Appendix E Allocating and releasing resources

In this section we do an overview of the facilities Vicare provides to handle resource allocation and release.

Vicare has ways to deal with releasing resources by relying on the garbage collector; if we use such mechanisms the resource is “asynchronous” with respect to code execution. These are the methods asynchronous resource handling:

• Directly use guardians, Guardians and garbage collection.
• Wrap the reference to the resource in a Vicare data structure and register a finalisation function in the structure type descriptor, Finalisation of structures.
• Wrap the reference to the resource in a R6RS record and register a finalisation function in the record type descriptor, Automatic finalisation of records.

Asynchronous resource management is often not good, because there is no guarantee that a resource is released before the Vicare process termination. Sometimes it is better to associate the life of an allocated resource to the dynamic extent of a call to function; if we use such mechanism the resource is “synchronous” with respect to code execution. These are the methods synchronous resource handling:

• The unwind protection mechanism; iklib unwind-protect, for details.
• The compensation stacks; iklib compensations, for details.