term% cat index.txt GALLOC(3) Library Functions Manual 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 collec‐
tion.
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 automatically. 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 external variables
declared
long gcmax = 5000, gcmin = 50;
No more than gcmax allocations may intervene between automatic collec‐
tions; 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 garbage collec‐
tion 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)
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.
GALLOC(3)