Pragma Profile

Syntax:

     pragma Profile (Ravenscar | Restricted | Rational);

This pragma is standard in Ada 2005, but is available in all earlier versions of Ada as an implementation-defined pragma. This is a configuration pragma that establishes a set of configiuration pragmas that depend on the argument. Ravenscar is standard in Ada 2005. The other two possibilities (Restricted or Rational) are implementation-defined. The set of configuration pragmas is defined in the following sections.

• Pragma Profile (Ravenscar) The Ravenscar profile is standard in Ada 2005, but is available in all earlier versions of Ada as an implementation-defined pragma. This profile establishes the following set of configuration pragmas:

  Task_Dispatching_Policy (FIFO_Within_Priorities)

  [RM D.2.2] Tasks are dispatched following a preemptive priority-ordered scheduling policy.
  

  Locking_Policy (Ceiling_Locking)

  [RM D.3] While tasks and interrupts execute a protected action, they inherit the ceiling priority of the corresponding protected object.
  

  Detect_Blocking

  This pragma forces the detection of potentially blocking operations within a protected operation, and to raise Program_Error if that happens.

  plus the following set of restrictions:

  Max_Entry_Queue_Length => 1

  No task can be queued on a protected entry.
  

  Max_Protected_Entries => 1
  

  Max_Task_Entries => 0

  No rendezvous statements are allowed.
  

  No_Abort_Statements
  

  No_Dynamic_Attachment
  

  No_Dynamic_Priorities
  

  No_Implicit_Heap_Allocations
  

  No_Local_Protected_Objects
  

  No_Local_Timing_Events
  

  No_Protected_Type_Allocators
  

  No_Relative_Delay
  

  No_Requeue_Statements
  

  No_Select_Statements
  

  No_Specific_Termination_Handlers
  

  No_Task_Allocators
  

  No_Task_Hierarchy
  

  No_Task_Termination
  

  Simple_Barriers

  The Ravenscar profile also includes the following restrictions that specify that there are no semantic dependences on the corresponding predefined packages:

  No_Dependence => Ada.Asynchronous_Task_Control
  

  No_Dependence => Ada.Calendar
  

  No_Dependence => Ada.Execution_Time.Group_Budget
  

  No_Dependence => Ada.Execution_Time.Timers
  

  No_Dependence => Ada.Task_Attributes
  

  No_Dependence => System.Multiprocessors.Dispatching_Domains

  This set of configuration pragmas and restrictions correspond to the definition of the “Ravenscar Profile” for limited tasking, devised and published by the International Real-Time Ada Workshop, 1997, and whose most recent description is available at http://www-users.cs.york.ac.uk/~burns/ravenscar.ps.

  The original definition of the profile was revised at subsequent IRTAW meetings. It has been included in the ISO Guide for the Use of the Ada Programming Language in High Integrity Systems, and has been approved by ISO/IEC/SC22/WG9 for inclusion in the next revision of the standard. The formal definition given by the Ada Rapporteur Group (ARG) can be found in two Ada Issues (AI-249 and AI-305) available at http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00249.txt and http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00305.txt.

  The above set is a superset of the restrictions provided by pragma Profile (Restricted), it includes six additional restrictions (Simple_Barriers, No_Select_Statements, No_Calendar, No_Implicit_Heap_Allocations, No_Relative_Delay and No_Task_Termination). This means that pragma Profile (Ravenscar), like the pragma Profile (Restricted), automatically causes the use of a simplified, more efficient version of the tasking run-time system.

• Pragma Profile (Restricted) This profile corresponds to the GNAT restricted run time. It establishes the following set of restrictions:
  • No_Abort_Statements
  • No_Entry_Queue
  • No_Task_Hierarchy
  • No_Task_Allocators
  • No_Dynamic_Priorities
  • No_Terminate_Alternatives
  • No_Dynamic_Attachment
  • No_Protected_Type_Allocators
  • No_Local_Protected_Objects
  • No_Requeue_Statements
  • No_Task_Attributes_Package
  • Max_Asynchronous_Select_Nesting = 0
  • Max_Task_Entries = 0
  • Max_Protected_Entries = 1
  • Max_Select_Alternatives = 0

  This set of restrictions causes the automatic selection of a simplified version of the run time that provides improved performance for the limited set of tasking functionality permitted by this set of restrictions.

• Pragma Profile (Rational) The Rational profile is intended to facilitate porting legacy code that compiles with the Rational APEX compiler, even when the code includes non- conforming Ada constructs. The profile enables the following three pragmas:
  • pragma Implicit_Packing
  • pragma Overriding_Renamings
  • pragma Use_VADS_Size