The anatomy of an FAA-qualifiable Ada subset compiler

To date, compilers used in the construction of FAA-certified software have not been specially qualified for use in safety-critical applications. This has resulted in costly test procedures that attempt to verify the correctness and achieve structural coverage of the object code program rather than the source program. The FAA has adapted the criteria set forth in the document RTCA DO-178B for the design, development, and verification of tools used in the construction of safety-critical software. Tools meeting those criteria can be qualified as code development tools, and their output can be used without additional verification. This paper describes the internals of a compiler for a subset of Ada that is designed to meet the qualification criteria. Use of the qualified compiler will reduce the test burden for certifying flight software at the highest levels of criticality.