Trait emacs::Transfer
[−]
[src]
pub trait Transfer: Sized { fn type_name() -> &'static str; unsafe extern "C" fn finalizer(ptr: *mut c_void) { ... } }
Allowing a type to be exposed to Lisp, where its values appear as opaque objects, or "embedded
user pointers" (printed as #<user-ptr ...>
).
When a (boxed) value of this type is transferred to Lisp, the GC becomes its owner. Afterwards, module code can only access it through immutable references.
Required Methods
fn type_name() -> &'static str
Returns the name of this type. This is used to report runtime type error, when a function expects this type, but some Lisp code passes a different type of "user pointer".
Provided Methods
unsafe extern "C" fn finalizer(ptr: *mut c_void)
Finalizes a value. This is called by the GC when it discards a value of this type. Module
code that needs custom destructor logic should implement [Drop
], instead of overriding
this.
This function also serves as a form of runtime type tag.