@comment{ $Source: e:\\cvsroot/ARM/Source/interface.mss,v $ } @comment{ $Revision: 1.71 $ $Date: 2014/02/06 02:27:09 $ $Author: randy $ } @Part(interface, Root="ada.mss") @Comment{$Date: 2014/02/06 02:27:09 $} @LabeledNormativeAnnex{Interface to Other Languages} @begin{Intro} @Defn{interface to other languages} @Defn2{Term=[language], Sec=(interface to non-Ada)} @Defn{mixed-language programs} This Annex describes features for writing mixed-language programs. General interface support is presented first; then specific support for C, COBOL, and Fortran is defined, in terms of language interface packages for each of these languages. @begin{Ramification} This Annex is not a @lquotes@;Specialized Needs@rquotes@; annex. Every implementation must support all nonoptional features defined here (mainly the package Interfaces). @end{Ramification} @end{Intro} @begin{MetaRules} Ada should have strong support for mixed-language programming. @end{MetaRules} @begin{ImplReq} @ChgRef{Version=[3],Kind=[AddedNormal],ARef=[AI05-0229-1],ARef=[AI05-0262-1],ARef=[AI05-0299-1]} @ChgAdded{Version=[3],Text=[Support for interfacing to any foreign language is optional. However, an implementation shall not provide any optional aspect, attribute, library unit, or pragma having the same name as an aspect, attribute, library unit, or pragma (respectively) specified in the subclauses of this Annex unless the provided construct is either as specified in those subclauses or is more limited in capability than that required by those subclauses. A program that attempts to use an unsupported capability of this Annex shall either be identified by the implementation before run time or shall raise an exception at run time.]} @begin{Discussion} @ChgRef{Version=[3],Kind=[AddedNormal]} @ChgAdded{Version=[3],Text=[The intent is that the same rules apply for the optional parts of language interfacing as apply for Specialized Needs Annexes. See @RefSecNum{Conformity of an Implementation with the Standard} for a discussion of the purpose of these rules.]} @end{Discussion} @end{ImplReq} @begin{Extend83} @Defn{extensions to Ada 83} Much of the functionality in this Annex is new to Ada 95. @end{Extend83} @begin{DiffWord83} This Annex contains what used to be RM83-13.8. @end{DiffWord83} @begin{DiffWord2005} @ChgRef{Version=[3],Kind=[AddedNormal],ARef=[AI05-0262-1]} @ChgAdded{Version=[3],Text=[Moved the clarification that interfacing to foreign languages is optional and has the same restrictions as a Specialized Needs Annex here.]} @end{DiffWord2005} @LabeledRevisedClause{Version=[3],New=[Interfacing Aspects],Old=[Interfacing Pragmas]} @begin{Intro} @ChgRef{Version=[3],Kind=[Added],ARef=[AI05-0229-1]} @ChgAdded{Version=[3],Text=[An @i aspect is a representation aspect that is one of the aspects Import, Export, Link_Name, External_Name, or Convention.@Defn{interfacing aspect}@Defn2{Term=[aspect],Sec=[interfacing]}]} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1],ARef=[AI05-0269-1]} @Chg{Version=[3],New=[@AspectDefn{Import}Specifying the],Old=[A @nt{pragma}]} Import @Chg{Version=[3],New=[aspect to have the value True ],Old=[]}is used to import an entity defined in a foreign language into an Ada program, thus allowing a foreign-language subprogram to be called from Ada, or a foreign-language variable to be accessed from Ada. In contrast, @Chg{Version=[3],New=[@AspectDefn{Export}specifying the],Old=[a @nt{pragma}]} Export @Chg{Version=[3],New=[aspect to have the value True ],Old=[]}is used to export an Ada entity to a foreign language, thus allowing an Ada subprogram to be called from a foreign language, or an Ada object to be accessed from a foreign language. The@Chg{Version=[3],New=[],Old=[ @nt[pragma]s]} Import and Export@Chg{Version=[3],New=[ aspects],Old=[]} are intended primarily for objects and subprograms, although implementations are allowed to support other entities.@Chg{Version=[3],New=[ The Link_Name and External_Name aspects are used to specify the link name and external name, respectively, to be used to identify imported or exported entities in the external environment.@AspectDefn{Link_Name}@AspectDefn{External_Name} @PDefn2{Term=[representation aspect], Sec=(convention, calling convention)} @PDefn2{Term=[representation aspect], Sec=(import)} @PDefn2{Term=[representation aspect], Sec=(export)} @PDefn2{Term=[representation aspect], Sec=(external_name)} @PDefn2{Term=[representation aspect], Sec=(link_name)}],Old=[]} @ChgAspectDesc{Version=[3],Kind=[AddedNormal],Aspect=[Import], Text=[@ChgAdded{Version=[3],Text=[Entity is imported from another language.]}]} @ChgAspectDesc{Version=[3],Kind=[AddedNormal],Aspect=[Export], Text=[@ChgAdded{Version=[3],Text=[Entity is exported to another language.]}]} @ChgAspectDesc{Version=[3],Kind=[AddedNormal],Aspect=[External_Name], Text=[@ChgAdded{Version=[3],Text=[Name used to identify an imported or exported entity.]}]} @ChgAspectDesc{Version=[3],Kind=[AddedNormal],Aspect=[Link_Name], Text=[@ChgAdded{Version=[3],Text=[Linker symbol used to identify an imported or exported entity.]}]} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @Chg{Version=[3],New=[The],Old=[A @nt{pragma}]} Convention @Chg{Version=[3],New=[aspect@AspectDefn{Convention} ],Old=[]}is used to @Chg{Version=[3],New=[indicate],Old=[specify]} that an Ada entity should use the conventions of another language. It is intended primarily for types and @lquotes@;callback@rquotes@; subprograms. For example, @lquotes@;@Chg{Version=[3],New=[@key{with}],Old=[@key{pragma}]} Convention@Chg{Version=[3],New=[ => ],Old=[(]}Fortran@Chg{Version=[3],New=[],Old=[, Matrix);]}@rquotes@; @Chg{Version=[3],New=[on the declaration of an array type Matrix ],Old=[]}implies that Matrix should be represented according to the conventions of the supported Fortran implementation, namely column-major order. @ChgAspectDesc{Version=[3],Kind=[AddedNormal],Aspect=[Convention], Text=[@ChgAdded{Version=[3],Text=[Calling convention or other convention used for interfacing to other languages.]}]} A @nt{pragma} Linker_Options is used to specify the system linker parameters needed when a given compilation unit is included in a partition. @end{Intro} @begin{Syntax} @begin{SyntaxText} @Leading@ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @Chg{Version=[3],New=[The form of a],Old=[@RootDefn{interfacing pragma} @PDefn2{Term=[interfacing pragma], Sec=(Import)} @PDefn2{Term=[pragma, interfacing], Sec=(Import)} @PDefn2{Term=[interfacing pragma], Sec=(Export)} @PDefn2{Term=[pragma, interfacing], Sec=(Export)} @PDefn2{Term=[interfacing pragma], Sec=(Convention)} @PDefn2{Term=[pragma, interfacing], Sec=(Convention)} @PDefn2{Term=[pragma, interfacing], Sec=(Linker_Options)} An @i{interfacing pragma} is a representation @nt[pragma] that is one of the @nt{pragma}s Import, Export, or Convention. Their forms, together with that of the related]} @nt[pragma] Linker_Options@Chg{Version=[3],New=[ is],Old=[, are]} as follows: @end{SyntaxText} @begin{NotIso} @ChgAdded{Version=[3],Noprefix=[T],Noparanum=[T],Text=[@Shrink{@i}]}@Comment{This message should be deleted if the paragraphs are ever renumbered.} @end{NotIso} @ChgRef{Version=[3],Kind=[DeletedNoDelMsg],ARef=[AI05-0229-1]} @DeletedPragmaSyn`Version=[3],InitialVersion=[0],@ChgDeleted{Version=[3], Text="@key{pragma} @prag(Import)(@* @ @ @ @ @ [Convention =>] @SynI{convention_}@Syn2{identifier}, [Entity =>] @Syn2{local_name}@* @ @ [, [External_Name =>] @SynI{string_}@Syn2{expression}] [, [Link_Name =>] @SynI{string_}@Syn2{expression}]);"}' @ChgRef{Version=[3],Kind=[DeletedNoDelMsg],ARef=[AI05-0229-1]} @DeletedPragmaSyn`Version=[3],InitialVersion=[0],@ChgDeleted{Version=[3], Text="@key{pragma} @prag(Export)(@* @ @ @ @ @ [Convention =>] @SynI{convention_}@Syn2{identifier}, [Entity =>] @Syn2{local_name}@* @ @ [, [External_Name =>] @SynI{string_}@Syn2{expression}] [, [Link_Name =>] @SynI{string_}@Syn2{expression}]);"}' @ChgRef{Version=[3],Kind=[DeletedNoDelMsg],ARef=[AI05-0229-1]} @DeletedPragmaSyn`Version=[3],InitialVersion=[0],@ChgDeleted{Version=[3], Text="@key{pragma} @prag(Convention)([Convention =>] @SynI{convention_}@Syn2{identifier},[Entity =>] @Syn2{local_name});"}' @PragmaSyn`@key{pragma} @prag(Linker_Options)(@SynI{string_}@Syn2{expression});' @begin{SyntaxText} A @nt[pragma] Linker_Options is allowed only at the place of a @nt[declarative_item]. @ChgRef{Version=[1],Kind=[Added],Ref=[8652/0058],ARef=[AI95-00036-01]} @ChgRef{Version=[3],Kind=[DeletedAdded],ARef=[AI05-0229-1]} @ChgAdded{Version=[1],Text=[@Chg{Version=[3],New=[],Old=[For @nt{pragma}s Import and Export, the argument for Link_Name shall not be given without the @i{pragma_@!argument_}@!@nt{identifier} unless the argument for External_Name is given.]}]} @end{SyntaxText} @end{Syntax} @begin{Resolution} @ChgRef{Version=[3],Kind=[Added],ARef=[AI05-0229-1]} @ChgAdded{Version=[3],Text=[The Import and Export aspects are of type Boolean.]} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} The @Chg{Version=[3],New=[Link_Name and External_Name aspects are of],Old=[expected]} type @Chg{Version=[3],New=[],Old=[for a @SynI{string_}@Syn2{expression}@PDefn2{Term=[expected type], Sec=(link name)} in an interfacing pragma or in pragma Linker_Options is ]}String. @begin{Ramification} @ChgRef{Version=[3],Kind=[Revised]} There is no language-defined support for external or link names of type Wide_String, or of other string types. Implementations may, of course, have additional @Chg{Version=[3],New=[aspects],Old=[pragmas]} for that purpose. Note that allowing both String and Wide_String in the same @Chg{Version=[3],New=[@nt{aspect_definition}],Old=[@nt{pragma}]} would cause ambiguities. @end{Ramification} @ChgRef{Version=[3],Kind=[Added],ARef=[AI05-0229-1]} @ChgAdded{Version=[3],Text=[@PDefn2{Term=[expected type],Sec=(linker options)} The expected type for the @SynI{string_}@Syn2{expression} in pragma Linker_Options is String.]} @end{Resolution} @begin{Legality} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @Defn{convention} The @Chg{Version=[3],New=[aspect Convention shall be specified by a ],Old=[]}@SynI{convention_}@nt{identifier} @Chg{Version=[3],New=[which],Old=[of an interfacing pragma]} shall be the name of a @i{convention}. The convention names are implementation defined, except for certain language-defined ones, such as Ada and Intrinsic, as explained in @RefSec{Conformance Rules}. @Redundant[Additional convention names generally represent the calling conventions of foreign languages, language implementations, or specific run-time models.] @Defn{calling convention} The convention of a callable entity is its @i{calling convention}. @ImplDef{Implementation-defined convention names.} @begin{Discussion} We considered representing the convention names using an enumeration type declared in System. Then, @SynI{convention_}@nt{identifier} would be changed to @SynI{convention_}@nt{name}, and we would make its expected type be the enumeration type. We didn't do this because it seems to introduce extra complexity, and because the list of available languages is better represented as the list of children of package Interfaces @em a more open-ended sort of list. @end{Discussion} @Leading@Defn2{Term=[compatible],Sec=[a type, with a convention]} If @i[L] is a @i[convention_]@nt[identifier] for a language, then a type T is said to be @i{compatible with convention L}, (alternatively, is said to be an @i[L-compatible type]) if any of the following conditions are met: @begin[itemize] T is declared in a language interface package corresponding to @i[L] and is defined to be @i[L]-compatible (see @refsecnum(Interfacing with C and C++), @refsecnum(The Package Interfaces.C.Strings), @refsecnum(The Generic Package Interfaces.C.Pointers), @refsecnum(Interfacing with COBOL), @refsecnum(Interfacing with Fortran)), @Leading@ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @Defn2{Term=[eligible],Sec=[a type, for a convention]} Convention @i[L] has been specified for T@Chg{Version=[3],New=[],Old=[ in a @nt[pragma] Convention]}, and T is @i{eligible for convention @i[L]}; that is: @begin[inneritemize] T is an array type with either an unconstrained or statically-constrained first subtype, and its component type is @i[L]-compatible, T is a record type that has no discriminants and that only has components with statically-constrained subtypes, and each component type is @i[L]-compatible, @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0002-1]} T is an access-to-object type, @Chg{Version=[3],New=[],Old=[and ]}its designated type is @i[L]-compatible,@Chg{Version=[3],New=[ and its designated subtype is not an unconstrained array subtype,],Old=[]} T is an access-to-subprogram type, and its designated profile's parameter and result types are all @i[L]-compatible. @end[inneritemize] T is derived from an @i[L]-compatible type, The implementation permits T as an @i[L]-compatible type. @begin{discussion} For example, an implementation might permit Integer as a C-compatible type, though the C type to which it corresponds might be different in different environments. @end{discussion} @end[itemize] @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} If @Chg{Version=[3],New=[the],Old=[@nt[pragma]]} Convention @Chg{Version=[3],New=[aspect is specified for],Old=[applies to]} a type, then the type shall either be compatible with or eligible for the @Chg{Version=[3],New=[specified ],Old=[]}convention@Chg{Version=[3], New=[],Old=[ specified in the pragma]}. @begin[ramification] @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} If a type is derived from an @i[L]-compatible type, the derived type is by default @i[L]-compatible, but it is also permitted to specify @Chg{Version=[3],New=[the],Old=[pragma]} Convention @Chg{Version=[3],New=[aspect ],Old=[]}for the derived type. @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} It is permitted to specify @Chg{Version=[3],New=[the],Old=[pragma]} Convention @Chg{Version=[3],New=[aspect ],Old=[]}for an incomplete type, but in the complete declaration each component must be @i[L]-compatible. @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} If each component of a record type is @i[L]-compatible, then the record type itself is only @i[L]-compatible if it has @Chg{Version=[3],New=[a specified],Old=[a pragma]} Convention. @end[Ramification] @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @Chg{Version=[3],New=[],Old=[A @nt{pragma} Import shall be the completion of a declaration.]}@Defn{notwithstanding} Notwithstanding any rule to the contrary, @Chg{Version=[3],New=[a declaration with a True],Old=[a @nt{pragma}]} Import @Chg{Version=[3],New=[aspect shall not have a],Old=[may serve as the]} completion@Chg{Version=[3],New=[],Old=[ of any kind of (explicit) declaration if supported by an implementation for that kind of declaration. If a completion is a @nt{pragma} Import, then it shall appear in the same @nt{declarative_part}, @nt{package_specification}, @nt{task_definition} or @nt{protected_definition} as the declaration. For a library unit, it shall appear in the same @nt{compilation}, before any subsequent @nt{compilation_unit}s other than @nt{pragma}s. If the @nt{local_name} denotes more than one entity, then the @nt{pragma} Import is the completion of all of them]}. @begin(Discussion) @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} For declarations of deferred constants and subprograms, we @Chg{Version=[3],New=[explicitly ],Old=[]}mention @Chg{Version=[3],New=[that no completion is allowed when aspect], Old=[pragma]} Import @Chg{Version=[3],New=[is True],Old=[explicitly as a possible completion]}. For other declarations that require completions, we ignore the possibility of @Chg{Version=[3],New=[the aspect],Old=[pragma]} Import@Chg{Version=[3],New=[ being True],Old=[]}. Nevertheless, if an implementation chooses to allow @Chg{Version=[3],New=[specifying aspect],Old=[a @nt{pragma}]} Import to @Chg{Version=[3],New=[be True for],Old=[complete]} the declaration of a task, protected type, incomplete type, private type, etc., it may do so, and the normal completion is then not allowed for that declaration. @end(Discussion) @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @Defn{imported entity} @Defn{exported entity} An entity @Chg{Version=[3],New=[with a True],Old=[specified as the Entity argument to a @nt[pragma]]} Import@Chg{Version=[3],New=[ aspect],Old=[]} (or @Chg{Version=[3],New=[],Old=[@nt[pragma] ]}Export@Chg{Version=[3],New=[ aspect],Old=[]}) is said to be @i{imported} (respectively, @i{exported}).@Chg{Version=[3],New=[ An entity shall not be both imported and exported.],Old=[]} The declaration of an imported object shall not include an explicit initialization expression. @Redundant[Default initializations are not performed.] @begin{TheProof} This follows from the @lquotes@;Notwithstanding ...@rquotes@; wording in the Dynamics Semantics paragraphs below. @end{TheProof} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} The type of an imported or exported object shall be compatible with the @Chg{Version=[3],New=[specified Convention aspect, if any], Old=[convention specified in the corresponding @nt{pragma}]}. @begin[Ramification] This implies, for example, that importing an Integer object might be illegal, whereas importing an object of type Interfaces.C.int would be permitted. @end[Ramification] @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} For an imported or exported subprogram, the result and parameter types shall each be compatible with the @Chg{Version=[3],New=[specified Convention aspect, if any], Old=[convention specified in the corresponding pragma]}. @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @Chg{Version=[3],New=[The @nt{aspect_definition} (if any) used to directly specify an],Old=[The external name and link name @SynI{string_}@nt[expression]s of a @nt{pragma}]} Import@Chg{Version=[3],New=[,],Old=[ or]} Export, @Chg{Version=[3],New=[External_Name, or Link_Name aspect shall be a static expression. The],Old=[and the]} @SynI[string_]@nt[expression] of a @nt[pragma] Linker_Options@Chg{Version=[3],New=[],Old=[,]} shall be static.@Chg{Version=[3],New=[ An External_Name or Link_Name aspect shall be specified only for an entity that is either imported or exported.],Old=[]} @end{Legality} @begin{StaticSem} @begin{NotIso} @ChgAdded{Version=[3],Noprefix=[T],Noparanum=[T],Text=[@Shrink{@i}]}@Comment{This message should be deleted if the paragraphs are ever renumbered.} @end{NotIso} @ChgRef{Version=[3],Kind=[DeletedNoDelMsg],ARef=[AI05-0229-1]} @ChgDeleted{Version=[3],Text=[@PDefn2{Term=[representation pragma], Sec=(Import)} @PDefn2{Term=[pragma, representation], Sec=(Import)} @PDefn2{Term=[representation pragma], Sec=(Export)} @PDefn2{Term=[pragma, representation], Sec=(Export)} @PDefn2{Term=[representation pragma], Sec=(Convention)} @PDefn2{Term=[pragma, representation], Sec=(Convention)} @PDefn2{Term=[aspect of representation], Sec=(convention, calling convention)} @Defn2{Term=[convention], Sec=(aspect of representation)} Import, Export, and Convention @nt{pragma}s are representation pragmas that specify the @i{convention} aspect of representation. @PDefn2{Term=[aspect of representation], Sec=(imported)} @Defn2{Term=[imported], Sec=(aspect of representation)} @PDefn2{Term=[aspect of representation], Sec=(exported)} @Defn2{Term=[exported], Sec=(aspect of representation)} In addition, Import and Export @nt{pragma}s specify the @i{imported} and @i{exported} aspects of representation, respectively.]} @ChgRef{Version=[3],Kind=[DeletedNoDelMsg],ARef=[AI05-0229-1]} @ChgDeleted{Version=[3],Text=[@PDefn2{Term=[program unit pragma], Sec=(Import)} @PDefn2{Term=[pragma, program unit], Sec=(Import)} @PDefn2{Term=[program unit pragma], Sec=(Export)} @PDefn2{Term=[pragma, program unit], Sec=(Export)} @PDefn2{Term=[program unit pragma], Sec=(Convention)} @PDefn2{Term=[pragma, program unit], Sec=(Convention)} An interfacing pragma is a program unit pragma when applied to a program unit (see @RefSecNum{Pragmas and Program Units}).]} @Leading@ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @Chg{Version=[3],New=[],Old=[An interfacing pragma defines the convention of the entity denoted by the @nt{local_name}. ]}The @Chg{Version=[3],New=[Convention aspect],Old=[convention]} represents the calling convention or representation convention of the entity. For an access-to-subprogram type, it represents the calling convention of designated subprograms. In addition: @begin{Itemize} @ChgRef{Version=[3],Kind=[Revised]} A @Chg{Version=[3],New=[True],Old=[@nt{pragma}]} Import @Chg{Version=[3],New=[aspect indicates],Old=[specifies]} that the entity is defined externally (that is, outside the Ada program).@Chg{Version=[3],New=[ This aspect is never inherited; if not directly specified, the Import aspect is False.],Old=[]} @ChgRef{Version=[3],Kind=[Revised]} A @Chg{Version=[3],New=[True],Old=[@nt{pragma}]} Export @Chg{Version=[3],New=[aspect indicates],Old=[specifies]} that the entity is used externally.@Chg{Version=[3],New=[ This aspect is never inherited; if not directly specified, the Export aspect is False.],Old=[]} @ChgRef{Version=[3],Kind=[Revised]} @Chg{Version=[3],New=[For an entity with a True],Old=[A @nt{pragma}]} Import or Export @Chg{Version=[3],New=[aspect, an],Old=[optionally specifies an entity's]} external name, link name, or both@Chg{Version=[3],New=[ may also be specified],Old=[]}. @end{Itemize} @Defn{external name} An @i{external name} is a string value for the name used by a foreign language program either for an entity that an Ada program imports, or for referring to an entity that an Ada program exports. @Defn{link name} A @i[link name] is a string value for the name of an exported or imported entity, based on the conventions of the foreign language's compiler in interfacing with the system's linker tool. The meaning of link names is implementation defined. If neither a link name nor the Address attribute of an imported or exported entity is specified, then a link name is chosen in an implementation-defined manner, based on the external name if one is specified. @ImplDef{The meaning of link names.} @begin{Ramification} For example, an implementation might always prepend "_", and then pass it to the system linker. @end{Ramification} @ImplDef{The manner of choosing link names when neither the link name nor the address of an imported or exported entity is specified.} @begin{Ramification} Normally, this will be the entity's defining name, or some simple transformation thereof. @end{Ramification} Pragma Linker_Options has the effect of passing its string argument as a parameter to the system linker (if one exists), if the immediately enclosing compilation unit is included in the partition being linked. The interpretation of the string argument, and the way in which the string arguments from multiple Linker_Options pragmas are combined, is implementation defined. @ImplDef(The effect of pragma Linker_Options.) @end{StaticSem} @begin{RunTime} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @Chg{Version=[3],New=[@PDefn2{Term=[elaboration], Sec=(declaration with a True Import aspect)}], Old=[@PDefn2{Term=[elaboration], Sec=(declaration named by a @nt{pragma} Import)}]} @Defn{notwithstanding} Notwithstanding what this International Standard says elsewhere, the elaboration of a declaration @Chg{Version=[3],New=[with a True Import aspect],Old=[denoted by the @nt{local_name} of a @nt{pragma} Import]} does not create the entity. Such an elaboration has no other effect than to allow the defining name to denote the external entity. @begin{Ramification} This implies that default initializations are skipped. (Explicit initializations are illegal.) For example, an imported access object is @i{not} initialized to @key[null]. @ChgRef{Version=[3],Kind=[Deleted],ARef=[AI05-0229-1]} @ChgDeleted{Version=[3],Text=[Note that the @nt{local_name} in a @nt{pragma} Import might denote more than one declaration; in that case, the entity of all of those declarations will be the external entity.]} @end{Ramification} @begin{Discussion} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} This @lquotes@;notwithstanding@rquotes@; wording is better than saying @lquotes@;unless @Chg{Version=[3],New=[aspect],Old=[named by a @nt{pragma}]} Import@Chg{Version=[3],New=[ is True],Old=[]}@rquotes@; on every definition of elaboration. It says we recognize the contradiction, and this rule takes precedence. @end{Discussion} @end{RunTime} @begin{Erron} @ChgRef{Version=[2],Kind=[Added],ARef=[AI95-00320-01]} @ChgRef{Version=[3],Kind=[RevisedAdded],ARef=[AI05-0229-1]} @ChgAdded{Version=[2],Text=[@PDefn2{Term=(erroneous execution),Sec=(cause)} It is the programmer's responsibility to ensure that the use of interfacing @Chg{Version=[3],New=[aspects],Old=[pragmas]} does not violate Ada semantics; otherwise, program execution is erroneous.]} @end{Erron} @begin{ImplAdvice} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} If an implementation supports @Chg{Version=[3],New=[],Old=[pragma ]}Export @Chg{Version=[3],New=[for],Old=[to]} a given language, then it should also allow the main subprogram to be written in that language. It should support some mechanism for invoking the elaboration of the Ada library units included in the system, and for invoking the finalization of the environment task. On typical systems, the recommended mechanism is to provide two subprograms whose link names are "adainit" and "adafinal". Adainit should contain the elaboration code for library units. Adafinal should contain the finalization code. These subprograms should have no effect the second and subsequent time they are called. @Chg{New=[@Defn{adainit}@Defn{adafinal}@Defn2{Term=[Elaboration], Sec=[of library units for a foreign language main subprogram]} @Defn2{Term=[Finalization], Sec=[of environment task for a foreign language main subprogram]}], Old=[]}@ChgNote{Presentation AI-00052. Index entries only; no real change, so no Chgref} @ChgImplAdvice{Version=[3],Kind=[RevisedAdded],InitialVersion=[2], Text=[@ChgAdded{Version=[2], Text=[If @Chg{Version=[3],New=[],Old=[@nt{pragma} ]} Export is supported for a language, the main program should be able to be written in that language. Subprograms named "adainit" and "adafinal" should be provided for elaboration and finalization of the environment task.]}]} @begin{ramification} For example, if the main subprogram is written in C, it can call adainit before the first call to an Ada subprogram, and adafinal after the last. @end{ramification} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1],ARef=[AI05-0269-1]} Automatic elaboration of preelaborated packages should be provided when @Chg{Version=[3],New=[specifying the],Old=[@nt[pragma]]} Export @Chg{Version=[3],New=[aspect as True ],Old=[]}is supported. @ChgImplAdvice{Version=[3],Kind=[RevisedAdded],InitialVersion=[2], Text=[@ChgAdded{Version=[2], Text=[Automatic elaboration of preelaborated packages should be provided when @Chg{Version=[3],New=[specifying the],Old=[@nt[pragma]]} Export @Chg{Version=[3],New=[aspect as True ],Old=[]}is supported.]}]} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} For each supported convention @i[L] other than Intrinsic, an implementation should support @Chg{Version=[3],New=[specifying the ],Old=[]}Import and Export @Chg{Version=[3],New=[aspects],Old=[@nt{pragma}s]} for objects of @i[L]-compatible types and for subprograms, and @Chg{Version=[3],New=[the],Old=[@nt(pragma)]} Convention @Chg{Version=[3],New=[aspect ],Old=[]}for @i[L]-eligible types and for subprograms, presuming the other language has corresponding features. @Chg{Version=[3],New=[Specifying the ],Old=[@nt{Pragma}]} Convention @Chg{Version=[3],New=[aspect ],Old=[]}need not be supported for scalar types. @ChgImplAdvice{Version=[3],Kind=[RevisedAdded],InitialVersion=[2], Text=[@ChgAdded{Version=[2], Text=[For each supported convention @i[L] other than Intrinsic, @Chg{Version=[3],New=[specifying the aspects],Old=[@nt{pragma}s]} Import and Export should be supported for objects of @i[L]-compatible types and for subprograms, and @Chg{Version=[3],New=[aspect],Old=[@nt(pragma)]} Convention should be supported for @i[L]-eligible types and for subprograms.]}]} @begin{reason} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @Chg{Version=[3],New=[Specifying aspect],Old=[Pragma]} Convention is not necessary for scalar types, since the language interface packages declare scalar types corresponding to those provided by the respective foreign languages. @end[reason] @begin{ImplNote} @ChgRef{Version=[2],Kind=[Revised],ARef=[AI95-00114-01]} If an implementation supports interfacing to @Chg{Version=[2],New=[the ], Old=[]}C++@Chg{Version=[2],New=[ entities not supported by @RefSecNum{Interfacing with C and C++}],Old=[]}, it should do so via the convention identifier C_Plus_Plus (in additional to any C++-implementation-specific ones). @end{ImplNote} @begin{Reason} @ChgRef{Version=[2],Kind=[Revised],ARef=[AI95-00114-01]} The reason for giving the advice about C++ is to encourage uniformity among implementations, given that the name of the language is not syntactically legal as an @nt{identifier}.@Chg{Version=[2],New=[],Old=[ We place this advice in the AARM, rather than the RM95 proper, because (as of this writing) C++ is not an international standard, and we don't want to refer to a such a language from an international standard.]} @end{Reason} @end{ImplAdvice} @begin{Notes} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} Implementations may place restrictions on interfacing @Chg{Version=[3],New=[aspects],Old=[pragmas]}; for example, requiring each exported entity to be declared at the library level. @begin{TheProof} Arbitrary restrictions are allowed by @RefSecNum{Operational and Representation Aspects}. @end{TheProof} @begin{Ramification} Such a restriction might be to disallow them altogether. Alternatively, the implementation might allow them only for certain kinds of entities, or only for certain conventions. @end{Ramification} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @Chg{Version=[3],New=[The Convention aspect in combination with the],Old=[A @nt{pragma}]} Import @Chg{Version=[3],New=[aspect indicates],Old=[specifies]} the conventions for accessing external entities. It is possible that the actual entity is written in assembly language, but reflects the conventions of a particular language. For example, @Chg{Version=[3],New=[@exam{@key[with] Convention => Ada}],Old=[@key{pragma} Import(Ada, ...)]} can be used to interface to an assembly language routine that obeys the Ada compiler's calling conventions. @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} To obtain @lquotes@;call-back@rquotes@; to an Ada subprogram from a foreign language environment, @Chg{Version=[3],New=[the],Old=[@key(pragma)]} Convention @Chg{Version=[3],New=[aspect ],Old=[]}should be specified both for the access-to-subprogram type and the specific subprogram(s) to which 'Access is applied. @begin{NotIso} @ChgAdded{Version=[3],Noprefix=[T],Noparanum=[T],Text=[@Shrink{@i}]}@Comment{This message should be deleted if the paragraphs are ever renumbered.} @end{NotIso} @ChgRef{Version=[3],Kind=[DeletedNoDelMsg],ARef=[AI05-0229-1]} @ChgDeleted{Version=[3],Text=[It is illegal to specify more than one of Import, Export, or Convention for a given entity.]} @ChgRef{Version=[3],Kind=[DeletedNoDelMsg],ARef=[AI05-0229-1]} @ChgDeleted{Version=[3],Text=[The @nt{local_name} in an interfacing pragma can denote more than one entity in the case of overloading. Such a @nt{pragma} applies to all of the denoted entities.]} See also @RefSec{Machine Code Insertions}. @begin{Ramification} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} The Intrinsic convention (see @refsecnum(Conformance Rules)) implies that the entity is somehow @lquotes@;built in@rquotes@; to the implementation. Thus, it generally does not make sense for users to specify Intrinsic @Chg{Version=[3],New=[along with specifying that the entity is imported], Old=[in a @nt{pragma} Import]}. The intention is that only implementations will specify Intrinsic @Chg{Version=[3],New=[for an imported entity],Old=[in a @nt{pragma} Import]}. The language also defines certain subprograms to be Intrinsic. @end{Ramification} @begin{Discussion} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} There are many imaginable interfacing @Chg{Version=[3],New=[aspects], Old=[pragmas]} that don't make any sense. For example, setting the Convention of a protected procedure to Ada is probably wrong. Rather than enumerating all such cases, however, we leave it up to implementations to decide what is sensible. @end{Discussion} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} If both External_Name and Link_Name are specified for @Chg{Version=[3], New=[a given entity],Old=[an Import or Export pragma]}, then the External_Name is ignored. @ChgRef{Version=[2],Kind=[Deleted],ARef=[AI95-00320-01]} @ChgDeleted{Version=[2],Text=[An interfacing pragma might result in an effect that violates Ada semantics.]} @end{Notes} @begin{Examples} @ChgRef{Version=[4],Kind=[Revised],ARef=[AI12-0080-1]} @leading@keepnext@i{Example of interfacing @Chg{Version=[4],New=[aspects],Old=[pragmas]}:} @begin{Example} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1],ARef=[AI05-0269-1]} @key[package] Fortran_Library @key[is] @key[function] Sqrt (X : Float) @key[return] Float@Chg{Version=[3],New=[ @key[with] Import => True, Convention => Fortran],Old=[]}; @Chg{Version=[3],New=[@key[type] Matrix @key[is array] (Natural @key[range] <>, Natural @key[range] <>) @key[of] Float @key[with] Convention => Fortran; ],Old=[]}@key[function] @Chg{Version=[3],New=[Invert (M : Matrix],Old=[Exp (X : Float]}) @key[return] @Chg{Version=[3],New=[Matrix @key[with] Import => True, Convention => Fortran],Old=[Float]};@Chg{Version=[3],New=[],Old=[ @key[private] @key[pragma] Import(Fortran, Sqrt); @key[pragma] Import(Fortran, Exp);]} @key[end] Fortran_Library; @end{Example} @end{Examples} @begin{Extend83} @Defn{extensions to Ada 83} Interfacing pragmas are new to Ada 95. Pragma Import replaces Ada 83's pragma Interface. Existing implementations can continue to support pragma Interface for upward compatibility. @end{Extend83} @begin{DiffWord95} @ChgRef{Version=[2],Kind=[AddedNormal],Ref=[8652/0058],ARef=[AI95-00036-01]} @ChgAdded{Version=[2],Text=[@b Clarified that @nt{pragma}s Import and Export work like a subprogram call; parameters cannot be omitted unless named notation is used. (Reordering is still not permitted, however.)]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00320-01]} @ChgAdded{Version=[2],Text=[Added wording to say all bets are off if foreign code doesn't follow the semantics promised by the Ada specifications.]} @end{DiffWord95} @begin{Incompatible2005} @ChgRef{Version=[3],Kind=[AddedNormal],ARef=[AI05-0002-1]} @ChgAdded{Version=[3],Text=[@Defn{incompatibilities with Ada 2005}@b Access types that designate unconstrained arrays are no longer defined to be @i[L]-compatible. Such access-to-arrays require bounds information, which is likely to be incompatible with a foreign language. The change will allow (but not require) compilers to reject bad uses, which probably will not work anyway. Note that implementations can still support any type that it wants as @i[L]-compatible; such uses will not be portable, however. As such, there should be little existing code that will be impacted (compilers probably already rejected cases that could not be translated, whether or not the language allowed doing so formally).]} @end{Incompatible2005} @begin{Extend2005} @ChgRef{Version=[3],Kind=[AddedNormal],ARef=[AI05-0229-1]} @ChgAdded{Version=[3],Text=[@Defn{extensions to Ada 2005} Aspects Convention, Import, Export, Link_Name, and External_Name are new; @nt{pragma}s Convention, Import, and Export are now obsolescent.]} @end{Extend2005} @LabeledClause{The Package Interfaces} @begin{Intro} Package Interfaces is the parent of several library packages that declare types and other entities useful for interfacing to foreign languages. It also contains some implementation-defined types that are useful across more than one language (in particular for interfacing to assembly language). @ImplDef{The contents of the visible part of package Interfaces and its language-defined descendants.} @end{Intro} @begin{StaticSem} @Leading@Keepnext@;The library package Interfaces has the following skeletal declaration: @begin{Example} @RootLibUnit{Interfaces} @key[package] Interfaces @key[is] @key[pragma] Pure(Interfaces); @key[type] Integer_@RI{n} @key[is] @key[range] -2**(@RI{n}-1) .. 2**(@RI{n}-1) - 1; --@RI{2's complement} @key[type] Unsigned_@RI{n} @key[is] @key[mod] 2**@RI{n}; @key[function] Shift_Left (Value : Unsigned_@RI{n}; Amount : Natural) @key[return] Unsigned_@RI{n}; @key[function] Shift_Right (Value : Unsigned_@RI{n}; Amount : Natural) @key[return] Unsigned_@RI{n}; @key[function] Shift_Right_Arithmetic (Value : Unsigned_@RI{n}; Amount : Natural) @key[return] Unsigned_@RI{n}; @key[function] Rotate_Left (Value : Unsigned_@RI{n}; Amount : Natural) @key[return] Unsigned_@RI{n}; @key[function] Rotate_Right (Value : Unsigned_@RI{n}; Amount : Natural) @key[return] Unsigned_@RI{n}; ...@Defn{Shift_Left}@Defn{Shift_Right}@Defn{Shift_Right_Arithmetic}@Defn{Rotate_Left}@Defn{Rotate_Right} @key[end] Interfaces; @end{Example} @end{StaticSem} @begin{ImplReq} @Leading@;An implementation shall provide the following declarations in the visible part of package Interfaces: @begin{Itemize} Signed and modular integer types of @i{n} bits, if supported by the target architecture, for each @i{n} that is at least the size of a storage element and that is a factor of the word size. The names of these types are of the form Integer_@i{n} for the signed types, and Unsigned_@i{n} for the modular types;@Defn{Unsigned_N}@Defn{Integer_N} @begin{Ramification} For example, for a typical 32-bit machine the corresponding types might be Integer_8, Unsigned_8, Integer_16, Unsigned_16, Integer_32, and Unsigned_32. The wording above implies, for example, that Integer_16'Size = Unsigned_16'Size = 16. Unchecked conversions between same-Sized types will work as expected. @end{Ramification} @Defn{shift}@Defn{rotate} For each such modular type in Interfaces, shifting and rotating subprograms as specified in the declaration of Interfaces above. These subprograms are Intrinsic. They operate on a bit-by-bit basis, using the binary representation of the value of the operands to yield a binary representation for the result. The Amount parameter gives the number of bits by which to shift or rotate. For shifting, zero bits are shifted in, except in the case of Shift_Right_Arithmetic, where one bits are shifted in if Value is at least half the modulus. @begin{Reason} We considered making shifting and rotating be primitive operations of all modular types. However, it is a design principle of Ada that all predefined operations should be operators (not functions named by identifiers). (Note that an early version of Ada had "@key[abs]" as an identifier, but it was changed to a reserved word operator before standardization of Ada 83.) This is important because the implicit declarations would hide nonoverloadable declarations with the same name, whereas operators are always overloadable. Therefore, we would have had to make shift and rotate into reserved words, which would have been upward incompatible, or else invent new operator symbols, which seemed like too much mechanism. @end{Reason} Floating point types corresponding to each floating point format fully supported by the hardware. @begin{ImplNote} The names for these floating point types are not specified. @Defn{IEEE floating point arithmetic} However, if IEEE arithmetic is supported, then the names should be IEEE_Float_32 and IEEE_Float_64 for single and double precision, respectively.@Defn{IEEE_Float_32}@Defn{IEEE_Float_64} @end{ImplNote} @end{Itemize} @ChgRef{Version=[2],Kind=[Added],ARef=[AI95-00204-01]} @ChgRef{Version=[3],Kind=[DeletedAddedNoDelMsg],ARef=[AI05-0262-1]} @ChgAdded{Version=[2],Text=[@Chg{Version=[3],New=[],Old=[Support for interfacing to any foreign language is optional. However, an implementation shall not provide any attribute, library unit, or pragma having the same name as an attribute, library unit, or pragma (respectively) specified in the following clauses of this Annex unless the provided construct is either as specified in those clauses or is more limited in capability than that required by those clauses. A program that attempts to use an unsupported capability of this Annex shall either be identified by the implementation before run time or shall raise an exception at run time.]}]} @begin{Discussion} @ChgRef{Version=[2],Kind=[AddedNormal]} @ChgRef{Version=[3],Kind=[DeletedNoDelMsg]} @ChgAdded{Version=[2],Text=[@Chg{Version=[3],New=[],Old=[The intent is that the same rules apply for language interfacing as apply for Specialized Needs Annexes. See @RefSecNum{Conformity of an Implementation with the Standard} for a discussion of the purpose of these rules.]}]} @end{Discussion} @end{ImplReq} @begin{ImplPerm} An implementation may provide implementation-defined library units that are children of Interfaces, and may add declarations to the visible part of Interfaces in addition to the ones defined above. @ChgImplDef{Version=[2],Kind=[Revised],InitialVersion=[0], Text=[Implementation-defined children of package Interfaces.@Chg{Version=[2],New=[],Old=[ The contents of the visible part of package Interfaces.]}]} @ChgNote{The latter sentence is given previously!} @ChgRef{Version=[2],Kind=[Added],ARef=[AI95-00204-01]} @ChgRef{Version=[3],Kind=[RevisedAdded],ARef=[AI05-0229-1]} @ChgAdded{Version=[2],Text=[A child package of package Interfaces with the name of a convention may be provided independently of whether the convention is supported by the @Chg{Version=[3],New=[],Old=[pragma ]}Convention @Chg{Version=[3],New=[aspect ],Old=[]}and vice versa. Such a child package should contain any declarations that would be useful for interfacing to the language (implementation) represented by the convention. Any declarations useful for interfacing to any language on the given hardware architecture should be provided directly in Interfaces.]} @begin{Ramification} @ChgRef{Version=[2],Kind=[AddedNormal]}@ChgNote{Moved from below} @ChgAdded{Version=[2],Text=[For example, package Interfaces.XYZ_Pascal might contain declarations of types that match the data types provided by the XYZ implementation of Pascal, so that it will be more convenient to pass parameters to a subprogram whose convention is XYZ_Pascal.]} @end{Ramification} @end{ImplPerm} @begin{ImplAdvice} @ChgRef{Version=[2],Kind=[Deleted],ARef=[AI95-00204-01]} @ChgDeleted{Version=[2],Text=[For each implementation-defined convention identifier, there should be a child package of package Interfaces with the corresponding name. This package should contain any declarations that would be useful for interfacing to the language (implementation) represented by the convention. Any declarations useful for interfacing to any language on the given hardware architecture should be provided directly in Interfaces.]} @begin{Ramification} @ChgRef{Version=[2],Kind=[Deleted]} @ChgDeleted{Version=[2],Text=[For example, package Interfaces.XYZ_Pascal might contain declarations of types that match the data types provided by the XYZ implementation of Pascal, so that it will be more convenient to pass parameters to a subprogram whose convention is XYZ_Pascal.]} @end{Ramification} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0299-1]} An implementation supporting an interface to C, COBOL, or Fortran should provide the corresponding package or packages described in the following @Chg{Version=[3],New=[subclauses],Old=[clauses]}. @ChgImplAdvice{Version=[2],Kind=[Added],Text=[@ChgAdded{Version=[2], Text=[If an interface to C, COBOL, or Fortran is provided, the corresponding package or packages described in @RefSec{Interface to Other Languages} should also be provided.]}]} @begin{ImplNote} @Leading@;The intention is that an implementation might support several implementations of the foreign language: Interfaces.This_Fortran and Interfaces.That_Fortran might both exist. The @lquotes@;default@rquotes@; implementation, overridable by the user, should be declared as a renaming: @begin{Example} @key[package] Interfaces.Fortran @key[renames] Interfaces.This_Fortran; @end{Example} @end{ImplNote} @end{ImplAdvice} @begin{DiffWord95} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00204-01]} @ChgAdded{Version=[2],Text=[Clarified that interfacing to foreign languages is optional and has the same restrictions as a Specialized Needs Annex.]} @end{DiffWord95} @begin{DiffWord2005} @ChgRef{Version=[3],Kind=[AddedNormal],ARef=[AI05-0262-1]} @ChgAdded{Version=[3],Text=[Move the restrictions on implementations of optional features to the start of this Annex.]} @end{DiffWord2005} @LabeledRevisedClause{Version=[2],New=[Interfacing with C and C++], Old=[Interfacing with C]} @begin{Intro} @ChgRef{Version=[1],Kind=[Revised],Ref=[8652/0059],ARef=[AI95-00131-01]} @ChgRef{Version=[2],Kind=[Revised],ARef=[AI95-00376-01]} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @ChgRef{Version=[4],Kind=[Revised],ARef=[AI12-0028-1]} @Defn{interface to C} @Defn{C interface} The facilities relevant to interfacing with the C language @Chg{Version=[2],New=[and the corresponding subset of the C++ language ],Old=[]}are the package Interfaces.C and its children@Chg{Version=[3],New=[, and ],Old=[; @Chg{New=[],Old=[and ]}]}support for @Chg{Version=[3],New=[specifying ],Old=[]}the @Chg{Version=[3],New=[],Old=[Import, Export, and]} Convention @Chg{Version=[3],New=[aspect],Old=[pragmas]} with @Chg{Version=[3],New=[@SynI{convention_}@nt{identifier}s],Old=[@SynI{convention_}@nt{identifier}]} C@Chg{New=[@Chg{Version=[3],New=[@Chg{Version=[4],New=[,],Old=[ and]}],Old=[; and support for the Convention pragma with @SynI{convention_}@nt{identifier}]} C_Pass_By_Copy@Chg{Version=[4],New=[, and any of the C_Variadic_@i conventions described below],Old=[]}],Old=[]}. @ChgRef{Version=[2],Kind=[Revised],ARef=[AI95-00376-01]} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI95-0262-1],ARef=[AI95-0299-1]} The package Interfaces.C contains the basic types, constants@Chg{Version=[3],New=[,],Old=[]} and subprograms that allow an Ada program to pass scalars and strings to C @Chg{Version=[2],New=[and C++ ],Old=[]}functions.@Chg{Version=[2],New=[ When this @Chg{Version=[3],New=[subclause],Old=[clause]} mentions a C entity, the reference also applies to the corresponding entity in C++.],Old=[]} @end{Intro} @begin{StaticSem} @Leading@Keepnext@;The library package Interfaces.C has the following declaration: @begin{Example} @key(package) Interfaces.C @key(is)@ChildUnit{Parent=[Interfaces],Child=[C]} @key(pragma) Pure(C); @RI{-- Declarations based on C's } @AdaObjDefn{CHAR_BIT} : @key(constant) := @RI{implementation-defined}; @RI{-- typically 8} @AdaObjDefn{SCHAR_MIN} : @key(constant) := @RI{implementation-defined}; @RI{-- typically @en@;128} @AdaObjDefn{SCHAR_MAX} : @key(constant) := @RI{implementation-defined}; @RI{-- typically 127} @AdaObjDefn{UCHAR_MAX} : @key(constant) := @RI{implementation-defined}; @RI{-- typically 255} @RI{-- Signed and Unsigned Integers} @key(type) @AdaTypeDefn{int} @key(is) @key(range) @RI{implementation-defined}; @key(type) @AdaTypeDefn{short} @key(is) @key(range) @RI{implementation-defined}; @key(type) @AdaTypeDefn{long} @key(is) @key(range) @RI{implementation-defined}; @key(type) @AdaTypeDefn{signed_char} @key(is) @key(range) SCHAR_MIN .. SCHAR_MAX; @key(for) signed_char'Size @key(use) CHAR_BIT; @key(type) @AdaTypeDefn{unsigned} @key(is) @key(mod) @RI{implementation-defined}; @key(type) @AdaTypeDefn{unsigned_short} @key(is) @key(mod) @RI{implementation-defined}; @key(type) @AdaTypeDefn{unsigned_long} @key(is) @key(mod) @RI{implementation-defined}; @key(type) @AdaTypeDefn{unsigned_char} @key(is) @key(mod) (UCHAR_MAX+1); @key(for) unsigned_char'Size @key(use) CHAR_BIT; @key(subtype) @AdaTypeDefn{plain_char} @key(is) @RI{implementation-defined}; @key(type) @AdaTypeDefn{ptrdiff_t} @key(is) @key(range) @RI{implementation-defined}; @key(type) @AdaTypeDefn{size_t} @key(is) @key(mod) @RI{implementation-defined}; @RI{-- Floating Point} @key(type) @AdaTypeDefn{C_float} @key(is) @key(digits) @RI{implementation-defined}; @key(type) @AdaTypeDefn{double} @key(is) @key(digits) @RI{implementation-defined}; @key(type) @AdaTypeDefn{long_double} @key(is) @key(digits) @RI{implementation-defined}; @RI{-- Characters and Strings } @key(type) @AdaTypeDefn{char} @key(is) @RI{}; @ChgRef{Version=[1],Kind=[Revised],Ref=[8652/0060],ARef=[AI95-00037-01]} @AdaObjDefn{nul} : @key(constant) char := @Chg{New=[@RI{implementation-defined}],Old=[char'First]}; @key[function] @AdaSubDefn{To_C} (Item : @key[in] Character) @key[return] char; @key[function] @AdaSubDefn{To_Ada} (Item : @key[in] char) @key[return] Character; @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1],ARef=[AI05-0269-1]} @key(type) @AdaTypeDefn{char_array} @key(is) @key(array) (size_t @key(range) <>) @key(of) @key[aliased] char@Chg{Version=[3],New=[ @key[with] Pack],Old=[; @key[pragma] Pack(char_array)]}; @key(for) char_array'Component_Size @key(use) CHAR_BIT; @key(function) @AdaSubDefn{Is_Nul_Terminated} (Item : @key(in) char_array) @key(return) Boolean; @key(function) @AdaSubDefn{To_C} (Item : @key(in) String; Append_Nul : @key(in) Boolean := True) @key(return) char_array; @key(function) @AdaSubDefn{To_Ada} (Item : @key(in) char_array; Trim_Nul : @key(in) Boolean := True) @key(return) String; @key(procedure) @AdaSubDefn{To_C} (Item : @key(in) String; Target : @key(out) char_array; Count : @key(out) size_t; Append_Nul : @key(in) Boolean := True); @key(procedure) @AdaSubDefn{To_Ada} (Item : @key(in) char_array; Target : @key(out) String; Count : @key(out) Natural; Trim_Nul : @key(in) Boolean := True); @RI{-- Wide Character and Wide String} @ChgRef{Version=[1],Kind=[Revised],Ref=[8652/0060],ARef=[AI95-00037-01]} @key(type) @AdaTypeDefn{wchar_t} @key(is) @Chg{New=[@RI{}], Old=[@RI{implementation-defined}]}; @ChgRef{Version=[1],Kind=[Revised],Ref=[8652/0060],ARef=[AI95-00037-01]} @AdaObjDefn{wide_nul} : @key(constant) wchar_t := @Chg{New=[@RI{implementation-defined}],Old=[wchar_t'First]}; @key(function) @AdaSubDefn{To_C} (Item : @key(in) Wide_Character) @key(return) wchar_t; @key(function) @AdaSubDefn{To_Ada} (Item : @key(in) wchar_t ) @key(return) Wide_Character; @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @key(type) @AdaTypeDefn{wchar_array} @key(is) @key(array) (size_t @key(range) <>) @key(of) @key(aliased) wchar_t@Chg{Version=[3],New=[ @key[with] Pack],Old=[]}; @ChgRef{Version=[3],Kind=[Deleted],ARef=[AI05-0229-1]} @ChgDeleted{Version=[3],Text=[ @key(pragma) Pack(wchar_array);]} @key(function) @AdaSubDefn{Is_Nul_Terminated} (Item : @key(in) wchar_array) @key(return) Boolean; @key(function) @AdaSubDefn{To_C} (Item : @key(in) Wide_String; Append_Nul : @key(in) Boolean := True) @key(return) wchar_array; @key(function) @AdaSubDefn{To_Ada} (Item : @key(in) wchar_array; Trim_Nul : @key(in) Boolean := True) @key(return) Wide_String; @key(procedure) @AdaSubDefn{To_C} (Item : @key(in) Wide_String; Target : @key(out) wchar_array; Count : @key(out) size_t; Append_Nul : @key(in) Boolean := True); @key(procedure) @AdaSubDefn{To_Ada} (Item : @key(in) wchar_array; Target : @key(out) Wide_String; Count : @key(out) Natural; Trim_Nul : @key(in) Boolean := True); @ChgRef{Version=[2],Kind=[Added],ARef=[AI95-00285-01]} @ChgAdded{Version=[2],Text=[ -- @RI[ISO/IEC 10646:2003 compatible types defined by ISO/IEC TR 19769:2004.]]} @ChgRef{Version=[2],Kind=[Added],ARef=[AI95-00285-01]} @ChgAdded{Version=[2],Text=[ @key @AdaTypeDefn{char16_t} @key @RI{};]} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],Text=[ @AdaObjDefn{char16_nul} : @key char16_t := @RI{implementation-defined};]} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],Text=[ @key @AdaSubDefn{To_C} (Item : @key Wide_Character) @key char16_t; @key @AdaSubDefn{To_Ada} (Item : @key char16_t) @key Wide_Character;]} @ChgRef{Version=[2],Kind=[Added]} @ChgRef{Version=[3],Kind=[RevisedAdded],ARef=[AI05-0229-1]} @ChgAdded{Version=[2],Text=[ @key @AdaTypeDefn{char16_array} @key (size_t @key <>) @key char16_t@Chg{Version=[3],New=[ @key[with] Pack],Old=[]};]} @ChgRef{Version=[2],Kind=[Added]} @ChgRef{Version=[3],Kind=[DeletedAdded],ARef=[AI05-0229-1]} @ChgAdded{Version=[2],Text=[@Chg{Version=[3],New=[],Old=[ @key Pack(char16_array);]}]} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],Text=[ @key @AdaSubDefn{Is_Nul_Terminated} (Item : @key char16_array) @key Boolean; @key @AdaSubDefn{To_C} (Item : @key Wide_String; Append_Nul : @key Boolean := True) @key char16_array;]} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],Text=[ @key @AdaSubDefn{To_Ada} (Item : @key char16_array; Trim_Nul : @key Boolean := True) @key Wide_String;]} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],Text=[ @key @AdaSubDefn{To_C} (Item : @key Wide_String; Target : @key char16_array; Count : @key size_t; Append_Nul : @key Boolean := True);]} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],Text=[ @key @AdaSubDefn{To_Ada} (Item : @key char16_array; Target : @key Wide_String; Count : @key Natural; Trim_Nul : @key Boolean := True);]} @ChgRef{Version=[2],Kind=[Added],ARef=[AI95-00285-01]} @ChgAdded{Version=[2],Text=[ @key @AdaTypeDefn{char32_t} @key @RI{};]} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],Text=[ @AdaObjDefn{char32_nul} : @key char32_t := @RI{implementation-defined};]} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],Text=[ @key @AdaSubDefn{To_C} (Item : @key Wide_Wide_Character) @key char32_t; @key @AdaSubDefn{To_Ada} (Item : @key char32_t) @key Wide_Wide_Character;]} @ChgRef{Version=[2],Kind=[Added]} @ChgRef{Version=[3],Kind=[RevisedAdded],ARef=[AI05-0229-1]} @ChgAdded{Version=[2],Text=[ @key @AdaTypeDefn{char32_array} @key (size_t @key <>) @key char32_t@Chg{Version=[3],New=[ @key[with] Pack],Old=[]};]} @ChgRef{Version=[2],Kind=[Added]} @ChgRef{Version=[3],Kind=[DeletedAdded],ARef=[AI05-0229-1]} @ChgAdded{Version=[2],Text=[@Chg{Version=[3],New=[],Old=[ @key Pack(char32_array);]}]} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],Text=[ @key @AdaSubDefn{Is_Nul_Terminated} (Item : @key char32_array) @key Boolean; @key @AdaSubDefn{To_C} (Item : @key Wide_Wide_String; Append_Nul : @key Boolean := True) @key char32_array;]} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],Text=[ @key @AdaSubDefn{To_Ada} (Item : @key char32_array; Trim_Nul : @key Boolean := True) @key Wide_Wide_String;]} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],Text=[ @key @AdaSubDefn{To_C} (Item : @key Wide_Wide_String; Target : @key char32_array; Count : @key size_t; Append_Nul : @key Boolean := True);]} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],Text=[ @key @AdaSubDefn{To_Ada} (Item : @key char32_array; Target : @key Wide_Wide_String; Count : @key Natural; Trim_Nul : @key Boolean := True);]} @AdaExcDefn{Terminator_Error} : @key(exception); @key(end) Interfaces.C; @end{Example} @ChgImplDef{Version=[2],Kind=[Added],InitialVersion=[1], Text=[@Chg{New=[The definitions of @Chg{Version=[2],New=[certain ],Old=[]}types and constants in Interfaces.C.],Old=[]}]} Each of the types declared in Interfaces.C is C-compatible. @ChgRef{Version=[2],Kind=[Revised],ARef=[AI95-00285-01]} The types int, short, long, unsigned, ptrdiff_t, size_t, double, char, @Chg{Version=[2],New=[],Old=[and ]}wchar_t@Chg{Version=[2],New=[, char16_t, and char32_t],Old=[]} correspond respectively to the C types having the same names. The types signed_char, unsigned_@!short, unsigned_@!long, unsigned_@!char, C_float, and long_@!double correspond respectively to the C types signed char, unsigned short, unsigned long, unsigned char, float, and long double. @begin{Discussion} @ChgRef{Version=[2],Kind=[AddedNormal]} @ChgAdded{Version=[2],Text=[The C types wchar_t and char16_t seem to be the same. However, wchar_t has an implementation-defined size, whereas char16_t is guaranteed to be an unsigned type of at least 16 bits. Also, char16_t and char32_t are encouraged to have UTF-16 and UTF-32 representations; that means that they are not directly the same as the Ada types, which most likely don't use any UTF encoding.]} @end{Discussion} @Trailing@;The type of the subtype plain_char is either signed_char or unsigned_char, depending on the C implementation. @begin{DescribeCode} @begin{Example}@Keepnext @key(function) To_C (Item : @key(in) Character) @key(return) char; @key(function) To_Ada (Item : @key(in) char ) @key(return) Character; @end{Example} @Trailing@;The functions To_C and To_Ada map between the Ada type Character and the C type char. @begin{ImplNote} @ChgRef{Version=[1],Kind=[Added],Ref=[8652/0114],ARef=[AI95-00038-01]} @ChgAdded{Version=[1],Text=[The To_C and To_Ada functions map between corresponding characters, not necessarily between characters with the same internal representation. Corresponding characters are characters defined by the same enumeration literal, if such exist; otherwise, the correspondence is unspecified.@PDefn{Unspecified}]} @ChgRef{Version=[1],Kind=[Added]} @ChgAdded{Version=[1],Type=[Leading],Text=[The following definition is equivalent to the above summary:]} @ChgRef{Version=[1],Kind=[Added]} @ChgAdded{Version=[1],Text=[@f{To_C (Latin_1_Char) = char'Value(Character'Image(Latin_1_Char))}@* provided that char'Value does not raise an exception; otherwise the result is unspecified.]} @ChgRef{Version=[1],Kind=[Added]} @ChgAdded{Version=[1],Text=[@f{To_Ada (Native_C_Char) = Character'Value(char'Image(Native_C_Char))}@* provided that Character'Value does not raise an exception; otherwise the result is unspecified.]} @end{ImplNote} @begin{Example}@Keepnext @key(function) Is_Nul_Terminated (Item : @key(in) char_array) @key(return) Boolean; @end{Example} @Trailing@;The result of Is_Nul_Terminated is True if Item contains nul, and is False otherwise. @begin{Example}@Keepnext @key(function) To_C (Item : @key(in) String; Append_Nul : @key(in) Boolean := True) @key(return) char_array; @Comment{Blank line} @key(function) To_Ada (Item : @key(in) char_array; Trim_Nul : @key(in) Boolean := True) @key(return) String; @end{Example} @ChgRef{Version=[2],Kind=[Revised],ARef=[AI95-00258-01]} The result of To_C is a char_array value of length Item'Length (if Append_Nul is False) or Item'Length+1 (if Append_Nul is True). The lower bound is 0. For each component Item(I), the corresponding component in the result is To_C applied to Item(I). The value nul is appended if Append_Nul is True.@Chg{Version=[2],New=[ If Append_Nul is False and Item'Length is 0, then To_C propagates Constraint_Error.],Old=[]} @Trailing@;The result of To_Ada is a String whose length is Item'Length (if Trim_Nul is False) or the length of the slice of Item preceding the first nul (if Trim_Nul is True). The lower bound of the result is 1. If Trim_Nul is False, then for each component Item(I) the corresponding component in the result is To_Ada applied to Item(I). If Trim_Nul is True, then for each component Item(I) before the first nul the corresponding component in the result is To_Ada applied to Item(I). The function propagates Terminator_Error if Trim_Nul is True and Item does not contain nul. @begin{Example}@Keepnext @key(procedure) To_C (Item : @key(in) String; Target : @key(out) char_array; Count : @key(out) size_t; Append_Nul : @key(in) Boolean := True); @Comment{Blank line} @key(procedure) To_Ada (Item : @key(in) char_array; Target : @key(out) String; Count : @key(out) Natural; Trim_Nul : @key(in) Boolean := True); @end{Example} For procedure To_C, each element of Item is converted (via the To_C function) to a char, which is assigned to the corresponding element of Target. If Append_Nul is True, nul is then assigned to the next element of Target. In either case, Count is set to the number of Target elements assigned. @Defn2{Term=[Constraint_Error],Sec=(raised by failure of run-time check)} If Target is not long enough, Constraint_Error is propagated. @Trailing@;For procedure To_Ada, each element of Item (if Trim_Nul is False) or each element of Item preceding the first nul (if Trim_Nul is True) is converted (via the To_Ada function) to a Character, which is assigned to the corresponding element of Target. Count is set to the number of Target elements assigned. @Defn2{Term=[Constraint_Error],Sec=(raised by failure of run-time check)} If Target is not long enough, Constraint_Error is propagated. If Trim_Nul is True and Item does not contain nul, then Terminator_Error is propagated. @begin{Example}@Keepnext @key(function) Is_Nul_Terminated (Item : @key(in) wchar_array) @key(return) Boolean; @end{Example} @Trailing@;The result of Is_Nul_Terminated is True if Item contains wide_nul, and is False otherwise. @begin{Example}@Keepnext @key(function) To_C (Item : @key(in) Wide_Character) @key(return) wchar_t; @key(function) To_Ada (Item : @key(in) wchar_t ) @key(return) Wide_Character; @end{Example} @Trailing@;To_C and To_Ada provide the mappings between the Ada and C wide character types. @begin{Example} @key(function) To_C (Item : @key(in) Wide_String; Append_Nul : @key(in) Boolean := True) @key(return) wchar_array; @Comment{Blank line} @key(function) To_Ada (Item : @key(in) wchar_array; Trim_Nul : @key(in) Boolean := True) @key(return) Wide_String; @Comment{Blank line} @key(procedure) To_C (Item : @key(in) Wide_String; Target : @key(out) wchar_array; Count : @key(out) size_t; Append_Nul : @key(in) Boolean := True); @Comment{Blank line} @key(procedure) To_Ada (Item : @key(in) wchar_array; Target : @key(out) Wide_String; Count : @key(out) Natural; Trim_Nul : @key(in) Boolean := True); @end{Example} The To_C and To_Ada subprograms that convert between Wide_String and wchar_array have analogous effects to the To_C and To_Ada subprograms that convert between String and char_array, except that wide_nul is used instead of nul. @begin{Example} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],KeepNext=[T],Text=[@key Is_Nul_Terminated (Item : @key char16_array) @key Boolean;]} @end{Example} @ChgRef{Version=[2],Kind=[Added],ARef=[AI95-00285-01]} @ChgAdded{Version=[2],Type=[Trailing],Text=[The result of Is_Nul_Terminated is True if Item contains char16_nul, and is False otherwise.]} @begin{Example} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],KeepNext=[T],Text=[@key To_C (Item : @key Wide_Character) @key char16_t; @key To_Ada (Item : @key char16_t ) @key Wide_Character;]} @end{Example} @ChgRef{Version=[2],Kind=[Added],ARef=[AI95-00285-01]} @ChgAdded{Version=[2],Type=[Trailing],Text=[To_C and To_Ada provide mappings between the Ada and C 16-bit character types.]} @begin{Example} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],Text=[@key To_C (Item : @key Wide_String; Append_Nul : @key Boolean := True) @key char16_array; @Comment{Blank line} @key To_Ada (Item : @key char16_array; Trim_Nul : @key Boolean := True) @key Wide_String; @Comment{Blank line} @key To_C (Item : @key Wide_String; Target : @key char16_array; Count : @key size_t; Append_Nul : @key Boolean := True); @Comment{Blank line} @key To_Ada (Item : @key char16_array; Target : @key Wide_String; Count : @key Natural; Trim_Nul : @key Boolean := True);]} @end{Example} @ChgRef{Version=[2],Kind=[Added],ARef=[AI95-00285-01]} @ChgAdded{Version=[2],Type=[Trailing],Text=[The To_C and To_Ada subprograms that convert between Wide_String and char16_array have analogous effects to the To_C and To_Ada subprograms that convert between String and char_array, except that char16_nul is used instead of nul.]} @begin{Example} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],KeepNext=[T],Text=[@key Is_Nul_Terminated (Item : @key char32_array) @key Boolean;]} @end{Example} @ChgRef{Version=[2],Kind=[Added],ARef=[AI95-00285-01]} @ChgAdded{Version=[2],Type=[Trailing],Text=[The result of Is_Nul_Terminated is True if Item contains char16_nul, and is False otherwise.]} @begin{Example} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],KeepNext=[T],Text=[@key To_C (Item : @key Wide_Wide_Character) @key char32_t; @key To_Ada (Item : @key char32_t ) @key Wide_Wide_Character;]} @end{Example} @ChgRef{Version=[2],Kind=[Added],ARef=[AI95-00285-01]} @ChgAdded{Version=[2],Type=[Trailing],Text=[To_C and To_Ada provide mappings between the Ada and C 32-bit character types.]} @begin{Example} @ChgRef{Version=[2],Kind=[Added]} @ChgAdded{Version=[2],Text=[@key To_C (Item : @key Wide_Wide_String; Append_Nul : @key Boolean := True) @key char32_array; @Comment{Blank line} @key To_Ada (Item : @key char32_array; Trim_Nul : @key Boolean := True) @key Wide_Wide_String; @Comment{Blank line} @key To_C (Item : @key Wide_Wide_String; Target : @key char32_array; Count : @key size_t; Append_Nul : @key Boolean := True); @Comment{Blank line} @key To_Ada (Item : @key char32_array; Target : @key Wide_Wide_String; Count : @key Natural; Trim_Nul : @key Boolean := True);]} @end{Example} @ChgRef{Version=[2],Kind=[Added],ARef=[AI95-00285-01]} @ChgAdded{Version=[2],Type=[Trailing],Text=[The To_C and To_Ada subprograms that convert between Wide_Wide_String and char32_array have analogous effects to the To_C and To_Ada subprograms that convert between String and char_array, except that char32_nul is used instead of nul.]} @begin{Discussion} The Interfaces.C package provides an implementation-defined character type, char, designed to model the C run-time character set, and mappings between the types char and Character. @Leading@;One application of the C interface package is to compose a C string and pass it to a C function. One way to do this is for the programmer to declare an object that will hold the C array, and then pass this array to the C function. This is realized via the type char_array: @begin{Example} @key(type) char_array @key(is) @key(array) (size_t @key(range) <>) of Char; @end{Example} The programmer can declare an Ada String, convert it to a char_array, and pass the char_array as actual parameter to the C function that is expecting a char *. An alternative approach is for the programmer to obtain a C char pointer from an Ada String (or from a char_array) by invoking an allocation function. The package Interfaces.C.Strings (see below) supplies the needed facilities, including a private type chars_ptr that corresponds to C's char *, and two allocation functions. To avoid storage leakage, a Free procedure releases the storage that was allocated by one of these allocate functions. It is typical for a C function that deals with strings to adopt the convention that the string is delimited by a nul char. The C interface packages support this convention. A constant nul of type Char is declared, and the function Value(Chars_Ptr) in Interfaces.C.Strings returns a char_array up to and including the first nul in the array that the chars_ptr points to. The Allocate_Chars function allocates an array that is nul terminated. Some C functions that deal with strings take an explicit length as a parameter, thus allowing strings to be passed that contain nul as a data element. Other C functions take an explicit length that is an upper bound: the prefix of the string up to the char before nul, or the prefix of the given length, is used by the function, whichever is shorter. The C Interface packages support calling such functions. @end{Discussion} @end{DescribeCode} @ChgRef{Version=[1],Kind=[Added],Ref=[8652/0059],ARef=[AI95-00131-01]} @ChgRef{Version=[3],Kind=[RevisedAdded],ARef=[AI05-0229-1]} @ChgAdded{Version=[1],Text=[@Chg{Version=[3],New=[The],Old=[A]} Convention @Chg{Version=[3],New=[aspect],Old=[pragma]} with @SynI{convention_}@nt{identifier} C_Pass_By_Copy shall only be @Chg{Version=[3],New=[specified for],Old=[applied to]} a type.]} @ChgRef{Version=[1],Kind=[Added],Ref=[8652/0059],ARef=[AI95-00131-01]} @ChgRef{Version=[2],Kind=[RevisedAdded],ARef=[AI95-00216-01]} @ChgAdded{Version=[1],Text=[The eligibility rules in @RefSecNum(Interfacing Aspects) do not apply to convention C_Pass_By_Copy. Instead, a type T is eligible for convention C_Pass_By_Copy @Chg{Version=[2],New=[if T is an unchecked union type or ], Old=[]}if T is a record type that has no discriminants and that only has components with statically constrained subtypes, and each component is C-compatible.]} @ChgRef{Version=[1],Kind=[Added],Ref=[8652/0059],ARef=[AI95-00131-01]} @ChgRef{Version=[3],Kind=[RevisedAdded],ARef=[AI05-0264-1]} @ChgAdded{Version=[1],Text=[If a type is C_Pass_By_Copy-compatible@Chg{Version=[3],New=[,],Old=[]} then it is also C-compatible.]} @ChgRef{Version=[4],Kind=[Added],ARef=[AI12-0028-1]} @ChgAdded{Version=[4],Text=[The identifiers C_Variadic_0, C_Variadic_1, C_Variadic_2, and so on are @SynI{convention_}@nt{identifier}s. These conventions are said to be @i. The convention C_Variadic_@i is the calling convention for a variadic C function taking @i fixed parameters and then a variable number of additional parameters. The C_Variadic_@i convention shall only be specified as the convention aspect for a subprogram, or for an access-to-subprogram type, having at least @i parameters. A type is compatible with a C_Variadic convention if and only if the type is C-compatible.@Defn{C_Variadic}@Defn2{Term=[variadic],Sec=[C]}]} @begin{Honest} @ChgRef{Version=[4],Kind=[AddedNormal]} @ChgAdded{Version=[4],Text=[It is implementation defined what the largest @i in C_Variadic_@i is supported. We don't say this because it complicates the wording and it is true for almost any @SynI{convention_}@nt{identifier} (only Ada is required to be supported by the language, all others need to be documented in order for programmers to know that they are available).]} @end{Honest} @end{StaticSem} @begin{ImplReq} @ChgRef{Version=[1],Kind=[Revised],Ref=[8652/0059],ARef=[AI95-00131-01]} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} An implementation shall support @Chg{Version=[3],New=[specifying aspect],Old=[pragma]} Convention with a C @SynI{convention_}@nt{identifier} for a C-eligible type (see @refsecnum(Interfacing Aspects))@Chg{New=[. An implementation shall support @Chg{Version=[3],New=[specifying aspect],Old=[pragma]} Convention with a C_Pass_By_Copy @SynI{convention_}@nt{identifier} for a C_Pass_By_Copy-eligible type.],Old=[]} @end{ImplReq} @begin{ImplPerm} An implementation may provide additional declarations in the C interface packages. @ChgRef{Version=[3],Kind=[Added],ARef=[AI05-0002-1],ARef=[AI05-0229-1]} @ChgAdded{Version=[3],Type=[Leading],Text=[An implementation need not support specifying the Convention aspect with @SynI@nt{identifier} C in the following cases:]} @begin{Itemize} @ChgRef{Version=[3],Kind=[Added],ARef=[AI05-0248-1]} @ChgAdded{Version=[3],Text=[for a subprogram that has a parameter of an unconstrained array subtype, unless the Import aspect has the value True for the subprogram;]} @ChgRef{Version=[3],Kind=[Added]} @ChgAdded{Version=[3],Text=[for a function with an unconstrained array result subtype;]} @ChgRef{Version=[3],Kind=[Added]} @ChgAdded{Version=[3],Text=[for an object whose nominal subtype is an unconstrained array subtype.]} @end{Itemize} @begin{ImplNote} @ChgRef{Version=[3],Kind=[AddedNormal],ARef=[AI05-0002-1]} @ChgAdded{Version=[3],Text=[These rules ensure that an implementation never needs to create bounds for an unconstrained array that originates in C (and thus does not have bounds). An implementation can do so if it wishes, of course. Note that these permissions do not extend to passing an unconstrained array as a parameter to a C function; in this case, the bounds can simply be dropped and thus support is required.]} @end{ImplNote} @end{ImplPerm} @begin{ImplAdvice} @ChgRef{Version=[1],Kind=[Added],Ref=[8652/0060],ARef=[AI95-00037-01]} @ChgRef{Version=[2],Kind=[RevisedAdded],ARef=[AI95-00285-01]} @ChgRef{Version=[3],Kind=[RevisedAdded]}@ChgNote{No change, just a new paragraph number} @ChgAdded{Version=[1],Text=[The constants nul@Chg{Version=[2],New=[,],Old=[ and]} wide_nul@Chg{Version=[2],New=[, char16_nul, and char32_nul],Old=[]} should have a representation of zero.]} @ChgImplAdvice{Version=[2],Kind=[AddedNormal],Text=[@ChgAdded{Version=[2], Text=[The constants nul, wide_nul, char16_nul, and char32_nul in package Interfaces.C should have a representation of zero.]}]} An implementation should support the following interface correspondences between Ada and C. @begin[itemize] An Ada procedure corresponds to a void-returning C function. @begin{discussion} The programmer can also choose an Ada procedure when the C function returns an int that is to be discarded.@end{discussion} An Ada function corresponds to a non-void C function. An Ada @key[in] scalar parameter is passed as a scalar argument to a C function. An Ada @key[in] parameter of an access-to-object type with designated type T is passed as a t* argument to a C function, where t is the C type corresponding to the Ada type T. An Ada @key[access] T parameter, or an Ada @key[out] or @key[in out] parameter of an elementary type T, is passed as a t* argument to a C function, where t is the C type corresponding to the Ada type T. In the case of an elementary @key[out] or @key[in out] parameter, a pointer to a temporary copy is used to preserve by-copy semantics. @ChgRef{Version=[1],Kind=[Added],Ref=[8652/0059],ARef=[AI95-00131-01]} @ChgRef{Version=[2],Kind=[RevisedAdded],ARef=[AI95-00343-01]} @ChgAdded{Version=[1],Text=[An Ada parameter of a @Chg{Version=[2], New=[(record) type T of convention ],Old=[]}C_Pass_By_Copy@Chg{Version=[2], New=[],Old=[-compatible (record) type T]}, of mode @key{in}, is passed as a t argument to a C function, where t is the C struct corresponding to the Ada type T.]} @ChgRef{Version=[1],Kind=[Revised],Ref=[8652/0059],ARef=[AI95-00131-01]} @ChgRef{Version=[2],Kind=[Revised],ARef=[AI95-00343-01]} An Ada parameter of a record type T, of any mode, @Chg{New=[other than an @key{in} parameter of a @Chg{Version=[2], New=[type of convention ],Old=[]}C_Pass_By_Copy@Chg{Version=[2], New=[],Old=[-compatible type]},],Old=[]} is passed as a t* argument to a C function, where t is the C struct corresponding to the Ada type T. An Ada parameter of an array type with component type T, of any mode, is passed as a t* argument to a C function, where t is the C type corresponding to the Ada type T. An Ada parameter of an access-to-subprogram type is passed as a pointer to a C function whose prototype corresponds to the designated subprogram's specification. @ChgRef{Version=[3],Kind=[Added],ARef=[AI05-0002-1]} @ChgAdded{Version=[3],Text=[An Ada parameter of a private type is passed as specified for the full view of the type.]} @ChgRef{Version=[3],Kind=[Added],ARef=[AI05-0002-1]} @ChgAdded{Version=[3],Text=[The rules of correspondence given above for parameters of mode @key[in] also apply to the return object of a function.]} @end[itemize] @ChgRef{Version=[2],Kind=[Added],ARef=[AI95-00337-01]} @ChgRef{Version=[3],Kind=[DeletedAdded],ARef=[AI05-0002-1]} @ChgDeleted{Version=[3],Text=[@Chg{Version=[2],New=[An Ada parameter of a private type is passed as specified for the full view of the type.],Old=[]}]} @ChgImplAdvice{Version=[2],Kind=[AddedNormal],Text=[@ChgAdded{Version=[2], Text=[If C interfacing is supported, the interface correspondences between Ada and C should be supported.]}]} @end{ImplAdvice} @begin{Notes} Values of type char_array are not implicitly terminated with nul. If a char_array is to be passed as a parameter to an imported C function requiring nul termination, it is the programmer's responsibility to obtain this effect. To obtain the effect of C's sizeof(item_type), where Item_Type is the corresponding Ada type, evaluate the expression: size_t(Item_Type'Size/CHAR_BIT). @ChgRef{Version=[2],Kind=[Deleted],ARef=[AI95-00216-01]} @ChgDeleted{Version=[2],Text=[There is no explicit support for C's union types. Unchecked conversions can be used to obtain the effect of C unions.]} @ChgRef{Version=[4],Kind=[Revised],ARef=[AI12-0028-1]} A @Chg{Version=[4],New=[variadic ],Old=[]}C function @Chg{Version=[4],New=[],Old=[that takes a variable number of arguments ]}can correspond to several Ada subprograms, taking various specific numbers and types of parameters. @end{Notes} @begin{Examples} @Leading@Keepnext@i{Example of using the Interfaces.C package:} @begin{Example} @RI{--Calling the C Library Function strcpy} @key(with) Interfaces.C; @key(procedure) Test @key(is) @key(package) C @key(renames) Interfaces.C; @key(use) @key(type) C.char_array; @RI{-- Call strcpy:} @RI{-- C definition of strcpy: char *strcpy(char *s1, const char *s2);} @RI{-- This function copies the string pointed to by s2 (including the terminating null character)} @RI{-- into the array pointed to by s1. If copying takes place between objects that overlap, } @RI{-- the behavior is undefined. The strcpy function returns the value of s1.} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @RI{-- Note: since the C function's return value is of no interest, the Ada interface is a procedure} @key(procedure) Strcpy (Target : @key(out) C.char_array; Source : @key(in) C.char_array)@Chg{Version=[3],New=[ @key(with) Import => True, Convention => C, External_Name => "strcpy"],Old=[]}; @ChgRef{Version=[3],Kind=[Deleted],ARef=[AI05-0229-1]} @ChgDeleted{Version=[3],Text=[ @key(pragma) Import(C, Strcpy, "strcpy");]} Chars1 : C.char_array(1..20); Chars2 : C.char_array(1..20); @key(begin) Chars2(1..6) := "qwert" & C.nul; Strcpy(Chars1, Chars2); @RI{-- Now Chars1(1..6) = "qwert" & C.Nul} @key(end) Test; @end{Example} @end{Examples} @begin{Incompatible95} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00285-01]} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0005-1]} @ChgAdded{Version=[2],Text=[@Defn{incompatibilities with Ada 95} Types char16_t and char32_t and their related types and operations are @Chg{Version=[3],New=[],Old=[newly ]}added to Interfaces.C. If Interfaces.C is referenced in a @nt{use_clause}, and an entity @i with the same @nt{defining_identifier} as a new entity in Interfaces.C is defined in a package that is also referenced in a @nt{use_clause}, the entity @i may no longer be use-visible, resulting in errors. This should be rare and is easily fixed if it does occur.]} @end{Incompatible95} @begin{Extend95} @ChgRef{Version=[2],Kind=[AddedNormal],Ref=[8652/0059],ARef=[AI95-00131-01]} @ChgAdded{Version=[2],Text=[@Defn{extensions to Ada 95} @b Convention C_Pass_By_Copy is new.]} @end{Extend95} @begin{DiffWord95} @ChgRef{Version=[2],Kind=[AddedNormal],Ref=[8652/0060],ARef=[AI95-00037-01]} @ChgAdded{Version=[2],Text=[@b Clarified the intent for Nul and Wide_Nul.]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgAdded{Version=[2],Text=[Specified that an unchecked union type (see @RefSecNum{Unchecked Union Types}) is eligible for convention C_Pass_By_Copy.]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00258-01]} @ChgAdded{Version=[2],Text=[Specified what happens if the To_C function tries to return a null string.]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00337-01]} @ChgAdded{Version=[2],Text=[Clarified that the interface correspondences also apply to private types whose full types have the specified characteristics.]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00343-01]} @ChgAdded{Version=[2],Text=[Clarified that a type must have convention C_Pass_By_Copy in order to be passed by copy (not just a type that could have that convention).]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00376-01]} @ChgAdded{Version=[2],Text=[Added wording to make it clear that these facilities can also be used with C++.]} @end{DiffWord95} @begin{Incompatible2005} @ChgRef{Version=[3],Kind=[AddedNormal],ARef=[AI05-0002-1]} @ChgAdded{Version=[3],Text=[@Defn{incompatibilities with Ada 2005}@b Added a definition of correspondences for function results. Also added wording to make it clear that we do not expect the implementation to conjure bounds for unconstrained arrays out of thin air. These changes allow (but don't require) compilers to reject unreasonable uses of array types. Such uses probably didn't work anyway (and probably were rejected, no matter what the language definition said), so little existing code should be impacted.]} @end{Incompatible2005} @begin{Extend2012} @ChgRef{Version=[4],Kind=[AddedNormal],ARef=[AI12-0028-1]} @ChgAdded{Version=[4],Text=[@Defn{extensions to Ada 2012}@b The @SynI{convention_}@nt{identifier}s C_Variadic_0, C_Variadic_1, and so on are new. These are classified as a correction as any implementation can add such identifiers and it is important that special conventions be available for variadic functions as typical x64 conventions are different for normal and variadic C functions.]} @end{Extend2012} @NotISORMNewPageVer{Version=[3]}@Comment{For printed version of Ada 2012 RM} @LabeledSubClause{The Package Interfaces.C.Strings} @begin{Intro} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} The package Interfaces.C.Strings declares types and subprograms allowing an Ada program to allocate, reference, update, and free C-style strings. In particular, the private type chars_ptr corresponds to a common use of @lquotes@;char *@rquotes@; in C programs, and an object of this type can be passed to a subprogram to which @Chg{Version=[3],New=[@exam{@key[with] Import => True, Convention => C}],Old=[@nt(pragma) Import(C,...)]} has been @Chg{Version=[3],New=[specified],Old=[applied]}, and for which @lquotes@;char *@rquotes@; is the type of the argument of the C function. @end{Intro} @begin{StaticSem} @Leading@;The library package Interfaces.C.Strings has the following declaration: @begin{example} @key(package) Interfaces.C.Strings @key(is)@ChildUnit{Parent=[Interfaces.C],Child=[Strings]} @key[pragma] Preelaborate(Strings); @key(type) @AdaTypeDefn{char_array_access} @key(is) @key(access) @key(all) char_array; @ChgRef{Version=[2],Kind=[Revised],ARef=[AI95-00161-01]} @key(type) @AdaTypeDefn{chars_ptr} @key(is) @key(private);@Chg{Version=[2],New=[ @key(pragma) Preelaborable_Initialization(chars_ptr);],Old=[]} @ChgRef{Version=[2],Kind=[Revised],ARef=[AI95-00276-01]} @key(type) @AdaTypeDefn{chars_ptr_array} @key(is) @key(array) (size_t @key(range) <>) @key(of) @Chg{Version=[2],New=[@key(aliased) ],Old=[]}chars_ptr; @AdaObjDefn{Null_Ptr} : @key(constant) chars_ptr; @key(function) @AdaSubDefn{To_Chars_Ptr} (Item : @key(in) char_array_access; Nul_Check : @key(in) Boolean := False) @key(return) chars_ptr; @key(function) @AdaSubDefn{New_Char_Array} (Chars : @key(in) char_array) @key(return) chars_ptr; @key(function) @AdaSubDefn{New_String} (Str : @key(in) String) @key(return) chars_ptr; @key(procedure) @AdaSubDefn{Free} (Item : @key(in) @key(out) chars_ptr); @AdaSubDefn{Dereference_Error} : @key(exception); @key(function) @AdaSubDefn{Value} (Item : @key(in) chars_ptr) @key(return) char_array; @key(function) @AdaSubDefn{Value} (Item : @key(in) chars_ptr; Length : @key(in) size_t) @key(return) char_array; @key(function) @AdaSubDefn{Value} (Item : @key(in) chars_ptr) @key(return) String; @key(function) @AdaSubDefn{Value} (Item : @key(in) chars_ptr; Length : @key(in) size_t) @key(return) String; @key(function) @AdaSubDefn{Strlen} (Item : @key(in) chars_ptr) @key(return) size_t; @key(procedure) @AdaSubDefn{Update} (Item : @key(in) chars_ptr; Offset : @key(in) size_t; Chars : @key(in) char_array; Check : @key(in) Boolean := True); @key(procedure) @AdaSubDefn{Update} (Item : @key(in) chars_ptr; Offset : @key(in) size_t; Str : @key(in) String; Check : @key(in) Boolean := True); @AdaSubDefn{Update_Error} : @key(exception); @key(private) ... -- @RI{not specified by the language} @key(end) Interfaces.C.Strings; @end{Example} @begin{discussion} The string manipulation types and subprograms appear in a child of Interfaces.C versus being there directly, since it is useful to have Interfaces.C specified as @nt(pragma) Pure. Differently named functions New_String and New_Char_Array are declared, since if there were a single overloaded function a call with a string literal as actual parameter would be ambiguous. @end{discussion} The type chars_ptr is C-compatible and corresponds to the use of C's @lquotes@;char *@rquotes@; for a pointer to the first char in a char array terminated by nul. When an object of type chars_ptr is declared, its value is by default set to Null_Ptr, unless the object is imported (see @RefSecNum(Interfacing Aspects)). @begin{discussion} The type char_array_access is not necessarily C-compatible, since an object of this type may carry @lquotes@;dope@rquotes@; information. The programmer should convert from char_array_access to chars_ptr for objects imported from, exported to, or passed to C.@end{discussion} @begin{DescribeCode} @begin{Example}@Keepnext @key(function) To_Chars_Ptr (Item : @key(in) char_array_access; Nul_Check : @key(in) Boolean := False) @key(return) chars_ptr; @end{Example} @Trailing@ChgRef{Version=[1],Kind=[Revised],Ref=[8652/0061],ARef=[AI95-00140-01]} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0264-1]} If Item is @key(null), then To_Chars_Ptr returns Null_Ptr. @Chg{New=[If Item is not @key(null),], Old=[Otherwise, if]} Nul_Check is True@Chg{New=[,],Old=[]} and Item.@key(all) does not contain nul, then the function propagates Terminator_Error; @Chg{New=[otherwise@Chg{Version=[3],New=[,],Old=[]}], Old=[if Nul_Check is True and Item.@key(all) does contain nul,]} To_Chars_Ptr performs a pointer conversion with no allocation of memory. @begin{Example}@Keepnext @key(function) New_Char_Array (Chars : @key(in) char_array) @key(return) chars_ptr; @end{Example} This function returns a pointer to an allocated object initialized to Chars(Chars'First .. Index) & nul, where @begin{itemize} Index = Chars'Last if Chars does not contain nul, or Index is the smallest size_t value I such that Chars(I+1) = nul. @end{itemize} @ChgNote{The following paragraph is missing a number in the original version. To give it a number in the new version, it is marked as an insertion.} @ChgRef{Version=[0],Kind=[Added]}@Trailing @Chg{New=[],Old=[@Noparanum@;]}Storage_Error is propagated if the allocation fails. @begin{Example}@Keepnext @key(function) New_String (Str : @key(in) String) @key(return) chars_ptr; @end{Example} @Trailing@;This function is equivalent to New_Char_Array(To_C(Str)). @begin{Example}@Keepnext @key(procedure) Free (Item : @key(in) @key(out) chars_ptr); @end{Example} @Trailing@;If Item is Null_Ptr, then Free has no effect. Otherwise, Free releases the storage occupied by Value(Item), and resets Item to Null_Ptr. @begin{Example}@Keepnext @key(function) Value (Item : @key(in) chars_ptr) @key(return) char_array; @end{Example} @Trailing@ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0264-1]} If Item = Null_Ptr@Chg{Version=[3],New=[,],Old=[]} then Value propagates Dereference_Error. Otherwise@Chg{Version=[3],New=[,],Old=[]} Value returns the prefix of the array of chars pointed to by Item, up to and including the first nul. The lower bound of the result is 0. If Item does not point to a nul-terminated string, then execution of Value is erroneous. @begin{Example}@Keepnext @key(function) Value (Item : @key(in) chars_ptr; Length : @key(in) size_t) @key(return) char_array; @end{Example} @ChgRef{Version=[1],Kind=[Revised],Ref=[8652/0062],ARef=[AI95-00139-01]} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0264-1]} @Trailing@;If Item = Null_Ptr@Chg{Version=[3],New=[,],Old=[]} then Value@Chg{New=[],Old=[(Item)]} propagates Dereference_Error. Otherwise@Chg{Version=[3],New=[,],Old=[]} Value returns the shorter of two arrays@Chg{New=[, either],Old=[:]} the first Length chars pointed to by Item, @Chg{New=[or],Old=[and]} Value(Item). The lower bound of the result is 0. @Chg{New=[If Length is 0, then Value propagates Constraint_Error.],Old=[]} @begin{Ramification} Value(New_Char_Array(Chars)) = Chars if Chars does not contain nul; else Value(New_Char_Array( Chars)) is the prefix of Chars up to and including the first nul. @end{Ramification} @begin{Example}@Keepnext @key(function) Value (Item : @key(in) chars_ptr) @key(return) String; @end{Example} @Trailing@;Equivalent to To_Ada(Value(Item), Trim_Nul=>True). @begin{Example}@Keepnext @key(function) Value (Item : @key(in) chars_ptr; Length : @key(in) size_t) @key(return) String; @end{Example} @ChgRef{Version=[1],Kind=[Revised],Ref=[8652/0063],ARef=[AI95-00177-01]} @Trailing@;Equivalent to To_Ada(Value(Item, Length)@Chg{New=[ & nul],Old=[]}, Trim_Nul=>True). @begin{Example}@Keepnext @key(function) Strlen (Item : @key(in) chars_ptr) @key(return) size_t; @end{Example} @Trailing@;Returns @i[Val]'Length@en@;1 where @i[Val] = Value(Item); propagates Dereference_Error if Item = Null_Ptr. @begin{ramification} Strlen returns the number of chars in the array pointed to by Item, up to and including the char immediately before the first nul. Strlen has the same possibility for erroneous execution as Value, in cases where the string has not been nul-terminated. Strlen has the effect of C's strlen function. @end{Ramification} @begin{Example}@Keepnext @key(procedure) Update (Item : @key(in) chars_ptr; Offset : @key(in) size_t; Chars : @key(in) char_array; Check : Boolean := True); @end{Example} @ChgRef{Version=[1],Kind=[Revised],Ref=[8652/0064],ARef=[AI95-00039-01]} @Leading@;@Chg{New=[If Item = Null_Ptr, then Update propagates Dereference_Error. Otherwise, t],Old=[T]}his procedure updates the value pointed to by Item, starting at position Offset, using Chars as the data to be copied into the array. Overwriting the nul terminator, and skipping with the Offset past the nul terminator, are both prevented if Check is True, as follows: @begin[itemize] Let N = Strlen(Item). If Check is True, then: @begin{inneritemize} If Offset+Chars'Length>N, propagate Update_Error. Otherwise, overwrite the data in the array pointed to by Item, starting at the char at position Offset, with the data in Chars. @end{inneritemize} @Trailing@;If Check is False, then processing is as above, but with no check that Offset+Chars'Length>N. @begin{Ramification} If Chars contains nul, Update's effect may be to @lquotes@;shorten@rquotes@; the pointed-to char array.@end{ramification} @end[itemize] @begin{Example}@Keepnext @key(procedure) Update (Item : @key(in) chars_ptr; Offset : @key(in) size_t; Str : @key(in) String; Check : @key(in) Boolean := True); @end{Example} @ChgRef{Version=[2],Kind=[Revised],ARef=[AI95-00242-01]} Equivalent to Update(Item, Offset, To_C(Str@Chg{Version=[2], New=[, Append_Nul => False],Old=[]}), Check). @begin{Discussion} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00242-01]} @ChgAdded{Version=[2],Text=[To truncate the Item to the length of Str, use Update(Item, Offset, To_C(Str), Check) instead of Update(Item, Offset, Str, Check). Note that when truncating Item, Item must be longer than Str.]} @end{Discussion} @end{DescribeCode} @end{StaticSem} @begin{erron} @PDefn2{Term=(erroneous execution),Sec=(cause)} Execution of any of the following is erroneous if the Item parameter is not null_ptr and Item does not point to a nul-terminated array of chars. @begin[itemize] a Value function not taking a Length parameter, the Free procedure, the Strlen function. @end[itemize] @PDefn2{Term=(erroneous execution),Sec=(cause)} Execution of Free(X) is also erroneous if the chars_ptr X was not returned by New_Char_Array or New_String. @PDefn2{Term=(erroneous execution),Sec=(cause)} Reading or updating a freed char_array is erroneous. @PDefn2{Term=(erroneous execution),Sec=(cause)} Execution of Update is erroneous if Check is False and a call with Check equal to True would have propagated Update_Error. @end{erron} @begin{Notes} New_Char_Array and New_String might be implemented either through the allocation function from the C environment (@lquotes@;malloc@rquotes@;) or through Ada dynamic memory allocation (@lquotes@;new@rquotes@;). The key points are @begin{itemize} the returned value (a chars_ptr) is represented as a C @lquotes@;char *@rquotes@; so that it may be passed to C functions; the allocated object should be freed by the programmer via a call of Free, not by a called C function. @end{itemize} @end{Notes} @begin{Inconsistent95} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00242-01]} @ChgAdded{Version=[2],Text=[@Defn{inconsistencies with Ada 95} @b[Amendment Correction:] Update for a String parameter is now defined to not add a nul character. It did add a nul in Ada 95. This means that programs that used this behavior of Update to truncate a string will no longer work (the string will not be truncated). This change makes Update for a string consistent with Update for a char_array (no implicit nul is added to the end of a char_array).]} @end{Inconsistent95} @begin{Extend95} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00161-01]} @ChgAdded{Version=[2],Text=[@Defn{extensions to Ada 95} @b[Amendment Correction:] Added @nt{pragma} Preelaborable_Initialization to type chars_ptr, so that it can be used in preelaborated units.]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00276-01]} @ChgAdded{Version=[2],Text=[@b[Amendment Correction:] The components of chars_ptr_array are aliased so that it can be used to instantiate Interfaces.C.Pointers (that is its intended purpose, which is otherwise mysterious as it has no operations).]} @end{Extend95} @begin{DiffWord95} @ChgRef{Version=[2],Kind=[AddedNormal],Ref=[8652/0061],ARef=[AI95-00140-01]} @ChgAdded{Version=[2],Text=[@b Fixed the missing semantics of To_Char_Ptr when Nul_Check is False.]} @ChgRef{Version=[2],Kind=[AddedNormal],Ref=[8652/0062],ARef=[AI95-00139-01]} @ChgAdded{Version=[2],Text=[@b Fixed the missing semantics of Value when the Length is 0.]} @ChgRef{Version=[2],Kind=[AddedNormal],Ref=[8652/0063],ARef=[AI95-00177-01]} @ChgAdded{Version=[2],Text=[@b Corrected the definition of Value to avoid raising Terminator_Error.]} @ChgRef{Version=[2],Kind=[AddedNormal],Ref=[8652/0064],ARef=[AI95-00039-01]} @ChgAdded{Version=[2],Text=[@b Fixed the missing semantics of Update when Item is Null_Ptr.]} @end{DiffWord95} @RMNewPageVer{Version=[3]}@Comment{For printed version of Ada 2012 RM} @LabeledSubClause{The Generic Package Interfaces.C.Pointers} @begin{Intro} The generic package Interfaces.C.Pointers allows the Ada programmer to perform C-style operations on pointers. It includes an access type Pointer, Value functions that dereference a Pointer and deliver the designated array, several pointer arithmetic operations, and @lquotes@;copy@rquotes@; procedures that copy the contents of a source pointer into the array designated by a destination pointer. As in C, it treats an object Ptr of type Pointer as a pointer to the first element of an array, so that for example, adding 1 to Ptr yields a pointer to the second element of the array. The generic allows two styles of usage: one in which the array is terminated by a special terminator element; and another in which the programmer needs to keep track of the length. @end{Intro} @begin{StaticSem} @Leading@;The generic library package Interfaces.C.Pointers has the following declaration: @begin{Example} @key(generic) @key(type) Index @key(is) (<>); @key(type) Element @key(is) @key(private); @key(type) Element_Array @key(is) @key(array) (Index @key(range) <>) @key(of) @key(aliased) Element; Default_Terminator : Element; @key(package) Interfaces.C.Pointers @key(is)@ChildUnit{Parent=[Interfaces.C],Child=[Pointers]} @key[pragma] Preelaborate(Pointers); @key(type) @AdaTypeDefn{Pointer} @key(is) @key(access) @key(all) Element; @key(function) @AdaSubDefn{Value}(Ref : @key(in) Pointer; Terminator : @key(in) Element := Default_Terminator) @key(return) Element_Array; @key(function) @AdaSubDefn{Value}(Ref : @key(in) Pointer; Length : @key(in) ptrdiff_t) @key(return) Element_Array; @AdaExcDefn{Pointer_Error} : @key(exception); @RI{-- C-style Pointer arithmetic} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @key(function) "+" (Left : @key(in) Pointer; Right : @key(in) ptrdiff_t) @key(return) Pointer@Chg{Version=[3],New=[ @key(with) Convention => Intrinsic],Old=[]}; @key(function) "+" (Left : @key(in) ptrdiff_t; Right : @key(in) Pointer) @key(return) Pointer@Chg{Version=[3],New=[ @key(with) Convention => Intrinsic],Old=[]}; @key(function) "-" (Left : @key(in) Pointer; Right : @key(in) ptrdiff_t) @key(return) Pointer@Chg{Version=[3],New=[ @key(with) Convention => Intrinsic],Old=[]}; @key(function) "-" (Left : @key(in) Pointer; Right : @key(in) Pointer) @key(return) ptrdiff_t@Chg{Version=[3],New=[ @key(with) Convention => Intrinsic],Old=[]}; @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @key(procedure) @AdaSubDefn{Increment} (Ref : @key(in) @key(out) Pointer)@Chg{Version=[3],New=[ @key(with) Convention => Intrinsic],Old=[]}; @key(procedure) @AdaSubDefn{Decrement} (Ref : @key(in) @key(out) Pointer)@Chg{Version=[3],New=[ @key(with) Convention => Intrinsic],Old=[]}; @ChgRef{Version=[3],Kind=[Deleted],ARef=[AI05-0229-1]} @ChgDeleted{Version=[3],Text=[ @key(pragma) Convention (Intrinsic, "+"); @key(pragma) Convention (Intrinsic, "-"); @key(pragma) Convention (Intrinsic, Increment); @key(pragma) Convention (Intrinsic, Decrement);]} @key(function) @AdaSubDefn{Virtual_Length} (Ref : @key(in) Pointer; Terminator : @key(in) Element := Default_Terminator) @key(return) ptrdiff_t; @key(procedure) @AdaSubDefn{Copy_Terminated_Array} (Source : @key(in) Pointer; Target : @key(in) Pointer; Limit : @key(in) ptrdiff_t := ptrdiff_t'Last; Terminator : @key(in) Element := Default_Terminator); @key(procedure) @AdaSubDefn{Copy_Array} (Source : @key(in) Pointer; Target : @key(in) Pointer; Length : @key(in) ptrdiff_t); @key(end) Interfaces.C.Pointers; @end{Example} @Leading@;The type Pointer is C-compatible and corresponds to one use of C's @lquotes@;Element *@rquotes@;. An object of type Pointer is interpreted as a pointer to the initial Element in an Element_Array. Two styles are supported: @begin{Itemize} Explicit termination of an array value with Default_Terminator (a special terminator value); @Trailing@;Programmer-managed length, with Default_Terminator treated simply as a data element. @end{Itemize} @begin{DescribeCode} @begin{Example}@Keepnext @key(function) Value(Ref : @key(in) Pointer; Terminator : @key(in) Element := Default_Terminator) @key(return) Element_Array; @end{Example} @Trailing@;This function returns an Element_Array whose value is the array pointed to by Ref, up to and including the first Terminator; the lower bound of the array is Index'First. Interfaces.C.Strings.Dereference_Error is propagated if Ref is @key(null). @begin{Example}@Keepnext @key(function) Value(Ref : @key(in) Pointer; Length : @key(in) ptrdiff_t) @key(return) Element_Array; @end{Example} @Trailing@;This function returns an Element_Array comprising the first Length elements pointed to by Ref. The exception Interfaces.C.Strings.Dereference_Error is propagated if Ref is @key(null). @end{DescribeCode} @Trailing@;The "+" and "@en@;" functions perform arithmetic on Pointer values, based on the Size of the array elements. In each of these functions, Pointer_Error is propagated if a Pointer parameter is @key(null). @begin{DescribeCode} @begin{Example}@Keepnext @key(procedure) Increment (Ref : @key(in) @key(out) Pointer); @end{Example} @Trailing@;Equivalent to Ref := Ref+1. @begin{Example}@Keepnext @key(procedure) Decrement (Ref : @key(in) @key(out) Pointer); @end{Example} @Trailing@;Equivalent to Ref := Ref@en@;1. @begin{Example}@Keepnext @key(function) Virtual_Length (Ref : @key(in) Pointer; Terminator : @key(in) Element := Default_Terminator) @key(return) ptrdiff_t; @end{Example} @Trailing@;Returns the number of Elements, up to the one just before the first Terminator, in Value(Ref, Terminator). @begin{Example}@Keepnext @key(procedure) Copy_Terminated_Array (Source : @key(in) Pointer; Target : @key(in) Pointer; Limit : @key(in) ptrdiff_t := ptrdiff_t'Last; Terminator : @key(in) Element := Default_Terminator); @end{Example} @Trailing@;This procedure copies Value(Source, Terminator) into the array pointed to by Target; it stops either after Terminator has been copied, or the number of elements copied is Limit, whichever occurs first. Dereference_Error is propagated if either Source or Target is @key(null). @begin{ramification} It is the programmer's responsibility to ensure that elements are not copied beyond the logical length of the target array. @end{ramification} @begin{ImplNote} The implementation has to take care to check the Limit first. @end{ImplNote} @begin{Example}@Keepnext @key(procedure) Copy_Array (Source : @key(in) Pointer; Target : @key(in) Pointer; Length : @key(in) ptrdiff_t); @end{Example} This procedure copies the first Length elements from the array pointed to by Source, into the array pointed to by Target. Dereference_Error is propagated if either Source or Target is @key(null). @end{DescribeCode} @end{StaticSem} @begin{erron} @PDefn2{Term=(erroneous execution),Sec=(cause)} It is erroneous to dereference a Pointer that does not designate an aliased Element. @begin{Discussion} Such a Pointer could arise via "+", "@en@;", Increment, or Decrement.@end{discussion} @PDefn2{Term=(erroneous execution),Sec=(cause)} Execution of Value(Ref, Terminator) is erroneous if Ref does not designate an aliased Element in an Element_Array terminated by Terminator. @PDefn2{Term=(erroneous execution),Sec=(cause)} Execution of Value(Ref, Length) is erroneous if Ref does not designate an aliased Element in an Element_Array containing at least Length Elements between the designated Element and the end of the array, inclusive. @PDefn2{Term=(erroneous execution),Sec=(cause)} Execution of Virtual_Length(Ref, Terminator) is erroneous if Ref does not designate an aliased Element in an Element_Array terminated by Terminator. @Leading@PDefn2{Term=(erroneous execution),Sec=(cause)} Execution of Copy_Terminated_Array(Source, Target, Limit, Terminator) is erroneous in either of the following situations: @begin[itemize] Execution of both Value(Source, Terminator) and Value(Source, Limit) are erroneous, or Copying writes past the end of the array containing the Element designated by Target. @end[Itemize] @PDefn2{Term=(erroneous execution),Sec=(cause)} Execution of Copy_Array(Source, Target, Length) is erroneous if either Value(Source, Length) is erroneous, or copying writes past the end of the array containing the Element designated by Target. @end{erron} @begin{Notes} @Leading@;To compose a Pointer from an Element_Array, use 'Access on the first element. For example (assuming appropriate instantiations): @begin{example} Some_Array : Element_Array(0..5) ; Some_Pointer : Pointer := Some_Array(0)'Access; @end{example} @end{Notes} @begin{Examples} @Leading@Keepnext@i{Example of Interfaces.C.Pointers:} @begin{Example} @key(with) Interfaces.C.Pointers; @key(with) Interfaces.C.Strings; @key(procedure) Test_Pointers @key(is) @key(package) C @key(renames) Interfaces.C; @key(package) Char_Ptrs @key(is) @key(new) C.Pointers (Index => C.size_t, Element => C.char, Element_Array => C.char_array, Default_Terminator => C.nul); @key(use) @key(type) Char_Ptrs.Pointer; @key(subtype) Char_Star @key(is) Char_Ptrs.Pointer; @key(procedure) Strcpy (Target_Ptr, Source_Ptr : Char_Star) @key(is) Target_Temp_Ptr : Char_Star := Target_Ptr; Source_Temp_Ptr : Char_Star := Source_Ptr; Element : C.char; @key(begin) @key(if) Target_Temp_Ptr = @key(null) @key(or) Source_Temp_Ptr = @key(null) @key(then) @key(raise) C.Strings.Dereference_Error; @key(end if); @ChgRef{Version=[1],Kind=[Revised],Ref=[8652/0065],ARef=[AI95-00142-01]} @key(loop) Element := Source_Temp_Ptr.@key(all); Target_Temp_Ptr.@key(all) := Element; @key(exit) @key(when) @Chg{New=[C."="(Element, C.nul)],Old=[Element = C.nul]}; Char_Ptrs.Increment(Target_Temp_Ptr); Char_Ptrs.Increment(Source_Temp_Ptr); @key(end) @key(loop); @key(end) Strcpy; @key(begin) ... @key(end) Test_Pointers; @end{Example} @end{Examples} @LabeledRevisedSubClause{Version=[3],InitialVersion=[2],New=[Unchecked Union Types],Old=[Pragma Unchecked_Union]} @begin{Intro} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1],ARef=[AI05-0269-1]} @ChgAdded{Version=[2],Text=[@Defn2{Term=[union],Sec=[C]} @Redundant[@Chg{Version=[3],New=[Specifying aspect],Old=[A pragma]} Unchecked_Union @Chg{Version=[3],New=[to have the value True defines],Old=[specifies]} an interface correspondence between a given discriminated type and some C union. The @Chg{Version=[3],New=[aspect requires],Old=[pragma specifies]} that the associated type shall be given a representation that @Chg{Version=[3],New=[allocates],Old=[leaves]} no space for its discriminant(s).]]} @end{Intro} @begin{NotIso} @ChgAdded{Version=[3],Noprefix=[T],Noparanum=[T],Text=[@Shrink{@i}]}@Comment{This message should be deleted if the paragraphs are ever renumbered.} @end{NotIso} @begin{Syntax} @begin{SyntaxText} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgRef{Version=[3],Kind=[DeletedNoDelMsg],ARef=[AI05-0229-1]} @ChgDeleted{Version=[3],Type=[Leading],KeepNext=[T],Text=[ @Chg{Version=[2],New=[The form of a pragma Unchecked_Union is as follows:],Old=[]}]} @Comment{We'd like a conditional insert of Leading, etc., but we don't have that.} @end{SyntaxText} @ChgRef{Version=[2],Kind=[AddedNormal]} @ChgRef{Version=[3],Kind=[DeletedNoDelMsg]} @DeletedPragmaSyn@Syn2);],Old=[]}]}> @end{Syntax} @begin{StaticSem} @ChgRef{Version=[3],Kind=[Added],ARef=[AI05-0229-1]} @ChgAdded{Version=[3],Type=[Leading],Text=[For a discriminated record type having a @nt{variant_part}, the following language-defined representation aspect may be specified:]} @begin{Description} @ChgRef{Version=[3],Kind=[Added]} @ChgAdded{Version=[3],Text=[Unchecked_Union@\The type of aspect Unchecked_Union is Boolean. If directly specified, the @nt{aspect_definition} shall be a static expression. If not specified (including by inheritance), the aspect is False.@AspectDefn{Unchecked_Union}]} @ChgAspectDesc{Version=[3],Kind=[AddedNormal],Aspect=[Unchecked_Union], Text=[@ChgAdded{Version=[3],Text=[Type is used to interface to a C union type.]}]} @end{Description} @end{StaticSem} @begin{Legality} @begin{NotIso} @ChgAdded{Version=[3],Noprefix=[T],Noparanum=[T],Text=[@Shrink{@i}]}@Comment{This message should be deleted if the paragraphs are ever renumbered.} @end{NotIso} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgRef{Version=[3],Kind=[DeletedNoDelMsg],ARef=[AI05-0229-1]} @ChgAdded{Version=[2],Text=[@Chg{Version=[3],New=[],Old=[Unchecked_Union is a representation pragma, specifying the unchecked union aspect of representation.]}]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgRef{Version=[3],Kind=[DeletedNoDelMsg],ARef=[AI05-0229-1]} @ChgAdded{Version=[2],Text=[@Chg{Version=[3],New=[],Old=[The @SynI{first_subtype_}@nt{local_name} of a @nt{pragma} Unchecked_Union shall denote an unconstrained discriminated record subtype having a @nt{variant_part}.]}]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @ChgAdded{Version=[2],Text=[@Defn{unchecked union type} @Defn{unchecked union subtype} @Defn{unchecked union object} A type @Chg{Version=[3],New=[for],Old=[to]} which @Chg{Version=[3],New=[aspect],Old=[a pragma]} Unchecked_Union @Chg{Version=[3],New=[is True],Old=[applies]} is called an @i. A subtype of an unchecked union type is defined to be an @i. An object of an unchecked union type is defined to be an @i.]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgAdded{Version=[2],Text=[All component subtypes of an unchecked union type shall be C-compatible.]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgAdded{Version=[2],Text=[If a component subtype of an unchecked union type is subject to a per-object constraint, then the component subtype shall be an unchecked union subtype.]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0026-1]} @ChgAdded{Version=[2],Text=[Any name that denotes a discriminant of an object of an unchecked union type shall occur within the declarative region of the type@Chg{Version=[3],New=[, and shall not occur within a @nt{record_representation_clause}],Old=[]}.]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0026-1]} @ChgAdded{Version=[2],Text=[@Chg{Version=[3],New=[The type of a],Old=[A]} component declared in a @nt{variant_part} of an unchecked union type shall not @Chg{Version=[3],New=[need finalization. In addition to the places where @LegalityTitle normally apply (see @RefSecNum{Generic Instantiation}), this rule also applies in the private part of an instance of a generic unit.@PDefn{generic contract issue} For an unchecked union type declared within the body of a generic unit, or within the body of any of its descendant library units, no part of the type of a component declared in a @nt{variant_part} of the unchecked union type shall be of a formal private type or formal private extension declared within the formal part of the generic unit],Old=[have a controlled, protected, or task part]}.]} @begin{Reason} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0026-1]} @ChgAdded{Version=[3],Text=[The last part is a classic assume-the-worst rule that avoids dependence on the actuals in a generic body. We did not include this in the definition of @ldquote@;needs finalization@rdquote as it has a bad interaction with the use of that term for the No_Nested_Finalization restriction.]} @end{Reason} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgAdded{Version=[2],Text=[The completion of an incomplete or private type declaration having a @nt{known_discriminant_part} shall not be an unchecked union type.]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgAdded{Version=[2],Text=[An unchecked union subtype shall only be passed as a generic actual parameter if the corresponding formal type has no known discriminants or is an unchecked union type.]} @begin{Ramification} @ChgRef{Version=[2],Kind=[AddedNormal]} @ChgAdded{Version=[2],Text=[This includes formal private types without a @nt{known_discriminant_part}, formal derived types that do not inherit any discriminants (formal derived types do not have @nt{known_discriminant_part}s), and formal derived types that are unchecked union types.]} @end{Ramification} @end{Legality} @begin{StaticSem} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgAdded{Version=[2],Text=[An unchecked union type is eligible for convention C.]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgAdded{Version=[2],Text=[All objects of an unchecked union type have the same size.]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgAdded{Version=[2],Text=[Discriminants of objects of an unchecked union type are of size zero.]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgAdded{Version=[2],Type=[Leading],Keepnext=[T], Text=[Any check which would require reading a discriminant of an unchecked union object is suppressed (see @RefSecNum{Suppressing Checks}). These checks include:]} @begin{Itemize} @ChgRef{Version=[2],Kind=[AddedNormal]} @ChgAdded{Version=[2],Text=[The check performed when addressing a variant component (i.e., a component that was declared in a variant part) of an unchecked union object that the object has this component (see @RefSecNum{Selected Components}).]} @ChgRef{Version=[2],Kind=[AddedNormal]} @ChgAdded{Version=[2],Text=[Any checks associated with a type or subtype conversion of a value of an unchecked union type (see @RefSecNum{Type Conversions}). This includes, for example, the check associated with the implicit subtype conversion of an assignment statement.]} @ChgRef{Version=[2],Kind=[AddedNormal]} @ChgAdded{Version=[2],Text=[The subtype membership check associated with the evaluation of a qualified expression (see @RefSecNum{Qualified Expressions}) or an uninitialized allocator (see @RefSecNum{Allocators}).]} @end{Itemize} @begin{Discussion} @ChgRef{Version=[2],Kind=[AddedNormal]} @ChgAdded{Version=[2],Text=[If a suppressed check would have failed, execution is erroneous (see @RefSecNum{Suppressing Checks}). An implementation is always allowed to make a suppressed check if it can somehow determine the discriminant value.]} @end{Discussion} @end{StaticSem} @begin{RunTime} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgAdded{Version=[2],Text=[A view of an unchecked union object (including a type conversion or function call) has @i if it has a constrained nominal subtype, unless the object is a component of an enclosing unchecked union object that is subject to a per-object constraint and the enclosing object lacks inferable discriminants.@Defn{inferable discriminants}]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgAdded{Version=[2],Text=[An expression of an unchecked union type has inferable discriminants if it is either a name of an object with inferable discriminants or a qualified expression whose @nt{subtype_mark} denotes a constrained subtype.]} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgAdded{Version=[2],Type=[Leading],Keepnext=[T], Text=[Program_Error is raised in the following cases:@Defn2{Term=[Program_Error],Sec=(raised by failure of run-time check)}]} @begin{Itemize} @ChgRef{Version=[2],Kind=[AddedNormal]} @ChgAdded{Version=[2],Text=[Evaluation of the predefined equality operator for an unchecked union type if either of the operands lacks inferable discriminants.]} @ChgRef{Version=[2],Kind=[AddedNormal]} @ChgAdded{Version=[2],Text=[Evaluation of the predefined equality operator for a type which has a subcomponent of an unchecked union type whose nominal subtype is unconstrained.]} @ChgRef{Version=[2],Kind=[AddedNormal]} @ChgAdded{Version=[2],Text=[Evaluation of a membership test if the @nt{subtype_mark} denotes a constrained unchecked union subtype and the expression lacks inferable discriminants.]} @ChgRef{Version=[2],Kind=[AddedNormal]} @ChgAdded{Version=[2],Text=[Conversion from a derived unchecked union type to an unconstrained non-unchecked-union type if the operand of the conversion lacks inferable discriminants.]} @ChgRef{Version=[2],Kind=[AddedNormal]} @ChgAdded{Version=[2],Text=[Execution of the default implementation of the Write or Read attribute of an unchecked union type.]} @ChgRef{Version=[2],Kind=[AddedNormal]} @ChgAdded{Version=[2],Text=[Execution of the default implementation of the Output or Input attribute of an unchecked union type if the type lacks default discriminant values.]} @end{Itemize} @end{RunTime} @begin{ImplPerm} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgRef{Version=[3],Kind=[DeletedNoDelMsg],ARef=[AI05-0229-1]} @ChgAdded{Version=[2],Text=[@Chg{Version=[3],New=[],Old=[An implementation may require that @nt{pragma} Controlled be specified for the type of an access subcomponent of an unchecked union type.]}]} @end{ImplPerm} @begin{NotIso} @ChgAdded{Version=[3],Noparanum=[T],Text=[@Shrink{@i}]}@Comment{This message should be deleted if the paragraphs are ever renumbered.} @end{NotIso} @begin{Notes} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgAdded{Version=[2],Type=[Leading],Keepnext=[T], Text=[The use of an unchecked union to obtain the effect of an unchecked conversion results in erroneous execution (see @RefSecNum{Suppressing Checks}). Execution of the following example is erroneous even if Float'Size = Integer'Size:]} @begin{Example} @ChgRef{Version=[2],Kind=[AddedNormal]} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @ChgAdded{Version=[2],Text=[@key T (Flag : Boolean := False) @key @key @key Flag @key @key False => F1 : Float := 0.0; @key True => F2 : Integer := 0; @key; @key@Chg{Version=[3],New=[ @key[with] Unchecked_Union],Old=[; @key Unchecked_Union (T)]};]} @ChgRef{Version=[2],Kind=[AddedNormal]} @ChgAdded{Version=[2],Text=[X : T; Y : Integer := X.F2; -- @RI[erroneous]]} @end{Example} @end{Notes} @begin{Extend95} @ChgRef{Version=[2],Kind=[AddedNormal],ARef=[AI95-00216-01]} @ChgAdded{Version=[2],Text=[@Defn{extensions to Ada 95} @nt{Pragma} Unchecked_Union is new.]} @end{Extend95} @begin{Incompatible2005} @ChgRef{Version=[3],Kind=[AddedNormal],ARef=[AI05-0026-1]} @ChgAdded{Version=[3],Text=[@Defn{incompatibilities with Ada 2005}@b The use of discriminants on Unchecked_Union types is now illegal in @nt{record_representation_clause}s, as it makes no sense to specify a position for something that is not supposed to exist. It is very unlikely that this change will have any impact on existing code.]} @end{Incompatible2005} @begin{Extend2005} @ChgRef{Version=[3],Kind=[AddedNormal],ARef=[AI05-0229-1]} @ChgAdded{Version=[3],Text=[@Defn{extensions to Ada 2005} Aspect Unchecked_Union is new; @nt{pragma} Unchecked_Union is now obsolescent.]} @end{Extend2005} @begin{DiffWord2005} @ChgRef{Version=[3],Kind=[AddedNormal],ARef=[AI05-0026-1]} @ChgAdded{Version=[3],Text=[@b Revised the rules to use the @ldquote@;needs finalization@rdquote definition, and eliminated generic contract issues.]} @end{DiffWord2005} @RMNewPageVer{Version=[2]}@Comment{For printed version of Ada 2005 RM} @LabeledClause{Interfacing with COBOL} @begin{Intro} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @Defn{interface to COBOL} @Defn{COBOL interface} The facilities relevant to interfacing with the COBOL language are the package Interfaces.COBOL and support for @Chg{Version=[3],New=[specifying ],Old=[]}the @Chg{Version=[3],New=[],Old=[Import, Export and ]}Convention @Chg{Version=[3],New=[aspect],Old=[pragmas]} with @SynI{convention_}@nt{identifier} COBOL. @Leading@;The COBOL interface package supplies several sets of facilities: @begin{itemize} A set of types corresponding to the native COBOL types of the supported COBOL implementation (so-called @lquotes@;internal COBOL representations@rquotes@;), allowing Ada data to be passed as parameters to COBOL programs A set of types and constants reflecting external data representations such as might be found in files or databases, allowing COBOL-generated data to be read by an Ada program, and Ada-generated data to be read by COBOL programs A generic package for converting between an Ada decimal type value and either an internal or external COBOL representation @end{itemize} @end{Intro} @begin{StaticSem} @Leading@Keepnext@;The library package Interfaces.COBOL has the following declaration: @begin{Example} @key(package) Interfaces.COBOL @key(is)@ChildUnit{Parent=[Interfaces],Child=[COBOL]} @key[pragma] Preelaborate(COBOL); @RI{-- Types and operations for internal data representations} @key(type) @AdaTypeDefn{Floating} @key(is) @key(digits) @RI{implementation-defined}; @key(type) @AdaTypeDefn{Long_Floating} @key(is) @key(digits) @RI{implementation-defined}; @key(type) @AdaTypeDefn{Binary} @key(is) @key(range) @RI{implementation-defined}; @key(type) @AdaTypeDefn{Long_Binary} @key(is) @key(range) @RI{implementation-defined}; @AdaObjDefn{Max_Digits_Binary} : @key(constant) := @RI{implementation-defined}; @AdaObjDefn{Max_Digits_Long_Binary} : @key(constant) := @RI{implementation-defined}; @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @key(type) @AdaTypeDefn{Decimal_Element} @key(is) @key(mod) @RI{implementation-defined}; @key(type) @AdaTypeDefn{Packed_Decimal} @key(is) @key(array) (Positive @key(range) <>) @key(of) Decimal_Element@Chg{Version=[3],New=[ @key[with] Pack],Old=[; @key(pragma) Pack(Packed_Decimal)]}; @key(type) @AdaTypeDefn{COBOL_Character} @key(is) @RI{implementation-defined character type}; @AdaObjDefn{Ada_To_COBOL} : @key(array) (Character) @key(of) COBOL_Character := @RI{implementation-defined}; @AdaObjDefn{COBOL_To_Ada} : @key(array) (COBOL_Character) @key(of) Character := @RI{implementation-defined}; @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @key(type) @AdaTypeDefn{Alphanumeric} @key(is) @key(array) (Positive range <>) @key(of) COBOL_Character@Chg{Version=[3],New=[ @key[with] Pack],Old=[; @key(pragma) Pack(Alphanumeric)]}; @key(function) @AdaSubDefn{To_COBOL} (Item : @key(in) String) @key(return) Alphanumeric; @key(function) @AdaSubDefn{To_Ada} (Item : @key(in) Alphanumeric) @key(return) String; @key(procedure) @AdaSubDefn{To_COBOL} (Item : @key(in) String; Target : @key(out) Alphanumeric; Last : @key(out) Natural); @key(procedure) @AdaSubDefn{To_Ada} (Item : @key(in) Alphanumeric; Target : @key(out) String; Last : @key(out) Natural); @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @key(type) @AdaTypeDefn{Numeric} @key(is) @key(array) (Positive @key[range] <>) @key(of) COBOL_Character@Chg{Version=[3],New=[ @key[with] Pack],Old=[; @key(pragma) Pack(Numeric)]}; @RI{-- Formats for COBOL data representations} @key(type) @AdaTypeDefn{Display_Format} @key(is) @key(private); @AdaObjDefn{Unsigned} : @key(constant) Display_Format; @AdaObjDefn{Leading_Separate} : @key(constant) Display_Format; @AdaObjDefn{Trailing_Separate} : @key(constant) Display_Format; @AdaObjDefn{Leading_Nonseparate} : @key(constant) Display_Format; @AdaObjDefn{Trailing_Nonseparate} : @key(constant) Display_Format; @key(type) @AdaTypeDefn{Binary_Format} @key(is) @key(private); @AdaObjDefn{High_Order_First} : @key(constant) Binary_Format; @AdaObjDefn{Low_Order_First} : @key(constant) Binary_Format; @AdaObjDefn{Native_Binary} : @key(constant) Binary_Format; @key(type) @AdaTypeDefn{Packed_Format} @key(is) @key(private); @AdaObjDefn{Packed_Unsigned} : @key(constant) Packed_Format; @AdaObjDefn{Packed_Signed} : @key(constant) Packed_Format; @RI{-- Types for external representation of COBOL binary data} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @key(type) @AdaTypeDefn{Byte} @key(is) @key(mod) 2**COBOL_Character'Size; @key(type) @AdaTypeDefn{Byte_Array} @key(is) @key(array) (Positive @key(range) <>) @key(of) Byte@Chg{Version=[3],New=[ @key[with] Pack],Old=[; @key(pragma) Pack (Byte_Array)]}; @AdaExcDefn{Conversion_Error} : @key(exception); @key(generic) @key(type) Num @key(is) @key(delta) <> @key(digits) <>; @key(package) @AdaPackDefn{Decimal_Conversions} @key(is) @RI{-- Display Formats: data values are represented as Numeric} @key(function) @AdaSubDefn{Valid} (Item : @key(in) Numeric; Format : @key(in) Display_Format) @key(return) Boolean; @key(function) @AdaSubDefn{Length} (Format : @key(in) Display_Format) @key(return) Natural; @key(function) @AdaSubDefn{To_Decimal} (Item : @key(in) Numeric; Format : @key(in) Display_Format) @key(return) Num; @key(function) @AdaSubDefn{To_Display} (Item : @key(in) Num; Format : @key(in) Display_Format) @key(return) Numeric; @RI{-- Packed Formats: data values are represented as Packed_Decimal} @key(function) @AdaSubDefn{Valid} (Item : @key(in) Packed_Decimal; Format : @key(in) Packed_Format) @key(return) Boolean; @key(function) @AdaSubDefn{Length} (Format : @key(in) Packed_Format) @key(return) Natural; @key(function) @AdaSubDefn{To_Decimal} (Item : @key(in) Packed_Decimal; Format : @key(in) Packed_Format) @key(return) Num; @key(function) @AdaSubDefn{To_Packed} (Item : @key(in) Num; Format : @key(in) Packed_Format) @key(return) Packed_Decimal; @RI{-- Binary Formats: external data values are represented as Byte_Array} @key(function) @AdaSubDefn{Valid} (Item : @key(in) Byte_Array; Format : @key(in) Binary_Format) @key(return) Boolean; @key(function) @AdaSubDefn{Length} (Format : @key(in) Binary_Format) @key(return) Natural; @key(function) @AdaSubDefn{To_Decimal} (Item : @key(in) Byte_Array; Format : @key(in) Binary_Format) @key(return) Num; @key(function) @AdaSubDefn{To_Binary} (Item : @key(in) Num; Format : @key(in) Binary_Format) @key(return) Byte_Array; @RI{-- Internal Binary formats: data values are of type Binary or Long_Binary} @key(function) @AdaSubDefn{To_Decimal} (Item : @key(in) Binary) @key(return) Num; @key(function) @AdaSubDefn{To_Decimal} (Item : @key(in) Long_Binary) @key(return) Num; @key(function) @AdaSubDefn{To_Binary} (Item : @key(in) Num) @key(return) Binary; @key(function) @AdaSubDefn{To_Long_Binary} (Item : @key(in) Num) @key(return) Long_Binary; @key(end) Decimal_Conversions; @key(private) ... -- @RI{not specified by the language} @key(end) Interfaces.COBOL; @end{Example} @ChgImplDef{Version=[1],Kind=[Revised],InitialVersion=[0], Text=[The types Floating, Long_Floating, Binary, Long_Binary, Decimal_Element, and COBOL_Character; and the initializations of the variables Ada_To_COBOL and COBOL_To_Ada, in Interfaces.COBOL@Chg{New=[.],Old=[]}]} Each of the types in Interfaces.COBOL is COBOL-compatible. The types Floating and Long_Floating correspond to the native types in COBOL for data items with computational usage implemented by floating point. The types Binary and Long_Binary correspond to the native types in COBOL for data items with binary usage, or with computational usage implemented by binary. Max_Digits_Binary is the largest number of decimal digits in a numeric value that is represented as Binary. Max_Digits_Long_Binary is the largest number of decimal digits in a numeric value that is represented as Long_Binary. The type Packed_Decimal corresponds to COBOL's packed-decimal usage. The type COBOL_Character defines the run-time character set used in the COBOL implementation. Ada_To_COBOL and COBOL_To_Ada are the mappings between the Ada and COBOL run-time character sets. @begin{reason} The character mappings are visible variables, since the user needs the ability to modify them at run time. @end{reason} Type Alphanumeric corresponds to COBOL's alphanumeric data category. Each of the functions To_COBOL and To_Ada converts its parameter based on the mappings Ada_To_COBOL and COBOL_To_Ada, respectively. The length of the result for each is the length of the parameter, and the lower bound of the result is 1. Each component of the result is obtained by applying the relevant mapping to the corresponding component of the parameter. Each of the procedures To_COBOL and To_Ada copies converted elements from Item to Target, using the appropriate mapping (Ada_To_COBOL or COBOL_To_Ada, respectively). The index in Target of the last element assigned is returned in Last (0 if Item is a null array). @Defn2{Term=[Constraint_Error],Sec=(raised by failure of run-time check)} If Item'Length exceeds Target'Length, Constraint_Error is propagated. Type Numeric corresponds to COBOL's numeric data category with display usage. @Trailing@;The types Display_Format, Binary_Format, and Packed_Format are used in conversions between Ada decimal type values and COBOL internal or external data representations. The value of the constant Native_Binary is either High_Order_First or Low_Order_First, depending on the implementation. @begin{DescribeCode} @begin{Example}@Keepnext @key(function) Valid (Item : @key(in) Numeric; Format : @key(in) Display_Format) @key(return) Boolean; @end{Example} @Leading@;The function Valid checks that the Item parameter has a value consistent with the value of Format. If the value of Format is other than Unsigned, Leading_Separate, and Trailing_Separate, the effect is implementation defined. If Format does have one of these values, the following rules apply: @begin{itemize} @ChgRef{Version=[1],Kind=[Revised],Ref=[8652/0066],ARef=[AI95-00071-01]} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0264-1]} Format=Unsigned: if Item comprises @Chg{New=[],Old=[zero or more leading space characters followed by ]}one or more decimal digit characters@Chg{Version=[3],New=[,],Old=[]} then Valid returns True, else it returns False. @ChgRef{Version=[1],Kind=[Revised],Ref=[8652/0066],ARef=[AI95-00071-01]} Format=Leading_Separate: if Item comprises @Chg{New=[],Old=[zero or more leading space characters, followed by ]}a single occurrence of the plus or minus sign character, and then one or more decimal digit characters, then Valid returns True, else it returns False. @ChgRef{Version=[1],Kind=[Revised],Ref=[8652/0066],ARef=[AI95-00071-01]} @Trailing@;Format=Trailing_Separate: if Item comprises @Chg{New=[],Old=[zero or more leading space characters, followed by ]}one or more decimal digit characters and finally a plus or minus sign character, then Valid returns True, else it returns False. @end{itemize} @begin{Example}@Keepnext @key(function) Length (Format : @key(in) Display_Format) @key(return) Natural; @end{Example} @Trailing@;The Length function returns the minimal length of a Numeric value sufficient to hold any value of type Num when represented as Format. @begin{Example}@Keepnext @key(function) To_Decimal (Item : @key(in) Numeric; Format : @key(in) Display_Format) @key(return) Num; @end{Example} @Trailing@;Produces a value of type Num corresponding to Item as represented by Format. The number of digits after the assumed radix point in Item is Num'Scale. Conversion_Error is propagated if the value represented by Item is outside the range of Num. @begin{discussion} There is no issue of truncation versus rounding, since the number of decimal places is established by Num'Scale.@end{discussion} @begin{Example}@Keepnext @key(function) To_Display (Item : @key(in) Num; Format : @key(in) Display_Format) @key(return) Numeric; @end{Example} @ChgRef{Version=[1],Kind=[Revised],Ref=[8652/0067],ARef=[AI95-00072-01]} @Trailing@;This function returns the Numeric value for Item, represented in accordance with Format. @Chg{New=[The length of the returned value is Length(Format), and the lower bound is 1. ],Old=[]}Conversion_Error is propagated if Num is negative and Format is Unsigned. @begin{Example}@Keepnext @key(function) Valid (Item : @key(in) Packed_Decimal; Format : @key(in) Packed_Format) @key(return) Boolean; @end{Example} @Trailing@;This function returns True if Item has a value consistent with Format, and False otherwise. The rules for the formation of Packed_Decimal values are implementation defined. @begin{Example}@Keepnext @key(function) Length (Format : @key(in) Packed_Format) @key(return) Natural; @end{Example} @Trailing@;This function returns the minimal length of a Packed_Decimal value sufficient to hold any value of type Num when represented as Format. @begin{Example}@Keepnext @key(function) To_Decimal (Item : @key(in) Packed_Decimal; Format : @key(in) Packed_Format) @key(return) Num; @end{Example} @Trailing@;Produces a value of type Num corresponding to Item as represented by Format. Num'Scale is the number of digits after the assumed radix point in Item. Conversion_Error is propagated if the value represented by Item is outside the range of Num. @begin{Example}@Keepnext @key(function) To_Packed (Item : @key(in) Num; Format : @key(in) Packed_Format) @key(return) Packed_Decimal; @end{Example} @ChgRef{Version=[1],Kind=[Revised],Ref=[8652/0067],ARef=[AI95-00072-01]} @Trailing@;This function returns the Packed_Decimal value for Item, represented in accordance with Format. @Chg{New=[The length of the returned value is Length(Format), and the lower bound is 1. ],Old=[]}Conversion_Error is propagated if Num is negative and Format is Packed_Unsigned. @begin{Example}@Keepnext @key(function) Valid (Item : @key(in) Byte_Array; Format : @key(in) Binary_Format) @key(return) Boolean; @end{Example} @Trailing@;This function returns True if Item has a value consistent with Format, and False otherwise. @begin{ramification} This function returns False only when the represented value is outside the range of Num.@end{ramification} @begin{Example}@Keepnext @key(function) Length (Format : @key(in) Binary_Format) @key(return) Natural; @end{Example} @Trailing@;This function returns the minimal length of a Byte_Array value sufficient to hold any value of type Num when represented as Format. @begin{Example}@Keepnext @key(function) To_Decimal (Item : @key(in) Byte_Array; Format : @key(in) Binary_Format) @key(return) Num; @end{Example} @Trailing@;Produces a value of type Num corresponding to Item as represented by Format. Num'Scale is the number of digits after the assumed radix point in Item. Conversion_Error is propagated if the value represented by Item is outside the range of Num. @begin{Example}@Keepnext @key(function) To_Binary (Item : @key(in) Num; Format : @key(in) Binary_Format) @key(return) Byte_Array; @end{Example} @ChgRef{Version=[1],Kind=[Revised],Ref=[8652/0067],ARef=[AI95-00072-01]} @Trailing@;This function returns the Byte_Array value for Item, represented in accordance with Format. @Chg{New=[The length of the returned value is Length(Format), and the lower bound is 1.],Old=[]} @begin{Example}@Keepnext @key(function) To_Decimal (Item : @key(in) Binary) @key(return) Num; @comment{Blank line} @key(function) To_Decimal (Item : @key(in) Long_Binary) @key(return) Num; @end{Example} @Trailing@;These functions convert from COBOL binary format to a corresponding value of the decimal type Num. Conversion_Error is propagated if Item is too large for Num. @begin{Ramification} There is no rescaling performed on the conversion. That is, the returned value in each case is a @lquotes@;bit copy@rquotes@; if Num has a binary radix. The programmer is responsible for maintaining the correct scale. @end{ramification} @begin{Example}@Keepnext @key(function) To_Binary (Item : @key(in) Num) @key(return) Binary; @comment{Blank line} @key(function) To_Long_Binary (Item : @key(in) Num) @key(return) Long_Binary; @end{Example} These functions convert from Ada decimal to COBOL binary format. Conversion_Error is propagated if the value of Item is too large to be represented in the result type. @begin{discussion} One style of interface supported for COBOL, similar to what is provided for C, is the ability to call and pass parameters to an existing COBOL program. Thus the interface package supplies types that can be used in an Ada program as parameters to subprograms whose bodies will be in COBOL. These types map to COBOL's alphanumeric and numeric data categories. Several types are provided for support of alphanumeric data. Since COBOL's run-time character set is not necessarily the same as Ada's, Interfaces.COBOL declares an implementation-defined character type COBOL_Character, and mappings between Character and COBOL_Character. These mappings are visible variables (rather than, say, functions or constant arrays), since in the situation where COBOL_Character is EBCDIC, the flexibility of dynamically modifying the mappings is needed. Corresponding to COBOL's alphanumeric data is the string type Alphanumeric. Numeric data may have either a @lquotes@;display@rquotes@; or @lquotes@;computational@rquotes@; representation in COBOL. On the Ada side, the data is of a decimal fixed point type. Passing an Ada decimal data item to a COBOL program requires conversion from the Ada decimal type to some type that reflects the representation expected on the COBOL side. @begin{Itemize} Computational Representation @NoPrefix@;Floating point representation is modeled by Ada floating point types, Floating and Long_Floating. Conversion between these types and Ada decimal types is obtained directly, since the type name serves as a conversion function. @NoPrefix@;Binary representation is modeled by an Ada integer type, Binary, and possibly other types such as Long_Binary. Conversion between, say, Binary and a decimal type is through functions from an instantiation of the generic package Decimal_Conversions. @NoPrefix@;Packed decimal representation is modeled by the Ada array type Packed_Decimal. Conversion between packed decimal and a decimal type is through functions from an instantiation of the generic package Decimal_Conversions. Display Representation @NoPrefix@;Display representation for numeric data is modeled by the array type Numeric. Conversion between display representation and a decimal type is through functions from an instantiation of the generic package Decimal_Conversions. A parameter to the conversion function indicates the desired interpretation of the data (e.g., signed leading separate, etc.) @end{Itemize} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @Chg{Version=[3],New=[The],Old=[Pragma]} Convention@Chg{Version=[3],New=[ of],Old=[(COBOL, T) may be applied to]} a record type @Chg{Version=[3],New=[may be specified as COBOL],Old=[T]} to direct the compiler to choose a COBOL-compatible representation for objects of the type. The package Interfaces.COBOL allows the Ada programmer to deal with data from files (or databases) created by a COBOL program. For data that is alphanumeric, or in display or packed decimal format, the approach is the same as for passing parameters (instantiate Decimal_Conversions to obtain the needed conversion functions). For binary data, the external representation is treated as a Byte array, and an instantiation of Decimal_IO produces a package that declares the needed conversion functions. A parameter to the conversion function indicates the desired interpretation of the data (e.g., high- versus low-order byte first). @end{discussion} @end{DescribeCode} @end{StaticSem} @begin{ImplReq} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} An implementation shall support @Chg{Version=[3],New=[specifying aspect],Old=[pragma]} Convention with a COBOL @i[convention]_@nt[identifier] for a COBOL-eligible type (see @RefSecNum(Interfacing Aspects)). @begin{ramification} An implementation supporting this package shall ensure that if the bounds of a Packed_Decimal, Alphanumeric, or Numeric variable are static, then the representation of the object comprises solely the array components (that is, there is no implicit run-time @lquotes@;descriptor@rquotes@; that is part of the object). @end{ramification} @end{ImplReq} @begin{ImplPerm} An implementation may provide additional constants of the private types Display_Format, Binary_Format, or Packed_Format. @begin{Reason} This is to allow exploitation of other external formats that may be available in the COBOL implementation.@end{reason} An implementation may provide further floating point and integer types in Interfaces.COBOL to match additional native COBOL types, and may also supply corresponding conversion functions in the generic package Decimal_Conversions. @end{ImplPerm} @begin{ImplAdvice} An Ada implementation should support the following interface correspondences between Ada and COBOL. @begin[itemize] An Ada @key[access] T parameter is passed as a @lquotes@;BY REFERENCE@rquotes@; data item of the COBOL type corresponding to T. An Ada @key[in] scalar parameter is passed as a @lquotes@;BY CONTENT@rquotes@; data item of the corresponding COBOL type. Any other Ada parameter is passed as a @lquotes@;BY REFERENCE@rquotes@; data item of the COBOL type corresponding to the Ada parameter type; for scalars, a local copy is used if necessary to ensure by-copy semantics. @end[itemize] @ChgImplAdvice{Version=[2],Kind=[AddedNormal],Text=[@ChgAdded{Version=[2], Text=[If COBOL interfacing is supported, the interface correspondences between Ada and COBOL should be supported.]}]} @end{ImplAdvice} @begin[Notes] @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} An implementation is not required to support @Chg{Version=[3],New=[specifying aspect],Old=[pragma]} Convention for access types, nor is it required to support @Chg{Version=[3],New=[specifying aspects],Old=[pragma]} Import, Export@Chg{Version=[3],New=[,],Old=[]} or Convention for functions. @begin{reason} COBOL does not have a pointer facility, and a COBOL program does not return a value.@end{reason} If an Ada subprogram is exported to COBOL, then a call from COBOL call may specify either @lquotes@;BY CONTENT@rquotes@; or @lquotes@;BY REFERENCE@rquotes@;. @end[Notes] @RMNewPageVer{Version=[3]}@Comment{For printed version of Ada 2012 RM} @begin{Examples} @Leading@Keepnext@i{Examples of Interfaces.COBOL:} @begin{Example} @key(with) Interfaces.COBOL; @key(procedure) Test_Call @key(is) @RI{-- Calling a foreign COBOL program} @RI{-- Assume that a COBOL program PROG has the following declaration} @RI{-- in its LINKAGE section:} @RI{-- 01 Parameter-Area} @RI{-- 05 NAME PIC X(20).} @RI{-- 05 SSN PIC X(9).} @RI{-- 05 SALARY PIC 99999V99 USAGE COMP.} @RI{-- The effect of PROG is to update SALARY based on some algorithm} @key(package) COBOL @key(renames) Interfaces.COBOL; @key(type) Salary_Type @key(is) @key(delta) 0.01 @key(digits) 7; @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @key(type) COBOL_Record @key(is) @key(record) Name : COBOL.Numeric(1..20); SSN : COBOL.Numeric(1..9); Salary : COBOL.Binary; @RI{-- Assume Binary = 32 bits} @key(end) @key(record)@Chg{Version=[3],New=[ @key[with] Convention => COBOL],Old=[; @key(pragma) Convention (COBOL, COBOL_Record)]}; @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @key(procedure) Prog (Item : @key(in) @key(out) COBOL_Record)@Chg{Version=[3],New=[ @key[with] Import => True, Convention => COBOL],Old=[; @key(pragma) Import (COBOL, Prog, "PROG")]}; @key(package) Salary_Conversions @key(is) @key(new) COBOL.Decimal_Conversions(Salary_Type); Some_Salary : Salary_Type := 12_345.67; Some_Record : COBOL_Record := (Name => "Johnson, John ", SSN => "111223333", Salary => Salary_Conversions.To_Binary(Some_Salary)); @key(begin) Prog (Some_Record); ... @key(end) Test_Call; @end{Example} @begin{Example} @key(with) Interfaces.COBOL; @key(with) COBOL_Sequential_IO; @RI{-- Assumed to be supplied by implementation} @key(procedure) Test_External_Formats @key(is) @RI{-- Using data created by a COBOL program} @RI{-- Assume that a COBOL program has created a sequential file with} @RI{-- the following record structure, and that we need to} @RI{-- process the records in an Ada program} @RI{-- 01 EMPLOYEE-RECORD} @RI{-- 05 NAME PIC X(20).} @RI{-- 05 SSN PIC X(9).} @RI{-- 05 SALARY PIC 99999V99 USAGE COMP.} @RI{-- 05 ADJUST PIC S999V999 SIGN LEADING SEPARATE.} @RI{-- The COMP data is binary (32 bits), high-order byte first} @key(package) COBOL @key(renames) Interfaces.COBOL; @key(type) Salary_Type @key(is) @key(delta) 0.01 @key(digits) 7; @key(type) Adjustments_Type @key(is) @key(delta) 0.001 @key(digits) 6; @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @key(type) COBOL_Employee_Record_Type @key(is) @RI{-- External representation} @key(record) Name : COBOL.Alphanumeric(1..20); SSN : COBOL.Alphanumeric(1..9); Salary : COBOL.Byte_Array(1..4); Adjust : COBOL.Numeric(1..7); @RI{-- Sign and 6 digits} @key(end) @key(record)@Chg{Version=[3],New=[ @key[with] Convention => COBOL],Old=[; @key(pragma) Convention (COBOL, COBOL_Employee_Record_Type)]}; @key(package) COBOL_Employee_IO @key(is) @key(new) COBOL_Sequential_IO(COBOL_Employee_Record_Type); @key(use) COBOL_Employee_IO; COBOL_File : File_Type; @key(type) Ada_Employee_Record_Type @key(is) @RI{-- Internal representation} @key(record) Name : String(1..20); SSN : String(1..9); Salary : Salary_Type; Adjust : Adjustments_Type; @key(end) @key(record); COBOL_Record : COBOL_Employee_Record_Type; Ada_Record : Ada_Employee_Record_Type; @key(package) Salary_Conversions @key(is) @key(new) COBOL.Decimal_Conversions(Salary_Type); @key(use) Salary_Conversions; @key(package) Adjustments_Conversions @key(is) @key(new) COBOL.Decimal_Conversions(Adjustments_Type); @key(use) Adjustments_Conversions; @key(begin) Open (COBOL_File, Name => "Some_File"); @key(loop) Read (COBOL_File, COBOL_Record); Ada_Record.Name := To_Ada(COBOL_Record.Name); Ada_Record.SSN := To_Ada(COBOL_Record.SSN); Ada_Record.Salary := To_Decimal(COBOL_Record.Salary, COBOL.High_Order_First); Ada_Record.Adjust := To_Decimal(COBOL_Record.Adjust, COBOL.Leading_Separate); ... @RI{-- Process Ada_Record} @key(end) @key(loop); @key(exception) @key[when] End_Error => ... @key(end) Test_External_Formats; @end{Example} @end{Examples} @begin{DiffWord95} @ChgRef{Version=[2],Kind=[AddedNormal],Ref=[8652/0066],ARef=[AI95-00071-01]} @ChgAdded{Version=[2],Text=[@b Corrected the definition of Valid to match COBOL.]} @ChgRef{Version=[2],Kind=[AddedNormal],Ref=[8652/0067],ARef=[AI95-00072-01]} @ChgAdded{Version=[2],Text=[@b Specified the bounds of the results of To_Display, To_Packed, and To_Binary.]} @end{DiffWord95} @LabeledClause{Interfacing with Fortran} @begin{Intro} @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @Defn{interface to Fortran} @Defn{Fortran interface} The facilities relevant to interfacing with the Fortran language are the package Interfaces.Fortran and support for @Chg{Version=[3],New=[specifying ],Old=[]}the @Chg{Version=[3],New=[],Old=[Import, Export and ]}Convention @Chg{Version=[3],New=[aspect],Old=[pragmas]} with @SynI{convention_}@nt{identifier} Fortran. The package Interfaces.Fortran defines Ada types whose representations are identical to the default representations of the Fortran intrinsic types Integer, Real, Double Precision, Complex, Logical, and Character in a supported Fortran implementation. These Ada types can therefore be used to pass objects between Ada and Fortran programs. @end{Intro} @begin{StaticSem} @Leading@Keepnext@;The library package Interfaces.Fortran has the following declaration: @begin{Example} @key[with] Ada.Numerics.Generic_Complex_Types; @RI{-- see @RefSecNum{Complex Types}} @key[pragma] Elaborate_All(Ada.Numerics.Generic_Complex_Types); @key[package] Interfaces.Fortran @key[is]@ChildUnit{Parent=[Interfaces],Child=[Fortran]} @key[pragma] Pure(Fortran); @key[type] @AdaTypeDefn{Fortran_Integer} @key[is] @key[range] @RI{implementation-defined}; @key[type] @AdaTypeDefn{Real} @key[is] @key[digits] @RI{implementation-defined}; @key[type] @AdaTypeDefn{Double_Precision} @key[is] @key[digits] @RI{implementation-defined}; @key[type] @AdaTypeDefn{Logical} @key[is] @key[new] Boolean; @key[package] @AdaPackDefn{Single_Precision_Complex_Types} @key[is] @key[new] Ada.Numerics.Generic_Complex_Types (Real); @key[type] @AdaTypeDefn{Complex} @key[is] @key[new] Single_Precision_Complex_Types.Complex; @key[subtype] @AdaSubtypeDefn{Name=[Imaginary],Of=[Imaginary]} @key[is] Single_Precision_Complex_Types.Imaginary; @AdaObjDefn{i} : Imaginary @key[renames] Single_Precision_Complex_Types.i; @AdaObjDefn{j} : Imaginary @key[renames] Single_Precision_Complex_Types.j; @key[type] @AdaTypeDefn{Character_Set} @key[is] @RI{implementation-defined character type}; @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @key[type] @AdaTypeDefn{Fortran_Character} @key[is] @key[array] (Positive @key[range] <>) @key[of] Character_Set@Chg{Version=[3],New=[ @key[with] Pack],Old=[; @key[pragma] Pack (Fortran_Character)]}; @key[function] @AdaSubDefn{To_Fortran} (Item : @key[in] Character) @key[return] Character_Set; @key[function] @AdaSubDefn{To_Ada} (Item : @key[in] Character_Set) @key[return] Character; @key(function) @AdaSubDefn{To_Fortran} (Item : @key(in) String) @key(return) Fortran_Character; @key(function) @AdaSubDefn{To_Ada} (Item : @key(in) Fortran_Character) @key(return) String; @key(procedure) @AdaSubDefn{To_Fortran} (Item : @key(in) String; Target : @key(out) Fortran_Character; Last : @key(out) Natural); @key(procedure) @AdaSubDefn{To_Ada} (Item : @key(in) Fortran_Character; Target : @key(out) String; Last : @key(out) Natural); @key[end] Interfaces.Fortran; @end{Example} @ChgImplDef{Version=[1],Kind=[Added],Text=[@Chg{New=[The types Fortran_Integer, Real, Double_Precision, and Character_Set in Interfaces.Fortran.],Old=[]}]} @begin{Ramification} The means by which the Complex type is provided in Interfaces.Fortran creates a dependence of Interfaces.Fortran on Numerics.Generic_Complex_Types (see @RefSecNum{Complex Types}). This dependence is intentional and unavoidable, if the Fortran-compatible Complex type is to be useful in Ada code without duplicating facilities defined elsewhere. @end{Ramification} The types Fortran_Integer, Real, Double_Precision, Logical, Complex, and Fortran_Character are Fortran-compatible. The To_Fortran and To_Ada functions map between the Ada type Character and the Fortran type Character_Set, and also between the Ada type String and the Fortran type Fortran_Character. The To_Fortran and To_Ada procedures have analogous effects to the string conversion subprograms found in Interfaces.COBOL. @end{StaticSem} @begin[ImplReq] @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} An implementation shall support @Chg{Version=[3],New=[specifying aspect],Old=[@nt[pragma]]} Convention with a Fortran @i[convention]_@nt[identifier] for a Fortran-eligible type (see @RefSecNum(Interfacing Aspects)). @end[ImplReq] @begin{ImplPerm} An implementation may add additional declarations to the Fortran interface packages. For example, the Fortran interface package for an implementation of Fortran 77 (ANSI X3.9-1978) that defines types like Integer*@i{n}, Real*@i{n}, Logical*@i{n}, and Complex*@i{n} may contain the declarations of types named Integer_@!Star_@i{n}, Real_@!Star_@i{n}, Logical_@!Star_@i{n}, and Complex_@!Star_@i{n}. (This convention should not apply to Character*@i{n}, for which the Ada analog is the constrained array subtype Fortran_Character (1..@i{n}).) Similarly, the Fortran interface package for an implementation of Fortran 90 that provides multiple @i{kinds} of intrinsic types, e.g. Integer (Kind=@i{n}), Real (Kind=@i{n}), Logical (Kind=@i{n}), Complex (Kind=@i{n}), and Character (Kind=@i{n}), may contain the declarations of types with the recommended names Integer_Kind_@i{n}, Real_Kind_@i{n}, Logical_Kind_@i{n}, Complex_Kind_@i{n}, and Character_Kind_@i{n}. @begin[discussion] Implementations may add auxiliary declarations as needed to assist in the declarations of additional Fortran-compatible types. For example, if a double precision complex type is defined, then Numerics.@!Generic_@!Complex_@!Types may be instantiated for the double precision type. Similarly, if a wide character type is defined to match a Fortran 90 wide character type (accessible in Fortran 90 with the Kind modifier), then an auxiliary character set may be declared to serve as its component type. @end[discussion] @end{ImplPerm} @begin{ImplAdvice} @Leading@;An Ada implementation should support the following interface correspondences between Ada and Fortran: @begin[itemize] An Ada procedure corresponds to a Fortran subroutine. An Ada function corresponds to a Fortran function. An Ada parameter of an elementary, array, or record type T is passed as a T@-(F) argument to a Fortran procedure, where T@-(F) is the Fortran type corresponding to the Ada type T, and where the INTENT attribute of the corresponding dummy argument matches the Ada formal parameter mode; the Fortran implementation's parameter passing conventions are used. For elementary types, a local copy is used if necessary to ensure by-copy semantics. An Ada parameter of an access-to-subprogram type is passed as a reference to a Fortran procedure whose interface corresponds to the designated subprogram's specification. @end[itemize] @ChgImplAdvice{Version=[2],Kind=[AddedNormal],Text=[@ChgAdded{Version=[2], Text=[If Fortran interfacing is supported, the interface correspondences between Ada and Fortran should be supported.]}]} @end{ImplAdvice} @begin[Notes] An object of a Fortran-compatible record type, declared in a library package or subprogram, can correspond to a Fortran common block; the type also corresponds to a Fortran @lquotes@;derived type@rquotes@;. @end[Notes] @begin{Examples} @Leading@Keepnext@i{Example of Interfaces.Fortran:} @begin{Example} @key[with] Interfaces.Fortran; @key[use] Interfaces.Fortran; @key[procedure] Ada_Application @key[is] @ChgRef{Version=[3],Kind=[Revised],ARef=[AI05-0229-1]} @key[type] Fortran_Matrix @key[is] @key[array] (Integer @key[range] <>, Integer @key[range] <>) @key[of] Double_Precision@Chg{Version=[3],New=[ @key[with] Convention => Fortran; ],Old=[; @key[pragma] Convention (Fortran, Fortran_Matrix);]} @RI{-- stored in Fortran's} @RI{-- column-major order} @key[procedure] Invert (Rank : @key[in] Fortran_Integer; X : @key[in] @key[out] Fortran_Matrix)@Chg{Version=[3],New=[ @key[with] Import => True, Convention => Fortran;],Old=[; @key[pragma] Import (Fortran, Invert); ]} @RI{-- a Fortran subroutine} Rank : @key[constant] Fortran_Integer := 100; My_Matrix : Fortran_Matrix (1 .. Rank, 1 .. Rank); @key[begin] ... My_Matrix := ...; ... Invert (Rank, My_Matrix); ... @key[end] Ada_Application; @end{Example} @end{Examples}