- This clause defines restrictions that can be used with pragma Restrictions
(see 13.12); these facilitate the demonstration of
program correctness by allowing tailored versions of the run-time system.
- The following restrictions, the same as in D.7, apply
in this Annex: No_Task_Hierarchy, No_Abort_Statement, No_Implicit_Heap_Allocation,
Max_Task_Entries is 0, Max_Asynchronous_Select_Nesting is 0, and Max_Tasks
is 0. The last three restrictions are checked prior to program execution.
- The following additional restrictions apply in this Annex.
- Tasking-related restriction:
There are no declarations of protected types or protected
- Memory-management related restrictions:
There are no occurrences of an allocator.
Allocators are prohibited in subprograms, generic subprograms, tasks, and entry bodies; instantiations of generic
packages are also prohibited in these contexts.
Semantic dependence on Unchecked_Deallocation is not allowed.
Except for storage occupied by objects created by allocators
and not deallocated via unchecked deallocation, any storage
reserved at run time for an object is immediately reclaimed
when the object no longer exists.
Raise_statements and exception_handlers are not allowed. No
language-defined run-time checks are generated; however, a
run-time check performed automatically by the hardware is
Uses of predefined floating point types and operations, and
declarations of new floating point types, are not allowed.
Uses of predefined fixed point types and operations, and
declarations of new fixed point types, are not allowed.
Semantic dependence on the predefined generic Unchecked_Conversion is not allowed.
The declaration of access-to-subprogram types is not allowed.
The Unchecked_Access attribute is not allowed.
Occurrences of T'Class are not allowed, for any (tagged)
Semantic dependence on any of the library units
Sequential_IO, Direct_IO, Text_IO, Wide_Text_IO, or Stream_IO
is not allowed.
Delay_Statements and semantic dependence on package Calendar
are not allowed.
As part of the execution of a subprogram, the same subprogram
is not invoked.
During the execution of a subprogram by a task, no other task
invokes the same subprogram.
- If an implementation supports pragma Restrictions for a particular
argument, then except for the restrictions No_Unchecked_Deallocation, No_Unchecked_Conversion, No_Access_Subprograms, and No_Unchecked_Access, the
associated restriction applies to the run-time system.
- If a pragma Restrictions(No_Exceptions) is specified, the implementation
shall document the effects of all constructs where language-defined checks
are still performed automatically (for example, an overflow check performed
by the processor).
- Program execution is erroneous if pragma Restrictions(No_Exceptions) has
been specified and the conditions arise under which a generated
language-defined run-time check would fail.
- Program execution is erroneous if pragma Restrictions(No_Recursion) has
been specified and a subprogram is invoked as part of its own execution, or
if pragma Restrictions(No_Reentrancy) has been specified and during the
execution of a subprogram by a task, another task invokes the same
-- Email comments, additions, corrections, gripes, kudos, etc. to:
Magnus Kempe -- Magnus.Kempe@di.epfl.ch
Page last generated: 95-03-12