this power of two, add an extra page to the
    # size of the bucket. This enables optimized allocations of sizes
    # close to powers of 2.  Note that the value is indexed at 0.
    FIRST_BIG_POW2 		15		# 32K, 16K is used too often

    # Estimate of minimal memory footprint.  malloc uses this value to
    # request the most reasonable largest blocks of memory from the system.
    FIRST_SBRK 			(48*1024)

    # Round up sbrk()s to multiples of this.
    MIN_SBRK 			2048

    # Round up sbrk()s to multiples of this percent of footprint.
    MIN_SBRK_FRAC 		3

    # Round up sbrk()s to multiples of this multiple of 1/1000 of footprint.
    MIN_SBRK_FRAC1000 		(10 * MIN_SBRK_FRAC)

    # Add this much memory to big powers of two to get the bucket size.
    PERL_PAGESIZE 		4096

    # This many sbrk() discontinuities should be tolerated even
    # from the start without deciding that sbrk() is usually
    # discontinuous.
    SBRK_ALLOW_FAILURES		3

    # This many continuous sbrk()s compensate for one discontinuous one.
    SBRK_FAILURE_PRICE		50

    # Some configurations may ask for 12-byte-or-so allocations which
    # require 8-byte alignment (?!).  In such situation one needs to
    # define this to disable 12-byte bucket (will increase memory footprint)
    STRICT_ALIGNMENT		undef

    # Do not allow configuration of runtime options at runtime
    NO_MALLOC_DYNAMIC_CFG	undef

    # Do not allow configuration of runtime options via $ENV{PERL_MALLOC_OPT}
    NO_PERL_MALLOC_ENV		undef

	[The variable consists of ;-separated parts of the form CODE=VALUE
	 with 1-character codes F, M, f, A, P, G, d, a, c for runtime
	 configuration of FIRST_SBRK, MIN_SBRK, MIN_SBRK_FRAC1000,
	 SBRK_ALLOW_FAILURES, SBRK_FAILURE_PRICE, sbrk_goodness,
	 filldead, fillalive, fillcheck.  The last 3 are for DEBUGGING
	 build, and allow switching the tests for free()ed memory read,
	 uninit memory reads, and free()ed memory write.]

  This implementation assumes that calling PerlIO_printf() does not
  result in any memory allocation calls (used during a panic).

 */

/*
   If used outside of Perl environment, it may be useful to redefine
   the following macros (listed below with defaults):

     # Type of address returned by allocation functions
     Malloc_t				void *

     # Type of size argument for allocation functions
     MEM_SIZE				unsigned long

     # size of void*
     PTRSIZE				4

     # Maximal value in LONG
     LONG_MAX				0x7FFFFFFF

     # Unsigned integer type big enough to keep a pointer
     UV					unsigned long

     # Signed integer of the same sizeof() as UV
     IV					long

     # Type of pointer with 1-byte granularity
     caddr_t				char *

     # Type returned by free()
     Free_t				void

     # Conversion of pointer to integer
     PTR2UV(ptr)			((UV)(ptr))

     # Conversion of integer to pointer
     INT2PTR(type, i)			((type)(i))

     # printf()-%-Conversion of UV to pointer
     UVuf				"lu"

     # printf()-%-Conversion of UV to hex pointer
     UVxf				"lx"

     # Alignment to use
     MEM_ALIGNBYTES			4

     # Very fatal condition reporting function (cannot call any )
     fatalcroak(arg)			write(2,arg,strlen(arg)) + exit(2)
  
     # Fatal error reporting function
     croak(format, arg)			warn(idem) + exit(1)
  
     # Fatal error reporting function
     croak2(format, arg1, arg2)		warn2(idem) + exit(1)
  
     # Error reporting function
     warn(format, arg)			fprintf(stderr, idem)

     # Error reporting function
     warn2(format, arg1, arg2)		fprintf(stderr, idem)

     # Locking/unlocking for MT operation
     MALLOC_LOCK			MUTEX_LOCK(&PL_malloc_mutex)
     MALLOC_UNLOCK			MUTEX_UNLOCK(&PL_malloc_mutex)

     # Locking/unlocking mutex for MT operation
     MUTEX_LOCK(l)			void
     MUTEX_UNLOCK(l)			void
 */

#ifdef HAVE_MALLOC_CFG_H
#  include "malloc_cfg.h"
#endif

#ifndef NO_FANCY_MALLOC
#  ifndef SMALL_BUCKET_VIA_TABLE
#    define SMALL_BUCKET_VIA_TABLE
#  endif 
#  ifndef BUCKETS_ROOT2
#    define BUCKETS_ROOT2
#  endif 
#  ifndef IGNORE_SMALL_BAD_FREE
#    define IGNORE_SMALL_BAD_FREE
#  endif 
#endif 

#ifndef PLAIN_MALLOC			/* Bulk enable features */
#  ifndef PACK_MALLOC
#      define PACK_MALLOC
#  endif 
#  ifndef TWO_POT_OPTIMIZE
#    define TWO_POT_OPTIMIZE
#  endif 
#  if (defined(PERL_CORE) || !defined(NO_MALLOC_DYNAMIC_CFG)) && !defined(PERL_EMERGENCY_SBRK)
#    define PERL_EMERGENCY_SBRK
#  endif 
#  if defined(PERL_CORE) && !defined(DEBUGGING_MSTATS)
#    define DEBUGGING_MSTATS
#  endif 
#endif

#define MIN_BUC_POW2 (sizeof(void*) > 4 ? 3 : 2) /* Allow for 4-byte arena. */
#define MIN_BUCKET (MIN_BUC_POW2 * BUCKETS_PER_POW2)

#if !(defined(I286) || defined(atarist) || defined(__MINT__))
	/* take 2k unless the block is bigger than that */
#  define LOG_OF_MIN_ARENA 11
#else
	/* take 16k unless the block is bigger than that 
	   (80286s like large segments!), probably good on the atari too */
#  define LOG_OF_MIN_ARENA 14
#endif

#ifndef lint
#  if defined(DEBUGGING) && !defined(NO_RCHECK)
#    define RCHECK
#  endif
#  if defined(DEBUGGING) && !defined(NO_RCHECK) && !defined(NO_MFILL) && !defined(MALLOC_FILL)
#    define MALLOC_FILL
#  endif
#  if defined(DEBUGGING) && !defined(NO_RCHECK) && !defined(NO_FILL_CHECK) && !defined(MALLOC_FILL_CHECK)
#    define MALLOC_FILL_CHECK
#  endif
#  if defined(RCHECK) && defined(IGNORE_SMALL_BAD_FREE)
#    undef IGNORE_SMALL_BAD_FREE
#  endif 
/*
 * malloc.c (Caltech) 2/21/82
 * Chris Kingsley, kingsley@cit-20.
 *
 * This is a very fast storage allocator.  It allocates blocks of a small 
 * number of different sizes, and keeps free lists of each size.  Blocks that
 * don't exactly fit are passed up to the next larger size.  In this 
 * implementation, the available sizes are 2^n-4 (or 2^n-12) bytes long.
 * If PACK_MALLOC is defined, small blocks are 2^n bytes long.
 * This is designed for use in a program that uses vast quantities of memory,
 * but bombs when it runs out.
 * 
 * Modifications Copyright Ilya Zakharevich 1996-99.
 * 
 * Still very quick, but much more thrifty.  (Std config is 10% slower
 * than it was, and takes 67% of old heap size for typical usage.)
 *
 * Allocations of small blocks are now table-driven to many different
 * buckets.  Sizes of really big buckets are increased to accomodata
 * common size=power-of-2 blocks.  Running-out-of-memory is made into
 * an exception.  Deeply configurable and thread-safe.
 * 
 */

#ifdef PERL_CORE
#  include "EXTERN.h"
#  define PERL_IN_MALLOC_C
#  include "perl.h"
#  if defined(PERL_IMPLICIT_CONTEXT)
#    define croak	Perl_croak_nocontext
#    define croak2	Perl_croak_nocontext
#    define warn	Perl_warn_nocontext
#    define warn2	Perl_warn_nocontext
#  else
#    define croak2	croak
#    define warn2	warn
#  endif
#  if defined(USE_5005THREADS) || defined(USE_ITHREADS)
#     define PERL_MAYBE_ALIVE	PL_thr_key
#  else
#     define PERL_MAYBE_ALIVE	1
#  endif
#else
#  ifdef PERL_FOR_X2P
#    include "../EXTERN.h"
#    include "../perl.h"
#  else
#    include <stdlib.h>
#    include <stdio.h>
#    include <memory.h>
#    ifdef OS2
#      include <io.h>
#    endif
#    include <string.h>
#    ifndef Malloc_t
#      define Malloc_t void *
#    endif
#    ifndef PTRSIZE
#      define PTRSIZE 4
#    endif
#    ifndef MEM_SIZE
#      define MEM_SIZE unsigned long
#    endif
#    ifndef LONG_MAX
#      define LONG_MAX 0x7FFFFFFF
#    endif
#    ifndef UV
#      define UV unsigned long
#    endif
#    ifndef IV
#      define IV long
#    endif
#    ifndef caddr_t
#      define caddr_t char *
#    endif
#    ifndef Free_t
#      define Free_t void
#    endif
#    define Copy(s,d,n,t) (void)memcpy((char*)(d),(char*)(s), (n) * sizeof(t))
#    define PerlEnv_getenv getenv
#    define PerlIO_printf fprintf
#    define PerlIO_stderr() stderr
#    define PerlIO_puts(f,s)		fputs(s,f)
#    ifndef INT2PTR
#      define INT2PTR(t,i)		((t)(i))
#    endif
#    ifndef PTR2UV
#      define PTR2UV(p)			((UV)(p))
#    endif
#    ifndef UVuf
#      define UVuf			"lu"
#    endif
#    ifndef UVxf
#      define UVxf			"lx"
#    endif
#    ifndef Nullch
#      define Nullch			NULL
#    endif
#    ifndef MEM_ALIGNBYTES
#      define MEM_ALIGNBYTES		4
#    endif
#  endif
#  ifndef croak				/* make depend */
#    define croak(mess, arg) (warn((mess), (arg)), exit(1))
#  endif 
#  ifndef croak2			/* make depend */
#    define croak2(mess, arg1, arg2) (warn2((mess), (arg1), (arg2)), exit(1))
#  endif 
#  ifndef warn
#    define warn(mess, arg) fprintf(stderr, (mess), (arg))
#  endif 
#  ifndef warn2
#    define warn2(mess, arg1, arg2) fprintf(stderr, (mess), (arg1), (arg2))
#  endif 
#  ifdef DEBUG_m
#    undef DEBUG_m
#  endif 
#  define DEBUG_m(a)
#  ifdef DEBUGGING
#     undef DEBUGGING
#  endif
#  ifndef pTHX
#     define pTHX		void
#     define pTHX_
#     ifdef HASATTRIBUTE
#        define dTHX		extern int Perl___notused PERL_UNUSED_DECL
#     else
#        define dTHX            extern int Perl___notused
#     endif
#     define WITH_THX(s)	s
#  endif
#  ifndef PERL_GET_INTERP
#     define PERL_GET_INTERP	PL_curinterp
#  endif
#  define PERL_MAYBE_ALIVE	1
#  ifndef Perl_malloc
#     define Perl_malloc malloc
#  endif
#  ifndef Perl_mfree
#     define Perl_mfree free
#  endif
#  ifndef Perl_realloc
#     define Perl_realloc realloc
#  endif
#  ifndef Perl_calloc
#     define Perl_calloc calloc
#  endif
#  ifndef Perl_strdup
#     define Perl_strdup strdup
#  endif
#endif	/* defined PERL_CORE */

#ifndef MUTEX_LOCK
#  define MUTEX_LOCK(l)
#endif 

#ifndef MUTEX_UNLOCK
#  define MUTEX_UNLOCK(l)
#endif 

#ifndef MALLOC_LOCK
#  define MALLOC_LOCK		MUTEX_LOCK(&PL_malloc_mutex)
#endif 

#ifndef MALLOC_UNLOCK
#  define MALLOC_UNLOCK		MUTEX_UNLOCK(&PL_malloc_mutex)
#endif 

#  ifndef fatalcroak				/* make depend */
#    define fatalcroak(mess)	(write(2, (mess), strlen(mess)), exit(2))
#  endif 

#ifdef DEBUGGING
#  undef DEBUG_m
#  define DEBUG_m(a) 							\
    STMT_START {							\
	if (PERL_MAYBE_ALIVE && PERL_GET_THX) {						\
	    dTHX;							\
	    if (DEBUG_m_TEST) {						\
		PL_debug &= ~DEBUG_m_FLAG;				\
		a;							\
		PL_debug |= DEBUG_m_FLAG;				\
	    }								\
	}								\
    } STMT_END
#endif

#ifdef PERL_IMPLICIT_CONTEXT
#  define PERL_IS_ALIVE		aTHX
#else
#  define PERL_IS_ALIVE		TRUE
#endif
    

/*
 * Layout of memory:
 * ~~~~~~~~~~~~~~~~
 * The memory is broken into "blocks" which occupy multiples of 2K (and
 * generally speaking, have size "close" to a power of 2).  The addresses
 * of such *unused* blocks are kept in nextf[i] with big enough i.  (nextf
 * is an array of linked lists.)  (Addresses of used blocks are not known.)
 * 
 * Moreover, since the algorithm may try to "bite" smaller blocks out
 * of unused bigger ones, there are also regions of "irregular" size,
 * managed separately, by a linked list chunk_chain.
 * 
 * The third type of storage is the sbrk()ed-but-not-yet-used space, its
 * end and size are kept in last_sbrk_top and sbrked_remains.
 * 
 * Growing blocks "in place":
 * ~~~~~~~~~~~~~~~~~~~~~~~~~
 * The address of the block with the greatest address is kept in last_op
 * (if not known, last_op is 0).  If it is known that the memory above
 * last_op is not continuous, or contains a chunk from chunk_chain,
 * last_op is set to 0.
 * 
 * The chunk with address last_op may be grown by expanding into
 * sbrk()ed-but-not-yet-used space, or trying to sbrk() more continuous
 * memory.
 * 
 * Management of last_op:
 * ~~~~~~~~~~~~~~~~~~~~~
 * 
 * free() never changes the boundaries of blocks, so is not relevant.
 * 
 * The only way realloc() may change the boundaries of blocks is if it
 * grows a block "in place".  However, in the case of success such a
 * chunk is automatically last_op, and it remains last_op.  In the case
 * of failure getpages_adjacent() clears last_op.
 * 
 * malloc() may change blocks by calling morecore() only.
 * 
 * morecore() may create new blocks by:
 *   a) biting pieces from chunk_chain (cannot create one above last_op);
 *   b) biting a piece from an unused block (if block was last_op, this
 *      may create a chunk from chain above last_op, thus last_op is
 *      invalidated in such a case).
 *   c) biting of sbrk()ed-but-not-yet-used space.  This creates 
 *      a block which is last_op.
 *   d) Allocating new pages by calling getpages();
 * 
 * getpages() creates a new block.  It marks last_op at the bottom of
 * the chunk of memory it returns.
 * 
 * Active pages footprint:
 * ~~~~~~~~~~~~~~~~~~~~~~
 * Note that we do not need to traverse the lists in nextf[i], just take
 * the first element of this list.  However, we *need* to traverse the
 * list in chunk_chain, but most the time it should be a very short one,
 * so we do not step on a lot of pages we are not going to use.
 * 
 * Flaws:
 * ~~~~~
 * get_from_bigger_buckets(): forget to increment price => Quite
 * aggressive.
 */

/* I don't much care whether these are defined in sys/types.h--LAW */

#define u_char unsigned char
#define u_int unsigned int
/* 
 * I removed the definition of u_bigint which appeared to be u_bigint = UV
 * u_bigint was only used in TWOK_MASKED and TWOK_SHIFT 
 * where I have used PTR2UV.  RMB
 */
#define u_short unsigned short

/* 286 and atarist like big chunks, which gives too much overhead. */
#if (defined(RCHECK) || defined(I286) || defined(atarist) || defined(__MINT__)) && defined(PACK_MALLOC)
#  undef PACK_MALLOC
#endif 

/*
 * The description below is applicable if PACK_MALLOC is not defined.
 *
 * The overhead on a block is at least 4 bytes.  When free, this space
 * contains a pointer to the next free block, and the bottom two bits must
 * be zero.  When in use, the first byte is set to MAGIC, and the second
 * byte is the size index.  The remaining bytes are for alignment.
 * If range checking is enabled and the size of the block fits
 * in two bytes, then the top two bytes hold the size of the requested block
 * plus the range checking words, and the header word MINUS ONE.
 */
union	overhead {
	union	overhead *ov_next;	/* when free */
#if MEM_ALIGNBYTES > 4
	double	strut;			/* alignment problems */
#endif
	struct {
/*
 * Keep the ovu_index and ovu_magic in this order, having a char
 * field first gives alignment indigestion in some systems, such as
 * MachTen.
 */
		u_char	ovu_index;	/* bucket # */
		u_char	ovu_magic;	/* magic number */
#ifdef RCHECK
		u_short	ovu_size;	/* block size (requested + overhead - 1) */
		u_int	ovu_rmagic;	/* range magic number */
#endif
	} ovu;
#define	ov_magic	ovu.ovu_magic
#define	ov_index	ovu.ovu_index
#define	ov_size		ovu.ovu_size
#define	ov_rmagic	ovu.ovu_rmagic
};

#define	MAGIC		0xff		/* magic # on accounting info */
#define RMAGIC		0x55555555	/* magic # on range info */
#define RMAGIC_C	0x55		/* magic # on range info */

#ifdef RCHECK
#  define	RSLOP		sizeof (u_int)
#  ifdef TWO_POT_OPTIMIZE
#    define MAX_SHORT_BUCKET (12 * BUCKETS_PER_POW2) /* size-1 fits in short */
#  else
#    define MAX_SHORT_BUCKET (13 * BUCKETS_PER_POW2)
#  endif 
#else
#  define	RSLOP		0
#endif

#if !defined(PACK_MALLOC) && defined(BUCKETS_ROOT2)
#  undef BUCKETS_ROOT2
#endif 

#ifdef BUCKETS_ROOT2
#  define BUCKET_TABLE_SHIFT 2
#  define BUCKET_POW2_SHIFT 1
#  define BUCKETS_PER_POW2 2
#else
#  define BUCKET_TABLE_SHIFT MIN_BUC_POW2
#  define BUCKET_POW2_SHIFT 0
#  define BUCKETS_PER_POW2 1
#endif 

#if !defined(MEM_ALIGNBYTES) || ((MEM_ALIGNBYTES > 4) && !defined(STRICT_ALIGNMENT))
/* Figure out the alignment of void*. */
struct aligner {
  char c;
  void *p;
};
#  define ALIGN_SMALL ((int)((caddr_t)&(((struct aligner*)0)->p)))
#else
#  define ALIGN_SMALL MEM_ALIGNBYTES
#endif

#define IF_ALIGN_8(yes,no)	((ALIGN_SMALL>4) ? (yes) : (no))

#ifdef BUCKETS_ROOT2
#  define MAX_BUCKET_BY_TABLE 13
static u_short buck_size[MAX_BUCKET_BY_TABLE + 1] = 
  { 
      0, 0, 0, 0, 4, 4, 8, 12, 16, 24, 32, 48, 64, 80,
  };
#  define BUCKET_SIZE(i) ((i) % 2 ? buck_size[i] : (1 << ((i) >> BUCKET_POW2_SHIFT)))
#  define BUCKET_SIZE_REAL(i) ((i) <= MAX_BUCKET_BY_TABLE		\
			       ? buck_size[i] 				\
			       : ((1 << ((i) >> BUCKET_POW2_SHIFT))	\
				  - MEM_OVERHEAD(i)			\
				  + POW2_OPTIMIZE_SURPLUS(i)))
#else
#  define BUCKET_SIZE(i) (1 << ((i) >> BUCKET_POW2_SHIFT))
#  define BUCKET_SIZE_REAL(i) (BUCKET_SIZE(i) - MEM_OVERHEAD(i) + POW2_OPTIMIZE_SURPLUS(i))
#endif 


#ifdef PACK_MALLOC
/* In this case there are several possible layout of arenas depending
 * on the size.  Arenas are of sizes multiple to 2K, 2K-aligned, and
 * have a size close to a power of 2.
 *
 * Arenas of the size >= 4K keep one chunk only.  Arenas of size 2K
 * may keep one chunk or multiple chunks.  Here are the possible
 * layouts of arenas:
 *
 *	# One chunk only, chunksize 2^k + SOMETHING - ALIGN, k >= 11
 *
 * INDEX MAGIC1 UNUSED CHUNK1
 *
 *	# Multichunk with sanity checking and chunksize 2^k-ALIGN, k>7
 *
 * INDEX MAGIC1 MAGIC2 MAGIC3 UNUSED CHUNK1 CHUNK2 CHUNK3 ...
 *
 *	# Multichunk with sanity checking and size 2^k-ALIGN, k=7
 *
 * INDEX MAGIC1 MAGIC2 MAGIC3 UNUSED CHUNK1 UNUSED CHUNK2 CHUNK3 ...
 *
 *	# Multichunk with sanity checking and size up to 80
 *
 * INDEX UNUSED MAGIC1 UNUSED MAGIC2 UNUSED ... CHUNK1 CHUNK2 CHUNK3 ...
 *
 *	# No sanity check (usually up to 48=byte-long buckets)
 * INDEX UNUSED CHUNK1 CHUNK2 ...
 *
 * Above INDEX and MAGIC are one-byte-long.  Sizes of UNUSED are
 * appropriate to keep algorithms simple and memory aligned.  INDEX
 * encodes the size of the chunk, while MAGICn encodes state (used,
 * free or non-managed-by-us-so-it-indicates-a-bug) of CHUNKn.  MAGIC
 * is used for sanity checking purposes only.  SOMETHING is 0 or 4K
 * (to make size of big CHUNK accomodate allocations for powers of two
 * better).
 *
 * [There is no need to alignment between chunks, since C rules ensure
 *  that structs which need 2^k alignment have sizeof which is
 *  divisible by 2^k.  Thus as far as the last chunk is aligned at the
 *  end of the arena, and 2K-alignment does not contradict things,
 *  everything is going to be OK for sizes of chunks 2^n and 2^n +
 *  2^k.  Say, 80-bit buckets will be 16-bit aligned, and as far as we
 *  put allocations for requests in 65..80 range, all is fine.
 *
 *  Note, however, that standard malloc() puts more strict
 *  requirements than the above C rules.  Moreover, our algorithms of
 *  realloc() may break this idyll, but we suppose that realloc() does
 *  need not change alignment.]
 *
 * Is very important to make calculation of the offset of MAGICm as
 * quick as possible, since it is done on each malloc()/free().  In
 * fact it is so quick that it has quite little effect on the speed of
 * doing malloc()/free().  [By default] We forego such calculations
 * for small chunks, but only to save extra 3% of memory, not because
 * of speed considerations.
 *
 * Here is the algorithm [which is the same for all the allocations
 * schemes above], see OV_MAGIC(block,bucket).  Let OFFSETm be the
 * offset of the CHUNKm from the start of ARENA.  Then offset of
 * MAGICm is (OFFSET1 >> SHIFT) + ADDOFFSET.  Here SHIFT and ADDOFFSET
 * are numbers which depend on the size of the chunks only.
 *
 * Let as check some sanity conditions.  Numbers OFFSETm>>SHIFT are
 * different for all the chunks in the arena if 2^SHIFT is not greater
 * than size of the chunks in the arena.  MAGIC1 will not overwrite
 * INDEX provided ADDOFFSET is >0 if OFFSET1 < 2^SHIFT.  MAGIClast
 * will not overwrite CHUNK1 if OFFSET1 > (OFFSETlast >> SHIFT) +
 * ADDOFFSET.
 * 
 * Make SHIFT the maximal possible (there is no point in making it
 * smaller).  Since OFFSETlast is 2K - CHUNKSIZE, above restrictions
 * give restrictions on OFFSET1 and on ADDOFFSET.
 * 
 * In particular, for chunks of size 2^k with k>=6 we can put
 * ADDOFFSET to be from 0 to 2^k - 2^(11-k), and have
 * OFFSET1==chunksize.  For chunks of size 80 OFFSET1 of 2K%80=48 is
 * large enough to have ADDOFFSET between 1 and 16 (similarly for 96,
 * when ADDOFFSET should be 1).  In particular, keeping MAGICs for
 * these sizes gives no additional size penalty.
 * 
 * However, for chunks of size 2^k with k<=5 this gives OFFSET1 >=
 * ADDOFSET + 2^(11-k).  Keeping ADDOFFSET 0 allows for 2^(11-k)-2^(11-2k)
 * chunks per arena.  This is smaller than 2^(11-k) - 1 which are
 * needed if no MAGIC is kept.  [In fact, having a negative ADDOFFSET
 * would allow for slightly more buckets per arena for k=2,3.]
 * 
 * Similarly, for chunks of size 3/2*2^k with k<=5 MAGICs would span
 * the area up to 2^(11-k)+ADDOFFSET.  For k=4 this give optimal
 * ADDOFFSET as -7..0.  For k=3 ADDOFFSET can go up to 4 (with tiny
 * savings for negative ADDOFFSET).  For k=5 ADDOFFSET can go -1..16
 * (with no savings for negative values).
 *
 * In particular, keeping ADDOFFSET 0 for sizes of chunks up to 2^6
 * leads to tiny pessimizations in case of sizes 4, 8, 12, 24, and
 * leads to no contradictions except for size=80 (or 96.)
 *
 * However, it also makes sense to keep no magic for sizes 48 or less.
 * This is what we do.  In this case one needs ADDOFFSET>=1 also for
 * chunksizes 12, 24, and 48, unless one gets one less chunk per
 * arena.
 *  
 * The algo of OV_MAGIC(block,bucket) keeps ADDOFFSET 0 until
 * chunksize of 64, then makes it 1. 
 *
 * This allows for an additional optimization: the above scheme leads
 * to giant overheads for sizes 128 or more (one whole chunk needs to
 * be sacrifised to keep INDEX).  Instead we use chunks not of size
 * 2^k, but of size 2^k-ALIGN.  If we pack these chunks at the end of
 * the arena, then the beginnings are still in different 2^k-long
 * sections of the arena if k>=7 for ALIGN==4, and k>=8 if ALIGN=8.
 * Thus for k>7 the above algo of calculating the offset of the magic
 * will still give different answers for different chunks.  And to
 * avoid the overrun of MAGIC1 into INDEX, one needs ADDOFFSET of >=1.
 * In the case k=7 we just move the first chunk an extra ALIGN
 * backward inside the ARENA (this is done once per arena lifetime,
 * thus is not a big overhead).  */
#  define MAX_PACKED_POW2 6
#  define MAX_PACKED (MAX_PACKED_POW2 * BUCKETS_PER_POW2 + BUCKET_POW2_SHIFT)
#  define MAX_POW2_ALGO ((1<<(MAX_PACKED_POW2 + 1)) - M_OVERHEAD)
#  define TWOK_MASK ((1<<LOG_OF_MIN_ARENA) - 1)
#  define TWOK_MASKED(x) (PTR2UV(x) & ~TWOK_MASK)
#  define TWOK_SHIFT(x) (PTR2UV(x) & TWOK_MASK)
#  define OV_INDEXp(block) (INT2PTR(u_char*,TWOK_MASKED(block)))
#  define OV_INDEX(block) (*OV_INDEXp(block))
#  define OV_MAGIC(block,bucket) (*(OV_INDEXp(block) +			\
				    (TWOK_SHIFT(block)>>		\
				     (bucket>>BUCKET_POW2_SHIFT)) +	\
				    (bucket >= MIN_NEEDS_SHIFT ? 1 : 0)))
    /* A bucket can have a shift smaller than it size, we need to
       shift its magic number so it will not overwrite index: */
#  ifdef BUCKETS_ROOT2
#    define MIN_NEEDS_SHIFT (7*BUCKETS_PER_POW2 - 1) /* Shift 80 greater than chunk 64. */
#  else
#    define MIN_NEEDS_SHIFT (7*BUCKETS_PER_POW2) /* Shift 128 greater than chunk 32. */
#  endif 
#  define CHUNK_SHIFT 0

/* Number of active buckets of given ordinal. */
#ifdef IGNORE_SMALL_BAD_FREE
#define FIRST_BUCKET_WITH_CHECK (6 * BUCKETS_PER_POW2) /* 64 */
#  define N_BLKS(bucket) ( (bucket) < FIRST_BUCKET_WITH_CHECK 		\
			 ? ((1<<LOG_OF_MIN_ARENA) - 1)/BUCKET_SIZE(bucket) \
			 : n_blks[bucket] )
#else
#  define N_BLKS(bucket) n_blks[bucket]
#endif 

static u_short n_blks[LOG_OF_MIN_ARENA * BUCKETS_PER_POW2] = 
  {
#  if BUCKETS_PER_POW2==1
      0, 0,
      (MIN_BUC_POW2==2 ? 384 : 0),
      224, 120, 62, 31, 16, 8, 4, 2
#  else
      0, 0, 0, 0,
      (MIN_BUC_POW2==2 ? 384 : 0), (MIN_BUC_POW2==2 ? 384 : 0),	/* 4, 4 */
      224, 149, 120, 80, 62, 41, 31, 25, 16, 16, 8, 8, 4, 4, 2, 2
#  endif
  };

/* Shift of the first bucket with the given ordinal inside 2K chunk. */
#ifdef IGNORE_SMALL_BAD_FREE
#  define BLK_SHIFT(bucket) ( (bucket) < FIRST_BUCKET_WITH_CHECK 	\
			      ? ((1<<LOG_OF_MIN_ARENA)			\
				 - BUCKET_SIZE(bucket) * N_BLKS(bucket)) \
			      : blk_shift[bucket])
#else
#  define BLK_SHIFT(bucket) blk_shift[bucket]
#endif 

static u_short blk_shift[LOG_OF_MIN_ARENA * BUCKETS_PER_POW2] = 
  { 
#  if BUCKETS_PER_POW2==1
      0, 0,
      (MIN_BUC_POW2==2 ? 512 : 0),
      256, 128, 64, 64,			/* 8 to 64 */
      16*sizeof(union overhead), 
      8*sizeof(union overhead), 
      4*sizeof(union overhead), 
      2*sizeof(union overhead), 
#  else
      0, 0, 0, 0,
      (MIN_BUC_POW2==2 ? 512 : 0), (MIN_BUC_POW2==2 ? 512 : 0),
      256, 260, 128, 128, 64, 80, 64, 48, /* 8 to 96 */
      16*sizeof(union overhead), 16*sizeof(union overhead), 
      8*sizeof(union overhead), 8*sizeof(union overhead), 
      4*sizeof(union overhead), 4*sizeof(union overhead), 
      2*sizeof(union overhead), 2*sizeof(union overhead), 
#  endif 
  };

#  define NEEDED_ALIGNMENT 0x800	/* 2k boundaries */
#  define WANTED_ALIGNMENT 0x800	/* 2k boundaries */

#else  /* !PACK_MALLOC */

#  define OV_MAGIC(block,bucket) (block)->ov_magic
#  define OV_INDEX(block) (block)->ov_index
#  define CHUNK_SHIFT 1
#  define MAX_PACKED -1
#  define NEEDED_ALIGNMENT MEM_ALIGNBYTES
#  define WANTED_ALIGNMENT 0x400	/* 1k boundaries */

#endif /* !PACK_MALLOC */

#define M_OVERHEAD (sizeof(union overhead) + RSLOP)

#ifdef PACK_MALLOC
#  define MEM_OVERHEAD(bucket) \
  (bucket <= MAX_PACKED ? 0 : M_OVERHEAD)
#  ifdef SMALL_BUCKET_VIA_TABLE
#    define START_SHIFTS_BUCKET ((MAX_PACKED_POW2 + 1) * BUCKETS_PER_POW2)
#    define START_SHIFT MAX_PACKED_POW2
#    ifdef BUCKETS_ROOT2		/* Chunks of size 3*2^n. */
#      define SIZE_TABLE_MAX 80
#    else
#      define SIZE_TABLE_MAX 64
#    endif 
static char bucket_of[] =
  {
#    ifdef BUCKETS_ROOT2		/* Chunks of size 3*2^n. */
      /* 0 to 15 in 4-byte increments. */
      (sizeof(void*) > 4 ? 6 : 5),	/* 4/8, 5-th bucket for better reports */
      6,				/* 8 */
      IF_ALIGN_8(8,7), 8,		/* 16/12, 16 */
      9, 9, 10, 10,			/* 24, 32 */
      11, 11, 11, 11,			/* 48 */
      12, 12, 12, 12,			/* 64 */
      13, 13, 13, 13,			/* 80 */
      13, 13, 13, 13			/* 80 */
#    else /* !BUCKETS_ROOT2 */
      /* 0 to 15 in 4-byte increments. */
      (sizeof(void*) > 4 ? 3 : 2),
      3, 
      4, 4, 
      5, 5, 5, 5,
      6, 6, 6, 6,
      6, 6, 6, 6
#    endif /* !BUCKETS_ROOT2 */
  };
#  else  /* !SMALL_BUCKET_VIA_TABLE */
#    define START_SHIFTS_BUCKET MIN_BUCKET
#    define START_SHIFT (MIN_BUC_POW2 - 1)
#  endif /* !SMALL_BUCKET_VIA_TABLE */
#else  /* !PACK_MALLOC */
#  define MEM_OVERHEAD(bucket) M_OVERHEAD
#  ifdef SMALL_BUCKET_VIA_TABLE
#    undef SMALL_BUCKET_VIA_TABLE
#  endif 
#  define START_SHIFTS_BUCKET MIN_BUCKET
#  define START_SHIFT (MIN_BUC_POW2 - 1)
#endif /* !PACK_MALLOC */

/*
 * Big allocations are often of the size 2^n bytes. To make them a
 * little bit better, make blocks of size 2^n+pagesize for big n.
 */

#ifdef TWO_POT_OPTIMIZE

#  ifndef PERL_PAGESIZE
#    define PERL_PAGESIZE 4096
#  endif 
#  ifndef FIRST_BIG_POW2
#    define FIRST_BIG_POW2 15	/* 32K, 16K is used too often. */
#  endif
#  define FIRST_BIG_BLOCK (1<<FIRST_BIG_POW2)
/* If this value or more, check against bigger blocks. */
#  define FIRST_BIG_BOUND (FIRST_BIG_BLOCK - M_OVERHEAD)
/* If less than this value, goes into 2^n-overhead-block. */
#  define LAST_SMALL_BOUND ((FIRST_BIG_BLOCK>>1) - M_OVERHEAD)

#  define POW2_OPTIMIZE_ADJUST(nbytes)				\
   ((nbytes >= FIRST_BIG_BOUND) ? nbytes -= PERL_PAGESIZE : 0)
#  define POW2_OPTIMIZE_SURPLUS(bucket)				\
   ((bucket >= FIRST_BIG_POW2 * BUCKETS_PER_POW2) ? PERL_PAGESIZE : 0)

#else  /* !TWO_POT_OPTIMIZE */
#  define POW2_OPTIMIZE_ADJUST(nbytes)
#  define POW2_OPTIMIZE_SURPLUS(bucket) 0
#endif /* !TWO_POT_OPTIMIZE */

#if defined(HAS_64K_LIMIT) && defined(PERL_CORE)
#  define BARK_64K_LIMIT(what,nbytes,size)				\
	if (nbytes > 0xffff) {						\
		PerlIO_printf(PerlIO_stderr(),				\
			      "%s too large: %lx\n", what, size);	\
		my_exit(1);						\
	}
#else /* !HAS_64K_LIMIT || !PERL_CORE */
#  define BARK_64K_LIMIT(what,nbytes,size)
#endif /* !HAS_64K_LIMIT || !PERL_CORE */

#ifndef MIN_SBRK
#  define MIN_SBRK 2048
#endif 

#ifndef FIRST_SBRK
#  define FIRST_SBRK (48*1024)
#endif 

/* Minimal sbrk in percents of what is already alloced. */
#ifndef MIN_SBRK_FRAC
#  define MIN_SBRK_FRAC 3
#endif 

#ifndef SBRK_ALLOW_FAILURES
#  define SBRK_ALLOW_FAILURES 3
#endif 

#ifndef SBRK_FAILURE_PRICE
#  define SBRK_FAILURE_PRICE 50
#endif 

static void	morecore	(register int bucket);
#  if defined(DEBUGGING)
static void	botch		(char *diag, char *s, char *file, int line);
#  endif
static void	add_to_chain	(void *p, MEM_SIZE size, MEM_SIZE chip);
static void*	get_from_chain	(MEM_SIZE size);
static void*	get_from_bigger_buckets(int bucket, MEM_SIZE size);
static union overhead *getpages	(MEM_SIZE needed, int *nblksp, int bucket);
static int	getpages_adjacent(MEM_SIZE require);

#ifdef PERL_CORE

#ifdef I_MACH_CTHREADS
#  undef  MUTEX_LOCK
#  define MUTEX_LOCK(m)   STMT_START { if (*m) mutex_lock(*m);   } STMT_END
#  undef  MUTEX_UNLOCK
#  define MUTEX_UNLOCK(m) STMT_START { if (*m) mutex_unlock(*m); } STMT_END
#endif

#endif	/* defined PERL_CORE */ 

#ifndef PTRSIZE
#  define PTRSIZE	sizeof(void*)
#endif

#ifndef BITS_IN_PTR
#  define BITS_IN_PTR (8*PTRSIZE)
#endif

/*
 * nextf[i] is the pointer to the next free block of size 2^i.  The
 * smallest allocatable block is 8 bytes.  The overhead information
 * precedes the data area returned to the user.
 */
#define	NBUCKETS (BITS_IN_PTR*BUCKETS_PER_POW2 + 1)
static	union overhead *nextf[NBUCKETS];

#if defined(PURIFY) && !defined(USE_PERL_SBRK)
#  define USE_PERL_SBRK
#endif

#ifdef USE_PERL_SBRK
# define sbrk(a) Perl_sbrk(a)
Malloc_t Perl_sbrk (int size);
#else
# ifndef HAS_SBRK_PROTO /* <unistd.h> usually takes care of this */
extern	Malloc_t sbrk(int);
# endif
#endif

#ifndef MIN_SBRK_FRAC1000	/* Backward compatibility */
#  define MIN_SBRK_FRAC1000	(MIN_SBRK_FRAC * 10)
#endif

#ifndef START_EXTERN_C
#  ifdef __cplusplus
#    define START_EXTERN_C	extern "C" {
#  else
#    define START_EXTERN_C
#  endif
#endif

#ifndef END_EXTERN_C
#  ifdef __cplusplus
#    define END_EXTERN_C		};
#  else
#    define END_EXTERN_C
#  endif
#endif

#include "malloc_ctl.h"

#ifndef NO_MALLOC_DYNAMIC_CFG
#  define PERL_MALLOC_OPT_CHARS "FMfAPGdac"

static IV MallocCfg[MallocCfg_last] = {
  FIRST_SBRK,
  MIN_SBRK,
  MIN_SBRK_FRAC,
  SBRK_ALLOW_FAILURES,
  SBRK_FAILURE_PRICE,
  SBRK_ALLOW_FAILURES * SBRK_FAILURE_PRICE,	/* sbrk_goodness */
  1,			/* FILL_DEAD */
  1,			/* FILL_ALIVE */
  1,			/* FILL_CHECK */
  0,			/* MallocCfg_skip_cfg_env */
  0,			/* MallocCfg_cfg_env_read */
  0,			/* MallocCfg_emergency_buffer_size */
  0,			/* MallocCfg_emergency_buffer_prepared_size */
  0			/* MallocCfg_emergency_buffer_last_req */
};
IV *MallocCfg_ptr = MallocCfg;

#  undef MIN_SBRK
#  undef FIRST_SBRK
#  undef MIN_SBRK_FRAC1000
#  undef SBRK_ALLOW_FAILURES
#  undef SBRK_FAILURE_PRICE

#  define MIN_SBRK		MallocCfg[MallocCfg_MIN_SBRK]
#  define FIRST_SBRK		MallocCfg[MallocCfg_FIRST_SBRK]
#  define MIN_SBRK_FRAC1000	MallocCfg[MallocCfg_MIN_SBRK_FRAC1000]
#  define SBRK_ALLOW_FAILURES	MallocCfg[MallocCfg_SBRK_ALLOW_FAILURES]
#  define SBRK_FAILURE_PRICE	MallocCfg[MallocCfg_SBRK_FAILURE_PRICE]

#  define sbrk_goodness		MallocCfg[MallocCfg_sbrk_goodness]

#  define emergency_buffer_size	MallocCfg[MallocCfg_emergency_buffer_size]
#  define emergency_buffer_last_req	MallocCfg[MallocCfg_emergency_buffer_last_req]

#  define FILL_DEAD		MallocCfg[MallocCfg_filldead]
#  define FILL_ALIVE		MallocCfg[MallocCfg_fillalive]
#  define FILL_CHECK_CFG	MallocCfg[MallocCfg_fillcheck]
#  define FILL_CHECK		(FILL_DEAD && FILL_CHECK_CFG)

#else	/* defined(NO_MALLOC_DYNAMIC_CFG) */

#  define FILL_DEAD	1
#  define FILL_ALIVE	1
#  define FILL_CHECK	1
static int sbrk_goodness = SBRK_ALLOW_FAILURES * SBRK_FAILURE_PRICE;

#  define NO_PERL_MALLOC_ENV

#endif

#ifdef DEBUGGING_MSTATS
/*
 * nmalloc[i] is the difference between the number of mallocs and frees
 * for a given block size.
 */
static	u_int nmalloc[NBUCKETS];
static  u_int sbrk_slack;
static  u_int start_slack;
#else	/* !( defined DEBUGGING_MSTATS ) */
#  define sbrk_slack	0
#endif

static	u_int goodsbrk;

#ifdef PERL_EMERGENCY_SBRK

#  ifndef BIG_SIZE
#    define BIG_SIZE (1<<16)		/* 64K */
#  endif

static char *emergency_buffer;
static char *emergency_buffer_prepared;

#  ifdef NO_MALLOC_DYNAMIC_CFG
static MEM_SIZE emergency_buffer_size;
	/* 0 if the last request for more memory succeeded.
	   Otherwise the size of the failing request. */
static MEM_SIZE emergency_buffer_last_req;
#  endif

#  ifndef emergency_sbrk_croak
#    define emergency_sbrk_croak	croak2
#  endif

#  ifdef PERL_CORE
static char *
perl_get_emergency_buffer(IV *size)
{
    dTHX;
    /* First offense, give a possibility to recover by dieing. */
    /* No malloc involved here: */
    GV **gvp = (GV**)hv_fetch(PL_defstash, "^M", 2, 0);
    SV *sv;
    char *pv;
    STRLEN n_a;

    if (!gvp) gvp = (GV**)hv_fetch(PL_defstash, "\015", 1, 0);
    if (!gvp || !(sv = GvSV(*gvp)) || !SvPOK(sv) 
        || (SvLEN(sv) < (1<<LOG_OF_MIN_ARENA) - M_OVERHEAD))
        return NULL;		/* Now die die die... */
    /* Got it, now detach SvPV: */
    pv = SvPV(sv, n_a);
    /* Check alignment: */
    if ((PTR2UV(pv) - sizeof(union overhead)) & (NEEDED_ALIGNMENT - 1)) {
        PerlIO_puts(PerlIO_stderr(),"Bad alignment of $^M!\n");
        return NULL;		/* die die die */
    }

    SvPOK_off(sv);
    SvPVX(sv) = Nullch;
    SvCUR(sv) = SvLEN(sv) = 0;
    *size = malloced_size(pv) + M_OVERHEAD;
    return pv - sizeof(union overhead);
}
#    define PERL_GET_EMERGENCY_BUFFER(p)	perl_get_emergency_buffer(p)
#  else
#    define PERL_GET_EMERGENCY_BUFFER(p)	NULL
#  endif	/* defined PERL_CORE */

#  ifndef NO_MALLOC_DYNAMIC_CFG
static char *
get_emergency_buffer(IV *size)
{
    char *pv = emergency_buffer_prepared;

    *size = MallocCfg[MallocCfg_emergency_buffer_prepared_size];
    emergency_buffer_prepared = 0;
    MallocCfg[MallocCfg_emergency_buffer_prepared_size] = 0;
    return pv;
}

/* Returns 0 on success, -1 on bad alignment, -2 if not implemented */
int
set_emergency_buffer(char *b, IV size)
{
    if (PTR2UV(b) & (NEEDED_ALIGNMENT - 1))
	return -1;
    if (MallocCfg[MallocCfg_emergency_buffer_prepared_size])
	add_to_chain((void*)emergency_buffer_prepared,
		     MallocCfg[MallocCfg_emergency_buffer_prepared_size], 0);
    emergency_buffer_prepared = b;
    MallocCfg[MallocCfg_emergency_buffer_prepared_size] = size;
    return 0;
}
#    define GET_EMERGENCY_BUFFER(p)	get_emergency_buffer(p)
#  else		/* NO_MALLOC_DYNAMIC_CFG */
#    define GET_EMERGENCY_BUFFER(p)	NULL
int
set_emergency_buffer(char *b, IV size)
{
    return -1;
}
#  endif

static Malloc_t
emergency_sbrk(MEM_SIZE size)
{
    MEM_SIZE rsize = (((size - 1)>>LOG_OF_MIN_ARENA) + 1)<<LOG_OF_MIN_ARENA;

    if (size >= BIG_SIZE
	&& (!emergency_buffer_last_req || (size < emergency_buffer_last_req))) {
	/* Give the possibility to recover, but avoid an infinite cycle. */
	MALLOC_UNLOCK;
	emergency_buffer_last_req = size;
	emergency_sbrk_croak("Out of memory during \"large\" request for %"UVuf" bytes, total sbrk() is %"UVuf" bytes", (UV)size, (UV)(goodsbrk + sbrk_slack));
    }

    if (emergency_buffer_size >= rsize) {
	char *old = emergency_buffer;
	
	emergency_buffer_size -= rsize;
	emergency_buffer += rsize;
	return old;
    } else {		
	/* First offense, give a possibility to recover by dieing. */
	/* No malloc involved here: */
	IV Size;
	char *pv = GET_EMERGENCY_BUFFER(&Size);
	int have = 0;

	if (emergency_buffer_size) {
	    add_to_chain(emergency_buffer, emergency_buffer_size, 0);
	    emergency_buffer_size = 0;
	    emergency_buffer = Nullch;
	    have = 1;
	}

	if (!pv)
	    pv = PERL_GET_EMERGENCY_BUFFER(&Size);
	if (!pv) {
	    if (have)
		goto do_croak;
	    return (char *)-1;		/* Now die die die... */
	}

	/* Check alignment: */
	if (PTR2UV(pv) & (NEEDED_ALIGNMENT - 1)) {
	    dTHX;

	    PerlIO_puts(PerlIO_stderr(),"Bad alignment of $^M!\n");
	    return (char *)-1;		/* die die die */
	}

	emergency_buffer = pv;
	emergency_buffer_size = Size;
    }
  do_croak:
    MALLOC_UNLOCK;
    emergency_sbrk_croak("Out of memory during request for %"UVuf" bytes, total sbrk() is %"UVuf" bytes", (UV)size, (UV)(goodsbrk + sbrk_slack));
    /* NOTREACHED */
    return Nullch;
}

#else /*  !defined(PERL_EMERGENCY_SBRK) */
#  define emergency_sbrk(size)	-1
#endif	/* defined PERL_EMERGENCY_SBRK */

static void
write2(char *mess)
{
  write(2, mess, strlen(mess));
}

#ifdef DEBUGGING
#undef ASSERT
#define	ASSERT(p,diag)   if (!(p)) botch(diag,STRINGIFY(p),__FILE__,__LINE__);  else
static void
botch(char *diag, char *s, char *file, int line)
{
    if (!(PERL_MAYBE_ALIVE && PERL_GET_THX))
	goto do_write;
    else {
	dTHX;
	char linebuf[10];

	if (PerlIO_printf(PerlIO_stderr(),
			  "assertion botched (%s?): %s%s %s:%d\n",
			  diag, s, file, line) != 0) {
	 do_write:		/* Can be initializing interpreter */
	    write2("assertion botched (");
	    write2(diag);
	    write2("?): ");
	    write2(s);
	    write2(" (");
	    write2(file);
	    write2(":");
	    sprintf(linebuf, "%d", line);
	    write2(linebuf);
	    write2(")\n");
	}
	PerlProc_abort();
    }
}
#else
#define	ASSERT(p, diag)
#endif

#ifdef MALLOC_FILL
/* Fill should be long enough to cover long */
static void
fill_pat_4bytes(unsigned char *s, size_t nbytes, const unsigned char *fill)
{
    unsigned char *e = s + nbytes;
    long *lp;
    long lfill = *(long*)fill;

    if (PTR2UV(s) & (sizeof(long)-1)) {		/* Align the pattern */
	int shift = sizeof(long) - (PTR2UV(s) & (sizeof(long)-1));
	unsigned const char *f = fill + sizeof(long) - shift;
	unsigned char *e1 = s + shift;

	while (s < e1)
	    *s++ = *f++;
    }
    lp = (long*)s;
    while ((unsigned char*)(lp + 1) <= e)
	*lp++ = lfill;
    s = (unsigned char*)lp;
    while (s < e)
	*s++ = *fill++;
}
/* Just malloc()ed */
static const unsigned char fill_feedadad[] =
 {0xFE, 0xED, 0xAD, 0xAD, 0xFE, 0xED, 0xAD, 0xAD,
  0xFE, 0xED, 0xAD, 0xAD, 0xFE, 0xED, 0xAD, 0xAD};
/* Just free()ed */
static const unsigned char fill_deadbeef[] =
 {0xDE, 0xAD, 0xBE, 0xEF, 0xDE, 0xAD, 0xBE, 0xEF,
  0xDE, 0xAD, 0xBE, 0xEF, 0xDE, 0xAD, 0xBE, 0xEF};
#  define FILL_DEADBEEF(s, n)	\
	(void)(FILL_DEAD?  (fill_pat_4bytes((s), (n), fill_deadbeef), 0) : 0)
#  define FILL_FEEDADAD(s, n)	\
	(void)(FILL_ALIVE? (fill_pat_4bytes((s), (n), fill_feedadad), 0) : 0)
#else
#  define FILL_DEADBEEF(s, n)	((void)0)
#  define FILL_FEEDADAD(s, n)	((void)0)
#  undef MALLOC_FILL_CHECK
#endif

#ifdef MALLOC_FILL_CHECK
static int
cmp_pat_4bytes(unsigned char *s, size_t nbytes, const unsigned char *fill)
{
    unsigned char *e = s + nbytes;
    long *lp;
    long lfill = *(long*)fill;

    if (PTR2UV(s) & (sizeof(long)-1)) {		/* Align the pattern */
	int shift = sizeof(long) - (PTR2UV(s) & (sizeof(long)-1));
	unsigned const char *f = fill + sizeof(long) - shift;
	unsigned char *e1 = s + shift;

	while (s < e1)
	    if (*s++ != *f++)
		return 1;
    }
    lp = (long*)s;
    while ((unsigned char*)(lp + 1) <= e)
	if (*lp++ != lfill)
	    return 1;
    s = (unsigned char*)lp;
    while (s < e)
	if (*s++ != *fill++)
	    return 1;
    return 0;
}
#  define FILLCHECK_DEADBEEF(s, n)					\
	ASSERT(!FILL_CHECK || !cmp_pat_4bytes(s, n, fill_deadbeef),	\
	       "free()ed/realloc()ed-away memory was overwritten")
#else
#  define FILLCHECK_DEADBEEF(s, n)	((void)0)
#endif

Malloc_t
Perl_malloc(register size_t nbytes)
{
  	register union overhead *p;
  	register int bucket;
  	register MEM_SIZE shiftr;

#if defined(DEBUGGING) || defined(RCHECK)
	MEM_SIZE size = nbytes;
#endif

	BARK_64K_LIMIT("Allocation",nbytes,nbytes);
#ifdef DEBUGGING
	if ((long)nbytes < 0)
	    croak("%s", "panic: malloc");
#endif

	/*
	 * Convert amount of memory requested into
	 * closest block size stored in hash buckets
	 * which satisfies request.  Account for
	 * space used per block for accounting.
	 */
#ifdef PACK_MALLOC
#  ifdef SMALL_BUCKET_VIA_TABLE
	if (nbytes == 0)
	    bucket = MIN_BUCKET;
	else if (nbytes <= SIZE_TABLE_MAX) {
	    bucket = bucket_of[(nbytes - 1) >> BUCKET_TABLE_SHIFT];
	} else
#  else
	if (nbytes == 0)
	    nbytes = 1;
	if (nbytes <= MAX_POW2_ALGO) goto do_shifts;
	else
#  endif
#endif 
	{
	    POW2_OPTIMIZE_ADJUST(nbytes);
	    nbytes += M_OVERHEAD;
	    nbytes = (nbytes + 3) &~ 3; 
#if defined(PACK_MALLOC) && !defined(SMALL_BUCKET_VIA_TABLE)
	  do_shifts:
#endif
	    shiftr = (nbytes - 1) >> START_SHIFT;
	    bucket = START_SHIFTS_BUCKET;
	    /* apart from this loop, this is O(1) */
	    while (shiftr >>= 1)
  		bucket += BUCKETS_PER_POW2;
	}
	MALLOC_LOCK;
	/*
	 * If nothing in hash bucket right now,
	 * request more memory from the system.
	 */
  	if (nextf[bucket] == NULL)    
  		morecore(bucket);
  	if ((p = nextf[bucket]) == NULL) {
		MALLOC_UNLOCK;
#ifdef PERL_CORE
		{
		    dTHX;
		    if (!PL_nomemok) {
#if defined(PLAIN_MALLOC) && defined(NO_FANCY_MALLOC)
		        PerlIO_puts(PerlIO_stderr(),"Out of memory!\n");
#else
			char buff[80];
			char *eb = buff + sizeof(buff) - 1;
			char *s = eb;
			size_t n = nbytes;

			PerlIO_puts(PerlIO_stderr(),"Out of memory during request for ");
#if defined(DEBUGGING) || defined(RCHECK)
			n = size;
#endif
			*s = 0;			
			do {
			    *--s = '0' + (n % 10);
			} while (n /= 10);
			PerlIO_puts(PerlIO_stderr(),s);
			PerlIO_puts(PerlIO_stderr()," bytes, total sbrk() is ");
			s = eb;
			n = goodsbrk + sbrk_slack;
			do {
			    *--s = '0' + (n % 10);
			} while (n /= 10);
			PerlIO_puts(PerlIO_stderr(),s);
			PerlIO_puts(PerlIO_stderr()," bytes!\n");
#endif /* defined(PLAIN_MALLOC) && defined(NO_FANCY_MALLOC) */
			my_exit(1);
		    }
		}
#endif
  		return (NULL);
	}

	/* remove from linked list */
#ifdef DEBUGGING
	if ( (PTR2UV(p) & (MEM_ALIGNBYTES - 1))
						/* Can't get this low */
	     || (p && PTR2UV(p) < (1<<LOG_OF_MIN_ARENA)) ) {
	    dTHX;
	    PerlIO_printf(PerlIO_stderr(),
			  "Unaligned pointer in the free chain 0x%"UVxf"\n",
			  PTR2UV(p));
	}
	if ( (PTR2UV(p->ov_next) & (MEM_ALIGNBYTES - 1))
	     || (p->ov_next && PTR2UV(p->ov_next) < (1<<LOG_OF_MIN_ARENA)) ) {
	    dTHX;
	    PerlIO_printf(PerlIO_stderr(),
			  "Unaligned `next' pointer in the free "
			  "chain 0x%"UVxf" at 0x%"UVxf"\n",
			  PTR2UV(p->ov_next), PTR2UV(p));
	}
#endif
  	nextf[bucket] = p->ov_next;

	MALLOC_UNLOCK;

	DEBUG_m(PerlIO_printf(Perl_debug_log,
			      "0x%"UVxf": (%05lu) malloc %ld bytes\n",
			      PTR2UV((Malloc_t)(p + CHUNK_SHIFT)), (unsigned long)(PL_an++),
			      (long)size));

	FILLCHECK_DEADBEEF((unsigned char*)(p + CHUNK_SHIFT),
			   BUCKET_SIZE_REAL(bucket));

#ifdef IGNORE_SMALL_BAD_FREE
	if (bucket >= FIRST_BUCKET_WITH_CHECK)
#endif 
	    OV_MAGIC(p, bucket) = MAGIC;
#ifndef PACK_MALLOC
	OV_INDEX(p) = bucket;
#endif
#ifdef RCHECK
	/*
	 * Record allocated size of block and
	 * bound space with magic numbers.
	 */
	p->ov_rmagic = RMAGIC;
	if (bucket <= MAX_SHORT_BUCKET) {
	    int i;
	    
	    nbytes = size + M_OVERHEAD; 
	    p->ov_size = nbytes - 1;
	    if ((i = nbytes & 3)) {
		i = 4 - i;
		while (i--)
		    *((char *)((caddr_t)p + nbytes - RSLOP + i)) = RMAGIC_C;
	    }
	    nbytes = (nbytes + 3) &~ 3; 
	    *((u_int *)((caddr_t)p + nbytes - RSLOP)) = RMAGIC;
	}
	FILL_FEEDADAD((unsigned char *)(p + CHUNK_SHIFT), size);
#endif
  	return ((Malloc_t)(p + CHUNK_SHIFT));
}

static char *last_sbrk_top;
static char *last_op;			/* This arena can be easily extended. */
static MEM_SIZE sbrked_remains;

#ifdef DEBUGGING_MSTATS
static int sbrks;
#endif 

struct chunk_chain_s {
    struct chunk_chain_s *next;
    MEM_SIZE size;
};
static struct chunk_chain_s *chunk_chain;
static int n_chunks;
static char max_bucket;

/* Cutoff a piece of one of the chunks in the chain.  Prefer smaller chunk. */
static void *
get_from_chain(MEM_SIZE size)
{
    struct chunk_chain_s *elt = chunk_chain, **oldp = &chunk_chain;
    struct chunk_chain_s **oldgoodp = NULL;
    long min_remain = LONG_MAX;

    while (elt) {
	if (elt->size >= size) {
	    long remains = elt->size - size;
	    if (remains >= 0 && remains < min_remain) {
		oldgoodp = oldp;
		min_remain = remains;
	    }
	    if (remains == 0) {
		break;
	    }
	}
	oldp = &( elt->next );
	elt = elt->next;
    }
    if (!oldgoodp) return NULL;
    if (min_remain) {
	void *ret = *oldgoodp;
	struct chunk_chain_s *next = (*oldgoodp)->next;
	
	*oldgoodp = (struct chunk_chain_s *)((char*)ret + size);
	(*oldgoodp)->size = min_remain;
	(*oldgoodp)->next = next;
	return ret;
    } else {
	void *ret = *oldgoodp;
	*oldgoodp = (*oldgoodp)->next;
	n_chunks--;
	return ret;
    }
}

static void
add_to_chain(void *p, MEM_SIZE size, MEM_SIZE chip)
{
    struct chunk_chain_s *next = chunk_chain;
    char *cp = (char*)p;
    
    cp += chip;
    chunk_chain = (struct chunk_chain_s *)cp;
    chunk_chain->size = size - chip;
    chunk_chain->next = next;
    n_chunks++;
}

static void *
get_from_bigger_buckets(int bucket, MEM_SIZE size)
{
    int price = 1;
    static int bucketprice[NBUCKETS];
    while (bucket <= max_bucket) {
	/* We postpone stealing from bigger buckets until we want it
	   often enough. */
	if (nextf[bucket] && bucketprice[bucket]++ >= price) {
	    /* Steal it! */
	    void *ret = (void*)(nextf[bucket] - 1 + CHUNK_SHIFT);
	    bucketprice[bucket] = 0;
	    if (((char*)nextf[bucket]) - M_OVERHEAD == last_op) {
		last_op = NULL;		/* Disable optimization */
	    }
	    nextf[bucket] = nextf[bucket]->ov_next;
#ifdef DEBUGGING_MSTATS
	    nmalloc[bucket]--;
	    start_slack -= M_OVERHEAD;
#endif 
	    add_to_chain(ret, (BUCKET_SIZE(bucket) +
			       POW2_OPTIMIZE_SURPLUS(bucket)), 
			 size);
	    return ret;
	}
	bucket++;
    }
    return NULL;
}

static union overhead *
getpages(MEM_SIZE needed, int *nblksp, int bucket)
{
    /* Need to do (possibly expensive) system call. Try to
       optimize it for rare calling. */
    MEM_SIZE require = needed - sbrked_remains;
    char *cp;
    union overhead *ovp;
    MEM_SIZE slack = 0;

    if (sbrk_goodness > 0) {
	if (!last_sbrk_top && require < FIRST_SBRK) 
	    require = FIRST_SBRK;
	else if (require < MIN_SBRK) require = MIN_SBRK;

	if (require < goodsbrk * MIN_SBRK_FRAC1000 / 1000)
	    require = goodsbrk * MIN_SBRK_FRAC1000 / 1000;
	require = ((require - 1 + MIN_SBRK) / MIN_SBRK) * MIN_SBRK;
    } else {
	require = needed;
	last_sbrk_top = 0;
	sbrked_remains = 0;
    }

    DEBUG_m(PerlIO_printf(Perl_debug_log, 
			  "sbrk(%ld) for %ld-byte-long arena\n",
			  (long)require, (long) needed));
    cp = (char *)sbrk(require);
#ifdef DEBUGGING_MSTATS
    sbrks++;
#endif 
    if (cp == last_sbrk_top) {
	/* Common case, anything is fine. */
	sbrk_goodness++;
	ovp = (union overhead *) (cp - sbrked_remains);
	last_op = cp - sbrked_remains;
	sbrked_remains = require - (needed - sbrked_remains);
    } else if (cp == (char *)-1) { /* no more room! */
	ovp = (union overhead *)emergency_sbrk(needed);
	if (ovp == (union overhead *)-1)
	    return 0;
	if (((char*)ovp) > last_op) {	/* Cannot happen with current emergency_sbrk() */
	    last_op = 0;
	}
	return ovp;
    } else {			/* Non-continuous or first sbrk(). */
	long add = sbrked_remains;
	char *newcp;

	if (sbrked_remains) {	/* Put rest into chain, we
				   cannot use it right now. */
	    add_to_chain((void*)(last_sbrk_top - sbrked_remains),
			 sbrked_remains, 0);
	}

	/* Second, check alignment. */
	slack = 0;

#if !defined(atarist) && !defined(__MINT__) /* on the atari we dont have to worry about this */
#  ifndef I286 	/* The sbrk(0) call on the I286 always returns the next segment */
	/* WANTED_ALIGNMENT may be more than NEEDED_ALIGNMENT, but this may
	   improve performance of memory access. */
	if (PTR2UV(cp) & (WANTED_ALIGNMENT - 1)) { /* Not aligned. */
	    slack = WANTED_ALIGNMENT - (PTR2UV(cp) & (WANTED_ALIGNMENT - 1));
	    add += slack;
	}
#  endif
#endif /* !atarist && !MINT */
		
	if (add) {
	    DEBUG_m(PerlIO_printf(Perl_debug_log, 
				  "sbrk(%ld) to fix non-continuous/off-page sbrk:\n\t%ld for alignement,\t%ld were assumed to come from the tail of the previous sbrk\n",
				  (long)add, (long) slack,
				  (long) sbrked_remains));
	    newcp = (char *)sbrk(add);
#if defined(DEBUGGING_MSTATS)
	    sbrks++;
	    sbrk_slack += add;
#endif
	    if (newcp != cp + require) {
		/* Too bad: even rounding sbrk() is not continuous.*/
		DEBUG_m(PerlIO_printf(Perl_debug_log, 
				      "failed to fix bad sbrk()\n"));
#ifdef PACK_MALLOC
		if (slack) {
		    MALLOC_UNLOCK;
		    fatalcroak("panic: Off-page sbrk\n");
		}
#endif
		if (sbrked_remains) {
		    /* Try again. */
#if defined(DEBUGGING_MSTATS)
		    sbrk_slack += require;
#endif
		    require = needed;
		    DEBUG_m(PerlIO_printf(Perl_debug_log, 
					  "straight sbrk(%ld)\n",
					  (long)require));
		    cp = (char *)sbrk(require);
#ifdef DEBUGGING_MSTATS
		    sbrks++;
#endif 
		    if (cp == (char *)-1)
			return 0;
		}
		sbrk_goodness = -1;	/* Disable optimization!
				   Continue with not-aligned... */
	    } else {
		cp += slack;
		require += sbrked_remains;
	    }
	}

	if (last_sbrk_top) {
	    sbrk_goodness -= SBRK_FAILURE_PRICE;
	}

	ovp = (union overhead *) cp;
	/*
	 * Round up to minimum allocation size boundary
	 * and deduct from block count to reflect.
	 */

#  if NEEDED_ALIGNMENT > MEM_ALIGNBYTES
	if (PTR2UV(ovp) & (NEEDED_ALIGNMENT - 1))
	    fatalcroak("Misalignment of sbrk()\n");
	else
#  endif
#ifndef I286	/* Again, this should always be ok on an 80286 */
	if (PTR2UV(ovp) & (MEM_ALIGNBYTES - 1)) {
	    DEBUG_m(PerlIO_printf(Perl_debug_log, 
				  "fixing sbrk(): %d bytes off machine alignement\n",
				  (int)(PTR2UV(ovp) & (MEM_ALIGNBYTES - 1))));
	    ovp = INT2PTR(union overhead *,(PTR2UV(ovp) + MEM_ALIGNBYTES) &
				     (MEM_ALIGNBYTES - 1));
	    (*nblksp)--;
# if defined(DEBUGGING_MSTATS)
	    /* This is only approx. if TWO_POT_OPTIMIZE: */
	    sbrk_slack += (1 << (bucket >> BUCKET_POW2_SHIFT));
# endif
	}
#endif
	;				/* Finish `else' */
	sbrked_remains = require - needed;
	last_op = cp;
    }
#if !defined(PLAIN_MALLOC) && !defined(NO_FANCY_MALLOC)
    emergency_buffer_last_req = 0;
#endif
    last_sbrk_top = cp + require;
#ifdef DEBUGGING_MSTATS
    goodsbrk += require;
#endif	
    return ovp;
}

static int
getpages_adjacent(MEM_SIZE require)
{	    
    if (require <= sbrked_remains) {
	sbrked_remains -= require;
    } else {
	char *cp;

	require -= sbrked_remains;
	/* We do not try to optimize sbrks here, we go for place. */
	cp = (char*) sbrk(require);
#ifdef DEBUGGING_MSTATS
	sbrks++;
	goodsbrk += require;
#endif 
	if (cp == last_sbrk_top) {
	    sbrked_remains = 0;
	    last_sbrk_top = cp + require;
	} else {
	    if (cp == (char*)-1) {	/* Out of memory */
#ifdef DEBUGGING_MSTATS
		goodsbrk -= require;
#endif
		return 0;
	    }
	    /* Report the failure: */
	    if (sbrked_remains)
		add_to_chain((void*)(last_sbrk_top - sbrked_remains),
			     sbrked_remains, 0);
	    add_to_chain((void*)cp, require, 0);
	    sbrk_goodness -= SBRK_FAILURE_PRICE;
	    sbrked_remains = 0;
	    last_sbrk_top = 0;
	    last_op = 0;
	    return 0;
	}
    }
	    
    return 1;
}

/*
 * Allocate more memory to the indicated bucket.
 */
static void
morecore(register int bucket)
{
  	register union overhead *ovp;
  	register int rnu;       /* 2^rnu bytes will be requested */
  	int nblks;		/* become nblks blocks of the desired size */
	register MEM_SIZE siz, needed;
	static int were_called = 0;

  	if (nextf[bucket])
  		return;
#ifndef NO_PERL_MALLOC_ENV
	if (!were_called) {
	    /* It's the our first time.  Initialize ourselves */
	    were_called = 1;	/* Avoid a loop */
	    if (!MallocCfg[MallocCfg_skip_cfg_env]) {
		char *s = getenv("PERL_MALLOC_OPT"), *t = s, *off;
		const char *opts = PERL_MALLOC_OPT_CHARS;
		int changed = 0;

		while ( t && t[0] && t[1] == '='
			&& ((off = strchr(opts, *t))) ) {
		    IV val = 0;

		    t += 2;
		    while (*t <= '9' && *t >= '0')
			val = 10*val + *t++ - '0';
		    if (!*t || *t == ';') {
			if (MallocCfg[off - opts] != val)
			    changed = 1;
			MallocCfg[off - opts] = val;
			if (*t)
			    t++;
		    }
		}
		if (t && *t) {
		    write2("Unrecognized part of PERL_MALLOC_OPT: `");
		    write2(t);
		    write2("'\n");
		}
		if (changed)
		    MallocCfg[MallocCfg_cfg_env_read] = 1;
	    }
	}
#endif
	if (bucket == sizeof(MEM_SIZE)*8*BUCKETS_PER_POW2) {
	    MALLOC_UNLOCK;
	    croak("%s", "Out of memory during ridiculously large request");
	}
	if (bucket > max_bucket)
	    max_bucket = bucket;

  	rnu = ( (bucket <= (LOG_OF_MIN_ARENA << BUCKET_POW2_SHIFT)) 
		? LOG_OF_MIN_ARENA 
		: (bucket >> BUCKET_POW2_SHIFT) );
	/* This may be overwritten later: */
  	nblks = 1 << (rnu - (bucket >> BUCKET_POW2_SHIFT)); /* how many blocks to get */
	needed = ((MEM_SIZE)1 << rnu) + POW2_OPTIMIZE_SURPLUS(bucket);
	if (nextf[rnu << BUCKET_POW2_SHIFT]) { /* 2048b bucket. */
	    ovp = nextf[rnu << BUCKET_POW2_SHIFT] - 1 + CHUNK_SHIFT;
	    nextf[rnu << BUCKET_POW2_SHIFT]
		= nextf[rnu << BUCKET_POW2_SHIFT]->ov_next;
#ifdef DEBUGGING_MSTATS
	    nmalloc[rnu << BUCKET_POW2_SHIFT]--;
	    start_slack -= M_OVERHEAD;
#endif 
	    DEBUG_m(PerlIO_printf(Perl_debug_log, 
				  "stealing %ld bytes from %ld arena\n",
				  (long) needed, (long) rnu << BUCKET_POW2_SHIFT));
	} else if (chunk_chain 
		   && (ovp = (union overhead*) get_from_chain(needed))) {
	    DEBUG_m(PerlIO_printf(Perl_debug_log, 
				  "stealing %ld bytes from chain\n",
				  (long) needed));
	} else if ( (ovp = (union overhead*)
		     get_from_bigger_buckets((rnu << BUCKET_POW2_SHIFT) + 1,
					     needed)) ) {
	    DEBUG_m(PerlIO_printf(Perl_debug_log, 
				  "stealing %ld bytes from bigger buckets\n",
				  (long) needed));
	} else if (needed <= sbrked_remains) {
	    ovp = (union overhead *)(last_sbrk_top - sbrked_remains);
	    sbrked_remains -= needed;
	    last_op = (char*)ovp;
	} else 
	    ovp = getpages(needed, &nblks, bucket);

	if (!ovp)
	    return;
	FILL_DEADBEEF((unsigned char*)ovp, needed);

	/*
	 * Add new memory allocated to that on
	 * free list for this hash bucket.
	 */
  	siz = BUCKET_SIZE(bucket);
#ifdef PACK_MALLOC
	*(u_char*)ovp = bucket;	/* Fill index. */
	if (bucket <= MAX_PACKED) {
	    ovp = (union overhead *) ((char*)ovp + BLK_SHIFT(bucket));
	    nblks = N_BLKS(bucket);
#  ifdef DEBUGGING_MSTATS
	    start_slack += BLK_SHIFT(bucket);
#  endif
	} else if (bucket < LOG_OF_MIN_ARENA * BUCKETS_PER_POW2) {
	    ovp = (union overhead *) ((char*)ovp + BLK_SHIFT(bucket));
	    siz -= sizeof(union overhead);
	} else ovp++;		/* One chunk per block. */
#endif /* PACK_MALLOC */
  	nextf[bucket] = ovp;
#ifdef DEBUGGING_MSTATS
	nmalloc[bucket] += nblks;
	if (bucket > MAX_PACKED) {
	    start_slack += M_OVERHEAD * nblks;
	}
#endif 

  	while (--nblks > 0) {
		ovp->ov_next = (union overhead *)((caddr_t)ovp + siz);
		ovp = (union overhead *)((caddr_t)ovp + siz);
  	}
	/* Not all sbrks return zeroed memory.*/
	ovp->ov_next = (union overhead *)NULL;
#ifdef PACK_MALLOC
	if (bucket == 7*BUCKETS_PER_POW2) { /* Special case, explanation is above. */
	    union overhead *n_op = nextf[7*BUCKETS_PER_POW2]->ov_next;
	    nextf[7*BUCKETS_PER_POW2] = 
		(union overhead *)((caddr_t)nextf[7*BUCKETS_PER_POW2] 
				   - sizeof(union overhead));
	    nextf[7*BUCKETS_PER_POW2]->ov_next = n_op;
	}
#endif /* !PACK_MALLOC */
}

Free_t
Perl_mfree(void *mp)
{
  	register MEM_SIZE size;
	register union overhead *ovp;
	char *cp = (char*)mp;
#ifdef PACK_MALLOC
	u_char bucket;
#endif 

	DEBUG_m(PerlIO_printf(Perl_debug_log, 
			      "0x%"UVxf": (%05lu) free\n",
			      PTR2UV(cp), (unsigned long)(PL_an++)));

	if (cp == NULL)
		return;
#ifdef DEBUGGING
	if (PTR2UV(cp) & (MEM_ALIGNBYTES - 1))
	    croak("%s", "wrong alignment in free()");
#endif
	ovp = (union overhead *)((caddr_t)cp 
				- sizeof (union overhead) * CHUNK_SHIFT);
#ifdef PACK_MALLOC
	bucket = OV_INDEX(ovp);
#endif 
#ifdef IGNORE_SMALL_BAD_FREE
	if ((bucket >= FIRST_BUCKET_WITH_CHECK) 
	    && (OV_MAGIC(ovp, bucket) != MAGIC))
#else
	if (OV_MAGIC(ovp, bucket) != MAGIC)
#endif 
	    {
		static int bad_free_warn = -1;
		if (bad_free_warn == -1) {
		    dTHX;
		    char *pbf = PerlEnv_getenv("PERL_BADFREE");
		    bad_free_warn = (pbf) ? atoi(pbf) : 1;
		}
		if (!bad_free_warn)
		    return;
#ifdef RCHECK
#ifdef PERL_CORE
		{
		    dTHX;
		    if (!PERL_IS_ALIVE || !PL_curcop || ckWARN_d(WARN_MALLOC))
			Perl_warner(aTHX_ packWARN(WARN_MALLOC), "%s free() ignored (RMAGIC, PERL_CORE)",
				    ovp->ov_rmagic == RMAGIC - 1 ?
				    "Duplicate" : "Bad");
		}
#else
		warn("%s free() ignored (RMAGIC)",
		    ovp->ov_rmagic == RMAGIC - 1 ? "Duplicate" : "Bad");
#endif		
#else
#ifdef PERL_CORE
		{
		    dTHX;
		    if (!PERL_IS_ALIVE || !PL_curcop || ckWARN_d(WARN_MALLOC))
			Perl_warner(aTHX_ packWARN(WARN_MALLOC), "%s", "Bad free() ignored (PERL_CORE)");
		}
#else
		warn("%s", "Bad free() ignored");
#endif
#endif
		return;				/* sanity */
	    }
#ifdef RCHECK
  	ASSERT(ovp->ov_rmagic == RMAGIC, "chunk's head overwrite");
	if (OV_INDEX(ovp) <= MAX_SHORT_BUCKET) {
	    int i;
	    MEM_SIZE nbytes = ovp->ov_size + 1;

	    if ((i = nbytes & 3)) {
		i = 4 - i;
		while (i--) {
		    ASSERT(*((char *)((caddr_t)ovp + nbytes - RSLOP + i))
			   == RMAGIC_C, "chunk's tail overwrite");
		}
	    }
	    nbytes = (nbytes + 3) &~ 3; 
	    ASSERT(*(u_int *)((caddr_t)ovp + nbytes - RSLOP) == RMAGIC, "chunk's tail overwrite");	    
	    FILLCHECK_DEADBEEF((unsigned char*)((caddr_t)ovp + nbytes - RSLOP + sizeof(u_int)),
			       BUCKET_SIZE_REAL(OV_INDEX(ovp)) - (nbytes - RSLOP + sizeof(u_int)));
	}
	FILL_DEADBEEF((unsigned char*)(ovp+1), BUCKET_SIZE_REAL(OV_INDEX(ovp)));
	ovp->ov_rmagic = RMAGIC - 1;
#endif
  	ASSERT(OV_INDEX(ovp) < NBUCKETS, "chunk's head overwrite");
  	size = OV_INDEX(ovp);

	MALLOC_LOCK;
	ovp->ov_next = nextf[size];
  	nextf[size] = ovp;
	MALLOC_UNLOCK;
}

/* There is no need to do any locking in realloc (with an exception of
   trying to grow in place if we are at the end of the chain).
   If somebody calls us from a different thread with the same address,
   we are sole anyway.  */

Malloc_t
Perl_realloc(void *mp, size_t nbytes)
{
  	register MEM_SIZE onb;
	union overhead *ovp;
  	char *res;
	int prev_bucket;
	register int bucket;
	int incr;		/* 1 if does not fit, -1 if "easily" fits in a
				   smaller bucket, otherwise 0.  */
	char *cp = (char*)mp;

#if defined(DEBUGGING) || !defined(PERL_CORE)
	MEM_SIZE size = nbytes;

	if ((long)nbytes < 0)
	    croak("%s", "panic: realloc");
#endif

	BARK_64K_LIMIT("Reallocation",nbytes,size);
	if (!cp)
		return Perl_malloc(nbytes);

	ovp = (union overhead *)((caddr_t)cp 
				- sizeof (union overhead) * CHUNK_SHIFT);
	bucket = OV_INDEX(ovp);

#ifdef IGNORE_SMALL_BAD_FREE
	if ((bucket >= FIRST_BUCKET_WITH_CHECK) 
	    && (OV_MAGIC(ovp, bucket) != MAGIC))
#else
	if (OV_MAGIC(ovp, bucket) != MAGIC)
#endif 
	    {
		static int bad_free_warn = -1;
		if (bad_free_warn == -1) {
		    dTHX;
		    char *pbf = PerlEnv_getenv("PERL_BADFREE");
		    bad_free_warn = (pbf) ? atoi(pbf) : 1;
		}
		if (!bad_free_warn)
		    return Nullch;
#ifdef RCHECK
#ifdef PERL_CORE
		{
		    dTHX;
		    if (!PERL_IS_ALIVE || !PL_curcop || ckWARN_d(WARN_MALLOC))
			Perl_warner(aTHX_ packWARN(WARN_MALLOC), "%srealloc() %signored",
				    (ovp->ov_rmagic == RMAGIC - 1 ? "" : "Bad "),
				    ovp->ov_rmagic == RMAGIC - 1
				    ? "of freed memory " : "");
		}
#else
		warn2("%srealloc() %signored",
		      (ovp->ov_rmagic == RMAGIC - 1 ? "" : "Bad "),
		      ovp->ov_rmagic == RMAGIC - 1 ? "of freed memory " : "");
#endif
#else
#ifdef PERL_CORE
		{
		    dTHX;
		    if (!PERL_IS_ALIVE || !PL_curcop || ckWARN_d(WARN_MALLOC))
			Perl_warner(aTHX_ packWARN(WARN_MALLOC), "%s",
				    "Bad realloc() ignored");
		}
#else
		warn("%s", "Bad realloc() ignored");
#endif
#endif
		return Nullch;			/* sanity */
	    }

	onb = BUCKET_SIZE_REAL(bucket);
	/* 
	 *  avoid the copy if same size block.
	 *  We are not agressive with boundary cases. Note that it might
	 *  (for a small number of cases) give false negative if
	 *  both new size and old one are in the bucket for
	 *  FIRST_BIG_POW2, but the new one is near the lower end.
	 *
	 *  We do not try to go to 1.5 times smaller bucket so far.
	 */
	if (nbytes > onb) incr = 1;
	else {
#ifdef DO_NOT_TRY_HARDER_WHEN_SHRINKING
	    if ( /* This is a little bit pessimal if PACK_MALLOC: */
		nbytes > ( (onb >> 1) - M_OVERHEAD )
#  ifdef TWO_POT_OPTIMIZE
		|| (bucket == FIRST_BIG_POW2 && nbytes >= LAST_SMALL_BOUND )
#  endif	
		)
#else  /* !DO_NOT_TRY_HARDER_WHEN_SHRINKING */
		prev_bucket = ( (bucket > MAX_PACKED + 1) 
				? bucket - BUCKETS_PER_POW2
				: bucket - 1);
	     if (nbytes > BUCKET_SIZE_REAL(prev_bucket))
#endif /* !DO_NOT_TRY_HARDER_WHEN_SHRINKING */
		 incr = 0;
	     else incr = -1;
	}
#ifdef STRESS_REALLOC
	goto hard_way;
#endif
	if (incr == 0) {
	  inplace_label:
#ifdef RCHECK
		/*
		 * Record new allocated size of block and
		 * bound space with magic numbers.
		 */
		if (OV_INDEX(ovp) <= MAX_SHORT_BUCKET) {
		       int i, nb = ovp->ov_size + 1;

		       if ((i = nb & 3)) {
			   i = 4 - i;
			   while (i--) {
			       ASSERT(*((char *)((caddr_t)ovp + nb - RSLOP + i)) == RMAGIC_C, "chunk's tail overwrite");
			   }
		       }
		       nb = (nb + 3) &~ 3; 
		       ASSERT(*(u_int *)((caddr_t)ovp + nb - RSLOP) == RMAGIC, "chunk's tail overwrite");
		       FILLCHECK_DEADBEEF((unsigned char*)((caddr_t)ovp + nb - RSLOP + sizeof(u_int)),
			       BUCKET_SIZE_REAL(OV_INDEX(ovp)) - (nb - RSLOP + sizeof(u_int)));
		       if (nbytes > ovp->ov_size + 1 - M_OVERHEAD)
			   FILL_FEEDADAD((unsigned char*)cp + ovp->ov_size + 1 - M_OVERHEAD,
				     nbytes - (ovp->ov_size + 1 - M_OVERHEAD));
		       else
			   FILL_DEADBEEF((unsigned char*)cp + nbytes,
					 nb - M_OVERHEAD + RSLOP - nbytes);
			/*
			 * Convert amount of memory requested into
			 * closest block size stored in hash buckets
			 * which satisfies request.  Account for
			 * space used per block for accounting.
			 */
			nbytes += M_OVERHEAD;
			ovp->ov_size = nbytes - 1;
			if ((i = nbytes & 3)) {
			    i = 4 - i;
			    while (i--)
				*((char *)((caddr_t)ovp + nbytes - RSLOP + i))
				    = RMAGIC_C;
			}
			nbytes = (nbytes + 3) &~ 3; 
			*((u_int *)((caddr_t)ovp + nbytes - RSLOP)) = RMAGIC;
		}
#endif
		res = cp;
		DEBUG_m(PerlIO_printf(Perl_debug_log, 
			      "0x%"UVxf": (%05lu) realloc %ld bytes inplace\n",
			      PTR2UV(res),(unsigned long)(PL_an++),
			      (long)size));
	} else if (incr == 1 && (cp - M_OVERHEAD == last_op) 
		   && (onb > (1 << LOG_OF_MIN_ARENA))) {
	    MEM_SIZE require, newarena = nbytes, pow;
	    int shiftr;

	    POW2_OPTIMIZE_ADJUST(newarena);
	    newarena = newarena + M_OVERHEAD;
	    /* newarena = (newarena + 3) &~ 3; */
	    shiftr = (newarena - 1) >> LOG_OF_MIN_ARENA;
	    pow = LOG_OF_MIN_ARENA + 1;
	    /* apart from this loop, this is O(1) */
	    while (shiftr >>= 1)
  		pow++;
	    newarena = (1 << pow) + POW2_OPTIMIZE_SURPLUS(pow * BUCKETS_PER_POW2);
	    require = newarena - onb - M_OVERHEAD;
	    
	    MALLOC_LOCK;
	    if (cp - M_OVERHEAD == last_op /* We *still* are the last chunk */
		&& getpages_adjacent(require)) {
#ifdef DEBUGGING_MSTATS
		nmalloc[bucket]--;
		nmalloc[pow * BUCKETS_PER_POW2]++;
#endif 	    
		*(cp - M_OVERHEAD) = pow * BUCKETS_PER_POW2; /* Fill index. */
		MALLOC_UNLOCK;
		goto inplace_label;
	    } else {
		MALLOC_UNLOCK;		
		goto hard_way;
	    }
	} else {
	  hard_way:
	    DEBUG_m(PerlIO_printf(Perl_debug_log, 
			      "0x%"UVxf": (%05lu) realloc %ld bytes the hard way\n",
			      PTR2UV(cp),(unsigned long)(PL_an++),
			      (long)size));
	    if ((res = (char*)Perl_malloc(nbytes)) == NULL)
		return (NULL);
	    if (cp != res)			/* common optimization */
		Copy(cp, res, (MEM_SIZE)(nbytes<onb?nbytes:onb), char);
	    Perl_mfree(cp);
	}
  	return ((Malloc_t)res);
}

Malloc_t
Perl_calloc(register size_t elements, register size_t size)
{
    long sz = elements * size;
    Malloc_t p = Perl_malloc(sz);

    if (p) {
	memset((void*)p, 0, sz);
    }
    return p;
}

char *
Perl_strdup(const char *s)
{
    MEM_SIZE l = strlen(s);
    char *s1 = (char *)Perl_malloc(l+1);

    Copy(s, s1, (MEM_SIZE)(l+1), char);
    return s1;
}

#ifdef PERL_CORE
int
Perl_putenv(char *a)
{
    /* Sometimes system's putenv conflicts with my_setenv() - this is system
       malloc vs Perl's free(). */
  dTHX;
  char *var;
  char *val = a;
  MEM_SIZE l;
  char buf[80];

  while (*val && *val != '=')
      val++;
  if (!*val)
      return -1;
  l = val - a;
  if (l < sizeof(buf))
      var = buf;
  else
      var = Perl_malloc(l + 1);
  Copy(a, var, l, char);
  var[l + 1] = 0;
  my_setenv(var, val+1);
  if (var != buf)
      Perl_mfree(var);
  return 0;
}
#  endif

MEM_SIZE
Perl_malloced_size(void *p)
{
    union overhead *ovp = (union overhead *)
	((caddr_t)p - sizeof (union overhead) * CHUNK_SHIFT);
    int bucket = OV_INDEX(ovp);
#ifdef RCHECK
    /* The caller wants to have a complete control over the chunk,
       disable the memory checking inside the chunk.  */
    if (bucket <= MAX_SHORT_BUCKET) {
	MEM_SIZE size = BUCKET_SIZE_REAL(bucket);
	ovp->ov_size = size + M_OVERHEAD - 1;
	*((u_int *)((caddr_t)ovp + size + M_OVERHEAD - RSLOP)) = RMAGIC;
    }
#endif
    return BUCKET_SIZE_REAL(bucket);
}

#  ifdef BUCKETS_ROOT2
#    define MIN_EVEN_REPORT 6
#  else
#    define MIN_EVEN_REPORT MIN_BUCKET
#  endif 

int
Perl_get_mstats(pTHX_ perl_mstats_t *buf, int buflen, int level)
{
#ifdef DEBUGGING_MSTATS
  	register int i, j;
  	register union overhead *p;
	struct chunk_chain_s* nextchain;

  	buf->topbucket = buf->topbucket_ev = buf->topbucket_odd 
	    = buf->totfree = buf->total = buf->total_chain = 0;

	buf->minbucket = MIN_BUCKET;
	MALLOC_LOCK;
  	for (i = MIN_BUCKET ; i < NBUCKETS; i++) {
  		for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
  			;
		if (i < buflen) {
		    buf->nfree[i] = j;
		    buf->ntotal[i] = nmalloc[i];
		}		
  		buf->totfree += j * BUCKET_SIZE_REAL(i);
  		buf->total += nmalloc[i] * BUCKET_SIZE_REAL(i);
		if (nmalloc[i]) {
		    i % 2 ? (buf->topbucket_odd = i) : (buf->topbucket_ev = i);
		    buf->topbucket = i;
		}
  	}
	nextchain = chunk_chain;
	while (nextchain) {
	    buf->total_chain += nextchain->size;
	    nextchain = nextchain->next;
	}
	buf->total_sbrk = goodsbrk + sbrk_slack;
	buf->sbrks = sbrks;
	buf->sbrk_good = sbrk_goodness;
	buf->sbrk_slack = sbrk_slack;
	buf->start_slack = start_slack;
	buf->sbrked_remains = sbrked_remains;
	MALLOC_UNLOCK;
	buf->nbuckets = NBUCKETS;
	if (level) {
	    for (i = MIN_BUCKET ; i < NBUCKETS; i++) {
		if (i >= buflen)
		    break;
		buf->bucket_mem_size[i] = BUCKET_SIZE(i);
		buf->bucket_available_size[i] = BUCKET_SIZE_REAL(i);
	    }
	}
#endif	/* defined DEBUGGING_MSTATS */
	return 0;		/* XXX unused */
}
/*
 * mstats - print out statistics about malloc
 * 
 * Prints two lines of numbers, one showing the length of the free list
 * for each size category, the second showing the number of mallocs -
 * frees for each size category.
 */
void
Perl_dump_mstats(pTHX_ char *s)
{
#ifdef DEBUGGING_MSTATS
  	register int i;
	perl_mstats_t buffer;
	UV nf[NBUCKETS];
	UV nt[NBUCKETS];

	buffer.nfree  = nf;
	buffer.ntotal = nt;
	get_mstats(&buffer, NBUCKETS, 0);

  	if (s)
	    PerlIO_printf(Perl_error_log,
			  "Memory allocation statistics %s (buckets %"IVdf"(%"IVdf")..%"IVdf"(%"IVdf")\n",
			  s, 
			  (IV)BUCKET_SIZE_REAL(MIN_BUCKET), 
			  (IV)BUCKET_SIZE(MIN_BUCKET),
			  (IV)BUCKET_SIZE_REAL(buffer.topbucket), 
			  (IV)BUCKET_SIZE(buffer.topbucket));
  	PerlIO_printf(Perl_error_log, "%8"IVdf" free:", buffer.totfree);
  	for (i = MIN_EVEN_REPORT; i <= buffer.topbucket; i += BUCKETS_PER_POW2) {
  		PerlIO_printf(Perl_error_log, 
			      ((i < 8*BUCKETS_PER_POW2 || i == 10*BUCKETS_PER_POW2)
			       ? " %5"UVuf 
			       : ((i < 12*BUCKETS_PER_POW2) ? " %3"UVuf : " %"UVuf)),
			      buffer.nfree[i]);
  	}
#ifdef BUCKETS_ROOT2
	PerlIO_printf(Perl_error_log, "\n\t   ");
  	for (i = MIN_BUCKET + 1; i <= buffer.topbucket_odd; i += BUCKETS_PER_POW2) {
  		PerlIO_printf(Perl_error_log, 
			      ((i < 8*BUCKETS_PER_POW2 || i == 10*BUCKETS_PER_POW2)
			       ? " %5"UVuf 
			       : ((i < 12*BUCKETS_PER_POW2) ? " %3"UVuf : " %"UVuf)),
			      buffer.nfree[i]);
  	}
#endif 
  	PerlIO_printf(Perl_error_log, "\n%8"IVdf" used:", buffer.total - buffer.totfree);
  	for (i = MIN_EVEN_REPORT; i <= buffer.topbucket; i += BUCKETS_PER_POW2) {
  		PerlIO_printf(Perl_error_log, 
			      ((i < 8*BUCKETS_PER_POW2 || i == 10*BUCKETS_PER_POW2)
			       ? " %5"IVdf
			       : ((i < 12*BUCKETS_PER_POW2) ? " %3"IVdf : " %"IVdf)), 
			      buffer.ntotal[i] - buffer.nfree[i]);
  	}
#ifdef BUCKETS_ROOT2
	PerlIO_printf(Perl_error_log, "\n\t   ");
  	for (i = MIN_BUCKET + 1; i <= buffer.topbucket_odd; i += BUCKETS_PER_POW2) {
  		PerlIO_printf(Perl_error_log, 
			      ((i < 8*BUCKETS_PER_POW2 || i == 10*BUCKETS_PER_POW2)
			       ? " %5"IVdf 
			       : ((i < 12*BUCKETS_PER_POW2) ? " %3"IVdf : " %"IVdf)),
			      buffer.ntotal[i] - buffer.nfree[i]);
  	}
#endif 
	PerlIO_printf(Perl_error_log, "\nTotal sbrk(): %"IVdf"/%"IVdf":%"IVdf". Odd ends: pad+heads+chain+tail: %"IVdf"+%"IVdf"+%"IVdf"+%"IVdf".\n",
		      buffer.total_sbrk, buffer.sbrks, buffer.sbrk_good,
		      buffer.sbrk_slack, buffer.start_slack,
		      buffer.total_chain, buffer.sbrked_remains);
#endif /* DEBUGGING_MSTATS */
}
#endif /* lint */

#ifdef USE_PERL_SBRK

#   if defined(__MACHTEN_PPC__) || defined(NeXT) || defined(__NeXT__) || defined(PURIFY)
#      define PERL_SBRK_VIA_MALLOC
#   endif

#   ifdef PERL_SBRK_VIA_MALLOC

/* it may seem schizophrenic to use perl's malloc and let it call system */
/* malloc, the reason for that is only the 3.2 version of the OS that had */
/* frequent core dumps within nxzonefreenolock. This sbrk routine put an */
/* end to the cores */

#      ifndef SYSTEM_ALLOC
#         define SYSTEM_ALLOC(a) malloc(a)
#      endif
#      ifndef SYSTEM_ALLOC_ALIGNMENT
#         define SYSTEM_ALLOC_ALIGNMENT MEM_ALIGNBYTES
#      endif

#   endif  /* PERL_SBRK_VIA_MALLOC */

static IV Perl_sbrk_oldchunk;
static long Perl_sbrk_oldsize;

#   define PERLSBRK_32_K (1<<15)
#   define PERLSBRK_64_K (1<<16)

Malloc_t
Perl_sbrk(int size)
{
    IV got;
    int small, reqsize;

    if (!size) return 0;
#ifdef PERL_CORE
    reqsize = size; /* just for the DEBUG_m statement */
#endif
#ifdef PACK_MALLOC
    size = (size + 0x7ff) & ~0x7ff;
#endif
    if (size <= Perl_sbrk_oldsize) {
	got = Perl_sbrk_oldchunk;
	Perl_sbrk_oldchunk += size;
	Perl_sbrk_oldsize -= size;
    } else {
      if (size >= PERLSBRK_32_K) {
	small = 0;
      } else {
	size = PERLSBRK_64_K;
	small = 1;
      }
#  if NEEDED_ALIGNMENT > SYSTEM_ALLOC_ALIGNMENT
      size += NEEDED_ALIGNMENT - SYSTEM_ALLOC_ALIGNMENT;
#  endif
      got = (IV)SYSTEM_ALLOC(size);
#  if NEEDED_ALIGNMENT > SYSTEM_ALLOC_ALIGNMENT
      got = (got + NEEDED_ALIGNMENT - 1) & ~(NEEDED_ALIGNMENT - 1);
#  endif
      if (small) {
	/* Chunk is small, register the rest for future allocs. */
	Perl_sbrk_oldchunk = got + reqsize;
	Perl_sbrk_oldsize = size - reqsize;
      }
    }

    DEBUG_m(PerlIO_printf(Perl_debug_log, "sbrk malloc size %ld (reqsize %ld), left size %ld, give addr 0x%"UVxf"\n",
		    size, reqsize, Perl_sbrk_oldsize, PTR2UV(got)));

    return (void *)got;
}

#endif /* ! defined USE_PERL_SBRK */