Exposing uninitialized variables: Strengthening and extending run-time checks in Ada

Since its inception, a main objective of the Ada language has been to assist in the development of large and robust applications. In addition to that, the language also provides support for building safety-critical applications, e.g. by facilitating validation and verification of such programs. The latest revision of the language has brought some additional improvements in the safety area, such as the Normalize-Scalars pragma, which ensures an automatic initialization of the non-explicitly initialized scalars. This paper presents Initialize-Scalars, an enrichment of the Normalize-Scalars concept, and an extended mode to verify at run-time the validity of scalars,,both designed for easy use in existing large applications. Their implementation in GNAT Pro (the GNU Ada 95 compiler) is discussed. The practical results obtained on a large Air Traffic Flow Management application are presented.