1 /* Malloc implementation for multiple threads without lock contention.
2 Copyright (C) 1996-2021 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 <https://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 */
228 #include <shlib-compat.h>
233 /* For va_arg, va_start, va_end. */
236 /* For MIN, MAX, powerof2. */
237 #include <sys/param.h>
239 /* For ALIGN_UP et. al. */
240 #include <libc-pointer-arith.h>
242 /* For DIAG_PUSH/POP_NEEDS_COMMENT et al. */
243 #include <libc-diag.h>
245 /* For memory tagging. */
246 #include <libc-mtag.h>
248 #include <malloc/malloc-internal.h>
250 /* For SINGLE_THREAD_P. */
251 #include <sysdep-cancel.h>
253 #include <libc-internal.h>
255 /* For tcache double-free check. */
256 #include <random-bits.h>
257 #include <sys/random.h>
262 Because freed chunks may be overwritten with bookkeeping fields, this
263 malloc will often die when freed memory is overwritten by user
264 programs. This can be very effective (albeit in an annoying way)
265 in helping track down dangling pointers.
267 If you compile with -DMALLOC_DEBUG, a number of assertion checks are
268 enabled that will catch more memory errors. You probably won't be
269 able to make much sense of the actual assertion errors, but they
270 should help you locate incorrectly overwritten memory. The checking
271 is fairly extensive, and will slow down execution
272 noticeably. Calling malloc_stats or mallinfo with MALLOC_DEBUG set
273 will attempt to check every non-mmapped allocated and free chunk in
274 the course of computing the summmaries. (By nature, mmapped regions
275 cannot be checked very much automatically.)
277 Setting MALLOC_DEBUG may also be helpful if you are trying to modify
278 this code. The assertions in the check routines spell out in more
279 detail the assumptions and invariants underlying the algorithms.
281 Setting MALLOC_DEBUG does NOT provide an automated mechanism for
282 checking that all accesses to malloced memory stay within their
283 bounds. However, there are several add-ons and adaptations of this
284 or other mallocs available that do this.
288 #define MALLOC_DEBUG 0
293 # define __assert_fail(assertion, file, line, function) \
294 __malloc_assert(assertion, file, line, function)
296 extern const char *__progname
;
299 __malloc_assert (const char *assertion
, const char *file
, unsigned int line
,
300 const char *function
)
302 (void) __fxprintf (NULL
, "%s%s%s:%u: %s%sAssertion `%s' failed.\n",
303 __progname
, __progname
[0] ? ": " : "",
305 function
? function
: "", function
? ": " : "",
314 /* We want 64 entries. This is an arbitrary limit, which tunables can reduce. */
315 # define TCACHE_MAX_BINS 64
316 # define MAX_TCACHE_SIZE tidx2usize (TCACHE_MAX_BINS-1)
318 /* Only used to pre-fill the tunables. */
319 # define tidx2usize(idx) (((size_t) idx) * MALLOC_ALIGNMENT + MINSIZE - SIZE_SZ)
321 /* When "x" is from chunksize(). */
322 # define csize2tidx(x) (((x) - MINSIZE + MALLOC_ALIGNMENT - 1) / MALLOC_ALIGNMENT)
323 /* When "x" is a user-provided size. */
324 # define usize2tidx(x) csize2tidx (request2size (x))
326 /* With rounding and alignment, the bins are...
327 idx 0 bytes 0..24 (64-bit) or 0..12 (32-bit)
328 idx 1 bytes 25..40 or 13..20
329 idx 2 bytes 41..56 or 21..28
332 /* This is another arbitrary limit, which tunables can change. Each
333 tcache bin will hold at most this number of chunks. */
334 # define TCACHE_FILL_COUNT 7
336 /* Maximum chunks in tcache bins for tunables. This value must fit the range
337 of tcache->counts[] entries, else they may overflow. */
338 # define MAX_TCACHE_COUNT UINT16_MAX
342 Use randomness from ASLR (mmap_base) to protect single-linked lists
343 of Fast-Bins and TCache. That is, mask the "next" pointers of the
344 lists' chunks, and also perform allocation alignment checks on them.
345 This mechanism reduces the risk of pointer hijacking, as was done with
346 Safe-Unlinking in the double-linked lists of Small-Bins.
347 It assumes a minimum page size of 4096 bytes (12 bits). Systems with
348 larger pages provide less entropy, although the pointer mangling
350 #define PROTECT_PTR(pos, ptr) \
351 ((__typeof (ptr)) ((((size_t) pos) >> 12) ^ ((size_t) ptr)))
352 #define REVEAL_PTR(ptr) PROTECT_PTR (&ptr, ptr)
355 The REALLOC_ZERO_BYTES_FREES macro controls the behavior of realloc (p, 0)
356 when p is nonnull. If the macro is nonzero, the realloc call returns NULL;
357 otherwise, the call returns what malloc (0) would. In either case,
358 p is freed. Glibc uses a nonzero REALLOC_ZERO_BYTES_FREES, which
359 implements common historical practice.
361 ISO C17 says the realloc call has implementation-defined behavior,
362 and it might not even free p.
365 #ifndef REALLOC_ZERO_BYTES_FREES
366 #define REALLOC_ZERO_BYTES_FREES 1
370 TRIM_FASTBINS controls whether free() of a very small chunk can
371 immediately lead to trimming. Setting to true (1) can reduce memory
372 footprint, but will almost always slow down programs that use a lot
375 Define this only if you are willing to give up some speed to more
376 aggressively reduce system-level memory footprint when releasing
377 memory in programs that use many small chunks. You can get
378 essentially the same effect by setting MXFAST to 0, but this can
379 lead to even greater slowdowns in programs using many small chunks.
380 TRIM_FASTBINS is an in-between compile-time option, that disables
381 only those chunks bordering topmost memory from being placed in
385 #ifndef TRIM_FASTBINS
386 #define TRIM_FASTBINS 0
389 /* Definition for getting more memory from the OS. */
390 #include "morecore.c"
392 #define MORECORE (*__glibc_morecore)
393 #define MORECORE_FAILURE 0
395 /* Memory tagging. */
397 /* Some systems support the concept of tagging (sometimes known as
398 coloring) memory locations on a fine grained basis. Each memory
399 location is given a color (normally allocated randomly) and
400 pointers are also colored. When the pointer is dereferenced, the
401 pointer's color is checked against the memory's color and if they
402 differ the access is faulted (sometimes lazily).
404 We use this in glibc by maintaining a single color for the malloc
405 data structures that are interleaved with the user data and then
406 assigning separate colors for each block allocation handed out. In
407 this way simple buffer overruns will be rapidly detected. When
408 memory is freed, the memory is recolored back to the glibc default
409 so that simple use-after-free errors can also be detected.
411 If memory is reallocated the buffer is recolored even if the
412 address remains the same. This has a performance impact, but
413 guarantees that the old pointer cannot mistakenly be reused (code
414 that compares old against new will see a mismatch and will then
415 need to behave as though realloc moved the data to a new location).
417 Internal API for memory tagging support.
419 The aim is to keep the code for memory tagging support as close to
420 the normal APIs in glibc as possible, so that if tagging is not
421 enabled in the library, or is disabled at runtime then standard
422 operations can continue to be used. Support macros are used to do
425 void *tag_new_zero_region (void *ptr, size_t size)
427 Allocates a new tag, colors the memory with that tag, zeros the
428 memory and returns a pointer that is correctly colored for that
429 location. The non-tagging version will simply call memset with 0.
431 void *tag_region (void *ptr, size_t size)
433 Color the region of memory pointed to by PTR and size SIZE with
434 the color of PTR. Returns the original pointer.
436 void *tag_new_usable (void *ptr)
438 Allocate a new random color and use it to color the user region of
439 a chunk; this may include data from the subsequent chunk's header
440 if tagging is sufficiently fine grained. Returns PTR suitably
441 recolored for accessing the memory there.
443 void *tag_at (void *ptr)
445 Read the current color of the memory at the address pointed to by
446 PTR (ignoring it's current color) and return PTR recolored to that
447 color. PTR must be valid address in all other respects. When
448 tagging is not enabled, it simply returns the original pointer.
452 static bool mtag_enabled
= false;
453 static int mtag_mmap_flags
= 0;
455 # define mtag_enabled false
456 # define mtag_mmap_flags 0
459 static __always_inline
void *
460 tag_region (void *ptr
, size_t size
)
462 if (__glibc_unlikely (mtag_enabled
))
463 return __libc_mtag_tag_region (ptr
, size
);
467 static __always_inline
void *
468 tag_new_zero_region (void *ptr
, size_t size
)
470 if (__glibc_unlikely (mtag_enabled
))
471 return __libc_mtag_tag_zero_region (__libc_mtag_new_tag (ptr
), size
);
472 return memset (ptr
, 0, size
);
477 tag_new_usable (void *ptr
);
479 static __always_inline
void *
482 if (__glibc_unlikely (mtag_enabled
))
483 return __libc_mtag_address_get_tag (ptr
);
490 MORECORE-related declarations. By default, rely on sbrk
495 MORECORE is the name of the routine to call to obtain more memory
496 from the system. See below for general guidance on writing
497 alternative MORECORE functions, as well as a version for WIN32 and a
498 sample version for pre-OSX macos.
502 #define MORECORE sbrk
506 MORECORE_FAILURE is the value returned upon failure of MORECORE
507 as well as mmap. Since it cannot be an otherwise valid memory address,
508 and must reflect values of standard sys calls, you probably ought not
512 #ifndef MORECORE_FAILURE
513 #define MORECORE_FAILURE (-1)
517 If MORECORE_CONTIGUOUS is true, take advantage of fact that
518 consecutive calls to MORECORE with positive arguments always return
519 contiguous increasing addresses. This is true of unix sbrk. Even
520 if not defined, when regions happen to be contiguous, malloc will
521 permit allocations spanning regions obtained from different
522 calls. But defining this when applicable enables some stronger
523 consistency checks and space efficiencies.
526 #ifndef MORECORE_CONTIGUOUS
527 #define MORECORE_CONTIGUOUS 1
531 Define MORECORE_CANNOT_TRIM if your version of MORECORE
532 cannot release space back to the system when given negative
533 arguments. This is generally necessary only if you are using
534 a hand-crafted MORECORE function that cannot handle negative arguments.
537 /* #define MORECORE_CANNOT_TRIM */
539 /* MORECORE_CLEARS (default 1)
540 The degree to which the routine mapped to MORECORE zeroes out
541 memory: never (0), only for newly allocated space (1) or always
542 (2). The distinction between (1) and (2) is necessary because on
543 some systems, if the application first decrements and then
544 increments the break value, the contents of the reallocated space
548 #ifndef MORECORE_CLEARS
549 # define MORECORE_CLEARS 1
554 MMAP_AS_MORECORE_SIZE is the minimum mmap size argument to use if
555 sbrk fails, and mmap is used as a backup. The value must be a
556 multiple of page size. This backup strategy generally applies only
557 when systems have "holes" in address space, so sbrk cannot perform
558 contiguous expansion, but there is still space available on system.
559 On systems for which this is known to be useful (i.e. most linux
560 kernels), this occurs only when programs allocate huge amounts of
561 memory. Between this, and the fact that mmap regions tend to be
562 limited, the size should be large, to avoid too many mmap calls and
563 thus avoid running out of kernel resources. */
565 #ifndef MMAP_AS_MORECORE_SIZE
566 #define MMAP_AS_MORECORE_SIZE (1024 * 1024)
570 Define HAVE_MREMAP to make realloc() use mremap() to re-allocate
575 #define HAVE_MREMAP 0
579 This version of malloc supports the standard SVID/XPG mallinfo
580 routine that returns a struct containing usage properties and
581 statistics. It should work on any SVID/XPG compliant system that has
582 a /usr/include/malloc.h defining struct mallinfo. (If you'd like to
583 install such a thing yourself, cut out the preliminary declarations
584 as described above and below and save them in a malloc.h file. But
585 there's no compelling reason to bother to do this.)
587 The main declaration needed is the mallinfo struct that is returned
588 (by-copy) by mallinfo(). The SVID/XPG malloinfo struct contains a
589 bunch of fields that are not even meaningful in this version of
590 malloc. These fields are are instead filled by mallinfo() with
591 other numbers that might be of interest.
595 /* ---------- description of public routines ------------ */
600 Returns a pointer to a newly allocated chunk of at least n bytes, or null
601 if no space is available. Additionally, on failure, errno is
602 set to ENOMEM on ANSI C systems.
604 If n is zero, malloc returns a minimum-sized chunk. (The minimum
605 size is 16 bytes on most 32bit systems, and 24 or 32 bytes on 64bit
606 systems.) On most systems, size_t is an unsigned type, so calls
607 with negative arguments are interpreted as requests for huge amounts
608 of space, which will often fail. The maximum supported value of n
609 differs across systems, but is in all cases less than the maximum
610 representable value of a size_t.
612 void* __libc_malloc(size_t);
613 libc_hidden_proto (__libc_malloc
)
617 Releases the chunk of memory pointed to by p, that had been previously
618 allocated using malloc or a related routine such as realloc.
619 It has no effect if p is null. It can have arbitrary (i.e., bad!)
620 effects if p has already been freed.
622 Unless disabled (using mallopt), freeing very large spaces will
623 when possible, automatically trigger operations that give
624 back unused memory to the system, thus reducing program footprint.
626 void __libc_free(void*);
627 libc_hidden_proto (__libc_free
)
630 calloc(size_t n_elements, size_t element_size);
631 Returns a pointer to n_elements * element_size bytes, with all locations
634 void* __libc_calloc(size_t, size_t);
637 realloc(void* p, size_t n)
638 Returns a pointer to a chunk of size n that contains the same data
639 as does chunk p up to the minimum of (n, p's size) bytes, or null
640 if no space is available.
642 The returned pointer may or may not be the same as p. The algorithm
643 prefers extending p when possible, otherwise it employs the
644 equivalent of a malloc-copy-free sequence.
646 If p is null, realloc is equivalent to malloc.
648 If space is not available, realloc returns null, errno is set (if on
649 ANSI) and p is NOT freed.
651 if n is for fewer bytes than already held by p, the newly unused
652 space is lopped off and freed if possible. Unless the #define
653 REALLOC_ZERO_BYTES_FREES is set, realloc with a size argument of
654 zero (re)allocates a minimum-sized chunk.
656 Large chunks that were internally obtained via mmap will always be
657 grown using malloc-copy-free sequences unless the system supports
658 MREMAP (currently only linux).
660 The old unix realloc convention of allowing the last-free'd chunk
661 to be used as an argument to realloc is not supported.
663 void* __libc_realloc(void*, size_t);
664 libc_hidden_proto (__libc_realloc
)
667 memalign(size_t alignment, size_t n);
668 Returns a pointer to a newly allocated chunk of n bytes, aligned
669 in accord with the alignment argument.
671 The alignment argument should be a power of two. If the argument is
672 not a power of two, the nearest greater power is used.
673 8-byte alignment is guaranteed by normal malloc calls, so don't
674 bother calling memalign with an argument of 8 or less.
676 Overreliance on memalign is a sure way to fragment space.
678 void* __libc_memalign(size_t, size_t);
679 libc_hidden_proto (__libc_memalign
)
683 Equivalent to memalign(pagesize, n), where pagesize is the page
684 size of the system. If the pagesize is unknown, 4096 is used.
686 void* __libc_valloc(size_t);
692 Returns (by copy) a struct containing various summary statistics:
694 arena: current total non-mmapped bytes allocated from system
695 ordblks: the number of free chunks
696 smblks: the number of fastbin blocks (i.e., small chunks that
697 have been freed but not use resused or consolidated)
698 hblks: current number of mmapped regions
699 hblkhd: total bytes held in mmapped regions
701 fsmblks: total bytes held in fastbin blocks
702 uordblks: current total allocated space (normal or mmapped)
703 fordblks: total free space
704 keepcost: the maximum number of bytes that could ideally be released
705 back to system via malloc_trim. ("ideally" means that
706 it ignores page restrictions etc.)
708 Because these fields are ints, but internal bookkeeping may
709 be kept as longs, the reported values may wrap around zero and
712 struct mallinfo2
__libc_mallinfo2(void);
713 libc_hidden_proto (__libc_mallinfo2
)
715 struct mallinfo
__libc_mallinfo(void);
720 Equivalent to valloc(minimum-page-that-holds(n)), that is,
721 round up n to nearest pagesize.
723 void* __libc_pvalloc(size_t);
726 malloc_trim(size_t pad);
728 If possible, gives memory back to the system (via negative
729 arguments to sbrk) if there is unused memory at the `high' end of
730 the malloc pool. You can call this after freeing large blocks of
731 memory to potentially reduce the system-level memory requirements
732 of a program. However, it cannot guarantee to reduce memory. Under
733 some allocation patterns, some large free blocks of memory will be
734 locked between two used chunks, so they cannot be given back to
737 The `pad' argument to malloc_trim represents the amount of free
738 trailing space to leave untrimmed. If this argument is zero,
739 only the minimum amount of memory to maintain internal data
740 structures will be left (one page or less). Non-zero arguments
741 can be supplied to maintain enough trailing space to service
742 future expected allocations without having to re-obtain memory
745 Malloc_trim returns 1 if it actually released any memory, else 0.
746 On systems that do not support "negative sbrks", it will always
749 int __malloc_trim(size_t);
752 malloc_usable_size(void* p);
754 Returns the number of bytes you can actually use in
755 an allocated chunk, which may be more than you requested (although
756 often not) due to alignment and minimum size constraints.
757 You can use this many bytes without worrying about
758 overwriting other allocated objects. This is not a particularly great
759 programming practice. malloc_usable_size can be more useful in
760 debugging and assertions, for example:
763 assert(malloc_usable_size(p) >= 256);
766 size_t __malloc_usable_size(void*);
770 Prints on stderr the amount of space obtained from the system (both
771 via sbrk and mmap), the maximum amount (which may be more than
772 current if malloc_trim and/or munmap got called), and the current
773 number of bytes allocated via malloc (or realloc, etc) but not yet
774 freed. Note that this is the number of bytes allocated, not the
775 number requested. It will be larger than the number requested
776 because of alignment and bookkeeping overhead. Because it includes
777 alignment wastage as being in use, this figure may be greater than
778 zero even when no user-level chunks are allocated.
780 The reported current and maximum system memory can be inaccurate if
781 a program makes other calls to system memory allocation functions
782 (normally sbrk) outside of malloc.
784 malloc_stats prints only the most commonly interesting statistics.
785 More information can be obtained by calling mallinfo.
788 void __malloc_stats(void);
791 posix_memalign(void **memptr, size_t alignment, size_t size);
793 POSIX wrapper like memalign(), checking for validity of size.
795 int __posix_memalign(void **, size_t, size_t);
796 #endif /* IS_IN (libc) */
799 mallopt(int parameter_number, int parameter_value)
800 Sets tunable parameters The format is to provide a
801 (parameter-number, parameter-value) pair. mallopt then sets the
802 corresponding parameter to the argument value if it can (i.e., so
803 long as the value is meaningful), and returns 1 if successful else
804 0. SVID/XPG/ANSI defines four standard param numbers for mallopt,
805 normally defined in malloc.h. Only one of these (M_MXFAST) is used
806 in this malloc. The others (M_NLBLKS, M_GRAIN, M_KEEP) don't apply,
807 so setting them has no effect. But this malloc also supports four
808 other options in mallopt. See below for details. Briefly, supported
809 parameters are as follows (listed defaults are for "typical"
812 Symbol param # default allowed param values
813 M_MXFAST 1 64 0-80 (0 disables fastbins)
814 M_TRIM_THRESHOLD -1 128*1024 any (-1U disables trimming)
816 M_MMAP_THRESHOLD -3 128*1024 any (or 0 if no MMAP support)
817 M_MMAP_MAX -4 65536 any (0 disables use of mmap)
819 int __libc_mallopt(int, int);
821 libc_hidden_proto (__libc_mallopt
)
824 /* mallopt tuning options */
827 M_MXFAST is the maximum request size used for "fastbins", special bins
828 that hold returned chunks without consolidating their spaces. This
829 enables future requests for chunks of the same size to be handled
830 very quickly, but can increase fragmentation, and thus increase the
831 overall memory footprint of a program.
833 This malloc manages fastbins very conservatively yet still
834 efficiently, so fragmentation is rarely a problem for values less
835 than or equal to the default. The maximum supported value of MXFAST
836 is 80. You wouldn't want it any higher than this anyway. Fastbins
837 are designed especially for use with many small structs, objects or
838 strings -- the default handles structs/objects/arrays with sizes up
839 to 8 4byte fields, or small strings representing words, tokens,
840 etc. Using fastbins for larger objects normally worsens
841 fragmentation without improving speed.
843 M_MXFAST is set in REQUEST size units. It is internally used in
844 chunksize units, which adds padding and alignment. You can reduce
845 M_MXFAST to 0 to disable all use of fastbins. This causes the malloc
846 algorithm to be a closer approximation of fifo-best-fit in all cases,
847 not just for larger requests, but will generally cause it to be
852 /* M_MXFAST is a standard SVID/XPG tuning option, usually listed in malloc.h */
857 #ifndef DEFAULT_MXFAST
858 #define DEFAULT_MXFAST (64 * SIZE_SZ / 4)
863 M_TRIM_THRESHOLD is the maximum amount of unused top-most memory
864 to keep before releasing via malloc_trim in free().
866 Automatic trimming is mainly useful in long-lived programs.
867 Because trimming via sbrk can be slow on some systems, and can
868 sometimes be wasteful (in cases where programs immediately
869 afterward allocate more large chunks) the value should be high
870 enough so that your overall system performance would improve by
871 releasing this much memory.
873 The trim threshold and the mmap control parameters (see below)
874 can be traded off with one another. Trimming and mmapping are
875 two different ways of releasing unused memory back to the
876 system. Between these two, it is often possible to keep
877 system-level demands of a long-lived program down to a bare
878 minimum. For example, in one test suite of sessions measuring
879 the XF86 X server on Linux, using a trim threshold of 128K and a
880 mmap threshold of 192K led to near-minimal long term resource
883 If you are using this malloc in a long-lived program, it should
884 pay to experiment with these values. As a rough guide, you
885 might set to a value close to the average size of a process
886 (program) running on your system. Releasing this much memory
887 would allow such a process to run in memory. Generally, it's
888 worth it to tune for trimming rather tham memory mapping when a
889 program undergoes phases where several large chunks are
890 allocated and released in ways that can reuse each other's
891 storage, perhaps mixed with phases where there are no such
892 chunks at all. And in well-behaved long-lived programs,
893 controlling release of large blocks via trimming versus mapping
896 However, in most programs, these parameters serve mainly as
897 protection against the system-level effects of carrying around
898 massive amounts of unneeded memory. Since frequent calls to
899 sbrk, mmap, and munmap otherwise degrade performance, the default
900 parameters are set to relatively high values that serve only as
903 The trim value It must be greater than page size to have any useful
904 effect. To disable trimming completely, you can set to
907 Trim settings interact with fastbin (MXFAST) settings: Unless
908 TRIM_FASTBINS is defined, automatic trimming never takes place upon
909 freeing a chunk with size less than or equal to MXFAST. Trimming is
910 instead delayed until subsequent freeing of larger chunks. However,
911 you can still force an attempted trim by calling malloc_trim.
913 Also, trimming is not generally possible in cases where
914 the main arena is obtained via mmap.
916 Note that the trick some people use of mallocing a huge space and
917 then freeing it at program startup, in an attempt to reserve system
918 memory, doesn't have the intended effect under automatic trimming,
919 since that memory will immediately be returned to the system.
922 #define M_TRIM_THRESHOLD -1
924 #ifndef DEFAULT_TRIM_THRESHOLD
925 #define DEFAULT_TRIM_THRESHOLD (128 * 1024)
929 M_TOP_PAD is the amount of extra `padding' space to allocate or
930 retain whenever sbrk is called. It is used in two ways internally:
932 * When sbrk is called to extend the top of the arena to satisfy
933 a new malloc request, this much padding is added to the sbrk
936 * When malloc_trim is called automatically from free(),
937 it is used as the `pad' argument.
939 In both cases, the actual amount of padding is rounded
940 so that the end of the arena is always a system page boundary.
942 The main reason for using padding is to avoid calling sbrk so
943 often. Having even a small pad greatly reduces the likelihood
944 that nearly every malloc request during program start-up (or
945 after trimming) will invoke sbrk, which needlessly wastes
948 Automatic rounding-up to page-size units is normally sufficient
949 to avoid measurable overhead, so the default is 0. However, in
950 systems where sbrk is relatively slow, it can pay to increase
951 this value, at the expense of carrying around more memory than
957 #ifndef DEFAULT_TOP_PAD
958 #define DEFAULT_TOP_PAD (0)
962 MMAP_THRESHOLD_MAX and _MIN are the bounds on the dynamically
963 adjusted MMAP_THRESHOLD.
966 #ifndef DEFAULT_MMAP_THRESHOLD_MIN
967 #define DEFAULT_MMAP_THRESHOLD_MIN (128 * 1024)
970 #ifndef DEFAULT_MMAP_THRESHOLD_MAX
971 /* For 32-bit platforms we cannot increase the maximum mmap
972 threshold much because it is also the minimum value for the
973 maximum heap size and its alignment. Going above 512k (i.e., 1M
974 for new heaps) wastes too much address space. */
975 # if __WORDSIZE == 32
976 # define DEFAULT_MMAP_THRESHOLD_MAX (512 * 1024)
978 # define DEFAULT_MMAP_THRESHOLD_MAX (4 * 1024 * 1024 * sizeof(long))
983 M_MMAP_THRESHOLD is the request size threshold for using mmap()
984 to service a request. Requests of at least this size that cannot
985 be allocated using already-existing space will be serviced via mmap.
986 (If enough normal freed space already exists it is used instead.)
988 Using mmap segregates relatively large chunks of memory so that
989 they can be individually obtained and released from the host
990 system. A request serviced through mmap is never reused by any
991 other request (at least not directly; the system may just so
992 happen to remap successive requests to the same locations).
994 Segregating space in this way has the benefits that:
996 1. Mmapped space can ALWAYS be individually released back
997 to the system, which helps keep the system level memory
998 demands of a long-lived program low.
999 2. Mapped memory can never become `locked' between
1000 other chunks, as can happen with normally allocated chunks, which
1001 means that even trimming via malloc_trim would not release them.
1002 3. On some systems with "holes" in address spaces, mmap can obtain
1003 memory that sbrk cannot.
1005 However, it has the disadvantages that:
1007 1. The space cannot be reclaimed, consolidated, and then
1008 used to service later requests, as happens with normal chunks.
1009 2. It can lead to more wastage because of mmap page alignment
1011 3. It causes malloc performance to be more dependent on host
1012 system memory management support routines which may vary in
1013 implementation quality and may impose arbitrary
1014 limitations. Generally, servicing a request via normal
1015 malloc steps is faster than going through a system's mmap.
1017 The advantages of mmap nearly always outweigh disadvantages for
1018 "large" chunks, but the value of "large" varies across systems. The
1019 default is an empirically derived value that works well in most
1024 The above was written in 2001. Since then the world has changed a lot.
1025 Memory got bigger. Applications got bigger. The virtual address space
1026 layout in 32 bit linux changed.
1028 In the new situation, brk() and mmap space is shared and there are no
1029 artificial limits on brk size imposed by the kernel. What is more,
1030 applications have started using transient allocations larger than the
1031 128Kb as was imagined in 2001.
1033 The price for mmap is also high now; each time glibc mmaps from the
1034 kernel, the kernel is forced to zero out the memory it gives to the
1035 application. Zeroing memory is expensive and eats a lot of cache and
1036 memory bandwidth. This has nothing to do with the efficiency of the
1037 virtual memory system, by doing mmap the kernel just has no choice but
1040 In 2001, the kernel had a maximum size for brk() which was about 800
1041 megabytes on 32 bit x86, at that point brk() would hit the first
1042 mmaped shared libaries and couldn't expand anymore. With current 2.6
1043 kernels, the VA space layout is different and brk() and mmap
1044 both can span the entire heap at will.
1046 Rather than using a static threshold for the brk/mmap tradeoff,
1047 we are now using a simple dynamic one. The goal is still to avoid
1048 fragmentation. The old goals we kept are
1049 1) try to get the long lived large allocations to use mmap()
1050 2) really large allocations should always use mmap()
1051 and we're adding now:
1052 3) transient allocations should use brk() to avoid forcing the kernel
1053 having to zero memory over and over again
1055 The implementation works with a sliding threshold, which is by default
1056 limited to go between 128Kb and 32Mb (64Mb for 64 bitmachines) and starts
1057 out at 128Kb as per the 2001 default.
1059 This allows us to satisfy requirement 1) under the assumption that long
1060 lived allocations are made early in the process' lifespan, before it has
1061 started doing dynamic allocations of the same size (which will
1062 increase the threshold).
1064 The upperbound on the threshold satisfies requirement 2)
1066 The threshold goes up in value when the application frees memory that was
1067 allocated with the mmap allocator. The idea is that once the application
1068 starts freeing memory of a certain size, it's highly probable that this is
1069 a size the application uses for transient allocations. This estimator
1070 is there to satisfy the new third requirement.
1074 #define M_MMAP_THRESHOLD -3
1076 #ifndef DEFAULT_MMAP_THRESHOLD
1077 #define DEFAULT_MMAP_THRESHOLD DEFAULT_MMAP_THRESHOLD_MIN
1081 M_MMAP_MAX is the maximum number of requests to simultaneously
1082 service using mmap. This parameter exists because
1083 some systems have a limited number of internal tables for
1084 use by mmap, and using more than a few of them may degrade
1087 The default is set to a value that serves only as a safeguard.
1088 Setting to 0 disables use of mmap for servicing large requests.
1091 #define M_MMAP_MAX -4
1093 #ifndef DEFAULT_MMAP_MAX
1094 #define DEFAULT_MMAP_MAX (65536)
1099 #ifndef RETURN_ADDRESS
1100 #define RETURN_ADDRESS(X_) (NULL)
1103 /* Forward declarations. */
1104 struct malloc_chunk
;
1105 typedef struct malloc_chunk
* mchunkptr
;
1107 /* Internal routines. */
1109 static void* _int_malloc(mstate
, size_t);
1110 static void _int_free(mstate
, mchunkptr
, int);
1111 static void* _int_realloc(mstate
, mchunkptr
, INTERNAL_SIZE_T
,
1113 static void* _int_memalign(mstate
, size_t, size_t);
1115 static void* _mid_memalign(size_t, size_t, void *);
1118 static void malloc_printerr(const char *str
) __attribute__ ((noreturn
));
1120 static void munmap_chunk(mchunkptr p
);
1122 static mchunkptr
mremap_chunk(mchunkptr p
, size_t new_size
);
1125 /* ------------------ MMAP support ------------------ */
1129 #include <sys/mman.h>
1131 #if !defined(MAP_ANONYMOUS) && defined(MAP_ANON)
1132 # define MAP_ANONYMOUS MAP_ANON
1135 #ifndef MAP_NORESERVE
1136 # define MAP_NORESERVE 0
1139 #define MMAP(addr, size, prot, flags) \
1140 __mmap((addr), (size), (prot), (flags)|MAP_ANONYMOUS|MAP_PRIVATE, -1, 0)
1144 ----------------------- Chunk representations -----------------------
1149 This struct declaration is misleading (but accurate and necessary).
1150 It declares a "view" into memory allowing access to necessary
1151 fields at known offsets from a given base. See explanation below.
1154 struct malloc_chunk
{
1156 INTERNAL_SIZE_T mchunk_prev_size
; /* Size of previous chunk (if free). */
1157 INTERNAL_SIZE_T mchunk_size
; /* Size in bytes, including overhead. */
1159 struct malloc_chunk
* fd
; /* double links -- used only if free. */
1160 struct malloc_chunk
* bk
;
1162 /* Only used for large blocks: pointer to next larger size. */
1163 struct malloc_chunk
* fd_nextsize
; /* double links -- used only if free. */
1164 struct malloc_chunk
* bk_nextsize
;
1169 malloc_chunk details:
1171 (The following includes lightly edited explanations by Colin Plumb.)
1173 Chunks of memory are maintained using a `boundary tag' method as
1174 described in e.g., Knuth or Standish. (See the paper by Paul
1175 Wilson ftp://ftp.cs.utexas.edu/pub/garbage/allocsrv.ps for a
1176 survey of such techniques.) Sizes of free chunks are stored both
1177 in the front of each chunk and at the end. This makes
1178 consolidating fragmented chunks into bigger chunks very fast. The
1179 size fields also hold bits representing whether chunks are free or
1182 An allocated chunk looks like this:
1185 chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1186 | Size of previous chunk, if unallocated (P clear) |
1187 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1188 | Size of chunk, in bytes |A|M|P|
1189 mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1190 | User data starts here... .
1192 . (malloc_usable_size() bytes) .
1194 nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1195 | (size of chunk, but used for application data) |
1196 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1197 | Size of next chunk, in bytes |A|0|1|
1198 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1200 Where "chunk" is the front of the chunk for the purpose of most of
1201 the malloc code, but "mem" is the pointer that is returned to the
1202 user. "Nextchunk" is the beginning of the next contiguous chunk.
1204 Chunks always begin on even word boundaries, so the mem portion
1205 (which is returned to the user) is also on an even word boundary, and
1206 thus at least double-word aligned.
1208 Free chunks are stored in circular doubly-linked lists, and look like this:
1210 chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1211 | Size of previous chunk, if unallocated (P clear) |
1212 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1213 `head:' | Size of chunk, in bytes |A|0|P|
1214 mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1215 | Forward pointer to next chunk in list |
1216 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1217 | Back pointer to previous chunk in list |
1218 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1219 | Unused space (may be 0 bytes long) .
1222 nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1223 `foot:' | Size of chunk, in bytes |
1224 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1225 | Size of next chunk, in bytes |A|0|0|
1226 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1228 The P (PREV_INUSE) bit, stored in the unused low-order bit of the
1229 chunk size (which is always a multiple of two words), is an in-use
1230 bit for the *previous* chunk. If that bit is *clear*, then the
1231 word before the current chunk size contains the previous chunk
1232 size, and can be used to find the front of the previous chunk.
1233 The very first chunk allocated always has this bit set,
1234 preventing access to non-existent (or non-owned) memory. If
1235 prev_inuse is set for any given chunk, then you CANNOT determine
1236 the size of the previous chunk, and might even get a memory
1237 addressing fault when trying to do so.
1239 The A (NON_MAIN_ARENA) bit is cleared for chunks on the initial,
1240 main arena, described by the main_arena variable. When additional
1241 threads are spawned, each thread receives its own arena (up to a
1242 configurable limit, after which arenas are reused for multiple
1243 threads), and the chunks in these arenas have the A bit set. To
1244 find the arena for a chunk on such a non-main arena, heap_for_ptr
1245 performs a bit mask operation and indirection through the ar_ptr
1246 member of the per-heap header heap_info (see arena.c).
1248 Note that the `foot' of the current chunk is actually represented
1249 as the prev_size of the NEXT chunk. This makes it easier to
1250 deal with alignments etc but can be very confusing when trying
1251 to extend or adapt this code.
1253 The three exceptions to all this are:
1255 1. The special chunk `top' doesn't bother using the
1256 trailing size field since there is no next contiguous chunk
1257 that would have to index off it. After initialization, `top'
1258 is forced to always exist. If it would become less than
1259 MINSIZE bytes long, it is replenished.
1261 2. Chunks allocated via mmap, which have the second-lowest-order
1262 bit M (IS_MMAPPED) set in their size fields. Because they are
1263 allocated one-by-one, each must contain its own trailing size
1264 field. If the M bit is set, the other bits are ignored
1265 (because mmapped chunks are neither in an arena, nor adjacent
1266 to a freed chunk). The M bit is also used for chunks which
1267 originally came from a dumped heap via malloc_set_state in
1270 3. Chunks in fastbins are treated as allocated chunks from the
1271 point of view of the chunk allocator. They are consolidated
1272 with their neighbors only in bulk, in malloc_consolidate.
1276 ---------- Size and alignment checks and conversions ----------
1279 /* Conversion from malloc headers to user pointers, and back. When
1280 using memory tagging the user data and the malloc data structure
1281 headers have distinct tags. Converting fully from one to the other
1282 involves extracting the tag at the other address and creating a
1283 suitable pointer using it. That can be quite expensive. There are
1284 cases when the pointers are not dereferenced (for example only used
1285 for alignment check) so the tags are not relevant, and there are
1286 cases when user data is not tagged distinctly from malloc headers
1287 (user data is untagged because tagging is done late in malloc and
1288 early in free). User memory tagging across internal interfaces:
1290 sysmalloc: Returns untagged memory.
1291 _int_malloc: Returns untagged memory.
1292 _int_free: Takes untagged memory.
1293 _int_memalign: Returns untagged memory.
1294 _int_memalign: Returns untagged memory.
1295 _mid_memalign: Returns tagged memory.
1296 _int_realloc: Takes and returns tagged memory.
1299 /* The chunk header is two SIZE_SZ elements, but this is used widely, so
1300 we define it here for clarity later. */
1301 #define CHUNK_HDR_SZ (2 * SIZE_SZ)
1303 /* Convert a chunk address to a user mem pointer without correcting
1305 #define chunk2mem(p) ((void*)((char*)(p) + CHUNK_HDR_SZ))
1307 /* Convert a chunk address to a user mem pointer and extract the right tag. */
1308 #define chunk2mem_tag(p) ((void*)tag_at ((char*)(p) + CHUNK_HDR_SZ))
1310 /* Convert a user mem pointer to a chunk address and extract the right tag. */
1311 #define mem2chunk(mem) ((mchunkptr)tag_at (((char*)(mem) - CHUNK_HDR_SZ)))
1313 /* The smallest possible chunk */
1314 #define MIN_CHUNK_SIZE (offsetof(struct malloc_chunk, fd_nextsize))
1316 /* The smallest size we can malloc is an aligned minimal chunk */
1319 (unsigned long)(((MIN_CHUNK_SIZE+MALLOC_ALIGN_MASK) & ~MALLOC_ALIGN_MASK))
1321 /* Check if m has acceptable alignment */
1323 #define aligned_OK(m) (((unsigned long)(m) & MALLOC_ALIGN_MASK) == 0)
1325 #define misaligned_chunk(p) \
1326 ((uintptr_t)(MALLOC_ALIGNMENT == CHUNK_HDR_SZ ? (p) : chunk2mem (p)) \
1327 & MALLOC_ALIGN_MASK)
1329 /* pad request bytes into a usable size -- internal version */
1330 /* Note: This must be a macro that evaluates to a compile time constant
1331 if passed a literal constant. */
1332 #define request2size(req) \
1333 (((req) + SIZE_SZ + MALLOC_ALIGN_MASK < MINSIZE) ? \
1335 ((req) + SIZE_SZ + MALLOC_ALIGN_MASK) & ~MALLOC_ALIGN_MASK)
1337 /* Check if REQ overflows when padded and aligned and if the resulting value
1338 is less than PTRDIFF_T. Returns TRUE and the requested size or MINSIZE in
1339 case the value is less than MINSIZE on SZ or false if any of the previous
1342 checked_request2size (size_t req
, size_t *sz
) __nonnull (1)
1344 if (__glibc_unlikely (req
> PTRDIFF_MAX
))
1347 /* When using tagged memory, we cannot share the end of the user
1348 block with the header for the next chunk, so ensure that we
1349 allocate blocks that are rounded up to the granule size. Take
1350 care not to overflow from close to MAX_SIZE_T to a small
1351 number. Ideally, this would be part of request2size(), but that
1352 must be a macro that produces a compile time constant if passed
1353 a constant literal. */
1354 if (__glibc_unlikely (mtag_enabled
))
1356 /* Ensure this is not evaluated if !mtag_enabled, see gcc PR 99551. */
1359 req
= (req
+ (__MTAG_GRANULE_SIZE
- 1)) &
1360 ~(size_t)(__MTAG_GRANULE_SIZE
- 1);
1363 *sz
= request2size (req
);
1368 --------------- Physical chunk operations ---------------
1372 /* size field is or'ed with PREV_INUSE when previous adjacent chunk in use */
1373 #define PREV_INUSE 0x1
1375 /* extract inuse bit of previous chunk */
1376 #define prev_inuse(p) ((p)->mchunk_size & PREV_INUSE)
1379 /* size field is or'ed with IS_MMAPPED if the chunk was obtained with mmap() */
1380 #define IS_MMAPPED 0x2
1382 /* check for mmap()'ed chunk */
1383 #define chunk_is_mmapped(p) ((p)->mchunk_size & IS_MMAPPED)
1386 /* size field is or'ed with NON_MAIN_ARENA if the chunk was obtained
1387 from a non-main arena. This is only set immediately before handing
1388 the chunk to the user, if necessary. */
1389 #define NON_MAIN_ARENA 0x4
1391 /* Check for chunk from main arena. */
1392 #define chunk_main_arena(p) (((p)->mchunk_size & NON_MAIN_ARENA) == 0)
1394 /* Mark a chunk as not being on the main arena. */
1395 #define set_non_main_arena(p) ((p)->mchunk_size |= NON_MAIN_ARENA)
1399 Bits to mask off when extracting size
1401 Note: IS_MMAPPED is intentionally not masked off from size field in
1402 macros for which mmapped chunks should never be seen. This should
1403 cause helpful core dumps to occur if it is tried by accident by
1404 people extending or adapting this malloc.
1406 #define SIZE_BITS (PREV_INUSE | IS_MMAPPED | NON_MAIN_ARENA)
1408 /* Get size, ignoring use bits */
1409 #define chunksize(p) (chunksize_nomask (p) & ~(SIZE_BITS))
1411 /* Like chunksize, but do not mask SIZE_BITS. */
1412 #define chunksize_nomask(p) ((p)->mchunk_size)
1414 /* Ptr to next physical malloc_chunk. */
1415 #define next_chunk(p) ((mchunkptr) (((char *) (p)) + chunksize (p)))
1417 /* Size of the chunk below P. Only valid if !prev_inuse (P). */
1418 #define prev_size(p) ((p)->mchunk_prev_size)
1420 /* Set the size of the chunk below P. Only valid if !prev_inuse (P). */
1421 #define set_prev_size(p, sz) ((p)->mchunk_prev_size = (sz))
1423 /* Ptr to previous physical malloc_chunk. Only valid if !prev_inuse (P). */
1424 #define prev_chunk(p) ((mchunkptr) (((char *) (p)) - prev_size (p)))
1426 /* Treat space at ptr + offset as a chunk */
1427 #define chunk_at_offset(p, s) ((mchunkptr) (((char *) (p)) + (s)))
1429 /* extract p's inuse bit */
1431 ((((mchunkptr) (((char *) (p)) + chunksize (p)))->mchunk_size) & PREV_INUSE)
1433 /* set/clear chunk as being inuse without otherwise disturbing */
1434 #define set_inuse(p) \
1435 ((mchunkptr) (((char *) (p)) + chunksize (p)))->mchunk_size |= PREV_INUSE
1437 #define clear_inuse(p) \
1438 ((mchunkptr) (((char *) (p)) + chunksize (p)))->mchunk_size &= ~(PREV_INUSE)
1441 /* check/set/clear inuse bits in known places */
1442 #define inuse_bit_at_offset(p, s) \
1443 (((mchunkptr) (((char *) (p)) + (s)))->mchunk_size & PREV_INUSE)
1445 #define set_inuse_bit_at_offset(p, s) \
1446 (((mchunkptr) (((char *) (p)) + (s)))->mchunk_size |= PREV_INUSE)
1448 #define clear_inuse_bit_at_offset(p, s) \
1449 (((mchunkptr) (((char *) (p)) + (s)))->mchunk_size &= ~(PREV_INUSE))
1452 /* Set size at head, without disturbing its use bit */
1453 #define set_head_size(p, s) ((p)->mchunk_size = (((p)->mchunk_size & SIZE_BITS) | (s)))
1455 /* Set size/use field */
1456 #define set_head(p, s) ((p)->mchunk_size = (s))
1458 /* Set size at footer (only when chunk is not in use) */
1459 #define set_foot(p, s) (((mchunkptr) ((char *) (p) + (s)))->mchunk_prev_size = (s))
1461 #pragma GCC poison mchunk_size
1462 #pragma GCC poison mchunk_prev_size
1464 /* This is the size of the real usable data in the chunk. Not valid for
1465 dumped heap chunks. */
1466 #define memsize(p) \
1467 (__MTAG_GRANULE_SIZE > SIZE_SZ && __glibc_unlikely (mtag_enabled) ? \
1468 chunksize (p) - CHUNK_HDR_SZ : \
1469 chunksize (p) - CHUNK_HDR_SZ + (chunk_is_mmapped (p) ? 0 : SIZE_SZ))
1471 /* If memory tagging is enabled the layout changes to accommodate the granule
1472 size, this is wasteful for small allocations so not done by default.
1473 Both the chunk header and user data has to be granule aligned. */
1474 _Static_assert (__MTAG_GRANULE_SIZE
<= CHUNK_HDR_SZ
,
1475 "memory tagging is not supported with large granule.");
1477 static __always_inline
void *
1478 tag_new_usable (void *ptr
)
1480 if (__glibc_unlikely (mtag_enabled
) && ptr
)
1482 mchunkptr cp
= mem2chunk(ptr
);
1483 ptr
= __libc_mtag_tag_region (__libc_mtag_new_tag (ptr
), memsize (cp
));
1489 -------------------- Internal data structures --------------------
1491 All internal state is held in an instance of malloc_state defined
1492 below. There are no other static variables, except in two optional
1494 * If USE_MALLOC_LOCK is defined, the mALLOC_MUTEx declared above.
1495 * If mmap doesn't support MAP_ANONYMOUS, a dummy file descriptor
1498 Beware of lots of tricks that minimize the total bookkeeping space
1499 requirements. The result is a little over 1K bytes (for 4byte
1500 pointers and size_t.)
1506 An array of bin headers for free chunks. Each bin is doubly
1507 linked. The bins are approximately proportionally (log) spaced.
1508 There are a lot of these bins (128). This may look excessive, but
1509 works very well in practice. Most bins hold sizes that are
1510 unusual as malloc request sizes, but are more usual for fragments
1511 and consolidated sets of chunks, which is what these bins hold, so
1512 they can be found quickly. All procedures maintain the invariant
1513 that no consolidated chunk physically borders another one, so each
1514 chunk in a list is known to be preceeded and followed by either
1515 inuse chunks or the ends of memory.
1517 Chunks in bins are kept in size order, with ties going to the
1518 approximately least recently used chunk. Ordering isn't needed
1519 for the small bins, which all contain the same-sized chunks, but
1520 facilitates best-fit allocation for larger chunks. These lists
1521 are just sequential. Keeping them in order almost never requires
1522 enough traversal to warrant using fancier ordered data
1525 Chunks of the same size are linked with the most
1526 recently freed at the front, and allocations are taken from the
1527 back. This results in LRU (FIFO) allocation order, which tends
1528 to give each chunk an equal opportunity to be consolidated with
1529 adjacent freed chunks, resulting in larger free chunks and less
1532 To simplify use in double-linked lists, each bin header acts
1533 as a malloc_chunk. This avoids special-casing for headers.
1534 But to conserve space and improve locality, we allocate
1535 only the fd/bk pointers of bins, and then use repositioning tricks
1536 to treat these as the fields of a malloc_chunk*.
1539 typedef struct malloc_chunk
*mbinptr
;
1541 /* addressing -- note that bin_at(0) does not exist */
1542 #define bin_at(m, i) \
1543 (mbinptr) (((char *) &((m)->bins[((i) - 1) * 2])) \
1544 - offsetof (struct malloc_chunk, fd))
1546 /* analog of ++bin */
1547 #define next_bin(b) ((mbinptr) ((char *) (b) + (sizeof (mchunkptr) << 1)))
1549 /* Reminders about list directionality within bins */
1550 #define first(b) ((b)->fd)
1551 #define last(b) ((b)->bk)
1556 Bins for sizes < 512 bytes contain chunks of all the same size, spaced
1557 8 bytes apart. Larger bins are approximately logarithmically spaced:
1563 4 bins of size 32768
1564 2 bins of size 262144
1565 1 bin of size what's left
1567 There is actually a little bit of slop in the numbers in bin_index
1568 for the sake of speed. This makes no difference elsewhere.
1570 The bins top out around 1MB because we expect to service large
1573 Bin 0 does not exist. Bin 1 is the unordered list; if that would be
1574 a valid chunk size the small bins are bumped up one.
1578 #define NSMALLBINS 64
1579 #define SMALLBIN_WIDTH MALLOC_ALIGNMENT
1580 #define SMALLBIN_CORRECTION (MALLOC_ALIGNMENT > CHUNK_HDR_SZ)
1581 #define MIN_LARGE_SIZE ((NSMALLBINS - SMALLBIN_CORRECTION) * SMALLBIN_WIDTH)
1583 #define in_smallbin_range(sz) \
1584 ((unsigned long) (sz) < (unsigned long) MIN_LARGE_SIZE)
1586 #define smallbin_index(sz) \
1587 ((SMALLBIN_WIDTH == 16 ? (((unsigned) (sz)) >> 4) : (((unsigned) (sz)) >> 3))\
1588 + SMALLBIN_CORRECTION)
1590 #define largebin_index_32(sz) \
1591 (((((unsigned long) (sz)) >> 6) <= 38) ? 56 + (((unsigned long) (sz)) >> 6) :\
1592 ((((unsigned long) (sz)) >> 9) <= 20) ? 91 + (((unsigned long) (sz)) >> 9) :\
1593 ((((unsigned long) (sz)) >> 12) <= 10) ? 110 + (((unsigned long) (sz)) >> 12) :\
1594 ((((unsigned long) (sz)) >> 15) <= 4) ? 119 + (((unsigned long) (sz)) >> 15) :\
1595 ((((unsigned long) (sz)) >> 18) <= 2) ? 124 + (((unsigned long) (sz)) >> 18) :\
1598 #define largebin_index_32_big(sz) \
1599 (((((unsigned long) (sz)) >> 6) <= 45) ? 49 + (((unsigned long) (sz)) >> 6) :\
1600 ((((unsigned long) (sz)) >> 9) <= 20) ? 91 + (((unsigned long) (sz)) >> 9) :\
1601 ((((unsigned long) (sz)) >> 12) <= 10) ? 110 + (((unsigned long) (sz)) >> 12) :\
1602 ((((unsigned long) (sz)) >> 15) <= 4) ? 119 + (((unsigned long) (sz)) >> 15) :\
1603 ((((unsigned long) (sz)) >> 18) <= 2) ? 124 + (((unsigned long) (sz)) >> 18) :\
1606 // XXX It remains to be seen whether it is good to keep the widths of
1607 // XXX the buckets the same or whether it should be scaled by a factor
1608 // XXX of two as well.
1609 #define largebin_index_64(sz) \
1610 (((((unsigned long) (sz)) >> 6) <= 48) ? 48 + (((unsigned long) (sz)) >> 6) :\
1611 ((((unsigned long) (sz)) >> 9) <= 20) ? 91 + (((unsigned long) (sz)) >> 9) :\
1612 ((((unsigned long) (sz)) >> 12) <= 10) ? 110 + (((unsigned long) (sz)) >> 12) :\
1613 ((((unsigned long) (sz)) >> 15) <= 4) ? 119 + (((unsigned long) (sz)) >> 15) :\
1614 ((((unsigned long) (sz)) >> 18) <= 2) ? 124 + (((unsigned long) (sz)) >> 18) :\
1617 #define largebin_index(sz) \
1618 (SIZE_SZ == 8 ? largebin_index_64 (sz) \
1619 : MALLOC_ALIGNMENT == 16 ? largebin_index_32_big (sz) \
1620 : largebin_index_32 (sz))
1622 #define bin_index(sz) \
1623 ((in_smallbin_range (sz)) ? smallbin_index (sz) : largebin_index (sz))
1625 /* Take a chunk off a bin list. */
1627 unlink_chunk (mstate av
, mchunkptr p
)
1629 if (chunksize (p
) != prev_size (next_chunk (p
)))
1630 malloc_printerr ("corrupted size vs. prev_size");
1632 mchunkptr fd
= p
->fd
;
1633 mchunkptr bk
= p
->bk
;
1635 if (__builtin_expect (fd
->bk
!= p
|| bk
->fd
!= p
, 0))
1636 malloc_printerr ("corrupted double-linked list");
1640 if (!in_smallbin_range (chunksize_nomask (p
)) && p
->fd_nextsize
!= NULL
)
1642 if (p
->fd_nextsize
->bk_nextsize
!= p
1643 || p
->bk_nextsize
->fd_nextsize
!= p
)
1644 malloc_printerr ("corrupted double-linked list (not small)");
1646 if (fd
->fd_nextsize
== NULL
)
1648 if (p
->fd_nextsize
== p
)
1649 fd
->fd_nextsize
= fd
->bk_nextsize
= fd
;
1652 fd
->fd_nextsize
= p
->fd_nextsize
;
1653 fd
->bk_nextsize
= p
->bk_nextsize
;
1654 p
->fd_nextsize
->bk_nextsize
= fd
;
1655 p
->bk_nextsize
->fd_nextsize
= fd
;
1660 p
->fd_nextsize
->bk_nextsize
= p
->bk_nextsize
;
1661 p
->bk_nextsize
->fd_nextsize
= p
->fd_nextsize
;
1669 All remainders from chunk splits, as well as all returned chunks,
1670 are first placed in the "unsorted" bin. They are then placed
1671 in regular bins after malloc gives them ONE chance to be used before
1672 binning. So, basically, the unsorted_chunks list acts as a queue,
1673 with chunks being placed on it in free (and malloc_consolidate),
1674 and taken off (to be either used or placed in bins) in malloc.
1676 The NON_MAIN_ARENA flag is never set for unsorted chunks, so it
1677 does not have to be taken into account in size comparisons.
1680 /* The otherwise unindexable 1-bin is used to hold unsorted chunks. */
1681 #define unsorted_chunks(M) (bin_at (M, 1))
1686 The top-most available chunk (i.e., the one bordering the end of
1687 available memory) is treated specially. It is never included in
1688 any bin, is used only if no other chunk is available, and is
1689 released back to the system if it is very large (see
1690 M_TRIM_THRESHOLD). Because top initially
1691 points to its own bin with initial zero size, thus forcing
1692 extension on the first malloc request, we avoid having any special
1693 code in malloc to check whether it even exists yet. But we still
1694 need to do so when getting memory from system, so we make
1695 initial_top treat the bin as a legal but unusable chunk during the
1696 interval between initialization and the first call to
1697 sysmalloc. (This is somewhat delicate, since it relies on
1698 the 2 preceding words to be zero during this interval as well.)
1701 /* Conveniently, the unsorted bin can be used as dummy top on first call */
1702 #define initial_top(M) (unsorted_chunks (M))
1707 To help compensate for the large number of bins, a one-level index
1708 structure is used for bin-by-bin searching. `binmap' is a
1709 bitvector recording whether bins are definitely empty so they can
1710 be skipped over during during traversals. The bits are NOT always
1711 cleared as soon as bins are empty, but instead only
1712 when they are noticed to be empty during traversal in malloc.
1715 /* Conservatively use 32 bits per map word, even if on 64bit system */
1716 #define BINMAPSHIFT 5
1717 #define BITSPERMAP (1U << BINMAPSHIFT)
1718 #define BINMAPSIZE (NBINS / BITSPERMAP)
1720 #define idx2block(i) ((i) >> BINMAPSHIFT)
1721 #define idx2bit(i) ((1U << ((i) & ((1U << BINMAPSHIFT) - 1))))
1723 #define mark_bin(m, i) ((m)->binmap[idx2block (i)] |= idx2bit (i))
1724 #define unmark_bin(m, i) ((m)->binmap[idx2block (i)] &= ~(idx2bit (i)))
1725 #define get_binmap(m, i) ((m)->binmap[idx2block (i)] & idx2bit (i))
1730 An array of lists holding recently freed small chunks. Fastbins
1731 are not doubly linked. It is faster to single-link them, and
1732 since chunks are never removed from the middles of these lists,
1733 double linking is not necessary. Also, unlike regular bins, they
1734 are not even processed in FIFO order (they use faster LIFO) since
1735 ordering doesn't much matter in the transient contexts in which
1736 fastbins are normally used.
1738 Chunks in fastbins keep their inuse bit set, so they cannot
1739 be consolidated with other free chunks. malloc_consolidate
1740 releases all chunks in fastbins and consolidates them with
1744 typedef struct malloc_chunk
*mfastbinptr
;
1745 #define fastbin(ar_ptr, idx) ((ar_ptr)->fastbinsY[idx])
1747 /* offset 2 to use otherwise unindexable first 2 bins */
1748 #define fastbin_index(sz) \
1749 ((((unsigned int) (sz)) >> (SIZE_SZ == 8 ? 4 : 3)) - 2)
1752 /* The maximum fastbin request size we support */
1753 #define MAX_FAST_SIZE (80 * SIZE_SZ / 4)
1755 #define NFASTBINS (fastbin_index (request2size (MAX_FAST_SIZE)) + 1)
1758 FASTBIN_CONSOLIDATION_THRESHOLD is the size of a chunk in free()
1759 that triggers automatic consolidation of possibly-surrounding
1760 fastbin chunks. This is a heuristic, so the exact value should not
1761 matter too much. It is defined at half the default trim threshold as a
1762 compromise heuristic to only attempt consolidation if it is likely
1763 to lead to trimming. However, it is not dynamically tunable, since
1764 consolidation reduces fragmentation surrounding large chunks even
1765 if trimming is not used.
1768 #define FASTBIN_CONSOLIDATION_THRESHOLD (65536UL)
1771 NONCONTIGUOUS_BIT indicates that MORECORE does not return contiguous
1772 regions. Otherwise, contiguity is exploited in merging together,
1773 when possible, results from consecutive MORECORE calls.
1775 The initial value comes from MORECORE_CONTIGUOUS, but is
1776 changed dynamically if mmap is ever used as an sbrk substitute.
1779 #define NONCONTIGUOUS_BIT (2U)
1781 #define contiguous(M) (((M)->flags & NONCONTIGUOUS_BIT) == 0)
1782 #define noncontiguous(M) (((M)->flags & NONCONTIGUOUS_BIT) != 0)
1783 #define set_noncontiguous(M) ((M)->flags |= NONCONTIGUOUS_BIT)
1784 #define set_contiguous(M) ((M)->flags &= ~NONCONTIGUOUS_BIT)
1786 /* Maximum size of memory handled in fastbins. */
1787 static INTERNAL_SIZE_T global_max_fast
;
1790 Set value of max_fast.
1791 Use impossibly small value if 0.
1792 Precondition: there are no existing fastbin chunks in the main arena.
1793 Since do_check_malloc_state () checks this, we call malloc_consolidate ()
1794 before changing max_fast. Note other arenas will leak their fast bin
1795 entries if max_fast is reduced.
1798 #define set_max_fast(s) \
1799 global_max_fast = (((size_t) (s) <= MALLOC_ALIGN_MASK - SIZE_SZ) \
1800 ? MIN_CHUNK_SIZE / 2 : ((s + SIZE_SZ) & ~MALLOC_ALIGN_MASK))
1802 static inline INTERNAL_SIZE_T
1805 /* Tell the GCC optimizers that global_max_fast is never larger
1806 than MAX_FAST_SIZE. This avoids out-of-bounds array accesses in
1807 _int_malloc after constant propagation of the size parameter.
1808 (The code never executes because malloc preserves the
1809 global_max_fast invariant, but the optimizers may not recognize
1811 if (global_max_fast
> MAX_FAST_SIZE
)
1812 __builtin_unreachable ();
1813 return global_max_fast
;
1817 ----------- Internal state representation and initialization -----------
1821 have_fastchunks indicates that there are probably some fastbin chunks.
1822 It is set true on entering a chunk into any fastbin, and cleared early in
1823 malloc_consolidate. The value is approximate since it may be set when there
1824 are no fastbin chunks, or it may be clear even if there are fastbin chunks
1825 available. Given it's sole purpose is to reduce number of redundant calls to
1826 malloc_consolidate, it does not affect correctness. As a result we can safely
1827 use relaxed atomic accesses.
1833 /* Serialize access. */
1834 __libc_lock_define (, mutex
);
1836 /* Flags (formerly in max_fast). */
1839 /* Set if the fastbin chunks contain recently inserted free blocks. */
1840 /* Note this is a bool but not all targets support atomics on booleans. */
1841 int have_fastchunks
;
1844 mfastbinptr fastbinsY
[NFASTBINS
];
1846 /* Base of the topmost chunk -- not otherwise kept in a bin */
1849 /* The remainder from the most recent split of a small request */
1850 mchunkptr last_remainder
;
1852 /* Normal bins packed as described above */
1853 mchunkptr bins
[NBINS
* 2 - 2];
1855 /* Bitmap of bins */
1856 unsigned int binmap
[BINMAPSIZE
];
1859 struct malloc_state
*next
;
1861 /* Linked list for free arenas. Access to this field is serialized
1862 by free_list_lock in arena.c. */
1863 struct malloc_state
*next_free
;
1865 /* Number of threads attached to this arena. 0 if the arena is on
1866 the free list. Access to this field is serialized by
1867 free_list_lock in arena.c. */
1868 INTERNAL_SIZE_T attached_threads
;
1870 /* Memory allocated from the system in this arena. */
1871 INTERNAL_SIZE_T system_mem
;
1872 INTERNAL_SIZE_T max_system_mem
;
1877 /* Tunable parameters */
1878 unsigned long trim_threshold
;
1879 INTERNAL_SIZE_T top_pad
;
1880 INTERNAL_SIZE_T mmap_threshold
;
1881 INTERNAL_SIZE_T arena_test
;
1882 INTERNAL_SIZE_T arena_max
;
1884 /* Memory map support */
1888 /* the mmap_threshold is dynamic, until the user sets
1889 it manually, at which point we need to disable any
1890 dynamic behavior. */
1891 int no_dyn_threshold
;
1894 INTERNAL_SIZE_T mmapped_mem
;
1895 INTERNAL_SIZE_T max_mmapped_mem
;
1897 /* First address handed out by MORECORE/sbrk. */
1901 /* Maximum number of buckets to use. */
1903 size_t tcache_max_bytes
;
1904 /* Maximum number of chunks in each bucket. */
1905 size_t tcache_count
;
1906 /* Maximum number of chunks to remove from the unsorted list, which
1907 aren't used to prefill the cache. */
1908 size_t tcache_unsorted_limit
;
1912 /* There are several instances of this struct ("arenas") in this
1913 malloc. If you are adapting this malloc in a way that does NOT use
1914 a static or mmapped malloc_state, you MUST explicitly zero-fill it
1915 before using. This malloc relies on the property that malloc_state
1916 is initialized to all zeroes (as is true of C statics). */
1918 static struct malloc_state main_arena
=
1920 .mutex
= _LIBC_LOCK_INITIALIZER
,
1921 .next
= &main_arena
,
1922 .attached_threads
= 1
1925 /* There is only one instance of the malloc parameters. */
1927 static struct malloc_par mp_
=
1929 .top_pad
= DEFAULT_TOP_PAD
,
1930 .n_mmaps_max
= DEFAULT_MMAP_MAX
,
1931 .mmap_threshold
= DEFAULT_MMAP_THRESHOLD
,
1932 .trim_threshold
= DEFAULT_TRIM_THRESHOLD
,
1933 #define NARENAS_FROM_NCORES(n) ((n) * (sizeof (long) == 4 ? 2 : 8))
1934 .arena_test
= NARENAS_FROM_NCORES (1)
1937 .tcache_count
= TCACHE_FILL_COUNT
,
1938 .tcache_bins
= TCACHE_MAX_BINS
,
1939 .tcache_max_bytes
= tidx2usize (TCACHE_MAX_BINS
-1),
1940 .tcache_unsorted_limit
= 0 /* No limit. */
1945 Initialize a malloc_state struct.
1947 This is called from ptmalloc_init () or from _int_new_arena ()
1948 when creating a new arena.
1952 malloc_init_state (mstate av
)
1957 /* Establish circular links for normal bins */
1958 for (i
= 1; i
< NBINS
; ++i
)
1960 bin
= bin_at (av
, i
);
1961 bin
->fd
= bin
->bk
= bin
;
1964 #if MORECORE_CONTIGUOUS
1965 if (av
!= &main_arena
)
1967 set_noncontiguous (av
);
1968 if (av
== &main_arena
)
1969 set_max_fast (DEFAULT_MXFAST
);
1970 atomic_store_relaxed (&av
->have_fastchunks
, false);
1972 av
->top
= initial_top (av
);
1976 Other internal utilities operating on mstates
1979 static void *sysmalloc (INTERNAL_SIZE_T
, mstate
);
1980 static int systrim (size_t, mstate
);
1981 static void malloc_consolidate (mstate
);
1984 /* -------------- Early definitions for debugging hooks ---------------- */
1986 /* This function is called from the arena shutdown hook, to free the
1987 thread cache (if it exists). */
1988 static void tcache_thread_shutdown (void);
1990 /* ------------------ Testing support ----------------------------------*/
1992 static int perturb_byte
;
1995 alloc_perturb (char *p
, size_t n
)
1997 if (__glibc_unlikely (perturb_byte
))
1998 memset (p
, perturb_byte
^ 0xff, n
);
2002 free_perturb (char *p
, size_t n
)
2004 if (__glibc_unlikely (perturb_byte
))
2005 memset (p
, perturb_byte
, n
);
2010 #include <stap-probe.h>
2012 /* ------------------- Support for multiple arenas -------------------- */
2018 These routines make a number of assertions about the states
2019 of data structures that should be true at all times. If any
2020 are not true, it's very likely that a user program has somehow
2021 trashed memory. (It's also possible that there is a coding error
2022 in malloc. In which case, please report it!)
2027 # define check_chunk(A, P)
2028 # define check_free_chunk(A, P)
2029 # define check_inuse_chunk(A, P)
2030 # define check_remalloced_chunk(A, P, N)
2031 # define check_malloced_chunk(A, P, N)
2032 # define check_malloc_state(A)
2036 # define check_chunk(A, P) do_check_chunk (A, P)
2037 # define check_free_chunk(A, P) do_check_free_chunk (A, P)
2038 # define check_inuse_chunk(A, P) do_check_inuse_chunk (A, P)
2039 # define check_remalloced_chunk(A, P, N) do_check_remalloced_chunk (A, P, N)
2040 # define check_malloced_chunk(A, P, N) do_check_malloced_chunk (A, P, N)
2041 # define check_malloc_state(A) do_check_malloc_state (A)
2044 Properties of all chunks
2048 do_check_chunk (mstate av
, mchunkptr p
)
2050 unsigned long sz
= chunksize (p
);
2051 /* min and max possible addresses assuming contiguous allocation */
2052 char *max_address
= (char *) (av
->top
) + chunksize (av
->top
);
2053 char *min_address
= max_address
- av
->system_mem
;
2055 if (!chunk_is_mmapped (p
))
2057 /* Has legal address ... */
2060 if (contiguous (av
))
2062 assert (((char *) p
) >= min_address
);
2063 assert (((char *) p
+ sz
) <= ((char *) (av
->top
)));
2068 /* top size is always at least MINSIZE */
2069 assert ((unsigned long) (sz
) >= MINSIZE
);
2070 /* top predecessor always marked inuse */
2071 assert (prev_inuse (p
));
2076 /* address is outside main heap */
2077 if (contiguous (av
) && av
->top
!= initial_top (av
))
2079 assert (((char *) p
) < min_address
|| ((char *) p
) >= max_address
);
2081 /* chunk is page-aligned */
2082 assert (((prev_size (p
) + sz
) & (GLRO (dl_pagesize
) - 1)) == 0);
2083 /* mem is aligned */
2084 assert (aligned_OK (chunk2mem (p
)));
2089 Properties of free chunks
2093 do_check_free_chunk (mstate av
, mchunkptr p
)
2095 INTERNAL_SIZE_T sz
= chunksize_nomask (p
) & ~(PREV_INUSE
| NON_MAIN_ARENA
);
2096 mchunkptr next
= chunk_at_offset (p
, sz
);
2098 do_check_chunk (av
, p
);
2100 /* Chunk must claim to be free ... */
2101 assert (!inuse (p
));
2102 assert (!chunk_is_mmapped (p
));
2104 /* Unless a special marker, must have OK fields */
2105 if ((unsigned long) (sz
) >= MINSIZE
)
2107 assert ((sz
& MALLOC_ALIGN_MASK
) == 0);
2108 assert (aligned_OK (chunk2mem (p
)));
2109 /* ... matching footer field */
2110 assert (prev_size (next_chunk (p
)) == sz
);
2111 /* ... and is fully consolidated */
2112 assert (prev_inuse (p
));
2113 assert (next
== av
->top
|| inuse (next
));
2115 /* ... and has minimally sane links */
2116 assert (p
->fd
->bk
== p
);
2117 assert (p
->bk
->fd
== p
);
2119 else /* markers are always of size SIZE_SZ */
2120 assert (sz
== SIZE_SZ
);
2124 Properties of inuse chunks
2128 do_check_inuse_chunk (mstate av
, mchunkptr p
)
2132 do_check_chunk (av
, p
);
2134 if (chunk_is_mmapped (p
))
2135 return; /* mmapped chunks have no next/prev */
2137 /* Check whether it claims to be in use ... */
2140 next
= next_chunk (p
);
2142 /* ... and is surrounded by OK chunks.
2143 Since more things can be checked with free chunks than inuse ones,
2144 if an inuse chunk borders them and debug is on, it's worth doing them.
2146 if (!prev_inuse (p
))
2148 /* Note that we cannot even look at prev unless it is not inuse */
2149 mchunkptr prv
= prev_chunk (p
);
2150 assert (next_chunk (prv
) == p
);
2151 do_check_free_chunk (av
, prv
);
2154 if (next
== av
->top
)
2156 assert (prev_inuse (next
));
2157 assert (chunksize (next
) >= MINSIZE
);
2159 else if (!inuse (next
))
2160 do_check_free_chunk (av
, next
);
2164 Properties of chunks recycled from fastbins
2168 do_check_remalloced_chunk (mstate av
, mchunkptr p
, INTERNAL_SIZE_T s
)
2170 INTERNAL_SIZE_T sz
= chunksize_nomask (p
) & ~(PREV_INUSE
| NON_MAIN_ARENA
);
2172 if (!chunk_is_mmapped (p
))
2174 assert (av
== arena_for_chunk (p
));
2175 if (chunk_main_arena (p
))
2176 assert (av
== &main_arena
);
2178 assert (av
!= &main_arena
);
2181 do_check_inuse_chunk (av
, p
);
2183 /* Legal size ... */
2184 assert ((sz
& MALLOC_ALIGN_MASK
) == 0);
2185 assert ((unsigned long) (sz
) >= MINSIZE
);
2186 /* ... and alignment */
2187 assert (aligned_OK (chunk2mem (p
)));
2188 /* chunk is less than MINSIZE more than request */
2189 assert ((long) (sz
) - (long) (s
) >= 0);
2190 assert ((long) (sz
) - (long) (s
+ MINSIZE
) < 0);
2194 Properties of nonrecycled chunks at the point they are malloced
2198 do_check_malloced_chunk (mstate av
, mchunkptr p
, INTERNAL_SIZE_T s
)
2200 /* same as recycled case ... */
2201 do_check_remalloced_chunk (av
, p
, s
);
2204 ... plus, must obey implementation invariant that prev_inuse is
2205 always true of any allocated chunk; i.e., that each allocated
2206 chunk borders either a previously allocated and still in-use
2207 chunk, or the base of its memory arena. This is ensured
2208 by making all allocations from the `lowest' part of any found
2209 chunk. This does not necessarily hold however for chunks
2210 recycled via fastbins.
2213 assert (prev_inuse (p
));
2218 Properties of malloc_state.
2220 This may be useful for debugging malloc, as well as detecting user
2221 programmer errors that somehow write into malloc_state.
2223 If you are extending or experimenting with this malloc, you can
2224 probably figure out how to hack this routine to print out or
2225 display chunk addresses, sizes, bins, and other instrumentation.
2229 do_check_malloc_state (mstate av
)
2236 INTERNAL_SIZE_T size
;
2237 unsigned long total
= 0;
2240 /* internal size_t must be no wider than pointer type */
2241 assert (sizeof (INTERNAL_SIZE_T
) <= sizeof (char *));
2243 /* alignment is a power of 2 */
2244 assert ((MALLOC_ALIGNMENT
& (MALLOC_ALIGNMENT
- 1)) == 0);
2246 /* Check the arena is initialized. */
2247 assert (av
->top
!= 0);
2249 /* No memory has been allocated yet, so doing more tests is not possible. */
2250 if (av
->top
== initial_top (av
))
2253 /* pagesize is a power of 2 */
2254 assert (powerof2(GLRO (dl_pagesize
)));
2256 /* A contiguous main_arena is consistent with sbrk_base. */
2257 if (av
== &main_arena
&& contiguous (av
))
2258 assert ((char *) mp_
.sbrk_base
+ av
->system_mem
==
2259 (char *) av
->top
+ chunksize (av
->top
));
2261 /* properties of fastbins */
2263 /* max_fast is in allowed range */
2264 assert ((get_max_fast () & ~1) <= request2size (MAX_FAST_SIZE
));
2266 max_fast_bin
= fastbin_index (get_max_fast ());
2268 for (i
= 0; i
< NFASTBINS
; ++i
)
2270 p
= fastbin (av
, i
);
2272 /* The following test can only be performed for the main arena.
2273 While mallopt calls malloc_consolidate to get rid of all fast
2274 bins (especially those larger than the new maximum) this does
2275 only happen for the main arena. Trying to do this for any
2276 other arena would mean those arenas have to be locked and
2277 malloc_consolidate be called for them. This is excessive. And
2278 even if this is acceptable to somebody it still cannot solve
2279 the problem completely since if the arena is locked a
2280 concurrent malloc call might create a new arena which then
2281 could use the newly invalid fast bins. */
2283 /* all bins past max_fast are empty */
2284 if (av
== &main_arena
&& i
> max_fast_bin
)
2289 if (__glibc_unlikely (misaligned_chunk (p
)))
2290 malloc_printerr ("do_check_malloc_state(): "
2291 "unaligned fastbin chunk detected");
2292 /* each chunk claims to be inuse */
2293 do_check_inuse_chunk (av
, p
);
2294 total
+= chunksize (p
);
2295 /* chunk belongs in this bin */
2296 assert (fastbin_index (chunksize (p
)) == i
);
2297 p
= REVEAL_PTR (p
->fd
);
2301 /* check normal bins */
2302 for (i
= 1; i
< NBINS
; ++i
)
2306 /* binmap is accurate (except for bin 1 == unsorted_chunks) */
2309 unsigned int binbit
= get_binmap (av
, i
);
2310 int empty
= last (b
) == b
;
2317 for (p
= last (b
); p
!= b
; p
= p
->bk
)
2319 /* each chunk claims to be free */
2320 do_check_free_chunk (av
, p
);
2321 size
= chunksize (p
);
2325 /* chunk belongs in bin */
2326 idx
= bin_index (size
);
2328 /* lists are sorted */
2329 assert (p
->bk
== b
||
2330 (unsigned long) chunksize (p
->bk
) >= (unsigned long) chunksize (p
));
2332 if (!in_smallbin_range (size
))
2334 if (p
->fd_nextsize
!= NULL
)
2336 if (p
->fd_nextsize
== p
)
2337 assert (p
->bk_nextsize
== p
);
2340 if (p
->fd_nextsize
== first (b
))
2341 assert (chunksize (p
) < chunksize (p
->fd_nextsize
));
2343 assert (chunksize (p
) > chunksize (p
->fd_nextsize
));
2346 assert (chunksize (p
) > chunksize (p
->bk_nextsize
));
2348 assert (chunksize (p
) < chunksize (p
->bk_nextsize
));
2352 assert (p
->bk_nextsize
== NULL
);
2355 else if (!in_smallbin_range (size
))
2356 assert (p
->fd_nextsize
== NULL
&& p
->bk_nextsize
== NULL
);
2357 /* chunk is followed by a legal chain of inuse chunks */
2358 for (q
= next_chunk (p
);
2359 (q
!= av
->top
&& inuse (q
) &&
2360 (unsigned long) (chunksize (q
)) >= MINSIZE
);
2362 do_check_inuse_chunk (av
, q
);
2366 /* top chunk is OK */
2367 check_chunk (av
, av
->top
);
2372 /* ----------------- Support for debugging hooks -------------------- */
2378 /* ----------- Routines dealing with system allocation -------------- */
2381 sysmalloc handles malloc cases requiring more memory from the system.
2382 On entry, it is assumed that av->top does not have enough
2383 space to service request for nb bytes, thus requiring that av->top
2384 be extended or replaced.
2388 sysmalloc (INTERNAL_SIZE_T nb
, mstate av
)
2390 mchunkptr old_top
; /* incoming value of av->top */
2391 INTERNAL_SIZE_T old_size
; /* its size */
2392 char *old_end
; /* its end address */
2394 long size
; /* arg to first MORECORE or mmap call */
2395 char *brk
; /* return value from MORECORE */
2397 long correction
; /* arg to 2nd MORECORE call */
2398 char *snd_brk
; /* 2nd return val */
2400 INTERNAL_SIZE_T front_misalign
; /* unusable bytes at front of new space */
2401 INTERNAL_SIZE_T end_misalign
; /* partial page left at end of new space */
2402 char *aligned_brk
; /* aligned offset into brk */
2404 mchunkptr p
; /* the allocated/returned chunk */
2405 mchunkptr remainder
; /* remainder from allocation */
2406 unsigned long remainder_size
; /* its size */
2409 size_t pagesize
= GLRO (dl_pagesize
);
2410 bool tried_mmap
= false;
2414 If have mmap, and the request size meets the mmap threshold, and
2415 the system supports mmap, and there are few enough currently
2416 allocated mmapped regions, try to directly map this request
2417 rather than expanding top.
2421 || ((unsigned long) (nb
) >= (unsigned long) (mp_
.mmap_threshold
)
2422 && (mp_
.n_mmaps
< mp_
.n_mmaps_max
)))
2424 char *mm
; /* return value from mmap call*/
2428 Round up size to nearest page. For mmapped chunks, the overhead
2429 is one SIZE_SZ unit larger than for normal chunks, because there
2430 is no following chunk whose prev_size field could be used.
2432 See the front_misalign handling below, for glibc there is no
2433 need for further alignments unless we have have high alignment.
2435 if (MALLOC_ALIGNMENT
== CHUNK_HDR_SZ
)
2436 size
= ALIGN_UP (nb
+ SIZE_SZ
, pagesize
);
2438 size
= ALIGN_UP (nb
+ SIZE_SZ
+ MALLOC_ALIGN_MASK
, pagesize
);
2441 /* Don't try if size wraps around 0 */
2442 if ((unsigned long) (size
) > (unsigned long) (nb
))
2444 mm
= (char *) (MMAP (0, size
,
2445 mtag_mmap_flags
| PROT_READ
| PROT_WRITE
, 0));
2447 if (mm
!= MAP_FAILED
)
2450 The offset to the start of the mmapped region is stored
2451 in the prev_size field of the chunk. This allows us to adjust
2452 returned start address to meet alignment requirements here
2453 and in memalign(), and still be able to compute proper
2454 address argument for later munmap in free() and realloc().
2457 if (MALLOC_ALIGNMENT
== CHUNK_HDR_SZ
)
2459 /* For glibc, chunk2mem increases the address by
2460 CHUNK_HDR_SZ and MALLOC_ALIGN_MASK is
2461 CHUNK_HDR_SZ-1. Each mmap'ed area is page
2462 aligned and therefore definitely
2463 MALLOC_ALIGN_MASK-aligned. */
2464 assert (((INTERNAL_SIZE_T
) chunk2mem (mm
) & MALLOC_ALIGN_MASK
) == 0);
2468 front_misalign
= (INTERNAL_SIZE_T
) chunk2mem (mm
) & MALLOC_ALIGN_MASK
;
2469 if (front_misalign
> 0)
2471 correction
= MALLOC_ALIGNMENT
- front_misalign
;
2472 p
= (mchunkptr
) (mm
+ correction
);
2473 set_prev_size (p
, correction
);
2474 set_head (p
, (size
- correction
) | IS_MMAPPED
);
2479 set_prev_size (p
, 0);
2480 set_head (p
, size
| IS_MMAPPED
);
2483 /* update statistics */
2485 int new = atomic_exchange_and_add (&mp_
.n_mmaps
, 1) + 1;
2486 atomic_max (&mp_
.max_n_mmaps
, new);
2489 sum
= atomic_exchange_and_add (&mp_
.mmapped_mem
, size
) + size
;
2490 atomic_max (&mp_
.max_mmapped_mem
, sum
);
2492 check_chunk (av
, p
);
2494 return chunk2mem (p
);
2499 /* There are no usable arenas and mmap also failed. */
2503 /* Record incoming configuration of top */
2506 old_size
= chunksize (old_top
);
2507 old_end
= (char *) (chunk_at_offset (old_top
, old_size
));
2509 brk
= snd_brk
= (char *) (MORECORE_FAILURE
);
2512 If not the first time through, we require old_size to be
2513 at least MINSIZE and to have prev_inuse set.
2516 assert ((old_top
== initial_top (av
) && old_size
== 0) ||
2517 ((unsigned long) (old_size
) >= MINSIZE
&&
2518 prev_inuse (old_top
) &&
2519 ((unsigned long) old_end
& (pagesize
- 1)) == 0));
2521 /* Precondition: not enough current space to satisfy nb request */
2522 assert ((unsigned long) (old_size
) < (unsigned long) (nb
+ MINSIZE
));
2525 if (av
!= &main_arena
)
2527 heap_info
*old_heap
, *heap
;
2528 size_t old_heap_size
;
2530 /* First try to extend the current heap. */
2531 old_heap
= heap_for_ptr (old_top
);
2532 old_heap_size
= old_heap
->size
;
2533 if ((long) (MINSIZE
+ nb
- old_size
) > 0
2534 && grow_heap (old_heap
, MINSIZE
+ nb
- old_size
) == 0)
2536 av
->system_mem
+= old_heap
->size
- old_heap_size
;
2537 set_head (old_top
, (((char *) old_heap
+ old_heap
->size
) - (char *) old_top
)
2540 else if ((heap
= new_heap (nb
+ (MINSIZE
+ sizeof (*heap
)), mp_
.top_pad
)))
2542 /* Use a newly allocated heap. */
2544 heap
->prev
= old_heap
;
2545 av
->system_mem
+= heap
->size
;
2546 /* Set up the new top. */
2547 top (av
) = chunk_at_offset (heap
, sizeof (*heap
));
2548 set_head (top (av
), (heap
->size
- sizeof (*heap
)) | PREV_INUSE
);
2550 /* Setup fencepost and free the old top chunk with a multiple of
2551 MALLOC_ALIGNMENT in size. */
2552 /* The fencepost takes at least MINSIZE bytes, because it might
2553 become the top chunk again later. Note that a footer is set
2554 up, too, although the chunk is marked in use. */
2555 old_size
= (old_size
- MINSIZE
) & ~MALLOC_ALIGN_MASK
;
2556 set_head (chunk_at_offset (old_top
, old_size
+ CHUNK_HDR_SZ
),
2558 if (old_size
>= MINSIZE
)
2560 set_head (chunk_at_offset (old_top
, old_size
),
2561 CHUNK_HDR_SZ
| PREV_INUSE
);
2562 set_foot (chunk_at_offset (old_top
, old_size
), CHUNK_HDR_SZ
);
2563 set_head (old_top
, old_size
| PREV_INUSE
| NON_MAIN_ARENA
);
2564 _int_free (av
, old_top
, 1);
2568 set_head (old_top
, (old_size
+ CHUNK_HDR_SZ
) | PREV_INUSE
);
2569 set_foot (old_top
, (old_size
+ CHUNK_HDR_SZ
));
2572 else if (!tried_mmap
)
2573 /* We can at least try to use to mmap memory. */
2576 else /* av == main_arena */
2579 { /* Request enough space for nb + pad + overhead */
2580 size
= nb
+ mp_
.top_pad
+ MINSIZE
;
2583 If contiguous, we can subtract out existing space that we hope to
2584 combine with new space. We add it back later only if
2585 we don't actually get contiguous space.
2588 if (contiguous (av
))
2592 Round to a multiple of page size.
2593 If MORECORE is not contiguous, this ensures that we only call it
2594 with whole-page arguments. And if MORECORE is contiguous and
2595 this is not first time through, this preserves page-alignment of
2596 previous calls. Otherwise, we correct to page-align below.
2599 size
= ALIGN_UP (size
, pagesize
);
2602 Don't try to call MORECORE if argument is so big as to appear
2603 negative. Note that since mmap takes size_t arg, it may succeed
2604 below even if we cannot call MORECORE.
2609 brk
= (char *) (MORECORE (size
));
2610 LIBC_PROBE (memory_sbrk_more
, 2, brk
, size
);
2613 if (brk
== (char *) (MORECORE_FAILURE
))
2616 If have mmap, try using it as a backup when MORECORE fails or
2617 cannot be used. This is worth doing on systems that have "holes" in
2618 address space, so sbrk cannot extend to give contiguous space, but
2619 space is available elsewhere. Note that we ignore mmap max count
2620 and threshold limits, since the space will not be used as a
2621 segregated mmap region.
2624 /* Cannot merge with old top, so add its size back in */
2625 if (contiguous (av
))
2626 size
= ALIGN_UP (size
+ old_size
, pagesize
);
2628 /* If we are relying on mmap as backup, then use larger units */
2629 if ((unsigned long) (size
) < (unsigned long) (MMAP_AS_MORECORE_SIZE
))
2630 size
= MMAP_AS_MORECORE_SIZE
;
2632 /* Don't try if size wraps around 0 */
2633 if ((unsigned long) (size
) > (unsigned long) (nb
))
2635 char *mbrk
= (char *) (MMAP (0, size
,
2636 mtag_mmap_flags
| PROT_READ
| PROT_WRITE
,
2639 if (mbrk
!= MAP_FAILED
)
2641 /* We do not need, and cannot use, another sbrk call to find end */
2643 snd_brk
= brk
+ size
;
2646 Record that we no longer have a contiguous sbrk region.
2647 After the first time mmap is used as backup, we do not
2648 ever rely on contiguous space since this could incorrectly
2651 set_noncontiguous (av
);
2656 if (brk
!= (char *) (MORECORE_FAILURE
))
2658 if (mp_
.sbrk_base
== 0)
2659 mp_
.sbrk_base
= brk
;
2660 av
->system_mem
+= size
;
2663 If MORECORE extends previous space, we can likewise extend top size.
2666 if (brk
== old_end
&& snd_brk
== (char *) (MORECORE_FAILURE
))
2667 set_head (old_top
, (size
+ old_size
) | PREV_INUSE
);
2669 else if (contiguous (av
) && old_size
&& brk
< old_end
)
2670 /* Oops! Someone else killed our space.. Can't touch anything. */
2671 malloc_printerr ("break adjusted to free malloc space");
2674 Otherwise, make adjustments:
2676 * If the first time through or noncontiguous, we need to call sbrk
2677 just to find out where the end of memory lies.
2679 * We need to ensure that all returned chunks from malloc will meet
2682 * If there was an intervening foreign sbrk, we need to adjust sbrk
2683 request size to account for fact that we will not be able to
2684 combine new space with existing space in old_top.
2686 * Almost all systems internally allocate whole pages at a time, in
2687 which case we might as well use the whole last page of request.
2688 So we allocate enough more memory to hit a page boundary now,
2689 which in turn causes future contiguous calls to page-align.
2699 /* handle contiguous cases */
2700 if (contiguous (av
))
2702 /* Count foreign sbrk as system_mem. */
2704 av
->system_mem
+= brk
- old_end
;
2706 /* Guarantee alignment of first new chunk made from this space */
2708 front_misalign
= (INTERNAL_SIZE_T
) chunk2mem (brk
) & MALLOC_ALIGN_MASK
;
2709 if (front_misalign
> 0)
2712 Skip over some bytes to arrive at an aligned position.
2713 We don't need to specially mark these wasted front bytes.
2714 They will never be accessed anyway because
2715 prev_inuse of av->top (and any chunk created from its start)
2716 is always true after initialization.
2719 correction
= MALLOC_ALIGNMENT
- front_misalign
;
2720 aligned_brk
+= correction
;
2724 If this isn't adjacent to existing space, then we will not
2725 be able to merge with old_top space, so must add to 2nd request.
2728 correction
+= old_size
;
2730 /* Extend the end address to hit a page boundary */
2731 end_misalign
= (INTERNAL_SIZE_T
) (brk
+ size
+ correction
);
2732 correction
+= (ALIGN_UP (end_misalign
, pagesize
)) - end_misalign
;
2734 assert (correction
>= 0);
2735 snd_brk
= (char *) (MORECORE (correction
));
2738 If can't allocate correction, try to at least find out current
2739 brk. It might be enough to proceed without failing.
2741 Note that if second sbrk did NOT fail, we assume that space
2742 is contiguous with first sbrk. This is a safe assumption unless
2743 program is multithreaded but doesn't use locks and a foreign sbrk
2744 occurred between our first and second calls.
2747 if (snd_brk
== (char *) (MORECORE_FAILURE
))
2750 snd_brk
= (char *) (MORECORE (0));
2754 /* handle non-contiguous cases */
2757 if (MALLOC_ALIGNMENT
== CHUNK_HDR_SZ
)
2758 /* MORECORE/mmap must correctly align */
2759 assert (((unsigned long) chunk2mem (brk
) & MALLOC_ALIGN_MASK
) == 0);
2762 front_misalign
= (INTERNAL_SIZE_T
) chunk2mem (brk
) & MALLOC_ALIGN_MASK
;
2763 if (front_misalign
> 0)
2766 Skip over some bytes to arrive at an aligned position.
2767 We don't need to specially mark these wasted front bytes.
2768 They will never be accessed anyway because
2769 prev_inuse of av->top (and any chunk created from its start)
2770 is always true after initialization.
2773 aligned_brk
+= MALLOC_ALIGNMENT
- front_misalign
;
2777 /* Find out current end of memory */
2778 if (snd_brk
== (char *) (MORECORE_FAILURE
))
2780 snd_brk
= (char *) (MORECORE (0));
2784 /* Adjust top based on results of second sbrk */
2785 if (snd_brk
!= (char *) (MORECORE_FAILURE
))
2787 av
->top
= (mchunkptr
) aligned_brk
;
2788 set_head (av
->top
, (snd_brk
- aligned_brk
+ correction
) | PREV_INUSE
);
2789 av
->system_mem
+= correction
;
2792 If not the first time through, we either have a
2793 gap due to foreign sbrk or a non-contiguous region. Insert a
2794 double fencepost at old_top to prevent consolidation with space
2795 we don't own. These fenceposts are artificial chunks that are
2796 marked as inuse and are in any case too small to use. We need
2797 two to make sizes and alignments work out.
2803 Shrink old_top to insert fenceposts, keeping size a
2804 multiple of MALLOC_ALIGNMENT. We know there is at least
2805 enough space in old_top to do this.
2807 old_size
= (old_size
- 2 * CHUNK_HDR_SZ
) & ~MALLOC_ALIGN_MASK
;
2808 set_head (old_top
, old_size
| PREV_INUSE
);
2811 Note that the following assignments completely overwrite
2812 old_top when old_size was previously MINSIZE. This is
2813 intentional. We need the fencepost, even if old_top otherwise gets
2816 set_head (chunk_at_offset (old_top
, old_size
),
2817 CHUNK_HDR_SZ
| PREV_INUSE
);
2818 set_head (chunk_at_offset (old_top
,
2819 old_size
+ CHUNK_HDR_SZ
),
2820 CHUNK_HDR_SZ
| PREV_INUSE
);
2822 /* If possible, release the rest. */
2823 if (old_size
>= MINSIZE
)
2825 _int_free (av
, old_top
, 1);
2831 } /* if (av != &main_arena) */
2833 if ((unsigned long) av
->system_mem
> (unsigned long) (av
->max_system_mem
))
2834 av
->max_system_mem
= av
->system_mem
;
2835 check_malloc_state (av
);
2837 /* finally, do the allocation */
2839 size
= chunksize (p
);
2841 /* check that one of the above allocation paths succeeded */
2842 if ((unsigned long) (size
) >= (unsigned long) (nb
+ MINSIZE
))
2844 remainder_size
= size
- nb
;
2845 remainder
= chunk_at_offset (p
, nb
);
2846 av
->top
= remainder
;
2847 set_head (p
, nb
| PREV_INUSE
| (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
2848 set_head (remainder
, remainder_size
| PREV_INUSE
);
2849 check_malloced_chunk (av
, p
, nb
);
2850 return chunk2mem (p
);
2853 /* catch all failure paths */
2854 __set_errno (ENOMEM
);
2860 systrim is an inverse of sorts to sysmalloc. It gives memory back
2861 to the system (via negative arguments to sbrk) if there is unused
2862 memory at the `high' end of the malloc pool. It is called
2863 automatically by free() when top space exceeds the trim
2864 threshold. It is also called by the public malloc_trim routine. It
2865 returns 1 if it actually released any memory, else 0.
2869 systrim (size_t pad
, mstate av
)
2871 long top_size
; /* Amount of top-most memory */
2872 long extra
; /* Amount to release */
2873 long released
; /* Amount actually released */
2874 char *current_brk
; /* address returned by pre-check sbrk call */
2875 char *new_brk
; /* address returned by post-check sbrk call */
2879 pagesize
= GLRO (dl_pagesize
);
2880 top_size
= chunksize (av
->top
);
2882 top_area
= top_size
- MINSIZE
- 1;
2883 if (top_area
<= pad
)
2886 /* Release in pagesize units and round down to the nearest page. */
2887 extra
= ALIGN_DOWN(top_area
- pad
, pagesize
);
2893 Only proceed if end of memory is where we last set it.
2894 This avoids problems if there were foreign sbrk calls.
2896 current_brk
= (char *) (MORECORE (0));
2897 if (current_brk
== (char *) (av
->top
) + top_size
)
2900 Attempt to release memory. We ignore MORECORE return value,
2901 and instead call again to find out where new end of memory is.
2902 This avoids problems if first call releases less than we asked,
2903 of if failure somehow altered brk value. (We could still
2904 encounter problems if it altered brk in some very bad way,
2905 but the only thing we can do is adjust anyway, which will cause
2906 some downstream failure.)
2910 new_brk
= (char *) (MORECORE (0));
2912 LIBC_PROBE (memory_sbrk_less
, 2, new_brk
, extra
);
2914 if (new_brk
!= (char *) MORECORE_FAILURE
)
2916 released
= (long) (current_brk
- new_brk
);
2920 /* Success. Adjust top. */
2921 av
->system_mem
-= released
;
2922 set_head (av
->top
, (top_size
- released
) | PREV_INUSE
);
2923 check_malloc_state (av
);
2932 munmap_chunk (mchunkptr p
)
2934 size_t pagesize
= GLRO (dl_pagesize
);
2935 INTERNAL_SIZE_T size
= chunksize (p
);
2937 assert (chunk_is_mmapped (p
));
2939 uintptr_t mem
= (uintptr_t) chunk2mem (p
);
2940 uintptr_t block
= (uintptr_t) p
- prev_size (p
);
2941 size_t total_size
= prev_size (p
) + size
;
2942 /* Unfortunately we have to do the compilers job by hand here. Normally
2943 we would test BLOCK and TOTAL-SIZE separately for compliance with the
2944 page size. But gcc does not recognize the optimization possibility
2945 (in the moment at least) so we combine the two values into one before
2947 if (__glibc_unlikely ((block
| total_size
) & (pagesize
- 1)) != 0
2948 || __glibc_unlikely (!powerof2 (mem
& (pagesize
- 1))))
2949 malloc_printerr ("munmap_chunk(): invalid pointer");
2951 atomic_decrement (&mp_
.n_mmaps
);
2952 atomic_add (&mp_
.mmapped_mem
, -total_size
);
2954 /* If munmap failed the process virtual memory address space is in a
2955 bad shape. Just leave the block hanging around, the process will
2956 terminate shortly anyway since not much can be done. */
2957 __munmap ((char *) block
, total_size
);
2963 mremap_chunk (mchunkptr p
, size_t new_size
)
2965 size_t pagesize
= GLRO (dl_pagesize
);
2966 INTERNAL_SIZE_T offset
= prev_size (p
);
2967 INTERNAL_SIZE_T size
= chunksize (p
);
2970 assert (chunk_is_mmapped (p
));
2972 uintptr_t block
= (uintptr_t) p
- offset
;
2973 uintptr_t mem
= (uintptr_t) chunk2mem(p
);
2974 size_t total_size
= offset
+ size
;
2975 if (__glibc_unlikely ((block
| total_size
) & (pagesize
- 1)) != 0
2976 || __glibc_unlikely (!powerof2 (mem
& (pagesize
- 1))))
2977 malloc_printerr("mremap_chunk(): invalid pointer");
2979 /* Note the extra SIZE_SZ overhead as in mmap_chunk(). */
2980 new_size
= ALIGN_UP (new_size
+ offset
+ SIZE_SZ
, pagesize
);
2982 /* No need to remap if the number of pages does not change. */
2983 if (total_size
== new_size
)
2986 cp
= (char *) __mremap ((char *) block
, total_size
, new_size
,
2989 if (cp
== MAP_FAILED
)
2992 p
= (mchunkptr
) (cp
+ offset
);
2994 assert (aligned_OK (chunk2mem (p
)));
2996 assert (prev_size (p
) == offset
);
2997 set_head (p
, (new_size
- offset
) | IS_MMAPPED
);
2999 INTERNAL_SIZE_T
new;
3000 new = atomic_exchange_and_add (&mp_
.mmapped_mem
, new_size
- size
- offset
)
3001 + new_size
- size
- offset
;
3002 atomic_max (&mp_
.max_mmapped_mem
, new);
3005 #endif /* HAVE_MREMAP */
3007 /*------------------------ Public wrappers. --------------------------------*/
3011 /* We overlay this structure on the user-data portion of a chunk when
3012 the chunk is stored in the per-thread cache. */
3013 typedef struct tcache_entry
3015 struct tcache_entry
*next
;
3016 /* This field exists to detect double frees. */
3020 /* There is one of these for each thread, which contains the
3021 per-thread cache (hence "tcache_perthread_struct"). Keeping
3022 overall size low is mildly important. Note that COUNTS and ENTRIES
3023 are redundant (we could have just counted the linked list each
3024 time), this is for performance reasons. */
3025 typedef struct tcache_perthread_struct
3027 uint16_t counts
[TCACHE_MAX_BINS
];
3028 tcache_entry
*entries
[TCACHE_MAX_BINS
];
3029 } tcache_perthread_struct
;
3031 static __thread
bool tcache_shutting_down
= false;
3032 static __thread tcache_perthread_struct
*tcache
= NULL
;
3034 /* Process-wide key to try and catch a double-free in the same thread. */
3035 static uintptr_t tcache_key
;
3037 /* The value of tcache_key does not really have to be a cryptographically
3038 secure random number. It only needs to be arbitrary enough so that it does
3039 not collide with values present in applications. If a collision does happen
3040 consistently enough, it could cause a degradation in performance since the
3041 entire list is checked to check if the block indeed has been freed the
3042 second time. The odds of this happening are exceedingly low though, about 1
3043 in 2^wordsize. There is probably a higher chance of the performance
3044 degradation being due to a double free where the first free happened in a
3045 different thread; that's a case this check does not cover. */
3047 tcache_key_initialize (void)
3049 if (__getrandom (&tcache_key
, sizeof(tcache_key
), GRND_NONBLOCK
)
3050 != sizeof (tcache_key
))
3052 tcache_key
= random_bits ();
3053 #if __WORDSIZE == 64
3054 tcache_key
= (tcache_key
<< 32) | random_bits ();
3059 /* Caller must ensure that we know tc_idx is valid and there's room
3061 static __always_inline
void
3062 tcache_put (mchunkptr chunk
, size_t tc_idx
)
3064 tcache_entry
*e
= (tcache_entry
*) chunk2mem (chunk
);
3066 /* Mark this chunk as "in the tcache" so the test in _int_free will
3067 detect a double free. */
3068 e
->key
= tcache_key
;
3070 e
->next
= PROTECT_PTR (&e
->next
, tcache
->entries
[tc_idx
]);
3071 tcache
->entries
[tc_idx
] = e
;
3072 ++(tcache
->counts
[tc_idx
]);
3075 /* Caller must ensure that we know tc_idx is valid and there's
3076 available chunks to remove. */
3077 static __always_inline
void *
3078 tcache_get (size_t tc_idx
)
3080 tcache_entry
*e
= tcache
->entries
[tc_idx
];
3081 if (__glibc_unlikely (!aligned_OK (e
)))
3082 malloc_printerr ("malloc(): unaligned tcache chunk detected");
3083 tcache
->entries
[tc_idx
] = REVEAL_PTR (e
->next
);
3084 --(tcache
->counts
[tc_idx
]);
3090 tcache_thread_shutdown (void)
3093 tcache_perthread_struct
*tcache_tmp
= tcache
;
3095 tcache_shutting_down
= true;
3100 /* Disable the tcache and prevent it from being reinitialized. */
3103 /* Free all of the entries and the tcache itself back to the arena
3104 heap for coalescing. */
3105 for (i
= 0; i
< TCACHE_MAX_BINS
; ++i
)
3107 while (tcache_tmp
->entries
[i
])
3109 tcache_entry
*e
= tcache_tmp
->entries
[i
];
3110 if (__glibc_unlikely (!aligned_OK (e
)))
3111 malloc_printerr ("tcache_thread_shutdown(): "
3112 "unaligned tcache chunk detected");
3113 tcache_tmp
->entries
[i
] = REVEAL_PTR (e
->next
);
3118 __libc_free (tcache_tmp
);
3126 const size_t bytes
= sizeof (tcache_perthread_struct
);
3128 if (tcache_shutting_down
)
3131 arena_get (ar_ptr
, bytes
);
3132 victim
= _int_malloc (ar_ptr
, bytes
);
3133 if (!victim
&& ar_ptr
!= NULL
)
3135 ar_ptr
= arena_get_retry (ar_ptr
, bytes
);
3136 victim
= _int_malloc (ar_ptr
, bytes
);
3141 __libc_lock_unlock (ar_ptr
->mutex
);
3143 /* In a low memory situation, we may not be able to allocate memory
3144 - in which case, we just keep trying later. However, we
3145 typically do this very early, so either there is sufficient
3146 memory, or there isn't enough memory to do non-trivial
3147 allocations anyway. */
3150 tcache
= (tcache_perthread_struct
*) victim
;
3151 memset (tcache
, 0, sizeof (tcache_perthread_struct
));
3156 # define MAYBE_INIT_TCACHE() \
3157 if (__glibc_unlikely (tcache == NULL)) \
3160 #else /* !USE_TCACHE */
3161 # define MAYBE_INIT_TCACHE()
3164 tcache_thread_shutdown (void)
3166 /* Nothing to do if there is no thread cache. */
3169 #endif /* !USE_TCACHE */
3173 __libc_malloc (size_t bytes
)
3178 _Static_assert (PTRDIFF_MAX
<= SIZE_MAX
/ 2,
3179 "PTRDIFF_MAX is not more than half of SIZE_MAX");
3181 if (!__malloc_initialized
)
3184 /* int_free also calls request2size, be careful to not pad twice. */
3186 if (!checked_request2size (bytes
, &tbytes
))
3188 __set_errno (ENOMEM
);
3191 size_t tc_idx
= csize2tidx (tbytes
);
3193 MAYBE_INIT_TCACHE ();
3195 DIAG_PUSH_NEEDS_COMMENT
;
3196 if (tc_idx
< mp_
.tcache_bins
3198 && tcache
->counts
[tc_idx
] > 0)
3200 victim
= tcache_get (tc_idx
);
3201 return tag_new_usable (victim
);
3203 DIAG_POP_NEEDS_COMMENT
;
3206 if (SINGLE_THREAD_P
)
3208 victim
= tag_new_usable (_int_malloc (&main_arena
, bytes
));
3209 assert (!victim
|| chunk_is_mmapped (mem2chunk (victim
)) ||
3210 &main_arena
== arena_for_chunk (mem2chunk (victim
)));
3214 arena_get (ar_ptr
, bytes
);
3216 victim
= _int_malloc (ar_ptr
, bytes
);
3217 /* Retry with another arena only if we were able to find a usable arena
3219 if (!victim
&& ar_ptr
!= NULL
)
3221 LIBC_PROBE (memory_malloc_retry
, 1, bytes
);
3222 ar_ptr
= arena_get_retry (ar_ptr
, bytes
);
3223 victim
= _int_malloc (ar_ptr
, bytes
);
3227 __libc_lock_unlock (ar_ptr
->mutex
);
3229 victim
= tag_new_usable (victim
);
3231 assert (!victim
|| chunk_is_mmapped (mem2chunk (victim
)) ||
3232 ar_ptr
== arena_for_chunk (mem2chunk (victim
)));
3235 libc_hidden_def (__libc_malloc
)
3238 __libc_free (void *mem
)
3241 mchunkptr p
; /* chunk corresponding to mem */
3243 if (mem
== 0) /* free(0) has no effect */
3246 /* Quickly check that the freed pointer matches the tag for the memory.
3247 This gives a useful double-free detection. */
3248 if (__glibc_unlikely (mtag_enabled
))
3249 *(volatile char *)mem
;
3253 p
= mem2chunk (mem
);
3255 if (chunk_is_mmapped (p
)) /* release mmapped memory. */
3257 /* See if the dynamic brk/mmap threshold needs adjusting.
3258 Dumped fake mmapped chunks do not affect the threshold. */
3259 if (!mp_
.no_dyn_threshold
3260 && chunksize_nomask (p
) > mp_
.mmap_threshold
3261 && chunksize_nomask (p
) <= DEFAULT_MMAP_THRESHOLD_MAX
)
3263 mp_
.mmap_threshold
= chunksize (p
);
3264 mp_
.trim_threshold
= 2 * mp_
.mmap_threshold
;
3265 LIBC_PROBE (memory_mallopt_free_dyn_thresholds
, 2,
3266 mp_
.mmap_threshold
, mp_
.trim_threshold
);
3272 MAYBE_INIT_TCACHE ();
3274 /* Mark the chunk as belonging to the library again. */
3275 (void)tag_region (chunk2mem (p
), memsize (p
));
3277 ar_ptr
= arena_for_chunk (p
);
3278 _int_free (ar_ptr
, p
, 0);
3283 libc_hidden_def (__libc_free
)
3286 __libc_realloc (void *oldmem
, size_t bytes
)
3289 INTERNAL_SIZE_T nb
; /* padded request size */
3291 void *newp
; /* chunk to return */
3293 if (!__malloc_initialized
)
3296 #if REALLOC_ZERO_BYTES_FREES
3297 if (bytes
== 0 && oldmem
!= NULL
)
3299 __libc_free (oldmem
); return 0;
3303 /* realloc of null is supposed to be same as malloc */
3305 return __libc_malloc (bytes
);
3307 /* Perform a quick check to ensure that the pointer's tag matches the
3309 if (__glibc_unlikely (mtag_enabled
))
3310 *(volatile char*) oldmem
;
3312 /* chunk corresponding to oldmem */
3313 const mchunkptr oldp
= mem2chunk (oldmem
);
3315 const INTERNAL_SIZE_T oldsize
= chunksize (oldp
);
3317 if (chunk_is_mmapped (oldp
))
3321 MAYBE_INIT_TCACHE ();
3322 ar_ptr
= arena_for_chunk (oldp
);
3325 /* Little security check which won't hurt performance: the allocator
3326 never wrapps around at the end of the address space. Therefore
3327 we can exclude some size values which might appear here by
3328 accident or by "design" from some intruder. */
3329 if ((__builtin_expect ((uintptr_t) oldp
> (uintptr_t) -oldsize
, 0)
3330 || __builtin_expect (misaligned_chunk (oldp
), 0)))
3331 malloc_printerr ("realloc(): invalid pointer");
3333 if (!checked_request2size (bytes
, &nb
))
3335 __set_errno (ENOMEM
);
3339 if (chunk_is_mmapped (oldp
))
3344 newp
= mremap_chunk (oldp
, nb
);
3347 void *newmem
= chunk2mem_tag (newp
);
3348 /* Give the new block a different tag. This helps to ensure
3349 that stale handles to the previous mapping are not
3350 reused. There's a performance hit for both us and the
3351 caller for doing this, so we might want to
3353 return tag_new_usable (newmem
);
3356 /* Note the extra SIZE_SZ overhead. */
3357 if (oldsize
- SIZE_SZ
>= nb
)
3358 return oldmem
; /* do nothing */
3360 /* Must alloc, copy, free. */
3361 newmem
= __libc_malloc (bytes
);
3363 return 0; /* propagate failure */
3365 memcpy (newmem
, oldmem
, oldsize
- CHUNK_HDR_SZ
);
3366 munmap_chunk (oldp
);
3370 if (SINGLE_THREAD_P
)
3372 newp
= _int_realloc (ar_ptr
, oldp
, oldsize
, nb
);
3373 assert (!newp
|| chunk_is_mmapped (mem2chunk (newp
)) ||
3374 ar_ptr
== arena_for_chunk (mem2chunk (newp
)));
3379 __libc_lock_lock (ar_ptr
->mutex
);
3381 newp
= _int_realloc (ar_ptr
, oldp
, oldsize
, nb
);
3383 __libc_lock_unlock (ar_ptr
->mutex
);
3384 assert (!newp
|| chunk_is_mmapped (mem2chunk (newp
)) ||
3385 ar_ptr
== arena_for_chunk (mem2chunk (newp
)));
3389 /* Try harder to allocate memory in other arenas. */
3390 LIBC_PROBE (memory_realloc_retry
, 2, bytes
, oldmem
);
3391 newp
= __libc_malloc (bytes
);
3394 size_t sz
= memsize (oldp
);
3395 memcpy (newp
, oldmem
, sz
);
3396 (void) tag_region (chunk2mem (oldp
), sz
);
3397 _int_free (ar_ptr
, oldp
, 0);
3403 libc_hidden_def (__libc_realloc
)
3406 __libc_memalign (size_t alignment
, size_t bytes
)
3408 if (!__malloc_initialized
)
3411 void *address
= RETURN_ADDRESS (0);
3412 return _mid_memalign (alignment
, bytes
, address
);
3416 _mid_memalign (size_t alignment
, size_t bytes
, void *address
)
3421 /* If we need less alignment than we give anyway, just relay to malloc. */
3422 if (alignment
<= MALLOC_ALIGNMENT
)
3423 return __libc_malloc (bytes
);
3425 /* Otherwise, ensure that it is at least a minimum chunk size */
3426 if (alignment
< MINSIZE
)
3427 alignment
= MINSIZE
;
3429 /* If the alignment is greater than SIZE_MAX / 2 + 1 it cannot be a
3430 power of 2 and will cause overflow in the check below. */
3431 if (alignment
> SIZE_MAX
/ 2 + 1)
3433 __set_errno (EINVAL
);
3438 /* Make sure alignment is power of 2. */
3439 if (!powerof2 (alignment
))
3441 size_t a
= MALLOC_ALIGNMENT
* 2;
3442 while (a
< alignment
)
3447 if (SINGLE_THREAD_P
)
3449 p
= _int_memalign (&main_arena
, alignment
, bytes
);
3450 assert (!p
|| chunk_is_mmapped (mem2chunk (p
)) ||
3451 &main_arena
== arena_for_chunk (mem2chunk (p
)));
3452 return tag_new_usable (p
);
3455 arena_get (ar_ptr
, bytes
+ alignment
+ MINSIZE
);
3457 p
= _int_memalign (ar_ptr
, alignment
, bytes
);
3458 if (!p
&& ar_ptr
!= NULL
)
3460 LIBC_PROBE (memory_memalign_retry
, 2, bytes
, alignment
);
3461 ar_ptr
= arena_get_retry (ar_ptr
, bytes
);
3462 p
= _int_memalign (ar_ptr
, alignment
, bytes
);
3466 __libc_lock_unlock (ar_ptr
->mutex
);
3468 assert (!p
|| chunk_is_mmapped (mem2chunk (p
)) ||
3469 ar_ptr
== arena_for_chunk (mem2chunk (p
)));
3470 return tag_new_usable (p
);
3473 weak_alias (__libc_memalign
, aligned_alloc
)
3474 libc_hidden_def (__libc_memalign
)
3477 __libc_valloc (size_t bytes
)
3479 if (!__malloc_initialized
)
3482 void *address
= RETURN_ADDRESS (0);
3483 size_t pagesize
= GLRO (dl_pagesize
);
3484 return _mid_memalign (pagesize
, bytes
, address
);
3488 __libc_pvalloc (size_t bytes
)
3490 if (!__malloc_initialized
)
3493 void *address
= RETURN_ADDRESS (0);
3494 size_t pagesize
= GLRO (dl_pagesize
);
3495 size_t rounded_bytes
;
3496 /* ALIGN_UP with overflow check. */
3497 if (__glibc_unlikely (__builtin_add_overflow (bytes
,
3501 __set_errno (ENOMEM
);
3504 rounded_bytes
= rounded_bytes
& -(pagesize
- 1);
3506 return _mid_memalign (pagesize
, rounded_bytes
, address
);
3510 __libc_calloc (size_t n
, size_t elem_size
)
3514 INTERNAL_SIZE_T sz
, oldtopsize
;
3516 unsigned long clearsize
;
3517 unsigned long nclears
;
3521 if (__glibc_unlikely (__builtin_mul_overflow (n
, elem_size
, &bytes
)))
3523 __set_errno (ENOMEM
);
3529 if (!__malloc_initialized
)
3532 MAYBE_INIT_TCACHE ();
3534 if (SINGLE_THREAD_P
)
3541 /* Check if we hand out the top chunk, in which case there may be no
3545 oldtopsize
= chunksize (top (av
));
3546 # if MORECORE_CLEARS < 2
3547 /* Only newly allocated memory is guaranteed to be cleared. */
3548 if (av
== &main_arena
&&
3549 oldtopsize
< mp_
.sbrk_base
+ av
->max_system_mem
- (char *) oldtop
)
3550 oldtopsize
= (mp_
.sbrk_base
+ av
->max_system_mem
- (char *) oldtop
);
3552 if (av
!= &main_arena
)
3554 heap_info
*heap
= heap_for_ptr (oldtop
);
3555 if (oldtopsize
< (char *) heap
+ heap
->mprotect_size
- (char *) oldtop
)
3556 oldtopsize
= (char *) heap
+ heap
->mprotect_size
- (char *) oldtop
;
3562 /* No usable arenas. */
3566 mem
= _int_malloc (av
, sz
);
3568 assert (!mem
|| chunk_is_mmapped (mem2chunk (mem
)) ||
3569 av
== arena_for_chunk (mem2chunk (mem
)));
3571 if (!SINGLE_THREAD_P
)
3573 if (mem
== 0 && av
!= NULL
)
3575 LIBC_PROBE (memory_calloc_retry
, 1, sz
);
3576 av
= arena_get_retry (av
, sz
);
3577 mem
= _int_malloc (av
, sz
);
3581 __libc_lock_unlock (av
->mutex
);
3584 /* Allocation failed even after a retry. */
3588 mchunkptr p
= mem2chunk (mem
);
3590 /* If we are using memory tagging, then we need to set the tags
3591 regardless of MORECORE_CLEARS, so we zero the whole block while
3593 if (__glibc_unlikely (mtag_enabled
))
3594 return tag_new_zero_region (mem
, memsize (p
));
3596 INTERNAL_SIZE_T csz
= chunksize (p
);
3598 /* Two optional cases in which clearing not necessary */
3599 if (chunk_is_mmapped (p
))
3601 if (__builtin_expect (perturb_byte
, 0))
3602 return memset (mem
, 0, sz
);
3608 if (perturb_byte
== 0 && (p
== oldtop
&& csz
> oldtopsize
))
3610 /* clear only the bytes from non-freshly-sbrked memory */
3615 /* Unroll clear of <= 36 bytes (72 if 8byte sizes). We know that
3616 contents have an odd number of INTERNAL_SIZE_T-sized words;
3618 d
= (INTERNAL_SIZE_T
*) mem
;
3619 clearsize
= csz
- SIZE_SZ
;
3620 nclears
= clearsize
/ sizeof (INTERNAL_SIZE_T
);
3621 assert (nclears
>= 3);
3624 return memset (d
, 0, clearsize
);
3650 #endif /* IS_IN (libc) */
3653 ------------------------------ malloc ------------------------------
3657 _int_malloc (mstate av
, size_t bytes
)
3659 INTERNAL_SIZE_T nb
; /* normalized request size */
3660 unsigned int idx
; /* associated bin index */
3661 mbinptr bin
; /* associated bin */
3663 mchunkptr victim
; /* inspected/selected chunk */
3664 INTERNAL_SIZE_T size
; /* its size */
3665 int victim_index
; /* its bin index */
3667 mchunkptr remainder
; /* remainder from a split */
3668 unsigned long remainder_size
; /* its size */
3670 unsigned int block
; /* bit map traverser */
3671 unsigned int bit
; /* bit map traverser */
3672 unsigned int map
; /* current word of binmap */
3674 mchunkptr fwd
; /* misc temp for linking */
3675 mchunkptr bck
; /* misc temp for linking */
3678 size_t tcache_unsorted_count
; /* count of unsorted chunks processed */
3682 Convert request size to internal form by adding SIZE_SZ bytes
3683 overhead plus possibly more to obtain necessary alignment and/or
3684 to obtain a size of at least MINSIZE, the smallest allocatable
3685 size. Also, checked_request2size returns false for request sizes
3686 that are so large that they wrap around zero when padded and
3690 if (!checked_request2size (bytes
, &nb
))
3692 __set_errno (ENOMEM
);
3696 /* There are no usable arenas. Fall back to sysmalloc to get a chunk from
3698 if (__glibc_unlikely (av
== NULL
))
3700 void *p
= sysmalloc (nb
, av
);
3702 alloc_perturb (p
, bytes
);
3707 If the size qualifies as a fastbin, first check corresponding bin.
3708 This code is safe to execute even if av is not yet initialized, so we
3709 can try it without checking, which saves some time on this fast path.
3712 #define REMOVE_FB(fb, victim, pp) \
3716 if (victim == NULL) \
3718 pp = REVEAL_PTR (victim->fd); \
3719 if (__glibc_unlikely (pp != NULL && misaligned_chunk (pp))) \
3720 malloc_printerr ("malloc(): unaligned fastbin chunk detected"); \
3722 while ((pp = catomic_compare_and_exchange_val_acq (fb, pp, victim)) \
3725 if ((unsigned long) (nb) <= (unsigned long) (get_max_fast ()))
3727 idx
= fastbin_index (nb
);
3728 mfastbinptr
*fb
= &fastbin (av
, idx
);
3734 if (__glibc_unlikely (misaligned_chunk (victim
)))
3735 malloc_printerr ("malloc(): unaligned fastbin chunk detected 2");
3737 if (SINGLE_THREAD_P
)
3738 *fb
= REVEAL_PTR (victim
->fd
);
3740 REMOVE_FB (fb
, pp
, victim
);
3741 if (__glibc_likely (victim
!= NULL
))
3743 size_t victim_idx
= fastbin_index (chunksize (victim
));
3744 if (__builtin_expect (victim_idx
!= idx
, 0))
3745 malloc_printerr ("malloc(): memory corruption (fast)");
3746 check_remalloced_chunk (av
, victim
, nb
);
3748 /* While we're here, if we see other chunks of the same size,
3749 stash them in the tcache. */
3750 size_t tc_idx
= csize2tidx (nb
);
3751 if (tcache
&& tc_idx
< mp_
.tcache_bins
)
3753 mchunkptr tc_victim
;
3755 /* While bin not empty and tcache not full, copy chunks. */
3756 while (tcache
->counts
[tc_idx
] < mp_
.tcache_count
3757 && (tc_victim
= *fb
) != NULL
)
3759 if (__glibc_unlikely (misaligned_chunk (tc_victim
)))
3760 malloc_printerr ("malloc(): unaligned fastbin chunk detected 3");
3761 if (SINGLE_THREAD_P
)
3762 *fb
= REVEAL_PTR (tc_victim
->fd
);
3765 REMOVE_FB (fb
, pp
, tc_victim
);
3766 if (__glibc_unlikely (tc_victim
== NULL
))
3769 tcache_put (tc_victim
, tc_idx
);
3773 void *p
= chunk2mem (victim
);
3774 alloc_perturb (p
, bytes
);
3781 If a small request, check regular bin. Since these "smallbins"
3782 hold one size each, no searching within bins is necessary.
3783 (For a large request, we need to wait until unsorted chunks are
3784 processed to find best fit. But for small ones, fits are exact
3785 anyway, so we can check now, which is faster.)
3788 if (in_smallbin_range (nb
))
3790 idx
= smallbin_index (nb
);
3791 bin
= bin_at (av
, idx
);
3793 if ((victim
= last (bin
)) != bin
)
3796 if (__glibc_unlikely (bck
->fd
!= victim
))
3797 malloc_printerr ("malloc(): smallbin double linked list corrupted");
3798 set_inuse_bit_at_offset (victim
, nb
);
3802 if (av
!= &main_arena
)
3803 set_non_main_arena (victim
);
3804 check_malloced_chunk (av
, victim
, nb
);
3806 /* While we're here, if we see other chunks of the same size,
3807 stash them in the tcache. */
3808 size_t tc_idx
= csize2tidx (nb
);
3809 if (tcache
&& tc_idx
< mp_
.tcache_bins
)
3811 mchunkptr tc_victim
;
3813 /* While bin not empty and tcache not full, copy chunks over. */
3814 while (tcache
->counts
[tc_idx
] < mp_
.tcache_count
3815 && (tc_victim
= last (bin
)) != bin
)
3819 bck
= tc_victim
->bk
;
3820 set_inuse_bit_at_offset (tc_victim
, nb
);
3821 if (av
!= &main_arena
)
3822 set_non_main_arena (tc_victim
);
3826 tcache_put (tc_victim
, tc_idx
);
3831 void *p
= chunk2mem (victim
);
3832 alloc_perturb (p
, bytes
);
3838 If this is a large request, consolidate fastbins before continuing.
3839 While it might look excessive to kill all fastbins before
3840 even seeing if there is space available, this avoids
3841 fragmentation problems normally associated with fastbins.
3842 Also, in practice, programs tend to have runs of either small or
3843 large requests, but less often mixtures, so consolidation is not
3844 invoked all that often in most programs. And the programs that
3845 it is called frequently in otherwise tend to fragment.
3850 idx
= largebin_index (nb
);
3851 if (atomic_load_relaxed (&av
->have_fastchunks
))
3852 malloc_consolidate (av
);
3856 Process recently freed or remaindered chunks, taking one only if
3857 it is exact fit, or, if this a small request, the chunk is remainder from
3858 the most recent non-exact fit. Place other traversed chunks in
3859 bins. Note that this step is the only place in any routine where
3860 chunks are placed in bins.
3862 The outer loop here is needed because we might not realize until
3863 near the end of malloc that we should have consolidated, so must
3864 do so and retry. This happens at most once, and only when we would
3865 otherwise need to expand memory to service a "small" request.
3869 INTERNAL_SIZE_T tcache_nb
= 0;
3870 size_t tc_idx
= csize2tidx (nb
);
3871 if (tcache
&& tc_idx
< mp_
.tcache_bins
)
3873 int return_cached
= 0;
3875 tcache_unsorted_count
= 0;
3881 while ((victim
= unsorted_chunks (av
)->bk
) != unsorted_chunks (av
))
3884 size
= chunksize (victim
);
3885 mchunkptr next
= chunk_at_offset (victim
, size
);
3887 if (__glibc_unlikely (size
<= CHUNK_HDR_SZ
)
3888 || __glibc_unlikely (size
> av
->system_mem
))
3889 malloc_printerr ("malloc(): invalid size (unsorted)");
3890 if (__glibc_unlikely (chunksize_nomask (next
) < CHUNK_HDR_SZ
)
3891 || __glibc_unlikely (chunksize_nomask (next
) > av
->system_mem
))
3892 malloc_printerr ("malloc(): invalid next size (unsorted)");
3893 if (__glibc_unlikely ((prev_size (next
) & ~(SIZE_BITS
)) != size
))
3894 malloc_printerr ("malloc(): mismatching next->prev_size (unsorted)");
3895 if (__glibc_unlikely (bck
->fd
!= victim
)
3896 || __glibc_unlikely (victim
->fd
!= unsorted_chunks (av
)))
3897 malloc_printerr ("malloc(): unsorted double linked list corrupted");
3898 if (__glibc_unlikely (prev_inuse (next
)))
3899 malloc_printerr ("malloc(): invalid next->prev_inuse (unsorted)");
3902 If a small request, try to use last remainder if it is the
3903 only chunk in unsorted bin. This helps promote locality for
3904 runs of consecutive small requests. This is the only
3905 exception to best-fit, and applies only when there is
3906 no exact fit for a small chunk.
3909 if (in_smallbin_range (nb
) &&
3910 bck
== unsorted_chunks (av
) &&
3911 victim
== av
->last_remainder
&&
3912 (unsigned long) (size
) > (unsigned long) (nb
+ MINSIZE
))
3914 /* split and reattach remainder */
3915 remainder_size
= size
- nb
;
3916 remainder
= chunk_at_offset (victim
, nb
);
3917 unsorted_chunks (av
)->bk
= unsorted_chunks (av
)->fd
= remainder
;
3918 av
->last_remainder
= remainder
;
3919 remainder
->bk
= remainder
->fd
= unsorted_chunks (av
);
3920 if (!in_smallbin_range (remainder_size
))
3922 remainder
->fd_nextsize
= NULL
;
3923 remainder
->bk_nextsize
= NULL
;
3926 set_head (victim
, nb
| PREV_INUSE
|
3927 (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
3928 set_head (remainder
, remainder_size
| PREV_INUSE
);
3929 set_foot (remainder
, remainder_size
);
3931 check_malloced_chunk (av
, victim
, nb
);
3932 void *p
= chunk2mem (victim
);
3933 alloc_perturb (p
, bytes
);
3937 /* remove from unsorted list */
3938 if (__glibc_unlikely (bck
->fd
!= victim
))
3939 malloc_printerr ("malloc(): corrupted unsorted chunks 3");
3940 unsorted_chunks (av
)->bk
= bck
;
3941 bck
->fd
= unsorted_chunks (av
);
3943 /* Take now instead of binning if exact fit */
3947 set_inuse_bit_at_offset (victim
, size
);
3948 if (av
!= &main_arena
)
3949 set_non_main_arena (victim
);
3951 /* Fill cache first, return to user only if cache fills.
3952 We may return one of these chunks later. */
3954 && tcache
->counts
[tc_idx
] < mp_
.tcache_count
)
3956 tcache_put (victim
, tc_idx
);
3963 check_malloced_chunk (av
, victim
, nb
);
3964 void *p
= chunk2mem (victim
);
3965 alloc_perturb (p
, bytes
);
3972 /* place chunk in bin */
3974 if (in_smallbin_range (size
))
3976 victim_index
= smallbin_index (size
);
3977 bck
= bin_at (av
, victim_index
);
3982 victim_index
= largebin_index (size
);
3983 bck
= bin_at (av
, victim_index
);
3986 /* maintain large bins in sorted order */
3989 /* Or with inuse bit to speed comparisons */
3991 /* if smaller than smallest, bypass loop below */
3992 assert (chunk_main_arena (bck
->bk
));
3993 if ((unsigned long) (size
)
3994 < (unsigned long) chunksize_nomask (bck
->bk
))
3999 victim
->fd_nextsize
= fwd
->fd
;
4000 victim
->bk_nextsize
= fwd
->fd
->bk_nextsize
;
4001 fwd
->fd
->bk_nextsize
= victim
->bk_nextsize
->fd_nextsize
= victim
;
4005 assert (chunk_main_arena (fwd
));
4006 while ((unsigned long) size
< chunksize_nomask (fwd
))
4008 fwd
= fwd
->fd_nextsize
;
4009 assert (chunk_main_arena (fwd
));
4012 if ((unsigned long) size
4013 == (unsigned long) chunksize_nomask (fwd
))
4014 /* Always insert in the second position. */
4018 victim
->fd_nextsize
= fwd
;
4019 victim
->bk_nextsize
= fwd
->bk_nextsize
;
4020 if (__glibc_unlikely (fwd
->bk_nextsize
->fd_nextsize
!= fwd
))
4021 malloc_printerr ("malloc(): largebin double linked list corrupted (nextsize)");
4022 fwd
->bk_nextsize
= victim
;
4023 victim
->bk_nextsize
->fd_nextsize
= victim
;
4027 malloc_printerr ("malloc(): largebin double linked list corrupted (bk)");
4031 victim
->fd_nextsize
= victim
->bk_nextsize
= victim
;
4034 mark_bin (av
, victim_index
);
4041 /* If we've processed as many chunks as we're allowed while
4042 filling the cache, return one of the cached ones. */
4043 ++tcache_unsorted_count
;
4045 && mp_
.tcache_unsorted_limit
> 0
4046 && tcache_unsorted_count
> mp_
.tcache_unsorted_limit
)
4048 return tcache_get (tc_idx
);
4052 #define MAX_ITERS 10000
4053 if (++iters
>= MAX_ITERS
)
4058 /* If all the small chunks we found ended up cached, return one now. */
4061 return tcache_get (tc_idx
);
4066 If a large request, scan through the chunks of current bin in
4067 sorted order to find smallest that fits. Use the skip list for this.
4070 if (!in_smallbin_range (nb
))
4072 bin
= bin_at (av
, idx
);
4074 /* skip scan if empty or largest chunk is too small */
4075 if ((victim
= first (bin
)) != bin
4076 && (unsigned long) chunksize_nomask (victim
)
4077 >= (unsigned long) (nb
))
4079 victim
= victim
->bk_nextsize
;
4080 while (((unsigned long) (size
= chunksize (victim
)) <
4081 (unsigned long) (nb
)))
4082 victim
= victim
->bk_nextsize
;
4084 /* Avoid removing the first entry for a size so that the skip
4085 list does not have to be rerouted. */
4086 if (victim
!= last (bin
)
4087 && chunksize_nomask (victim
)
4088 == chunksize_nomask (victim
->fd
))
4089 victim
= victim
->fd
;
4091 remainder_size
= size
- nb
;
4092 unlink_chunk (av
, victim
);
4095 if (remainder_size
< MINSIZE
)
4097 set_inuse_bit_at_offset (victim
, size
);
4098 if (av
!= &main_arena
)
4099 set_non_main_arena (victim
);
4104 remainder
= chunk_at_offset (victim
, nb
);
4105 /* We cannot assume the unsorted list is empty and therefore
4106 have to perform a complete insert here. */
4107 bck
= unsorted_chunks (av
);
4109 if (__glibc_unlikely (fwd
->bk
!= bck
))
4110 malloc_printerr ("malloc(): corrupted unsorted chunks");
4111 remainder
->bk
= bck
;
4112 remainder
->fd
= fwd
;
4113 bck
->fd
= remainder
;
4114 fwd
->bk
= remainder
;
4115 if (!in_smallbin_range (remainder_size
))
4117 remainder
->fd_nextsize
= NULL
;
4118 remainder
->bk_nextsize
= NULL
;
4120 set_head (victim
, nb
| PREV_INUSE
|
4121 (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4122 set_head (remainder
, remainder_size
| PREV_INUSE
);
4123 set_foot (remainder
, remainder_size
);
4125 check_malloced_chunk (av
, victim
, nb
);
4126 void *p
= chunk2mem (victim
);
4127 alloc_perturb (p
, bytes
);
4133 Search for a chunk by scanning bins, starting with next largest
4134 bin. This search is strictly by best-fit; i.e., the smallest
4135 (with ties going to approximately the least recently used) chunk
4136 that fits is selected.
4138 The bitmap avoids needing to check that most blocks are nonempty.
4139 The particular case of skipping all bins during warm-up phases
4140 when no chunks have been returned yet is faster than it might look.
4144 bin
= bin_at (av
, idx
);
4145 block
= idx2block (idx
);
4146 map
= av
->binmap
[block
];
4147 bit
= idx2bit (idx
);
4151 /* Skip rest of block if there are no more set bits in this block. */
4152 if (bit
> map
|| bit
== 0)
4156 if (++block
>= BINMAPSIZE
) /* out of bins */
4159 while ((map
= av
->binmap
[block
]) == 0);
4161 bin
= bin_at (av
, (block
<< BINMAPSHIFT
));
4165 /* Advance to bin with set bit. There must be one. */
4166 while ((bit
& map
) == 0)
4168 bin
= next_bin (bin
);
4173 /* Inspect the bin. It is likely to be non-empty */
4174 victim
= last (bin
);
4176 /* If a false alarm (empty bin), clear the bit. */
4179 av
->binmap
[block
] = map
&= ~bit
; /* Write through */
4180 bin
= next_bin (bin
);
4186 size
= chunksize (victim
);
4188 /* We know the first chunk in this bin is big enough to use. */
4189 assert ((unsigned long) (size
) >= (unsigned long) (nb
));
4191 remainder_size
= size
- nb
;
4194 unlink_chunk (av
, victim
);
4197 if (remainder_size
< MINSIZE
)
4199 set_inuse_bit_at_offset (victim
, size
);
4200 if (av
!= &main_arena
)
4201 set_non_main_arena (victim
);
4207 remainder
= chunk_at_offset (victim
, nb
);
4209 /* We cannot assume the unsorted list is empty and therefore
4210 have to perform a complete insert here. */
4211 bck
= unsorted_chunks (av
);
4213 if (__glibc_unlikely (fwd
->bk
!= bck
))
4214 malloc_printerr ("malloc(): corrupted unsorted chunks 2");
4215 remainder
->bk
= bck
;
4216 remainder
->fd
= fwd
;
4217 bck
->fd
= remainder
;
4218 fwd
->bk
= remainder
;
4220 /* advertise as last remainder */
4221 if (in_smallbin_range (nb
))
4222 av
->last_remainder
= remainder
;
4223 if (!in_smallbin_range (remainder_size
))
4225 remainder
->fd_nextsize
= NULL
;
4226 remainder
->bk_nextsize
= NULL
;
4228 set_head (victim
, nb
| PREV_INUSE
|
4229 (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4230 set_head (remainder
, remainder_size
| PREV_INUSE
);
4231 set_foot (remainder
, remainder_size
);
4233 check_malloced_chunk (av
, victim
, nb
);
4234 void *p
= chunk2mem (victim
);
4235 alloc_perturb (p
, bytes
);
4242 If large enough, split off the chunk bordering the end of memory
4243 (held in av->top). Note that this is in accord with the best-fit
4244 search rule. In effect, av->top is treated as larger (and thus
4245 less well fitting) than any other available chunk since it can
4246 be extended to be as large as necessary (up to system
4249 We require that av->top always exists (i.e., has size >=
4250 MINSIZE) after initialization, so if it would otherwise be
4251 exhausted by current request, it is replenished. (The main
4252 reason for ensuring it exists is that we may need MINSIZE space
4253 to put in fenceposts in sysmalloc.)
4257 size
= chunksize (victim
);
4259 if (__glibc_unlikely (size
> av
->system_mem
))
4260 malloc_printerr ("malloc(): corrupted top size");
4262 if ((unsigned long) (size
) >= (unsigned long) (nb
+ MINSIZE
))
4264 remainder_size
= size
- nb
;
4265 remainder
= chunk_at_offset (victim
, nb
);
4266 av
->top
= remainder
;
4267 set_head (victim
, nb
| PREV_INUSE
|
4268 (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4269 set_head (remainder
, remainder_size
| PREV_INUSE
);
4271 check_malloced_chunk (av
, victim
, nb
);
4272 void *p
= chunk2mem (victim
);
4273 alloc_perturb (p
, bytes
);
4277 /* When we are using atomic ops to free fast chunks we can get
4278 here for all block sizes. */
4279 else if (atomic_load_relaxed (&av
->have_fastchunks
))
4281 malloc_consolidate (av
);
4282 /* restore original bin index */
4283 if (in_smallbin_range (nb
))
4284 idx
= smallbin_index (nb
);
4286 idx
= largebin_index (nb
);
4290 Otherwise, relay to handle system-dependent cases
4294 void *p
= sysmalloc (nb
, av
);
4296 alloc_perturb (p
, bytes
);
4303 ------------------------------ free ------------------------------
4307 _int_free (mstate av
, mchunkptr p
, int have_lock
)
4309 INTERNAL_SIZE_T size
; /* its size */
4310 mfastbinptr
*fb
; /* associated fastbin */
4311 mchunkptr nextchunk
; /* next contiguous chunk */
4312 INTERNAL_SIZE_T nextsize
; /* its size */
4313 int nextinuse
; /* true if nextchunk is used */
4314 INTERNAL_SIZE_T prevsize
; /* size of previous contiguous chunk */
4315 mchunkptr bck
; /* misc temp for linking */
4316 mchunkptr fwd
; /* misc temp for linking */
4318 size
= chunksize (p
);
4320 /* Little security check which won't hurt performance: the
4321 allocator never wrapps around at the end of the address space.
4322 Therefore we can exclude some size values which might appear
4323 here by accident or by "design" from some intruder. */
4324 if (__builtin_expect ((uintptr_t) p
> (uintptr_t) -size
, 0)
4325 || __builtin_expect (misaligned_chunk (p
), 0))
4326 malloc_printerr ("free(): invalid pointer");
4327 /* We know that each chunk is at least MINSIZE bytes in size or a
4328 multiple of MALLOC_ALIGNMENT. */
4329 if (__glibc_unlikely (size
< MINSIZE
|| !aligned_OK (size
)))
4330 malloc_printerr ("free(): invalid size");
4332 check_inuse_chunk(av
, p
);
4336 size_t tc_idx
= csize2tidx (size
);
4337 if (tcache
!= NULL
&& tc_idx
< mp_
.tcache_bins
)
4339 /* Check to see if it's already in the tcache. */
4340 tcache_entry
*e
= (tcache_entry
*) chunk2mem (p
);
4342 /* This test succeeds on double free. However, we don't 100%
4343 trust it (it also matches random payload data at a 1 in
4344 2^<size_t> chance), so verify it's not an unlikely
4345 coincidence before aborting. */
4346 if (__glibc_unlikely (e
->key
== tcache_key
))
4350 LIBC_PROBE (memory_tcache_double_free
, 2, e
, tc_idx
);
4351 for (tmp
= tcache
->entries
[tc_idx
];
4353 tmp
= REVEAL_PTR (tmp
->next
), ++cnt
)
4355 if (cnt
>= mp_
.tcache_count
)
4356 malloc_printerr ("free(): too many chunks detected in tcache");
4357 if (__glibc_unlikely (!aligned_OK (tmp
)))
4358 malloc_printerr ("free(): unaligned chunk detected in tcache 2");
4360 malloc_printerr ("free(): double free detected in tcache 2");
4361 /* If we get here, it was a coincidence. We've wasted a
4362 few cycles, but don't abort. */
4366 if (tcache
->counts
[tc_idx
] < mp_
.tcache_count
)
4368 tcache_put (p
, tc_idx
);
4376 If eligible, place chunk on a fastbin so it can be found
4377 and used quickly in malloc.
4380 if ((unsigned long)(size
) <= (unsigned long)(get_max_fast ())
4384 If TRIM_FASTBINS set, don't place chunks
4385 bordering top into fastbins
4387 && (chunk_at_offset(p
, size
) != av
->top
)
4391 if (__builtin_expect (chunksize_nomask (chunk_at_offset (p
, size
))
4393 || __builtin_expect (chunksize (chunk_at_offset (p
, size
))
4394 >= av
->system_mem
, 0))
4397 /* We might not have a lock at this point and concurrent modifications
4398 of system_mem might result in a false positive. Redo the test after
4399 getting the lock. */
4402 __libc_lock_lock (av
->mutex
);
4403 fail
= (chunksize_nomask (chunk_at_offset (p
, size
)) <= CHUNK_HDR_SZ
4404 || chunksize (chunk_at_offset (p
, size
)) >= av
->system_mem
);
4405 __libc_lock_unlock (av
->mutex
);
4409 malloc_printerr ("free(): invalid next size (fast)");
4412 free_perturb (chunk2mem(p
), size
- CHUNK_HDR_SZ
);
4414 atomic_store_relaxed (&av
->have_fastchunks
, true);
4415 unsigned int idx
= fastbin_index(size
);
4416 fb
= &fastbin (av
, idx
);
4418 /* Atomically link P to its fastbin: P->FD = *FB; *FB = P; */
4419 mchunkptr old
= *fb
, old2
;
4421 if (SINGLE_THREAD_P
)
4423 /* Check that the top of the bin is not the record we are going to
4424 add (i.e., double free). */
4425 if (__builtin_expect (old
== p
, 0))
4426 malloc_printerr ("double free or corruption (fasttop)");
4427 p
->fd
= PROTECT_PTR (&p
->fd
, old
);
4433 /* Check that the top of the bin is not the record we are going to
4434 add (i.e., double free). */
4435 if (__builtin_expect (old
== p
, 0))
4436 malloc_printerr ("double free or corruption (fasttop)");
4438 p
->fd
= PROTECT_PTR (&p
->fd
, old
);
4440 while ((old
= catomic_compare_and_exchange_val_rel (fb
, p
, old2
))
4443 /* Check that size of fastbin chunk at the top is the same as
4444 size of the chunk that we are adding. We can dereference OLD
4445 only if we have the lock, otherwise it might have already been
4447 if (have_lock
&& old
!= NULL
4448 && __builtin_expect (fastbin_index (chunksize (old
)) != idx
, 0))
4449 malloc_printerr ("invalid fastbin entry (free)");
4453 Consolidate other non-mmapped chunks as they arrive.
4456 else if (!chunk_is_mmapped(p
)) {
4458 /* If we're single-threaded, don't lock the arena. */
4459 if (SINGLE_THREAD_P
)
4463 __libc_lock_lock (av
->mutex
);
4465 nextchunk
= chunk_at_offset(p
, size
);
4467 /* Lightweight tests: check whether the block is already the
4469 if (__glibc_unlikely (p
== av
->top
))
4470 malloc_printerr ("double free or corruption (top)");
4471 /* Or whether the next chunk is beyond the boundaries of the arena. */
4472 if (__builtin_expect (contiguous (av
)
4473 && (char *) nextchunk
4474 >= ((char *) av
->top
+ chunksize(av
->top
)), 0))
4475 malloc_printerr ("double free or corruption (out)");
4476 /* Or whether the block is actually not marked used. */
4477 if (__glibc_unlikely (!prev_inuse(nextchunk
)))
4478 malloc_printerr ("double free or corruption (!prev)");
4480 nextsize
= chunksize(nextchunk
);
4481 if (__builtin_expect (chunksize_nomask (nextchunk
) <= CHUNK_HDR_SZ
, 0)
4482 || __builtin_expect (nextsize
>= av
->system_mem
, 0))
4483 malloc_printerr ("free(): invalid next size (normal)");
4485 free_perturb (chunk2mem(p
), size
- CHUNK_HDR_SZ
);
4487 /* consolidate backward */
4488 if (!prev_inuse(p
)) {
4489 prevsize
= prev_size (p
);
4491 p
= chunk_at_offset(p
, -((long) prevsize
));
4492 if (__glibc_unlikely (chunksize(p
) != prevsize
))
4493 malloc_printerr ("corrupted size vs. prev_size while consolidating");
4494 unlink_chunk (av
, p
);
4497 if (nextchunk
!= av
->top
) {
4498 /* get and clear inuse bit */
4499 nextinuse
= inuse_bit_at_offset(nextchunk
, nextsize
);
4501 /* consolidate forward */
4503 unlink_chunk (av
, nextchunk
);
4506 clear_inuse_bit_at_offset(nextchunk
, 0);
4509 Place the chunk in unsorted chunk list. Chunks are
4510 not placed into regular bins until after they have
4511 been given one chance to be used in malloc.
4514 bck
= unsorted_chunks(av
);
4516 if (__glibc_unlikely (fwd
->bk
!= bck
))
4517 malloc_printerr ("free(): corrupted unsorted chunks");
4520 if (!in_smallbin_range(size
))
4522 p
->fd_nextsize
= NULL
;
4523 p
->bk_nextsize
= NULL
;
4528 set_head(p
, size
| PREV_INUSE
);
4531 check_free_chunk(av
, p
);
4535 If the chunk borders the current high end of memory,
4536 consolidate into top
4541 set_head(p
, size
| PREV_INUSE
);
4547 If freeing a large space, consolidate possibly-surrounding
4548 chunks. Then, if the total unused topmost memory exceeds trim
4549 threshold, ask malloc_trim to reduce top.
4551 Unless max_fast is 0, we don't know if there are fastbins
4552 bordering top, so we cannot tell for sure whether threshold
4553 has been reached unless fastbins are consolidated. But we
4554 don't want to consolidate on each free. As a compromise,
4555 consolidation is performed if FASTBIN_CONSOLIDATION_THRESHOLD
4559 if ((unsigned long)(size
) >= FASTBIN_CONSOLIDATION_THRESHOLD
) {
4560 if (atomic_load_relaxed (&av
->have_fastchunks
))
4561 malloc_consolidate(av
);
4563 if (av
== &main_arena
) {
4564 #ifndef MORECORE_CANNOT_TRIM
4565 if ((unsigned long)(chunksize(av
->top
)) >=
4566 (unsigned long)(mp_
.trim_threshold
))
4567 systrim(mp_
.top_pad
, av
);
4570 /* Always try heap_trim(), even if the top chunk is not
4571 large, because the corresponding heap might go away. */
4572 heap_info
*heap
= heap_for_ptr(top(av
));
4574 assert(heap
->ar_ptr
== av
);
4575 heap_trim(heap
, mp_
.top_pad
);
4580 __libc_lock_unlock (av
->mutex
);
4583 If the chunk was allocated via mmap, release via munmap().
4592 ------------------------- malloc_consolidate -------------------------
4594 malloc_consolidate is a specialized version of free() that tears
4595 down chunks held in fastbins. Free itself cannot be used for this
4596 purpose since, among other things, it might place chunks back onto
4597 fastbins. So, instead, we need to use a minor variant of the same
4601 static void malloc_consolidate(mstate av
)
4603 mfastbinptr
* fb
; /* current fastbin being consolidated */
4604 mfastbinptr
* maxfb
; /* last fastbin (for loop control) */
4605 mchunkptr p
; /* current chunk being consolidated */
4606 mchunkptr nextp
; /* next chunk to consolidate */
4607 mchunkptr unsorted_bin
; /* bin header */
4608 mchunkptr first_unsorted
; /* chunk to link to */
4610 /* These have same use as in free() */
4611 mchunkptr nextchunk
;
4612 INTERNAL_SIZE_T size
;
4613 INTERNAL_SIZE_T nextsize
;
4614 INTERNAL_SIZE_T prevsize
;
4617 atomic_store_relaxed (&av
->have_fastchunks
, false);
4619 unsorted_bin
= unsorted_chunks(av
);
4622 Remove each chunk from fast bin and consolidate it, placing it
4623 then in unsorted bin. Among other reasons for doing this,
4624 placing in unsorted bin avoids needing to calculate actual bins
4625 until malloc is sure that chunks aren't immediately going to be
4629 maxfb
= &fastbin (av
, NFASTBINS
- 1);
4630 fb
= &fastbin (av
, 0);
4632 p
= atomic_exchange_acq (fb
, NULL
);
4636 if (__glibc_unlikely (misaligned_chunk (p
)))
4637 malloc_printerr ("malloc_consolidate(): "
4638 "unaligned fastbin chunk detected");
4640 unsigned int idx
= fastbin_index (chunksize (p
));
4641 if ((&fastbin (av
, idx
)) != fb
)
4642 malloc_printerr ("malloc_consolidate(): invalid chunk size");
4645 check_inuse_chunk(av
, p
);
4646 nextp
= REVEAL_PTR (p
->fd
);
4648 /* Slightly streamlined version of consolidation code in free() */
4649 size
= chunksize (p
);
4650 nextchunk
= chunk_at_offset(p
, size
);
4651 nextsize
= chunksize(nextchunk
);
4653 if (!prev_inuse(p
)) {
4654 prevsize
= prev_size (p
);
4656 p
= chunk_at_offset(p
, -((long) prevsize
));
4657 if (__glibc_unlikely (chunksize(p
) != prevsize
))
4658 malloc_printerr ("corrupted size vs. prev_size in fastbins");
4659 unlink_chunk (av
, p
);
4662 if (nextchunk
!= av
->top
) {
4663 nextinuse
= inuse_bit_at_offset(nextchunk
, nextsize
);
4667 unlink_chunk (av
, nextchunk
);
4669 clear_inuse_bit_at_offset(nextchunk
, 0);
4671 first_unsorted
= unsorted_bin
->fd
;
4672 unsorted_bin
->fd
= p
;
4673 first_unsorted
->bk
= p
;
4675 if (!in_smallbin_range (size
)) {
4676 p
->fd_nextsize
= NULL
;
4677 p
->bk_nextsize
= NULL
;
4680 set_head(p
, size
| PREV_INUSE
);
4681 p
->bk
= unsorted_bin
;
4682 p
->fd
= first_unsorted
;
4688 set_head(p
, size
| PREV_INUSE
);
4692 } while ( (p
= nextp
) != 0);
4695 } while (fb
++ != maxfb
);
4699 ------------------------------ realloc ------------------------------
4703 _int_realloc (mstate av
, mchunkptr oldp
, INTERNAL_SIZE_T oldsize
,
4706 mchunkptr newp
; /* chunk to return */
4707 INTERNAL_SIZE_T newsize
; /* its size */
4708 void* newmem
; /* corresponding user mem */
4710 mchunkptr next
; /* next contiguous chunk after oldp */
4712 mchunkptr remainder
; /* extra space at end of newp */
4713 unsigned long remainder_size
; /* its size */
4716 if (__builtin_expect (chunksize_nomask (oldp
) <= CHUNK_HDR_SZ
, 0)
4717 || __builtin_expect (oldsize
>= av
->system_mem
, 0))
4718 malloc_printerr ("realloc(): invalid old size");
4720 check_inuse_chunk (av
, oldp
);
4722 /* All callers already filter out mmap'ed chunks. */
4723 assert (!chunk_is_mmapped (oldp
));
4725 next
= chunk_at_offset (oldp
, oldsize
);
4726 INTERNAL_SIZE_T nextsize
= chunksize (next
);
4727 if (__builtin_expect (chunksize_nomask (next
) <= CHUNK_HDR_SZ
, 0)
4728 || __builtin_expect (nextsize
>= av
->system_mem
, 0))
4729 malloc_printerr ("realloc(): invalid next size");
4731 if ((unsigned long) (oldsize
) >= (unsigned long) (nb
))
4733 /* already big enough; split below */
4740 /* Try to expand forward into top */
4741 if (next
== av
->top
&&
4742 (unsigned long) (newsize
= oldsize
+ nextsize
) >=
4743 (unsigned long) (nb
+ MINSIZE
))
4745 set_head_size (oldp
, nb
| (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4746 av
->top
= chunk_at_offset (oldp
, nb
);
4747 set_head (av
->top
, (newsize
- nb
) | PREV_INUSE
);
4748 check_inuse_chunk (av
, oldp
);
4749 return tag_new_usable (chunk2mem (oldp
));
4752 /* Try to expand forward into next chunk; split off remainder below */
4753 else if (next
!= av
->top
&&
4755 (unsigned long) (newsize
= oldsize
+ nextsize
) >=
4756 (unsigned long) (nb
))
4759 unlink_chunk (av
, next
);
4762 /* allocate, copy, free */
4765 newmem
= _int_malloc (av
, nb
- MALLOC_ALIGN_MASK
);
4767 return 0; /* propagate failure */
4769 newp
= mem2chunk (newmem
);
4770 newsize
= chunksize (newp
);
4773 Avoid copy if newp is next chunk after oldp.
4782 void *oldmem
= chunk2mem (oldp
);
4783 size_t sz
= memsize (oldp
);
4784 (void) tag_region (oldmem
, sz
);
4785 newmem
= tag_new_usable (newmem
);
4786 memcpy (newmem
, oldmem
, sz
);
4787 _int_free (av
, oldp
, 1);
4788 check_inuse_chunk (av
, newp
);
4794 /* If possible, free extra space in old or extended chunk */
4796 assert ((unsigned long) (newsize
) >= (unsigned long) (nb
));
4798 remainder_size
= newsize
- nb
;
4800 if (remainder_size
< MINSIZE
) /* not enough extra to split off */
4802 set_head_size (newp
, newsize
| (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4803 set_inuse_bit_at_offset (newp
, newsize
);
4805 else /* split remainder */
4807 remainder
= chunk_at_offset (newp
, nb
);
4808 /* Clear any user-space tags before writing the header. */
4809 remainder
= tag_region (remainder
, remainder_size
);
4810 set_head_size (newp
, nb
| (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4811 set_head (remainder
, remainder_size
| PREV_INUSE
|
4812 (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4813 /* Mark remainder as inuse so free() won't complain */
4814 set_inuse_bit_at_offset (remainder
, remainder_size
);
4815 _int_free (av
, remainder
, 1);
4818 check_inuse_chunk (av
, newp
);
4819 return tag_new_usable (chunk2mem (newp
));
4823 ------------------------------ memalign ------------------------------
4827 _int_memalign (mstate av
, size_t alignment
, size_t bytes
)
4829 INTERNAL_SIZE_T nb
; /* padded request size */
4830 char *m
; /* memory returned by malloc call */
4831 mchunkptr p
; /* corresponding chunk */
4832 char *brk
; /* alignment point within p */
4833 mchunkptr newp
; /* chunk to return */
4834 INTERNAL_SIZE_T newsize
; /* its size */
4835 INTERNAL_SIZE_T leadsize
; /* leading space before alignment point */
4836 mchunkptr remainder
; /* spare room at end to split off */
4837 unsigned long remainder_size
; /* its size */
4838 INTERNAL_SIZE_T size
;
4842 if (!checked_request2size (bytes
, &nb
))
4844 __set_errno (ENOMEM
);
4849 Strategy: find a spot within that chunk that meets the alignment
4850 request, and then possibly free the leading and trailing space.
4853 /* Call malloc with worst case padding to hit alignment. */
4855 m
= (char *) (_int_malloc (av
, nb
+ alignment
+ MINSIZE
));
4858 return 0; /* propagate failure */
4862 if ((((unsigned long) (m
)) % alignment
) != 0) /* misaligned */
4865 Find an aligned spot inside chunk. Since we need to give back
4866 leading space in a chunk of at least MINSIZE, if the first
4867 calculation places us at a spot with less than MINSIZE leader,
4868 we can move to the next aligned spot -- we've allocated enough
4869 total room so that this is always possible.
4871 brk
= (char *) mem2chunk (((unsigned long) (m
+ alignment
- 1)) &
4872 - ((signed long) alignment
));
4873 if ((unsigned long) (brk
- (char *) (p
)) < MINSIZE
)
4876 newp
= (mchunkptr
) brk
;
4877 leadsize
= brk
- (char *) (p
);
4878 newsize
= chunksize (p
) - leadsize
;
4880 /* For mmapped chunks, just adjust offset */
4881 if (chunk_is_mmapped (p
))
4883 set_prev_size (newp
, prev_size (p
) + leadsize
);
4884 set_head (newp
, newsize
| IS_MMAPPED
);
4885 return chunk2mem (newp
);
4888 /* Otherwise, give back leader, use the rest */
4889 set_head (newp
, newsize
| PREV_INUSE
|
4890 (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4891 set_inuse_bit_at_offset (newp
, newsize
);
4892 set_head_size (p
, leadsize
| (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4893 _int_free (av
, p
, 1);
4896 assert (newsize
>= nb
&&
4897 (((unsigned long) (chunk2mem (p
))) % alignment
) == 0);
4900 /* Also give back spare room at the end */
4901 if (!chunk_is_mmapped (p
))
4903 size
= chunksize (p
);
4904 if ((unsigned long) (size
) > (unsigned long) (nb
+ MINSIZE
))
4906 remainder_size
= size
- nb
;
4907 remainder
= chunk_at_offset (p
, nb
);
4908 set_head (remainder
, remainder_size
| PREV_INUSE
|
4909 (av
!= &main_arena
? NON_MAIN_ARENA
: 0));
4910 set_head_size (p
, nb
);
4911 _int_free (av
, remainder
, 1);
4915 check_inuse_chunk (av
, p
);
4916 return chunk2mem (p
);
4921 ------------------------------ malloc_trim ------------------------------
4925 mtrim (mstate av
, size_t pad
)
4927 /* Ensure all blocks are consolidated. */
4928 malloc_consolidate (av
);
4930 const size_t ps
= GLRO (dl_pagesize
);
4931 int psindex
= bin_index (ps
);
4932 const size_t psm1
= ps
- 1;
4935 for (int i
= 1; i
< NBINS
; ++i
)
4936 if (i
== 1 || i
>= psindex
)
4938 mbinptr bin
= bin_at (av
, i
);
4940 for (mchunkptr p
= last (bin
); p
!= bin
; p
= p
->bk
)
4942 INTERNAL_SIZE_T size
= chunksize (p
);
4944 if (size
> psm1
+ sizeof (struct malloc_chunk
))
4946 /* See whether the chunk contains at least one unused page. */
4947 char *paligned_mem
= (char *) (((uintptr_t) p
4948 + sizeof (struct malloc_chunk
)
4951 assert ((char *) chunk2mem (p
) + 2 * CHUNK_HDR_SZ
4953 assert ((char *) p
+ size
> paligned_mem
);
4955 /* This is the size we could potentially free. */
4956 size
-= paligned_mem
- (char *) p
;
4961 /* When debugging we simulate destroying the memory
4963 memset (paligned_mem
, 0x89, size
& ~psm1
);
4965 __madvise (paligned_mem
, size
& ~psm1
, MADV_DONTNEED
);
4973 #ifndef MORECORE_CANNOT_TRIM
4974 return result
| (av
== &main_arena
? systrim (pad
, av
) : 0);
4983 __malloc_trim (size_t s
)
4987 if (!__malloc_initialized
)
4990 mstate ar_ptr
= &main_arena
;
4993 __libc_lock_lock (ar_ptr
->mutex
);
4994 result
|= mtrim (ar_ptr
, s
);
4995 __libc_lock_unlock (ar_ptr
->mutex
);
4997 ar_ptr
= ar_ptr
->next
;
4999 while (ar_ptr
!= &main_arena
);
5006 ------------------------- malloc_usable_size -------------------------
5017 p
= mem2chunk (mem
);
5019 if (chunk_is_mmapped (p
))
5020 result
= chunksize (p
) - CHUNK_HDR_SZ
;
5022 result
= memsize (p
);
5031 __malloc_usable_size (void *m
)
5035 result
= musable (m
);
5041 ------------------------------ mallinfo ------------------------------
5042 Accumulate malloc statistics for arena AV into M.
5045 int_mallinfo (mstate av
, struct mallinfo2
*m
)
5050 INTERNAL_SIZE_T avail
;
5051 INTERNAL_SIZE_T fastavail
;
5055 check_malloc_state (av
);
5057 /* Account for top */
5058 avail
= chunksize (av
->top
);
5059 nblocks
= 1; /* top always exists */
5061 /* traverse fastbins */
5065 for (i
= 0; i
< NFASTBINS
; ++i
)
5067 for (p
= fastbin (av
, i
);
5069 p
= REVEAL_PTR (p
->fd
))
5071 if (__glibc_unlikely (misaligned_chunk (p
)))
5072 malloc_printerr ("int_mallinfo(): "
5073 "unaligned fastbin chunk detected");
5075 fastavail
+= chunksize (p
);
5081 /* traverse regular bins */
5082 for (i
= 1; i
< NBINS
; ++i
)
5085 for (p
= last (b
); p
!= b
; p
= p
->bk
)
5088 avail
+= chunksize (p
);
5092 m
->smblks
+= nfastblocks
;
5093 m
->ordblks
+= nblocks
;
5094 m
->fordblks
+= avail
;
5095 m
->uordblks
+= av
->system_mem
- avail
;
5096 m
->arena
+= av
->system_mem
;
5097 m
->fsmblks
+= fastavail
;
5098 if (av
== &main_arena
)
5100 m
->hblks
= mp_
.n_mmaps
;
5101 m
->hblkhd
= mp_
.mmapped_mem
;
5103 m
->keepcost
= chunksize (av
->top
);
5109 __libc_mallinfo2 (void)
5114 if (!__malloc_initialized
)
5117 memset (&m
, 0, sizeof (m
));
5118 ar_ptr
= &main_arena
;
5121 __libc_lock_lock (ar_ptr
->mutex
);
5122 int_mallinfo (ar_ptr
, &m
);
5123 __libc_lock_unlock (ar_ptr
->mutex
);
5125 ar_ptr
= ar_ptr
->next
;
5127 while (ar_ptr
!= &main_arena
);
5131 libc_hidden_def (__libc_mallinfo2
)
5134 __libc_mallinfo (void)
5137 struct mallinfo2 m2
= __libc_mallinfo2 ();
5140 m
.ordblks
= m2
.ordblks
;
5141 m
.smblks
= m2
.smblks
;
5143 m
.hblkhd
= m2
.hblkhd
;
5144 m
.usmblks
= m2
.usmblks
;
5145 m
.fsmblks
= m2
.fsmblks
;
5146 m
.uordblks
= m2
.uordblks
;
5147 m
.fordblks
= m2
.fordblks
;
5148 m
.keepcost
= m2
.keepcost
;
5155 ------------------------------ malloc_stats ------------------------------
5159 __malloc_stats (void)
5163 unsigned int in_use_b
= mp_
.mmapped_mem
, system_b
= in_use_b
;
5165 if (!__malloc_initialized
)
5167 _IO_flockfile (stderr
);
5168 int old_flags2
= stderr
->_flags2
;
5169 stderr
->_flags2
|= _IO_FLAGS2_NOTCANCEL
;
5170 for (i
= 0, ar_ptr
= &main_arena
;; i
++)
5172 struct mallinfo2 mi
;
5174 memset (&mi
, 0, sizeof (mi
));
5175 __libc_lock_lock (ar_ptr
->mutex
);
5176 int_mallinfo (ar_ptr
, &mi
);
5177 fprintf (stderr
, "Arena %d:\n", i
);
5178 fprintf (stderr
, "system bytes = %10u\n", (unsigned int) mi
.arena
);
5179 fprintf (stderr
, "in use bytes = %10u\n", (unsigned int) mi
.uordblks
);
5180 #if MALLOC_DEBUG > 1
5182 dump_heap (heap_for_ptr (top (ar_ptr
)));
5184 system_b
+= mi
.arena
;
5185 in_use_b
+= mi
.uordblks
;
5186 __libc_lock_unlock (ar_ptr
->mutex
);
5187 ar_ptr
= ar_ptr
->next
;
5188 if (ar_ptr
== &main_arena
)
5191 fprintf (stderr
, "Total (incl. mmap):\n");
5192 fprintf (stderr
, "system bytes = %10u\n", system_b
);
5193 fprintf (stderr
, "in use bytes = %10u\n", in_use_b
);
5194 fprintf (stderr
, "max mmap regions = %10u\n", (unsigned int) mp_
.max_n_mmaps
);
5195 fprintf (stderr
, "max mmap bytes = %10lu\n",
5196 (unsigned long) mp_
.max_mmapped_mem
);
5197 stderr
->_flags2
= old_flags2
;
5198 _IO_funlockfile (stderr
);
5203 ------------------------------ mallopt ------------------------------
5205 static __always_inline
int
5206 do_set_trim_threshold (size_t value
)
5208 LIBC_PROBE (memory_mallopt_trim_threshold
, 3, value
, mp_
.trim_threshold
,
5209 mp_
.no_dyn_threshold
);
5210 mp_
.trim_threshold
= value
;
5211 mp_
.no_dyn_threshold
= 1;
5215 static __always_inline
int
5216 do_set_top_pad (size_t value
)
5218 LIBC_PROBE (memory_mallopt_top_pad
, 3, value
, mp_
.top_pad
,
5219 mp_
.no_dyn_threshold
);
5220 mp_
.top_pad
= value
;
5221 mp_
.no_dyn_threshold
= 1;
5225 static __always_inline
int
5226 do_set_mmap_threshold (size_t value
)
5228 /* Forbid setting the threshold too high. */
5229 if (value
<= HEAP_MAX_SIZE
/ 2)
5231 LIBC_PROBE (memory_mallopt_mmap_threshold
, 3, value
, mp_
.mmap_threshold
,
5232 mp_
.no_dyn_threshold
);
5233 mp_
.mmap_threshold
= value
;
5234 mp_
.no_dyn_threshold
= 1;
5240 static __always_inline
int
5241 do_set_mmaps_max (int32_t value
)
5243 LIBC_PROBE (memory_mallopt_mmap_max
, 3, value
, mp_
.n_mmaps_max
,
5244 mp_
.no_dyn_threshold
);
5245 mp_
.n_mmaps_max
= value
;
5246 mp_
.no_dyn_threshold
= 1;
5250 static __always_inline
int
5251 do_set_mallopt_check (int32_t value
)
5256 static __always_inline
int
5257 do_set_perturb_byte (int32_t value
)
5259 LIBC_PROBE (memory_mallopt_perturb
, 2, value
, perturb_byte
);
5260 perturb_byte
= value
;
5264 static __always_inline
int
5265 do_set_arena_test (size_t value
)
5267 LIBC_PROBE (memory_mallopt_arena_test
, 2, value
, mp_
.arena_test
);
5268 mp_
.arena_test
= value
;
5272 static __always_inline
int
5273 do_set_arena_max (size_t value
)
5275 LIBC_PROBE (memory_mallopt_arena_max
, 2, value
, mp_
.arena_max
);
5276 mp_
.arena_max
= value
;
5281 static __always_inline
int
5282 do_set_tcache_max (size_t value
)
5284 if (value
<= MAX_TCACHE_SIZE
)
5286 LIBC_PROBE (memory_tunable_tcache_max_bytes
, 2, value
, mp_
.tcache_max_bytes
);
5287 mp_
.tcache_max_bytes
= value
;
5288 mp_
.tcache_bins
= csize2tidx (request2size(value
)) + 1;
5294 static __always_inline
int
5295 do_set_tcache_count (size_t value
)
5297 if (value
<= MAX_TCACHE_COUNT
)
5299 LIBC_PROBE (memory_tunable_tcache_count
, 2, value
, mp_
.tcache_count
);
5300 mp_
.tcache_count
= value
;
5306 static __always_inline
int
5307 do_set_tcache_unsorted_limit (size_t value
)
5309 LIBC_PROBE (memory_tunable_tcache_unsorted_limit
, 2, value
, mp_
.tcache_unsorted_limit
);
5310 mp_
.tcache_unsorted_limit
= value
;
5317 do_set_mxfast (size_t value
)
5319 if (value
<= MAX_FAST_SIZE
)
5321 LIBC_PROBE (memory_mallopt_mxfast
, 2, value
, get_max_fast ());
5322 set_max_fast (value
);
5329 __libc_mallopt (int param_number
, int value
)
5331 mstate av
= &main_arena
;
5334 if (!__malloc_initialized
)
5336 __libc_lock_lock (av
->mutex
);
5338 LIBC_PROBE (memory_mallopt
, 2, param_number
, value
);
5340 /* We must consolidate main arena before changing max_fast
5341 (see definition of set_max_fast). */
5342 malloc_consolidate (av
);
5344 /* Many of these helper functions take a size_t. We do not worry
5345 about overflow here, because negative int values will wrap to
5346 very large size_t values and the helpers have sufficient range
5347 checking for such conversions. Many of these helpers are also
5348 used by the tunables macros in arena.c. */
5350 switch (param_number
)
5353 res
= do_set_mxfast (value
);
5356 case M_TRIM_THRESHOLD
:
5357 res
= do_set_trim_threshold (value
);
5361 res
= do_set_top_pad (value
);
5364 case M_MMAP_THRESHOLD
:
5365 res
= do_set_mmap_threshold (value
);
5369 res
= do_set_mmaps_max (value
);
5372 case M_CHECK_ACTION
:
5373 res
= do_set_mallopt_check (value
);
5377 res
= do_set_perturb_byte (value
);
5382 res
= do_set_arena_test (value
);
5387 res
= do_set_arena_max (value
);
5390 __libc_lock_unlock (av
->mutex
);
5393 libc_hidden_def (__libc_mallopt
)
5397 -------------------- Alternative MORECORE functions --------------------
5402 General Requirements for MORECORE.
5404 The MORECORE function must have the following properties:
5406 If MORECORE_CONTIGUOUS is false:
5408 * MORECORE must allocate in multiples of pagesize. It will
5409 only be called with arguments that are multiples of pagesize.
5411 * MORECORE(0) must return an address that is at least
5412 MALLOC_ALIGNMENT aligned. (Page-aligning always suffices.)
5414 else (i.e. If MORECORE_CONTIGUOUS is true):
5416 * Consecutive calls to MORECORE with positive arguments
5417 return increasing addresses, indicating that space has been
5418 contiguously extended.
5420 * MORECORE need not allocate in multiples of pagesize.
5421 Calls to MORECORE need not have args of multiples of pagesize.
5423 * MORECORE need not page-align.
5427 * MORECORE may allocate more memory than requested. (Or even less,
5428 but this will generally result in a malloc failure.)
5430 * MORECORE must not allocate memory when given argument zero, but
5431 instead return one past the end address of memory from previous
5432 nonzero call. This malloc does NOT call MORECORE(0)
5433 until at least one call with positive arguments is made, so
5434 the initial value returned is not important.
5436 * Even though consecutive calls to MORECORE need not return contiguous
5437 addresses, it must be OK for malloc'ed chunks to span multiple
5438 regions in those cases where they do happen to be contiguous.
5440 * MORECORE need not handle negative arguments -- it may instead
5441 just return MORECORE_FAILURE when given negative arguments.
5442 Negative arguments are always multiples of pagesize. MORECORE
5443 must not misinterpret negative args as large positive unsigned
5444 args. You can suppress all such calls from even occurring by defining
5445 MORECORE_CANNOT_TRIM,
5447 There is some variation across systems about the type of the
5448 argument to sbrk/MORECORE. If size_t is unsigned, then it cannot
5449 actually be size_t, because sbrk supports negative args, so it is
5450 normally the signed type of the same width as size_t (sometimes
5451 declared as "intptr_t", and sometimes "ptrdiff_t"). It doesn't much
5452 matter though. Internally, we use "long" as arguments, which should
5453 work across all reasonable possibilities.
5455 Additionally, if MORECORE ever returns failure for a positive
5456 request, then mmap is used as a noncontiguous system allocator. This
5457 is a useful backup strategy for systems with holes in address spaces
5458 -- in this case sbrk cannot contiguously expand the heap, but mmap
5459 may be able to map noncontiguous space.
5461 If you'd like mmap to ALWAYS be used, you can define MORECORE to be
5462 a function that always returns MORECORE_FAILURE.
5464 If you are using this malloc with something other than sbrk (or its
5465 emulation) to supply memory regions, you probably want to set
5466 MORECORE_CONTIGUOUS as false. As an example, here is a custom
5467 allocator kindly contributed for pre-OSX macOS. It uses virtually
5468 but not necessarily physically contiguous non-paged memory (locked
5469 in, present and won't get swapped out). You can use it by
5470 uncommenting this section, adding some #includes, and setting up the
5471 appropriate defines above:
5473 *#define MORECORE osMoreCore
5474 *#define MORECORE_CONTIGUOUS 0
5476 There is also a shutdown routine that should somehow be called for
5477 cleanup upon program exit.
5479 *#define MAX_POOL_ENTRIES 100
5480 *#define MINIMUM_MORECORE_SIZE (64 * 1024)
5481 static int next_os_pool;
5482 void *our_os_pools[MAX_POOL_ENTRIES];
5484 void *osMoreCore(int size)
5487 static void *sbrk_top = 0;
5491 if (size < MINIMUM_MORECORE_SIZE)
5492 size = MINIMUM_MORECORE_SIZE;
5493 if (CurrentExecutionLevel() == kTaskLevel)
5494 ptr = PoolAllocateResident(size + RM_PAGE_SIZE, 0);
5497 return (void *) MORECORE_FAILURE;
5499 // save ptrs so they can be freed during cleanup
5500 our_os_pools[next_os_pool] = ptr;
5502 ptr = (void *) ((((unsigned long) ptr) + RM_PAGE_MASK) & ~RM_PAGE_MASK);
5503 sbrk_top = (char *) ptr + size;
5508 // we don't currently support shrink behavior
5509 return (void *) MORECORE_FAILURE;
5517 // cleanup any allocated memory pools
5518 // called as last thing before shutting down driver
5520 void osCleanupMem(void)
5524 for (ptr = our_os_pools; ptr < &our_os_pools[MAX_POOL_ENTRIES]; ptr++)
5527 PoolDeallocate(*ptr);
5537 extern char **__libc_argv attribute_hidden
;
5540 malloc_printerr (const char *str
)
5543 __libc_message (do_abort
, "%s\n", str
);
5547 __builtin_unreachable ();
5551 /* We need a wrapper function for one of the additions of POSIX. */
5553 __posix_memalign (void **memptr
, size_t alignment
, size_t size
)
5557 if (!__malloc_initialized
)
5560 /* Test whether the SIZE argument is valid. It must be a power of
5561 two multiple of sizeof (void *). */
5562 if (alignment
% sizeof (void *) != 0
5563 || !powerof2 (alignment
/ sizeof (void *))
5568 void *address
= RETURN_ADDRESS (0);
5569 mem
= _mid_memalign (alignment
, size
, address
);
5579 weak_alias (__posix_memalign
, posix_memalign
)
5584 __malloc_info (int options
, FILE *fp
)
5586 /* For now, at least. */
5591 size_t total_nblocks
= 0;
5592 size_t total_nfastblocks
= 0;
5593 size_t total_avail
= 0;
5594 size_t total_fastavail
= 0;
5595 size_t total_system
= 0;
5596 size_t total_max_system
= 0;
5597 size_t total_aspace
= 0;
5598 size_t total_aspace_mprotect
= 0;
5602 if (!__malloc_initialized
)
5605 fputs ("<malloc version=\"1\">\n", fp
);
5607 /* Iterate over all arenas currently in use. */
5608 mstate ar_ptr
= &main_arena
;
5611 fprintf (fp
, "<heap nr=\"%d\">\n<sizes>\n", n
++);
5614 size_t nfastblocks
= 0;
5616 size_t fastavail
= 0;
5623 } sizes
[NFASTBINS
+ NBINS
- 1];
5624 #define nsizes (sizeof (sizes) / sizeof (sizes[0]))
5626 __libc_lock_lock (ar_ptr
->mutex
);
5628 /* Account for top chunk. The top-most available chunk is
5629 treated specially and is never in any bin. See "initial_top"
5631 avail
= chunksize (ar_ptr
->top
);
5632 nblocks
= 1; /* Top always exists. */
5634 for (size_t i
= 0; i
< NFASTBINS
; ++i
)
5636 mchunkptr p
= fastbin (ar_ptr
, i
);
5639 size_t nthissize
= 0;
5640 size_t thissize
= chunksize (p
);
5644 if (__glibc_unlikely (misaligned_chunk (p
)))
5645 malloc_printerr ("__malloc_info(): "
5646 "unaligned fastbin chunk detected");
5648 p
= REVEAL_PTR (p
->fd
);
5651 fastavail
+= nthissize
* thissize
;
5652 nfastblocks
+= nthissize
;
5653 sizes
[i
].from
= thissize
- (MALLOC_ALIGNMENT
- 1);
5654 sizes
[i
].to
= thissize
;
5655 sizes
[i
].count
= nthissize
;
5658 sizes
[i
].from
= sizes
[i
].to
= sizes
[i
].count
= 0;
5660 sizes
[i
].total
= sizes
[i
].count
* sizes
[i
].to
;
5665 struct malloc_chunk
*r
;
5667 for (size_t i
= 1; i
< NBINS
; ++i
)
5669 bin
= bin_at (ar_ptr
, i
);
5671 sizes
[NFASTBINS
- 1 + i
].from
= ~((size_t) 0);
5672 sizes
[NFASTBINS
- 1 + i
].to
= sizes
[NFASTBINS
- 1 + i
].total
5673 = sizes
[NFASTBINS
- 1 + i
].count
= 0;
5678 size_t r_size
= chunksize_nomask (r
);
5679 ++sizes
[NFASTBINS
- 1 + i
].count
;
5680 sizes
[NFASTBINS
- 1 + i
].total
+= r_size
;
5681 sizes
[NFASTBINS
- 1 + i
].from
5682 = MIN (sizes
[NFASTBINS
- 1 + i
].from
, r_size
);
5683 sizes
[NFASTBINS
- 1 + i
].to
= MAX (sizes
[NFASTBINS
- 1 + i
].to
,
5689 if (sizes
[NFASTBINS
- 1 + i
].count
== 0)
5690 sizes
[NFASTBINS
- 1 + i
].from
= 0;
5691 nblocks
+= sizes
[NFASTBINS
- 1 + i
].count
;
5692 avail
+= sizes
[NFASTBINS
- 1 + i
].total
;
5695 size_t heap_size
= 0;
5696 size_t heap_mprotect_size
= 0;
5697 size_t heap_count
= 0;
5698 if (ar_ptr
!= &main_arena
)
5700 /* Iterate over the arena heaps from back to front. */
5701 heap_info
*heap
= heap_for_ptr (top (ar_ptr
));
5704 heap_size
+= heap
->size
;
5705 heap_mprotect_size
+= heap
->mprotect_size
;
5709 while (heap
!= NULL
);
5712 __libc_lock_unlock (ar_ptr
->mutex
);
5714 total_nfastblocks
+= nfastblocks
;
5715 total_fastavail
+= fastavail
;
5717 total_nblocks
+= nblocks
;
5718 total_avail
+= avail
;
5720 for (size_t i
= 0; i
< nsizes
; ++i
)
5721 if (sizes
[i
].count
!= 0 && i
!= NFASTBINS
)
5723 <size from=\"%zu\" to=\"%zu\" total=\"%zu\" count=\"%zu\"/>\n",
5724 sizes
[i
].from
, sizes
[i
].to
, sizes
[i
].total
, sizes
[i
].count
);
5726 if (sizes
[NFASTBINS
].count
!= 0)
5728 <unsorted from=\"%zu\" to=\"%zu\" total=\"%zu\" count=\"%zu\"/>\n",
5729 sizes
[NFASTBINS
].from
, sizes
[NFASTBINS
].to
,
5730 sizes
[NFASTBINS
].total
, sizes
[NFASTBINS
].count
);
5732 total_system
+= ar_ptr
->system_mem
;
5733 total_max_system
+= ar_ptr
->max_system_mem
;
5736 "</sizes>\n<total type=\"fast\" count=\"%zu\" size=\"%zu\"/>\n"
5737 "<total type=\"rest\" count=\"%zu\" size=\"%zu\"/>\n"
5738 "<system type=\"current\" size=\"%zu\"/>\n"
5739 "<system type=\"max\" size=\"%zu\"/>\n",
5740 nfastblocks
, fastavail
, nblocks
, avail
,
5741 ar_ptr
->system_mem
, ar_ptr
->max_system_mem
);
5743 if (ar_ptr
!= &main_arena
)
5746 "<aspace type=\"total\" size=\"%zu\"/>\n"
5747 "<aspace type=\"mprotect\" size=\"%zu\"/>\n"
5748 "<aspace type=\"subheaps\" size=\"%zu\"/>\n",
5749 heap_size
, heap_mprotect_size
, heap_count
);
5750 total_aspace
+= heap_size
;
5751 total_aspace_mprotect
+= heap_mprotect_size
;
5756 "<aspace type=\"total\" size=\"%zu\"/>\n"
5757 "<aspace type=\"mprotect\" size=\"%zu\"/>\n",
5758 ar_ptr
->system_mem
, ar_ptr
->system_mem
);
5759 total_aspace
+= ar_ptr
->system_mem
;
5760 total_aspace_mprotect
+= ar_ptr
->system_mem
;
5763 fputs ("</heap>\n", fp
);
5764 ar_ptr
= ar_ptr
->next
;
5766 while (ar_ptr
!= &main_arena
);
5769 "<total type=\"fast\" count=\"%zu\" size=\"%zu\"/>\n"
5770 "<total type=\"rest\" count=\"%zu\" size=\"%zu\"/>\n"
5771 "<total type=\"mmap\" count=\"%d\" size=\"%zu\"/>\n"
5772 "<system type=\"current\" size=\"%zu\"/>\n"
5773 "<system type=\"max\" size=\"%zu\"/>\n"
5774 "<aspace type=\"total\" size=\"%zu\"/>\n"
5775 "<aspace type=\"mprotect\" size=\"%zu\"/>\n"
5777 total_nfastblocks
, total_fastavail
, total_nblocks
, total_avail
,
5778 mp_
.n_mmaps
, mp_
.mmapped_mem
,
5779 total_system
, total_max_system
,
5780 total_aspace
, total_aspace_mprotect
);
5785 weak_alias (__malloc_info
, malloc_info
)
5787 strong_alias (__libc_calloc
, __calloc
) weak_alias (__libc_calloc
, calloc
)
5788 strong_alias (__libc_free
, __free
) strong_alias (__libc_free
, free
)
5789 strong_alias (__libc_malloc
, __malloc
) strong_alias (__libc_malloc
, malloc
)
5790 strong_alias (__libc_memalign
, __memalign
)
5791 weak_alias (__libc_memalign
, memalign
)
5792 strong_alias (__libc_realloc
, __realloc
) strong_alias (__libc_realloc
, realloc
)
5793 strong_alias (__libc_valloc
, __valloc
) weak_alias (__libc_valloc
, valloc
)
5794 strong_alias (__libc_pvalloc
, __pvalloc
) weak_alias (__libc_pvalloc
, pvalloc
)
5795 strong_alias (__libc_mallinfo
, __mallinfo
)
5796 weak_alias (__libc_mallinfo
, mallinfo
)
5797 strong_alias (__libc_mallinfo2
, __mallinfo2
)
5798 weak_alias (__libc_mallinfo2
, mallinfo2
)
5799 strong_alias (__libc_mallopt
, __mallopt
) weak_alias (__libc_mallopt
, mallopt
)
5801 weak_alias (__malloc_stats
, malloc_stats
)
5802 weak_alias (__malloc_usable_size
, malloc_usable_size
)
5803 weak_alias (__malloc_trim
, malloc_trim
)
5806 #if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_26)
5807 compat_symbol (libc
, __libc_free
, cfree
, GLIBC_2_0
);
5810 /* ------------------------------------------------------------
5813 [see ftp://g.oswego.edu/pub/misc/malloc.c for the history of dlmalloc]