GNAT Reference Manual: Implementation of Ada 2012 Features

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# 15. Implementation of Ada 2012 Features

This chapter contains a complete list of Ada 2012 features that have been implemented as of GNAT version 6.4. Generally, these features are only available if the ``-gnat12'` (Ada 2012 features enabled) flag is set or if the configuration pragma `Ada_2012` is used. However, new pragmas, attributes, and restrictions are unconditionally available, since the Ada 95 standard allows the addition of new pragmas, attributes, and restrictions (there are exceptions, which are documented in the individual descriptions), and also certain packages were made available in earlier versions of Ada.

An ISO date (YYYY-MM-DD) appears in parentheses on the description line. This date shows the implementation date of the feature. Any wavefront subsequent to this date will contain the indicated feature, as will any subsequent releases. A date of 0000-00-00 means that GNAT has always implemented the feature, or implemented it as soon as it appeared as a binding interpretation.

Each feature corresponds to an Ada Issue ("AI") approved by the Ada standardization group (ISO/IEC JTC1/SC22/WG9) for inclusion in Ada 2012. The features are ordered based on the relevant sections of the Ada Reference Manual ("RM"). When a given AI relates to multiple points in the RM, the earliest is used.

A complete description of the AIs may be found in www.ada-auth.org/ai05-summary.html.

- AI-0176 Quantified expressions (2010-09-29)

  Both universally and existentially quantified expressions are implemented. They use the new syntax for iterators proposed in AI05-139-2, as well as the standard Ada loop syntax.

  RM References: 1.01.04 (12) 2.09 (2/2) 4.04 (7) 4.05.09 (0)

- AI-0079 Allow other_format characters in source (2010-07-10)

  Wide characters in the unicode category other_format are now allowed in source programs between tokens, but not within a token such as an identifier.

  RM References: 2.01 (4/2) 2.02 (7)

- AI-0091 Do not allow other_format in identifiers (0000-00-00)

  Wide characters in the unicode category other_format are not permitted within an identifier, since this can be a security problem. The error message for this case has been improved to be more specific, but GNAT has never allowed such characters to appear in identifiers.

  RM References: 2.03 (3.1/2) 2.03 (4/2) 2.03 (5/2) 2.03 (5.1/2) 2.03 (5.2/2) 2.03 (5.3/2) 2.09 (2/2)

- AI-0100 Placement of pragmas (2010-07-01)

  This AI is an earlier version of AI-163. It simplifies the rules for legal placement of pragmas. In the case of lists that allow pragmas, if the list may have no elements, then the list may consist solely of pragmas.

  RM References: 2.08 (7)

- AI-0163 Pragmas in place of null (2010-07-01)

  A statement sequence may be composed entirely of pragmas. It is no longer necessary to add a dummy `null` statement to make the sequence legal.

  RM References: 2.08 (7) 2.08 (16)

- AI-0080 "View of" not needed if clear from context (0000-00-00)

  This is an editorial change only, described as non-testable in the AI.

  RM References: 3.01 (7)

- AI-0183 Aspect specifications (2010-08-16)

  Aspect specifications have been fully implemented except for pre and post- conditions, and type invariants, which have their own separate AI's. All forms of declarations listed in the AI are supported. The following is a list of the aspects supported (with GNAT implementation aspects marked)

  `Ada_2005` | -- GNAT
  `Ada_2012` | -- GNAT
  `Address` |
  `Alignment` |
  `Atomic` |
  `Atomic_Components` |
  `Bit_Order` |
  `Component_Size` |
  `Contract_Cases` | -- GNAT
  `Discard_Names` |
  `External_Tag` |
  `Favor_Top_Level` | -- GNAT
  `Inline` |
  `Inline_Always` | -- GNAT
  `Invariant` | -- GNAT
  `Machine_Radix` |
  `No_Return` |
  `Object_Size` | -- GNAT
  `Pack` |
  `Persistent_BSS` | -- GNAT
  `Post` |
  `Pre` |
  `Predicate` |
  `Preelaborable_Initialization` |
  `Pure_Function` | -- GNAT
  `Remote_Access_Type` | -- GNAT
  `Shared` | -- GNAT
  `Size` |
  `Storage_Pool` |
  `Storage_Size` |
  `Stream_Size` |
  `Suppress` |
  `Suppress_Debug_Info` | -- GNAT
  `Test_Case` | -- GNAT
  `Thread_Local_Storage` | -- GNAT
  `Type_Invariant` |
  `Unchecked_Union` |
  `Universal_Aliasing` | -- GNAT
  `Unmodified` | -- GNAT
  `Unreferenced` | -- GNAT
  `Unreferenced_Objects` | -- GNAT
  `Unsuppress` |
  `Value_Size` | -- GNAT
  `Volatile` |
  `Volatile_Components`
  `Warnings` | -- GNAT

  Note that for aspects with an expression, e.g. `Size`, the expression is treated like a default expression (visibility is analyzed at the point of occurrence of the aspect, but evaluation of the expression occurs at the freeze point of the entity involved).

  RM References: 3.02.01 (3) 3.02.02 (2) 3.03.01 (2/2) 3.08 (6) 3.09.03 (1.1/2) 6.01 (2/2) 6.07 (2/2) 9.05.02 (2/2) 7.01 (3) 7.03 (2) 7.03 (3) 9.01 (2/2) 9.01 (3/2) 9.04 (2/2) 9.04 (3/2) 9.05.02 (2/2) 11.01 (2) 12.01 (3) 12.03 (2/2) 12.04 (2/2) 12.05 (2) 12.06 (2.1/2) 12.06 (2.2/2) 12.07 (2) 13.01 (0.1/2) 13.03 (5/1) 13.03.01 (0)

- AI-0128 Inequality is a primitive operation (0000-00-00)

  If an equality operator ("=") is declared for a type, then the implicitly declared inequality operator ("/=") is a primitive operation of the type. This is the only reasonable interpretation, and is the one always implemented by GNAT, but the RM was not entirely clear in making this point.

  RM References: 3.02.03 (6) 6.06 (6)

- AI-0003 Qualified expressions as names (2010-07-11)

  In Ada 2012, a qualified expression is considered to be syntactically a name, meaning that constructs such as `A'(F(X)).B` are now legal. This is useful in disambiguating some cases of overloading.

  RM References: 3.03 (11) 3.03 (21) 4.01 (2) 4.04 (7) 4.07 (3) 5.04 (7)

- AI-0120 Constant instance of protected object (0000-00-00)

  This is an RM editorial change only. The section that lists objects that are constant failed to include the current instance of a protected object within a protected function. This has always been treated as a constant in GNAT.

  RM References: 3.03 (21)

- AI-0008 General access to constrained objects (0000-00-00)

  The wording in the RM implied that if you have a general access to a constrained object, it could be used to modify the discriminants. This was obviously not intended. `Constraint_Error` should be raised, and GNAT has always done so in this situation.

  RM References: 3.03 (23) 3.10.02 (26/2) 4.01 (9) 6.04.01 (17) 8.05.01 (5/2)

- AI-0093 Additional rules use immutably limited (0000-00-00)

  This is an editorial change only, to make more widespread use of the Ada 2012 "immutably limited".

  RM References: 3.03 (23.4/3)

- AI-0096 Deriving from formal private types (2010-07-20)

  In general it is illegal for a type derived from a formal limited type to be nonlimited. This AI makes an exception to this rule: derivation is legal if it appears in the private part of the generic, and the formal type is not tagged. If the type is tagged, the legality check must be applied to the private part of the package.

  RM References: 3.04 (5.1/2) 6.02 (7)

- AI-0181 Soft hyphen is a non-graphic character (2010-07-23)

  From Ada 2005 on, soft hyphen is considered a non-graphic character, which means that it has a special name (`SOFT_HYPHEN`) in conjunction with the `Image` and `Value` attributes for the character types. Strictly speaking this is an inconsistency with Ada 95, but in practice the use of these attributes is so obscure that it will not cause problems.

  RM References: 3.05.02 (2/2) A.01 (35/2) A.03.03 (21)

- AI-0182 Additional forms for `Character'Value` (0000-00-00)

  This AI allows `Character'Value` to accept the string `'?'` where `?` is any character including non-graphic control characters. GNAT has always accepted such strings. It also allows strings such as `HEX_00000041` to be accepted, but GNAT does not take advantage of this permission and raises `Constraint_Error`, as is certainly still permitted.

  RM References: 3.05 (56/2)

- AI-0214 Defaulted discriminants for limited tagged (2010-10-01)

  Ada 2012 relaxes the restriction that forbids discriminants of tagged types to have default expressions by allowing them when the type is limited. It is often useful to define a default value for a discriminant even though it can't be changed by assignment.

  RM References: 3.07 (9.1/2) 3.07.02 (3)

- AI-0102 Some implicit conversions are illegal (0000-00-00)

  It is illegal to assign an anonymous access constant to an anonymous access variable. The RM did not have a clear rule to prevent this, but GNAT has always generated an error for this usage.

  RM References: 3.07 (16) 3.07.01 (9) 6.04.01 (6) 8.06 (27/2)

- AI-0158 Generalizing membership tests (2010-09-16)

  This AI extends the syntax of membership tests to simplify complex conditions that can be expressed as membership in a subset of values of any type. It introduces syntax for a list of expressions that may be used in loop contexts as well.

  RM References: 3.08.01 (5) 4.04 (3) 4.05.02 (3) 4.05.02 (5) 4.05.02 (27)

- AI-0173 Testing if tags represent abstract types (2010-07-03)

  The function `Ada.Tags.Type_Is_Abstract` returns `True` if invoked with the tag of an abstract type, and `False` otherwise.

  RM References: 3.09 (7.4/2) 3.09 (12.4/2)

- AI-0076 function with controlling result (0000-00-00)

  This is an editorial change only. The RM defines calls with controlling results, but uses the term "function with controlling result" without an explicit definition.

  RM References: 3.09.02 (2/2)

- AI-0126 Dispatching with no declared operation (0000-00-00)

  This AI clarifies dispatching rules, and simply confirms that dispatching executes the operation of the parent type when there is no explicitly or implicitly declared operation for the descendant type. This has always been the case in all versions of GNAT.

  RM References: 3.09.02 (20/2) 3.09.02 (20.1/2) 3.09.02 (20.2/2)

- AI-0097 Treatment of abstract null extension (2010-07-19)

  The RM as written implied that in some cases it was possible to create an object of an abstract type, by having an abstract extension inherit a non- abstract constructor from its parent type. This mistake has been corrected in GNAT and in the RM, and this construct is now illegal.

  RM References: 3.09.03 (4/2)

- AI-0203 Extended return cannot be abstract (0000-00-00)

  A return_subtype_indication cannot denote an abstract subtype. GNAT has never permitted such usage.

  RM References: 3.09.03 (8/3)

- AI-0198 Inheriting abstract operators (0000-00-00)

  This AI resolves a conflict between two rules involving inherited abstract operations and predefined operators. If a derived numeric type inherits an abstract operator, it overrides the predefined one. This interpretation was always the one implemented in GNAT.

  RM References: 3.09.03 (4/3)

- AI-0073 Functions returning abstract types (2010-07-10)

  This AI covers a number of issues regarding returning abstract types. In particular generic functions cannot have abstract result types or access result types designated an abstract type. There are some other cases which are detailed in the AI. Note that this binding interpretation has not been retrofitted to operate before Ada 2012 mode, since it caused a significant number of regressions.

  RM References: 3.09.03 (8) 3.09.03 (10) 6.05 (8/2)

- AI-0070 Elaboration of interface types (0000-00-00)

  This is an editorial change only, there are no testable consequences short of checking for the absence of generated code for an interface declaration.

  RM References: 3.09.04 (18/2)

- AI-0208 Characteristics of incomplete views (0000-00-00)

  The wording in the Ada 2005 RM concerning characteristics of incomplete views was incorrect and implied that some programs intended to be legal were now illegal. GNAT had never considered such programs illegal, so it has always implemented the intent of this AI.

  RM References: 3.10.01 (2.4/2) 3.10.01 (2.6/2)

- AI-0162 Incomplete type completed by partial view (2010-09-15)

  Incomplete types are made more useful by allowing them to be completed by private types and private extensions.

  RM References: 3.10.01 (2.5/2) 3.10.01 (2.6/2) 3.10.01 (3) 3.10.01 (4/2)

- AI-0098 Anonymous subprogram access restrictions (0000-00-00)

  An unintentional omission in the RM implied some inconsistent restrictions on the use of anonymous access to subprogram values. These restrictions were not intentional, and have never been enforced by GNAT.

  RM References: 3.10.01 (6) 3.10.01 (9.2/2)

- AI-0199 Aggregate with anonymous access components (2010-07-14)

  A choice list in a record aggregate can include several components of (distinct) anonymous access types as long as they have matching designated subtypes.

  RM References: 4.03.01 (16)

- AI-0220 Needed components for aggregates (0000-00-00)

  This AI addresses a wording problem in the RM that appears to permit some complex cases of aggregates with non-static discriminants. GNAT has always implemented the intended semantics.

  RM References: 4.03.01 (17)

- AI-0147 Conditional expressions (2009-03-29)

  Conditional expressions are permitted. The form of such an expression is:

          (if expr then expr {elsif expr then expr} [else expr])

  The parentheses can be omitted in contexts where parentheses are present anyway, such as subprogram arguments and pragma arguments. If the else clause is omitted, else True is assumed; thus `(if A then B)` is a way to conveniently represent (A implies B) in standard logic.

  RM References: 4.03.03 (15) 4.04 (1) 4.04 (7) 4.05.07 (0) 4.07 (2) 4.07 (3) 4.09 (12) 4.09 (33) 5.03 (3) 5.03 (4) 7.05 (2.1/2)

- AI-0037 Out-of-range box associations in aggregate (0000-00-00)

  This AI confirms that an association of the form `Indx => <>` in an array aggregate must raise `Constraint_Error` if `Indx` is out of range. The RM specified a range check on other associations, but not when the value of the association was defaulted. GNAT has always inserted a constraint check on the index value.

  RM References: 4.03.03 (29)

- AI-0123 Composability of equality (2010-04-13)

  Equality of untagged record composes, so that the predefined equality for a composite type that includes a component of some untagged record type `R` uses the equality operation of `R` (which may be user-defined or predefined). This makes the behavior of untagged records identical to that of tagged types in this respect.

  This change is an incompatibility with previous versions of Ada, but it corrects a non-uniformity that was often a source of confusion. Analysis of a large number of industrial programs indicates that in those rare cases where a composite type had an untagged record component with a user-defined equality, either there was no use of the composite equality, or else the code expected the same composability as for tagged types, and thus had a bug that would be fixed by this change.

  RM References: 4.05.02 (9.7/2) 4.05.02 (14) 4.05.02 (15) 4.05.02 (24) 8.05.04 (8)

- AI-0088 The value of exponentiation (0000-00-00)

  This AI clarifies the equivalence rule given for the dynamic semantics of exponentiation: the value of the operation can be obtained by repeated multiplication, but the operation can be implemented otherwise (for example using the familiar divide-by-two-and-square algorithm, even if this is less accurate), and does not imply repeated reads of a volatile base.

  RM References: 4.05.06 (11)

- AI-0188 Case expressions (2010-01-09)

  Case expressions are permitted. This allows use of constructs such as:

        X := (case Y is when 1 => 2, when 2 => 3, when others => 31)

  RM References: 4.05.07 (0) 4.05.08 (0) 4.09 (12) 4.09 (33)

- AI-0104 Null exclusion and uninitialized allocator (2010-07-15)

  The assignment `Ptr := new not null Some_Ptr;` will raise `Constraint_Error` because the default value of the allocated object is null. This useless construct is illegal in Ada 2012.

  RM References: 4.08 (2)

- AI-0157 Allocation/Deallocation from empty pool (2010-07-11)

  Allocation and Deallocation from an empty storage pool (i.e. allocation or deallocation of a pointer for which a static storage size clause of zero has been given) is now illegal and is detected as such. GNAT previously gave a warning but not an error.

  RM References: 4.08 (5.3/2) 13.11.02 (4) 13.11.02 (17)

- AI-0179 Statement not required after label (2010-04-10)

  It is not necessary to have a statement following a label, so a label can appear at the end of a statement sequence without the need for putting a null statement afterwards, but it is not allowable to have only labels and no real statements in a statement sequence.

  RM References: 5.01 (2)

- AI-139-2 Syntactic sugar for iterators (2010-09-29)

  The new syntax for iterating over arrays and containers is now implemented. Iteration over containers is for now limited to read-only iterators. Only default iterators are supported, with the syntax: `for Elem of C`.

  RM References: 5.05

- AI-0134 Profiles must match for full conformance (0000-00-00)

  For full conformance, the profiles of anonymous-access-to-subprogram parameters must match. GNAT has always enforced this rule.

  RM References: 6.03.01 (18)

- AI-0207 Mode conformance and access constant (0000-00-00)

  This AI confirms that access_to_constant indication must match for mode conformance. This was implemented in GNAT when the qualifier was originally introduced in Ada 2005.

  RM References: 6.03.01 (16/2)

- AI-0046 Null exclusion match for full conformance (2010-07-17)

  For full conformance, in the case of access parameters, the null exclusion must match (either both or neither must have `not null`).

  RM References: 6.03.02 (18)

- AI-0118 The association of parameter associations (0000-00-00)

  This AI clarifies the rules for named associations in subprogram calls and generic instantiations. The rules have been in place since Ada 83.

  RM References: 6.04.01 (2) 12.03 (9)

- AI-0196 Null exclusion tests for out parameters (0000-00-00)

  Null exclusion checks are not made for `out` parameters when evaluating the actual parameters. GNAT has never generated these checks.

  RM References: 6.04.01 (13)

- AI-0015 Constant return objects (0000-00-00)

  The return object declared in an extended_return_statement may be declared constant. This was always intended, and GNAT has always allowed it.

  RM References: 6.05 (2.1/2) 3.03 (10/2) 3.03 (21) 6.05 (5/2) 6.05 (5.7/2)

- AI-0032 Extended return for class-wide functions (0000-00-00)

  If a function returns a class-wide type, the object of an extended return statement can be declared with a specific type that is covered by the class- wide type. This has been implemented in GNAT since the introduction of extended returns. Note AI-0103 complements this AI by imposing matching rules for constrained return types.

  RM References: 6.05 (5.2/2) 6.05 (5.3/2) 6.05 (5.6/2) 6.05 (5.8/2) 6.05 (8/2)

- AI-0103 Static matching for extended return (2010-07-23)

  If the return subtype of a function is an elementary type or a constrained type, the subtype indication in an extended return statement must match statically this return subtype.

  RM References: 6.05 (5.2/2)

- AI-0058 Abnormal completion of an extended return (0000-00-00)

  The RM had some incorrect wording implying wrong treatment of abnormal completion in an extended return. GNAT has always implemented the intended correct semantics as described by this AI.

  RM References: 6.05 (22/2)

- AI-0050 Raising Constraint_Error early for function call (0000-00-00)

  The implementation permissions for raising `Constraint_Error` early on a function call when it was clear an exception would be raised were over-permissive and allowed mishandling of discriminants in some cases. GNAT did not take advantage of these incorrect permissions in any case.

  RM References: 6.05 (24/2)

- AI-0125 Nonoverridable operations of an ancestor (2010-09-28)

  In Ada 2012, the declaration of a primitive operation of a type extension or private extension can also override an inherited primitive that is not visible at the point of this declaration.

  RM References: 7.03.01 (6) 8.03 (23) 8.03.01 (5/2) 8.03.01 (6/2)

- AI-0062 Null exclusions and deferred constants (0000-00-00)

  A full constant may have a null exclusion even if its associated deferred constant does not. GNAT has always allowed this.

  RM References: 7.04 (6/2) 7.04 (7.1/2)

- AI-0178 Incomplete views are limited (0000-00-00)

  This AI clarifies the role of incomplete views and plugs an omission in the RM. GNAT always correctly restricted the use of incomplete views and types.

  RM References: 7.05 (3/2) 7.05 (6/2)

- AI-0087 Actual for formal nonlimited derived type (2010-07-15)

  The actual for a formal nonlimited derived type cannot be limited. In particular, a formal derived type that extends a limited interface but which is not explicitly limited cannot be instantiated with a limited type.

  RM References: 7.05 (5/2) 12.05.01 (5.1/2)

- AI-0099 Tag determines whether finalization needed (0000-00-00)

  This AI clarifies that "needs finalization" is part of dynamic semantics, and therefore depends on the run-time characteristics of an object (i.e. its tag) and not on its nominal type. As the AI indicates: "we do not expect this to affect any implementation".

  RM References: 7.06.01 (6) 7.06.01 (7) 7.06.01 (8) 7.06.01 (9/2)

- AI-0064 Redundant finalization rule (0000-00-00)

  This is an editorial change only. The intended behavior is already checked by an existing ACATS test, which GNAT has always executed correctly.

  RM References: 7.06.01 (17.1/1)

- AI-0026 Missing rules for Unchecked_Union (2010-07-07)

  Record representation clauses concerning Unchecked_Union types cannot mention the discriminant of the type. The type of a component declared in the variant part of an Unchecked_Union cannot be controlled, have controlled components, nor have protected or task parts. If an Unchecked_Union type is declared within the body of a generic unit or its descendants, then the type of a component declared in the variant part cannot be a formal private type or a formal private extension declared within the same generic unit.

  RM References: 7.06 (9.4/2) B.03.03 (9/2) B.03.03 (10/2)

- AI-0205 Extended return declares visible name (0000-00-00)

  This AI corrects a simple omission in the RM. Return objects have always been visible within an extended return statement.

  RM References: 8.03 (17)

- AI-0042 Overriding versus implemented-by (0000-00-00)

  This AI fixes a wording gap in the RM. An operation of a synchronized interface can be implemented by a protected or task entry, but the abstract operation is not being overridden in the usual sense, and it must be stated separately that this implementation is legal. This has always been the case in GNAT.

  RM References: 9.01 (9.2/2) 9.04 (11.1/2)

- AI-0030 Requeue on synchronized interfaces (2010-07-19)

  Requeue is permitted to a protected, synchronized or task interface primitive providing it is known that the overriding operation is an entry. Otherwise the requeue statement has the same effect as a procedure call. Use of pragma `Implemented` provides a way to impose a static requirement on the overriding operation by adhering to one of the implementation kinds: entry, protected procedure or any of the above.

  RM References: 9.05 (9) 9.05.04 (2) 9.05.04 (3) 9.05.04 (5) 9.05.04 (6) 9.05.04 (7) 9.05.04 (12)

- AI-0201 Independence of atomic object components (2010-07-22)

  If an Atomic object has a pragma `Pack` or a `Component_Size` attribute, then individual components may not be addressable by independent tasks. However, if the representation clause has no effect (is confirming), then independence is not compromised. Furthermore, in GNAT, specification of other appropriately addressable component sizes (e.g. 16 for 8-bit characters) also preserves independence. GNAT now gives very clear warnings both for the declaration of such a type, and for any assignment to its components.

  RM References: 9.10 (1/3) C.06 (22/2) C.06 (23/2)

- AI-0009 Pragma Independent[_Components] (2010-07-23)

  This AI introduces the new pragmas `Independent` and `Independent_Components`, which control guaranteeing independence of access to objects and components. The AI also requires independence not unaffected by confirming rep clauses.

  RM References: 9.10 (1) 13.01 (15/1) 13.02 (9) 13.03 (13) C.06 (2) C.06 (4) C.06 (6) C.06 (9) C.06 (13) C.06 (14)

- AI-0072 Task signalling using 'Terminated (0000-00-00)

  This AI clarifies that task signalling for reading `'Terminated` only occurs if the result is True. GNAT semantics has always been consistent with this notion of task signalling.

  RM References: 9.10 (6.1/1)

- AI-0108 Limited incomplete view and discriminants (0000-00-00)

  This AI confirms that an incomplete type from a limited view does not have discriminants. This has always been the case in GNAT.

  RM References: 10.01.01 (12.3/2)

- AI-0129 Limited views and incomplete types (0000-00-00)

  This AI clarifies the description of limited views: a limited view of a package includes only one view of a type that has an incomplete declaration and a full declaration (there is no possible ambiguity in a client package). This AI also fixes an omission: a nested package in the private part has no limited view. GNAT always implemented this correctly.

  RM References: 10.01.01 (12.2/2) 10.01.01 (12.3/2)

- AI-0077 Limited withs and scope of declarations (0000-00-00)

  This AI clarifies that a declaration does not include a context clause, and confirms that it is illegal to have a context in which both a limited and a nonlimited view of a package are accessible. Such double visibility was always rejected by GNAT.

  RM References: 10.01.02 (12/2) 10.01.02 (21/2) 10.01.02 (22/2)

- AI-0122 Private with and children of generics (0000-00-00)

  This AI clarifies the visibility of private children of generic units within instantiations of a parent. GNAT has always handled this correctly.

  RM References: 10.01.02 (12/2)

- AI-0040 Limited with clauses on descendant (0000-00-00)

  This AI confirms that a limited with clause in a child unit cannot name an ancestor of the unit. This has always been checked in GNAT.

  RM References: 10.01.02 (20/2)

- AI-0132 Placement of library unit pragmas (0000-00-00)

  This AI fills a gap in the description of library unit pragmas. The pragma clearly must apply to a library unit, even if it does not carry the name of the enclosing unit. GNAT has always enforced the required check.

  RM References: 10.01.05 (7)

- AI-0034 Categorization of limited views (0000-00-00)

  The RM makes certain limited with clauses illegal because of categorization considerations, when the corresponding normal with would be legal. This is not intended, and GNAT has always implemented the recommended behavior.

  RM References: 10.02.01 (11/1) 10.02.01 (17/2)

- AI-0035 Inconsistencies with Pure units (0000-00-00)

  This AI remedies some inconsistencies in the legality rules for Pure units. Derived access types are legal in a pure unit (on the assumption that the rule for a zero storage pool size has been enforced on the ancestor type). The rules are enforced in generic instances and in subunits. GNAT has always implemented the recommended behavior.

  RM References: 10.02.01 (15.1/2) 10.02.01 (15.4/2) 10.02.01 (15.5/2) 10.02.01 (17/2)

- AI-0219 Pure permissions and limited parameters (2010-05-25)

  This AI refines the rules for the cases with limited parameters which do not allow the implementations to omit "redundant". GNAT now properly conforms to the requirements of this binding interpretation.

  RM References: 10.02.01 (18/2)

- AI-0043 Rules about raising exceptions (0000-00-00)

  This AI covers various omissions in the RM regarding the raising of exceptions. GNAT has always implemented the intended semantics.

  RM References: 11.04.01 (10.1/2) 11 (2)

- AI-0200 Mismatches in formal package declarations (0000-00-00)

  This AI plugs a gap in the RM which appeared to allow some obviously intended illegal instantiations. GNAT has never allowed these instantiations.

  RM References: 12.07 (16)

- AI-0112 Detection of duplicate pragmas (2010-07-24)

  This AI concerns giving names to various representation aspects, but the practical effect is simply to make the use of duplicate `Atomic`[`_Components`], `Volatile`[`_Components`] and `Independent`[`_Components`] pragmas illegal, and GNAT now performs this required check.

  RM References: 13.01 (8)

- AI-0106 No representation pragmas on generic formals (0000-00-00)

  The RM appeared to allow representation pragmas on generic formal parameters, but this was not intended, and GNAT has never permitted this usage.

  RM References: 13.01 (9.1/1)

- AI-0012 Pack/Component_Size for aliased/atomic (2010-07-15)

  It is now illegal to give an inappropriate component size or a pragma `Pack` that attempts to change the component size in the case of atomic or aliased components. Previously GNAT ignored such an attempt with a warning.

  RM References: 13.02 (6.1/2) 13.02 (7) C.06 (10) C.06 (11) C.06 (21)

- AI-0039 Stream attributes cannot be dynamic (0000-00-00)

  The RM permitted the use of dynamic expressions (such as `ptr.all)` for stream attributes, but these were never useful and are now illegal. GNAT has always regarded such expressions as illegal.

  RM References: 13.03 (4) 13.03 (6) 13.13.02 (38/2)

- AI-0095 Address of intrinsic subprograms (0000-00-00)

  The prefix of `'Address` cannot statically denote a subprogram with convention `Intrinsic`. The use of the `Address` attribute raises `Program_Error` if the prefix denotes a subprogram with convention `Intrinsic`.

  RM References: 13.03 (11/1)

- AI-0116 Alignment of class-wide objects (0000-00-00)

  This AI requires that the alignment of a class-wide object be no greater than the alignment of any type in the class. GNAT has always followed this recommendation.

  RM References: 13.03 (29) 13.11 (16)

- AI-0146 Type invariants (2009-09-21)

  Type invariants may be specified for private types using the aspect notation. Aspect `Type_Invariant` may be specified for any private type, `Type_Invariant'Class` can only be specified for tagged types, and is inherited by any descendent of the tagged types. The invariant is a boolean expression that is tested for being true in the following situations: conversions to the private type, object declarations for the private type that are default initialized, and [in] out parameters and returned result on return from any primitive operation for the type that is visible to a client. GNAT defines the synonyms `Invariant` for `Type_Invariant` and `Invariant'Class` for `Type_Invariant'Class`.

  RM References: 13.03.03 (00)

- AI-0078 Relax Unchecked_Conversion alignment rules (0000-00-00)

  In Ada 2012, compilers are required to support unchecked conversion where the target alignment is a multiple of the source alignment. GNAT always supported this case (and indeed all cases of differing alignments, doing copies where required if the alignment was reduced).

  RM References: 13.09 (7)

- AI-0195 Invalid value handling is implementation defined (2010-07-03)

  The handling of invalid values is now designated to be implementation defined. This is a documentation change only, requiring Annex M in the GNAT Reference Manual to document this handling. In GNAT, checks for invalid values are made only when necessary to avoid erroneous behavior. Operations like assignments which cannot cause erroneous behavior ignore the possibility of invalid values and do not do a check. The date given above applies only to the documentation change, this behavior has always been implemented by GNAT.

  RM References: 13.09.01 (10)

- AI-0193 Alignment of allocators (2010-09-16)

  This AI introduces a new attribute `Max_Alignment_For_Allocation`, analogous to `Max_Size_In_Storage_Elements`, but for alignment instead of size.

  RM References: 13.11 (16) 13.11 (21) 13.11.01 (0) 13.11.01 (1) 13.11.01 (2) 13.11.01 (3)

- AI-0177 Parameterized expressions (2010-07-10)

  The new Ada 2012 notion of parameterized expressions is implemented. The form is:

        function specification is (expression)

  This is exactly equivalent to the corresponding function body that returns the expression, but it can appear in a package spec. Note that the expression must be parenthesized.

  RM References: 13.11.01 (3/2)

- AI-0033 Attach/Interrupt_Handler in generic (2010-07-24)

  Neither of these two pragmas may appear within a generic template, because the generic might be instantiated at other than the library level.

  RM References: 13.11.02 (16) C.03.01 (7/2) C.03.01 (8/2)

- AI-0161 Restriction No_Default_Stream_Attributes (2010-09-11)

  A new restriction `No_Default_Stream_Attributes` prevents the use of any of the default stream attributes for elementary types. If this restriction is in force, then it is necessary to provide explicit subprograms for any stream attributes used.

  RM References: 13.12.01 (4/2) 13.13.02 (40/2) 13.13.02 (52/2)

- AI-0194 Value of Stream_Size attribute (0000-00-00)

  The `Stream_Size` attribute returns the default number of bits in the stream representation of the given type. This value is not affected by the presence of stream subprogram attributes for the type. GNAT has always implemented this interpretation.

  RM References: 13.13.02 (1.2/2)

- AI-0109 Redundant check in S'Class'Input (0000-00-00)

  This AI is an editorial change only. It removes the need for a tag check that can never fail.

  RM References: 13.13.02 (34/2)

- AI-0007 Stream read and private scalar types (0000-00-00)

  The RM as written appeared to limit the possibilities of declaring read attribute procedures for private scalar types. This limitation was not intended, and has never been enforced by GNAT.

  RM References: 13.13.02 (50/2) 13.13.02 (51/2)

- AI-0065 Remote access types and external streaming (0000-00-00)

  This AI clarifies the fact that all remote access types support external streaming. This fixes an obvious oversight in the definition of the language, and GNAT always implemented the intended correct rules.

  RM References: 13.13.02 (52/2)

- AI-0019 Freezing of primitives for tagged types (0000-00-00)

  The RM suggests that primitive subprograms of a specific tagged type are frozen when the tagged type is frozen. This would be an incompatible change and is not intended. GNAT has never attempted this kind of freezing and its behavior is consistent with the recommendation of this AI.

  RM References: 13.14 (2) 13.14 (3/1) 13.14 (8.1/1) 13.14 (10) 13.14 (14) 13.14 (15.1/2)

- AI-0017 Freezing and incomplete types (0000-00-00)

  So-called "Taft-amendment types" (i.e., types that are completed in package bodies) are not frozen by the occurrence of bodies in the enclosing declarative part. GNAT always implemented this properly.

  RM References: 13.14 (3/1)

- AI-0060 Extended definition of remote access types (0000-00-00)

  This AI extends the definition of remote access types to include access to limited, synchronized, protected or task class-wide interface types. GNAT already implemented this extension.

  RM References: A (4) E.02.02 (9/1) E.02.02 (9.2/1) E.02.02 (14/2) E.02.02 (18)

- AI-0114 Classification of letters (0000-00-00)

  The code points 170 (`FEMININE ORDINAL INDICATOR`), 181 (`MICRO SIGN`), and 186 (`MASCULINE ORDINAL INDICATOR`) are technically considered lower case letters by Unicode. However, they are not allowed in identifiers, and they return `False` to `Ada.Characters.Handling.Is_Letter/Is_Lower`. This behavior is consistent with that defined in Ada 95.

  RM References: A.03.02 (59) A.04.06 (7)

- AI-0185 Ada.Wide_[Wide_]Characters.Handling (2010-07-06)

  Two new packages `Ada.Wide_[Wide_]Characters.Handling` provide classification functions for `Wide_Character` and `Wide_Wide_Character`, as well as providing case folding routines for `Wide_[Wide_]Character` and `Wide_[Wide_]String`.

  RM References: A.03.05 (0) A.03.06 (0)

- AI-0031 Add From parameter to Find_Token (2010-07-25)

  A new version of `Find_Token` is added to all relevant string packages, with an extra parameter `From`. Instead of starting at the first character of the string, the search for a matching Token starts at the character indexed by the value of `From`. These procedures are available in all versions of Ada but if used in versions earlier than Ada 2012 they will generate a warning that an Ada 2012 subprogram is being used.

  RM References: A.04.03 (16) A.04.03 (67) A.04.03 (68/1) A.04.04 (51) A.04.05 (46)

- AI-0056 Index on null string returns zero (0000-00-00)

  The wording in the Ada 2005 RM implied an incompatible handling of the `Index` functions, resulting in raising an exception instead of returning zero in some situations. This was not intended and has been corrected. GNAT always returned zero, and is thus consistent with this AI.

  RM References: A.04.03 (56.2/2) A.04.03 (58.5/2)

- AI-0137 String encoding package (2010-03-25)

  The packages `Ada.Strings.UTF_Encoding`, together with its child packages, `Conversions`, `Strings`, `Wide_Strings`, and `Wide_Wide_Strings` have been implemented. These packages (whose documentation can be found in the spec files ``a-stuten.ads'`, ``a-suenco.ads'`, ``a-suenst.ads'`, ``a-suewst.ads'`, ``a-suezst.ads'`) allow encoding and decoding of `String`, `Wide_String`, and `Wide_Wide_String` values using UTF coding schemes (including UTF-8, UTF-16LE, UTF-16BE, and UTF-16), as well as conversions between the different UTF encodings. With the exception of `Wide_Wide_Strings`, these packages are available in Ada 95 and Ada 2005 mode as well as Ada 2012 mode. The `Wide_Wide_Strings package` is available in Ada 2005 mode as well as Ada 2012 mode (but not in Ada 95 mode since it uses `Wide_Wide_Character`).

  RM References: A.04.11

- AI-0038 Minor errors in Text_IO (0000-00-00)

  These are minor errors in the description on three points. The intent on all these points has always been clear, and GNAT has always implemented the correct intended semantics.

  RM References: A.10.05 (37) A.10.07 (8/1) A.10.07 (10) A.10.07 (12) A.10.08 (10) A.10.08 (24)

- AI-0044 Restrictions on container instantiations (0000-00-00)

  This AI places restrictions on allowed instantiations of generic containers. These restrictions are not checked by the compiler, so there is nothing to change in the implementation. This affects only the RM documentation.

  RM References: A.18 (4/2) A.18.02 (231/2) A.18.03 (145/2) A.18.06 (56/2) A.18.08 (66/2) A.18.09 (79/2) A.18.26 (5/2) A.18.26 (9/2)

- AI-0127 Adding Locale Capabilities (2010-09-29)

  This package provides an interface for identifying the current locale.

  RM References: A.19 A.19.01 A.19.02 A.19.03 A.19.05 A.19.06 A.19.07 A.19.08 A.19.09 A.19.10 A.19.11 A.19.12 A.19.13

- AI-0002 Export C with unconstrained arrays (0000-00-00)

  The compiler is not required to support exporting an Ada subprogram with convention C if there are parameters or a return type of an unconstrained array type (such as `String`). GNAT allows such declarations but generates warnings. It is possible, but complicated, to write the corresponding C code and certainly such code would be specific to GNAT and non-portable.

  RM References: B.01 (17) B.03 (62) B.03 (71.1/2)

- AI-0216 No_Task_Hierarchy forbids local tasks (0000-00-00)

  It is clearly the intention that `No_Task_Hierarchy` is intended to forbid tasks declared locally within subprograms, or functions returning task objects, and that is the implementation that GNAT has always provided. However the language in the RM was not sufficiently clear on this point. Thus this is a documentation change in the RM only.

  RM References: D.07 (3/3)

- AI-0211 No_Relative_Delays forbids Set_Handler use (2010-07-09)

  The restriction `No_Relative_Delays` forbids any calls to the subprogram `Ada.Real_Time.Timing_Events.Set_Handler`.

  RM References: D.07 (5) D.07 (10/2) D.07 (10.4/2) D.07 (10.7/2)

- AI-0190 pragma Default_Storage_Pool (2010-09-15)

  This AI introduces a new pragma `Default_Storage_Pool`, which can be used to control storage pools globally. In particular, you can force every access type that is used for allocation (new) to have an explicit storage pool, or you can declare a pool globally to be used for all access types that lack an explicit one.

  RM References: D.07 (8)

- AI-0189 No_Allocators_After_Elaboration (2010-01-23)

  This AI introduces a new restriction `No_Allocators_After_Elaboration`, which says that no dynamic allocation will occur once elaboration is completed. In general this requires a run-time check, which is not required, and which GNAT does not attempt. But the static cases of allocators in a task body or in the body of the main program are detected and flagged at compile or bind time.

  RM References: D.07 (19.1/2) H.04 (23.3/2)

- AI-0171 Pragma CPU and Ravenscar Profile (2010-09-24)

  A new package `System.Multiprocessors` is added, together with the definition of pragma `CPU` for controlling task affinity. A new no dependence restriction, on `System.Multiprocessors.Dispatching_Domains`, is added to the Ravenscar profile.

  RM References: D.13.01 (4/2) D.16

- AI-0210 Correct Timing_Events metric (0000-00-00)

  This is a documentation only issue regarding wording of metric requirements, that does not affect the implementation of the compiler.

  RM References: D.15 (24/2)

- AI-0206 Remote types packages and preelaborate (2010-07-24)

  Remote types packages are now allowed to depend on preelaborated packages. This was formerly considered illegal.

  RM References: E.02.02 (6)

- AI-0152 Restriction No_Anonymous_Allocators (2010-09-08)

  Restriction `No_Anonymous_Allocators` prevents the use of allocators where the type of the returned value is an anonymous access type.

  RM References: H.04 (8/1)

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