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dlmalloc.c
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dlmalloc.c
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/*==========================================================================
//
// dlmalloc.c
//
// Port of Doug Lea's malloc implementation
//
//==========================================================================
//
// This file is part of the MemPool library.
// Copyright (C) 2017 Bernd Edlinger
//
// MemPool is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free
// Software Foundation; either version 3 or (at your option) any later
// version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
// for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
//
// As a special exception, if other files instantiate templates or use
// macros or inline functions from this file, or you compile this file
// and link it with other works to produce a work based on this file,
// this file does not by itself cause the resulting work to be covered by
// the GNU General Public License. However the source code for this file
// must still be made available in accordance with section (6) of the GNU
// General Public License v3.
//
// This exception does not invalidate any other reasons why a work based
// on this file might be covered by the GNU General Public License.
//
//==========================================================================
// ####ORIGINALCOPYRIGHTBEGIN####
// -------------------------------------------
// This file is part of eCos, the Embedded Configurable Operating System.
// Copyright (C) 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
//
// eCos is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free
// Software Foundation; either version 2 or (at your option) any later
// version.
//
// eCos is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
// for more details.
//
// You should have received a copy of the GNU General Public License
// along with eCos; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
//
// As a special exception, if other files instantiate templates or use
// macros or inline functions from this file, or you compile this file
// and link it with other works to produce a work based on this file,
// this file does not by itself cause the resulting work to be covered by
// the GNU General Public License. However the source code for this file
// must still be made available in accordance with section (3) of the GNU
// General Public License v2.
//
// This exception does not invalidate any other reasons why a work based
// on this file might be covered by the GNU General Public License.
// -------------------------------------------
// ####ORIGINALCOPYRIGHTEND####
//==========================================================================
//#####DESCRIPTIONBEGIN####
//
// Author(s): Doug Lea (dl at g.oswego.edu), jlarmour
// Contributors: Bernd Edlinger
// Date: 2000-06-18
// Purpose: Doug Lea's malloc implementation
// Description: Doug Lea's malloc has been ported to eCos. This file
// provides the implementation in a way acceptable to eCos.
// Substantial amounts of unnecessary bits (to eCos) of the
// original implementation have been removed to make the
// code more tractable. Note this may make a number of the
// comments appear to make little sense, or no longer apply!
// In particular, mmap support is removed entirely.
// Also the memory is "sbrked" all at once at the
// beginning, covering the entire memory region given at
// construction, and there can be no more afterwards.
// Usage: #include <cyg/memalloc/dlmalloc.hxx>
//
//
//####DESCRIPTIONEND####
//
//==========================================================================*/
/* DOCUMENTATION FROM ORIGINAL FILE: */
/* (some now irrelevant parts elided) */
/*----------------------------------------------------------------------------*/
/*
A version of malloc/free/realloc written by Doug Lea and released to the
public domain. Send questions/comments/complaints/performance data
to dl at cs.oswego.edu
* VERSION 2.6.6 Sun Mar 5 19:10:03 2000 Doug Lea (dl at gee)
Note: There may be an updated version of this malloc obtainable at
ftp://g.oswego.edu/pub/misc/malloc.c
Check before installing!
* 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 a high-level description, see
http://g.oswego.edu/dl/html/malloc.html
* Synopsis of public routines
(Much fuller descriptions are contained in the program documentation below.)
[ these have of course been renamed in the eCos port ]a
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. realloc of
zero bytes calls free(p)
* Vital statistics:
Alignment: 8-byte
8 byte alignment is currently hardwired into the design. This
seems to suffice for all current machines and C compilers.
Assumed pointer representation: 4 or 8 bytes
Code for 8-byte pointers is untested by me but has worked
reliably by Wolfram Gloger, who contributed most of the
changes supporting this.
Assumed size_t representation: 4 or 8 bytes
Note that size_t is allowed to be 4 bytes even if pointers are 8.
Minimum overhead per allocated chunk: 4 or 8 bytes
Each malloced chunk has a hidden overhead of 4 bytes 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.
Maximum allocated size: 4-byte size_t: 2^31 - 8 bytes
8-byte size_t: 2^63 - 16 bytes
It is assumed that (possibly signed) size_t bit 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. To be conservative, values that would appear
as negative numbers are avoided.
Requests for sizes with a negative sign bit when the request
size is treaded as a long will return null.
Maximum overhead wastage per allocated chunk: normally 15 bytes
Alignnment demands, plus the minimum allocatable size restriction
make the normal worst-case wastage 15 bytes (i.e., up to 15
more bytes will be allocated than were requested in malloc), with
one exception: because requests for zero bytes allocate non-zero space,
the worst case wastage for a request of zero bytes is 24 bytes.
* Limitations
Here are some features that are NOT currently supported
* No user-definable hooks for callbacks and the like.
* No automated mechanism for fully checking that all accesses
to malloced memory stay within their bounds.
* 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 have also reported adapting this malloc for use in
stand-alone embedded systems.
The implementation is in straight, hand-tuned ANSI C. Among other
consequences, it uses a lot of macros. Because of this, to be at
all usable, this code should be compiled using an optimizing compiler
(for example gcc -O2) that can simplify expressions and control
paths.
CYGDBG_MEMALLOC_ALLOCATOR_DLMALLOC_DEBUG (default: NOT defined)
Define to enable debugging. Adds fairly extensive assertion-based
checking to help track down memory errors, but noticeably slows down
execution.
MALLOC_LOCK (default: NOT defined)
MALLOC_UNLOCK (default: NOT defined)
Define these to C expressions which are run to lock and unlock
the malloc data structures. Calls may be nested; that is,
MALLOC_LOCK may be called more than once before the corresponding
MALLOC_UNLOCK calls. MALLOC_LOCK must avoid waiting for a lock
that it already holds.
MALLOC_ALIGNMENT (default: NOT defined)
Define this to 16 if you need 16 byte alignment instead of 8 byte alignment
which is the normal default.
SIZE_T_SMALLER_THAN_LONG (default: NOT defined)
Define this when the platform you are compiling has
sizeof(long) > sizeof(size_t).
The option causes some extra code to be generated to handle operations
that use size_t operands and have long results.
INTERNAL_SIZE_T (default: size_t)
Define to a 32-bit type (probably `unsigned int') if you are on a
64-bit machine, yet do not want or need to allow malloc requests of
greater than 2^31 to be handled. This saves space, especially for
very small chunks.
*/
/*----------------------------------------------------------------------------*/
#if defined _WIN32 || defined _WIN32_WCE
#pragma warning(push)
#pragma warning(disable: 4127)
/* warning C4127: conditional expression is constant */
#endif
/* Preliminaries */
#include <stddef.h> /* for size_t */
#include "dlmalloc.h"
/*
Debugging:
Because freed chunks may be overwritten with link 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 CYGDBG_MEMALLOC_ALLOCATOR_DLMALLOC_DEBUG enabled, 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 get_status() with DEBUG set will
attempt to check every allocated and free chunk in the
course of computing the summmaries.
Setting CYGDBG_MEMALLOC_ALLOCATOR_DLMALLOC_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.
*/
/* MACROS */
#define CYG_MEMALLOC_FAIL( size )
#define CYG_ASSERT( test, msg )
#define CYG_ASSERTC( test )
#define CYG_FAIL( msg )
/* CONSTANTS */
/*#define CYGDBG_MEMALLOC_ALLOCATOR_DLMALLOC_DEBUG */
#define CYGIMP_MEMALLOC_ALLOCATOR_DLMALLOC_USE_MEMCPY
/* number of bins - but changing this alone will not change the number of */
/* bins! */
#define CYGPRI_MEMALLOC_ALLOCATOR_DLMALLOC_NAV 128
/* TYPE DEFINITIONS */
/* cyg_dlmalloc_size_t is the word-size used for internal bookkeeping
of chunk sizes. On a 64-bit machine, you can reduce malloc
overhead, especially for very small chunks, by defining
cyg_dlmalloc_size_t to be a 32-bit type at the expense of not
being able to handle requests greater than 2^31. This limitation is
hardly ever a concern; you are encouraged to set this. However, the
default version is the same as size_t. */
typedef cyg_uint32 Cyg_dlmalloc_size_t;
struct malloc_chunk
{
Cyg_dlmalloc_size_t prev_size; /* Size of previous chunk (if free). */
Cyg_dlmalloc_size_t size; /* Size in bytes, including overhead. */
struct malloc_chunk* fd; /* double links -- used only if free. */
struct malloc_chunk* bk;
struct malloc_chunk* fd_samesize; /* double links -- used only if large free block. */
struct malloc_chunk* bk_samesize;
};
/* The first value returned from sbrk */
static cyg_uint8 *arenabase;
/* The total memory in the pool */
static cyg_uint32 arenasize;
/* The actual of allocated memory */
static cyg_uint32 actualAllocBytes;
/* The maximum of allocated memory */
static cyg_uint32 maxAllocBytes;
#ifdef CYGDBG_MEMALLOC_ALLOCATOR_DLMALLOC_DEBUG
# define ASSERT(x) CYG_ASSERTC( x )
#else
# define ASSERT(x) ((void)0)
#endif
/*
Define MALLOC_LOCK and MALLOC_UNLOCK to C expressions to run to
lock and unlock the malloc data structures. MALLOC_LOCK may be
called recursively.
*/
#ifndef MALLOC_LOCK
#define MALLOC_LOCK
#endif
#ifndef MALLOC_UNLOCK
#define MALLOC_UNLOCK
#endif
/*
INTERNAL_SIZE_T is the word-size used for internal bookkeeping
of chunk sizes. On a 64-bit machine, you can reduce malloc
overhead by defining INTERNAL_SIZE_T to be a 32 bit `unsigned int'
at the expense of not being able to handle requests greater than
2^31. This limitation is hardly ever a concern; you are encouraged
to set this. However, the default version is the same as size_t.
*/
#ifndef INTERNAL_SIZE_T
#define INTERNAL_SIZE_T Cyg_dlmalloc_size_t
#endif
/*
Following is needed on implementations whereby long > size_t.
The problem is caused because the code performs subtractions of
size_t values and stores the result in long values. In the case
where long > size_t and the first value is actually less than
the second value, the resultant value is positive. For example,
(long)(x - y) where x = 0 and y is 1 ends up being 0x00000000FFFFFFFF
which is 2*31 - 1 instead of 0xFFFFFFFFFFFFFFFF. This is due to the
fact that assignment from unsigned to signed won't sign extend.
*/
#define SIZE_T_SMALLER_THAN_LONG
#ifdef SIZE_T_SMALLER_THAN_LONG
#define long_sub_size_t(x, y) ( (x < y) ? -((long)(y - x)) : (x - y) );
#else
#define long_sub_size_t(x, y) ( (long)(x - y) )
#endif
#ifdef CYGIMP_MEMALLOC_ALLOCATOR_DLMALLOC_USE_MEMCPY
#include <string.h> /* memmove, memset */
/* The following macros are only invoked with (2n+1)-multiples of
INTERNAL_SIZE_T units, with a positive integer n. This is exploited
for fast inline execution when n is small. */
#define MALLOC_ZERO(charp, nbytes) \
do { \
INTERNAL_SIZE_T mzsz = (nbytes); \
if(mzsz <= 9*sizeof(mzsz)) { \
INTERNAL_SIZE_T* mz = (INTERNAL_SIZE_T*) (charp); \
if(mzsz >= 5*sizeof(mzsz)) { *mz++ = 0; \
*mz++ = 0; \
if(mzsz >= 7*sizeof(mzsz)) { *mz++ = 0; \
*mz++ = 0; \
if(mzsz >= 9*sizeof(mzsz)) { *mz++ = 0; \
*mz++ = 0; }}} \
*mz++ = 0; \
*mz++ = 0; \
*mz = 0; \
} else memset((charp), 0, mzsz); \
} while(0)
#define MALLOC_COPY(dest,src,nbytes) \
do { \
INTERNAL_SIZE_T mcsz = (nbytes); \
if(mcsz <= 9*sizeof(mcsz)) { \
INTERNAL_SIZE_T* mcsrc = (INTERNAL_SIZE_T*) (src); \
INTERNAL_SIZE_T* mcdst = (INTERNAL_SIZE_T*) (dest); \
if(mcsz >= 5*sizeof(mcsz)) { *mcdst++ = *mcsrc++; \
*mcdst++ = *mcsrc++; \
if(mcsz >= 7*sizeof(mcsz)) { *mcdst++ = *mcsrc++; \
*mcdst++ = *mcsrc++; \
if(mcsz >= 9*sizeof(mcsz)) { *mcdst++ = *mcsrc++; \
*mcdst++ = *mcsrc++; }}} \
*mcdst++ = *mcsrc++; \
*mcdst++ = *mcsrc++; \
*mcdst = *mcsrc ; \
} else memmove(dest, src, mcsz); \
} while(0)
#else /* !CYGIMP_MEMALLOC_ALLOCATOR_DLMALLOC_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)
#define MALLOC_COPY(dest,src,nbytes) \
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
/*----------------------------------------------------------------------------*/
/*
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.)
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 exception to all this is the special chunk `top', which 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. )
Available chunks are kept in any of several places (all declared below):
* `av': An array of chunks serving as bin headers for consolidated
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. All procedures maintain the invariant that no
consolidated chunk physically borders another one. Chunks in
bins are kept in size order, with ties going to the
approximately least recently used chunk.
The chunks in each bin are maintained in decreasing sorted order by
size. This 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 or 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.
* `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.
*/
typedef struct malloc_chunk* mchunkptr;
/* sizes, alignments */
#define SIZE_SZ (sizeof(INTERNAL_SIZE_T))
#ifdef CYGNUM_MEMALLOC_ALLOCATOR_DLMALLOC_ALIGNMENT
#define MALLOC_ALIGNMENT (1<<(CYGNUM_MEMALLOC_ALLOCATOR_DLMALLOC_ALIGNMENT))
#endif
#ifndef MALLOC_ALIGNMENT
#define MALLOC_ALIGNMENT (SIZE_SZ + SIZE_SZ)
#endif
#define MALLOC_ALIGN_MASK (MALLOC_ALIGNMENT - 1)
#define MINSIZE \
(offsetof(struct malloc_chunk, fd_samesize))
/* conversion from malloc headers to user pointers, and back */
#define chunk2mem(p) ((cyg_uint8*)((char*)(p) + 2*SIZE_SZ))
#define mem2chunk(mem) ((mchunkptr)((char*)(mem) - 2*SIZE_SZ))
/* pad request bytes into a usable size */
#define request2size(req) \
(((long)((req) + (SIZE_SZ + MALLOC_ALIGN_MASK)) < \
(long)(MINSIZE + MALLOC_ALIGN_MASK)) ? ((MINSIZE + MALLOC_ALIGN_MASK) & ~(MALLOC_ALIGN_MASK)) : \
(((req) + (SIZE_SZ + MALLOC_ALIGN_MASK)) & ~(MALLOC_ALIGN_MASK)))
/* Check if m has acceptable alignment */
#define aligned_OK(m) (((unsigned long)((m)) & (MALLOC_ALIGN_MASK)) == 0)
/*
Physical chunk operations
*/
/* size field is or'ed with PREV_INUSE when previous adjacent chunk in use */
#define PREV_INUSE 0x1
/* Bits to mask off when extracting size */
#define SIZE_BITS (PREV_INUSE)
/* 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
*/
/* 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)
/* set/clear chunk as in use 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 ignoring previous bits in header */
#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))
/*----------------------------------------------------------------------------*/
/*
Bins
The bins, `av_' are an array of pairs of pointers serving as the
heads of (initially empty) doubly-linked lists of chunks, laid out
in a way so that each pair can be treated as if it were in a
malloc_chunk. (This way, the fd/bk offsets for linking bin heads
and chunks are the same).
Bins for sizes < 512 bytes contain chunks of all the same size, spaced
8 bytes apart. Larger bins are approximately logarithmically
spaced. (See the table below.) The `av_' array is never mentioned
directly in the code, but instead via bin access macros.
Bin layout:
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 special chunks `top' and `last_remainder' get their own bins,
(this is implemented via yet more trickery with the av_ array),
although `top' is never properly linked to its bin since it is
always handled specially.
*/
typedef struct malloc_chunk* mbinptr;
/* access macros */
#define bin_at(i) ((mbinptr)((char*)&(av_[2*(i) + 2]) - 2*SIZE_SZ))
#define next_bin(b) ((mbinptr)((char*)(b) + 2 * sizeof(mbinptr)))
#define prev_bin(b) ((mbinptr)((char*)(b) - 2 * sizeof(mbinptr)))
/*
The first 2 bins are never indexed. The corresponding av_ cells are instead
used for bookkeeping. This is not to save space, but to simplify
indexing, maintain locality, and avoid some initialization tests.
*/
#define top (bin_at(0)->fd) /* The topmost chunk */
/* Helper macro to initialize bins */
#define IAV(i) bin_at(i), bin_at(i)
static mbinptr av_[CYGPRI_MEMALLOC_ALLOCATOR_DLMALLOC_NAV * 2 + 2] = {
0, 0,
IAV(0), IAV(1), IAV(2), IAV(3), IAV(4), IAV(5), IAV(6), IAV(7),
IAV(8), IAV(9), IAV(10), IAV(11), IAV(12), IAV(13), IAV(14), IAV(15),
IAV(16), IAV(17), IAV(18), IAV(19), IAV(20), IAV(21), IAV(22), IAV(23),
IAV(24), IAV(25), IAV(26), IAV(27), IAV(28), IAV(29), IAV(30), IAV(31),
IAV(32), IAV(33), IAV(34), IAV(35), IAV(36), IAV(37), IAV(38), IAV(39),
IAV(40), IAV(41), IAV(42), IAV(43), IAV(44), IAV(45), IAV(46), IAV(47),
IAV(48), IAV(49), IAV(50), IAV(51), IAV(52), IAV(53), IAV(54), IAV(55),
IAV(56), IAV(57), IAV(58), IAV(59), IAV(60), IAV(61), IAV(62), IAV(63),
IAV(64), IAV(65), IAV(66), IAV(67), IAV(68), IAV(69), IAV(70), IAV(71),
IAV(72), IAV(73), IAV(74), IAV(75), IAV(76), IAV(77), IAV(78), IAV(79),
IAV(80), IAV(81), IAV(82), IAV(83), IAV(84), IAV(85), IAV(86), IAV(87),
IAV(88), IAV(89), IAV(90), IAV(91), IAV(92), IAV(93), IAV(94), IAV(95),
IAV(96), IAV(97), IAV(98), IAV(99), IAV(100), IAV(101), IAV(102), IAV(103),
IAV(104), IAV(105), IAV(106), IAV(107), IAV(108), IAV(109), IAV(110), IAV(111),
IAV(112), IAV(113), IAV(114), IAV(115), IAV(116), IAV(117), IAV(118), IAV(119),
IAV(120), IAV(121), IAV(122), IAV(123), IAV(124), IAV(125), IAV(126), IAV(127)
};
/* field-extraction macros */
#define first(b) ((b)->fd)
#define last(b) ((b)->bk)
/*
Indexing into bins
*/
#define bin_index(sz) \
(((((unsigned long)(sz)) >> 9) == 0) ? (((unsigned long)(sz)) >> 3): \
((((unsigned long)(sz)) >> 9) <= 4) ? 56 + (((unsigned long)(sz)) >> 6): \
((((unsigned long)(sz)) >> 9) <= 20) ? 91 + (((unsigned long)(sz)) >> 9): \
((((unsigned long)(sz)) >> 9) <= 84) ? 110 + (((unsigned long)(sz)) >> 12): \
((((unsigned long)(sz)) >> 9) <= 340) ? 119 + (((unsigned long)(sz)) >> 15): \
((((unsigned long)(sz)) >> 9) <= 1364) ? 124 + (((unsigned long)(sz)) >> 18): \
126)
/*
bins for chunks < 512 are all spaced SMALLBIN_WIDTH bytes apart, and hold
identically sized chunks. This is exploited in malloc.
*/
#define MAX_SMALLBIN_SIZE 512
#define SMALLBIN_WIDTH 8
#define SMALLBIN_WIDTH_BITS 3
#define smallbin_index(sz) (((unsigned long)(sz)) >> SMALLBIN_WIDTH_BITS)
/*
To help compensate for the large number of bins, a one-level index
structure is used for bin-by-bin searching. `binblocks' is a
one-word bitvector recording whether groups of BINBLOCKWIDTH bins
have any (possibly) non-empty bins, so they can be skipped over
all at once during during traversals. The bits are NOT always
cleared as soon as all bins in a block are empty, but instead only
when all are noticed to be empty during traversal in malloc.
*/
#define BINBLOCKWIDTH 4 /* bins per block */
#define binblocks (bin_at(0)->size) /* bitvector of nonempty blocks */
/* bin<->block macros */
#define idx2binblock(ix) ((unsigned long)1 << (ix / BINBLOCKWIDTH))
#define mark_binblock(ii) (binblocks |= idx2binblock(ii))
#define clear_binblock(ii) (binblocks &= ~(idx2binblock(ii)))
/*----------------------------------------------------------------------------*/
/*
Debugging support
*/
#ifdef CYGDBG_MEMALLOC_ALLOCATOR_DLMALLOC_DEBUG
/*
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!)
*/
static void
do_check_chunk( mchunkptr p )
{
INTERNAL_SIZE_T sz = p->size & ~PREV_INUSE;
/* Check for legal address ... */
ASSERT((cyg_uint8 *)p >= arenabase);
if (p != top)
ASSERT((cyg_uint8 *)p + sz <= (cyg_uint8 *)top);
else
ASSERT((cyg_uint8 *)p + sz <= arenabase + arenasize);
} /* do_check_chunk() */
static void
do_check_free_chunk(mchunkptr p)
{
INTERNAL_SIZE_T sz = p->size & ~PREV_INUSE;
mchunkptr next = chunk_at_offset(p, sz);
do_check_chunk(p);
/* Check whether it claims to be free ... */
ASSERT(!inuse(p));
/* Unless a special marker, must have OK fields */
if ((long)sz >= (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 == top || inuse(next));
/* ... and has minimally sane links */
ASSERT(sz<MAX_SMALLBIN_SIZE ? p->fd->bk == p : p->fd_samesize->bk_samesize == p);
ASSERT(sz<MAX_SMALLBIN_SIZE ? p->bk->fd == p : p->bk_samesize->fd_samesize == p);
}
else /* markers are always of size SIZE_SZ */
ASSERT(sz == SIZE_SZ);
} /* do_check_free_chunk() */
static void
do_check_inuse_chunk(mchunkptr p)
{
mchunkptr next = next_chunk(p);
do_check_chunk(p);
/* Check whether it claims to be in use ... */
ASSERT(inuse(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))
{
mchunkptr prv = prev_chunk(p);
ASSERT(next_chunk(prv) == p);
do_check_free_chunk(prv);
}
if (next == top)
{
ASSERT(prev_inuse(next));
ASSERT(chunksize(next) >= MINSIZE);
}
else if (!inuse(next))
do_check_free_chunk(next);
} /* do_check_inuse_chunk() */
static void
do_check_malloced_chunk(mchunkptr p, INTERNAL_SIZE_T s)
{
INTERNAL_SIZE_T sz = p->size & ~PREV_INUSE;
long room = long_sub_size_t(sz, s);
do_check_inuse_chunk(p);
/* Legal size ... */
ASSERT((long)sz >= (long)MINSIZE);
ASSERT((sz & MALLOC_ALIGN_MASK) == 0);
ASSERT(room >= 0);
ASSERT(room < (long)MINSIZE);
/* ... and alignment */
ASSERT(aligned_OK(chunk2mem(p)));
/* ... and was allocated at front of an available chunk */
ASSERT(prev_inuse(p));
} /* do_check_malloced_chunk() */
#define check_free_chunk(P) do_check_free_chunk(P)
#define check_inuse_chunk(P) do_check_inuse_chunk(P)
#define check_chunk(P) do_check_chunk(P)
#define check_malloced_chunk(P,N) do_check_malloced_chunk(P,N)
#else
#define check_free_chunk(P)
#define check_inuse_chunk(P)
#define check_chunk(P)
#define check_malloced_chunk(P,N)
#endif
/*----------------------------------------------------------------------------*/
/*
Macro-based internal utilities
*/
/*
Linking chunks in bin lists.
Call these only with variables, not arbitrary expressions, as arguments.
*/
/*
Place chunk p of size s in its bin, in size order,
putting it ahead of others of same size.
*/
#define frontlink(P, S, IDX, BK, FD) \
{ \
if (S < MAX_SMALLBIN_SIZE) \
{ \
IDX = smallbin_index(S); \
mark_binblock(IDX); \
BK = bin_at(IDX); \
FD = BK->fd; \
P->fd = FD; \
P->bk = BK; \
FD->bk = BK->fd = P; \
} \
else \
{ \
IDX = bin_index(S); \
BK = bin_at(IDX); \
FD = BK->fd; \
if (FD == BK) \
{ \
mark_binblock(IDX); \
P->fd = FD; \
P->bk = BK; \
P->bk_samesize = P->fd_samesize = P; \
FD->bk = BK->fd = P; \
} \
else \
{ \
while (FD != BK && S < chunksize(FD)) FD = FD->fd; \
if (FD != BK && S == chunksize(FD)) \
{ \
BK = FD; \
FD = FD->fd_samesize; \
P->fd_samesize = FD; \
P->bk_samesize = BK; \
FD->bk_samesize = BK->fd_samesize = P; \
P->bk = P->fd = NULL; \
} \
else \
{ \
BK = FD->bk; \
P->fd = FD; \
P->bk = BK; \
P->bk_samesize = P->fd_samesize = P; \
FD->bk = BK->fd = P; \
} \
} \
} \
}