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.TH MALLOC 3
.CT 2 mem_man
.SH NAME
malloc, free, realloc, calloc, cfree \- memory allocator
.SH SYNOPSIS
.nf
.B char *malloc(size)
.B unsigned size;
.PP
.B free(ptr)
.B char *ptr;
.PP
.B char *realloc(ptr, size)
.B char *ptr;
.B unsigned size;
.PP
.B char *calloc(nelem, elsize)
.B unsigned nelem, elsize;
.PP
.B cfree(ptr)
.B char *ptr;
.fi
.SH DESCRIPTION
.I Malloc
and
.I free
provide a simple memory allocation package.
.I Malloc
returns a pointer to a new block of at least
.I size
bytes.
The block is suitably aligned for storage of any type of object.
No two active pointers from
.I malloc
will have the same value.
.PP
The argument to
.I free
is a pointer to a block previously allocated by
.IR malloc ;
this space is made available for further allocation.
.PP
.I Realloc
changes the size of the block pointed to by
.I ptr
to
.I 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.
The call
.B "realloc((char*)0, size)
means the same as
.LR malloc(size) .
.PP
.I Calloc
allocates space for
an array of
.I nelem
elements of size
.I elsize.
The space is initialized to zeros.
.I Cfree
frees such a block.
.SH SEE ALSO
.IR galloc (3),
.IR brk (2),
.IR pool (3),
.IR block (3)
.SH DIAGNOSTICS
.I Malloc, realloc
and
.I calloc
return 0 if there is no available memory
or if the arena has been detectably corrupted.
.SH BUGS
When
.I realloc
returns 0, the block pointed to by
.I ptr
may have been destroyed.
.PP
User errors can corrupt the storage arena.
The most common gaffes are (1) freeing an already freed block,
(2) storing beyond the bounds of an allocated block, and (3)
freeing data that was not obtained from the allocator.
To help find such errors, a diagnosing allocator
may be loaded; use flag
.B -ldmalloc
of
.IR cc (1).
An even more stringently checking version may be created
by recompilation; see the source.
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