Ada 95 RM - C.7.1 The Package Task

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C.7.1 The Package Task_Identification

Static Semantics

(1): The following language-defined library package exists:

(2)
       package Ada.Task_Identification is
          type Task_ID is private;
          Null_Task_ID : constant Task_ID;
          function  "=" (Left, Right : Task_ID) return Boolean;
(3)
          function  Image        (T : Task_ID) return String;
          function  Current_Task return Task_ID;
          procedure Abort_Task   (T : in out Task_ID);
(4)
          function  Is_Terminated(T : Task_ID) return Boolean;
          function  Is_Callable  (T : Task_ID) return Boolean;
       private
          ... -- not specified by the language
       end Ada.Task_Identification;

Dynamic Semantics

(5)

A value of the type Task_ID identifies an existent task. The constant Null_Task_ID does not identify any task. Each object of the type Task_ID is default initialized to the value of Null_Task_ID.

(6)

The function "=" returns True if and only if Left and Right identify the same task or both have the value Null_Task_ID.

(7)

The function Image returns an implementation-defined string that identifies T. If T equals Null_Task_ID, Image returns an empty string.

(8)

The function Current_Task returns a value that identifies the calling task.

(9)

The effect of Abort_Task is the same as the abort_statement for the task identified by T. In addition, if T identifies the environment task, the entire partition is aborted, See E.1.

(10)

The functions Is_Terminated and Is_Callable return the value of the corresponding attribute of the task identified by T.

(11)

For a prefix T that is of a task type (after any implicit dereference), the following attribute is defined:

(12)

T'Identity

Yields a value of the type Task_ID that identifies the task denoted by T.

(13)

For a prefix E that denotes an entry_declaration, the following attribute is defined:

(14)

E'Caller

Yields a value of the type Task_ID that identifies the task whose call is now being serviced. Use of this attribute is allowed only inside an entry_body or accept_statement corresponding to the entry_declaration denoted by E.

(15)

Program_Error is raised if a value of Null_Task_ID is passed as a parameter to Abort_Task, Is_Terminated, and Is_Callable.

(16)

Abort_Task is a potentially blocking operation (see 9.5.1).

Bounded (Run-Time) Errors

(17): It is a bounded error to call the Current_Task function from an entry body or an interrupt handler. Program_Error is raised, or an implementation-defined value of the type Task_ID is returned.

Erroneous Execution

(18): If a value of Task_ID is passed as a parameter to any of the operations declared in this package (or any language-defined child of this package), and the corresponding task object no longer exists, the execution of the program is erroneous.