When an extension allocates resources that must be explicitly freed (in the same way that a port must be explicitly closed), a Scheme object associated with the resource should be placed into the management of the current custodian with scheme_add_managed.
Before allocating the resource, call scheme_custodian_check_available to ensure that the relevant custodian is not already shut down. If it is, scheme_custodian_check_available will raise an exception. If the custodian is shut down when scheme_add_managed is called, the close function provided to scheme_add_managed will be called immediately, and no exception will be reported.
Creates a new custodian as a subordinate of m. If m is NULL, then the main custodian is used as the new custodian’s supervisor. Do not use NULL for m unless you intend to create an especially privileged custodian.
Places the value o into the management of the custodian m. If m is NULL, the current custodian is used.
The f function is called by the custodian if it is ever asked to “shutdown” its values; o and data are passed on to f, which has the type
typedef void (*Scheme_Close_Custodian_Client)(Scheme_Object *o,
If strong is non-zero, then the newly managed value will be remembered until either the custodian shuts it down or scheme_remove_managed is called. If strong is zero, the value is allowed to be garbaged collected (and automatically removed from the custodian).
The return value from scheme_add_managed can be used to refer to the value’s custodian later in a call to scheme_remove_managed. A value can be registered with at most one custodian.
If m (or the current custodian if m is NULL)is shut down, then f is called immediately, and the result is NULL.
Removes o from the management of its custodian. The mref argument must be a value returned by scheme_add_managed or NULL.
Instructs the custodian m to shutdown all of its managed values.
Installs a function to be called on each custodian-registered item and its closer when MzScheme is about to exit. The registered function has the type
void (*Scheme_Exit_Closer_Func)(Scheme_Object *o,
where d is the second argument for f.