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.TH GALLOC 3
.CT 2 mem_man
.SH NAME
galloc, gfree, garbage \(mi storage allocation with garbage collection
.SH SYNOPSIS
.nf
.B char *galloc(n)
.B unsigned n;
.PP
.B void gfree(p)
.B char *p;
.PP
.B void garbage()
.fi
.SH DESCRIPTION
These functions perform heap storage allocation with
garbage collection.
.PP
.I Galloc
allocates a block of at least
.I n
bytes and returns a pointer to it.
.I Gfree
frees a block previously allocated by
.I galloc.
.PP
When space gets tight, garbage blocks
are freed automatically.
A block allocated by
.I 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.
.PP
The frequency of garbage collection is controlled by external
variables declared
.IP
.B "long gcmax = 5000, gcmin = 50;"
.LP
No more than
.I gcmax
allocations may intervene between automatic collections; this feature
will help contain the growth of virtual address space.
At least
.I gcmin
allocations must intervene, otherwise
garbage collection will be abandoned as fruitless.
.I Garbage
may be called to do garbage collection at an arbitrary time.
.PP
.IR Malloc (3)
and
.I galloc
allocate from the same arena, but garbage collection
affects only
.I galloc
blocks.
.I Free
(see
.IR malloc (3))
must not be used on blocks allocated with
.IR galloc .
.SH SEE ALSO
.IR malloc (3)
.SH DIAGNOSTICS
.I Galloc
returns 0
when space cannot be found.
.SH 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.

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