1 #include <common.h>
2
3 #if 0 /* Moved to malloc.h */
4 /* ---------- To make a malloc.h, start cutting here ------------ */
5
6 /*
7 A version of malloc/free/realloc written by Doug Lea and released to the
8 public domain. Send questions/comments/complaints/performance data
9 to dl@cs.oswego.edu
10
11 * VERSION 2.6.6 Sun Mar 5 19:10:03 2000 Doug Lea (dl at gee)
12
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!
16
17 * Why use this malloc?
18
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
25
26 * Synopsis of public routines
27
28 (Much fuller descriptions are contained in the program documentation below.)
29
30 malloc(size_t n);
31 Return a pointer to a newly allocated chunk of at least n bytes, or null
32 if no space is available.
33 free(Void_t* p);
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
45 two.
46 valloc(size_t n);
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.)
50 pvalloc(size_t n);
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
55 set to zero.
56 cfree(Void_t* p);
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.
65 malloc_stats();
66 Prints brief summary statistics.
67 mallinfo()
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.
72
73 * Vital statistics:
74
75 Alignment: 8-byte
76 8 byte alignment is currently hardwired into the design. This
77 seems to suffice for all current machines and C compilers.
78
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.
83
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.
86
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.
90
91 Minimum allocated size: 4-byte ptrs: 16 bytes (including 4 overhead)
92 8-byte ptrs: 24/32 bytes (including, 4/8 overhead)
93
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.
99
100 Even a request for zero bytes (i.e., malloc(0)) returns a
101 pointer to something of the minimum allocatable size.
102
103 Maximum allocated size: 4-byte size_t: 2^31 - 8 bytes
104 8-byte size_t: 2^63 - 16 bytes
105
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.
113
114 Maximum overhead wastage per allocated chunk: normally 15 bytes
115
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
119 two exceptions:
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.
125
126 * Limitations
127
128 Here are some features that are NOT currently supported
129
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.
134
135 * Synopsis of compile-time options:
136
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.
143
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
148 paths.
149
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
156 execution.
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
186 very small chunks.
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
192 affect anything.
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
205 holds for sbrk).
206 DEFAULT_TRIM_THRESHOLD
207 DEFAULT_TOP_PAD
208 DEFAULT_MMAP_THRESHOLD
209 DEFAULT_MMAP_MAX
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
214 programs/systems.
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.
219
220
221 */
222
223
224
225
226 /* Preliminaries */
227
228 #ifndef __STD_C
229 #ifdef __STDC__
230 #define __STD_C 1
231 #else
232 #if __cplusplus
233 #define __STD_C 1
234 #else
235 #define __STD_C 0
236 #endif /*__cplusplus*/
237 #endif /*__STDC__*/
238 #endif /*__STD_C*/
239
240 #ifndef Void_t
241 #if (__STD_C || defined(WIN32))
242 #define Void_t void
243 #else
244 #define Void_t char
245 #endif
246 #endif /*Void_t*/
247
248 #if __STD_C
249 #include <stddef.h> /* for size_t */
250 #else
251 #include <sys/types.h>
252 #endif
253
254 #ifdef __cplusplus
255 extern "C" {
256 #endif
257
258 #include <stdio.h> /* needed for malloc_stats */
259
260
261 /*
262 Compile-time options
263 */
264
265
266 /*
267 Debugging:
268
269 Because freed chunks may be overwritten with link fields, this
270 malloc will often die when freed memory is overwritten by user
271 programs. This can be very effective (albeit in an annoying way)
272 in helping track down dangling pointers.
273
274 If you compile with -DDEBUG, a number of assertion checks are
275 enabled that will catch more memory errors. You probably won't be
276 able to make much sense of the actual assertion errors, but they
277 should help you locate incorrectly overwritten memory. The
278 checking is fairly extensive, and will slow down execution
279 noticeably. Calling malloc_stats or mallinfo with DEBUG set will
280 attempt to check every non-mmapped allocated and free chunk in the
281 course of computing the summmaries. (By nature, mmapped regions
282 cannot be checked very much automatically.)
283
284 Setting DEBUG may also be helpful if you are trying to modify
285 this code. The assertions in the check routines spell out in more
286 detail the assumptions and invariants underlying the algorithms.
287
288 */
289
290 #ifdef DEBUG
291 #include <assert.h>
292 #else
293 #define assert(x) ((void)0)
294 #endif
295
296
297 /*
298 INTERNAL_SIZE_T is the word-size used for internal bookkeeping
299 of chunk sizes. On a 64-bit machine, you can reduce malloc
300 overhead by defining INTERNAL_SIZE_T to be a 32 bit `unsigned int'
301 at the expense of not being able to handle requests greater than
302 2^31. This limitation is hardly ever a concern; you are encouraged
303 to set this. However, the default version is the same as size_t.
304 */
305
306 #ifndef INTERNAL_SIZE_T
307 #define INTERNAL_SIZE_T size_t
308 #endif
309
310 /*
311 REALLOC_ZERO_BYTES_FREES should be set if a call to
312 realloc with zero bytes should be the same as a call to free.
313 Some people think it should. Otherwise, since this malloc
314 returns a unique pointer for malloc(0), so does realloc(p, 0).
315 */
316
317
318 /* #define REALLOC_ZERO_BYTES_FREES */
319
320
321 /*
322 WIN32 causes an emulation of sbrk to be compiled in
323 mmap-based options are not currently supported in WIN32.
324 */
325
326 /* #define WIN32 */
327 #ifdef WIN32
328 #define MORECORE wsbrk
329 #define HAVE_MMAP 0
330
331 #define LACKS_UNISTD_H
332 #define LACKS_SYS_PARAM_H
333
334 /*
335 Include 'windows.h' to get the necessary declarations for the
336 Microsoft Visual C++ data structures and routines used in the 'sbrk'
337 emulation.
338
339 Define WIN32_LEAN_AND_MEAN so that only the essential Microsoft
340 Visual C++ header files are included.
341 */
342 #define WIN32_LEAN_AND_MEAN
343 #include <windows.h>
344 #endif
345
346
347 /*
348 HAVE_MEMCPY should be defined if you are not otherwise using
349 ANSI STD C, but still have memcpy and memset in your C library
350 and want to use them in calloc and realloc. Otherwise simple
351 macro versions are defined here.
352
353 USE_MEMCPY should be defined as 1 if you actually want to
354 have memset and memcpy called. People report that the macro
355 versions are often enough faster than libc versions on many
356 systems that it is better to use them.
357
358 */
359
360 #define HAVE_MEMCPY
361
362 #ifndef USE_MEMCPY
363 #ifdef HAVE_MEMCPY
364 #define USE_MEMCPY 1
365 #else
366 #define USE_MEMCPY 0
367 #endif
368 #endif
369
370 #if (__STD_C || defined(HAVE_MEMCPY))
371
372 #if __STD_C
373 void* memset(void*, int, size_t);
374 void* memcpy(void*, const void*, size_t);
375 #else
376 #ifdef WIN32
377 /* On Win32 platforms, 'memset()' and 'memcpy()' are already declared in */
378 /* 'windows.h' */
379 #else
380 Void_t* memset();
381 Void_t* memcpy();
382 #endif
383 #endif
384 #endif
385
386 #if USE_MEMCPY
387
388 /* The following macros are only invoked with (2n+1)-multiples of
389 INTERNAL_SIZE_T units, with a positive integer n. This is exploited
390 for fast inline execution when n is small. */
391
392 #define MALLOC_ZERO(charp, nbytes) \
393 do { \
394 INTERNAL_SIZE_T mzsz = (nbytes); \
395 if(mzsz <= 9*sizeof(mzsz)) { \
396 INTERNAL_SIZE_T* mz = (INTERNAL_SIZE_T*) (charp); \
397 if(mzsz >= 5*sizeof(mzsz)) { *mz++ = 0; \
398 *mz++ = 0; \
399 if(mzsz >= 7*sizeof(mzsz)) { *mz++ = 0; \
400 *mz++ = 0; \
401 if(mzsz >= 9*sizeof(mzsz)) { *mz++ = 0; \
402 *mz++ = 0; }}} \
403 *mz++ = 0; \
404 *mz++ = 0; \
405 *mz = 0; \
406 } else memset((charp), 0, mzsz); \
407 } while(0)
408
409 #define MALLOC_COPY(dest,src,nbytes) \
410 do { \
411 INTERNAL_SIZE_T mcsz = (nbytes); \
412 if(mcsz <= 9*sizeof(mcsz)) { \
413 INTERNAL_SIZE_T* mcsrc = (INTERNAL_SIZE_T*) (src); \
414 INTERNAL_SIZE_T* mcdst = (INTERNAL_SIZE_T*) (dest); \
415 if(mcsz >= 5*sizeof(mcsz)) { *mcdst++ = *mcsrc++; \
416 *mcdst++ = *mcsrc++; \
417 if(mcsz >= 7*sizeof(mcsz)) { *mcdst++ = *mcsrc++; \
418 *mcdst++ = *mcsrc++; \
419 if(mcsz >= 9*sizeof(mcsz)) { *mcdst++ = *mcsrc++; \
420 *mcdst++ = *mcsrc++; }}} \
421 *mcdst++ = *mcsrc++; \
422 *mcdst++ = *mcsrc++; \
423 *mcdst = *mcsrc ; \
424 } else memcpy(dest, src, mcsz); \
425 } while(0)
426
427 #else /* !USE_MEMCPY */
428
429 /* Use Duff's device for good zeroing/copying performance. */
430
431 #define MALLOC_ZERO(charp, nbytes) \
432 do { \
433 INTERNAL_SIZE_T* mzp = (INTERNAL_SIZE_T*)(charp); \
434 long mctmp = (nbytes)/sizeof(INTERNAL_SIZE_T), mcn; \
435 if (mctmp < 8) mcn = 0; else { mcn = (mctmp-1)/8; mctmp %= 8; } \
436 switch (mctmp) { \
437 case 0: for(;;) { *mzp++ = 0; \
438 case 7: *mzp++ = 0; \
439 case 6: *mzp++ = 0; \
440 case 5: *mzp++ = 0; \
441 case 4: *mzp++ = 0; \
442 case 3: *mzp++ = 0; \
443 case 2: *mzp++ = 0; \
444 case 1: *mzp++ = 0; if(mcn <= 0) break; mcn--; } \
445 } \
446 } while(0)
447
448 #define MALLOC_COPY(dest,src,nbytes) \
449 do { \
450 INTERNAL_SIZE_T* mcsrc = (INTERNAL_SIZE_T*) src; \
451 INTERNAL_SIZE_T* mcdst = (INTERNAL_SIZE_T*) dest; \
452 long mctmp = (nbytes)/sizeof(INTERNAL_SIZE_T), mcn; \
453 if (mctmp < 8) mcn = 0; else { mcn = (mctmp-1)/8; mctmp %= 8; } \
454 switch (mctmp) { \
455 case 0: for(;;) { *mcdst++ = *mcsrc++; \
456 case 7: *mcdst++ = *mcsrc++; \
457 case 6: *mcdst++ = *mcsrc++; \
458 case 5: *mcdst++ = *mcsrc++; \
459 case 4: *mcdst++ = *mcsrc++; \
460 case 3: *mcdst++ = *mcsrc++; \
461 case 2: *mcdst++ = *mcsrc++; \
462 case 1: *mcdst++ = *mcsrc++; if(mcn <= 0) break; mcn--; } \
463 } \
464 } while(0)
465
466 #endif
467
468
469 /*
470 Define HAVE_MMAP to optionally make malloc() use mmap() to
471 allocate very large blocks. These will be returned to the
472 operating system immediately after a free().
473 */
474
475 #ifndef HAVE_MMAP
476 #define HAVE_MMAP 1
477 #endif
478
479 /*
480 Define HAVE_MREMAP to make realloc() use mremap() to re-allocate
481 large blocks. This is currently only possible on Linux with
482 kernel versions newer than 1.3.77.
483 */
484
485 #ifndef HAVE_MREMAP
486 #ifdef INTERNAL_LINUX_C_LIB
487 #define HAVE_MREMAP 1
488 #else
489 #define HAVE_MREMAP 0
490 #endif
491 #endif
492
493 #if HAVE_MMAP
494
495 #include <unistd.h>
496 #include <fcntl.h>
497 #include <sys/mman.h>
498
499 #if !defined(MAP_ANONYMOUS) && defined(MAP_ANON)
500 #define MAP_ANONYMOUS MAP_ANON
501 #endif
502
503 #endif /* HAVE_MMAP */
504
505 /*
506 Access to system page size. To the extent possible, this malloc
507 manages memory from the system in page-size units.
508
509 The following mechanics for getpagesize were adapted from
510 bsd/gnu getpagesize.h
511 */
512
513 #ifndef LACKS_UNISTD_H
514 # include <unistd.h>
515 #endif
516
517 #ifndef malloc_getpagesize
518 # ifdef _SC_PAGESIZE /* some SVR4 systems omit an underscore */
519 # ifndef _SC_PAGE_SIZE
520 # define _SC_PAGE_SIZE _SC_PAGESIZE
521 # endif
522 # endif
523 # ifdef _SC_PAGE_SIZE
524 # define malloc_getpagesize sysconf(_SC_PAGE_SIZE)
525 # else
526 # if defined(BSD) || defined(DGUX) || defined(HAVE_GETPAGESIZE)
527 extern size_t getpagesize();
528 # define malloc_getpagesize getpagesize()
529 # else
530 # ifdef WIN32
531 # define malloc_getpagesize (4096) /* TBD: Use 'GetSystemInfo' instead */
532 # else
533 # ifndef LACKS_SYS_PARAM_H
534 # include <sys/param.h>
535 # endif
536 # ifdef EXEC_PAGESIZE
537 # define malloc_getpagesize EXEC_PAGESIZE
538 # else
539 # ifdef NBPG
540 # ifndef CLSIZE
541 # define malloc_getpagesize NBPG
542 # else
543 # define malloc_getpagesize (NBPG * CLSIZE)
544 # endif
545 # else
546 # ifdef NBPC
547 # define malloc_getpagesize NBPC
548 # else
549 # ifdef PAGESIZE
550 # define malloc_getpagesize PAGESIZE
551 # else
552 # define malloc_getpagesize (4096) /* just guess */
553 # endif
554 # endif
555 # endif
556 # endif
557 # endif
558 # endif
559 # endif
560 #endif
561
562
563 /*
564
565 This version of malloc supports the standard SVID/XPG mallinfo
566 routine that returns a struct containing the same kind of
567 information you can get from malloc_stats. It should work on
568 any SVID/XPG compliant system that has a /usr/include/malloc.h
569 defining struct mallinfo. (If you'd like to install such a thing
570 yourself, cut out the preliminary declarations as described above
571 and below and save them in a malloc.h file. But there's no
572 compelling reason to bother to do this.)
573
574 The main declaration needed is the mallinfo struct that is returned
575 (by-copy) by mallinfo(). The SVID/XPG malloinfo struct contains a
576 bunch of fields, most of which are not even meaningful in this
577 version of malloc. Some of these fields are are instead filled by
578 mallinfo() with other numbers that might possibly be of interest.
579
580 HAVE_USR_INCLUDE_MALLOC_H should be set if you have a
581 /usr/include/malloc.h file that includes a declaration of struct
582 mallinfo. If so, it is included; else an SVID2/XPG2 compliant
583 version is declared below. These must be precisely the same for
584 mallinfo() to work.
585
586 */
587
588 /* #define HAVE_USR_INCLUDE_MALLOC_H */
589
590 #if HAVE_USR_INCLUDE_MALLOC_H
591 #include "/usr/include/malloc.h"
592 #else
593
594 /* SVID2/XPG mallinfo structure */
595
596 struct mallinfo {
597 int arena; /* total space allocated from system */
598 int ordblks; /* number of non-inuse chunks */
599 int smblks; /* unused -- always zero */
600 int hblks; /* number of mmapped regions */
601 int hblkhd; /* total space in mmapped regions */
602 int usmblks; /* unused -- always zero */
603 int fsmblks; /* unused -- always zero */
604 int uordblks; /* total allocated space */
605 int fordblks; /* total non-inuse space */
606 int keepcost; /* top-most, releasable (via malloc_trim) space */
607 };
608
609 /* SVID2/XPG mallopt options */
610
611 #define M_MXFAST 1 /* UNUSED in this malloc */
612 #define M_NLBLKS 2 /* UNUSED in this malloc */
613 #define M_GRAIN 3 /* UNUSED in this malloc */
614 #define M_KEEP 4 /* UNUSED in this malloc */
615
616 #endif
617
618 /* mallopt options that actually do something */
619
620 #define M_TRIM_THRESHOLD -1
621 #define M_TOP_PAD -2
622 #define M_MMAP_THRESHOLD -3
623 #define M_MMAP_MAX -4
624
625
626 #ifndef DEFAULT_TRIM_THRESHOLD
627 #define DEFAULT_TRIM_THRESHOLD (128 * 1024)
628 #endif
629
630 /*
631 M_TRIM_THRESHOLD is the maximum amount of unused top-most memory
632 to keep before releasing via malloc_trim in free().
633
634 Automatic trimming is mainly useful in long-lived programs.
635 Because trimming via sbrk can be slow on some systems, and can
636 sometimes be wasteful (in cases where programs immediately
637 afterward allocate more large chunks) the value should be high
638 enough so that your overall system performance would improve by
639 releasing.
640
641 The trim threshold and the mmap control parameters (see below)
642 can be traded off with one another. Trimming and mmapping are
643 two different ways of releasing unused memory back to the
644 system. Between these two, it is often possible to keep
645 system-level demands of a long-lived program down to a bare
646 minimum. For example, in one test suite of sessions measuring
647 the XF86 X server on Linux, using a trim threshold of 128K and a
648 mmap threshold of 192K led to near-minimal long term resource
649 consumption.
650
651 If you are using this malloc in a long-lived program, it should
652 pay to experiment with these values. As a rough guide, you
653 might set to a value close to the average size of a process
654 (program) running on your system. Releasing this much memory
655 would allow such a process to run in memory. Generally, it's
656 worth it to tune for trimming rather tham memory mapping when a
657 program undergoes phases where several large chunks are
658 allocated and released in ways that can reuse each other's
659 storage, perhaps mixed with phases where there are no such
660 chunks at all. And in well-behaved long-lived programs,
661 controlling release of large blocks via trimming versus mapping
662 is usually faster.
663
664 However, in most programs, these parameters serve mainly as
665 protection against the system-level effects of carrying around
666 massive amounts of unneeded memory. Since frequent calls to
667 sbrk, mmap, and munmap otherwise degrade performance, the default
668 parameters are set to relatively high values that serve only as
669 safeguards.
670
671 The default trim value is high enough to cause trimming only in
672 fairly extreme (by current memory consumption standards) cases.
673 It must be greater than page size to have any useful effect. To
674 disable trimming completely, you can set to (unsigned long)(-1);
675
676
677 */
678
679
680 #ifndef DEFAULT_TOP_PAD
681 #define DEFAULT_TOP_PAD (0)
682 #endif
683
684 /*
685 M_TOP_PAD is the amount of extra `padding' space to allocate or
686 retain whenever sbrk is called. It is used in two ways internally:
687
688 * When sbrk is called to extend the top of the arena to satisfy
689 a new malloc request, this much padding is added to the sbrk
690 request.
691
692 * When malloc_trim is called automatically from free(),
693 it is used as the `pad' argument.
694
695 In both cases, the actual amount of padding is rounded
696 so that the end of the arena is always a system page boundary.
697
698 The main reason for using padding is to avoid calling sbrk so
699 often. Having even a small pad greatly reduces the likelihood
700 that nearly every malloc request during program start-up (or
701 after trimming) will invoke sbrk, which needlessly wastes
702 time.
703
704 Automatic rounding-up to page-size units is normally sufficient
705 to avoid measurable overhead, so the default is 0. However, in
706 systems where sbrk is relatively slow, it can pay to increase
707 this value, at the expense of carrying around more memory than
708 the program needs.
709
710 */
711
712
713 #ifndef DEFAULT_MMAP_THRESHOLD
714 #define DEFAULT_MMAP_THRESHOLD (128 * 1024)
715 #endif
716
717 /*
718
719 M_MMAP_THRESHOLD is the request size threshold for using mmap()
720 to service a request. Requests of at least this size that cannot
721 be allocated using already-existing space will be serviced via mmap.
722 (If enough normal freed space already exists it is used instead.)
723
724 Using mmap segregates relatively large chunks of memory so that
725 they can be individually obtained and released from the host
726 system. A request serviced through mmap is never reused by any
727 other request (at least not directly; the system may just so
728 happen to remap successive requests to the same locations).
729
730 Segregating space in this way has the benefit that mmapped space
731 can ALWAYS be individually released back to the system, which
732 helps keep the system level memory demands of a long-lived
733 program low. Mapped memory can never become `locked' between
734 other chunks, as can happen with normally allocated chunks, which
735 menas that even trimming via malloc_trim would not release them.
736
737 However, it has the disadvantages that:
738
739 1. The space cannot be reclaimed, consolidated, and then
740 used to service later requests, as happens with normal chunks.
741 2. It can lead to more wastage because of mmap page alignment
742 requirements
743 3. It causes malloc performance to be more dependent on host
744 system memory management support routines which may vary in
745 implementation quality and may impose arbitrary
746 limitations. Generally, servicing a request via normal
747 malloc steps is faster than going through a system's mmap.
748
749 All together, these considerations should lead you to use mmap
750 only for relatively large requests.
751
752
753 */
754
755
756 #ifndef DEFAULT_MMAP_MAX
757 #if HAVE_MMAP
758 #define DEFAULT_MMAP_MAX (64)
759 #else
760 #define DEFAULT_MMAP_MAX (0)
761 #endif
762 #endif
763
764 /*
765 M_MMAP_MAX is the maximum number of requests to simultaneously
766 service using mmap. This parameter exists because:
767
768 1. Some systems have a limited number of internal tables for
769 use by mmap.
770 2. In most systems, overreliance on mmap can degrade overall
771 performance.
772 3. If a program allocates many large regions, it is probably
773 better off using normal sbrk-based allocation routines that
774 can reclaim and reallocate normal heap memory. Using a
775 small value allows transition into this mode after the
776 first few allocations.
777
778 Setting to 0 disables all use of mmap. If HAVE_MMAP is not set,
779 the default value is 0, and attempts to set it to non-zero values
780 in mallopt will fail.
781 */
782
783
784 /*
785 USE_DL_PREFIX will prefix all public routines with the string 'dl'.
786 Useful to quickly avoid procedure declaration conflicts and linker
787 symbol conflicts with existing memory allocation routines.
788
789 */
790
791 /* #define USE_DL_PREFIX */
792
793
794 /*
795
796 Special defines for linux libc
797
798 Except when compiled using these special defines for Linux libc
799 using weak aliases, this malloc is NOT designed to work in
800 multithreaded applications. No semaphores or other concurrency
801 control are provided to ensure that multiple malloc or free calls
802 don't run at the same time, which could be disasterous. A single
803 semaphore could be used across malloc, realloc, and free (which is
804 essentially the effect of the linux weak alias approach). It would
805 be hard to obtain finer granularity.
806
807 */
808
809
810 #ifdef INTERNAL_LINUX_C_LIB
811
812 #if __STD_C
813
814 Void_t * __default_morecore_init (ptrdiff_t);
815 Void_t *(*__morecore)(ptrdiff_t) = __default_morecore_init;
816
817 #else
818
819 Void_t * __default_morecore_init ();
820 Void_t *(*__morecore)() = __default_morecore_init;
821
822 #endif
823
824 #define MORECORE (*__morecore)
825 #define MORECORE_FAILURE 0
826 #define MORECORE_CLEARS 1
827
828 #else /* INTERNAL_LINUX_C_LIB */
829
830 #if __STD_C
831 extern Void_t* sbrk(ptrdiff_t);
832 #else
833 extern Void_t* sbrk();
834 #endif
835
836 #ifndef MORECORE
837 #define MORECORE sbrk
838 #endif
839
840 #ifndef MORECORE_FAILURE
841 #define MORECORE_FAILURE -1
842 #endif
843
844 #ifndef MORECORE_CLEARS
845 #define MORECORE_CLEARS 1
846 #endif
847
848 #endif /* INTERNAL_LINUX_C_LIB */
849
850 #if defined(INTERNAL_LINUX_C_LIB) && defined(__ELF__)
851
852 #define cALLOc __libc_calloc
853 #define fREe __libc_free
854 #define mALLOc __libc_malloc
855 #define mEMALIGn __libc_memalign
856 #define rEALLOc __libc_realloc
857 #define vALLOc __libc_valloc
858 #define pvALLOc __libc_pvalloc
859 #define mALLINFo __libc_mallinfo
860 #define mALLOPt __libc_mallopt
861
862 #pragma weak calloc = __libc_calloc
863 #pragma weak free = __libc_free
864 #pragma weak cfree = __libc_free
865 #pragma weak malloc = __libc_malloc
866 #pragma weak memalign = __libc_memalign
867 #pragma weak realloc = __libc_realloc
868 #pragma weak valloc = __libc_valloc
869 #pragma weak pvalloc = __libc_pvalloc
870 #pragma weak mallinfo = __libc_mallinfo
871 #pragma weak mallopt = __libc_mallopt
872
873 #else
874
875 #ifdef USE_DL_PREFIX
876 #define cALLOc dlcalloc
877 #define fREe dlfree
878 #define mALLOc dlmalloc
879 #define mEMALIGn dlmemalign
880 #define rEALLOc dlrealloc
881 #define vALLOc dlvalloc
882 #define pvALLOc dlpvalloc
883 #define mALLINFo dlmallinfo
884 #define mALLOPt dlmallopt
885 #else /* USE_DL_PREFIX */
886 #define cALLOc calloc
887 #define fREe free
888 #define mALLOc malloc
889 #define mEMALIGn memalign
890 #define rEALLOc realloc
891 #define vALLOc valloc
892 #define pvALLOc pvalloc
893 #define mALLINFo mallinfo
894 #define mALLOPt mallopt
895 #endif /* USE_DL_PREFIX */
896
897 #endif
898
899 /* Public routines */
900
901 #if __STD_C
902
903 Void_t* mALLOc(size_t);
904 void fREe(Void_t*);
905 Void_t* rEALLOc(Void_t*, size_t);
906 Void_t* mEMALIGn(size_t, size_t);
907 Void_t* vALLOc(size_t);
908 Void_t* pvALLOc(size_t);
909 Void_t* cALLOc(size_t, size_t);
910 void cfree(Void_t*);
911 int malloc_trim(size_t);
912 size_t malloc_usable_size(Void_t*);
913 void malloc_stats();
914 int mALLOPt(int, int);
915 struct mallinfo mALLINFo(void);
916 #else
917 Void_t* mALLOc();
918 void fREe();
919 Void_t* rEALLOc();
920 Void_t* mEMALIGn();
921 Void_t* vALLOc();
922 Void_t* pvALLOc();
923 Void_t* cALLOc();
924 void cfree();
925 int malloc_trim();
926 size_t malloc_usable_size();
927 void malloc_stats();
928 int mALLOPt();
929 struct mallinfo mALLINFo();
930 #endif
931
932
933 #ifdef __cplusplus
934 }; /* end of extern "C" */
935 #endif
936
937 /* ---------- To make a malloc.h, end cutting here ------------ */
938 #else /* Moved to malloc.h */
939
940 #include <malloc.h>
941 #if 0
942 #if __STD_C
943 static void malloc_update_mallinfo (void);
944 void malloc_stats (void);
945 #else
946 static void malloc_update_mallinfo ();
947 void malloc_stats();
948 #endif
949 #endif /* 0 */
950
951 #endif /* 0 */ /* Moved to malloc.h */
952
953 DECLARE_GLOBAL_DATA_PTR;
954
955 /*
956 Emulation of sbrk for WIN32
957 All code within the ifdef WIN32 is untested by me.
958
959 Thanks to Martin Fong and others for supplying this.
960 */
961
962
963 #ifdef WIN32
964
965 #define AlignPage(add) (((add) + (malloc_getpagesize-1)) & \
966 ~(malloc_getpagesize-1))
967 #define AlignPage64K(add) (((add) + (0x10000 - 1)) & ~(0x10000 - 1))
968
969 /* resrve 64MB to insure large contiguous space */
970 #define RESERVED_SIZE (1024*1024*64)
971 #define NEXT_SIZE (2048*1024)
972 #define TOP_MEMORY ((unsigned long)2*1024*1024*1024)
973
974 struct GmListElement;
975 typedef struct GmListElement GmListElement;
976
977 struct GmListElement
978 {
979 GmListElement* next;
980 void* base;
981 };
982
983 static GmListElement* head = 0;
984 static unsigned int gNextAddress = 0;
985 static unsigned int gAddressBase = 0;
986 static unsigned int gAllocatedSize = 0;
987
988 static
makeGmListElement(void * bas)989 GmListElement* makeGmListElement (void* bas)
990 {
991 GmListElement* this;
992 this = (GmListElement*)(void*)LocalAlloc (0, sizeof (GmListElement));
993 assert (this);
994 if (this)
995 {
996 this->base = bas;
997 this->next = head;
998 head = this;
999 }
1000 return this;
1001 }
1002
gcleanup()1003 void gcleanup ()
1004 {
1005 BOOL rval;
1006 assert ( (head == NULL) || (head->base == (void*)gAddressBase));
1007 if (gAddressBase && (gNextAddress - gAddressBase))
1008 {
1009 rval = VirtualFree ((void*)gAddressBase,
1010 gNextAddress - gAddressBase,
1011 MEM_DECOMMIT);
1012 assert (rval);
1013 }
1014 while (head)
1015 {
1016 GmListElement* next = head->next;
1017 rval = VirtualFree (head->base, 0, MEM_RELEASE);
1018 assert (rval);
1019 LocalFree (head);
1020 head = next;
1021 }
1022 }
1023
1024 static
findRegion(void * start_address,unsigned long size)1025 void* findRegion (void* start_address, unsigned long size)
1026 {
1027 MEMORY_BASIC_INFORMATION info;
1028 if (size >= TOP_MEMORY) return NULL;
1029
1030 while ((unsigned long)start_address + size < TOP_MEMORY)
1031 {
1032 VirtualQuery (start_address, &info, sizeof (info));
1033 if ((info.State == MEM_FREE) && (info.RegionSize >= size))
1034 return start_address;
1035 else
1036 {
1037 /* Requested region is not available so see if the */
1038 /* next region is available. Set 'start_address' */
1039 /* to the next region and call 'VirtualQuery()' */
1040 /* again. */
1041
1042 start_address = (char*)info.BaseAddress + info.RegionSize;
1043
1044 /* Make sure we start looking for the next region */
1045 /* on the *next* 64K boundary. Otherwise, even if */
1046 /* the new region is free according to */
1047 /* 'VirtualQuery()', the subsequent call to */
1048 /* 'VirtualAlloc()' (which follows the call to */
1049 /* this routine in 'wsbrk()') will round *down* */
1050 /* the requested address to a 64K boundary which */
1051 /* we already know is an address in the */
1052 /* unavailable region. Thus, the subsequent call */
1053 /* to 'VirtualAlloc()' will fail and bring us back */
1054 /* here, causing us to go into an infinite loop. */
1055
1056 start_address =
1057 (void *) AlignPage64K((unsigned long) start_address);
1058 }
1059 }
1060 return NULL;
1061
1062 }
1063
1064
wsbrk(long size)1065 void* wsbrk (long size)
1066 {
1067 void* tmp;
1068 if (size > 0)
1069 {
1070 if (gAddressBase == 0)
1071 {
1072 gAllocatedSize = max (RESERVED_SIZE, AlignPage (size));
1073 gNextAddress = gAddressBase =
1074 (unsigned int)VirtualAlloc (NULL, gAllocatedSize,
1075 MEM_RESERVE, PAGE_NOACCESS);
1076 } else if (AlignPage (gNextAddress + size) > (gAddressBase +
1077 gAllocatedSize))
1078 {
1079 long new_size = max (NEXT_SIZE, AlignPage (size));
1080 void* new_address = (void*)(gAddressBase+gAllocatedSize);
1081 do
1082 {
1083 new_address = findRegion (new_address, new_size);
1084
1085 if (new_address == 0)
1086 return (void*)-1;
1087
1088 gAddressBase = gNextAddress =
1089 (unsigned int)VirtualAlloc (new_address, new_size,
1090 MEM_RESERVE, PAGE_NOACCESS);
1091 /* repeat in case of race condition */
1092 /* The region that we found has been snagged */
1093 /* by another thread */
1094 }
1095 while (gAddressBase == 0);
1096
1097 assert (new_address == (void*)gAddressBase);
1098
1099 gAllocatedSize = new_size;
1100
1101 if (!makeGmListElement ((void*)gAddressBase))
1102 return (void*)-1;
1103 }
1104 if ((size + gNextAddress) > AlignPage (gNextAddress))
1105 {
1106 void* res;
1107 res = VirtualAlloc ((void*)AlignPage (gNextAddress),
1108 (size + gNextAddress -
1109 AlignPage (gNextAddress)),
1110 MEM_COMMIT, PAGE_READWRITE);
1111 if (res == 0)
1112 return (void*)-1;
1113 }
1114 tmp = (void*)gNextAddress;
1115 gNextAddress = (unsigned int)tmp + size;
1116 return tmp;
1117 }
1118 else if (size < 0)
1119 {
1120 unsigned int alignedGoal = AlignPage (gNextAddress + size);
1121 /* Trim by releasing the virtual memory */
1122 if (alignedGoal >= gAddressBase)
1123 {
1124 VirtualFree ((void*)alignedGoal, gNextAddress - alignedGoal,
1125 MEM_DECOMMIT);
1126 gNextAddress = gNextAddress + size;
1127 return (void*)gNextAddress;
1128 }
1129 else
1130 {
1131 VirtualFree ((void*)gAddressBase, gNextAddress - gAddressBase,
1132 MEM_DECOMMIT);
1133 gNextAddress = gAddressBase;
1134 return (void*)-1;
1135 }
1136 }
1137 else
1138 {
1139 return (void*)gNextAddress;
1140 }
1141 }
1142
1143 #endif
1144
1145
1146
1147 /*
1148 Type declarations
1149 */
1150
1151
1152 struct malloc_chunk
1153 {
1154 INTERNAL_SIZE_T prev_size; /* Size of previous chunk (if free). */
1155 INTERNAL_SIZE_T size; /* Size in bytes, including overhead. */
1156 struct malloc_chunk* fd; /* double links -- used only if free. */
1157 struct malloc_chunk* bk;
1158 };
1159
1160 typedef struct malloc_chunk* mchunkptr;
1161
1162 /*
1163
1164 malloc_chunk details:
1165
1166 (The following includes lightly edited explanations by Colin Plumb.)
1167
1168 Chunks of memory are maintained using a `boundary tag' method as
1169 described in e.g., Knuth or Standish. (See the paper by Paul
1170 Wilson ftp://ftp.cs.utexas.edu/pub/garbage/allocsrv.ps for a
1171 survey of such techniques.) Sizes of free chunks are stored both
1172 in the front of each chunk and at the end. This makes
1173 consolidating fragmented chunks into bigger chunks very fast. The
1174 size fields also hold bits representing whether chunks are free or
1175 in use.
1176
1177 An allocated chunk looks like this:
1178
1179
1180 chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1181 | Size of previous chunk, if allocated | |
1182 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1183 | Size of chunk, in bytes |P|
1184 mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1185 | User data starts here... .
1186 . .
1187 . (malloc_usable_space() bytes) .
1188 . |
1189 nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1190 | Size of chunk |
1191 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1192
1193
1194 Where "chunk" is the front of the chunk for the purpose of most of
1195 the malloc code, but "mem" is the pointer that is returned to the
1196 user. "Nextchunk" is the beginning of the next contiguous chunk.
1197
1198 Chunks always begin on even word boundries, so the mem portion
1199 (which is returned to the user) is also on an even word boundary, and
1200 thus double-word aligned.
1201
1202 Free chunks are stored in circular doubly-linked lists, and look like this:
1203
1204 chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1205 | Size of previous chunk |
1206 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1207 `head:' | Size of chunk, in bytes |P|
1208 mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1209 | Forward pointer to next chunk in list |
1210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1211 | Back pointer to previous chunk in list |
1212 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1213 | Unused space (may be 0 bytes long) .
1214 . .
1215 . |
1216 nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1217 `foot:' | Size of chunk, in bytes |
1218 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1219
1220 The P (PREV_INUSE) bit, stored in the unused low-order bit of the
1221 chunk size (which is always a multiple of two words), is an in-use
1222 bit for the *previous* chunk. If that bit is *clear*, then the
1223 word before the current chunk size contains the previous chunk
1224 size, and can be used to find the front of the previous chunk.
1225 (The very first chunk allocated always has this bit set,
1226 preventing access to non-existent (or non-owned) memory.)
1227
1228 Note that the `foot' of the current chunk is actually represented
1229 as the prev_size of the NEXT chunk. (This makes it easier to
1230 deal with alignments etc).
1231
1232 The two exceptions to all this are
1233
1234 1. The special chunk `top', which doesn't bother using the
1235 trailing size field since there is no
1236 next contiguous chunk that would have to index off it. (After
1237 initialization, `top' is forced to always exist. If it would
1238 become less than MINSIZE bytes long, it is replenished via
1239 malloc_extend_top.)
1240
1241 2. Chunks allocated via mmap, which have the second-lowest-order
1242 bit (IS_MMAPPED) set in their size fields. Because they are
1243 never merged or traversed from any other chunk, they have no
1244 foot size or inuse information.
1245
1246 Available chunks are kept in any of several places (all declared below):
1247
1248 * `av': An array of chunks serving as bin headers for consolidated
1249 chunks. Each bin is doubly linked. The bins are approximately
1250 proportionally (log) spaced. There are a lot of these bins
1251 (128). This may look excessive, but works very well in
1252 practice. All procedures maintain the invariant that no
1253 consolidated chunk physically borders another one. Chunks in
1254 bins are kept in size order, with ties going to the
1255 approximately least recently used chunk.
1256
1257 The chunks in each bin are maintained in decreasing sorted order by
1258 size. This is irrelevant for the small bins, which all contain
1259 the same-sized chunks, but facilitates best-fit allocation for
1260 larger chunks. (These lists are just sequential. Keeping them in
1261 order almost never requires enough traversal to warrant using
1262 fancier ordered data structures.) Chunks of the same size are
1263 linked with the most recently freed at the front, and allocations
1264 are taken from the back. This results in LRU or FIFO allocation
1265 order, which tends to give each chunk an equal opportunity to be
1266 consolidated with adjacent freed chunks, resulting in larger free
1267 chunks and less fragmentation.
1268
1269 * `top': The top-most available chunk (i.e., the one bordering the
1270 end of available memory) is treated specially. It is never
1271 included in any bin, is used only if no other chunk is
1272 available, and is released back to the system if it is very
1273 large (see M_TRIM_THRESHOLD).
1274
1275 * `last_remainder': A bin holding only the remainder of the
1276 most recently split (non-top) chunk. This bin is checked
1277 before other non-fitting chunks, so as to provide better
1278 locality for runs of sequentially allocated chunks.
1279
1280 * Implicitly, through the host system's memory mapping tables.
1281 If supported, requests greater than a threshold are usually
1282 serviced via calls to mmap, and then later released via munmap.
1283
1284 */
1285
1286 /* sizes, alignments */
1287
1288 #define SIZE_SZ (sizeof(INTERNAL_SIZE_T))
1289 #define MALLOC_ALIGNMENT (SIZE_SZ + SIZE_SZ)
1290 #define MALLOC_ALIGN_MASK (MALLOC_ALIGNMENT - 1)
1291 #define MINSIZE (sizeof(struct malloc_chunk))
1292
1293 /* conversion from malloc headers to user pointers, and back */
1294
1295 #define chunk2mem(p) ((Void_t*)((char*)(p) + 2*SIZE_SZ))
1296 #define mem2chunk(mem) ((mchunkptr)((char*)(mem) - 2*SIZE_SZ))
1297
1298 /* pad request bytes into a usable size */
1299
1300 #define request2size(req) \
1301 (((long)((req) + (SIZE_SZ + MALLOC_ALIGN_MASK)) < \
1302 (long)(MINSIZE + MALLOC_ALIGN_MASK)) ? MINSIZE : \
1303 (((req) + (SIZE_SZ + MALLOC_ALIGN_MASK)) & ~(MALLOC_ALIGN_MASK)))
1304
1305 /* Check if m has acceptable alignment */
1306
1307 #define aligned_OK(m) (((unsigned long)((m)) & (MALLOC_ALIGN_MASK)) == 0)
1308
1309
1310
1311
1312 /*
1313 Physical chunk operations
1314 */
1315
1316
1317 /* size field is or'ed with PREV_INUSE when previous adjacent chunk in use */
1318
1319 #define PREV_INUSE 0x1
1320
1321 /* size field is or'ed with IS_MMAPPED if the chunk was obtained with mmap() */
1322
1323 #define IS_MMAPPED 0x2
1324
1325 /* Bits to mask off when extracting size */
1326
1327 #define SIZE_BITS (PREV_INUSE|IS_MMAPPED)
1328
1329
1330 /* Ptr to next physical malloc_chunk. */
1331
1332 #define next_chunk(p) ((mchunkptr)( ((char*)(p)) + ((p)->size & ~PREV_INUSE) ))
1333
1334 /* Ptr to previous physical malloc_chunk */
1335
1336 #define prev_chunk(p)\
1337 ((mchunkptr)( ((char*)(p)) - ((p)->prev_size) ))
1338
1339
1340 /* Treat space at ptr + offset as a chunk */
1341
1342 #define chunk_at_offset(p, s) ((mchunkptr)(((char*)(p)) + (s)))
1343
1344
1345
1346
1347 /*
1348 Dealing with use bits
1349 */
1350
1351 /* extract p's inuse bit */
1352
1353 #define inuse(p)\
1354 ((((mchunkptr)(((char*)(p))+((p)->size & ~PREV_INUSE)))->size) & PREV_INUSE)
1355
1356 /* extract inuse bit of previous chunk */
1357
1358 #define prev_inuse(p) ((p)->size & PREV_INUSE)
1359
1360 /* check for mmap()'ed chunk */
1361
1362 #define chunk_is_mmapped(p) ((p)->size & IS_MMAPPED)
1363
1364 /* set/clear chunk as in use without otherwise disturbing */
1365
1366 #define set_inuse(p)\
1367 ((mchunkptr)(((char*)(p)) + ((p)->size & ~PREV_INUSE)))->size |= PREV_INUSE
1368
1369 #define clear_inuse(p)\
1370 ((mchunkptr)(((char*)(p)) + ((p)->size & ~PREV_INUSE)))->size &= ~(PREV_INUSE)
1371
1372 /* check/set/clear inuse bits in known places */
1373
1374 #define inuse_bit_at_offset(p, s)\
1375 (((mchunkptr)(((char*)(p)) + (s)))->size & PREV_INUSE)
1376
1377 #define set_inuse_bit_at_offset(p, s)\
1378 (((mchunkptr)(((char*)(p)) + (s)))->size |= PREV_INUSE)
1379
1380 #define clear_inuse_bit_at_offset(p, s)\
1381 (((mchunkptr)(((char*)(p)) + (s)))->size &= ~(PREV_INUSE))
1382
1383
1384
1385
1386 /*
1387 Dealing with size fields
1388 */
1389
1390 /* Get size, ignoring use bits */
1391
1392 #define chunksize(p) ((p)->size & ~(SIZE_BITS))
1393
1394 /* Set size at head, without disturbing its use bit */
1395
1396 #define set_head_size(p, s) ((p)->size = (((p)->size & PREV_INUSE) | (s)))
1397
1398 /* Set size/use ignoring previous bits in header */
1399
1400 #define set_head(p, s) ((p)->size = (s))
1401
1402 /* Set size at footer (only when chunk is not in use) */
1403
1404 #define set_foot(p, s) (((mchunkptr)((char*)(p) + (s)))->prev_size = (s))
1405
1406
1407
1408
1409
1410 /*
1411 Bins
1412
1413 The bins, `av_' are an array of pairs of pointers serving as the
1414 heads of (initially empty) doubly-linked lists of chunks, laid out
1415 in a way so that each pair can be treated as if it were in a
1416 malloc_chunk. (This way, the fd/bk offsets for linking bin heads
1417 and chunks are the same).
1418
1419 Bins for sizes < 512 bytes contain chunks of all the same size, spaced
1420 8 bytes apart. Larger bins are approximately logarithmically
1421 spaced. (See the table below.) The `av_' array is never mentioned
1422 directly in the code, but instead via bin access macros.
1423
1424 Bin layout:
1425
1426 64 bins of size 8
1427 32 bins of size 64
1428 16 bins of size 512
1429 8 bins of size 4096
1430 4 bins of size 32768
1431 2 bins of size 262144
1432 1 bin of size what's left
1433
1434 There is actually a little bit of slop in the numbers in bin_index
1435 for the sake of speed. This makes no difference elsewhere.
1436
1437 The special chunks `top' and `last_remainder' get their own bins,
1438 (this is implemented via yet more trickery with the av_ array),
1439 although `top' is never properly linked to its bin since it is
1440 always handled specially.
1441
1442 */
1443
1444 #define NAV 128 /* number of bins */
1445
1446 typedef struct malloc_chunk* mbinptr;
1447
1448 /* access macros */
1449
1450 #define bin_at(i) ((mbinptr)((char*)&(av_[2*(i) + 2]) - 2*SIZE_SZ))
1451 #define next_bin(b) ((mbinptr)((char*)(b) + 2 * sizeof(mbinptr)))
1452 #define prev_bin(b) ((mbinptr)((char*)(b) - 2 * sizeof(mbinptr)))
1453
1454 /*
1455 The first 2 bins are never indexed. The corresponding av_ cells are instead
1456 used for bookkeeping. This is not to save space, but to simplify
1457 indexing, maintain locality, and avoid some initialization tests.
1458 */
1459
1460 #define top (av_[2]) /* The topmost chunk */
1461 #define last_remainder (bin_at(1)) /* remainder from last split */
1462
1463
1464 /*
1465 Because top initially points to its own bin with initial
1466 zero size, thus forcing extension on the first malloc request,
1467 we avoid having any special code in malloc to check whether
1468 it even exists yet. But we still need to in malloc_extend_top.
1469 */
1470
1471 #define initial_top ((mchunkptr)(bin_at(0)))
1472
1473 /* Helper macro to initialize bins */
1474
1475 #define IAV(i) bin_at(i), bin_at(i)
1476
1477 static mbinptr av_[NAV * 2 + 2] = {
1478 0, 0,
1479 IAV(0), IAV(1), IAV(2), IAV(3), IAV(4), IAV(5), IAV(6), IAV(7),
1480 IAV(8), IAV(9), IAV(10), IAV(11), IAV(12), IAV(13), IAV(14), IAV(15),
1481 IAV(16), IAV(17), IAV(18), IAV(19), IAV(20), IAV(21), IAV(22), IAV(23),
1482 IAV(24), IAV(25), IAV(26), IAV(27), IAV(28), IAV(29), IAV(30), IAV(31),
1483 IAV(32), IAV(33), IAV(34), IAV(35), IAV(36), IAV(37), IAV(38), IAV(39),
1484 IAV(40), IAV(41), IAV(42), IAV(43), IAV(44), IAV(45), IAV(46), IAV(47),
1485 IAV(48), IAV(49), IAV(50), IAV(51), IAV(52), IAV(53), IAV(54), IAV(55),
1486 IAV(56), IAV(57), IAV(58), IAV(59), IAV(60), IAV(61), IAV(62), IAV(63),
1487 IAV(64), IAV(65), IAV(66), IAV(67), IAV(68), IAV(69), IAV(70), IAV(71),
1488 IAV(72), IAV(73), IAV(74), IAV(75), IAV(76), IAV(77), IAV(78), IAV(79),
1489 IAV(80), IAV(81), IAV(82), IAV(83), IAV(84), IAV(85), IAV(86), IAV(87),
1490 IAV(88), IAV(89), IAV(90), IAV(91), IAV(92), IAV(93), IAV(94), IAV(95),
1491 IAV(96), IAV(97), IAV(98), IAV(99), IAV(100), IAV(101), IAV(102), IAV(103),
1492 IAV(104), IAV(105), IAV(106), IAV(107), IAV(108), IAV(109), IAV(110), IAV(111),
1493 IAV(112), IAV(113), IAV(114), IAV(115), IAV(116), IAV(117), IAV(118), IAV(119),
1494 IAV(120), IAV(121), IAV(122), IAV(123), IAV(124), IAV(125), IAV(126), IAV(127)
1495 };
1496
1497 #ifndef CONFIG_RELOC_FIXUP_WORKS
malloc_bin_reloc(void)1498 void malloc_bin_reloc (void)
1499 {
1500 unsigned long *p = (unsigned long *)(&av_[2]);
1501 int i;
1502 for (i=2; i<(sizeof(av_)/sizeof(mbinptr)); ++i) {
1503 *p++ += gd->reloc_off;
1504 }
1505 }
1506 #endif
1507
1508 ulong mem_malloc_start = 0;
1509 ulong mem_malloc_end = 0;
1510 ulong mem_malloc_brk = 0;
1511
sbrk(ptrdiff_t increment)1512 void *sbrk(ptrdiff_t increment)
1513 {
1514 ulong old = mem_malloc_brk;
1515 ulong new = old + increment;
1516
1517 if ((new < mem_malloc_start) || (new > mem_malloc_end))
1518 return (void *)MORECORE_FAILURE;
1519
1520 mem_malloc_brk = new;
1521
1522 return (void *)old;
1523 }
1524
mem_malloc_init(ulong start,ulong size)1525 void mem_malloc_init(ulong start, ulong size)
1526 {
1527 mem_malloc_start = start;
1528 mem_malloc_end = start + size;
1529 mem_malloc_brk = start;
1530
1531 memset((void *)mem_malloc_start, 0, size);
1532 }
1533
1534 /* field-extraction macros */
1535
1536 #define first(b) ((b)->fd)
1537 #define last(b) ((b)->bk)
1538
1539 /*
1540 Indexing into bins
1541 */
1542
1543 #define bin_index(sz) \
1544 (((((unsigned long)(sz)) >> 9) == 0) ? (((unsigned long)(sz)) >> 3): \
1545 ((((unsigned long)(sz)) >> 9) <= 4) ? 56 + (((unsigned long)(sz)) >> 6): \
1546 ((((unsigned long)(sz)) >> 9) <= 20) ? 91 + (((unsigned long)(sz)) >> 9): \
1547 ((((unsigned long)(sz)) >> 9) <= 84) ? 110 + (((unsigned long)(sz)) >> 12): \
1548 ((((unsigned long)(sz)) >> 9) <= 340) ? 119 + (((unsigned long)(sz)) >> 15): \
1549 ((((unsigned long)(sz)) >> 9) <= 1364) ? 124 + (((unsigned long)(sz)) >> 18): \
1550 126)
1551 /*
1552 bins for chunks < 512 are all spaced 8 bytes apart, and hold
1553 identically sized chunks. This is exploited in malloc.
1554 */
1555
1556 #define MAX_SMALLBIN 63
1557 #define MAX_SMALLBIN_SIZE 512
1558 #define SMALLBIN_WIDTH 8
1559
1560 #define smallbin_index(sz) (((unsigned long)(sz)) >> 3)
1561
1562 /*
1563 Requests are `small' if both the corresponding and the next bin are small
1564 */
1565
1566 #define is_small_request(nb) (nb < MAX_SMALLBIN_SIZE - SMALLBIN_WIDTH)
1567
1568
1569
1570 /*
1571 To help compensate for the large number of bins, a one-level index
1572 structure is used for bin-by-bin searching. `binblocks' is a
1573 one-word bitvector recording whether groups of BINBLOCKWIDTH bins
1574 have any (possibly) non-empty bins, so they can be skipped over
1575 all at once during during traversals. The bits are NOT always
1576 cleared as soon as all bins in a block are empty, but instead only
1577 when all are noticed to be empty during traversal in malloc.
1578 */
1579
1580 #define BINBLOCKWIDTH 4 /* bins per block */
1581
1582 #define binblocks_r ((INTERNAL_SIZE_T)av_[1]) /* bitvector of nonempty blocks */
1583 #define binblocks_w (av_[1])
1584
1585 /* bin<->block macros */
1586
1587 #define idx2binblock(ix) ((unsigned)1 << (ix / BINBLOCKWIDTH))
1588 #define mark_binblock(ii) (binblocks_w = (mbinptr)(binblocks_r | idx2binblock(ii)))
1589 #define clear_binblock(ii) (binblocks_w = (mbinptr)(binblocks_r & ~(idx2binblock(ii))))
1590
1591
1592
1593
1594
1595 /* Other static bookkeeping data */
1596
1597 /* variables holding tunable values */
1598
1599 static unsigned long trim_threshold = DEFAULT_TRIM_THRESHOLD;
1600 static unsigned long top_pad = DEFAULT_TOP_PAD;
1601 static unsigned int n_mmaps_max = DEFAULT_MMAP_MAX;
1602 static unsigned long mmap_threshold = DEFAULT_MMAP_THRESHOLD;
1603
1604 /* The first value returned from sbrk */
1605 static char* sbrk_base = (char*)(-1);
1606
1607 /* The maximum memory obtained from system via sbrk */
1608 static unsigned long max_sbrked_mem = 0;
1609
1610 /* The maximum via either sbrk or mmap */
1611 static unsigned long max_total_mem = 0;
1612
1613 /* internal working copy of mallinfo */
1614 static struct mallinfo current_mallinfo = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
1615
1616 /* The total memory obtained from system via sbrk */
1617 #define sbrked_mem (current_mallinfo.arena)
1618
1619 /* Tracking mmaps */
1620
1621 #if 0
1622 static unsigned int n_mmaps = 0;
1623 #endif /* 0 */
1624 static unsigned long mmapped_mem = 0;
1625 #if HAVE_MMAP
1626 static unsigned int max_n_mmaps = 0;
1627 static unsigned long max_mmapped_mem = 0;
1628 #endif
1629
1630
1631
1632 /*
1633 Debugging support
1634 */
1635
1636 #ifdef DEBUG
1637
1638
1639 /*
1640 These routines make a number of assertions about the states
1641 of data structures that should be true at all times. If any
1642 are not true, it's very likely that a user program has somehow
1643 trashed memory. (It's also possible that there is a coding error
1644 in malloc. In which case, please report it!)
1645 */
1646
1647 #if __STD_C
do_check_chunk(mchunkptr p)1648 static void do_check_chunk(mchunkptr p)
1649 #else
1650 static void do_check_chunk(p) mchunkptr p;
1651 #endif
1652 {
1653 #if 0 /* causes warnings because assert() is off */
1654 INTERNAL_SIZE_T sz = p->size & ~PREV_INUSE;
1655 #endif /* 0 */
1656
1657 /* No checkable chunk is mmapped */
1658 assert(!chunk_is_mmapped(p));
1659
1660 /* Check for legal address ... */
1661 assert((char*)p >= sbrk_base);
1662 if (p != top)
1663 assert((char*)p + sz <= (char*)top);
1664 else
1665 assert((char*)p + sz <= sbrk_base + sbrked_mem);
1666
1667 }
1668
1669
1670 #if __STD_C
do_check_free_chunk(mchunkptr p)1671 static void do_check_free_chunk(mchunkptr p)
1672 #else
1673 static void do_check_free_chunk(p) mchunkptr p;
1674 #endif
1675 {
1676 INTERNAL_SIZE_T sz = p->size & ~PREV_INUSE;
1677 #if 0 /* causes warnings because assert() is off */
1678 mchunkptr next = chunk_at_offset(p, sz);
1679 #endif /* 0 */
1680
1681 do_check_chunk(p);
1682
1683 /* Check whether it claims to be free ... */
1684 assert(!inuse(p));
1685
1686 /* Unless a special marker, must have OK fields */
1687 if ((long)sz >= (long)MINSIZE)
1688 {
1689 assert((sz & MALLOC_ALIGN_MASK) == 0);
1690 assert(aligned_OK(chunk2mem(p)));
1691 /* ... matching footer field */
1692 assert(next->prev_size == sz);
1693 /* ... and is fully consolidated */
1694 assert(prev_inuse(p));
1695 assert (next == top || inuse(next));
1696
1697 /* ... and has minimally sane links */
1698 assert(p->fd->bk == p);
1699 assert(p->bk->fd == p);
1700 }
1701 else /* markers are always of size SIZE_SZ */
1702 assert(sz == SIZE_SZ);
1703 }
1704
1705 #if __STD_C
do_check_inuse_chunk(mchunkptr p)1706 static void do_check_inuse_chunk(mchunkptr p)
1707 #else
1708 static void do_check_inuse_chunk(p) mchunkptr p;
1709 #endif
1710 {
1711 mchunkptr next = next_chunk(p);
1712 do_check_chunk(p);
1713
1714 /* Check whether it claims to be in use ... */
1715 assert(inuse(p));
1716
1717 /* ... and is surrounded by OK chunks.
1718 Since more things can be checked with free chunks than inuse ones,
1719 if an inuse chunk borders them and debug is on, it's worth doing them.
1720 */
1721 if (!prev_inuse(p))
1722 {
1723 mchunkptr prv = prev_chunk(p);
1724 assert(next_chunk(prv) == p);
1725 do_check_free_chunk(prv);
1726 }
1727 if (next == top)
1728 {
1729 assert(prev_inuse(next));
1730 assert(chunksize(next) >= MINSIZE);
1731 }
1732 else if (!inuse(next))
1733 do_check_free_chunk(next);
1734
1735 }
1736
1737 #if __STD_C
do_check_malloced_chunk(mchunkptr p,INTERNAL_SIZE_T s)1738 static void do_check_malloced_chunk(mchunkptr p, INTERNAL_SIZE_T s)
1739 #else
1740 static void do_check_malloced_chunk(p, s) mchunkptr p; INTERNAL_SIZE_T s;
1741 #endif
1742 {
1743 #if 0 /* causes warnings because assert() is off */
1744 INTERNAL_SIZE_T sz = p->size & ~PREV_INUSE;
1745 long room = sz - s;
1746 #endif /* 0 */
1747
1748 do_check_inuse_chunk(p);
1749
1750 /* Legal size ... */
1751 assert((long)sz >= (long)MINSIZE);
1752 assert((sz & MALLOC_ALIGN_MASK) == 0);
1753 assert(room >= 0);
1754 assert(room < (long)MINSIZE);
1755
1756 /* ... and alignment */
1757 assert(aligned_OK(chunk2mem(p)));
1758
1759
1760 /* ... and was allocated at front of an available chunk */
1761 assert(prev_inuse(p));
1762
1763 }
1764
1765
1766 #define check_free_chunk(P) do_check_free_chunk(P)
1767 #define check_inuse_chunk(P) do_check_inuse_chunk(P)
1768 #define check_chunk(P) do_check_chunk(P)
1769 #define check_malloced_chunk(P,N) do_check_malloced_chunk(P,N)
1770 #else
1771 #define check_free_chunk(P)
1772 #define check_inuse_chunk(P)
1773 #define check_chunk(P)
1774 #define check_malloced_chunk(P,N)
1775 #endif
1776
1777
1778
1779 /*
1780 Macro-based internal utilities
1781 */
1782
1783
1784 /*
1785 Linking chunks in bin lists.
1786 Call these only with variables, not arbitrary expressions, as arguments.
1787 */
1788
1789 /*
1790 Place chunk p of size s in its bin, in size order,
1791 putting it ahead of others of same size.
1792 */
1793
1794
1795 #define frontlink(P, S, IDX, BK, FD) \
1796 { \
1797 if (S < MAX_SMALLBIN_SIZE) \
1798 { \
1799 IDX = smallbin_index(S); \
1800 mark_binblock(IDX); \
1801 BK = bin_at(IDX); \
1802 FD = BK->fd; \
1803 P->bk = BK; \
1804 P->fd = FD; \
1805 FD->bk = BK->fd = P; \
1806 } \
1807 else \
1808 { \
1809 IDX = bin_index(S); \
1810 BK = bin_at(IDX); \
1811 FD = BK->fd; \
1812 if (FD == BK) mark_binblock(IDX); \
1813 else \
1814 { \
1815 while (FD != BK && S < chunksize(FD)) FD = FD->fd; \
1816 BK = FD->bk; \
1817 } \
1818 P->bk = BK; \
1819 P->fd = FD; \
1820 FD->bk = BK->fd = P; \
1821 } \
1822 }
1823
1824
1825 /* take a chunk off a list */
1826
1827 #define unlink(P, BK, FD) \
1828 { \
1829 BK = P->bk; \
1830 FD = P->fd; \
1831 FD->bk = BK; \
1832 BK->fd = FD; \
1833 } \
1834
1835 /* Place p as the last remainder */
1836
1837 #define link_last_remainder(P) \
1838 { \
1839 last_remainder->fd = last_remainder->bk = P; \
1840 P->fd = P->bk = last_remainder; \
1841 }
1842
1843 /* Clear the last_remainder bin */
1844
1845 #define clear_last_remainder \
1846 (last_remainder->fd = last_remainder->bk = last_remainder)
1847
1848
1849
1850
1851
1852 /* Routines dealing with mmap(). */
1853
1854 #if HAVE_MMAP
1855
1856 #if __STD_C
mmap_chunk(size_t size)1857 static mchunkptr mmap_chunk(size_t size)
1858 #else
1859 static mchunkptr mmap_chunk(size) size_t size;
1860 #endif
1861 {
1862 size_t page_mask = malloc_getpagesize - 1;
1863 mchunkptr p;
1864
1865 #ifndef MAP_ANONYMOUS
1866 static int fd = -1;
1867 #endif
1868
1869 if(n_mmaps >= n_mmaps_max) return 0; /* too many regions */
1870
1871 /* For mmapped chunks, the overhead is one SIZE_SZ unit larger, because
1872 * there is no following chunk whose prev_size field could be used.
1873 */
1874 size = (size + SIZE_SZ + page_mask) & ~page_mask;
1875
1876 #ifdef MAP_ANONYMOUS
1877 p = (mchunkptr)mmap(0, size, PROT_READ|PROT_WRITE,
1878 MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
1879 #else /* !MAP_ANONYMOUS */
1880 if (fd < 0)
1881 {
1882 fd = open("/dev/zero", O_RDWR);
1883 if(fd < 0) return 0;
1884 }
1885 p = (mchunkptr)mmap(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
1886 #endif
1887
1888 if(p == (mchunkptr)-1) return 0;
1889
1890 n_mmaps++;
1891 if (n_mmaps > max_n_mmaps) max_n_mmaps = n_mmaps;
1892
1893 /* We demand that eight bytes into a page must be 8-byte aligned. */
1894 assert(aligned_OK(chunk2mem(p)));
1895
1896 /* The offset to the start of the mmapped region is stored
1897 * in the prev_size field of the chunk; normally it is zero,
1898 * but that can be changed in memalign().
1899 */
1900 p->prev_size = 0;
1901 set_head(p, size|IS_MMAPPED);
1902
1903 mmapped_mem += size;
1904 if ((unsigned long)mmapped_mem > (unsigned long)max_mmapped_mem)
1905 max_mmapped_mem = mmapped_mem;
1906 if ((unsigned long)(mmapped_mem + sbrked_mem) > (unsigned long)max_total_mem)
1907 max_total_mem = mmapped_mem + sbrked_mem;
1908 return p;
1909 }
1910
1911 #if __STD_C
munmap_chunk(mchunkptr p)1912 static void munmap_chunk(mchunkptr p)
1913 #else
1914 static void munmap_chunk(p) mchunkptr p;
1915 #endif
1916 {
1917 INTERNAL_SIZE_T size = chunksize(p);
1918 int ret;
1919
1920 assert (chunk_is_mmapped(p));
1921 assert(! ((char*)p >= sbrk_base && (char*)p < sbrk_base + sbrked_mem));
1922 assert((n_mmaps > 0));
1923 assert(((p->prev_size + size) & (malloc_getpagesize-1)) == 0);
1924
1925 n_mmaps--;
1926 mmapped_mem -= (size + p->prev_size);
1927
1928 ret = munmap((char *)p - p->prev_size, size + p->prev_size);
1929
1930 /* munmap returns non-zero on failure */
1931 assert(ret == 0);
1932 }
1933
1934 #if HAVE_MREMAP
1935
1936 #if __STD_C
mremap_chunk(mchunkptr p,size_t new_size)1937 static mchunkptr mremap_chunk(mchunkptr p, size_t new_size)
1938 #else
1939 static mchunkptr mremap_chunk(p, new_size) mchunkptr p; size_t new_size;
1940 #endif
1941 {
1942 size_t page_mask = malloc_getpagesize - 1;
1943 INTERNAL_SIZE_T offset = p->prev_size;
1944 INTERNAL_SIZE_T size = chunksize(p);
1945 char *cp;
1946
1947 assert (chunk_is_mmapped(p));
1948 assert(! ((char*)p >= sbrk_base && (char*)p < sbrk_base + sbrked_mem));
1949 assert((n_mmaps > 0));
1950 assert(((size + offset) & (malloc_getpagesize-1)) == 0);
1951
1952 /* Note the extra SIZE_SZ overhead as in mmap_chunk(). */
1953 new_size = (new_size + offset + SIZE_SZ + page_mask) & ~page_mask;
1954
1955 cp = (char *)mremap((char *)p - offset, size + offset, new_size, 1);
1956
1957 if (cp == (char *)-1) return 0;
1958
1959 p = (mchunkptr)(cp + offset);
1960
1961 assert(aligned_OK(chunk2mem(p)));
1962
1963 assert((p->prev_size == offset));
1964 set_head(p, (new_size - offset)|IS_MMAPPED);
1965
1966 mmapped_mem -= size + offset;
1967 mmapped_mem += new_size;
1968 if ((unsigned long)mmapped_mem > (unsigned long)max_mmapped_mem)
1969 max_mmapped_mem = mmapped_mem;
1970 if ((unsigned long)(mmapped_mem + sbrked_mem) > (unsigned long)max_total_mem)
1971 max_total_mem = mmapped_mem + sbrked_mem;
1972 return p;
1973 }
1974
1975 #endif /* HAVE_MREMAP */
1976
1977 #endif /* HAVE_MMAP */
1978
1979
1980
1981
1982 /*
1983 Extend the top-most chunk by obtaining memory from system.
1984 Main interface to sbrk (but see also malloc_trim).
1985 */
1986
1987 #if __STD_C
malloc_extend_top(INTERNAL_SIZE_T nb)1988 static void malloc_extend_top(INTERNAL_SIZE_T nb)
1989 #else
1990 static void malloc_extend_top(nb) INTERNAL_SIZE_T nb;
1991 #endif
1992 {
1993 char* brk; /* return value from sbrk */
1994 INTERNAL_SIZE_T front_misalign; /* unusable bytes at front of sbrked space */
1995 INTERNAL_SIZE_T correction; /* bytes for 2nd sbrk call */
1996 char* new_brk; /* return of 2nd sbrk call */
1997 INTERNAL_SIZE_T top_size; /* new size of top chunk */
1998
1999 mchunkptr old_top = top; /* Record state of old top */
2000 INTERNAL_SIZE_T old_top_size = chunksize(old_top);
2001 char* old_end = (char*)(chunk_at_offset(old_top, old_top_size));
2002
2003 /* Pad request with top_pad plus minimal overhead */
2004
2005 INTERNAL_SIZE_T sbrk_size = nb + top_pad + MINSIZE;
2006 unsigned long pagesz = malloc_getpagesize;
2007
2008 /* If not the first time through, round to preserve page boundary */
2009 /* Otherwise, we need to correct to a page size below anyway. */
2010 /* (We also correct below if an intervening foreign sbrk call.) */
2011
2012 if (sbrk_base != (char*)(-1))
2013 sbrk_size = (sbrk_size + (pagesz - 1)) & ~(pagesz - 1);
2014
2015 brk = (char*)(MORECORE (sbrk_size));
2016
2017 /* Fail if sbrk failed or if a foreign sbrk call killed our space */
2018 if (brk == (char*)(MORECORE_FAILURE) ||
2019 (brk < old_end && old_top != initial_top))
2020 return;
2021
2022 sbrked_mem += sbrk_size;
2023
2024 if (brk == old_end) /* can just add bytes to current top */
2025 {
2026 top_size = sbrk_size + old_top_size;
2027 set_head(top, top_size | PREV_INUSE);
2028 }
2029 else
2030 {
2031 if (sbrk_base == (char*)(-1)) /* First time through. Record base */
2032 sbrk_base = brk;
2033 else /* Someone else called sbrk(). Count those bytes as sbrked_mem. */
2034 sbrked_mem += brk - (char*)old_end;
2035
2036 /* Guarantee alignment of first new chunk made from this space */
2037 front_misalign = (unsigned long)chunk2mem(brk) & MALLOC_ALIGN_MASK;
2038 if (front_misalign > 0)
2039 {
2040 correction = (MALLOC_ALIGNMENT) - front_misalign;
2041 brk += correction;
2042 }
2043 else
2044 correction = 0;
2045
2046 /* Guarantee the next brk will be at a page boundary */
2047
2048 correction += ((((unsigned long)(brk + sbrk_size))+(pagesz-1)) &
2049 ~(pagesz - 1)) - ((unsigned long)(brk + sbrk_size));
2050
2051 /* Allocate correction */
2052 new_brk = (char*)(MORECORE (correction));
2053 if (new_brk == (char*)(MORECORE_FAILURE)) return;
2054
2055 sbrked_mem += correction;
2056
2057 top = (mchunkptr)brk;
2058 top_size = new_brk - brk + correction;
2059 set_head(top, top_size | PREV_INUSE);
2060
2061 if (old_top != initial_top)
2062 {
2063
2064 /* There must have been an intervening foreign sbrk call. */
2065 /* A double fencepost is necessary to prevent consolidation */
2066
2067 /* If not enough space to do this, then user did something very wrong */
2068 if (old_top_size < MINSIZE)
2069 {
2070 set_head(top, PREV_INUSE); /* will force null return from malloc */
2071 return;
2072 }
2073
2074 /* Also keep size a multiple of MALLOC_ALIGNMENT */
2075 old_top_size = (old_top_size - 3*SIZE_SZ) & ~MALLOC_ALIGN_MASK;
2076 set_head_size(old_top, old_top_size);
2077 chunk_at_offset(old_top, old_top_size )->size =
2078 SIZE_SZ|PREV_INUSE;
2079 chunk_at_offset(old_top, old_top_size + SIZE_SZ)->size =
2080 SIZE_SZ|PREV_INUSE;
2081 /* If possible, release the rest. */
2082 if (old_top_size >= MINSIZE)
2083 fREe(chunk2mem(old_top));
2084 }
2085 }
2086
2087 if ((unsigned long)sbrked_mem > (unsigned long)max_sbrked_mem)
2088 max_sbrked_mem = sbrked_mem;
2089 if ((unsigned long)(mmapped_mem + sbrked_mem) > (unsigned long)max_total_mem)
2090 max_total_mem = mmapped_mem + sbrked_mem;
2091
2092 /* We always land on a page boundary */
2093 assert(((unsigned long)((char*)top + top_size) & (pagesz - 1)) == 0);
2094 }
2095
2096
2097
2098
2099 /* Main public routines */
2100
2101
2102 /*
2103 Malloc Algorthim:
2104
2105 The requested size is first converted into a usable form, `nb'.
2106 This currently means to add 4 bytes overhead plus possibly more to
2107 obtain 8-byte alignment and/or to obtain a size of at least
2108 MINSIZE (currently 16 bytes), the smallest allocatable size.
2109 (All fits are considered `exact' if they are within MINSIZE bytes.)
2110
2111 From there, the first successful of the following steps is taken:
2112
2113 1. The bin corresponding to the request size is scanned, and if
2114 a chunk of exactly the right size is found, it is taken.
2115
2116 2. The most recently remaindered chunk is used if it is big
2117 enough. This is a form of (roving) first fit, used only in
2118 the absence of exact fits. Runs of consecutive requests use
2119 the remainder of the chunk used for the previous such request
2120 whenever possible. This limited use of a first-fit style
2121 allocation strategy tends to give contiguous chunks
2122 coextensive lifetimes, which improves locality and can reduce
2123 fragmentation in the long run.
2124
2125 3. Other bins are scanned in increasing size order, using a
2126 chunk big enough to fulfill the request, and splitting off
2127 any remainder. This search is strictly by best-fit; i.e.,
2128 the smallest (with ties going to approximately the least
2129 recently used) chunk that fits is selected.
2130
2131 4. If large enough, the chunk bordering the end of memory
2132 (`top') is split off. (This use of `top' is in accord with
2133 the best-fit search rule. In effect, `top' is treated as
2134 larger (and thus less well fitting) than any other available
2135 chunk since it can be extended to be as large as necessary
2136 (up to system limitations).
2137
2138 5. If the request size meets the mmap threshold and the
2139 system supports mmap, and there are few enough currently
2140 allocated mmapped regions, and a call to mmap succeeds,
2141 the request is allocated via direct memory mapping.
2142
2143 6. Otherwise, the top of memory is extended by
2144 obtaining more space from the system (normally using sbrk,
2145 but definable to anything else via the MORECORE macro).
2146 Memory is gathered from the system (in system page-sized
2147 units) in a way that allows chunks obtained across different
2148 sbrk calls to be consolidated, but does not require
2149 contiguous memory. Thus, it should be safe to intersperse
2150 mallocs with other sbrk calls.
2151
2152
2153 All allocations are made from the the `lowest' part of any found
2154 chunk. (The implementation invariant is that prev_inuse is
2155 always true of any allocated chunk; i.e., that each allocated
2156 chunk borders either a previously allocated and still in-use chunk,
2157 or the base of its memory arena.)
2158
2159 */
2160
2161 #if __STD_C
mALLOc(size_t bytes)2162 Void_t* mALLOc(size_t bytes)
2163 #else
2164 Void_t* mALLOc(bytes) size_t bytes;
2165 #endif
2166 {
2167 mchunkptr victim; /* inspected/selected chunk */
2168 INTERNAL_SIZE_T victim_size; /* its size */
2169 int idx; /* index for bin traversal */
2170 mbinptr bin; /* associated bin */
2171 mchunkptr remainder; /* remainder from a split */
2172 long remainder_size; /* its size */
2173 int remainder_index; /* its bin index */
2174 unsigned long block; /* block traverser bit */
2175 int startidx; /* first bin of a traversed block */
2176 mchunkptr fwd; /* misc temp for linking */
2177 mchunkptr bck; /* misc temp for linking */
2178 mbinptr q; /* misc temp */
2179
2180 INTERNAL_SIZE_T nb;
2181
2182 /* check if mem_malloc_init() was run */
2183 if ((mem_malloc_start == 0) && (mem_malloc_end == 0)) {
2184 /* not initialized yet */
2185 return 0;
2186 }
2187
2188 if ((long)bytes < 0) return 0;
2189
2190 nb = request2size(bytes); /* padded request size; */
2191
2192 /* Check for exact match in a bin */
2193
2194 if (is_small_request(nb)) /* Faster version for small requests */
2195 {
2196 idx = smallbin_index(nb);
2197
2198 /* No traversal or size check necessary for small bins. */
2199
2200 q = bin_at(idx);
2201 victim = last(q);
2202
2203 /* Also scan the next one, since it would have a remainder < MINSIZE */
2204 if (victim == q)
2205 {
2206 q = next_bin(q);
2207 victim = last(q);
2208 }
2209 if (victim != q)
2210 {
2211 victim_size = chunksize(victim);
2212 unlink(victim, bck, fwd);
2213 set_inuse_bit_at_offset(victim, victim_size);
2214 check_malloced_chunk(victim, nb);
2215 return chunk2mem(victim);
2216 }
2217
2218 idx += 2; /* Set for bin scan below. We've already scanned 2 bins. */
2219
2220 }
2221 else
2222 {
2223 idx = bin_index(nb);
2224 bin = bin_at(idx);
2225
2226 for (victim = last(bin); victim != bin; victim = victim->bk)
2227 {
2228 victim_size = chunksize(victim);
2229 remainder_size = victim_size - nb;
2230
2231 if (remainder_size >= (long)MINSIZE) /* too big */
2232 {
2233 --idx; /* adjust to rescan below after checking last remainder */
2234 break;
2235 }
2236
2237 else if (remainder_size >= 0) /* exact fit */
2238 {
2239 unlink(victim, bck, fwd);
2240 set_inuse_bit_at_offset(victim, victim_size);
2241 check_malloced_chunk(victim, nb);
2242 return chunk2mem(victim);
2243 }
2244 }
2245
2246 ++idx;
2247
2248 }
2249
2250 /* Try to use the last split-off remainder */
2251
2252 if ( (victim = last_remainder->fd) != last_remainder)
2253 {
2254 victim_size = chunksize(victim);
2255 remainder_size = victim_size - nb;
2256
2257 if (remainder_size >= (long)MINSIZE) /* re-split */
2258 {
2259 remainder = chunk_at_offset(victim, nb);
2260 set_head(victim, nb | PREV_INUSE);
2261 link_last_remainder(remainder);
2262 set_head(remainder, remainder_size | PREV_INUSE);
2263 set_foot(remainder, remainder_size);
2264 check_malloced_chunk(victim, nb);
2265 return chunk2mem(victim);
2266 }
2267
2268 clear_last_remainder;
2269
2270 if (remainder_size >= 0) /* exhaust */
2271 {
2272 set_inuse_bit_at_offset(victim, victim_size);
2273 check_malloced_chunk(victim, nb);
2274 return chunk2mem(victim);
2275 }
2276
2277 /* Else place in bin */
2278
2279 frontlink(victim, victim_size, remainder_index, bck, fwd);
2280 }
2281
2282 /*
2283 If there are any possibly nonempty big-enough blocks,
2284 search for best fitting chunk by scanning bins in blockwidth units.
2285 */
2286
2287 if ( (block = idx2binblock(idx)) <= binblocks_r)
2288 {
2289
2290 /* Get to the first marked block */
2291
2292 if ( (block & binblocks_r) == 0)
2293 {
2294 /* force to an even block boundary */
2295 idx = (idx & ~(BINBLOCKWIDTH - 1)) + BINBLOCKWIDTH;
2296 block <<= 1;
2297 while ((block & binblocks_r) == 0)
2298 {
2299 idx += BINBLOCKWIDTH;
2300 block <<= 1;
2301 }
2302 }
2303
2304 /* For each possibly nonempty block ... */
2305 for (;;)
2306 {
2307 startidx = idx; /* (track incomplete blocks) */
2308 q = bin = bin_at(idx);
2309
2310 /* For each bin in this block ... */
2311 do
2312 {
2313 /* Find and use first big enough chunk ... */
2314
2315 for (victim = last(bin); victim != bin; victim = victim->bk)
2316 {
2317 victim_size = chunksize(victim);
2318 remainder_size = victim_size - nb;
2319
2320 if (remainder_size >= (long)MINSIZE) /* split */
2321 {
2322 remainder = chunk_at_offset(victim, nb);
2323 set_head(victim, nb | PREV_INUSE);
2324 unlink(victim, bck, fwd);
2325 link_last_remainder(remainder);
2326 set_head(remainder, remainder_size | PREV_INUSE);
2327 set_foot(remainder, remainder_size);
2328 check_malloced_chunk(victim, nb);
2329 return chunk2mem(victim);
2330 }
2331
2332 else if (remainder_size >= 0) /* take */
2333 {
2334 set_inuse_bit_at_offset(victim, victim_size);
2335 unlink(victim, bck, fwd);
2336 check_malloced_chunk(victim, nb);
2337 return chunk2mem(victim);
2338 }
2339
2340 }
2341
2342 bin = next_bin(bin);
2343
2344 } while ((++idx & (BINBLOCKWIDTH - 1)) != 0);
2345
2346 /* Clear out the block bit. */
2347
2348 do /* Possibly backtrack to try to clear a partial block */
2349 {
2350 if ((startidx & (BINBLOCKWIDTH - 1)) == 0)
2351 {
2352 av_[1] = (mbinptr)(binblocks_r & ~block);
2353 break;
2354 }
2355 --startidx;
2356 q = prev_bin(q);
2357 } while (first(q) == q);
2358
2359 /* Get to the next possibly nonempty block */
2360
2361 if ( (block <<= 1) <= binblocks_r && (block != 0) )
2362 {
2363 while ((block & binblocks_r) == 0)
2364 {
2365 idx += BINBLOCKWIDTH;
2366 block <<= 1;
2367 }
2368 }
2369 else
2370 break;
2371 }
2372 }
2373
2374
2375 /* Try to use top chunk */
2376
2377 /* Require that there be a remainder, ensuring top always exists */
2378 if ( (remainder_size = chunksize(top) - nb) < (long)MINSIZE)
2379 {
2380
2381 #if HAVE_MMAP
2382 /* If big and would otherwise need to extend, try to use mmap instead */
2383 if ((unsigned long)nb >= (unsigned long)mmap_threshold &&
2384 (victim = mmap_chunk(nb)) != 0)
2385 return chunk2mem(victim);
2386 #endif
2387
2388 /* Try to extend */
2389 malloc_extend_top(nb);
2390 if ( (remainder_size = chunksize(top) - nb) < (long)MINSIZE)
2391 return 0; /* propagate failure */
2392 }
2393
2394 victim = top;
2395 set_head(victim, nb | PREV_INUSE);
2396 top = chunk_at_offset(victim, nb);
2397 set_head(top, remainder_size | PREV_INUSE);
2398 check_malloced_chunk(victim, nb);
2399 return chunk2mem(victim);
2400
2401 }
2402
2403
2404
2405
2406 /*
2407
2408 free() algorithm :
2409
2410 cases:
2411
2412 1. free(0) has no effect.
2413
2414 2. If the chunk was allocated via mmap, it is release via munmap().
2415
2416 3. If a returned chunk borders the current high end of memory,
2417 it is consolidated into the top, and if the total unused
2418 topmost memory exceeds the trim threshold, malloc_trim is
2419 called.
2420
2421 4. Other chunks are consolidated as they arrive, and
2422 placed in corresponding bins. (This includes the case of
2423 consolidating with the current `last_remainder').
2424
2425 */
2426
2427
2428 #if __STD_C
fREe(Void_t * mem)2429 void fREe(Void_t* mem)
2430 #else
2431 void fREe(mem) Void_t* mem;
2432 #endif
2433 {
2434 mchunkptr p; /* chunk corresponding to mem */
2435 INTERNAL_SIZE_T hd; /* its head field */
2436 INTERNAL_SIZE_T sz; /* its size */
2437 int idx; /* its bin index */
2438 mchunkptr next; /* next contiguous chunk */
2439 INTERNAL_SIZE_T nextsz; /* its size */
2440 INTERNAL_SIZE_T prevsz; /* size of previous contiguous chunk */
2441 mchunkptr bck; /* misc temp for linking */
2442 mchunkptr fwd; /* misc temp for linking */
2443 int islr; /* track whether merging with last_remainder */
2444
2445 if (mem == 0) /* free(0) has no effect */
2446 return;
2447
2448 p = mem2chunk(mem);
2449 hd = p->size;
2450
2451 #if HAVE_MMAP
2452 if (hd & IS_MMAPPED) /* release mmapped memory. */
2453 {
2454 munmap_chunk(p);
2455 return;
2456 }
2457 #endif
2458
2459 check_inuse_chunk(p);
2460
2461 sz = hd & ~PREV_INUSE;
2462 next = chunk_at_offset(p, sz);
2463 nextsz = chunksize(next);
2464
2465 if (next == top) /* merge with top */
2466 {
2467 sz += nextsz;
2468
2469 if (!(hd & PREV_INUSE)) /* consolidate backward */
2470 {
2471 prevsz = p->prev_size;
2472 p = chunk_at_offset(p, -((long) prevsz));
2473 sz += prevsz;
2474 unlink(p, bck, fwd);
2475 }
2476
2477 set_head(p, sz | PREV_INUSE);
2478 top = p;
2479 if ((unsigned long)(sz) >= (unsigned long)trim_threshold)
2480 malloc_trim(top_pad);
2481 return;
2482 }
2483
2484 set_head(next, nextsz); /* clear inuse bit */
2485
2486 islr = 0;
2487
2488 if (!(hd & PREV_INUSE)) /* consolidate backward */
2489 {
2490 prevsz = p->prev_size;
2491 p = chunk_at_offset(p, -((long) prevsz));
2492 sz += prevsz;
2493
2494 if (p->fd == last_remainder) /* keep as last_remainder */
2495 islr = 1;
2496 else
2497 unlink(p, bck, fwd);
2498 }
2499
2500 if (!(inuse_bit_at_offset(next, nextsz))) /* consolidate forward */
2501 {
2502 sz += nextsz;
2503
2504 if (!islr && next->fd == last_remainder) /* re-insert last_remainder */
2505 {
2506 islr = 1;
2507 link_last_remainder(p);
2508 }
2509 else
2510 unlink(next, bck, fwd);
2511 }
2512
2513
2514 set_head(p, sz | PREV_INUSE);
2515 set_foot(p, sz);
2516 if (!islr)
2517 frontlink(p, sz, idx, bck, fwd);
2518 }
2519
2520
2521
2522
2523
2524 /*
2525
2526 Realloc algorithm:
2527
2528 Chunks that were obtained via mmap cannot be extended or shrunk
2529 unless HAVE_MREMAP is defined, in which case mremap is used.
2530 Otherwise, if their reallocation is for additional space, they are
2531 copied. If for less, they are just left alone.
2532
2533 Otherwise, if the reallocation is for additional space, and the
2534 chunk can be extended, it is, else a malloc-copy-free sequence is
2535 taken. There are several different ways that a chunk could be
2536 extended. All are tried:
2537
2538 * Extending forward into following adjacent free chunk.
2539 * Shifting backwards, joining preceding adjacent space
2540 * Both shifting backwards and extending forward.
2541 * Extending into newly sbrked space
2542
2543 Unless the #define REALLOC_ZERO_BYTES_FREES is set, realloc with a
2544 size argument of zero (re)allocates a minimum-sized chunk.
2545
2546 If the reallocation is for less space, and the new request is for
2547 a `small' (<512 bytes) size, then the newly unused space is lopped
2548 off and freed.
2549
2550 The old unix realloc convention of allowing the last-free'd chunk
2551 to be used as an argument to realloc is no longer supported.
2552 I don't know of any programs still relying on this feature,
2553 and allowing it would also allow too many other incorrect
2554 usages of realloc to be sensible.
2555
2556
2557 */
2558
2559
2560 #if __STD_C
rEALLOc(Void_t * oldmem,size_t bytes)2561 Void_t* rEALLOc(Void_t* oldmem, size_t bytes)
2562 #else
2563 Void_t* rEALLOc(oldmem, bytes) Void_t* oldmem; size_t bytes;
2564 #endif
2565 {
2566 INTERNAL_SIZE_T nb; /* padded request size */
2567
2568 mchunkptr oldp; /* chunk corresponding to oldmem */
2569 INTERNAL_SIZE_T oldsize; /* its size */
2570
2571 mchunkptr newp; /* chunk to return */
2572 INTERNAL_SIZE_T newsize; /* its size */
2573 Void_t* newmem; /* corresponding user mem */
2574
2575 mchunkptr next; /* next contiguous chunk after oldp */
2576 INTERNAL_SIZE_T nextsize; /* its size */
2577
2578 mchunkptr prev; /* previous contiguous chunk before oldp */
2579 INTERNAL_SIZE_T prevsize; /* its size */
2580
2581 mchunkptr remainder; /* holds split off extra space from newp */
2582 INTERNAL_SIZE_T remainder_size; /* its size */
2583
2584 mchunkptr bck; /* misc temp for linking */
2585 mchunkptr fwd; /* misc temp for linking */
2586
2587 #ifdef REALLOC_ZERO_BYTES_FREES
2588 if (bytes == 0) { fREe(oldmem); return 0; }
2589 #endif
2590
2591 if ((long)bytes < 0) return 0;
2592
2593 /* realloc of null is supposed to be same as malloc */
2594 if (oldmem == 0) return mALLOc(bytes);
2595
2596 newp = oldp = mem2chunk(oldmem);
2597 newsize = oldsize = chunksize(oldp);
2598
2599
2600 nb = request2size(bytes);
2601
2602 #if HAVE_MMAP
2603 if (chunk_is_mmapped(oldp))
2604 {
2605 #if HAVE_MREMAP
2606 newp = mremap_chunk(oldp, nb);
2607 if(newp) return chunk2mem(newp);
2608 #endif
2609 /* Note the extra SIZE_SZ overhead. */
2610 if(oldsize - SIZE_SZ >= nb) return oldmem; /* do nothing */
2611 /* Must alloc, copy, free. */
2612 newmem = mALLOc(bytes);
2613 if (newmem == 0) return 0; /* propagate failure */
2614 MALLOC_COPY(newmem, oldmem, oldsize - 2*SIZE_SZ);
2615 munmap_chunk(oldp);
2616 return newmem;
2617 }
2618 #endif
2619
2620 check_inuse_chunk(oldp);
2621
2622 if ((long)(oldsize) < (long)(nb))
2623 {
2624
2625 /* Try expanding forward */
2626
2627 next = chunk_at_offset(oldp, oldsize);
2628 if (next == top || !inuse(next))
2629 {
2630 nextsize = chunksize(next);
2631
2632 /* Forward into top only if a remainder */
2633 if (next == top)
2634 {
2635 if ((long)(nextsize + newsize) >= (long)(nb + MINSIZE))
2636 {
2637 newsize += nextsize;
2638 top = chunk_at_offset(oldp, nb);
2639 set_head(top, (newsize - nb) | PREV_INUSE);
2640 set_head_size(oldp, nb);
2641 return chunk2mem(oldp);
2642 }
2643 }
2644
2645 /* Forward into next chunk */
2646 else if (((long)(nextsize + newsize) >= (long)(nb)))
2647 {
2648 unlink(next, bck, fwd);
2649 newsize += nextsize;
2650 goto split;
2651 }
2652 }
2653 else
2654 {
2655 next = 0;
2656 nextsize = 0;
2657 }
2658
2659 /* Try shifting backwards. */
2660
2661 if (!prev_inuse(oldp))
2662 {
2663 prev = prev_chunk(oldp);
2664 prevsize = chunksize(prev);
2665
2666 /* try forward + backward first to save a later consolidation */
2667
2668 if (next != 0)
2669 {
2670 /* into top */
2671 if (next == top)
2672 {
2673 if ((long)(nextsize + prevsize + newsize) >= (long)(nb + MINSIZE))
2674 {
2675 unlink(prev, bck, fwd);
2676 newp = prev;
2677 newsize += prevsize + nextsize;
2678 newmem = chunk2mem(newp);
2679 MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ);
2680 top = chunk_at_offset(newp, nb);
2681 set_head(top, (newsize - nb) | PREV_INUSE);
2682 set_head_size(newp, nb);
2683 return newmem;
2684 }
2685 }
2686
2687 /* into next chunk */
2688 else if (((long)(nextsize + prevsize + newsize) >= (long)(nb)))
2689 {
2690 unlink(next, bck, fwd);
2691 unlink(prev, bck, fwd);
2692 newp = prev;
2693 newsize += nextsize + prevsize;
2694 newmem = chunk2mem(newp);
2695 MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ);
2696 goto split;
2697 }
2698 }
2699
2700 /* backward only */
2701 if (prev != 0 && (long)(prevsize + newsize) >= (long)nb)
2702 {
2703 unlink(prev, bck, fwd);
2704 newp = prev;
2705 newsize += prevsize;
2706 newmem = chunk2mem(newp);
2707 MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ);
2708 goto split;
2709 }
2710 }
2711
2712 /* Must allocate */
2713
2714 newmem = mALLOc (bytes);
2715
2716 if (newmem == 0) /* propagate failure */
2717 return 0;
2718
2719 /* Avoid copy if newp is next chunk after oldp. */
2720 /* (This can only happen when new chunk is sbrk'ed.) */
2721
2722 if ( (newp = mem2chunk(newmem)) == next_chunk(oldp))
2723 {
2724 newsize += chunksize(newp);
2725 newp = oldp;
2726 goto split;
2727 }
2728
2729 /* Otherwise copy, free, and exit */
2730 MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ);
2731 fREe(oldmem);
2732 return newmem;
2733 }
2734
2735
2736 split: /* split off extra room in old or expanded chunk */
2737
2738 if (newsize - nb >= MINSIZE) /* split off remainder */
2739 {
2740 remainder = chunk_at_offset(newp, nb);
2741 remainder_size = newsize - nb;
2742 set_head_size(newp, nb);
2743 set_head(remainder, remainder_size | PREV_INUSE);
2744 set_inuse_bit_at_offset(remainder, remainder_size);
2745 fREe(chunk2mem(remainder)); /* let free() deal with it */
2746 }
2747 else
2748 {
2749 set_head_size(newp, newsize);
2750 set_inuse_bit_at_offset(newp, newsize);
2751 }
2752
2753 check_inuse_chunk(newp);
2754 return chunk2mem(newp);
2755 }
2756
2757
2758
2759
2760 /*
2761
2762 memalign algorithm:
2763
2764 memalign requests more than enough space from malloc, finds a spot
2765 within that chunk that meets the alignment request, and then
2766 possibly frees the leading and trailing space.
2767
2768 The alignment argument must be a power of two. This property is not
2769 checked by memalign, so misuse may result in random runtime errors.
2770
2771 8-byte alignment is guaranteed by normal malloc calls, so don't
2772 bother calling memalign with an argument of 8 or less.
2773
2774 Overreliance on memalign is a sure way to fragment space.
2775
2776 */
2777
2778
2779 #if __STD_C
mEMALIGn(size_t alignment,size_t bytes)2780 Void_t* mEMALIGn(size_t alignment, size_t bytes)
2781 #else
2782 Void_t* mEMALIGn(alignment, bytes) size_t alignment; size_t bytes;
2783 #endif
2784 {
2785 INTERNAL_SIZE_T nb; /* padded request size */
2786 char* m; /* memory returned by malloc call */
2787 mchunkptr p; /* corresponding chunk */
2788 char* brk; /* alignment point within p */
2789 mchunkptr newp; /* chunk to return */
2790 INTERNAL_SIZE_T newsize; /* its size */
2791 INTERNAL_SIZE_T leadsize; /* leading space befor alignment point */
2792 mchunkptr remainder; /* spare room at end to split off */
2793 long remainder_size; /* its size */
2794
2795 if ((long)bytes < 0) return 0;
2796
2797 /* If need less alignment than we give anyway, just relay to malloc */
2798
2799 if (alignment <= MALLOC_ALIGNMENT) return mALLOc(bytes);
2800
2801 /* Otherwise, ensure that it is at least a minimum chunk size */
2802
2803 if (alignment < MINSIZE) alignment = MINSIZE;
2804
2805 /* Call malloc with worst case padding to hit alignment. */
2806
2807 nb = request2size(bytes);
2808 m = (char*)(mALLOc(nb + alignment + MINSIZE));
2809
2810 if (m == 0) return 0; /* propagate failure */
2811
2812 p = mem2chunk(m);
2813
2814 if ((((unsigned long)(m)) % alignment) == 0) /* aligned */
2815 {
2816 #if HAVE_MMAP
2817 if(chunk_is_mmapped(p))
2818 return chunk2mem(p); /* nothing more to do */
2819 #endif
2820 }
2821 else /* misaligned */
2822 {
2823 /*
2824 Find an aligned spot inside chunk.
2825 Since we need to give back leading space in a chunk of at
2826 least MINSIZE, if the first calculation places us at
2827 a spot with less than MINSIZE leader, we can move to the
2828 next aligned spot -- we've allocated enough total room so that
2829 this is always possible.
2830 */
2831
2832 brk = (char*)mem2chunk(((unsigned long)(m + alignment - 1)) & -((signed) alignment));
2833 if ((long)(brk - (char*)(p)) < MINSIZE) brk = brk + alignment;
2834
2835 newp = (mchunkptr)brk;
2836 leadsize = brk - (char*)(p);
2837 newsize = chunksize(p) - leadsize;
2838
2839 #if HAVE_MMAP
2840 if(chunk_is_mmapped(p))
2841 {
2842 newp->prev_size = p->prev_size + leadsize;
2843 set_head(newp, newsize|IS_MMAPPED);
2844 return chunk2mem(newp);
2845 }
2846 #endif
2847
2848 /* give back leader, use the rest */
2849
2850 set_head(newp, newsize | PREV_INUSE);
2851 set_inuse_bit_at_offset(newp, newsize);
2852 set_head_size(p, leadsize);
2853 fREe(chunk2mem(p));
2854 p = newp;
2855
2856 assert (newsize >= nb && (((unsigned long)(chunk2mem(p))) % alignment) == 0);
2857 }
2858
2859 /* Also give back spare room at the end */
2860
2861 remainder_size = chunksize(p) - nb;
2862
2863 if (remainder_size >= (long)MINSIZE)
2864 {
2865 remainder = chunk_at_offset(p, nb);
2866 set_head(remainder, remainder_size | PREV_INUSE);
2867 set_head_size(p, nb);
2868 fREe(chunk2mem(remainder));
2869 }
2870
2871 check_inuse_chunk(p);
2872 return chunk2mem(p);
2873
2874 }
2875
2876
2877
2878
2879 /*
2880 valloc just invokes memalign with alignment argument equal
2881 to the page size of the system (or as near to this as can
2882 be figured out from all the includes/defines above.)
2883 */
2884
2885 #if __STD_C
vALLOc(size_t bytes)2886 Void_t* vALLOc(size_t bytes)
2887 #else
2888 Void_t* vALLOc(bytes) size_t bytes;
2889 #endif
2890 {
2891 return mEMALIGn (malloc_getpagesize, bytes);
2892 }
2893
2894 /*
2895 pvalloc just invokes valloc for the nearest pagesize
2896 that will accommodate request
2897 */
2898
2899
2900 #if __STD_C
pvALLOc(size_t bytes)2901 Void_t* pvALLOc(size_t bytes)
2902 #else
2903 Void_t* pvALLOc(bytes) size_t bytes;
2904 #endif
2905 {
2906 size_t pagesize = malloc_getpagesize;
2907 return mEMALIGn (pagesize, (bytes + pagesize - 1) & ~(pagesize - 1));
2908 }
2909
2910 /*
2911
2912 calloc calls malloc, then zeroes out the allocated chunk.
2913
2914 */
2915
2916 #if __STD_C
cALLOc(size_t n,size_t elem_size)2917 Void_t* cALLOc(size_t n, size_t elem_size)
2918 #else
2919 Void_t* cALLOc(n, elem_size) size_t n; size_t elem_size;
2920 #endif
2921 {
2922 mchunkptr p;
2923 INTERNAL_SIZE_T csz;
2924
2925 INTERNAL_SIZE_T sz = n * elem_size;
2926
2927
2928 /* check if expand_top called, in which case don't need to clear */
2929 #if MORECORE_CLEARS
2930 mchunkptr oldtop = top;
2931 INTERNAL_SIZE_T oldtopsize = chunksize(top);
2932 #endif
2933 Void_t* mem = mALLOc (sz);
2934
2935 if ((long)n < 0) return 0;
2936
2937 if (mem == 0)
2938 return 0;
2939 else
2940 {
2941 p = mem2chunk(mem);
2942
2943 /* Two optional cases in which clearing not necessary */
2944
2945
2946 #if HAVE_MMAP
2947 if (chunk_is_mmapped(p)) return mem;
2948 #endif
2949
2950 csz = chunksize(p);
2951
2952 #if MORECORE_CLEARS
2953 if (p == oldtop && csz > oldtopsize)
2954 {
2955 /* clear only the bytes from non-freshly-sbrked memory */
2956 csz = oldtopsize;
2957 }
2958 #endif
2959
2960 MALLOC_ZERO(mem, csz - SIZE_SZ);
2961 return mem;
2962 }
2963 }
2964
2965 /*
2966
2967 cfree just calls free. It is needed/defined on some systems
2968 that pair it with calloc, presumably for odd historical reasons.
2969
2970 */
2971
2972 #if !defined(INTERNAL_LINUX_C_LIB) || !defined(__ELF__)
2973 #if __STD_C
cfree(Void_t * mem)2974 void cfree(Void_t *mem)
2975 #else
2976 void cfree(mem) Void_t *mem;
2977 #endif
2978 {
2979 fREe(mem);
2980 }
2981 #endif
2982
2983
2984
2985 /*
2986
2987 Malloc_trim gives memory back to the system (via negative
2988 arguments to sbrk) if there is unused memory at the `high' end of
2989 the malloc pool. You can call this after freeing large blocks of
2990 memory to potentially reduce the system-level memory requirements
2991 of a program. However, it cannot guarantee to reduce memory. Under
2992 some allocation patterns, some large free blocks of memory will be
2993 locked between two used chunks, so they cannot be given back to
2994 the system.
2995
2996 The `pad' argument to malloc_trim represents the amount of free
2997 trailing space to leave untrimmed. If this argument is zero,
2998 only the minimum amount of memory to maintain internal data
2999 structures will be left (one page or less). Non-zero arguments
3000 can be supplied to maintain enough trailing space to service
3001 future expected allocations without having to re-obtain memory
3002 from the system.
3003
3004 Malloc_trim returns 1 if it actually released any memory, else 0.
3005
3006 */
3007
3008 #if __STD_C
malloc_trim(size_t pad)3009 int malloc_trim(size_t pad)
3010 #else
3011 int malloc_trim(pad) size_t pad;
3012 #endif
3013 {
3014 long top_size; /* Amount of top-most memory */
3015 long extra; /* Amount to release */
3016 char* current_brk; /* address returned by pre-check sbrk call */
3017 char* new_brk; /* address returned by negative sbrk call */
3018
3019 unsigned long pagesz = malloc_getpagesize;
3020
3021 top_size = chunksize(top);
3022 extra = ((top_size - pad - MINSIZE + (pagesz-1)) / pagesz - 1) * pagesz;
3023
3024 if (extra < (long)pagesz) /* Not enough memory to release */
3025 return 0;
3026
3027 else
3028 {
3029 /* Test to make sure no one else called sbrk */
3030 current_brk = (char*)(MORECORE (0));
3031 if (current_brk != (char*)(top) + top_size)
3032 return 0; /* Apparently we don't own memory; must fail */
3033
3034 else
3035 {
3036 new_brk = (char*)(MORECORE (-extra));
3037
3038 if (new_brk == (char*)(MORECORE_FAILURE)) /* sbrk failed? */
3039 {
3040 /* Try to figure out what we have */
3041 current_brk = (char*)(MORECORE (0));
3042 top_size = current_brk - (char*)top;
3043 if (top_size >= (long)MINSIZE) /* if not, we are very very dead! */
3044 {
3045 sbrked_mem = current_brk - sbrk_base;
3046 set_head(top, top_size | PREV_INUSE);
3047 }
3048 check_chunk(top);
3049 return 0;
3050 }
3051
3052 else
3053 {
3054 /* Success. Adjust top accordingly. */
3055 set_head(top, (top_size - extra) | PREV_INUSE);
3056 sbrked_mem -= extra;
3057 check_chunk(top);
3058 return 1;
3059 }
3060 }
3061 }
3062 }
3063
3064
3065
3066 /*
3067 malloc_usable_size:
3068
3069 This routine tells you how many bytes you can actually use in an
3070 allocated chunk, which may be more than you requested (although
3071 often not). You can use this many bytes without worrying about
3072 overwriting other allocated objects. Not a particularly great
3073 programming practice, but still sometimes useful.
3074
3075 */
3076
3077 #if __STD_C
malloc_usable_size(Void_t * mem)3078 size_t malloc_usable_size(Void_t* mem)
3079 #else
3080 size_t malloc_usable_size(mem) Void_t* mem;
3081 #endif
3082 {
3083 mchunkptr p;
3084 if (mem == 0)
3085 return 0;
3086 else
3087 {
3088 p = mem2chunk(mem);
3089 if(!chunk_is_mmapped(p))
3090 {
3091 if (!inuse(p)) return 0;
3092 check_inuse_chunk(p);
3093 return chunksize(p) - SIZE_SZ;
3094 }
3095 return chunksize(p) - 2*SIZE_SZ;
3096 }
3097 }
3098
3099
3100
3101
3102 /* Utility to update current_mallinfo for malloc_stats and mallinfo() */
3103
3104 #if 0
3105 static void malloc_update_mallinfo()
3106 {
3107 int i;
3108 mbinptr b;
3109 mchunkptr p;
3110 #ifdef DEBUG
3111 mchunkptr q;
3112 #endif
3113
3114 INTERNAL_SIZE_T avail = chunksize(top);
3115 int navail = ((long)(avail) >= (long)MINSIZE)? 1 : 0;
3116
3117 for (i = 1; i < NAV; ++i)
3118 {
3119 b = bin_at(i);
3120 for (p = last(b); p != b; p = p->bk)
3121 {
3122 #ifdef DEBUG
3123 check_free_chunk(p);
3124 for (q = next_chunk(p);
3125 q < top && inuse(q) && (long)(chunksize(q)) >= (long)MINSIZE;
3126 q = next_chunk(q))
3127 check_inuse_chunk(q);
3128 #endif
3129 avail += chunksize(p);
3130 navail++;
3131 }
3132 }
3133
3134 current_mallinfo.ordblks = navail;
3135 current_mallinfo.uordblks = sbrked_mem - avail;
3136 current_mallinfo.fordblks = avail;
3137 current_mallinfo.hblks = n_mmaps;
3138 current_mallinfo.hblkhd = mmapped_mem;
3139 current_mallinfo.keepcost = chunksize(top);
3140
3141 }
3142 #endif /* 0 */
3143
3144
3145
3146 /*
3147
3148 malloc_stats:
3149
3150 Prints on the amount of space obtain from the system (both
3151 via sbrk and mmap), the maximum amount (which may be more than
3152 current if malloc_trim and/or munmap got called), the maximum
3153 number of simultaneous mmap regions used, and the current number
3154 of bytes allocated via malloc (or realloc, etc) but not yet
3155 freed. (Note that this is the number of bytes allocated, not the
3156 number requested. It will be larger than the number requested
3157 because of alignment and bookkeeping overhead.)
3158
3159 */
3160
3161 #if 0
3162 void malloc_stats()
3163 {
3164 malloc_update_mallinfo();
3165 printf("max system bytes = %10u\n",
3166 (unsigned int)(max_total_mem));
3167 printf("system bytes = %10u\n",
3168 (unsigned int)(sbrked_mem + mmapped_mem));
3169 printf("in use bytes = %10u\n",
3170 (unsigned int)(current_mallinfo.uordblks + mmapped_mem));
3171 #if HAVE_MMAP
3172 printf("max mmap regions = %10u\n",
3173 (unsigned int)max_n_mmaps);
3174 #endif
3175 }
3176 #endif /* 0 */
3177
3178 /*
3179 mallinfo returns a copy of updated current mallinfo.
3180 */
3181
3182 #if 0
3183 struct mallinfo mALLINFo()
3184 {
3185 malloc_update_mallinfo();
3186 return current_mallinfo;
3187 }
3188 #endif /* 0 */
3189
3190
3191
3192
3193 /*
3194 mallopt:
3195
3196 mallopt is the general SVID/XPG interface to tunable parameters.
3197 The format is to provide a (parameter-number, parameter-value) pair.
3198 mallopt then sets the corresponding parameter to the argument
3199 value if it can (i.e., so long as the value is meaningful),
3200 and returns 1 if successful else 0.
3201
3202 See descriptions of tunable parameters above.
3203
3204 */
3205
3206 #if __STD_C
mALLOPt(int param_number,int value)3207 int mALLOPt(int param_number, int value)
3208 #else
3209 int mALLOPt(param_number, value) int param_number; int value;
3210 #endif
3211 {
3212 switch(param_number)
3213 {
3214 case M_TRIM_THRESHOLD:
3215 trim_threshold = value; return 1;
3216 case M_TOP_PAD:
3217 top_pad = value; return 1;
3218 case M_MMAP_THRESHOLD:
3219 mmap_threshold = value; return 1;
3220 case M_MMAP_MAX:
3221 #if HAVE_MMAP
3222 n_mmaps_max = value; return 1;
3223 #else
3224 if (value != 0) return 0; else n_mmaps_max = value; return 1;
3225 #endif
3226
3227 default:
3228 return 0;
3229 }
3230 }
3231
3232 /*
3233
3234 History:
3235
3236 V2.6.6 Sun Dec 5 07:42:19 1999 Doug Lea (dl at gee)
3237 * return null for negative arguments
3238 * Added Several WIN32 cleanups from Martin C. Fong <mcfong@yahoo.com>
3239 * Add 'LACKS_SYS_PARAM_H' for those systems without 'sys/param.h'
3240 (e.g. WIN32 platforms)
3241 * Cleanup up header file inclusion for WIN32 platforms
3242 * Cleanup code to avoid Microsoft Visual C++ compiler complaints
3243 * Add 'USE_DL_PREFIX' to quickly allow co-existence with existing
3244 memory allocation routines
3245 * Set 'malloc_getpagesize' for WIN32 platforms (needs more work)
3246 * Use 'assert' rather than 'ASSERT' in WIN32 code to conform to
3247 usage of 'assert' in non-WIN32 code
3248 * Improve WIN32 'sbrk()' emulation's 'findRegion()' routine to
3249 avoid infinite loop
3250 * Always call 'fREe()' rather than 'free()'
3251
3252 V2.6.5 Wed Jun 17 15:57:31 1998 Doug Lea (dl at gee)
3253 * Fixed ordering problem with boundary-stamping
3254
3255 V2.6.3 Sun May 19 08:17:58 1996 Doug Lea (dl at gee)
3256 * Added pvalloc, as recommended by H.J. Liu
3257 * Added 64bit pointer support mainly from Wolfram Gloger
3258 * Added anonymously donated WIN32 sbrk emulation
3259 * Malloc, calloc, getpagesize: add optimizations from Raymond Nijssen
3260 * malloc_extend_top: fix mask error that caused wastage after
3261 foreign sbrks
3262 * Add linux mremap support code from HJ Liu
3263
3264 V2.6.2 Tue Dec 5 06:52:55 1995 Doug Lea (dl at gee)
3265 * Integrated most documentation with the code.
3266 * Add support for mmap, with help from
3267 Wolfram Gloger (Gloger@lrz.uni-muenchen.de).
3268 * Use last_remainder in more cases.
3269 * Pack bins using idea from colin@nyx10.cs.du.edu
3270 * Use ordered bins instead of best-fit threshhold
3271 * Eliminate block-local decls to simplify tracing and debugging.
3272 * Support another case of realloc via move into top
3273 * Fix error occuring when initial sbrk_base not word-aligned.
3274 * Rely on page size for units instead of SBRK_UNIT to
3275 avoid surprises about sbrk alignment conventions.
3276 * Add mallinfo, mallopt. Thanks to Raymond Nijssen
3277 (raymond@es.ele.tue.nl) for the suggestion.
3278 * Add `pad' argument to malloc_trim and top_pad mallopt parameter.
3279 * More precautions for cases where other routines call sbrk,
3280 courtesy of Wolfram Gloger (Gloger@lrz.uni-muenchen.de).
3281 * Added macros etc., allowing use in linux libc from
3282 H.J. Lu (hjl@gnu.ai.mit.edu)
3283 * Inverted this history list
3284
3285 V2.6.1 Sat Dec 2 14:10:57 1995 Doug Lea (dl at gee)
3286 * Re-tuned and fixed to behave more nicely with V2.6.0 changes.
3287 * Removed all preallocation code since under current scheme
3288 the work required to undo bad preallocations exceeds
3289 the work saved in good cases for most test programs.
3290 * No longer use return list or unconsolidated bins since
3291 no scheme using them consistently outperforms those that don't
3292 given above changes.
3293 * Use best fit for very large chunks to prevent some worst-cases.
3294 * Added some support for debugging
3295
3296 V2.6.0 Sat Nov 4 07:05:23 1995 Doug Lea (dl at gee)
3297 * Removed footers when chunks are in use. Thanks to
3298 Paul Wilson (wilson@cs.texas.edu) for the suggestion.
3299
3300 V2.5.4 Wed Nov 1 07:54:51 1995 Doug Lea (dl at gee)
3301 * Added malloc_trim, with help from Wolfram Gloger
3302 (wmglo@Dent.MED.Uni-Muenchen.DE).
3303
3304 V2.5.3 Tue Apr 26 10:16:01 1994 Doug Lea (dl at g)
3305
3306 V2.5.2 Tue Apr 5 16:20:40 1994 Doug Lea (dl at g)
3307 * realloc: try to expand in both directions
3308 * malloc: swap order of clean-bin strategy;
3309 * realloc: only conditionally expand backwards
3310 * Try not to scavenge used bins
3311 * Use bin counts as a guide to preallocation
3312 * Occasionally bin return list chunks in first scan
3313 * Add a few optimizations from colin@nyx10.cs.du.edu
3314
3315 V2.5.1 Sat Aug 14 15:40:43 1993 Doug Lea (dl at g)
3316 * faster bin computation & slightly different binning
3317 * merged all consolidations to one part of malloc proper
3318 (eliminating old malloc_find_space & malloc_clean_bin)
3319 * Scan 2 returns chunks (not just 1)
3320 * Propagate failure in realloc if malloc returns 0
3321 * Add stuff to allow compilation on non-ANSI compilers
3322 from kpv@research.att.com
3323
3324 V2.5 Sat Aug 7 07:41:59 1993 Doug Lea (dl at g.oswego.edu)
3325 * removed potential for odd address access in prev_chunk
3326 * removed dependency on getpagesize.h
3327 * misc cosmetics and a bit more internal documentation
3328 * anticosmetics: mangled names in macros to evade debugger strangeness
3329 * tested on sparc, hp-700, dec-mips, rs6000
3330 with gcc & native cc (hp, dec only) allowing
3331 Detlefs & Zorn comparison study (in SIGPLAN Notices.)
3332
3333 Trial version Fri Aug 28 13:14:29 1992 Doug Lea (dl at g.oswego.edu)
3334 * Based loosely on libg++-1.2X malloc. (It retains some of the overall
3335 structure of old version, but most details differ.)
3336
3337 */
3338