# 8. Using AUnit with Restricted Run-Time Libraries

AUnit 3 - like AUnit 2 - is designed so that it can be used in environments with restricted Ada run-time libraries, such as ZFP and the cert run-time profile on Wind River’s VxWorks 653. The patterns given in this document for writing tests, suites and harnesses are not the only patterns that can be used with AUnit, but they are compatible with the restricted run-time libraries provided with GNAT Pro.

In general, dynamic allocation and deallocation must be used carefully in test code. For the cert profile on VxWorks 653, all dynamic allocation must be done prior to setting the application partition into ‘normal’ mode. Deallocation is prohibited in this profile. For some restricted profiles, dynamic memory management is not provided as part of the run-time, and should not be used unless you have provided implementations as described in the GNAT User’s Guide Supplement for GNAT Pro Safety-Critical and GNAT Pro High-Security.

Starting with AUnit 3, a simple memory management mechanism has been included in the framework, using a kind of storage pool. This memory management mechanism uses a static array allocated at startup, and simulates dynamic allocation afterwards by allocating parts of this array upon request. Deallocation is not permitted.

By default, an array of 100KB is allocated. The size can be changed by modifying the value in the file `aunit-<version>-src/aunit/framework/staticmemory/aunit-memory.adb` before building AUnit.

To allocate a new object, you use `AUnit.Memory.Utils.Gen_Alloc`.

Additional restrictions relevant to the default ZFP profile include:

- Normally the ZFP profile requires a user-defined `__gnat_last_chance_handler` routine to handle raised exceptions. However, AUnit now provides a mechanism to simulate exception propagation using gcc builtin setjmp/longjmp mechanism. This mechanism defines the `__gnat_last_chance_handler` routine, so it should not be redefined elsewhere. In order to be compatible with this restriction, the user-defined last chance handler routine can be defined as a “weak” symbol; this way, it will still be linked into the standalone executable, but will be replaced by the AUnit implementation when linked with the harness. The pragma `Weak_External` can be used for that; e.g.:

      pragma Weak_External (Last_Chance_Handler);

- AUnit requires `GNAT.IO` provided in `g-io.ad?` in the full or cert profile run-time library sources (or as implemented by the user). Since this is a run-time library unit it must be compiled with the gnatmake `-a` switch.

- The AUnit framework has been modified so that no call to the secondary stack is performed, nor any call to `memcpy` or `memset`. However, if the unit under test, or the tests themselves require use of those routines, then the application or test framework must define those symbols and provide the requisite implementations.

- The timed parameter of the Harness `Run` routine has no effect when used with the ZFP profile, and on profiles not supporting `Ada.Calendar`.