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pjs/xpcom/build/malloc.c

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r=waterson sr=cls Adding a newer version of the libc malloc.c from the author. It is compiled switched in via --enable-lea.
2001-02-06 07:52:19 +03:00
#define USE_MALLOC_LOCK
#define DEFAULT_TRIM_THRESHOLD (256 * 1024)
/* ---------- To make a malloc.h, start cutting here ------------ */
/*
****************************************************************
* THIS IS A PRERELEASE. It has not yet been tested adequately. *
* If you use it, please send back comments, suggestions, *
* performance reports, etc. *
****************************************************************
*/
/*
A version (aka dlmalloc) of malloc/free/realloc written by Doug
Lea and released to the public domain. Use this code without
permission or acknowledgement in any way you wish. Send questions,
comments, complaints, performance data, etc to dl@cs.oswego.edu
* VERSION 2.7.0pre7 Wed Jan 10 13:33:01 2001 Doug Lea (dl at gee)
Note: There may be an updated version of this malloc obtainable at
ftp://gee.cs.oswego.edu/pub/misc/malloc.c
Check before installing!
* Quickstart
This library is all in one file to simplify the most common usage:
ftp it, compile it (-O), and link it into another program. All
of the compile-time options default to reasonable values for use on
most unix platforms. Compile -DWIN32 for reasonable defaults on windows.
You might later want to step through various compile options.
* Why use this malloc?
This is not the fastest, most space-conserving, most portable, or
most tunable malloc ever written. However it is among the fastest
while also being among the most space-conserving, portable and tunable.
Consistent balance across these factors results in a good general-purpose
allocator for malloc-intensive programs.
The main properties of the algorithms are:
* For large (>= 512 bytes) requests, it is a pure best-fit allocator,
with ties normally decided via FIFO (i.e. least recently used).
* For small (<= 64 bytes by default) requests, it is a caching
allocator, that maintains pools of quickly recycled chunks.
* In between, and for combinations of large and small requests, it does
the best it can trying to meet both goals at once.
Compared to 2.6.X versions, this version is generally faster,
especially for programs that allocate and free many small chunks.
For a longer but slightly out of date high-level description, see
http://gee.cs.oswego.edu/dl/html/malloc.html
You may already by default be using a c library containing a malloc
that is somehow based on some version of this malloc (for example in
linux). You might still want to use the one in this file in order to
customize settings or to avoid overheads associated with library
versions.
* Synopsis of public routines
(Much fuller descriptions are contained in the program documentation below.)
malloc(size_t n);
Return a pointer to a newly allocated chunk of at least n bytes, or null
if no space is available.
free(Void_t* p);
Release the chunk of memory pointed to by p, or no effect if p is null.
realloc(Void_t* p, size_t n);
Return a pointer to a chunk of size n that contains the same data
as does chunk p up to the minimum of (n, p's size) bytes, or null
if no space is available. The returned pointer may or may not be
the same as p. If p is null, equivalent to malloc. Unless the
#define REALLOC_ZERO_BYTES_FREES below is set, realloc with a
size argument of zero (re)allocates a minimum-sized chunk.
memalign(size_t alignment, size_t n);
Return a pointer to a newly allocated chunk of n bytes, aligned
in accord with the alignment argument, which must be a power of
two.
valloc(size_t n);
Equivalent to memalign(pagesize, n), where pagesize is the page
size of the system (or as near to this as can be figured out from
all the includes/defines below.)
pvalloc(size_t n);
Equivalent to valloc(minimum-page-that-holds(n)), that is,
round up n to nearest pagesize.
calloc(size_t unit, size_t quantity);
Returns a pointer to quantity * unit bytes, with all locations
set to zero.
cfree(Void_t* p);
Equivalent to free(p).
malloc_trim(size_t pad);
Release all but pad bytes of freed top-most memory back
to the system. Return 1 if successful, else 0.
malloc_usable_size(Void_t* p);
Report the number usable allocated bytes associated with allocated
chunk p. This may or may not report more bytes than were requested,
due to alignment and minimum size constraints.
malloc_stats();
Prints brief summary statistics on stderr.
mallinfo()
Returns (by copy) a struct containing various summary statistics.
mallopt(int parameter_number, int parameter_value)
Changes one of the tunable parameters described below. Returns
1 if successful in changing the parameter, else 0.
* Vital statistics:
Assumed pointer representation: 4 or 8 bytes
(Thanks to Wolfram Gloger for contributing most of the
changes supporting dual 4/8.)
Assumed size_t representation: 4 or 8 bytes
Note that size_t is allowed to be 4 bytes even if pointers are 8.
You can adjust this by defining INTERNAL_SIZE_T
Alignment: 2 * sizeof(size_t)
(i.e., 8 byte alignment with 4byte size_t). This suffices for
nearly all current machines and C compilers. However, you can
define MALLOC_ALIGNMENT to be wider than this if necessary.
Minimum overhead per allocated chunk: 4 or 8 bytes
Each malloced chunk has a hidden word of overhead holding size
and status information.
Minimum allocated size: 4-byte ptrs: 16 bytes (including 4 overhead)
8-byte ptrs: 24/32 bytes (including, 4/8 overhead)
When a chunk is freed, 12 (for 4byte ptrs) or 20 (for 8 byte
ptrs but 4 byte size) or 24 (for 8/8) additional bytes are
needed; 4 (8) for a trailing size field and 8 (16) bytes for
free list pointers. Thus, the minimum allocatable size is
16/24/32 bytes.
Even a request for zero bytes (i.e., malloc(0)) returns a
pointer to something of the minimum allocatable size.
The maximum overhead wastage (i.e., number of extra bytes
allocated than were requested in malloc) is less than or equal
to the minimum size, except for requests >= mmap_threshold that
are serviced via mmap(), where the worst case wastage is 2 *
sizeof(size_t) bytes plus the remainder from a system page (the
minimal mmap unit); typically 4096 bytes.
Maximum allocated size: 4-byte size_t: 2^31 minus about two pages
8-byte size_t: 2^63 minus about two pages
It is assumed that (possibly signed) size_t values suffice
to represent chunk sizes. `Possibly signed' is due to the fact
that `size_t' may be defined on a system as either a signed or
an unsigned type. The ISO C standard says that it must be
unsigned, but a few systems are known not to adhere to this.
Additionally, even when size_t is unsigned, sbrk (which is by
default used to obtain memory from system) accepts signed
arguments, and may not be able to handle size_t-wide arguments
with negative sign bit. To be conservative, values that would
appear as negative after accounting for overhead and alignment
are rejected.
Requests for sizes outside this range will perform an optional
failure action and then return null. (Requests may also
also fail because a system is out of memory.)
Thread-safety: NOT thread-safe unless USE_MALLOC_LOCK defined
When USE_MALLOC_LOCK is defined, wrappers are created to
surround every public call with either a pthread mutex or
a win32 critical section (depending on WIN32). This is not
especially fast, and can be a major bottleneck in programs with
many threads. It is designed only to provide minimal protection
in concurrent environments, and to provide a basis for
extensions. If you are using malloc in a concurrent program,
you would be far better off obtaining ptmalloc, which is
derived from a version of this malloc, and is well-tuned for
concurrent programs. (See http://www.malloc.de)
Compliance: I believe it is compliant with the 1997 Single Unix Specification
(See http://www.opennc.org). Probably other standards as well.
* Limitations
Here are some features that are NOT currently supported
* No automated mechanism for fully checking that all accesses
to malloced memory stay within their bounds. However, there
are several add-ons and adaptations of this or other mallocs
available that do this.
* No support for compaction.
* Synopsis of compile-time options:
People have reported using previous versions of this malloc on all
versions of Unix, sometimes by tweaking some of the defines
below. It has been tested most extensively on Solaris and
Linux. It is also reported to work on WIN32 platforms.
People also report using it in stand-alone embedded systems.
The implementation is in straight, hand-tuned ANSI C. It is not
at all modular. (Sorry!) It uses a lot of macros. To be at all
usable, this code should be compiled using an optimizing compiler
(for example gcc -O3) that can simplify expressions and control
paths. (FAQ: some macros import variables as arguments rather than
declare locals because people reported that some debuggers
otherwise get confused.)
OPTION DEFAULT VALUE
Compilation Environment options:
__STD_C derived from C compiler defines
WIN32 NOT defined
HAVE_MEMCPY defined
USE_MEMCPY 1 if HAVE_MEMCPY is defined
HAVE_MMAP defined as 1
MMAP_AS_MORECORE_SIZE (1024 * 1024)
HAVE_MREMAP defined as 0 unless linux defined
malloc_getpagesize derived from system #includes, or 4096 if not
HAVE_USR_INCLUDE_MALLOC_H NOT defined
LACKS_UNISTD_H NOT defined unless WIN32
LACKS_SYS_PARAM_H NOT defined unless WIN32
LACKS_SYS_MMAN_H NOT defined unless WIN32
Changing default word sizes:
INTERNAL_SIZE_T size_t
MALLOC_ALIGNMENT 2 * sizeof(INTERNAL_SIZE_T)
Configuration and functionality options:
USE_DL_PREFIX NOT defined
USE_PUBLIC_MALLOC_WRAPPERS NOT defined
USE_MALLOC_LOCK NOT defined
DEBUG NOT defined
REALLOC_ZERO_BYTES_FREES NOT defined
MALLOC_FAILURE_ACTION errno = ENOMEM, if __STD_C defined, else no-op
TRIM_FASTBINS 0
Options for customizing MORECORE:
MORECORE sbrk
MORECORE_CONTIGUOUS 1
Tuning options that are also dynamically changeable via mallopt:
DEFAULT_MXFAST 64
DEFAULT_TRIM_THRESHOLD 128 * 1024
DEFAULT_TOP_PAD 0
DEFAULT_MMAP_THRESHOLD 128 * 1024
DEFAULT_MMAP_MAX 256
There are several other #defined constants and macros that you
probably don't want to touch unless you are extending or adapting malloc.
*/
Split private xpcom defines into separate header. Bug #210409 r=dougt
2003-07-04 00:55:23 +04:00
#include "xpcom-private.h"
r=waterson sr=cls Adding a newer version of the libc malloc.c from the author. It is compiled switched in via --enable-lea.
2001-02-06 07:52:19 +03:00
/*
WIN32 sets up defaults for MS environment and compilers.
Otherwise defaults are for unix.
*/
/* #define WIN32 */
#ifdef WIN32
#include <windows.h>
/* Win32 doesn't supply or need the following headers */
#define LACKS_UNISTD_H
#define LACKS_SYS_PARAM_H
#define LACKS_SYS_MMAN_H
/* Use the supplied emulation of sbrk */
#define MORECORE sbrk
#define MORECORE_CONTIGUOUS 1
#define MORECORE_FAILURE ((void*)(-1))
/* Use the supplied emulation mmap, munmap */
#define HAVE_MMAP 1
#define MUNMAP_FAILURE (-1)
/* These values don't really matter in windows mmap emulation */
#define MAP_PRIVATE 1
#define MAP_ANONYMOUS 2
#define PROT_READ 1
#define PROT_WRITE 2
/* Emulation functions defined at the end of this file */
/* If USE_MALLOC_LOCK, use supplied critical-section-based lock functions */
#ifdef USE_MALLOC_LOCK
static int slwait(int *sl);
static int slrelease(int *sl);
#endif
static long getpagesize(void);
static long getregionsize(void);
static void *sbrk(long size);
static void *mmap(void *ptr, long size, long prot, long type, long handle, long arg);
static long munmap(void *ptr, long size);
static void vminfo (unsigned long *free, unsigned long *reserved, unsigned long *committed);
static int cpuinfo (int whole, unsigned long *kernel, unsigned long *user);
#endif
/*
__STD_C should be nonzero if using ANSI-standard C compiler, a C++
compiler, or a C compiler sufficiently close to ANSI to get away
with it.
*/
#ifndef __STD_C
#ifdef __STDC__
#define __STD_C 1
#else
#if __cplusplus
#define __STD_C 1
#else
#define __STD_C 0
#endif /*__cplusplus*/
#endif /*__STDC__*/
#endif /*__STD_C*/
/*
Void_t* is the pointer type that malloc should say it returns
*/
#ifndef Void_t
#if (__STD_C || defined(WIN32))
#define Void_t void
#else
#define Void_t char
#endif
#endif /*Void_t*/
#if __STD_C
#include <stddef.h> /* for size_t */
#else
#include <sys/types.h>
#endif
#ifdef __cplusplus
extern "C" {
#endif
/* define LACKS_UNISTD_H if your system does not have a <unistd.h>. */
/* #define LACKS_UNISTD_H */
#ifndef LACKS_UNISTD_H
#include <unistd.h>
#endif
/* define LACKS_SYS_PARAM_H if your system does not have a <sys/param.h>. */
/* #define LACKS_SYS_PARAM_H */
#include <stdio.h> /* needed for malloc_stats */
#include <errno.h> /* needed for optional MALLOC_FAILURE_ACTION */
/*
Debugging:
Because freed chunks may be overwritten with bookkeeping fields, this
malloc will often die when freed memory is overwritten by user
programs. This can be very effective (albeit in an annoying way)
in helping track down dangling pointers.
If you compile with -DDEBUG, a number of assertion checks are
enabled that will catch more memory errors. You probably won't be
able to make much sense of the actual assertion errors, but they
should help you locate incorrectly overwritten memory. The
checking is fairly extensive, and will slow down execution
noticeably. Calling malloc_stats or mallinfo with DEBUG set will
attempt to check every non-mmapped allocated and free chunk in the
course of computing the summmaries. (By nature, mmapped regions
cannot be checked very much automatically.)
Setting DEBUG may also be helpful if you are trying to modify
this code. The assertions in the check routines spell out in more
detail the assumptions and invariants underlying the algorithms.
*/
#if DEBUG
#include <assert.h>
#else
#define assert(x) ((void)0)
#endif
/*
INTERNAL_SIZE_T is the word-size used for internal bookkeeping
of chunk sizes.
The default version is the same as size_t.
While not strictly necessary, it is best to define this as an
unsigned type, even if size_t is a signed type. This may avoid some
artificial size limitations on some systems.
On a 64-bit machine, you may be able to reduce malloc overhead by
defining INTERNAL_SIZE_T to be a 32 bit `unsigned int' at the
expense of not being able to handle more than 2^32 of malloced
space. If this limitation is acceptable, you are encouraged to set
this unless you are on a platform requiring 16byte alignments. In
this case the alignment requirements turn out to negate any
potential advantages of decreasing size_t word size.
Note to implementors: To deal with all this, comparisons and
difference computations among INTERNAL_SIZE_Ts should normally cast
INTERNAL_SIZE_T's to long or unsigned long, as appropriate, being
aware of the fact that casting an unsigned int to a wider long does not
sign-extend. (This also makes checking for negative numbers awkward.)
*/
#ifndef INTERNAL_SIZE_T
#define INTERNAL_SIZE_T size_t
#endif
/* The corresponding word size */
#define SIZE_SZ (sizeof(INTERNAL_SIZE_T))
/*
MALLOC_ALIGNMENT is the minimum alignment for malloc'ed chunks.
It must be a power of two at least 2 * SIZE_SZ, even on machines
for which smaller alignments would suffice. It may be defined as
larger than this though. (Note however that code and data structures
are optimized for the case of 8-byte alignment.)
*/
/* #define MALLOC_ALIGNMENT 16 */
#ifndef MALLOC_ALIGNMENT
#define MALLOC_ALIGNMENT (2 * SIZE_SZ)
#endif
/* The corresponding bit mask value */
#define MALLOC_ALIGN_MASK (MALLOC_ALIGNMENT - 1)
/*
REALLOC_ZERO_BYTES_FREES should be set if a call to
realloc with zero bytes should be the same as a call to free.
Some people think it should. Otherwise, since this malloc
returns a unique pointer for malloc(0), so does realloc(p, 0).
*/
/* #define REALLOC_ZERO_BYTES_FREES */
/*
USE_DL_PREFIX will prefix all public routines with the string 'dl'.
This is necessary when you only want to use this malloc in one part
of a program, using your regular system malloc elsewhere.
*/
/* #define USE_DL_PREFIX */
/*
USE_MALLOC_LOCK causes wrapper functions to surround each
callable routine with pthread mutex lock/unlock.
USE_MALLOC_LOCK forces USE_PUBLIC_MALLOC_WRAPPERS to be defined
*/
/* #define USE_MALLOC_LOCK */
/*
If USE_PUBLIC_MALLOC_WRAPPERS is defined, every public routine is
actually a wrapper function that first calls MALLOC_PREACTION, then
calls the internal routine, and follows it with
MALLOC_POSTACTION. This is needed for locking, but you can also use
this, without USE_MALLOC_LOCK, for purposes of interception,
instrumentation, etc. It is a sad fact that using wrappers often
noticeably degrades performance of malloc-intensive programs.
*/
#ifdef USE_MALLOC_LOCK
#define USE_PUBLIC_MALLOC_WRAPPERS
#else
/* #define USE_PUBLIC_MALLOC_WRAPPERS */
#endif
/*
HAVE_MEMCPY should be defined if you are not otherwise using
ANSI STD C, but still have memcpy and memset in your C library
and want to use them in calloc and realloc. Otherwise simple
macro versions are defined below.
USE_MEMCPY should be defined as 1 if you actually want to
have memset and memcpy called. People report that the macro
versions are faster than libc versions on some systems.
Even if USE_MEMCPY is set to 1, loops to copy/clear small chunks
(of <= 36 bytes) are manually unrolled in realloc and calloc.
*/
#define HAVE_MEMCPY
#ifndef USE_MEMCPY
#ifdef HAVE_MEMCPY
#define USE_MEMCPY 1
#else
#define USE_MEMCPY 0
#endif
#endif
#if (__STD_C || defined(HAVE_MEMCPY))
#ifdef WIN32
/*
On Win32 platforms, 'memset()' and 'memcpy()' are already declared in
'windows.h'
*/
#else
#if __STD_C
void* memset(void*, int, size_t);
void* memcpy(void*, const void*, size_t);
void* memmove(void*, const void*, size_t);
#else
Void_t* memset();
Void_t* memcpy();
Void_t* memmove();
#endif
#endif
#endif
/*
MALLOC_FAILURE_ACTION is the action to take before "return 0" when
malloc fails to be able to return memory, either because memory is
exhausted or because of illegal arguments.
By default, sets errno if running on STD_C platform, else does nothing.
*/
#ifndef MALLOC_FAILURE_ACTION
#if __STD_C
#define MALLOC_FAILURE_ACTION \
errno = ENOMEM;
#else
#define MALLOC_FAILURE_ACTION
#endif
#endif
/*
Define HAVE_MMAP as true to optionally make malloc() use mmap() to
allocate very large blocks. These will be returned to the
operating system immediately after a free(). Also, if mmap
is available, it is used as a backup strategy in cases where
MORECORE fails to provide space from system.
This malloc is best tuned to work with mmap for large requests.
If you do not have mmap, allocation of very large chunks (1MB
or so) may be slower than you'd like.
*/
#ifndef HAVE_MMAP
#define HAVE_MMAP 1
#endif
/*
MMAP_AS_MORECORE_SIZE is the minimum mmap size argument to use if
sbrk fails, and mmap is used as a backup (which is done only if
HAVE_MMAP). The value must be a multiple of page size. This
backup strategy generally applies only when systems have "holes" in
address space, so sbrk cannot perform contiguous expansion, but
there is still space available on system. On systems for which
this is known to be useful (i.e. most linux kernels), this occurs
only when programs allocate huge amounts of memory. Between this,
and the fact that mmap regions tend to be limited, the size should
be large, to avoid too many mmap calls and thus avoid running out
of kernel resources.
*/
#ifndef MMAP_AS_MORECORE_SIZE
#define MMAP_AS_MORECORE_SIZE (1024 * 1024)
#endif
/*
Define HAVE_MREMAP to make realloc() use mremap() to re-allocate
large blocks. This is currently only possible on Linux with
kernel versions newer than 1.3.77.
*/
#ifndef HAVE_MREMAP
#ifdef linux
#define HAVE_MREMAP 1
#else
#define HAVE_MREMAP 0
#endif
#endif /* HAVE_MMAP */
/*
This version of malloc supports the standard SVID/XPG mallinfo
routine that returns a struct containing usage properties and
statistics. It should work on any SVID/XPG compliant system that has
a /usr/include/malloc.h defining struct mallinfo. (If you'd like to
install such a thing yourself, cut out the preliminary declarations
as described above and below and save them in a malloc.h file. But
there's no compelling reason to bother to do this.)
The main declaration needed is the mallinfo struct that is returned
(by-copy) by mallinfo(). The SVID/XPG malloinfo struct contains a
bunch of field that are not even meaningful in this version of
malloc. These fields are are instead filled by mallinfo() with
other numbers that might be of interest.
HAVE_USR_INCLUDE_MALLOC_H should be set if you have a
/usr/include/malloc.h file that includes a declaration of struct
mallinfo. If so, it is included; else an SVID2/XPG2 compliant
version is declared below. These must be precisely the same for
mallinfo() to work.
*/
/* #define HAVE_USR_INCLUDE_MALLOC_H */
#ifdef HAVE_USR_INCLUDE_MALLOC_H
#include "/usr/include/malloc.h"
#else
/* SVID2/XPG mallinfo structure */
struct mallinfo {
int arena; /* non-mmapped space allocated from system */
int ordblks; /* number of free chunks */
int smblks; /* number of fastbin blocks */
int hblks; /* number of mmapped regions */
int hblkhd; /* space in mmapped regions */
int usmblks; /* maximum total allocated space */
int fsmblks; /* space available in freed fastbin blocks */
int uordblks; /* total allocated space */
int fordblks; /* total free space */
int keepcost; /* top-most, releasable (via malloc_trim) space */
};
/* SVID2/XPG mallopt options */
#define M_MXFAST 1 /* Set maximum fastbin size */
#define M_NLBLKS 2 /* UNUSED in this malloc */
#define M_GRAIN 3 /* UNUSED in this malloc */
#define M_KEEP 4 /* UNUSED in this malloc */
#endif
/* Additional mallopt options supported in this malloc */
#ifndef M_TRIM_THRESHOLD
#define M_TRIM_THRESHOLD -1
#endif
#ifndef M_TOP_PAD
#define M_TOP_PAD -2
#endif
#ifndef M_MMAP_THRESHOLD
#define M_MMAP_THRESHOLD -3
#endif
#ifndef M_MMAP_MAX
#define M_MMAP_MAX -4
#endif
/*
MXFAST is the maximum request size used for "fastbins", special bins
that hold returned chunks without consolidating their spaces. This
enables future requests for chunks of the same size to be handled
very quickly, but can increase fragmentation, and thus increase the
overall memory footprint of a program.
This malloc manages fastbins very conservatively yet still
efficiently, so fragmentation is rarely a problem for values less
than or equal to the default. The maximum supported value of MXFAST
is 80. You wouldn't want it any higher than this anyway. Fastbins
are designed especially for use with many small structs, objects or
strings -- the default handles structs/objects/arrays with sizes up
to 8 4byte fields, or small strings representing words, tokens,
etc. Using fastbins for larger objects normally worsens
fragmentation without improving speed.
MXFAST is set in REQUEST size units. It is internally used in
chunksize units, which adds padding and alignment. You can reduce
MXFAST to 0 to disable all use of fastbins. This causes the malloc
algorithm to be a close approximation of fifo-best-fit in all cases,
not just for larger requests, but will generally cause it to be
slower.
*/
#ifndef DEFAULT_MXFAST
#define DEFAULT_MXFAST 64
#endif
/*
M_TRIM_THRESHOLD is the maximum amount of unused top-most memory
to keep before releasing via malloc_trim in free().
Automatic trimming is mainly useful in long-lived programs.
Because trimming via sbrk can be slow on some systems, and can
sometimes be wasteful (in cases where programs immediately
afterward allocate more large chunks) the value should be high
enough so that your overall system performance would improve by
releasing.
The trim threshold and the mmap control parameters (see below)
can be traded off with one another. Trimming and mmapping are
two different ways of releasing unused memory back to the
system. Between these two, it is often possible to keep
system-level demands of a long-lived program down to a bare
minimum. For example, in one test suite of sessions measuring
the XF86 X server on Linux, using a trim threshold of 128K and a
mmap threshold of 192K led to near-minimal long term resource
consumption.
If you are using this malloc in a long-lived program, it should
pay to experiment with these values. As a rough guide, you
might set to a value close to the average size of a process
(program) running on your system. Releasing this much memory
would allow such a process to run in memory. Generally, it's
worth it to tune for trimming rather tham memory mapping when a
program undergoes phases where several large chunks are
allocated and released in ways that can reuse each other's
storage, perhaps mixed with phases where there are no such
chunks at all. And in well-behaved long-lived programs,
controlling release of large blocks via trimming versus mapping
is usually faster.
However, in most programs, these parameters serve mainly as
protection against the system-level effects of carrying around
massive amounts of unneeded memory. Since frequent calls to
sbrk, mmap, and munmap otherwise degrade performance, the default
parameters are set to relatively high values that serve only as
safeguards.
The default trim value is high enough to cause trimming only in
fairly extreme (by current memory consumption standards) cases.
It must be greater than page size to have any useful effect. To
disable trimming completely, you can set to (unsigned long)(-1);
Trim settings interact with fastbin (MXFAST) settings: Unless
TRIM_FASTBINS is defined, automatic trimming never takes place upon
freeing a chunk with size less than or equal to MXFAST. Trimming is
instead delayed until subsequent freeing of larger chunks. However,
you can still force an attempted trim by calling malloc_trim.
Also, trimming is not generally possible in cases where
the main arena is obtained via mmap.
*/
#ifndef DEFAULT_TRIM_THRESHOLD
#define DEFAULT_TRIM_THRESHOLD (128 * 1024)
#endif
/*
M_TOP_PAD is the amount of extra `padding' space to allocate or
retain whenever sbrk is called. It is used in two ways internally:
* When sbrk is called to extend the top of the arena to satisfy
a new malloc request, this much padding is added to the sbrk
request.
* When malloc_trim is called automatically from free(),
it is used as the `pad' argument.
In both cases, the actual amount of padding is rounded
so that the end of the arena is always a system page boundary.
The main reason for using padding is to avoid calling sbrk so
often. Having even a small pad greatly reduces the likelihood
that nearly every malloc request during program start-up (or
after trimming) will invoke sbrk, which needlessly wastes
time.
Automatic rounding-up to page-size units is normally sufficient
to avoid measurable overhead, so the default is 0. However, in
systems where sbrk is relatively slow, it can pay to increase
this value, at the expense of carrying around more memory than
the program needs.
*/
#ifndef DEFAULT_TOP_PAD
#define DEFAULT_TOP_PAD (0)
#endif
/*
M_MMAP_THRESHOLD is the request size threshold for using mmap()
to service a request. Requests of at least this size that cannot
be allocated using already-existing space will be serviced via mmap.
(If enough normal freed space already exists it is used instead.)
Using mmap segregates relatively large chunks of memory so that
they can be individually obtained and released from the host
system. A request serviced through mmap is never reused by any
other request (at least not directly; the system may just so
happen to remap successive requests to the same locations).
Segregating space in this way has the benefit that mmapped space
can ALWAYS be individually released back to the system, which
helps keep the system level memory demands of a long-lived
program low. Mapped memory can never become `locked' between
other chunks, as can happen with normally allocated chunks, which
means that even trimming via malloc_trim would not release them.
However, it has the disadvantages that:
1. The space cannot be reclaimed, consolidated, and then
used to service later requests, as happens with normal chunks.
2. It can lead to more wastage because of mmap page alignment
requirements
3. It causes malloc performance to be more dependent on host
system memory management support routines which may vary in
implementation quality and may impose arbitrary
limitations. Generally, servicing a request via normal
malloc steps is faster than going through a system's mmap.
All together, these considerations should lead you to use mmap
only for relatively large requests.
*/
#ifndef DEFAULT_MMAP_THRESHOLD
#define DEFAULT_MMAP_THRESHOLD (128 * 1024)
#endif
/*
M_MMAP_MAX is the maximum number of requests to simultaneously
service using mmap. This parameter exists because:
1. Some systems have a limited number of internal tables for
use by mmap.
2. In most systems, overreliance on mmap can degrade overall
performance.
3. If a program allocates many large regions, it is probably
better off using normal sbrk-based allocation routines that
can reclaim and reallocate normal heap memory.
Setting to 0 disables use of mmap for servicing large requests. If
HAVE_MMAP is not set, the default value is 0, and attempts to set it
to non-zero values in mallopt will fail.
*/
#ifndef DEFAULT_MMAP_MAX
#if HAVE_MMAP
#define DEFAULT_MMAP_MAX (256)
#else
#define DEFAULT_MMAP_MAX (0)
#endif
#endif
/*
TRIM_FASTBINS controls whether free() of a very small chunk can
immediately lead to trimming. Setting to true (1) can reduce memory
footprint, but will almost always slow down (by a few percent)
programs that use a lot of small chunks.
Define this only if you are willing to give up some speed to more
aggressively reduce system-level memory footprint when releasing
memory in programs that use many small chunks. You can get
essentially the same effect by setting MXFAST to 0, but this can
lead to even greater slowdowns in programs using many small chunks.
TRIM_FASTBINS is an in-between compile-time option, that disables
only those chunks bordering topmost memory from being placed in
fastbins.
*/
#ifndef TRIM_FASTBINS
#define TRIM_FASTBINS 0
#endif
/*
MORECORE-related declarations. By default, rely on sbrk
*/
#ifdef LACKS_UNISTD_H
#if !defined(__FreeBSD__) && !defined(__OpenBSD__) && !defined(__NetBSD__)
#if __STD_C
extern Void_t* sbrk(ptrdiff_t);
#else
extern Void_t* sbrk();
#endif
#endif
#endif
/*
MORECORE is the name of the routine to call to obtain more memory
from the system. See below for general guidance on writing
alternative MORECORE functions, as well as a version for WIN32 and a
sample version for pre-OSX macos.
*/
#ifndef MORECORE
#define MORECORE sbrk
#endif
/*
MORECORE_FAILURE is the value returned upon failure of MORECORE
as well as mmap. Since it cannot be an otherwise valid memory address,
and must reflect values of standard sys calls, you probably ought not
try to redefine it.
*/
#ifndef MORECORE_FAILURE
#define MORECORE_FAILURE (-1)
#endif
/*
If MORECORE_CONTIGUOUS is true, take advantage of fact that
consecutive calls to MORECORE with positive arguments always return
contiguous increasing addresses. This is true of unix sbrk. Even
if not defined, when regions happen to be contiguous, malloc will
permit allocations spanning regions obtained from different
calls. But defining this when applicable enables some stronger
consistency checks and space efficiencies.
*/
#ifndef MORECORE_CONTIGUOUS
#define MORECORE_CONTIGUOUS 1
#endif
/*
The system page size. To the extent possible, this malloc manages
memory from the system in page-size units. Note that this value is
cached during initialization into a field of malloc_state. So even
if malloc_getpagesize is a function, it is only called once.
The following mechanics for getpagesize were adapted from bsd/gnu
getpagesize.h. If none of the system-probes here apply, a value of
4096 is used, which should be OK: If they don't apply, then using
the actual value probably doesn't impact performance.
*/
#ifndef malloc_getpagesize
#ifndef LACKS_UNISTD_H
# include <unistd.h>
#endif
# ifdef _SC_PAGESIZE /* some SVR4 systems omit an underscore */
# ifndef _SC_PAGE_SIZE
# define _SC_PAGE_SIZE _SC_PAGESIZE
# endif
# endif
# ifdef _SC_PAGE_SIZE
# define malloc_getpagesize sysconf(_SC_PAGE_SIZE)
# else
# if defined(BSD) || defined(DGUX) || defined(HAVE_GETPAGESIZE)
extern size_t getpagesize();
# define malloc_getpagesize getpagesize()
# else
# ifdef WIN32 /* use supplied emulation of getpagesize */
# define malloc_getpagesize getpagesize()
# else
# ifndef LACKS_SYS_PARAM_H
# include <sys/param.h>
# endif
# ifdef EXEC_PAGESIZE
# define malloc_getpagesize EXEC_PAGESIZE
# else
# ifdef NBPG
# ifndef CLSIZE
# define malloc_getpagesize NBPG
# else
# define malloc_getpagesize (NBPG * CLSIZE)
# endif
# else
# ifdef NBPC
# define malloc_getpagesize NBPC
# else
# ifdef PAGESIZE
# define malloc_getpagesize PAGESIZE
# else /* just guess */
# define malloc_getpagesize (4096)
# endif
# endif
# endif
# endif
# endif
# endif
# endif
#endif
/* Two-phase Name mangling */
#ifndef USE_PUBLIC_MALLOC_WRAPPERS
#define cALLOc public_cALLOc
#define fREe public_fREe
#define cFREe public_cFREe
#define mALLOc public_mALLOc
#define mEMALIGn public_mEMALIGn
#define rEALLOc public_rEALLOc
#define vALLOc public_vALLOc
#define pVALLOc public_pVALLOc
#define mALLINFo public_mALLINFo
#define mALLOPt public_mALLOPt
#define mTRIm public_mTRIm
#define mSTATs public_mSTATs
#define mUSABLe public_mUSABLe
#endif
#ifdef USE_DL_PREFIX
#define public_cALLOc dlcalloc
#define public_fREe dlfree
#define public_cFREe dlcfree
#define public_mALLOc dlmalloc
#define public_mEMALIGn dlmemalign
#define public_rEALLOc dlrealloc
#define public_vALLOc dlvalloc
#define public_pVALLOc dlpvalloc
#define public_mALLINFo dlmallinfo
#define public_mALLOPt dlmallopt
#define public_mTRIm dlmalloc_trim
#define public_mSTATs dlmalloc_stats
#define public_mUSABLe dlmalloc_usable_size
#else /* USE_DL_PREFIX */
#define public_cALLOc calloc
#define public_fREe free
#define public_cFREe cfree
#define public_mALLOc malloc
#define public_mEMALIGn memalign
#define public_rEALLOc realloc
#define public_vALLOc valloc
#define public_pVALLOc pvalloc
#define public_mALLINFo mallinfo
#define public_mALLOPt mallopt
#define public_mTRIm malloc_trim
#define public_mSTATs malloc_stats
#define public_mUSABLe malloc_usable_size
#endif /* USE_DL_PREFIX */
#if __STD_C
Void_t* public_mALLOc(size_t);
void public_fREe(Void_t*);
Void_t* public_rEALLOc(Void_t*, size_t);
Void_t* public_mEMALIGn(size_t, size_t);
Void_t* public_vALLOc(size_t);
Void_t* public_pVALLOc(size_t);
Void_t* public_cALLOc(size_t, size_t);
void public_cFREe(Void_t*);
int public_mTRIm(size_t);
size_t public_mUSABLe(Void_t*);
void public_mSTATs();
int public_mALLOPt(int, int);
struct mallinfo public_mALLINFo(void);
#else
Void_t* public_mALLOc();
void public_fREe();
Void_t* public_rEALLOc();
Void_t* public_mEMALIGn();
Void_t* public_vALLOc();
Void_t* public_pVALLOc();
Void_t* public_cALLOc();
void public_cFREe();
int public_mTRIm();
size_t public_mUSABLe();
void public_mSTATs();
int public_mALLOPt();
struct mallinfo public_mALLINFo();
#endif
#ifdef __cplusplus
}; /* end of extern "C" */
#endif
/* ---------- To make a malloc.h, end cutting here ------------ */
/* Declarations of internal utilities defined below */
#ifdef USE_PUBLIC_MALLOC_WRAPPERS
#if __STD_C
static Void_t* mALLOc(size_t);
static void fREe(Void_t*);
static Void_t* rEALLOc(Void_t*, size_t);
static Void_t* mEMALIGn(size_t, size_t);
static Void_t* vALLOc(size_t);
static Void_t* pVALLOc(size_t);
static Void_t* cALLOc(size_t, size_t);
static void cFREe(Void_t*);
static int mTRIm(size_t);
static size_t mUSABLe(Void_t*);
static void mSTATs();
static int mALLOPt(int, int);
static struct mallinfo mALLINFo(void);
#else
static Void_t* mALLOc();
static void fREe();
static Void_t* rEALLOc();
static Void_t* mEMALIGn();
static Void_t* vALLOc();
static Void_t* pVALLOc();
static Void_t* cALLOc();
static void cFREe();
static int mTRIm();
static size_t mUSABLe();
static void mSTATs();
static int mALLOPt();
static struct mallinfo mALLINFo();
#endif
#endif
/* ---------- public wrappers --------------- */
#ifdef USE_PUBLIC_MALLOC_WRAPPERS
/*
MALLOC_PREACTION and MALLOC_POSTACTION should be
defined to return 0 on success, and nonzero on failure.
The return value of MALLOC_POSTACTION is currently ignored
in wrapper functions since there is no reasonable default
action to take on failure.
*/
#ifdef USE_MALLOC_LOCK
#ifdef WIN32
static int mALLOC_MUTEx;
#define MALLOC_PREACTION slwait(&mALLOC_MUTEx)
#define MALLOC_POSTACTION slrelease(&mALLOC_MUTEx)
#else
#include <pthread.h>
static pthread_mutex_t mALLOC_MUTEx = PTHREAD_MUTEX_INITIALIZER;
#define MALLOC_PREACTION pthread_mutex_lock(&mALLOC_MUTEx)
#define MALLOC_POSTACTION pthread_mutex_unlock(&mALLOC_MUTEx)
#endif /* USE_MALLOC_LOCK */
#else
/* Substitute anything you like for these */
#define MALLOC_PREACTION (0)
#define MALLOC_POSTACTION (0)
#endif
Void_t* public_mALLOc(size_t bytes) {
Void_t* m;
if (MALLOC_PREACTION != 0) {
return 0;
}
m = mALLOc(bytes);
if (MALLOC_POSTACTION != 0) {
}
return m;
}
void public_fREe(Void_t* m) {
if (MALLOC_PREACTION != 0) {
return;
}
fREe(m);
if (MALLOC_POSTACTION != 0) {
}
}
Void_t* public_rEALLOc(Void_t* m, size_t bytes) {
if (MALLOC_PREACTION != 0) {
return 0;
}
m = rEALLOc(m, bytes);
if (MALLOC_POSTACTION != 0) {
}
return m;
}
Void_t* public_mEMALIGn(size_t alignment, size_t bytes) {
Void_t* m;
if (MALLOC_PREACTION != 0) {
return 0;
}
m = mEMALIGn(alignment, bytes);
if (MALLOC_POSTACTION != 0) {
}
return m;
}
Void_t* public_vALLOc(size_t bytes) {
Void_t* m;
if (MALLOC_PREACTION != 0) {
return 0;
}
m = vALLOc(bytes);
if (MALLOC_POSTACTION != 0) {
}
return m;
}
Void_t* public_pVALLOc(size_t bytes) {
Void_t* m;
if (MALLOC_PREACTION != 0) {
return 0;
}
m = pVALLOc(bytes);
if (MALLOC_POSTACTION != 0) {
}
return m;
}
Void_t* public_cALLOc(size_t n, size_t elem_size) {
Void_t* m;
if (MALLOC_PREACTION != 0) {
return 0;
}
m = cALLOc(n, elem_size);
if (MALLOC_POSTACTION != 0) {
}
return m;
}
void public_cFREe(Void_t* m) {
if (MALLOC_PREACTION != 0) {
return;
}
cFREe(m);
if (MALLOC_POSTACTION != 0) {
}
}
int public_mTRIm(size_t s) {
int result;
if (MALLOC_PREACTION != 0) {
return 0;
}
result = mTRIm(s);
if (MALLOC_POSTACTION != 0) {
}
return result;
}
size_t public_mUSABLe(Void_t* m) {
size_t result;
if (MALLOC_PREACTION != 0) {
return 0;
}
result = mUSABLe(m);
if (MALLOC_POSTACTION != 0) {
}
return result;
}
void public_mSTATs() {
if (MALLOC_PREACTION != 0) {
return;
}
mSTATs();
if (MALLOC_POSTACTION != 0) {
}
}
struct mallinfo public_mALLINFo() {
struct mallinfo m;
if (MALLOC_PREACTION != 0) {
return m;
}
m = mALLINFo();
if (MALLOC_POSTACTION != 0) {
}
return m;
}
int public_mALLOPt(int p, int v) {
int result;
if (MALLOC_PREACTION != 0) {
return 0;
}
result = mALLOPt(p, v);
if (MALLOC_POSTACTION != 0) {
}
return result;
}
#endif
/* ------------- Optional versions of memcopy ---------------- */
#if USE_MEMCPY
#define MALLOC_COPY(dest, src, nbytes, overlap) \
((overlap) ? memmove(dest, src, nbytes) : memcpy(dest, src, nbytes))
#define MALLOC_ZERO(dest, nbytes) memset(dest, 0, nbytes)
#else /* !USE_MEMCPY */
/* Use Duff's device for good zeroing/copying performance. */
#define MALLOC_ZERO(charp, nbytes) \
do { \
INTERNAL_SIZE_T* mzp = (INTERNAL_SIZE_T*)(charp); \
long mctmp = (nbytes)/sizeof(INTERNAL_SIZE_T), mcn; \
if (mctmp < 8) mcn = 0; else { mcn = (mctmp-1)/8; mctmp %= 8; } \
switch (mctmp) { \
case 0: for(;;) { *mzp++ = 0; \
case 7: *mzp++ = 0; \
case 6: *mzp++ = 0; \
case 5: *mzp++ = 0; \
case 4: *mzp++ = 0; \
case 3: *mzp++ = 0; \
case 2: *mzp++ = 0; \
case 1: *mzp++ = 0; if(mcn <= 0) break; mcn--; } \
} \
} while(0)
/* For overlapping case, dest is always _below_ src. */
#define MALLOC_COPY(dest,src,nbytes,overlap) \
do { \
INTERNAL_SIZE_T* mcsrc = (INTERNAL_SIZE_T*) src; \
INTERNAL_SIZE_T* mcdst = (INTERNAL_SIZE_T*) dest; \
long mctmp = (nbytes)/sizeof(INTERNAL_SIZE_T), mcn; \
if (mctmp < 8) mcn = 0; else { mcn = (mctmp-1)/8; mctmp %= 8; } \
switch (mctmp) { \
case 0: for(;;) { *mcdst++ = *mcsrc++; \
case 7: *mcdst++ = *mcsrc++; \
case 6: *mcdst++ = *mcsrc++; \
case 5: *mcdst++ = *mcsrc++; \
case 4: *mcdst++ = *mcsrc++; \
case 3: *mcdst++ = *mcsrc++; \
case 2: *mcdst++ = *mcsrc++; \
case 1: *mcdst++ = *mcsrc++; if(mcn <= 0) break; mcn--; } \
} \
} while(0)
#endif
/* ------------------ MMAP support ------------------ */
#if HAVE_MMAP
#include <fcntl.h>
#ifndef LACKS_SYS_MMAN_H
#include <sys/mman.h>
#endif
#if !defined(MAP_ANONYMOUS) && defined(MAP_ANON)
#define MAP_ANONYMOUS MAP_ANON
#endif
/*
Nearly all versions of mmap support MAP_ANONYMOUS,
so the following is unlikely to be needed, but is
supplied just in case.
*/
#ifndef MAP_ANONYMOUS
static int dev_zero_fd = -1; /* Cached file descriptor for /dev/zero. */
#define MMAP(addr, size, prot, flags) ((dev_zero_fd < 0) ? \
(dev_zero_fd = open("/dev/zero", O_RDWR), \
mmap((addr), (size), (prot), (flags), dev_zero_fd, 0)) : \
mmap((addr), (size), (prot), (flags), dev_zero_fd, 0))
#else
#define MMAP(addr, size, prot, flags) \
(mmap((addr), (size), (prot), (flags)|MAP_ANONYMOUS, -1, 0))
#endif
#endif /* HAVE_MMAP */
/* ---------- Alternative MORECORE functions ------------ */
/*
General Requirements for MORECORE.
The MORECORE function must have the following properties:
If MORECORE_CONTIGUOUS is false:
* MORECORE must allocate in multiples of pagesize. It will
only be called with arguments that are multiples of pagesize.
* MORECORE must page-align. That is, MORECORE(0) must
return an address at a page boundary.
else (i.e. If MORECORE_CONTIGUOUS is true):
* Consecutive calls to MORECORE with positive arguments
return increasing addresses, indicating that space has been
contiguously extended.
* MORECORE need not allocate in multiples of pagesize.
Calls to MORECORE need not have args of multiples of pagesize.
* MORECORE need not page-align.
In either case:
* MORECORE may allocate more memory than requested. (Or even less,
but this will generally result in a malloc failure.)
* MORECORE must not allocate memory when given argument zero, but
instead return one past the end address of memory from previous
nonzero call. This malloc does NOT call MORECORE(0)
until at least one call with positive arguments is made, so
the initial value returned is not important.
* Even though consecutive calls to MORECORE need not return contiguous
addresses, it must be OK for malloc'ed chunks to span multiple
regions in those cases where they do happen to be contiguous.
* MORECORE need not handle negative arguments -- it may instead
just return MORECORE_FAILURE when given negative arguments.
Negative arguments are always multiples of pagesize. MORECORE
must not misinterpret negative args as large positive unsigned
args.
There is some variation across systems about the type of the
argument to sbrk/MORECORE. If size_t is unsigned, then it cannot
actually be size_t, because sbrk supports negative args, so it is
normally the signed type of the same width as size_t (sometimes
declared as "intptr_t", and sometimes "ptrdiff_t"). It doesn't much
matter though. Internally, we use "long" as arguments, which should
work across all reasonable possibilities.
Additionally, if MORECORE ever returns failure for a positive
request, and HAVE_MMAP is true, then mmap is used as a noncontiguous
system allocator. This is a useful backup strategy for systems with
holes in address spaces -- in this case sbrk cannot contiguously
expand the heap, but mmap may be able to map noncontiguous space.
If you'd like mmap to ALWAYS be used, you can define MORECORE to be
a function that always returns MORECORE_FAILURE.
If you are using this malloc with something other than unix sbrk to
supply memory regions, you probably want to set MORECORE_CONTIGUOUS
as false. As an example, here is a custom allocator kindly
contributed for pre-OSX macOS. It uses virtually but not
necessarily physically contiguous non-paged memory (locked in,
present and won't get swapped out). You can use it by uncommenting
this section, adding some #includes, and setting up the appropriate
defines above:
#define MORECORE osMoreCore
#define MORECORE_CONTIGUOUS 0
There is also a shutdown routine that should somehow be called for
cleanup upon program exit.
#define MAX_POOL_ENTRIES 100
#define MINIMUM_MORECORE_SIZE (64 * 1024)
static int next_os_pool;
void *our_os_pools[MAX_POOL_ENTRIES];
void *osMoreCore(int size)
{
void *ptr = 0;
static void *sbrk_top = 0;
if (size > 0)
{
if (size < MINIMUM_MORECORE_SIZE)
size = MINIMUM_MORECORE_SIZE;
if (CurrentExecutionLevel() == kTaskLevel)
ptr = PoolAllocateResident(size + RM_PAGE_SIZE, 0);
if (ptr == 0)
{
return (void *) MORECORE_FAILURE;
}
// save ptrs so they can be freed during cleanup
our_os_pools[next_os_pool] = ptr;
next_os_pool++;
ptr = (void *) ((((unsigned long) ptr) + RM_PAGE_MASK) & ~RM_PAGE_MASK);
sbrk_top = (char *) ptr + size;
return ptr;
}
else if (size < 0)
{
// we don't currently support shrink behavior
return (void *) MORECORE_FAILURE;
}
else
{
return sbrk_top;
}
}
// cleanup any allocated memory pools
// called as last thing before shutting down driver
void osCleanupMem(void)
{
void **ptr;
for (ptr = our_os_pools; ptr < &our_os_pools[MAX_POOL_ENTRIES]; ptr++)
if (*ptr)
{
PoolDeallocate(*ptr);
*ptr = 0;
}
}
*/
/*
----------------------- Chunk representations -----------------------
*/
/*
This struct declaration is misleading (but accurate and necessary).
It declares a "view" into memory allowing access to necessary
fields at known offsets from a given base. See explanation below.
*/
struct malloc_chunk {
INTERNAL_SIZE_T prev_size; /* Size of previous chunk (if free). */
INTERNAL_SIZE_T size; /* Size in bytes, including overhead. */
struct malloc_chunk* fd; /* double links -- used only if free. */
struct malloc_chunk* bk;
};
typedef struct malloc_chunk* mchunkptr;
/*
malloc_chunk details:
(The following includes lightly edited explanations by Colin Plumb.)
Chunks of memory are maintained using a `boundary tag' method as
described in e.g., Knuth or Standish. (See the paper by Paul
Wilson ftp://ftp.cs.utexas.edu/pub/garbage/allocsrv.ps for a
survey of such techniques.) Sizes of free chunks are stored both
in the front of each chunk and at the end. This makes
consolidating fragmented chunks into bigger chunks very fast. The
size fields also hold bits representing whether chunks are free or
in use.
An allocated chunk looks like this:
chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Size of previous chunk, if allocated | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Size of chunk, in bytes |P|
mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| User data starts here... .
. .
. (malloc_usable_space() bytes) .
. |
nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Size of chunk |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where "chunk" is the front of the chunk for the purpose of most of
the malloc code, but "mem" is the pointer that is returned to the
user. "Nextchunk" is the beginning of the next contiguous chunk.
Chunks always begin on even word boundries, so the mem portion
(which is returned to the user) is also on an even word boundary, and
thus double-word aligned.
Free chunks are stored in circular doubly-linked lists, and look like this:
chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Size of previous chunk |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
`head:' | Size of chunk, in bytes |P|
mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Forward pointer to next chunk in list |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Back pointer to previous chunk in list |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unused space (may be 0 bytes long) .
. .
. |
nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
`foot:' | Size of chunk, in bytes |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The P (PREV_INUSE) bit, stored in the unused low-order bit of the
chunk size (which is always a multiple of two words), is an in-use
bit for the *previous* chunk. If that bit is *clear*, then the
word before the current chunk size contains the previous chunk
size, and can be used to find the front of the previous chunk.
The very first chunk allocated always has this bit set,
preventing access to non-existent (or non-owned) memory. If
prev_inuse is set for any given chunk, then you CANNOT determine
the size of the previous chunk, and might even get a memory
addressing fault when trying to do so.
Note that the `foot' of the current chunk is actually represented
as the prev_size of the NEXT chunk. (This makes it easier to
deal with alignments etc).
The two exceptions to all this are
1. The special chunk `top' doesn't bother using the
trailing size field since there is no next contiguous chunk
that would have to index off it. After initialization, `top'
is forced to always exist. If it would become less than
MINSIZE bytes long, it is replenished.
2. Chunks allocated via mmap, which have the second-lowest-order
bit (IS_MMAPPED) set in their size fields. Because they are
allocated one-by-one, each must contain its own trailing size field.
*/
/*
Size and alignment checks and conversions
*/
/* conversion from malloc headers to user pointers, and back */
#define chunk2mem(p) ((Void_t*)((char*)(p) + 2*SIZE_SZ))
#define mem2chunk(mem) ((mchunkptr)((char*)(mem) - 2*SIZE_SZ))
/* The smallest possible chunk */
#define MIN_CHUNK_SIZE (sizeof(struct malloc_chunk))
/* The smallest size we can malloc is an aligned minimal chunk */
#define MINSIZE ((MIN_CHUNK_SIZE+MALLOC_ALIGN_MASK) & ~MALLOC_ALIGN_MASK)
/* Check if m has acceptable alignment */
#define aligned_OK(m) (((unsigned long)((m)) & (MALLOC_ALIGN_MASK)) == 0)
/*
Check for negative/huge sizes.
This cannot just test for < 0 because argument might
be an unsigned type of uncertain width.
*/
#define IS_NEGATIVE(x) \
((unsigned long)x >= \
(unsigned long)((((INTERNAL_SIZE_T)(1)) << ((SIZE_SZ)*8 - 1))))
/* pad request bytes into a usable size -- internal version */
#define request2size(req) \
(((req) + SIZE_SZ + MALLOC_ALIGN_MASK < MINSIZE) ? \
MINSIZE : \
((req) + SIZE_SZ + MALLOC_ALIGN_MASK) & ~MALLOC_ALIGN_MASK)
/*
Same, except check for negative/huge arguments.
This lets through args that are positive but wrap into
negatives when padded. However, these are trapped
elsewhere.
*/
#define checked_request2size(req, sz) \
if (IS_NEGATIVE(req)) { \
MALLOC_FAILURE_ACTION; \
return 0; \
} \
(sz) = request2size(req);
/*
Physical chunk operations
*/
/* size field is or'ed with PREV_INUSE when previous adjacent chunk in use */
#define PREV_INUSE 0x1
/* size field is or'ed with IS_MMAPPED if the chunk was obtained with mmap() */
#define IS_MMAPPED 0x2
/* Bits to mask off when extracting size */
#define SIZE_BITS (PREV_INUSE|IS_MMAPPED)
/* Ptr to next physical malloc_chunk. */
#define next_chunk(p) ((mchunkptr)( ((char*)(p)) + ((p)->size & ~PREV_INUSE) ))
/* Ptr to previous physical malloc_chunk */
#define prev_chunk(p) ((mchunkptr)( ((char*)(p)) - ((p)->prev_size) ))
/* Treat space at ptr + offset as a chunk */
#define chunk_at_offset(p, s) ((mchunkptr)(((char*)(p)) + (s)))
/*
Dealing with use bits
Note: IS_MMAPPED is intentionally not masked off from size field in
macros for which mmapped chunks should never be seen. This should
cause helpful core dumps to occur if it is tried by accident by
people extending or adapting this malloc.
*/
/* extract p's inuse bit */
#define inuse(p)\
((((mchunkptr)(((char*)(p))+((p)->size & ~PREV_INUSE)))->size) & PREV_INUSE)
/* extract inuse bit of previous chunk */
#define prev_inuse(p) ((p)->size & PREV_INUSE)
/* check for mmap()'ed chunk */
#define chunk_is_mmapped(p) ((p)->size & IS_MMAPPED)
/* set/clear chunk as being inuse without otherwise disturbing */
#define set_inuse(p)\
((mchunkptr)(((char*)(p)) + ((p)->size & ~PREV_INUSE)))->size |= PREV_INUSE
#define clear_inuse(p)\
((mchunkptr)(((char*)(p)) + ((p)->size & ~PREV_INUSE)))->size &= ~(PREV_INUSE)
/* check/set/clear inuse bits in known places */
#define inuse_bit_at_offset(p, s)\
(((mchunkptr)(((char*)(p)) + (s)))->size & PREV_INUSE)
#define set_inuse_bit_at_offset(p, s)\
(((mchunkptr)(((char*)(p)) + (s)))->size |= PREV_INUSE)
#define clear_inuse_bit_at_offset(p, s)\
(((mchunkptr)(((char*)(p)) + (s)))->size &= ~(PREV_INUSE))
/*
Dealing with size fields
*/
/* Get size, ignoring use bits */
#define chunksize(p) ((p)->size & ~(SIZE_BITS))
/* Set size at head, without disturbing its use bit */
#define set_head_size(p, s) ((p)->size = (((p)->size & PREV_INUSE) | (s)))
/* Set size/use field */
#define set_head(p, s) ((p)->size = (s))
/* Set size at footer (only when chunk is not in use) */
#define set_foot(p, s) (((mchunkptr)((char*)(p) + (s)))->prev_size = (s))
/*
------------------ Internal data structures --------------------
All internal state is held in an instance of malloc_state defined
below. There are no other static variables, except in two optional
cases:
* If USE_MALLOC_LOCK is defined, the mALLOC_MUTEx declared
above.
* If HAVE_MMAP is true, but mmap doesn't support
MAP_ANONYMOUS, a dummy file descriptor for mmap.
Beware of lots of tricks that minimize the total space
requirements. The result is a little over 1K bytes (for 4byte
pointers and size_t.)
*/
/*
Bins
An array of bin headers for free chunks. Each bin is doubly
linked. The bins are approximately proportionally (log) spaced.
There are a lot of these bins (128). This may look excessive, but
works very well in practice. Most bins hold sizes that are
unusual as malloc request sizes, but are more usual for fragments
and consolidated sets of chunks, which is what these bins hold, so
they can be found quickly. All procedures maintain the invariant
that no consolidated chunk physically borders another one, so each
chunk in a list is known to be preceeded and followed by either
inuse chunks or the ends of memory.
Chunks in bins are kept in size order, with ties going to the
approximately least recently used chunk. Ordering is irrelevant
for the small bins, which all contain the same-sized chunks, but
facilitates best-fit allocation for larger chunks. (These lists
are just sequential. Keeping them in order almost never requires
enough traversal to warrant using fancier ordered data
structures.) Chunks of the same size are linked with the most
recently freed at the front, and allocations are taken from the
back. This results in LRU (FIFO) allocation order, which tends
to give each chunk an equal opportunity to be consolidated with
adjacent freed chunks, resulting in larger free chunks and less
fragmentation.
To simplify use in double-linked lists, each bin header acts
as a malloc_chunk. This avoids special-casing for headers.
But to conserve space and (mainly) improve locality, we allocate
only the fd/bk pointers of bins, and then use repositioning tricks
to treat these as the fields of a malloc_chunk*.
*/
typedef struct malloc_chunk* mbinptr;
#define NBINS 128
/* addressing -- note that bin_at(0) does not exist */
#define bin_at(m, i) ((mbinptr)((char*)&((m)->bins[(i)<<1]) - (SIZE_SZ<<1)))
/* analog of ++bin */
#define next_bin(b) ((mbinptr)((char*)(b) + (sizeof(mchunkptr)<<1)))
/* Reminders about list directionality within bins */
#define first(b) ((b)->fd)
#define last(b) ((b)->bk)
/*
Take a chunk off a bin list
*/
#define unlink(P, BK, FD) { \
FD = P->fd; \
BK = P->bk; \
FD->bk = BK; \
BK->fd = FD; \
}
/*
Indexing bins
Bins for sizes < 512 bytes contain chunks of all the same size, spaced
8 bytes apart. Larger bins are approximately logarithmically spaced:
64 bins of size 8
32 bins of size 64
16 bins of size 512
8 bins of size 4096
4 bins of size 32768
2 bins of size 262144
1 bin of size what's left
There is actually a little bit of slop in the numbers in bin_index
for the sake of speed. This makes no difference elsewhere.
The bins top out at around 1mb because we expect to service large
chunks via mmap.
*/
/* The first NSMALLBIN bins (and fastbins) hold only one size */
#define NSMALLBINS 64
#define SMALLBIN_WIDTH 8
#define MIN_LARGE_SIZE 512
#define in_smallbin_range(sz) ((sz) < MIN_LARGE_SIZE)
#define smallbin_index(sz) (((unsigned)(sz)) >> 3)
#define largebin_index(sz) \
(((((unsigned long)(sz)) >> 6) <= 32)? 56 + (((unsigned long)(sz)) >> 6): \
((((unsigned long)(sz)) >> 9) <= 20)? 91 + (((unsigned long)(sz)) >> 9): \
((((unsigned long)(sz)) >> 12) <= 10)? 110 + (((unsigned long)(sz)) >> 12): \
((((unsigned long)(sz)) >> 15) <= 4)? 119 + (((unsigned long)(sz)) >> 15): \
((((unsigned long)(sz)) >> 18) <= 2)? 124 + (((unsigned long)(sz)) >> 18): \
126)
#define bin_index(sz) \
((in_smallbin_range(sz)) ? smallbin_index(sz) : largebin_index(sz))
/*
Unsorted chunks
All remainders from chunk splits, as well as all returned chunks,
are first placed in the "unsorted" bin. They are then placed
in regular bins after malloc gives them ONE chance to be used before
binning. So, basically, the unsorted_chunks list acts as a queue,
with chunks being placed on it in free (and malloc_consolidate),
and taken off (to be either used or placed in bins) in malloc.
*/
/* The otherwise unindexable 1-bin is used to hold unsorted chunks. */
#define unsorted_chunks(M) (bin_at(M, 1))
/*
Top
The top-most available chunk (i.e., the one bordering the end of
available memory) is treated specially. It is never included in
any bin, is used only if no other chunk is available, and is
released back to the system if it is very large (see
M_TRIM_THRESHOLD). `top' is never properly linked to its bin
since it is always handled specially. Because top initially
points to its own bin with initial zero size, thus forcing
extension on the first malloc request, we avoid having any special
code in malloc to check whether it even exists yet. But we still
need to do so when getting memory from system, so we make
initial_top treat the bin as a legal but unusable chunk during the
interval between initialization and the first call to
sYSMALLOc. (This is somewhat delicate, since it relies on
the 2 preceding words to be zero during this interval as well.)
*/
/* Conveniently, the unsorted bin can be used as dummy top on first call */
#define initial_top(M) (unsorted_chunks(M))
/*
Binmap
To help compensate for the large number of bins, a one-level index
structure is used for bin-by-bin searching. `binmap' is a
bitvector recording whether bins are definitely empty so they can
be skipped over during during traversals. The bits are NOT always
cleared as soon as bins are empty, but instead only
when they are noticed to be empty during traversal in malloc.
*/
/* Conservatively use 32 bits per map word, even if on 64bit system */
#define BINMAPSHIFT 5
#define BITSPERMAP (1U << BINMAPSHIFT)
#define BINMAPSIZE (NBINS / BITSPERMAP)
#define idx2block(i) ((i) >> BINMAPSHIFT)
#define idx2bit(i) ((1U << ((i) & ((1U << BINMAPSHIFT)-1))))
#define mark_bin(m,i) ((m)->binmap[idx2block(i)] |= idx2bit(i))
#define unmark_bin(m,i) ((m)->binmap[idx2block(i)] &= ~(idx2bit(i)))
#define get_binmap(m,i) ((m)->binmap[idx2block(i)] & idx2bit(i))
/*
Fastbins
An array of lists holding recently freed small chunks. Fastbins
are not doubly linked. It is faster to single-link them, and
since chunks are never removed from the middles of these lists,
double linking is not necessary.
Chunks in fastbins keep their inuse bit set, so they cannot
be consolidated with other free chunks. malloc_consolidate
releases all chunks in fastbins and consolidates them with
other free chunks.
*/
typedef struct malloc_chunk* mfastbinptr;
/* offset 2 to use otherwise unindexable first 2 bins */
#define fastbin_index(sz) ((((unsigned int)(sz)) >> 3) - 2)
/* The maximum fastbin request size we support */
#define MAX_FAST_SIZE 80
#define NFASTBINS (fastbin_index(request2size(MAX_FAST_SIZE))+1)
/*
Flag bit held in max_fast indicating that there probably are some
fastbin chunks . It is set true on entering a chunk into any fastbin,
and cleared only in malloc_consolidate.
The truth value is inverted so that have_fastchunks will be true
upon startup (since statics are zero-filled).
*/
#define have_fastchunks(M) (((M)->max_fast & 1U) == 0)
#define clear_fastchunks(M) ((M)->max_fast |= 1U)
#define set_fastchunks(M) ((M)->max_fast &= ~1U)
/*
Initialization value of max_fast.
Use impossibly small value if 0.
Value also has flag bit clear.
*/
#define req2max_fast(s) (((((s) == 0)? SMALLBIN_WIDTH: request2size(s))) | 1U)
/*
NONCONTIGUOUS_REGIONS is a special value for sbrk_base indicating that
MORECORE does not return contiguous regions. In this case, we do not check
or assume that the address of each chunk is at least sbrk_base. Otherwise,
contiguity is exploited in merging together, when possible, results
from consecutive MORECORE calls.
The possible values for sbrk_base are:
MORECORE_FAILURE:
MORECORE has not yet been called, but we expect contiguous space
NONCONTIGUOUS_REGIONS:
we don't expect or rely on contiguous space
any other legal address:
the first address returned by MORECORE when contiguous
*/
#define NONCONTIGUOUS_REGIONS ((char*)(-3))
/*
----------- Internal state representation and initialization -----------
*/
struct malloc_state {
/* The maximum chunk size to be eligible for fastbin */
INTERNAL_SIZE_T max_fast; /* low bit used as fastbin flag */
/* Base of the topmost chunk -- not otherwise kept in a bin */
mchunkptr top;
/* The remainder from the most recent split of a small request */
mchunkptr last_remainder;
/* Fastbins */
mfastbinptr fastbins[NFASTBINS];
/* Normal bins packed as described above */
mchunkptr bins[NBINS * 2];
/* Bitmap of bins */
unsigned int binmap[BINMAPSIZE];
/* Tunable parameters */
unsigned long trim_threshold;
INTERNAL_SIZE_T top_pad;
INTERNAL_SIZE_T mmap_threshold;
/* Memory map support */
int n_mmaps;
int n_mmaps_max;
int max_n_mmaps;
/* Bookkeeping for sbrk */
unsigned int pagesize; /* Cache malloc_getpagesize */
char* sbrk_base; /* first address returned by sbrk,
or NONCONTIGUOUS_REGIONS */
/* Statistics */
INTERNAL_SIZE_T mmapped_mem;
INTERNAL_SIZE_T sbrked_mem;
INTERNAL_SIZE_T max_sbrked_mem;
INTERNAL_SIZE_T max_mmapped_mem;
INTERNAL_SIZE_T max_total_mem;
};
typedef struct malloc_state *mstate;
/*
There is exactly one instance of this struct in this malloc.
If you are adapting this malloc in a way that does NOT use a static
malloc_state, you MUST explicitly zero-fill it before using. This
malloc relies on the property that malloc_state is initialized to
all zeroes (as is true of C statics).
*/
static struct malloc_state av_; /* never directly referenced */
/*
All uses of av_ are via get_malloc_state().
This simplifies construction of multithreaded, etc extensions.
At most one call to get_malloc_state is made per invocation of
the public versions of malloc, free, and all other routines
except realloc, valloc, and vpalloc. Also, it is called
in check* routines if DEBUG is set.
*/
#define get_malloc_state() (&(av_))
/*
Initialize a malloc_state struct.
This is called only from within malloc_consolidate, which needs
be called in the same contexts anyway. It is never called directly
outside of malloc_consolidate because some optimizing compilers try
to inline it at all call points, which turns out not to be an
optimization at all. (Inlining it only in malloc_consolidate is fine though.)
*/
#if __STD_C
static void malloc_init_state(mstate av)
#else
static void malloc_init_state(av) mstate av;
#endif
{
int i;
mbinptr bin;
/* Uncomment this if you are not using a static av */
/* MALLOC_ZERO(av, sizeof(struct malloc_state); */
/* Establish circular links for normal bins */
for (i = 1; i < NBINS; ++i) {
bin = bin_at(av,i);
bin->fd = bin->bk = bin;
}
av->max_fast = req2max_fast(DEFAULT_MXFAST);
av->top_pad = DEFAULT_TOP_PAD;
av->n_mmaps_max = DEFAULT_MMAP_MAX;
av->mmap_threshold = DEFAULT_MMAP_THRESHOLD;
#if MORECORE_CONTIGUOUS
av->trim_threshold = DEFAULT_TRIM_THRESHOLD;
av->sbrk_base = (char*)MORECORE_FAILURE;
#else
av->trim_threshold = (unsigned long)(-1);
av->sbrk_base = NONCONTIGUOUS_REGIONS;
#endif
av->top = initial_top(av);
av->pagesize = malloc_getpagesize;
}
/*
Other internal utilities operating on mstates
*/
#if __STD_C
static Void_t* sYSMALLOc(INTERNAL_SIZE_T, mstate);
static int sYSTRIm(size_t, mstate);
static void malloc_consolidate(mstate);
#else
static Void_t* sYSMALLOc();
static int sYSTRIm();
static void malloc_consolidate();
#endif
/*
Debugging support
These routines make a number of assertions about the states
of data structures that should be true at all times. If any
are not true, it's very likely that a user program has somehow
trashed memory. (It's also possible that there is a coding error
in malloc. In which case, please report it!)
*/
#if ! DEBUG
#define check_chunk(P)
#define check_free_chunk(P)
#define check_inuse_chunk(P)
#define check_remalloced_chunk(P,N)
#define check_malloced_chunk(P,N)
#define check_malloc_state()
#else
#define check_chunk(P) do_check_chunk(P)
#define check_free_chunk(P) do_check_free_chunk(P)
#define check_inuse_chunk(P) do_check_inuse_chunk(P)
#define check_remalloced_chunk(P,N) do_check_remalloced_chunk(P,N)
#define check_malloced_chunk(P,N) do_check_malloced_chunk(P,N)
#define check_malloc_state() do_check_malloc_state()
/*
Properties of all chunks
*/
#if __STD_C
static void do_check_chunk(mchunkptr p)
#else
static void do_check_chunk(p) mchunkptr p;
#endif
{
mstate av = get_malloc_state();
unsigned long sz = chunksize(p);
if (!chunk_is_mmapped(p)) {
/* Has legal address ... */
if (av->sbrk_base != NONCONTIGUOUS_REGIONS) {
assert(((char*)p) >= ((char*)(av->sbrk_base)));
}
if (p != av->top) {
if (av->sbrk_base != NONCONTIGUOUS_REGIONS) {
assert(((char*)p + sz) <= ((char*)(av->top)));
}
}
else {
if (av->sbrk_base != NONCONTIGUOUS_REGIONS) {
assert(((char*)p + sz) <= ((char*)(av->sbrk_base) + av->sbrked_mem));
}
/* top size is always at least MINSIZE */
assert((long)(sz) >= (long)(MINSIZE));
/* top predecessor always marked inuse */
assert(prev_inuse(p));
}
}
else {
#if HAVE_MMAP
/* address is outside main heap */
/* unless mmap has been used as sbrk backup */
if (av->sbrk_base != NONCONTIGUOUS_REGIONS) {
assert(! (((char*)p) >= ((char*)av->sbrk_base) &&
((char*)p) < ((char*)(av->sbrk_base) + av->sbrked_mem)));
}
/* chunk is page-aligned */
assert(((p->prev_size + sz) & (av->pagesize-1)) == 0);
/* mem is aligned */
assert(aligned_OK(chunk2mem(p)));
#else
/* force an appropriate assert violation if debug set */
assert(!chunk_is_mmapped(p));
#endif
}
}
/*
Properties of free chunks
*/
#if __STD_C
static void do_check_free_chunk(mchunkptr p)
#else
static void do_check_free_chunk(p) mchunkptr p;
#endif
{
mstate av = get_malloc_state();
INTERNAL_SIZE_T sz = p->size & ~PREV_INUSE;
mchunkptr next = chunk_at_offset(p, sz);
do_check_chunk(p);
/* Chunk must claim to be free ... */
assert(!inuse(p));
assert (!chunk_is_mmapped(p));
/* Unless a special marker, must have OK fields */
if ((unsigned long)sz >= (unsigned long)MINSIZE)
{
assert((sz & MALLOC_ALIGN_MASK) == 0);
assert(aligned_OK(chunk2mem(p)));
/* ... matching footer field */
assert(next->prev_size == sz);
/* ... and is fully consolidated */
assert(prev_inuse(p));
assert (next == av->top || inuse(next));
/* ... and has minimally sane links */
assert(p->fd->bk == p);
assert(p->bk->fd == p);
}
else /* markers are always of size SIZE_SZ */
assert(sz == SIZE_SZ);
}
/*
Properties of inuse chunks
*/
#if __STD_C
static void do_check_inuse_chunk(mchunkptr p)
#else
static void do_check_inuse_chunk(p) mchunkptr p;
#endif
{
mstate av = get_malloc_state();
mchunkptr next;
do_check_chunk(p);
if (chunk_is_mmapped(p))
return; /* mmapped chunks have no next/prev */
/* Check whether it claims to be in use ... */
assert(inuse(p));
next = next_chunk(p);
/* ... and is surrounded by OK chunks.
Since more things can be checked with free chunks than inuse ones,
if an inuse chunk borders them and debug is on, it's worth doing them.
*/
if (!prev_inuse(p)) {
/* Note that we cannot even look at prev unless it is not inuse */
mchunkptr prv = prev_chunk(p);
assert(next_chunk(prv) == p);
do_check_free_chunk(prv);
}
if (next == av->top) {
assert(prev_inuse(next));
assert(chunksize(next) >= MINSIZE);
}
else if (!inuse(next))
do_check_free_chunk(next);
}
/*
Properties of chunks recycled from fastbins
*/
#if __STD_C
static void do_check_remalloced_chunk(mchunkptr p, INTERNAL_SIZE_T s)
#else
static void do_check_remalloced_chunk(p, s) mchunkptr p; INTERNAL_SIZE_T s;
#endif
{
INTERNAL_SIZE_T sz = p->size & ~PREV_INUSE;
do_check_inuse_chunk(p);
/* Legal size ... */
assert((sz & MALLOC_ALIGN_MASK) == 0);
assert((long)sz - (long)MINSIZE >= 0);
assert((long)sz - (long)s >= 0);
assert((long)sz - (long)(s + MINSIZE) < 0);
/* ... and alignment */
assert(aligned_OK(chunk2mem(p)));
}
/*
Properties of nonrecycled chunks at the point they are malloced
*/
#if __STD_C
static void do_check_malloced_chunk(mchunkptr p, INTERNAL_SIZE_T s)
#else
static void do_check_malloced_chunk(p, s) mchunkptr p; INTERNAL_SIZE_T s;
#endif
{
/* same as recycled case ... */
do_check_remalloced_chunk(p, s);
/*
... plus, must obey implementation invariant that prev_inuse is
always true of any allocated chunk; i.e., that each allocated
chunk borders either a previously allocated and still in-use
chunk, or the base of its memory arena. This is ensured
by making all allocations from the the `lowest' part of any found
chunk. This does not necessarily hold however for chunks
recycled via fastbins.
*/
assert(prev_inuse(p));
}
/*
Properties of malloc_state.
This may be useful for debugging malloc, as well as detecting user
programmer errors that somehow write into malloc_state.
*/
static void do_check_malloc_state()
{
mstate av = get_malloc_state();
int i;
mchunkptr p;
mchunkptr q;
mbinptr b;
unsigned int biton;
int empty;
unsigned int idx;
INTERNAL_SIZE_T size;
unsigned long total = 0;
int max_fast_bin;
/* internal size_t must be no wider than pointer type */
assert(sizeof(INTERNAL_SIZE_T) <= sizeof(char*));
/* alignment is a power of 2 */
assert((MALLOC_ALIGNMENT & (MALLOC_ALIGNMENT-1)) == 0);
/* cannot run remaining checks until fully initialized */
if (av->top == 0 || av->top == initial_top(av))
return;
/* pagesize is a power of 2 */
assert((av->pagesize & (av->pagesize-1)) == 0);
/* properties of fastbins */
/* max_fast is in allowed range */
assert((av->max_fast & ~1) <= request2size(MAX_FAST_SIZE));
max_fast_bin = fastbin_index(av->max_fast);
for (i = 0; i < NFASTBINS; ++i) {
p = av->fastbins[i];
/* all bins past max_fast are empty */
if (i > max_fast_bin)
assert(p == 0);
while (p != 0) {
/* each chunk claims to be inuse */
do_check_inuse_chunk(p);
total += chunksize(p);
/* chunk belongs in this bin */
assert(fastbin_index(chunksize(p)) == i);
p = p->fd;
}
}
if (total != 0)
assert(have_fastchunks(av));
/* check normal bins */
for (i = 1; i < NBINS; ++i) {
b = bin_at(av,i);
/* binmap is accurate (except for bin 1 == unsorted_chunks) */
if (i >= 2) {
biton = get_binmap(av,i);
empty = last(b) == b;
if (!biton)
assert(empty);
else if (!empty)
assert(biton);
}
for (p = last(b); p != b; p = p->bk) {
/* each chunk claims to be free */
do_check_free_chunk(p);
size = chunksize(p);
total += size;
if (i >= 2) {
/* chunk belongs in bin */
idx = bin_index(size);
assert(idx == i);
/* lists are sorted */
assert(p->bk == b || chunksize(p->bk) >= chunksize(p));
}
/* chunk is followed by a legal chain of inuse chunks */
for (q = next_chunk(p);
q != av->top && inuse(q) && (long)(chunksize(q)) >= (long)MINSIZE;
q = next_chunk(q))
do_check_inuse_chunk(q);
}
}
/* top chunk is OK */
check_chunk(av->top);
/* sanity checks for statistics */
assert(total <= (unsigned long)(av->max_total_mem));
assert(av->n_mmaps >= 0);
assert(av->n_mmaps <= av->n_mmaps_max);
assert(av->n_mmaps <= av->max_n_mmaps);
assert(av->max_n_mmaps <= av->n_mmaps_max);
assert((unsigned long)(av->sbrked_mem) <=
(unsigned long)(av->max_sbrked_mem));
assert((unsigned long)(av->mmapped_mem) <=
(unsigned long)(av->max_mmapped_mem));
assert((unsigned long)(av->max_total_mem) >=
(unsigned long)(av->mmapped_mem) + (unsigned long)(av->sbrked_mem));
}
#endif
/* ----------- Routines dealing with system allocation -------------- */
/*
Handle malloc cases requiring more memory from system.
malloc relays to sYSMALLOc if it cannot allocate out of
existing memory.
On entry, it is assumed that av->top does not have enough
space to service request for nb bytes, thus requiring more meory
from system.
*/
#if __STD_C
static Void_t* sYSMALLOc(INTERNAL_SIZE_T nb, mstate av)
#else
static Void_t* sYSMALLOc(nb, av) INTERNAL_SIZE_T nb; mstate av;
#endif
{
mchunkptr old_top; /* incoming value of av->top */
INTERNAL_SIZE_T old_size; /* its size */
char* old_end; /* its end address */
long size; /* arg to first MORECORE or mmap call */
char* brk; /* return value from MORECORE */
char* mm; /* return value from mmap call*/
long correction; /* arg to 2nd MORECORE call */
char* snd_brk; /* 2nd return val */
INTERNAL_SIZE_T front_misalign; /* unusable bytes at front of new space */
INTERNAL_SIZE_T end_misalign; /* partial page left at end of new space */
char* aligned_brk; /* aligned offset into brk */
mchunkptr p; /* the allocated/returned chunk */
mchunkptr remainder; /* remainder from allocation */
long remainder_size; /* its size */
unsigned long sum; /* for updating stats */
size_t pagemask = av->pagesize - 1;
/*
If have mmap, and the request size meets the mmap threshold, and
the system supports mmap, and there are few enough currently
allocated mmapped regions, and a call to mmap succeeds, try to
directly map this request rather than expanding top.
*/
#if HAVE_MMAP
if ((unsigned long)nb >= (unsigned long)(av->mmap_threshold) &&
(av->n_mmaps < av->n_mmaps_max)) {
/*
Round up size to nearest page. For mmapped chunks, the overhead
is one SIZE_SZ unit larger than for normal chunks, because there
is no following chunk whose prev_size field could be used.
*/
size = (nb + SIZE_SZ + MALLOC_ALIGN_MASK + pagemask) & ~pagemask;
mm = (char*)(MMAP(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE));
if (mm != (char*)(MORECORE_FAILURE)) {
/*
The offset to the start of the mmapped region is stored
in the prev_size field of the chunk. This allows us to adjust
returned start address to meet alignment requirements here
and in memalign(), and still be able to compute proper
address argument for later munmap in free() and realloc().
*/
front_misalign = (INTERNAL_SIZE_T)chunk2mem(mm) & MALLOC_ALIGN_MASK;
if (front_misalign > 0) {
correction = MALLOC_ALIGNMENT - front_misalign;
p = (mchunkptr)(mm + correction);
p->prev_size = correction;
set_head(p, (size - correction) |IS_MMAPPED);
}
else {
p = (mchunkptr)mm;
set_head(p, size|IS_MMAPPED);
}
check_chunk(p);
/* update statistics */
if (++av->n_mmaps > av->max_n_mmaps)
av->max_n_mmaps = av->n_mmaps;
sum = av->mmapped_mem += size;
if (sum > (unsigned long)(av->max_mmapped_mem))
av->max_mmapped_mem = sum;
sum += av->sbrked_mem;
if (sum > (unsigned long)(av->max_total_mem))
av->max_total_mem = sum;
return chunk2mem(p);
}
}
#endif
/* record incoming configuration of top */
old_top = av->top;
old_size = chunksize(old_top);
old_end = (char*)(chunk_at_offset(old_top, old_size));
brk = snd_brk = (char*)(MORECORE_FAILURE);
/*
If not the first time through, we require old_size to be
at least MINSIZE and to have prev_inuse set.
*/
assert(old_top == initial_top(av) ||
((unsigned long) (old_size) >= (unsigned long)(MINSIZE) &&
prev_inuse(old_top)));
/* Request enough space for nb + pad + overhead */
size = nb + av->top_pad + MINSIZE;
/*
If contiguous, we can subtract out existing space that we hope to
combine with new space. We add it back later only if
we don't actually get contiguous space.
*/
if (av->sbrk_base != NONCONTIGUOUS_REGIONS)
size -= old_size;
/*
Round to a multiple of page size.
If MORECORE is not contiguous, this ensures that we only call it
with whole-page arguments. And if MORECORE is contiguous and
this is not first time through, this preserves page-alignment of
previous calls. Otherwise, we re-correct anyway to page-align below.
*/
size = (size + pagemask) & ~pagemask;
/*
Don't try to call MORECORE if argument is so big as to appear
negative. Note that since mmap takes size_t arg, it may succeed
below even if we cannot call MORECORE.
*/
if (size > 0)
brk = (char*)(MORECORE(size));
/*
If have mmap, try using it as a backup when MORECORE fails. This
is worth doing on systems that have "holes" in address space, so
sbrk cannot extend to give contiguous space, but space is available
elsewhere. Note that we ignore mmap max count and threshold limits,
since there is no reason to artificially limit use here.
*/
#if HAVE_MMAP
if (brk == (char*)(MORECORE_FAILURE)) {
/* Cannot merge with old top, so add its size back in */
if (av->sbrk_base != NONCONTIGUOUS_REGIONS)
size = (size + old_size + pagemask) & ~pagemask;
/* If we are relying on mmap as backup, then use larger units */
if ((unsigned long)size < (unsigned long)MMAP_AS_MORECORE_SIZE)
size = MMAP_AS_MORECORE_SIZE;
brk = (char*)(MMAP(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE));
if (brk != (char*)(MORECORE_FAILURE)) {
/* We do not need, and cannot use, another sbrk call to find end */
snd_brk = brk + size;
/*
Record that we no longer have a contiguous sbrk region.
After the first time mmap is used as backup, we cannot
ever rely on contiguous space.
*/
av->sbrk_base = NONCONTIGUOUS_REGIONS;
}
}
#endif
if (brk != (char*)(MORECORE_FAILURE)) {
av->sbrked_mem += size;
/*
If MORECORE extends previous space, we can likewise extend top size.
*/
if (brk == old_end && snd_brk == (char*)(MORECORE_FAILURE)) {
set_head(old_top, (size + old_size) | PREV_INUSE);
}
/*
Otherwise, make adjustments guided by the special values of
av->sbrk_base (MORECORE_FAILURE or NONCONTIGUOUS_REGIONS):
* If the first time through or noncontiguous, we need to call sbrk
just to find out where the end of memory lies.
* We need to ensure that all returned chunks from malloc will meet
MALLOC_ALIGNMENT
* If there was an intervening foreign sbrk, we need to adjust sbrk
request size to account for fact that we will not be able to
combine new space with existing space in old_top.
* Almost all systems internally allocate whole pages at a time, in
which case we might as well use the whole last page of request.
So we allocate enough more memory to hit a page boundary now,
which in turn causes future contiguous calls to page-align.
*/
else {
front_misalign = 0;
end_misalign = 0;
correction = 0;
aligned_brk = brk;
/* handle contiguous cases */
if (av->sbrk_base != NONCONTIGUOUS_REGIONS) {
/* Guarantee alignment of first new chunk made from this space */
front_misalign = (INTERNAL_SIZE_T)chunk2mem(brk) & MALLOC_ALIGN_MASK;
if (front_misalign > 0) {
/*
Skip over some bytes to arrive at an aligned position.
We don't need to specially mark these wasted front bytes.
They will never be accessed anyway because
prev_inuse of av->top (and any chunk created from its start)
is always true after initialization.
*/
correction = MALLOC_ALIGNMENT - front_misalign;
aligned_brk += correction;
}
/*
If this isn't adjacent to a previous sbrk, then we will not
be able to merge with old_top space, so must add to 2nd request.
*/
correction += old_size;
/* Pad out to hit a page boundary */
end_misalign = (INTERNAL_SIZE_T)(brk + size + correction);
correction += ((end_misalign + pagemask) & ~pagemask) - end_misalign;
assert(correction >= 0);
snd_brk = (char*)(MORECORE(correction));
/*
If can't allocate correction, try to at least find out current
brk. It might be enough to proceed without failing.
Note that if second sbrk did NOT fail, we assume that space
is contiguous with first sbrk. This is a safe assumption unless
program is multithreaded but doesn't use locks and a foreign sbrk
occurred between our first and second calls.
*/
if (snd_brk == (char*)(MORECORE_FAILURE)) {
correction = 0;
snd_brk = (char*)(MORECORE(0));
}
}
/* handle non-contiguous cases */
else {
/* MORECORE/mmap must correctly align etc */
assert(((unsigned long)chunk2mem(brk) & MALLOC_ALIGN_MASK) == 0);
/* Find out current end of memory */
if (snd_brk == (char*)(MORECORE_FAILURE)) {
snd_brk = (char*)(MORECORE(0));
}
/* This must lie on a page boundary */
if (snd_brk != (char*)(MORECORE_FAILURE)) {
assert(((INTERNAL_SIZE_T)(snd_brk) & pagemask) == 0);
}
}
/* Adjust top based on results of second sbrk */
if (snd_brk != (char*)(MORECORE_FAILURE)) {
av->top = (mchunkptr)aligned_brk;
set_head(av->top, (snd_brk - aligned_brk + correction) | PREV_INUSE);
av->sbrked_mem += correction;
/* If first time through and contiguous, record base */
if (old_top == initial_top(av)) {
if (av->sbrk_base == (char*)(MORECORE_FAILURE))
av->sbrk_base = brk;
}
/*
Otherwise, we either have a gap due to foreign sbrk or a
non-contiguous region. Insert a double fencepost at old_top
to prevent consolidation with space we don't own. These
fenceposts are artificial chunks that are marked as inuse
and are in any case too small to use. We need two to make
sizes and alignments work out.
*/
else {
/*
Shrink old_top to insert fenceposts, keeping size a
multiple of MALLOC_ALIGNMENT.
*/
old_size = (old_size - 3*SIZE_SZ) & ~MALLOC_ALIGN_MASK;
set_head(old_top, old_size | PREV_INUSE);
/*
Note that the following assignments overwrite old_top when
old_size was previously MINSIZE. This is intentional. We
need the fencepost, even if old_top otherwise gets lost.
*/
chunk_at_offset(old_top, old_size )->size =
SIZE_SZ|PREV_INUSE;
chunk_at_offset(old_top, old_size + SIZE_SZ)->size =
SIZE_SZ|PREV_INUSE;
/* If possible, release the rest. */
if (old_size >= MINSIZE)
fREe(chunk2mem(old_top));
}
}
}
/* Update statistics */
sum = av->sbrked_mem;
if (sum > (unsigned long)(av->max_sbrked_mem))
av->max_sbrked_mem = sum;
sum += av->mmapped_mem;
if (sum > (unsigned long)(av->max_total_mem))
av->max_total_mem = sum;
check_malloc_state();
/* finally, do the allocation */
p = av->top;
size = chunksize(p);
remainder_size = (long)size - (long)nb;
/* check that one of the above allocation paths succeeded */
if (remainder_size >= (long)MINSIZE) {
remainder = chunk_at_offset(p, nb);
av->top = remainder;
set_head(p, nb | PREV_INUSE);
set_head(remainder, remainder_size | PREV_INUSE);
check_malloced_chunk(p, nb);
return chunk2mem(p);
}
}
/* catch all failure paths */
MALLOC_FAILURE_ACTION;
return 0;
}
/*
sYSTRIm is an inverse of sorts to sYSMALLOc.
It gives memory back to the system (via negative
arguments to sbrk) if there is unused memory at the `high' end of
the malloc pool. It is called automatically by free()
when top space exceeds the trim threshold.
returns 1 if it actually released any memory, else 0.
*/
#if __STD_C
static int sYSTRIm(size_t pad, mstate av)
#else
static int sYSTRIm(pad, av) size_t pad; mstate av;
#endif
{
long top_size; /* Amount of top-most memory */
long extra; /* Amount to release */
long released; /* Amount actually released */
char* current_brk; /* address returned by pre-check sbrk call */
char* new_brk; /* address returned by post-check sbrk call */
size_t pagesz;
/* Don't bother trying if sbrk doesn't provide contiguous regions */
if (av->sbrk_base != NONCONTIGUOUS_REGIONS) {
pagesz = av->pagesize;
top_size = chunksize(av->top);
/* Release in pagesize units, keeping at least one page */
extra = ((top_size - pad - MINSIZE + (pagesz-1)) / pagesz - 1) * pagesz;
if (extra > 0) {
/*
Only proceed if end of memory is where we last set it.
This avoids problems if there were foreign sbrk calls.
*/
current_brk = (char*)(MORECORE(0));
if (current_brk == (char*)(av->top) + top_size) {
/*
Attempt to release memory. We ignore return value,
and instead call again to find out where new end of memory is.
This avoids problems if first call releases less than we asked,
of if failure somehow altered brk value. (We could still
encounter problems if it altered brk in some very bad way,
but the only thing we can do is adjust anyway, which will cause
some downstream failure.)
*/
MORECORE(-extra);
new_brk = (char*)(MORECORE(0));
if (new_brk != (char*)MORECORE_FAILURE) {
released = (long)(current_brk - new_brk);
if (released != 0) {
/* Success. Adjust top. */
av->sbrked_mem -= released;
set_head(av->top, (top_size - released) | PREV_INUSE);
check_malloc_state();
return 1;
}
}
}
}
}
return 0;
}
/* ----------------------- Main public routines ----------------------- */
/*
Malloc routine. See running comments for algorithm description.
*/
#if __STD_C
Void_t* mALLOc(size_t bytes)
#else
Void_t* mALLOc(bytes) size_t bytes;
#endif
{
mstate av = get_malloc_state();
INTERNAL_SIZE_T nb; /* normalized request size */
unsigned int idx; /* associated bin index */
mbinptr bin; /* associated bin */
mfastbinptr* fb; /* associated fastbin */
mchunkptr victim; /* inspected/selected chunk */
INTERNAL_SIZE_T size; /* its size */
int victim_index; /* its bin index */
mchunkptr remainder; /* remainder from a split */
long remainder_size; /* its size */
unsigned int block; /* bit map traverser */
unsigned int bit; /* bit map traverser */
unsigned int map; /* current word of binmap */
mchunkptr fwd; /* misc temp for linking */
mchunkptr bck; /* misc temp for linking */
/*
Check request for legality and convert to internal form, nb.
This rejects negative arguments when size_t is treated as
signed. It also rejects arguments that are so large that the size
appears negative when aligned and padded. The converted form
adds SIZE_T bytes overhead plus possibly more to obtain necessary
alignment and/or to obtain a size of at least MINSIZE, the
smallest allocatable size.
*/
checked_request2size(bytes, nb);
/*
If the size qualifies as a fastbin, first check corresponding bin.
This code is safe to execute even if av not yet initialized, so we
can try it first, which saves some time on this fast path.
*/
if (nb <= av->max_fast) {
fb = &(av->fastbins[(fastbin_index(nb))]);
if ( (victim = *fb) != 0) {
*fb = victim->fd;
check_remalloced_chunk(victim, nb);
return chunk2mem(victim);
}
}
/*
If a small request, check regular bin. Since these "smallbins"
hold one size each, no searching within bins is necessary.
(If a large request, we need to wait until unsorted chunks are
processed to find best fit. But for small ones, fits are exact
anyway, so we can check now, which is faster.)
*/
if (in_smallbin_range(nb)) {
idx = smallbin_index(nb);
bin = bin_at(av,idx);
if ( (victim = last(bin)) != bin) {
if (victim == 0) /* initialization check */
malloc_consolidate(av);
else {
bck = victim->bk;
set_inuse_bit_at_offset(victim, nb);
bin->bk = bck;
bck->fd = bin;
check_malloced_chunk(victim, nb);
return chunk2mem(victim);
}
}
}
/*
If a large request, consolidate fastbins before continuing.
While it might look excessive to kill all fastbins before
even seeing if there is space available, this avoids
fragmentation problems normally associated with fastbins.
Also, in practice, programs tend to have runs of either small or
large requests, but less often mixtures, so consolidation is not
usually invoked all that often.
*/
else {
idx = largebin_index(nb);
if (have_fastchunks(av)) /* consolidation/initialization check */
malloc_consolidate(av);
}
/*
Process recently freed or remaindered chunks, taking one only if
it is exact fit, or, if a small request, it is the remainder from
the most recent non-exact fit. Place other traversed chunks in
bins. Note that this step is the only place in any routine where
chunks are placed in bins.
The outer loop here is needed because we might not realize until
near the end of malloc that we should have consolidated, so must
do so and retry. This happens at most once, and only when we would
otherwise need to expand memory to service a "small" request.
*/
for(;;) {
while ( (victim = unsorted_chunks(av)->bk) != unsorted_chunks(av)) {
bck = victim->bk;
size = chunksize(victim);
/*
If a small request, try to use last remainder if it is the
only chunk in unsorted bin. This helps promote locality for
runs of consecutive small requests. This is the only
exception to best-fit.
*/
if (in_smallbin_range(nb) &&
victim == av->last_remainder &&
bck == unsorted_chunks(av) &&
(remainder_size = (long)size - (long)nb) >= (long)MINSIZE) {
/* split and reattach remainder */
remainder = chunk_at_offset(victim, nb);
unsorted_chunks(av)->bk = unsorted_chunks(av)->fd = remainder;
av->last_remainder = remainder;
remainder->bk = remainder->fd = unsorted_chunks(av);
set_head(victim, nb | PREV_INUSE);
set_head(remainder, remainder_size | PREV_INUSE);
set_foot(remainder, remainder_size);
check_malloced_chunk(victim, nb);
return chunk2mem(victim);
}
/* remove from unsorted list */
unsorted_chunks(av)->bk = bck;
bck->fd = unsorted_chunks(av);
/* Take now instead of binning if exact fit */
if (size == nb) {
set_inuse_bit_at_offset(victim, size);
check_malloced_chunk(victim, nb);
return chunk2mem(victim);
}
/* place chunk in bin */
if (in_smallbin_range(size)) {
victim_index = smallbin_index(size);
bck = bin_at(av, victim_index);
fwd = bck->fd;
}
else {
victim_index = largebin_index(size);
bck = bin_at(av, victim_index);
fwd = bck->fd;
/* maintain large bins in sorted order */
if (fwd != bck) {
/* if smaller than smallest, bypass loop below */
if ((unsigned long)size <=
(unsigned long)(chunksize(bck->bk))) {
fwd = bck;
bck = bck->bk;
}
else {
while (fwd != bck &&
(unsigned long)size < (unsigned long)(chunksize(fwd))) {
fwd = fwd->fd;
}
bck = fwd->bk;
}
}
}
mark_bin(av, victim_index);
victim->bk = bck;
victim->fd = fwd;
fwd->bk = victim;
bck->fd = victim;
}
/*
If a large request, scan through the chunks of current bin in
sorted order to find smallest that fits. This is the only step
where an unbounded number of chunks might be scanned without doing
anything useful with them. However the lists tend to be very
short.
*/
if (!in_smallbin_range(nb)) {
bin = bin_at(av, idx);
/* skip scan if largest chunk is too small */
if ((victim = last(bin)) != bin &&
(long)(chunksize(first(bin))) - (long)(nb) >= 0) {
do {
size = chunksize(victim);
remainder_size = (long)size - (long)nb;
if (remainder_size >= 0) {
unlink(victim, bck, fwd);
/* Exhaust */
if (remainder_size < (long)MINSIZE) {
set_inuse_bit_at_offset(victim, size);
check_malloced_chunk(victim, nb);
return chunk2mem(victim);
}
/* Split */
else {
remainder = chunk_at_offset(victim, nb);
unsorted_chunks(av)->bk = unsorted_chunks(av)->fd = remainder;
remainder->bk = remainder->fd = unsorted_chunks(av);
set_head(victim, nb | PREV_INUSE);
set_head(remainder, remainder_size | PREV_INUSE);
set_foot(remainder, remainder_size);
check_malloced_chunk(victim, nb);
return chunk2mem(victim);
}
}
} while ( (victim = victim->bk) != bin);
}
}
/*
Search for a chunk by scanning bins, starting with next largest
bin. This search is strictly by best-fit; i.e., the smallest
(with ties going to approximately the least recently used) chunk
that fits is selected.
The bitmap avoids needing to check that most blocks are nonempty.
The particular case of skipping all bins during warm-up phases
when no chunks have been returned yet is faster than it might look.
*/
++idx;
bin = bin_at(av,idx);
block = idx2block(idx);
map = av->binmap[block];
bit = idx2bit(idx);
for (;;) {
/*
Skip rest of block if there are no more set bits in this block.
*/
if (bit > map || bit == 0) {
for (;;) {
if (++block >= BINMAPSIZE) /* out of bins */
break;
else if ( (map = av->binmap[block]) != 0) {
bin = bin_at(av, (block << BINMAPSHIFT));
bit = 1;
break;
}
}
/* Optimizers seem to like this double-break better than goto */
if (block >= BINMAPSIZE)
break;
}
/* Advance to bin with set bit. There must be one. */
while ((bit & map) == 0) {
bin = next_bin(bin);
bit <<= 1;
}
victim = last(bin);
/* False alarm -- the bin is empty. Clear the bit. */
if (victim == bin) {
av->binmap[block] = map &= ~bit; /* Write through */
bin = next_bin(bin);
bit <<= 1;
}
/* We know the first chunk in this bin is big enough to use. */
else {
size = chunksize(victim);
remainder_size = (long)size - (long)nb;
assert(remainder_size >= 0);
/* unlink */
bck = victim->bk;
bin->bk = bck;
bck->fd = bin;
/* Exhaust */
if (remainder_size < (long)MINSIZE) {
set_inuse_bit_at_offset(victim, size);
check_malloced_chunk(victim, nb);
return chunk2mem(victim);
}
/* Split */
else {
remainder = chunk_at_offset(victim, nb);
unsorted_chunks(av)->bk = unsorted_chunks(av)->fd = remainder;
remainder->bk = remainder->fd = unsorted_chunks(av);
/* advertise as last remainder */
if (in_smallbin_range(nb))
av->last_remainder = remainder;
set_head(victim, nb | PREV_INUSE);
set_head(remainder, remainder_size | PREV_INUSE);
set_foot(remainder, remainder_size);
check_malloced_chunk(victim, nb);
return chunk2mem(victim);
}
}
}
/*
If large enough, split off the chunk bordering the end of memory
("top"). Note that this use of top is in accord with the best-fit search
rule. In effect, top is treated as larger (and thus less well
fitting) than any other available chunk since it can be extended
to be as large as necessary (up to system limitations).
We require that "top" always exists (i.e., has size >= MINSIZE)
after initialization, so if it would otherwise be exhuasted by
current request, it is replenished. (Among the reasons for
ensuring it exists is that we may need MINSIZE space to put in
fenceposts in sysmalloc.)
*/
victim = av->top;
size = chunksize(victim);
remainder_size = (long)size - (long)nb;
if (remainder_size >= (long)MINSIZE) {
remainder = chunk_at_offset(victim, nb);
av->top = remainder;
set_head(victim, nb | PREV_INUSE);
set_head(remainder, remainder_size | PREV_INUSE);
check_malloced_chunk(victim, nb);
return chunk2mem(victim);
}
/*
If there is space available in fastbins, consolidate and retry,
to possibly avoid expanding memory. This can occur only if nb is
in smallbin range so we didn't consolidate upon entry.
*/
else if (have_fastchunks(av)) {
assert(in_smallbin_range(nb));
idx = smallbin_index(nb); /* restore original bin index */
malloc_consolidate(av);
}
/*
Otherwise, relay to handle system-dependent cases
*/
else
return sYSMALLOc(nb, av);
}
}
/*
Free routine. See running comments for algorithm description.
*/
#if __STD_C
void fREe(Void_t* mem)
#else
void fREe(mem) Void_t* mem;
#endif
{
mstate av = get_malloc_state();
mchunkptr p; /* chunk corresponding to mem */
INTERNAL_SIZE_T size; /* its size */
mfastbinptr* fb; /* associated fastbin */
mchunkptr nextchunk; /* next contiguous chunk */
INTERNAL_SIZE_T nextsize; /* its size */
int nextinuse; /* true if nextchunk is used */
INTERNAL_SIZE_T prevsize; /* size of previous contiguous chunk */
mchunkptr bck; /* misc temp for linking */
mchunkptr fwd; /* misc temp for linking */
/* free(0) has no effect */
if (mem != 0) {
p = mem2chunk(mem);
check_inuse_chunk(p);
size = chunksize(p);
/*
If eligible, place chunk on a fastbin so it can be found
and used quickly in malloc.
*/
if ((unsigned long)size <= (unsigned long)av->max_fast
#if TRIM_FASTBINS
/*
If TRIM_FASTBINS set, don't place chunks
bordering top into fastbins
*/
&& (chunk_at_offset(p, size) != av->top)
#endif
) {
set_fastchunks(av);
fb = &(av->fastbins[fastbin_index(size)]);
p->fd = *fb;
*fb = p;
}
/*
Consolidate non-mmapped chunks as they arrive.
*/
else if (!chunk_is_mmapped(p)) {
nextchunk = chunk_at_offset(p, size);
/* consolidate backward */
if (!prev_inuse(p)) {
prevsize = p->prev_size;
size += prevsize;
p = chunk_at_offset(p, -((long) prevsize));
unlink(p, bck, fwd);
}
nextsize = chunksize(nextchunk);
if (nextchunk != av->top) {
/* get and clear inuse bit */
nextinuse = inuse_bit_at_offset(nextchunk, nextsize);
set_head(nextchunk, nextsize);
/* consolidate forward */
if (!nextinuse) {
unlink(nextchunk, bck, fwd);
size += nextsize;
}
/*
Place chunk in unsorted chunk list. Chunks are
not placed into regular bins until after they have
been given one chance to be used in malloc.
*/
bck = unsorted_chunks(av);
fwd = bck->fd;
p->bk = bck;
p->fd = fwd;
bck->fd = p;
fwd->bk = p;
set_head(p, size | PREV_INUSE);
set_foot(p, size);
}
/*
If the chunk borders the current high end of memory,
consolidate into top
*/
else {
size += nextsize;
set_head(p, size | PREV_INUSE);
av->top = p;
/*
If the total unused topmost memory exceeds trim
threshold, ask malloc_trim to reduce top.
Unless max_fast is 0, we don't know if there are fastbins
bordering top, so we cannot tell for sure whether threshold has
been reached unless fastbins are consolidated. But we don't
want to consolidate on each free. As a compromise,
consolidation is performed if half the threshold is
reached.
*/
if ((unsigned long)(size) > (unsigned long)(av->trim_threshold / 2)) {
if (have_fastchunks(av)) {
malloc_consolidate(av);
size = chunksize(av->top);
}
if ((unsigned long)(size) > (unsigned long)(av->trim_threshold))
sYSTRIm(av->top_pad, av);
}
}
}
/*
If the chunk was allocated via mmap, release via munmap()
Note that if HAVE_MMAP is false but chunk_is_mmapped is
true, then user must have overwritten memory. There's nothing
we can do to catch this error unless DEBUG is set, in which case
check_inuse_chunk (above) will have triggered error.
*/
else {
#if HAVE_MMAP
int ret;
INTERNAL_SIZE_T offset = p->prev_size;
av->n_mmaps--;
av->mmapped_mem -= (size + offset);
ret = munmap((char*)p - offset, size + offset);
/* munmap returns non-zero on failure */
assert(ret == 0);
#endif
}
}
}
/*
malloc_consolidate is a specialized version of free() that tears
down chunks held in fastbins. Free itself cannot be used for this
purpose since, among other things, it might place chunks back onto
fastbins. So, instead, we need to use a minor variant of the same
code.
Also, because this routine needs to be called the first time through
malloc anyway, it turns out to be the perfect place to bury
initialization code.
*/
#if __STD_C
static void malloc_consolidate(mstate av)
#else
static void malloc_consolidate(av) mstate av;
#endif
{
mfastbinptr* fb;
mfastbinptr* maxfb;
mchunkptr p;
mchunkptr nextp;
mchunkptr unsorted_bin;
mchunkptr first_unsorted;
/* These have same use as in free() */
mchunkptr nextchunk;
INTERNAL_SIZE_T size;
INTERNAL_SIZE_T nextsize;
INTERNAL_SIZE_T prevsize;
int nextinuse;
mchunkptr bck;
mchunkptr fwd;
/*
If max_fast is 0, we know that malloc hasn't
yet been initialized, in which case do so.
*/
if (av->max_fast == 0) {
malloc_init_state(av);
check_malloc_state();
}
else if (have_fastchunks(av)) {
clear_fastchunks(av);
unsorted_bin = unsorted_chunks(av);
/*
Remove each chunk from fast bin and consolidate it, placing it
then in unsorted bin. Among other reasons for doing this,
placing in unsorted bin avoids needing to calculate actual bins
until malloc is sure that chunks aren't immediately going to be
reused anyway.
*/
maxfb = &(av->fastbins[fastbin_index(av->max_fast)]);
fb = &(av->fastbins[0]);
do {
if ( (p = *fb) != 0) {
*fb = 0;
do {
check_inuse_chunk(p);
nextp = p->fd;
/* Slightly streamlined version of consolidation code in free() */
size = p->size & ~PREV_INUSE;
nextchunk = chunk_at_offset(p, size);
if (!prev_inuse(p)) {
prevsize = p->prev_size;
size += prevsize;
p = chunk_at_offset(p, -((long) prevsize));
unlink(p, bck, fwd);
}
nextsize = chunksize(nextchunk);
if (nextchunk != av->top) {
nextinuse = inuse_bit_at_offset(nextchunk, nextsize);
set_head(nextchunk, nextsize);
if (!nextinuse) {
size += nextsize;
unlink(nextchunk, bck, fwd);
}
first_unsorted = unsorted_bin->fd;
unsorted_bin->fd = p;
first_unsorted->bk = p;
set_head(p, size | PREV_INUSE);
p->bk = unsorted_bin;
p->fd = first_unsorted;
set_foot(p, size);
}
else {
size += nextsize;
set_head(p, size | PREV_INUSE);
av->top = p;
}
} while ( (p = nextp) != 0);
}
} while (fb++ != maxfb);
}
}
/*
Realloc algorithm cases:
* Chunks that were obtained via mmap cannot be extended or shrunk
unless HAVE_MREMAP is defined, in which case mremap is used.
Otherwise, if the reallocation is for additional space, they are
copied. If for less, they are just left alone.
* Otherwise, if the reallocation is for additional space, and the
chunk can be extended, it is, else a malloc-copy-free sequence is
taken. There are several different ways that a chunk could be
extended. All are tried:
* Extending forward into following adjacent free chunk.
* Shifting backwards, joining preceding adjacent space
* Both shifting backwards and extending forward.
* Extending into newly sbrked space
* If there is not enough memory available to realloc, realloc
returns null, but does NOT free the existing space.
* If the reallocation is for less space, the newly unused space is
lopped off and freed. Unless the #define REALLOC_ZERO_BYTES_FREES
is set, realloc with a size argument of zero (re)allocates a
minimum-sized chunk.
The old unix realloc convention of allowing the last-free'd chunk
to be used as an argument to realloc is no longer supported.
I don't know of any programs still relying on this feature,
and allowing it would also allow too many other incorrect
usages of realloc to be sensible.
*/
#if __STD_C
Void_t* rEALLOc(Void_t* oldmem, size_t bytes)
#else
Void_t* rEALLOc(oldmem, bytes) Void_t* oldmem; size_t bytes;
#endif
{
mstate av = get_malloc_state();
INTERNAL_SIZE_T nb; /* padded request size */
mchunkptr oldp; /* chunk corresponding to oldmem */
INTERNAL_SIZE_T oldsize; /* its size */
mchunkptr newp; /* chunk to return */
INTERNAL_SIZE_T newsize; /* its size */
Void_t* newmem; /* corresponding user mem */
mchunkptr next; /* next contiguous chunk after oldp */
mchunkptr prev; /* previous contiguous chunk before oldp */
mchunkptr remainder; /* extra space at end of newp */
long remainder_size; /* its size */
mchunkptr bck; /* misc temp for linking */
mchunkptr fwd; /* misc temp for linking */
INTERNAL_SIZE_T copysize; /* bytes to copy */
int ncopies; /* INTERNAL_SIZE_T words to copy */
INTERNAL_SIZE_T* s; /* copy source */
INTERNAL_SIZE_T* d; /* copy destination */
#ifdef REALLOC_ZERO_BYTES_FREES
if (bytes == 0) {
fREe(oldmem);
return 0;
}
#endif
/* realloc of null is supposed to be same as malloc */
if (oldmem == 0) return mALLOc(bytes);
checked_request2size(bytes, nb);
oldp = mem2chunk(oldmem);
oldsize = chunksize(oldp);
check_inuse_chunk(oldp);
if (!chunk_is_mmapped(oldp)) {
if ((unsigned long)(oldsize) >= (unsigned long)(nb)) {
/* already big enough; split below */
newp = oldp;
newsize = oldsize;
}
else {
newp = 0;
newsize = 0;
next = chunk_at_offset(oldp, oldsize);
if (next == av->top) { /* Expand forward into top */
newsize = oldsize + chunksize(next);
if ((unsigned long)(newsize) >= (unsigned long)(nb + MINSIZE)) {
set_head_size(oldp, nb);
av->top = chunk_at_offset(oldp, nb);
set_head(av->top, (newsize - nb) | PREV_INUSE);
return chunk2mem(oldp);
}
else if (!prev_inuse(oldp)) { /* Shift backwards + top */
prev = prev_chunk(oldp);
newsize += chunksize(prev);
if ((unsigned long)(newsize) >= (unsigned long)(nb + MINSIZE)) {
newp = prev;
unlink(prev, bck, fwd);
av->top = chunk_at_offset(newp, nb);
set_head(av->top, (newsize - nb) | PREV_INUSE);
newsize = nb;
}
}
}
else if (!inuse(next)) { /* Forward into next chunk */
newsize = oldsize + chunksize(next);
if (((unsigned long)(newsize) >= (unsigned long)(nb))) {
newp = oldp;
unlink(next, bck, fwd);
}
else if (!prev_inuse(oldp)) { /* Forward + backward */
prev = prev_chunk(oldp);
newsize += chunksize(prev);
if (((unsigned long)(newsize) >= (unsigned long)(nb))) {
newp = prev;
unlink(prev, bck, fwd);
unlink(next, bck, fwd);
}
}
}
else if (!prev_inuse(oldp)) { /* Backward only */
prev = prev_chunk(oldp);
newsize = oldsize + chunksize(prev);
if ((unsigned long)(newsize) >= (unsigned long)(nb)) {
newp = prev;
unlink(prev, bck, fwd);
}
}
if (newp != 0) {
if (newp != oldp) {
/* Backward copies are not worth unrolling */
MALLOC_COPY(chunk2mem(newp), oldmem, oldsize - SIZE_SZ, 1);
}
}
/* Must allocate */
else {
newmem = mALLOc(nb - MALLOC_ALIGN_MASK);
if (newmem == 0)
return 0; /* propagate failure */
newp = mem2chunk(newmem);
newsize = chunksize(newp);
/*
Avoid copy if newp is next chunk after oldp.
*/
if (newp == next) {
newsize += oldsize;
newp = oldp;
}
else {
/*
Unroll copy of <= 36 bytes (72 if 8byte sizes)
We know that contents have an odd number of
INTERNAL_SIZE_T-sized words; minimally 3.
*/
copysize = oldsize - SIZE_SZ;
s = (INTERNAL_SIZE_T*)oldmem;
d = (INTERNAL_SIZE_T*)(chunk2mem(newp));
ncopies = copysize / sizeof(INTERNAL_SIZE_T);
assert(ncopies >= 3);
if (ncopies > 9)
MALLOC_COPY(d, s, copysize, 0);
else {
*(d+0) = *(s+0);
*(d+1) = *(s+1);
*(d+2) = *(s+2);
if (ncopies > 4) {
*(d+3) = *(s+3);
*(d+4) = *(s+4);
if (ncopies > 6) {
*(d+5) = *(s+5);
*(d+6) = *(s+6);
if (ncopies > 8) {
*(d+7) = *(s+7);
*(d+8) = *(s+8);
}
}
}
}
fREe(oldmem);
check_inuse_chunk(newp);
return chunk2mem(newp);
}
}
}
/* If possible, free extra space in old or extended chunk */
remainder_size = (long)newsize - (long)nb;
assert(remainder_size >= 0);
if (remainder_size >= (long)MINSIZE) { /* split remainder */
remainder = chunk_at_offset(newp, nb);
set_head_size(newp, nb);
set_head(remainder, remainder_size | PREV_INUSE);
/* Mark remainder as inuse so free() won't complain */
set_inuse_bit_at_offset(remainder, remainder_size);
fREe(chunk2mem(remainder));
}
else { /* not enough extra to split off */
set_head_size(newp, newsize);
set_inuse_bit_at_offset(newp, newsize);
}
check_inuse_chunk(newp);
return chunk2mem(newp);
}
/*
Handle mmap cases
*/
else {
#if HAVE_MMAP
#if HAVE_MREMAP
INTERNAL_SIZE_T offset = oldp->prev_size;
size_t pagemask = av->pagesize - 1;
char *cp;
unsigned long sum;
/* Note the extra SIZE_SZ overhead */
newsize = (nb + offset + SIZE_SZ + pagemask) & ~pagemask;
/* don't need to remap if still within same page */
if (oldsize == newsize - offset)
return oldmem;
cp = (char*)mremap((char*)oldp - offset, oldsize + offset, newsize, 1);
if (cp != (char*)MORECORE_FAILURE) {
newp = (mchunkptr)(cp + offset);
set_head(newp, (newsize - offset)|IS_MMAPPED);
assert(aligned_OK(chunk2mem(newp)));
assert((newp->prev_size == offset));
/* update statistics */
sum = av->mmapped_mem += newsize - oldsize;
if (sum > (unsigned long)(av->max_mmapped_mem))
av->max_mmapped_mem = sum;
sum += av->sbrked_mem;
if (sum > (unsigned long)(av->max_total_mem))
av->max_total_mem = sum;
return chunk2mem(newp);
}
#endif
/* Note the extra SIZE_SZ overhead. */
if ((long)oldsize - (long)SIZE_SZ >= (long)nb)
newmem = oldmem; /* do nothing */
else {
/* Must alloc, copy, free. */
newmem = mALLOc(nb - MALLOC_ALIGN_MASK);
if (newmem != 0) {
MALLOC_COPY(newmem, oldmem, oldsize - 2*SIZE_SZ, 0);
fREe(oldmem);
}
}
return newmem;
#else
/* If !HAVE_MMAP, but chunk_is_mmapped, user must have overwritten mem */
check_malloc_state();
MALLOC_FAILURE_ACTION;
return 0;
#endif
}
}
/*
memalign requests more than enough space from malloc, finds a spot
within that chunk that meets the alignment request, and then
possibly frees the leading and trailing space.
Alignments must be powers of two. If the argument is not a
power of two, the nearest greater power is used.
8-byte alignment is guaranteed by normal malloc calls, so don't
bother calling memalign with an argument of 8 or less.
Overreliance on memalign is a sure way to fragment space.
*/
#if __STD_C
Void_t* mEMALIGn(size_t alignment, size_t bytes)
#else
Void_t* mEMALIGn(alignment, bytes) size_t alignment; size_t bytes;
#endif
{
INTERNAL_SIZE_T nb; /* padded request size */
char* m; /* memory returned by malloc call */
mchunkptr p; /* corresponding chunk */
char* brk; /* alignment point within p */
mchunkptr newp; /* chunk to return */
INTERNAL_SIZE_T newsize; /* its size */
INTERNAL_SIZE_T leadsize; /* leading space befor alignment point */
mchunkptr remainder; /* spare room at end to split off */
long remainder_size; /* its size */
/* If need less alignment than we give anyway, just relay to malloc */
if (alignment <= MALLOC_ALIGNMENT) return mALLOc(bytes);
/* Otherwise, ensure that it is at least a minimum chunk size */
if (alignment < MINSIZE) alignment = MINSIZE;
/* Make sure alignment is power of 2 (in case MINSIZE is not). */
if ((alignment & (alignment - 1)) != 0) {
size_t a = MALLOC_ALIGNMENT * 2;
while ((unsigned long)a < (unsigned long)alignment) a <<= 1;
alignment = a;
}
checked_request2size(bytes, nb);
/* Call malloc with worst case padding to hit alignment. */
m = (char*)(mALLOc(nb + alignment + MINSIZE));
if (m == 0) return 0; /* propagate failure */
p = mem2chunk(m);
if ((((unsigned long)(m)) % alignment) != 0) { /* misaligned */
/*
Find an aligned spot inside chunk. Since we need to give back
leading space in a chunk of at least MINSIZE, if the first
calculation places us at a spot with less than MINSIZE leader,
we can move to the next aligned spot -- we've allocated enough
total room so that this is always possible.
*/
brk = (char*)mem2chunk(((unsigned long)(m + alignment - 1)) &
-((signed long) alignment));
if ((long)(brk - (char*)(p)) < (long)MINSIZE)
brk = brk + alignment;
newp = (mchunkptr)brk;
leadsize = brk - (char*)(p);
newsize = chunksize(p) - leadsize;
/* For mmapped chunks, just adjust offset */
if (chunk_is_mmapped(p)) {
newp->prev_size = p->prev_size + leadsize;
set_head(newp, newsize|IS_MMAPPED);
return chunk2mem(newp);
}
/* Otherwise, give back leader, use the rest */
set_head(newp, newsize | PREV_INUSE);
set_inuse_bit_at_offset(newp, newsize);
set_head_size(p, leadsize);
fREe(chunk2mem(p));
p = newp;
assert (newsize >= nb &&
(((unsigned long)(chunk2mem(p))) % alignment) == 0);
}
/* Also give back spare room at the end */
if (!chunk_is_mmapped(p)) {
remainder_size = (long)(chunksize(p)) - (long)nb;
if (remainder_size >= (long)MINSIZE) {
remainder = chunk_at_offset(p, nb);
set_head(remainder, remainder_size | PREV_INUSE);
set_head_size(p, nb);
fREe(chunk2mem(remainder));
}
}
check_inuse_chunk(p);
return chunk2mem(p);
}
/*
calloc calls malloc, then zeroes out the allocated chunk.
*/
#if __STD_C
Void_t* cALLOc(size_t n_elements, size_t elem_size)
#else
Void_t* cALLOc(n_elements, elem_size) size_t n_elements; size_t elem_size;
#endif
{
mchunkptr p;
INTERNAL_SIZE_T clearsize;
int nclears;
INTERNAL_SIZE_T* d;
Void_t* mem = mALLOc(n_elements * elem_size);
if (mem != 0) {
p = mem2chunk(mem);
if (!chunk_is_mmapped(p)) { /* don't need to clear mmapped space */
/*
Unroll clear of <= 36 bytes (72 if 8byte sizes)
We know that contents have an odd number of
INTERNAL_SIZE_T-sized words; minimally 3.
*/
d = (INTERNAL_SIZE_T*)mem;
clearsize = chunksize(p) - SIZE_SZ;
nclears = clearsize / sizeof(INTERNAL_SIZE_T);
assert(nclears >= 3);
if (nclears > 9)
MALLOC_ZERO(d, clearsize);
else {
*(d+0) = 0;
*(d+1) = 0;
*(d+2) = 0;
if (nclears > 4) {
*(d+3) = 0;
*(d+4) = 0;
if (nclears > 6) {
*(d+5) = 0;
*(d+6) = 0;
if (nclears > 8) {
*(d+7) = 0;
*(d+8) = 0;
}
}
}
}
}
}
return mem;
}
/*
cfree just calls free. It is needed/defined on some systems
that pair it with calloc, presumably for odd historical reasons
(such as: cfree is used in example code in first edition of K&R).
*/
#if __STD_C
void cFREe(Void_t *mem)
#else
void cFREe(mem) Void_t *mem;
#endif
{
fREe(mem);
}
/*
valloc just invokes memalign with alignment argument equal
to the page size of the system (or as near to this as can
be figured out from all the includes/defines above.)
*/
#if __STD_C
Void_t* vALLOc(size_t bytes)
#else
Void_t* vALLOc(bytes) size_t bytes;
#endif
{
/* Ensure initialization/consolidation */
mstate av = get_malloc_state();
malloc_consolidate(av);
return mEMALIGn(av->pagesize, bytes);
}
/*
pvalloc just invokes valloc for the nearest pagesize
that will accommodate request
*/
#if __STD_C
Void_t* pVALLOc(size_t bytes)
#else
Void_t* pVALLOc(bytes) size_t bytes;
#endif
{
mstate av = get_malloc_state();
size_t pagesz;
/* Ensure initialization/consolidation */
malloc_consolidate(av);
pagesz = av->pagesize;
return mEMALIGn(pagesz, (bytes + pagesz - 1) & ~(pagesz - 1));
}
/*
Malloc_Trim gives memory back to the system (via negative
arguments to sbrk) if there is unused memory at the `high' end of
the malloc pool. You can call this after freeing large blocks of
memory to potentially reduce the system-level memory requirements
of a program. However, it cannot guarantee to reduce memory. Under
some allocation patterns, some large free blocks of memory will be
locked between two used chunks, so they cannot be given back to
the system.
The `pad' argument to malloc_trim represents the amount of free
trailing space to leave untrimmed. If this argument is zero,
only the minimum amount of memory to maintain internal data
structures will be left (one page or less). Non-zero arguments
can be supplied to maintain enough trailing space to service
future expected allocations without having to re-obtain memory
from the system.
Malloc_trim returns 1 if it actually released any memory, else 0.
*/
#if __STD_C
int mTRIm(size_t pad)
#else
int mTRIm(pad) size_t pad;
#endif
{
mstate av = get_malloc_state();
/* Ensure initialization/consolidation */
malloc_consolidate(av);
return sYSTRIm(pad, av);
}
/*
malloc_usable_size tells you how many bytes you can actually use in
an allocated chunk, which may be more than you requested (although
often not). You can use this many bytes without worrying about
overwriting other allocated objects. Not a particularly great
programming practice, but still sometimes useful.
*/
#if __STD_C
size_t mUSABLe(Void_t* mem)
#else
size_t mUSABLe(mem) Void_t* mem;
#endif
{
mchunkptr p;
if (mem != 0) {
p = mem2chunk(mem);
if (chunk_is_mmapped(p))
return chunksize(p) - 2*SIZE_SZ;
else if (inuse(p))
return chunksize(p) - SIZE_SZ;
}
return 0;
}
/*
mallinfo returns a copy of updated current mallinfo.
*/
struct mallinfo mALLINFo()
{
mstate av = get_malloc_state();
struct mallinfo mi;
int i;
mbinptr b;
mchunkptr p;
INTERNAL_SIZE_T avail;
int navail;
int nfastblocks;
int fastbytes;
/* Ensure initialization */
if (av->top == 0) malloc_consolidate(av);
check_malloc_state();
/* Account for top */
avail = chunksize(av->top);
navail = 1; /* top always exists */
/* traverse fastbins */
nfastblocks = 0;
fastbytes = 0;
for (i = 0; i < NFASTBINS; ++i) {
for (p = av->fastbins[i]; p != 0; p = p->fd) {
++nfastblocks;
fastbytes += chunksize(p);
}
}
avail += fastbytes;
/* traverse regular bins */
for (i = 1; i < NBINS; ++i) {
b = bin_at(av, i);
for (p = last(b); p != b; p = p->bk) {
avail += chunksize(p);
navail++;
}
}
mi.smblks = nfastblocks;
mi.ordblks = navail;
mi.fordblks = avail;
mi.uordblks = av->sbrked_mem - avail;
mi.arena = av->sbrked_mem;
mi.hblks = av->n_mmaps;
mi.hblkhd = av->mmapped_mem;
mi.fsmblks = fastbytes;
mi.keepcost = chunksize(av->top);
mi.usmblks = av->max_total_mem;
return mi;
}
/*
malloc_stats prints on stderr the amount of space obtained from the
system (both via sbrk and mmap), the maximum amount (which may be
more than current if malloc_trim and/or munmap got called), and the
current number of bytes allocated via malloc (or realloc, etc) but
not yet freed. Note that this is the number of bytes allocated, not
the number requested. It will be larger than the number requested
because of alignment and bookkeeping overhead. Because it includes
alignment wastage as being in use, this figure may be greater than zero
even when no user-level chunks are allocated.
The reported current and maximum system memory can be inaccurate if
a program makes other calls to system memory allocation functions
(normally sbrk) outside of malloc.
malloc_stats prints only the most commonly interesting statistics.
More information can be obtained by calling mallinfo.
*/
void mSTATs()
{
struct mallinfo mi = mALLINFo();
#ifdef WIN32
{
unsigned long free, reserved, committed;
vminfo (&free, &reserved, &committed);
fprintf(stderr, "free bytes = %10lu\n",
free);
fprintf(stderr, "reserved bytes = %10lu\n",
reserved);
fprintf(stderr, "committed bytes = %10lu\n",
committed);
}
#endif
fprintf(stderr, "max system bytes = %10lu\n",
(unsigned long)(mi.usmblks));
fprintf(stderr, "system bytes = %10lu\n",
(unsigned long)(mi.arena + mi.hblkhd));
fprintf(stderr, "in use bytes = %10lu\n",
(unsigned long)(mi.uordblks + mi.hblkhd));
#ifdef WIN32
{
unsigned long kernel, user;
if (cpuinfo (TRUE, &kernel, &user)) {
fprintf(stderr, "kernel ms = %10lu\n",
kernel);
fprintf(stderr, "user ms = %10lu\n",
user);
}
}
#endif
}
/*
mallopt is the general SVID/XPG interface to tunable parameters.
The format is to provide a (parameter-number, parameter-value)
pair. mallopt then sets the corresponding parameter to the
argument value if it can (i.e., so long as the value is
meaningful), and returns 1 if successful else 0. See descriptions
of tunable parameters above for meanings.
*/
#if __STD_C
int mALLOPt(int param_number, int value)
#else
int mALLOPt(param_number, value) int param_number; int value;
#endif
{
mstate av = get_malloc_state();
/* Ensure initialization/consolidation */
malloc_consolidate(av);
switch(param_number) {
case M_MXFAST:
if (value >= 0 && value <= MAX_FAST_SIZE) {
av->max_fast = req2max_fast(value);
return 1;
}
else
return 0;
case M_TRIM_THRESHOLD:
av->trim_threshold = value;
return 1;
case M_TOP_PAD:
av->top_pad = value;
return 1;
case M_MMAP_THRESHOLD:
av->mmap_threshold = value;
return 1;
case M_MMAP_MAX:
#if HAVE_MMAP
av->n_mmaps_max = value;
return 1;
#else
if (value != 0)
return 0;
else {
av->n_mmaps_max = value;
return 1;
}
#endif
default:
return 0;
}
}
/* -------------------------------------------------------------- */
/*
Emulation of sbrk for win32.
Donated by J. Walter <Walter@GeNeSys-e.de>.
For additional information about this code, and malloc on Win32, see
http://www.genesys-e.de/jwalter/
*/
#ifdef WIN32
#ifdef _DEBUG
/* #define TRACE */
#endif
/* Support for USE_MALLOC_LOCK */
#ifdef USE_MALLOC_LOCK
/* Wait for spin lock */
static int slwait (int *sl) {
while (InterlockedCompareExchange ((void **) sl, (void *) 1, (void *) 0) != 0)
Sleep (0);
return 0;
}
/* Release spin lock */
static int slrelease (int *sl) {
InterlockedExchange (sl, 0);
return 0;
}
#ifdef NEEDED
/* Spin lock for emulation code */
static int g_sl;
#endif
#endif /* USE_MALLOC_LOCK */
/* getpagesize for windows */
static long getpagesize (void) {
static long g_pagesize = 0;
if (! g_pagesize) {
SYSTEM_INFO system_info;
GetSystemInfo (&system_info);
g_pagesize = system_info.dwPageSize;
}
return g_pagesize;
}
static long getregionsize (void) {
static long g_regionsize = 0;
if (! g_regionsize) {
SYSTEM_INFO system_info;
GetSystemInfo (&system_info);
g_regionsize = system_info.dwAllocationGranularity;
}
return g_regionsize;
}
/* A region list entry */
typedef struct _region_list_entry {
void *top_allocated;
void *top_committed;
void *top_reserved;
long reserve_size;
struct _region_list_entry *previous;
} region_list_entry;
/* Allocate and link a region entry in the region list */
static int region_list_append (region_list_entry **last, void *base_reserved, long reserve_size) {
region_list_entry *next = HeapAlloc (GetProcessHeap (), 0, sizeof (region_list_entry));
if (! next)
return FALSE;
next->top_allocated = (char *) base_reserved;
next->top_committed = (char *) base_reserved;
next->top_reserved = (char *) base_reserved + reserve_size;
next->reserve_size = reserve_size;
next->previous = *last;
*last = next;
return TRUE;
}
/* Free and unlink the last region entry from the region list */
static int region_list_remove (region_list_entry **last) {
region_list_entry *previous = (*last)->previous;
if (! HeapFree (GetProcessHeap (), sizeof (region_list_entry), *last))
return FALSE;
*last = previous;
return TRUE;
}
#define CEIL(size,to) (((size)+(to)-1)&~((to)-1))
#define FLOOR(size,to) ((size)&~((to)-1))
#define SBRK_SCALE 0
/* #define SBRK_SCALE 1 */
/* #define SBRK_SCALE 2 */
/* #define SBRK_SCALE 4 */
/* sbrk for windows */
static void *sbrk (long size) {
static long g_pagesize, g_my_pagesize;
static long g_regionsize, g_my_regionsize;
static region_list_entry *g_last;
void *result = (void *) MORECORE_FAILURE;
#ifdef TRACE
printf ("sbrk %d\n", size);
#endif
#if defined (USE_MALLOC_LOCK) && defined (NEEDED)
/* Wait for spin lock */
slwait (&g_sl);
#endif
/* First time initialization */
if (! g_pagesize) {
g_pagesize = getpagesize ();
g_my_pagesize = g_pagesize << SBRK_SCALE;
}
if (! g_regionsize) {
g_regionsize = getregionsize ();
g_my_regionsize = g_regionsize << SBRK_SCALE;
}
if (! g_last) {
if (! region_list_append (&g_last, 0, 0))
goto sbrk_exit;
}
/* Assert invariants */
assert (g_last);
assert ((char *) g_last->top_reserved - g_last->reserve_size <= (char *) g_last->top_allocated &&
g_last->top_allocated <= g_last->top_committed);
assert ((char *) g_last->top_reserved - g_last->reserve_size <= (char *) g_last->top_committed &&
g_last->top_committed <= g_last->top_reserved &&
(unsigned) g_last->top_committed % g_pagesize == 0);
assert ((unsigned) g_last->top_reserved % g_regionsize == 0);
assert ((unsigned) g_last->reserve_size % g_regionsize == 0);
/* Allocation requested? */
if (size >= 0) {
/* Allocation size is the requested size */
long allocate_size = size;
/* Compute the size to commit */
long to_commit = (char *) g_last->top_allocated + allocate_size - (char *) g_last->top_committed;
/* Do we reach the commit limit? */
if (to_commit > 0) {
/* Round size to commit */
long commit_size = CEIL (to_commit, g_my_pagesize);
/* Compute the size to reserve */
long to_reserve = (char *) g_last->top_committed + commit_size - (char *) g_last->top_reserved;
/* Do we reach the reserve limit? */
if (to_reserve > 0) {
/* Compute the remaining size to commit in the current region */
long remaining_commit_size = (char *) g_last->top_reserved - (char *) g_last->top_committed;
if (remaining_commit_size > 0) {
/* Assert preconditions */
assert ((unsigned) g_last->top_committed % g_pagesize == 0);
assert (0 < remaining_commit_size && remaining_commit_size % g_pagesize == 0); {
/* Commit this */
void *base_committed = VirtualAlloc (g_last->top_committed, remaining_commit_size,
MEM_COMMIT, PAGE_READWRITE);
/* Check returned pointer for consistency */
if (base_committed != g_last->top_committed)
goto sbrk_exit;
/* Assert postconditions */
assert ((unsigned) base_committed % g_pagesize == 0);
#ifdef TRACE
printf ("Commit %p %d\n", base_committed, remaining_commit_size);
#endif
/* Adjust the regions commit top */
g_last->top_committed = (char *) base_committed + remaining_commit_size;
}
} {
/* Now we are going to search and reserve. */
int contiguous = -1;
int found = FALSE;
MEMORY_BASIC_INFORMATION memory_info;
void *base_reserved;
long reserve_size;
do {
/* Assume contiguous memory */
contiguous = TRUE;
/* Round size to reserve */
reserve_size = CEIL (to_reserve, g_my_regionsize);
/* Start with the current region's top */
memory_info.BaseAddress = g_last->top_reserved;
/* Assert preconditions */
assert ((unsigned) memory_info.BaseAddress % g_pagesize == 0);
assert (0 < reserve_size && reserve_size % g_regionsize == 0);
while (VirtualQuery (memory_info.BaseAddress, &memory_info, sizeof (memory_info))) {
/* Assert postconditions */
assert ((unsigned) memory_info.BaseAddress % g_pagesize == 0);
#ifdef TRACE
printf ("Query %p %d %s\n", memory_info.BaseAddress, memory_info.RegionSize,
memory_info.State == MEM_FREE ? "FREE":
(memory_info.State == MEM_RESERVE ? "RESERVED":
(memory_info.State == MEM_COMMIT ? "COMMITTED": "?")));
#endif
/* Region is free, well aligned and big enough: we are done */
if (memory_info.State == MEM_FREE &&
(unsigned) memory_info.BaseAddress % g_regionsize == 0 &&
memory_info.RegionSize >= (unsigned) reserve_size) {
found = TRUE;
break;
}
/* From now on we can't get contiguous memory! */
contiguous = FALSE;
/* Recompute size to reserve */
reserve_size = CEIL (allocate_size, g_my_regionsize);
memory_info.BaseAddress = (char *) memory_info.BaseAddress + memory_info.RegionSize;
/* Assert preconditions */
assert ((unsigned) memory_info.BaseAddress % g_pagesize == 0);
assert (0 < reserve_size && reserve_size % g_regionsize == 0);
}
/* Search failed? */
if (! found)
goto sbrk_exit;
/* Assert preconditions */
assert ((unsigned) memory_info.BaseAddress % g_regionsize == 0);
assert (0 < reserve_size && reserve_size % g_regionsize == 0);
/* Try to reserve this */
base_reserved = VirtualAlloc (memory_info.BaseAddress, reserve_size,
MEM_RESERVE, PAGE_NOACCESS);
if (! base_reserved) {
int rc = GetLastError ();
if (rc != ERROR_INVALID_ADDRESS)
goto sbrk_exit;
}
/* A null pointer signals (hopefully) a race condition with another thread. */
/* In this case, we try again. */
} while (! base_reserved);
/* Check returned pointer for consistency */
if (memory_info.BaseAddress && base_reserved != memory_info.BaseAddress)
goto sbrk_exit;
/* Assert postconditions */
assert ((unsigned) base_reserved % g_regionsize == 0);
#ifdef TRACE
printf ("Reserve %p %d\n", base_reserved, reserve_size);
#endif
/* Did we get contiguous memory? */
if (contiguous) {
long start_size = (char *) g_last->top_committed - (char *) g_last->top_allocated;
/* Adjust allocation size */
allocate_size -= start_size;
/* Adjust the regions allocation top */
g_last->top_allocated = g_last->top_committed;
/* Recompute the size to commit */
to_commit = (char *) g_last->top_allocated + allocate_size - (char *) g_last->top_committed;
/* Round size to commit */
commit_size = CEIL (to_commit, g_my_pagesize);
}
/* Append the new region to the list */
if (! region_list_append (&g_last, base_reserved, reserve_size))
goto sbrk_exit;
/* Didn't we get contiguous memory? */
if (! contiguous) {
/* Recompute the size to commit */
to_commit = (char *) g_last->top_allocated + allocate_size - (char *) g_last->top_committed;
/* Round size to commit */
commit_size = CEIL (to_commit, g_my_pagesize);
}
}
}
/* Assert preconditions */
assert ((unsigned) g_last->top_committed % g_pagesize == 0);
assert (0 < commit_size && commit_size % g_pagesize == 0); {
/* Commit this */
void *base_committed = VirtualAlloc (g_last->top_committed, commit_size,
MEM_COMMIT, PAGE_READWRITE);
/* Check returned pointer for consistency */
if (base_committed != g_last->top_committed)
goto sbrk_exit;
/* Assert postconditions */
assert ((unsigned) base_committed % g_pagesize == 0);
#ifdef TRACE
printf ("Commit %p %d\n", base_committed, commit_size);
#endif
/* Adjust the regions commit top */
g_last->top_committed = (char *) base_committed + commit_size;
}
}
/* Adjust the regions allocation top */
g_last->top_allocated = (char *) g_last->top_allocated + allocate_size;
result = (char *) g_last->top_allocated - size;
/* Deallocation requested? */
} else if (size < 0) {
long deallocate_size = - size;
/* As long as we have a region to release */
while ((char *) g_last->top_allocated - deallocate_size < (char *) g_last->top_reserved - g_last->reserve_size) {
/* Get the size to release */
long release_size = g_last->reserve_size;
/* Get the base address */
void *base_reserved = (char *) g_last->top_reserved - release_size;
/* Assert preconditions */
assert ((unsigned) base_reserved % g_regionsize == 0);
assert (0 < release_size && release_size % g_regionsize == 0); {
/* Release this */
int rc = VirtualFree (base_reserved, 0,
MEM_RELEASE);
/* Check returned code for consistency */
if (! rc)
goto sbrk_exit;
#ifdef TRACE
printf ("Release %p %d\n", base_reserved, release_size);
#endif
}
/* Adjust deallocation size */
deallocate_size -= (char *) g_last->top_allocated - (char *) base_reserved;
/* Remove the old region from the list */
if (! region_list_remove (&g_last))
goto sbrk_exit;
} {
/* Compute the size to decommit */
long to_decommit = (char *) g_last->top_committed - ((char *) g_last->top_allocated - deallocate_size);
if (to_decommit >= g_my_pagesize) {
/* Compute the size to decommit */
long decommit_size = FLOOR (to_decommit, g_my_pagesize);
/* Compute the base address */
void *base_committed = (char *) g_last->top_committed - decommit_size;
/* Assert preconditions */
assert ((unsigned) base_committed % g_pagesize == 0);
assert (0 < decommit_size && decommit_size % g_pagesize == 0); {
/* Decommit this */
int rc = VirtualFree ((char *) base_committed, decommit_size,
MEM_DECOMMIT);
/* Check returned code for consistency */
if (! rc)
goto sbrk_exit;
#ifdef TRACE
printf ("Decommit %p %d\n", base_committed, decommit_size);
#endif
}
/* Adjust deallocation size and regions commit and allocate top */
deallocate_size -= (char *) g_last->top_allocated - (char *) base_committed;
g_last->top_committed = base_committed;
g_last->top_allocated = base_committed;
}
}
/* Adjust regions allocate top */
g_last->top_allocated = (char *) g_last->top_allocated - deallocate_size;
/* Check for underflow */
if ((char *) g_last->top_reserved - g_last->reserve_size > (char *) g_last->top_allocated ||
g_last->top_allocated > g_last->top_committed) {
/* Adjust regions allocate top */
g_last->top_allocated = (char *) g_last->top_reserved - g_last->reserve_size;
goto sbrk_exit;
}
result = g_last->top_allocated;
}
/* Assert invariants */
assert (g_last);
assert ((char *) g_last->top_reserved - g_last->reserve_size <= (char *) g_last->top_allocated &&
g_last->top_allocated <= g_last->top_committed);
assert ((char *) g_last->top_reserved - g_last->reserve_size <= (char *) g_last->top_committed &&
g_last->top_committed <= g_last->top_reserved &&
(unsigned) g_last->top_committed % g_pagesize == 0);
assert ((unsigned) g_last->top_reserved % g_regionsize == 0);
assert ((unsigned) g_last->reserve_size % g_regionsize == 0);
sbrk_exit:
#if defined (USE_MALLOC_LOCK) && defined (NEEDED)
/* Release spin lock */
slrelease (&g_sl);
#endif
return result;
}
/* mmap for windows */
static void *mmap (void *ptr, long size, long prot, long type, long handle, long arg) {
static long g_pagesize;
static long g_regionsize;
#ifdef TRACE
printf ("mmap %d\n", size);
#endif
#if defined (USE_MALLOC_LOCK) && defined (NEEDED)
/* Wait for spin lock */
slwait (&g_sl);
#endif
/* First time initialization */
if (! g_pagesize)
g_pagesize = getpagesize ();
if (! g_regionsize)
g_regionsize = getregionsize ();
/* Assert preconditions */
assert ((unsigned) ptr % g_regionsize == 0);
assert (size % g_pagesize == 0);
/* Allocate this */
ptr = VirtualAlloc (ptr, size,
MEM_RESERVE | MEM_COMMIT | MEM_TOP_DOWN, PAGE_READWRITE);
if (! ptr) {
ptr = (void *) MORECORE_FAILURE;
goto mmap_exit;
}
/* Assert postconditions */
assert ((unsigned) ptr % g_regionsize == 0);
#ifdef TRACE
printf ("Commit %p %d\n", ptr, size);
#endif
mmap_exit:
#if defined (USE_MALLOC_LOCK) && defined (NEEDED)
/* Release spin lock */
slrelease (&g_sl);
#endif
return ptr;
}
/* munmap for windows */
static long munmap (void *ptr, long size) {
static long g_pagesize;
static long g_regionsize;
int rc = MUNMAP_FAILURE;
#ifdef TRACE
printf ("munmap %p %d\n", ptr, size);
#endif
#if defined (USE_MALLOC_LOCK) && defined (NEEDED)
/* Wait for spin lock */
slwait (&g_sl);
#endif
/* First time initialization */
if (! g_pagesize)
g_pagesize = getpagesize ();
if (! g_regionsize)
g_regionsize = getregionsize ();
/* Assert preconditions */
assert ((unsigned) ptr % g_regionsize == 0);
assert (size % g_pagesize == 0);
/* Free this */
if (! VirtualFree (ptr, 0,
MEM_RELEASE))
goto munmap_exit;
rc = 0;
#ifdef TRACE
printf ("Release %p %d\n", ptr, size);
#endif
munmap_exit:
#if defined (USE_MALLOC_LOCK) && defined (NEEDED)
/* Release spin lock */
slrelease (&g_sl);
#endif
return rc;
}
static void vminfo (unsigned long *free, unsigned long *reserved, unsigned long *committed) {
MEMORY_BASIC_INFORMATION memory_info;
memory_info.BaseAddress = 0;
*free = *reserved = *committed = 0;
while (VirtualQuery (memory_info.BaseAddress, &memory_info, sizeof (memory_info))) {
switch (memory_info.State) {
case MEM_FREE:
*free += memory_info.RegionSize;
break;
case MEM_RESERVE:
*reserved += memory_info.RegionSize;
break;
case MEM_COMMIT:
*committed += memory_info.RegionSize;
break;
}
memory_info.BaseAddress = (char *) memory_info.BaseAddress + memory_info.RegionSize;
}
}
static int cpuinfo (int whole, unsigned long *kernel, unsigned long *user) {
if (whole) {
__int64 creation64, exit64, kernel64, user64;
int rc = GetProcessTimes (GetCurrentProcess (),
(FILETIME *) &creation64,
(FILETIME *) &exit64,
(FILETIME *) &kernel64,
(FILETIME *) &user64);
if (! rc) {
*kernel = 0;
*user = 0;
return FALSE;
}
*kernel = (unsigned long) (kernel64 / 10000);
*user = (unsigned long) (user64 / 10000);
return TRUE;
} else {
__int64 creation64, exit64, kernel64, user64;
int rc = GetThreadTimes (GetCurrentThread (),
(FILETIME *) &creation64,
(FILETIME *) &exit64,
(FILETIME *) &kernel64,
(FILETIME *) &user64);
if (! rc) {
*kernel = 0;
*user = 0;
return FALSE;
}
*kernel = (unsigned long) (kernel64 / 10000);
*user = (unsigned long) (user64 / 10000);
return TRUE;
}
}
#endif /* WIN32 */
/*
History:
V2.7.0
* new WIN32 sbrk, mmap, munmap, lock code from <Walter@GeNeSys-e.de>.
* Allow override of MALLOC_ALIGNMENT (Thanks to Ruud Waij for
helping test this.)
* memalign: check alignment arg
* realloc: use memmove when regions may overlap.
* Collect all cases in malloc requiring system memory into sYSMALLOc
* Use mmap as backup to sbrk, if available; fold these mmap-related
operations into others.
* Place all internal state in malloc_state
* Introduce fastbins (although similar to 2.5.1)
* Many minor tunings and cosmetic improvements
* Introduce USE_PUBLIC_MALLOC_WRAPPERS, USE_MALLOC_LOCK
* Introduce MALLOC_FAILURE_ACTION, MORECORE_CONTIGUOUS
Thanks to Tony E. Bennett <tbennett@nvidia.com> and others.
* Adjust request2size to fit with MALLOC_FAILURE_ACTION.
* Include errno.h to support default failure action.
* Further improve WIN32 'sbrk()' emulation's 'findRegion()' routine
to avoid infinite loop when allocating initial memory larger
than RESERVED_SIZE and/or subsequent memory larger than
NEXT_SIZE. Thanks to Andreas Mueller <a.mueller at paradatec.de>
for finding this one.
V2.6.6 Sun Dec 5 07:42:19 1999 Doug Lea (dl at gee)
* return null for negative arguments
* Added Several WIN32 cleanups from Martin C. Fong <mcfong at yahoo.com>
* Add 'LACKS_SYS_PARAM_H' for those systems without 'sys/param.h'
(e.g. WIN32 platforms)
* Cleanup header file inclusion for WIN32 platforms
* Cleanup code to avoid Microsoft Visual C++ compiler complaints
* Add 'USE_DL_PREFIX' to quickly allow co-existence with existing
memory allocation routines
* Set 'malloc_getpagesize' for WIN32 platforms (needs more work)
* Use 'assert' rather than 'ASSERT' in WIN32 code to conform to
usage of 'assert' in non-WIN32 code
* Improve WIN32 'sbrk()' emulation's 'findRegion()' routine to
avoid infinite loop
* Always call 'fREe()' rather than 'free()'
V2.6.5 Wed Jun 17 15:57:31 1998 Doug Lea (dl at gee)
* Fixed ordering problem with boundary-stamping
V2.6.3 Sun May 19 08:17:58 1996 Doug Lea (dl at gee)
* Added pvalloc, as recommended by H.J. Liu
* Added 64bit pointer support mainly from Wolfram Gloger
* Added anonymously donated WIN32 sbrk emulation
* Malloc, calloc, getpagesize: add optimizations from Raymond Nijssen
* malloc_extend_top: fix mask error that caused wastage after
foreign sbrks
* Add linux mremap support code from HJ Liu
V2.6.2 Tue Dec 5 06:52:55 1995 Doug Lea (dl at gee)
* Integrated most documentation with the code.
* Add support for mmap, with help from
Wolfram Gloger (Gloger@lrz.uni-muenchen.de).
* Use last_remainder in more cases.
* Pack bins using idea from colin@nyx10.cs.du.edu
* Use ordered bins instead of best-fit threshhold
* Eliminate block-local decls to simplify tracing and debugging.
* Support another case of realloc via move into top
* Fix error occuring when initial sbrk_base not word-aligned.
* Rely on page size for units instead of SBRK_UNIT to
avoid surprises about sbrk alignment conventions.
* Add mallinfo, mallopt. Thanks to Raymond Nijssen
(raymond@es.ele.tue.nl) for the suggestion.
* Add `pad' argument to malloc_trim and top_pad mallopt parameter.
* More precautions for cases where other routines call sbrk,
courtesy of Wolfram Gloger (Gloger@lrz.uni-muenchen.de).
* Added macros etc., allowing use in linux libc from
H.J. Lu (hjl@gnu.ai.mit.edu)
* Inverted this history list
V2.6.1 Sat Dec 2 14:10:57 1995 Doug Lea (dl at gee)
* Re-tuned and fixed to behave more nicely with V2.6.0 changes.
* Removed all preallocation code since under current scheme
the work required to undo bad preallocations exceeds
the work saved in good cases for most test programs.
* No longer use return list or unconsolidated bins since
no scheme using them consistently outperforms those that don't
given above changes.
* Use best fit for very large chunks to prevent some worst-cases.
* Added some support for debugging
V2.6.0 Sat Nov 4 07:05:23 1995 Doug Lea (dl at gee)
* Removed footers when chunks are in use. Thanks to
Paul Wilson (wilson@cs.texas.edu) for the suggestion.
V2.5.4 Wed Nov 1 07:54:51 1995 Doug Lea (dl at gee)
* Added malloc_trim, with help from Wolfram Gloger
(wmglo@Dent.MED.Uni-Muenchen.DE).
V2.5.3 Tue Apr 26 10:16:01 1994 Doug Lea (dl at g)
V2.5.2 Tue Apr 5 16:20:40 1994 Doug Lea (dl at g)
* realloc: try to expand in both directions
* malloc: swap order of clean-bin strategy;
* realloc: only conditionally expand backwards
* Try not to scavenge used bins
* Use bin counts as a guide to preallocation
* Occasionally bin return list chunks in first scan
* Add a few optimizations from colin@nyx10.cs.du.edu
V2.5.1 Sat Aug 14 15:40:43 1993 Doug Lea (dl at g)
* faster bin computation & slightly different binning
* merged all consolidations to one part of malloc proper
(eliminating old malloc_find_space & malloc_clean_bin)
* Scan 2 returns chunks (not just 1)
* Propagate failure in realloc if malloc returns 0
* Add stuff to allow compilation on non-ANSI compilers
from kpv@research.att.com
V2.5 Sat Aug 7 07:41:59 1993 Doug Lea (dl at g.oswego.edu)
* removed potential for odd address access in prev_chunk
* removed dependency on getpagesize.h
* misc cosmetics and a bit more internal documentation
* anticosmetics: mangled names in macros to evade debugger strangeness
* tested on sparc, hp-700, dec-mips, rs6000
with gcc & native cc (hp, dec only) allowing
Detlefs & Zorn comparison study (in SIGPLAN Notices.)
Trial version Fri Aug 28 13:14:29 1992 Doug Lea (dl at g.oswego.edu)
* Based loosely on libg++-1.2X malloc. (It retains some of the overall
structure of old version, but most details differ.)
*/