-- --
-- S p e c --
-- --
--- $Revision$
--- --
--- Copyright (C) 1992-2001 Free Software Foundation, Inc. --
+-- Copyright (C) 1992-2006, 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- --
-- 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. --
+-- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
+-- Boston, MA 02110-1301, USA. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
--- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
+-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
function Access_Checks_Suppressed (E : Entity_Id) return Boolean;
function Accessibility_Checks_Suppressed (E : Entity_Id) return Boolean;
+ function Alignment_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 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.
+ function Validity_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
-- operate anyway since they may generate useful compile time warnings.
procedure Apply_Access_Check (N : Node_Id);
- -- Determines whether an expression node should be flagged as needing
- -- a runtime access check. If the node requires such a check, the
- -- Do_Access_Check flag is turned on.
+ -- 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
-- 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_Address_Clause_Check (E : Entity_Id; N : Node_Id);
+ -- E is the entity for an object which has an address clause. If 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. check is also made for the case of
+ -- a clear overlay situation that the size of the overlaying object is not
+ -- larger than the overlaid object.
procedure Apply_Array_Size_Check (N : Node_Id; Typ : Entity_Id);
-- N is the node for an object declaration that declares an object of
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 --
+ -------------------------------------------------------
+
+ -- 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 --
-- 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.
-
- procedure Enable_Range_Check (N : Node_Id);
- pragma Inline (Enable_Range_Check);
- -- Set Do_Range_Check flag in node N to True unless Kill_Range_Check flag
- -- is set in N (the purpose of the latter flag is precisely to prevent
- -- Do_Range_Check from being set).
+ -- 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;
-- 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 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
- -- 9 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)
-- If all possible stored values are valid, then any uninitialized
-- value must be valid.
- -- Literals, including enumeration literals, are clearly always 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
-- 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
-- the sense of the 'Valid attribute returning True. Constraint_Error
-- will be raised if the value is not valid.
+ procedure Null_Exclusion_Static_Checks (N : Node_Id);
+ -- Ada 2005 (AI-231): Check bad usages of the null-exclusion issue
+
+ 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).
+
+ procedure Validity_Check_Range (N : Node_Id);
+ -- If N is an N_Range node, then Ensure_Valid is called on its bounds,
+ -- if validity checking of operands is enabled.
+
private
type Check_Result is array (Positive range 1 .. 2) of Node_Id;
-- 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.
-
- pragma Inline (Access_Checks_Suppressed);
- pragma Inline (Accessibility_Checks_Suppressed);
- pragma Inline (Discriminant_Checks_Suppressed);
- pragma Inline (Division_Checks_Suppressed);
- pragma Inline (Elaboration_Checks_Suppressed);
- pragma Inline (Index_Checks_Suppressed);
- pragma Inline (Length_Checks_Suppressed);
- pragma Inline (Overflow_Checks_Suppressed);
- pragma Inline (Range_Checks_Suppressed);
- pragma Inline (Storage_Checks_Suppressed);
- pragma Inline (Tag_Checks_Suppressed);
+ -- 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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