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diff --git a/gcc/ada/sem_attr.ads b/gcc/ada/sem_attr.ads new file mode 100644 index 00000000000..ccbc3f49d4c --- /dev/null +++ b/gcc/ada/sem_attr.ads @@ -0,0 +1,595 @@ +------------------------------------------------------------------------------ +-- -- +-- GNAT COMPILER COMPONENTS -- +-- -- +-- S E M _ A T T R -- +-- -- +-- S p e c -- +-- -- +-- $Revision: 1.26 $ +-- -- +-- Copyright (C) 1992-1999, Free Software Foundation, Inc. -- +-- -- +-- GNAT is free software; you can redistribute it and/or modify it under -- +-- terms of the GNU General Public License as published by the Free Soft- -- +-- ware Foundation; either version 2, or (at your option) any later ver- -- +-- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- +-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- +-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- +-- for more details. You should have received a copy of the GNU General -- +-- Public License distributed with GNAT; see file COPYING. If not, write -- +-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, -- +-- MA 02111-1307, USA. -- +-- -- +-- GNAT was originally developed by the GNAT team at New York University. -- +-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). -- +-- -- +------------------------------------------------------------------------------ + +-- Attribute handling is isolated in a separate package to ease the addition +-- of implementation defined attributes. Logically this processing belongs +-- in chapter 4. See Sem_Ch4 for a description of the relation of the +-- Analyze and Resolve routines for expression components. + +-- This spec also documents all GNAT implementation defined pragmas + +with Snames; use Snames; +with Types; use Types; + +package Sem_Attr is + + type Attribute_Class_Array is array (Attribute_Id) of Boolean; + -- Type used to build attribute classification flag arrays + + ----------------------------------------- + -- Implementation Dependent Attributes -- + ----------------------------------------- + + -- This section describes the implementation dependent attributes + -- provided in GNAT, as well as constructing an array of flags + -- indicating which attributes these are. + + Attribute_Impl_Def : Attribute_Class_Array := Attribute_Class_Array'( + + ------------------ + -- Abort_Signal -- + ------------------ + + Attribute_Abort_Signal => True, + -- + -- Standard'Abort_Signal (Standard is the only allowed prefix) + -- provides the entity for the special exception used to signal + -- task abort or asynchronous transfer of control. Normally this + -- attribute should only be used in the tasking runtime (it is + -- highly peculiar, and completely outside the normal semantics + -- of Ada, for a user program to intercept the abort exception). + + ------------------ + -- Address_Size -- + ------------------ + + Attribute_Address_Size => True, + -- + -- Standard'Address_Size (Standard is the only allowed prefix) is + -- a static constant giving the number of bits in an Address. It + -- is used primarily for constructing the definition of Memory_Size + -- in package Standard, but may be freely used in user programs. + -- This is a static attribute. + + --------------- + -- Asm_Input -- + --------------- + + Attribute_Asm_Input => True, + -- + -- Used only in conjunction with the Asm and Asm_Volatile subprograms + -- in package Machine_Code to construct machine instructions. See + -- documentation in package Machine_Code in file s-maccod.ads. + + ---------------- + -- Asm_Output -- + ---------------- + + Attribute_Asm_Output => True, + -- + -- Used only in conjunction with the Asm and Asm_Volatile subprograms + -- in package Machine_Code to construct machine instructions. See + -- documentation in package Machine_Code in file s-maccod.ads. + + --------------- + -- AST_Entry -- + --------------- + + Attribute_AST_Entry => True, + -- + -- E'Ast_Entry, where E is a task entry, yields a value of the + -- predefined type System.DEC.AST_Handler, that enables the given + -- entry to be called when an AST occurs. If the name to which the + -- attribute applies has not been specified with the pragma AST_Entry, + -- the attribute returns the value No_Ast_Handler, and no AST occurs. + -- If the entry is for a task that is not callable (T'Callable False), + -- the exception program error is raised. If an AST occurs for an + -- entry of a task that is terminated, the program is erroneous. + -- + -- The attribute AST_Entry is supported only in OpenVMS versions + -- of GNAT. It will be rejected as illegal in other GNAT versions. + + --------- + -- Bit -- + --------- + + Attribute_Bit => True, + -- + -- Obj'Bit, where Obj is any object, yields the bit offset within + -- the storage unit (byte) that contains the first bit of storage + -- allocated for the object. The value of this attribute is of the + -- type Universal_Integer, and is always a non-negative number not + -- exceeding the value of System.Storage_Unit. + -- + -- For an object that is a variable or a constant allocated in a + -- register, the value is zero. (The use of this attribute does not + -- force the allocation of a variable to memory). + -- + -- For an object that is a formal parameter, this attribute applies + -- to either the matching actual parameter or to a copy of the + -- matching actual parameter. + -- + -- For an access object the value is zero. Note that Obj.all'Bit is + -- subject to an Access_Check for the designated object. Similarly + -- for a record component X.C'Bit is subject to a discriminant check + -- and X(I).Bit and X(I1..I2)'Bit are subject to index checks. + -- + -- This attribute is designed to be compatible with the DEC Ada + -- definition and implementation of the Bit attribute. + + ------------------ + -- Code_Address -- + ------------------ + + Attribute_Code_Address => True, + -- + -- subp'Code_Address, where subp is a subprogram entity, gives the + -- address of the first generated instruction for a subprogram. This + -- is often, but not always the same as the 'Address value, which is + -- the address to be used in a call. The differences occur in the case + -- of a nested procedure (where Address yields the address of the + -- trampoline code used to load the static link), and on some systems + -- which use procedure descriptors (in which case Address yields the + -- address of the descriptor). + + ----------------------- + -- Default_Bit_Order -- + ----------------------- + + Attribute_Default_Bit_Order => True, + -- + -- Standard'Default_Bit_Order (Standard is the only permissible prefix), + -- provides the value System.Default_Bit_Order as a Pos value (0 for + -- High_Order_First, 1 for Low_Order_First). This is used to construct + -- the definition of Default_Bit_Order in package System. This is a + -- static attribute. + + --------------- + -- Elab_Body -- + --------------- + + Attribute_Elab_Body => True, + -- + -- This attribute can only be applied to a program unit name. It + -- returns the entity for the corresponding elaboration procedure + -- for elaborating the body of the referenced unit. This is used + -- in the main generated elaboration procedure by the binder, and + -- is not normally used in any other context, but there may be + -- specialized situations in which it is useful to be able to + -- call this elaboration procedure from Ada code, e.g. if it + -- is necessary to do selective reelaboration to fix some error. + + --------------- + -- Elab_Spec -- + --------------- + + Attribute_Elab_Spec => True, + -- + -- This attribute can only be applied to a program unit name. It + -- returns the entity for the corresponding elaboration procedure + -- for elaborating the spec of the referenced unit. This is used + -- in the main generated elaboration procedure by the binder, and + -- is not normally used in any other context, but there may be + -- specialized situations in which it is useful to be able to + -- call this elaboration procedure from Ada code, e.g. if it + -- is necessary to do selective reelaboration to fix some error. + + ---------------- + -- Elaborated -- + ---------------- + + Attribute_Elaborated => True, + -- + -- Lunit'Elaborated, where Lunit is a library unit, yields a boolean + -- value indicating whether or not the body of the designated library + -- unit has been elaborated yet. + + + -------------- + -- Enum_Rep -- + -------------- + + Attribute_Enum_Rep => True, + -- + -- For every enumeration subtype S, S'Enum_Rep denotes a function + -- with the following specification: + -- + -- function S'Enum_Rep (Arg : S'Base) return universal_integer; + -- + -- The function returns the representation value for the given + -- enumeration value. This will be equal to the 'Pos value in the + -- absence of an enumeration representation clause. This is a static + -- attribute (i.e. the result is static if the argument is static). + + ----------------- + -- Fixed_Value -- + ----------------- + + Attribute_Fixed_Value => True, + -- + -- For every fixed-point type S, S'Fixed_Value denotes a function + -- with the following specification: + -- + -- function S'Fixed_Value (Arg : universal_integer) return S; + -- + -- The value returned is the fixed-point value V such that + -- + -- V = Arg * S'Small + -- + -- The effect is thus equivalent to first converting the argument + -- to the integer type used to represent S, and then doing an + -- unchecked conversion to the fixed-point type. This attribute is + -- primarily intended for use in implementation of the input-output + -- functions for fixed-point values. + + ----------------------- + -- Has_Discriminants -- + ----------------------- + + Attribute_Has_Discriminants => True, + -- + -- Gtyp'Has_Discriminants, where Gtyp is a generic formal type, yields + -- a Boolean value indicating whether or not the actual instantiation + -- type has discriminants. + + --------- + -- Img -- + --------- + + Attribute_Img => True, + -- + -- The 'Img function is defined for any prefix, P, that denotes an + -- object of scalar type T. P'Img is equivalent to T'Image (P). This + -- is convenient for debugging. For example: + -- + -- Put_Line ("X = " & X'Img); + -- + -- has the same meaning as the more verbose: + -- + -- Put_Line ("X = " & Temperature_Type'Image (X)); + -- + -- where Temperature_Type is the subtype of the object X. + + ------------------- + -- Integer_Value -- + ------------------- + + Attribute_Integer_Value => True, + -- + -- For every integer type S, S'Integer_Value denotes a function + -- with the following specification: + -- + -- function S'Integer_Value (Arg : universal_fixed) return S; + -- + -- The value returned is the integer value V, such that + -- + -- Arg = V * fixed-type'Small + -- + -- The effect is thus equivalent to first doing an unchecked convert + -- from the fixed-point type to its corresponding implementation type, + -- and then converting the result to the target integer type. This + -- attribute is primarily intended for use in implementation of the + -- standard input-output functions for fixed-point values. + + ------------------ + -- Machine_Size -- + ------------------ + + Attribute_Machine_Size => True, + -- + -- This attribute is identical to the Object_Size attribute. It is + -- provided for compatibility with the DEC attribute of this name. + + ---------------------------- + -- Max_Interrupt_Priority -- + ---------------------------- + + Attribute_Max_Interrupt_Priority => True, + -- + -- Standard'Max_Interrupt_Priority (Standard is the only permissible + -- prefix), provides the value System.Max_Interrupt_Priority, and is + -- intended primarily for constructing this definition in package + -- System (see note above in Default_Bit_Order description}. This + -- is a static attribute. + + ------------------ + -- Max_Priority -- + ------------------ + + Attribute_Max_Priority => True, + -- + -- Standard'Max_Priority (Standard is the only permissible prefix) + -- provides the value System.Max_Priority, and is intended primarily + -- for constructing this definition in package System (see note above + -- in Default_Bit_Order description). This is a static attribute. + + ----------------------- + -- Maximum_Alignment -- + ----------------------- + + Attribute_Maximum_Alignment => True, + -- + -- Standard'Maximum_Alignment (Standard is the only permissible prefix) + -- provides the maximum useful alignment value for the target. This + -- is a static value that can be used to specify the alignment for an + -- object, guaranteeing that it is properly aligned in all cases. The + -- time this is useful is when an external object is imported and its + -- alignment requirements are unknown. This is a static attribute. + + -------------------- + -- Mechanism_Code -- + -------------------- + + Attribute_Mechanism_Code => True, + -- + -- function'Mechanism_Code yeilds an integer code for the mechanism + -- used for the result of function, and subprogram'Mechanism_Code (n) + -- yields the mechanism used for formal parameter number n (a static + -- integer value, 1 = first parameter). The code returned is: + -- + -- 1 = by copy (value) + -- 2 = by reference + -- 3 = by descriptor (default descriptor type) + -- 4 = by descriptor (UBS unaligned bit string) + -- 5 = by descriptor (UBSB aligned bit string with arbitrary bounds) + -- 6 = by descriptor (UBA unaligned bit array) + -- 7 = by descriptor (S string, also scalar access type parameter) + -- 8 = by descriptor (SB string with arbitrary bounds) + -- 9 = by descriptor (A contiguous array) + -- 10 = by descriptor (NCA non-contiguous array) + + -------------------- + -- Null_Parameter -- + -------------------- + + Attribute_Null_Parameter => True, + -- + -- A reference T'Null_Parameter denotes an (imaginary) object of + -- type or subtype T allocated at (machine) address zero. The + -- attribute is allowed only as the default expression of a formal + -- parameter, or as an actual expression of a subporgram call. In + -- either case, the subprogram must be imported. + -- + -- The identity of the object is represented by the address zero + -- in the argument list, independent of the passing mechanism + -- (explicit or default). + -- + -- The reason that this capability is needed is that for a record + -- or other composite object passed by reference, there is no other + -- way of specifying that a zero address should be passed. + + ----------------- + -- Object_Size -- + ----------------- + + Attribute_Object_Size => True, + -- + -- Type'Object_Size is the same as Type'Size for all types except + -- fixed-point types and discrete types. For fixed-point types and + -- discrete types, this attribute gives the size used for default + -- allocation of objects and components of the size. See section + -- in Einfo ("Handling of type'Size values") for further details. + + ------------------------- + -- Passed_By_Reference -- + ------------------------- + + Attribute_Passed_By_Reference => True, + -- + -- T'Passed_By_Reference for any subtype T returns a boolean value + -- that is true if the type is normally passed by reference and + -- false if the type is normally passed by copy in calls. For scalar + -- types, the result is always False and is static. For non-scalar + -- types, the result is non-static (since it is computed by Gigi). + + ------------------ + -- Range_Length -- + ------------------ + + Attribute_Range_Length => True, + -- + -- T'Range_Length for any discrete type T yields the number of + -- values represented by the subtype (zero for a null range). The + -- result is static for static subtypes. Note that Range_Length + -- applied to the index subtype of a one dimensional array always + -- gives the same result as Range applied to the array itself. + -- The result is of type universal integer. + + ------------------ + -- Storage_Unit -- + ------------------ + + Attribute_Storage_Unit => True, + -- + -- Standard'Storage_Unit (Standard is the only permissible prefix) + -- provides the value System.Storage_Unit, and is intended primarily + -- for constructing this definition in package System (see note above + -- in Default_Bit_Order description). The is a static attribute. + + ---------- + -- Tick -- + ---------- + + Attribute_Tick => True, + -- + -- Standard'Tick (Standard is the only permissible prefix) provides + -- the value System.Tick, and is intended primarily for constructing + -- this definition in package System (see note above in description + -- of Default_Bit_Order). This is a static attribute. + + ---------------- + -- To_Address -- + ---------------- + + Attribute_To_Address => True, + -- + -- System'To_Address (Address is the only permissible prefix) + -- is a function that takes any integer value, and converts it into + -- an address value. The semantics is to first convert the integer + -- value to type Integer_Address according to normal conversion + -- rules, and then to convert this to an address using the same + -- semantics as the System.Storage_Elements.To_Address function. + -- The important difference is that this is a static attribute + -- so it can be used in initializations in preealborate packages. + + ---------------- + -- Type_Class -- + ---------------- + + Attribute_Type_Class => True, + -- + -- T'Type_Class for any type or subtype T yields the value of the + -- type class for the full type of T. If T is a generic formal type, + -- then the value is the value for the corresponding actual subtype. + -- The value of this attribute is of type System.Aux_DEC.Type_Class, + -- which has the following definition: + -- + -- type Type_Class is + -- (Type_Class_Enumeration, + -- Type_Class_Integer, + -- Type_Class_Fixed_Point, + -- Type_Class_Floating_Point, + -- Type_Class_Array, + -- Type_Class_Record, + -- Type_Class_Access, + -- Type_Class_Task, + -- Type_Class_Address); + -- + -- Protected types yield the value Type_Class_Task, which thus + -- applies to all concurrent types. This attribute is designed to + -- be compatible with the DEC Ada attribute of the same name. + -- + -- Note: if pragma Extend_System is used to merge the definitions of + -- Aux_DEC into System, then the type Type_Class can be referenced + -- as an entity within System, as can its enumeration literals. + + ----------------- + -- UET_Address -- + ----------------- + + Attribute_UET_Address => True, + -- + -- Unit'UET_Address, where Unit is a program unit, yields the address + -- of the unit exception table for the specified unit. This is only + -- used in the internal implementation of exception handling. See the + -- implementation of unit Ada.Exceptions for details on its use. + + ------------------------------ + -- Universal_Literal_String -- + ------------------------------ + + Attribute_Universal_Literal_String => True, + -- + -- The prefix of 'Universal_Literal_String must be a named number. + -- The static result is the string consisting of the characters of + -- the number as defined in the original source. This allows the + -- user program to access the actual text of named numbers without + -- intermediate conversions and without the need to enclose the + -- strings in quotes (which would preclude their use as numbers). + -- This is used internally for the construction of values of the + -- floating-point attributes from the file ttypef.ads, but may + -- also be used by user programs. + + ------------------------- + -- Unrestricted_Access -- + ------------------------- + + Attribute_Unrestricted_Access => True, + -- + -- The Unrestricted_Access attribute is similar to Access except that + -- all accessibility and aliased view checks are omitted. This is very + -- much a user-beware attribute. Basically its status is very similar + -- to Address, for which it is a desirable replacement where the value + -- desired is an access type. In other words, its effect is identical + -- to first taking 'Address and then doing an unchecked conversion to + -- a desired access type. Note that in GNAT, but not necessarily in + -- other implementations, the use of static chains for inner level + -- subprograms means that Unrestricted_Access applied to a subprogram + -- yields a value that can be called as long as the subprogram is in + -- scope (normal Ada 95 accessibility rules restrict this usage). + + --------------- + -- VADS_Size -- + --------------- + + Attribute_VADS_Size => True, + -- + -- Typ'VADS_Size yields the Size value typically yielded by some + -- Ada 83 compilers. The differences between VADS_Size and Size + -- is that for scalar types for which no Size has been specified, + -- VADS_Size yields the Object_Size rather than the Value_Size. + -- For example, while Natural'Size is typically 31, the value of + -- Natural'VADS_Size is 32. For all other types, Size and VADS_Size + -- yield the same value. + + ---------------- + -- Value_Size -- + ---------------- + + Attribute_Value_Size => True, + -- + -- Type'Value_Size is the number of bits required to represent a + -- value of the given subtype. It is the same as Type'Size, but, + -- unlike Size, may be set for non-first subtypes. See section + -- in Einfo ("Handling of type'Size values") for further details. + + --------------- + -- Word_Size -- + --------------- + + Attribute_Word_Size => True, + -- + -- Standard'Word_Size (Standard is the only permissible prefix) + -- provides the value System.Word_Size, and is intended primarily + -- for constructing this definition in package System (see note above + -- in Default_Bit_Order description). This is a static attribute. + + others => False); + + ----------------- + -- Subprograms -- + ----------------- + + procedure Analyze_Attribute (N : Node_Id); + -- Performs bottom up semantic analysis of an attribute. Note that the + -- parser has already checked that type returning attributes appear only + -- in appropriate contexts (i.e. in subtype marks, or as prefixes for + -- other attributes). + + procedure Resolve_Attribute (N : Node_Id; Typ : Entity_Id); + -- Performs type resolution of attribute. If the attribute yields + -- a universal value, mark its type as that of the context. On + -- the other hand, if the context itself is universal (as in + -- T'Val (T'Pos (X)), mark the type as being the largest type of + -- that class that can be used at run-time. This is correct since + -- either the value gets folded (in which case it doesn't matter + -- what type of the class we give if, since the folding uses universal + -- arithmetic anyway) or it doesn't get folded (in which case it is + -- going to be dealt with at runtime, and the largest type is right). + +end Sem_Attr; |