Ownership boundary

• get borrows access while ownership stays in the wrapper.
• clear destroys the owned object and leaves the wrapper empty.
• release returns one Ref and leaves the wrapper empty. Automatic destruction no longer applies to that object after release.
• lower transfers the same owned allocation to one base-typed owner and empties the original owner.
• valid? reports whether the wrapper currently owns one object.

OwnerWithDestructor (Value destructor -- ownerSchema)

Constructs an owner schema from an element schema and an explicit destructor callable.

Known issue: an OwnerWithDestructor fails to compile when its explicit destructor omits the allocation size: its DIE and acquire paths then call mplFree with the address only while mplFree expects the size and the address (Argument (target) is not on the stack reported from memory.mpl). A destructor with stack effect (element -- allocationSize) can compile when it returns the size of the original allocation. Owner and owner are unaffected.

• Value is the owned element schema, destructor is called with the allocated element before its storage is freed, and ownerSchema is named Owner<Value>.
• The resulting schema exposes the same ownership operations as Owner, including validity, acquisition, clearing, borrowing, lowering, initialization, and release.
• owner constructs Owner, which is OwnerWithDestructor with a generated destructor (manuallyDestroyVariable, then objectSize, whose result is the size mplFree consumes). ownerDerived passes an explicit base schema and destructor to OwnerWithDestructor and is subject to the known issue above.

objectSize (object -- size)

Returns the storage size for a value or the size supplied by its SIZE field.

• The default overload calls storageSize and returns one Natx.
• For an object exposing SIZE, the second overload returns .SIZE instead.

Owner

Methods

Fields

• OWNER: marker field used by generic ownership helpers.
• destructor: destructor routine used when the owned object is destroyed.
• elementType: Ref to the owned element schema.
• memory: stored Ref to the owned object; empty owners store NIL.

owner (element -- owner)

Constructs Owner from one element and transfers ownership of newly allocated storage to the result.

Compile-time owner and release types

"Owner"   use
"control" use

{} 0 {} [
  holder: 5 owner;
  holder.valid? printStack _:;
  holder.get printStack _:;
  @holder.release printStack _:;
  holder.valid? printStack _:;
  0
] "main" exportFunction

Expected Output During Compilation

Cond
Int32 Cref
Int32 Ref
FALSE

Runtime example

"Owner"   use
"String"  use
"control" use

{} Int32 {} [
  holder: 5 owner;
  ("value=" @holder.get new LF) printList
  released: @holder.release;
  ("released=" @released new LF) printList
  0
] "main" exportFunction

Expected Output

value=5
released=5

Runtime example: clear resets validity

"Owner"   use
"String"  use
"control" use

{} Int32 {} [
  holder: 5 owner;
  ("valid0=" holder.valid? LF) printList
  @holder.clear
  ("valid1=" holder.valid? LF) printList
  0
] "main" exportFunction

Expected Output

valid0=TRUE
valid1=FALSE

ownerDerived (element base destructor -- owner)

Constructs an owner with explicit base type and destructor handling.

Known issue: the result is an OwnerWithDestructor; it fails when the supplied destructor omits the required allocation size.

getHeapUsedSize (owner -- size)

Returns total heap usage of the owned object as Natx.

• If the owner is empty, the result is 0nx.
• If the owned element participates in getHeapUsedSize, that result is included recursively.

See also

• Mref: Minimal Ref type with custom semantics.
• Pool: Pooled storage with reusable numeric keys.