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-- --
-- --
-- T T Y P E S --
-- --
-- S p e c --
-- --
-- Copyright (C) 1992-2021, 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 3, 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 COPYING3. If not, go to --
-- for a complete copy of the license. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
-- This package contains constants describing target properties
with Types; use Types;
with Set_Targ;
package Ttypes is
-- Host/Target Dependencies --
-- It is vital to maintain a clear distinction between properties of
-- types on the host and types on the target, since in the general
-- case of a cross-compiler these will be different.
-- This package provides definitions of values that describe the properties
-- of the target types. All instances of target dependencies, including the
-- definitions of such packages as Standard and System depend directly or
-- indirectly on the definitions in the Ttypes packages.
-- In the source of the compiler, references to attributes such as
-- Integer'Size will give information regarding the host types (i.e.
-- the types within the compiler itself). Such references are therefore
-- almost always suspicious (it is hard for example to see that the
-- code in the compiler should even be using type Integer very much,
-- and certainly this code should not depend on the size of Integer).
-- On the other hand, it is perfectly reasonable for the compiler to
-- require access to the size of type Integer for the target machine,
-- e.g. in constructing the internal representation of package Standard.
-- For this purpose, instead of referencing the attribute Integer'Size,
-- a reference to Ttypes.Standard_Integer_Size will provide the needed
-- value for the target type.
-- Two approaches are used for handling target dependent values in the
-- standard library packages. Package Standard is handled specially,
-- being constructed internally (by package Stand). Target dependent
-- values needed in Stand are obtained by direct reference to Ttypes
-- and Ttypef.
-- For package System, there is a separate version for each target, with
-- explicit declarations of the required, constants.
-- Historical note: Originally we had in mind dealing with target dependent
-- differences by referencing appropriate attributes. Ada 95 already
-- defines most of the required attributes, and GNAT specific attributes
-- were defined to cover the remaining cases (such as Storage_Unit).
-- The additional attributes that have been added to GNAT (Address_Size,
-- Storage_Unit, and Word_Size) are redundant with respect to the
-- corresponding references to System constants. For example in a program,
-- System.Address_Size and Standard'Address_Size yield the same value.
-- These attributes have been retained for compatibility purposes, but
-- serve no purpose at this stage.
-- Note that during compilation there are two versions of package System
-- around. The version that is directly with'ed by compiler packages
-- contains host-dependent definitions, which is what is needed in that
-- case (for example, System.Storage_Unit referenced in the source of the
-- compiler refers to the storage unit of the host, not the target). This
-- means that, like attribute references, any references to constants in
-- package System in the compiler code are suspicious, since it is strange
-- for the compiler to have such host dependencies. If the compiler needs
-- to access the target dependent values of such quantities as Storage_Unit
-- then it should reference the constants in this package (Ttypes), rather
-- than referencing System.Storage_Unit, or Standard'Storage_Unit, both of
-- which would yield the host value.
-- Target-Dependent Values for Types in Standard --
-- Note: GNAT always supplies all the following integer and float types,
-- but depending on the machine, some of the types may be identical. For
-- example, on some machines, Short_Float may be the same as Float, and
-- Long_Long_Float may be the same as Long_Float.
Standard_Short_Short_Integer_Size : constant Pos :=
Standard_Short_Integer_Size : constant Pos :=
Standard_Integer_Size : constant Pos :=
Standard_Long_Integer_Size : constant Pos :=
Standard_Long_Long_Integer_Size : constant Pos :=
Standard_Long_Long_Long_Integer_Size : Pos :=
Standard_Short_Float_Size : constant Pos :=
Standard_Float_Size : constant Pos :=
Standard_Long_Float_Size : constant Pos :=
Standard_Long_Long_Float_Size : constant Pos :=
Standard_Character_Size : constant Pos := Set_Targ.Char_Size;
Standard_Wide_Character_Size : constant Pos := 16;
Standard_Wide_Wide_Character_Size : constant Pos := 32;
-- Standard wide character sizes
-- Note: there is no specific control over the representation of
-- enumeration types. The convention used is that if an enumeration
-- type has fewer than 2**(Character'Size) elements, then the size
-- used is Character'Size, otherwise Integer'Size is used.
-- Similarly, the size of fixed-point types depends on the size of the
-- corresponding integer type, which is the smallest predefined integer
-- type capable of representing the required range of values.
-- Target-Dependent Values for Types in System --
System_Address_Size : constant Pos := Set_Targ.Pointer_Size;
-- System.Address'Size (also size of all thin pointers)
System_Max_Integer_Size : Pos := Standard_Long_Long_Long_Integer_Size;
System_Max_Binary_Modulus_Power : Pos :=
System_Max_Nonbinary_Modulus_Power : constant Pos := Standard_Integer_Size;
System_Storage_Unit : constant Pos := Set_Targ.Bits_Per_Unit;
System_Word_Size : constant Pos := Set_Targ.Bits_Per_Word;
System_Tick_Nanoseconds : constant Pos := 1_000_000_000;
-- Value of System.Tick in nanoseconds. At the moment, this is a fixed
-- constant (with value of 1.0 seconds), but later we should add this
-- value to the GCC configuration file so that its value can be made
-- configuration dependent.
-- Target-Dependent Values for Types in Interfaces --
Interfaces_Wchar_T_Size : constant Pos := Set_Targ.Wchar_T_Size;
-- Other Target-Dependent Definitions --
Maximum_Alignment : constant Pos := Set_Targ.Maximum_Alignment;
-- The maximum alignment, in storage units, that an object or type may
-- require on the target machine.
System_Allocator_Alignment : constant Pos :=
-- The alignment in storage units of addresses returned by malloc
Max_Unaligned_Field : constant Pos := Set_Targ.Max_Unaligned_Field;
-- The maximum supported size in bits for a field that is not aligned
-- on a storage unit boundary.
Bytes_Big_Endian : Boolean := Set_Targ.Bytes_BE /= 0;
-- Important note: for Ada purposes, the important setting is the bytes
-- endianness (Bytes_Big_Endian), not the bits value (Bits_Big_Endian).
-- This is because Ada bit addressing must be compatible with the byte
-- ordering (otherwise we would end up with non-contiguous fields). It
-- is rare for the two to be different, but if they are, Bits_Big_Endian
-- is relevant only for the generation of instructions with bit numbers,
-- and thus relevant only to the back end. Note that this is a variable
-- rather than a constant, since it can be modified (flipped) by -gnatd8.
Target_Short_Enums : constant Boolean := Set_Targ.Short_Enums /= 0;
-- True if we are in short enums mode, where foreign convention
-- (in particular C and C++) enumeration types will be sized as in Ada,
-- using the shortest possibility from 8,16,32 bits, signed or unsigned.
-- A zero value means Short_Enums are not in use, and in this case all
-- foreign convention enumeration types are given the same size as c int.
Target_Strict_Alignment : Boolean :=
Set_Targ.Strict_Alignment /= 0;
-- True if instructions will fail if data is misaligned. Note that this
-- is a variable rather than a constant since it can be modified (set to
-- True) if the debug flag -gnatd.a is used.
Target_Double_Float_Alignment : constant Nat :=
-- The default alignment of "double" floating-point types, i.e. floating
-- point types whose size is equal to 64 bits, or 0 if this alignment is
-- not lower than the largest power of 2 multiple of System.Storage_Unit
-- that does not exceed either the object size of the type or the maximum
-- allowed alignment.
Target_Double_Scalar_Alignment : constant Nat :=
-- The default alignment of "double" or larger scalar types, i.e. scalar
-- types whose size is greater or equal to 64 bits, or 0 if this alignment
-- is not lower than the largest power of 2 multiple of System.Storage_Unit
-- that does not exceed either the object size of the type or the maximum
-- allowed alignment.
end Ttypes;