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-- --
-- --
-- C H E C K S --
-- --
-- S p e c --
-- --
-- Copyright (C) 1992-2002 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. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
-- Package containing routines used to deal with runtime checks. These
-- routines are used both by the semantics and by the expander. In some
-- cases, checks are enabled simply by setting flags for gigi, and in
-- other cases the code for the check is expanded.
-- The approach used for range and length checks, in regards to suppressed
-- checks, is to attempt to detect at compilation time that a constraint
-- error will occur. If this is detected a warning or error is issued and the
-- offending expression or statement replaced with a constraint error node.
-- This always occurs whether checks are suppressed or not. Dynamic range
-- checks are, of course, not inserted if checks are suppressed.
with Types; use Types;
with Uintp; use Uintp;
package Checks is
procedure Initialize;
-- Called for each new main source program, to initialize internal
-- variables used in the package body of the Checks unit.
function Access_Checks_Suppressed (E : Entity_Id) return Boolean;
function Accessibility_Checks_Suppressed (E : Entity_Id) return Boolean;
function Discriminant_Checks_Suppressed (E : Entity_Id) return Boolean;
function Division_Checks_Suppressed (E : Entity_Id) return Boolean;
function Elaboration_Checks_Suppressed (E : Entity_Id) return Boolean;
function Index_Checks_Suppressed (E : Entity_Id) return Boolean;
function Length_Checks_Suppressed (E : Entity_Id) return Boolean;
function Overflow_Checks_Suppressed (E : Entity_Id) return Boolean;
function Range_Checks_Suppressed (E : Entity_Id) return Boolean;
function Storage_Checks_Suppressed (E : Entity_Id) return Boolean;
function Tag_Checks_Suppressed (E : Entity_Id) return Boolean;
-- These functions check to see if the named check is suppressed,
-- either by an active scope suppress setting, or because the check
-- has been specifically suppressed for the given entity. If no entity
-- is relevant for the current check, then Empty is used as an argument.
-- Note: the reason we insist on specifying Empty is to force the
-- caller to think about whether there is any relevant entity that
-- should be checked.
-- General note on following checks. These checks are always active if
-- Expander_Active and not Inside_A_Generic. They are inactive and have
-- no effect Inside_A_Generic. In the case where not Expander_Active
-- and not Inside_A_Generic, most of them are inactive, but some of them
-- operate anyway since they may generate useful compile time warnings.
procedure Apply_Access_Check (N : Node_Id);
-- Determines whether an expression node requires a runtime access
-- check and if so inserts the appropriate run-time check.
procedure Apply_Accessibility_Check (N : Node_Id; Typ : Entity_Id);
-- Given a name N denoting an access parameter, emits a run-time
-- accessibility check (if necessary), checking that the level of
-- the object denoted by the access parameter is not deeper than the
-- level of the type Typ. Program_Error is raised if the check fails.
procedure Apply_Alignment_Check (E : Entity_Id; N : Node_Id);
-- E is the entity for an object. If there is an address clause for
-- this entity, and checks are enabled, then this procedure generates
-- a check that the specified address has an alignment consistent with
-- the alignment of the object, raising PE if this is not the case. The
-- resulting check (if one is generated) is inserted before node N.
procedure Apply_Array_Size_Check (N : Node_Id; Typ : Entity_Id);
-- N is the node for an object declaration that declares an object of
-- array type Typ. This routine generates, if necessary, a check that
-- the size of the array is not too large, raising Storage_Error if so.
procedure Apply_Arithmetic_Overflow_Check (N : Node_Id);
-- Given a binary arithmetic operator (+ - *) expand a software integer
-- overflow check using range checks on a larger checking type or a call
-- to an appropriate runtime routine. This is used for all three operators
-- for the signed integer case, and for +/- in the fixed-point case. The
-- check is expanded only if Software_Overflow_Checking is enabled and
-- Do_Overflow_Check is set on node N. Note that divide is handled
-- separately using Apply_Arithmetic_Divide_Overflow_Check.
procedure Apply_Constraint_Check
(N : Node_Id;
Typ : Entity_Id;
No_Sliding : Boolean := False);
-- Top-level procedure, calls all the others depending on the class of Typ.
-- Checks that expression N verifies the constraint of type Typ. No_Sliding
-- is only relevant for constrained array types, id set to true, it
-- checks that indexes are in range.
procedure Apply_Discriminant_Check
(N : Node_Id;
Typ : Entity_Id;
Lhs : Node_Id := Empty);
-- Given an expression N of a discriminated type, or of an access type
-- whose designated type is a discriminanted type, generates a check to
-- ensure that the expression can be converted to the subtype given as
-- the second parameter. Lhs is empty except in the case of assignments,
-- where the target object may be needed to determine the subtype to
-- check against (such as the cases of unconstrained formal parameters
-- and unconstrained aliased objects). For the case of unconstrained
-- formals, the check is peformed only if the corresponding actual is
-- constrained, i.e., whether Lhs'Constrained is True.
function Build_Discriminant_Checks
(N : Node_Id;
T_Typ : Entity_Id)
return Node_Id;
-- Subsidiary routine for Apply_Discriminant_Check. Builds the expression
-- that compares discriminants of the expression with discriminants of the
-- type. Also used directly for membership tests (see Exp_Ch4.Expand_N_In).
procedure Apply_Divide_Check (N : Node_Id);
-- The node kind is N_Op_Divide, N_Op_Mod, or N_Op_Rem. An appropriate
-- check is generated to ensure that the right operand is non-zero. In
-- the divide case, we also check that we do not have the annoying case
-- of the largest negative number divided by minus one.
procedure Apply_Type_Conversion_Checks (N : Node_Id);
-- N is an N_Type_Conversion node. A type conversion actually involves
-- two sorts of checks. The first check is the checks that ensures that
-- the operand in the type conversion fits onto the base type of the
-- subtype it is being converted to (see RM 4.6 (28)-(50)). The second
-- check is there to ensure that once the operand has been converted to
-- a value of the target type, this converted value meets the
-- constraints imposed by the target subtype (see RM 4.6 (51)).
procedure Apply_Universal_Integer_Attribute_Checks (N : Node_Id);
-- The argument N is an attribute reference node intended for processing
-- by gigi. The attribute is one that returns a universal integer, but
-- the attribute reference node is currently typed with the expected
-- result type. This routine deals with range and overflow checks needed
-- to make sure that the universal result is in range.
procedure Determine_Range
(N : Node_Id;
OK : out Boolean;
Lo : out Uint;
Hi : out Uint);
-- N is a node for a subexpression. If N is of a discrete type with
-- no error indications, and no other peculiarities (e.g. missing
-- type fields), then OK is True on return, and Lo and Hi are set
-- to a conservative estimate of the possible range of values of N.
-- Thus if OK is True on return, the value of the subexpression N is
-- known to like in the range Lo .. Hi (inclusive). If the expression
-- is not of a discrete type, or some kind of error condition is
-- detected, then OK is False on exit, and Lo/Hi are set to No_Uint.
-- Thus the significance of OK being False on return is that no
-- useful information is available on the range of the expression.
-- Control and Optimization of Range/Overflow Checks --
-- Range checks are controlled by the Do_Range_Check flag. The front end
-- is responsible for setting this flag in relevant nodes. Originally
-- the back end generated all corresponding range checks. But later on
-- we decided to generate all range checks in the front end. We are now
-- in the transitional phase where some of these checks are still done
-- by the back end, but many are done by the front end.
-- Overflow checks are similarly controlled by the Do_Overflow_Check
-- flag. The difference here is that if Backend_Overflow_Checks is
-- is (Backend_Overflow_Checks_On_Target set False), then the actual
-- overflow checks are generated by the front end, but if back end
-- overflow checks are active (Backend_Overflow_Checks_On_Target
-- set True), then the back end does generate the checks.
-- The following two routines are used to set these flags, they allow
-- for the possibility of eliminating checks. Checks can be eliminated
-- if an identical check has already been performed.
procedure Enable_Overflow_Check (N : Node_Id);
-- First this routine determines if an overflow check is needed by doing
-- an appropriate range check. If a check is not needed, then the call
-- has no effect. If a check is needed then this routine sets the flag
-- Set Do_Overflow_Check in node N to True, unless it can be determined
-- that the check is not needed. The only condition under which this is
-- the case is if there was an identical check earlier on.
procedure Enable_Range_Check (N : Node_Id);
-- Set Do_Range_Check flag in node N True, unless it can be determined
-- that the check is not needed. The only condition under which this is
-- the case is if there was an identical check earlier on. This routine
-- is not responsible for doing range analysis to determine whether or
-- not such a check is needed -- the caller is expected to do this. The
-- one other case in which the request to set the flag is ignored is
-- when Kill_Range_Check is set in an N_Unchecked_Conversion node.
-- The following routines are used to keep track of processing sequences
-- of statements (e.g. the THEN statements of an IF statement). A check
-- that appears within such a sequence can eliminate an identical check
-- within this sequence of statements. However, after the end of the
-- sequence of statements, such a check is no longer of interest, since
-- it may not have been executed.
procedure Conditional_Statements_Begin;
-- This call marks the start of processing of a sequence of statements.
-- Every call to this procedure must be followed by a matching call to
-- Conditional_Statements_End.
procedure Conditional_Statements_End;
-- This call removes from consideration all saved checks since the
-- corresponding call to Conditional_Statements_Begin. These two
-- procedures operate in a stack like manner.
-- The mechanism for optimizing checks works by remembering checks
-- that have already been made, but certain conditions, for example
-- an assignment to a variable involved in a check, may mean that the
-- remembered check is no longer valid, in the sense that if the same
-- expression appears again, another check is required because the
-- value may have changed.
-- The following routines are used to note conditions which may render
-- some or all of the stored and remembered checks to be invalidated.
procedure Kill_Checks (V : Entity_Id);
-- This procedure records an assignment or other condition that causes
-- the value of the variable to be changed, invalidating any stored
-- checks that reference the value. Note that all such checks must
-- be discarded, even if they are not in the current statement range.
procedure Kill_All_Checks;
-- This procedure kills all remembered checks.
-- Length and Range Checks --
-- In the following procedures, there are three arguments which have
-- a common meaning as follows:
-- Expr The expression to be checked. If a check is required,
-- the appropriate flag will be placed on this node. Whether
-- this node is further examined depends on the setting of
-- the parameter Source_Typ, as described below.
-- Target_Typ The target type on which the check is to be based. For
-- example, if we have a scalar range check, then the check
-- is that we are in range of this type.
-- Source_Typ Normally Empty, but can be set to a type, in which case
-- this type is used for the check, see below.
-- The checks operate in one of two modes:
-- If Source_Typ is Empty, then the node Expr is examined, at the
-- very least to get the source subtype. In addition for some of
-- the checks, the actual form of the node may be examined. For
-- example, a node of type Integer whose actual form is an Integer
-- conversion from a type with range 0 .. 3 can be determined to
-- have a value in the range 0 .. 3.
-- If Source_Typ is given, then nothing can be assumed about the
-- Expr, and indeed its contents are not examined. In this case the
-- check is based on the assumption that Expr can be an arbitrary
-- value of the given Source_Typ.
-- Currently, the only case in which a Source_Typ is explicitly supplied
-- is for the case of Out and In_Out parameters, where, for the conversion
-- on return (the Out direction), the types must be reversed. This is
-- handled by the caller.
procedure Apply_Length_Check
(Ck_Node : Node_Id;
Target_Typ : Entity_Id;
Source_Typ : Entity_Id := Empty);
-- This procedure builds a sequence of declarations to do a length check
-- that checks if the lengths of the two arrays Target_Typ and source type
-- are the same. The resulting actions are inserted at Node using a call
-- to Insert_Actions.
-- For access types, the Directly_Designated_Type is retrieved and
-- processing continues as enumerated above, with a guard against
-- null values.
-- Note: calls to Apply_Length_Check currently never supply an explicit
-- Source_Typ parameter, but Apply_Length_Check takes this parameter and
-- processes it as described above for consistency with the other routines
-- in this section.
procedure Apply_Range_Check
(Ck_Node : Node_Id;
Target_Typ : Entity_Id;
Source_Typ : Entity_Id := Empty);
-- For an Node of kind N_Range, constructs a range check action that
-- tests first that the range is not null and then that the range
-- is contained in the Target_Typ range.
-- For scalar types, constructs a range check action that first tests that
-- the expression is contained in the Target_Typ range. The difference
-- between this and Apply_Scalar_Range_Check is that the latter generates
-- the actual checking code in gigi against the Etype of the expression.
-- For constrained array types, construct series of range check actions
-- to check that each Expr range is properly contained in the range of
-- Target_Typ.
-- For a type conversion to an unconstrained array type, constructs
-- a range check action to check that the bounds of the source type
-- are within the constraints imposed by the Target_Typ.
-- For access types, the Directly_Designated_Type is retrieved and
-- processing continues as enumerated above, with a guard against
-- null values.
-- The source type is used by type conversions to unconstrained array
-- types to retrieve the corresponding bounds.
procedure Apply_Static_Length_Check
(Expr : Node_Id;
Target_Typ : Entity_Id;
Source_Typ : Entity_Id := Empty);
-- Tries to determine statically whether the two array types source type
-- and Target_Typ have the same length. If it can be determined at compile
-- time that they do not, then an N_Raise_Constraint_Error node replaces
-- Expr, and a warning message is issued.
procedure Apply_Scalar_Range_Check
(Expr : Node_Id;
Target_Typ : Entity_Id;
Source_Typ : Entity_Id := Empty;
Fixed_Int : Boolean := False);
-- For scalar types, determines whether an expression node should be
-- flagged as needing a runtime range check. If the node requires such
-- a check, the Do_Range_Check flag is turned on. The Fixed_Int flag
-- if set causes any fixed-point values to be treated as though they
-- were discrete values (i.e. the underlying integer value is used).
type Check_Result is private;
-- Type used to return result of Range_Check call, for later use in
-- call to Insert_Range_Checks procedure.
procedure Append_Range_Checks
(Checks : Check_Result;
Stmts : List_Id;
Suppress_Typ : Entity_Id;
Static_Sloc : Source_Ptr;
Flag_Node : Node_Id);
-- Called to append range checks as returned by a call to Range_Check.
-- Stmts is a list to which either the dynamic check is appended or
-- the raise Constraint_Error statement is appended (for static checks).
-- Static_Sloc is the Sloc at which the raise CE node points,
-- Flag_Node is used as the node at which to set the Has_Dynamic_Check
-- flag. Checks_On is a boolean value that says if range and index checking
-- is on or not.
procedure Insert_Range_Checks
(Checks : Check_Result;
Node : Node_Id;
Suppress_Typ : Entity_Id;
Static_Sloc : Source_Ptr := No_Location;
Flag_Node : Node_Id := Empty;
Do_Before : Boolean := False);
-- Called to insert range checks as returned by a call to Range_Check.
-- Node is the node after which either the dynamic check is inserted or
-- the raise Constraint_Error statement is inserted (for static checks).
-- Suppress_Typ is the type to check to determine if checks are suppressed.
-- Static_Sloc, if passed, is the Sloc at which the raise CE node points,
-- otherwise Sloc (Node) is used. The Has_Dynamic_Check flag is normally
-- set at Node. If Flag_Node is present, then this is used instead as the
-- node at which to set the Has_Dynamic_Check flag. Normally the check is
-- inserted after, if Do_Before is True, the check is inserted before
-- Node.
function Range_Check
(Ck_Node : Node_Id;
Target_Typ : Entity_Id;
Source_Typ : Entity_Id := Empty;
Warn_Node : Node_Id := Empty)
return Check_Result;
-- Like Apply_Range_Check, except it does not modify anything. Instead
-- it returns an encapsulated result of the check operations for later
-- use in a call to Insert_Range_Checks. If Warn_Node is non-empty, its
-- Sloc is used, in the static case, for the generated warning or error.
-- Additionally, it is used rather than Expr (or Low/High_Bound of Expr)
-- in constructing the check.
-- Expander Routines --
-- Some of the earlier processing for checks results in temporarily
-- setting the Do_Range_Check flag rather than actually generating
-- checks. Now we are moving the generation of such checks into the
-- front end for reasons of efficiency and simplicity (there were
-- difficutlies in handling this in the back end when side effects
-- were present in the expressions being checked).
-- Probably we could eliminate the Do_Range_Check flag entirely and
-- generate the checks earlier, but this is a delicate area and it
-- seemed safer to implement the following routines, which are called
-- late on in the expansion process. They check the Do_Range_Check flag
-- and if it is set, generate the actual checks and reset the flag.
procedure Generate_Range_Check
(N : Node_Id;
Target_Type : Entity_Id;
Reason : RT_Exception_Code);
-- This procedure is called to actually generate and insert a range
-- check. A check is generated to ensure that the value of N lies
-- within the range of the target type. Note that the base type of
-- N may be different from the base type of the target type. This
-- happens in the conversion case. The Reason parameter is the
-- exception code to be used for the exception if raised.
-- Note on the relation of this routine to the Do_Range_Check flag.
-- Mostly for historical reasons, we often set the Do_Range_Check
-- flag and then later we call Generate_Range_Check if this flag is
-- set. Most probably we could eliminate this intermediate setting
-- of the flag (historically the back end dealt with range checks,
-- using this flag to indicate if a check was required, then we
-- moved checks into the front end).
procedure Generate_Index_Checks (N : Node_Id);
-- This procedure is called to generate index checks on the subscripts
-- for the indexed component node N. Each subscript expression is
-- examined, and if the Do_Range_Check flag is set, an appropriate
-- index check is generated and the flag is reset.
-- Similarly, we set the flag Do_Discriminant_Check in the semantic
-- analysis to indicate that a discriminant check is required for a
-- selected component of a discriminated type. The following routine
-- is called from the expander to actually generate the call.
procedure Generate_Discriminant_Check (N : Node_Id);
-- N is a selected component for which a discriminant check is required
-- to make sure that the discriminants have appropriate values for the
-- selection. This is done by calling the appropriate discriminant
-- checking routine for the selector.
-- Validity Checking --
-- In (RM 13.9.1(9-11)) we have the following rules on invalid values
-- If the representation of a scalar object does not represent a
-- value of the object's subtype (perhaps because the object was not
-- initialized), the object is said to have an invalid representation.
-- It is a bounded error to evaluate the value of such an object. If
-- the error is detected, either Constraint_Error or Program_Error is
-- raised. Otherwise, execution continues using the invalid
-- representation. The rules of the language outside this subclause
-- assume that all objects have valid representations. The semantics
-- of operations on invalid representations are as follows:
-- 10 If the representation of the object represents a value of the
-- object's type, the value of the type is used.
-- 11 If the representation of the object does not represent a value
-- of the object's type, the semantics of operations on such
-- representations is implementation-defined, but does not by
-- itself lead to erroneous or unpredictable execution, or to
-- other objects becoming abnormal.
-- We quote the rules in full here since they are quite delicate. Most
-- of the time, we can just compute away with wrong values, and get a
-- possibly wrong result, which is well within the range of allowed
-- implementation defined behavior. The two tricky cases are subscripted
-- array assignments, where we don't want to do wild stores, and case
-- statements where we don't want to do wild jumps.
-- In GNAT, we control validity checking with a switch -gnatV that
-- can take three parameters, n/d/f for None/Default/Full. These
-- modes have the following meanings:
-- None (no validity checking)
-- In this mode, there is no specific checking for invalid values
-- and the code generator assumes that all stored values are always
-- within the bounds of the object subtype. The consequences are as
-- follows:
-- For case statements, an out of range invalid value will cause
-- Constraint_Error to be raised, or an arbitrary one of the case
-- alternatives will be executed. Wild jumps cannot result even
-- in this mode, since we always do a range check
-- For subscripted array assignments, wild stores will result in
-- the expected manner when addresses are calculated using values
-- of subscripts that are out of range.
-- It could perhaps be argued that this mode is still conformant with
-- the letter of the RM, since implementation defined is a rather
-- broad category, but certainly it is not in the spirit of the
-- RM requirement, since wild stores certainly seem to be a case of
-- erroneous behavior.
-- Default (default standard RM-compatible validity checking)
-- In this mode, which is the default, minimal validity checking is
-- performed to ensure no erroneous behavior as follows:
-- For case statements, an out of range invalid value will cause
-- Constraint_Error to be raised.
-- For subscripted array assignments, invalid out of range
-- subscript values will cause Constraint_Error to be raised.
-- Full (Full validity checking)
-- In this mode, the protections guaranteed by the standard mode are
-- in place, and the following additional checks are made:
-- For every assignment, the right side is checked for validity
-- For every call, IN and IN OUT parameters are checked for validity
-- For every subscripted array reference, both for stores and loads,
-- all subscripts are checked for validity.
-- These checks are not required by the RM, but will in practice
-- improve the detection of uninitialized variables, particularly
-- if used in conjunction with pragma Normalize_Scalars.
-- In the above description, we talk about performing validity checks,
-- but we don't actually generate a check in a case where the compiler
-- can be sure that the value is valid. Note that this assurance must
-- be achieved without assuming that any uninitialized value lies within
-- the range of its type. The following are cases in which values are
-- known to be valid. The flag Is_Known_Valid is used to keep track of
-- some of these cases.
-- If all possible stored values are valid, then any uninitialized
-- value must be valid.
-- Literals, including enumeration literals, are clearly always valid.
-- Constants are always assumed valid, with a validity check being
-- performed on the initializing value where necessary to ensure that
-- this is the case.
-- For variables, the status is set to known valid if there is an
-- initializing expression. Again a check is made on the initializing
-- value if necessary to ensure that this assumption is valid. The
-- status can change as a result of local assignments to a variable.
-- If a known valid value is unconditionally assigned, then we mark
-- the left side as known valid. If a value is assigned that is not
-- known to be valid, then we mark the left side as invalid. This
-- kind of processing does NOT apply to non-local variables since we
-- are not following the flow graph (more properly the flow of actual
-- processing only corresponds to the flow graph for local assignments).
-- For non-local variables, we preserve the current setting, i.e. a
-- validity check is performed when assigning to a knonwn valid global.
-- Note: no validity checking is required if range checks are suppressed
-- regardless of the setting of the validity checking mode.
-- The following procedures are used in handling validity checking
procedure Apply_Subscript_Validity_Checks (Expr : Node_Id);
-- Expr is the node for an indexed component. If validity checking and
-- range checking are enabled, all subscripts for this indexed component
-- are checked for validity.
procedure Check_Valid_Lvalue_Subscripts (Expr : Node_Id);
-- Expr is a lvalue, i.e. an expression representing the target of
-- an assignment. This procedure checks for this expression involving
-- an assignment to an array value. We have to be sure that all the
-- subscripts in such a case are valid, since according to the rules
-- in (RM 13.9.1(9-11)) such assignments are not permitted to result
-- in erroneous behavior in the case of invalid subscript values.
procedure Ensure_Valid (Expr : Node_Id; Holes_OK : Boolean := False);
-- Ensure that Expr represents a valid value of its type. If this type
-- is not a scalar type, then the call has no effect, since validity
-- is only an issue for scalar types. The effect of this call is to
-- check if the value is known valid, if so, nothing needs to be done.
-- If this is not known, then either Expr is set to be range checked,
-- or specific checking code is inserted so that an exception is raised
-- if the value is not valid.
-- The optional argument Holes_OK indicates whether it is necessary to
-- worry about enumeration types with non-standard representations leading
-- to "holes" in the range of possible representations. If Holes_OK is
-- True, then such values are assumed valid (this is used when the caller
-- will make a separate check for this case anyway). If Holes_OK is False,
-- then this case is checked, and code is inserted to ensure that Expr is
-- valid, raising Constraint_Error if the value is not valid.
function Expr_Known_Valid (Expr : Node_Id) return Boolean;
-- This function tests it the value of Expr is known to be valid in
-- the sense of RM 13.9.1(9-11). In the case of GNAT, it is only
-- discrete types which are a concern, since for non-discrete types
-- we simply continue computation with invalid values, which does
-- not lead to erroneous behavior. Thus Expr_Known_Valid always
-- returns True if the type of Expr is non-discrete. For discrete
-- types the value returned is True only if it can be determined
-- that the value is Valid. Otherwise False is returned.
procedure Insert_Valid_Check (Expr : Node_Id);
-- Inserts code that will check for the value of Expr being valid, in
-- the sense of the 'Valid attribute returning True. Constraint_Error
-- will be raised if the value is not valid.
procedure Remove_Checks (Expr : Node_Id);
-- Remove all checks from Expr except those that are only executed
-- conditionally (on the right side of And Then/Or Else. This call
-- removes only embedded checks (Do_Range_Check, Do_Overflow_Check).
type Check_Result is array (Positive range 1 .. 2) of Node_Id;
-- There are two cases for the result returned by Range_Check:
-- For the static case the result is one or two nodes that should cause
-- a Constraint_Error. Typically these will include Expr itself or the
-- direct descendents of Expr, such as Low/High_Bound (Expr)). It is the
-- responsibility of the caller to rewrite and substitute the nodes with
-- N_Raise_Constraint_Error nodes.
-- For the non-static case a single N_Raise_Constraint_Error node
-- with a non-empty Condition field is returned.
-- Unused entries in Check_Result, if any, are simply set to Empty
-- For external clients, the required processing on this result is
-- achieved using the Insert_Range_Checks routine.
pragma Inline (Apply_Length_Check);
pragma Inline (Apply_Range_Check);
pragma Inline (Apply_Static_Length_Check);
end Checks;