Memory Management

shim_val_t is a thin opaque pointer to a V8 heap object. Memory management of shim_val_t's is by and large explicit. Aside from the noted exceptions below, all returned shim_val_t's should be passed to shim_value_release(). This will only cleanup any resources the addon layer has allocated. Releasing a shim_val_t does not indicate to V8 that it may now garbage collect the underlying object.

Local vs Persistent

In V8 there are two basic kinds of values:

• Local
  • A value that is valid until the end of a scope, i.e. after the current scope is done executing, if no more references to the value are held the GC may free the resources associated with the value.
• Persistent
  • A value which is valid beyond the current scope

shim_val_t's will be a Local unless it was returned by shim_persistent_new(), in which case you'll be returned a shim_val_t that wraps a Persistent.

Wrapped Persistents should only be released by calling shim_persistent_dispose(). Do not use shim_value_release().

If you want to be notified when the GC is about to collect a value, see shim_obj_make_weak().

Arguments

shim_val_t's retrieved from:

• shim_args_get()
• shim_args_get_this()

or passed to:

• shim_args_set_rval()

do not need to be shim_value_release()'d, the addon layer will handle the releasing when the boundary function has finished executing.

Singletons

shim_null() and shim_undefined() are singletons, they are ignored when passed to shim_value_release(), it's neither necessary or harmful to do so.