malloc(3C)																malloc(3C)

NAME

       malloc, calloc, free, memalign, realloc, valloc, alloca - memory allocator

SYNOPSIS

       #include <stdlib.h>

       void *malloc(size_t size);

       void *calloc(size_t nelem, size_t elsize);

       void free(void *ptr);

       void *memalign(size_t alignment, size_t size);

       void *realloc(void *ptr, size_t size);

       void *valloc(size_t size);

       #include <alloca.h>

       void *alloca(size_t size);

       The malloc() and free() functions provide a simple, general-purpose memory allocation package. The malloc() function returns a pointer to a
       block of at least size bytes suitably aligned for any use. If the space assigned by malloc() is overrun, the results are undefined.

       The argument to free() is a pointer to a block previously allocated by malloc(), calloc(), or realloc(). After  free()  is  executed,  this
       space is made available for further allocation by the application, though not returned to the system. Memory is returned to the system only
       upon termination of the application. If	ptr is a null pointer, no action occurs. If a random number is passed to free(), the  results  are
       undefined.

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

       The  memalign()	function allocates size bytes on a specified alignment boundary and returns a pointer to the allocated block. The value of
       the returned address is guaranteed to be an even multiple of alignment. The value of alignment must be a power of two and must  be  greater
       than or equal to the size of a word.

       The  realloc()  function changes the size of the block pointed to by ptr to size bytes and returns a pointer to the (possibly moved) block.
       The contents will be unchanged up to the lesser of the new and old sizes. If the new size of the block requires movement of the block,  the
       space  for  the previous instantiation of the block is freed. If the new size is larger, the contents of the newly allocated portion of the
       block are unspecified. If ptr is NULL, realloc() behaves like malloc() for the specified size. If size is 0 and ptr is not a null  pointer,
       the space pointed to is freed.

       The valloc() function has the same effect as malloc(), except that the allocated memory will be aligned to a multiple of the value returned
       by sysconf(_SC_PAGESIZE).

       The alloca() function allocates size bytes of space in the stack frame of the caller, and returns a pointer to the  allocated  block.  This
       temporary  space  is  automatically  freed when the caller returns. If the allocated block is beyond the current stack limit, the resulting
       behavior is undefined.

       Upon successful completion, each of the allocation functions returns a pointer to space suitably aligned (after possible pointer  coercion)
       for storage of any type of object.

       If  there  is  no available memory, malloc(), realloc(), memalign(), valloc(), and calloc() return a null pointer. When realloc() is called
       with size > 0 and returns NULL, the block pointed to by ptr is left intact. If size, nelem, or elsize is 0, either  a  null  pointer  or  a
       unique pointer that can be passed to free() is returned.

       If  malloc(),  calloc(),  or  realloc()	returns  unsuccessfully, errno will be set to indicate the error. The free() function does not set
       errno.

       The malloc(), calloc(), and realloc() functions will fail if:

       ENOMEM	       The physical limits of the system are exceeded by size bytes of memory which cannot be allocated.

       EAGAIN	       There is not enough memory available to allocate size bytes of memory; but the application could try again later.

USAGE

       Portable applications should avoid using valloc() but should instead use malloc() or mmap(2). On systems with a large page size, the number
       of successful valloc() operations might be 0.

       These default memory allocation routines are safe for use in multithreaded applications but are not scalable. Concurrent accesses by multi-
       ple threads are single-threaded through the use of a single lock. Multithreaded applications that make heavy use of dynamic memory  alloca-
       tion  should  be  linked with allocation libraries designed for concurrent access, such as libumem(3LIB) or libmtmalloc(3LIB). Applications
       that want to avoid using heap allocations (with brk(2)) can do so by using either libumem or libmapmalloc(3LIB). The  allocation  libraries
       libmalloc(3LIB) and libbsdmalloc(3LIB) are available for special needs.

       Comparative features of the various allocation libraries can be found in the umem_alloc(3MALLOC) manual page.

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |See below.		   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Safe			   |
       +-----------------------------+-----------------------------+

       The malloc(), calloc(), free(), realloc(), valloc() functions are Standard. The memalign() and alloca() functions are Stable.

       brk(2),	getrlimit(2),  libbsdmalloc(3LIB),  libmalloc(3LIB),  libmapmalloc(3LIB),  libmtmalloc(3LIB),  libumem(3LIB), umem_alloc(3MALLOC),
       watchmalloc(3MALLOC), attributes(5)

WARNINGS

       Undefined results will occur if the size requested for a block of memory exceeds the maximum  size  of  a  process's  heap,  which  can	be
       obtained with getrlimit(2)

       The alloca() function is machine-, compiler-, and most of all, system-dependent. Its use is strongly discouraged.

								    21 Mar 2005 							malloc(3C)