3 #if 0 /* Moved to malloc.h */
4 /* ---------- To make a malloc.h, start cutting here ------------ */
7 A version of malloc/free/realloc written by Doug Lea and released to the
8 public domain. Send questions/comments/complaints/performance data
11 * VERSION 2.6.6 Sun Mar 5 19:10:03 2000 Doug Lea (dl at gee)
13 Note: There may be an updated version of this malloc obtainable at
14 ftp://g.oswego.edu/pub/misc/malloc.c
15 Check before installing!
17 * Why use this malloc?
19 This is not the fastest, most space-conserving, most portable, or
20 most tunable malloc ever written. However it is among the fastest
21 while also being among the most space-conserving, portable and tunable.
22 Consistent balance across these factors results in a good general-purpose
23 allocator. For a high-level description, see
24 http://g.oswego.edu/dl/html/malloc.html
26 * Synopsis of public routines
28 (Much fuller descriptions are contained in the program documentation below.)
31 Return a pointer to a newly allocated chunk of at least n bytes, or null
32 if no space is available.
34 Release the chunk of memory pointed to by p, or no effect if p is null.
35 realloc(Void_t* p, size_t n);
36 Return a pointer to a chunk of size n that contains the same data
37 as does chunk p up to the minimum of (n, p's size) bytes, or null
38 if no space is available. The returned pointer may or may not be
39 the same as p. If p is null, equivalent to malloc. Unless the
40 #define REALLOC_ZERO_BYTES_FREES below is set, realloc with a
41 size argument of zero (re)allocates a minimum-sized chunk.
42 memalign(size_t alignment, size_t n);
43 Return a pointer to a newly allocated chunk of n bytes, aligned
44 in accord with the alignment argument, which must be a power of
47 Equivalent to memalign(pagesize, n), where pagesize is the page
48 size of the system (or as near to this as can be figured out from
49 all the includes/defines below.)
51 Equivalent to valloc(minimum-page-that-holds(n)), that is,
52 round up n to nearest pagesize.
53 calloc(size_t unit, size_t quantity);
54 Returns a pointer to quantity * unit bytes, with all locations
57 Equivalent to free(p).
58 malloc_trim(size_t pad);
59 Release all but pad bytes of freed top-most memory back
60 to the system. Return 1 if successful, else 0.
61 malloc_usable_size(Void_t* p);
62 Report the number usable allocated bytes associated with allocated
63 chunk p. This may or may not report more bytes than were requested,
64 due to alignment and minimum size constraints.
66 Prints brief summary statistics.
68 Returns (by copy) a struct containing various summary statistics.
69 mallopt(int parameter_number, int parameter_value)
70 Changes one of the tunable parameters described below. Returns
71 1 if successful in changing the parameter, else 0.
76 8 byte alignment is currently hardwired into the design. This
77 seems to suffice for all current machines and C compilers.
79 Assumed pointer representation: 4 or 8 bytes
80 Code for 8-byte pointers is untested by me but has worked
81 reliably by Wolfram Gloger, who contributed most of the
82 changes supporting this.
84 Assumed size_t representation: 4 or 8 bytes
85 Note that size_t is allowed to be 4 bytes even if pointers are 8.
87 Minimum overhead per allocated chunk: 4 or 8 bytes
88 Each malloced chunk has a hidden overhead of 4 bytes holding size
89 and status information.
91 Minimum allocated size: 4-byte ptrs: 16 bytes (including 4 overhead)
92 8-byte ptrs: 24/32 bytes (including, 4/8 overhead)
94 When a chunk is freed, 12 (for 4byte ptrs) or 20 (for 8 byte
95 ptrs but 4 byte size) or 24 (for 8/8) additional bytes are
96 needed; 4 (8) for a trailing size field
97 and 8 (16) bytes for free list pointers. Thus, the minimum
98 allocatable size is 16/24/32 bytes.
100 Even a request for zero bytes (i.e., malloc(0)) returns a
101 pointer to something of the minimum allocatable size.
103 Maximum allocated size: 4-byte size_t: 2^31 - 8 bytes
104 8-byte size_t: 2^63 - 16 bytes
106 It is assumed that (possibly signed) size_t bit values suffice to
107 represent chunk sizes. `Possibly signed' is due to the fact
108 that `size_t' may be defined on a system as either a signed or
109 an unsigned type. To be conservative, values that would appear
110 as negative numbers are avoided.
111 Requests for sizes with a negative sign bit when the request
112 size is treaded as a long will return null.
114 Maximum overhead wastage per allocated chunk: normally 15 bytes
116 Alignnment demands, plus the minimum allocatable size restriction
117 make the normal worst-case wastage 15 bytes (i.e., up to 15
118 more bytes will be allocated than were requested in malloc), with
120 1. Because requests for zero bytes allocate non-zero space,
121 the worst case wastage for a request of zero bytes is 24 bytes.
122 2. For requests >= mmap_threshold that are serviced via
123 mmap(), the worst case wastage is 8 bytes plus the remainder
124 from a system page (the minimal mmap unit); typically 4096 bytes.
128 Here are some features that are NOT currently supported
130 * No user-definable hooks for callbacks and the like.
131 * No automated mechanism for fully checking that all accesses
132 to malloced memory stay within their bounds.
133 * No support for compaction.
135 * Synopsis of compile-time options:
137 People have reported using previous versions of this malloc on all
138 versions of Unix, sometimes by tweaking some of the defines
139 below. It has been tested most extensively on Solaris and
140 Linux. It is also reported to work on WIN32 platforms.
141 People have also reported adapting this malloc for use in
142 stand-alone embedded systems.
144 The implementation is in straight, hand-tuned ANSI C. Among other
145 consequences, it uses a lot of macros. Because of this, to be at
146 all usable, this code should be compiled using an optimizing compiler
147 (for example gcc -O2) that can simplify expressions and control
150 __STD_C (default: derived from C compiler defines)
151 Nonzero if using ANSI-standard C compiler, a C++ compiler, or
152 a C compiler sufficiently close to ANSI to get away with it.
153 DEBUG (default: NOT defined)
154 Define to enable debugging. Adds fairly extensive assertion-based
155 checking to help track down memory errors, but noticeably slows down
157 REALLOC_ZERO_BYTES_FREES (default: NOT defined)
158 Define this if you think that realloc(p, 0) should be equivalent
159 to free(p). Otherwise, since malloc returns a unique pointer for
160 malloc(0), so does realloc(p, 0).
161 HAVE_MEMCPY (default: defined)
162 Define if you are not otherwise using ANSI STD C, but still
163 have memcpy and memset in your C library and want to use them.
164 Otherwise, simple internal versions are supplied.
165 USE_MEMCPY (default: 1 if HAVE_MEMCPY is defined, 0 otherwise)
166 Define as 1 if you want the C library versions of memset and
167 memcpy called in realloc and calloc (otherwise macro versions are used).
168 At least on some platforms, the simple macro versions usually
169 outperform libc versions.
170 HAVE_MMAP (default: defined as 1)
171 Define to non-zero to optionally make malloc() use mmap() to
172 allocate very large blocks.
173 HAVE_MREMAP (default: defined as 0 unless Linux libc set)
174 Define to non-zero to optionally make realloc() use mremap() to
175 reallocate very large blocks.
176 malloc_getpagesize (default: derived from system #includes)
177 Either a constant or routine call returning the system page size.
178 HAVE_USR_INCLUDE_MALLOC_H (default: NOT defined)
179 Optionally define if you are on a system with a /usr/include/malloc.h
180 that declares struct mallinfo. It is not at all necessary to
181 define this even if you do, but will ensure consistency.
182 INTERNAL_SIZE_T (default: size_t)
183 Define to a 32-bit type (probably `unsigned int') if you are on a
184 64-bit machine, yet do not want or need to allow malloc requests of
185 greater than 2^31 to be handled. This saves space, especially for
187 INTERNAL_LINUX_C_LIB (default: NOT defined)
188 Defined only when compiled as part of Linux libc.
189 Also note that there is some odd internal name-mangling via defines
190 (for example, internally, `malloc' is named `mALLOc') needed
191 when compiling in this case. These look funny but don't otherwise
193 WIN32 (default: undefined)
194 Define this on MS win (95, nt) platforms to compile in sbrk emulation.
195 LACKS_UNISTD_H (default: undefined if not WIN32)
196 Define this if your system does not have a <unistd.h>.
197 LACKS_SYS_PARAM_H (default: undefined if not WIN32)
198 Define this if your system does not have a <sys/param.h>.
199 MORECORE (default: sbrk)
200 The name of the routine to call to obtain more memory from the system.
201 MORECORE_FAILURE (default: -1)
202 The value returned upon failure of MORECORE.
203 MORECORE_CLEARS (default 1)
204 true (1) if the routine mapped to MORECORE zeroes out memory (which
206 DEFAULT_TRIM_THRESHOLD
208 DEFAULT_MMAP_THRESHOLD
210 Default values of tunable parameters (described in detail below)
211 controlling interaction with host system routines (sbrk, mmap, etc).
212 These values may also be changed dynamically via mallopt(). The
213 preset defaults are those that give best performance for typical
215 USE_DL_PREFIX (default: undefined)
216 Prefix all public routines with the string 'dl'. Useful to
217 quickly avoid procedure declaration conflicts and linker symbol
218 conflicts with existing memory allocation routines.
235 #endif /*__cplusplus*/
240 #if (__STD_C || defined(WIN32))
248 #include <stddef.h> /* for size_t */
250 #include <sys/types.h>
257 #include <stdio.h> /* needed for malloc_stats */
268 Because freed chunks may be overwritten with link fields, this
269 malloc will often die when freed memory is overwritten by user
270 programs. This can be very effective (albeit in an annoying way)
271 in helping track down dangling pointers.
273 If you compile with -DDEBUG, a number of assertion checks are
274 enabled that will catch more memory errors. You probably won't be
275 able to make much sense of the actual assertion errors, but they
276 should help you locate incorrectly overwritten memory. The
277 checking is fairly extensive, and will slow down execution
278 noticeably. Calling malloc_stats or mallinfo with DEBUG set will
279 attempt to check every non-mmapped allocated and free chunk in the
280 course of computing the summmaries. (By nature, mmapped regions
281 cannot be checked very much automatically.)
283 Setting DEBUG may also be helpful if you are trying to modify
284 this code. The assertions in the check routines spell out in more
285 detail the assumptions and invariants underlying the algorithms.
290 INTERNAL_SIZE_T is the word-size used for internal bookkeeping
291 of chunk sizes. On a 64-bit machine, you can reduce malloc
292 overhead by defining INTERNAL_SIZE_T to be a 32 bit `unsigned int'
293 at the expense of not being able to handle requests greater than
294 2^31. This limitation is hardly ever a concern; you are encouraged
295 to set this. However, the default version is the same as size_t.
298 #ifndef INTERNAL_SIZE_T
299 #define INTERNAL_SIZE_T size_t
303 REALLOC_ZERO_BYTES_FREES should be set if a call to
304 realloc with zero bytes should be the same as a call to free.
305 Some people think it should. Otherwise, since this malloc
306 returns a unique pointer for malloc(0), so does realloc(p, 0).
310 /* #define REALLOC_ZERO_BYTES_FREES */
314 WIN32 causes an emulation of sbrk to be compiled in
315 mmap-based options are not currently supported in WIN32.
320 #define MORECORE wsbrk
323 #define LACKS_UNISTD_H
324 #define LACKS_SYS_PARAM_H
327 Include 'windows.h' to get the necessary declarations for the
328 Microsoft Visual C++ data structures and routines used in the 'sbrk'
331 Define WIN32_LEAN_AND_MEAN so that only the essential Microsoft
332 Visual C++ header files are included.
334 #define WIN32_LEAN_AND_MEAN
340 HAVE_MEMCPY should be defined if you are not otherwise using
341 ANSI STD C, but still have memcpy and memset in your C library
342 and want to use them in calloc and realloc. Otherwise simple
343 macro versions are defined here.
345 USE_MEMCPY should be defined as 1 if you actually want to
346 have memset and memcpy called. People report that the macro
347 versions are often enough faster than libc versions on many
348 systems that it is better to use them.
362 #if (__STD_C || defined(HAVE_MEMCPY))
365 void* memset(void*, int, size_t);
366 void* memcpy(void*, const void*, size_t);
369 /* On Win32 platforms, 'memset()' and 'memcpy()' are already declared in */
380 /* The following macros are only invoked with (2n+1)-multiples of
381 INTERNAL_SIZE_T units, with a positive integer n. This is exploited
382 for fast inline execution when n is small. */
384 #define MALLOC_ZERO(charp, nbytes) \
386 INTERNAL_SIZE_T mzsz = (nbytes); \
387 if(mzsz <= 9*sizeof(mzsz)) { \
388 INTERNAL_SIZE_T* mz = (INTERNAL_SIZE_T*) (charp); \
389 if(mzsz >= 5*sizeof(mzsz)) { *mz++ = 0; \
391 if(mzsz >= 7*sizeof(mzsz)) { *mz++ = 0; \
393 if(mzsz >= 9*sizeof(mzsz)) { *mz++ = 0; \
398 } else memset((charp), 0, mzsz); \
401 #define MALLOC_COPY(dest,src,nbytes) \
403 INTERNAL_SIZE_T mcsz = (nbytes); \
404 if(mcsz <= 9*sizeof(mcsz)) { \
405 INTERNAL_SIZE_T* mcsrc = (INTERNAL_SIZE_T*) (src); \
406 INTERNAL_SIZE_T* mcdst = (INTERNAL_SIZE_T*) (dest); \
407 if(mcsz >= 5*sizeof(mcsz)) { *mcdst++ = *mcsrc++; \
408 *mcdst++ = *mcsrc++; \
409 if(mcsz >= 7*sizeof(mcsz)) { *mcdst++ = *mcsrc++; \
410 *mcdst++ = *mcsrc++; \
411 if(mcsz >= 9*sizeof(mcsz)) { *mcdst++ = *mcsrc++; \
412 *mcdst++ = *mcsrc++; }}} \
413 *mcdst++ = *mcsrc++; \
414 *mcdst++ = *mcsrc++; \
416 } else memcpy(dest, src, mcsz); \
419 #else /* !USE_MEMCPY */
421 /* Use Duff's device for good zeroing/copying performance. */
423 #define MALLOC_ZERO(charp, nbytes) \
425 INTERNAL_SIZE_T* mzp = (INTERNAL_SIZE_T*)(charp); \
426 long mctmp = (nbytes)/sizeof(INTERNAL_SIZE_T), mcn; \
427 if (mctmp < 8) mcn = 0; else { mcn = (mctmp-1)/8; mctmp %= 8; } \
429 case 0: for(;;) { *mzp++ = 0; \
430 case 7: *mzp++ = 0; \
431 case 6: *mzp++ = 0; \
432 case 5: *mzp++ = 0; \
433 case 4: *mzp++ = 0; \
434 case 3: *mzp++ = 0; \
435 case 2: *mzp++ = 0; \
436 case 1: *mzp++ = 0; if(mcn <= 0) break; mcn--; } \
440 #define MALLOC_COPY(dest,src,nbytes) \
442 INTERNAL_SIZE_T* mcsrc = (INTERNAL_SIZE_T*) src; \
443 INTERNAL_SIZE_T* mcdst = (INTERNAL_SIZE_T*) dest; \
444 long mctmp = (nbytes)/sizeof(INTERNAL_SIZE_T), mcn; \
445 if (mctmp < 8) mcn = 0; else { mcn = (mctmp-1)/8; mctmp %= 8; } \
447 case 0: for(;;) { *mcdst++ = *mcsrc++; \
448 case 7: *mcdst++ = *mcsrc++; \
449 case 6: *mcdst++ = *mcsrc++; \
450 case 5: *mcdst++ = *mcsrc++; \
451 case 4: *mcdst++ = *mcsrc++; \
452 case 3: *mcdst++ = *mcsrc++; \
453 case 2: *mcdst++ = *mcsrc++; \
454 case 1: *mcdst++ = *mcsrc++; if(mcn <= 0) break; mcn--; } \
462 Define HAVE_MMAP to optionally make malloc() use mmap() to
463 allocate very large blocks. These will be returned to the
464 operating system immediately after a free().
472 Define HAVE_MREMAP to make realloc() use mremap() to re-allocate
473 large blocks. This is currently only possible on Linux with
474 kernel versions newer than 1.3.77.
478 #ifdef INTERNAL_LINUX_C_LIB
479 #define HAVE_MREMAP 1
481 #define HAVE_MREMAP 0
489 #include <sys/mman.h>
491 #if !defined(MAP_ANONYMOUS) && defined(MAP_ANON)
492 #define MAP_ANONYMOUS MAP_ANON
495 #endif /* HAVE_MMAP */
498 Access to system page size. To the extent possible, this malloc
499 manages memory from the system in page-size units.
501 The following mechanics for getpagesize were adapted from
502 bsd/gnu getpagesize.h
505 #ifndef LACKS_UNISTD_H
509 #ifndef malloc_getpagesize
510 # ifdef _SC_PAGESIZE /* some SVR4 systems omit an underscore */
511 # ifndef _SC_PAGE_SIZE
512 # define _SC_PAGE_SIZE _SC_PAGESIZE
515 # ifdef _SC_PAGE_SIZE
516 # define malloc_getpagesize sysconf(_SC_PAGE_SIZE)
518 # if defined(BSD) || defined(DGUX) || defined(HAVE_GETPAGESIZE)
519 extern size_t getpagesize();
520 # define malloc_getpagesize getpagesize()
523 # define malloc_getpagesize (4096) /* TBD: Use 'GetSystemInfo' instead */
525 # ifndef LACKS_SYS_PARAM_H
526 # include <sys/param.h>
528 # ifdef EXEC_PAGESIZE
529 # define malloc_getpagesize EXEC_PAGESIZE
533 # define malloc_getpagesize NBPG
535 # define malloc_getpagesize (NBPG * CLSIZE)
539 # define malloc_getpagesize NBPC
542 # define malloc_getpagesize PAGESIZE
544 # define malloc_getpagesize (4096) /* just guess */
557 This version of malloc supports the standard SVID/XPG mallinfo
558 routine that returns a struct containing the same kind of
559 information you can get from malloc_stats. It should work on
560 any SVID/XPG compliant system that has a /usr/include/malloc.h
561 defining struct mallinfo. (If you'd like to install such a thing
562 yourself, cut out the preliminary declarations as described above
563 and below and save them in a malloc.h file. But there's no
564 compelling reason to bother to do this.)
566 The main declaration needed is the mallinfo struct that is returned
567 (by-copy) by mallinfo(). The SVID/XPG malloinfo struct contains a
568 bunch of fields, most of which are not even meaningful in this
569 version of malloc. Some of these fields are are instead filled by
570 mallinfo() with other numbers that might possibly be of interest.
572 HAVE_USR_INCLUDE_MALLOC_H should be set if you have a
573 /usr/include/malloc.h file that includes a declaration of struct
574 mallinfo. If so, it is included; else an SVID2/XPG2 compliant
575 version is declared below. These must be precisely the same for
580 /* #define HAVE_USR_INCLUDE_MALLOC_H */
582 #if HAVE_USR_INCLUDE_MALLOC_H
583 #include "/usr/include/malloc.h"
586 /* SVID2/XPG mallinfo structure */
589 int arena; /* total space allocated from system */
590 int ordblks; /* number of non-inuse chunks */
591 int smblks; /* unused -- always zero */
592 int hblks; /* number of mmapped regions */
593 int hblkhd; /* total space in mmapped regions */
594 int usmblks; /* unused -- always zero */
595 int fsmblks; /* unused -- always zero */
596 int uordblks; /* total allocated space */
597 int fordblks; /* total non-inuse space */
598 int keepcost; /* top-most, releasable (via malloc_trim) space */
601 /* SVID2/XPG mallopt options */
603 #define M_MXFAST 1 /* UNUSED in this malloc */
604 #define M_NLBLKS 2 /* UNUSED in this malloc */
605 #define M_GRAIN 3 /* UNUSED in this malloc */
606 #define M_KEEP 4 /* UNUSED in this malloc */
610 /* mallopt options that actually do something */
612 #define M_TRIM_THRESHOLD -1
614 #define M_MMAP_THRESHOLD -3
615 #define M_MMAP_MAX -4
618 #ifndef DEFAULT_TRIM_THRESHOLD
619 #define DEFAULT_TRIM_THRESHOLD (128 * 1024)
623 M_TRIM_THRESHOLD is the maximum amount of unused top-most memory
624 to keep before releasing via malloc_trim in free().
626 Automatic trimming is mainly useful in long-lived programs.
627 Because trimming via sbrk can be slow on some systems, and can
628 sometimes be wasteful (in cases where programs immediately
629 afterward allocate more large chunks) the value should be high
630 enough so that your overall system performance would improve by
633 The trim threshold and the mmap control parameters (see below)
634 can be traded off with one another. Trimming and mmapping are
635 two different ways of releasing unused memory back to the
636 system. Between these two, it is often possible to keep
637 system-level demands of a long-lived program down to a bare
638 minimum. For example, in one test suite of sessions measuring
639 the XF86 X server on Linux, using a trim threshold of 128K and a
640 mmap threshold of 192K led to near-minimal long term resource
643 If you are using this malloc in a long-lived program, it should
644 pay to experiment with these values. As a rough guide, you
645 might set to a value close to the average size of a process
646 (program) running on your system. Releasing this much memory
647 would allow such a process to run in memory. Generally, it's
648 worth it to tune for trimming rather tham memory mapping when a
649 program undergoes phases where several large chunks are
650 allocated and released in ways that can reuse each other's
651 storage, perhaps mixed with phases where there are no such
652 chunks at all. And in well-behaved long-lived programs,
653 controlling release of large blocks via trimming versus mapping
656 However, in most programs, these parameters serve mainly as
657 protection against the system-level effects of carrying around
658 massive amounts of unneeded memory. Since frequent calls to
659 sbrk, mmap, and munmap otherwise degrade performance, the default
660 parameters are set to relatively high values that serve only as
663 The default trim value is high enough to cause trimming only in
664 fairly extreme (by current memory consumption standards) cases.
665 It must be greater than page size to have any useful effect. To
666 disable trimming completely, you can set to (unsigned long)(-1);
672 #ifndef DEFAULT_TOP_PAD
673 #define DEFAULT_TOP_PAD (0)
677 M_TOP_PAD is the amount of extra `padding' space to allocate or
678 retain whenever sbrk is called. It is used in two ways internally:
680 * When sbrk is called to extend the top of the arena to satisfy
681 a new malloc request, this much padding is added to the sbrk
684 * When malloc_trim is called automatically from free(),
685 it is used as the `pad' argument.
687 In both cases, the actual amount of padding is rounded
688 so that the end of the arena is always a system page boundary.
690 The main reason for using padding is to avoid calling sbrk so
691 often. Having even a small pad greatly reduces the likelihood
692 that nearly every malloc request during program start-up (or
693 after trimming) will invoke sbrk, which needlessly wastes
696 Automatic rounding-up to page-size units is normally sufficient
697 to avoid measurable overhead, so the default is 0. However, in
698 systems where sbrk is relatively slow, it can pay to increase
699 this value, at the expense of carrying around more memory than
705 #ifndef DEFAULT_MMAP_THRESHOLD
706 #define DEFAULT_MMAP_THRESHOLD (128 * 1024)
711 M_MMAP_THRESHOLD is the request size threshold for using mmap()
712 to service a request. Requests of at least this size that cannot
713 be allocated using already-existing space will be serviced via mmap.
714 (If enough normal freed space already exists it is used instead.)
716 Using mmap segregates relatively large chunks of memory so that
717 they can be individually obtained and released from the host
718 system. A request serviced through mmap is never reused by any
719 other request (at least not directly; the system may just so
720 happen to remap successive requests to the same locations).
722 Segregating space in this way has the benefit that mmapped space
723 can ALWAYS be individually released back to the system, which
724 helps keep the system level memory demands of a long-lived
725 program low. Mapped memory can never become `locked' between
726 other chunks, as can happen with normally allocated chunks, which
727 menas that even trimming via malloc_trim would not release them.
729 However, it has the disadvantages that:
731 1. The space cannot be reclaimed, consolidated, and then
732 used to service later requests, as happens with normal chunks.
733 2. It can lead to more wastage because of mmap page alignment
735 3. It causes malloc performance to be more dependent on host
736 system memory management support routines which may vary in
737 implementation quality and may impose arbitrary
738 limitations. Generally, servicing a request via normal
739 malloc steps is faster than going through a system's mmap.
741 All together, these considerations should lead you to use mmap
742 only for relatively large requests.
748 #ifndef DEFAULT_MMAP_MAX
750 #define DEFAULT_MMAP_MAX (64)
752 #define DEFAULT_MMAP_MAX (0)
757 M_MMAP_MAX is the maximum number of requests to simultaneously
758 service using mmap. This parameter exists because:
760 1. Some systems have a limited number of internal tables for
762 2. In most systems, overreliance on mmap can degrade overall
764 3. If a program allocates many large regions, it is probably
765 better off using normal sbrk-based allocation routines that
766 can reclaim and reallocate normal heap memory. Using a
767 small value allows transition into this mode after the
768 first few allocations.
770 Setting to 0 disables all use of mmap. If HAVE_MMAP is not set,
771 the default value is 0, and attempts to set it to non-zero values
772 in mallopt will fail.
777 USE_DL_PREFIX will prefix all public routines with the string 'dl'.
778 Useful to quickly avoid procedure declaration conflicts and linker
779 symbol conflicts with existing memory allocation routines.
783 /* #define USE_DL_PREFIX */
788 Special defines for linux libc
790 Except when compiled using these special defines for Linux libc
791 using weak aliases, this malloc is NOT designed to work in
792 multithreaded applications. No semaphores or other concurrency
793 control are provided to ensure that multiple malloc or free calls
794 don't run at the same time, which could be disasterous. A single
795 semaphore could be used across malloc, realloc, and free (which is
796 essentially the effect of the linux weak alias approach). It would
797 be hard to obtain finer granularity.
802 #ifdef INTERNAL_LINUX_C_LIB
806 Void_t * __default_morecore_init (ptrdiff_t);
807 Void_t *(*__morecore)(ptrdiff_t) = __default_morecore_init;
811 Void_t * __default_morecore_init ();
812 Void_t *(*__morecore)() = __default_morecore_init;
816 #define MORECORE (*__morecore)
817 #define MORECORE_FAILURE 0
818 #define MORECORE_CLEARS 1
820 #else /* INTERNAL_LINUX_C_LIB */
823 extern Void_t* sbrk(ptrdiff_t);
825 extern Void_t* sbrk();
829 #define MORECORE sbrk
832 #ifndef MORECORE_FAILURE
833 #define MORECORE_FAILURE -1
836 #ifndef MORECORE_CLEARS
837 #define MORECORE_CLEARS 1
840 #endif /* INTERNAL_LINUX_C_LIB */
842 #if defined(INTERNAL_LINUX_C_LIB) && defined(__ELF__)
844 #define cALLOc __libc_calloc
845 #define fREe __libc_free
846 #define mALLOc __libc_malloc
847 #define mEMALIGn __libc_memalign
848 #define rEALLOc __libc_realloc
849 #define vALLOc __libc_valloc
850 #define pvALLOc __libc_pvalloc
851 #define mALLINFo __libc_mallinfo
852 #define mALLOPt __libc_mallopt
854 #pragma weak calloc = __libc_calloc
855 #pragma weak free = __libc_free
856 #pragma weak cfree = __libc_free
857 #pragma weak malloc = __libc_malloc
858 #pragma weak memalign = __libc_memalign
859 #pragma weak realloc = __libc_realloc
860 #pragma weak valloc = __libc_valloc
861 #pragma weak pvalloc = __libc_pvalloc
862 #pragma weak mallinfo = __libc_mallinfo
863 #pragma weak mallopt = __libc_mallopt
868 #define cALLOc dlcalloc
870 #define mALLOc dlmalloc
871 #define mEMALIGn dlmemalign
872 #define rEALLOc dlrealloc
873 #define vALLOc dlvalloc
874 #define pvALLOc dlpvalloc
875 #define mALLINFo dlmallinfo
876 #define mALLOPt dlmallopt
877 #else /* USE_DL_PREFIX */
878 #define cALLOc calloc
880 #define mALLOc malloc
881 #define mEMALIGn memalign
882 #define rEALLOc realloc
883 #define vALLOc valloc
884 #define pvALLOc pvalloc
885 #define mALLINFo mallinfo
886 #define mALLOPt mallopt
887 #endif /* USE_DL_PREFIX */
891 /* Public routines */
895 Void_t* mALLOc(size_t);
897 Void_t* rEALLOc(Void_t*, size_t);
898 Void_t* mEMALIGn(size_t, size_t);
899 Void_t* vALLOc(size_t);
900 Void_t* pvALLOc(size_t);
901 Void_t* cALLOc(size_t, size_t);
903 int malloc_trim(size_t);
904 size_t malloc_usable_size(Void_t*);
906 int mALLOPt(int, int);
907 struct mallinfo mALLINFo(void);
918 size_t malloc_usable_size();
921 struct mallinfo mALLINFo();
926 }; /* end of extern "C" */
929 /* ---------- To make a malloc.h, end cutting here ------------ */
930 #endif /* 0 */ /* Moved to malloc.h */
937 static void malloc_update_mallinfo (void);
938 void malloc_stats (void);
940 static void malloc_update_mallinfo ();
945 DECLARE_GLOBAL_DATA_PTR;
948 Emulation of sbrk for WIN32
949 All code within the ifdef WIN32 is untested by me.
951 Thanks to Martin Fong and others for supplying this.
957 #define AlignPage(add) (((add) + (malloc_getpagesize-1)) & \
958 ~(malloc_getpagesize-1))
959 #define AlignPage64K(add) (((add) + (0x10000 - 1)) & ~(0x10000 - 1))
961 /* resrve 64MB to insure large contiguous space */
962 #define RESERVED_SIZE (1024*1024*64)
963 #define NEXT_SIZE (2048*1024)
964 #define TOP_MEMORY ((unsigned long)2*1024*1024*1024)
966 struct GmListElement;
967 typedef struct GmListElement GmListElement;
975 static GmListElement* head = 0;
976 static unsigned int gNextAddress = 0;
977 static unsigned int gAddressBase = 0;
978 static unsigned int gAllocatedSize = 0;
981 GmListElement* makeGmListElement (void* bas)
984 this = (GmListElement*)(void*)LocalAlloc (0, sizeof (GmListElement));
998 assert ( (head == NULL) || (head->base == (void*)gAddressBase));
999 if (gAddressBase && (gNextAddress - gAddressBase))
1001 rval = VirtualFree ((void*)gAddressBase,
1002 gNextAddress - gAddressBase,
1008 GmListElement* next = head->next;
1009 rval = VirtualFree (head->base, 0, MEM_RELEASE);
1017 void* findRegion (void* start_address, unsigned long size)
1019 MEMORY_BASIC_INFORMATION info;
1020 if (size >= TOP_MEMORY) return NULL;
1022 while ((unsigned long)start_address + size < TOP_MEMORY)
1024 VirtualQuery (start_address, &info, sizeof (info));
1025 if ((info.State == MEM_FREE) && (info.RegionSize >= size))
1026 return start_address;
1029 /* Requested region is not available so see if the */
1030 /* next region is available. Set 'start_address' */
1031 /* to the next region and call 'VirtualQuery()' */
1034 start_address = (char*)info.BaseAddress + info.RegionSize;
1036 /* Make sure we start looking for the next region */
1037 /* on the *next* 64K boundary. Otherwise, even if */
1038 /* the new region is free according to */
1039 /* 'VirtualQuery()', the subsequent call to */
1040 /* 'VirtualAlloc()' (which follows the call to */
1041 /* this routine in 'wsbrk()') will round *down* */
1042 /* the requested address to a 64K boundary which */
1043 /* we already know is an address in the */
1044 /* unavailable region. Thus, the subsequent call */
1045 /* to 'VirtualAlloc()' will fail and bring us back */
1046 /* here, causing us to go into an infinite loop. */
1049 (void *) AlignPage64K((unsigned long) start_address);
1057 void* wsbrk (long size)
1062 if (gAddressBase == 0)
1064 gAllocatedSize = max (RESERVED_SIZE, AlignPage (size));
1065 gNextAddress = gAddressBase =
1066 (unsigned int)VirtualAlloc (NULL, gAllocatedSize,
1067 MEM_RESERVE, PAGE_NOACCESS);
1068 } else if (AlignPage (gNextAddress + size) > (gAddressBase +
1071 long new_size = max (NEXT_SIZE, AlignPage (size));
1072 void* new_address = (void*)(gAddressBase+gAllocatedSize);
1075 new_address = findRegion (new_address, new_size);
1077 if (new_address == 0)
1080 gAddressBase = gNextAddress =
1081 (unsigned int)VirtualAlloc (new_address, new_size,
1082 MEM_RESERVE, PAGE_NOACCESS);
1083 /* repeat in case of race condition */
1084 /* The region that we found has been snagged */
1085 /* by another thread */
1087 while (gAddressBase == 0);
1089 assert (new_address == (void*)gAddressBase);
1091 gAllocatedSize = new_size;
1093 if (!makeGmListElement ((void*)gAddressBase))
1096 if ((size + gNextAddress) > AlignPage (gNextAddress))
1099 res = VirtualAlloc ((void*)AlignPage (gNextAddress),
1100 (size + gNextAddress -
1101 AlignPage (gNextAddress)),
1102 MEM_COMMIT, PAGE_READWRITE);
1106 tmp = (void*)gNextAddress;
1107 gNextAddress = (unsigned int)tmp + size;
1112 unsigned int alignedGoal = AlignPage (gNextAddress + size);
1113 /* Trim by releasing the virtual memory */
1114 if (alignedGoal >= gAddressBase)
1116 VirtualFree ((void*)alignedGoal, gNextAddress - alignedGoal,
1118 gNextAddress = gNextAddress + size;
1119 return (void*)gNextAddress;
1123 VirtualFree ((void*)gAddressBase, gNextAddress - gAddressBase,
1125 gNextAddress = gAddressBase;
1131 return (void*)gNextAddress;
1146 INTERNAL_SIZE_T prev_size; /* Size of previous chunk (if free). */
1147 INTERNAL_SIZE_T size; /* Size in bytes, including overhead. */
1148 struct malloc_chunk* fd; /* double links -- used only if free. */
1149 struct malloc_chunk* bk;
1150 } __attribute__((__may_alias__)) ;
1152 typedef struct malloc_chunk* mchunkptr;
1156 malloc_chunk details:
1158 (The following includes lightly edited explanations by Colin Plumb.)
1160 Chunks of memory are maintained using a `boundary tag' method as
1161 described in e.g., Knuth or Standish. (See the paper by Paul
1162 Wilson ftp://ftp.cs.utexas.edu/pub/garbage/allocsrv.ps for a
1163 survey of such techniques.) Sizes of free chunks are stored both
1164 in the front of each chunk and at the end. This makes
1165 consolidating fragmented chunks into bigger chunks very fast. The
1166 size fields also hold bits representing whether chunks are free or
1169 An allocated chunk looks like this:
1172 chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1173 | Size of previous chunk, if allocated | |
1174 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1175 | Size of chunk, in bytes |P|
1176 mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1177 | User data starts here... .
1179 . (malloc_usable_space() bytes) .
1181 nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1183 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1186 Where "chunk" is the front of the chunk for the purpose of most of
1187 the malloc code, but "mem" is the pointer that is returned to the
1188 user. "Nextchunk" is the beginning of the next contiguous chunk.
1190 Chunks always begin on even word boundries, so the mem portion
1191 (which is returned to the user) is also on an even word boundary, and
1192 thus double-word aligned.
1194 Free chunks are stored in circular doubly-linked lists, and look like this:
1196 chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1197 | Size of previous chunk |
1198 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1199 `head:' | Size of chunk, in bytes |P|
1200 mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1201 | Forward pointer to next chunk in list |
1202 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1203 | Back pointer to previous chunk in list |
1204 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1205 | Unused space (may be 0 bytes long) .
1208 nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1209 `foot:' | Size of chunk, in bytes |
1210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1212 The P (PREV_INUSE) bit, stored in the unused low-order bit of the
1213 chunk size (which is always a multiple of two words), is an in-use
1214 bit for the *previous* chunk. If that bit is *clear*, then the
1215 word before the current chunk size contains the previous chunk
1216 size, and can be used to find the front of the previous chunk.
1217 (The very first chunk allocated always has this bit set,
1218 preventing access to non-existent (or non-owned) memory.)
1220 Note that the `foot' of the current chunk is actually represented
1221 as the prev_size of the NEXT chunk. (This makes it easier to
1222 deal with alignments etc).
1224 The two exceptions to all this are
1226 1. The special chunk `top', which doesn't bother using the
1227 trailing size field since there is no
1228 next contiguous chunk that would have to index off it. (After
1229 initialization, `top' is forced to always exist. If it would
1230 become less than MINSIZE bytes long, it is replenished via
1233 2. Chunks allocated via mmap, which have the second-lowest-order
1234 bit (IS_MMAPPED) set in their size fields. Because they are
1235 never merged or traversed from any other chunk, they have no
1236 foot size or inuse information.
1238 Available chunks are kept in any of several places (all declared below):
1240 * `av': An array of chunks serving as bin headers for consolidated
1241 chunks. Each bin is doubly linked. The bins are approximately
1242 proportionally (log) spaced. There are a lot of these bins
1243 (128). This may look excessive, but works very well in
1244 practice. All procedures maintain the invariant that no
1245 consolidated chunk physically borders another one. Chunks in
1246 bins are kept in size order, with ties going to the
1247 approximately least recently used chunk.
1249 The chunks in each bin are maintained in decreasing sorted order by
1250 size. This is irrelevant for the small bins, which all contain
1251 the same-sized chunks, but facilitates best-fit allocation for
1252 larger chunks. (These lists are just sequential. Keeping them in
1253 order almost never requires enough traversal to warrant using
1254 fancier ordered data structures.) Chunks of the same size are
1255 linked with the most recently freed at the front, and allocations
1256 are taken from the back. This results in LRU or FIFO allocation
1257 order, which tends to give each chunk an equal opportunity to be
1258 consolidated with adjacent freed chunks, resulting in larger free
1259 chunks and less fragmentation.
1261 * `top': The top-most available chunk (i.e., the one bordering the
1262 end of available memory) is treated specially. It is never
1263 included in any bin, is used only if no other chunk is
1264 available, and is released back to the system if it is very
1265 large (see M_TRIM_THRESHOLD).
1267 * `last_remainder': A bin holding only the remainder of the
1268 most recently split (non-top) chunk. This bin is checked
1269 before other non-fitting chunks, so as to provide better
1270 locality for runs of sequentially allocated chunks.
1272 * Implicitly, through the host system's memory mapping tables.
1273 If supported, requests greater than a threshold are usually
1274 serviced via calls to mmap, and then later released via munmap.
1278 /* sizes, alignments */
1280 #define SIZE_SZ (sizeof(INTERNAL_SIZE_T))
1281 #define MALLOC_ALIGNMENT (SIZE_SZ + SIZE_SZ)
1282 #define MALLOC_ALIGN_MASK (MALLOC_ALIGNMENT - 1)
1283 #define MINSIZE (sizeof(struct malloc_chunk))
1285 /* conversion from malloc headers to user pointers, and back */
1287 #define chunk2mem(p) ((Void_t*)((char*)(p) + 2*SIZE_SZ))
1288 #define mem2chunk(mem) ((mchunkptr)((char*)(mem) - 2*SIZE_SZ))
1290 /* pad request bytes into a usable size */
1292 #define request2size(req) \
1293 (((long)((req) + (SIZE_SZ + MALLOC_ALIGN_MASK)) < \
1294 (long)(MINSIZE + MALLOC_ALIGN_MASK)) ? MINSIZE : \
1295 (((req) + (SIZE_SZ + MALLOC_ALIGN_MASK)) & ~(MALLOC_ALIGN_MASK)))
1297 /* Check if m has acceptable alignment */
1299 #define aligned_OK(m) (((unsigned long)((m)) & (MALLOC_ALIGN_MASK)) == 0)
1305 Physical chunk operations
1309 /* size field is or'ed with PREV_INUSE when previous adjacent chunk in use */
1311 #define PREV_INUSE 0x1
1313 /* size field is or'ed with IS_MMAPPED if the chunk was obtained with mmap() */
1315 #define IS_MMAPPED 0x2
1317 /* Bits to mask off when extracting size */
1319 #define SIZE_BITS (PREV_INUSE|IS_MMAPPED)
1322 /* Ptr to next physical malloc_chunk. */
1324 #define next_chunk(p) ((mchunkptr)( ((char*)(p)) + ((p)->size & ~PREV_INUSE) ))
1326 /* Ptr to previous physical malloc_chunk */
1328 #define prev_chunk(p)\
1329 ((mchunkptr)( ((char*)(p)) - ((p)->prev_size) ))
1332 /* Treat space at ptr + offset as a chunk */
1334 #define chunk_at_offset(p, s) ((mchunkptr)(((char*)(p)) + (s)))
1340 Dealing with use bits
1343 /* extract p's inuse bit */
1346 ((((mchunkptr)(((char*)(p))+((p)->size & ~PREV_INUSE)))->size) & PREV_INUSE)
1348 /* extract inuse bit of previous chunk */
1350 #define prev_inuse(p) ((p)->size & PREV_INUSE)
1352 /* check for mmap()'ed chunk */
1354 #define chunk_is_mmapped(p) ((p)->size & IS_MMAPPED)
1356 /* set/clear chunk as in use without otherwise disturbing */
1358 #define set_inuse(p)\
1359 ((mchunkptr)(((char*)(p)) + ((p)->size & ~PREV_INUSE)))->size |= PREV_INUSE
1361 #define clear_inuse(p)\
1362 ((mchunkptr)(((char*)(p)) + ((p)->size & ~PREV_INUSE)))->size &= ~(PREV_INUSE)
1364 /* check/set/clear inuse bits in known places */
1366 #define inuse_bit_at_offset(p, s)\
1367 (((mchunkptr)(((char*)(p)) + (s)))->size & PREV_INUSE)
1369 #define set_inuse_bit_at_offset(p, s)\
1370 (((mchunkptr)(((char*)(p)) + (s)))->size |= PREV_INUSE)
1372 #define clear_inuse_bit_at_offset(p, s)\
1373 (((mchunkptr)(((char*)(p)) + (s)))->size &= ~(PREV_INUSE))
1379 Dealing with size fields
1382 /* Get size, ignoring use bits */
1384 #define chunksize(p) ((p)->size & ~(SIZE_BITS))
1386 /* Set size at head, without disturbing its use bit */
1388 #define set_head_size(p, s) ((p)->size = (((p)->size & PREV_INUSE) | (s)))
1390 /* Set size/use ignoring previous bits in header */
1392 #define set_head(p, s) ((p)->size = (s))
1394 /* Set size at footer (only when chunk is not in use) */
1396 #define set_foot(p, s) (((mchunkptr)((char*)(p) + (s)))->prev_size = (s))
1405 The bins, `av_' are an array of pairs of pointers serving as the
1406 heads of (initially empty) doubly-linked lists of chunks, laid out
1407 in a way so that each pair can be treated as if it were in a
1408 malloc_chunk. (This way, the fd/bk offsets for linking bin heads
1409 and chunks are the same).
1411 Bins for sizes < 512 bytes contain chunks of all the same size, spaced
1412 8 bytes apart. Larger bins are approximately logarithmically
1413 spaced. (See the table below.) The `av_' array is never mentioned
1414 directly in the code, but instead via bin access macros.
1422 4 bins of size 32768
1423 2 bins of size 262144
1424 1 bin of size what's left
1426 There is actually a little bit of slop in the numbers in bin_index
1427 for the sake of speed. This makes no difference elsewhere.
1429 The special chunks `top' and `last_remainder' get their own bins,
1430 (this is implemented via yet more trickery with the av_ array),
1431 although `top' is never properly linked to its bin since it is
1432 always handled specially.
1436 #define NAV 128 /* number of bins */
1438 typedef struct malloc_chunk* mbinptr;
1442 #define bin_at(i) ((mbinptr)((char*)&(av_[2*(i) + 2]) - 2*SIZE_SZ))
1443 #define next_bin(b) ((mbinptr)((char*)(b) + 2 * sizeof(mbinptr)))
1444 #define prev_bin(b) ((mbinptr)((char*)(b) - 2 * sizeof(mbinptr)))
1447 The first 2 bins are never indexed. The corresponding av_ cells are instead
1448 used for bookkeeping. This is not to save space, but to simplify
1449 indexing, maintain locality, and avoid some initialization tests.
1452 #define top (av_[2]) /* The topmost chunk */
1453 #define last_remainder (bin_at(1)) /* remainder from last split */
1457 Because top initially points to its own bin with initial
1458 zero size, thus forcing extension on the first malloc request,
1459 we avoid having any special code in malloc to check whether
1460 it even exists yet. But we still need to in malloc_extend_top.
1463 #define initial_top ((mchunkptr)(bin_at(0)))
1465 /* Helper macro to initialize bins */
1467 #define IAV(i) bin_at(i), bin_at(i)
1469 static mbinptr av_[NAV * 2 + 2] = {
1471 IAV(0), IAV(1), IAV(2), IAV(3), IAV(4), IAV(5), IAV(6), IAV(7),
1472 IAV(8), IAV(9), IAV(10), IAV(11), IAV(12), IAV(13), IAV(14), IAV(15),
1473 IAV(16), IAV(17), IAV(18), IAV(19), IAV(20), IAV(21), IAV(22), IAV(23),
1474 IAV(24), IAV(25), IAV(26), IAV(27), IAV(28), IAV(29), IAV(30), IAV(31),
1475 IAV(32), IAV(33), IAV(34), IAV(35), IAV(36), IAV(37), IAV(38), IAV(39),
1476 IAV(40), IAV(41), IAV(42), IAV(43), IAV(44), IAV(45), IAV(46), IAV(47),
1477 IAV(48), IAV(49), IAV(50), IAV(51), IAV(52), IAV(53), IAV(54), IAV(55),
1478 IAV(56), IAV(57), IAV(58), IAV(59), IAV(60), IAV(61), IAV(62), IAV(63),
1479 IAV(64), IAV(65), IAV(66), IAV(67), IAV(68), IAV(69), IAV(70), IAV(71),
1480 IAV(72), IAV(73), IAV(74), IAV(75), IAV(76), IAV(77), IAV(78), IAV(79),
1481 IAV(80), IAV(81), IAV(82), IAV(83), IAV(84), IAV(85), IAV(86), IAV(87),
1482 IAV(88), IAV(89), IAV(90), IAV(91), IAV(92), IAV(93), IAV(94), IAV(95),
1483 IAV(96), IAV(97), IAV(98), IAV(99), IAV(100), IAV(101), IAV(102), IAV(103),
1484 IAV(104), IAV(105), IAV(106), IAV(107), IAV(108), IAV(109), IAV(110), IAV(111),
1485 IAV(112), IAV(113), IAV(114), IAV(115), IAV(116), IAV(117), IAV(118), IAV(119),
1486 IAV(120), IAV(121), IAV(122), IAV(123), IAV(124), IAV(125), IAV(126), IAV(127)
1489 #ifdef CONFIG_NEEDS_MANUAL_RELOC
1490 static void malloc_bin_reloc(void)
1492 mbinptr *p = &av_[2];
1495 for (i = 2; i < ARRAY_SIZE(av_); ++i, ++p)
1496 *p = (mbinptr)((ulong)*p + gd->reloc_off);
1499 static inline void malloc_bin_reloc(void) {}
1502 ulong mem_malloc_start = 0;
1503 ulong mem_malloc_end = 0;
1504 ulong mem_malloc_brk = 0;
1506 void *sbrk(ptrdiff_t increment)
1508 ulong old = mem_malloc_brk;
1509 ulong new = old + increment;
1512 * if we are giving memory back make sure we clear it out since
1513 * we set MORECORE_CLEARS to 1
1516 memset((void *)new, 0, -increment);
1518 if ((new < mem_malloc_start) || (new > mem_malloc_end))
1519 return (void *)MORECORE_FAILURE;
1521 mem_malloc_brk = new;
1526 void mem_malloc_init(ulong start, ulong size)
1528 mem_malloc_start = start;
1529 mem_malloc_end = start + size;
1530 mem_malloc_brk = start;
1532 memset((void *)mem_malloc_start, 0, size);
1537 /* field-extraction macros */
1539 #define first(b) ((b)->fd)
1540 #define last(b) ((b)->bk)
1546 #define bin_index(sz) \
1547 (((((unsigned long)(sz)) >> 9) == 0) ? (((unsigned long)(sz)) >> 3): \
1548 ((((unsigned long)(sz)) >> 9) <= 4) ? 56 + (((unsigned long)(sz)) >> 6): \
1549 ((((unsigned long)(sz)) >> 9) <= 20) ? 91 + (((unsigned long)(sz)) >> 9): \
1550 ((((unsigned long)(sz)) >> 9) <= 84) ? 110 + (((unsigned long)(sz)) >> 12): \
1551 ((((unsigned long)(sz)) >> 9) <= 340) ? 119 + (((unsigned long)(sz)) >> 15): \
1552 ((((unsigned long)(sz)) >> 9) <= 1364) ? 124 + (((unsigned long)(sz)) >> 18): \
1555 bins for chunks < 512 are all spaced 8 bytes apart, and hold
1556 identically sized chunks. This is exploited in malloc.
1559 #define MAX_SMALLBIN 63
1560 #define MAX_SMALLBIN_SIZE 512
1561 #define SMALLBIN_WIDTH 8
1563 #define smallbin_index(sz) (((unsigned long)(sz)) >> 3)
1566 Requests are `small' if both the corresponding and the next bin are small
1569 #define is_small_request(nb) (nb < MAX_SMALLBIN_SIZE - SMALLBIN_WIDTH)
1574 To help compensate for the large number of bins, a one-level index
1575 structure is used for bin-by-bin searching. `binblocks' is a
1576 one-word bitvector recording whether groups of BINBLOCKWIDTH bins
1577 have any (possibly) non-empty bins, so they can be skipped over
1578 all at once during during traversals. The bits are NOT always
1579 cleared as soon as all bins in a block are empty, but instead only
1580 when all are noticed to be empty during traversal in malloc.
1583 #define BINBLOCKWIDTH 4 /* bins per block */
1585 #define binblocks_r ((INTERNAL_SIZE_T)av_[1]) /* bitvector of nonempty blocks */
1586 #define binblocks_w (av_[1])
1588 /* bin<->block macros */
1590 #define idx2binblock(ix) ((unsigned)1 << (ix / BINBLOCKWIDTH))
1591 #define mark_binblock(ii) (binblocks_w = (mbinptr)(binblocks_r | idx2binblock(ii)))
1592 #define clear_binblock(ii) (binblocks_w = (mbinptr)(binblocks_r & ~(idx2binblock(ii))))
1598 /* Other static bookkeeping data */
1600 /* variables holding tunable values */
1602 static unsigned long trim_threshold = DEFAULT_TRIM_THRESHOLD;
1603 static unsigned long top_pad = DEFAULT_TOP_PAD;
1604 static unsigned int n_mmaps_max = DEFAULT_MMAP_MAX;
1605 static unsigned long mmap_threshold = DEFAULT_MMAP_THRESHOLD;
1607 /* The first value returned from sbrk */
1608 static char* sbrk_base = (char*)(-1);
1610 /* The maximum memory obtained from system via sbrk */
1611 static unsigned long max_sbrked_mem = 0;
1613 /* The maximum via either sbrk or mmap */
1614 static unsigned long max_total_mem = 0;
1616 /* internal working copy of mallinfo */
1617 static struct mallinfo current_mallinfo = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
1619 /* The total memory obtained from system via sbrk */
1620 #define sbrked_mem (current_mallinfo.arena)
1622 /* Tracking mmaps */
1625 static unsigned int n_mmaps = 0;
1627 static unsigned long mmapped_mem = 0;
1629 static unsigned int max_n_mmaps = 0;
1630 static unsigned long max_mmapped_mem = 0;
1643 These routines make a number of assertions about the states
1644 of data structures that should be true at all times. If any
1645 are not true, it's very likely that a user program has somehow
1646 trashed memory. (It's also possible that there is a coding error
1647 in malloc. In which case, please report it!)
1651 static void do_check_chunk(mchunkptr p)
1653 static void do_check_chunk(p) mchunkptr p;
1656 INTERNAL_SIZE_T sz = p->size & ~PREV_INUSE;
1658 /* No checkable chunk is mmapped */
1659 assert(!chunk_is_mmapped(p));
1661 /* Check for legal address ... */
1662 assert((char*)p >= sbrk_base);
1664 assert((char*)p + sz <= (char*)top);
1666 assert((char*)p + sz <= sbrk_base + sbrked_mem);
1672 static void do_check_free_chunk(mchunkptr p)
1674 static void do_check_free_chunk(p) mchunkptr p;
1677 INTERNAL_SIZE_T sz = p->size & ~PREV_INUSE;
1678 mchunkptr next = chunk_at_offset(p, sz);
1682 /* Check whether it claims to be free ... */
1685 /* Unless a special marker, must have OK fields */
1686 if ((long)sz >= (long)MINSIZE)
1688 assert((sz & MALLOC_ALIGN_MASK) == 0);
1689 assert(aligned_OK(chunk2mem(p)));
1690 /* ... matching footer field */
1691 assert(next->prev_size == sz);
1692 /* ... and is fully consolidated */
1693 assert(prev_inuse(p));
1694 assert (next == top || inuse(next));
1696 /* ... and has minimally sane links */
1697 assert(p->fd->bk == p);
1698 assert(p->bk->fd == p);
1700 else /* markers are always of size SIZE_SZ */
1701 assert(sz == SIZE_SZ);
1705 static void do_check_inuse_chunk(mchunkptr p)
1707 static void do_check_inuse_chunk(p) mchunkptr p;
1710 mchunkptr next = next_chunk(p);
1713 /* Check whether it claims to be in use ... */
1716 /* ... and is surrounded by OK chunks.
1717 Since more things can be checked with free chunks than inuse ones,
1718 if an inuse chunk borders them and debug is on, it's worth doing them.
1722 mchunkptr prv = prev_chunk(p);
1723 assert(next_chunk(prv) == p);
1724 do_check_free_chunk(prv);
1728 assert(prev_inuse(next));
1729 assert(chunksize(next) >= MINSIZE);
1731 else if (!inuse(next))
1732 do_check_free_chunk(next);
1737 static void do_check_malloced_chunk(mchunkptr p, INTERNAL_SIZE_T s)
1739 static void do_check_malloced_chunk(p, s) mchunkptr p; INTERNAL_SIZE_T s;
1742 INTERNAL_SIZE_T sz = p->size & ~PREV_INUSE;
1745 do_check_inuse_chunk(p);
1747 /* Legal size ... */
1748 assert((long)sz >= (long)MINSIZE);
1749 assert((sz & MALLOC_ALIGN_MASK) == 0);
1751 assert(room < (long)MINSIZE);
1753 /* ... and alignment */
1754 assert(aligned_OK(chunk2mem(p)));
1757 /* ... and was allocated at front of an available chunk */
1758 assert(prev_inuse(p));
1763 #define check_free_chunk(P) do_check_free_chunk(P)
1764 #define check_inuse_chunk(P) do_check_inuse_chunk(P)
1765 #define check_chunk(P) do_check_chunk(P)
1766 #define check_malloced_chunk(P,N) do_check_malloced_chunk(P,N)
1768 #define check_free_chunk(P)
1769 #define check_inuse_chunk(P)
1770 #define check_chunk(P)
1771 #define check_malloced_chunk(P,N)
1777 Macro-based internal utilities
1782 Linking chunks in bin lists.
1783 Call these only with variables, not arbitrary expressions, as arguments.
1787 Place chunk p of size s in its bin, in size order,
1788 putting it ahead of others of same size.
1792 #define frontlink(P, S, IDX, BK, FD) \
1794 if (S < MAX_SMALLBIN_SIZE) \
1796 IDX = smallbin_index(S); \
1797 mark_binblock(IDX); \
1802 FD->bk = BK->fd = P; \
1806 IDX = bin_index(S); \
1809 if (FD == BK) mark_binblock(IDX); \
1812 while (FD != BK && S < chunksize(FD)) FD = FD->fd; \
1817 FD->bk = BK->fd = P; \
1822 /* take a chunk off a list */
1824 #define unlink(P, BK, FD) \
1832 /* Place p as the last remainder */
1834 #define link_last_remainder(P) \
1836 last_remainder->fd = last_remainder->bk = P; \
1837 P->fd = P->bk = last_remainder; \
1840 /* Clear the last_remainder bin */
1842 #define clear_last_remainder \
1843 (last_remainder->fd = last_remainder->bk = last_remainder)
1849 /* Routines dealing with mmap(). */
1854 static mchunkptr mmap_chunk(size_t size)
1856 static mchunkptr mmap_chunk(size) size_t size;
1859 size_t page_mask = malloc_getpagesize - 1;
1862 #ifndef MAP_ANONYMOUS
1866 if(n_mmaps >= n_mmaps_max) return 0; /* too many regions */
1868 /* For mmapped chunks, the overhead is one SIZE_SZ unit larger, because
1869 * there is no following chunk whose prev_size field could be used.
1871 size = (size + SIZE_SZ + page_mask) & ~page_mask;
1873 #ifdef MAP_ANONYMOUS
1874 p = (mchunkptr)mmap(0, size, PROT_READ|PROT_WRITE,
1875 MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
1876 #else /* !MAP_ANONYMOUS */
1879 fd = open("/dev/zero", O_RDWR);
1880 if(fd < 0) return 0;
1882 p = (mchunkptr)mmap(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
1885 if(p == (mchunkptr)-1) return 0;
1888 if (n_mmaps > max_n_mmaps) max_n_mmaps = n_mmaps;
1890 /* We demand that eight bytes into a page must be 8-byte aligned. */
1891 assert(aligned_OK(chunk2mem(p)));
1893 /* The offset to the start of the mmapped region is stored
1894 * in the prev_size field of the chunk; normally it is zero,
1895 * but that can be changed in memalign().
1898 set_head(p, size|IS_MMAPPED);
1900 mmapped_mem += size;
1901 if ((unsigned long)mmapped_mem > (unsigned long)max_mmapped_mem)
1902 max_mmapped_mem = mmapped_mem;
1903 if ((unsigned long)(mmapped_mem + sbrked_mem) > (unsigned long)max_total_mem)
1904 max_total_mem = mmapped_mem + sbrked_mem;
1909 static void munmap_chunk(mchunkptr p)
1911 static void munmap_chunk(p) mchunkptr p;
1914 INTERNAL_SIZE_T size = chunksize(p);
1917 assert (chunk_is_mmapped(p));
1918 assert(! ((char*)p >= sbrk_base && (char*)p < sbrk_base + sbrked_mem));
1919 assert((n_mmaps > 0));
1920 assert(((p->prev_size + size) & (malloc_getpagesize-1)) == 0);
1923 mmapped_mem -= (size + p->prev_size);
1925 ret = munmap((char *)p - p->prev_size, size + p->prev_size);
1927 /* munmap returns non-zero on failure */
1934 static mchunkptr mremap_chunk(mchunkptr p, size_t new_size)
1936 static mchunkptr mremap_chunk(p, new_size) mchunkptr p; size_t new_size;
1939 size_t page_mask = malloc_getpagesize - 1;
1940 INTERNAL_SIZE_T offset = p->prev_size;
1941 INTERNAL_SIZE_T size = chunksize(p);
1944 assert (chunk_is_mmapped(p));
1945 assert(! ((char*)p >= sbrk_base && (char*)p < sbrk_base + sbrked_mem));
1946 assert((n_mmaps > 0));
1947 assert(((size + offset) & (malloc_getpagesize-1)) == 0);
1949 /* Note the extra SIZE_SZ overhead as in mmap_chunk(). */
1950 new_size = (new_size + offset + SIZE_SZ + page_mask) & ~page_mask;
1952 cp = (char *)mremap((char *)p - offset, size + offset, new_size, 1);
1954 if (cp == (char *)-1) return 0;
1956 p = (mchunkptr)(cp + offset);
1958 assert(aligned_OK(chunk2mem(p)));
1960 assert((p->prev_size == offset));
1961 set_head(p, (new_size - offset)|IS_MMAPPED);
1963 mmapped_mem -= size + offset;
1964 mmapped_mem += new_size;
1965 if ((unsigned long)mmapped_mem > (unsigned long)max_mmapped_mem)
1966 max_mmapped_mem = mmapped_mem;
1967 if ((unsigned long)(mmapped_mem + sbrked_mem) > (unsigned long)max_total_mem)
1968 max_total_mem = mmapped_mem + sbrked_mem;
1972 #endif /* HAVE_MREMAP */
1974 #endif /* HAVE_MMAP */
1980 Extend the top-most chunk by obtaining memory from system.
1981 Main interface to sbrk (but see also malloc_trim).
1985 static void malloc_extend_top(INTERNAL_SIZE_T nb)
1987 static void malloc_extend_top(nb) INTERNAL_SIZE_T nb;
1990 char* brk; /* return value from sbrk */
1991 INTERNAL_SIZE_T front_misalign; /* unusable bytes at front of sbrked space */
1992 INTERNAL_SIZE_T correction; /* bytes for 2nd sbrk call */
1993 char* new_brk; /* return of 2nd sbrk call */
1994 INTERNAL_SIZE_T top_size; /* new size of top chunk */
1996 mchunkptr old_top = top; /* Record state of old top */
1997 INTERNAL_SIZE_T old_top_size = chunksize(old_top);
1998 char* old_end = (char*)(chunk_at_offset(old_top, old_top_size));
2000 /* Pad request with top_pad plus minimal overhead */
2002 INTERNAL_SIZE_T sbrk_size = nb + top_pad + MINSIZE;
2003 unsigned long pagesz = malloc_getpagesize;
2005 /* If not the first time through, round to preserve page boundary */
2006 /* Otherwise, we need to correct to a page size below anyway. */
2007 /* (We also correct below if an intervening foreign sbrk call.) */
2009 if (sbrk_base != (char*)(-1))
2010 sbrk_size = (sbrk_size + (pagesz - 1)) & ~(pagesz - 1);
2012 brk = (char*)(MORECORE (sbrk_size));
2014 /* Fail if sbrk failed or if a foreign sbrk call killed our space */
2015 if (brk == (char*)(MORECORE_FAILURE) ||
2016 (brk < old_end && old_top != initial_top))
2019 sbrked_mem += sbrk_size;
2021 if (brk == old_end) /* can just add bytes to current top */
2023 top_size = sbrk_size + old_top_size;
2024 set_head(top, top_size | PREV_INUSE);
2028 if (sbrk_base == (char*)(-1)) /* First time through. Record base */
2030 else /* Someone else called sbrk(). Count those bytes as sbrked_mem. */
2031 sbrked_mem += brk - (char*)old_end;
2033 /* Guarantee alignment of first new chunk made from this space */
2034 front_misalign = (unsigned long)chunk2mem(brk) & MALLOC_ALIGN_MASK;
2035 if (front_misalign > 0)
2037 correction = (MALLOC_ALIGNMENT) - front_misalign;
2043 /* Guarantee the next brk will be at a page boundary */
2045 correction += ((((unsigned long)(brk + sbrk_size))+(pagesz-1)) &
2046 ~(pagesz - 1)) - ((unsigned long)(brk + sbrk_size));
2048 /* Allocate correction */
2049 new_brk = (char*)(MORECORE (correction));
2050 if (new_brk == (char*)(MORECORE_FAILURE)) return;
2052 sbrked_mem += correction;
2054 top = (mchunkptr)brk;
2055 top_size = new_brk - brk + correction;
2056 set_head(top, top_size | PREV_INUSE);
2058 if (old_top != initial_top)
2061 /* There must have been an intervening foreign sbrk call. */
2062 /* A double fencepost is necessary to prevent consolidation */
2064 /* If not enough space to do this, then user did something very wrong */
2065 if (old_top_size < MINSIZE)
2067 set_head(top, PREV_INUSE); /* will force null return from malloc */
2071 /* Also keep size a multiple of MALLOC_ALIGNMENT */
2072 old_top_size = (old_top_size - 3*SIZE_SZ) & ~MALLOC_ALIGN_MASK;
2073 set_head_size(old_top, old_top_size);
2074 chunk_at_offset(old_top, old_top_size )->size =
2076 chunk_at_offset(old_top, old_top_size + SIZE_SZ)->size =
2078 /* If possible, release the rest. */
2079 if (old_top_size >= MINSIZE)
2080 fREe(chunk2mem(old_top));
2084 if ((unsigned long)sbrked_mem > (unsigned long)max_sbrked_mem)
2085 max_sbrked_mem = sbrked_mem;
2086 if ((unsigned long)(mmapped_mem + sbrked_mem) > (unsigned long)max_total_mem)
2087 max_total_mem = mmapped_mem + sbrked_mem;
2089 /* We always land on a page boundary */
2090 assert(((unsigned long)((char*)top + top_size) & (pagesz - 1)) == 0);
2096 /* Main public routines */
2102 The requested size is first converted into a usable form, `nb'.
2103 This currently means to add 4 bytes overhead plus possibly more to
2104 obtain 8-byte alignment and/or to obtain a size of at least
2105 MINSIZE (currently 16 bytes), the smallest allocatable size.
2106 (All fits are considered `exact' if they are within MINSIZE bytes.)
2108 From there, the first successful of the following steps is taken:
2110 1. The bin corresponding to the request size is scanned, and if
2111 a chunk of exactly the right size is found, it is taken.
2113 2. The most recently remaindered chunk is used if it is big
2114 enough. This is a form of (roving) first fit, used only in
2115 the absence of exact fits. Runs of consecutive requests use
2116 the remainder of the chunk used for the previous such request
2117 whenever possible. This limited use of a first-fit style
2118 allocation strategy tends to give contiguous chunks
2119 coextensive lifetimes, which improves locality and can reduce
2120 fragmentation in the long run.
2122 3. Other bins are scanned in increasing size order, using a
2123 chunk big enough to fulfill the request, and splitting off
2124 any remainder. This search is strictly by best-fit; i.e.,
2125 the smallest (with ties going to approximately the least
2126 recently used) chunk that fits is selected.
2128 4. If large enough, the chunk bordering the end of memory
2129 (`top') is split off. (This use of `top' is in accord with
2130 the best-fit search rule. In effect, `top' is treated as
2131 larger (and thus less well fitting) than any other available
2132 chunk since it can be extended to be as large as necessary
2133 (up to system limitations).
2135 5. If the request size meets the mmap threshold and the
2136 system supports mmap, and there are few enough currently
2137 allocated mmapped regions, and a call to mmap succeeds,
2138 the request is allocated via direct memory mapping.
2140 6. Otherwise, the top of memory is extended by
2141 obtaining more space from the system (normally using sbrk,
2142 but definable to anything else via the MORECORE macro).
2143 Memory is gathered from the system (in system page-sized
2144 units) in a way that allows chunks obtained across different
2145 sbrk calls to be consolidated, but does not require
2146 contiguous memory. Thus, it should be safe to intersperse
2147 mallocs with other sbrk calls.
2150 All allocations are made from the the `lowest' part of any found
2151 chunk. (The implementation invariant is that prev_inuse is
2152 always true of any allocated chunk; i.e., that each allocated
2153 chunk borders either a previously allocated and still in-use chunk,
2154 or the base of its memory arena.)
2159 Void_t* mALLOc(size_t bytes)
2161 Void_t* mALLOc(bytes) size_t bytes;
2164 mchunkptr victim; /* inspected/selected chunk */
2165 INTERNAL_SIZE_T victim_size; /* its size */
2166 int idx; /* index for bin traversal */
2167 mbinptr bin; /* associated bin */
2168 mchunkptr remainder; /* remainder from a split */
2169 long remainder_size; /* its size */
2170 int remainder_index; /* its bin index */
2171 unsigned long block; /* block traverser bit */
2172 int startidx; /* first bin of a traversed block */
2173 mchunkptr fwd; /* misc temp for linking */
2174 mchunkptr bck; /* misc temp for linking */
2175 mbinptr q; /* misc temp */
2179 #ifdef CONFIG_SYS_MALLOC_F_LEN
2180 if (!(gd->flags & GD_FLG_RELOC)) {
2184 new_ptr = gd->malloc_ptr + bytes;
2185 if (new_ptr > gd->malloc_limit)
2186 panic("Out of pre-reloc memory");
2187 ptr = map_sysmem(gd->malloc_base + gd->malloc_ptr, bytes);
2188 gd->malloc_ptr = ALIGN(new_ptr, sizeof(new_ptr));
2193 /* check if mem_malloc_init() was run */
2194 if ((mem_malloc_start == 0) && (mem_malloc_end == 0)) {
2195 /* not initialized yet */
2199 if ((long)bytes < 0) return NULL;
2201 nb = request2size(bytes); /* padded request size; */
2203 /* Check for exact match in a bin */
2205 if (is_small_request(nb)) /* Faster version for small requests */
2207 idx = smallbin_index(nb);
2209 /* No traversal or size check necessary for small bins. */
2214 /* Also scan the next one, since it would have a remainder < MINSIZE */
2222 victim_size = chunksize(victim);
2223 unlink(victim, bck, fwd);
2224 set_inuse_bit_at_offset(victim, victim_size);
2225 check_malloced_chunk(victim, nb);
2226 return chunk2mem(victim);
2229 idx += 2; /* Set for bin scan below. We've already scanned 2 bins. */
2234 idx = bin_index(nb);
2237 for (victim = last(bin); victim != bin; victim = victim->bk)
2239 victim_size = chunksize(victim);
2240 remainder_size = victim_size - nb;
2242 if (remainder_size >= (long)MINSIZE) /* too big */
2244 --idx; /* adjust to rescan below after checking last remainder */
2248 else if (remainder_size >= 0) /* exact fit */
2250 unlink(victim, bck, fwd);
2251 set_inuse_bit_at_offset(victim, victim_size);
2252 check_malloced_chunk(victim, nb);
2253 return chunk2mem(victim);
2261 /* Try to use the last split-off remainder */
2263 if ( (victim = last_remainder->fd) != last_remainder)
2265 victim_size = chunksize(victim);
2266 remainder_size = victim_size - nb;
2268 if (remainder_size >= (long)MINSIZE) /* re-split */
2270 remainder = chunk_at_offset(victim, nb);
2271 set_head(victim, nb | PREV_INUSE);
2272 link_last_remainder(remainder);
2273 set_head(remainder, remainder_size | PREV_INUSE);
2274 set_foot(remainder, remainder_size);
2275 check_malloced_chunk(victim, nb);
2276 return chunk2mem(victim);
2279 clear_last_remainder;
2281 if (remainder_size >= 0) /* exhaust */
2283 set_inuse_bit_at_offset(victim, victim_size);
2284 check_malloced_chunk(victim, nb);
2285 return chunk2mem(victim);
2288 /* Else place in bin */
2290 frontlink(victim, victim_size, remainder_index, bck, fwd);
2294 If there are any possibly nonempty big-enough blocks,
2295 search for best fitting chunk by scanning bins in blockwidth units.
2298 if ( (block = idx2binblock(idx)) <= binblocks_r)
2301 /* Get to the first marked block */
2303 if ( (block & binblocks_r) == 0)
2305 /* force to an even block boundary */
2306 idx = (idx & ~(BINBLOCKWIDTH - 1)) + BINBLOCKWIDTH;
2308 while ((block & binblocks_r) == 0)
2310 idx += BINBLOCKWIDTH;
2315 /* For each possibly nonempty block ... */
2318 startidx = idx; /* (track incomplete blocks) */
2319 q = bin = bin_at(idx);
2321 /* For each bin in this block ... */
2324 /* Find and use first big enough chunk ... */
2326 for (victim = last(bin); victim != bin; victim = victim->bk)
2328 victim_size = chunksize(victim);
2329 remainder_size = victim_size - nb;
2331 if (remainder_size >= (long)MINSIZE) /* split */
2333 remainder = chunk_at_offset(victim, nb);
2334 set_head(victim, nb | PREV_INUSE);
2335 unlink(victim, bck, fwd);
2336 link_last_remainder(remainder);
2337 set_head(remainder, remainder_size | PREV_INUSE);
2338 set_foot(remainder, remainder_size);
2339 check_malloced_chunk(victim, nb);
2340 return chunk2mem(victim);
2343 else if (remainder_size >= 0) /* take */
2345 set_inuse_bit_at_offset(victim, victim_size);
2346 unlink(victim, bck, fwd);
2347 check_malloced_chunk(victim, nb);
2348 return chunk2mem(victim);
2353 bin = next_bin(bin);
2355 } while ((++idx & (BINBLOCKWIDTH - 1)) != 0);
2357 /* Clear out the block bit. */
2359 do /* Possibly backtrack to try to clear a partial block */
2361 if ((startidx & (BINBLOCKWIDTH - 1)) == 0)
2363 av_[1] = (mbinptr)(binblocks_r & ~block);
2368 } while (first(q) == q);
2370 /* Get to the next possibly nonempty block */
2372 if ( (block <<= 1) <= binblocks_r && (block != 0) )
2374 while ((block & binblocks_r) == 0)
2376 idx += BINBLOCKWIDTH;
2386 /* Try to use top chunk */
2388 /* Require that there be a remainder, ensuring top always exists */
2389 if ( (remainder_size = chunksize(top) - nb) < (long)MINSIZE)
2393 /* If big and would otherwise need to extend, try to use mmap instead */
2394 if ((unsigned long)nb >= (unsigned long)mmap_threshold &&
2395 (victim = mmap_chunk(nb)) != 0)
2396 return chunk2mem(victim);
2400 malloc_extend_top(nb);
2401 if ( (remainder_size = chunksize(top) - nb) < (long)MINSIZE)
2402 return NULL; /* propagate failure */
2406 set_head(victim, nb | PREV_INUSE);
2407 top = chunk_at_offset(victim, nb);
2408 set_head(top, remainder_size | PREV_INUSE);
2409 check_malloced_chunk(victim, nb);
2410 return chunk2mem(victim);
2423 1. free(0) has no effect.
2425 2. If the chunk was allocated via mmap, it is release via munmap().
2427 3. If a returned chunk borders the current high end of memory,
2428 it is consolidated into the top, and if the total unused
2429 topmost memory exceeds the trim threshold, malloc_trim is
2432 4. Other chunks are consolidated as they arrive, and
2433 placed in corresponding bins. (This includes the case of
2434 consolidating with the current `last_remainder').
2440 void fREe(Void_t* mem)
2442 void fREe(mem) Void_t* mem;
2445 mchunkptr p; /* chunk corresponding to mem */
2446 INTERNAL_SIZE_T hd; /* its head field */
2447 INTERNAL_SIZE_T sz; /* its size */
2448 int idx; /* its bin index */
2449 mchunkptr next; /* next contiguous chunk */
2450 INTERNAL_SIZE_T nextsz; /* its size */
2451 INTERNAL_SIZE_T prevsz; /* size of previous contiguous chunk */
2452 mchunkptr bck; /* misc temp for linking */
2453 mchunkptr fwd; /* misc temp for linking */
2454 int islr; /* track whether merging with last_remainder */
2456 #ifdef CONFIG_SYS_MALLOC_F_LEN
2457 /* free() is a no-op - all the memory will be freed on relocation */
2458 if (!(gd->flags & GD_FLG_RELOC))
2462 if (mem == NULL) /* free(0) has no effect */
2469 if (hd & IS_MMAPPED) /* release mmapped memory. */
2476 check_inuse_chunk(p);
2478 sz = hd & ~PREV_INUSE;
2479 next = chunk_at_offset(p, sz);
2480 nextsz = chunksize(next);
2482 if (next == top) /* merge with top */
2486 if (!(hd & PREV_INUSE)) /* consolidate backward */
2488 prevsz = p->prev_size;
2489 p = chunk_at_offset(p, -((long) prevsz));
2491 unlink(p, bck, fwd);
2494 set_head(p, sz | PREV_INUSE);
2496 if ((unsigned long)(sz) >= (unsigned long)trim_threshold)
2497 malloc_trim(top_pad);
2501 set_head(next, nextsz); /* clear inuse bit */
2505 if (!(hd & PREV_INUSE)) /* consolidate backward */
2507 prevsz = p->prev_size;
2508 p = chunk_at_offset(p, -((long) prevsz));
2511 if (p->fd == last_remainder) /* keep as last_remainder */
2514 unlink(p, bck, fwd);
2517 if (!(inuse_bit_at_offset(next, nextsz))) /* consolidate forward */
2521 if (!islr && next->fd == last_remainder) /* re-insert last_remainder */
2524 link_last_remainder(p);
2527 unlink(next, bck, fwd);
2531 set_head(p, sz | PREV_INUSE);
2534 frontlink(p, sz, idx, bck, fwd);
2545 Chunks that were obtained via mmap cannot be extended or shrunk
2546 unless HAVE_MREMAP is defined, in which case mremap is used.
2547 Otherwise, if their reallocation is for additional space, they are
2548 copied. If for less, they are just left alone.
2550 Otherwise, if the reallocation is for additional space, and the
2551 chunk can be extended, it is, else a malloc-copy-free sequence is
2552 taken. There are several different ways that a chunk could be
2553 extended. All are tried:
2555 * Extending forward into following adjacent free chunk.
2556 * Shifting backwards, joining preceding adjacent space
2557 * Both shifting backwards and extending forward.
2558 * Extending into newly sbrked space
2560 Unless the #define REALLOC_ZERO_BYTES_FREES is set, realloc with a
2561 size argument of zero (re)allocates a minimum-sized chunk.
2563 If the reallocation is for less space, and the new request is for
2564 a `small' (<512 bytes) size, then the newly unused space is lopped
2567 The old unix realloc convention of allowing the last-free'd chunk
2568 to be used as an argument to realloc is no longer supported.
2569 I don't know of any programs still relying on this feature,
2570 and allowing it would also allow too many other incorrect
2571 usages of realloc to be sensible.
2578 Void_t* rEALLOc(Void_t* oldmem, size_t bytes)
2580 Void_t* rEALLOc(oldmem, bytes) Void_t* oldmem; size_t bytes;
2583 INTERNAL_SIZE_T nb; /* padded request size */
2585 mchunkptr oldp; /* chunk corresponding to oldmem */
2586 INTERNAL_SIZE_T oldsize; /* its size */
2588 mchunkptr newp; /* chunk to return */
2589 INTERNAL_SIZE_T newsize; /* its size */
2590 Void_t* newmem; /* corresponding user mem */
2592 mchunkptr next; /* next contiguous chunk after oldp */
2593 INTERNAL_SIZE_T nextsize; /* its size */
2595 mchunkptr prev; /* previous contiguous chunk before oldp */
2596 INTERNAL_SIZE_T prevsize; /* its size */
2598 mchunkptr remainder; /* holds split off extra space from newp */
2599 INTERNAL_SIZE_T remainder_size; /* its size */
2601 mchunkptr bck; /* misc temp for linking */
2602 mchunkptr fwd; /* misc temp for linking */
2604 #ifdef REALLOC_ZERO_BYTES_FREES
2605 if (bytes == 0) { fREe(oldmem); return 0; }
2608 if ((long)bytes < 0) return NULL;
2610 /* realloc of null is supposed to be same as malloc */
2611 if (oldmem == NULL) return mALLOc(bytes);
2613 #ifdef CONFIG_SYS_MALLOC_F_LEN
2614 if (!(gd->flags & GD_FLG_RELOC)) {
2615 /* This is harder to support and should not be needed */
2616 panic("pre-reloc realloc() is not supported");
2620 newp = oldp = mem2chunk(oldmem);
2621 newsize = oldsize = chunksize(oldp);
2624 nb = request2size(bytes);
2627 if (chunk_is_mmapped(oldp))
2630 newp = mremap_chunk(oldp, nb);
2631 if(newp) return chunk2mem(newp);
2633 /* Note the extra SIZE_SZ overhead. */
2634 if(oldsize - SIZE_SZ >= nb) return oldmem; /* do nothing */
2635 /* Must alloc, copy, free. */
2636 newmem = mALLOc(bytes);
2637 if (newmem == 0) return 0; /* propagate failure */
2638 MALLOC_COPY(newmem, oldmem, oldsize - 2*SIZE_SZ);
2644 check_inuse_chunk(oldp);
2646 if ((long)(oldsize) < (long)(nb))
2649 /* Try expanding forward */
2651 next = chunk_at_offset(oldp, oldsize);
2652 if (next == top || !inuse(next))
2654 nextsize = chunksize(next);
2656 /* Forward into top only if a remainder */
2659 if ((long)(nextsize + newsize) >= (long)(nb + MINSIZE))
2661 newsize += nextsize;
2662 top = chunk_at_offset(oldp, nb);
2663 set_head(top, (newsize - nb) | PREV_INUSE);
2664 set_head_size(oldp, nb);
2665 return chunk2mem(oldp);
2669 /* Forward into next chunk */
2670 else if (((long)(nextsize + newsize) >= (long)(nb)))
2672 unlink(next, bck, fwd);
2673 newsize += nextsize;
2683 /* Try shifting backwards. */
2685 if (!prev_inuse(oldp))
2687 prev = prev_chunk(oldp);
2688 prevsize = chunksize(prev);
2690 /* try forward + backward first to save a later consolidation */
2697 if ((long)(nextsize + prevsize + newsize) >= (long)(nb + MINSIZE))
2699 unlink(prev, bck, fwd);
2701 newsize += prevsize + nextsize;
2702 newmem = chunk2mem(newp);
2703 MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ);
2704 top = chunk_at_offset(newp, nb);
2705 set_head(top, (newsize - nb) | PREV_INUSE);
2706 set_head_size(newp, nb);
2711 /* into next chunk */
2712 else if (((long)(nextsize + prevsize + newsize) >= (long)(nb)))
2714 unlink(next, bck, fwd);
2715 unlink(prev, bck, fwd);
2717 newsize += nextsize + prevsize;
2718 newmem = chunk2mem(newp);
2719 MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ);
2725 if (prev != NULL && (long)(prevsize + newsize) >= (long)nb)
2727 unlink(prev, bck, fwd);
2729 newsize += prevsize;
2730 newmem = chunk2mem(newp);
2731 MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ);
2738 newmem = mALLOc (bytes);
2740 if (newmem == NULL) /* propagate failure */
2743 /* Avoid copy if newp is next chunk after oldp. */
2744 /* (This can only happen when new chunk is sbrk'ed.) */
2746 if ( (newp = mem2chunk(newmem)) == next_chunk(oldp))
2748 newsize += chunksize(newp);
2753 /* Otherwise copy, free, and exit */
2754 MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ);
2760 split: /* split off extra room in old or expanded chunk */
2762 if (newsize - nb >= MINSIZE) /* split off remainder */
2764 remainder = chunk_at_offset(newp, nb);
2765 remainder_size = newsize - nb;
2766 set_head_size(newp, nb);
2767 set_head(remainder, remainder_size | PREV_INUSE);
2768 set_inuse_bit_at_offset(remainder, remainder_size);
2769 fREe(chunk2mem(remainder)); /* let free() deal with it */
2773 set_head_size(newp, newsize);
2774 set_inuse_bit_at_offset(newp, newsize);
2777 check_inuse_chunk(newp);
2778 return chunk2mem(newp);
2788 memalign requests more than enough space from malloc, finds a spot
2789 within that chunk that meets the alignment request, and then
2790 possibly frees the leading and trailing space.
2792 The alignment argument must be a power of two. This property is not
2793 checked by memalign, so misuse may result in random runtime errors.
2795 8-byte alignment is guaranteed by normal malloc calls, so don't
2796 bother calling memalign with an argument of 8 or less.
2798 Overreliance on memalign is a sure way to fragment space.
2804 Void_t* mEMALIGn(size_t alignment, size_t bytes)
2806 Void_t* mEMALIGn(alignment, bytes) size_t alignment; size_t bytes;
2809 INTERNAL_SIZE_T nb; /* padded request size */
2810 char* m; /* memory returned by malloc call */
2811 mchunkptr p; /* corresponding chunk */
2812 char* brk; /* alignment point within p */
2813 mchunkptr newp; /* chunk to return */
2814 INTERNAL_SIZE_T newsize; /* its size */
2815 INTERNAL_SIZE_T leadsize; /* leading space befor alignment point */
2816 mchunkptr remainder; /* spare room at end to split off */
2817 long remainder_size; /* its size */
2819 if ((long)bytes < 0) return NULL;
2821 /* If need less alignment than we give anyway, just relay to malloc */
2823 if (alignment <= MALLOC_ALIGNMENT) return mALLOc(bytes);
2825 /* Otherwise, ensure that it is at least a minimum chunk size */
2827 if (alignment < MINSIZE) alignment = MINSIZE;
2829 /* Call malloc with worst case padding to hit alignment. */
2831 nb = request2size(bytes);
2832 m = (char*)(mALLOc(nb + alignment + MINSIZE));
2834 if (m == NULL) return NULL; /* propagate failure */
2838 if ((((unsigned long)(m)) % alignment) == 0) /* aligned */
2841 if(chunk_is_mmapped(p))
2842 return chunk2mem(p); /* nothing more to do */
2845 else /* misaligned */
2848 Find an aligned spot inside chunk.
2849 Since we need to give back leading space in a chunk of at
2850 least MINSIZE, if the first calculation places us at
2851 a spot with less than MINSIZE leader, we can move to the
2852 next aligned spot -- we've allocated enough total room so that
2853 this is always possible.
2856 brk = (char*)mem2chunk(((unsigned long)(m + alignment - 1)) & -((signed) alignment));
2857 if ((long)(brk - (char*)(p)) < MINSIZE) brk = brk + alignment;
2859 newp = (mchunkptr)brk;
2860 leadsize = brk - (char*)(p);
2861 newsize = chunksize(p) - leadsize;
2864 if(chunk_is_mmapped(p))
2866 newp->prev_size = p->prev_size + leadsize;
2867 set_head(newp, newsize|IS_MMAPPED);
2868 return chunk2mem(newp);
2872 /* give back leader, use the rest */
2874 set_head(newp, newsize | PREV_INUSE);
2875 set_inuse_bit_at_offset(newp, newsize);
2876 set_head_size(p, leadsize);
2880 assert (newsize >= nb && (((unsigned long)(chunk2mem(p))) % alignment) == 0);
2883 /* Also give back spare room at the end */
2885 remainder_size = chunksize(p) - nb;
2887 if (remainder_size >= (long)MINSIZE)
2889 remainder = chunk_at_offset(p, nb);
2890 set_head(remainder, remainder_size | PREV_INUSE);
2891 set_head_size(p, nb);
2892 fREe(chunk2mem(remainder));
2895 check_inuse_chunk(p);
2896 return chunk2mem(p);
2904 valloc just invokes memalign with alignment argument equal
2905 to the page size of the system (or as near to this as can
2906 be figured out from all the includes/defines above.)
2910 Void_t* vALLOc(size_t bytes)
2912 Void_t* vALLOc(bytes) size_t bytes;
2915 return mEMALIGn (malloc_getpagesize, bytes);
2919 pvalloc just invokes valloc for the nearest pagesize
2920 that will accommodate request
2925 Void_t* pvALLOc(size_t bytes)
2927 Void_t* pvALLOc(bytes) size_t bytes;
2930 size_t pagesize = malloc_getpagesize;
2931 return mEMALIGn (pagesize, (bytes + pagesize - 1) & ~(pagesize - 1));
2936 calloc calls malloc, then zeroes out the allocated chunk.
2941 Void_t* cALLOc(size_t n, size_t elem_size)
2943 Void_t* cALLOc(n, elem_size) size_t n; size_t elem_size;
2947 INTERNAL_SIZE_T csz;
2949 INTERNAL_SIZE_T sz = n * elem_size;
2952 /* check if expand_top called, in which case don't need to clear */
2954 mchunkptr oldtop = top;
2955 INTERNAL_SIZE_T oldtopsize = chunksize(top);
2957 Void_t* mem = mALLOc (sz);
2959 if ((long)n < 0) return NULL;
2965 #ifdef CONFIG_SYS_MALLOC_F_LEN
2966 if (!(gd->flags & GD_FLG_RELOC)) {
2967 MALLOC_ZERO(mem, sz);
2973 /* Two optional cases in which clearing not necessary */
2977 if (chunk_is_mmapped(p)) return mem;
2983 if (p == oldtop && csz > oldtopsize)
2985 /* clear only the bytes from non-freshly-sbrked memory */
2990 MALLOC_ZERO(mem, csz - SIZE_SZ);
2997 cfree just calls free. It is needed/defined on some systems
2998 that pair it with calloc, presumably for odd historical reasons.
3002 #if !defined(INTERNAL_LINUX_C_LIB) || !defined(__ELF__)
3004 void cfree(Void_t *mem)
3006 void cfree(mem) Void_t *mem;
3017 Malloc_trim gives memory back to the system (via negative
3018 arguments to sbrk) if there is unused memory at the `high' end of
3019 the malloc pool. You can call this after freeing large blocks of
3020 memory to potentially reduce the system-level memory requirements
3021 of a program. However, it cannot guarantee to reduce memory. Under
3022 some allocation patterns, some large free blocks of memory will be
3023 locked between two used chunks, so they cannot be given back to
3026 The `pad' argument to malloc_trim represents the amount of free
3027 trailing space to leave untrimmed. If this argument is zero,
3028 only the minimum amount of memory to maintain internal data
3029 structures will be left (one page or less). Non-zero arguments
3030 can be supplied to maintain enough trailing space to service
3031 future expected allocations without having to re-obtain memory
3034 Malloc_trim returns 1 if it actually released any memory, else 0.
3039 int malloc_trim(size_t pad)
3041 int malloc_trim(pad) size_t pad;
3044 long top_size; /* Amount of top-most memory */
3045 long extra; /* Amount to release */
3046 char* current_brk; /* address returned by pre-check sbrk call */
3047 char* new_brk; /* address returned by negative sbrk call */
3049 unsigned long pagesz = malloc_getpagesize;
3051 top_size = chunksize(top);
3052 extra = ((top_size - pad - MINSIZE + (pagesz-1)) / pagesz - 1) * pagesz;
3054 if (extra < (long)pagesz) /* Not enough memory to release */
3059 /* Test to make sure no one else called sbrk */
3060 current_brk = (char*)(MORECORE (0));
3061 if (current_brk != (char*)(top) + top_size)
3062 return 0; /* Apparently we don't own memory; must fail */
3066 new_brk = (char*)(MORECORE (-extra));
3068 if (new_brk == (char*)(MORECORE_FAILURE)) /* sbrk failed? */
3070 /* Try to figure out what we have */
3071 current_brk = (char*)(MORECORE (0));
3072 top_size = current_brk - (char*)top;
3073 if (top_size >= (long)MINSIZE) /* if not, we are very very dead! */
3075 sbrked_mem = current_brk - sbrk_base;
3076 set_head(top, top_size | PREV_INUSE);
3084 /* Success. Adjust top accordingly. */
3085 set_head(top, (top_size - extra) | PREV_INUSE);
3086 sbrked_mem -= extra;
3099 This routine tells you how many bytes you can actually use in an
3100 allocated chunk, which may be more than you requested (although
3101 often not). You can use this many bytes without worrying about
3102 overwriting other allocated objects. Not a particularly great
3103 programming practice, but still sometimes useful.
3108 size_t malloc_usable_size(Void_t* mem)
3110 size_t malloc_usable_size(mem) Void_t* mem;
3119 if(!chunk_is_mmapped(p))
3121 if (!inuse(p)) return 0;
3122 check_inuse_chunk(p);
3123 return chunksize(p) - SIZE_SZ;
3125 return chunksize(p) - 2*SIZE_SZ;
3132 /* Utility to update current_mallinfo for malloc_stats and mallinfo() */
3135 static void malloc_update_mallinfo()
3144 INTERNAL_SIZE_T avail = chunksize(top);
3145 int navail = ((long)(avail) >= (long)MINSIZE)? 1 : 0;
3147 for (i = 1; i < NAV; ++i)
3150 for (p = last(b); p != b; p = p->bk)
3153 check_free_chunk(p);
3154 for (q = next_chunk(p);
3155 q < top && inuse(q) && (long)(chunksize(q)) >= (long)MINSIZE;
3157 check_inuse_chunk(q);
3159 avail += chunksize(p);
3164 current_mallinfo.ordblks = navail;
3165 current_mallinfo.uordblks = sbrked_mem - avail;
3166 current_mallinfo.fordblks = avail;
3167 current_mallinfo.hblks = n_mmaps;
3168 current_mallinfo.hblkhd = mmapped_mem;
3169 current_mallinfo.keepcost = chunksize(top);
3180 Prints on the amount of space obtain from the system (both
3181 via sbrk and mmap), the maximum amount (which may be more than
3182 current if malloc_trim and/or munmap got called), the maximum
3183 number of simultaneous mmap regions used, and the current number
3184 of bytes allocated via malloc (or realloc, etc) but not yet
3185 freed. (Note that this is the number of bytes allocated, not the
3186 number requested. It will be larger than the number requested
3187 because of alignment and bookkeeping overhead.)
3194 malloc_update_mallinfo();
3195 printf("max system bytes = %10u\n",
3196 (unsigned int)(max_total_mem));
3197 printf("system bytes = %10u\n",
3198 (unsigned int)(sbrked_mem + mmapped_mem));
3199 printf("in use bytes = %10u\n",
3200 (unsigned int)(current_mallinfo.uordblks + mmapped_mem));
3202 printf("max mmap regions = %10u\n",
3203 (unsigned int)max_n_mmaps);
3209 mallinfo returns a copy of updated current mallinfo.
3213 struct mallinfo mALLINFo()
3215 malloc_update_mallinfo();
3216 return current_mallinfo;
3226 mallopt is the general SVID/XPG interface to tunable parameters.
3227 The format is to provide a (parameter-number, parameter-value) pair.
3228 mallopt then sets the corresponding parameter to the argument
3229 value if it can (i.e., so long as the value is meaningful),
3230 and returns 1 if successful else 0.
3232 See descriptions of tunable parameters above.
3237 int mALLOPt(int param_number, int value)
3239 int mALLOPt(param_number, value) int param_number; int value;
3242 switch(param_number)
3244 case M_TRIM_THRESHOLD:
3245 trim_threshold = value; return 1;
3247 top_pad = value; return 1;
3248 case M_MMAP_THRESHOLD:
3249 mmap_threshold = value; return 1;
3252 n_mmaps_max = value; return 1;
3254 if (value != 0) return 0; else n_mmaps_max = value; return 1;
3266 V2.6.6 Sun Dec 5 07:42:19 1999 Doug Lea (dl at gee)
3267 * return null for negative arguments
3268 * Added Several WIN32 cleanups from Martin C. Fong <mcfong@yahoo.com>
3269 * Add 'LACKS_SYS_PARAM_H' for those systems without 'sys/param.h'
3270 (e.g. WIN32 platforms)
3271 * Cleanup up header file inclusion for WIN32 platforms
3272 * Cleanup code to avoid Microsoft Visual C++ compiler complaints
3273 * Add 'USE_DL_PREFIX' to quickly allow co-existence with existing
3274 memory allocation routines
3275 * Set 'malloc_getpagesize' for WIN32 platforms (needs more work)
3276 * Use 'assert' rather than 'ASSERT' in WIN32 code to conform to
3277 usage of 'assert' in non-WIN32 code
3278 * Improve WIN32 'sbrk()' emulation's 'findRegion()' routine to
3280 * Always call 'fREe()' rather than 'free()'
3282 V2.6.5 Wed Jun 17 15:57:31 1998 Doug Lea (dl at gee)
3283 * Fixed ordering problem with boundary-stamping
3285 V2.6.3 Sun May 19 08:17:58 1996 Doug Lea (dl at gee)
3286 * Added pvalloc, as recommended by H.J. Liu
3287 * Added 64bit pointer support mainly from Wolfram Gloger
3288 * Added anonymously donated WIN32 sbrk emulation
3289 * Malloc, calloc, getpagesize: add optimizations from Raymond Nijssen
3290 * malloc_extend_top: fix mask error that caused wastage after
3292 * Add linux mremap support code from HJ Liu
3294 V2.6.2 Tue Dec 5 06:52:55 1995 Doug Lea (dl at gee)
3295 * Integrated most documentation with the code.
3296 * Add support for mmap, with help from
3297 Wolfram Gloger (Gloger@lrz.uni-muenchen.de).
3298 * Use last_remainder in more cases.
3299 * Pack bins using idea from colin@nyx10.cs.du.edu
3300 * Use ordered bins instead of best-fit threshhold
3301 * Eliminate block-local decls to simplify tracing and debugging.
3302 * Support another case of realloc via move into top
3303 * Fix error occuring when initial sbrk_base not word-aligned.
3304 * Rely on page size for units instead of SBRK_UNIT to
3305 avoid surprises about sbrk alignment conventions.
3306 * Add mallinfo, mallopt. Thanks to Raymond Nijssen
3307 (raymond@es.ele.tue.nl) for the suggestion.
3308 * Add `pad' argument to malloc_trim and top_pad mallopt parameter.
3309 * More precautions for cases where other routines call sbrk,
3310 courtesy of Wolfram Gloger (Gloger@lrz.uni-muenchen.de).
3311 * Added macros etc., allowing use in linux libc from
3312 H.J. Lu (hjl@gnu.ai.mit.edu)
3313 * Inverted this history list
3315 V2.6.1 Sat Dec 2 14:10:57 1995 Doug Lea (dl at gee)
3316 * Re-tuned and fixed to behave more nicely with V2.6.0 changes.
3317 * Removed all preallocation code since under current scheme
3318 the work required to undo bad preallocations exceeds
3319 the work saved in good cases for most test programs.
3320 * No longer use return list or unconsolidated bins since
3321 no scheme using them consistently outperforms those that don't
3322 given above changes.
3323 * Use best fit for very large chunks to prevent some worst-cases.
3324 * Added some support for debugging
3326 V2.6.0 Sat Nov 4 07:05:23 1995 Doug Lea (dl at gee)
3327 * Removed footers when chunks are in use. Thanks to
3328 Paul Wilson (wilson@cs.texas.edu) for the suggestion.
3330 V2.5.4 Wed Nov 1 07:54:51 1995 Doug Lea (dl at gee)
3331 * Added malloc_trim, with help from Wolfram Gloger
3332 (wmglo@Dent.MED.Uni-Muenchen.DE).
3334 V2.5.3 Tue Apr 26 10:16:01 1994 Doug Lea (dl at g)
3336 V2.5.2 Tue Apr 5 16:20:40 1994 Doug Lea (dl at g)
3337 * realloc: try to expand in both directions
3338 * malloc: swap order of clean-bin strategy;
3339 * realloc: only conditionally expand backwards
3340 * Try not to scavenge used bins
3341 * Use bin counts as a guide to preallocation
3342 * Occasionally bin return list chunks in first scan
3343 * Add a few optimizations from colin@nyx10.cs.du.edu
3345 V2.5.1 Sat Aug 14 15:40:43 1993 Doug Lea (dl at g)
3346 * faster bin computation & slightly different binning
3347 * merged all consolidations to one part of malloc proper
3348 (eliminating old malloc_find_space & malloc_clean_bin)
3349 * Scan 2 returns chunks (not just 1)
3350 * Propagate failure in realloc if malloc returns 0
3351 * Add stuff to allow compilation on non-ANSI compilers
3352 from kpv@research.att.com
3354 V2.5 Sat Aug 7 07:41:59 1993 Doug Lea (dl at g.oswego.edu)
3355 * removed potential for odd address access in prev_chunk
3356 * removed dependency on getpagesize.h
3357 * misc cosmetics and a bit more internal documentation
3358 * anticosmetics: mangled names in macros to evade debugger strangeness
3359 * tested on sparc, hp-700, dec-mips, rs6000
3360 with gcc & native cc (hp, dec only) allowing
3361 Detlefs & Zorn comparison study (in SIGPLAN Notices.)
3363 Trial version Fri Aug 28 13:14:29 1992 Doug Lea (dl at g.oswego.edu)
3364 * Based loosely on libg++-1.2X malloc. (It retains some of the overall
3365 structure of old version, but most details differ.)