-- --
-- S p e c --
-- --
--- Copyright (C) 1992-2004 Free Software Foundation, Inc. --
+-- Copyright (C) 1992-2005 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- --
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.
+ -- 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.
+
+ procedure Install_Null_Excluding_Check (N : Node_Id);
+ -- Determines whether an access node requires a runtime access check and
+ -- if so inserts the appropriate run-time check.
-------------------------------------------------------
-- Control and Optimization of Range/Overflow Checks --
-- 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.
+ -- 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
-- 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 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 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.
+ -- 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
-- to Insert_Actions.
--
-- For access types, the Directly_Designated_Type is retrieved and
- -- processing continues as enumerated above, with a guard against
- -- null values.
+ -- 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
(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 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
-- 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 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.
+ -- 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.
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).
+ -- 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
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.
+ -- 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;
-- 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).
+ -- 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
(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.
+ -- 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).
+ -- 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.
+ -- 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.
+ -- analysis to indicate that a discriminant check is required for 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.
+ -- 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:
+ -- If the representation of a scalar object does not represent 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.
-- 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:
+ -- 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)
-- 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.
+ -- 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
-- 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.
+ -- 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
-- 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.
+ -- 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.
+ -- 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);
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