/*

This is a version (aka dlmalloc) of malloc/free/realloc written by

Doug Lea and released to the public domain, as explained at

http://creativecommons.org/licenses/publicdomain. Send questions,

comments, complaints, performance data, etc to dl@cs.oswego.edu

* Version 2.8.3 Thu Sep 22 11:16:15 2005 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 (-O3), and link it into another program. All of

the compile-time options default to reasonable values for use on

most platforms. You might later want to step through various

compile-time and dynamic tuning options.

For convenience, an include file for code using this malloc is at:

ftp://gee.cs.oswego.edu/pub/misc/malloc-2.8.3.h

You don't really need this .h file unless you call functions not

defined in your system include files. The .h file contains only the

excerpts from this file needed for using this malloc on ANSI C/C++

systems, so long as you haven't changed compile-time options about

naming and tuning parameters. If you do, then you can create your

own malloc.h that does include all settings by cutting at the point

indicated below. Note that you may already by default be using a C

library containing a malloc that is based on some version of this

malloc (for example in linux). You might still want to use the one

in this file to customize settings or to avoid overheads associated

with library versions.

* Vital statistics:

Supported pointer/size_t representation: 4 or 8 bytes

size_t MUST be an unsigned type of the same width as

pointers. (If you are using an ancient system that declares

size_t as a signed type, or need it to be a different width

than pointers, you can use a previous release of this malloc

(e.g. 2.7.2) supporting these.)

Alignment: 8 bytes (default)

This suffices for nearly all current machines and C compilers.

However, you can define MALLOC_ALIGNMENT to be wider than this

if necessary (up to 128bytes), at the expense of using more space.

Minimum overhead per allocated chunk: 4 or 8 bytes (if 4byte sizes)

8 or 16 bytes (if 8byte sizes)

Each malloced chunk has a hidden word of overhead holding size

and status information, and additional cross-check word

if FOOTERS is defined.

Minimum allocated size: 4-byte ptrs: 16 bytes (including overhead)

8-byte ptrs: 32 bytes (including overhead)

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 about

32 bytes plus the remainder from a system page (the minimal

mmap unit); typically 4096 or 8192 bytes.

Security: static-safe; optionally more or less

The "security" of malloc refers to the ability of malicious

code to accentuate the effects of errors (for example, freeing

space that is not currently malloc'ed or overwriting past the

ends of chunks) in code that calls malloc. This malloc

guarantees not to modify any memory locations below the base of

heap, i.e., static variables, even in the presence of usage

errors. The routines additionally detect most improper frees

and reallocs. All this holds as long as the static bookkeeping

for malloc itself is not corrupted by some other means. This

is only one aspect of security -- these checks do not, and

cannot, detect all possible programming errors.

If FOOTERS is defined nonzero, then each allocated chunk

carries an additional check word to verify that it was malloced

from its space. These check words are the same within each

execution of a program using malloc, but differ across

executions, so externally crafted fake chunks cannot be

freed. This improves security by rejecting frees/reallocs that

could corrupt heap memory, in addition to the checks preventing

writes to statics that are always on. This may further improve

security at the expense of time and space overhead. (Note that

FOOTERS may also be worth using with MSPACES.)

By default detected errors cause the program to abort (calling

"abort()"). You can override this to instead proceed past

errors by defining PROCEED_ON_ERROR. In this case, a bad free

has no effect, and a malloc that encounters a bad address

caused by user overwrites will ignore the bad address by

dropping pointers and indices to all known memory. This may

be appropriate for programs that should continue if at all

possible in the face of programming errors, although they may

run out of memory because dropped memory is never reclaimed.

If you don't like either of these options, you can define

CORRUPTION_ERROR_ACTION and USAGE_ERROR_ACTION to do anything

else. And if if you are sure that your program using malloc has

no errors or vulnerabilities, you can define INSECURE to 1,

which might (or might not) provide a small performance improvement.

Thread-safety: NOT thread-safe unless USE_LOCKS defined

When USE_LOCKS is defined, each public call to malloc, free,

etc is surrounded with either a pthread mutex or a win32

spinlock (depending on WIN32). This is not especially fast, and

can be a major bottleneck. 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, consider instead using ptmalloc, which is derived from

a version of this malloc. (See http://www.malloc.de).

System requirements: Any combination of MORECORE and/or MMAP/MUNMAP

This malloc can use unix sbrk or any emulation (invoked using

the CALL_MORECORE macro) and/or mmap/munmap or any emulation

(invoked using CALL_MMAP/CALL_MUNMAP) to get and release system

memory. On most unix systems, it tends to work best if both

MORECORE and MMAP are enabled. On Win32, it uses emulations

based on VirtualAlloc. It also uses common C library functions

like memset.

Compliance: I believe it is compliant with the Single Unix Specification

(See http://www.unix.org). Also SVID/XPG, ANSI C, and probably

others as well.

* Overview of algorithms

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.

In most ways, this malloc is a best-fit allocator. Generally, it

chooses the best-fitting existing chunk for a request, with ties

broken in approximately least-recently-used order. (This strategy

normally maintains low fragmentation.) However, for requests less

than 256bytes, it deviates from best-fit when there is not an

exactly fitting available chunk by preferring to use space adjacent

to that used for the previous small request, as well as by breaking

ties in approximately most-recently-used order. (These enhance

locality of series of small allocations.) And for very large requests

(>= 256Kb by default), it relies on system memory mapping

facilities, if supported. (This helps avoid carrying around and

possibly fragmenting memory used only for large chunks.)

All operations (except malloc_stats and mallinfo) have execution

times that are bounded by a constant factor of the number of bits in

a size_t, not counting any clearing in calloc or copying in realloc,

or actions surrounding MORECORE and MMAP that have times

proportional to the number of non-contiguous regions returned by

system allocation routines, which is often just 1.

The implementation is not very modular and seriously overuses

macros. Perhaps someday all C compilers will do as good a job

inlining modular code as can now be done by brute-force expansion,

but now, enough of them seem not to.

Some compilers issue a lot of warnings about code that is

dead/unreachable only on some platforms, and also about intentional

uses of negation on unsigned types. All known cases of each can be

ignored.

For a longer but out of date high-level description, see

http://gee.cs.oswego.edu/dl/html/malloc.html

* MSPACES

If MSPACES is defined, then in addition to malloc, free, etc.,

this file also defines mspace_malloc, mspace_free, etc. These

are versions of malloc routines that take an "mspace" argument

obtained using create_mspace, to control all internal bookkeeping.

If ONLY_MSPACES is defined, only these versions are compiled.

So if you would like to use this allocator for only some allocations,

and your system malloc for others, you can compile with

ONLY_MSPACES and then do something like...

static mspace mymspace = create_mspace(0,0); // for example

#define mymalloc(bytes) mspace_malloc(mymspace, bytes)

(Note: If you only need one instance of an mspace, you can instead

use "USE_DL_PREFIX" to relabel the global malloc.)

You can similarly create thread-local allocators by storing

mspaces as thread-locals. For example:

static __thread mspace tlms = 0;

void* tlmalloc(size_t bytes) {

if (tlms == 0) tlms = create_mspace(0, 0);

return mspace_malloc(tlms, bytes);

}

void tlfree(void* mem) { mspace_free(tlms, mem); }

Unless FOOTERS is defined, each mspace is completely independent.

You cannot allocate from one and free to another (although

conformance is only weakly checked, so usage errors are not always

caught). If FOOTERS is defined, then each chunk carries around a tag

indicating its originating mspace, and frees are directed to their

originating spaces.

------------------------- Compile-time options ---------------------------

Be careful in setting #define values for numerical constants of type

size_t. On some systems, literal values are not automatically extended

to size_t precision unless they are explicitly casted.

WIN32 default: defined if _WIN32 defined

Defining WIN32 sets up defaults for MS environment and compilers.

Otherwise defaults are for unix.

MALLOC_ALIGNMENT default: (size_t)8

Controls the minimum alignment for malloc'ed chunks. It must be a

power of two and at least 8, 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.

MSPACES default: 0 (false)

If true, compile in support for independent allocation spaces.

This is only supported if HAVE_MMAP is true.

ONLY_MSPACES default: 0 (false)

If true, only compile in mspace versions, not regular versions.

USE_LOCKS default: 0 (false)

Causes each call to each public routine to be surrounded with

pthread or WIN32 mutex lock/unlock. (If set true, this can be

overridden on a per-mspace basis for mspace versions.)

FOOTERS default: 0

If true, provide extra checking and dispatching by placing

information in the footers of allocated chunks. This adds

space and time overhead.

INSECURE default: 0

If true, omit checks for usage errors and heap space overwrites.

USE_DL_PREFIX default: NOT defined

Causes compiler to prefix all public routines with the string 'dl'.

This can be useful when you only want to use this malloc in one part

of a program, using your regular system malloc elsewhere.

ABORT default: defined as abort()

Defines how to abort on failed checks. On most systems, a failed

check cannot die with an "assert" or even print an informative

message, because the underlying print routines in turn call malloc,

which will fail again. Generally, the best policy is to simply call

abort(). It's not very useful to do more than this because many

errors due to overwriting will show up as address faults (null, odd

addresses etc) rather than malloc-triggered checks, so will also

abort. Also, most compilers know that abort() does not return, so

can better optimize code conditionally calling it.

PROCEED_ON_ERROR default: defined as 0 (false)

Controls whether detected bad addresses cause them to bypassed

rather than aborting. If set, detected bad arguments to free and

realloc are ignored. And all bookkeeping information is zeroed out

upon a detected overwrite of freed heap space, thus losing the

ability to ever return it from malloc again, but enabling the

application to proceed. If PROCEED_ON_ERROR is defined, the

static variable malloc_corruption_error_count is compiled in

and can be examined to see if errors have occurred. This option

generates slower code than the default abort policy.

DEBUG default: NOT defined

The DEBUG setting is mainly intended for people trying to modify

this code or diagnose problems when porting to new platforms.

However, it may also be able to better isolate user errors than just

using runtime checks. The assertions in the check routines spell

out in more detail the assumptions and invariants underlying the

algorithms. 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 summaries.

ABORT_ON_ASSERT_FAILURE default: defined as 1 (true)

Debugging assertion failures can be nearly impossible if your

version of the assert macro causes malloc to be called, which will

lead to a cascade of further failures, blowing the runtime stack.

ABORT_ON_ASSERT_FAILURE cause assertions failures to call abort(),

which will usually make debugging easier.

MALLOC_FAILURE_ACTION default: sets errno to ENOMEM, or no-op on win32

The action to take before "return 0" when malloc fails to be able to

return memory because there is none available.

HAVE_MORECORE default: 1 (true) unless win32 or ONLY_MSPACES

True if this system supports sbrk or an emulation of it.

MORECORE default: sbrk

The name of the sbrk-style system routine to call to obtain more

memory. See below for guidance on writing custom MORECORE

functions. The type of the argument to sbrk/MORECORE varies across

systems. It cannot be size_t, because it supports negative

arguments, so it is normally the signed type of the same width as

size_t (sometimes declared as "intptr_t"). It doesn't much matter

though. Internally, we only call it with arguments less than half

the max value of a size_t, which should work across all reasonable

possibilities, although sometimes generating compiler warnings. See

near the end of this file for guidelines for creating a custom

version of MORECORE.

MORECORE_CONTIGUOUS default: 1 (true)

If true, take advantage of fact that consecutive calls to MORECORE

with positive arguments always return contiguous increasing

addresses. This is true of unix sbrk. It does not hurt too much to

set it true anyway, since malloc copes with non-contiguities.

Setting it false when definitely non-contiguous saves time

and possibly wasted space it would take to discover this though.

MORECORE_CANNOT_TRIM default: NOT defined

True if MORECORE cannot release space back to the system when given

negative arguments. This is generally necessary only if you are

using a hand-crafted MORECORE function that cannot handle negative

arguments.

HAVE_MMAP default: 1 (true)

True if this system supports mmap or an emulation of it. If so, and

HAVE_MORECORE is not true, MMAP is used for all system

allocation. If set and HAVE_MORECORE is true as well, MMAP is

primarily used to directly allocate very large blocks. It is also

used as a backup strategy in cases where MORECORE fails to provide

space from system. Note: A single call to MUNMAP is assumed to be

able to unmap memory that may have be allocated using multiple calls

to MMAP, so long as they are adjacent.

HAVE_MREMAP default: 1 on linux, else 0

If true realloc() uses mremap() to re-allocate large blocks and

extend or shrink allocation spaces.

MMAP_CLEARS default: 1 on unix

True if mmap clears memory so calloc doesn't need to. This is true

for standard unix mmap using /dev/zero.

USE_BUILTIN_FFS default: 0 (i.e., not used)

Causes malloc to use the builtin ffs() function to compute indices.

Some compilers may recognize and intrinsify ffs to be faster than the

supplied C version. Also, the case of x86 using gcc is special-cased

to an asm instruction, so is already as fast as it can be, and so

this setting has no effect. (On most x86s, the asm version is only

slightly faster than the C version.)

malloc_getpagesize default: derive from system includes, or 4096.

The system page size. To the extent possible, this malloc manages

memory from the system in page-size units. This may be (and

usually is) a function rather than a constant. This is ignored

if WIN32, where page size is determined using getSystemInfo during

initialization.

USE_DEV_RANDOM default: 0 (i.e., not used)

Causes malloc to use /dev/random to initialize secure magic seed for

stamping footers. Otherwise, the current time is used.

NO_MALLINFO default: 0

If defined, don't compile "mallinfo". This can be a simple way

of dealing with mismatches between system declarations and

those in this file.

MALLINFO_FIELD_TYPE default: size_t

The type of the fields in the mallinfo struct. This was originally

defined as "int" in SVID etc, but is more usefully defined as

size_t. The value is used only if HAVE_USR_INCLUDE_MALLOC_H is not set

REALLOC_ZERO_BYTES_FREES default: not defined

This 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).

LACKS_UNISTD_H, LACKS_FCNTL_H, LACKS_SYS_PARAM_H, LACKS_SYS_MMAN_H

LACKS_STRINGS_H, LACKS_STRING_H, LACKS_SYS_TYPES_H, LACKS_ERRNO_H

LACKS_STDLIB_H default: NOT defined unless on WIN32

Define these if your system does not have these header files.

You might need to manually insert some of the declarations they provide.

DEFAULT_GRANULARITY default: page size if MORECORE_CONTIGUOUS,

system_info.dwAllocationGranularity in WIN32,

otherwise 64K.

Also settable using mallopt(M_GRANULARITY, x)

The unit for allocating and deallocating memory from the system. On

most systems with contiguous MORECORE, there is no reason to

make this more than a page. However, systems with MMAP tend to

either require or encourage larger granularities. You can increase

this value to prevent system allocation functions to be called so

often, especially if they are slow. The value must be at least one

page and must be a power of two. Setting to 0 causes initialization

to either page size or win32 region size. (Note: In previous

versions of malloc, the equivalent of this option was called

"TOP_PAD")

DEFAULT_TRIM_THRESHOLD default: 2MB

Also settable using mallopt(M_TRIM_THRESHOLD, x)

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 using contiguous MORECORE. 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 this much

memory. 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 is worth tuning trim thresholds 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. The trim

value must be greater than page size to have any useful effect. To

disable trimming completely, you can set to MAX_SIZE_T. Note that the trick

some people use of mallocing a huge space and then freeing it at

program startup, in an attempt to reserve system memory, doesn't

have the intended effect under automatic trimming, since that memory

will immediately be returned to the system.

DEFAULT_MMAP_THRESHOLD default: 256K

Also settable using mallopt(M_MMAP_THRESHOLD, x)

The request size threshold for using MMAP to directly 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 benefits 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. Also, mapped memory doesn't 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 disadvantage that the space

cannot be reclaimed, consolidated, and then used to service later

requests, as happens with normal chunks. The advantages of mmap

nearly always outweigh disadvantages for "large" chunks, but the

value of "large" may vary across systems. The default is an

empirically derived value that works well in most systems. You can

disable mmap by setting to MAX_SIZE_T.

*/

#if defined __linux__ && !defined _GNU_SOURCE

/* mremap() on Linux requires this via sys/mman.h */

#define _GNU_SOURCE 1

#endif

#ifndef WIN32

#ifdef _WIN32

#define WIN32 1

#endif /* _WIN32 */

#endif /* WIN32 */

#ifdef WIN32

#define WIN32_LEAN_AND_MEAN

#include <windows.h>

#define HAVE_MMAP 1

#define HAVE_MORECORE 0

#define LACKS_UNISTD_H

#define LACKS_SYS_PARAM_H

#define LACKS_SYS_MMAN_H

#define LACKS_STRING_H

#define LACKS_STRINGS_H

#define LACKS_SYS_TYPES_H

#define LACKS_ERRNO_H

#define MALLOC_FAILURE_ACTION

#define MMAP_CLEARS 0 /* WINCE and some others apparently don't clear */

#endif /* WIN32 */

#ifdef __OS2__

#define INCL_DOS

#include <os2.h>

#define HAVE_MMAP 1

#define HAVE_MORECORE 0

#define LACKS_SYS_MMAN_H

#endif /* __OS2__ */

#if defined(DARWIN) || defined(_DARWIN)

/* Mac OSX docs advise not to use sbrk; it seems better to use mmap */

#ifndef HAVE_MORECORE

#define HAVE_MORECORE 0

#define HAVE_MMAP 1

#endif /* HAVE_MORECORE */

#endif /* DARWIN */

#ifndef LACKS_SYS_TYPES_H

#include <sys/types.h> /* For size_t */

#endif /* LACKS_SYS_TYPES_H */

/* The maximum possible size_t value has all bits set */

#define MAX_SIZE_T (~(size_t)0)

#ifndef ONLY_MSPACES

#define ONLY_MSPACES 0

#endif /* ONLY_MSPACES */

#ifndef MSPACES

#if ONLY_MSPACES

#define MSPACES 1

#else /* ONLY_MSPACES */

#define MSPACES 0

#endif /* ONLY_MSPACES */

#endif /* MSPACES */

#ifndef MALLOC_ALIGNMENT

#define MALLOC_ALIGNMENT ((size_t)8U)

#endif /* MALLOC_ALIGNMENT */

#ifndef FOOTERS

#define FOOTERS 0

#endif /* FOOTERS */

#ifndef ABORT

#define ABORT abort()

#endif /* ABORT */

#ifndef ABORT_ON_ASSERT_FAILURE

#define ABORT_ON_ASSERT_FAILURE 1

#endif /* ABORT_ON_ASSERT_FAILURE */

#ifndef PROCEED_ON_ERROR

#define PROCEED_ON_ERROR 0

#endif /* PROCEED_ON_ERROR */

#ifndef USE_LOCKS

#define USE_LOCKS 0

#endif /* USE_LOCKS */

#ifndef INSECURE

#define INSECURE 0

#endif /* INSECURE */

#ifndef HAVE_MMAP

#define HAVE_MMAP 1

#endif /* HAVE_MMAP */

#ifndef MMAP_CLEARS

#define MMAP_CLEARS 1

#endif /* MMAP_CLEARS */

#ifndef HAVE_MREMAP

#ifdef linux

#define HAVE_MREMAP 1

#else /* linux */

#define HAVE_MREMAP 0

#endif /* linux */

#endif /* HAVE_MREMAP */

#ifndef MALLOC_FAILURE_ACTION

#define MALLOC_FAILURE_ACTION errno = ENOMEM;

#endif /* MALLOC_FAILURE_ACTION */

#ifndef HAVE_MORECORE

#if ONLY_MSPACES

#define HAVE_MORECORE 0

#else /* ONLY_MSPACES */

#define HAVE_MORECORE 1

#endif /* ONLY_MSPACES */

#endif /* HAVE_MORECORE */

#if !HAVE_MORECORE

#define MORECORE_CONTIGUOUS 0

#else /* !HAVE_MORECORE */

#ifndef MORECORE

#define MORECORE sbrk

#endif /* MORECORE */

#ifndef MORECORE_CONTIGUOUS

#define MORECORE_CONTIGUOUS 1

#endif /* MORECORE_CONTIGUOUS */

#endif /* HAVE_MORECORE */

#ifndef DEFAULT_GRANULARITY

#if MORECORE_CONTIGUOUS

#define DEFAULT_GRANULARITY (0) /* 0 means to compute in init_mparams */

#else /* MORECORE_CONTIGUOUS */

#define DEFAULT_GRANULARITY ((size_t)64U * (size_t)1024U)

#endif /* MORECORE_CONTIGUOUS */

#endif /* DEFAULT_GRANULARITY */

#ifndef DEFAULT_TRIM_THRESHOLD

#ifndef MORECORE_CANNOT_TRIM

#define DEFAULT_TRIM_THRESHOLD ((size_t)2U * (size_t)1024U * (size_t)1024U)

#else /* MORECORE_CANNOT_TRIM */

#define DEFAULT_TRIM_THRESHOLD MAX_SIZE_T

#endif /* MORECORE_CANNOT_TRIM */

#endif /* DEFAULT_TRIM_THRESHOLD */

#ifndef DEFAULT_MMAP_THRESHOLD

#if HAVE_MMAP

#define DEFAULT_MMAP_THRESHOLD ((size_t)256U * (size_t)1024U)

#else /* HAVE_MMAP */

#define DEFAULT_MMAP_THRESHOLD MAX_SIZE_T

#endif /* HAVE_MMAP */

#endif /* DEFAULT_MMAP_THRESHOLD */

#ifndef USE_BUILTIN_FFS

#define USE_BUILTIN_FFS 0

#endif /* USE_BUILTIN_FFS */

#ifndef USE_DEV_RANDOM

#define USE_DEV_RANDOM 0

#endif /* USE_DEV_RANDOM */

#ifndef NO_MALLINFO

#define NO_MALLINFO 0

#endif /* NO_MALLINFO */

#ifndef MALLINFO_FIELD_TYPE

#define MALLINFO_FIELD_TYPE size_t

#endif /* MALLINFO_FIELD_TYPE */

/*

mallopt tuning options. SVID/XPG defines four standard parameter

numbers for mallopt, normally defined in malloc.h. None of these

are used in this malloc, so setting them has no effect. But this

malloc does support the following options.

*/

/* The system's malloc.h may have conflicting defines. */

#undef M_TRIM_THRESHOLD

#undef M_GRANULARITY

#undef M_MMAP_THRESHOLD

#define M_TRIM_THRESHOLD (-1)

#define M_GRANULARITY (-2)

#define M_MMAP_THRESHOLD (-3)

/* ------------------------ Mallinfo declarations ------------------------ */

#if !NO_MALLINFO

/*

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 system that has a

/usr/include/malloc.h defining struct mallinfo. The main

declaration needed is the mallinfo struct that is returned (by-copy)

by mallinfo(). The malloinfo struct contains a bunch of fields 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 a compliant version is

declared below. These must be precisely the same for mallinfo() to

work. The original SVID version of this struct, defined on most

systems with mallinfo, declares all fields as ints. But some others

define as unsigned long. If your system defines the fields using a

type of different width than listed here, you MUST #include your

system version and #define HAVE_USR_INCLUDE_MALLOC_H.

*/

/* #define HAVE_USR_INCLUDE_MALLOC_H */

#ifdef HAVE_USR_INCLUDE_MALLOC_H

#include "/usr/include/malloc.h"

#else /* HAVE_USR_INCLUDE_MALLOC_H */

/* HP-UX's stdlib.h redefines mallinfo unless _STRUCT_MALLINFO is defined */

#define _STRUCT_MALLINFO

struct mallinfo {

MALLINFO_FIELD_TYPE arena; /* non-mmapped space allocated from system */

MALLINFO_FIELD_TYPE ordblks; /* number of free chunks */

MALLINFO_FIELD_TYPE smblks; /* always 0 */

MALLINFO_FIELD_TYPE hblks; /* always 0 */

MALLINFO_FIELD_TYPE hblkhd; /* space in mmapped regions */

MALLINFO_FIELD_TYPE usmblks; /* maximum total allocated space */

MALLINFO_FIELD_TYPE fsmblks; /* always 0 */

MALLINFO_FIELD_TYPE uordblks; /* total allocated space */

MALLINFO_FIELD_TYPE fordblks; /* total free space */

MALLINFO_FIELD_TYPE keepcost; /* releasable (via malloc_trim) space */

};

#endif /* HAVE_USR_INCLUDE_MALLOC_H */

#endif /* NO_MALLINFO */

#ifdef __cplusplus

extern "C" {

#endif /* __cplusplus */

#if !ONLY_MSPACES

/* ------------------- Declarations of public routines ------------------- */

#ifndef USE_DL_PREFIX

#define dlcalloc calloc

#define dlfree free

#define dlmalloc malloc

#define dlmemalign memalign

#define dlrealloc realloc

#define dlvalloc valloc

#define dlpvalloc pvalloc

#define dlmallinfo mallinfo

#define dlmallopt mallopt

#define dlmalloc_trim malloc_trim

#define dlmalloc_stats malloc_stats

#define dlmalloc_usable_size malloc_usable_size

#define dlmalloc_footprint malloc_footprint

#define dlmalloc_max_footprint malloc_max_footprint

#define dlindependent_calloc independent_calloc

#define dlindependent_comalloc independent_comalloc

#endif /* USE_DL_PREFIX */

/*

malloc(size_t n)

Returns a pointer to a newly allocated chunk of at least n bytes, or

null if no space is available, in which case errno is set to ENOMEM

on ANSI C systems.

If n is zero, malloc returns a minimum-sized chunk. (The minimum

size is 16 bytes on most 32bit systems, and 32 bytes on 64bit

systems.) Note that size_t is an unsigned type, so calls with

arguments that would be negative if signed are interpreted as

requests for huge amounts of space, which will often fail. The

maximum supported value of n differs across systems, but is in all

cases less than the maximum representable value of a size_t.

*/

void* dlmalloc(size_t);

/*

free(void* p)

Releases the chunk of memory pointed to by p, that had been previously

allocated using malloc or a related routine such as realloc.

It has no effect if p is null. If p was not malloced or already

freed, free(p) will by default cause the current program to abort.

*/

void dlfree(void*);

/*

calloc(size_t n_elements, size_t element_size);

Returns a pointer to n_elements * element_size bytes, with all locations

set to zero.

*/

void* dlcalloc(size_t, size_t);

/*

realloc(void* p, size_t n)

Returns 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. The algorithm

prefers extending p in most cases when possible, otherwise it

employs the equivalent of a malloc-copy-free sequence.

If p is null, realloc is equivalent to malloc.

If space is not available, realloc returns null, errno is set (if on

ANSI) and p is NOT freed.

if n is for fewer bytes than already held by p, the newly unused

space is lopped off and freed if possible. 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 not supported.

*/

void* dlrealloc(void*, size_t);

/*

memalign(size_t alignment, size_t n);

Returns a pointer to a newly allocated chunk of n bytes, aligned

in accord with the alignment argument.

The alignment argument should be a power 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.

*/

void* dlmemalign(size_t, size_t);

/*

valloc(size_t n);

Equivalent to memalign(pagesize, n), where pagesize is the page

size of the system. If the pagesize is unknown, 4096 is used.

*/

void* dlvalloc(size_t);

/*

mallopt(int parameter_number, int parameter_value)

Sets 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. SVID/XPG/ANSI defines four standard param numbers for mallopt,

normally defined in malloc.h. None of these are use in this malloc,

so setting them has no effect. But this malloc also supports other

options in mallopt. See below for details. Briefly, supported

parameters are as follows (listed defaults are for "typical"

configurations).

Symbol param # default allowed param values

M_TRIM_THRESHOLD -1 2*1024*1024 any (MAX_SIZE_T disables)

M_GRANULARITY -2 page size any power of 2 >= page size

M_MMAP_THRESHOLD -3 256*1024 any (or 0 if no MMAP support)

*/

int dlmallopt(int, int);

/*

malloc_footprint();

Returns the number of bytes obtained from the system. The total

number of bytes allocated by malloc, realloc etc., is less than this

value. Unlike mallinfo, this function returns only a precomputed

result, so can be called frequently to monitor memory consumption.

Even if locks are otherwise defined, this function does not use them,

so results might not be up to date.

*/

size_t dlmalloc_footprint(void);

/*

malloc_max_footprint();

Returns the maximum number of bytes obtained from the system. This

value will be greater than current footprint if deallocated space

has been reclaimed by the system. The peak number of bytes allocated

by malloc, realloc etc., is less than this value. Unlike mallinfo,

this function returns only a precomputed result, so can be called

frequently to monitor memory consumption. Even if locks are

otherwise defined, this function does not use them, so results might

not be up to date.

*/

size_t dlmalloc_max_footprint(void);

#if !NO_MALLINFO

/*

mallinfo()

Returns (by copy) a struct containing various summary statistics:

arena: current total non-mmapped bytes allocated from system

ordblks: the number of free chunks

smblks: always zero.

hblks: current number of mmapped regions

hblkhd: total bytes held in mmapped regions

usmblks: the maximum total allocated space. This will be greater

than current total if trimming has occurred.

fsmblks: always zero

uordblks: current total allocated space (normal or mmapped)

fordblks: total free space

keepcost: the maximum number of bytes that could ideally be released

back to system via malloc_trim. ("ideally" means that

it ignores page restrictions etc.)

Because these fields are ints, but internal bookkeeping may

be kept as longs, the reported values may wrap around zero and

thus be inaccurate.

*/

struct mallinfo dlmallinfo(void);

#endif /* NO_MALLINFO */

/*

independent_calloc(size_t n_elements, size_t element_size, void* chunks[]);

independent_calloc is similar to calloc, but instead of returning a

single cleared space, it returns an array of pointers to n_elements

independent elements that can hold contents of size elem_size, each

of which starts out cleared, and can be independently freed,

realloc'ed etc. The elements are guaranteed to be adjacently

allocated (this is not guaranteed to occur with multiple callocs or

mallocs), which may also improve cache locality in some

applications.

The "chunks" argument is optional (i.e., may be null, which is

probably the most typical usage). If it is null, the returned array

is itself dynamically allocated and should also be freed when it is

no longer needed. Otherwise, the chunks array must be of at least

n_elements in length. It is filled in with the pointers to the

chunks.

In either case, independent_calloc returns this pointer array, or

null if the allocation failed. If n_elements is zero and "chunks"

is null, it returns a chunk representing an array with zero elements

(which should be freed if not wanted).

Each element must be individually freed when it is no longer

needed. If you'd like to instead be able to free all at once, you

should instead use regular calloc and assign pointers into this

space to represent elements. (In this case though, you cannot

independently free elements.)

independent_calloc simplifies and speeds up implementations of many

kinds of pools. It may also be useful when constructing large data

structures that initially have a fixed number of fixed-sized nodes,

but the number is not known at compile time, and some of the nodes

may later need to be freed. For example:

struct Node { int item; struct Node* next; };

struct Node* build_list() {

struct Node** pool;

int n = read_number_of_nodes_needed();

if (n <= 0) return 0;

pool = (struct Node**)(independent_calloc(n, sizeof(struct Node), 0);

if (pool == 0) die();

// organize into a linked list...

struct Node* first = pool[0];

for (i = 0; i < n-1; ++i)

pool[i]->next = pool[i+1];

free(pool); // Can now free the array (or not, if it is needed later)

return first;

}

*/

void** dlindependent_calloc(size_t, size_t, void**);

/*

independent_comalloc(size_t n_elements, size_t sizes[], void* chunks[]);

independent_comalloc allocates, all at once, a set of n_elements

chunks with sizes indicated in the "sizes" array. It returns

an array of pointers to these elements, each of which can be

independently freed, realloc'ed etc. The elements are guaranteed to

be adjacently allocated (this is not guaranteed to occur with

multiple callocs or mallocs), which may also improve cache locality

in some applications.

The "chunks" argument is optional (i.e., may be null). If it is null

the returned array is itself dynamically allocated and should also

be freed when it is no longer needed. Otherwise, the chunks array

must be of at least n_elements in length. It is filled in with the

pointers to the chunks.

In either case, independent_comalloc returns this pointer array, or

null if the allocation failed. If n_elements is zero and chunks is

null, it returns a chunk representing an array with zero elements

(which should be freed if not wanted).

Each element must be individually freed when it is no longer

needed. If you'd like to instead be able to free all at once, you

should instead use a single regular malloc, and assign pointers at

particular offsets in the aggregate space. (In this case though, you

cannot independently free elements.)

independent_comallac differs from independent_calloc in that each

element may have a different size, and also that it does not

automatically clear elements.

independent_comalloc can be used to speed up allocation in cases

where several structs or objects must always be allocated at the

same time. For example:

struct Head { ... }

struct Foot { ... }

void send_message(char* msg) {

int msglen = strlen(msg);

size_t sizes[3] = { sizeof(struct Head), msglen, sizeof(struct Foot) };

void* chunks[3];

if (independent_comalloc(3, sizes, chunks) == 0)

die();

struct Head* head = (struct Head*)(chunks[0]);

char* body = (char*)(chunks[1]);

struct Foot* foot = (struct Foot*)(chunks[2]);

// ...

}

In general though, independent_comalloc is worth using only for

larger values of n_elements. For small values, you probably won't

detect enough difference from series of malloc calls to bother.

Overuse of independent_comalloc can increase overall memory usage,

since it cannot reuse existing noncontiguous small chunks that

might be available for some of the elements.

*/

void** dlindependent_comalloc(size_t, size_t*, void**);

/*

pvalloc(size_t n);

Equivalent to valloc(minimum-page-that-holds(n)), that is,

round up n to nearest pagesize.

*/

void* dlpvalloc(size_t);

/*

malloc_trim(size_t pad);

If possible, gives memory back to the system (via negative arguments

to sbrk) if there is unused memory at the `high' end of the malloc

pool or in unused MMAP segments. 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. 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.

*/

int dlmalloc_trim(size_t);

/*

malloc_usable_size(void* p);

Returns the number of bytes you can actually use in

an allocated chunk, which may be more than you requested (although

often not) due to alignment and minimum size constraints.

You can use this many bytes without worrying about

overwriting other allocated objects. This is not a particularly great

programming practice. malloc_usable_size can be more useful in

debugging and assertions, for example:

p = malloc(n);

assert(malloc_usable_size(p) >= 256);

*/

size_t dlmalloc_usable_size(void*);

/*

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