Memory allocation

Show how to explicitly allocate and deallocate blocks of memory in your language. Show access to different types of memory (i.e. heap, stack, shared, foreign) if applicable.

C

TODO: malloc() and free()

Forth

Forth has two main bulk memory areas, each with their own word sets and semantics for allocation and deallocation.

Dictionary

All Forth implementations have a stack-like memory space called the dictionary. It is used both for code definitions and data structures. <lang forth> unused . \ memory available for use in dictionary here . \ current dictionary memory pointer

mem, ( addr len -- ) here over allot swap move ;

s, ( str len -- ) here over char+ allot place align ; \ built-in on some forths

," [char] " parse s, ;

variable num create array 60 cells allot create struct 0 , 10 , char A c, ," string" unused . here . </lang>

Dictionary space is meant for static code definitions and supporting data structures, so it is not as easy to deallocate from it. For ad-hoc allocations without intervening definitions, you may give a negative value to ALLOT to reclaim the space. You may also lay down a named MARKER to reclaim the space used by all subsequent definitions. <lang forth> marker foo

temp ... ;

create dummy 300 allot -150 allot \ trim the size of dummy by 150 bytes foo \ removes foo, temp, and dummy from the list of definitions </lang>

Heap

Most Forth implementations also give access to a larger random-access memory heap. <lang forth>

 4096 allocate throw  ( addr )
 dup 4096 erase
 ( addr ) free throw

</lang>

Oberon-2

TODO:

Pascal

TODO: