malloc(3X)           UNIX System V(Specialized Libraries)            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:





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malloc(3X)           UNIX System V(Specialized Libraries)            malloc(3X)


     M_MXFAST
             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_GRAIN
             Set 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)           UNIX System V(Specialized Libraries)            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 applications.
      New applications should include <stdlib.h> to access the prototypes for
      these functions.



































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