Heap allocation supports deallocation of allocated memory in any order. It does not affect dictionary allocation (i.e., heap allocation does not end a contiguous region). In Gforth, these words are implemented using the standard C library calls malloc(), free() and realloc().
The memory region produced by one invocation of allocate or
resize is internally contiguous. There is no contiguity between
such a region and any other region (including others allocated from the
heap).
allocate ( u – a_addr wior ) memory “allocate”
Allocate u address units of contiguous data space. This data space is not initialized. If the allocation is successful, a-addr is the start address of the allocated region and wior is 0. If the allocation fails, a-addr is arbitrary and wior is a non-zero I/O result code.
free ( a_addr – wior ) memory “free”
Return the region of data space starting at a-addr to the
system. The region must originally have been obtained using
allocate or resize, otherwise the result of
free is unpredictable. If the operation is successful,
wior is 0. If the operation fails, wior is a non-zero
I/O result code.
resize ( a_addr1 u – a_addr2 wior ) memory “resize”
Change the size of the allocated area at a-addr1 to u
address units, possibly moving the contents to a different
area. a-addr2 is the address of the resulting area. If the
operation is successful, wior is 0. If the operation
fails, wior is a non-zero I/O result code. If a-addr1
is 0, Gforth’s (but not the Standard) resize
allocates u address units.