diff options
Diffstat (limited to 'include/malloc.h')
| -rw-r--r-- | include/malloc.h | 949 |
1 files changed, 949 insertions, 0 deletions
diff --git a/include/malloc.h b/include/malloc.h new file mode 100644 index 000000000..08469bc1b --- /dev/null +++ b/include/malloc.h @@ -0,0 +1,949 @@ +/* + A version of malloc/free/realloc written by Doug Lea and released to the + public domain. Send questions/comments/complaints/performance data + to dl@cs.oswego.edu + +* VERSION 2.6.6 Sun Mar 5 19:10:03 2000 Doug Lea (dl at gee) + + Note: There may be an updated version of this malloc obtainable at + ftp://g.oswego.edu/pub/misc/malloc.c + Check before installing! + +* Why use this malloc? + + This is not the fastest, most space-conserving, most portable, or + most tunable malloc ever written. However it is among the fastest + while also being among the most space-conserving, portable and tunable. + Consistent balance across these factors results in a good general-purpose + allocator. For a high-level description, see + http://g.oswego.edu/dl/html/malloc.html + +* Synopsis of public routines + + (Much fuller descriptions are contained in the program documentation below.) + + 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 when the request + size is treaded as a long will return null. + + Maximum overhead wastage per allocated chunk: normally 15 bytes + + Alignnment demands, plus the minimum allocatable size restriction + make the normal worst-case wastage 15 bytes (i.e., up to 15 + more bytes will be allocated than were requested in malloc), with + 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. It is also reported to work on WIN32 platforms. + People have also reported adapting this malloc for use in + stand-alone embedded systems. + + The implementation is in straight, hand-tuned ANSI C. Among other + consequences, it uses a lot of macros. Because of this, to be at + all usable, this code should be compiled using an optimizing compiler + (for example gcc -O2) that can simplify expressions and control + paths. + + __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. + 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. + INTERNAL_LINUX_C_LIB (default: NOT defined) + Defined only when compiled as part of Linux libc. + 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. + WIN32 (default: undefined) + Define this on MS win (95, nt) platforms to compile in sbrk emulation. + LACKS_UNISTD_H (default: undefined if not WIN32) + Define this if your system does not have a <unistd.h>. + LACKS_SYS_PARAM_H (default: undefined if not WIN32) + Define this if your system does not have a <sys/param.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. + USE_DL_PREFIX (default: undefined) + Prefix all public routines with the string 'dl'. Useful to + quickly avoid procedure declaration conflicts and linker symbol + conflicts with existing memory allocation routines. + + +*/ + + + + +/* Preliminaries */ + +#ifndef __STD_C +#ifdef __STDC__ +#define __STD_C 1 +#else +#if __cplusplus +#define __STD_C 1 +#else +#define __STD_C 0 +#endif /*__cplusplus*/ +#endif /*__STDC__*/ +#endif /*__STD_C*/ + +#ifndef Void_t +#if (__STD_C || defined(WIN32)) +#define Void_t void +#else +#define Void_t char +#endif +#endif /*Void_t*/ + +#if __STD_C +#include <linux/stddef.h> /* for size_t */ +#else +#include <sys/types.h> +#endif /* __STD_C */ + +#ifdef __cplusplus +extern "C" { +#endif + +#if 0 /* not for U-Boot */ +#include <stdio.h> /* needed for malloc_stats */ +#endif + + +/* + 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 -DDEBUG, a number of assertion checks are + enabled that will catch more memory errors. You probably won't be + able to make much sense of the actual assertion errors, but they + should help you locate incorrectly overwritten memory. The + checking is fairly extensive, and will slow down execution + noticeably. Calling malloc_stats or mallinfo with DEBUG set will + attempt to check every non-mmapped allocated and free chunk in the + course of computing the summmaries. (By nature, mmapped regions + cannot be checked very much automatically.) + + Setting DEBUG may also be helpful if you are trying to modify + this code. The assertions in the check routines spell out in more + detail the assumptions and invariants underlying the algorithms. + +*/ + +#ifdef DEBUG +/* #include <assert.h> */ +#define assert(x) ((void)0) +#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 */ + + +/* + WIN32 causes an emulation of sbrk to be compiled in + mmap-based options are not currently supported in WIN32. +*/ + +/* #define WIN32 */ +#ifdef WIN32 +#define MORECORE wsbrk +#define HAVE_MMAP 0 + +#define LACKS_UNISTD_H +#define LACKS_SYS_PARAM_H + +/* + Include 'windows.h' to get the necessary declarations for the + Microsoft Visual C++ data structures and routines used in the 'sbrk' + emulation. + + Define WIN32_LEAN_AND_MEAN so that only the essential Microsoft + Visual C++ header files are included. +*/ +#define WIN32_LEAN_AND_MEAN +#include <windows.h> +#endif + + +/* + HAVE_MEMCPY should be defined if you are not otherwise using + ANSI STD C, but still have memcpy and memset in your C library + and want to use them in calloc and realloc. Otherwise simple + macro versions are defined 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 +#ifdef WIN32 +// On Win32 platforms, 'memset()' and 'memcpy()' are already declared in +// 'windows.h' +#else +Void_t* memset(); +Void_t* memcpy(); +#endif +#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 +***/ +#undef HAVE_MMAP /* Not available for U-Boot */ + +/* + Define HAVE_MREMAP to make realloc() use mremap() to re-allocate + large blocks. This is currently only possible on Linux with + kernel versions newer than 1.3.77. +*/ + +/*** +#ifndef HAVE_MREMAP +#ifdef INTERNAL_LINUX_C_LIB +#define HAVE_MREMAP 1 +#else +#define HAVE_MREMAP 0 +#endif +#endif +***/ +#undef HAVE_MREMAP /* Not available for U-Boot */ + +#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 +*/ + +#define LACKS_UNISTD_H /* Shortcut for U-Boot */ +#define malloc_getpagesize 4096 + +#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 +# ifdef WIN32 +# define malloc_getpagesize (4096) /* TBD: Use 'GetSystemInfo' instead */ +# else +# ifndef LACKS_SYS_PARAM_H +# include <sys/param.h> +# endif +# ifdef EXEC_PAGESIZE +# define malloc_getpagesize EXEC_PAGESIZE +# else +# ifdef NBPG +# ifndef CLSIZE +# define malloc_getpagesize NBPG +# else +# define malloc_getpagesize (NBPG * CLSIZE) +# endif +# else +# ifdef NBPC +# define malloc_getpagesize NBPC +# else +# ifdef PAGESIZE +# define malloc_getpagesize PAGESIZE +# else +# define malloc_getpagesize (4096) /* just guess */ +# endif +# 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 + +/* SVID2/XPG mallinfo structure */ + +struct mallinfo { + int arena; /* total space allocated from system */ + int ordblks; /* number of non-inuse chunks */ + int smblks; /* unused -- always zero */ + int hblks; /* number of mmapped regions */ + int hblkhd; /* total space in mmapped regions */ + int usmblks; /* unused -- always zero */ + int fsmblks; /* unused -- always zero */ + int uordblks; /* total allocated space */ + int fordblks; /* total non-inuse space */ + int keepcost; /* top-most, releasable (via malloc_trim) space */ +}; + +/* SVID2/XPG mallopt options */ + +#define M_MXFAST 1 /* UNUSED in this malloc */ +#define M_NLBLKS 2 /* UNUSED in this malloc */ +#define M_GRAIN 3 /* UNUSED in this malloc */ +#define M_KEEP 4 /* UNUSED in this malloc */ + +#endif + +/* mallopt options that actually do something */ + +#define M_TRIM_THRESHOLD -1 +#define M_TOP_PAD -2 +#define M_MMAP_THRESHOLD -3 +#define M_MMAP_MAX -4 + + + +#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 (64) +#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. +*/ + + + + +/* + USE_DL_PREFIX will prefix all public routines with the string 'dl'. + Useful to quickly avoid procedure declaration conflicts and linker + symbol conflicts with existing memory allocation routines. + +*/ + +/* #define USE_DL_PREFIX */ + + + + +/* + + Special defines for linux libc + + Except when compiled using these special defines for Linux libc + using weak aliases, this malloc is NOT designed to work in + multithreaded applications. No semaphores or other concurrency + control are provided to ensure that multiple malloc or free calls + don't run at the same time, which could be disasterous. A single + semaphore could be used across malloc, realloc, and free (which is + essentially the effect of the linux weak alias approach). It would + be hard to obtain finer granularity. + +*/ + + +#ifdef INTERNAL_LINUX_C_LIB + +#if __STD_C + +Void_t * __default_morecore_init (ptrdiff_t); +Void_t *(*__morecore)(ptrdiff_t) = __default_morecore_init; + +#else + +Void_t * __default_morecore_init (); +Void_t *(*__morecore)() = __default_morecore_init; + +#endif + +#define MORECORE (*__morecore) +#define MORECORE_FAILURE 0 +#define MORECORE_CLEARS 1 + +#else /* INTERNAL_LINUX_C_LIB */ + +#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 /* INTERNAL_LINUX_C_LIB */ + +#if defined(INTERNAL_LINUX_C_LIB) && defined(__ELF__) + +#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 + +#ifdef USE_DL_PREFIX +#define cALLOc dlcalloc +#define fREe dlfree +#define mALLOc dlmalloc +#define mEMALIGn dlmemalign +#define rEALLOc dlrealloc +#define vALLOc dlvalloc +#define pvALLOc dlpvalloc +#define mALLINFo dlmallinfo +#define mALLOPt dlmallopt +#else /* USE_DL_PREFIX */ +#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 /* USE_DL_PREFIX */ + +#endif + +/* Public routines */ + +#if __STD_C + +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 +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 |