malloc(3f) [bsd man page]

MALLOC(3F)																MALLOC(3F)

NAME

       malloc, free, falloc - memory allocator

SYNOPSIS

       subroutine malloc (size, addr)
       integer size, addr

       subroutine free (addr)
       integer addr

       subroutine falloc (nelem, elsize, clean, basevec, addr, offset)
       integer nelem, elsize, clean, addr, offset

DESCRIPTION

       Malloc, falloc  and  free  provide  a general-purpose memory allocation package.  Malloc returns in addr the address of a block of at least
       size bytes beginning on an even-byte boundary.

       Falloc allocates space for an array of nelem elements of size elsize and returns the address of the block in addr.  It zeros the  block	if
       clean  is  1.  It returns in offset an index such that the storage may be addressed as basevec(offset+1) ... basevec(offset+nelem).  Falloc
       gets extra bytes so that after address arithmetic, all the objects so addressed are within the block.

       The argument to free is the address of a block previously allocated by malloc or falloc; this space is made available for  further  alloca-
       tion, but its contents are left undisturbed.  To free blocks allocated by falloc, use addr in calls to free, do not use basevec(offset+1).

       Needless to say, grave disorder will result if the space assigned by mallocorfalloc is overrun or if some random number is handed to free.

DIAGNOSTICS

       Malloc and falloc set addr to 0 if there is no available memory or if the arena has been detectably corrupted by storing outside the bounds
       of a block.

       The following example shows how to obtain memory and use it within a subprogram:

	     integer addr, work(1), offset
		...
	     call falloc ( n, 4, 0, work, addr, offset )
	     do 10 i = 1, n
	     work(offset+i) = ...
       10    continue

       The next example reads in dimension information, allocates space for two arrays and two vectors, and calls subroutine doit to do the compu-
       tations:

	     integer addr, dummy(1), offs
	     read *, k, l, m
	     indm1   = 1
	     indm2   = indm1 + k*l
	     indm3   = indm2 + l*m
	     indsym  = indm3 + k*m
	     lsym = n*(n+1)/2
	     indv  = indsym + lsym
	     indtot = indv + m
	     call falloc ( indtot, 4, 0, dummy, addr, offs )
	     call doit( dummy(indm1+offs), dummy(indm2+offs),
	    .		dummy(indm3+offs), dummy(indsym+offs),
	    .		dummy(indv +offs), m, n, lsym )
	     end
	     subroutine doit( arr1, arr2, arr3, vsym, vec, m, n, lsym )
	     real arr1(k,l), arr2(l,m), arr3(k,m), vsym(lsym), v2(m)
		...

FILES

       /usr/lib/libU77.a

SEE ALSO

       malloc(3)

4.3 Berkeley Distribution					   May 15, 1985 							MALLOC(3F)

MALLOC(3)						     Library Functions Manual							 MALLOC(3)

NAME

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

SYNOPSIS

       char *malloc(size)
       unsigned size;

       free(ptr)
       char *ptr;

       char *realloc(ptr, size)
       char *ptr;
       unsigned size;

       char *calloc(nelem, elsize)
       unsigned nelem, elsize;

       char *alloca(size)
       int size;

DESCRIPTION

       Malloc  and free provide a general-purpose memory allocation package.  Malloc returns a pointer to a block of at least size bytes beginning
       on a word boundary.

       The argument to free is a pointer to a block previously allocated by malloc; this space is made available for further allocation,  but  its
       contents are left undisturbed.

       Needless to say, grave disorder will result if the space assigned by malloc is overrun or if some random number is handed to free.

       Malloc  maintains  multiple lists of free blocks according to size, allocating space from the appropriate list.	It calls sbrk (see brk(2))
       to get more memory from the system when there is no suitable space already 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
       will be unchanged up to the lesser of the new and old sizes.

       In  order to be compatible with older versions, realloc also works if ptr points to a block freed since the last call of malloc, realloc or
       calloc; sequences of free, malloc and realloc were previously used to attempt storage compaction.  This procedure is no longer recommended.

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

       Alloca allocates size bytes of space in the stack frame of the caller.  This temporary space is automatically freed on return.

       Each of the allocation routines returns a pointer to space suitably aligned (after possible pointer coercion) for storage of  any  type	of
       object.	If the space is of pagesize or larger, the memory returned will be page-aligned.

SEE ALSO

       brk(2), pagesize(2)

DIAGNOSTICS

       Malloc, realloc and calloc return a null pointer (0) if there is no available memory or if the arena has been detectably corrupted by stor-
       ing outside the bounds of a block.  Malloc may be recompiled to check the arena very stringently on every transaction; those sites  with  a
       source code license may check the source code to see how this can be done.

BUGS

       When realloc returns 0, the block pointed to by ptr may be destroyed.

       The  current  implementation  of  malloc does not always fail gracefully when system memory limits are approached.  It may fail to allocate
       memory when larger free blocks could be broken up, or when limits are exceeded because the size is rounded up.  It is optimized	for  sizes
       that are powers of two.

       Alloca is machine dependent; its use is discouraged.

4th Berkeley Distribution					   May 14, 1986 							 MALLOC(3)