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# Design Notes

This section tells reasons behind various design choices of Ahven. Since Ahven is meant to be buildable with multiple different Ada compilers on multiple different operating systems, we have made certain amount of compromises.

## Timeout Feature

Starting from version 2.0, tests can be interrupted after a given time. This feature is implemented using tasks.

Ahven spawns a new local task for each test routine (procedure), and kills it with “abort” statement of Ada. The task and the test routine is aborted if the runtime system of the used compiler can abort the task. The test routine should include at least one “abort completion point” to make the abortion successful.

However, some environments allow the task abortion even without abort completion points in some cases. FSF GCC on OpenBSD with user space threads is one such environment.

## Bounded Strings

All strings in Ahven are either type of String or type of Ahven.AStrings.Bounded_String, which is an instantiation of Ada.Strings.Bounded.Generic_Bounded_Length with maximum length of 160.

The limitation is there because some versions of Janus/Ada have a buggy Unbounded_String implementation and use of Unbounded_String causes memory leaks and random crashes.

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