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------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- S E M _ C H 5 -- -- -- -- B o d y -- -- -- -- Copyright (C) 1992-2011, 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 Aspects; use Aspects; with Atree; use Atree; with Checks; use Checks; with Einfo; use Einfo; with Errout; use Errout; with Expander; use Expander; with Exp_Ch6; use Exp_Ch6; 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 Restrict; use Restrict; with Rident; use Rident; 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_Ch6; use Sem_Ch6; with Sem_Ch8; use Sem_Ch8; with Sem_Dim; use Sem_Dim; 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. procedure Pre_Analyze_Range (R_Copy : Node_Id); -- Determine expected type of range or domain of iteration of Ada 2012 -- loop by analyzing separate copy. Do the analysis and resolution of the -- copy of the bound(s) with expansion disabled, to prevent the generation -- of finalization actions. This prevents memory leaks when the bounds -- contain calls to functions returning controlled arrays or when the -- domain of iteration is a container. ------------------------ -- 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); -- Ensure that we never do an assignment on a variable marked as -- as Safe_To_Reevaluate. pragma Assert (not Is_Entity_Name (Lhs) or else Ekind (Entity (Lhs)) /= E_Variable or else not Is_Safe_To_Reevaluate (Entity (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 -- Handle assignment to an Ada 2012 stand-alone object -- of an anonymous access type. or else (Ekind (T1) = E_Anonymous_Access_Type and then Nkind (Associated_Node_For_Itype (T1)) = N_Object_Declaration) 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 -- is 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). 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. 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); 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; -- If assigning to an object in whole or in part, 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. declare Ent : constant Entity_Id := Get_Enclosing_Object (Lhs); begin if Present (Ent) and then Safe_To_Capture_Value (N, Ent) and then Nkind (N) = N_Assignment_Statement and then Warn_On_Modified_Unread and then Is_Assignable (Ent) and then Comes_From_Source (N) and then In_Extended_Main_Source_Unit (Ent) then Set_Last_Assignment (Ent, Lhs); end if; end; Analyze_Dimension (N); end Analyze_Assignment; ----------------------------- -- Analyze_Block_Statement -- ----------------------------- procedure Analyze_Block_Statement (N : Node_Id) is procedure Install_Return_Entities (Scop : Entity_Id); -- Install all entities of return statement scope Scop in the visibility -- chain except for the return object since its entity is reused in a -- renaming. ----------------------------- -- Install_Return_Entities -- ----------------------------- procedure Install_Return_Entities (Scop : Entity_Id) is Id : Entity_Id; begin Id := First_Entity (Scop); while Present (Id) loop -- Do not install the return object if not Ekind_In (Id, E_Constant, E_Variable) or else not Is_Return_Object (Id) then Install_Entity (Id); end if; Next_Entity (Id); end loop; end Install_Return_Entities; -- Local constants and variables Decls : constant List_Id := Declarations (N); Id : constant Node_Id := Identifier (N); HSS : constant Node_Id := Handled_Statement_Sequence (N); Is_BIP_Return_Statement : Boolean; -- Start of processing for Analyze_Block_Statement begin -- In SPARK mode, we reject block statements. Note that the case of -- block statements generated by the expander is fine. if Nkind (Original_Node (N)) = N_Block_Statement then Check_SPARK_Restriction ("block statement is not allowed", N); end if; -- If no handled statement sequence is present, things are really messed -- up, and we just return immediately (defence against previous errors). if No (HSS) then return; end if; -- Detect whether the block is actually a rewritten return statement of -- a build-in-place function. Is_BIP_Return_Statement := Present (Id) and then Present (Entity (Id)) and then Ekind (Entity (Id)) = E_Return_Statement and then Is_Build_In_Place_Function (Return_Applies_To (Entity (Id))); -- 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 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); -- The block served as an extended return statement. Ensure that any -- entities created during the analysis and expansion of the return -- object declaration are once again visible. if Is_BIP_Return_Statement then Install_Return_Entities (Ent); end if; 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); -- A case statement with a single OTHERS alternative is not allowed -- in SPARK. if Others_Present and then List_Length (Alternatives (N)) = 1 then Check_SPARK_Restriction ("OTHERS as unique case alternative is not allowed", N); end if; 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. -- Additionally, in SPARK mode: -- The exit can only name the closest enclosing loop; -- An exit with a when clause must be directly contained in a loop; -- An exit without a when clause must be directly contained in an -- if-statement with no elsif or else, which is itself directly contained -- in a loop. The exit must be the last statement in the if-statement. 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 if Has_Loop_In_Inner_Open_Scopes (U_Name) then Check_SPARK_Restriction ("exit label must name the closest enclosing loop", N); end if; 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; -- In SPARK mode, verify that the exit statement respects the SPARK -- restrictions. if Present (Cond) then if Nkind (Parent (N)) /= N_Loop_Statement then Check_SPARK_Restriction ("exit with when clause must be directly in loop", N); end if; else if Nkind (Parent (N)) /= N_If_Statement then if Nkind (Parent (N)) = N_Elsif_Part then Check_SPARK_Restriction ("exit must be in IF without ELSIF", N); else Check_SPARK_Restriction ("exit must be directly in IF", N); end if; elsif Nkind (Parent (Parent (N))) /= N_Loop_Statement then Check_SPARK_Restriction ("exit must be in IF directly in loop", N); -- First test the presence of ELSE, so that an exit in an ELSE leads -- to an error mentioning the ELSE. elsif Present (Else_Statements (Parent (N))) then Check_SPARK_Restriction ("exit must be in IF without ELSE", N); -- An exit in an ELSIF does not reach here, as it would have been -- detected in the case (Nkind (Parent (N)) /= N_If_Statement). elsif Present (Elsif_Parts (Parent (N))) then Check_SPARK_Restriction ("exit must be in IF without ELSIF", N); end if; 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_SPARK_Restriction ("goto statement is not allowed", N); -- Actual semantic checks 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, and 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. function Has_Call_Using_Secondary_Stack (N : Node_Id) return Boolean; -- N is the node for an arbitrary construct. This function searches the -- construct N to see if any expressions within it contain function -- calls that use the secondary stack, returning True if any such call -- is found, and False otherwise. -------------------- -- 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; 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); -- 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. if not Has_Call_Using_Secondary_Stack (Original_Bound) then Force_Evaluation (Original_Bound); return Original_Bound; end if; Id := Make_Temporary (Loc, 'R', Original_Bound); -- 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)); -- We must recursively clean in the relocated expression the flag -- analyzed to ensure that the expression is reanalyzed. Required -- to ensure that the transient scope is established now (because -- Establish_Transient_Scope discarded generating transient scopes -- in the analysis of the iteration scheme). Reset_Analyzed_Flags (Expression (Assign)); Insert_Actions (Parent (N), New_List (Decl, Assign)); -- Now that this temporary variable is initialized we decorate it -- as safe-to-reevaluate to inform to the backend that no further -- asignment will be issued and hence it can be handled as side -- effect free. Note that this decoration must be done when the -- assignment has been analyzed because otherwise it will be -- rejected (see Analyze_Assignment). Set_Is_Safe_To_Reevaluate (Id); 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 Set_Parent (R_Copy, Parent (R)); Pre_Analyze_Range (R_Copy); 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 with 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; ------------------------------------ -- Has_Call_Using_Secondary_Stack -- ------------------------------------ function Has_Call_Using_Secondary_Stack (N : Node_Id) return Boolean is function Check_Call (N : Node_Id) return Traverse_Result; -- Check if N is a function call which uses the secondary stack ---------------- -- Check_Call -- ---------------- function Check_Call (N : Node_Id) return Traverse_Result is Nam : Node_Id; Subp : Entity_Id; Return_Typ : Entity_Id; begin if Nkind (N) = N_Function_Call then Nam := Name (N); -- Call using access to subprogram with explicit dereference if Nkind (Nam) = N_Explicit_Dereference then Subp := Etype (Nam); -- Normal case else Subp := Entity (Nam); end if; Return_Typ := Etype (Subp); if Is_Composite_Type (Return_Typ) and then not Is_Constrained (Return_Typ) then return Abandon; elsif Sec_Stack_Needed_For_Return (Subp) then return Abandon; end if; end if; -- Continue traversing the tree return OK; end Check_Call; function Check_Calls is new Traverse_Func (Check_Call); -- Start of processing for Has_Call_Using_Secondary_Stack begin return Check_Calls (N) = Abandon; end Has_Call_Using_Secondary_Stack; -- 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; -- For an iterator specification with "of", pre-analyze range to -- capture function calls that may require finalization actions. elsif Present (Iterator_Specification (N)) then Pre_Analyze_Range (Name (Iterator_Specification (N))); 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); D_Copy : Node_Id; 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; -- Loop parameter specification must include subtype mark in -- SPARK. if Nkind (DS) = N_Range then Check_SPARK_Restriction ("loop parameter specification must include subtype mark", N); end if; -- 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); -- Expander not active or else range of iteration is a subtype -- indication, an entity, or a function call that yields an -- aggregate or a container. else D_Copy := New_Copy_Tree (DS); Set_Parent (D_Copy, Parent (DS)); Pre_Analyze_Range (D_Copy); -- Ada 2012: If the domain of iteration is a function call, -- it is the new iterator form. -- We have also implemented the shorter form : for X in S -- for Alfa use. In this case, 'Old and 'Result must be -- treated as entity names over which iterators are legal. if Nkind (D_Copy) = N_Function_Call or else (Alfa_Mode and then (Nkind (D_Copy) = N_Attribute_Reference and then (Attribute_Name (D_Copy) = Name_Result or else Attribute_Name (D_Copy) = Name_Old))) or else (Is_Entity_Name (D_Copy) and then not Is_Type (Entity (D_Copy))) then -- This is an iterator specification. Rewrite as such -- and analyze, to capture function calls that may -- require finalization actions. declare I_Spec : constant Node_Id := Make_Iterator_Specification (Sloc (LP), Defining_Identifier => Relocate_Node (Id), Name => D_Copy, 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); -- In a generic context, analyze the original domain -- of iteration, for name capture. if not Expander_Active then Analyze (DS); end if; -- Set kind of loop parameter, which may be used in -- the subsequent analysis of the condition in a -- quantified expression. Set_Ekind (Id, E_Loop_Parameter); return; end; -- Domain of iteration is not a function call, and is -- side-effect free. else Analyze (DS); 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, In_Iter_Schm => True); Set_Ekind (Id, E_Loop_Parameter); -- If the loop is part of a predicate or precondition, it may -- be analyzed twice, once in the source and once on the copy -- used to check conformance. Preserve the original itype -- because the second one may be created in a different scope, -- e.g. a precondition procedure, leading to a crash in GIGI. if No (Etype (Id)) or else Etype (Id) = Any_Type then Set_Etype (Id, Etype (DS)); end if; -- 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 Loc : constant Source_Ptr := Sloc (N); Def_Id : constant Node_Id := Defining_Identifier (N); Subt : constant Node_Id := Subtype_Indication (N); Iter_Name : constant Node_Id := Name (N); Ent : Entity_Id; Typ : Entity_Id; begin -- In semantics/Alfa modes, we won't be further expanding the loop, so -- introduce loop variable so that loop body can be properly analyzed. -- Otherwise this happens after expansion. if Operating_Mode = Check_Semantics or else Alfa_Mode then Enter_Name (Def_Id); end if; Set_Ekind (Def_Id, E_Variable); if Present (Subt) then Analyze (Subt); end if; -- If domain of iteration is an expression, create a declaration for -- it, so that finalization actions are introduced outside of the loop. -- The declaration must be a renaming because the body of the loop may -- assign to elements. if not Is_Entity_Name (Iter_Name) then declare Id : constant Entity_Id := Make_Temporary (Loc, 'R', Iter_Name); Decl : Node_Id; begin Typ := Etype (Iter_Name); -- The name in the renaming declaration may be a function call. -- Indicate that it does not come from source, to suppress -- spurious warnings on renamings of parameterless functions, -- a common enough idiom in user-defined iterators. Decl := Make_Object_Renaming_Declaration (Loc, Defining_Identifier => Id, Subtype_Mark => New_Occurrence_Of (Typ, Loc), Name => New_Copy_Tree (Iter_Name, New_Sloc => Loc)); Insert_Actions (Parent (Parent (N)), New_List (Decl)); Rewrite (Name (N), New_Occurrence_Of (Id, Loc)); Set_Etype (Id, Typ); Set_Etype (Name (N), Typ); end; -- Container is an entity or an array with uncontrolled components, or -- else it is a container iterator given by a function call, typically -- called Iterate in the case of predefined containers, even though -- Iterate is not a reserved name. What matter is that the return type -- of the function is an iterator type. else Analyze (Iter_Name); if Nkind (Iter_Name) = N_Function_Call then declare C : constant Node_Id := Name (Iter_Name); I : Interp_Index; It : Interp; begin if not Is_Overloaded (Iter_Name) then Resolve (Iter_Name, Etype (C)); else Get_First_Interp (C, I, It); while It.Typ /= Empty loop if Reverse_Present (N) then if Is_Reversible_Iterator (It.Typ) then Resolve (Iter_Name, It.Typ); exit; end if; elsif Is_Iterator (It.Typ) then Resolve (Iter_Name, It.Typ); exit; end if; Get_Next_Interp (I, It); end loop; end if; end; -- Domain of iteration is not overloaded else Resolve (Iter_Name, Etype (Iter_Name)); end if; end if; Typ := Etype (Iter_Name); if Is_Array_Type (Typ) then if Of_Present (N) then Set_Etype (Def_Id, Component_Type (Typ)); -- Here we have a missing Range attribute else Error_Msg_N ("missing Range attribute in iteration over an array", N); -- In Ada 2012 mode, this may be an attempt at an iterator if Ada_Version >= Ada_2012 then Error_Msg_NE ("\if& is meant to designate an element of the array, use OF", N, Def_Id); end if; -- Prevent cascaded errors Set_Ekind (Def_Id, E_Loop_Parameter); Set_Etype (Def_Id, Etype (First_Index (Typ))); end if; -- Check for type error in iterator elsif Typ = Any_Type then return; -- Iteration over a container else Set_Ekind (Def_Id, E_Loop_Parameter); if Of_Present (N) then -- The type of the loop variable is the Iterator_Element aspect of -- the container type. declare Element : constant Entity_Id := Find_Aspect (Typ, Aspect_Iterator_Element); begin if No (Element) then Error_Msg_NE ("cannot iterate over&", N, Typ); return; else Set_Etype (Def_Id, Entity (Element)); end if; end; else -- For an iteration of the form IN, the name must denote an -- iterator, typically the result of a call to Iterate. Give a -- useful error message when the name is a container by itself. if Is_Entity_Name (Original_Node (Name (N))) and then not Is_Iterator (Typ) then if No (Find_Aspect (Typ, Aspect_Iterator_Element)) then Error_Msg_NE ("cannot iterate over&", Name (N), Typ); else Error_Msg_N ("name must be an iterator, not a container", Name (N)); end if; Error_Msg_NE ("\to iterate directly over the elements of a container, " & "write `of &`", Name (N), Original_Node (Name (N))); end if; -- The result type of Iterate function is the classwide type of -- the interface parent. We need the specific Cursor type defined -- in the container package. Ent := First_Entity (Scope (Typ)); while Present (Ent) loop if Chars (Ent) = Name_Cursor then Set_Etype (Def_Id, Etype (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 function Is_Container_Iterator (Iter : Node_Id) return Boolean; -- Given a loop iteration scheme, determine whether it is an Ada 2012 -- container iteration. function Is_Wrapped_In_Block (N : Node_Id) return Boolean; -- Determine whether node N is the sole statement of a block --------------------------- -- Is_Container_Iterator -- --------------------------- function Is_Container_Iterator (Iter : Node_Id) return Boolean is begin -- Infinite loop if No (Iter) then return False; -- While loop elsif Present (Condition (Iter)) then return False; -- for Def_Id in [reverse] Name loop -- for Def_Id [: Subtype_Indication] of [reverse] Name loop elsif Present (Iterator_Specification (Iter)) then declare Nam : constant Node_Id := Name (Iterator_Specification (Iter)); Nam_Copy : Node_Id; begin Nam_Copy := New_Copy_Tree (Nam); Set_Parent (Nam_Copy, Parent (Nam)); Pre_Analyze_Range (Nam_Copy); -- The only two options here are iteration over a container or -- an array. return not Is_Array_Type (Etype (Nam_Copy)); end; -- for Def_Id in [reverse] Discrete_Subtype_Definition loop else declare LP : constant Node_Id := Loop_Parameter_Specification (Iter); DS : constant Node_Id := Discrete_Subtype_Definition (LP); DS_Copy : Node_Id; begin DS_Copy := New_Copy_Tree (DS); Set_Parent (DS_Copy, Parent (DS)); Pre_Analyze_Range (DS_Copy); -- Check for a call to Iterate () return Nkind (DS_Copy) = N_Function_Call and then Needs_Finalization (Etype (DS_Copy)); end; end if; end Is_Container_Iterator; ------------------------- -- Is_Wrapped_In_Block -- ------------------------- function Is_Wrapped_In_Block (N : Node_Id) return Boolean is HSS : constant Node_Id := Parent (N); begin return Nkind (HSS) = N_Handled_Sequence_Of_Statements and then Nkind (Parent (HSS)) = N_Block_Statement and then First (Statements (HSS)) = N and then No (Next (First (Statements (HSS)))); end Is_Wrapped_In_Block; -- Local declarations Id : constant Node_Id := Identifier (N); Iter : constant Node_Id := Iteration_Scheme (N); Loc : constant Source_Ptr := Sloc (N); Ent : Entity_Id; -- Start of processing for Analyze_Loop_Statement 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, Loc, 'L'); else raise Program_Error; end if; else Generate_Reference (Ent, N, ' '); 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), N); end if; end if; end if; -- Case of no identifier present else Ent := New_Internal_Entity (E_Loop, Current_Scope, Loc, 'L'); Set_Etype (Ent, Standard_Void_Type); Set_Parent (Ent, N); end if; -- Iteration over a container in Ada 2012 involves the creation of a -- controlled iterator object. Wrap the loop in a block to ensure the -- timely finalization of the iterator and release of container locks. if Ada_Version >= Ada_2012 and then Is_Container_Iterator (Iter) and then not Is_Wrapped_In_Block (N) then Rewrite (N, Make_Block_Statement (Loc, Declarations => New_List, Handled_Statement_Sequence => Make_Handled_Sequence_Of_Statements (Loc, Statements => New_List (Relocate_Node (N))))); Analyze (N); return; end if; -- Kill current values on entry to loop, since statements in the body of -- the 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 the statements of the body except in the case of an Ada 2012 -- iterator with the expander active. In this case the expander will do -- a rewrite of the loop into a while loop. We will then analyze the -- loop body when we analyze this while loop. -- We need to do this delay because if the container is for indefinite -- types the actual subtype of the components will only be determined -- when the cursor declaration is analyzed. -- If the expander is not active, then we want to analyze the loop body -- now even in the Ada 2012 iterator case, since the rewriting will not -- be done. Insert the loop variable in the current scope, if not done -- when analysing the iteration scheme. if No (Iter) or else No (Iterator_Specification (Iter)) or else not Expander_Active then if Present (Iter) and then Present (Iterator_Specification (Iter)) then declare Id : constant Entity_Id := Defining_Identifier (Iterator_Specification (Iter)); begin if Scope (Id) /= Current_Scope then Enter_Name (Id); end if; end; end if; Analyze_Statements (Statements (N)); end if; -- Finish up processing for the loop. We kill all current values, since -- in general we don't know if the statements in the loop have been -- executed. We could do a bit better than this with a loop that we -- know will execute at least once, but it's not worth the trouble and -- the front end is not in the business of flow tracing. Process_End_Label (N, '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); -- Remove dimension in all statements Remove_Dimension_In_Statement (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_Node : Node_Id; 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, unless -- we are in formal mode where goto statements are not allowed. if Nkind (Nxt) = N_Label and then not Restriction_Check_Required (SPARK) 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_Node := 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 (or error in formal mode) if Restriction_Check_Required (SPARK) then Check_SPARK_Restriction ("unreachable code is not allowed", Error_Node); else Error_Msg ("?unreachable code!", Sloc (Error_Node)); end if; 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; ----------------------- -- Pre_Analyze_Range -- ----------------------- procedure Pre_Analyze_Range (R_Copy : Node_Id) is Save_Analysis : constant Boolean := Full_Analysis; begin Full_Analysis := False; Expander_Mode_Save_And_Set (False); Analyze (R_Copy); if Nkind (R_Copy) in N_Subexpr and then 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; -- Subtype mark in iteration scheme if Is_Entity_Name (R_Copy) and then Is_Type (Entity (R_Copy)) then null; -- Expression in range, or Ada 2012 iterator elsif Nkind (R_Copy) in N_Subexpr then Resolve (R_Copy); end if; Expander_Mode_Restore; Full_Analysis := Save_Analysis; end Pre_Analyze_Range; end Sem_Ch5;
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