Annex A
(normative)
Predefined Language Environment
[
This Annex contains the specifications of library
units that shall be provided by every implementation. There are three
root library units: Ada, Interfaces, and System; other library units
are children of these:]
[
Standard — A.1
Ada — A.2
Assertions — 11.4.2
Asynchronous_Task_Control — D.11
Calendar — 9.6
Arithmetic — 9.6.1
Formatting — 9.6.1
Time_Zones — 9.6.1
Characters — A.3.1
Conversions — A.3.4
Handling — A.3.2
Latin_1 — A.3.3
Command_Line — A.15
Complex_Text_IO — G.1.3
Containers — A.18.1
Bounded_Doubly_Linked_Lists
— A.18.20
Bounded_Hashed_Maps — A.18.21
Bounded_Hashed_Sets — A.18.23
Bounded_Indefinite_Holders — A.18.32
Bounded_Multiway_Trees — A.18.25
Bounded_Ordered_Maps — A.18.22
Bounded_Ordered_Sets — A.18.24
Bounded_Priority_Queues — A.18.31
Bounded_Synchronized_Queues
— A.18.29
Bounded_Vectors — A.18.19
Doubly_Linked_Lists — A.18.3
Generic_Array_Sort — A.18.26
Generic_Constrained_Array_Sort
— A.18.26
Generic_Sort — A.18.26
Hashed_Maps — A.18.5
Hashed_Sets — A.18.8
Indefinite_Doubly_Linked_Lists
— A.18.12
Indefinite_Hashed_Maps — A.18.13
Indefinite_Hashed_Sets — A.18.15Standard (...continued)
Ada (...continued)
Containers (...continued)
Indefinite_Holders — A.18.18
Indefinite_Multiway_Trees — A.18.17
Indefinite_Ordered_Maps — A.18.14
Indefinite_Ordered_Sets — A.18.16
Indefinite_Vectors — A.18.11
Multiway_Trees — A.18.10
Ordered_Maps — A.18.6
Ordered_Sets — A.18.9
Synchronized_Queue_Interfaces
— A.18.27
Unbounded_Priority_Queues
— A.18.30
Unbounded_Synchronized_Queues
— A.18.28
Vectors — A.18.2
Decimal — F.2
Direct_IO — A.8.4
Directories — A.16
Hierarchical_File_Names — A.16.1
Information — A.16
Dispatching — D.2.1
EDF — D.2.6
Non_Preemptive — D.2.4
Round_Robin — D.2.5
Dynamic_Priorities — D.5.1
Environment_Variables — A.17
Exceptions — 11.4.1
Execution_Time — D.14
Group_Budgets — D.14.2
Interrupts — D.14.3
Timers — D.14.1
Finalization — 7.6
Float_Text_IO — A.10.9
Float_Wide_Text_IO — A.11
Float_Wide_Wide_Text_IO — A.11Standard (...continued)
Ada (...continued)
Integer_Text_IO — A.10.8
Integer_Wide_Text_IO — A.11
Integer_Wide_Wide_Text_IO — A.11
Interrupts — C.3.2
Names — C.3.2
IO_Exceptions — A.13
Iterator_Interfaces — 5.5.1
Locales — A.19 Numerics — A.5
Big_Numbers — A.5.5
Big_Integers — A.5.6
Big_Reals — A.5.7
Complex_Arrays — G.3.2
Complex_Elementary_Functions — G.1.2
Complex_Types — G.1.1
Discrete_Random — A.5.2
Elementary_Functions — A.5.1
Float_Random — A.5.2
Generic_Complex_Arrays — G.3.2
Generic_Complex_Elementary_Functions
— G.1.2
Generic_Complex_Types — G.1.1
Generic_Elementary_Functions — A.5.1
Generic_Real_Arrays — G.3.1
Real_Arrays — G.3.1
Real_Time — D.8
Timing_Events — D.15
Sequential_IO — A.8.1
Storage_IO — A.9
Streams — 13.13.1
Storage_Streams — 13.13.1
Bounded_FIFO_Streams — 13.13.1
FIFO_Streams — 13.13.1
Stream_IO — A.12.1
Strings — A.4.1
Bounded — A.4.4
Equal_Case_Insensitive — A.4.10
Hash — A.4.9
Hash_Case_Insensitive — A.4.9
Less_Case_Insensitive — A.4.10
Equal_Case_Insensitive — A.4.10
Fixed — A.4.3
Equal_Case_Insensitive — A.4.10
Hash — A.4.9
Hash_Case_Insensitive — A.4.9
Less_Case_Insensitive — A.4.10Standard (...continued)
Ada (...continued)
Strings (...continued)
Hash — A.4.9
Hash_Case_Insensitive — A.4.9
Less_Case_Insensitive — A.4.10
Maps — A.4.2
Constants — A.4.6
Text_Buffers — A.4.12
Bounded — A.4.12
Unbounded — A.4.12
Unbounded — A.4.5
Equal_Case_Insensitive — A.4.10
Hash — A.4.9
Hash_Case_Insensitive — A.4.9
Less_Case_Insensitive — A.4.10
UTF_Encoding — A.4.11
Conversions — A.4.11
Strings — A.4.11
Wide_Strings — A.4.11
Wide_Wide_Strings — A.4.11
Wide_Bounded — A.4.7
Wide_Equal_Case_Insensitive
— A.4.7
Wide_Hash — A.4.7
Wide_Hash_Case_Insensitive — A.4.7
Wide_Equal_Case_Insensitive — A.4.7
Wide_Fixed — A.4.7
Wide_Equal_Case_Insensitive
— A.4.7
Wide_Hash — A.4.7
Wide_Hash_Case_Insensitive — A.4.7
Wide_Hash — A.4.7
Wide_Hash_Case_Insensitive — A.4.7
Wide_Maps — A.4.7
Wide_Constants — A.4.7
Wide_Unbounded — A.4.7
Wide_Equal_Case_Insensitive
— A.4.7
Wide_Hash — A.4.7
Wide_Hash_Case_Insensitive — A.4.7
Wide_Wide_Bounded — A.4.8
Wide_Wide_Equal_Case_Insensitive
— A.4.8
Wide_Wide_Hash — A.4.8
Wide_Wide_Hash_Case_Insensitive
— A.4.8
Standard (...continued)
Ada (...continued)
Strings (...continued)
Wide_Wide_Equal_Case_Insensitive
— A.4.8
Wide_Wide_Fixed — A.4.8
Wide_Wide_Equal_Case_Insensitive
— A.4.8
Wide_Wide_Hash — A.4.8
Wide_Wide_Hash_Case_Insensitive
— A.4.8
Wide_Wide_Hash — A.4.8
Wide_Wide_Hash_Case_Insensitive
— A.4.8
Wide_Wide_Maps — A.4.8
Wide_Wide_Constants — A.4.8
Wide_Wide_Unbounded — A.4.8
Wide_Wide_Equal_Case_Insensitive
— A.4.8
Wide_Wide_Hash — A.4.8
Wide_Wide_Hash_Case_Insensitive
— A.4.8
Synchronous_Barriers — D.10.1
Synchronous_Task_Control — D.10
EDF — D.10
Tags — 3.9
Generic_Dispatching_Constructor — 3.9
Task_Attributes — C.7.2
Task_Identification — C.7.1
Task_Termination — C.7.3
Text_IO — A.10.1
Bounded_IO — A.10.11
Complex_IO — G.1.3
Editing — F.3.3
Text_Streams — A.12.2
Unbounded_IO — A.10.12
Unchecked_Conversion — 13.9
Unchecked_Deallocate_Subpool — 13.11.5
Unchecked_Deallocation — 13.11.2
Wide_Characters — A.3.1
Handling — A.3.5
Wide_Command_Line — A.15.1
Wide_Directories — A.16.2
Wide_Environment_Variables — A.17.1Standard (...continued)
Ada (...continued)
Wide_Text_IO — A.11
Complex_IO — G.1.4
Editing — F.3.4
Text_Streams — A.12.3
Wide_Bounded_IO — A.11
Wide_Unbounded_IO — A.11 Wide_Wide_Characters — A.3.1
Handling — A.3.6
Wide_Wide_Command_Line — A.15.1
Wide_Wide_Directories — A.16.2
Wide_Wide_Environment_Variables —
A.17.1
Wide_Wide_Text_IO — A.11
Complex_IO — G.1.5
Editing — F.3.5
Text_Streams — A.12.4
Wide_Wide_Bounded_IO — A.11
Wide_Wide_Unbounded_IO — A.11Discussion: In running text, we generally
leave out the “Ada.” when referring to a child of Ada.
Reason: We had no strict rule for which
of Ada, Interfaces, or System should be the parent of a given library
unit. However, we have tried to place as many things as possible under
Ada, except that interfacing is a separate category, and we have tried
to place library units whose use is highly nonportable under System.
Implementation Requirements
{
AI95-00434-01}
{
AI12-0052-1}
{
AI12-0114-1}
{
AI12-0200-1}
{
AI12-0439-1}
The implementation shall ensure that concurrent calls on any two (possibly
the same) language-defined subprograms perform as specified, so long
as all pairs of objects (one from each call) that are either denoted
by parameters that can be passed by reference, or are designated by parameters
of an access type, are nonoverlapping.
Ramification: {
AI12-0052-1}
{
AI12-0114-1}
So long as the parameters are disjoint, concurrent calls on the same
language-defined subprogram, and concurrent calls on two different language-defined
subprograms are required to work. But concurrent calls operating on overlapping
objects (be they of the same or different language-defined subprograms)
are
not required to work (being an erroneous use of shared variables)
unless both subprograms are required to pass the associated parameter
by-copy.
For example, simultaneous calls to Text_IO.Put
will work properly, so long as they are going to two different files.
On the other hand, simultaneous output to the same file constitutes erroneous
use of shared variables.
To be honest: Here, “language defined
subprogram” means a language defined library subprogram, a subprogram
declared in the visible part of a language defined library package, an
instance of a language defined generic library subprogram, or a subprogram
declared in the visible part of an instance of a language defined generic
library package.
Ramification: {
AI12-0052-1}
This rule applies to all language-defined subprograms, including those
defined in packages that manage some global state (like environment variables
or the current directory). Unless specified above, such subprograms need
to work when the explicit parameters are not overlapping; in particular,
the existence of the global state is not considered.
{
AI12-0052-1}
The rule implies that any data local to the private part or body of the
package (including global state as described above) has to be somehow
protected against simultaneous access.
{
AI12-0052-1}
{
AI12-0159-1}
For the purpose of determining whether concurrent calls on text input-output
subprograms are required to perform as specified above, when calling
a subprogram within Text_IO or its children that implicitly operates
on one of the default input-output files, the subprogram is considered
to have a parameter of Current_Input or Current_Output (as appropriate).
{
AI05-0048-1}
If a descendant of a language-defined tagged type is declared, the implementation
shall ensure that each inherited language-defined subprogram behaves
as described in this Reference Manual. In particular, overriding a language-defined
subprogram shall not alter the effect of any inherited language-defined
subprogram.
Reason: This means that internally the
implementation must not do redispatching unless it is required by the
Standard. So when we say that some subprogram Bar is equivalent to Foo,
overriding Foo for a derived type doesn't change the semantics of Bar,
and in particular it means that Bar may no longer be equivalent to Foo.
The word “equivalent” is always a bit of a lie anyway.
Implementation Permissions
The implementation may restrict the replacement of
language-defined compilation units. The implementation may restrict children
of language-defined library units (other than Standard).
Ramification: For example, the implementation
may say, “you cannot compile a library unit called System”
or “you cannot compile a child of package System” or “if
you compile a library unit called System, it has to be a package, and
it has to contain at least the following declarations: ...”.
Ramification: {
AI12-0112-1}
Implementations are of course allowed to make changes to the specifications
of language-defined units, so long as those changes are semantically
neutral (that is, no program could change legality or effect because
of the changes). In particular, an implementation can
with additional
units (especially implementation-defined units) so long as those units
do not change the elaboration of the language-defined unit.
Similarly, an implementation can add postconditions
to language-defined subprograms, so long as those postconditions always
evaluate to True. This is useful if the implementation can use those
postconditions for optimization.
Wording Changes from Ada 83
Many of Ada 83's language-defined library units
are now children of Ada or System. For upward compatibility, these are
renamed as root library units (see
J.1).
The order and lettering of the annexes has been
changed.
Wording Changes from Ada 95
Wording Changes from Ada 2005
{
AI05-0048-1}
Correction: Added wording to ban redispatching unless it is explicitly
required, in order to safeguard portability when overriding language-defined
routines.
{
AI05-0060-1}
{
AI05-0206-1}
Correction: Added a permission to omit pragma Remote_Types from
language-defined units if Annex E is not supported. This was later removed,
as a better method of supporting the reason is now available. Note that
this requires all implementations to provide minimal support for the
Remote_Types categorization even if Annex E is not supported; being unable
to compile language-defined units is not allowed.
Incompatibilities With Ada 2012
{
AI12-0005-1}
When a new entity
E is added to a package
P that is
used in client code,
use clause conflicts
are possible. Specifically, if
P is referenced in a
use_clause,
and an entity
F with the same defining identifier as
E
is defined in some other package that is also referenced in a
use_clause,
the user-defined entity
F may no longer be use-visible, resulting
in errors. This is an incompatibility when the new entity is added to
a language-defined package. Note that use clause conflicts are rare and
easily fixed by using an expanded name.
Wording Changes from Ada 2012
{
AI12-0052-1}
{
AI12-0114-1}
{
AI12-0159-1}
Corrigendum: The rules requiring concurrent access of language-defined
subprograms were expanded to include implicit Text_IO objects, overlapping
objects designated by parameters of an access type, and simultaneous
calls on different language-defined subprograms. While this might change
behavior of some programs, it would do so by eliminating erroneous execution,
so we don't consider this an inconsistency.
{
AI12-0200-1}
Correction: The rules requiring concurrent access of language-defined
subprograms were clarified further.
Ada 2005 and 2012 Editions sponsored in part by Ada-Europe
