D.7 Tasking Restrictions

1. This clause defines restrictions that can be used with a pragma Restrictions, See section 13.12 Pragma Restrictions, to facilitate the construction of highly efficient tasking run-time systems.
   Static Semantics
   
2. The following restriction_identifiers are language defined:
3. No_Task_Hierarchy

   All (nonenvironment) tasks depend directly on the environment
   task of the partition.
   

4. No_Nested_Finalization

   Objects with controlled parts and access types that designate
   such objects shall be declared only at library level.
   

5. No_Abort_Statements

   There are no abort_statements, and there are no calls on
   Task_Identification.Abort_Task.
   

6. No_Terminate_Alternatives

   There are no selective_accepts with terminate_alternatives.
   

7. No_Task_Allocators

   There are no allocators for task types or types containing
   task subcomponents.
   

8. No_Implicit_Heap_Allocations

   There are no operations that implicitly require heap storage
   allocation to be performed by the implementation. The
   operations that implicitly require heap storage allocation
   are implementation defined.
   

9. No_Dynamic_Priorities

   There are no semantic dependences on the package
   Dynamic_Priorities.
   

10. No_Asynchronous_Control

    There are no semantic dependences on the package
    Asynchronous_Task_Control.
    

11. The following restriction_parameter_identifiers are language defined:
12. Max_Select_Alternatives

    Specifies the maximum number of alternatives in a
    selective_accept.
    

13. Max_Task_Entries

    Specifies the maximum number of entries per task. The bounds
    of every entry family of a task unit shall be static, or
    shall be defined by a discriminant of a subtype whose
    corresponding bound is static. A value of zero indicates
    that no rendezvous are possible.
    

14. Max_Protected_Entries

    Specifies the maximum number of entries per protected type.
    The bounds of every entry family of a protected unit shall be
    static, or shall be defined by a discriminant of a subtype
    whose corresponding bound is static.
    

    Dynamic Semantics
    
15. If the following restrictions are violated, the behavior is implementation defined. If an implementation chooses to detect such a violation, Storage_Error should be raised.
16. The following restriction_parameter_identifiers are language defined:
17. Max_Storage_At_Blocking

    Specifies the maximum portion (in storage elements) of a
    task's Storage_Size that can be retained by a blocked task.
    

18. Max_Asynchronous_Select_Nesting

    Specifies the maximum dynamic nesting level of
    asynchronous_selects. A value of zero prevents the use of any
    asynchronous_select.
    

19. Max_Tasks

    Specifies the maximum number of task creations that may be
    executed over the lifetime of a partition, not counting the
    creation of the environment task.
    

20. It is implementation defined whether the use of pragma Restrictions results in a reduction in executable program size, storage requirements, or execution time. If possible, the implementation should provide quantitative descriptions of such effects for each restriction.
    Implementation Advice
    
21. When feasible, the implementation should take advantage of the specified restrictions to produce a more efficient implementation.
    

    NOTES
    

22. (29) The above Storage_Checks can be suppressed with pragma Suppress.

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