/* Malloc implementation for multiple threads without lock contention. Copyright (C) 1996 Free Software Foundation, Inc. This file is part of the GNU C Library. Contributed by Wolfram Gloger <wmglo@dent.med.uni-muenchen.de>, 1996. The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The GNU C Library 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 Library General Public License for more details. You should have received a copy of the GNU Library General Public License along with the GNU C Library; see the file COPYING.LIB. If not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ /* VERSION 2.6.4-pt Wed Dec 4 00:35:54 MET 1996 This work is mainly derived from malloc-2.6.4 by Doug Lea <dl@cs.oswego.edu>, which is available from: ftp://g.oswego.edu/pub/misc/malloc.c Most of the original comments are reproduced in the code below. * 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 On many systems, the standard malloc implementation is by itself not thread-safe, and therefore wrapped with a single global lock around all malloc-related functions. In some applications, especially with multiple available processors, this can lead to contention problems and bad performance. This malloc version was designed with the goal to avoid waiting for locks as much as possible. Statistics indicate that this goal is achieved in many cases. * Synopsis of public routines (Much fuller descriptions are contained in the program documentation below.) ptmalloc_init(); Initialize global configuration. When compiled for multiple threads, this function must be called once before any other function in the package. It is not required otherwise. It is called automatically in the Linux/GNU C libray. malloc(size_t n); Return a pointer to a newly allocated chunk of at least n bytes, or null if no space is available. free(Void_t* p); Release the chunk of memory pointed to by p, or no effect if p is null. realloc(Void_t* p, size_t n); Return a pointer to a chunk of size n that contains the same data as does chunk p up to the minimum of (n, p's size) bytes, or null if no space is available. The returned pointer may or may not be the same as p. If p is null, equivalent to malloc. Unless the #define REALLOC_ZERO_BYTES_FREES below is set, realloc with a size argument of zero (re)allocates a minimum-sized chunk. memalign(size_t alignment, size_t n); Return a pointer to a newly allocated chunk of n bytes, aligned in accord with the alignment argument, which must be a power of two. valloc(size_t n); Equivalent to memalign(pagesize, n), where pagesize is the page size of the system (or as near to this as can be figured out from all the includes/defines below.) pvalloc(size_t n); Equivalent to valloc(minimum-page-that-holds(n)), that is, round up n to nearest pagesize. calloc(size_t unit, size_t quantity); Returns a pointer to quantity * unit bytes, with all locations set to zero. cfree(Void_t* p); Equivalent to free(p). malloc_trim(size_t pad); Release all but pad bytes of freed top-most memory back to the system. Return 1 if successful, else 0. malloc_usable_size(Void_t* p); Report the number usable allocated bytes associated with allocated chunk p. This may or may not report more bytes than were requested, due to alignment and minimum size constraints. malloc_stats(); Prints brief summary statistics on stderr. mallinfo() Returns (by copy) a struct containing various summary statistics. mallopt(int parameter_number, int parameter_value) Changes one of the tunable parameters described below. Returns 1 if successful in changing the parameter, else 0. * Vital statistics: 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 will return a minimum-sized chunk. 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 two exceptions: 1. Because requests for zero bytes allocate non-zero space, the worst case wastage for a request of zero bytes is 24 bytes. 2. For requests >= mmap_threshold that are serviced via mmap(), the worst case wastage is 8 bytes plus the remainder from a system page (the minimal mmap unit); typically 4096 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. 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. __STD_C (default: derived from C compiler defines) Nonzero if using ANSI-standard C compiler, a C++ compiler, or a C compiler sufficiently close to ANSI to get away with it. MALLOC_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. REALLOC_ZERO_BYTES_FREES (default: NOT defined) Define this if you think that realloc(p, 0) should be equivalent to free(p). Otherwise, since malloc returns a unique pointer for malloc(0), so does realloc(p, 0). HAVE_MEMCPY (default: defined) Define if you are not otherwise using ANSI STD C, but still have memcpy and memset in your C library and want to use them. Otherwise, simple internal versions are supplied. USE_MEMCPY (default: 1 if HAVE_MEMCPY is defined, 0 otherwise) Define as 1 if you want the C library versions of memset and memcpy called in realloc and calloc (otherwise macro versions are used). At least on some platforms, the simple macro versions usually outperform libc versions. HAVE_MMAP (default: defined as 1) Define to non-zero to optionally make malloc() use mmap() to allocate very large blocks. HAVE_MREMAP (default: defined as 0 unless Linux libc set) Define to non-zero to optionally make realloc() use mremap() to reallocate very large blocks. malloc_getpagesize (default: derived from system #includes) Either a constant or routine call returning the system page size. HAVE_USR_INCLUDE_MALLOC_H (default: NOT defined) Optionally define if you are on a system with a /usr/include/malloc.h that declares struct mallinfo. It is not at all necessary to define this even if you do, but will ensure consistency. 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. _LIBC (default: NOT defined) Defined only when compiled as part of the Linux libc/glibc. Also note that there is some odd internal name-mangling via defines (for example, internally, `malloc' is named `mALLOc') needed when compiling in this case. These look funny but don't otherwise affect anything. LACKS_UNISTD_H (default: undefined) Define this if your system does not have a <unistd.h>. MORECORE (default: sbrk) The name of the routine to call to obtain more memory from the system. MORECORE_FAILURE (default: -1) The value returned upon failure of MORECORE. MORECORE_CLEARS (default 1) True (1) if the routine mapped to MORECORE zeroes out memory (which holds for sbrk). DEFAULT_TRIM_THRESHOLD DEFAULT_TOP_PAD DEFAULT_MMAP_THRESHOLD DEFAULT_MMAP_MAX Default values of tunable parameters (described in detail below) controlling interaction with host system routines (sbrk, mmap, etc). These values may also be changed dynamically via mallopt(). The preset defaults are those that give best performance for typical programs/systems. */ /* * Compile-time options for multiple threads: USE_PTHREADS, USE_THR, USE_SPROC Define one of these as 1 to select the thread interface: POSIX threads, Solaris threads or SGI sproc's, respectively. If none of these is defined as non-zero, you get a `normal' malloc implementation which is not thread-safe. Support for multiple threads requires HAVE_MMAP=1. As an exception, when compiling for GNU libc, i.e. when _LIBC is defined, then none of the USE_... symbols have to be defined. HEAP_MIN_SIZE HEAP_MAX_SIZE When thread support is enabled, additional `heap's are created with mmap calls. These are limited in size; HEAP_MIN_SIZE should be a multiple of the page size, while HEAP_MAX_SIZE must be a power of two for alignment reasons. HEAP_MAX_SIZE should be at least twice as large as the mmap threshold. THREAD_STATS When this is defined as non-zero, some statistics on mutex locking are computed. */ /* Macros for handling mutexes and thread-specific data. This is included first, because some thread-related header files (such as pthread.h) should be included before any others. */ #include "thread-m.h" /* Preliminaries */ #ifndef __STD_C #if defined (__STDC__) #define __STD_C 1 #else #if __cplusplus #define __STD_C 1 #else #define __STD_C 0 #endif /*__cplusplus*/ #endif /*__STDC__*/ #endif /*__STD_C*/ #ifndef Void_t #if __STD_C #define Void_t void #else #define Void_t char #endif #endif /*Void_t*/ #if __STD_C #include <stddef.h> /* for size_t */ #else #include <sys/types.h> #endif #ifdef __cplusplus extern "C" { #endif #include <stdio.h> /* needed for malloc_stats */ /* Compile-time options */ /* 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 -DMALLOC_DEBUG, a number of assertion checks are enabled that will catch more memory errors. You probably won't be able to make much sense of the actual assertion errors, but they should help you locate incorrectly overwritten memory. The checking is fairly extensive, and will slow down execution noticeably. Calling malloc_stats or mallinfo with MALLOC_DEBUG set will attempt to check every non-mmapped allocated and free chunk in the course of computing the summmaries. (By nature, mmapped regions cannot be checked very much automatically.) Setting MALLOC_DEBUG may also be helpful if you are trying to modify this code. The assertions in the check routines spell out in more detail the assumptions and invariants underlying the algorithms. */ #if MALLOC_DEBUG #include <assert.h> #else #define assert(x) ((void)0) #endif /* INTERNAL_SIZE_T is the word-size used for internal bookkeeping of chunk sizes. 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 size_t #endif /* REALLOC_ZERO_BYTES_FREES should be set if a call to realloc with zero bytes should be the same as a call to free. Some people think it should. Otherwise, since this malloc returns a unique pointer for malloc(0), so does realloc(p, 0). */ /* #define REALLOC_ZERO_BYTES_FREES */ /* HAVE_MEMCPY should be defined if you are not otherwise using ANSI STD C, but still have memcpy and memset in your C library and want to use them in calloc and realloc. Otherwise simple macro versions are defined here. USE_MEMCPY should be defined as 1 if you actually want to have memset and memcpy called. People report that the macro versions are often enough faster than libc versions on many systems that it is better to use them. */ #define HAVE_MEMCPY #ifndef USE_MEMCPY #ifdef HAVE_MEMCPY #define USE_MEMCPY 1 #else #define USE_MEMCPY 0 #endif #endif #if (__STD_C || defined(HAVE_MEMCPY)) #if __STD_C void* memset(void*, int, size_t); void* memcpy(void*, const void*, size_t); #else Void_t* memset(); Void_t* memcpy(); #endif #endif #if USE_MEMCPY /* 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 memcpy(dest, src, mcsz); \ } while(0) #else /* !USE_MEMCPY */ /* Use Duff's device for good zeroing/copying performance. */ #define MALLOC_ZERO(charp, nbytes) \ do { \ INTERNAL_SIZE_T* mzp = (INTERNAL_SIZE_T*)(charp); \ long mctmp = (nbytes)/sizeof(INTERNAL_SIZE_T), mcn; \ if (mctmp < 8) mcn = 0; else { mcn = (mctmp-1)/8; mctmp %= 8; } \ switch (mctmp) { \ case 0: for(;;) { *mzp++ = 0; \ case 7: *mzp++ = 0; \ case 6: *mzp++ = 0; \ case 5: *mzp++ = 0; \ case 4: *mzp++ = 0; \ case 3: *mzp++ = 0; \ case 2: *mzp++ = 0; \ case 1: *mzp++ = 0; if(mcn <= 0) break; mcn--; } \ } \ } while(0) #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 /* Define HAVE_MMAP to optionally make malloc() use mmap() to allocate very large blocks. These will be returned to the operating system immediately after a free(). */ #ifndef HAVE_MMAP #define HAVE_MMAP 1 #endif /* Define HAVE_MREMAP to make realloc() use mremap() to re-allocate large blocks. This is currently only possible on Linux with kernel versions newer than 1.3.77. */ #ifndef HAVE_MREMAP #define HAVE_MREMAP defined(__linux__) #endif #if HAVE_MMAP #include <unistd.h> #include <fcntl.h> #include <sys/mman.h> #if !defined(MAP_ANONYMOUS) && defined(MAP_ANON) #define MAP_ANONYMOUS MAP_ANON #endif #endif /* HAVE_MMAP */ /* Access to system page size. To the extent possible, this malloc manages memory from the system in page-size units. The following mechanics for getpagesize were adapted from bsd/gnu getpagesize.h */ #ifndef LACKS_UNISTD_H # include <unistd.h> #endif #ifndef malloc_getpagesize # ifdef _SC_PAGESIZE /* some SVR4 systems omit an underscore */ # ifndef _SC_PAGE_SIZE # define _SC_PAGE_SIZE _SC_PAGESIZE # endif # endif # ifdef _SC_PAGE_SIZE # define malloc_getpagesize sysconf(_SC_PAGE_SIZE) # else # if defined(BSD) || defined(DGUX) || defined(HAVE_GETPAGESIZE) extern size_t getpagesize(); # define malloc_getpagesize getpagesize() # else # include <sys/param.h> # ifdef EXEC_PAGESIZE # define malloc_getpagesize EXEC_PAGESIZE # else # ifdef NBPG # ifndef CLSIZE # define malloc_getpagesize NBPG # else # define malloc_getpagesize (NBPG * CLSIZE) # endif # else # ifdef NBPC # define malloc_getpagesize NBPC # else # ifdef PAGESIZE # define malloc_getpagesize PAGESIZE # else # define malloc_getpagesize (4096) /* just guess */ # endif # endif # endif # endif # endif # endif #endif /* This version of malloc supports the standard SVID/XPG mallinfo routine that returns a struct containing the same kind of information you can get from malloc_stats. It should work on any SVID/XPG compliant system that has a /usr/include/malloc.h defining struct mallinfo. (If you'd like to install such a thing yourself, cut out the preliminary declarations as described above and below and save them in a malloc.h file. But there's no compelling reason to bother to do this.) The main declaration needed is the mallinfo struct that is returned (by-copy) by mallinfo(). The SVID/XPG malloinfo struct contains a bunch of fields, most of which are not even meaningful in this version of malloc. Some of these fields are are instead filled by mallinfo() with other numbers that might possibly be of interest. HAVE_USR_INCLUDE_MALLOC_H should be set if you have a /usr/include/malloc.h file that includes a declaration of struct mallinfo. If so, it is included; else an SVID2/XPG2 compliant version is declared below. These must be precisely the same for mallinfo() to work. */ /* #define HAVE_USR_INCLUDE_MALLOC_H */ #if HAVE_USR_INCLUDE_MALLOC_H #include "/usr/include/malloc.h" #else #include "malloc.h" #endif #ifndef DEFAULT_TRIM_THRESHOLD #define DEFAULT_TRIM_THRESHOLD (128 * 1024) #endif /* M_TRIM_THRESHOLD is the maximum amount of unused top-most memory to keep before releasing via malloc_trim in free(). Automatic trimming is mainly useful in long-lived programs. Because trimming via sbrk can be slow on some systems, and can sometimes be wasteful (in cases where programs immediately afterward allocate more large chunks) the value should be high enough so that your overall system performance would improve by releasing. The trim threshold and the mmap control parameters (see below) can be traded off with one another. Trimming and mmapping are two different ways of releasing unused memory back to the system. Between these two, it is often possible to keep system-level demands of a long-lived program down to a bare minimum. For example, in one test suite of sessions measuring the XF86 X server on Linux, using a trim threshold of 128K and a mmap threshold of 192K led to near-minimal long term resource consumption. If you are using this malloc in a long-lived program, it should pay to experiment with these values. As a rough guide, you might set to a value close to the average size of a process (program) running on your system. Releasing this much memory would allow such a process to run in memory. Generally, it's worth it to tune for trimming rather tham memory mapping when a program undergoes phases where several large chunks are allocated and released in ways that can reuse each other's storage, perhaps mixed with phases where there are no such chunks at all. And in well-behaved long-lived programs, controlling release of large blocks via trimming versus mapping is usually faster. However, in most programs, these parameters serve mainly as protection against the system-level effects of carrying around massive amounts of unneeded memory. Since frequent calls to sbrk, mmap, and munmap otherwise degrade performance, the default parameters are set to relatively high values that serve only as safeguards. The default trim value is high enough to cause trimming only in fairly extreme (by current memory consumption standards) cases. It must be greater than page size to have any useful effect. To disable trimming completely, you can set to (unsigned long)(-1); */ #ifndef DEFAULT_TOP_PAD #define DEFAULT_TOP_PAD (0) #endif /* M_TOP_PAD is the amount of extra `padding' space to allocate or retain whenever sbrk is called. It is used in two ways internally: * When sbrk is called to extend the top of the arena to satisfy a new malloc request, this much padding is added to the sbrk request. * When malloc_trim is called automatically from free(), it is used as the `pad' argument. In both cases, the actual amount of padding is rounded so that the end of the arena is always a system page boundary. The main reason for using padding is to avoid calling sbrk so often. Having even a small pad greatly reduces the likelihood that nearly every malloc request during program start-up (or after trimming) will invoke sbrk, which needlessly wastes time. Automatic rounding-up to page-size units is normally sufficient to avoid measurable overhead, so the default is 0. However, in systems where sbrk is relatively slow, it can pay to increase this value, at the expense of carrying around more memory than the program needs. */ #ifndef DEFAULT_MMAP_THRESHOLD #define DEFAULT_MMAP_THRESHOLD (128 * 1024) #endif /* M_MMAP_THRESHOLD is the request size threshold for using mmap() to service a request. Requests of at least this size that cannot be allocated using already-existing space will be serviced via mmap. (If enough normal freed space already exists it is used instead.) Using mmap segregates relatively large chunks of memory so that they can be individually obtained and released from the host system. A request serviced through mmap is never reused by any other request (at least not directly; the system may just so happen to remap successive requests to the same locations). Segregating space in this way has the benefit that mmapped space can ALWAYS be individually released back to the system, which helps keep the system level memory demands of a long-lived program low. Mapped memory can never become `locked' between other chunks, as can happen with normally allocated chunks, which menas that even trimming via malloc_trim would not release them. However, it has the disadvantages that: 1. The space cannot be reclaimed, consolidated, and then used to service later requests, as happens with normal chunks. 2. It can lead to more wastage because of mmap page alignment requirements 3. It causes malloc performance to be more dependent on host system memory management support routines which may vary in implementation quality and may impose arbitrary limitations. Generally, servicing a request via normal malloc steps is faster than going through a system's mmap. All together, these considerations should lead you to use mmap only for relatively large requests. */ #ifndef DEFAULT_MMAP_MAX #if HAVE_MMAP #define DEFAULT_MMAP_MAX (1024) #else #define DEFAULT_MMAP_MAX (0) #endif #endif /* M_MMAP_MAX is the maximum number of requests to simultaneously service using mmap. This parameter exists because: 1. Some systems have a limited number of internal tables for use by mmap. 2. In most systems, overreliance on mmap can degrade overall performance. 3. If a program allocates many large regions, it is probably better off using normal sbrk-based allocation routines that can reclaim and reallocate normal heap memory. Using a small value allows transition into this mode after the first few allocations. Setting to 0 disables all use of mmap. If HAVE_MMAP is not set, the default value is 0, and attempts to set it to non-zero values in mallopt will fail. */ #define HEAP_MIN_SIZE (32*1024) #define HEAP_MAX_SIZE (1024*1024) /* must be a power of two */ /* HEAP_MIN_SIZE and HEAP_MAX_SIZE limit the size of mmap()ed heaps that are dynamically created for multi-threaded programs. The maximum size must be a power of two, for fast determination of which heap belongs to a chunk. It should be much larger than the mmap threshold, so that requests with a size just below that threshold can be fulfilled without creating too many heaps. */ #ifndef THREAD_STATS #define THREAD_STATS 0 #endif /* If THREAD_STATS is non-zero, some statistics on mutex locking are computed. */ /* Special defines for the Linux/GNU C library. */ #ifdef _LIBC #if __STD_C Void_t * __default_morecore (ptrdiff_t); static Void_t *(*__morecore)(ptrdiff_t) = __default_morecore; #else Void_t * __default_morecore (); static Void_t *(*__morecore)() = __default_morecore; #endif #define MORECORE (*__morecore) #define MORECORE_FAILURE 0 #define MORECORE_CLEARS 1 #else /* _LIBC */ #if __STD_C extern Void_t* sbrk(ptrdiff_t); #else extern Void_t* sbrk(); #endif #ifndef MORECORE #define MORECORE sbrk #endif #ifndef MORECORE_FAILURE #define MORECORE_FAILURE -1 #endif #ifndef MORECORE_CLEARS #define MORECORE_CLEARS 1 #endif #endif /* _LIBC */ #if 0 && defined(_LIBC) #define cALLOc __libc_calloc #define fREe __libc_free #define mALLOc __libc_malloc #define mEMALIGn __libc_memalign #define rEALLOc __libc_realloc #define vALLOc __libc_valloc #define pvALLOc __libc_pvalloc #define mALLINFo __libc_mallinfo #define mALLOPt __libc_mallopt #pragma weak calloc = __libc_calloc #pragma weak free = __libc_free #pragma weak cfree = __libc_free #pragma weak malloc = __libc_malloc #pragma weak memalign = __libc_memalign #pragma weak realloc = __libc_realloc #pragma weak valloc = __libc_valloc #pragma weak pvalloc = __libc_pvalloc #pragma weak mallinfo = __libc_mallinfo #pragma weak mallopt = __libc_mallopt #else #define cALLOc calloc #define fREe free #define mALLOc malloc #define mEMALIGn memalign #define rEALLOc realloc #define vALLOc valloc #define pvALLOc pvalloc #define mALLINFo mallinfo #define mALLOPt mallopt #endif /* Public routines */ #if __STD_C #ifndef _LIBC void ptmalloc_init(void); #endif Void_t* mALLOc(size_t); void fREe(Void_t*); Void_t* rEALLOc(Void_t*, size_t); Void_t* mEMALIGn(size_t, size_t); Void_t* vALLOc(size_t); Void_t* pvALLOc(size_t); Void_t* cALLOc(size_t, size_t); void cfree(Void_t*); int malloc_trim(size_t); size_t malloc_usable_size(Void_t*); void malloc_stats(void); int mALLOPt(int, int); struct mallinfo mALLINFo(void); #else #ifndef _LIBC void ptmalloc_init(); #endif Void_t* mALLOc(); void fREe(); Void_t* rEALLOc(); Void_t* mEMALIGn(); Void_t* vALLOc(); Void_t* pvALLOc(); Void_t* cALLOc(); void cfree(); int malloc_trim(); size_t malloc_usable_size(); void malloc_stats(); int mALLOPt(); struct mallinfo mALLINFo(); #endif #ifdef __cplusplus }; /* end of extern "C" */ #endif #if !defined(NO_THREADS) && !HAVE_MMAP "Can't have threads support without mmap" #endif /* Type declarations */ struct malloc_chunk { INTERNAL_SIZE_T prev_size; /* Size of previous chunk (if free). */ INTERNAL_SIZE_T size; /* Size in bytes, including overhead. */ struct malloc_chunk* fd; /* double links -- used only if free. */ struct malloc_chunk* bk; }; typedef struct malloc_chunk* mchunkptr; /* malloc_chunk details: (The following includes lightly edited explanations by Colin Plumb.) Chunks of memory are maintained using a `boundary tag' method as described in e.g., Knuth or Standish. (See the paper by Paul Wilson ftp://ftp.cs.utexas.edu/pub/garbage/allocsrv.ps for a survey of such techniques.) Sizes of free chunks are stored both in the front of each chunk and at the end. This makes consolidating fragmented chunks into bigger chunks very fast. The size fields also hold bits representing whether chunks are free or in use. An allocated chunk looks like this: chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Size of previous chunk, if allocated | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Size of chunk, in bytes |P| mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | User data starts here... . . . . (malloc_usable_space() bytes) . . | nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Size of chunk | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Where "chunk" is the front of the chunk for the purpose of most of the malloc code, but "mem" is the pointer that is returned to the user. "Nextchunk" is the beginning of the next contiguous chunk. Chunks always begin on even word boundries, so the mem portion (which is returned to the user) is also on an even word boundary, and thus double-word aligned. Free chunks are stored in circular doubly-linked lists, and look like this: chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Size of previous chunk | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ `head:' | Size of chunk, in bytes |P| mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Forward pointer to next chunk in list | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Back pointer to previous chunk in list | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Unused space (may be 0 bytes long) . . . . | nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ `foot:' | Size of chunk, in bytes | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The P (PREV_INUSE) bit, stored in the unused low-order bit of the chunk size (which is always a multiple of two words), is an in-use bit for the *previous* chunk. If that bit is *clear*, then the word before the current chunk size contains the previous chunk size, and can be used to find the front of the previous chunk. (The very first chunk allocated always has this bit set, preventing access to non-existent (or non-owned) memory.) Note that the `foot' of the current chunk is actually represented as the prev_size of the NEXT chunk. (This makes it easier to deal with alignments etc). The two exceptions to all this are 1. The special chunk `top', 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. If it would become less than MINSIZE bytes long, it is replenished via malloc_extend_top.) 2. Chunks allocated via mmap, which have the second-lowest-order bit (IS_MMAPPED) set in their size fields. Because they are never merged or traversed from any other chunk, they have no foot size or inuse information. 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, and is released back to the system if it is very large (see M_TRIM_THRESHOLD). * `last_remainder': A bin holding only the remainder of the most recently split (non-top) chunk. This bin is checked before other non-fitting chunks, so as to provide better locality for runs of sequentially allocated chunks. * Implicitly, through the host system's memory mapping tables. If supported, requests greater than a threshold are usually serviced via calls to mmap, and then later released via munmap. */ /* Bins The bins 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.) 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. */ #define NAV 128 /* number of bins */ typedef struct malloc_chunk* mbinptr; /* An arena is a configuration of malloc_chunks together with an array of bins. With multiple threads, it must be locked via a mutex before changing its data structures. One or more `heaps' are associated with each arena, except for the main_arena, which is associated only with the `main heap', i.e. the conventional free store obtained with calls to MORECORE() (usually sbrk). The `av' array is never mentioned directly in the code, but instead used via bin access macros. */ typedef struct _arena { mbinptr av[2*NAV + 2]; struct _arena *next; mutex_t mutex; } arena; /* A heap is a single contiguous memory region holding (coalescable) malloc_chunks. It is allocated with mmap() and always starts at an address aligned to HEAP_MAX_SIZE. Not used unless compiling for multiple threads. */ typedef struct _heap_info { arena *ar_ptr; size_t size; } heap_info; /* Static functions (forward declarations) */ #if __STD_C static void chunk_free(arena *ar_ptr, mchunkptr p); static mchunkptr chunk_alloc(arena *ar_ptr, INTERNAL_SIZE_T size); static int arena_trim(arena *ar_ptr, size_t pad); #else static void chunk_free(); static mchunkptr chunk_alloc(); static int arena_trim(); #endif /* sizes, alignments */ #define SIZE_SZ (sizeof(INTERNAL_SIZE_T)) #define MALLOC_ALIGNMENT (SIZE_SZ + SIZE_SZ) #define MALLOC_ALIGN_MASK (MALLOC_ALIGNMENT - 1) #define MINSIZE (sizeof(struct malloc_chunk)) /* conversion from malloc headers to user pointers, and back */ #define chunk2mem(p) ((Void_t*)((char*)(p) + 2*SIZE_SZ)) #define mem2chunk(mem) ((mchunkptr)((char*)(mem) - 2*SIZE_SZ)) /* pad request bytes into a usable size */ #define request2size(req) \ (((long)((req) + (SIZE_SZ + MALLOC_ALIGN_MASK)) < \ (long)(MINSIZE + MALLOC_ALIGN_MASK)) ? MINSIZE : \ (((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 /* size field is or'ed with IS_MMAPPED if the chunk was obtained with mmap() */ #define IS_MMAPPED 0x2 /* Bits to mask off when extracting size */ #define SIZE_BITS (PREV_INUSE|IS_MMAPPED) /* Ptr to next physical malloc_chunk. */ #define next_chunk(p) ((mchunkptr)( ((char*)(p)) + ((p)->size & ~PREV_INUSE) )) /* Ptr to previous physical malloc_chunk */ #define prev_chunk(p) ((mchunkptr)( ((char*)(p)) - ((p)->prev_size) )) /* Treat space at ptr + offset as a chunk */ #define chunk_at_offset(p, s) ((mchunkptr)(((char*)(p)) + (s))) /* Dealing with use bits */ /* extract p's inuse bit */ #define inuse(p) \ ((((mchunkptr)(((char*)(p))+((p)->size & ~PREV_INUSE)))->size) & PREV_INUSE) /* extract inuse bit of previous chunk */ #define prev_inuse(p) ((p)->size & PREV_INUSE) /* check for mmap()'ed chunk */ #define chunk_is_mmapped(p) ((p)->size & IS_MMAPPED) /* set/clear chunk as 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)) /* access macros */ #define bin_at(a, i) ((mbinptr)((char*)&(((a)->av)[2*(i) + 2]) - 2*SIZE_SZ)) #define init_bin(a, i) ((a)->av[2*i+2] = (a)->av[2*i+3] = bin_at((a), i)) #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 binblocks(a) (bin_at(a,0)->size)/* bitvector of nonempty blocks */ #define top(a) (bin_at(a,0)->fd) /* The topmost chunk */ #define last_remainder(a) (bin_at(a,1)) /* remainder from last split */ /* Because top initially points to its own bin with initial zero size, thus forcing extension on the first malloc request, we avoid having any special code in malloc to check whether it even exists yet. But we still need to in malloc_extend_top. */ #define initial_top(a) ((mchunkptr)bin_at(a, 0)) /* 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 8 bytes apart, and hold identically sized chunks. This is exploited in malloc. */ #define MAX_SMALLBIN 63 #define MAX_SMALLBIN_SIZE 512 #define SMALLBIN_WIDTH 8 #define smallbin_index(sz) (((unsigned long)(sz)) >> 3) /* Requests are `small' if both the corresponding and the next bin are small */ #define is_small_request(nb) ((nb) < MAX_SMALLBIN_SIZE - SMALLBIN_WIDTH) /* 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 */ /* bin<->block macros */ #define idx2binblock(ix) ((unsigned)1 << ((ix) / BINBLOCKWIDTH)) #define mark_binblock(a, ii) (binblocks(a) |= idx2binblock(ii)) #define clear_binblock(a, ii) (binblocks(a) &= ~(idx2binblock(ii))) /* Static bookkeeping data */ /* Helper macro to initialize bins */ #define IAV(i) bin_at(&main_arena, i), bin_at(&main_arena, i) static arena main_arena = { { 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) }, NULL, /* next */ MUTEX_INITIALIZER /* mutex */ }; #undef IAV /* Thread specific data */ static tsd_key_t arena_key; static mutex_t list_lock = MUTEX_INITIALIZER; #if THREAD_STATS static int stat_n_arenas = 0; static int stat_n_heaps = 0; static long stat_lock_direct = 0; static long stat_lock_loop = 0; #define THREAD_STAT(x) x #else #define THREAD_STAT(x) do ; while(0) #endif /* variables holding tunable values */ static unsigned long trim_threshold = DEFAULT_TRIM_THRESHOLD; static unsigned long top_pad = DEFAULT_TOP_PAD; static unsigned int n_mmaps_max = DEFAULT_MMAP_MAX; static unsigned long mmap_threshold = DEFAULT_MMAP_THRESHOLD; /* The first value returned from sbrk */ static char* sbrk_base = (char*)(-1); /* The maximum memory obtained from system via sbrk */ static unsigned long max_sbrked_mem = 0; /* The maximum via either sbrk or mmap */ static unsigned long max_total_mem = 0; /* internal working copy of mallinfo */ static struct mallinfo current_mallinfo = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }; /* The total memory obtained from system via sbrk */ #define sbrked_mem (current_mallinfo.arena) /* Tracking mmaps */ static unsigned int n_mmaps = 0; static unsigned int max_n_mmaps = 0; static unsigned long mmapped_mem = 0; static unsigned long max_mmapped_mem = 0; /* Initialization routine. */ #if defined(_LIBC) static void ptmalloc_init __MALLOC_P ((void)) __attribute__ ((constructor)); static void ptmalloc_init __MALLOC_P((void)) #else void ptmalloc_init __MALLOC_P((void)) #endif { static int first = 1; #if defined(_LIBC) /* Initialize the pthread. */ if (__pthread_initialize != NULL) __pthread_initialize (); #endif if(first) { first = 0; mutex_init(&main_arena.mutex); mutex_init(&list_lock); tsd_key_create(&arena_key, NULL); tsd_setspecific(arena_key, (Void_t *)&main_arena); } } /* Routines dealing with mmap(). */ #if HAVE_MMAP #ifndef MAP_ANONYMOUS static int dev_zero_fd = -1; /* Cached file descriptor for /dev/zero. */ #define MMAP(size, prot) ((dev_zero_fd < 0) ? \ (dev_zero_fd = open("/dev/zero", O_RDWR), \ mmap(0, (size), (prot), MAP_PRIVATE, dev_zero_fd, 0)) : \ mmap(0, (size), (prot), MAP_PRIVATE, dev_zero_fd, 0)) #else #define MMAP(size, prot) \ (mmap(0, (size), (prot), MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)) #endif #if __STD_C static mchunkptr mmap_chunk(size_t size) #else static mchunkptr mmap_chunk(size) size_t size; #endif { size_t page_mask = malloc_getpagesize - 1; mchunkptr p; if(n_mmaps >= n_mmaps_max) return 0; /* too many regions */ /* For mmapped chunks, the overhead is one SIZE_SZ unit larger, because * there is no following chunk whose prev_size field could be used. */ size = (size + SIZE_SZ + page_mask) & ~page_mask; p = (mchunkptr)MMAP(size, PROT_READ|PROT_WRITE); if(p == (mchunkptr)-1) return 0; n_mmaps++; if (n_mmaps > max_n_mmaps) max_n_mmaps = n_mmaps; /* We demand that eight bytes into a page must be 8-byte aligned. */ assert(aligned_OK(chunk2mem(p))); /* The offset to the start of the mmapped region is stored * in the prev_size field of the chunk; normally it is zero, * but that can be changed in memalign(). */ p->prev_size = 0; set_head(p, size|IS_MMAPPED); mmapped_mem += size; if ((unsigned long)mmapped_mem > (unsigned long)max_mmapped_mem) max_mmapped_mem = mmapped_mem; if ((unsigned long)(mmapped_mem + sbrked_mem) > (unsigned long)max_total_mem) max_total_mem = mmapped_mem + sbrked_mem; return p; } #if __STD_C static void munmap_chunk(mchunkptr p) #else static void munmap_chunk(p) mchunkptr p; #endif { INTERNAL_SIZE_T size = chunksize(p); int ret; assert (chunk_is_mmapped(p)); assert(! ((char*)p >= sbrk_base && (char*)p < sbrk_base + sbrked_mem)); assert((n_mmaps > 0)); assert(((p->prev_size + size) & (malloc_getpagesize-1)) == 0); n_mmaps--; mmapped_mem -= (size + p->prev_size); ret = munmap((char *)p - p->prev_size, size + p->prev_size); /* munmap returns non-zero on failure */ assert(ret == 0); } #if HAVE_MREMAP #if __STD_C static mchunkptr mremap_chunk(mchunkptr p, size_t new_size) #else static mchunkptr mremap_chunk(p, new_size) mchunkptr p; size_t new_size; #endif { size_t page_mask = malloc_getpagesize - 1; INTERNAL_SIZE_T offset = p->prev_size; INTERNAL_SIZE_T size = chunksize(p); char *cp; assert (chunk_is_mmapped(p)); assert(! ((char*)p >= sbrk_base && (char*)p < sbrk_base + sbrked_mem)); assert((n_mmaps > 0)); assert(((size + offset) & (malloc_getpagesize-1)) == 0); /* Note the extra SIZE_SZ overhead as in mmap_chunk(). */ new_size = (new_size + offset + SIZE_SZ + page_mask) & ~page_mask; cp = (char *)mremap((char *)p - offset, size + offset, new_size, MREMAP_MAYMOVE); if (cp == (char *)-1) return 0; p = (mchunkptr)(cp + offset); assert(aligned_OK(chunk2mem(p))); assert((p->prev_size == offset)); set_head(p, (new_size - offset)|IS_MMAPPED); mmapped_mem -= size + offset; mmapped_mem += new_size; if ((unsigned long)mmapped_mem > (unsigned long)max_mmapped_mem) max_mmapped_mem = mmapped_mem; if ((unsigned long)(mmapped_mem + sbrked_mem) > (unsigned long)max_total_mem) max_total_mem = mmapped_mem + sbrked_mem; return p; } #endif /* HAVE_MREMAP */ #endif /* HAVE_MMAP */ /* Managing heaps and arenas (for concurrent threads) */ #ifndef NO_THREADS /* Create a new heap. size is automatically rounded up to a multiple of the page size. */ static heap_info * #if __STD_C new_heap(size_t size) #else new_heap(size) size_t size; #endif { size_t page_mask = malloc_getpagesize - 1; char *p1, *p2; unsigned long ul; heap_info *h; if(size < HEAP_MIN_SIZE) size = HEAP_MIN_SIZE; size = (size + page_mask) & ~page_mask; if(size > HEAP_MAX_SIZE) return 0; p1 = (char *)MMAP(HEAP_MAX_SIZE<<1, PROT_NONE); if(p1 == (char *)-1) return 0; p2 = (char *)(((unsigned long)p1 + HEAP_MAX_SIZE) & ~(HEAP_MAX_SIZE-1)); ul = p2 - p1; munmap(p1, ul); munmap(p2 + HEAP_MAX_SIZE, HEAP_MAX_SIZE - ul); if(mprotect(p2, size, PROT_READ|PROT_WRITE) != 0) { munmap(p2, HEAP_MAX_SIZE); return 0; } h = (heap_info *)p2; h->size = size; THREAD_STAT(stat_n_heaps++); return h; } /* Grow or shrink a heap. size is automatically rounded up to a multiple of the page size. */ static int #if __STD_C grow_heap(heap_info *h, long diff) #else grow_heap(h, diff) heap_info *h; long diff; #endif { size_t page_mask = malloc_getpagesize - 1; long new_size; if(diff >= 0) { diff = (diff + page_mask) & ~page_mask; new_size = (long)h->size + diff; if(new_size > HEAP_MAX_SIZE) return -1; if(mprotect((char *)h + h->size, diff, PROT_READ|PROT_WRITE) != 0) return -2; } else { new_size = (long)h->size + diff; if(new_size < 0) return -1; if(mprotect((char *)h + new_size, -diff, PROT_NONE) != 0) return -2; } h->size = new_size; return 0; } /* arena_get() acquires an arena and locks the corresponding mutex. First, try the one last locked successfully by this thread. (This is the common case and handled with a macro for speed.) Then, loop over the singly linked list of arenas. If no arena is readily available, create a new one. */ #define arena_get(ptr, size) do { \ Void_t *vptr = NULL; \ ptr = (arena *)tsd_getspecific(arena_key, vptr); \ if(ptr && !mutex_trylock(&ptr->mutex)) { \ THREAD_STAT(stat_lock_direct++); \ } else { \ ptr = arena_get2(ptr, (size)); \ } \ } while(0) static arena * #if __STD_C arena_get2(arena *a_tsd, size_t size) #else arena_get2(a_tsd, size) arena *a_tsd; size_t size; #endif { arena *a; heap_info *h; char *ptr; int i; unsigned long misalign; /* Check the list for unlocked arenas. */ if(a_tsd) { for(a = a_tsd->next; a; a = a->next) { if(!mutex_trylock(&a->mutex)) goto done; } for(a = &main_arena; a != a_tsd; a = a->next) { if(!mutex_trylock(&a->mutex)) goto done; } } else { for(a = &main_arena; a; a = a->next) { if(!mutex_trylock(&a->mutex)) goto done; } } /* Nothing immediately available, so generate a new arena. */ h = new_heap(size + (sizeof(*h) + sizeof(*a) + MALLOC_ALIGNMENT)); if(!h) return 0; a = h->ar_ptr = (arena *)(h+1); for(i=0; i<NAV; i++) init_bin(a, i); mutex_init(&a->mutex); i = mutex_lock(&a->mutex); /* remember result */ /* Set up the top chunk, with proper alignment. */ ptr = (char *)(a + 1); misalign = (unsigned long)chunk2mem(ptr) & MALLOC_ALIGN_MASK; if (misalign > 0) ptr += MALLOC_ALIGNMENT - misalign; top(a) = (mchunkptr)ptr; set_head(top(a), (h->size - (ptr-(char*)h)) | PREV_INUSE); /* Add the new arena to the list. */ (void)mutex_lock(&list_lock); a->next = main_arena.next; main_arena.next = a; THREAD_STAT(stat_n_arenas++); (void)mutex_unlock(&list_lock); if(i) /* locking failed; keep arena for further attempts later */ return 0; done: THREAD_STAT(stat_lock_loop++); tsd_setspecific(arena_key, (Void_t *)a); return a; } /* find the heap and corresponding arena for a given ptr */ #define heap_for_ptr(ptr) \ ((heap_info *)((unsigned long)(ptr) & ~(HEAP_MAX_SIZE-1))) #define arena_for_ptr(ptr) \ (((mchunkptr)(ptr) < top(&main_arena) && (char *)(ptr) >= sbrk_base) ? \ &main_arena : heap_for_ptr(ptr)->ar_ptr) #else /* defined(NO_THREADS) */ /* Without concurrent threads, there is only one arena. */ #define arena_get(ptr, sz) (ptr = &main_arena) #define arena_for_ptr(ptr) (&main_arena) #endif /* !defined(NO_THREADS) */ /* Debugging support */ #if MALLOC_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!) */ #if __STD_C static void do_check_chunk(arena *ar_ptr, mchunkptr p) #else static void do_check_chunk(ar_ptr, p) arena *ar_ptr; mchunkptr p; #endif { INTERNAL_SIZE_T sz = p->size & ~PREV_INUSE; /* No checkable chunk is mmapped */ assert(!chunk_is_mmapped(p)); #ifndef NO_THREADS if(ar_ptr != &main_arena) { heap_info *heap = heap_for_ptr(p); assert(heap->ar_ptr == ar_ptr); assert((char *)p + sz <= (char *)heap + heap->size); return; } #endif /* Check for legal address ... */ assert((char*)p >= sbrk_base); if (p != top(ar_ptr)) assert((char*)p + sz <= (char*)top(ar_ptr)); else assert((char*)p + sz <= sbrk_base + sbrked_mem); } #if __STD_C static void do_check_free_chunk(arena *ar_ptr, mchunkptr p) #else static void do_check_free_chunk(ar_ptr, p) arena *ar_ptr; mchunkptr p; #endif { INTERNAL_SIZE_T sz = p->size & ~PREV_INUSE; mchunkptr next = chunk_at_offset(p, sz); do_check_chunk(ar_ptr, 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(ar_ptr) || inuse(next)); /* ... and has minimally sane links */ assert(p->fd->bk == p); assert(p->bk->fd == p); } else /* markers are always of size SIZE_SZ */ assert(sz == SIZE_SZ); } #if __STD_C static void do_check_inuse_chunk(arena *ar_ptr, mchunkptr p) #else static void do_check_inuse_chunk(ar_ptr, p) arena *ar_ptr; mchunkptr p; #endif { mchunkptr next = next_chunk(p); do_check_chunk(ar_ptr, 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(ar_ptr, prv); } if (next == top(ar_ptr)) { assert(prev_inuse(next)); assert(chunksize(next) >= MINSIZE); } else if (!inuse(next)) do_check_free_chunk(ar_ptr, next); } #if __STD_C static void do_check_malloced_chunk(arena *ar_ptr, mchunkptr p, INTERNAL_SIZE_T s) #else static void do_check_malloced_chunk(ar_ptr, p, s) arena *ar_ptr; mchunkptr p; INTERNAL_SIZE_T s; #endif { INTERNAL_SIZE_T sz = p->size & ~PREV_INUSE; long room = sz - s; do_check_inuse_chunk(ar_ptr, 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)); } #define check_free_chunk(A,P) do_check_free_chunk(A,P) #define check_inuse_chunk(A,P) do_check_inuse_chunk(A,P) #define check_chunk(A,P) do_check_chunk(A,P) #define check_malloced_chunk(A,P,N) do_check_malloced_chunk(A,P,N) #else #define check_free_chunk(A,P) #define check_inuse_chunk(A,P) #define check_chunk(A,P) #define check_malloced_chunk(A,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(A, P, S, IDX, BK, FD) \ { \ if (S < MAX_SMALLBIN_SIZE) \ { \ IDX = smallbin_index(S); \ mark_binblock(A, IDX); \ BK = bin_at(A, IDX); \ FD = BK->fd; \ P->bk = BK; \ P->fd = FD; \ FD->bk = BK->fd = P; \ } \ else \ { \ IDX = bin_index(S); \ BK = bin_at(A, IDX); \ FD = BK->fd; \ if (FD == BK) mark_binblock(A, IDX); \ else \ { \ while (FD != BK && S < chunksize(FD)) FD = FD->fd; \ BK = FD->bk; \ } \ P->bk = BK; \ P->fd = FD; \ FD->bk = BK->fd = P; \ } \ } /* take a chunk off a list */ #define unlink(P, BK, FD) \ { \ BK = P->bk; \ FD = P->fd; \ FD->bk = BK; \ BK->fd = FD; \ } \ /* Place p as the last remainder */ #define link_last_remainder(A, P) \ { \ last_remainder(A)->fd = last_remainder(A)->bk = P; \ P->fd = P->bk = last_remainder(A); \ } /* Clear the last_remainder bin */ #define clear_last_remainder(A) \ (last_remainder(A)->fd = last_remainder(A)->bk = last_remainder(A)) /* Extend the top-most chunk by obtaining memory from system. Main interface to sbrk (but see also malloc_trim). */ #if __STD_C static void malloc_extend_top(arena *ar_ptr, INTERNAL_SIZE_T nb) #else static void malloc_extend_top(ar_ptr, nb) arena *ar_ptr; INTERNAL_SIZE_T nb; #endif { unsigned long pagesz = malloc_getpagesize; mchunkptr old_top = top(ar_ptr); /* Record state of old top */ INTERNAL_SIZE_T old_top_size = chunksize(old_top); INTERNAL_SIZE_T top_size; /* new size of top chunk */ #ifndef NO_THREADS if(ar_ptr == &main_arena) { #endif char* brk; /* return value from sbrk */ INTERNAL_SIZE_T front_misalign; /* unusable bytes at front of sbrked space */ INTERNAL_SIZE_T correction; /* bytes for 2nd sbrk call */ char* new_brk; /* return of 2nd sbrk call */ char* old_end = (char*)(chunk_at_offset(old_top, old_top_size)); /* Pad request with top_pad plus minimal overhead */ INTERNAL_SIZE_T sbrk_size = nb + top_pad + MINSIZE; /* If not the first time through, round to preserve page boundary */ /* Otherwise, we need to correct to a page size below anyway. */ /* (We also correct below if an intervening foreign sbrk call.) */ if (sbrk_base != (char*)(-1)) sbrk_size = (sbrk_size + (pagesz - 1)) & ~(pagesz - 1); brk = (char*)(MORECORE (sbrk_size)); /* Fail if sbrk failed or if a foreign sbrk call killed our space */ if (brk == (char*)(MORECORE_FAILURE) || (brk < old_end && old_top != initial_top(&main_arena))) return; sbrked_mem += sbrk_size; if (brk == old_end) { /* can just add bytes to current top */ top_size = sbrk_size + old_top_size; set_head(old_top, top_size | PREV_INUSE); old_top = 0; /* don't free below */ } else { if (sbrk_base == (char*)(-1)) /* First time through. Record base */ sbrk_base = brk; else /* Someone else called sbrk(). Count those bytes as sbrked_mem. */ sbrked_mem += brk - (char*)old_end; /* Guarantee alignment of first new chunk made from this space */ front_misalign = (unsigned long)chunk2mem(brk) & MALLOC_ALIGN_MASK; if (front_misalign > 0) { correction = (MALLOC_ALIGNMENT) - front_misalign; brk += correction; } else correction = 0; /* Guarantee the next brk will be at a page boundary */ correction += pagesz - ((unsigned long)(brk + sbrk_size) & (pagesz - 1)); /* Allocate correction */ new_brk = (char*)(MORECORE (correction)); if (new_brk == (char*)(MORECORE_FAILURE)) return; sbrked_mem += correction; top(&main_arena) = (mchunkptr)brk; top_size = new_brk - brk + correction; set_head(top(&main_arena), top_size | PREV_INUSE); if (old_top == initial_top(&main_arena)) old_top = 0; /* don't free below */ } if ((unsigned long)sbrked_mem > (unsigned long)max_sbrked_mem) max_sbrked_mem = sbrked_mem; if ((unsigned long)(mmapped_mem + sbrked_mem) > (unsigned long)max_total_mem) max_total_mem = mmapped_mem + sbrked_mem; #ifndef NO_THREADS } else { /* ar_ptr != &main_arena */ heap_info *heap; if(old_top_size < MINSIZE) /* this should never happen */ return; /* First try to extend the current heap. */ if(MINSIZE + nb <= old_top_size) return; heap = heap_for_ptr(old_top); if(grow_heap(heap, MINSIZE + nb - old_top_size) == 0) { top_size = heap->size - ((char *)old_top - (char *)heap); set_head(old_top, top_size | PREV_INUSE); return; } /* A new heap must be created. */ heap = new_heap(nb + top_pad + (MINSIZE + sizeof(*heap))); if(!heap) return; heap->ar_ptr = ar_ptr; /* Set up the new top, so we can safely use chunk_free() below. */ top(ar_ptr) = chunk_at_offset(heap, sizeof(*heap)); top_size = heap->size - sizeof(*heap); set_head(top(ar_ptr), top_size | PREV_INUSE); } #endif /* !defined(NO_THREADS) */ /* We always land on a page boundary */ assert(((unsigned long)((char*)top(ar_ptr) + top_size) & (pagesz-1)) == 0); /* Setup fencepost and free the old top chunk. */ if(old_top) { /* Keep size a multiple of MALLOC_ALIGNMENT. */ old_top_size = (old_top_size - 3*SIZE_SZ) & ~MALLOC_ALIGN_MASK; /* If possible, release the rest. */ if (old_top_size >= MINSIZE) { set_head(chunk_at_offset(old_top, old_top_size ), SIZE_SZ|PREV_INUSE); set_head(chunk_at_offset(old_top, old_top_size+SIZE_SZ), SIZE_SZ|PREV_INUSE); set_head_size(old_top, old_top_size); chunk_free(ar_ptr, old_top); } else { set_head(old_top, SIZE_SZ|PREV_INUSE); set_head(chunk_at_offset(old_top, SIZE_SZ), SIZE_SZ|PREV_INUSE); } } } /* Main public routines */ /* Malloc Algorthim: The requested size is first converted into a usable form, `nb'. This currently means to add 4 bytes overhead plus possibly more to obtain 8-byte alignment and/or to obtain a size of at least MINSIZE (currently 16 bytes), the smallest allocatable size. (All fits are considered `exact' if they are within MINSIZE bytes.) From there, the first successful of the following steps is taken: 1. The bin corresponding to the request size is scanned, and if a chunk of exactly the right size is found, it is taken. 2. The most recently remaindered chunk is used if it is big enough. This is a form of (roving) first fit, used only in the absence of exact fits. Runs of consecutive requests use the remainder of the chunk used for the previous such request whenever possible. This limited use of a first-fit style allocation strategy tends to give contiguous chunks coextensive lifetimes, which improves locality and can reduce fragmentation in the long run. 3. Other bins are scanned in increasing size order, using a chunk big enough to fulfill the request, and splitting off any remainder. This search is strictly by best-fit; i.e., the smallest (with ties going to approximately the least recently used) chunk that fits is selected. 4. If large enough, the chunk bordering the end of memory (`top') is split off. (This use of `top' is in accord with the best-fit search rule. In effect, `top' is treated as larger (and thus less well fitting) than any other available chunk since it can be extended to be as large as necessary (up to system limitations). 5. If the request size meets the mmap threshold and the system supports mmap, and there are few enough currently allocated mmapped regions, and a call to mmap succeeds, the request is allocated via direct memory mapping. 6. Otherwise, the top of memory is extended by obtaining more space from the system (normally using sbrk, but definable to anything else via the MORECORE macro). Memory is gathered from the system (in system page-sized units) in a way that allows chunks obtained across different sbrk calls to be consolidated, but does not require contiguous memory. Thus, it should be safe to intersperse mallocs with other sbrk calls. All allocations are made from the the `lowest' part of any found chunk. (The implementation invariant is that prev_inuse is always true of any allocated chunk; i.e., that each allocated chunk borders either a previously allocated and still in-use chunk, or the base of its memory arena.) */ #if __STD_C Void_t* mALLOc(size_t bytes) #else Void_t* mALLOc(bytes) size_t bytes; #endif { arena *ar_ptr; INTERNAL_SIZE_T nb = request2size(bytes); /* padded request size; */ mchunkptr victim; arena_get(ar_ptr, nb + top_pad); if(!ar_ptr) return 0; victim = chunk_alloc(ar_ptr, nb); (void)mutex_unlock(&ar_ptr->mutex); return victim ? chunk2mem(victim) : 0; } static mchunkptr #if __STD_C chunk_alloc(arena *ar_ptr, INTERNAL_SIZE_T nb) #else chunk_alloc(ar_ptr, nb) arena *ar_ptr; INTERNAL_SIZE_T nb; #endif { mchunkptr victim; /* inspected/selected chunk */ INTERNAL_SIZE_T victim_size; /* its size */ int idx; /* index for bin traversal */ mbinptr bin; /* associated bin */ mchunkptr remainder; /* remainder from a split */ long remainder_size; /* its size */ int remainder_index; /* its bin index */ unsigned long block; /* block traverser bit */ int startidx; /* first bin of a traversed block */ mchunkptr fwd; /* misc temp for linking */ mchunkptr bck; /* misc temp for linking */ mbinptr q; /* misc temp */ /* Check for exact match in a bin */ if (is_small_request(nb)) /* Faster version for small requests */ { idx = smallbin_index(nb); /* No traversal or size check necessary for small bins. */ q = bin_at(ar_ptr, idx); victim = last(q); /* Also scan the next one, since it would have a remainder < MINSIZE */ if (victim == q) { q = next_bin(q); victim = last(q); } if (victim != q) { victim_size = chunksize(victim); unlink(victim, bck, fwd); set_inuse_bit_at_offset(victim, victim_size); check_malloced_chunk(ar_ptr, victim, nb); return victim; } idx += 2; /* Set for bin scan below. We've already scanned 2 bins. */ } else { idx = bin_index(nb); bin = bin_at(ar_ptr, idx); for (victim = last(bin); victim != bin; victim = victim->bk) { victim_size = chunksize(victim); remainder_size = victim_size - nb; if (remainder_size >= (long)MINSIZE) /* too big */ { --idx; /* adjust to rescan below after checking last remainder */ break; } else if (remainder_size >= 0) /* exact fit */ { unlink(victim, bck, fwd); set_inuse_bit_at_offset(victim, victim_size); check_malloced_chunk(ar_ptr, victim, nb); return victim; } } ++idx; } /* Try to use the last split-off remainder */ if ( (victim = last_remainder(ar_ptr)->fd) != last_remainder(ar_ptr)) { victim_size = chunksize(victim); remainder_size = victim_size - nb; if (remainder_size >= (long)MINSIZE) /* re-split */ { remainder = chunk_at_offset(victim, nb); set_head(victim, nb | PREV_INUSE); link_last_remainder(ar_ptr, remainder); set_head(remainder, remainder_size | PREV_INUSE); set_foot(remainder, remainder_size); check_malloced_chunk(ar_ptr, victim, nb); return victim; } clear_last_remainder(ar_ptr); if (remainder_size >= 0) /* exhaust */ { set_inuse_bit_at_offset(victim, victim_size); check_malloced_chunk(ar_ptr, victim, nb); return victim; } /* Else place in bin */ frontlink(ar_ptr, victim, victim_size, remainder_index, bck, fwd); } /* If there are any possibly nonempty big-enough blocks, search for best fitting chunk by scanning bins in blockwidth units. */ if ( (block = idx2binblock(idx)) <= binblocks(ar_ptr)) { /* Get to the first marked block */ if ( (block & binblocks(ar_ptr)) == 0) { /* force to an even block boundary */ idx = (idx & ~(BINBLOCKWIDTH - 1)) + BINBLOCKWIDTH; block <<= 1; while ((block & binblocks(ar_ptr)) == 0) { idx += BINBLOCKWIDTH; block <<= 1; } } /* For each possibly nonempty block ... */ for (;;) { startidx = idx; /* (track incomplete blocks) */ q = bin = bin_at(ar_ptr, idx); /* For each bin in this block ... */ do { /* Find and use first big enough chunk ... */ for (victim = last(bin); victim != bin; victim = victim->bk) { victim_size = chunksize(victim); remainder_size = victim_size - nb; if (remainder_size >= (long)MINSIZE) /* split */ { remainder = chunk_at_offset(victim, nb); set_head(victim, nb | PREV_INUSE); unlink(victim, bck, fwd); link_last_remainder(ar_ptr, remainder); set_head(remainder, remainder_size | PREV_INUSE); set_foot(remainder, remainder_size); check_malloced_chunk(ar_ptr, victim, nb); return victim; } else if (remainder_size >= 0) /* take */ { set_inuse_bit_at_offset(victim, victim_size); unlink(victim, bck, fwd); check_malloced_chunk(ar_ptr, victim, nb); return victim; } } bin = next_bin(bin); } while ((++idx & (BINBLOCKWIDTH - 1)) != 0); /* Clear out the block bit. */ do /* Possibly backtrack to try to clear a partial block */ { if ((startidx & (BINBLOCKWIDTH - 1)) == 0) { binblocks(ar_ptr) &= ~block; break; } --startidx; q = prev_bin(q); } while (first(q) == q); /* Get to the next possibly nonempty block */ if ( (block <<= 1) <= binblocks(ar_ptr) && (block != 0) ) { while ((block & binblocks(ar_ptr)) == 0) { idx += BINBLOCKWIDTH; block <<= 1; } } else break; } } /* Try to use top chunk */ /* Require that there be a remainder, ensuring top always exists */ if ( (remainder_size = chunksize(top(ar_ptr)) - nb) < (long)MINSIZE) { #if HAVE_MMAP /* If big and would otherwise need to extend, try to use mmap instead */ if ((unsigned long)nb >= (unsigned long)mmap_threshold && (victim = mmap_chunk(nb)) != 0) return victim; #endif /* Try to extend */ malloc_extend_top(ar_ptr, nb); if ((remainder_size = chunksize(top(ar_ptr)) - nb) < (long)MINSIZE) return 0; /* propagate failure */ } victim = top(ar_ptr); set_head(victim, nb | PREV_INUSE); top(ar_ptr) = chunk_at_offset(victim, nb); set_head(top(ar_ptr), remainder_size | PREV_INUSE); check_malloced_chunk(ar_ptr, victim, nb); return victim; } /* free() algorithm : cases: 1. free(0) has no effect. 2. If the chunk was allocated via mmap, it is released via munmap(). 3. If a returned chunk borders the current high end of memory, it is consolidated into the top, and if the total unused topmost memory exceeds the trim threshold, malloc_trim is called. 4. Other chunks are consolidated as they arrive, and placed in corresponding bins. (This includes the case of consolidating with the current `last_remainder'). */ #if __STD_C void fREe(Void_t* mem) #else void fREe(mem) Void_t* mem; #endif { arena *ar_ptr; mchunkptr p; /* chunk corresponding to mem */ if (mem == 0) /* free(0) has no effect */ return; p = mem2chunk(mem); #if HAVE_MMAP if (chunk_is_mmapped(p)) /* release mmapped memory. */ { munmap_chunk(p); return; } #endif ar_ptr = arena_for_ptr(p); (void)mutex_lock(&ar_ptr->mutex); chunk_free(ar_ptr, p); (void)mutex_unlock(&ar_ptr->mutex); } static void #if __STD_C chunk_free(arena *ar_ptr, mchunkptr p) #else chunk_free(ar_ptr, p) arena *ar_ptr; mchunkptr p; #endif { INTERNAL_SIZE_T hd = p->size; /* its head field */ INTERNAL_SIZE_T sz; /* its size */ int idx; /* its bin index */ mchunkptr next; /* next contiguous chunk */ INTERNAL_SIZE_T nextsz; /* its size */ INTERNAL_SIZE_T prevsz; /* size of previous contiguous chunk */ mchunkptr bck; /* misc temp for linking */ mchunkptr fwd; /* misc temp for linking */ int islr; /* track whether merging with last_remainder */ check_inuse_chunk(ar_ptr, p); sz = hd & ~PREV_INUSE; next = chunk_at_offset(p, sz); nextsz = chunksize(next); if (next == top(ar_ptr)) /* merge with top */ { sz += nextsz; if (!(hd & PREV_INUSE)) /* consolidate backward */ { prevsz = p->prev_size; p = chunk_at_offset(p, -prevsz); sz += prevsz; unlink(p, bck, fwd); } set_head(p, sz | PREV_INUSE); top(ar_ptr) = p; if ((unsigned long)(sz) >= (unsigned long)trim_threshold) arena_trim(ar_ptr, top_pad); return; } set_head(next, nextsz); /* clear inuse bit */ islr = 0; if (!(hd & PREV_INUSE)) /* consolidate backward */ { prevsz = p->prev_size; p = chunk_at_offset(p, -prevsz); sz += prevsz; if (p->fd == last_remainder(ar_ptr)) /* keep as last_remainder */ islr = 1; else unlink(p, bck, fwd); } if (!(inuse_bit_at_offset(next, nextsz))) /* consolidate forward */ { sz += nextsz; if (!islr && next->fd == last_remainder(ar_ptr)) /* re-insert last_remainder */ { islr = 1; link_last_remainder(ar_ptr, p); } else unlink(next, bck, fwd); } set_head(p, sz | PREV_INUSE); set_foot(p, sz); if (!islr) frontlink(ar_ptr, p, sz, idx, bck, fwd); } /* Realloc algorithm: Chunks that were obtained via mmap cannot be extended or shrunk unless HAVE_MREMAP is defined, in which case mremap is used. Otherwise, if their reallocation is for additional space, they are copied. If for less, they are just left alone. Otherwise, if the reallocation is for additional space, and the chunk can be extended, it is, else a malloc-copy-free sequence is taken. There are several different ways that a chunk could be extended. All are tried: * Extending forward into following adjacent free chunk. * Shifting backwards, joining preceding adjacent space * Both shifting backwards and extending forward. * Extending into newly sbrked space Unless the #define REALLOC_ZERO_BYTES_FREES is set, realloc with a size argument of zero (re)allocates a minimum-sized chunk. If the reallocation is for less space, and the new request is for a `small' (<512 bytes) size, then the newly unused space is lopped off and freed. The old unix realloc convention of allowing the last-free'd chunk to be used as an argument to realloc is no longer supported. I don't know of any programs still relying on this feature, and allowing it would also allow too many other incorrect usages of realloc to be sensible. */ #if __STD_C Void_t* rEALLOc(Void_t* oldmem, size_t bytes) #else Void_t* rEALLOc(oldmem, bytes) Void_t* oldmem; size_t bytes; #endif { arena *ar_ptr; INTERNAL_SIZE_T nb; /* padded request size */ mchunkptr oldp; /* chunk corresponding to oldmem */ INTERNAL_SIZE_T oldsize; /* its size */ mchunkptr newp; /* chunk to return */ INTERNAL_SIZE_T newsize; /* its size */ Void_t* newmem; /* corresponding user mem */ mchunkptr next; /* next contiguous chunk after oldp */ INTERNAL_SIZE_T nextsize; /* its size */ mchunkptr prev; /* previous contiguous chunk before oldp */ INTERNAL_SIZE_T prevsize; /* its size */ mchunkptr remainder; /* holds split off extra space from newp */ INTERNAL_SIZE_T remainder_size; /* its size */ mchunkptr bck; /* misc temp for linking */ mchunkptr fwd; /* misc temp for linking */ #ifdef REALLOC_ZERO_BYTES_FREES if (bytes == 0) { fREe(oldmem); return 0; } #endif /* realloc of null is supposed to be same as malloc */ if (oldmem == 0) return mALLOc(bytes); newp = oldp = mem2chunk(oldmem); newsize = oldsize = chunksize(oldp); nb = request2size(bytes); #if HAVE_MMAP if (chunk_is_mmapped(oldp)) { #if HAVE_MREMAP newp = mremap_chunk(oldp, nb); if(newp) return chunk2mem(newp); #endif /* Note the extra SIZE_SZ overhead. */ if(oldsize - SIZE_SZ >= nb) return oldmem; /* do nothing */ /* Must alloc, copy, free. */ newmem = mALLOc(bytes); if (newmem == 0) return 0; /* propagate failure */ MALLOC_COPY(newmem, oldmem, oldsize - 2*SIZE_SZ); munmap_chunk(oldp); return newmem; } #endif ar_ptr = arena_for_ptr(oldp); (void)mutex_lock(&ar_ptr->mutex); /* As in malloc(), remember this arena for the next allocation. */ tsd_setspecific(arena_key, (Void_t *)ar_ptr); check_inuse_chunk(ar_ptr, oldp); if ((long)(oldsize) < (long)(nb)) { /* Try expanding forward */ next = chunk_at_offset(oldp, oldsize); if (next == top(ar_ptr) || !inuse(next)) { nextsize = chunksize(next); /* Forward into top only if a remainder */ if (next == top(ar_ptr)) { if ((long)(nextsize + newsize) >= (long)(nb + MINSIZE)) { newsize += nextsize; top(ar_ptr) = chunk_at_offset(oldp, nb); set_head(top(ar_ptr), (newsize - nb) | PREV_INUSE); set_head_size(oldp, nb); (void)mutex_unlock(&ar_ptr->mutex); return chunk2mem(oldp); } } /* Forward into next chunk */ else if (((long)(nextsize + newsize) >= (long)(nb))) { unlink(next, bck, fwd); newsize += nextsize; goto split; } } else { next = 0; nextsize = 0; } /* Try shifting backwards. */ if (!prev_inuse(oldp)) { prev = prev_chunk(oldp); prevsize = chunksize(prev); /* try forward + backward first to save a later consolidation */ if (next != 0) { /* into top */ if (next == top(ar_ptr)) { if ((long)(nextsize + prevsize + newsize) >= (long)(nb + MINSIZE)) { unlink(prev, bck, fwd); newp = prev; newsize += prevsize + nextsize; newmem = chunk2mem(newp); MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ); top(ar_ptr) = chunk_at_offset(newp, nb); set_head(top(ar_ptr), (newsize - nb) | PREV_INUSE); set_head_size(newp, nb); (void)mutex_unlock(&ar_ptr->mutex); return newmem; } } /* into next chunk */ else if (((long)(nextsize + prevsize + newsize) >= (long)(nb))) { unlink(next, bck, fwd); unlink(prev, bck, fwd); newp = prev; newsize += nextsize + prevsize; newmem = chunk2mem(newp); MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ); goto split; } } /* backward only */ if (prev != 0 && (long)(prevsize + newsize) >= (long)nb) { unlink(prev, bck, fwd); newp = prev; newsize += prevsize; newmem = chunk2mem(newp); MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ); goto split; } } /* Must allocate */ newp = chunk_alloc (ar_ptr, nb); if (newp == 0) /* propagate failure */ return 0; /* Avoid copy if newp is next chunk after oldp. */ /* (This can only happen when new chunk is sbrk'ed.) */ if ( newp == next_chunk(oldp)) { newsize += chunksize(newp); newp = oldp; goto split; } /* Otherwise copy, free, and exit */ newmem = chunk2mem(newp); MALLOC_COPY(newmem, oldmem, oldsize - SIZE_SZ); chunk_free(ar_ptr, oldp); (void)mutex_unlock(&ar_ptr->mutex); return newmem; } split: /* split off extra room in old or expanded chunk */ if (newsize - nb >= MINSIZE) /* split off remainder */ { remainder = chunk_at_offset(newp, nb); remainder_size = newsize - nb; set_head_size(newp, nb); set_head(remainder, remainder_size | PREV_INUSE); set_inuse_bit_at_offset(remainder, remainder_size); chunk_free(ar_ptr, remainder); } else { set_head_size(newp, newsize); set_inuse_bit_at_offset(newp, newsize); } check_inuse_chunk(ar_ptr, newp); (void)mutex_unlock(&ar_ptr->mutex); return chunk2mem(newp); } /* memalign algorithm: memalign requests more than enough space from malloc, finds a spot within that chunk that meets the alignment request, and then possibly frees the leading and trailing space. The alignment argument must be a power of two. This property is not checked by memalign, so misuse may result in random runtime errors. 8-byte alignment is guaranteed by normal malloc calls, so don't bother calling memalign with an argument of 8 or less. Overreliance on memalign is a sure way to fragment space. */ #if __STD_C Void_t* mEMALIGn(size_t alignment, size_t bytes) #else Void_t* mEMALIGn(alignment, bytes) size_t alignment; size_t bytes; #endif { arena *ar_ptr; INTERNAL_SIZE_T nb; /* padded request size */ char* m; /* memory returned by malloc call */ mchunkptr p; /* corresponding chunk */ char* brk; /* alignment point within p */ mchunkptr newp; /* chunk to return */ INTERNAL_SIZE_T newsize; /* its size */ INTERNAL_SIZE_T leadsize; /* leading space befor alignment point */ mchunkptr remainder; /* spare room at end to split off */ long remainder_size; /* its size */ /* If need less alignment than we give anyway, just relay to malloc */ if (alignment <= MALLOC_ALIGNMENT) return mALLOc(bytes); /* Otherwise, ensure that it is at least a minimum chunk size */ if (alignment < MINSIZE) alignment = MINSIZE; /* Call malloc with worst case padding to hit alignment. */ nb = request2size(bytes); arena_get(ar_ptr, nb + alignment + MINSIZE); if(!ar_ptr) return 0; p = chunk_alloc(ar_ptr, nb + alignment + MINSIZE); if (p == 0) { (void)mutex_unlock(&ar_ptr->mutex); return 0; /* propagate failure */ } m = chunk2mem(p); if ((((unsigned long)(m)) % alignment) == 0) /* aligned */ { #if HAVE_MMAP if(chunk_is_mmapped(p)) { (void)mutex_unlock(&ar_ptr->mutex); return chunk2mem(p); /* nothing more to do */ } #endif } else /* misaligned */ { /* Find an aligned spot inside chunk. Since we need to give back leading space in a chunk of at least MINSIZE, if the first calculation places us at a spot with less than MINSIZE leader, we can move to the next aligned spot -- we've allocated enough total room so that this is always possible. */ brk = (char*)mem2chunk(((unsigned long)(m + alignment - 1)) & -alignment); if ((long)(brk - (char*)(p)) < (long) MINSIZE) brk = brk + alignment; newp = (mchunkptr)brk; leadsize = brk - (char*)(p); newsize = chunksize(p) - leadsize; #if HAVE_MMAP if(chunk_is_mmapped(p)) { newp->prev_size = p->prev_size + leadsize; set_head(newp, newsize|IS_MMAPPED); (void)mutex_unlock(&ar_ptr->mutex); return chunk2mem(newp); } #endif /* give back leader, use the rest */ set_head(newp, newsize | PREV_INUSE); set_inuse_bit_at_offset(newp, newsize); set_head_size(p, leadsize); chunk_free(ar_ptr, p); p = newp; assert (newsize>=nb && (((unsigned long)(chunk2mem(p))) % alignment) == 0); } /* Also give back spare room at the end */ remainder_size = chunksize(p) - nb; if (remainder_size >= (long)MINSIZE) { remainder = chunk_at_offset(p, nb); set_head(remainder, remainder_size | PREV_INUSE); set_head_size(p, nb); chunk_free(ar_ptr, remainder); } check_inuse_chunk(ar_ptr, p); (void)mutex_unlock(&ar_ptr->mutex); return chunk2mem(p); } /* valloc just invokes memalign with alignment argument equal to the page size of the system (or as near to this as can be figured out from all the includes/defines above.) */ #if __STD_C Void_t* vALLOc(size_t bytes) #else Void_t* vALLOc(bytes) size_t bytes; #endif { return mEMALIGn (malloc_getpagesize, bytes); } /* pvalloc just invokes valloc for the nearest pagesize that will accommodate request */ #if __STD_C Void_t* pvALLOc(size_t bytes) #else Void_t* pvALLOc(bytes) size_t bytes; #endif { size_t pagesize = malloc_getpagesize; return mEMALIGn (pagesize, (bytes + pagesize - 1) & ~(pagesize - 1)); } /* calloc calls malloc, then zeroes out the allocated chunk. */ #if __STD_C Void_t* cALLOc(size_t n, size_t elem_size) #else Void_t* cALLOc(n, elem_size) size_t n; size_t elem_size; #endif { arena *ar_ptr; mchunkptr p, oldtop; INTERNAL_SIZE_T csz, oldtopsize; Void_t* mem; INTERNAL_SIZE_T sz = request2size(n * elem_size); arena_get(ar_ptr, sz); if(!ar_ptr) return 0; /* check if expand_top called, in which case don't need to clear */ #if MORECORE_CLEARS oldtop = top(ar_ptr); oldtopsize = chunksize(top(ar_ptr)); #endif p = chunk_alloc (ar_ptr, sz); /* Only clearing follows, so we can unlock early. */ (void)mutex_unlock(&ar_ptr->mutex); if (p == 0) return 0; else { mem = chunk2mem(p); /* Two optional cases in which clearing not necessary */ #if HAVE_MMAP if (chunk_is_mmapped(p)) return mem; #endif csz = chunksize(p); #if MORECORE_CLEARS if (p == oldtop && csz > oldtopsize) { /* clear only the bytes from non-freshly-sbrked memory */ csz = oldtopsize; } #endif MALLOC_ZERO(mem, csz - SIZE_SZ); return mem; } } /* cfree just calls free. It is needed/defined on some systems that pair it with calloc, presumably for odd historical reasons. */ #if !defined(_LIBC) #if __STD_C void cfree(Void_t *mem) #else void cfree(mem) Void_t *mem; #endif { free(mem); } #endif /* Malloc_trim gives memory back to the system (via negative arguments to sbrk) if there is unused memory at the `high' end of the malloc pool. You can call this after freeing large blocks of memory to potentially reduce the system-level memory requirements of a program. However, it cannot guarantee to reduce memory. Under some allocation patterns, some large free blocks of memory will be locked between two used chunks, so they cannot be given back to the system. The `pad' argument to malloc_trim represents the amount of free trailing space to leave untrimmed. If this argument is zero, only the minimum amount of memory to maintain internal data structures will be left (one page or less). Non-zero arguments can be supplied to maintain enough trailing space to service future expected allocations without having to re-obtain memory from the system. Malloc_trim returns 1 if it actually released any memory, else 0. */ #if __STD_C int malloc_trim(size_t pad) #else int malloc_trim(pad) size_t pad; #endif { int res; (void)mutex_lock(&main_arena.mutex); res = arena_trim(&main_arena, pad); (void)mutex_unlock(&main_arena.mutex); return res; } static int #if __STD_C arena_trim(arena *ar_ptr, size_t pad) #else arena_trim(ar_ptr, pad) arena *ar_ptr; size_t pad; #endif { mchunkptr top_chunk; /* The current top chunk */ long top_size; /* Amount of top-most memory */ long extra; /* Amount to release */ char* current_brk; /* address returned by pre-check sbrk call */ char* new_brk; /* address returned by negative sbrk call */ unsigned long pagesz = malloc_getpagesize; top_chunk = top(ar_ptr); top_size = chunksize(top_chunk); extra = ((top_size - pad - MINSIZE + (pagesz-1)) / pagesz - 1) * pagesz; if (extra < (long)pagesz) /* Not enough memory to release */ return 0; #ifndef NO_THREADS if(ar_ptr == &main_arena) { #endif /* Test to make sure no one else called sbrk */ current_brk = (char*)(MORECORE (0)); if (current_brk != (char*)(top_chunk) + top_size) return 0; /* Apparently we don't own memory; must fail */ new_brk = (char*)(MORECORE (-extra)); if (new_brk == (char*)(MORECORE_FAILURE)) { /* sbrk failed? */ /* Try to figure out what we have */ current_brk = (char*)(MORECORE (0)); top_size = current_brk - (char*)top_chunk; if (top_size >= (long)MINSIZE) /* if not, we are very very dead! */ { sbrked_mem = current_brk - sbrk_base; set_head(top_chunk, top_size | PREV_INUSE); } check_chunk(ar_ptr, top_chunk); return 0; } sbrked_mem -= extra; #ifndef NO_THREADS } else { if(grow_heap(heap_for_ptr(top_chunk), -extra) != 0) return 0; } #endif /* Success. Adjust top accordingly. */ set_head(top_chunk, (top_size - extra) | PREV_INUSE); check_chunk(ar_ptr, top_chunk); return 1; } /* malloc_usable_size: This routine tells you how many bytes you can actually use in an allocated chunk, which may be more than you requested (although often not). You can use this many bytes without worrying about overwriting other allocated objects. Not a particularly great programming practice, but still sometimes useful. */ #if __STD_C size_t malloc_usable_size(Void_t* mem) #else size_t malloc_usable_size(mem) Void_t* mem; #endif { mchunkptr p; if (mem == 0) return 0; else { p = mem2chunk(mem); if(!chunk_is_mmapped(p)) { if (!inuse(p)) return 0; check_inuse_chunk(arena_for_ptr(mem), p); return chunksize(p) - SIZE_SZ; } return chunksize(p) - 2*SIZE_SZ; } } /* Utility to update current_mallinfo for malloc_stats and mallinfo() */ static void malloc_update_mallinfo __MALLOC_P ((void)) { arena *ar_ptr = &main_arena; int i, navail; mbinptr b; mchunkptr p; #if MALLOC_DEBUG mchunkptr q; #endif INTERNAL_SIZE_T avail; (void)mutex_lock(&ar_ptr->mutex); avail = chunksize(top(ar_ptr)); navail = ((long)(avail) >= (long)MINSIZE)? 1 : 0; for (i = 1; i < NAV; ++i) { b = bin_at(ar_ptr, i); for (p = last(b); p != b; p = p->bk) { #if MALLOC_DEBUG check_free_chunk(ar_ptr, p); for (q = next_chunk(p); q < top(ar_ptr) && inuse(q) && (long)chunksize(q) >= (long)MINSIZE; q = next_chunk(q)) check_inuse_chunk(ar_ptr, q); #endif avail += chunksize(p); navail++; } } current_mallinfo.ordblks = navail; current_mallinfo.uordblks = sbrked_mem - avail; current_mallinfo.fordblks = avail; current_mallinfo.hblks = n_mmaps; current_mallinfo.hblkhd = mmapped_mem; current_mallinfo.keepcost = chunksize(top(ar_ptr)); (void)mutex_unlock(&ar_ptr->mutex); } /* malloc_stats: Prints on stderr the amount of space obtain 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), the maximum number of simultaneous mmap regions used, 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.) */ void malloc_stats() { malloc_update_mallinfo(); fprintf(stderr, "max system bytes = %10u\n", (unsigned int)(max_total_mem)); fprintf(stderr, "system bytes = %10u\n", (unsigned int)(sbrked_mem + mmapped_mem)); fprintf(stderr, "in use bytes = %10u\n", (unsigned int)(current_mallinfo.uordblks + mmapped_mem)); #if HAVE_MMAP fprintf(stderr, "max mmap regions = %10u\n", (unsigned int)max_n_mmaps); #endif #if THREAD_STATS fprintf(stderr, "arenas created = %10d\n", stat_n_arenas); fprintf(stderr, "heaps created = %10d\n", stat_n_heaps); fprintf(stderr, "locked directly = %10ld\n", stat_lock_direct); fprintf(stderr, "locked in loop = %10ld\n", stat_lock_loop); #endif } /* mallinfo returns a copy of updated current mallinfo. */ struct mallinfo mALLINFo() { malloc_update_mallinfo(); return current_mallinfo; } /* mallopt: mallopt is the general SVID/XPG interface to tunable parameters. The format is to provide a (parameter-number, parameter-value) pair. mallopt then sets the corresponding parameter to the argument value if it can (i.e., so long as the value is meaningful), and returns 1 if successful else 0. See descriptions of tunable parameters above. */ #if __STD_C int mALLOPt(int param_number, int value) #else int mALLOPt(param_number, value) int param_number; int value; #endif { switch(param_number) { case M_TRIM_THRESHOLD: trim_threshold = value; return 1; case M_TOP_PAD: top_pad = value; return 1; case M_MMAP_THRESHOLD: #ifndef NO_THREADS /* Forbid setting the threshold too high. */ if((unsigned long)value > HEAP_MAX_SIZE/2) return 0; #endif mmap_threshold = value; return 1; case M_MMAP_MAX: #if HAVE_MMAP n_mmaps_max = value; return 1; #else if (value != 0) return 0; else n_mmaps_max = value; return 1; #endif default: return 0; } } #if 0 && defined(_LIBC) weak_alias (__libc_calloc, calloc) weak_alias (__libc_free, cfree) weak_alias (__libc_free, free) weak_alias (__libc_malloc, malloc) weak_alias (__libc_memalign, memalign) weak_alias (__libc_realloc, realloc) weak_alias (__libc_valloc, valloc) weak_alias (__libc_pvalloc, pvalloc) weak_alias (__libc_mallinfo, mallinfo) weak_alias (__libc_mallopt, mallopt) #endif /* History: V2.6.4-pt Wed Dec 4 1996 Wolfram Gloger (wmglo@dent.med.uni-muenchen.de) * Very minor updates from the released 2.6.4 version. * Trimmed include file down to exported data structures. * Changes from H.J. Lu for glibc-2.0. V2.6.3i-pt Sep 16 1996 Wolfram Gloger (wmglo@dent.med.uni-muenchen.de) * Many changes for multiple threads * Introduced arenas and heaps 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.) */