malloc(3X)       MISCELLANEOUS LIBRARY FUNCTIONS       malloc(3X)



NAME
     malloc, free, realloc, calloc, mallopt,  mallinfo  -  memory
     allocator

SYNOPSIS
     cc [flag ...] file ...  -lmalloc [library ...]

     #include <stdlib.h>
     void *malloc (size_t size)

     void free (void *ptr)

     void *realloc (void *ptr, size_t size)

     void *calloc (size_t nelem, size_t elsize)

     #include <malloc.h>
     int mallopt (int cmd, int value)

     struct mallinfo mallinfo (void)

DESCRIPTION
     malloc and free  provide  a  simple  general-purpose  memory
     allocation package.

     malloc returns a pointer to a block of at least  size  bytes
     suitably aligned for any use.

     The argument to free is a  pointer  to  a  block  previously
     allocated  by  malloc; after free is performed this space is
     made available for further allocation, and its contents have
     been  destroyed  (but  see mallopt below for a way to change
     this behavior).  If ptr is a null pointer, no action occurs.

     Undefined results occur if the space assigned by  malloc  is
     overrun or if some random number is handed to free.

     realloc changes the size of the block pointed to by  ptr  to
     size  bytes  and  returns  a pointer to the (possibly moved)
     block.  The contents are unchanged up to the lesser  of  the
     new  and  old  sizes.   If  ptr  is  a null pointer, realloc
     behaves like malloc for the specified size. If size is  zero
     and  ptr  is  not a null pointer, the object it points to is
     freed.

     calloc allocates space for an array  of  nelem  elements  of
     size elsize.  The space is initialized to zeros.

     mallopt provides for control over the allocation  algorithm.
     The available values for cmd are:

     M_MXFAST



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malloc(3X)       MISCELLANEOUS LIBRARY FUNCTIONS       malloc(3X)



            Set maxfast to value.  The  algorithm  allocates  all
            blocks  below the size of maxfast in large groups and
            then doles them out very quickly.  The default  value
            for maxfast is 24.

     M_NLBLKS
            Set numlblks to value.  The above  mentioned  ``large
            groups''  each contain numlblks blocks. numlblks must
            be greater than 0.  The default value for numlblks is
            100.

     M_GRAINSet grain to value.  The sizes of all blocks  smaller
            than  maxfast  are considered to be rounded up to the
            nearest multiple of grain.   grain  must  be  greater
            than  0.   The default value of grain is the smallest
            number of bytes that will allow alignment of any data
            type.   Value will be rounded up to a multiple of the
            default when grain is set.

     M_KEEP Preserve data in a freed block until the next malloc,
            realloc, or calloc.  This option is provided only for
            compatibility with the old version of malloc  and  is
            not recommended.

     These values are defined in the malloc.h header file.

     mallopt may be called repeatedly,  but  may  not  be  called
     after the first small block is allocated.

     mallinfo provides instrumentation  describing  space  usage.
     It returns the structure:

          struct mallinfo  {
               int arena;      /* total space in arena */
               int ordblks;    /* number of ordinary blocks */
               int smblks;     /* number of small blocks */
               int hblkhd;     /* space in holding block headers */
               int hblks;      /* number of holding blocks */
               int usmblks;    /* space in small blocks in use */
               int fsmblks;    /* space in free small blocks */
               int uordblks;   /* space in ordinary blocks in use */
               int fordblks;   /* space in free ordinary blocks */
               int keepcost;   /* space penalty if keep option */
                               /* is used */
          }

     This structure is defined in the malloc.h header file.

     Each of the allocation routines returns a pointer  to  space
     suitably  aligned  (after  possible  pointer  coercion)  for
     storage of any type of object.




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malloc(3X)       MISCELLANEOUS LIBRARY FUNCTIONS       malloc(3X)



SEE ALSO
     brk(2), malloc(3C).

DIAGNOSTICS
     malloc, realloc, and calloc return a NULL pointer  if  there
     is  not enough available memory.  When realloc returns NULL,
     the block pointed to by ptr is left intact.  If  mallopt  is
     called  after any allocation or if cmd or value are invalid,
     non-zero is returned.  Otherwise, it returns zero.

NOTES
     Note that unlike malloc(3C), this package does not  preserve
     the  contents of a block when it is freed, unless the M_KEEP
     option  of  mallopt  is  used.   Undocumented  features   of
     malloc(3C)  have  not  been duplicated.  Function prototypes
     for malloc, realloc, calloc and free are also defined in the
     <malloc.h>  header  file for compatibility with old applica-
     tions. New applications should include <stdlib.h> to  access
     the prototypes for these functions.




































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