OCaml’s automatic memory management guarantees that a value will eventually be freed when it’s no longer in use, either via the GC sweeping it or the program terminating. It’s sometimes useful to run extra code just before a value is freed by the GC, for example, to check that a file descriptor has been closed, or that a log message is recorded.
+OCaml’s automatic memory management guarantees that a value will eventually be freed when it’s no longer in use, either via the GC sweeping it or the program terminating. It’s sometimes useful to run extra code just before a value is freed by the GC, for example, to check that a file descriptor has been closed, or that a log message is recorded.
Various values cannot have finalizers attached since they aren’t heap-allocated. Some examples of values that are not heap-allocated are integers, constant constructors, Booleans, the empty array, the empty list, and the unit value. The exact list of what is heap-allocated or not is implementation-dependent, which is why Core provides the Heap_block module to explicitly check before attaching the finalizer.