Chapter 7: Portability - TOC - 7.4 TASKING

7.4.2 Delay Statements

guideline

Do not depend on a particular delay being achievable (Nissen and Wallis 1984).

Never use knowledge of the execution pattern of tasks to achieve timing requirements.

rationale

The rationale for this appears in Guideline 6.1.7. In addition, the treatment of delay statements varies from implementation to implementation, thereby hindering portability.

Using knowledge of the execution pattern of tasks to achieve timing requirements is nonportable. Ada does not specify the underlying scheduling algorithm, and there is no guarantee that system clock ticks will be consistently precise between different systems. Thus, when you change system clocks, your delay behavior also changes.