malloc.c

俄罗斯高人Mamaich的Pocket gcc编译器（运行在PocketPC上）的全部源代码。

/* 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 <[e-mail]>
   and Doug Lea <[e-mail]>, 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,v 1.1.1.1 2003/08/19 22:29:46 craigv Exp $

  This work is mainly derived from malloc-2.6.4 by Doug Lea
  <[e-mail]>, 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*/

#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.