-- --
-- S p e c --
-- --
--- --
--- Copyright (C) 1999-2001 Free Software Foundation, Inc. --
+-- Copyright (C) 1999-2004 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- --
-- System, to indicate parameters relevant to the target environment.
-- Conceptually, these parameters could be obtained using rtsfind, but
--- we do not do this for three reasons:
+-- 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.
-- 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 three
+-- 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 ommitted for a version of system.ads to be used with
+-- the full Ada 95 run time.
+
+with Rident; use Rident;
+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 Polling (On) appears, then the flag Opt.Polling_Required
+ -- is set to True.
+
+ -- 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.
+
+ Restrictions_On_Target : Restrictions_Info;
+ -- 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 parametrize
+ -- messages that complain about non-supported run-time features.
+ -- The name should contain only letters A-Z, digits 1-9, spaces,
+ -- and underscores.
+
+ -----------------------
+ -- 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
-- 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 System.
+ -- Get_Target_Parameters routine which reads the values from a provided
+ -- text buffer containing the source of the system package.
+
+ ----------------------------
+ -- Special Target Control --
+ ----------------------------
+
+ -- The great majority of GNAT ports are based on GCC. The switches in
+ -- This section indicate the use of some non-standard target back end.
+
+ AAMP_On_Target : Boolean;
+ -- Set to True if target is AAMP.
-------------------------------
-- Backend Arithmetic Checks --
-- Control of Exception Handling --
-----------------------------------
- -- GNAT provides two methods of implementing exceptions:
+ -- GNAT implements three methods of implementing exceptions:
- -- Longjmp/Setjmp (-gnatL)
+ -- Front-End Longjmp/Setjmp Exceptions
-- This approach uses longjmp/setjmp to handle exceptions. It
-- uses less storage, and can often propagate exceptions faster,
-- up an exception handler. This approach is available on all
-- targets, and is the default where it is the only approach.
- -- Zero Cost (-gnatZ)
+ -- 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
+ -- suport (such as the GCC3 exception handling mechanism). When
+ -- this approach is used, the compiler generates special exception
+ -- handlers for handling cleanups when an exception is raised.
+
+ -- Front-End Zero Cost Exceptions
-- This approach uses separate exception tables. These use extra
-- storage, and exception propagation can be quite slow, but there
-- is only available on some targets, and is the default where it is
-- available.
+ -- The generation of the exception tables is handled by the front
+ -- end of the compiler. 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 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 generally uses a zero-cost
+ -- mechanism with tables, but the tables are generated by the back
+ -- end. However, since the back-end is entirely responsible for the
+ -- handling of exceptions, another mechanism might be used. In the
+ -- case of GCC3 for instance, it might be the case that the compiler
+ -- is configured for setjmp/longjmp handling, then everything will
+ -- work correctly. However, it is definitely preferred that the
+ -- back end provide zero cost exception handling.
+
+ -- Controlling the selection of methods
+
+ -- The Front-End Longjmp/Setjmp approach is always available in
+ -- all implementations. If it is not the default method, then it
+ -- may be explicitly specified by the use of -gnatL. Note however
+ -- that there is a requirement that all Ada units in a partition
+ -- be compiled with this overriding option if it is not the default.
+
+ -- On some, but not all, implementations of GNAT, one of the two
+ -- ZCX approaches (but not both) is implemented. If this is the
+ -- case, and ZCX is not the default mechanism, then ZCX handling
+ -- (front-end or back-end according to the implementation) may be
+ -- specified by use of the -gnatZ switch. Again, this switch must
+ -- be used to compile all Ada units in a partition. The use of
+ -- the -gnatZ switch will cause termination with a fatal error.
+
+ -- Finally the debug option -gnatdX can be used to force the
+ -- compiler to operate in front-end ZCX exception mode and force
+ -- the front end to generate exception tables. This is only useful
+ -- for debugging purposes for implementations which do not provide
+ -- the possibility of front-end ZCX mode. The resulting object file
+ -- is unusable, but this debug switch may still be useful (e.g. in
+ -- conjunction with -gnatG) for front-end debugging purposes.
+
+ -- Control of Available Methods and Defaults
+
+ -- The following switches specify which of the two ZCX methods
+ -- (if any) is available in an implementation, and which method
+ -- is the default method.
+
ZCX_By_Default_On_Target : Boolean;
- -- Indicates if zero cost exceptions are active by default.
+ -- Indicates if zero cost exceptions are active by default. If this
+ -- variable is False, then the only possible exception method is the
+ -- front-end setjmp/longjmp approach, and this is the default. If
+ -- this variable is True, then one of the following two flags must
+ -- be True, and represents the method to be used by default.
GCC_ZCX_Support_On_Target : Boolean;
- -- Indicates that when ZCX is active the mechanism to be used is the
- -- standard GCC ZCX mechanism (introduced in GCC 3.1)
+ -- Indicates that when ZCX is active, the mechanism to be used is the
+ -- back-end ZCX exception approach. If this variable is set to True,
+ -- then Front_End_ZCX_Support_On_Target must be False.
Front_End_ZCX_Support_On_Target : Boolean;
- -- Indicates that when ZCX is active (and GCC_ZCX_Support is not set)
- -- the mechanism to be used is the GNAT front end specific ZCX mechanism
-
- ---------------------------------------
- -- High_Integrity (No Run Time) Mode --
- ---------------------------------------
-
- -- In High_Integrity mode, there is no system run-time, and the flag
- -- Opt.No_Run_Time is set so that the language is appropriately
- -- restricted to forbid construct that would generate run-time calls.
-
- High_Integrity_Mode_On_Target : Boolean;
- -- Indicates that this build is for a high integrity mode version of
- -- GNAT, so that no run time is permitted.
+ -- Indicates that when ZCX is active, the mechanism to be used is the
+ -- front-end ZCX exception approach. If this variable is set to True,
+ -- then GCC_ZCX_Support_On_Target must be False.
+
+ --------------------------------
+ -- Configurable Run-Time Mode --
+ --------------------------------
+
+ -- 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;
+ -- 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;
+ -- 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 generation of exception tables is suppressed for front end
+ -- ZCX exception handling (since we assume no exception handling).
+ --
+ -- The calls to __gnat_initialize and __gnat_finalize are omitted
+ --
+ -- All finalization and initialization (controlled types) is omitted
+ --
+ -- The routine __gnat_handler_installed is not imported
+
+ ---------------------
+ -- 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;
+ -- 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.
+
+ Support_64_Bit_Divides_On_Target : Boolean;
+ -- If True, the back end supports 64-bit divide operations. If False, then
+ -- the source program may not contain 64-bit divide operations. This is
+ -- specifically useful in the zero foot-print case, where the issue is
+ -- whether there is a hardware divide instruction for 64-bits so that
+ -- no run-time support is required. It should always be set True if the
+ -- necessary run-time support is present.
+
+ Support_Aggregates_On_Target : Boolean;
+ -- 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_Composite_Assign_On_Target : Boolean;
+ -- 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;
+ -- 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;
+ -- 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.
-------------------------------
-- Control of Stack Checking --
-- For most ports of GNAT, command line arguments are supported. The
-- following flag is set to False for targets that do not support
- -- command line arguments (notably VxWorks).
+ -- command line arguments (VxWorks and AAMP). Note that support of
+ -- command line arguments is not required on such targets (RM A.15(13)).
Command_Line_Args_On_Target : Boolean;
- -- Set False if no command line arguments on target
+ -- 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 ports support the use of an exit status, but AAMP
+ -- is an exception (as allowed by RM A.15(18-20))
- -- Note: this is prepared for future use, but not yet used, since we
- -- do not yet have a way of propagating Targparm params to the binder
+ Exit_Status_Supported_On_Target : Boolean;
+ -- 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 recod the exit status.
-----------------------
-- Main Program Name --
Use_Ada_Main_Program_Name_On_Target : Boolean;
-- Set True to use the Ada main program name as the main name
- -- Note: this is prepared for future use, but not yet used, since we
- -- do not yet have a way of propagating Targparm params to the binder
-
- ----------------------------
- -- Support of Long Shifts --
- ----------------------------
-
- -- In GNORT mode, we cannot call library routines, and in particular
- -- we cannot call routines for long (64-bit) shifts if such routines
- -- are required on the target. This comes up in the context of support
- -- of packed arrays. We can only represent packed arrays whose length
- -- is in the range 33- to 64-bits as modular types if long shifts are
- -- done with inline code.
-
- -- For the default version, for now we set long shifts inlined as True
- -- This may not be quite accurate, but until we get proper separate
- -- System's for each target, it is a safer choice.
-
- Long_Shifts_Inlined_On_Target : Boolean;
- -- Indicates if long (double word) shifts are generated using inlined
- -- code (and thus are permissible in No_Run_Time mode).
-
----------------------------------------------
-- Boolean-Valued Floating-Point Attributes --
----------------------------------------------
-- the partition. We probably should add such consistency checks in future,
-- but for now we don't do this.
- AAMP_On_Target : Boolean;
- -- Set to True if target is AAMP.
-
Denorm_On_Target : Boolean;
-- Set to False on targets that do not reliably support denormals.
-- Reliably here means for all settings of the relevant -m flag, so
-- 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.
+
+ procedure Get_Target_Parameters
+ (System_Text : Source_Buffer_Ptr;
+ Source_First : Source_Ptr;
+ Source_Last : Source_Ptr);
+ -- 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)).
+
procedure Get_Target_Parameters;
- -- Called at the start of execution to read the source of System and
- -- obtain and set the values of the above parameters.
+ -- 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;
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