Lazy allocation is a model for allocating objects on the execution stack of a high-level language which does not create dangling references. Our model provides safe transportation into the heap for objects that may survive the deallocation of the surrounding stack frame. Space for objects that do not survive the deallocation of the surrounding stack frame is reclaimed without additional effort when the stack is popped. Lazy allocation thus performs a first-level garbage collection, and if the language supports garbage collection of the heap, then our model can reduce the amortized cost of allocation in such a heap by filtering out the short-lived objects that can be more efficiently managed in LIFO order. A run-time mechanism called result expectation further filters out unneeded results from functions called only for their effects. In a shared-memory multi-processor environment, this filtering reduces contention for the allocation and management of global memory. Our model performs s...

This paper discusses work which is a continuation of [Baker90]. Our birth control scheme for objects of LP type bears a strong resemblance to Barnes'es scheme for controlling access to a resource [Barnes89,9.3]. Barnes does not export a nesting generic unit to handle deallocation, however.

This paper and [Baker91SP] show that Mendal was needlessly pessimistic.

. Ada 83 did not provide enough control on the creation, assignment, and destruction of objects of userdefined types. This lack of control restricted type composition and prevented the full exercise of information hiding for abstract data types. Ada 9X brings new mechanisms supporting the full control of abstract data types, powerful type composition, and more extensive information hiding. With better control of abstract data types, Ada code will be easier to write, understand, maintain, and reuse. Thus, applications written in Ada 9X will be safer. KEYWORDS. Abstract data types, Information hiding, Ada 9X, Object initialization, User-defined assignment, Object finalization, Memory reclamation, Storage management, Reference counting, Type composition, Collections. 1. INTRODUCTION Ada is known for the quality of its design and the power of its basic mechanisms, especially in support of the construction and composition of abstract data types (ADTs). Today, Ada is emerging from its firs...