4.3 Garbage collection

Garbage collection is relatively straightforward, because most values are retained on the stackframe of an interpreter call. However, two storage types and possibly user-defined type garbage collector definitions require attention: BATs and strings.

A key issue is to deal with temporary BATs in an efficient way. References to bats in the buffer pool may cause dangling references at the language level. This appears as soons as your share a reference and delete the BAT from one angle. If not carefull, the dangling pointer may subsequently be associated with another BAT

All string values are private to the VALrecord, which means they have to be freed explicitly before a MAL function returns. The first step is to always safe the destination variable before a function call is made.

All operations are responsible to properly set the reference count of the BATs being produced or destroyed. The libraries should not leave the physical reference count being set. This is only allowed during the execution of a GDK operation. All references should be logical.