GALLOC(3) GALLOC(3)
NAME
galloc, gfree, garbage - storage allocation with garbage
collection
SYNOPSIS
char *galloc(n)
unsigned n;
gfree(p)
char *p;
garbage( )
DESCRIPTION
These functions perform heap storage allocation with garbage
collection.
Galloc allocates a block of at least n bytes and returns a
pointer to it. Gfree frees a block previously allocated by
galloc.
When space gets tight, garbage blocks are freed automati-
cally. A block allocated by galloc is deemed to be garbage
unless it is reachable. A reachable block is one whose
first byte is pointed to by a declared C variable or by a
pointer in a reachable block.
The frequency of garbage collection is controlled by exter-
nal variables declared
long gcmax = 5000, gcmin = 50;
No more than gcmax allocations may intervene between auto-
matic collections; this feature will help contain the growth
of virtual address space. At least gcmin allocations must
intervene, otherwise garbage collection will be abandoned as
fruitless. Garbage may be called to do garbage collection
at an arbitrary time.
Malloc(3) and galloc allocate from the same arena, but gar-
bage collection affects only galloc blocks. Free (see
malloc(3)) must not be used on blocks allocated with galloc.
DIAGNOSTICS
Galloc returns a null (0) pointer when space cannot be
found.
SEE ALSO
malloc(3)
GALLOC(3) GALLOC(3)
BUGS
Garbage collection is conservative; blocks that appear to be
pointed to from within declared storage will not be freed,
regardless of whether the apparent `pointers' were declared
as such.