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malloc(3C)		 Standard C Library Functions		    malloc(3C)

NAME
       malloc,	calloc, free, memalign, realloc, valloc, alloca - memory allo‐
       cator

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);

DESCRIPTION
       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 ter‐
       mination	 of  the  application.	If   ptr  is a null pointer, no action
       occurs. If a random number is passed to free(), the results  are	 unde‐
       fined.

       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 size is 0, the space pointed to by ptr is freed	and  a
       magic  pointer  is  returned,  which is considered as a NULL pointer if
       passed to free(). If ptr is NULL, realloc() behaves like	 malloc()  for
       the specified size.

       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  tem‐
       porary  space  is  automatically	 freed when the caller returns. If the
       allocated block is beyond the current stack limit, the resulting behav‐
       ior is undefined.

RETURN VALUES
       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(), val‐
       loc(), 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.

ERRORS
       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	multi‐
       threaded applications but are not scalable. Concurrent accesses by mul‐
       tiple threads are single-threaded through the use  of  a	 single	 lock.
       Multithreaded  applications that make heavy use of dynamic memory allo‐
       cation should be linked with allocation libraries designed for  concur‐
       rent  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.

ATTRIBUTES
       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 Stan‐
       dard. The memalign() and alloca() functions are Stable.

SEE ALSO
       brk(2), getrlimit(2), libbsdmalloc(3LIB),  libmalloc(3LIB),  libmapmal‐
       loc(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  mem‐
       ory 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.

SunOS 5.10			  20 Sep 2012			    malloc(3C)
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