Ada Programming, Pragmas, Restrictions

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Summary

The pragma Restrictions is used to forbid the utilization of some language features.

List of language defined restrictions identifiers

Some restrictions are specially marked:

Ada 2005
This is a new Ada 2005 restrictions identifier.
Ada 2012
This is a new Ada 2012 restrictions identifier.

• Immediate_Reclamation
• Max_Asynchronous_Select_Nesting
• Max_Entry_Queue_Length (Ada 2005)
• Max_Protected_Entries
• Max_Select_Alternatives
• Max_Storage_At_Blocking
• Max_Task_Entries
• Max_Tasks
• No_Abort_Statements
• No_Access_Parameter_Allocators (Ada 2012)
• No_Access_Subprograms
• No_Allocators
• No_Anonymous_Allocators (Ada 2012)
• No_Asynchronous_Control
• No_Coextensions (Ada 2012)
• No_Delay
• No_Dependence (Ada 2005)
• No_Dispatch
• No_Dynamic_Attachment (Ada 2005)
• No_Dynamic_Priorities
• No_Exceptions
• No_Fixed_Point
• No_Floating_Point
• No_Implementation_Aspect_Specifications (Ada 2012)
• No_Implementation_Attributes (Ada 2005)
• No_Implementation_Identifiers (Ada 2012)
• No_Implementation_Pragmas (Ada 2005)
• No_Implementation_Units (Ada 2012)
• No_Implicit_Heap_Allocations
• No_IO
• No_Local_Allocators
• No_Local_Protected_Objects (Ada 2005)
• No_Local_Timing_Events (Ada 2005)
• No_Nested_Finalization
• No_Obsolescent_Features (Ada 2005)
• No_Protected_Type_Allocators (Ada 2005)
• No_Protected_Types
• No_Recursion
• No_Reentrancy
• No_Relative_Delay (Ada 2005)
• No_Requeue_Statements (Ada 2005)
• No_Select_Statements (Ada 2005)
• No_Specific_Termination_Handlers (Ada 2005)
• No_Specification_of_Aspect (Ada 2012)
• No_Standard_Allocators_After_Elaboration (Ada 2012)
• No_Task_Allocators
• No_Task_Hierarchy
• No_Task_Termination (Ada 2005)
• No_Terminate_Alternatives
• No_Unchecked_Access
• No_Unchecked_Conversion
• No_Unchecked_Deallocation
• No_Use_of_Attribute (Ada 2012)
• No_Use_of_Pragma (Ada 2012)
• Simple_Barriers (Ada 2005)

List of implementation defined restrictions identifiers

The following restrictions are not available in all Ada compilers, only in those that had implemented them:

GNAT
This is an implementation defined restriction identifier of the GNAT compiler.

• No_Calendar (GNAT)
• No_Default_Initialization (GNAT)
• No_Direct_Boolean_Operators (GNAT)
• No_Dispatching_Calls (GNAT)
• No_Elaboration_Code (GNAT)
• No_Enumeration_Maps (GNAT)
• No_Entry_Calls_In_Elaboration_Code (GNAT)
• No_Entry_Queue (GNAT)
• No_Exception_Handlers (GNAT)
• No_Exception_Propagation (GNAT)
• No_Exception_Registration, previously named 'No_Exception_Streams' (GNAT)
• No_Implementation_Restrictions (GNAT)
• No_Implicit_Aliasing (GNAT)
• No_Implicit_Conditionals (GNAT)
• No_Implicit_Dynamic_Code (GNAT)
• No_Implicit_Loops (GNAT)
• No_Initialize_Scalars (GNAT)
• No_Secondary_Stack (GNAT)
• No_Select_Statements (GNAT)
• No_Standard_Storage_Pools (GNAT)
• No_Streams (GNAT)
• No_Task_Attributes_Package (GNAT)
• No_Tasking (GNAT)
• No_Wide_Characters (GNAT)
• SPARK (GNAT)
• Static_Priorities (GNAT)
• Static_Storage_Size (GNAT)

"Hello, world!" with restrictions

The following sample demonstrates the use of pragma Restrictions. Note that on Windows, Linux and macOS the given restrictions won't change the generated code.

File: hello_world_restricted.adb, Crate: pragmas_restrictions (view, plain text, download with Alire, Alire crate info)

(Image: Varnent, CC BY-SA 3.0)

Code:

pragma Restrictions (
Simple_Barriers,
No_Abort_Statements,
No_Asynchronous_Control,
No_Calendar,
No_Delay,
No_Dynamic_Attachment,
No_Dynamic_Priorities,
No_Enumeration_Maps,
No_Entry_Calls_In_Elaboration_Code,
No_Entry_Queue,
No_Exception_Registration,
No_Initialize_Scalars,
No_Local_Protected_Objects,
No_Protected_Type_Allocators,
No_Protected_Types,
No_Relative_Delay,
No_Requeue_Statements,
No_Select_Statements,
No_Streams,
No_Task_Allocators,
No_Task_Attributes_Package,
No_Task_Hierarchy,
No_Task_Termination,
No_Tasking,
No_Terminate_Alternatives,
No_Wide_Characters,
Static_Priorities,
Static_Storage_Size,
Immediate_Reclamation,
No_Implementation_Restrictions,
Max_Protected_Entries => 0,
Max_Protected_Entries => 0,
Max_Select_Alternatives => 0,
Max_Task_Entries => 0,
Max_Tasks => 0,
Max_Asynchronous_Select_Nesting => 0);

with Ada.Text_IO;

procedure Hello_World_Restricted is
begin
Ada.Text_IO.Put_Line ("Hello World!");
Ada.Text_IO.New_Line;
Ada.Text_IO.Put_Line ("This is a program with restricted runtime.");
end Hello_World_Restricted;

Output:

>alr run hello_world_restricted
ⓘ Building pragmas_restrictions=1.0.1/pragmas_restrictions.gpr...
Compile
[Ada] hello_world_restricted.adb
Bind
[gprbind] hello_world_restricted.bexch
[Ada] hello_world_restricted.ali
Link
[link] hello_world_restricted.adb
✓ Build finished successfully in 0.83 seconds.
Hello World!

This is a program with restricted runtime.

See also

Wikibook

• Ada Programming
• Ada Programming/Pragmas

Ada Reference Manual

• 13.12 Pragma Restrictions (Annotated)
• D.7 Tasking Restrictions (Annotated)
• H.4 Safety and Security Restrictions (Annotated)

Ada Quality and Style Guide

• 10.7.2 Pragma Restrictions

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