path: root/include/malloc.h

/*
  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.


*/

#ifndef __MALLOC_H
#define __MALLOC_H

#include <types.h>

/* 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*/

#if __STD_C
#include <linux/stddef.h>	/* for size_t */
#else
#include <sys/types.h>
#endif	/* __STD_C */

#ifdef __cplusplus
extern "C" {
#endif



/*
  Compile-time options
*/



#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* mALLOc(size_t);
void    fREe(void*);
void* rEALLOc(void*, size_t);
void* mEMALIGn(size_t, size_t);
void* vALLOc(size_t);
void* pvALLOc(size_t);
void* cALLOc(size_t, size_t);
void    cfree(void*);
int     malloc_trim(size_t);
size_t  malloc_usable_size(void*);
void    malloc_stats(void);
int     mALLOPt(int, int);
struct mallinfo mALLINFo(void);
#else
void* mALLOc();
void    fREe();
void* rEALLOc();
void* mEMALIGn();
void* vALLOc();
void* pvALLOc();
void* 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

#endif