Heap allocation supports deallocation of allocated memory in any order. Dictionary allocation is not affected by it (i.e., it 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. The initial contents of the data space is undefined. 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 undefined 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. 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.