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------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- T A R G P A R M --
-- --
-- S p e c --
-- --
-- Copyright (C) 1999-2022, 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 --
-- http://www.gnu.org/licenses 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 obtains parameters from the target runtime version of System,
-- to indicate parameters relevant to the target environment.
-- Conceptually, these parameters could be obtained using rtsfind, but
-- we do not do this for four reasons:
-- 1. Compiling System for every compilation wastes time
-- 2. This compilation impedes debugging by adding extra compile steps
-- 3. There are recursion problems coming from compiling System itself
-- or any of its children.
-- 4. The binder also needs the parameters, and we do not want to have
-- to drag a lot of front end stuff into the binder.
-- For all these reasons, we read in the source of System, and then scan
-- it at the text level to extract the parameter values.
-- Note however, that later on, when the ali file is written, we make sure
-- that the System file is at least parsed, so that the checksum is properly
-- computed and set in the ali file. This partially negates points 1 and 2
-- above although just parsing is quick and does not impact debugging much.
-- The parameters acquired by this routine from system.ads fall into four
-- categories:
-- 1. Configuration pragmas, that must appear at the start of the file.
-- Any such pragmas automatically apply to any unit compiled in the
-- presence of this system file. Only a limited set of such pragmas
-- may appear as documented in the corresponding section below.
-- 2. Target parameters. These are boolean constants that are defined
-- in the private part of the package giving fixed information
-- about the target architecture, and the capabilities of the
-- code generator and run-time library.
-- 3. Identification information. This is an optional string constant
-- that gives the name of the run-time library configuration. This
-- line may be omitted for a version of system.ads to be used with
-- the full Ada 95 run time.
-- 4. Other characteristics of package System. At the current time the
-- only item in this category is whether type Address is private.
with Rident; use Rident;
with Namet; use Namet;
with Types; use Types;
package Targparm is
---------------------------
-- Configuration Pragmas --
---------------------------
-- The following switches get set if the corresponding configuration
-- pragma is scanned from the source of system.ads. No other pragmas
-- are permitted to appear at the start of the system.ads source file.
-- If a pragma Discard_Names appears, then Opt.Global_Discard_Names is
-- set to True to indicate that all units must be compiled in this mode.
-- If a pragma Locking_Policy appears, then Opt.Locking_Policy is set
-- to the first character of the policy name, and Opt.Locking_Policy_Sloc
-- is set to System_Location.
-- If a pragma Normalize_Scalars appears, then Opt.Normalize_Scalars
-- is set True, as well as Opt.Init_Or_Norm_Scalars.
-- If a pragma Queuing_Policy appears, then Opt.Queuing_Policy is set
-- to the first character of the policy name, and Opt.Queuing_Policy_Sloc
-- is set to System_Location.
-- If a pragma Task_Dispatching_Policy appears, then the flag
-- Opt.Task_Dispatching_Policy is set to the first character of the
-- policy name, and Opt.Task_Dispatching_Policy_Sloc is set to
-- System_Location.
-- If a pragma Detect_Blocking appears, then the flag Opt.Detect_Blocking
-- is set to True.
-- If a pragma Suppress_Exception_Locations appears, then the flag
-- Opt.Exception_Locations_Suppressed is set to True.
-- If a pragma Profile with a valid profile argument appears, then
-- the appropriate restrictions and policy flags are set.
-- The only other pragma allowed is a pragma Restrictions that specifies
-- a restriction that will be imposed on all units in the partition. Note
-- that in this context, only one restriction can be specified in a single
-- pragma, and the pragma must appear on its own on a single source line.
-- If package System contains exactly the line "type Address is private;"
-- then the flag Opt.Address_Is_Private is set True, otherwise this flag
-- is set False.
Restrictions_On_Target : Restrictions_Info := No_Restrictions;
-- Records restrictions specified by system.ads. Only the Set and Value
-- members are modified. The Violated and Count fields are never modified.
-- Note that entries can be set either by a pragma Restrictions or by
-- a pragma Profile.
-------------------
-- Run Time Name --
-------------------
-- This parameter should be regarded as read only by all clients of
-- of package. The only way they get modified is by calling the
-- Get_Target_Parameters routine which reads the values from a provided
-- text buffer containing the source of the system package.
-- The corresponding string constant is placed immediately at the start
-- of the private part of system.ads if is present, e.g. in the form:
-- Run_Time_Name : constant String := "Zero Footprint Run Time";
-- the corresponding messages will look something like
-- xxx not supported (Zero Footprint Run Time)
Run_Time_Name_On_Target : Name_Id := No_Name;
-- Set to appropriate names table entry Id value if a Run_Time_Name
-- string constant is defined in system.ads. This name is used only
-- for the configurable run-time case, and is used to parameterize
-- messages that complain about non-supported run-time features.
-- The name should contain only letters A-Z, digits 1-9, spaces,
-- and underscores.
--------------------------
-- Executable Extension --
--------------------------
Executable_Extension_On_Target : Name_Id := No_Name;
-- Executable extension on the target. This name is useful for setting
-- the executable extension in a dynamic way, e.g. depending on the
-- run time used, rather than using a configure-time macro as done by
-- Get_Target_Executable_Suffix. If not set (No_Name), instead use
-- System.OS_Lib.Get_Target_Executable_Suffix.
-----------------------
-- Target Parameters --
-----------------------
-- The following parameters correspond to the variables defined in the
-- private part of System (without the terminating _On_Target). Note
-- that it is required that all parameters defined here be specified
-- in the target specific version of system.ads. Thus, to add a new
-- parameter, add it to all system*.ads files. (There is a defaulting
-- mechanism, but we don't normally take advantage of it, as explained
-- below.)
-- The default values here are used if no value is found in system.ads.
-- This should normally happen if the special version of system.ads used
-- by the compiler itself is in use or if the value is only relevant to a
-- particular target. The default values are suitable for use in normal
-- environments. This approach allows the possibility of new versions of
-- the compiler (possibly with new system parameters added) being used to
-- compile older versions of the compiler sources, as well as avoiding
-- duplicating values in all system-*.ads files for flags that are used on
-- a few platforms only.
-- All these parameters should be regarded as read only by all clients
-- of the package. The only way they get modified is by calling the
-- Get_Target_Parameters routine which reads the values from a provided
-- text buffer containing the source of the system package.
-------------------------------
-- Backend Arithmetic Checks --
-------------------------------
-- Divide and overflow checks are either done in the front end or
-- back end. The front end will generate checks when required unless
-- the corresponding parameter here is set to indicate that the back
-- end will generate the required checks (or that the checks are
-- automatically performed by the hardware in an appropriate form).
Backend_Divide_Checks_On_Target : Boolean := False;
-- Set True if the back end generates divide checks, or if the hardware
-- checks automatically. Set False if the front end must generate the
-- required tests using explicit expanded code.
Backend_Overflow_Checks_On_Target : Boolean := False;
-- Set True if the back end generates arithmetic overflow checks, or if
-- the hardware checks automatically. Set False if the front end must
-- generate the required tests using explicit expanded code.
-----------------------------------
-- Control of Exception Handling --
-----------------------------------
-- GNAT implements three methods of implementing exceptions:
-- Front-End Longjmp/Setjmp Exceptions
-- This approach uses longjmp/setjmp to handle exceptions. It
-- uses less storage, and can often propagate exceptions faster,
-- at the expense of (sometimes considerable) overhead in setting
-- up an exception handler.
-- The generation of the setjmp and longjmp calls is handled by
-- the front end of the compiler (this includes gigi in the case
-- of the standard GCC back end). It does not use any back end
-- support (such as the GCC3 exception handling mechanism). When
-- this approach is used, the compiler generates special exception
-- handlers for handling cleanups (AT-END actions) when an exception
-- is raised.
-- Back-End Zero Cost Exceptions
-- With this approach, the back end handles the generation and
-- handling of exceptions. For example, the GCC3 exception handling
-- mechanisms are used in this mode. The front end simply generates
-- code for explicit exception handlers, and AT-END cleanup handlers
-- are simply passed unchanged to the backend for generating cleanups
-- both in the exceptional and non-exceptional cases.
-- As the name implies, this approach uses a table-based mechanism,
-- which incurs no setup when entering a region covered by handlers
-- but requires complex unwinding to walk up the call chain and search
-- for handlers at propagation time.
-- Back-End Setjmp/Longjmp Exceptions
-- With this approach, the back end also handles the generation and
-- handling of exceptions, using setjmp/longjmp to set up receivers and
-- propagate. AT-END actions on exceptional paths are also taken care
-- of by the back end and the front end doesn't need to generate
-- explicit exception handlers for these.
-- Control of Available Methods and Defaults
-- The following switches specify whether we're using a front-end or a
-- back-end mechanism and whether this is a zero-cost or a sjlj scheme.
-- The per-switch default values correspond to the default value of
-- Opt.Exception_Mechanism.
ZCX_By_Default_On_Target : Boolean := False;
-- Indicates if zero cost scheme for exceptions
Frontend_Exceptions_On_Target : Boolean := True;
-- Indicates if we're using a front-end scheme for exceptions
------------------------------------
-- Run-Time Library Configuration --
------------------------------------
-- In configurable run-time mode, the system run-time may not support
-- the full Ada language. The effect of setting this switch is to let
-- the compiler know that it is not surprising (i.e. the system is not
-- misconfigured) if run-time library units or entities within units are
-- not present in the run-time.
Configurable_Run_Time_On_Target : Boolean := False;
-- Indicates that the system.ads file is for a configurable run-time
--
-- This has some specific effects as follows
--
-- The binder generates the gnat_argc/argv/envp variables in the
-- binder file instead of being imported from the run-time library.
-- If Command_Line_Args_On_Target is set to False, then the
-- generation of these variables is suppressed completely.
--
-- The binder generates the gnat_exit_status variable in the binder
-- file instead of being imported from the run-time library. If
-- Exit_Status_Supported_On_Target is set to False, then the
-- generation of this variable is suppressed entirely.
--
-- The routine __gnat_break_start is defined within the binder file
-- instead of being imported from the run-time library.
--
-- The variable __gnat_exit_status is generated within the binder file
-- instead of being imported from the run-time library.
Suppress_Standard_Library_On_Target : Boolean := False;
-- If this flag is True, then the standard library is not included by
-- default in the executable (see unit System.Standard_Library in file
-- s-stalib.ads for details of what this includes). This is for example
-- set True for the zero foot print case, where these files should not
-- be included by default.
--
-- This flag has some other related effects:
--
-- The generation of global variables in the bind file is suppressed,
-- with the exception of the priority of the environment task, which
-- is needed by the Ravenscar run-time.
--
-- The calls to __gnat_initialize and __gnat_finalize are omitted
--
-- All finalization and initialization (controlled types) is omitted
Preallocated_Stacks_On_Target : Boolean := False;
-- If this flag is True, then the expander preallocates all task stacks
-- at compile time. If the flag is False, then task stacks are not pre-
-- allocated, and task stack allocation is the responsibility of the
-- run-time (which typically delegates the task to the underlying
-- operating system environment).
---------------------
-- Duration Format --
---------------------
-- By default, type Duration is a 64-bit fixed-point type with a delta
-- and small of 10**(-9) (i.e. it is a count in nanoseconds). This flag
-- allows that standard format to be modified.
Duration_32_Bits_On_Target : Boolean := False;
-- If True, then Duration is represented in 32 bits and the delta and
-- small values are set to 20.0*(10**(-3)) (i.e. it is a count in units
-- of 20 milliseconds).
------------------------------------
-- Back-End Code Generation Flags --
------------------------------------
-- These flags indicate possible limitations in what the code generator
-- can handle. They will all be True for a full run-time, but one or more
-- of these may be false for a configurable run-time, and if a feature is
-- used at the source level, and the corresponding flag is false, then an
-- error message will be issued saying the feature is not supported.
Atomic_Sync_Default_On_Target : Boolean := True;
-- Access to atomic variables requires memory barrier synchronization in
-- the general case to ensure proper behavior when such accesses are used
-- on a multi-processor to synchronize tasks (e.g. by using spin locks).
-- The setting of this flag determines the default behavior. Normally this
-- is True, which will mean that appropriate synchronization instructions
-- are generated by default. If it is False, then the default will be that
-- these synchronization instructions are not generated. This may be a more
-- appropriate default in some cases, e.g. on embedded targets which do not
-- allow the possibility of multi-processors. The default can be overridden
-- using pragmas Enable/Disable_Atomic_Synchronization and also by use of
-- the corresponding debug flags -gnatd.e and -gnatd.d.
Support_Aggregates_On_Target : Boolean := True;
-- In the general case, the use of aggregates may generate calls
-- to run-time routines in the C library, including memset, memcpy,
-- memmove, and bcopy. This flag is set to True if these routines
-- are available. If any of these routines is not available, then
-- this flag is False, and the use of aggregates is not permitted.
Support_Atomic_Primitives_On_Target : Boolean := False;
-- If this flag is True, then the back end supports GCC built-in atomic
-- operations for memory model, such as atomic load or atomic compare
-- exchange (see the GCC manual for more information). If the flag is
-- False, then the back end doesn't provide this support. Note that this
-- flag is set to True only if the target supports all atomic primitives
-- up to 64 bits.
Support_Composite_Assign_On_Target : Boolean := True;
-- The assignment of composite objects other than small records and
-- arrays whose size is 64-bits or less and is set by an explicit
-- size clause may generate calls to memcpy, memmove, and bcopy.
-- If versions of all these routines are available, then this flag
-- is set to True. If any of these routines is not available, then
-- the flag is set False, and composite assignments are not allowed.
Support_Composite_Compare_On_Target : Boolean := True;
-- If this flag is True, then the back end supports bit-wise comparison
-- of composite objects for equality, either generating inline code or
-- calling appropriate (and available) run-time routines. If this flag
-- is False, then the back end does not provide this support, and the
-- front end uses component by component comparison for composites.
Support_Long_Shifts_On_Target : Boolean := True;
-- If True, the back end supports 64-bit shift operations. If False, then
-- the source program may not contain explicit 64-bit shifts. In addition,
-- the code generated for packed arrays will avoid the use of long shifts.
Support_Nondefault_SSO_On_Target : Boolean := True;
-- If True, the back end supports the non-default Scalar_Storage_Order
-- (i.e. allows non-confirming Scalar_Storage_Order attribute definition
-- clauses).
--------------------
-- Indirect Calls --
--------------------
Always_Compatible_Rep_On_Target : Boolean := True;
-- If True, the Can_Use_Internal_Rep flag (see Einfo) is set to False in
-- all cases. This corresponds to the traditional code generation
-- strategy. False allows the front end to choose a policy that partly or
-- entirely eliminates dynamically generated trampolines.
-------------------------------
-- Control of Stack Checking --
-------------------------------
-- GNAT provides three methods of implementing exceptions:
-- GCC Probing Mechanism
-- This approach uses the standard GCC mechanism for
-- stack checking. The method assumes that accessing
-- storage immediately beyond the end of the stack
-- will result in a trap that is converted to a storage
-- error by the runtime system. This mechanism has
-- minimal overhead, but requires complex hardware,
-- operating system and run-time support. Probing is
-- the default method where it is available. The stack
-- size for the environment task depends on the operating
-- system and cannot be set in a system-independent way.
-- GCC Stack-limit Mechanism
-- This approach uses the GCC stack limits mechanism.
-- It relies on comparing the stack pointer with the
-- values of a global symbol. If the check fails, a
-- trap is explicitly generated. The advantage is
-- that the mechanism requires no memory protection,
-- but operating system and run-time support are
-- needed to manage the per-task values of the symbol.
-- This is the default method after probing where it
-- is available.
-- GNAT Stack-limit Checking
-- This method relies on comparing the stack pointer
-- with per-task stack limits. If the check fails, an
-- exception is explicitly raised. The advantage is
-- that the method requires no extra system dependent
-- runtime support and can be used on systems without
-- memory protection as well, but at the cost of more
-- overhead for doing the check. This is the fallback
-- method if the above two are not supported.
Stack_Check_Probes_On_Target : Boolean := False;
-- Indicates if the GCC probing mechanism is used
-- WARNING: There is a matching C declaration of this variable in fe.h
Stack_Check_Limits_On_Target : Boolean := False;
-- Indicates if the GCC stack-limit mechanism is used
-- Both flags cannot be simultaneously set to True. If neither
-- is, the target independent fallback method is used.
-- WARNING: There is a matching C declaration of this variable in fe.h
Stack_Check_Default_On_Target : Boolean := False;
-- Indicates if stack checking is on by default
----------------------------
-- Command Line Arguments --
----------------------------
-- Command line arguments are supported on most targets. The following flag
-- is set to False for targets that do not support command line arguments
-- (i.e. VxWorks). Note that support for command line arguments is not
-- required on such targets (RM A.15(13)).
Command_Line_Args_On_Target : Boolean := True;
-- Set False if no command line arguments on target. Note that if this
-- is False in with Configurable_Run_Time_On_Target set to True, then
-- this causes suppression of generation of the argv/argc variables
-- used to record command line arguments.
-- Similarly, most targets support the use of an exit status, but other
-- targets might not, as allowed by RM A.15(18-20).
Exit_Status_Supported_On_Target : Boolean := True;
-- Set False if returning of an exit status is not supported on target.
-- Note that if this False in with Configurable_Run_Time_On_Target
-- set to True, then this causes suppression of the gnat_exit_status
-- variable used to record the exit status.
-----------------------
-- Main Program Name --
-----------------------
-- When the binder generates the main program to be used to create the
-- executable, the main program name is main by default (to match the
-- usual Unix practice). If this parameter is set to True, then the
-- name is instead by default taken from the actual Ada main program
-- name (just the name of the child if the main program is a child unit).
-- In either case, this value can be overridden using -M name.
Use_Ada_Main_Program_Name_On_Target : Boolean := False;
-- Set True to use the Ada main program name as the main name
----------------------------------------------
-- Boolean-Valued Floating-Point Attributes --
----------------------------------------------
-- The constants below give the values for representation oriented
-- floating-point attributes that are the same for all float types
-- on the target. These are all boolean values.
-- A value is only True if the target reliably supports the corresponding
-- feature. Reliably here means that support is guaranteed for all
-- possible settings of the relevant compiler switches (like -mieee),
-- since we cannot control the user setting of those switches.
-- The attributes cannot dependent on the current setting of compiler
-- switches, since the values must be static and consistent throughout
-- the partition. We probably should add such consistency checks in future,
-- but for now we don't do this.
-- Note: the compiler itself does not use floating-point, so the
-- settings of the defaults here are not really relevant.
-- Note: in some cases, proper support of some of these floating point
-- features may require a specific switch (e.g. -mieee on the Alpha)
-- to be used to obtain full RM compliant support.
Denorm_On_Target : Boolean := False;
-- Set to False on targets that do not reliably support denormals
Machine_Rounds_On_Target : Boolean := True;
-- Set to False for targets where S'Machine_Rounds is False
Machine_Overflows_On_Target : Boolean := False;
-- Set to True for targets where S'Machine_Overflows is True
-- WARNING: There is a matching C declaration of this variable in fe.h
Signed_Zeros_On_Target : Boolean := True;
-- Set to False on targets that do not reliably support signed zeros
-- WARNING: There is a matching C declaration of this variable in fe.h
-----------------
-- Subprograms --
-----------------
-- These subprograms are used to initialize the target parameter values
-- from the system.ads file. Note that this is only done once, so if more
-- than one call is made to either routine, the second and subsequent
-- calls are ignored. It also reads restriction pragmas from system.ads
-- and records them, though as further detailed below, the caller has some
-- control over the handling of No_Dependence restrictions.
type Make_Id_Type is access function (Str : Text_Buffer) return Node_Id;
-- Parameter type for Get_Target_Parameters for function that creates an
-- identifier node with Sloc value System_Location and given string as the
-- Chars value.
type Make_SC_Type is access function (Pre, Sel : Node_Id) return Node_Id;
-- Parameter type for Get_Target_Parameters for function that creates a
-- selected component with Sloc value System_Location and given Prefix
-- (Pre) and Selector (Sel) values.
type Set_NOD_Type is access procedure (Unit : Node_Id);
-- Parameter type for Get_Target_Parameters that records a Restriction
-- No_Dependence for the given unit (identifier or selected component).
type Set_NSA_Type is access procedure (Asp : Name_Id; OK : out Boolean);
-- Parameter type for Get_Target_Parameters that records a Restriction
-- No_Specification_Of_Aspect. Asp is the aspect name. OK is set True
-- if this is an OK aspect name, and False if it is not an aspect name.
type Set_NUA_Type is access procedure (Attr : Name_Id; OK : out Boolean);
-- Parameter type for Get_Target_Parameters that records a Restriction
-- No_Use_Of_Attribute. Attr is the attribute name. OK is set True if
-- this is an OK attribute name, and False if it is not an attribute name.
type Set_NUP_Type is access procedure (Prag : Name_Id; OK : out Boolean);
-- Parameter type for Get_Target_Parameters that records a Restriction
-- No_Use_Of_Pragma. Prag is the pragma name. OK is set True if this is
-- an OK pragma name, and False if it is not a recognized pragma name.
procedure Get_Target_Parameters
(System_Text : Source_Buffer_Ptr;
Source_First : Source_Ptr;
Source_Last : Source_Ptr;
Make_Id : Make_Id_Type := null;
Make_SC : Make_SC_Type := null;
Set_NOD : Set_NOD_Type := null;
Set_NSA : Set_NSA_Type := null;
Set_NUA : Set_NUA_Type := null;
Set_NUP : Set_NUP_Type := null);
-- Called at the start of execution to obtain target parameters from the
-- source of package System. The parameters provide the source text to be
-- scanned (in System_Text (Source_First .. Source_Last)). If the three
-- subprograms Make_Id, Make_SC, and Set_NOD are left at their default
-- value of null, Get_Target_Parameters will ignore pragma Restrictions
-- (No_Dependence) lines; otherwise it will use these three subprograms to
-- record them. Similarly, if Set_NUP is left at its default value of null,
-- then any occurrences of pragma Restrictions (No_Use_Of_Pragma => XXX)
-- will be ignored; otherwise it will use this procedure to record the
-- pragma. Similarly for the NSA and NUA cases.
procedure Get_Target_Parameters
(Make_Id : Make_Id_Type := null;
Make_SC : Make_SC_Type := null;
Set_NOD : Set_NOD_Type := null;
Set_NSA : Set_NSA_Type := null;
Set_NUA : Set_NUA_Type := null;
Set_NUP : Set_NUP_Type := null);
-- This version reads in system.ads using Osint. The idea is that the
-- caller uses the first version if they have to read system.ads anyway
-- (e.g. the compiler) and uses this simpler interface if system.ads is
-- not otherwise needed.
end Targparm;