1 /* Malloc implementation for multiple threads without lock contention.
2 Copyright (C) 1996-2018 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Wolfram Gloger <wg@malloc.de>
5 and Doug Lea <dl@cs.oswego.edu>, 2001.
7 The GNU C Library is free software; you can redistribute it and/or
8 modify it under the terms of the GNU Lesser General Public License as
9 published by the Free Software Foundation; either version 2.1 of the
10 License, or (at your option) any later version.
12 The GNU C Library is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Lesser General Public License for more details.
17 You should have received a copy of the GNU Lesser General Public
18 License along with the GNU C Library; see the file COPYING.LIB. If
19 not, see <http://www.gnu.org/licenses/>. */
22 This is a version (aka ptmalloc2) of malloc/free/realloc written by
23 Doug Lea and adapted to multiple threads/arenas by Wolfram Gloger.
25 There have been substantial changes made after the integration into
26 glibc in all parts of the code. Do not look for much commonality
27 with the ptmalloc2 version.
29 * Version ptmalloc2-20011215
31 VERSION 2.7.0 Sun Mar 11 14:14:06 2001 Doug Lea (dl at gee)
35 In order to compile this implementation, a Makefile is provided with
36 the ptmalloc2 distribution, which has pre-defined targets for some
37 popular systems (e.g. "make posix" for Posix threads). All that is
38 typically required with regard to compiler flags is the selection of
39 the thread package via defining one out of USE_PTHREADS, USE_THR or
40 USE_SPROC. Check the thread-m.h file for what effects this has.
41 Many/most systems will additionally require USE_TSD_DATA_HACK to be
42 defined, so this is the default for "make posix".
44 * Why use this malloc?
46 This is not the fastest, most space-conserving, most portable, or
47 most tunable malloc ever written. However it is among the fastest
48 while also being among the most space-conserving, portable and tunable.
49 Consistent balance across these factors results in a good general-purpose
50 allocator for malloc-intensive programs.
52 The main properties of the algorithms are:
53 * For large (>= 512 bytes) requests, it is a pure best-fit allocator,
54 with ties normally decided via FIFO (i.e. least recently used).
55 * For small (<= 64 bytes by default) requests, it is a caching
56 allocator, that maintains pools of quickly recycled chunks.
57 * In between, and for combinations of large and small requests, it does
58 the best it can trying to meet both goals at once.
59 * For very large requests (>= 128KB by default), it relies on system
60 memory mapping facilities, if supported.
62 For a longer but slightly out of date high-level description, see
63 http://gee.cs.oswego.edu/dl/html/malloc.html
65 You may already by default be using a C library containing a malloc
66 that is based on some version of this malloc (for example in
67 linux). You might still want to use the one in this file in order to
68 customize settings or to avoid overheads associated with library
71 * Contents, described in more detail in "description of public routines" below.
73 Standard (ANSI/SVID/...) functions:
75 calloc(size_t n_elements, size_t element_size);
77 realloc(void* p, size_t n);
78 memalign(size_t alignment, size_t n);
81 mallopt(int parameter_number, int parameter_value)
84 independent_calloc(size_t n_elements, size_t size, void* chunks[]);
85 independent_comalloc(size_t n_elements, size_t sizes[], void* chunks[]);
87 malloc_trim(size_t pad);
88 malloc_usable_size(void* p);
93 Supported pointer representation: 4 or 8 bytes
94 Supported size_t representation: 4 or 8 bytes
95 Note that size_t is allowed to be 4 bytes even if pointers are 8.
96 You can adjust this by defining INTERNAL_SIZE_T
98 Alignment: 2 * sizeof(size_t) (default)
99 (i.e., 8 byte alignment with 4byte size_t). This suffices for
100 nearly all current machines and C compilers. However, you can
101 define MALLOC_ALIGNMENT to be wider than this if necessary.
103 Minimum overhead per allocated chunk: 4 or 8 bytes
104 Each malloced chunk has a hidden word of overhead holding size
105 and status information.
107 Minimum allocated size: 4-byte ptrs: 16 bytes (including 4 overhead)
108 8-byte ptrs: 24/32 bytes (including, 4/8 overhead)
110 When a chunk is freed, 12 (for 4byte ptrs) or 20 (for 8 byte
111 ptrs but 4 byte size) or 24 (for 8/8) additional bytes are
112 needed; 4 (8) for a trailing size field and 8 (16) bytes for
113 free list pointers. Thus, the minimum allocatable size is
116 Even a request for zero bytes (i.e., malloc(0)) returns a
117 pointer to something of the minimum allocatable size.
119 The maximum overhead wastage (i.e., number of extra bytes
120 allocated than were requested in malloc) is less than or equal
121 to the minimum size, except for requests >= mmap_threshold that
122 are serviced via mmap(), where the worst case wastage is 2 *
123 sizeof(size_t) bytes plus the remainder from a system page (the
124 minimal mmap unit); typically 4096 or 8192 bytes.
126 Maximum allocated size: 4-byte size_t: 2^32 minus about two pages
127 8-byte size_t: 2^64 minus about two pages
129 It is assumed that (possibly signed) size_t values suffice to
130 represent chunk sizes. `Possibly signed' is due to the fact
131 that `size_t' may be defined on a system as either a signed or
132 an unsigned type. The ISO C standard says that it must be
133 unsigned, but a few systems are known not to adhere to this.
134 Additionally, even when size_t is unsigned, sbrk (which is by
135 default used to obtain memory from system) accepts signed
136 arguments, and may not be able to handle size_t-wide arguments
137 with negative sign bit. Generally, values that would
138 appear as negative after accounting for overhead and alignment
139 are supported only via mmap(), which does not have this
142 Requests for sizes outside the allowed range will perform an optional
143 failure action and then return null. (Requests may also
144 also fail because a system is out of memory.)
146 Thread-safety: thread-safe
148 Compliance: I believe it is compliant with the 1997 Single Unix Specification
149 Also SVID/XPG, ANSI C, and probably others as well.
151 * Synopsis of compile-time options:
153 People have reported using previous versions of this malloc on all
154 versions of Unix, sometimes by tweaking some of the defines
155 below. It has been tested most extensively on Solaris and Linux.
156 People also report using it in stand-alone embedded systems.
158 The implementation is in straight, hand-tuned ANSI C. It is not
159 at all modular. (Sorry!) It uses a lot of macros. To be at all
160 usable, this code should be compiled using an optimizing compiler
161 (for example gcc -O3) that can simplify expressions and control
162 paths. (FAQ: some macros import variables as arguments rather than
163 declare locals because people reported that some debuggers
164 otherwise get confused.)
168 Compilation Environment options:
172 Changing default word sizes:
174 INTERNAL_SIZE_T size_t
176 Configuration and functionality options:
178 USE_PUBLIC_MALLOC_WRAPPERS NOT defined
179 USE_MALLOC_LOCK NOT defined
180 MALLOC_DEBUG NOT defined
181 REALLOC_ZERO_BYTES_FREES 1
184 Options for customizing MORECORE:
188 MORECORE_CONTIGUOUS 1
189 MORECORE_CANNOT_TRIM NOT defined
191 MMAP_AS_MORECORE_SIZE (1024 * 1024)
193 Tuning options that are also dynamically changeable via mallopt:
195 DEFAULT_MXFAST 64 (for 32bit), 128 (for 64bit)
196 DEFAULT_TRIM_THRESHOLD 128 * 1024
198 DEFAULT_MMAP_THRESHOLD 128 * 1024
199 DEFAULT_MMAP_MAX 65536
201 There are several other #defined constants and macros that you
202 probably don't want to touch unless you are extending or adapting malloc. */
205 void* is the pointer type that malloc should say it returns
212 #include <stddef.h> /* for size_t */
213 #include <stdlib.h> /* for getenv(), abort() */
214 #include <unistd.h> /* for __libc_enable_secure */
218 #include <bits/wordsize.h>
219 #include <sys/sysinfo.h>
221 #include <ldsodefs.h>
224 #include <stdio.h> /* needed for malloc_stats */
227 #include <shlib-compat.h>
232 /* For va_arg, va_start, va_end. */
235 /* For MIN, MAX, powerof2. */
236 #include <sys/param.h>
238 /* For ALIGN_UP et. al. */
239 #include <libc-pointer-arith.h>
241 /* For DIAG_PUSH/POP_NEEDS_COMMENT et al. */
242 #include <libc-diag.h>
244 #include <malloc/malloc-internal.h>
246 /* For SINGLE_THREAD_P. */
247 #include <sysdep-cancel.h>
252 Because freed chunks may be overwritten with bookkeeping fields, this
253 malloc will often die when freed memory is overwritten by user
254 programs. This can be very effective (albeit in an annoying way)
255 in helping track down dangling pointers.
257 If you compile with -DMALLOC_DEBUG, a number of assertion checks are
258 enabled that will catch more memory errors. You probably won't be
259 able to make much sense of the actual assertion errors, but they
260 should help you locate incorrectly overwritten memory. The checking
261 is fairly extensive, and will slow down execution
262 noticeably. Calling malloc_stats or mallinfo with MALLOC_DEBUG set
263 will attempt to check every non-mmapped allocated and free chunk in
264 the course of computing the summmaries. (By nature, mmapped regions
265 cannot be checked very much automatically.)
267 Setting MALLOC_DEBUG may also be helpful if you are trying to modify
268 this code. The assertions in the check routines spell out in more
269 detail the assumptions and invariants underlying the algorithms.
271 Setting MALLOC_DEBUG does NOT provide an automated mechanism for
272 checking that all accesses to malloced memory stay within their
273 bounds. However, there are several add-ons and adaptations of this
274 or other mallocs available that do this.
278 #define MALLOC_DEBUG 0
282 # define assert(expr) ((void) 0)
284 # define assert(expr) \
287 : __malloc_assert (#expr, __FILE__, __LINE__, __func__))
289 extern const char *__progname
;
292 __malloc_assert (const char *assertion
, const char *file
, unsigned int line
,
293 const char *function
)
295 (void) __fxprintf (NULL
, "%s%s%s:%u: %s%sAssertion `%s' failed.\n",
296 __progname
, __progname
[0] ? ": " : "",
298 function
? function
: "", function
? ": " : "",
306 /* We want 64 entries. This is an arbitrary limit, which tunables can reduce. */
307 # define TCACHE_MAX_BINS 64
308 # define MAX_TCACHE_SIZE tidx2usize (TCACHE_MAX_BINS-1)
310 /* Only used to pre-fill the tunables. */
311 # define tidx2usize(idx) (((size_t) idx) * MALLOC_ALIGNMENT + MINSIZE - SIZE_SZ)
313 /* When "x" is from chunksize(). */
314 # define csize2tidx(x) (((x) - MINSIZE + MALLOC_ALIGNMENT - 1) / MALLOC_ALIGNMENT)
315 /* When "x" is a user-provided size. */
316 # define usize2tidx(x) csize2tidx (request2size (x))
318 /* With rounding and alignment, the bins are...
319 idx 0 bytes 0..24 (64-bit) or 0..12 (32-bit)
320 idx 1 bytes 25..40 or 13..20
321 idx 2 bytes 41..56 or 21..28
324 /* This is another arbitrary limit, which tunables can change. Each
325 tcache bin will hold at most this number of chunks. */
326 # define TCACHE_FILL_COUNT 7
331 REALLOC_ZERO_BYTES_FREES should be set if a call to
332 realloc with zero bytes should be the same as a call to free.
333 This is required by the C standard. Otherwise, since this malloc
334 returns a unique pointer for malloc(0), so does realloc(p, 0).
337 #ifndef REALLOC_ZERO_BYTES_FREES
338 #define REALLOC_ZERO_BYTES_FREES 1
342 TRIM_FASTBINS controls whether free() of a very small chunk can
343 immediately lead to trimming. Setting to true (1) can reduce memory
344 footprint, but will almost always slow down programs that use a lot
347 Define this only if you are willing to give up some speed to more
348 aggressively reduce system-level memory footprint when releasing
349 memory in programs that use many small chunks. You can get
350 essentially the same effect by setting MXFAST to 0, but this can
351 lead to even greater slowdowns in programs using many small chunks.
352 TRIM_FASTBINS is an in-between compile-time option, that disables
353 only those chunks bordering topmost memory from being placed in
357 #ifndef TRIM_FASTBINS
358 #define TRIM_FASTBINS 0
362 /* Definition for getting more memory from the OS. */
363 #define MORECORE (*__morecore)
364 #define MORECORE_FAILURE 0
365 void * __default_morecore (ptrdiff_t);
366 void *(*__morecore
)(ptrdiff_t) = __default_morecore
;
372 MORECORE-related declarations. By default, rely on sbrk
377 MORECORE is the name of the routine to call to obtain more memory
378 from the system. See below for general guidance on writing
379 alternative MORECORE functions, as well as a version for WIN32 and a
380 sample version for pre-OSX macos.
384 #define MORECORE sbrk
388 MORECORE_FAILURE is the value returned upon failure of MORECORE
389 as well as mmap. Since it cannot be an otherwise valid memory address,
390 and must reflect values of standard sys calls, you probably ought not
394 #ifndef MORECORE_FAILURE
395 #define MORECORE_FAILURE (-1)
399 If MORECORE_CONTIGUOUS is true, take advantage of fact that
400 consecutive calls to MORECORE with positive arguments always return
401 contiguous increasing addresses. This is true of unix sbrk. Even
402 if not defined, when regions happen to be contiguous, malloc will
403 permit allocations spanning regions obtained from different
404 calls. But defining this when applicable enables some stronger
405 consistency checks and space efficiencies.
408 #ifndef MORECORE_CONTIGUOUS
409 #define MORECORE_CONTIGUOUS 1
413 Define MORECORE_CANNOT_TRIM if your version of MORECORE
414 cannot release space back to the system when given negative
415 arguments. This is generally necessary only if you are using
416 a hand-crafted MORECORE function that cannot handle negative arguments.
419 /* #define MORECORE_CANNOT_TRIM */
421 /* MORECORE_CLEARS (default 1)
422 The degree to which the routine mapped to MORECORE zeroes out
423 memory: never (0), only for newly allocated space (1) or always
424 (2). The distinction between (1) and (2) is necessary because on
425 some systems, if the application first decrements and then
426 increments the break value, the contents of the reallocated space
430 #ifndef MORECORE_CLEARS
431 # define MORECORE_CLEARS 1
436 MMAP_AS_MORECORE_SIZE is the minimum mmap size argument to use if
437 sbrk fails, and mmap is used as a backup. The value must be a
438 multiple of page size. This backup strategy generally applies only
439 when systems have "holes" in address space, so sbrk cannot perform
440 contiguous expansion, but there is still space available on system.
441 On systems for which this is known to be useful (i.e. most linux
442 kernels), this occurs only when programs allocate huge amounts of
443 memory. Between this, and the fact that mmap regions tend to be
444 limited, the size should be large, to avoid too many mmap calls and
445 thus avoid running out of kernel resources. */
447 #ifndef MMAP_AS_MORECORE_SIZE
448 #define MMAP_AS_MORECORE_SIZE (1024 * 1024)
452 Define HAVE_MREMAP to make realloc() use mremap() to re-allocate
457 #define HAVE_MREMAP 0
460 /* We may need to support __malloc_initialize_hook for backwards
463 #if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_24)
464 # define HAVE_MALLOC_INIT_HOOK 1
466 # define HAVE_MALLOC_INIT_HOOK 0
471 This version of malloc supports the standard SVID/XPG mallinfo
472 routine that returns a struct containing usage properties and
473 statistics. It should work on any SVID/XPG compliant system that has
474 a /usr/include/malloc.h defining struct mallinfo. (If you'd like to
475 install such a thing yourself, cut out the preliminary declarations
476 as described above and below and save them in a malloc.h file. But
477 there's no compelling reason to bother to do this.)
479 The main declaration needed is the mallinfo struct that is returned
480 (by-copy) by mallinfo(). The SVID/XPG malloinfo struct contains a
481 bunch of fields that are not even meaningful in this version of
482 malloc. These fields are are instead filled by mallinfo() with
483 other numbers that might be of interest.
487 /* ---------- description of public routines ------------ */
491 Returns a pointer to a newly allocated chunk of at least n bytes, or null
492 if no space is available. Additionally, on failure, errno is
493 set to ENOMEM on ANSI C systems.
495 If n is zero, malloc returns a minumum-sized chunk. (The minimum
496 size is 16 bytes on most 32bit systems, and 24 or 32 bytes on 64bit
497 systems.) On most systems, size_t is an unsigned type, so calls
498 with negative arguments are interpreted as requests for huge amounts
499 of space, which will often fail. The maximum supported value of n
500 differs across systems, but is in all cases less than the maximum
501 representable value of a size_t.
503 void* __libc_malloc(size_t);
504 libc_hidden_proto (__libc_malloc
)
508 Releases the chunk of memory pointed to by p, that had been previously
509 allocated using malloc or a related routine such as realloc.
510 It has no effect if p is null. It can have arbitrary (i.e., bad!)
511 effects if p has already been freed.
513 Unless disabled (using mallopt), freeing very large spaces will
514 when possible, automatically trigger operations that give
515 back unused memory to the system, thus reducing program footprint.
517 void __libc_free(void*);
518 libc_hidden_proto (__libc_free
)
521 calloc(size_t n_elements, size_t element_size);
522 Returns a pointer to n_elements * element_size bytes, with all locations
525 void* __libc_calloc(size_t, size_t);
528 realloc(void* p, size_t n)
529 Returns a pointer to a chunk of size n that contains the same data
530 as does chunk p up to the minimum of (n, p's size) bytes, or null
531 if no space is available.
533 The returned pointer may or may not be the same as p. The algorithm
534 prefers extending p when possible, otherwise it employs the
535 equivalent of a malloc-copy-free sequence.
537 If p is null, realloc is equivalent to malloc.
539 If space is not available, realloc returns null, errno is set (if on
540 ANSI) and p is NOT freed.
542 if n is for fewer bytes than already held by p, the newly unused
543 space is lopped off and freed if possible. Unless the #define
544 REALLOC_ZERO_BYTES_FREES is set, realloc with a size argument of
545 zero (re)allocates a minimum-sized chunk.
547 Large chunks that were internally obtained via mmap will always be
548 grown using malloc-copy-free sequences unless the system supports
549 MREMAP (currently only linux).
551 The old unix realloc convention of allowing the last-free'd chunk
552 to be used as an argument to realloc is not supported.
554 void* __libc_realloc(void*, size_t);
555 libc_hidden_proto (__libc_realloc
)
558 memalign(size_t alignment, size_t n);
559 Returns a pointer to a newly allocated chunk of n bytes, aligned
560 in accord with the alignment argument.
562 The alignment argument should be a power of two. If the argument is
563 not a power of two, the nearest greater power is used.
564 8-byte alignment is guaranteed by normal malloc calls, so don't
565 bother calling memalign with an argument of 8 or less.
567 Overreliance on memalign is a sure way to fragment space.
569 void* __libc_memalign(size_t, size_t);
570 libc_hidden_proto (__libc_memalign
)
574 Equivalent to memalign(pagesize, n), where pagesize is the page
575 size of the system. If the pagesize is unknown, 4096 is used.
577 void* __libc_valloc(size_t);
582 mallopt(int parameter_number, int parameter_value)
583 Sets tunable parameters The format is to provide a
584 (parameter-number, parameter-value) pair. mallopt then sets the
585 corresponding parameter to the argument value if it can (i.e., so
586 long as the value is meaningful), and returns 1 if successful else
587 0. SVID/XPG/ANSI defines four standard param numbers for mallopt,
588 normally defined in malloc.h. Only one of these (M_MXFAST) is used
589 in this malloc. The others (M_NLBLKS, M_GRAIN, M_KEEP) don't apply,
590 so setting them has no effect. But this malloc also supports four
591 other options in mallopt. See below for details. Briefly, supported
592 parameters are as follows (listed defaults are for "typical"
595 Symbol param # default allowed param values
596 M_MXFAST 1 64 0-80 (0 disables fastbins)
597 M_TRIM_THRESHOLD -1 128*1024 any (-1U disables trimming)
599 M_MMAP_THRESHOLD -3 128*1024 any (or 0 if no MMAP support)
600 M_MMAP_MAX -4 65536 any (0 disables use of mmap)
602 int __libc_mallopt(int, int);
603 libc_hidden_proto (__libc_mallopt
)
608 Returns (by copy) a struct containing various summary statistics:
610 arena: current total non-mmapped bytes allocated from system
611 ordblks: the number of free chunks
612 smblks: the number of fastbin blocks (i.e., small chunks that
613 have been freed but not use resused or consolidated)
614 hblks: current number of mmapped regions
615 hblkhd: total bytes held in mmapped regions
617 fsmblks: total bytes held in fastbin blocks
618 uordblks: current total allocated space (normal or mmapped)
619 fordblks: total free space
620 keepcost: the maximum number of bytes that could ideally be released
621 back to system via malloc_trim. ("ideally" means that
622 it ignores page restrictions etc.)
624 Because these fields are ints, but internal bookkeeping may
625 be kept as longs, the reported values may wrap around zero and
628 struct mallinfo
__libc_mallinfo(void);
633 Equivalent to valloc(minimum-page-that-holds(n)), that is,
634 round up n to nearest pagesize.
636 void* __libc_pvalloc(size_t);
639 malloc_trim(size_t pad);
641 If possible, gives memory back to the system (via negative
642 arguments to sbrk) if there is unused memory at the `high' end of
643 the malloc pool. You can call this after freeing large blocks of
644 memory to potentially reduce the system-level memory requirements
645 of a program. However, it cannot guarantee to reduce memory. Under
646 some allocation patterns, some large free blocks of memory will be
647 locked between two used chunks, so they cannot be given back to
650 The `pad' argument to malloc_trim represents the amount of free
651 trailing space to leave untrimmed. If this argument is zero,
652 only the minimum amount of memory to maintain internal data
653 structures will be left (one page or less). Non-zero arguments
654 can be supplied to maintain enough trailing space to service
655 future expected allocations without having to re-obtain memory
658 Malloc_trim returns 1 if it actually released any memory, else 0.
659 On systems that do not support "negative sbrks", it will always
662 int __malloc_trim(size_t);
665 malloc_usable_size(void* p);
667 Returns the number of bytes you can actually use in
668 an allocated chunk, which may be more than you requested (although
669 often not) due to alignment and minimum size constraints.
670 You can use this many bytes without worrying about
671 overwriting other allocated objects. This is not a particularly great
672 programming practice. malloc_usable_size can be more useful in
673 debugging and assertions, for example:
676 assert(malloc_usable_size(p) >= 256);
679 size_t __malloc_usable_size(void*);
683 Prints on stderr the amount of space obtained from the system (both
684 via sbrk and mmap), the maximum amount (which may be more than
685 current if malloc_trim and/or munmap got called), and the current
686 number of bytes allocated via malloc (or realloc, etc) but not yet
687 freed. Note that this is the number of bytes allocated, not the
688 number requested. It will be larger than the number requested
689 because of alignment and bookkeeping overhead. Because it includes
690 alignment wastage as being in use, this figure may be greater than
691 zero even when no user-level chunks are allocated.
693 The reported current and maximum system memory can be inaccurate if
694 a program makes other calls to system memory allocation functions
695 (normally sbrk) outside of malloc.
697 malloc_stats prints only the most commonly interesting statistics.
698 More information can be obtained by calling mallinfo.
701 void __malloc_stats(void);
704 malloc_get_state(void);
706 Returns the state of all malloc variables in an opaque data
709 void* __malloc_get_state(void);
712 malloc_set_state(void* state);
714 Restore the state of all malloc variables from data obtained with
717 int __malloc_set_state(void*);
720 posix_memalign(void **memptr, size_t alignment, size_t size);
722 POSIX wrapper like memalign(), checking for validity of size.
724 int __posix_memalign(void **, size_t, size_t);
726 /* mallopt tuning options */
729 M_MXFAST is the maximum request size used for "fastbins", special bins
730 that hold returned chunks without consolidating their spaces. This
731 enables future requests for chunks of the same size to be handled
732 very quickly, but can increase fragmentation, and thus increase the
733 overall memory footprint of a program.
735 This malloc manages fastbins very conservatively yet still
736 efficiently, so fragmentation is rarely a problem for values less
737 than or equal to the default. The maximum supported value of MXFAST
738 is 80. You wouldn't want it any higher than this anyway. Fastbins
739 are designed especially for use with many small structs, objects or
740 strings -- the default handles structs/objects/arrays with sizes up
741 to 8 4byte fields, or small strings representing words, tokens,
742 etc. Using fastbins for larger objects normally worsens
743 fragmentation without improving speed.
745 M_MXFAST is set in REQUEST size units. It is internally used in
746 chunksize units, which adds padding and alignment. You can reduce
747 M_MXFAST to 0 to disable all use of fastbins. This causes the malloc
748 algorithm to be a closer approximation of fifo-best-fit in all cases,
749 not just for larger requests, but will generally cause it to be
754 /* M_MXFAST is a standard SVID/XPG tuning option, usually listed in malloc.h */
759 #ifndef DEFAULT_MXFAST
760 #define DEFAULT_MXFAST (64 * SIZE_SZ / 4)
765 M_TRIM_THRESHOLD is the maximum amount of unused top-most memory
766 to keep before releasing via malloc_trim in free().
768 Automatic trimming is mainly useful in long-lived programs.
769 Because trimming via sbrk can be slow on some systems, and can
770 sometimes be wasteful (in cases where programs immediately
771 afterward allocate more large chunks) the value should be high
772 enough so that your overall system performance would improve by
773 releasing this much memory.
775 The trim threshold and the mmap control parameters (see below)
776 can be traded off with one another. Trimming and mmapping are
777 two different ways of releasing unused memory back to the
778 system. Between these two, it is often possible to keep
779 system-level demands of a long-lived program down to a bare
780 minimum. For example, in one test suite of sessions measuring
781 the XF86 X server on Linux, using a trim threshold of 128K and a
782 mmap threshold of 192K led to near-minimal long term resource
785 If you are using this malloc in a long-lived program, it should
786 pay to experiment with these values. As a rough guide, you
787 might set to a value close to the average size of a process
788 (program) running on your system. Releasing this much memory
789 would allow such a process to run in memory. Generally, it's
790 worth it to tune for trimming rather tham memory mapping when a
791 program undergoes phases where several large chunks are
792 allocated and released in ways that can reuse each other's
793 storage, perhaps mixed with phases where there are no such
794 chunks at all. And in well-behaved long-lived programs,
795 controlling release of large blocks via trimming versus mapping
798 However, in most programs, these parameters serve mainly as
799 protection against the system-level effects of carrying around
800 massive amounts of unneeded memory. Since frequent calls to
801 sbrk, mmap, and munmap otherwise degrade performance, the default
802 parameters are set to relatively high values that serve only as
805 The trim value It must be greater than page size to have any useful
806 effect. To disable trimming completely, you can set to
809 Trim settings interact with fastbin (MXFAST) settings: Unless
810 TRIM_FASTBINS is defined, automatic trimming never takes place upon
811 freeing a chunk with size less than or equal to MXFAST. Trimming is
812 instead delayed until subsequent freeing of larger chunks. However,
813 you can still force an attempted trim by calling malloc_trim.
815 Also, trimming is not generally possible in cases where
816 the main arena is obtained via mmap.
818 Note that the trick some people use of mallocing a huge space and
819 then freeing it at program startup, in an attempt to reserve system
820 memory, doesn't have the intended effect under automatic trimming,
821 since that memory will immediately be returned to the system.
824 #define M_TRIM_THRESHOLD -1
826 #ifndef DEFAULT_TRIM_THRESHOLD
827 #define DEFAULT_TRIM_THRESHOLD (128 * 1024)
831 M_TOP_PAD is the amount of extra `padding' space to allocate or
832 retain whenever sbrk is called. It is used in two ways internally:
834 * When sbrk is called to extend the top of the arena to satisfy
835 a new malloc request, this much padding is added to the sbrk
838 * When malloc_trim is called automatically from free(),
839 it is used as the `pad' argument.
841 In both cases, the actual amount of padding is rounded
842 so that the end of the arena is always a system page boundary.
844 The main reason for using padding is to avoid calling sbrk so
845 often. Having even a small pad greatly reduces the likelihood
846 that nearly every malloc request during program start-up (or
847 after trimming) will invoke sbrk, which needlessly wastes
850 Automatic rounding-up to page-size units is normally sufficient
851 to avoid measurable overhead, so the default is 0. However, in
852 systems where sbrk is relatively slow, it can pay to increase
853 this value, at the expense of carrying around more memory than
859 #ifndef DEFAULT_TOP_PAD
860 #define DEFAULT_TOP_PAD (0)
864 MMAP_THRESHOLD_MAX and _MIN are the bounds on the dynamically
865 adjusted MMAP_THRESHOLD.
868 #ifndef DEFAULT_MMAP_THRESHOLD_MIN
869 #define DEFAULT_MMAP_THRESHOLD_MIN (128 * 1024)
872 #ifndef DEFAULT_MMAP_THRESHOLD_MAX
873 /* For 32-bit platforms we cannot increase the maximum mmap
874 threshold much because it is also the minimum value for the
875 maximum heap size and its alignment. Going above 512k (i.e., 1M
876 for new heaps) wastes too much address space. */
877 # if __WORDSIZE == 32
878 # define DEFAULT_MMAP_THRESHOLD_MAX (512 * 1024)
880 # define DEFAULT_MMAP_THRESHOLD_MAX (4 * 1024 * 1024 * sizeof(long))
885 M_MMAP_THRESHOLD is the request size threshold for using mmap()
886 to service a request. Requests of at least this size that cannot
887 be allocated using already-existing space will be serviced via mmap.
888 (If enough normal freed space already exists it is used instead.)
890 Using mmap segregates relatively large chunks of memory so that
891 they can be individually obtained and released from the host
892 system. A request serviced through mmap is never reused by any
893 other request (at least not directly; the system may just so
894 happen to remap successive requests to the same locations).
896 Segregating space in this way has the benefits that:
898 1. Mmapped space can ALWAYS be individually released back
899 to the system, which helps keep the system level memory
900 demands of a long-lived program low.
901 2. Mapped memory can never become `locked' between
902 other chunks, as can happen with normally allocated chunks, which
903 means that even trimming via malloc_trim would not release them.
904 3. On some systems with "holes" in address spaces, mmap can obtain
905 memory that sbrk cannot.
907 However, it has the disadvantages that:
909 1. The space cannot be reclaimed, consolidated, and then
910 used to service later requests, as happens with normal chunks.
911 2. It can lead to more wastage because of mmap page alignment
913 3. It causes malloc performance to be more dependent on host
914 system memory management support routines which may vary in
915 implementation quality and may impose arbitrary
916 limitations. Generally, servicing a request via normal
917 malloc steps is faster than going through a system's mmap.
919 The advantages of mmap nearly always outweigh disadvantages for
920 "large" chunks, but the value of "large" varies across systems. The
921 default is an empirically derived value that works well in most
926 The above was written in 2001. Since then the world has changed a lot.
927 Memory got bigger. Applications got bigger. The virtual address space
928 layout in 32 bit linux changed.
930 In the new situation, brk() and mmap space is shared and there are no
931 artificial limits on brk size imposed by the kernel. What is more,
932 applications have started using transient allocations larger than the
933 128Kb as was imagined in 2001.
935 The price for mmap is also high now; each time glibc mmaps from the
936 kernel, the kernel is forced to zero out the memory it gives to the
937 application. Zeroing memory is expensive and eats a lot of cache and
938 memory bandwidth. This has nothing to do with the efficiency of the
939 virtual memory system, by doing mmap the kernel just has no choice but
942 In 2001, the kernel had a maximum size for brk() which was about 800
943 megabytes on 32 bit x86, at that point brk() would hit the first
944 mmaped shared libaries and couldn't expand anymore. With current 2.6
945 kernels, the VA space layout is different and brk() and mmap
946 both can span the entire heap at will.
948 Rather than using a static threshold for the brk/mmap tradeoff,
949 we are now using a simple dynamic one. The goal is still to avoid
950 fragmentation. The old goals we kept are
951 1) try to get the long lived large allocations to use mmap()
952 2) really large allocations should always use mmap()
953 and we're adding now:
954 3) transient allocations should use brk() to avoid forcing the kernel
955 having to zero memory over and over again
957 The implementation works with a sliding threshold, which is by default
958 limited to go between 128Kb and 32Mb (64Mb for 64 bitmachines) and starts
959 out at 128Kb as per the 2001 default.
961 This allows us to satisfy requirement 1) under the assumption that long
962 lived allocations are made early in the process' lifespan, before it has
963 started doing dynamic allocations of the same size (which will
964 increase the threshold).
966 The upperbound on the threshold satisfies requirement 2)
968 The threshold goes up in value when the application frees memory that was
969 allocated with the mmap allocator. The idea is that once the application
970 starts freeing memory of a certain size, it's highly probable that this is
971 a size the application uses for transient allocations. This estimator
972 is there to satisfy the new third requirement.
976 #define M_MMAP_THRESHOLD -3
978 #ifndef DEFAULT_MMAP_THRESHOLD
979 #define DEFAULT_MMAP_THRESHOLD DEFAULT_MMAP_THRESHOLD_MIN
983 M_MMAP_MAX is the maximum number of requests to simultaneously
984 service using mmap. This parameter exists because
985 some systems have a limited number of internal tables for
986 use by mmap, and using more than a few of them may degrade
989 The default is set to a value that serves only as a safeguard.
990 Setting to 0 disables use of mmap for servicing large requests.
993 #define M_MMAP_MAX -4
995 #ifndef DEFAULT_MMAP_MAX
996 #define DEFAULT_MMAP_MAX (65536)
1001 #ifndef RETURN_ADDRESS
1002 #define RETURN_ADDRESS(X_) (NULL)
1005 /* Forward declarations. */
1006 struct malloc_chunk
;
1007 typedef struct malloc_chunk
* mchunkptr
;
1009 /* Internal routines. */
1011 static void* _int_malloc(mstate
, size_t);
1012 static void _int_free(mstate
, mchunkptr
, int);
1013 static void* _int_realloc(mstate
, mchunkptr
, INTERNAL_SIZE_T
,
1015 static void* _int_memalign(mstate
, size_t, size_t);
1016 static void* _mid_memalign(size_t, size_t, void *);
1018 static void malloc_printerr(const char *str
) __attribute__ ((noreturn
));
1020 static void* mem2mem_check(void *p
, size_t sz
);
1021 static void top_check(void);
1022 static void munmap_chunk(mchunkptr p
);
1024 static mchunkptr
mremap_chunk(mchunkptr p
, size_t new_size
);
1027 static void* malloc_check(size_t sz
, const void *caller
);
1028 static void free_check(void* mem
, const void *caller
);
1029 static void* realloc_check(void* oldmem
, size_t bytes
,
1030 const void *caller
);
1031 static void* memalign_check(size_t alignment
, size_t bytes
,
1032 const void *caller
);
1034 /* ------------------ MMAP support ------------------ */
1038 #include <sys/mman.h>
1040 #if !defined(MAP_ANONYMOUS) && defined(MAP_ANON)
1041 # define MAP_ANONYMOUS MAP_ANON
1044 #ifndef MAP_NORESERVE
1045 # define MAP_NORESERVE 0
1048 #define MMAP(addr, size, prot, flags) \
1049 __mmap((addr), (size), (prot), (flags)|MAP_ANONYMOUS|MAP_PRIVATE, -1, 0)
1053 ----------------------- Chunk representations -----------------------
1058 This struct declaration is misleading (but accurate and necessary).
1059 It declares a "view" into memory allowing access to necessary
1060 fields at known offsets from a given base. See explanation below.
1063 struct malloc_chunk
{
1065 INTERNAL_SIZE_T mchunk_prev_size
; /* Size of previous chunk (if free). */
1066 INTERNAL_SIZE_T mchunk_size
; /* Size in bytes, including overhead. */
1068 struct malloc_chunk
* fd
; /* double links -- used only if free. */
1069 struct malloc_chunk
* bk
;
1071 /* Only used for large blocks: pointer to next larger size. */
1072 struct malloc_chunk
* fd_nextsize
; /* double links -- used only if free. */
1073 struct malloc_chunk
* bk_nextsize
;
1078 malloc_chunk details:
1080 (The following includes lightly edited explanations by Colin Plumb.)
1082 Chunks of memory are maintained using a `boundary tag' method as
1083 described in e.g., Knuth or Standish. (See the paper by Paul
1084 Wilson ftp://ftp.cs.utexas.edu/pub/garbage/allocsrv.ps for a
1085 survey of such techniques.) Sizes of free chunks are stored both
1086 in the front of each chunk and at the end. This makes
1087 consolidating fragmented chunks into bigger chunks very fast. The
1088 size fields also hold bits representing whether chunks are free or
1091 An allocated chunk looks like this:
1094 chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1095 | Size of previous chunk, if unallocated (P clear) |
1096 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1097 | Size of chunk, in bytes |A|M|P|
1098 mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1099 | User data starts here... .
1101 . (malloc_usable_size() bytes) .
1103 nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1104 | (size of chunk, but used for application data) |
1105 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1106 | Size of next chunk, in bytes |A|0|1|
1107 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1109 Where "chunk" is the front of the chunk for the purpose of most of
1110 the malloc code, but "mem" is the pointer that is returned to the
1111 user. "Nextchunk" is the beginning of the next contiguous chunk.
1113 Chunks always begin on even word boundaries, so the mem portion
1114 (which is returned to the user) is also on an even word boundary, and
1115 thus at least double-word aligned.
1117 Free chunks are stored in circular doubly-linked lists, and look like this:
1119 chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1120 | Size of previous chunk, if unallocated (P clear) |
1121 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1122 `head:' | Size of chunk, in bytes |A|0|P|
1123 mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1124 | Forward pointer to next chunk in list |
1125 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1126 | Back pointer to previous chunk in list |
1127 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1128 | Unused space (may be 0 bytes long) .
1131 nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1132 `foot:' | Size of chunk, in bytes |
1133 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1134 | Size of next chunk, in bytes |A|0|0|
1135 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1137 The P (PREV_INUSE) bit, stored in the unused low-order bit of the
1138 chunk size (which is always a multiple of two words), is an in-use
1139 bit for the *previous* chunk. If that bit is *clear*, then the
1140 word before the current chunk size contains the previous chunk
1141 size, and can be used to find the front of the previous chunk.
1142 The very first chunk allocated always has this bit set,
1143 preventing access to non-existent (or non-owned) memory. If
1144 prev_inuse is set for any given chunk, then you CANNOT determine
1145 the size of the previous chunk, and might even get a memory
1146 addressing fault when trying to do so.
1148 The A (NON_MAIN_ARENA) bit is cleared for chunks on the initial,
1149 main arena, described by the main_arena variable. When additional
1150 threads are spawned, each thread receives its own arena (up to a
1151 configurable limit, after which arenas are reused for multiple
1152 threads), and the chunks in these arenas have the A bit set. To
1153 find the arena for a chunk on such a non-main arena, heap_for_ptr
1154 performs a bit mask operation and indirection through the ar_ptr
1155 member of the per-heap header heap_info (see arena.c).
1157 Note that the `foot' of the current chunk is actually represented
1158 as the prev_size of the NEXT chunk. This makes it easier to
1159 deal with alignments etc but can be very confusing when trying
1160 to extend or adapt this code.
1162 The three exceptions to all this are:
1164 1. The special chunk `top' doesn't bother using the
1165 trailing size field since there is no next contiguous chunk
1166 that would have to index off it. After initialization, `top'
1167 is forced to always exist. If it would become less than
1168 MINSIZE bytes long, it is replenished.
1170 2. Chunks allocated via mmap, which have the second-lowest-order
1171 bit M (IS_MMAPPED) set in their size fields. Because they are
1172 allocated one-by-one, each must contain its own trailing size
1173 field. If the M bit is set, the other bits are ignored
1174 (because mmapped chunks are neither in an arena, nor adjacent
1175 to a freed chunk). The M bit is also used for chunks which
1176 originally came from a dumped heap via malloc_set_state in
1179 3. Chunks in fastbins are treated as allocated chunks from the
1180 point of view of the chunk allocator. They are consolidated
1181 with their neighbors only in bulk, in malloc_consolidate.
1185 ---------- Size and alignment checks and conversions ----------
1188 /* conversion from malloc headers to user pointers, and back */
1190 #define chunk2mem(p) ((void*)((char*)(p) + 2*SIZE_SZ))
1191 #define mem2chunk(mem) ((mchunkptr)((char*)(mem) - 2*SIZE_SZ))
1193 /* The smallest possible chunk */
1194 #define MIN_CHUNK_SIZE (offsetof(struct malloc_chunk, fd_nextsize))
1196 /* The smallest size we can malloc is an aligned minimal chunk */
1199 (unsigned long)(((MIN_CHUNK_SIZE+MALLOC_ALIGN_MASK) & ~MALLOC_ALIGN_MASK))
1201 /* Check if m has acceptable alignment */
1203 #define aligned_OK(m) (((unsigned long)(m) & MALLOC_ALIGN_MASK) == 0)
1205 #define misaligned_chunk(p) \
1206 ((uintptr_t)(MALLOC_ALIGNMENT == 2 * SIZE_SZ ? (p) : chunk2mem (p)) \
1207 & MALLOC_ALIGN_MASK)
1211 Check if a request is so large that it would wrap around zero when
1212 padded and aligned. To simplify some other code, the bound is made
1213 low enough so that adding MINSIZE will also not wrap around zero.
1216 #define REQUEST_OUT_OF_RANGE(req) \
1217 ((unsigned long) (req) >= \
1218 (unsigned long) (INTERNAL_SIZE_T) (-2 * MINSIZE))
1220 /* pad request bytes into a usable size -- internal version */
1222 #define request2size(req) \
1223 (((req) + SIZE_SZ + MALLOC_ALIGN_MASK < MINSIZE) ? \
1225 ((req) + SIZE_SZ + MALLOC_ALIGN_MASK) & ~MALLOC_ALIGN_MASK)
1227 /* Same, except also perform an argument and result check. First, we check
1228 that the padding done by request2size didn't result in an integer
1229 overflow. Then we check (using REQUEST_OUT_OF_RANGE) that the resulting
1230 size isn't so large that a later alignment would lead to another integer
1232 #define checked_request2size(req, sz) \
1234 (sz) = request2size (req); \
1235 if (((sz) < (req)) \
1236 || REQUEST_OUT_OF_RANGE (sz)) \
1238 __set_errno (ENOMEM); \
1244 --------------- Physical chunk operations ---------------
1248 /* size field is or'ed with PREV_INUSE when previous adjacent chunk in use */
1249 #define PREV_INUSE 0x1
1251 /* extract inuse bit of previous chunk */
1252 #define prev_inuse(p) ((p)->mchunk_size & PREV_INUSE)
1255 /* size field is or'ed with IS_MMAPPED if the chunk was obtained with mmap() */
1256 #define IS_MMAPPED 0x2
1258 /* check for mmap()'ed chunk */
1259 #define chunk_is_mmapped(p) ((p)->mchunk_size & IS_MMAPPED)
1262 /* size field is or'ed with NON_MAIN_ARENA if the chunk was obtained
1263 from a non-main arena. This is only set immediately before handing
1264 the chunk to the user, if necessary. */
1265 #define NON_MAIN_ARENA 0x4
1267 /* Check for chunk from main arena. */
1268 #define chunk_main_arena(p) (((p)->mchunk_size & NON_MAIN_ARENA) == 0)
1270 /* Mark a chunk as not being on the main arena. */
1271 #define set_non_main_arena(p) ((p)->mchunk_size |= NON_MAIN_ARENA)
1275 Bits to mask off when extracting size
1277 Note: IS_MMAPPED is intentionally not masked off from size field in
1278 macros for which mmapped chunks should never be seen. This should
1279 cause helpful core dumps to occur if it is tried by accident by
1280 people extending or adapting this malloc.
1282 #define SIZE_BITS (PREV_INUSE | IS_MMAPPED | NON_MAIN_ARENA)
1284 /* Get size, ignoring use bits */
1285 #define chunksize(p) (chunksize_nomask (p) & ~(SIZE_BITS))
1287 /* Like chunksize, but do not mask SIZE_BITS. */
1288 #define chunksize_nomask(p) ((p)->mchunk_size)
1290 /* Ptr to next physical malloc_chunk. */
1291 #define next_chunk(p) ((mchunkptr) (((char *) (p)) + chunksize (p)))
1293 /* Size of the chunk below P. Only valid if prev_inuse (P). */
1294 #define prev_size(p) ((p)->mchunk_prev_size)
1296 /* Set the size of the chunk below P. Only valid if prev_inuse (P). */
1297 #define set_prev_size(p, sz) ((p)->mchunk_prev_size = (sz))
1299 /* Ptr to previous physical malloc_chunk. Only valid if prev_inuse (P). */
1300 #define prev_chunk(p) ((mchunkptr) (((char *) (p)) - prev_size (p)))
1302 /* Treat space at ptr + offset as a chunk */
1303 #define chunk_at_offset(p, s) ((mchunkptr) (((char *) (p)) + (s)))
1305 /* extract p's inuse bit */
1307 ((((mchunkptr) (((char *) (p)) + chunksize (p)))->mchunk_size) & PREV_INUSE)
1309 /* set/clear chunk as being inuse without otherwise disturbing */
1310 #define set_inuse(p) \
1311 ((mchunkptr) (((char *) (p)) + chunksize (p)))->mchunk_size |= PREV_INUSE
1313 #define clear_inuse(p) \
1314 ((mchunkptr) (((char *) (p)) + chunksize (p)))->mchunk_size &= ~(PREV_INUSE)
1317 /* check/set/clear inuse bits in known places */
1318 #define inuse_bit_at_offset(p, s) \
1319 (((mchunkptr) (((char *) (p)) + (s)))->mchunk_size & PREV_INUSE)
1321 #define set_inuse_bit_at_offset(p, s) \
1322 (((mchunkptr) (((char *) (p)) + (s)))->mchunk_size |= PREV_INUSE)
1324 #define clear_inuse_bit_at_offset(p, s) \
1325 (((mchunkptr) (((char *) (p)) + (s)))->mchunk_size &= ~(PREV_INUSE))
1328 /* Set size at head, without disturbing its use bit */
1329 #define set_head_size(p, s) ((p)->mchunk_size = (((p)->mchunk_size & SIZE_BITS) | (s)))
1331 /* Set size/use field */
1332 #define set_head(p, s) ((p)->mchunk_size = (s))
1334 /* Set size at footer (only when chunk is not in use) */
1335 #define set_foot(p, s) (((mchunkptr) ((char *) (p) + (s)))->mchunk_prev_size = (s))
1338 #pragma GCC poison mchunk_size
1339 #pragma GCC poison mchunk_prev_size
1342 -------------------- Internal data structures --------------------
1344 All internal state is held in an instance of malloc_state defined
1345 below. There are no other static variables, except in two optional
1347 * If USE_MALLOC_LOCK is defined, the mALLOC_MUTEx declared above.
1348 * If mmap doesn't support MAP_ANONYMOUS, a dummy file descriptor
1351 Beware of lots of tricks that minimize the total bookkeeping space
1352 requirements. The result is a little over 1K bytes (for 4byte
1353 pointers and size_t.)
1359 An array of bin headers for free chunks. Each bin is doubly
1360 linked. The bins are approximately proportionally (log) spaced.
1361 There are a lot of these bins (128). This may look excessive, but
1362 works very well in practice. Most bins hold sizes that are
1363 unusual as malloc request sizes, but are more usual for fragments
1364 and consolidated sets of chunks, which is what these bins hold, so
1365 they can be found quickly. All procedures maintain the invariant
1366 that no consolidated chunk physically borders another one, so each
1367 chunk in a list is known to be preceeded and followed by either
1368 inuse chunks or the ends of memory.
1370 Chunks in bins are kept in size order, with ties going to the
1371 approximately least recently used chunk. Ordering isn't needed
1372 for the small bins, which all contain the same-sized chunks, but
1373 facilitates best-fit allocation for larger chunks. These lists
1374 are just sequential. Keeping them in order almost never requires
1375 enough traversal to warrant using fancier ordered data
1378 Chunks of the same size are linked with the most
1379 recently freed at the front, and allocations are taken from the
1380 back. This results in LRU (FIFO) allocation order, which tends
1381 to give each chunk an equal opportunity to be consolidated with
1382 adjacent freed chunks, resulting in larger free chunks and less
1385 To simplify use in double-linked lists, each bin header acts
1386 as a malloc_chunk. This avoids special-casing for headers.
1387 But to conserve space and improve locality, we allocate
1388 only the fd/bk pointers of bins, and then use repositioning tricks
1389 to treat these as the fields of a malloc_chunk*.
1392 typedef struct malloc_chunk
*mbinptr
;
1394 /* addressing -- note that bin_at(0) does not exist */
1395 #define bin_at(m, i) \
1396 (mbinptr) (((char *) &((m)->bins[((i) - 1) * 2])) \
1397 - offsetof (struct malloc_chunk, fd))
1399 /* analog of ++bin */
1400 #define next_bin(b) ((mbinptr) ((char *) (b) + (sizeof (mchunkptr) << 1)))
1402 /* Reminders about list directionality within bins */
1403 #define first(b) ((b)->fd)
1404 #define last(b) ((b)->bk)
1406 /* Take a chunk off a bin list */
1407 #define unlink(AV, P, BK, FD) { \
1408 if (__builtin_expect (chunksize(P) != prev_size (next_chunk(P)), 0)) \
1409 malloc_printerr ("corrupted size vs. prev_size"); \
1412 if (__builtin_expect (FD->bk != P || BK->fd != P, 0)) \
1413 malloc_printerr ("corrupted double-linked list"); \
1417 if (!in_smallbin_range (chunksize_nomask (P)) \
1418 && __builtin_expect (P->fd_nextsize != NULL, 0)) { \
1419 if (__builtin_expect (P->fd_nextsize->bk_nextsize != P, 0) \
1420 || __builtin_expect (P->bk_nextsize->fd_nextsize != P, 0)) \
1421 malloc_printerr ("corrupted double-linked list (not small)"); \
1422 if (FD->fd_nextsize == NULL) { \
1423 if (P->fd_nextsize == P) \
1424 FD->fd_nextsize = FD->bk_nextsize = FD; \
1426 FD->fd_nextsize = P->fd_nextsize; \
1427 FD->bk_nextsize = P->bk_nextsize; \
1428 P->fd_nextsize->bk_nextsize = FD; \
1429 P->bk_nextsize->fd_nextsize = FD; \
1432 P->fd_nextsize->bk_nextsize = P->bk_nextsize; \
1433 P->bk_nextsize->fd_nextsize = P->fd_nextsize; \
1442 Bins for sizes < 512 bytes contain chunks of all the same size, spaced
1443 8 bytes apart. Larger bins are approximately logarithmically spaced:
1449 4 bins of size 32768
1450 2 bins of size 262144
1451 1 bin of size what's left
1453 There is actually a little bit of slop in the numbers in bin_index
1454 for the sake of speed. This makes no difference elsewhere.
1456 The bins top out around 1MB because we expect to service large
1459 Bin 0 does not exist. Bin 1 is the unordered list; if that would be
1460 a valid chunk size the small bins are bumped up one.
1464 #define NSMALLBINS 64
1465 #define SMALLBIN_WIDTH MALLOC_ALIGNMENT
1466 #define SMALLBIN_CORRECTION (MALLOC_ALIGNMENT > 2 * SIZE_SZ)
1467 #define MIN_LARGE_SIZE ((NSMALLBINS - SMALLBIN_CORRECTION) * SMALLBIN_WIDTH)
1469 #define in_smallbin_range(sz) \
1470 ((unsigned long) (sz) < (unsigned long) MIN_LARGE_SIZE)
1472 #define smallbin_index(sz) \
1473 ((SMALLBIN_WIDTH == 16 ? (((unsigned) (sz)) >> 4) : (((unsigned) (sz)) >> 3))\
1474 + SMALLBIN_CORRECTION)
1476 #define largebin_index_32(sz) \
1477 (((((unsigned long) (sz)) >> 6) <= 38) ? 56 + (((unsigned long) (sz)) >> 6) :\
1478 ((((unsigned long) (sz)) >> 9) <= 20) ? 91 + (((unsigned long) (sz)) >> 9) :\
1479 ((((unsigned long) (sz)) >> 12) <= 10) ? 110 + (((unsigned long) (sz)) >> 12) :\
1480 ((((unsigned long) (sz)) >> 15) <= 4) ? 119 + (((unsigned long) (sz)) >> 15) :\
1481 ((((unsigned long) (sz)) >> 18) <= 2) ? 124 + (((unsigned long) (sz)) >> 18) :\
1484 #define largebin_index_32_big(sz) \
1485 (((((unsigned long) (sz)) >> 6) <= 45) ? 49 + (((unsigned long) (sz)) >> 6) :\
1486 ((((unsigned long) (sz)) >> 9) <= 20) ? 91 + (((unsigned long) (sz)) >> 9) :\
1487 ((((unsigned long) (sz)) >> 12) <= 10) ? 110 + (((unsigned long) (sz)) >> 12) :\
1488 ((((unsigned long) (sz)) >> 15) <= 4) ? 119 + (((unsigned long) (sz)) >> 15) :\
1489 ((((unsigned long) (sz)) >> 18) <= 2) ? 124 + (((unsigned long) (sz)) >> 18) :\
1492 // XXX It remains to be seen whether it is good to keep the widths of
1493 // XXX the buckets the same or whether it should be scaled by a factor
1494 // XXX of two as well.
1495 #define largebin_index_64(sz) \
1496 (((((unsigned long) (sz)) >> 6) <= 48) ? 48 + (((unsigned long) (sz)) >> 6) :\
1497 ((((unsigned long) (sz)) >> 9) <= 20) ? 91 + (((unsigned long) (sz)) >> 9) :\
1498 ((((unsigned long) (sz)) >> 12) <= 10) ? 110 + (((unsigned long) (sz)) >> 12) :\
1499 ((((unsigned long) (sz)) >> 15) <= 4) ? 119 + (((unsigned long) (sz)) >> 15) :\
1500 ((((unsigned long) (sz)) >> 18) <= 2) ? 124 + (((unsigned long) (sz)) >> 18) :\
1503 #define largebin_index(sz) \
1504 (SIZE_SZ == 8 ? largebin_index_64 (sz) \
1505 : MALLOC_ALIGNMENT == 16 ? largebin_index_32_big (sz) \
1506 : largebin_index_32 (sz))
1508 #define bin_index(sz) \
1509 ((in_smallbin_range (sz)) ? smallbin_index (sz) : largebin_index (sz))
1515 All remainders from chunk splits, as well as all returned chunks,
1516 are first placed in the "unsorted" bin. They are then placed
1517 in regular bins after malloc gives them ONE chance to be used before
1518 binning. So, basically, the unsorted_chunks list acts as a queue,
1519 with chunks being placed on it in free (and malloc_consolidate),
1520 and taken off (to be either used or placed in bins) in malloc.
1522 The NON_MAIN_ARENA flag is never set for unsorted chunks, so it
1523 does not have to be taken into account in size comparisons.
1526 /* The otherwise unindexable 1-bin is used to hold unsorted chunks. */
1527 #define unsorted_chunks(M) (bin_at (M, 1))
1532 The top-most available chunk (i.e., the one bordering the end of
1533 available memory) is treated specially. It is never included in
1534 any bin, is used only if no other chunk is available, and is
1535 released back to the system if it is very large (see
1536 M_TRIM_THRESHOLD). Because top initially
1537 points to its own bin with initial zero size, thus forcing
1538 extension on the first malloc request, we avoid having any special
1539 code in malloc to check whether it even exists yet. But we still
1540 need to do so when getting memory from system, so we make
1541 initial_top treat the bin as a legal but unusable chunk during the
1542 interval between initialization and the first call to
1543 sysmalloc. (This is somewhat delicate, since it relies on
1544 the 2 preceding words to be zero during this interval as well.)
1547 /* Conveniently, the unsorted bin can be used as dummy top on first call */
1548 #define initial_top(M) (unsorted_chunks (M))
1553 To help compensate for the large number of bins, a one-level index
1554 structure is used for bin-by-bin searching. `binmap' is a
1555 bitvector recording whether bins are definitely empty so they can
1556 be skipped over during during traversals. The bits are NOT always
1557 cleared as soon as bins are empty, but instead only
1558 when they are noticed to be empty during traversal in malloc.
1561 /* Conservatively use 32 bits per map word, even if on 64bit system */
1562 #define BINMAPSHIFT 5
1563 #define BITSPERMAP (1U << BINMAPSHIFT)
1564 #define BINMAPSIZE (NBINS / BITSPERMAP)
1566 #define idx2block(i) ((i) >> BINMAPSHIFT)
1567 #define idx2bit(i) ((1U << ((i) & ((1U << BINMAPSHIFT) - 1))))
1569 #define mark_bin(m, i) ((m)->binmap[idx2block (i)] |= idx2bit (i))
1570 #define unmark_bin(m, i) ((m)->binmap[idx2block (i)] &= ~(idx2bit (i)))
1571 #define get_binmap(m, i) ((m)->binmap[idx2block (i)] & idx2bit (i))
1576 An array of lists holding recently freed small chunks. Fastbins
1577 are not doubly linked. It is faster to single-link them, and
1578 since chunks are never removed from the middles of these lists,
1579 double linking is not necessary. Also, unlike regular bins, they
1580 are not even processed in FIFO order (they use faster LIFO) since
1581 ordering doesn't much matter in the transient contexts in which
1582 fastbins are normally used.
1584 Chunks in fastbins keep their inuse bit set, so they cannot
1585 be consolidated with other free chunks. malloc_consolidate
1586 releases all chunks in fastbins and consolidates them with
1590 typedef struct malloc_chunk
*mfastbinptr
;
1591 #define fastbin(ar_ptr, idx) ((ar_ptr)->fastbinsY[idx])
1593 /* offset 2 to use otherwise unindexable first 2 bins */
1594 #define fastbin_index(sz) \
1595 ((((unsigned int) (sz)) >> (SIZE_SZ == 8 ? 4 : 3)) - 2)
1598 /* The maximum fastbin request size we support */
1599 #define MAX_FAST_SIZE (80 * SIZE_SZ / 4)
1601 #define NFASTBINS (fastbin_index (request2size (MAX_FAST_SIZE)) + 1)
1604 FASTBIN_CONSOLIDATION_THRESHOLD is the size of a chunk in free()
1605 that triggers automatic consolidation of possibly-surrounding
1606 fastbin chunks. This is a heuristic, so the exact value should not
1607 matter too much. It is defined at half the default trim threshold as a
1608 compromise heuristic to only attempt consolidation if it is likely
1609 to lead to trimming. However, it is not dynamically tunable, since
1610 consolidation reduces fragmentation surrounding large chunks even
1611 if trimming is not used.
1614 #define FASTBIN_CONSOLIDATION_THRESHOLD (65536UL)
1617 NONCONTIGUOUS_BIT indicates that MORECORE does not return contiguous
1618 regions. Otherwise, contiguity is exploited in merging together,
1619 when possible, results from consecutive MORECORE calls.
1621 The initial value comes from MORECORE_CONTIGUOUS, but is
1622 changed dynamically if mmap is ever used as an sbrk substitute.
1625 #define NONCONTIGUOUS_BIT (2U)
1627 #define contiguous(M) (((M)->flags & NONCONTIGUOUS_BIT) == 0)
1628 #define noncontiguous(M) (((M)->flags & NONCONTIGUOUS_BIT) != 0)
1629 #define set_noncontiguous(M) ((M)->flags |= NONCONTIGUOUS_BIT)
1630 #define set_contiguous(M) ((M)->flags &= ~NONCONTIGUOUS_BIT)
1632 /* Maximum size of memory handled in fastbins. */
1633 static INTERNAL_SIZE_T global_max_fast
;
1636 Set value of max_fast.
1637 Use impossibly small value if 0.
1638 Precondition: there are no existing fastbin chunks in the main arena.
1639 Since do_check_malloc_state () checks this, we call malloc_consolidate ()
1640 before changing max_fast. Note other arenas will leak their fast bin
1641 entries if max_fast is reduced.
1644 #define set_max_fast(s) \
1645 global_max_fast = (((s) == 0) \
1646 ? SMALLBIN_WIDTH : ((s + SIZE_SZ) & ~MALLOC_ALIGN_MASK))
1648 static inline INTERNAL_SIZE_T
1651 /* Tell the GCC optimizers that global_max_fast is never larger
1652 than MAX_FAST_SIZE. This avoids out-of-bounds array accesses in
1653 _int_malloc after constant propagation of the size parameter.
1654 (The code never executes because malloc preserves the
1655 global_max_fast invariant, but the optimizers may not recognize
1657 if (global_max_fast
> MAX_FAST_SIZE
)
1658 __builtin_unreachable ();
1659 return global_max_fast
;
1663 ----------- Internal state representation and initialization -----------
1667 have_fastchunks indicates that there are probably some fastbin chunks.
1668 It is set true on entering a chunk into any fastbin, and cleared early in
1669 malloc_consolidate. The value is approximate since it may be set when there
1670 are no fastbin chunks, or it may be clear even if there are fastbin chunks
1671 available. Given it's sole purpose is to reduce number of redundant calls to
1672 malloc_consolidate, it does not affect correctness. As a result we can safely
1673 use relaxed atomic accesses.
1679 /* Serialize access. */
1680 __libc_lock_define (, mutex
);
1682 /* Flags (formerly in max_fast). */
1685 /* Set if the fastbin chunks contain recently inserted free blocks. */
1686 /* Note this is a bool but not all targets support atomics on booleans. */
1687 int have_fastchunks
;
1690 mfastbinptr fastbinsY
[NFASTBINS
];
1692 /* Base of the topmost chunk -- not otherwise kept in a bin */
1695 /* The remainder from the most recent split of a small request */
1696 mchunkptr last_remainder
;
1698 /* Normal bins packed as described above */
1699 mchunkptr bins
[NBINS
* 2 - 2];
1701 /* Bitmap of bins */
1702 unsigned int binmap
[BINMAPSIZE
];
1705 struct malloc_state
*next
;
1707 /* Linked list for free arenas. Access to this field is serialized
1708 by free_list_lock in arena.c. */
1709 struct malloc_state
*next_free
;
1711 /* Number of threads attached to this arena. 0 if the arena is on
1712 the free list. Access to this field is serialized by
1713 free_list_lock in arena.c. */
1714 INTERNAL_SIZE_T attached_threads
;
1716 /* Memory allocated from the system in this arena. */
1717 INTERNAL_SIZE_T system_mem
;
1718 INTERNAL_SIZE_T max_system_mem
;
1723 /* Tunable parameters */
1724 unsigned long trim_threshold
;
1725 INTERNAL_SIZE_T top_pad
;
1726 INTERNAL_SIZE_T mmap_threshold
;
1727 INTERNAL_SIZE_T arena_test
;
1728 INTERNAL_SIZE_T arena_max
;
1730 /* Memory map support */
1734 /* the mmap_threshold is dynamic, until the user sets
1735 it manually, at which point we need to disable any
1736 dynamic behavior. */
1737 int no_dyn_threshold
;
1740 INTERNAL_SIZE_T mmapped_mem
;
1741 INTERNAL_SIZE_T max_mmapped_mem
;
1743 /* First address handed out by MORECORE/sbrk. */
1747 /* Maximum number of buckets to use. */
1749 size_t tcache_max_bytes
;
1750 /* Maximum number of chunks in each bucket. */
1751 size_t tcache_count
;
1752 /* Maximum number of chunks to remove from the unsorted list, which
1753 aren't used to prefill the cache. */
1754 size_t tcache_unsorted_limit
;
1758 /* There are several instances of this struct ("arenas") in this
1759 malloc. If you are adapting this malloc in a way that does NOT use
1760 a static or mmapped malloc_state, you MUST explicitly zero-fill it
1761 before using. This malloc relies on the property that malloc_state
1762 is initialized to all zeroes (as is true of C statics). */
1764 static struct malloc_state main_arena
=
1766 .mutex
= _LIBC_LOCK_INITIALIZER
,
1767 .next
= &main_arena
,
1768 .attached_threads
= 1
1771 /* These variables are used for undumping support. Chunked are marked
1772 as using mmap, but we leave them alone if they fall into this
1773 range. NB: The chunk size for these chunks only includes the
1774 initial size field (of SIZE_SZ bytes), there is no trailing size
1775 field (unlike with regular mmapped chunks). */
1776 static mchunkptr dumped_main_arena_start
; /* Inclusive. */
1777 static mchunkptr dumped_main_arena_end
; /* Exclusive. */
1779 /* True if the pointer falls into the dumped arena. Use this after
1780 chunk_is_mmapped indicates a chunk is mmapped. */
1781 #define DUMPED_MAIN_ARENA_CHUNK(p) \
1782 ((p) >= dumped_main_arena_start && (p) < dumped_main_arena_end)
1784 /* There is only one instance of the malloc parameters. */
1786 static struct malloc_par mp_
=
1788 .top_pad
= DEFAULT_TOP_PAD
,
1789 .n_mmaps_max
= DEFAULT_MMAP_MAX
,
1790 .mmap_threshold
= DEFAULT_MMAP_THRESHOLD
,
1791 .trim_threshold
= DEFAULT_TRIM_THRESHOLD
,
1792 #define NARENAS_FROM_NCORES(n) ((n) * (sizeof (long) == 4 ? 2 : 8))
1793 .arena_test
= NARENAS_FROM_NCORES (1)
1796 .tcache_count
= TCACHE_FILL_COUNT
,
1797 .tcache_bins
= TCACHE_MAX_BINS
,
1798 .tcache_max_bytes
= tidx2usize (TCACHE_MAX_BINS
-1),
1799 .tcache_unsorted_limit
= 0 /* No limit. */
1804 Initialize a malloc_state struct.
1806 This is called from ptmalloc_init () or from _int_new_arena ()
1807 when creating a new arena.
1811 malloc_init_state (mstate av
)
1816 /* Establish circular links for normal bins */
1817 for (i
= 1; i
< NBINS
; ++i
)
1819 bin
= bin_at (av
, i
);
1820 bin
->fd
= bin
->bk
= bin
;
1823 #if MORECORE_CONTIGUOUS
1824 if (av
!= &main_arena
)
1826 set_noncontiguous (av
);
1827 if (av
== &main_arena
)
1828 set_max_fast (DEFAULT_MXFAST
);
1829 atomic_store_relaxed (&av
->have_fastchunks
, false);
1831 av
->top
= initial_top (av
);
1835 Other internal utilities operating on mstates
1838 static void *sysmalloc (INTERNAL_SIZE_T
, mstate
);
1839 static int systrim (size_t, mstate
);
1840 static void malloc_consolidate (mstate
);
1843 /* -------------- Early definitions for debugging hooks ---------------- */
1845 /* Define and initialize the hook variables. These weak definitions must
1846 appear before any use of the variables in a function (arena.c uses one). */
1847 #ifndef weak_variable
1848 /* In GNU libc we want the hook variables to be weak definitions to
1849 avoid a problem with Emacs. */
1850 # define weak_variable weak_function
1853 /* Forward declarations. */
1854 static void *malloc_hook_ini (size_t sz
,
1855 const void *caller
) __THROW
;
1856 static void *realloc_hook_ini (void *ptr
, size_t sz
,
1857 const void *caller
) __THROW
;
1858 static void *memalign_hook_ini (size_t alignment
, size_t sz
,
1859 const void *caller
) __THROW
;
1861 #if HAVE_MALLOC_INIT_HOOK
1862 void weak_variable (*__malloc_initialize_hook
) (void) = NULL
;
1863 compat_symbol (libc
, __malloc_initialize_hook
,
1864 __malloc_initialize_hook
, GLIBC_2_0
);
1867 void weak_variable (*__free_hook
) (void *__ptr
,
1868 const void *) = NULL
;
1869 void *weak_variable (*__malloc_hook
)
1870 (size_t __size
, const void *) = malloc_hook_ini
;
1871 void *weak_variable (*__realloc_hook
)
1872 (void *__ptr
, size_t __size
, const void *)
1874 void *weak_variable (*__memalign_hook
)
1875 (size_t __alignment
, size_t __size
, const void *)
1876 = memalign_hook_ini
;
1877 void weak_variable (*__after_morecore_hook
) (void) = NULL
;
1879 /* This function is called from the arena shutdown hook, to free the
1880 thread cache (if it exists). */
1881 static void tcache_thread_shutdown (void);
1883 /* ------------------ Testing support ----------------------------------*/
1885 static int perturb_byte
;
1888 alloc_perturb (char *p
, size_t n
)
1890 if (__glibc_unlikely (perturb_byte
))
1891 memset (p
, perturb_byte
^ 0xff, n
);
1895 free_perturb (char *p
, size_t n
)
1897 if (__glibc_unlikely (perturb_byte
))
1898 memset (p
, perturb_byte
, n
);
1903 #include <stap-probe.h>
1905 /* ------------------- Support for multiple arenas -------------------- */
1911 These routines make a number of assertions about the states
1912 of data structures that should be true at all times. If any
1913 are not true, it's very likely that a user program has somehow
1914 trashed memory. (It's also possible that there is a coding error
1915 in malloc. In which case, please report it!)
1920 # define check_chunk(A, P)
1921 # define check_free_chunk(A, P)
1922 # define check_inuse_chunk(A, P)
1923 # define check_remalloced_chunk(A, P, N)
1924 # define check_malloced_chunk(A, P, N)
1925 # define check_malloc_state(A)
1929 # define check_chunk(A, P) do_check_chunk (A, P)
1930 # define check_free_chunk(A, P) do_check_free_chunk (A, P)
1931 # define check_inuse_chunk(A, P) do_check_inuse_chunk (A, P)
1932 # define check_remalloced_chunk(A, P, N) do_check_remalloced_chunk (A, P, N)
1933 # define check_malloced_chunk(A, P, N) do_check_malloced_chunk (A, P, N)
1934 # define check_malloc_state(A) do_check_malloc_state (A)
1937 Properties of all chunks
1941 do_check_chunk (mstate av
, mchunkptr p
)
1943 unsigned long sz
= chunksize (p
);
1944 /* min and max possible addresses assuming contiguous allocation */
1945 char *max_address
= (char *) (av
->top
) + chunksize (av
->top
);
1946 char *min_address
= max_address
- av
->system_mem
;
1948 if (!chunk_is_mmapped (p
))
1950 /* Has legal address ... */
1953 if (contiguous (av
))
1955 assert (((char *) p
) >= min_address
);
1956 assert (((char *) p
+ sz
) <= ((char *) (av
->top
)));
1961 /* top size is always at least MINSIZE */
1962 assert ((unsigned long) (sz
) >= MINSIZE
);
1963 /* top predecessor always marked inuse */
1964 assert (prev_inuse (p
));
1967 else if (!DUMPED_MAIN_ARENA_CHUNK (p
))
1969 /* address is outside main heap */
1970 if (contiguous (av
) && av
->top
!= initial_top (av
))
1972 assert (((char *) p
) < min_address
|| ((char *) p
) >= max_address
);
1974 /* chunk is page-aligned */
1975 assert (((prev_size (p
) + sz
) & (GLRO (dl_pagesize
) - 1)) == 0);
1976 /* mem is aligned */
1977 assert (aligned_OK (chunk2mem (p
)));
1982 Properties of free chunks
1986 do_check_free_chunk (mstate av
, mchunkptr p
)
1988 INTERNAL_SIZE_T sz
= chunksize_nomask (p
) & ~(PREV_INUSE
| NON_MAIN_ARENA
);
1989 mchunkptr next
= chunk_at_offset (p
, sz
);
1991 do_check_chunk (av
, p
);
1993 /* Chunk must claim to be free ... */
1994 assert (!inuse (p
));
1995 assert (!chunk_is_mmapped (p
));
1997 /* Unless a special marker, must have OK fields */
1998 if ((unsigned long) (sz
) >= MINSIZE
)
2000 assert ((sz
& MALLOC_ALIGN_MASK
) == 0);
2001 assert (aligned_OK (chunk2mem (p
)));
2002 /* ... matching footer field */
2003 assert (prev_size (next_chunk (p
)) == sz
);
2004 /* ... and is fully consolidated */
2005 assert (prev_inuse (p
));
2006 assert (next
== av
->top
|| inuse (next
));
2008 /* ... and has minimally sane links */
2009 assert (p
->fd
->bk
== p
);
2010 assert (p
->bk
->fd
== p
);
2012 else /* markers are always of size SIZE_SZ */
2013 assert (sz
== SIZE_SZ
);
2017 Properties of inuse chunks
2021 do_check_inuse_chunk (mstate av
, mchunkptr p
)
2025 do_check_chunk (av
, p
);
2027 if (chunk_is_mmapped (p
))
2028 return; /* mmapped chunks have no next/prev */
2030 /* Check whether it claims to be in use ... */
2033 next
= next_chunk (p
);
2035 /* ... and is surrounded by OK chunks.
2036 Since more things can be checked with free chunks than inuse ones,
2037 if an inuse chunk borders them and debug is on, it's worth doing them.
2039 if (!prev_inuse (p
))
2041 /* Note that we cannot even look at prev unless it is not inuse */
2042 mchunkptr prv
= prev_chunk (p
);
2043 assert (next_chunk (prv
) == p
);
2044 do_check_free_chunk (av
, prv
);
2047 if (next
== av
->top
)
2049 assert (prev_inuse (next
));
2050 assert (chunksize (next
) >= MINSIZE
);
2052 else if (!inuse (next
))
2053 do_check_free_chunk (av
, next
);
2057 Properties of chunks recycled from fastbins
2061 do_check_remalloced_chunk (mstate av
, mchunkptr p
, INTERNAL_SIZE_T s
)
2063 INTERNAL_SIZE_T sz
= chunksize_nomask (p
) & ~(PREV_INUSE
| NON_MAIN_ARENA
);
2065 if (!chunk_is_mmapped (p
))
2067 assert (av
== arena_for_chunk (p
));
2068 if (chunk_main_arena (p
))
2069 assert (av
== &main_arena
);
2071 assert (av
!= &main_arena
);
2074 do_check_inuse_chunk (av
, p
);
2076 /* Legal size ... */
2077 assert ((sz
& MALLOC_ALIGN_MASK
) == 0);
2078 assert ((unsigned long) (sz
) >= MINSIZE
);
2079 /* ... and alignment */
2080 assert (aligned_OK (chunk2mem (p
)));
2081 /* chunk is less than MINSIZE more than request */
2082 assert ((long) (sz
) - (long) (s
) >= 0);
2083 assert ((long) (sz
) - (long) (s
+ MINSIZE
) < 0);
2087 Properties of nonrecycled chunks at the point they are malloced
2091 do_check_malloced_chunk (mstate av
, mchunkptr p
, INTERNAL_SIZE_T s
)
2093 /* same as recycled case ... */
2094 do_check_remalloced_chunk (av
, p
, s
);
2097 ... plus, must obey implementation invariant that prev_inuse is
2098 always true of any allocated chunk; i.e., that each allocated
2099 chunk borders either a previously allocated and still in-use
2100 chunk, or the base of its memory arena. This is ensured
2101 by making all allocations from the `lowest' part of any found
2102 chunk. This does not necessarily hold however for chunks
2103 recycled via fastbins.
2106 assert (prev_inuse (p
));
2111 Properties of malloc_state.
2113 This may be useful for debugging malloc, as well as detecting user
2114 programmer errors that somehow write into malloc_state.
2116 If you are extending or experimenting with this malloc, you can
2117 probably figure out how to hack this routine to print out or
2118 display chunk addresses, sizes, bins, and other instrumentation.
2122 do_check_malloc_state (mstate av
)
2129 INTERNAL_SIZE_T size
;
2130 unsigned long total
= 0;
2133 /* internal size_t must be no wider than pointer type */
2134 assert (sizeof (INTERNAL_SIZE_T
) <= sizeof (char *));
2136 /* alignment is a power of 2 */
2137 assert ((MALLOC_ALIGNMENT
& (MALLOC_ALIGNMENT
- 1)) == 0);
2139 /* Check the arena is initialized. */
2140 assert (av
->top
!= 0);
2142 /* No memory has been allocated yet, so doing more tests is not possible. */
2143 if (av
->top
== initial_top (av
))
2146 /* pagesize is a power of 2 */
2147 assert (powerof2(GLRO (dl_pagesize
)));
2149 /* A contiguous main_arena is consistent with sbrk_base. */
2150 if (av
== &main_arena
&& contiguous (av
))
2151 assert ((char *) mp_
.sbrk_base
+ av
->system_mem
==
2152 (char *) av
->top
+ chunksize (av
->top
));
2154 /* properties of fastbins */
2156 /* max_fast is in allowed range */
2157 assert ((get_max_fast () & ~1) <= request2size (MAX_FAST_SIZE
));
2159 max_fast_bin
= fastbin_index (get_max_fast ());
2161 for (i
= 0; i
< NFASTBINS
; ++i
)
2163 p
= fastbin (av
, i
);
2165 /* The following test can only be performed for the main arena.
2166 While mallopt calls malloc_consolidate to get rid of all fast
2167 bins (especially those larger than the new maximum) this does
2168 only happen for the main arena. Trying to do this for any
2169 other arena would mean those arenas have to be locked and
2170 malloc_consolidate be called for them. This is excessive. And
2171 even if this is acceptable to somebody it still cannot solve
2172 the problem completely since if the arena is locked a
2173 concurrent malloc call might create a new arena which then
2174 could use the newly invalid fast bins. */
2176 /* all bins past max_fast are empty */
2177 if (av
== &main_arena
&& i
> max_fast_bin
)
2182 /* each chunk claims to be inuse */
2183 do_check_inuse_chunk (av
, p
);
2184 total
+= chunksize (p
);
2185 /* chunk belongs in this bin */
2186 assert (fastbin_index (chunksize (p
)) == i
);
2191 /* check normal bins */
2192 for (i
= 1; i
< NBINS
; ++i
)
2196 /* binmap is accurate (except for bin 1 == unsorted_chunks) */
2199 unsigned int binbit
= get_binmap (av
, i
);
2200 int empty
= last (b
) == b
;
2207 for (p
= last (b
); p
!= b
; p
= p
->bk
)
2209 /* each chunk claims to be free */
2210 do_check_free_chunk (av
, p
);
2211 size
= chunksize (p
);
2215 /* chunk belongs in bin */
2216 idx
= bin_index (size
);
2218 /* lists are sorted */
2219 assert (p
->bk
== b
||
2220 (unsigned long) chunksize (p
->bk
) >= (unsigned long) chunksize (p
));
2222 if (!in_smallbin_range (size
))
2224 if (p
->fd_nextsize
!= NULL
)
2226 if (p
->fd_nextsize
== p
)
2227 assert (p
->bk_nextsize
== p
);
2230 if (p
->fd_nextsize
== first (b
))
2231 assert (chunksize (p
) < chunksize (p
->fd_nextsize
));
2233 assert (chunksize (p
) > chunksize (p
->fd_nextsize
));
2236 assert (chunksize (p
) > chunksize (p
->bk_nextsize
));
2238 assert (chunksize (p
) < chunksize (p
->bk_nextsize
));
2242 assert (p
->bk_nextsize
== NULL
);
2245 else if (!in_smallbin_range (size
))
2246 assert (p
->fd_nextsize
== NULL
&& p
->bk_nextsize
== NULL
);
2247 /* chunk is followed by a legal chain of inuse chunks */
2248 for (q
= next_chunk (p
);
2249 (q
!= av
->top
&& inuse (q
) &&
2250 (unsigned long) (chunksize (q
)) >= MINSIZE
);
2252 do_check_inuse_chunk (av
, q
);
2256 /* top chunk is OK */
2257 check_chunk (av
, av
->top
);
2262 /* ----------------- Support for debugging hooks -------------------- */
2266 /* ----------- Routines dealing with system allocation -------------- */
2269 sysmalloc handles malloc cases requiring more memory from the system.
2270 On entry, it is assumed that av->top does not have enough
2271 space to service request for nb bytes, thus requiring that av->top
2272 be extended or replaced.
2276 sysmalloc (INTERNAL_SIZE_T nb
, mstate av
)
2278 mchunkptr old_top
; /* incoming value of av->top */
2279 INTERNAL_SIZE_T old_size
; /* its size */
2280 char *old_end
; /* its end address */
2282 long size
; /* arg to first MORECORE or mmap call */
2283 char *brk
; /* return value from MORECORE */
2285 long correction
; /* arg to 2nd MORECORE call */
2286 char *snd_brk
; /* 2nd return val */
2288 INTERNAL_SIZE_T front_misalign
; /* unusable bytes at front of new space */
2289 INTERNAL_SIZE_T end_misalign
; /* partial page left at end of new space */
2290 char *aligned_brk
; /* aligned offset into brk */
2292 mchunkptr p
; /* the allocated/returned chunk */
2293 mchunkptr remainder
; /* remainder from allocation */
2294 unsigned long remainder_size
; /* its size */
2297 size_t pagesize
= GLRO (dl_pagesize
);
2298 bool tried_mmap
= false;
2302 If have mmap, and the request size meets the mmap threshold, and
2303 the system supports mmap, and there are few enough currently
2304 allocated mmapped regions, try to directly map this request
2305 rather than expanding top.
2309 || ((unsigned long) (nb
) >= (unsigned long) (mp_
.mmap_threshold
)
2310 && (mp_
.n_mmaps
< mp_
.n_mmaps_max
)))
2312 char *mm
; /* return value from mmap call*/
2316 Round up size to nearest page. For mmapped chunks, the overhead
2317 is one SIZE_SZ unit larger than for normal chunks, because there
2318 is no following chunk whose prev_size field could be used.
2320 See the front_misalign handling below, for glibc there is no
2321 need for further alignments unless we have have high alignment.
2323 if (MALLOC_ALIGNMENT
== 2 * SIZE_SZ
)
2324 size
= ALIGN_UP (nb
+ SIZE_SZ
, pagesize
);
2326 size
= ALIGN_UP (nb
+ SIZE_SZ
+ MALLOC_ALIGN_MASK
, pagesize
);
2329 /* Don't try if size wraps around 0 */
2330 if ((unsigned long) (size
) > (unsigned long) (nb
))
2332 mm
= (char *) (MMAP (0, size
, PROT_READ
| PROT_WRITE
, 0));
2334 if (mm
!= MAP_FAILED
)
2337 The offset to the start of the mmapped region is stored
2338 in the prev_size field of the chunk. This allows us to adjust
2339 returned start address to meet alignment requirements here
2340 and in memalign(), and still be able to compute proper
2341 address argument for later munmap in free() and realloc().
2344 if (MALLOC_ALIGNMENT
== 2 * SIZE_SZ
)
2346 /* For glibc, chunk2mem increases the address by 2*SIZE_SZ and
2347 MALLOC_ALIGN_MASK is 2*SIZE_SZ-1. Each mmap'ed area is page
2348 aligned and therefore definitely MALLOC_ALIGN_MASK-aligned. */
2349 assert (((INTERNAL_SIZE_T
) chunk2mem (mm
) & MALLOC_ALIGN_MASK
) == 0);
2353 front_misalign
= (INTERNAL_SIZE_T
) chunk2mem (mm
) & MALLOC_ALIGN_MASK
;
2354 if (front_misalign
> 0)
2356 correction
= MALLOC_ALIGNMENT
- front_misalign
;
2357 p
= (mchunkptr
) (mm
+ correction
);
2358 set_prev_size (p
, correction
);
2359 set_head (p
, (size
- correction
) | IS_MMAPPED
);
2364 set_prev_size (p
, 0);
2365 set_head (p
, size
| IS_MMAPPED
);
2368 /* update statistics */
2370 int new = atomic_exchange_and_add (&mp_
.n_mmaps
, 1) + 1;
2371 atomic_max (&mp_
.max_n_mmaps
, new);
2374 sum
= atomic_exchange_and_add (&mp_
.mmapped_mem
, size
) + size
;
2375 atomic_max (&mp_
.max_mmapped_mem
, sum
);
2377 check_chunk (av
, p
);
2379 return chunk2mem (p
);
2384 /* There are no usable arenas and mmap also failed. */
2388 /* Record incoming configuration of top */
2391 old_size
= chunksize (old_top
);
2392 old_end
= (char *) (chunk_at_offset (old_top
, old_size
));
2394 brk
= snd_brk
= (char *) (MORECORE_FAILURE
);
2397 If not the first time through, we require old_size to be
2398 at least MINSIZE and to have prev_inuse set.
2401 assert ((old_top
== initial_top (av
) && old_size
== 0) ||
2402 ((unsigned long) (old_size
) >= MINSIZE
&&
2403 prev_inuse (old_top
) &&
2404 ((unsigned long) old_end
& (pagesize
- 1)) == 0));
2406 /* Precondition: not enough current space to satisfy nb request */
2407 assert ((unsigned long) (old_size
) < (unsigned long) (nb
+ MINSIZE
));
2410 if (av
!= &main_arena
)
2412 heap_info
*old_heap
, *heap
;
2413 size_t old_heap_size
;
2415 /* First try to extend the current heap. */
2416 old_heap
= heap_for_ptr (old_top
);
2417 old_heap_size
= old_heap
->size
;
2418 if ((long) (MINSIZE
+ nb
- old_size
) > 0
2419 && grow_heap (old_heap
, MINSIZE
+ nb
- old_size
) == 0)
2421 av
->system_mem
+= old_heap
->size
- old_heap_size
;
2422 set_head (old_top
, (((char *) old_heap
+ old_heap
->size
) - (char *) old_top
)
2425 else if ((heap
= new_heap (nb
+ (MINSIZE
+ sizeof (*heap
)), mp_
.top_pad
)))
2427 /* Use a newly allocated heap. */
2429 heap
->prev
= old_heap
;
2430 av
->system_mem
+= heap
->size
;
2431 /* Set up the new top. */
2432 top (av
) = chunk_at_offset (heap
, sizeof (*heap
));
2433 set_head (top (av
), (heap
->size
- sizeof (*heap
)) | PREV_INUSE
);
2435 /* Setup fencepost and free the old top chunk with a multiple of
2436 MALLOC_ALIGNMENT in size. */
2437 /* The fencepost takes at least MINSIZE bytes, because it might
2438 become the top chunk again later. Note that a footer is set
2439 up, too, although the chunk is marked in use. */
2440 old_size
= (old_size
- MINSIZE
) & ~MALLOC_ALIGN_MASK
;
2441 set_head (chunk_at_offset (old_top
, old_size
+ 2 * SIZE_SZ
), 0 | PREV_INUSE
);
2442 if (old_size
>= MINSIZE
)
2444 set_head (chunk_at_offset (old_top
, old_size
), (2 * SIZE_SZ
) | PREV_INUSE
);
2445 set_foot (chunk_at_offset (old_top
, old_size
), (2 * SIZE_SZ
));
2446 set_head (old_top
, old_size
| PREV_INUSE
| NON_MAIN_ARENA
);
2447 _int_free (av
, old_top
, 1);
2451 set_head (old_top
, (old_size
+ 2 * SIZE_SZ
) | PREV_INUSE
);
2452 set_foot (old_top
, (old_size
+ 2 * SIZE_SZ
));
2455 else if (!tried_mmap
)
2456 /* We can at least try to use to mmap memory. */
2459 else /* av == main_arena */
2462 { /* Request enough space for nb + pad + overhead */
2463 size
= nb
+ mp_
.top_pad
+ MINSIZE
;
2466 If contiguous, we can subtract out existing space that we hope to
2467 combine with new space. We add it back later only if
2468 we don't actually get contiguous space.
2471 if (contiguous (av
))
2475 Round to a multiple of page size.
2476 If MORECORE is not contiguous, this ensures that we only call it
2477 with whole-page arguments. And if MORECORE is contiguous and
2478 this is not first time through, this preserves page-alignment of
2479 previous calls. Otherwise, we correct to page-align below.
2482 size
= ALIGN_UP (size
, pagesize
);
2485 Don't try to call MORECORE if argument is so big as to appear
2486 negative. Note that since mmap takes size_t arg, it may succeed
2487 below even if we cannot call MORECORE.
2492 brk
= (char *) (MORECORE (size
));
2493 LIBC_PROBE (memory_sbrk_more
, 2, brk
, size
);
2496 if (brk
!= (char *) (MORECORE_FAILURE
))
2498 /* Call the `morecore' hook if necessary. */
2499 void (*hook
) (void) = atomic_forced_read (__after_morecore_hook
);
2500 if (__builtin_expect (hook
!= NULL
, 0))
2506 If have mmap, try using it as a backup when MORECORE fails or
2507 cannot be used. This is worth doing on systems that have "holes" in
2508 address space, so sbrk cannot extend to give contiguous space, but
2509 space is available elsewhere. Note that we ignore mmap max count
2510 and threshold limits, since the space will not be used as a
2511 segregated mmap region.
2514 /* Cannot merge with old top, so add its size back in */
2515 if (contiguous (av
))
2516 size
= ALIGN_UP (size
+ old_size
, pagesize
);
2518 /* If we are relying on mmap as backup, then use larger units */
2519 if ((unsigned long) (size
) < (unsigned long) (MMAP_AS_MORECORE_SIZE
))
2520 size
= MMAP_AS_MORECORE_SIZE
;
2522 /* Don't try if size wraps around 0 */
2523 if ((unsigned long) (size
) > (unsigned long) (nb
))
2525 char *mbrk
= (char *) (MMAP (0, size
, PROT_READ
| PROT_WRITE
, 0));
2527 if (mbrk
!= MAP_FAILED
)
2529 /* We do not need, and cannot use, another sbrk call to find end */
2531 snd_brk
= brk
+ size
;
2534 Record that we no longer have a contiguous sbrk region.
2535 After the first time mmap is used as backup, we do not
2536 ever rely on contiguous space since this could incorrectly
2539 set_noncontiguous (av
);
2544 if (brk
!= (char *) (MORECORE_FAILURE
))
2546 if (mp_
.sbrk_base
== 0)
2547 mp_
.sbrk_base
= brk
;
2548 av
->system_mem
+= size
;
2551 If MORECORE extends previous space, we can likewise extend top size.
2554 if (brk
== old_end
&& snd_brk
== (char *) (MORECORE_FAILURE
))
2555 set_head (old_top
, (size
+ old_size
) | PREV_INUSE
);
2557 else if (contiguous (av
) && old_size
&& brk
< old_end
)
2558 /* Oops! Someone else killed our space.. Can't touch anything. */
2559 malloc_printerr ("break adjusted to free malloc space");
2562 Otherwise, make adjustments:
2564 * If the first time through or noncontiguous, we need to call sbrk
2565 just to find out where the end of memory lies.
2567 * We need to ensure that all returned chunks from malloc will meet
2570 * If there was an intervening foreign sbrk, we need to adjust sbrk
2571 request size to account for fact that we will not be able to
2572 combine new space with existing space in old_top.
2574 * Almost all systems internally allocate whole pages at a time, in
2575 which case we might as well use the whole last page of request.
2576 So we allocate enough more memory to hit a page boundary now,
2577 which in turn causes future contiguous calls to page-align.
2587 /* handle contiguous cases */
2588 if (contiguous (av
))
2590 /* Count foreign sbrk as system_mem. */
2592 av
->system_mem
+= brk
- old_end
;
2594 /* Guarantee alignment of first new chunk made from this space */
2596 front_misalign
= (INTERNAL_SIZE_T
) chunk2mem (brk
) & MALLOC_ALIGN_MASK
;
2597 if (front_misalign
> 0)
2600 Skip over some bytes to arrive at an aligned position.
2601 We don't need to specially mark these wasted front bytes.
2602 They will never be accessed anyway because
2603 prev_inuse of av->top (and any chunk created from its start)
2604 is always true after initialization.
2607 correction
= MALLOC_ALIGNMENT
- front_misalign
;
2608 aligned_brk
+= correction
;
2612 If this isn't adjacent to existing space, then we will not
2613 be able to merge with old_top space, so must add to 2nd request.
2616 correction
+= old_size
;
2618 /* Extend the end address to hit a page boundary */
2619 end_misalign
= (INTERNAL_SIZE_T
) (brk
+ size
+ correction
);
2620 correction
+= (ALIGN_UP (end_misalign
, pagesize
)) - end_misalign
;
2622 assert (correction
>= 0);
2623 snd_brk
= (char *) (MORECORE (correction
));
2626 If can't allocate correction, try to at least find out current
2627 brk. It might be enough to proceed without failing.
2629 Note that if second sbrk did NOT fail, we assume that space
2630 is contiguous with first sbrk. This is a safe assumption unless
2631 program is multithreaded but doesn't use locks and a foreign sbrk
2632 occurred between our first and second calls.
2635 if (snd_brk
== (char *) (MORECORE_FAILURE
))
2638 snd_brk
= (char *) (MORECORE (0));
2642 /* Call the `morecore' hook if necessary. */
2643 void (*hook
) (void) = atomic_forced_read (__after_morecore_hook
);
2644 if (__builtin_expect (hook
!= NULL
, 0))
2649 /* handle non-contiguous cases */
2652 if (MALLOC_ALIGNMENT
== 2 * SIZE_SZ
)
2653 /* MORECORE/mmap must correctly align */
2654 assert (((unsigned long) chunk2mem (brk
) & MALLOC_ALIGN_MASK
) == 0);
2657 front_misalign
= (INTERNAL_SIZE_T
) chunk2mem (brk
) & MALLOC_ALIGN_MASK
;
2658 if (front_misalign
> 0)
2661 Skip over some bytes to arrive at an aligned position.
2662 We don't need to specially mark these wasted front bytes.
2663 They will never be accessed anyway because
2664 prev_inuse of av->top (and any chunk created from its start)
2665 is always true after initialization.
2668 aligned_brk
+= MALLOC_ALIGNMENT
- front_misalign
;
2672 /* Find out current end of memory */
2673 if (snd_brk
== (char *) (MORECORE_FAILURE
))
2675 snd_brk
= (char *) (MORECORE (0));
2679 /* Adjust top based on results of second sbrk */
2680 if (snd_brk
!= (char *) (MORECORE_FAILURE
))
2682 av
->top
= (mchunkptr
) aligned_brk
;
2683 set_head (av
->top
, (snd_brk
- aligned_brk
+ correction
) | PREV_INUSE
);
2684 av
->system_mem
+= correction
;
2687 If not the first time through, we either have a
2688 gap due to foreign sbrk or a non-contiguous region. Insert a
2689 double fencepost at old_top to prevent consolidation with space
2690 we don't own. These fenceposts are artificial chunks that are
2691 marked as inuse and are in any case too small to use. We need
2692 two to make sizes and alignments work out.
2698 Shrink old_top to insert fenceposts, keeping size a
2699 multiple of MALLOC_ALIGNMENT. We know there is at least
2700 enough space in old_top to do this.
2702 old_size
= (old_size
- 4 * SIZE_SZ
) & ~MALLOC_ALIGN_MASK
;
2703 set_head (old_top
, old_size
| PREV_INUSE
);
2706 Note that the following assignments completely overwrite
2707 old_top when old_size was previously MINSIZE. This is
2708 intentional. We need the fencepost, even if old_top otherwise gets
2711 set_head (chunk_at_offset (old_top
, old_size
),
2712 (2 * SIZE_SZ
) | PREV_INUSE
);
2713 set_head (chunk_at_offset (old_top
, old_size
+ 2 * SIZE_SZ
),
2714 (2 * SIZE_SZ
) | PREV_INUSE
);
2716 /* If possible, release the rest. */
2717 if (old_size
>= MINSIZE
)
2719 _int_free (av
, old_top
, 1);
2725 } /* if (av != &main_arena) */
2727 if ((unsigned long) av
->system_mem
> (unsigned long) (av
->max_system_mem
))
2728 av
->max_system_mem
= av
->system_mem
;
2729 check_malloc_state (av
);
2731 /* finally, do the allocation */
2733 size
= chunksize (p
);
2735 /* check that one of the above allocation paths succeeded */
2736 if ((unsigned long) (size
) >= (unsigned long) (nb
+ MINSIZE
))
2738 remainder_size
= size
- nb
;
2739 remainder
= chunk_at_offset (p
, nb
);
2740 av
->top
= remainder
;
2741 set_head (p
, nb
| PREV_INUSE
| (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
2742 set_head (remainder
, remainder_size
| PREV_INUSE
);
2743 check_malloced_chunk (av
, p
, nb
);
2744 return chunk2mem (p
);
2747 /* catch all failure paths */
2748 __set_errno (ENOMEM
);
2754 systrim is an inverse of sorts to sysmalloc. It gives memory back
2755 to the system (via negative arguments to sbrk) if there is unused
2756 memory at the `high' end of the malloc pool. It is called
2757 automatically by free() when top space exceeds the trim
2758 threshold. It is also called by the public malloc_trim routine. It
2759 returns 1 if it actually released any memory, else 0.
2763 systrim (size_t pad
, mstate av
)
2765 long top_size
; /* Amount of top-most memory */
2766 long extra
; /* Amount to release */
2767 long released
; /* Amount actually released */
2768 char *current_brk
; /* address returned by pre-check sbrk call */
2769 char *new_brk
; /* address returned by post-check sbrk call */
2773 pagesize
= GLRO (dl_pagesize
);
2774 top_size
= chunksize (av
->top
);
2776 top_area
= top_size
- MINSIZE
- 1;
2777 if (top_area
<= pad
)
2780 /* Release in pagesize units and round down to the nearest page. */
2781 extra
= ALIGN_DOWN(top_area
- pad
, pagesize
);
2787 Only proceed if end of memory is where we last set it.
2788 This avoids problems if there were foreign sbrk calls.
2790 current_brk
= (char *) (MORECORE (0));
2791 if (current_brk
== (char *) (av
->top
) + top_size
)
2794 Attempt to release memory. We ignore MORECORE return value,
2795 and instead call again to find out where new end of memory is.
2796 This avoids problems if first call releases less than we asked,
2797 of if failure somehow altered brk value. (We could still
2798 encounter problems if it altered brk in some very bad way,
2799 but the only thing we can do is adjust anyway, which will cause
2800 some downstream failure.)
2804 /* Call the `morecore' hook if necessary. */
2805 void (*hook
) (void) = atomic_forced_read (__after_morecore_hook
);
2806 if (__builtin_expect (hook
!= NULL
, 0))
2808 new_brk
= (char *) (MORECORE (0));
2810 LIBC_PROBE (memory_sbrk_less
, 2, new_brk
, extra
);
2812 if (new_brk
!= (char *) MORECORE_FAILURE
)
2814 released
= (long) (current_brk
- new_brk
);
2818 /* Success. Adjust top. */
2819 av
->system_mem
-= released
;
2820 set_head (av
->top
, (top_size
- released
) | PREV_INUSE
);
2821 check_malloc_state (av
);
2830 munmap_chunk (mchunkptr p
)
2832 INTERNAL_SIZE_T size
= chunksize (p
);
2834 assert (chunk_is_mmapped (p
));
2836 /* Do nothing if the chunk is a faked mmapped chunk in the dumped
2837 main arena. We never free this memory. */
2838 if (DUMPED_MAIN_ARENA_CHUNK (p
))
2841 uintptr_t block
= (uintptr_t) p
- prev_size (p
);
2842 size_t total_size
= prev_size (p
) + size
;
2843 /* Unfortunately we have to do the compilers job by hand here. Normally
2844 we would test BLOCK and TOTAL-SIZE separately for compliance with the
2845 page size. But gcc does not recognize the optimization possibility
2846 (in the moment at least) so we combine the two values into one before
2848 if (__builtin_expect (((block
| total_size
) & (GLRO (dl_pagesize
) - 1)) != 0, 0))
2849 malloc_printerr ("munmap_chunk(): invalid pointer");
2851 atomic_decrement (&mp_
.n_mmaps
);
2852 atomic_add (&mp_
.mmapped_mem
, -total_size
);
2854 /* If munmap failed the process virtual memory address space is in a
2855 bad shape. Just leave the block hanging around, the process will
2856 terminate shortly anyway since not much can be done. */
2857 __munmap ((char *) block
, total_size
);
2863 mremap_chunk (mchunkptr p
, size_t new_size
)
2865 size_t pagesize
= GLRO (dl_pagesize
);
2866 INTERNAL_SIZE_T offset
= prev_size (p
);
2867 INTERNAL_SIZE_T size
= chunksize (p
);
2870 assert (chunk_is_mmapped (p
));
2871 assert (((size
+ offset
) & (GLRO (dl_pagesize
) - 1)) == 0);
2873 /* Note the extra SIZE_SZ overhead as in mmap_chunk(). */
2874 new_size
= ALIGN_UP (new_size
+ offset
+ SIZE_SZ
, pagesize
);
2876 /* No need to remap if the number of pages does not change. */
2877 if (size
+ offset
== new_size
)
2880 cp
= (char *) __mremap ((char *) p
- offset
, size
+ offset
, new_size
,
2883 if (cp
== MAP_FAILED
)
2886 p
= (mchunkptr
) (cp
+ offset
);
2888 assert (aligned_OK (chunk2mem (p
)));
2890 assert (prev_size (p
) == offset
);
2891 set_head (p
, (new_size
- offset
) | IS_MMAPPED
);
2893 INTERNAL_SIZE_T
new;
2894 new = atomic_exchange_and_add (&mp_
.mmapped_mem
, new_size
- size
- offset
)
2895 + new_size
- size
- offset
;
2896 atomic_max (&mp_
.max_mmapped_mem
, new);
2899 #endif /* HAVE_MREMAP */
2901 /*------------------------ Public wrappers. --------------------------------*/
2905 /* We overlay this structure on the user-data portion of a chunk when
2906 the chunk is stored in the per-thread cache. */
2907 typedef struct tcache_entry
2909 struct tcache_entry
*next
;
2912 /* There is one of these for each thread, which contains the
2913 per-thread cache (hence "tcache_perthread_struct"). Keeping
2914 overall size low is mildly important. Note that COUNTS and ENTRIES
2915 are redundant (we could have just counted the linked list each
2916 time), this is for performance reasons. */
2917 typedef struct tcache_perthread_struct
2919 char counts
[TCACHE_MAX_BINS
];
2920 tcache_entry
*entries
[TCACHE_MAX_BINS
];
2921 } tcache_perthread_struct
;
2923 static __thread
bool tcache_shutting_down
= false;
2924 static __thread tcache_perthread_struct
*tcache
= NULL
;
2926 /* Caller must ensure that we know tc_idx is valid and there's room
2928 static __always_inline
void
2929 tcache_put (mchunkptr chunk
, size_t tc_idx
)
2931 tcache_entry
*e
= (tcache_entry
*) chunk2mem (chunk
);
2932 assert (tc_idx
< TCACHE_MAX_BINS
);
2933 e
->next
= tcache
->entries
[tc_idx
];
2934 tcache
->entries
[tc_idx
] = e
;
2935 ++(tcache
->counts
[tc_idx
]);
2938 /* Caller must ensure that we know tc_idx is valid and there's
2939 available chunks to remove. */
2940 static __always_inline
void *
2941 tcache_get (size_t tc_idx
)
2943 tcache_entry
*e
= tcache
->entries
[tc_idx
];
2944 assert (tc_idx
< TCACHE_MAX_BINS
);
2945 assert (tcache
->entries
[tc_idx
] > 0);
2946 tcache
->entries
[tc_idx
] = e
->next
;
2947 --(tcache
->counts
[tc_idx
]);
2952 tcache_thread_shutdown (void)
2955 tcache_perthread_struct
*tcache_tmp
= tcache
;
2960 /* Disable the tcache and prevent it from being reinitialized. */
2962 tcache_shutting_down
= true;
2964 /* Free all of the entries and the tcache itself back to the arena
2965 heap for coalescing. */
2966 for (i
= 0; i
< TCACHE_MAX_BINS
; ++i
)
2968 while (tcache_tmp
->entries
[i
])
2970 tcache_entry
*e
= tcache_tmp
->entries
[i
];
2971 tcache_tmp
->entries
[i
] = e
->next
;
2976 __libc_free (tcache_tmp
);
2984 const size_t bytes
= sizeof (tcache_perthread_struct
);
2986 if (tcache_shutting_down
)
2989 arena_get (ar_ptr
, bytes
);
2990 victim
= _int_malloc (ar_ptr
, bytes
);
2991 if (!victim
&& ar_ptr
!= NULL
)
2993 ar_ptr
= arena_get_retry (ar_ptr
, bytes
);
2994 victim
= _int_malloc (ar_ptr
, bytes
);
2999 __libc_lock_unlock (ar_ptr
->mutex
);
3001 /* In a low memory situation, we may not be able to allocate memory
3002 - in which case, we just keep trying later. However, we
3003 typically do this very early, so either there is sufficient
3004 memory, or there isn't enough memory to do non-trivial
3005 allocations anyway. */
3008 tcache
= (tcache_perthread_struct
*) victim
;
3009 memset (tcache
, 0, sizeof (tcache_perthread_struct
));
3014 # define MAYBE_INIT_TCACHE() \
3015 if (__glibc_unlikely (tcache == NULL)) \
3018 #else /* !USE_TCACHE */
3019 # define MAYBE_INIT_TCACHE()
3022 tcache_thread_shutdown (void)
3024 /* Nothing to do if there is no thread cache. */
3027 #endif /* !USE_TCACHE */
3030 __libc_malloc (size_t bytes
)
3035 void *(*hook
) (size_t, const void *)
3036 = atomic_forced_read (__malloc_hook
);
3037 if (__builtin_expect (hook
!= NULL
, 0))
3038 return (*hook
)(bytes
, RETURN_ADDRESS (0));
3040 /* int_free also calls request2size, be careful to not pad twice. */
3042 checked_request2size (bytes
, tbytes
);
3043 size_t tc_idx
= csize2tidx (tbytes
);
3045 MAYBE_INIT_TCACHE ();
3047 DIAG_PUSH_NEEDS_COMMENT
;
3048 if (tc_idx
< mp_
.tcache_bins
3049 /*&& tc_idx < TCACHE_MAX_BINS*/ /* to appease gcc */
3051 && tcache
->entries
[tc_idx
] != NULL
)
3053 return tcache_get (tc_idx
);
3055 DIAG_POP_NEEDS_COMMENT
;
3058 if (SINGLE_THREAD_P
)
3060 victim
= _int_malloc (&main_arena
, bytes
);
3061 assert (!victim
|| chunk_is_mmapped (mem2chunk (victim
)) ||
3062 &main_arena
== arena_for_chunk (mem2chunk (victim
)));
3066 arena_get (ar_ptr
, bytes
);
3068 victim
= _int_malloc (ar_ptr
, bytes
);
3069 /* Retry with another arena only if we were able to find a usable arena
3071 if (!victim
&& ar_ptr
!= NULL
)
3073 LIBC_PROBE (memory_malloc_retry
, 1, bytes
);
3074 ar_ptr
= arena_get_retry (ar_ptr
, bytes
);
3075 victim
= _int_malloc (ar_ptr
, bytes
);
3079 __libc_lock_unlock (ar_ptr
->mutex
);
3081 assert (!victim
|| chunk_is_mmapped (mem2chunk (victim
)) ||
3082 ar_ptr
== arena_for_chunk (mem2chunk (victim
)));
3085 libc_hidden_def (__libc_malloc
)
3088 __libc_free (void *mem
)
3091 mchunkptr p
; /* chunk corresponding to mem */
3093 void (*hook
) (void *, const void *)
3094 = atomic_forced_read (__free_hook
);
3095 if (__builtin_expect (hook
!= NULL
, 0))
3097 (*hook
)(mem
, RETURN_ADDRESS (0));
3101 if (mem
== 0) /* free(0) has no effect */
3104 p
= mem2chunk (mem
);
3106 if (chunk_is_mmapped (p
)) /* release mmapped memory. */
3108 /* See if the dynamic brk/mmap threshold needs adjusting.
3109 Dumped fake mmapped chunks do not affect the threshold. */
3110 if (!mp_
.no_dyn_threshold
3111 && chunksize_nomask (p
) > mp_
.mmap_threshold
3112 && chunksize_nomask (p
) <= DEFAULT_MMAP_THRESHOLD_MAX
3113 && !DUMPED_MAIN_ARENA_CHUNK (p
))
3115 mp_
.mmap_threshold
= chunksize (p
);
3116 mp_
.trim_threshold
= 2 * mp_
.mmap_threshold
;
3117 LIBC_PROBE (memory_mallopt_free_dyn_thresholds
, 2,
3118 mp_
.mmap_threshold
, mp_
.trim_threshold
);
3124 MAYBE_INIT_TCACHE ();
3126 ar_ptr
= arena_for_chunk (p
);
3127 _int_free (ar_ptr
, p
, 0);
3129 libc_hidden_def (__libc_free
)
3132 __libc_realloc (void *oldmem
, size_t bytes
)
3135 INTERNAL_SIZE_T nb
; /* padded request size */
3137 void *newp
; /* chunk to return */
3139 void *(*hook
) (void *, size_t, const void *) =
3140 atomic_forced_read (__realloc_hook
);
3141 if (__builtin_expect (hook
!= NULL
, 0))
3142 return (*hook
)(oldmem
, bytes
, RETURN_ADDRESS (0));
3144 #if REALLOC_ZERO_BYTES_FREES
3145 if (bytes
== 0 && oldmem
!= NULL
)
3147 __libc_free (oldmem
); return 0;
3151 /* realloc of null is supposed to be same as malloc */
3153 return __libc_malloc (bytes
);
3155 /* chunk corresponding to oldmem */
3156 const mchunkptr oldp
= mem2chunk (oldmem
);
3158 const INTERNAL_SIZE_T oldsize
= chunksize (oldp
);
3160 if (chunk_is_mmapped (oldp
))
3164 MAYBE_INIT_TCACHE ();
3165 ar_ptr
= arena_for_chunk (oldp
);
3168 /* Little security check which won't hurt performance: the allocator
3169 never wrapps around at the end of the address space. Therefore
3170 we can exclude some size values which might appear here by
3171 accident or by "design" from some intruder. We need to bypass
3172 this check for dumped fake mmap chunks from the old main arena
3173 because the new malloc may provide additional alignment. */
3174 if ((__builtin_expect ((uintptr_t) oldp
> (uintptr_t) -oldsize
, 0)
3175 || __builtin_expect (misaligned_chunk (oldp
), 0))
3176 && !DUMPED_MAIN_ARENA_CHUNK (oldp
))
3177 malloc_printerr ("realloc(): invalid pointer");
3179 checked_request2size (bytes
, nb
);
3181 if (chunk_is_mmapped (oldp
))
3183 /* If this is a faked mmapped chunk from the dumped main arena,
3184 always make a copy (and do not free the old chunk). */
3185 if (DUMPED_MAIN_ARENA_CHUNK (oldp
))
3187 /* Must alloc, copy, free. */
3188 void *newmem
= __libc_malloc (bytes
);
3191 /* Copy as many bytes as are available from the old chunk
3192 and fit into the new size. NB: The overhead for faked
3193 mmapped chunks is only SIZE_SZ, not 2 * SIZE_SZ as for
3194 regular mmapped chunks. */
3195 if (bytes
> oldsize
- SIZE_SZ
)
3196 bytes
= oldsize
- SIZE_SZ
;
3197 memcpy (newmem
, oldmem
, bytes
);
3204 newp
= mremap_chunk (oldp
, nb
);
3206 return chunk2mem (newp
);
3208 /* Note the extra SIZE_SZ overhead. */
3209 if (oldsize
- SIZE_SZ
>= nb
)
3210 return oldmem
; /* do nothing */
3212 /* Must alloc, copy, free. */
3213 newmem
= __libc_malloc (bytes
);
3215 return 0; /* propagate failure */
3217 memcpy (newmem
, oldmem
, oldsize
- 2 * SIZE_SZ
);
3218 munmap_chunk (oldp
);
3222 if (SINGLE_THREAD_P
)
3224 newp
= _int_realloc (ar_ptr
, oldp
, oldsize
, nb
);
3225 assert (!newp
|| chunk_is_mmapped (mem2chunk (newp
)) ||
3226 ar_ptr
== arena_for_chunk (mem2chunk (newp
)));
3231 __libc_lock_lock (ar_ptr
->mutex
);
3233 newp
= _int_realloc (ar_ptr
, oldp
, oldsize
, nb
);
3235 __libc_lock_unlock (ar_ptr
->mutex
);
3236 assert (!newp
|| chunk_is_mmapped (mem2chunk (newp
)) ||
3237 ar_ptr
== arena_for_chunk (mem2chunk (newp
)));
3241 /* Try harder to allocate memory in other arenas. */
3242 LIBC_PROBE (memory_realloc_retry
, 2, bytes
, oldmem
);
3243 newp
= __libc_malloc (bytes
);
3246 memcpy (newp
, oldmem
, oldsize
- SIZE_SZ
);
3247 _int_free (ar_ptr
, oldp
, 0);
3253 libc_hidden_def (__libc_realloc
)
3256 __libc_memalign (size_t alignment
, size_t bytes
)
3258 void *address
= RETURN_ADDRESS (0);
3259 return _mid_memalign (alignment
, bytes
, address
);
3263 _mid_memalign (size_t alignment
, size_t bytes
, void *address
)
3268 void *(*hook
) (size_t, size_t, const void *) =
3269 atomic_forced_read (__memalign_hook
);
3270 if (__builtin_expect (hook
!= NULL
, 0))
3271 return (*hook
)(alignment
, bytes
, address
);
3273 /* If we need less alignment than we give anyway, just relay to malloc. */
3274 if (alignment
<= MALLOC_ALIGNMENT
)
3275 return __libc_malloc (bytes
);
3277 /* Otherwise, ensure that it is at least a minimum chunk size */
3278 if (alignment
< MINSIZE
)
3279 alignment
= MINSIZE
;
3281 /* If the alignment is greater than SIZE_MAX / 2 + 1 it cannot be a
3282 power of 2 and will cause overflow in the check below. */
3283 if (alignment
> SIZE_MAX
/ 2 + 1)
3285 __set_errno (EINVAL
);
3289 /* Check for overflow. */
3290 if (bytes
> SIZE_MAX
- alignment
- MINSIZE
)
3292 __set_errno (ENOMEM
);
3297 /* Make sure alignment is power of 2. */
3298 if (!powerof2 (alignment
))
3300 size_t a
= MALLOC_ALIGNMENT
* 2;
3301 while (a
< alignment
)
3306 if (SINGLE_THREAD_P
)
3308 p
= _int_memalign (&main_arena
, alignment
, bytes
);
3309 assert (!p
|| chunk_is_mmapped (mem2chunk (p
)) ||
3310 &main_arena
== arena_for_chunk (mem2chunk (p
)));
3315 arena_get (ar_ptr
, bytes
+ alignment
+ MINSIZE
);
3317 p
= _int_memalign (ar_ptr
, alignment
, bytes
);
3318 if (!p
&& ar_ptr
!= NULL
)
3320 LIBC_PROBE (memory_memalign_retry
, 2, bytes
, alignment
);
3321 ar_ptr
= arena_get_retry (ar_ptr
, bytes
);
3322 p
= _int_memalign (ar_ptr
, alignment
, bytes
);
3326 __libc_lock_unlock (ar_ptr
->mutex
);
3328 assert (!p
|| chunk_is_mmapped (mem2chunk (p
)) ||
3329 ar_ptr
== arena_for_chunk (mem2chunk (p
)));
3333 weak_alias (__libc_memalign
, aligned_alloc
)
3334 libc_hidden_def (__libc_memalign
)
3337 __libc_valloc (size_t bytes
)
3339 if (__malloc_initialized
< 0)
3342 void *address
= RETURN_ADDRESS (0);
3343 size_t pagesize
= GLRO (dl_pagesize
);
3344 return _mid_memalign (pagesize
, bytes
, address
);
3348 __libc_pvalloc (size_t bytes
)
3350 if (__malloc_initialized
< 0)
3353 void *address
= RETURN_ADDRESS (0);
3354 size_t pagesize
= GLRO (dl_pagesize
);
3355 size_t rounded_bytes
= ALIGN_UP (bytes
, pagesize
);
3357 /* Check for overflow. */
3358 if (bytes
> SIZE_MAX
- 2 * pagesize
- MINSIZE
)
3360 __set_errno (ENOMEM
);
3364 return _mid_memalign (pagesize
, rounded_bytes
, address
);
3368 __libc_calloc (size_t n
, size_t elem_size
)
3371 mchunkptr oldtop
, p
;
3372 INTERNAL_SIZE_T bytes
, sz
, csz
, oldtopsize
;
3374 unsigned long clearsize
;
3375 unsigned long nclears
;
3378 /* size_t is unsigned so the behavior on overflow is defined. */
3379 bytes
= n
* elem_size
;
3380 #define HALF_INTERNAL_SIZE_T \
3381 (((INTERNAL_SIZE_T) 1) << (8 * sizeof (INTERNAL_SIZE_T) / 2))
3382 if (__builtin_expect ((n
| elem_size
) >= HALF_INTERNAL_SIZE_T
, 0))
3384 if (elem_size
!= 0 && bytes
/ elem_size
!= n
)
3386 __set_errno (ENOMEM
);
3391 void *(*hook
) (size_t, const void *) =
3392 atomic_forced_read (__malloc_hook
);
3393 if (__builtin_expect (hook
!= NULL
, 0))
3396 mem
= (*hook
)(sz
, RETURN_ADDRESS (0));
3400 return memset (mem
, 0, sz
);
3405 MAYBE_INIT_TCACHE ();
3407 if (SINGLE_THREAD_P
)
3414 /* Check if we hand out the top chunk, in which case there may be no
3418 oldtopsize
= chunksize (top (av
));
3419 # if MORECORE_CLEARS < 2
3420 /* Only newly allocated memory is guaranteed to be cleared. */
3421 if (av
== &main_arena
&&
3422 oldtopsize
< mp_
.sbrk_base
+ av
->max_system_mem
- (char *) oldtop
)
3423 oldtopsize
= (mp_
.sbrk_base
+ av
->max_system_mem
- (char *) oldtop
);
3425 if (av
!= &main_arena
)
3427 heap_info
*heap
= heap_for_ptr (oldtop
);
3428 if (oldtopsize
< (char *) heap
+ heap
->mprotect_size
- (char *) oldtop
)
3429 oldtopsize
= (char *) heap
+ heap
->mprotect_size
- (char *) oldtop
;
3435 /* No usable arenas. */
3439 mem
= _int_malloc (av
, sz
);
3441 assert (!mem
|| chunk_is_mmapped (mem2chunk (mem
)) ||
3442 av
== arena_for_chunk (mem2chunk (mem
)));
3444 if (!SINGLE_THREAD_P
)
3446 if (mem
== 0 && av
!= NULL
)
3448 LIBC_PROBE (memory_calloc_retry
, 1, sz
);
3449 av
= arena_get_retry (av
, sz
);
3450 mem
= _int_malloc (av
, sz
);
3454 __libc_lock_unlock (av
->mutex
);
3457 /* Allocation failed even after a retry. */
3461 p
= mem2chunk (mem
);
3463 /* Two optional cases in which clearing not necessary */
3464 if (chunk_is_mmapped (p
))
3466 if (__builtin_expect (perturb_byte
, 0))
3467 return memset (mem
, 0, sz
);
3472 csz
= chunksize (p
);
3475 if (perturb_byte
== 0 && (p
== oldtop
&& csz
> oldtopsize
))
3477 /* clear only the bytes from non-freshly-sbrked memory */
3482 /* Unroll clear of <= 36 bytes (72 if 8byte sizes). We know that
3483 contents have an odd number of INTERNAL_SIZE_T-sized words;
3485 d
= (INTERNAL_SIZE_T
*) mem
;
3486 clearsize
= csz
- SIZE_SZ
;
3487 nclears
= clearsize
/ sizeof (INTERNAL_SIZE_T
);
3488 assert (nclears
>= 3);
3491 return memset (d
, 0, clearsize
);
3519 ------------------------------ malloc ------------------------------
3523 _int_malloc (mstate av
, size_t bytes
)
3525 INTERNAL_SIZE_T nb
; /* normalized request size */
3526 unsigned int idx
; /* associated bin index */
3527 mbinptr bin
; /* associated bin */
3529 mchunkptr victim
; /* inspected/selected chunk */
3530 INTERNAL_SIZE_T size
; /* its size */
3531 int victim_index
; /* its bin index */
3533 mchunkptr remainder
; /* remainder from a split */
3534 unsigned long remainder_size
; /* its size */
3536 unsigned int block
; /* bit map traverser */
3537 unsigned int bit
; /* bit map traverser */
3538 unsigned int map
; /* current word of binmap */
3540 mchunkptr fwd
; /* misc temp for linking */
3541 mchunkptr bck
; /* misc temp for linking */
3544 size_t tcache_unsorted_count
; /* count of unsorted chunks processed */
3548 Convert request size to internal form by adding SIZE_SZ bytes
3549 overhead plus possibly more to obtain necessary alignment and/or
3550 to obtain a size of at least MINSIZE, the smallest allocatable
3551 size. Also, checked_request2size traps (returning 0) request sizes
3552 that are so large that they wrap around zero when padded and
3556 checked_request2size (bytes
, nb
);
3558 /* There are no usable arenas. Fall back to sysmalloc to get a chunk from
3560 if (__glibc_unlikely (av
== NULL
))
3562 void *p
= sysmalloc (nb
, av
);
3564 alloc_perturb (p
, bytes
);
3569 If the size qualifies as a fastbin, first check corresponding bin.
3570 This code is safe to execute even if av is not yet initialized, so we
3571 can try it without checking, which saves some time on this fast path.
3574 #define REMOVE_FB(fb, victim, pp) \
3578 if (victim == NULL) \
3581 while ((pp = catomic_compare_and_exchange_val_acq (fb, victim->fd, victim)) \
3584 if ((unsigned long) (nb) <= (unsigned long) (get_max_fast ()))
3586 idx
= fastbin_index (nb
);
3587 mfastbinptr
*fb
= &fastbin (av
, idx
);
3593 if (SINGLE_THREAD_P
)
3596 REMOVE_FB (fb
, pp
, victim
);
3597 if (__glibc_likely (victim
!= NULL
))
3599 size_t victim_idx
= fastbin_index (chunksize (victim
));
3600 if (__builtin_expect (victim_idx
!= idx
, 0))
3601 malloc_printerr ("malloc(): memory corruption (fast)");
3602 check_remalloced_chunk (av
, victim
, nb
);
3604 /* While we're here, if we see other chunks of the same size,
3605 stash them in the tcache. */
3606 size_t tc_idx
= csize2tidx (nb
);
3607 if (tcache
&& tc_idx
< mp_
.tcache_bins
)
3609 mchunkptr tc_victim
;
3611 /* While bin not empty and tcache not full, copy chunks. */
3612 while (tcache
->counts
[tc_idx
] < mp_
.tcache_count
3613 && (tc_victim
= *fb
) != NULL
)
3615 if (SINGLE_THREAD_P
)
3616 *fb
= tc_victim
->fd
;
3619 REMOVE_FB (fb
, pp
, tc_victim
);
3620 if (__glibc_unlikely (tc_victim
== NULL
))
3623 tcache_put (tc_victim
, tc_idx
);
3627 void *p
= chunk2mem (victim
);
3628 alloc_perturb (p
, bytes
);
3635 If a small request, check regular bin. Since these "smallbins"
3636 hold one size each, no searching within bins is necessary.
3637 (For a large request, we need to wait until unsorted chunks are
3638 processed to find best fit. But for small ones, fits are exact
3639 anyway, so we can check now, which is faster.)
3642 if (in_smallbin_range (nb
))
3644 idx
= smallbin_index (nb
);
3645 bin
= bin_at (av
, idx
);
3647 if ((victim
= last (bin
)) != bin
)
3650 if (__glibc_unlikely (bck
->fd
!= victim
))
3651 malloc_printerr ("malloc(): smallbin double linked list corrupted");
3652 set_inuse_bit_at_offset (victim
, nb
);
3656 if (av
!= &main_arena
)
3657 set_non_main_arena (victim
);
3658 check_malloced_chunk (av
, victim
, nb
);
3660 /* While we're here, if we see other chunks of the same size,
3661 stash them in the tcache. */
3662 size_t tc_idx
= csize2tidx (nb
);
3663 if (tcache
&& tc_idx
< mp_
.tcache_bins
)
3665 mchunkptr tc_victim
;
3667 /* While bin not empty and tcache not full, copy chunks over. */
3668 while (tcache
->counts
[tc_idx
] < mp_
.tcache_count
3669 && (tc_victim
= last (bin
)) != bin
)
3673 bck
= tc_victim
->bk
;
3674 set_inuse_bit_at_offset (tc_victim
, nb
);
3675 if (av
!= &main_arena
)
3676 set_non_main_arena (tc_victim
);
3680 tcache_put (tc_victim
, tc_idx
);
3685 void *p
= chunk2mem (victim
);
3686 alloc_perturb (p
, bytes
);
3692 If this is a large request, consolidate fastbins before continuing.
3693 While it might look excessive to kill all fastbins before
3694 even seeing if there is space available, this avoids
3695 fragmentation problems normally associated with fastbins.
3696 Also, in practice, programs tend to have runs of either small or
3697 large requests, but less often mixtures, so consolidation is not
3698 invoked all that often in most programs. And the programs that
3699 it is called frequently in otherwise tend to fragment.
3704 idx
= largebin_index (nb
);
3705 if (atomic_load_relaxed (&av
->have_fastchunks
))
3706 malloc_consolidate (av
);
3710 Process recently freed or remaindered chunks, taking one only if
3711 it is exact fit, or, if this a small request, the chunk is remainder from
3712 the most recent non-exact fit. Place other traversed chunks in
3713 bins. Note that this step is the only place in any routine where
3714 chunks are placed in bins.
3716 The outer loop here is needed because we might not realize until
3717 near the end of malloc that we should have consolidated, so must
3718 do so and retry. This happens at most once, and only when we would
3719 otherwise need to expand memory to service a "small" request.
3723 INTERNAL_SIZE_T tcache_nb
= 0;
3724 size_t tc_idx
= csize2tidx (nb
);
3725 if (tcache
&& tc_idx
< mp_
.tcache_bins
)
3727 int return_cached
= 0;
3729 tcache_unsorted_count
= 0;
3735 while ((victim
= unsorted_chunks (av
)->bk
) != unsorted_chunks (av
))
3738 if (__builtin_expect (chunksize_nomask (victim
) <= 2 * SIZE_SZ
, 0)
3739 || __builtin_expect (chunksize_nomask (victim
)
3740 > av
->system_mem
, 0))
3741 malloc_printerr ("malloc(): memory corruption");
3742 size
= chunksize (victim
);
3745 If a small request, try to use last remainder if it is the
3746 only chunk in unsorted bin. This helps promote locality for
3747 runs of consecutive small requests. This is the only
3748 exception to best-fit, and applies only when there is
3749 no exact fit for a small chunk.
3752 if (in_smallbin_range (nb
) &&
3753 bck
== unsorted_chunks (av
) &&
3754 victim
== av
->last_remainder
&&
3755 (unsigned long) (size
) > (unsigned long) (nb
+ MINSIZE
))
3757 /* split and reattach remainder */
3758 remainder_size
= size
- nb
;
3759 remainder
= chunk_at_offset (victim
, nb
);
3760 unsorted_chunks (av
)->bk
= unsorted_chunks (av
)->fd
= remainder
;
3761 av
->last_remainder
= remainder
;
3762 remainder
->bk
= remainder
->fd
= unsorted_chunks (av
);
3763 if (!in_smallbin_range (remainder_size
))
3765 remainder
->fd_nextsize
= NULL
;
3766 remainder
->bk_nextsize
= NULL
;
3769 set_head (victim
, nb
| PREV_INUSE
|
3770 (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
3771 set_head (remainder
, remainder_size
| PREV_INUSE
);
3772 set_foot (remainder
, remainder_size
);
3774 check_malloced_chunk (av
, victim
, nb
);
3775 void *p
= chunk2mem (victim
);
3776 alloc_perturb (p
, bytes
);
3780 /* remove from unsorted list */
3781 unsorted_chunks (av
)->bk
= bck
;
3782 bck
->fd
= unsorted_chunks (av
);
3784 /* Take now instead of binning if exact fit */
3788 set_inuse_bit_at_offset (victim
, size
);
3789 if (av
!= &main_arena
)
3790 set_non_main_arena (victim
);
3792 /* Fill cache first, return to user only if cache fills.
3793 We may return one of these chunks later. */
3795 && tcache
->counts
[tc_idx
] < mp_
.tcache_count
)
3797 tcache_put (victim
, tc_idx
);
3804 check_malloced_chunk (av
, victim
, nb
);
3805 void *p
= chunk2mem (victim
);
3806 alloc_perturb (p
, bytes
);
3813 /* place chunk in bin */
3815 if (in_smallbin_range (size
))
3817 victim_index
= smallbin_index (size
);
3818 bck
= bin_at (av
, victim_index
);
3823 victim_index
= largebin_index (size
);
3824 bck
= bin_at (av
, victim_index
);
3827 /* maintain large bins in sorted order */
3830 /* Or with inuse bit to speed comparisons */
3832 /* if smaller than smallest, bypass loop below */
3833 assert (chunk_main_arena (bck
->bk
));
3834 if ((unsigned long) (size
)
3835 < (unsigned long) chunksize_nomask (bck
->bk
))
3840 victim
->fd_nextsize
= fwd
->fd
;
3841 victim
->bk_nextsize
= fwd
->fd
->bk_nextsize
;
3842 fwd
->fd
->bk_nextsize
= victim
->bk_nextsize
->fd_nextsize
= victim
;
3846 assert (chunk_main_arena (fwd
));
3847 while ((unsigned long) size
< chunksize_nomask (fwd
))
3849 fwd
= fwd
->fd_nextsize
;
3850 assert (chunk_main_arena (fwd
));
3853 if ((unsigned long) size
3854 == (unsigned long) chunksize_nomask (fwd
))
3855 /* Always insert in the second position. */
3859 victim
->fd_nextsize
= fwd
;
3860 victim
->bk_nextsize
= fwd
->bk_nextsize
;
3861 fwd
->bk_nextsize
= victim
;
3862 victim
->bk_nextsize
->fd_nextsize
= victim
;
3868 victim
->fd_nextsize
= victim
->bk_nextsize
= victim
;
3871 mark_bin (av
, victim_index
);
3878 /* If we've processed as many chunks as we're allowed while
3879 filling the cache, return one of the cached ones. */
3880 ++tcache_unsorted_count
;
3882 && mp_
.tcache_unsorted_limit
> 0
3883 && tcache_unsorted_count
> mp_
.tcache_unsorted_limit
)
3885 return tcache_get (tc_idx
);
3889 #define MAX_ITERS 10000
3890 if (++iters
>= MAX_ITERS
)
3895 /* If all the small chunks we found ended up cached, return one now. */
3898 return tcache_get (tc_idx
);
3903 If a large request, scan through the chunks of current bin in
3904 sorted order to find smallest that fits. Use the skip list for this.
3907 if (!in_smallbin_range (nb
))
3909 bin
= bin_at (av
, idx
);
3911 /* skip scan if empty or largest chunk is too small */
3912 if ((victim
= first (bin
)) != bin
3913 && (unsigned long) chunksize_nomask (victim
)
3914 >= (unsigned long) (nb
))
3916 victim
= victim
->bk_nextsize
;
3917 while (((unsigned long) (size
= chunksize (victim
)) <
3918 (unsigned long) (nb
)))
3919 victim
= victim
->bk_nextsize
;
3921 /* Avoid removing the first entry for a size so that the skip
3922 list does not have to be rerouted. */
3923 if (victim
!= last (bin
)
3924 && chunksize_nomask (victim
)
3925 == chunksize_nomask (victim
->fd
))
3926 victim
= victim
->fd
;
3928 remainder_size
= size
- nb
;
3929 unlink (av
, victim
, bck
, fwd
);
3932 if (remainder_size
< MINSIZE
)
3934 set_inuse_bit_at_offset (victim
, size
);
3935 if (av
!= &main_arena
)
3936 set_non_main_arena (victim
);
3941 remainder
= chunk_at_offset (victim
, nb
);
3942 /* We cannot assume the unsorted list is empty and therefore
3943 have to perform a complete insert here. */
3944 bck
= unsorted_chunks (av
);
3946 if (__glibc_unlikely (fwd
->bk
!= bck
))
3947 malloc_printerr ("malloc(): corrupted unsorted chunks");
3948 remainder
->bk
= bck
;
3949 remainder
->fd
= fwd
;
3950 bck
->fd
= remainder
;
3951 fwd
->bk
= remainder
;
3952 if (!in_smallbin_range (remainder_size
))
3954 remainder
->fd_nextsize
= NULL
;
3955 remainder
->bk_nextsize
= NULL
;
3957 set_head (victim
, nb
| PREV_INUSE
|
3958 (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
3959 set_head (remainder
, remainder_size
| PREV_INUSE
);
3960 set_foot (remainder
, remainder_size
);
3962 check_malloced_chunk (av
, victim
, nb
);
3963 void *p
= chunk2mem (victim
);
3964 alloc_perturb (p
, bytes
);
3970 Search for a chunk by scanning bins, starting with next largest
3971 bin. This search is strictly by best-fit; i.e., the smallest
3972 (with ties going to approximately the least recently used) chunk
3973 that fits is selected.
3975 The bitmap avoids needing to check that most blocks are nonempty.
3976 The particular case of skipping all bins during warm-up phases
3977 when no chunks have been returned yet is faster than it might look.
3981 bin
= bin_at (av
, idx
);
3982 block
= idx2block (idx
);
3983 map
= av
->binmap
[block
];
3984 bit
= idx2bit (idx
);
3988 /* Skip rest of block if there are no more set bits in this block. */
3989 if (bit
> map
|| bit
== 0)
3993 if (++block
>= BINMAPSIZE
) /* out of bins */
3996 while ((map
= av
->binmap
[block
]) == 0);
3998 bin
= bin_at (av
, (block
<< BINMAPSHIFT
));
4002 /* Advance to bin with set bit. There must be one. */
4003 while ((bit
& map
) == 0)
4005 bin
= next_bin (bin
);
4010 /* Inspect the bin. It is likely to be non-empty */
4011 victim
= last (bin
);
4013 /* If a false alarm (empty bin), clear the bit. */
4016 av
->binmap
[block
] = map
&= ~bit
; /* Write through */
4017 bin
= next_bin (bin
);
4023 size
= chunksize (victim
);
4025 /* We know the first chunk in this bin is big enough to use. */
4026 assert ((unsigned long) (size
) >= (unsigned long) (nb
));
4028 remainder_size
= size
- nb
;
4031 unlink (av
, victim
, bck
, fwd
);
4034 if (remainder_size
< MINSIZE
)
4036 set_inuse_bit_at_offset (victim
, size
);
4037 if (av
!= &main_arena
)
4038 set_non_main_arena (victim
);
4044 remainder
= chunk_at_offset (victim
, nb
);
4046 /* We cannot assume the unsorted list is empty and therefore
4047 have to perform a complete insert here. */
4048 bck
= unsorted_chunks (av
);
4050 if (__glibc_unlikely (fwd
->bk
!= bck
))
4051 malloc_printerr ("malloc(): corrupted unsorted chunks 2");
4052 remainder
->bk
= bck
;
4053 remainder
->fd
= fwd
;
4054 bck
->fd
= remainder
;
4055 fwd
->bk
= remainder
;
4057 /* advertise as last remainder */
4058 if (in_smallbin_range (nb
))
4059 av
->last_remainder
= remainder
;
4060 if (!in_smallbin_range (remainder_size
))
4062 remainder
->fd_nextsize
= NULL
;
4063 remainder
->bk_nextsize
= NULL
;
4065 set_head (victim
, nb
| PREV_INUSE
|
4066 (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4067 set_head (remainder
, remainder_size
| PREV_INUSE
);
4068 set_foot (remainder
, remainder_size
);
4070 check_malloced_chunk (av
, victim
, nb
);
4071 void *p
= chunk2mem (victim
);
4072 alloc_perturb (p
, bytes
);
4079 If large enough, split off the chunk bordering the end of memory
4080 (held in av->top). Note that this is in accord with the best-fit
4081 search rule. In effect, av->top is treated as larger (and thus
4082 less well fitting) than any other available chunk since it can
4083 be extended to be as large as necessary (up to system
4086 We require that av->top always exists (i.e., has size >=
4087 MINSIZE) after initialization, so if it would otherwise be
4088 exhausted by current request, it is replenished. (The main
4089 reason for ensuring it exists is that we may need MINSIZE space
4090 to put in fenceposts in sysmalloc.)
4094 size
= chunksize (victim
);
4096 if ((unsigned long) (size
) >= (unsigned long) (nb
+ MINSIZE
))
4098 remainder_size
= size
- nb
;
4099 remainder
= chunk_at_offset (victim
, nb
);
4100 av
->top
= remainder
;
4101 set_head (victim
, nb
| PREV_INUSE
|
4102 (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4103 set_head (remainder
, remainder_size
| PREV_INUSE
);
4105 check_malloced_chunk (av
, victim
, nb
);
4106 void *p
= chunk2mem (victim
);
4107 alloc_perturb (p
, bytes
);
4111 /* When we are using atomic ops to free fast chunks we can get
4112 here for all block sizes. */
4113 else if (atomic_load_relaxed (&av
->have_fastchunks
))
4115 malloc_consolidate (av
);
4116 /* restore original bin index */
4117 if (in_smallbin_range (nb
))
4118 idx
= smallbin_index (nb
);
4120 idx
= largebin_index (nb
);
4124 Otherwise, relay to handle system-dependent cases
4128 void *p
= sysmalloc (nb
, av
);
4130 alloc_perturb (p
, bytes
);
4137 ------------------------------ free ------------------------------
4141 _int_free (mstate av
, mchunkptr p
, int have_lock
)
4143 INTERNAL_SIZE_T size
; /* its size */
4144 mfastbinptr
*fb
; /* associated fastbin */
4145 mchunkptr nextchunk
; /* next contiguous chunk */
4146 INTERNAL_SIZE_T nextsize
; /* its size */
4147 int nextinuse
; /* true if nextchunk is used */
4148 INTERNAL_SIZE_T prevsize
; /* size of previous contiguous chunk */
4149 mchunkptr bck
; /* misc temp for linking */
4150 mchunkptr fwd
; /* misc temp for linking */
4152 size
= chunksize (p
);
4154 /* Little security check which won't hurt performance: the
4155 allocator never wrapps around at the end of the address space.
4156 Therefore we can exclude some size values which might appear
4157 here by accident or by "design" from some intruder. */
4158 if (__builtin_expect ((uintptr_t) p
> (uintptr_t) -size
, 0)
4159 || __builtin_expect (misaligned_chunk (p
), 0))
4160 malloc_printerr ("free(): invalid pointer");
4161 /* We know that each chunk is at least MINSIZE bytes in size or a
4162 multiple of MALLOC_ALIGNMENT. */
4163 if (__glibc_unlikely (size
< MINSIZE
|| !aligned_OK (size
)))
4164 malloc_printerr ("free(): invalid size");
4166 check_inuse_chunk(av
, p
);
4170 size_t tc_idx
= csize2tidx (size
);
4173 && tc_idx
< mp_
.tcache_bins
4174 && tcache
->counts
[tc_idx
] < mp_
.tcache_count
)
4176 tcache_put (p
, tc_idx
);
4183 If eligible, place chunk on a fastbin so it can be found
4184 and used quickly in malloc.
4187 if ((unsigned long)(size
) <= (unsigned long)(get_max_fast ())
4191 If TRIM_FASTBINS set, don't place chunks
4192 bordering top into fastbins
4194 && (chunk_at_offset(p
, size
) != av
->top
)
4198 if (__builtin_expect (chunksize_nomask (chunk_at_offset (p
, size
))
4200 || __builtin_expect (chunksize (chunk_at_offset (p
, size
))
4201 >= av
->system_mem
, 0))
4204 /* We might not have a lock at this point and concurrent modifications
4205 of system_mem might result in a false positive. Redo the test after
4206 getting the lock. */
4209 __libc_lock_lock (av
->mutex
);
4210 fail
= (chunksize_nomask (chunk_at_offset (p
, size
)) <= 2 * SIZE_SZ
4211 || chunksize (chunk_at_offset (p
, size
)) >= av
->system_mem
);
4212 __libc_lock_unlock (av
->mutex
);
4216 malloc_printerr ("free(): invalid next size (fast)");
4219 free_perturb (chunk2mem(p
), size
- 2 * SIZE_SZ
);
4221 atomic_store_relaxed (&av
->have_fastchunks
, true);
4222 unsigned int idx
= fastbin_index(size
);
4223 fb
= &fastbin (av
, idx
);
4225 /* Atomically link P to its fastbin: P->FD = *FB; *FB = P; */
4226 mchunkptr old
= *fb
, old2
;
4228 if (SINGLE_THREAD_P
)
4230 /* Check that the top of the bin is not the record we are going to
4231 add (i.e., double free). */
4232 if (__builtin_expect (old
== p
, 0))
4233 malloc_printerr ("double free or corruption (fasttop)");
4240 /* Check that the top of the bin is not the record we are going to
4241 add (i.e., double free). */
4242 if (__builtin_expect (old
== p
, 0))
4243 malloc_printerr ("double free or corruption (fasttop)");
4246 while ((old
= catomic_compare_and_exchange_val_rel (fb
, p
, old2
))
4249 /* Check that size of fastbin chunk at the top is the same as
4250 size of the chunk that we are adding. We can dereference OLD
4251 only if we have the lock, otherwise it might have already been
4253 if (have_lock
&& old
!= NULL
4254 && __builtin_expect (fastbin_index (chunksize (old
)) != idx
, 0))
4255 malloc_printerr ("invalid fastbin entry (free)");
4259 Consolidate other non-mmapped chunks as they arrive.
4262 else if (!chunk_is_mmapped(p
)) {
4264 /* If we're single-threaded, don't lock the arena. */
4265 if (SINGLE_THREAD_P
)
4269 __libc_lock_lock (av
->mutex
);
4271 nextchunk
= chunk_at_offset(p
, size
);
4273 /* Lightweight tests: check whether the block is already the
4275 if (__glibc_unlikely (p
== av
->top
))
4276 malloc_printerr ("double free or corruption (top)");
4277 /* Or whether the next chunk is beyond the boundaries of the arena. */
4278 if (__builtin_expect (contiguous (av
)
4279 && (char *) nextchunk
4280 >= ((char *) av
->top
+ chunksize(av
->top
)), 0))
4281 malloc_printerr ("double free or corruption (out)");
4282 /* Or whether the block is actually not marked used. */
4283 if (__glibc_unlikely (!prev_inuse(nextchunk
)))
4284 malloc_printerr ("double free or corruption (!prev)");
4286 nextsize
= chunksize(nextchunk
);
4287 if (__builtin_expect (chunksize_nomask (nextchunk
) <= 2 * SIZE_SZ
, 0)
4288 || __builtin_expect (nextsize
>= av
->system_mem
, 0))
4289 malloc_printerr ("free(): invalid next size (normal)");
4291 free_perturb (chunk2mem(p
), size
- 2 * SIZE_SZ
);
4293 /* consolidate backward */
4294 if (!prev_inuse(p
)) {
4295 prevsize
= prev_size (p
);
4297 p
= chunk_at_offset(p
, -((long) prevsize
));
4298 unlink(av
, p
, bck
, fwd
);
4301 if (nextchunk
!= av
->top
) {
4302 /* get and clear inuse bit */
4303 nextinuse
= inuse_bit_at_offset(nextchunk
, nextsize
);
4305 /* consolidate forward */
4307 unlink(av
, nextchunk
, bck
, fwd
);
4310 clear_inuse_bit_at_offset(nextchunk
, 0);
4313 Place the chunk in unsorted chunk list. Chunks are
4314 not placed into regular bins until after they have
4315 been given one chance to be used in malloc.
4318 bck
= unsorted_chunks(av
);
4320 if (__glibc_unlikely (fwd
->bk
!= bck
))
4321 malloc_printerr ("free(): corrupted unsorted chunks");
4324 if (!in_smallbin_range(size
))
4326 p
->fd_nextsize
= NULL
;
4327 p
->bk_nextsize
= NULL
;
4332 set_head(p
, size
| PREV_INUSE
);
4335 check_free_chunk(av
, p
);
4339 If the chunk borders the current high end of memory,
4340 consolidate into top
4345 set_head(p
, size
| PREV_INUSE
);
4351 If freeing a large space, consolidate possibly-surrounding
4352 chunks. Then, if the total unused topmost memory exceeds trim
4353 threshold, ask malloc_trim to reduce top.
4355 Unless max_fast is 0, we don't know if there are fastbins
4356 bordering top, so we cannot tell for sure whether threshold
4357 has been reached unless fastbins are consolidated. But we
4358 don't want to consolidate on each free. As a compromise,
4359 consolidation is performed if FASTBIN_CONSOLIDATION_THRESHOLD
4363 if ((unsigned long)(size
) >= FASTBIN_CONSOLIDATION_THRESHOLD
) {
4364 if (atomic_load_relaxed (&av
->have_fastchunks
))
4365 malloc_consolidate(av
);
4367 if (av
== &main_arena
) {
4368 #ifndef MORECORE_CANNOT_TRIM
4369 if ((unsigned long)(chunksize(av
->top
)) >=
4370 (unsigned long)(mp_
.trim_threshold
))
4371 systrim(mp_
.top_pad
, av
);
4374 /* Always try heap_trim(), even if the top chunk is not
4375 large, because the corresponding heap might go away. */
4376 heap_info
*heap
= heap_for_ptr(top(av
));
4378 assert(heap
->ar_ptr
== av
);
4379 heap_trim(heap
, mp_
.top_pad
);
4384 __libc_lock_unlock (av
->mutex
);
4387 If the chunk was allocated via mmap, release via munmap().
4396 ------------------------- malloc_consolidate -------------------------
4398 malloc_consolidate is a specialized version of free() that tears
4399 down chunks held in fastbins. Free itself cannot be used for this
4400 purpose since, among other things, it might place chunks back onto
4401 fastbins. So, instead, we need to use a minor variant of the same
4405 static void malloc_consolidate(mstate av
)
4407 mfastbinptr
* fb
; /* current fastbin being consolidated */
4408 mfastbinptr
* maxfb
; /* last fastbin (for loop control) */
4409 mchunkptr p
; /* current chunk being consolidated */
4410 mchunkptr nextp
; /* next chunk to consolidate */
4411 mchunkptr unsorted_bin
; /* bin header */
4412 mchunkptr first_unsorted
; /* chunk to link to */
4414 /* These have same use as in free() */
4415 mchunkptr nextchunk
;
4416 INTERNAL_SIZE_T size
;
4417 INTERNAL_SIZE_T nextsize
;
4418 INTERNAL_SIZE_T prevsize
;
4423 atomic_store_relaxed (&av
->have_fastchunks
, false);
4425 unsorted_bin
= unsorted_chunks(av
);
4428 Remove each chunk from fast bin and consolidate it, placing it
4429 then in unsorted bin. Among other reasons for doing this,
4430 placing in unsorted bin avoids needing to calculate actual bins
4431 until malloc is sure that chunks aren't immediately going to be
4435 maxfb
= &fastbin (av
, NFASTBINS
- 1);
4436 fb
= &fastbin (av
, 0);
4438 p
= atomic_exchange_acq (fb
, NULL
);
4442 unsigned int idx
= fastbin_index (chunksize (p
));
4443 if ((&fastbin (av
, idx
)) != fb
)
4444 malloc_printerr ("malloc_consolidate(): invalid chunk size");
4447 check_inuse_chunk(av
, p
);
4450 /* Slightly streamlined version of consolidation code in free() */
4451 size
= chunksize (p
);
4452 nextchunk
= chunk_at_offset(p
, size
);
4453 nextsize
= chunksize(nextchunk
);
4455 if (!prev_inuse(p
)) {
4456 prevsize
= prev_size (p
);
4458 p
= chunk_at_offset(p
, -((long) prevsize
));
4459 unlink(av
, p
, bck
, fwd
);
4462 if (nextchunk
!= av
->top
) {
4463 nextinuse
= inuse_bit_at_offset(nextchunk
, nextsize
);
4467 unlink(av
, nextchunk
, bck
, fwd
);
4469 clear_inuse_bit_at_offset(nextchunk
, 0);
4471 first_unsorted
= unsorted_bin
->fd
;
4472 unsorted_bin
->fd
= p
;
4473 first_unsorted
->bk
= p
;
4475 if (!in_smallbin_range (size
)) {
4476 p
->fd_nextsize
= NULL
;
4477 p
->bk_nextsize
= NULL
;
4480 set_head(p
, size
| PREV_INUSE
);
4481 p
->bk
= unsorted_bin
;
4482 p
->fd
= first_unsorted
;
4488 set_head(p
, size
| PREV_INUSE
);
4492 } while ( (p
= nextp
) != 0);
4495 } while (fb
++ != maxfb
);
4499 ------------------------------ realloc ------------------------------
4503 _int_realloc(mstate av
, mchunkptr oldp
, INTERNAL_SIZE_T oldsize
,
4506 mchunkptr newp
; /* chunk to return */
4507 INTERNAL_SIZE_T newsize
; /* its size */
4508 void* newmem
; /* corresponding user mem */
4510 mchunkptr next
; /* next contiguous chunk after oldp */
4512 mchunkptr remainder
; /* extra space at end of newp */
4513 unsigned long remainder_size
; /* its size */
4515 mchunkptr bck
; /* misc temp for linking */
4516 mchunkptr fwd
; /* misc temp for linking */
4518 unsigned long copysize
; /* bytes to copy */
4519 unsigned int ncopies
; /* INTERNAL_SIZE_T words to copy */
4520 INTERNAL_SIZE_T
* s
; /* copy source */
4521 INTERNAL_SIZE_T
* d
; /* copy destination */
4524 if (__builtin_expect (chunksize_nomask (oldp
) <= 2 * SIZE_SZ
, 0)
4525 || __builtin_expect (oldsize
>= av
->system_mem
, 0))
4526 malloc_printerr ("realloc(): invalid old size");
4528 check_inuse_chunk (av
, oldp
);
4530 /* All callers already filter out mmap'ed chunks. */
4531 assert (!chunk_is_mmapped (oldp
));
4533 next
= chunk_at_offset (oldp
, oldsize
);
4534 INTERNAL_SIZE_T nextsize
= chunksize (next
);
4535 if (__builtin_expect (chunksize_nomask (next
) <= 2 * SIZE_SZ
, 0)
4536 || __builtin_expect (nextsize
>= av
->system_mem
, 0))
4537 malloc_printerr ("realloc(): invalid next size");
4539 if ((unsigned long) (oldsize
) >= (unsigned long) (nb
))
4541 /* already big enough; split below */
4548 /* Try to expand forward into top */
4549 if (next
== av
->top
&&
4550 (unsigned long) (newsize
= oldsize
+ nextsize
) >=
4551 (unsigned long) (nb
+ MINSIZE
))
4553 set_head_size (oldp
, nb
| (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4554 av
->top
= chunk_at_offset (oldp
, nb
);
4555 set_head (av
->top
, (newsize
- nb
) | PREV_INUSE
);
4556 check_inuse_chunk (av
, oldp
);
4557 return chunk2mem (oldp
);
4560 /* Try to expand forward into next chunk; split off remainder below */
4561 else if (next
!= av
->top
&&
4563 (unsigned long) (newsize
= oldsize
+ nextsize
) >=
4564 (unsigned long) (nb
))
4567 unlink (av
, next
, bck
, fwd
);
4570 /* allocate, copy, free */
4573 newmem
= _int_malloc (av
, nb
- MALLOC_ALIGN_MASK
);
4575 return 0; /* propagate failure */
4577 newp
= mem2chunk (newmem
);
4578 newsize
= chunksize (newp
);
4581 Avoid copy if newp is next chunk after oldp.
4591 Unroll copy of <= 36 bytes (72 if 8byte sizes)
4592 We know that contents have an odd number of
4593 INTERNAL_SIZE_T-sized words; minimally 3.
4596 copysize
= oldsize
- SIZE_SZ
;
4597 s
= (INTERNAL_SIZE_T
*) (chunk2mem (oldp
));
4598 d
= (INTERNAL_SIZE_T
*) (newmem
);
4599 ncopies
= copysize
/ sizeof (INTERNAL_SIZE_T
);
4600 assert (ncopies
>= 3);
4603 memcpy (d
, s
, copysize
);
4607 *(d
+ 0) = *(s
+ 0);
4608 *(d
+ 1) = *(s
+ 1);
4609 *(d
+ 2) = *(s
+ 2);
4612 *(d
+ 3) = *(s
+ 3);
4613 *(d
+ 4) = *(s
+ 4);
4616 *(d
+ 5) = *(s
+ 5);
4617 *(d
+ 6) = *(s
+ 6);
4620 *(d
+ 7) = *(s
+ 7);
4621 *(d
+ 8) = *(s
+ 8);
4627 _int_free (av
, oldp
, 1);
4628 check_inuse_chunk (av
, newp
);
4629 return chunk2mem (newp
);
4634 /* If possible, free extra space in old or extended chunk */
4636 assert ((unsigned long) (newsize
) >= (unsigned long) (nb
));
4638 remainder_size
= newsize
- nb
;
4640 if (remainder_size
< MINSIZE
) /* not enough extra to split off */
4642 set_head_size (newp
, newsize
| (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4643 set_inuse_bit_at_offset (newp
, newsize
);
4645 else /* split remainder */
4647 remainder
= chunk_at_offset (newp
, nb
);
4648 set_head_size (newp
, nb
| (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4649 set_head (remainder
, remainder_size
| PREV_INUSE
|
4650 (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4651 /* Mark remainder as inuse so free() won't complain */
4652 set_inuse_bit_at_offset (remainder
, remainder_size
);
4653 _int_free (av
, remainder
, 1);
4656 check_inuse_chunk (av
, newp
);
4657 return chunk2mem (newp
);
4661 ------------------------------ memalign ------------------------------
4665 _int_memalign (mstate av
, size_t alignment
, size_t bytes
)
4667 INTERNAL_SIZE_T nb
; /* padded request size */
4668 char *m
; /* memory returned by malloc call */
4669 mchunkptr p
; /* corresponding chunk */
4670 char *brk
; /* alignment point within p */
4671 mchunkptr newp
; /* chunk to return */
4672 INTERNAL_SIZE_T newsize
; /* its size */
4673 INTERNAL_SIZE_T leadsize
; /* leading space before alignment point */
4674 mchunkptr remainder
; /* spare room at end to split off */
4675 unsigned long remainder_size
; /* its size */
4676 INTERNAL_SIZE_T size
;
4680 checked_request2size (bytes
, nb
);
4683 Strategy: find a spot within that chunk that meets the alignment
4684 request, and then possibly free the leading and trailing space.
4688 /* Check for overflow. */
4689 if (nb
> SIZE_MAX
- alignment
- MINSIZE
)
4691 __set_errno (ENOMEM
);
4695 /* Call malloc with worst case padding to hit alignment. */
4697 m
= (char *) (_int_malloc (av
, nb
+ alignment
+ MINSIZE
));
4700 return 0; /* propagate failure */
4704 if ((((unsigned long) (m
)) % alignment
) != 0) /* misaligned */
4707 Find an aligned spot inside chunk. Since we need to give back
4708 leading space in a chunk of at least MINSIZE, if the first
4709 calculation places us at a spot with less than MINSIZE leader,
4710 we can move to the next aligned spot -- we've allocated enough
4711 total room so that this is always possible.
4713 brk
= (char *) mem2chunk (((unsigned long) (m
+ alignment
- 1)) &
4714 - ((signed long) alignment
));
4715 if ((unsigned long) (brk
- (char *) (p
)) < MINSIZE
)
4718 newp
= (mchunkptr
) brk
;
4719 leadsize
= brk
- (char *) (p
);
4720 newsize
= chunksize (p
) - leadsize
;
4722 /* For mmapped chunks, just adjust offset */
4723 if (chunk_is_mmapped (p
))
4725 set_prev_size (newp
, prev_size (p
) + leadsize
);
4726 set_head (newp
, newsize
| IS_MMAPPED
);
4727 return chunk2mem (newp
);
4730 /* Otherwise, give back leader, use the rest */
4731 set_head (newp
, newsize
| PREV_INUSE
|
4732 (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4733 set_inuse_bit_at_offset (newp
, newsize
);
4734 set_head_size (p
, leadsize
| (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4735 _int_free (av
, p
, 1);
4738 assert (newsize
>= nb
&&
4739 (((unsigned long) (chunk2mem (p
))) % alignment
) == 0);
4742 /* Also give back spare room at the end */
4743 if (!chunk_is_mmapped (p
))
4745 size
= chunksize (p
);
4746 if ((unsigned long) (size
) > (unsigned long) (nb
+ MINSIZE
))
4748 remainder_size
= size
- nb
;
4749 remainder
= chunk_at_offset (p
, nb
);
4750 set_head (remainder
, remainder_size
| PREV_INUSE
|
4751 (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4752 set_head_size (p
, nb
);
4753 _int_free (av
, remainder
, 1);
4757 check_inuse_chunk (av
, p
);
4758 return chunk2mem (p
);
4763 ------------------------------ malloc_trim ------------------------------
4767 mtrim (mstate av
, size_t pad
)
4769 /* Ensure all blocks are consolidated. */
4770 malloc_consolidate (av
);
4772 const size_t ps
= GLRO (dl_pagesize
);
4773 int psindex
= bin_index (ps
);
4774 const size_t psm1
= ps
- 1;
4777 for (int i
= 1; i
< NBINS
; ++i
)
4778 if (i
== 1 || i
>= psindex
)
4780 mbinptr bin
= bin_at (av
, i
);
4782 for (mchunkptr p
= last (bin
); p
!= bin
; p
= p
->bk
)
4784 INTERNAL_SIZE_T size
= chunksize (p
);
4786 if (size
> psm1
+ sizeof (struct malloc_chunk
))
4788 /* See whether the chunk contains at least one unused page. */
4789 char *paligned_mem
= (char *) (((uintptr_t) p
4790 + sizeof (struct malloc_chunk
)
4793 assert ((char *) chunk2mem (p
) + 4 * SIZE_SZ
<= paligned_mem
);
4794 assert ((char *) p
+ size
> paligned_mem
);
4796 /* This is the size we could potentially free. */
4797 size
-= paligned_mem
- (char *) p
;
4802 /* When debugging we simulate destroying the memory
4804 memset (paligned_mem
, 0x89, size
& ~psm1
);
4806 __madvise (paligned_mem
, size
& ~psm1
, MADV_DONTNEED
);
4814 #ifndef MORECORE_CANNOT_TRIM
4815 return result
| (av
== &main_arena
? systrim (pad
, av
) : 0);
4824 __malloc_trim (size_t s
)
4828 if (__malloc_initialized
< 0)
4831 mstate ar_ptr
= &main_arena
;
4834 __libc_lock_lock (ar_ptr
->mutex
);
4835 result
|= mtrim (ar_ptr
, s
);
4836 __libc_lock_unlock (ar_ptr
->mutex
);
4838 ar_ptr
= ar_ptr
->next
;
4840 while (ar_ptr
!= &main_arena
);
4847 ------------------------- malloc_usable_size -------------------------
4856 p
= mem2chunk (mem
);
4858 if (__builtin_expect (using_malloc_checking
== 1, 0))
4859 return malloc_check_get_size (p
);
4861 if (chunk_is_mmapped (p
))
4863 if (DUMPED_MAIN_ARENA_CHUNK (p
))
4864 return chunksize (p
) - SIZE_SZ
;
4866 return chunksize (p
) - 2 * SIZE_SZ
;
4869 return chunksize (p
) - SIZE_SZ
;
4876 __malloc_usable_size (void *m
)
4880 result
= musable (m
);
4885 ------------------------------ mallinfo ------------------------------
4886 Accumulate malloc statistics for arena AV into M.
4890 int_mallinfo (mstate av
, struct mallinfo
*m
)
4895 INTERNAL_SIZE_T avail
;
4896 INTERNAL_SIZE_T fastavail
;
4900 check_malloc_state (av
);
4902 /* Account for top */
4903 avail
= chunksize (av
->top
);
4904 nblocks
= 1; /* top always exists */
4906 /* traverse fastbins */
4910 for (i
= 0; i
< NFASTBINS
; ++i
)
4912 for (p
= fastbin (av
, i
); p
!= 0; p
= p
->fd
)
4915 fastavail
+= chunksize (p
);
4921 /* traverse regular bins */
4922 for (i
= 1; i
< NBINS
; ++i
)
4925 for (p
= last (b
); p
!= b
; p
= p
->bk
)
4928 avail
+= chunksize (p
);
4932 m
->smblks
+= nfastblocks
;
4933 m
->ordblks
+= nblocks
;
4934 m
->fordblks
+= avail
;
4935 m
->uordblks
+= av
->system_mem
- avail
;
4936 m
->arena
+= av
->system_mem
;
4937 m
->fsmblks
+= fastavail
;
4938 if (av
== &main_arena
)
4940 m
->hblks
= mp_
.n_mmaps
;
4941 m
->hblkhd
= mp_
.mmapped_mem
;
4943 m
->keepcost
= chunksize (av
->top
);
4949 __libc_mallinfo (void)
4954 if (__malloc_initialized
< 0)
4957 memset (&m
, 0, sizeof (m
));
4958 ar_ptr
= &main_arena
;
4961 __libc_lock_lock (ar_ptr
->mutex
);
4962 int_mallinfo (ar_ptr
, &m
);
4963 __libc_lock_unlock (ar_ptr
->mutex
);
4965 ar_ptr
= ar_ptr
->next
;
4967 while (ar_ptr
!= &main_arena
);
4973 ------------------------------ malloc_stats ------------------------------
4977 __malloc_stats (void)
4981 unsigned int in_use_b
= mp_
.mmapped_mem
, system_b
= in_use_b
;
4983 if (__malloc_initialized
< 0)
4985 _IO_flockfile (stderr
);
4986 int old_flags2
= ((_IO_FILE
*) stderr
)->_flags2
;
4987 ((_IO_FILE
*) stderr
)->_flags2
|= _IO_FLAGS2_NOTCANCEL
;
4988 for (i
= 0, ar_ptr
= &main_arena
;; i
++)
4992 memset (&mi
, 0, sizeof (mi
));
4993 __libc_lock_lock (ar_ptr
->mutex
);
4994 int_mallinfo (ar_ptr
, &mi
);
4995 fprintf (stderr
, "Arena %d:\n", i
);
4996 fprintf (stderr
, "system bytes = %10u\n", (unsigned int) mi
.arena
);
4997 fprintf (stderr
, "in use bytes = %10u\n", (unsigned int) mi
.uordblks
);
4998 #if MALLOC_DEBUG > 1
5000 dump_heap (heap_for_ptr (top (ar_ptr
)));
5002 system_b
+= mi
.arena
;
5003 in_use_b
+= mi
.uordblks
;
5004 __libc_lock_unlock (ar_ptr
->mutex
);
5005 ar_ptr
= ar_ptr
->next
;
5006 if (ar_ptr
== &main_arena
)
5009 fprintf (stderr
, "Total (incl. mmap):\n");
5010 fprintf (stderr
, "system bytes = %10u\n", system_b
);
5011 fprintf (stderr
, "in use bytes = %10u\n", in_use_b
);
5012 fprintf (stderr
, "max mmap regions = %10u\n", (unsigned int) mp_
.max_n_mmaps
);
5013 fprintf (stderr
, "max mmap bytes = %10lu\n",
5014 (unsigned long) mp_
.max_mmapped_mem
);
5015 ((_IO_FILE
*) stderr
)->_flags2
|= old_flags2
;
5016 _IO_funlockfile (stderr
);
5021 ------------------------------ mallopt ------------------------------
5025 do_set_trim_threshold (size_t value
)
5027 LIBC_PROBE (memory_mallopt_trim_threshold
, 3, value
, mp_
.trim_threshold
,
5028 mp_
.no_dyn_threshold
);
5029 mp_
.trim_threshold
= value
;
5030 mp_
.no_dyn_threshold
= 1;
5036 do_set_top_pad (size_t value
)
5038 LIBC_PROBE (memory_mallopt_top_pad
, 3, value
, mp_
.top_pad
,
5039 mp_
.no_dyn_threshold
);
5040 mp_
.top_pad
= value
;
5041 mp_
.no_dyn_threshold
= 1;
5047 do_set_mmap_threshold (size_t value
)
5049 /* Forbid setting the threshold too high. */
5050 if (value
<= HEAP_MAX_SIZE
/ 2)
5052 LIBC_PROBE (memory_mallopt_mmap_threshold
, 3, value
, mp_
.mmap_threshold
,
5053 mp_
.no_dyn_threshold
);
5054 mp_
.mmap_threshold
= value
;
5055 mp_
.no_dyn_threshold
= 1;
5063 do_set_mmaps_max (int32_t value
)
5065 LIBC_PROBE (memory_mallopt_mmap_max
, 3, value
, mp_
.n_mmaps_max
,
5066 mp_
.no_dyn_threshold
);
5067 mp_
.n_mmaps_max
= value
;
5068 mp_
.no_dyn_threshold
= 1;
5074 do_set_mallopt_check (int32_t value
)
5081 do_set_perturb_byte (int32_t value
)
5083 LIBC_PROBE (memory_mallopt_perturb
, 2, value
, perturb_byte
);
5084 perturb_byte
= value
;
5090 do_set_arena_test (size_t value
)
5092 LIBC_PROBE (memory_mallopt_arena_test
, 2, value
, mp_
.arena_test
);
5093 mp_
.arena_test
= value
;
5099 do_set_arena_max (size_t value
)
5101 LIBC_PROBE (memory_mallopt_arena_max
, 2, value
, mp_
.arena_max
);
5102 mp_
.arena_max
= value
;
5109 do_set_tcache_max (size_t value
)
5111 if (value
>= 0 && value
<= MAX_TCACHE_SIZE
)
5113 LIBC_PROBE (memory_tunable_tcache_max_bytes
, 2, value
, mp_
.tcache_max_bytes
);
5114 mp_
.tcache_max_bytes
= value
;
5115 mp_
.tcache_bins
= csize2tidx (request2size(value
)) + 1;
5122 do_set_tcache_count (size_t value
)
5124 LIBC_PROBE (memory_tunable_tcache_count
, 2, value
, mp_
.tcache_count
);
5125 mp_
.tcache_count
= value
;
5131 do_set_tcache_unsorted_limit (size_t value
)
5133 LIBC_PROBE (memory_tunable_tcache_unsorted_limit
, 2, value
, mp_
.tcache_unsorted_limit
);
5134 mp_
.tcache_unsorted_limit
= value
;
5140 __libc_mallopt (int param_number
, int value
)
5142 mstate av
= &main_arena
;
5145 if (__malloc_initialized
< 0)
5147 __libc_lock_lock (av
->mutex
);
5149 LIBC_PROBE (memory_mallopt
, 2, param_number
, value
);
5151 /* We must consolidate main arena before changing max_fast
5152 (see definition of set_max_fast). */
5153 malloc_consolidate (av
);
5155 switch (param_number
)
5158 if (value
>= 0 && value
<= MAX_FAST_SIZE
)
5160 LIBC_PROBE (memory_mallopt_mxfast
, 2, value
, get_max_fast ());
5161 set_max_fast (value
);
5167 case M_TRIM_THRESHOLD
:
5168 do_set_trim_threshold (value
);
5172 do_set_top_pad (value
);
5175 case M_MMAP_THRESHOLD
:
5176 res
= do_set_mmap_threshold (value
);
5180 do_set_mmaps_max (value
);
5183 case M_CHECK_ACTION
:
5184 do_set_mallopt_check (value
);
5188 do_set_perturb_byte (value
);
5193 do_set_arena_test (value
);
5198 do_set_arena_max (value
);
5201 __libc_lock_unlock (av
->mutex
);
5204 libc_hidden_def (__libc_mallopt
)
5208 -------------------- Alternative MORECORE functions --------------------
5213 General Requirements for MORECORE.
5215 The MORECORE function must have the following properties:
5217 If MORECORE_CONTIGUOUS is false:
5219 * MORECORE must allocate in multiples of pagesize. It will
5220 only be called with arguments that are multiples of pagesize.
5222 * MORECORE(0) must return an address that is at least
5223 MALLOC_ALIGNMENT aligned. (Page-aligning always suffices.)
5225 else (i.e. If MORECORE_CONTIGUOUS is true):
5227 * Consecutive calls to MORECORE with positive arguments
5228 return increasing addresses, indicating that space has been
5229 contiguously extended.
5231 * MORECORE need not allocate in multiples of pagesize.
5232 Calls to MORECORE need not have args of multiples of pagesize.
5234 * MORECORE need not page-align.
5238 * MORECORE may allocate more memory than requested. (Or even less,
5239 but this will generally result in a malloc failure.)
5241 * MORECORE must not allocate memory when given argument zero, but
5242 instead return one past the end address of memory from previous
5243 nonzero call. This malloc does NOT call MORECORE(0)
5244 until at least one call with positive arguments is made, so
5245 the initial value returned is not important.
5247 * Even though consecutive calls to MORECORE need not return contiguous
5248 addresses, it must be OK for malloc'ed chunks to span multiple
5249 regions in those cases where they do happen to be contiguous.
5251 * MORECORE need not handle negative arguments -- it may instead
5252 just return MORECORE_FAILURE when given negative arguments.
5253 Negative arguments are always multiples of pagesize. MORECORE
5254 must not misinterpret negative args as large positive unsigned
5255 args. You can suppress all such calls from even occurring by defining
5256 MORECORE_CANNOT_TRIM,
5258 There is some variation across systems about the type of the
5259 argument to sbrk/MORECORE. If size_t is unsigned, then it cannot
5260 actually be size_t, because sbrk supports negative args, so it is
5261 normally the signed type of the same width as size_t (sometimes
5262 declared as "intptr_t", and sometimes "ptrdiff_t"). It doesn't much
5263 matter though. Internally, we use "long" as arguments, which should
5264 work across all reasonable possibilities.
5266 Additionally, if MORECORE ever returns failure for a positive
5267 request, then mmap is used as a noncontiguous system allocator. This
5268 is a useful backup strategy for systems with holes in address spaces
5269 -- in this case sbrk cannot contiguously expand the heap, but mmap
5270 may be able to map noncontiguous space.
5272 If you'd like mmap to ALWAYS be used, you can define MORECORE to be
5273 a function that always returns MORECORE_FAILURE.
5275 If you are using this malloc with something other than sbrk (or its
5276 emulation) to supply memory regions, you probably want to set
5277 MORECORE_CONTIGUOUS as false. As an example, here is a custom
5278 allocator kindly contributed for pre-OSX macOS. It uses virtually
5279 but not necessarily physically contiguous non-paged memory (locked
5280 in, present and won't get swapped out). You can use it by
5281 uncommenting this section, adding some #includes, and setting up the
5282 appropriate defines above:
5284 *#define MORECORE osMoreCore
5285 *#define MORECORE_CONTIGUOUS 0
5287 There is also a shutdown routine that should somehow be called for
5288 cleanup upon program exit.
5290 *#define MAX_POOL_ENTRIES 100
5291 *#define MINIMUM_MORECORE_SIZE (64 * 1024)
5292 static int next_os_pool;
5293 void *our_os_pools[MAX_POOL_ENTRIES];
5295 void *osMoreCore(int size)
5298 static void *sbrk_top = 0;
5302 if (size < MINIMUM_MORECORE_SIZE)
5303 size = MINIMUM_MORECORE_SIZE;
5304 if (CurrentExecutionLevel() == kTaskLevel)
5305 ptr = PoolAllocateResident(size + RM_PAGE_SIZE, 0);
5308 return (void *) MORECORE_FAILURE;
5310 // save ptrs so they can be freed during cleanup
5311 our_os_pools[next_os_pool] = ptr;
5313 ptr = (void *) ((((unsigned long) ptr) + RM_PAGE_MASK) & ~RM_PAGE_MASK);
5314 sbrk_top = (char *) ptr + size;
5319 // we don't currently support shrink behavior
5320 return (void *) MORECORE_FAILURE;
5328 // cleanup any allocated memory pools
5329 // called as last thing before shutting down driver
5331 void osCleanupMem(void)
5335 for (ptr = our_os_pools; ptr < &our_os_pools[MAX_POOL_ENTRIES]; ptr++)
5338 PoolDeallocate(*ptr);
5348 extern char **__libc_argv attribute_hidden
;
5351 malloc_printerr (const char *str
)
5353 __libc_message (do_abort
, "%s\n", str
);
5354 __builtin_unreachable ();
5357 /* We need a wrapper function for one of the additions of POSIX. */
5359 __posix_memalign (void **memptr
, size_t alignment
, size_t size
)
5363 /* Test whether the SIZE argument is valid. It must be a power of
5364 two multiple of sizeof (void *). */
5365 if (alignment
% sizeof (void *) != 0
5366 || !powerof2 (alignment
/ sizeof (void *))
5371 void *address
= RETURN_ADDRESS (0);
5372 mem
= _mid_memalign (alignment
, size
, address
);
5382 weak_alias (__posix_memalign
, posix_memalign
)
5386 __malloc_info (int options
, FILE *fp
)
5388 /* For now, at least. */
5393 size_t total_nblocks
= 0;
5394 size_t total_nfastblocks
= 0;
5395 size_t total_avail
= 0;
5396 size_t total_fastavail
= 0;
5397 size_t total_system
= 0;
5398 size_t total_max_system
= 0;
5399 size_t total_aspace
= 0;
5400 size_t total_aspace_mprotect
= 0;
5404 if (__malloc_initialized
< 0)
5407 fputs ("<malloc version=\"1\">\n", fp
);
5409 /* Iterate over all arenas currently in use. */
5410 mstate ar_ptr
= &main_arena
;
5413 fprintf (fp
, "<heap nr=\"%d\">\n<sizes>\n", n
++);
5416 size_t nfastblocks
= 0;
5418 size_t fastavail
= 0;
5425 } sizes
[NFASTBINS
+ NBINS
- 1];
5426 #define nsizes (sizeof (sizes) / sizeof (sizes[0]))
5428 __libc_lock_lock (ar_ptr
->mutex
);
5430 for (size_t i
= 0; i
< NFASTBINS
; ++i
)
5432 mchunkptr p
= fastbin (ar_ptr
, i
);
5435 size_t nthissize
= 0;
5436 size_t thissize
= chunksize (p
);
5444 fastavail
+= nthissize
* thissize
;
5445 nfastblocks
+= nthissize
;
5446 sizes
[i
].from
= thissize
- (MALLOC_ALIGNMENT
- 1);
5447 sizes
[i
].to
= thissize
;
5448 sizes
[i
].count
= nthissize
;
5451 sizes
[i
].from
= sizes
[i
].to
= sizes
[i
].count
= 0;
5453 sizes
[i
].total
= sizes
[i
].count
* sizes
[i
].to
;
5458 struct malloc_chunk
*r
;
5460 for (size_t i
= 1; i
< NBINS
; ++i
)
5462 bin
= bin_at (ar_ptr
, i
);
5464 sizes
[NFASTBINS
- 1 + i
].from
= ~((size_t) 0);
5465 sizes
[NFASTBINS
- 1 + i
].to
= sizes
[NFASTBINS
- 1 + i
].total
5466 = sizes
[NFASTBINS
- 1 + i
].count
= 0;
5471 size_t r_size
= chunksize_nomask (r
);
5472 ++sizes
[NFASTBINS
- 1 + i
].count
;
5473 sizes
[NFASTBINS
- 1 + i
].total
+= r_size
;
5474 sizes
[NFASTBINS
- 1 + i
].from
5475 = MIN (sizes
[NFASTBINS
- 1 + i
].from
, r_size
);
5476 sizes
[NFASTBINS
- 1 + i
].to
= MAX (sizes
[NFASTBINS
- 1 + i
].to
,
5482 if (sizes
[NFASTBINS
- 1 + i
].count
== 0)
5483 sizes
[NFASTBINS
- 1 + i
].from
= 0;
5484 nblocks
+= sizes
[NFASTBINS
- 1 + i
].count
;
5485 avail
+= sizes
[NFASTBINS
- 1 + i
].total
;
5488 size_t heap_size
= 0;
5489 size_t heap_mprotect_size
= 0;
5490 size_t heap_count
= 0;
5491 if (ar_ptr
!= &main_arena
)
5493 /* Iterate over the arena heaps from back to front. */
5494 heap_info
*heap
= heap_for_ptr (top (ar_ptr
));
5497 heap_size
+= heap
->size
;
5498 heap_mprotect_size
+= heap
->mprotect_size
;
5502 while (heap
!= NULL
);
5505 __libc_lock_unlock (ar_ptr
->mutex
);
5507 total_nfastblocks
+= nfastblocks
;
5508 total_fastavail
+= fastavail
;
5510 total_nblocks
+= nblocks
;
5511 total_avail
+= avail
;
5513 for (size_t i
= 0; i
< nsizes
; ++i
)
5514 if (sizes
[i
].count
!= 0 && i
!= NFASTBINS
)
5516 <size from=\"%zu\" to=\"%zu\" total=\"%zu\" count=\"%zu\"/>\n",
5517 sizes
[i
].from
, sizes
[i
].to
, sizes
[i
].total
, sizes
[i
].count
);
5519 if (sizes
[NFASTBINS
].count
!= 0)
5521 <unsorted from=\"%zu\" to=\"%zu\" total=\"%zu\" count=\"%zu\"/>\n",
5522 sizes
[NFASTBINS
].from
, sizes
[NFASTBINS
].to
,
5523 sizes
[NFASTBINS
].total
, sizes
[NFASTBINS
].count
);
5525 total_system
+= ar_ptr
->system_mem
;
5526 total_max_system
+= ar_ptr
->max_system_mem
;
5529 "</sizes>\n<total type=\"fast\" count=\"%zu\" size=\"%zu\"/>\n"
5530 "<total type=\"rest\" count=\"%zu\" size=\"%zu\"/>\n"
5531 "<system type=\"current\" size=\"%zu\"/>\n"
5532 "<system type=\"max\" size=\"%zu\"/>\n",
5533 nfastblocks
, fastavail
, nblocks
, avail
,
5534 ar_ptr
->system_mem
, ar_ptr
->max_system_mem
);
5536 if (ar_ptr
!= &main_arena
)
5539 "<aspace type=\"total\" size=\"%zu\"/>\n"
5540 "<aspace type=\"mprotect\" size=\"%zu\"/>\n"
5541 "<aspace type=\"subheaps\" size=\"%zu\"/>\n",
5542 heap_size
, heap_mprotect_size
, heap_count
);
5543 total_aspace
+= heap_size
;
5544 total_aspace_mprotect
+= heap_mprotect_size
;
5549 "<aspace type=\"total\" size=\"%zu\"/>\n"
5550 "<aspace type=\"mprotect\" size=\"%zu\"/>\n",
5551 ar_ptr
->system_mem
, ar_ptr
->system_mem
);
5552 total_aspace
+= ar_ptr
->system_mem
;
5553 total_aspace_mprotect
+= ar_ptr
->system_mem
;
5556 fputs ("</heap>\n", fp
);
5557 ar_ptr
= ar_ptr
->next
;
5559 while (ar_ptr
!= &main_arena
);
5562 "<total type=\"fast\" count=\"%zu\" size=\"%zu\"/>\n"
5563 "<total type=\"rest\" count=\"%zu\" size=\"%zu\"/>\n"
5564 "<total type=\"mmap\" count=\"%d\" size=\"%zu\"/>\n"
5565 "<system type=\"current\" size=\"%zu\"/>\n"
5566 "<system type=\"max\" size=\"%zu\"/>\n"
5567 "<aspace type=\"total\" size=\"%zu\"/>\n"
5568 "<aspace type=\"mprotect\" size=\"%zu\"/>\n"
5570 total_nfastblocks
, total_fastavail
, total_nblocks
, total_avail
,
5571 mp_
.n_mmaps
, mp_
.mmapped_mem
,
5572 total_system
, total_max_system
,
5573 total_aspace
, total_aspace_mprotect
);
5577 weak_alias (__malloc_info
, malloc_info
)
5580 strong_alias (__libc_calloc
, __calloc
) weak_alias (__libc_calloc
, calloc
)
5581 strong_alias (__libc_free
, __free
) strong_alias (__libc_free
, free
)
5582 strong_alias (__libc_malloc
, __malloc
) strong_alias (__libc_malloc
, malloc
)
5583 strong_alias (__libc_memalign
, __memalign
)
5584 weak_alias (__libc_memalign
, memalign
)
5585 strong_alias (__libc_realloc
, __realloc
) strong_alias (__libc_realloc
, realloc
)
5586 strong_alias (__libc_valloc
, __valloc
) weak_alias (__libc_valloc
, valloc
)
5587 strong_alias (__libc_pvalloc
, __pvalloc
) weak_alias (__libc_pvalloc
, pvalloc
)
5588 strong_alias (__libc_mallinfo
, __mallinfo
)
5589 weak_alias (__libc_mallinfo
, mallinfo
)
5590 strong_alias (__libc_mallopt
, __mallopt
) weak_alias (__libc_mallopt
, mallopt
)
5592 weak_alias (__malloc_stats
, malloc_stats
)
5593 weak_alias (__malloc_usable_size
, malloc_usable_size
)
5594 weak_alias (__malloc_trim
, malloc_trim
)
5596 #if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_26)
5597 compat_symbol (libc
, __libc_free
, cfree
, GLIBC_2_0
);
5600 /* ------------------------------------------------------------
5603 [see ftp://g.oswego.edu/pub/misc/malloc.c for the history of dlmalloc]