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/publicdomain/zero/1.0/ Send questions,
comments, complaints, performance data, etc to dl@cs.oswego.edu
Version 2.8.6 Wed Aug 29 06:57:58 2012 Doug Lea
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-2.8.6.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 (minimum)
Is set to 16 for NexGen32e.
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 TRUSTWORTHY to 1,
which might (or might not) provide a small performance improvement.
It is also possible to limit the maximum total allocatable
space, using malloc_set_footprint_limit. This is not
designed as a security feature in itself (calls to set limits
are not screened or privileged), but may be useful as one
aspect of a secure implementation.
Thread-safety: NOT thread-safe unless USE_LOCKS defined non-zero
When USE_LOCKS is defined, each public call to malloc, free,
etc is surrounded with a lock. By default, this uses a plain
pthread mutex, win32 critical section, or a spin-lock if if
available for the platform and not disabled by setting
USE_SPIN_LOCKS=0. However, if USE_RECURSIVE_LOCKS is defined,
recursive versions are used instead (which are not required for
base functionality but may be needed in layered extensions).
Using a global lock 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 nedmalloc
(http://www.nedprod.com/programs/portable/nedmalloc/) or
ptmalloc (See http://www.malloc.de), which are derived from
versions of this malloc.
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. In real-time
applications, you can optionally suppress segment traversals using
NO_SEGMENT_TRAVERSAL, which assures bounded execution even when
system allocators return non-contiguous spaces, at the typical
expense of carrying around more memory and increased fragmentation.
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. Normally, this requires use of locks.
───────────────────────── 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. You can also
use the symbolic values SIZE_MAX, SIZE_T_ONE, etc below.
WIN32 default: defined if _WIN32 defined
Defining WIN32 sets up defaults for MS environment and compilers.
Otherwise defaults are for unix. Beware that there seem to be some
cases where this malloc might not be a pure drop-in replacement for
Win32 malloc: Random-looking failures from Win32 GDI API's (eg;
SetDIBits()) may be due to bugs in some video driver implementations
when pixel buffers are malloc()ed, and the region spans more than
one VirtualAlloc()ed region. Because dlmalloc uses a small (64Kb)
default granularity, pixel buffers may straddle virtual allocation
regions more often than when using the Microsoft allocator. You can
avoid this by using VirtualAlloc() and VirtualFree() for all pixel
buffers rather than using malloc(). If this is not possible,
recompile this malloc with a larger DEFAULT_GRANULARITY. Note:
in cases where MSC and gcc (cygwin) are known to differ on WIN32,
conditions use _MSC_VER to distinguish them.
DLMALLOC_EXPORT default: extern
Defines how public APIs are declared. If you want to export via a
Windows DLL, you might define this as
#define DLMALLOC_EXPORT extern __declspec(dllexport)
If you want a POSIX ELF shared object, you might use
#define DLMALLOC_EXPORT extern __attribute__((visibility("default")))
MALLOC_ALIGNMENT default: (size_t)(2 * sizeof(void *))
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.) If set to a
non-zero value other than 1, locks are used, but their
implementation is left out, so lock functions must be supplied manually,
as described below.
USE_SPIN_LOCKS default: 1 iff USE_LOCKS and spin locks available
If true, uses custom spin locks for locking. This is currently
supported only gcc >= 4.1, older gccs on x86 platforms, and recent
MS compilers. Otherwise, posix locks or win32 critical sections are
used.
USE_RECURSIVE_LOCKS default: not defined
If defined nonzero, uses recursive (aka reentrant) locks, otherwise
uses plain mutexes. This is not required for malloc proper, but may
be needed for layered allocators such as nedmalloc.
LOCK_AT_FORK default: not defined
If defined nonzero, performs pthread_atfork upon initialization
to initialize child lock while holding parent lock. The implementation
assumes that pthread locks (not custom locks) are being used. In other
cases, you may need to customize the implementation.
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.
TRUSTWORTHY 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.
MALLOC_INSPECT_ALL default: NOT defined
If defined, compiles malloc_inspect_all and mspace_inspect_all, that
perform traversal of all heap space. Unless access to these
functions is otherwise restricted, you probably do not want to
include them in secure implementations.
MALLOC_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.
MORECORE_CONTIGUOUS default: 1 (true) if HAVE_MORECORE
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.
NO_SEGMENT_TRAVERSAL default: 0
If non-zero, suppresses traversals of memory segments
returned by either MORECORE or CALL_MMAP. This disables
merging of segments that are contiguous, and selectively
releasing them to the OS if unused, but bounds execution times.
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 except on WINCE.
True if mmap clears memory so calloc doesn't need to. This is true
for standard unix mmap using /dev/zero and on WIN32 except for WINCE.
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. Similarly for Win32 under recent MS compilers.
(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.
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
NO_MALLOC_STATS default: 0
If defined, don't compile "malloc_stats". This avoids calls to
fprintf and bringing in stdio dependencies you might not want.
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 LACKS_SCHED_H LACKS_TIME_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 SIZE_MAX. 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 SIZE_MAX.
MAX_RELEASE_CHECK_RATE default: 4095 unless not HAVE_MMAP
The number of consolidated frees between checks to release
unused segments when freeing. When using non-contiguous segments,
especially with multiple mspaces, checking only for topmost space
doesn't always suffice to trigger trimming. To compensate for this,
free() will, with a period of MAX_RELEASE_CHECK_RATE (or the
current number of segments, if greater) try to release unused
segments to the OS when freeing chunks that result in
consolidation. The best value for this parameter is a compromise
between slowing down frees with relatively costly checks that
rarely trigger versus holding on to unused memory. To effectively
disable, set to SIZE_MAX. This may lead to a very slight speed
improvement at the expense of carrying around more memory.
────────────────────────────────────────────────────────────────────────────────
History:
v2.8.6 Wed Aug 29 06:57:58 2012 Doug Lea
* fix bad comparison in dlposix_memalign
* don't reuse adjusted asize in sys_alloc
* add LOCK_AT_FORK -- thanks to Kirill Artamonov for the suggestion
* reduce compiler warnings -- thanks to all who reported/suggested these
v2.8.5 Sun May 22 10:26:02 2011 Doug Lea (dl at gee)
* Always perform unlink checks unless TRUSTWORTHY
* Add posix_memalign.
* Improve realloc to expand in more cases; expose realloc_in_place.
Thanks to Peter Buhr for the suggestion.
* Add footprint_limit, inspect_all, bulk_free. Thanks
to Barry Hayes and others for the suggestions.
* Internal refactorings to avoid calls while holding locks
* Use non-reentrant locks by default. Thanks to Roland McGrath
for the suggestion.
* Small fixes to mspace_destroy, reset_on_error.
* Various configuration extensions/changes. Thanks
to all who contributed these.
V2.8.4a Thu Apr 28 14:39:43 2011 (dl at gee.cs.oswego.edu)
* Update Creative Commons URL
V2.8.4 Wed May 27 09:56:23 2009 Doug Lea (dl at gee)
* Use zeros instead of prev foot for is_mmapped
* Add mspace_track_large_chunks; thanks to Jean Brouwers
* Fix set_inuse in internal_realloc; thanks to Jean Brouwers
* Fix insufficient sys_alloc padding when using 16byte alignment
* Fix bad error check in mspace_footprint
* Adaptations for ptmalloc; thanks to Wolfram Gloger.
* Reentrant spin locks; thanks to Earl Chew and others
* Win32 improvements; thanks to Niall Douglas and Earl Chew
* Add NO_SEGMENT_TRAVERSAL and MAX_RELEASE_CHECK_RATE options
* Extension hook in malloc_state
* Various small adjustments to reduce warnings on some compilers
* Various configuration extensions/changes for more platforms. Thanks
to all who contributed these.
V2.8.3 Thu Sep 22 11:16:32 2005 Doug Lea (dl at gee)
* Add max_footprint functions
* Ensure all appropriate literals are size_t
* Fix conditional compilation problem for some #define settings
* Avoid concatenating segments with the one provided
in create_mspace_with_base
* Rename some variables to avoid compiler shadowing warnings
* Use explicit lock initialization.
* Better handling of sbrk interference.
* Simplify and fix segment insertion, trimming and mspace_destroy
* Reinstate REALLOC_ZERO_BYTES_FREES option from 2.7.x
* Thanks especially to Dennis Flanagan for help on these.
V2.8.2 Sun Jun 12 16:01:10 2005 Doug Lea (dl at gee)
* Fix memalign brace error.
V2.8.1 Wed Jun 8 16:11:46 2005 Doug Lea (dl at gee)
* Fix improper #endif nesting in C++
* Add explicit casts needed for C++
V2.8.0 Mon May 30 14:09:02 2005 Doug Lea (dl at gee)
* Use trees for large bins
* Support mspaces
* Use segments to unify sbrk-based and mmap-based system allocation,
removing need for emulation on most platforms without sbrk.
* Default safety checks
* Optional footer checks. Thanks to William Robertson for the idea.
* Internal code refactoring
* Incorporate suggestions and platform-specific changes.
Thanks to Dennis Flanagan, Colin Plumb, Niall Douglas,
Aaron Bachmann, Emery Berger, and others.
* Speed up non-fastbin processing enough to remove fastbins.
* Remove useless cfree() to avoid conflicts with other apps.
* Remove internal memcpy, memset. Compilers handle builtins better.
* Remove some options that no one ever used and rename others.
V2.7.2 Sat Aug 17 09:07:30 2002 Doug Lea (dl at gee)
* Fix malloc_state bitmap array misdeclaration
V2.7.1 Thu Jul 25 10:58:03 2002 Doug Lea (dl at gee)
* Allow tuning of FIRST_SORTED_BIN_SIZE
* Use PTR_UINT as type for all ptr->int casts. Thanks to John Belmonte.
* Better detection and support for non-contiguousness of MORECORE.
Thanks to Andreas Mueller, Conal Walsh, and Wolfram Gloger
* Bypass most of malloc if no frees. Thanks To Emery Berger.
* Fix freeing of old top non-contiguous chunk im sysmalloc.
* Raised default trim and map thresholds to 256K.
* Fix mmap-related #defines. Thanks to Lubos Lunak.
* Fix copy macros; added LACKS_FCNTL_H. Thanks to Neal Walfield.
* Branch-free bin calculation
* Default trim and mmap thresholds now 256K.
V2.7.0 Sun Mar 11 14:14:06 2001 Doug Lea (dl at gee)
* Introduce independent_comalloc and independent_calloc.
Thanks to Michael Pachos for motivation and help.
* Make optional .h file available
* Allow > 2GB requests on 32bit systems.
* new WIN32 sbrk, mmap, munmap, lock code from <Walter@GeNeSys-e.de>.
Thanks also to Andreas Mueller <a.mueller at paradatec.de>,
and Anonymous.
* Allow override of MALLOC_ALIGNMENT (Thanks to Ruud Waij for
helping test this.)
* memalign: check alignment arg
* realloc: don't try to shift chunks backwards, since this
leads to more fragmentation in some programs and doesn't
seem to help in any others.
* Collect all cases in malloc requiring system memory into sysmalloc
* Use mmap as backup to sbrk
* 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.
* Include errno.h to support default failure action.
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.)
/* ──────────────────── Alternative MORECORE functions ─────────────────── */
/*
Guidelines for creating a custom version of MORECORE:
* For best performance, MORECORE should allocate in multiples of pagesize.
* MORECORE may allocate more memory than requested. (Or even less,
but this will usually 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.
* For best performance, consecutive calls to MORECORE with positive
arguments should return increasing addresses, indicating that
space has been contiguously extended.
* 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 MFAIL when given negative arguments.
Negative arguments are always multiples of pagesize. MORECORE
must not misinterpret negative args as large positive unsigned
args. You can suppress all such calls from even occurring by defining
MORECORE_CANNOT_TRIM,
As an example alternative MORECORE, 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
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 * 1024U)
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 *) MFAIL;
}
// save ptrs so they can be freed during cleanup
our_os_pools[next_os_pool] = ptr;
next_os_pool++;
ptr = (void *) ((((size_t) 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 *) MFAIL;
}
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;
}
}
*/
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