pragma Profile (Ravenscar | Restricted | Rational | GNAT_Extended_Ravenscar | GNAT_Ravenscar_EDF );
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 configuration pragmas that depend on the argument. Ravenscar is standard in Ada 2005. The other possibilities (Restricted, Rational, GNAT_Extended_Ravenscar, GNAT_Ravenscar_EDF) are implementation-defined. The set of configuration pragmas is defined in the following sections.
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:
[RM D.2.2] Tasks are dispatched following a preemptive priority-ordered scheduling policy.
[RM D.3] While tasks and interrupts execute a protected action, they inherit the ceiling priority of the corresponding protected object.
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.
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.
A description is also available at
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 was made part of the Ada 2005 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
The above set is a superset of the restrictions provided by pragma
Profile (Restricted), it includes six additional restrictions
No_Task_Termination). This means
Profile (Ravenscar), like the pragma
automatically causes the use of a simplified,
more efficient version of the tasking run-time library.
This profile corresponds to a GNAT specific extension of the Ravenscar profile. The profile may change in the future although only in a compatible way: some restrictions may be removed or relaxed. It is defined as a variation of the Ravenscar profile.
No_Implicit_Heap_Allocations restriction has been replaced
Simple_Barriers restriction has been replaced by
No_Relative_Delay restrictions have been removed.
This profile corresponds to the Ravenscar profile but using EDF_Across_Priority as the Task_Scheduling_Policy.
This profile corresponds to the GNAT restricted run time. It establishes the following set of restrictions:
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.
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: