Sophia Drossopoulou

Overloading in preliminary Ada

Ada permits the overloading of enumeration literals, aggregates, subprograms and operators, i.e. the declaration of the same designator with different meanings in the same scope. This leads to difficulties during the semantic analysis of expressions and subprogram calls. For selecting the meaning not only the designator but also the types of its operands or parameters and the type of its result must be used. We show that the identification of expressions is possible in two passes, the first bottom-up, the second top-down.

An LALR (1) grammar for (revised) Ada

In transforming the initial grammar given in [R-ADA] first all obvious ambiguities have been removed. Most of them arise from the use of the nonterminal type mark which is equivalent to name. The more severe LALR([) conflicts are the identifier list in declarations, indexed names and similiar constructs, the sequencing in declarative parts [Cro], subprogram bodies and instantiations, and entry names in accept statements.

A Separate Compilation System for Ada

The programming language Ada provides a concept for the separate compilation of program units where checks have to be done across the unit bounds at compile time. Here we describe the Separate Compilation System which was developed for the Ada Compiler Project at the University of Karlsruhe. The realization of the separate compilation facility of Ada is mainly based on the use of a library which contains information about previously compiled units. The separate compilation system maintains the library and provides the functions to support the compiler and other programming tools.

Optimization in Ada

1. Introductio n Naive compilation of highly modular programs written i n high Level programming Languages usually results in grea t inefficiencies in object code. For this reason high Leve l languages are not used universally for programming. Since Ada is intended to be used in a wide range o f applications even in very time critical areas Like rea l time application, it will be necessary to bring th e efficiency of generated code into a tolerable range whe n compared with hand coded assembly programs. Within the Ada Project at the University of Karlsruhe w e have studied the applicability of classical optimizatio n techniques to Ada. An extended list of these techniques i s presented in CKirc827. For the analysis which underlies optimization, the progra m is first decomposed into basic blocks. A flow graph is the n constructed with the basic blocks building the nodes an d the flow of control (between the basic blocks) building th e edges. Based on this this flow graph data flow analysis an d optimization can be performed ECoMa80]. In this paper we want to study the influence of some Ad a features on flow analysis and thus optimization. Thes e features are exception handling, separate compilation , tasking, and generics. All citations are from the Ada Reference Manual (RM) CAdaS ]. 2. Exception s The exception facility in Ada deals with errors and othe r exceptional situations that arise during program execution. Such situations are called exception=. In the case of a program error (like arithmetic overflow) a predefined exception is raised. Predefined exceptions ca n be raised implicitly at almost any point of the program. Ada provides five predefined exceptions .