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diff --git a/gcc-4.8.3/gcc/ada/checks.ads b/gcc-4.8.3/gcc/ada/checks.ads new file mode 100644 index 000000000..fb7370628 --- /dev/null +++ b/gcc-4.8.3/gcc/ada/checks.ads @@ -0,0 +1,857 @@ +------------------------------------------------------------------------------ +-- -- +-- GNAT COMPILER COMPONENTS -- +-- -- +-- C H E C K S -- +-- -- +-- S p e c -- +-- -- +-- Copyright (C) 1992-2012, Free Software Foundation, Inc. -- +-- -- +-- GNAT is free software; you can redistribute it and/or modify it under -- +-- terms of the GNU General Public License as published by the Free Soft- -- +-- ware Foundation; either version 3, or (at your option) any later ver- -- +-- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- +-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- +-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- +-- for more details. You should have received a copy of the GNU General -- +-- Public License distributed with GNAT; see file COPYING3. If not, go to -- +-- http://www.gnu.org/licenses for a complete copy of the license. -- +-- -- +-- GNAT was originally developed by the GNAT team at New York University. -- +-- Extensive contributions were provided by Ada Core Technologies Inc. -- +-- -- +------------------------------------------------------------------------------ + +-- 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 Namet; use Namet; +with Table; +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 Alignment_Checks_Suppressed (E : Entity_Id) return Boolean; + function Atomic_Synchronization_Disabled (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; + 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. + + function Is_Check_Suppressed (E : Entity_Id; C : Check_Id) return Boolean; + -- This function is called if Checks_May_Be_Suppressed (E) is True to + -- determine whether check C is suppressed either on the entity E or + -- as the result of a scope suppress pragma. If Checks_May_Be_Suppressed + -- is False, then the status of the check can be determined simply by + -- examining Scope_Suppress, so this routine is not called in that case. + + function Overflow_Check_Mode return Overflow_Mode_Type; + -- Returns current overflow checking mode, taking into account whether + -- we are inside an assertion expression. + + ------------------------------------------- + -- Procedures to Activate Checking Flags -- + ------------------------------------------- + + procedure Activate_Division_Check (N : Node_Id); + pragma Inline (Activate_Division_Check); + -- Sets Do_Division_Check flag in node N, and handles possible local raise. + -- Always call this routine rather than calling Set_Do_Division_Check to + -- set an explicit value of True, to ensure handling the local raise case. + + procedure Activate_Overflow_Check (N : Node_Id); + pragma Inline (Activate_Overflow_Check); + -- Sets Do_Overflow_Check flag in node N, and handles possible local raise. + -- Always call this routine rather than calling Set_Do_Overflow_Check to + -- set an explicit value of True, to ensure handling the local raise case. + -- Note that this call has no effect for MOD, REM, and unary "+" for which + -- overflow is never possible in any case. + + procedure Activate_Range_Check (N : Node_Id); + pragma Inline (Activate_Range_Check); + -- Sets Do_Range_Check flag in node N, and handles possible local raise + -- Always call this routine rather than calling Set_Do_Range_Check to + -- set an explicit value of True, to ensure handling the local raise case. + + -------------------------------- + -- Procedures to Apply Checks -- + -------------------------------- + + -- 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; + Insert_Node : Node_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. + -- Insert_Node indicates the node where the check should be inserted. + + 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 prepended to the Actions list of N_Freeze_Entity node N. + -- Note that the check references E'Alignment, so it cannot be emitted + -- before N (its freeze node), otherwise this would cause an illegal + -- access before elaboration error in GIGI. For the case of a clear overlay + -- situation, we also check that the size of the overlaying object is not + -- larger than the overlaid object. + + procedure Apply_Arithmetic_Overflow_Check (N : Node_Id); + -- Handle overflow checking for an arithmetic operator. Also handles the + -- cases of ELIMINATED and MINIMIZED overflow checking mode. If the mode + -- is one of the latter two, then this routine can also be called with + -- an if or case expression node to make sure that we properly handle + -- overflow checking for dependent expressions. This routine handles + -- front end vs back end overflow checks (in the front end case it expands + -- the necessary check). Note that divide is handled separately using + -- Apply_Divide_Checks. Node N may or may not have Do_Overflow_Check. + -- In STRICT mode, there is nothing to do if this flag is off, but in + -- MINIMIZED/ELIMINATED mode we still have to deal with possible use + -- of doing operations in Long_Long_Integer or Bignum mode. + + 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 satisfies the constraint of type Typ. + -- No_Sliding is only relevant for constrained array types, if 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 performed only if the corresponding actual is + -- constrained, i.e., whether Lhs'Constrained is True. + + procedure Apply_Divide_Checks (N : Node_Id); + -- The node kind is N_Op_Divide, N_Op_Mod, or N_Op_Rem if either of the + -- flags Do_Division_Check or Do_Overflow_Check is set, then this routine + -- ensures that the appropriate checks are made. Note that overflow can + -- occur in the signed case for the case of the largest negative number + -- divided by minus one. + + procedure Apply_Parameter_Aliasing_Checks + (Call : Node_Id; + Subp : Entity_Id); + -- Given a subprogram call Call, add a check to verify that none of the + -- actuals overlap. Subp denotes the subprogram being called. + + procedure Apply_Parameter_Validity_Checks (Subp : Entity_Id); + -- Given a subprogram Subp, add both a pre and post condition pragmas that + -- verify the proper initialization of scalars in parameters and function + -- results. + + procedure Apply_Predicate_Check (N : Node_Id; Typ : Entity_Id); + -- N is an expression to which a predicate check may need to be applied + -- for Typ, if Typ has a predicate function. The check is applied only + -- if the type of N does not match Typ. + + 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. + + 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). + + function Convert_From_Bignum (N : Node_Id) return Node_Id; + -- Returns result of converting node N from Bignum. The returned value is + -- not analyzed, the caller takes responsibility for this. Node N must be + -- a subexpression node of type Bignum. The result is Long_Long_Integer. + + function Convert_To_Bignum (N : Node_Id) return Node_Id; + -- Returns result of converting node N to Bignum. The returned value is not + -- analyzed, the caller takes responsibility for this. Node N must be a + -- subexpression node of a signed integer type or Bignum type (if it is + -- already a Bignum, the returned value is Relocate_Node (N)). + + procedure Determine_Range + (N : Node_Id; + OK : out Boolean; + Lo : out Uint; + Hi : out Uint; + Assume_Valid : Boolean := False); + -- 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 Etype), + -- 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 lie 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. Assume_Valid determines whether the processing is allowed to + -- assume that values are in range of their subtypes. If it is set to True, + -- then this assumption is valid, if False, then processing is done using + -- base types to allow invalid values. + + 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. + + function Make_Bignum_Block (Loc : Source_Ptr) return Node_Id; + -- This function is used by top level overflow checking routines to do a + -- mark/release operation on the secondary stack around bignum operations. + -- The block created looks like: + -- + -- declare + -- M : Mark_Id := SS_Mark; + -- begin + -- SS_Release (M); + -- end; + -- + -- The idea is that the caller will insert any needed extra declarations + -- after the declaration of M, and any needed statements (in particular + -- the bignum operations) before the call to SS_Release, and then do an + -- Insert_Action of the whole block (it is returned unanalyzed). The Loc + -- parameter is used to supply Sloc values for the constructed tree. + + procedure Minimize_Eliminate_Overflows + (N : Node_Id; + Lo : out Uint; + Hi : out Uint; + Top_Level : Boolean); + -- This is the main routine for handling MINIMIZED and ELIMINATED overflow + -- processing. On entry N is a node whose result is a signed integer + -- subtype. The Do_Overflow_Check flag may or may not be set on N. If the + -- node is an arithmetic operation, then a range analysis is carried out, + -- and there are three possibilities: + -- + -- The node is left unchanged (apart from expansion of an exponentiation + -- operation). This happens if the routine can determine that the result + -- is definitely in range. The Do_Overflow_Check flag is turned off in + -- this case. + -- + -- The node is transformed into an arithmetic operation with a result + -- type of Long_Long_Integer. + -- + -- The node is transformed into a function call that calls an appropriate + -- function in the System.Bignums package to compute a Bignum result. + -- + -- In the first two cases, Lo and Hi are set to the bounds of the possible + -- range of results, computed as accurately as possible. In the third case + -- Lo and Hi are set to No_Uint (there are some cases where we could get an + -- advantage from keeping result ranges for Bignum values, but it could use + -- a lot of space and is very unlikely to be valuable). + -- + -- If the node is not an arithmetic operation, then it is unchanged but + -- Lo and Hi are still set (to the bounds of the result subtype if nothing + -- better can be determined). + -- + -- Note: this function is recursive, if called with an arithmetic operator, + -- recursive calls are made to process the operands using this procedure. + -- So we end up doing things top down. Nothing happens to an arithmetic + -- expression until this procedure is called on the top level node and + -- then the recursive calls process all the children. We have to do it + -- this way. If we try to do it bottom up in natural expansion order, then + -- there are two problems. First, where do we stash the bounds, and more + -- importantly, semantic processing will be messed up. Consider A+B+C where + -- A,B,C are all of type integer, if we processed A+B before doing semantic + -- analysis of the addition of this result to C, that addition could end up + -- with a Long_Long_Integer left operand and an Integer right operand, and + -- we would get a semantic error. + -- + -- The routine is called in three situations if we are operating in either + -- MINIMIZED or ELIMINATED modes. + -- + -- Overflow processing applied to the top node of an expression tree when + -- that node is an arithmetic operator. In this case the result is + -- converted to the appropriate result type (there is special processing + -- when the parent is a conversion, see body for details). + -- + -- Overflow processing applied to the operands of a comparison operation. + -- In this case, the comparison is done on the result Long_Long_Integer + -- or Bignum values, without raising any exceptions. + -- + -- Overflow processing applied to the left operand of a membership test. + -- In this case no exception is raised if a Long_Long_Integer or Bignum + -- result is outside the range of the type of that left operand (it is + -- just that the result of IN is false in that case). + -- + -- Note that if Bignum values appear, the caller must take care of doing + -- the appropriate mark/release operations on the secondary stack. + -- + -- Top_Level is used to avoid inefficient unnecessary transitions into the + -- Bignum domain. If Top_Level is True, it means that the caller will have + -- to convert any Bignum value back to Long_Long_Integer, possibly checking + -- that the value is in range. This is the normal case for a top level + -- operator in a subexpression. There is no point in going into Bignum mode + -- to avoid an overflow just so we can check for overflow the next moment. + -- For calls from comparisons and membership tests, and for all recursive + -- calls, we do want to transition into the Bignum domain if necessary. + -- Note that this setting is only relevant in ELIMINATED mode. + + ------------------------------------------------------- + -- 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 many 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. It is possible + -- that in the future we might move all the checks to the front end. The + -- main remaining back end checks are for subscript checking. + + -- Overflow checks are similarly controlled by the Do_Overflow_Check flag. + -- The difference here is that if back end overflow checks are inactive + -- (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 + -- 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. + + -- ??? Apply_Length_Check and Apply_Range_Check do not have an Expr + -- formal + + -- ??? Apply_Length_Check and Apply_Range_Check have a Ck_Node formal + -- which is undocumented, is it the same as Expr? + + -- 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 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 a 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 Get_Range_Checks call, for later use in + -- call to Insert_Range_Checks procedure. + + function Get_Range_Checks + (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. + + 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 Get_Range_Checks. + -- 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 Get_Range_Checks. + -- 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. + + ----------------------- + -- 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 difficulties 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 + + -- 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. + -- + -- 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 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. + + ----------------------------- + -- Handling of Check Names -- + ----------------------------- + + -- The following table contains Name_Id's for recognized checks. The first + -- entries (corresponding to the values of the subtype Predefined_Check_Id) + -- contain the Name_Id values for the checks that are predefined, including + -- All_Checks (see Types). Remaining entries are those that are introduced + -- by pragma Check_Names. + + package Check_Names is new Table.Table ( + Table_Component_Type => Name_Id, + Table_Index_Type => Check_Id, + Table_Low_Bound => 1, + Table_Initial => 30, + Table_Increment => 200, + Table_Name => "Name_Check_Names"); + + function Get_Check_Id (N : Name_Id) return Check_Id; + -- Function to search above table for matching name. If found returns the + -- corresponding Check_Id value in the range 1 .. Check_Name.Last. If not + -- found returns No_Check_Id. + +private + + 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; |