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diff --git a/gcc/ada/sem_ch5.adb b/gcc/ada/sem_ch5.adb new file mode 100644 index 000000000..68305d6e8 --- /dev/null +++ b/gcc/ada/sem_ch5.adb @@ -0,0 +1,2402 @@ +------------------------------------------------------------------------------ +-- -- +-- GNAT COMPILER COMPONENTS -- +-- -- +-- S E M _ C H 5 -- +-- -- +-- B o d y -- +-- -- +-- Copyright (C) 1992-2010, 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. -- +-- -- +------------------------------------------------------------------------------ + +with Atree; use Atree; +with Checks; use Checks; +with Einfo; use Einfo; +with Errout; use Errout; +with Expander; use Expander; +with Exp_Util; use Exp_Util; +with Freeze; use Freeze; +with Lib; use Lib; +with Lib.Xref; use Lib.Xref; +with Namet; use Namet; +with Nlists; use Nlists; +with Nmake; use Nmake; +with Opt; use Opt; +with Rtsfind; use Rtsfind; +with Sem; use Sem; +with Sem_Aux; use Sem_Aux; +with Sem_Case; use Sem_Case; +with Sem_Ch3; use Sem_Ch3; +with Sem_Ch8; use Sem_Ch8; +with Sem_Disp; use Sem_Disp; +with Sem_Elab; use Sem_Elab; +with Sem_Eval; use Sem_Eval; +with Sem_Res; use Sem_Res; +with Sem_Type; use Sem_Type; +with Sem_Util; use Sem_Util; +with Sem_Warn; use Sem_Warn; +with Snames; use Snames; +with Stand; use Stand; +with Sinfo; use Sinfo; +with Targparm; use Targparm; +with Tbuild; use Tbuild; +with Uintp; use Uintp; + +package body Sem_Ch5 is + + Unblocked_Exit_Count : Nat := 0; + -- This variable is used when processing if statements, case statements, + -- and block statements. It counts the number of exit points that are not + -- blocked by unconditional transfer instructions: for IF and CASE, these + -- are the branches of the conditional; for a block, they are the statement + -- sequence of the block, and the statement sequences of any exception + -- handlers that are part of the block. When processing is complete, if + -- this count is zero, it means that control cannot fall through the IF, + -- CASE or block statement. This is used for the generation of warning + -- messages. This variable is recursively saved on entry to processing the + -- construct, and restored on exit. + + ------------------------ + -- Analyze_Assignment -- + ------------------------ + + procedure Analyze_Assignment (N : Node_Id) is + Lhs : constant Node_Id := Name (N); + Rhs : constant Node_Id := Expression (N); + T1 : Entity_Id; + T2 : Entity_Id; + Decl : Node_Id; + + procedure Diagnose_Non_Variable_Lhs (N : Node_Id); + -- N is the node for the left hand side of an assignment, and it is not + -- a variable. This routine issues an appropriate diagnostic. + + procedure Kill_Lhs; + -- This is called to kill current value settings of a simple variable + -- on the left hand side. We call it if we find any error in analyzing + -- the assignment, and at the end of processing before setting any new + -- current values in place. + + procedure Set_Assignment_Type + (Opnd : Node_Id; + Opnd_Type : in out Entity_Id); + -- Opnd is either the Lhs or Rhs of the assignment, and Opnd_Type + -- is the nominal subtype. This procedure is used to deal with cases + -- where the nominal subtype must be replaced by the actual subtype. + + ------------------------------- + -- Diagnose_Non_Variable_Lhs -- + ------------------------------- + + procedure Diagnose_Non_Variable_Lhs (N : Node_Id) is + begin + -- Not worth posting another error if left hand side already + -- flagged as being illegal in some respect. + + if Error_Posted (N) then + return; + + -- Some special bad cases of entity names + + elsif Is_Entity_Name (N) then + declare + Ent : constant Entity_Id := Entity (N); + + begin + if Ekind (Ent) = E_In_Parameter then + Error_Msg_N + ("assignment to IN mode parameter not allowed", N); + + -- Renamings of protected private components are turned into + -- constants when compiling a protected function. In the case + -- of single protected types, the private component appears + -- directly. + + elsif (Is_Prival (Ent) + and then + (Ekind (Current_Scope) = E_Function + or else Ekind (Enclosing_Dynamic_Scope ( + Current_Scope)) = E_Function)) + or else + (Ekind (Ent) = E_Component + and then Is_Protected_Type (Scope (Ent))) + then + Error_Msg_N + ("protected function cannot modify protected object", N); + + elsif Ekind (Ent) = E_Loop_Parameter then + Error_Msg_N + ("assignment to loop parameter not allowed", N); + + else + Error_Msg_N + ("left hand side of assignment must be a variable", N); + end if; + end; + + -- For indexed components or selected components, test prefix + + elsif Nkind (N) = N_Indexed_Component then + Diagnose_Non_Variable_Lhs (Prefix (N)); + + -- Another special case for assignment to discriminant + + elsif Nkind (N) = N_Selected_Component then + if Present (Entity (Selector_Name (N))) + and then Ekind (Entity (Selector_Name (N))) = E_Discriminant + then + Error_Msg_N + ("assignment to discriminant not allowed", N); + else + Diagnose_Non_Variable_Lhs (Prefix (N)); + end if; + + else + -- If we fall through, we have no special message to issue! + + Error_Msg_N ("left hand side of assignment must be a variable", N); + end if; + end Diagnose_Non_Variable_Lhs; + + -------------- + -- Kill_LHS -- + -------------- + + procedure Kill_Lhs is + begin + if Is_Entity_Name (Lhs) then + declare + Ent : constant Entity_Id := Entity (Lhs); + begin + if Present (Ent) then + Kill_Current_Values (Ent); + end if; + end; + end if; + end Kill_Lhs; + + ------------------------- + -- Set_Assignment_Type -- + ------------------------- + + procedure Set_Assignment_Type + (Opnd : Node_Id; + Opnd_Type : in out Entity_Id) + is + begin + Require_Entity (Opnd); + + -- If the assignment operand is an in-out or out parameter, then we + -- get the actual subtype (needed for the unconstrained case). + -- If the operand is the actual in an entry declaration, then within + -- the accept statement it is replaced with a local renaming, which + -- may also have an actual subtype. + + if Is_Entity_Name (Opnd) + and then (Ekind (Entity (Opnd)) = E_Out_Parameter + or else Ekind (Entity (Opnd)) = + E_In_Out_Parameter + or else Ekind (Entity (Opnd)) = + E_Generic_In_Out_Parameter + or else + (Ekind (Entity (Opnd)) = E_Variable + and then Nkind (Parent (Entity (Opnd))) = + N_Object_Renaming_Declaration + and then Nkind (Parent (Parent (Entity (Opnd)))) = + N_Accept_Statement)) + then + Opnd_Type := Get_Actual_Subtype (Opnd); + + -- If assignment operand is a component reference, then we get the + -- actual subtype of the component for the unconstrained case. + + elsif Nkind_In (Opnd, N_Selected_Component, N_Explicit_Dereference) + and then not Is_Unchecked_Union (Opnd_Type) + then + Decl := Build_Actual_Subtype_Of_Component (Opnd_Type, Opnd); + + if Present (Decl) then + Insert_Action (N, Decl); + Mark_Rewrite_Insertion (Decl); + Analyze (Decl); + Opnd_Type := Defining_Identifier (Decl); + Set_Etype (Opnd, Opnd_Type); + Freeze_Itype (Opnd_Type, N); + + elsif Is_Constrained (Etype (Opnd)) then + Opnd_Type := Etype (Opnd); + end if; + + -- For slice, use the constrained subtype created for the slice + + elsif Nkind (Opnd) = N_Slice then + Opnd_Type := Etype (Opnd); + end if; + end Set_Assignment_Type; + + -- Start of processing for Analyze_Assignment + + begin + Mark_Coextensions (N, Rhs); + + Analyze (Rhs); + Analyze (Lhs); + + -- Start type analysis for assignment + + T1 := Etype (Lhs); + + -- In the most general case, both Lhs and Rhs can be overloaded, and we + -- must compute the intersection of the possible types on each side. + + if Is_Overloaded (Lhs) then + declare + I : Interp_Index; + It : Interp; + + begin + T1 := Any_Type; + Get_First_Interp (Lhs, I, It); + + while Present (It.Typ) loop + if Has_Compatible_Type (Rhs, It.Typ) then + if T1 /= Any_Type then + + -- An explicit dereference is overloaded if the prefix + -- is. Try to remove the ambiguity on the prefix, the + -- error will be posted there if the ambiguity is real. + + if Nkind (Lhs) = N_Explicit_Dereference then + declare + PI : Interp_Index; + PI1 : Interp_Index := 0; + PIt : Interp; + Found : Boolean; + + begin + Found := False; + Get_First_Interp (Prefix (Lhs), PI, PIt); + + while Present (PIt.Typ) loop + if Is_Access_Type (PIt.Typ) + and then Has_Compatible_Type + (Rhs, Designated_Type (PIt.Typ)) + then + if Found then + PIt := + Disambiguate (Prefix (Lhs), + PI1, PI, Any_Type); + + if PIt = No_Interp then + Error_Msg_N + ("ambiguous left-hand side" + & " in assignment", Lhs); + exit; + else + Resolve (Prefix (Lhs), PIt.Typ); + end if; + + exit; + else + Found := True; + PI1 := PI; + end if; + end if; + + Get_Next_Interp (PI, PIt); + end loop; + end; + + else + Error_Msg_N + ("ambiguous left-hand side in assignment", Lhs); + exit; + end if; + else + T1 := It.Typ; + end if; + end if; + + Get_Next_Interp (I, It); + end loop; + end; + + if T1 = Any_Type then + Error_Msg_N + ("no valid types for left-hand side for assignment", Lhs); + Kill_Lhs; + return; + end if; + end if; + + -- The resulting assignment type is T1, so now we will resolve the + -- left hand side of the assignment using this determined type. + + Resolve (Lhs, T1); + + -- Cases where Lhs is not a variable + + if not Is_Variable (Lhs) then + + -- Ada 2005 (AI-327): Check assignment to the attribute Priority of + -- a protected object. + + declare + Ent : Entity_Id; + S : Entity_Id; + + begin + if Ada_Version >= Ada_2005 then + + -- Handle chains of renamings + + Ent := Lhs; + while Nkind (Ent) in N_Has_Entity + and then Present (Entity (Ent)) + and then Present (Renamed_Object (Entity (Ent))) + loop + Ent := Renamed_Object (Entity (Ent)); + end loop; + + if (Nkind (Ent) = N_Attribute_Reference + and then Attribute_Name (Ent) = Name_Priority) + + -- Renamings of the attribute Priority applied to protected + -- objects have been previously expanded into calls to the + -- Get_Ceiling run-time subprogram. + + or else + (Nkind (Ent) = N_Function_Call + and then (Entity (Name (Ent)) = RTE (RE_Get_Ceiling) + or else + Entity (Name (Ent)) = RTE (RO_PE_Get_Ceiling))) + then + -- The enclosing subprogram cannot be a protected function + + S := Current_Scope; + while not (Is_Subprogram (S) + and then Convention (S) = Convention_Protected) + and then S /= Standard_Standard + loop + S := Scope (S); + end loop; + + if Ekind (S) = E_Function + and then Convention (S) = Convention_Protected + then + Error_Msg_N + ("protected function cannot modify protected object", + Lhs); + end if; + + -- Changes of the ceiling priority of the protected object + -- are only effective if the Ceiling_Locking policy is in + -- effect (AARM D.5.2 (5/2)). + + if Locking_Policy /= 'C' then + Error_Msg_N ("assignment to the attribute PRIORITY has " & + "no effect?", Lhs); + Error_Msg_N ("\since no Locking_Policy has been " & + "specified", Lhs); + end if; + + return; + end if; + end if; + end; + + Diagnose_Non_Variable_Lhs (Lhs); + return; + + -- Error of assigning to limited type. We do however allow this in + -- certain cases where the front end generates the assignments. + + elsif Is_Limited_Type (T1) + and then not Assignment_OK (Lhs) + and then not Assignment_OK (Original_Node (Lhs)) + and then not Is_Value_Type (T1) + then + -- CPP constructors can only be called in declarations + + if Is_CPP_Constructor_Call (Rhs) then + Error_Msg_N ("invalid use of 'C'P'P constructor", Rhs); + else + Error_Msg_N + ("left hand of assignment must not be limited type", Lhs); + Explain_Limited_Type (T1, Lhs); + end if; + return; + + -- Enforce RM 3.9.3 (8): the target of an assignment operation cannot be + -- abstract. This is only checked when the assignment Comes_From_Source, + -- because in some cases the expander generates such assignments (such + -- in the _assign operation for an abstract type). + + elsif Is_Abstract_Type (T1) and then Comes_From_Source (N) then + Error_Msg_N + ("target of assignment operation must not be abstract", Lhs); + end if; + + -- Resolution may have updated the subtype, in case the left-hand + -- side is a private protected component. Use the correct subtype + -- to avoid scoping issues in the back-end. + + T1 := Etype (Lhs); + + -- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete + -- type. For example: + + -- limited with P; + -- package Pkg is + -- type Acc is access P.T; + -- end Pkg; + + -- with Pkg; use Acc; + -- procedure Example is + -- A, B : Acc; + -- begin + -- A.all := B.all; -- ERROR + -- end Example; + + if Nkind (Lhs) = N_Explicit_Dereference + and then Ekind (T1) = E_Incomplete_Type + then + Error_Msg_N ("invalid use of incomplete type", Lhs); + Kill_Lhs; + return; + end if; + + -- Now we can complete the resolution of the right hand side + + Set_Assignment_Type (Lhs, T1); + Resolve (Rhs, T1); + + -- This is the point at which we check for an unset reference + + Check_Unset_Reference (Rhs); + Check_Unprotected_Access (Lhs, Rhs); + + -- Remaining steps are skipped if Rhs was syntactically in error + + if Rhs = Error then + Kill_Lhs; + return; + end if; + + T2 := Etype (Rhs); + + if not Covers (T1, T2) then + Wrong_Type (Rhs, Etype (Lhs)); + Kill_Lhs; + return; + end if; + + -- Ada 2005 (AI-326): In case of explicit dereference of incomplete + -- types, use the non-limited view if available + + if Nkind (Rhs) = N_Explicit_Dereference + and then Ekind (T2) = E_Incomplete_Type + and then Is_Tagged_Type (T2) + and then Present (Non_Limited_View (T2)) + then + T2 := Non_Limited_View (T2); + end if; + + Set_Assignment_Type (Rhs, T2); + + if Total_Errors_Detected /= 0 then + if No (T1) then + T1 := Any_Type; + end if; + + if No (T2) then + T2 := Any_Type; + end if; + end if; + + if T1 = Any_Type or else T2 = Any_Type then + Kill_Lhs; + return; + end if; + + -- If the rhs is class-wide or dynamically tagged, then require the lhs + -- to be class-wide. The case where the rhs is a dynamically tagged call + -- to a dispatching operation with a controlling access result is + -- excluded from this check, since the target has an access type (and + -- no tag propagation occurs in that case). + + if (Is_Class_Wide_Type (T2) + or else (Is_Dynamically_Tagged (Rhs) + and then not Is_Access_Type (T1))) + and then not Is_Class_Wide_Type (T1) + then + Error_Msg_N ("dynamically tagged expression not allowed!", Rhs); + + elsif Is_Class_Wide_Type (T1) + and then not Is_Class_Wide_Type (T2) + and then not Is_Tag_Indeterminate (Rhs) + and then not Is_Dynamically_Tagged (Rhs) + then + Error_Msg_N ("dynamically tagged expression required!", Rhs); + end if; + + -- Propagate the tag from a class-wide target to the rhs when the rhs + -- is a tag-indeterminate call. + + if Is_Tag_Indeterminate (Rhs) then + if Is_Class_Wide_Type (T1) then + Propagate_Tag (Lhs, Rhs); + + elsif Nkind (Rhs) = N_Function_Call + and then Is_Entity_Name (Name (Rhs)) + and then Is_Abstract_Subprogram (Entity (Name (Rhs))) + then + Error_Msg_N + ("call to abstract function must be dispatching", Name (Rhs)); + + elsif Nkind (Rhs) = N_Qualified_Expression + and then Nkind (Expression (Rhs)) = N_Function_Call + and then Is_Entity_Name (Name (Expression (Rhs))) + and then + Is_Abstract_Subprogram (Entity (Name (Expression (Rhs)))) + then + Error_Msg_N + ("call to abstract function must be dispatching", + Name (Expression (Rhs))); + end if; + end if; + + -- Ada 2005 (AI-385): When the lhs type is an anonymous access type, + -- apply an implicit conversion of the rhs to that type to force + -- appropriate static and run-time accessibility checks. This applies + -- as well to anonymous access-to-subprogram types that are component + -- subtypes or formal parameters. + + if Ada_Version >= Ada_2005 + and then Is_Access_Type (T1) + then + if Is_Local_Anonymous_Access (T1) + or else Ekind (T2) = E_Anonymous_Access_Subprogram_Type + then + Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs))); + Analyze_And_Resolve (Rhs, T1); + end if; + end if; + + -- Ada 2005 (AI-231): Assignment to not null variable + + if Ada_Version >= Ada_2005 + and then Can_Never_Be_Null (T1) + and then not Assignment_OK (Lhs) + then + -- Case where we know the right hand side is null + + if Known_Null (Rhs) then + Apply_Compile_Time_Constraint_Error + (N => Rhs, + Msg => "(Ada 2005) null not allowed in null-excluding objects?", + Reason => CE_Null_Not_Allowed); + + -- We still mark this as a possible modification, that's necessary + -- to reset Is_True_Constant, and desirable for xref purposes. + + Note_Possible_Modification (Lhs, Sure => True); + return; + + -- If we know the right hand side is non-null, then we convert to the + -- target type, since we don't need a run time check in that case. + + elsif not Can_Never_Be_Null (T2) then + Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs))); + Analyze_And_Resolve (Rhs, T1); + end if; + end if; + + if Is_Scalar_Type (T1) then + Apply_Scalar_Range_Check (Rhs, Etype (Lhs)); + + -- For array types, verify that lengths match. If the right hand side + -- if a function call that has been inlined, the assignment has been + -- rewritten as a block, and the constraint check will be applied to the + -- assignment within the block. + + elsif Is_Array_Type (T1) + and then + (Nkind (Rhs) /= N_Type_Conversion + or else Is_Constrained (Etype (Rhs))) + and then + (Nkind (Rhs) /= N_Function_Call + or else Nkind (N) /= N_Block_Statement) + then + -- Assignment verifies that the length of the Lsh and Rhs are equal, + -- but of course the indexes do not have to match. If the right-hand + -- side is a type conversion to an unconstrained type, a length check + -- is performed on the expression itself during expansion. In rare + -- cases, the redundant length check is computed on an index type + -- with a different representation, triggering incorrect code in + -- the back end. + + Apply_Length_Check (Rhs, Etype (Lhs)); + + else + -- Discriminant checks are applied in the course of expansion + + null; + end if; + + -- Note: modifications of the Lhs may only be recorded after + -- checks have been applied. + + Note_Possible_Modification (Lhs, Sure => True); + Check_Order_Dependence; + + -- ??? a real accessibility check is needed when ??? + + -- Post warning for redundant assignment or variable to itself + + if Warn_On_Redundant_Constructs + + -- We only warn for source constructs + + and then Comes_From_Source (N) + + -- Where the object is the same on both sides + + and then Same_Object (Lhs, Original_Node (Rhs)) + + -- But exclude the case where the right side was an operation + -- that got rewritten (e.g. JUNK + K, where K was known to be + -- zero). We don't want to warn in such a case, since it is + -- reasonable to write such expressions especially when K is + -- defined symbolically in some other package. + + and then Nkind (Original_Node (Rhs)) not in N_Op + then + if Nkind (Lhs) in N_Has_Entity then + Error_Msg_NE -- CODEFIX + ("?useless assignment of & to itself!", N, Entity (Lhs)); + else + Error_Msg_N -- CODEFIX + ("?useless assignment of object to itself!", N); + end if; + end if; + + -- Check for non-allowed composite assignment + + if not Support_Composite_Assign_On_Target + and then (Is_Array_Type (T1) or else Is_Record_Type (T1)) + and then (not Has_Size_Clause (T1) or else Esize (T1) > 64) + then + Error_Msg_CRT ("composite assignment", N); + end if; + + -- Check elaboration warning for left side if not in elab code + + if not In_Subprogram_Or_Concurrent_Unit then + Check_Elab_Assign (Lhs); + end if; + + -- Set Referenced_As_LHS if appropriate. We only set this flag if the + -- assignment is a source assignment in the extended main source unit. + -- We are not interested in any reference information outside this + -- context, or in compiler generated assignment statements. + + if Comes_From_Source (N) + and then In_Extended_Main_Source_Unit (Lhs) + then + Set_Referenced_Modified (Lhs, Out_Param => False); + end if; + + -- Final step. If left side is an entity, then we may be able to + -- reset the current tracked values to new safe values. We only have + -- something to do if the left side is an entity name, and expansion + -- has not modified the node into something other than an assignment, + -- and of course we only capture values if it is safe to do so. + + if Is_Entity_Name (Lhs) + and then Nkind (N) = N_Assignment_Statement + then + declare + Ent : constant Entity_Id := Entity (Lhs); + + begin + if Safe_To_Capture_Value (N, Ent) then + + -- If simple variable on left side, warn if this assignment + -- blots out another one (rendering it useless) and note + -- location of assignment in case no one references value. + -- We only do this for source assignments, otherwise we can + -- generate bogus warnings when an assignment is rewritten as + -- another assignment, and gets tied up with itself. + + -- Note: we don't use Record_Last_Assignment here, because we + -- have lots of other stuff to do under control of this test. + + if Warn_On_Modified_Unread + and then Is_Assignable (Ent) + and then Comes_From_Source (N) + and then In_Extended_Main_Source_Unit (Ent) + then + Warn_On_Useless_Assignment (Ent, N); + Set_Last_Assignment (Ent, Lhs); + end if; + + -- If we are assigning an access type and the left side is an + -- entity, then make sure that the Is_Known_[Non_]Null flags + -- properly reflect the state of the entity after assignment. + + if Is_Access_Type (T1) then + if Known_Non_Null (Rhs) then + Set_Is_Known_Non_Null (Ent, True); + + elsif Known_Null (Rhs) + and then not Can_Never_Be_Null (Ent) + then + Set_Is_Known_Null (Ent, True); + + else + Set_Is_Known_Null (Ent, False); + + if not Can_Never_Be_Null (Ent) then + Set_Is_Known_Non_Null (Ent, False); + end if; + end if; + + -- For discrete types, we may be able to set the current value + -- if the value is known at compile time. + + elsif Is_Discrete_Type (T1) + and then Compile_Time_Known_Value (Rhs) + then + Set_Current_Value (Ent, Rhs); + else + Set_Current_Value (Ent, Empty); + end if; + + -- If not safe to capture values, kill them + + else + Kill_Lhs; + end if; + end; + end if; + end Analyze_Assignment; + + ----------------------------- + -- Analyze_Block_Statement -- + ----------------------------- + + procedure Analyze_Block_Statement (N : Node_Id) is + Decls : constant List_Id := Declarations (N); + Id : constant Node_Id := Identifier (N); + HSS : constant Node_Id := Handled_Statement_Sequence (N); + + begin + -- If no handled statement sequence is present, things are really + -- messed up, and we just return immediately (this is a defence + -- against previous errors). + + if No (HSS) then + return; + end if; + + -- Normal processing with HSS present + + declare + EH : constant List_Id := Exception_Handlers (HSS); + Ent : Entity_Id := Empty; + S : Entity_Id; + + Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count; + -- Recursively save value of this global, will be restored on exit + + begin + -- Initialize unblocked exit count for statements of begin block + -- plus one for each exception handler that is present. + + Unblocked_Exit_Count := 1; + + if Present (EH) then + Unblocked_Exit_Count := Unblocked_Exit_Count + List_Length (EH); + end if; + + -- If a label is present analyze it and mark it as referenced + + if Present (Id) then + Analyze (Id); + Ent := Entity (Id); + + -- An error defense. If we have an identifier, but no entity, + -- then something is wrong. If we have previous errors, then + -- just remove the identifier and continue, otherwise raise + -- an exception. + + if No (Ent) then + if Total_Errors_Detected /= 0 then + Set_Identifier (N, Empty); + else + raise Program_Error; + end if; + + else + Set_Ekind (Ent, E_Block); + Generate_Reference (Ent, N, ' '); + Generate_Definition (Ent); + + if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then + Set_Label_Construct (Parent (Ent), N); + end if; + end if; + end if; + + -- If no entity set, create a label entity + + if No (Ent) then + Ent := New_Internal_Entity (E_Block, Current_Scope, Sloc (N), 'B'); + Set_Identifier (N, New_Occurrence_Of (Ent, Sloc (N))); + Set_Parent (Ent, N); + end if; + + Set_Etype (Ent, Standard_Void_Type); + Set_Block_Node (Ent, Identifier (N)); + Push_Scope (Ent); + + if Present (Decls) then + Analyze_Declarations (Decls); + Check_Completion; + Inspect_Deferred_Constant_Completion (Decls); + end if; + + Analyze (HSS); + Process_End_Label (HSS, 'e', Ent); + + -- If exception handlers are present, then we indicate that + -- enclosing scopes contain a block with handlers. We only + -- need to mark non-generic scopes. + + if Present (EH) then + S := Scope (Ent); + loop + Set_Has_Nested_Block_With_Handler (S); + exit when Is_Overloadable (S) + or else Ekind (S) = E_Package + or else Is_Generic_Unit (S); + S := Scope (S); + end loop; + end if; + + Check_References (Ent); + Warn_On_Useless_Assignments (Ent); + End_Scope; + + if Unblocked_Exit_Count = 0 then + Unblocked_Exit_Count := Save_Unblocked_Exit_Count; + Check_Unreachable_Code (N); + else + Unblocked_Exit_Count := Save_Unblocked_Exit_Count; + end if; + end; + end Analyze_Block_Statement; + + ---------------------------- + -- Analyze_Case_Statement -- + ---------------------------- + + procedure Analyze_Case_Statement (N : Node_Id) is + Exp : Node_Id; + Exp_Type : Entity_Id; + Exp_Btype : Entity_Id; + Last_Choice : Nat; + Dont_Care : Boolean; + Others_Present : Boolean; + + pragma Warnings (Off, Last_Choice); + pragma Warnings (Off, Dont_Care); + -- Don't care about assigned values + + Statements_Analyzed : Boolean := False; + -- Set True if at least some statement sequences get analyzed. + -- If False on exit, means we had a serious error that prevented + -- full analysis of the case statement, and as a result it is not + -- a good idea to output warning messages about unreachable code. + + Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count; + -- Recursively save value of this global, will be restored on exit + + procedure Non_Static_Choice_Error (Choice : Node_Id); + -- Error routine invoked by the generic instantiation below when + -- the case statement has a non static choice. + + procedure Process_Statements (Alternative : Node_Id); + -- Analyzes all the statements associated with a case alternative. + -- Needed by the generic instantiation below. + + package Case_Choices_Processing is new + Generic_Choices_Processing + (Get_Alternatives => Alternatives, + Get_Choices => Discrete_Choices, + Process_Empty_Choice => No_OP, + Process_Non_Static_Choice => Non_Static_Choice_Error, + Process_Associated_Node => Process_Statements); + use Case_Choices_Processing; + -- Instantiation of the generic choice processing package + + ----------------------------- + -- Non_Static_Choice_Error -- + ----------------------------- + + procedure Non_Static_Choice_Error (Choice : Node_Id) is + begin + Flag_Non_Static_Expr + ("choice given in case statement is not static!", Choice); + end Non_Static_Choice_Error; + + ------------------------ + -- Process_Statements -- + ------------------------ + + procedure Process_Statements (Alternative : Node_Id) is + Choices : constant List_Id := Discrete_Choices (Alternative); + Ent : Entity_Id; + + begin + Unblocked_Exit_Count := Unblocked_Exit_Count + 1; + Statements_Analyzed := True; + + -- An interesting optimization. If the case statement expression + -- is a simple entity, then we can set the current value within + -- an alternative if the alternative has one possible value. + + -- case N is + -- when 1 => alpha + -- when 2 | 3 => beta + -- when others => gamma + + -- Here we know that N is initially 1 within alpha, but for beta + -- and gamma, we do not know anything more about the initial value. + + if Is_Entity_Name (Exp) then + Ent := Entity (Exp); + + if Ekind_In (Ent, E_Variable, + E_In_Out_Parameter, + E_Out_Parameter) + then + if List_Length (Choices) = 1 + and then Nkind (First (Choices)) in N_Subexpr + and then Compile_Time_Known_Value (First (Choices)) + then + Set_Current_Value (Entity (Exp), First (Choices)); + end if; + + Analyze_Statements (Statements (Alternative)); + + -- After analyzing the case, set the current value to empty + -- since we won't know what it is for the next alternative + -- (unless reset by this same circuit), or after the case. + + Set_Current_Value (Entity (Exp), Empty); + return; + end if; + end if; + + -- Case where expression is not an entity name of a variable + + Analyze_Statements (Statements (Alternative)); + end Process_Statements; + + -- Start of processing for Analyze_Case_Statement + + begin + Unblocked_Exit_Count := 0; + Exp := Expression (N); + Analyze (Exp); + + -- The expression must be of any discrete type. In rare cases, the + -- expander constructs a case statement whose expression has a private + -- type whose full view is discrete. This can happen when generating + -- a stream operation for a variant type after the type is frozen, + -- when the partial of view of the type of the discriminant is private. + -- In that case, use the full view to analyze case alternatives. + + if not Is_Overloaded (Exp) + and then not Comes_From_Source (N) + and then Is_Private_Type (Etype (Exp)) + and then Present (Full_View (Etype (Exp))) + and then Is_Discrete_Type (Full_View (Etype (Exp))) + then + Resolve (Exp, Etype (Exp)); + Exp_Type := Full_View (Etype (Exp)); + + else + Analyze_And_Resolve (Exp, Any_Discrete); + Exp_Type := Etype (Exp); + end if; + + Check_Unset_Reference (Exp); + Exp_Btype := Base_Type (Exp_Type); + + -- The expression must be of a discrete type which must be determinable + -- independently of the context in which the expression occurs, but + -- using the fact that the expression must be of a discrete type. + -- Moreover, the type this expression must not be a character literal + -- (which is always ambiguous) or, for Ada-83, a generic formal type. + + -- If error already reported by Resolve, nothing more to do + + if Exp_Btype = Any_Discrete + or else Exp_Btype = Any_Type + then + return; + + elsif Exp_Btype = Any_Character then + Error_Msg_N + ("character literal as case expression is ambiguous", Exp); + return; + + elsif Ada_Version = Ada_83 + and then (Is_Generic_Type (Exp_Btype) + or else Is_Generic_Type (Root_Type (Exp_Btype))) + then + Error_Msg_N + ("(Ada 83) case expression cannot be of a generic type", Exp); + return; + end if; + + -- If the case expression is a formal object of mode in out, then + -- treat it as having a nonstatic subtype by forcing use of the base + -- type (which has to get passed to Check_Case_Choices below). Also + -- use base type when the case expression is parenthesized. + + if Paren_Count (Exp) > 0 + or else (Is_Entity_Name (Exp) + and then Ekind (Entity (Exp)) = E_Generic_In_Out_Parameter) + then + Exp_Type := Exp_Btype; + end if; + + -- Call instantiated Analyze_Choices which does the rest of the work + + Analyze_Choices (N, Exp_Type, Dont_Care, Others_Present); + + if Exp_Type = Universal_Integer and then not Others_Present then + Error_Msg_N ("case on universal integer requires OTHERS choice", Exp); + end if; + + -- If all our exits were blocked by unconditional transfers of control, + -- then the entire CASE statement acts as an unconditional transfer of + -- control, so treat it like one, and check unreachable code. Skip this + -- test if we had serious errors preventing any statement analysis. + + if Unblocked_Exit_Count = 0 and then Statements_Analyzed then + Unblocked_Exit_Count := Save_Unblocked_Exit_Count; + Check_Unreachable_Code (N); + else + Unblocked_Exit_Count := Save_Unblocked_Exit_Count; + end if; + + if not Expander_Active + and then Compile_Time_Known_Value (Expression (N)) + and then Serious_Errors_Detected = 0 + then + declare + Chosen : constant Node_Id := Find_Static_Alternative (N); + Alt : Node_Id; + + begin + Alt := First (Alternatives (N)); + while Present (Alt) loop + if Alt /= Chosen then + Remove_Warning_Messages (Statements (Alt)); + end if; + + Next (Alt); + end loop; + end; + end if; + end Analyze_Case_Statement; + + ---------------------------- + -- Analyze_Exit_Statement -- + ---------------------------- + + -- If the exit includes a name, it must be the name of a currently open + -- loop. Otherwise there must be an innermost open loop on the stack, + -- to which the statement implicitly refers. + + procedure Analyze_Exit_Statement (N : Node_Id) is + Target : constant Node_Id := Name (N); + Cond : constant Node_Id := Condition (N); + Scope_Id : Entity_Id; + U_Name : Entity_Id; + Kind : Entity_Kind; + + begin + if No (Cond) then + Check_Unreachable_Code (N); + end if; + + if Present (Target) then + Analyze (Target); + U_Name := Entity (Target); + + if not In_Open_Scopes (U_Name) or else Ekind (U_Name) /= E_Loop then + Error_Msg_N ("invalid loop name in exit statement", N); + return; + else + Set_Has_Exit (U_Name); + end if; + + else + U_Name := Empty; + end if; + + for J in reverse 0 .. Scope_Stack.Last loop + Scope_Id := Scope_Stack.Table (J).Entity; + Kind := Ekind (Scope_Id); + + if Kind = E_Loop + and then (No (Target) or else Scope_Id = U_Name) then + Set_Has_Exit (Scope_Id); + exit; + + elsif Kind = E_Block + or else Kind = E_Loop + or else Kind = E_Return_Statement + then + null; + + else + Error_Msg_N + ("cannot exit from program unit or accept statement", N); + return; + end if; + end loop; + + -- Verify that if present the condition is a Boolean expression + + if Present (Cond) then + Analyze_And_Resolve (Cond, Any_Boolean); + Check_Unset_Reference (Cond); + end if; + + -- Chain exit statement to associated loop entity + + Set_Next_Exit_Statement (N, First_Exit_Statement (Scope_Id)); + Set_First_Exit_Statement (Scope_Id, N); + + -- Since the exit may take us out of a loop, any previous assignment + -- statement is not useless, so clear last assignment indications. It + -- is OK to keep other current values, since if the exit statement + -- does not exit, then the current values are still valid. + + Kill_Current_Values (Last_Assignment_Only => True); + end Analyze_Exit_Statement; + + ---------------------------- + -- Analyze_Goto_Statement -- + ---------------------------- + + procedure Analyze_Goto_Statement (N : Node_Id) is + Label : constant Node_Id := Name (N); + Scope_Id : Entity_Id; + Label_Scope : Entity_Id; + Label_Ent : Entity_Id; + + begin + Check_Unreachable_Code (N); + Kill_Current_Values (Last_Assignment_Only => True); + + Analyze (Label); + Label_Ent := Entity (Label); + + -- Ignore previous error + + if Label_Ent = Any_Id then + return; + + -- We just have a label as the target of a goto + + elsif Ekind (Label_Ent) /= E_Label then + Error_Msg_N ("target of goto statement must be a label", Label); + return; + + -- Check that the target of the goto is reachable according to Ada + -- scoping rules. Note: the special gotos we generate for optimizing + -- local handling of exceptions would violate these rules, but we mark + -- such gotos as analyzed when built, so this code is never entered. + + elsif not Reachable (Label_Ent) then + Error_Msg_N ("target of goto statement is not reachable", Label); + return; + end if; + + -- Here if goto passes initial validity checks + + Label_Scope := Enclosing_Scope (Label_Ent); + + for J in reverse 0 .. Scope_Stack.Last loop + Scope_Id := Scope_Stack.Table (J).Entity; + + if Label_Scope = Scope_Id + or else (Ekind (Scope_Id) /= E_Block + and then Ekind (Scope_Id) /= E_Loop + and then Ekind (Scope_Id) /= E_Return_Statement) + then + if Scope_Id /= Label_Scope then + Error_Msg_N + ("cannot exit from program unit or accept statement", N); + end if; + + return; + end if; + end loop; + + raise Program_Error; + end Analyze_Goto_Statement; + + -------------------------- + -- Analyze_If_Statement -- + -------------------------- + + -- A special complication arises in the analysis of if statements + + -- The expander has circuitry to completely delete code that it + -- can tell will not be executed (as a result of compile time known + -- conditions). In the analyzer, we ensure that code that will be + -- deleted in this manner is analyzed but not expanded. This is + -- obviously more efficient, but more significantly, difficulties + -- arise if code is expanded and then eliminated (e.g. exception + -- table entries disappear). Similarly, itypes generated in deleted + -- code must be frozen from start, because the nodes on which they + -- depend will not be available at the freeze point. + + procedure Analyze_If_Statement (N : Node_Id) is + E : Node_Id; + + Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count; + -- Recursively save value of this global, will be restored on exit + + Save_In_Deleted_Code : Boolean; + + Del : Boolean := False; + -- This flag gets set True if a True condition has been found, + -- which means that remaining ELSE/ELSIF parts are deleted. + + procedure Analyze_Cond_Then (Cnode : Node_Id); + -- This is applied to either the N_If_Statement node itself or + -- to an N_Elsif_Part node. It deals with analyzing the condition + -- and the THEN statements associated with it. + + ----------------------- + -- Analyze_Cond_Then -- + ----------------------- + + procedure Analyze_Cond_Then (Cnode : Node_Id) is + Cond : constant Node_Id := Condition (Cnode); + Tstm : constant List_Id := Then_Statements (Cnode); + + begin + Unblocked_Exit_Count := Unblocked_Exit_Count + 1; + Analyze_And_Resolve (Cond, Any_Boolean); + Check_Unset_Reference (Cond); + Set_Current_Value_Condition (Cnode); + + -- If already deleting, then just analyze then statements + + if Del then + Analyze_Statements (Tstm); + + -- Compile time known value, not deleting yet + + elsif Compile_Time_Known_Value (Cond) then + Save_In_Deleted_Code := In_Deleted_Code; + + -- If condition is True, then analyze the THEN statements + -- and set no expansion for ELSE and ELSIF parts. + + if Is_True (Expr_Value (Cond)) then + Analyze_Statements (Tstm); + Del := True; + Expander_Mode_Save_And_Set (False); + In_Deleted_Code := True; + + -- If condition is False, analyze THEN with expansion off + + else -- Is_False (Expr_Value (Cond)) + Expander_Mode_Save_And_Set (False); + In_Deleted_Code := True; + Analyze_Statements (Tstm); + Expander_Mode_Restore; + In_Deleted_Code := Save_In_Deleted_Code; + end if; + + -- Not known at compile time, not deleting, normal analysis + + else + Analyze_Statements (Tstm); + end if; + end Analyze_Cond_Then; + + -- Start of Analyze_If_Statement + + begin + -- Initialize exit count for else statements. If there is no else + -- part, this count will stay non-zero reflecting the fact that the + -- uncovered else case is an unblocked exit. + + Unblocked_Exit_Count := 1; + Analyze_Cond_Then (N); + + -- Now to analyze the elsif parts if any are present + + if Present (Elsif_Parts (N)) then + E := First (Elsif_Parts (N)); + while Present (E) loop + Analyze_Cond_Then (E); + Next (E); + end loop; + end if; + + if Present (Else_Statements (N)) then + Analyze_Statements (Else_Statements (N)); + end if; + + -- If all our exits were blocked by unconditional transfers of control, + -- then the entire IF statement acts as an unconditional transfer of + -- control, so treat it like one, and check unreachable code. + + if Unblocked_Exit_Count = 0 then + Unblocked_Exit_Count := Save_Unblocked_Exit_Count; + Check_Unreachable_Code (N); + else + Unblocked_Exit_Count := Save_Unblocked_Exit_Count; + end if; + + if Del then + Expander_Mode_Restore; + In_Deleted_Code := Save_In_Deleted_Code; + end if; + + if not Expander_Active + and then Compile_Time_Known_Value (Condition (N)) + and then Serious_Errors_Detected = 0 + then + if Is_True (Expr_Value (Condition (N))) then + Remove_Warning_Messages (Else_Statements (N)); + + if Present (Elsif_Parts (N)) then + E := First (Elsif_Parts (N)); + while Present (E) loop + Remove_Warning_Messages (Then_Statements (E)); + Next (E); + end loop; + end if; + + else + Remove_Warning_Messages (Then_Statements (N)); + end if; + end if; + end Analyze_If_Statement; + + ---------------------------------------- + -- Analyze_Implicit_Label_Declaration -- + ---------------------------------------- + + -- An implicit label declaration is generated in the innermost + -- enclosing declarative part. This is done for labels as well as + -- block and loop names. + + -- Note: any changes in this routine may need to be reflected in + -- Analyze_Label_Entity. + + procedure Analyze_Implicit_Label_Declaration (N : Node_Id) is + Id : constant Node_Id := Defining_Identifier (N); + begin + Enter_Name (Id); + Set_Ekind (Id, E_Label); + Set_Etype (Id, Standard_Void_Type); + Set_Enclosing_Scope (Id, Current_Scope); + end Analyze_Implicit_Label_Declaration; + + ------------------------------ + -- Analyze_Iteration_Scheme -- + ------------------------------ + + procedure Analyze_Iteration_Scheme (N : Node_Id) is + + procedure Process_Bounds (R : Node_Id); + -- If the iteration is given by a range, create temporaries and + -- assignment statements block to capture the bounds and perform + -- required finalization actions in case a bound includes a function + -- call that uses the temporary stack. We first pre-analyze a copy of + -- the range in order to determine the expected type, and analyze and + -- resolve the original bounds. + + procedure Check_Controlled_Array_Attribute (DS : Node_Id); + -- If the bounds are given by a 'Range reference on a function call + -- that returns a controlled array, introduce an explicit declaration + -- to capture the bounds, so that the function result can be finalized + -- in timely fashion. + + -------------------- + -- Process_Bounds -- + -------------------- + + procedure Process_Bounds (R : Node_Id) is + Loc : constant Source_Ptr := Sloc (N); + R_Copy : constant Node_Id := New_Copy_Tree (R); + Lo : constant Node_Id := Low_Bound (R); + Hi : constant Node_Id := High_Bound (R); + New_Lo_Bound : Node_Id; + New_Hi_Bound : Node_Id; + Typ : Entity_Id; + Save_Analysis : Boolean; + + function One_Bound + (Original_Bound : Node_Id; + Analyzed_Bound : Node_Id) return Node_Id; + -- Capture value of bound and return captured value + + --------------- + -- One_Bound -- + --------------- + + function One_Bound + (Original_Bound : Node_Id; + Analyzed_Bound : Node_Id) return Node_Id + is + Assign : Node_Id; + Id : Entity_Id; + Decl : Node_Id; + + begin + -- If the bound is a constant or an object, no need for a separate + -- declaration. If the bound is the result of previous expansion + -- it is already analyzed and should not be modified. Note that + -- the Bound will be resolved later, if needed, as part of the + -- call to Make_Index (literal bounds may need to be resolved to + -- type Integer). + + if Analyzed (Original_Bound) then + return Original_Bound; + + elsif Nkind_In (Analyzed_Bound, N_Integer_Literal, + N_Character_Literal) + or else Is_Entity_Name (Analyzed_Bound) + then + Analyze_And_Resolve (Original_Bound, Typ); + return Original_Bound; + end if; + + -- Here we need to capture the value + + Analyze_And_Resolve (Original_Bound, Typ); + + Id := Make_Temporary (Loc, 'S', Original_Bound); + + -- Normally, the best approach is simply to generate a constant + -- declaration that captures the bound. However, there is a nasty + -- case where this is wrong. If the bound is complex, and has a + -- possible use of the secondary stack, we need to generate a + -- separate assignment statement to ensure the creation of a block + -- which will release the secondary stack. + + -- We prefer the constant declaration, since it leaves us with a + -- proper trace of the value, useful in optimizations that get rid + -- of junk range checks. + + -- Probably we want something like the Side_Effect_Free routine + -- in Exp_Util, but for now, we just optimize the cases of 'Last + -- and 'First applied to an entity, since these are the important + -- cases for range check optimizations. + + if Nkind (Original_Bound) = N_Attribute_Reference + and then (Attribute_Name (Original_Bound) = Name_First + or else + Attribute_Name (Original_Bound) = Name_Last) + and then Is_Entity_Name (Prefix (Original_Bound)) + then + Decl := + Make_Object_Declaration (Loc, + Defining_Identifier => Id, + Constant_Present => True, + Object_Definition => New_Occurrence_Of (Typ, Loc), + Expression => Relocate_Node (Original_Bound)); + + -- Insert declaration at proper place. If loop comes from an + -- enclosing quantified expression, the insertion point is + -- arbitrarily far up in the tree. + + Insert_Action (Parent (N), Decl); + Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc)); + return Expression (Decl); + end if; + + -- Here we make a declaration with a separate assignment + -- statement, and insert before loop header. + + Decl := + Make_Object_Declaration (Loc, + Defining_Identifier => Id, + Object_Definition => New_Occurrence_Of (Typ, Loc)); + + Assign := + Make_Assignment_Statement (Loc, + Name => New_Occurrence_Of (Id, Loc), + Expression => Relocate_Node (Original_Bound)); + + Insert_Actions (Parent (N), New_List (Decl, Assign)); + + Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc)); + + if Nkind (Assign) = N_Assignment_Statement then + return Expression (Assign); + else + return Original_Bound; + end if; + end One_Bound; + + -- Start of processing for Process_Bounds + + begin + -- Determine expected type of range by analyzing separate copy + -- Do the analysis and resolution of the copy of the bounds with + -- expansion disabled, to prevent the generation of finalization + -- actions on each bound. This prevents memory leaks when the + -- bounds contain calls to functions returning controlled arrays. + + Set_Parent (R_Copy, Parent (R)); + Save_Analysis := Full_Analysis; + Full_Analysis := False; + Expander_Mode_Save_And_Set (False); + + Analyze (R_Copy); + + if Is_Overloaded (R_Copy) then + + -- Apply preference rules for range of predefined integer types, + -- or diagnose true ambiguity. + + declare + I : Interp_Index; + It : Interp; + Found : Entity_Id := Empty; + + begin + Get_First_Interp (R_Copy, I, It); + while Present (It.Typ) loop + if Is_Discrete_Type (It.Typ) then + if No (Found) then + Found := It.Typ; + else + if Scope (Found) = Standard_Standard then + null; + + elsif Scope (It.Typ) = Standard_Standard then + Found := It.Typ; + + else + -- Both of them are user-defined + + Error_Msg_N + ("ambiguous bounds in range of iteration", + R_Copy); + Error_Msg_N ("\possible interpretations:", R_Copy); + Error_Msg_NE ("\\} ", R_Copy, Found); + Error_Msg_NE ("\\} ", R_Copy, It.Typ); + exit; + end if; + end if; + end if; + + Get_Next_Interp (I, It); + end loop; + end; + end if; + + Resolve (R_Copy); + Expander_Mode_Restore; + Full_Analysis := Save_Analysis; + + Typ := Etype (R_Copy); + + -- If the type of the discrete range is Universal_Integer, then + -- the bound's type must be resolved to Integer, and any object + -- used to hold the bound must also have type Integer, unless the + -- literal bounds are constant-folded expressions that carry a user- + -- defined type. + + if Typ = Universal_Integer then + if Nkind (Lo) = N_Integer_Literal + and then Present (Etype (Lo)) + and then Scope (Etype (Lo)) /= Standard_Standard + then + Typ := Etype (Lo); + + elsif Nkind (Hi) = N_Integer_Literal + and then Present (Etype (Hi)) + and then Scope (Etype (Hi)) /= Standard_Standard + then + Typ := Etype (Hi); + + else + Typ := Standard_Integer; + end if; + end if; + + Set_Etype (R, Typ); + + New_Lo_Bound := One_Bound (Lo, Low_Bound (R_Copy)); + New_Hi_Bound := One_Bound (Hi, High_Bound (R_Copy)); + + -- Propagate staticness to loop range itself, in case the + -- corresponding subtype is static. + + if New_Lo_Bound /= Lo + and then Is_Static_Expression (New_Lo_Bound) + then + Rewrite (Low_Bound (R), New_Copy (New_Lo_Bound)); + end if; + + if New_Hi_Bound /= Hi + and then Is_Static_Expression (New_Hi_Bound) + then + Rewrite (High_Bound (R), New_Copy (New_Hi_Bound)); + end if; + end Process_Bounds; + + -------------------------------------- + -- Check_Controlled_Array_Attribute -- + -------------------------------------- + + procedure Check_Controlled_Array_Attribute (DS : Node_Id) is + begin + if Nkind (DS) = N_Attribute_Reference + and then Is_Entity_Name (Prefix (DS)) + and then Ekind (Entity (Prefix (DS))) = E_Function + and then Is_Array_Type (Etype (Entity (Prefix (DS)))) + and then + Is_Controlled ( + Component_Type (Etype (Entity (Prefix (DS))))) + and then Expander_Active + then + declare + Loc : constant Source_Ptr := Sloc (N); + Arr : constant Entity_Id := Etype (Entity (Prefix (DS))); + Indx : constant Entity_Id := + Base_Type (Etype (First_Index (Arr))); + Subt : constant Entity_Id := Make_Temporary (Loc, 'S'); + Decl : Node_Id; + + begin + Decl := + Make_Subtype_Declaration (Loc, + Defining_Identifier => Subt, + Subtype_Indication => + Make_Subtype_Indication (Loc, + Subtype_Mark => New_Reference_To (Indx, Loc), + Constraint => + Make_Range_Constraint (Loc, + Relocate_Node (DS)))); + Insert_Before (Parent (N), Decl); + Analyze (Decl); + + Rewrite (DS, + Make_Attribute_Reference (Loc, + Prefix => New_Reference_To (Subt, Loc), + Attribute_Name => Attribute_Name (DS))); + Analyze (DS); + end; + end if; + end Check_Controlled_Array_Attribute; + + -- Start of processing for Analyze_Iteration_Scheme + + begin + -- If this is a rewritten quantified expression, the iteration + -- scheme has been analyzed already. Do no repeat analysis because + -- the loop variable is already declared. + + if Analyzed (N) then + return; + end if; + + -- For an infinite loop, there is no iteration scheme + + if No (N) then + return; + end if; + + -- Iteration scheme is present + + declare + Cond : constant Node_Id := Condition (N); + + begin + -- For WHILE loop, verify that the condition is a Boolean + -- expression and resolve and check it. + + if Present (Cond) then + Analyze_And_Resolve (Cond, Any_Boolean); + Check_Unset_Reference (Cond); + Set_Current_Value_Condition (N); + return; + + elsif Present (Iterator_Specification (N)) then + Analyze_Iterator_Specification (Iterator_Specification (N)); + + -- Else we have a FOR loop + + else + declare + LP : constant Node_Id := Loop_Parameter_Specification (N); + Id : constant Entity_Id := Defining_Identifier (LP); + DS : constant Node_Id := Discrete_Subtype_Definition (LP); + + begin + Enter_Name (Id); + + -- We always consider the loop variable to be referenced, + -- since the loop may be used just for counting purposes. + + Generate_Reference (Id, N, ' '); + + -- Check for the case of loop variable hiding a local variable + -- (used later on to give a nice warning if the hidden variable + -- is never assigned). + + declare + H : constant Entity_Id := Homonym (Id); + begin + if Present (H) + and then Enclosing_Dynamic_Scope (H) = + Enclosing_Dynamic_Scope (Id) + and then Ekind (H) = E_Variable + and then Is_Discrete_Type (Etype (H)) + then + Set_Hiding_Loop_Variable (H, Id); + end if; + end; + + -- Now analyze the subtype definition. If it is a range, create + -- temporaries for bounds. + + if Nkind (DS) = N_Range + and then Expander_Active + then + Process_Bounds (DS); + + -- Not a range or expander not active (is that right???) + + else + Analyze (DS); + + if Nkind (DS) = N_Function_Call + or else + (Is_Entity_Name (DS) + and then not Is_Type (Entity (DS))) + then + -- This is an iterator specification. Rewrite as such + -- and analyze. + + declare + I_Spec : constant Node_Id := + Make_Iterator_Specification (Sloc (LP), + Defining_Identifier => + Relocate_Node (Id), + Name => + Relocate_Node (DS), + Subtype_Indication => + Empty, + Reverse_Present => + Reverse_Present (LP)); + begin + Set_Iterator_Specification (N, I_Spec); + Set_Loop_Parameter_Specification (N, Empty); + Analyze_Iterator_Specification (I_Spec); + return; + end; + end if; + end if; + + if DS = Error then + return; + end if; + + -- Some additional checks if we are iterating through a type + + if Is_Entity_Name (DS) + and then Present (Entity (DS)) + and then Is_Type (Entity (DS)) + then + -- The subtype indication may denote the completion of an + -- incomplete type declaration. + + if Ekind (Entity (DS)) = E_Incomplete_Type then + Set_Entity (DS, Get_Full_View (Entity (DS))); + Set_Etype (DS, Entity (DS)); + end if; + + -- Attempt to iterate through non-static predicate + + if Is_Discrete_Type (Entity (DS)) + and then Present (Predicate_Function (Entity (DS))) + and then No (Static_Predicate (Entity (DS))) + then + Bad_Predicated_Subtype_Use + ("cannot use subtype& with non-static " + & "predicate for loop iteration", DS, Entity (DS)); + end if; + end if; + + -- Error if not discrete type + + if not Is_Discrete_Type (Etype (DS)) then + Wrong_Type (DS, Any_Discrete); + Set_Etype (DS, Any_Type); + end if; + + Check_Controlled_Array_Attribute (DS); + + Make_Index (DS, LP); + + Set_Ekind (Id, E_Loop_Parameter); + Set_Etype (Id, Etype (DS)); + + -- Treat a range as an implicit reference to the type, to + -- inhibit spurious warnings. + + Generate_Reference (Base_Type (Etype (DS)), N, ' '); + Set_Is_Known_Valid (Id, True); + + -- The loop is not a declarative part, so the only entity + -- declared "within" must be frozen explicitly. + + declare + Flist : constant List_Id := Freeze_Entity (Id, N); + begin + if Is_Non_Empty_List (Flist) then + Insert_Actions (N, Flist); + end if; + end; + + -- Check for null or possibly null range and issue warning. We + -- suppress such messages in generic templates and instances, + -- because in practice they tend to be dubious in these cases. + + if Nkind (DS) = N_Range and then Comes_From_Source (N) then + declare + L : constant Node_Id := Low_Bound (DS); + H : constant Node_Id := High_Bound (DS); + + begin + -- If range of loop is null, issue warning + + if Compile_Time_Compare + (L, H, Assume_Valid => True) = GT + then + -- Suppress the warning if inside a generic template + -- or instance, since in practice they tend to be + -- dubious in these cases since they can result from + -- intended parametrization. + + if not Inside_A_Generic + and then not In_Instance + then + -- Specialize msg if invalid values could make + -- the loop non-null after all. + + if Compile_Time_Compare + (L, H, Assume_Valid => False) = GT + then + Error_Msg_N + ("?loop range is null, loop will not execute", + DS); + + -- Since we know the range of the loop is + -- null, set the appropriate flag to remove + -- the loop entirely during expansion. + + Set_Is_Null_Loop (Parent (N)); + + -- Here is where the loop could execute because + -- of invalid values, so issue appropriate + -- message and in this case we do not set the + -- Is_Null_Loop flag since the loop may execute. + + else + Error_Msg_N + ("?loop range may be null, " + & "loop may not execute", + DS); + Error_Msg_N + ("?can only execute if invalid values " + & "are present", + DS); + end if; + end if; + + -- In either case, suppress warnings in the body of + -- the loop, since it is likely that these warnings + -- will be inappropriate if the loop never actually + -- executes, which is likely. + + Set_Suppress_Loop_Warnings (Parent (N)); + + -- The other case for a warning is a reverse loop + -- where the upper bound is the integer literal zero + -- or one, and the lower bound can be positive. + + -- For example, we have + + -- for J in reverse N .. 1 loop + + -- In practice, this is very likely to be a case of + -- reversing the bounds incorrectly in the range. + + elsif Reverse_Present (LP) + and then Nkind (Original_Node (H)) = + N_Integer_Literal + and then (Intval (Original_Node (H)) = Uint_0 + or else + Intval (Original_Node (H)) = Uint_1) + then + Error_Msg_N ("?loop range may be null", DS); + Error_Msg_N ("\?bounds may be wrong way round", DS); + end if; + end; + end if; + end; + end if; + end; + end Analyze_Iteration_Scheme; + + ------------------------------------- + -- Analyze_Iterator_Specification -- + ------------------------------------- + + procedure Analyze_Iterator_Specification (N : Node_Id) is + Def_Id : constant Node_Id := Defining_Identifier (N); + Subt : constant Node_Id := Subtype_Indication (N); + Container : constant Node_Id := Name (N); + + Ent : Entity_Id; + Typ : Entity_Id; + + begin + Enter_Name (Def_Id); + Set_Ekind (Def_Id, E_Variable); + + if Present (Subt) then + Analyze (Subt); + end if; + + Analyze_And_Resolve (Container); + Typ := Etype (Container); + + if Is_Array_Type (Typ) then + if Of_Present (N) then + Set_Etype (Def_Id, Component_Type (Typ)); + else + Error_Msg_N + ("to iterate over the elements of an array, use OF", N); + Set_Etype (Def_Id, Etype (First_Index (Typ))); + end if; + + -- Iteration over a container + + else + Set_Ekind (Def_Id, E_Loop_Parameter); + + if Of_Present (N) then + + -- Find the Element_Type in the package instance that defines the + -- container type. + + Ent := First_Entity (Scope (Typ)); + while Present (Ent) loop + if Chars (Ent) = Name_Element_Type then + Set_Etype (Def_Id, Ent); + exit; + end if; + + Next_Entity (Ent); + end loop; + + else + -- Find the Cursor type in similar fashion + + Ent := First_Entity (Scope (Typ)); + while Present (Ent) loop + if Chars (Ent) = Name_Cursor then + Set_Etype (Def_Id, Ent); + exit; + end if; + + Next_Entity (Ent); + end loop; + end if; + end if; + end Analyze_Iterator_Specification; + + ------------------- + -- Analyze_Label -- + ------------------- + + -- Note: the semantic work required for analyzing labels (setting them as + -- reachable) was done in a prepass through the statements in the block, + -- so that forward gotos would be properly handled. See Analyze_Statements + -- for further details. The only processing required here is to deal with + -- optimizations that depend on an assumption of sequential control flow, + -- since of course the occurrence of a label breaks this assumption. + + procedure Analyze_Label (N : Node_Id) is + pragma Warnings (Off, N); + begin + Kill_Current_Values; + end Analyze_Label; + + -------------------------- + -- Analyze_Label_Entity -- + -------------------------- + + procedure Analyze_Label_Entity (E : Entity_Id) is + begin + Set_Ekind (E, E_Label); + Set_Etype (E, Standard_Void_Type); + Set_Enclosing_Scope (E, Current_Scope); + Set_Reachable (E, True); + end Analyze_Label_Entity; + + ---------------------------- + -- Analyze_Loop_Statement -- + ---------------------------- + + procedure Analyze_Loop_Statement (N : Node_Id) is + Loop_Statement : constant Node_Id := N; + + Id : constant Node_Id := Identifier (Loop_Statement); + Iter : constant Node_Id := Iteration_Scheme (Loop_Statement); + Ent : Entity_Id; + + begin + if Present (Id) then + + -- Make name visible, e.g. for use in exit statements. Loop + -- labels are always considered to be referenced. + + Analyze (Id); + Ent := Entity (Id); + + -- Guard against serious error (typically, a scope mismatch when + -- semantic analysis is requested) by creating loop entity to + -- continue analysis. + + if No (Ent) then + if Total_Errors_Detected /= 0 then + Ent := + New_Internal_Entity + (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L'); + else + raise Program_Error; + end if; + + else + Generate_Reference (Ent, Loop_Statement, ' '); + Generate_Definition (Ent); + + -- If we found a label, mark its type. If not, ignore it, since it + -- means we have a conflicting declaration, which would already + -- have been diagnosed at declaration time. Set Label_Construct + -- of the implicit label declaration, which is not created by the + -- parser for generic units. + + if Ekind (Ent) = E_Label then + Set_Ekind (Ent, E_Loop); + + if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then + Set_Label_Construct (Parent (Ent), Loop_Statement); + end if; + end if; + end if; + + -- Case of no identifier present + + else + Ent := + New_Internal_Entity + (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L'); + Set_Etype (Ent, Standard_Void_Type); + Set_Parent (Ent, Loop_Statement); + end if; + + -- Kill current values on entry to loop, since statements in body of + -- loop may have been executed before the loop is entered. Similarly we + -- kill values after the loop, since we do not know that the body of the + -- loop was executed. + + Kill_Current_Values; + Push_Scope (Ent); + Analyze_Iteration_Scheme (Iter); + Analyze_Statements (Statements (Loop_Statement)); + Process_End_Label (Loop_Statement, 'e', Ent); + End_Scope; + Kill_Current_Values; + + -- Check for infinite loop. Skip check for generated code, since it + -- justs waste time and makes debugging the routine called harder. + + -- Note that we have to wait till the body of the loop is fully analyzed + -- before making this call, since Check_Infinite_Loop_Warning relies on + -- being able to use semantic visibility information to find references. + + if Comes_From_Source (N) then + Check_Infinite_Loop_Warning (N); + end if; + + -- Code after loop is unreachable if the loop has no WHILE or FOR + -- and contains no EXIT statements within the body of the loop. + + if No (Iter) and then not Has_Exit (Ent) then + Check_Unreachable_Code (N); + end if; + end Analyze_Loop_Statement; + + ---------------------------- + -- Analyze_Null_Statement -- + ---------------------------- + + -- Note: the semantics of the null statement is implemented by a single + -- null statement, too bad everything isn't as simple as this! + + procedure Analyze_Null_Statement (N : Node_Id) is + pragma Warnings (Off, N); + begin + null; + end Analyze_Null_Statement; + + ------------------------ + -- Analyze_Statements -- + ------------------------ + + procedure Analyze_Statements (L : List_Id) is + S : Node_Id; + Lab : Entity_Id; + + begin + -- The labels declared in the statement list are reachable from + -- statements in the list. We do this as a prepass so that any + -- goto statement will be properly flagged if its target is not + -- reachable. This is not required, but is nice behavior! + + S := First (L); + while Present (S) loop + if Nkind (S) = N_Label then + Analyze (Identifier (S)); + Lab := Entity (Identifier (S)); + + -- If we found a label mark it as reachable + + if Ekind (Lab) = E_Label then + Generate_Definition (Lab); + Set_Reachable (Lab); + + if Nkind (Parent (Lab)) = N_Implicit_Label_Declaration then + Set_Label_Construct (Parent (Lab), S); + end if; + + -- If we failed to find a label, it means the implicit declaration + -- of the label was hidden. A for-loop parameter can do this to + -- a label with the same name inside the loop, since the implicit + -- label declaration is in the innermost enclosing body or block + -- statement. + + else + Error_Msg_Sloc := Sloc (Lab); + Error_Msg_N + ("implicit label declaration for & is hidden#", + Identifier (S)); + end if; + end if; + + Next (S); + end loop; + + -- Perform semantic analysis on all statements + + Conditional_Statements_Begin; + + S := First (L); + while Present (S) loop + Analyze (S); + Next (S); + end loop; + + Conditional_Statements_End; + + -- Make labels unreachable. Visibility is not sufficient, because + -- labels in one if-branch for example are not reachable from the + -- other branch, even though their declarations are in the enclosing + -- declarative part. + + S := First (L); + while Present (S) loop + if Nkind (S) = N_Label then + Set_Reachable (Entity (Identifier (S)), False); + end if; + + Next (S); + end loop; + end Analyze_Statements; + + ---------------------------- + -- Check_Unreachable_Code -- + ---------------------------- + + procedure Check_Unreachable_Code (N : Node_Id) is + Error_Loc : Source_Ptr; + P : Node_Id; + + begin + if Is_List_Member (N) + and then Comes_From_Source (N) + then + declare + Nxt : Node_Id; + + begin + Nxt := Original_Node (Next (N)); + + -- If a label follows us, then we never have dead code, since + -- someone could branch to the label, so we just ignore it. + + if Nkind (Nxt) = N_Label then + return; + + -- Otherwise see if we have a real statement following us + + elsif Present (Nxt) + and then Comes_From_Source (Nxt) + and then Is_Statement (Nxt) + then + -- Special very annoying exception. If we have a return that + -- follows a raise, then we allow it without a warning, since + -- the Ada RM annoyingly requires a useless return here! + + if Nkind (Original_Node (N)) /= N_Raise_Statement + or else Nkind (Nxt) /= N_Simple_Return_Statement + then + -- The rather strange shenanigans with the warning message + -- here reflects the fact that Kill_Dead_Code is very good + -- at removing warnings in deleted code, and this is one + -- warning we would prefer NOT to have removed. + + Error_Loc := Sloc (Nxt); + + -- If we have unreachable code, analyze and remove the + -- unreachable code, since it is useless and we don't + -- want to generate junk warnings. + + -- We skip this step if we are not in code generation mode. + -- This is the one case where we remove dead code in the + -- semantics as opposed to the expander, and we do not want + -- to remove code if we are not in code generation mode, + -- since this messes up the ASIS trees. + + -- Note that one might react by moving the whole circuit to + -- exp_ch5, but then we lose the warning in -gnatc mode. + + if Operating_Mode = Generate_Code then + loop + Nxt := Next (N); + + -- Quit deleting when we have nothing more to delete + -- or if we hit a label (since someone could transfer + -- control to a label, so we should not delete it). + + exit when No (Nxt) or else Nkind (Nxt) = N_Label; + + -- Statement/declaration is to be deleted + + Analyze (Nxt); + Remove (Nxt); + Kill_Dead_Code (Nxt); + end loop; + end if; + + -- Now issue the warning + + Error_Msg ("?unreachable code!", Error_Loc); + end if; + + -- If the unconditional transfer of control instruction is + -- the last statement of a sequence, then see if our parent + -- is one of the constructs for which we count unblocked exits, + -- and if so, adjust the count. + + else + P := Parent (N); + + -- Statements in THEN part or ELSE part of IF statement + + if Nkind (P) = N_If_Statement then + null; + + -- Statements in ELSIF part of an IF statement + + elsif Nkind (P) = N_Elsif_Part then + P := Parent (P); + pragma Assert (Nkind (P) = N_If_Statement); + + -- Statements in CASE statement alternative + + elsif Nkind (P) = N_Case_Statement_Alternative then + P := Parent (P); + pragma Assert (Nkind (P) = N_Case_Statement); + + -- Statements in body of block + + elsif Nkind (P) = N_Handled_Sequence_Of_Statements + and then Nkind (Parent (P)) = N_Block_Statement + then + null; + + -- Statements in exception handler in a block + + elsif Nkind (P) = N_Exception_Handler + and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements + and then Nkind (Parent (Parent (P))) = N_Block_Statement + then + null; + + -- None of these cases, so return + + else + return; + end if; + + -- This was one of the cases we are looking for (i.e. the + -- parent construct was IF, CASE or block) so decrement count. + + Unblocked_Exit_Count := Unblocked_Exit_Count - 1; + end if; + end; + end if; + end Check_Unreachable_Code; + +end Sem_Ch5; |