Mercurial > hg > CbC > CbC_gcc
diff gcc/ada/sem_ch5.adb @ 111:04ced10e8804
gcc 7
| author | kono |
|---|---|
| date | Fri, 27 Oct 2017 22:46:09 +0900 |
| parents | |
| children | 84e7813d76e9 |
line wrap: on
line diff
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/gcc/ada/sem_ch5.adb Fri Oct 27 22:46:09 2017 +0900 @@ -0,0 +1,4080 @@ +------------------------------------------------------------------------------ +-- -- +-- GNAT COMPILER COMPONENTS -- +-- -- +-- S E M _ C H 5 -- +-- -- +-- B o d y -- +-- -- +-- Copyright (C) 1992-2017, 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 Ghost; use Ghost; +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 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 + + Current_Assignment : Node_Id := Empty; + -- This variable holds the node for an assignment that contains target + -- names. The corresponding flag has been set by the parser, and when + -- set the analysis of the RHS must be done with all expansion disabled, + -- because the assignment is reanalyzed after expansion has replaced all + -- occurrences of the target name appropriately. + + 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 Preanalyze_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 -- + ------------------------ + + -- WARNING: This routine manages Ghost regions. Return statements must be + -- replaced by gotos which jump to the end of the routine and restore the + -- Ghost mode. + + procedure Analyze_Assignment (N : Node_Id) is + Lhs : constant Node_Id := Name (N); + Rhs : Node_Id := Expression (N); + + 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. + + procedure Transform_BIP_Assignment (Typ : Entity_Id); + function Should_Transform_BIP_Assignment + (Typ : Entity_Id) return Boolean; + -- If the right-hand side of an assignment statement is a build-in-place + -- call we cannot build in place, so we insert a temp initialized with + -- the call, and transform the assignment statement to copy the temp. + -- Transform_BIP_Assignment does the tranformation, and + -- Should_Transform_BIP_Assignment determines whether we should. + -- The same goes for qualified expressions and conversions whose + -- operand is such a call. + -- + -- This is only for nonlimited types; assignment statements are illegal + -- for limited types, but are generated internally for aggregates and + -- init procs. These limited-type are not really assignment statements + -- -- conceptually, they are initializations, so should not be + -- transformed. + -- + -- Similarly, for nonlimited types, aggregates and init procs generate + -- assignment statements that are really initializations. These are + -- marked No_Ctrl_Actions. + + ------------------------------- + -- 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); + return; + + -- 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); + return; + + elsif Ekind (Ent) = E_Loop_Parameter then + Error_Msg_N ("assignment to loop parameter not allowed", N); + return; + end if; + end; + + -- For indexed components, test prefix if it is in array. We do not + -- want to recurse for cases where the prefix is a pointer, since we + -- may get a message confusing the pointer and what it references. + + elsif Nkind (N) = N_Indexed_Component + and then Is_Array_Type (Etype (Prefix (N))) + then + Diagnose_Non_Variable_Lhs (Prefix (N)); + return; + + -- 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); + return; + + -- For selection from record, diagnose prefix, but note that again + -- we only do this for a record, not e.g. for a pointer. + + elsif Is_Record_Type (Etype (Prefix (N))) then + Diagnose_Non_Variable_Lhs (Prefix (N)); + return; + end if; + end if; + + -- 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 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 + Decl : Node_Id; + + 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_In (Entity (Opnd), + E_In_Out_Parameter, + 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; + + ------------------------------------- + -- Should_Transform_BIP_Assignment -- + ------------------------------------- + + function Should_Transform_BIP_Assignment + (Typ : Entity_Id) return Boolean + is + Result : Boolean; + + begin + if Expander_Active + and then not Is_Limited_View (Typ) + and then Is_Build_In_Place_Result_Type (Typ) + and then not No_Ctrl_Actions (N) + then + -- This function is called early, before name resolution is + -- complete, so we have to deal with things that might turn into + -- function calls later. N_Function_Call and N_Op nodes are the + -- obvious case. An N_Identifier or N_Expanded_Name is a + -- parameterless function call if it denotes a function. + -- Finally, an attribute reference can be a function call. + + case Nkind (Unqual_Conv (Rhs)) is + when N_Function_Call + | N_Op + => + Result := True; + + when N_Expanded_Name + | N_Identifier + => + case Ekind (Entity (Unqual_Conv (Rhs))) is + when E_Function + | E_Operator + => + Result := True; + + when others => + Result := False; + end case; + + when N_Attribute_Reference => + Result := Attribute_Name (Unqual_Conv (Rhs)) = Name_Input; + -- T'Input will turn into a call whose result type is T + + when others => + Result := False; + end case; + else + Result := False; + end if; + + return Result; + end Should_Transform_BIP_Assignment; + + ------------------------------ + -- Transform_BIP_Assignment -- + ------------------------------ + + procedure Transform_BIP_Assignment (Typ : Entity_Id) is + + -- Tranform "X : [constant] T := F (...);" into: + -- + -- Temp : constant T := F (...); + -- X := Temp; + + Loc : constant Source_Ptr := Sloc (N); + Def_Id : constant Entity_Id := Make_Temporary (Loc, 'Y', Rhs); + Obj_Decl : constant Node_Id := + Make_Object_Declaration (Loc, + Defining_Identifier => Def_Id, + Constant_Present => True, + Object_Definition => New_Occurrence_Of (Typ, Loc), + Expression => Rhs, + Has_Init_Expression => True); + + begin + Set_Etype (Def_Id, Typ); + Set_Expression (N, New_Occurrence_Of (Def_Id, Loc)); + + -- At this point, Rhs is no longer equal to Expression (N), so: + + Rhs := Expression (N); + + Insert_Action (N, Obj_Decl); + end Transform_BIP_Assignment; + + -- Local variables + + T1 : Entity_Id; + T2 : Entity_Id; + + Save_Full_Analysis : Boolean; + + Saved_GM : constant Ghost_Mode_Type := Ghost_Mode; + -- Save the Ghost mode to restore on exit + + -- Start of processing for Analyze_Assignment + + begin + Mark_Coextensions (N, Rhs); + + -- Preserve relevant elaboration-related attributes of the context which + -- are no longer available or very expensive to recompute once analysis, + -- resolution, and expansion are over. + + Mark_Elaboration_Attributes + (N_Id => N, + Checks => True, + Modes => True); + + -- Analyze the target of the assignment first in case the expression + -- contains references to Ghost entities. The checks that verify the + -- proper use of a Ghost entity need to know the enclosing context. + + Analyze (Lhs); + + -- An assignment statement is Ghost when the left hand side denotes a + -- Ghost entity. Set the mode now to ensure that any nodes generated + -- during analysis and expansion are properly marked as Ghost. + + if Has_Target_Names (N) then + Current_Assignment := N; + Expander_Mode_Save_And_Set (False); + Save_Full_Analysis := Full_Analysis; + Full_Analysis := False; + else + Current_Assignment := Empty; + end if; + + Mark_And_Set_Ghost_Assignment (N); + Analyze (Rhs); + + -- Ensure that we never do an assignment on a variable marked as + -- Is_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 + + -- An indexed component with generalized indexing is always + -- overloaded with the corresponding dereference. Discard the + -- interpretation that yields a reference type, which is not + -- assignable. + + if Nkind (Lhs) = N_Indexed_Component + and then Present (Generalized_Indexing (Lhs)) + and then Has_Implicit_Dereference (It.Typ) + then + null; + + -- This may be a call to a parameterless function through an + -- implicit dereference, so discard interpretation as well. + + elsif Is_Entity_Name (Lhs) + and then Has_Implicit_Dereference (It.Typ) + then + null; + + elsif Has_Compatible_Type (Rhs, It.Typ) then + if T1 = Any_Type then + T1 := It.Typ; + else + -- 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; + 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; + goto Leave; + end if; + end if; + + -- Deal with build-in-place calls for nonlimited types. We don't do this + -- later, because resolving the rhs tranforms it incorrectly for build- + -- in-place. + + if Should_Transform_BIP_Assignment (Typ => T1) then + Transform_BIP_Assignment (Typ => T1); + end if; + + pragma Assert (not Should_Transform_BIP_Assignment (Typ => T1)); + + -- 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. In an instance or an inlined body + -- no need for further check because assignment was legal in template. + + if In_Inlined_Body then + null; + + elsif 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 Is_Expanded_Priority_Attribute (Ent) + 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; + + goto Leave; + end if; + end if; + end; + + Diagnose_Non_Variable_Lhs (Lhs); + goto Leave; + + -- 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)) + 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; + + goto Leave; + + -- A class-wide type may be a limited view. This illegal case is not + -- caught by previous checks. + + elsif Ekind (T1) = E_Class_Wide_Type and then From_Limited_With (T1) then + Error_Msg_NE ("invalid use of limited view of&", Lhs, T1); + goto Leave; + + -- 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; + goto Leave; + end if; + + -- Now we can complete the resolution of the right hand side + + Set_Assignment_Type (Lhs, T1); + + -- If the target of the assignment is an entity of a mutable type and + -- the expression is a conditional expression, its alternatives can be + -- of different subtypes of the nominal type of the LHS, so they must be + -- resolved with the base type, given that their subtype may differ from + -- that of the target mutable object. + + if Is_Entity_Name (Lhs) + and then Ekind_In (Entity (Lhs), E_In_Out_Parameter, + E_Out_Parameter, + E_Variable) + and then Is_Composite_Type (T1) + and then not Is_Constrained (Etype (Entity (Lhs))) + and then Nkind_In (Rhs, N_If_Expression, N_Case_Expression) + then + Resolve (Rhs, Base_Type (T1)); + + else + Resolve (Rhs, T1); + end if; + + -- 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; + goto Leave; + end if; + + T2 := Etype (Rhs); + + if not Covers (T1, T2) then + Wrong_Type (Rhs, Etype (Lhs)); + Kill_Lhs; + goto Leave; + 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 Is_Tagged_Type (T2) + and then Has_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; + goto Leave; + 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); + goto Leave; + + -- 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); + + -- ??? 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 + ("?r?useless assignment of & to itself!", N, Entity (Lhs)); + else + Error_Msg_N -- CODEFIX + ("?r?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; + + -- Save the scenario for later examination by the ABE Processing phase + + Record_Elaboration_Scenario (N); + + -- 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; + + -- RM 7.3.2 (12/3): An assignment to a view conversion (from a type to + -- one of its ancestors) requires an invariant check. Apply check only + -- if expression comes from source, otherwise it will be applied when + -- value is assigned to source entity. This is not done in GNATprove + -- mode, as GNATprove handles invariant checks itself. + + if Nkind (Lhs) = N_Type_Conversion + and then Has_Invariants (Etype (Expression (Lhs))) + and then Comes_From_Source (Expression (Lhs)) + and then not GNATprove_Mode + then + Insert_After (N, Make_Invariant_Call (Expression (Lhs))); + 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. + + -- There may have been a previous reference to a component of + -- the variable, which in general removes the Last_Assignment + -- field of the variable to indicate a relevant use of the + -- previous assignment. However, if the assignment is to a + -- subcomponent the reference may not have registered, because + -- it is not possible to determine whether the context is an + -- assignment. In those cases we generate a Deferred_Reference, + -- to be used at the end of compilation to generate the right + -- kind of reference, and we suppress a potential warning for + -- a useless assignment, which might be premature. This may + -- lose a warning in rare cases, but seems preferable to a + -- misleading warning. + + if Warn_On_Modified_Unread + and then Is_Assignable (Ent) + and then Comes_From_Source (N) + and then In_Extended_Main_Source_Unit (Ent) + and then not Has_Deferred_Reference (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); + + <<Leave>> + Restore_Ghost_Mode (Saved_GM); + + -- If the right-hand side contains target names, expansion has been + -- disabled to prevent expansion that might move target names out of + -- the context of the assignment statement. Restore the expander mode + -- now so that assignment statement can be properly expanded. + + if Nkind (N) = N_Assignment_Statement then + if Has_Target_Names (N) then + Expander_Mode_Restore; + Full_Analysis := Save_Full_Analysis; + end if; + + pragma Assert (not Should_Transform_BIP_Assignment (Typ => T1)); + end if; + 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_05_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 + Check_Error_Detected; + 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 + Check_Error_Detected; + Set_Identifier (N, Empty); + + 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); + Update_Use_Clause_Chain; + 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_Compound_Statement -- + -------------------------------- + + procedure Analyze_Compound_Statement (N : Node_Id) is + begin + Analyze_List (Actions (N)); + end Analyze_Compound_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; + + Others_Present : Boolean; + -- Indicates if Others was present + + pragma Warnings (Off, Last_Choice); + -- Don't care about assigned value + + 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 the statements associated with a case alternative. Needed + -- by instantiation below. + + package Analyze_Case_Choices is new + Generic_Analyze_Choices + (Process_Associated_Node => Process_Statements); + use Analyze_Case_Choices; + -- Instantiation of the generic choice analysis package + + package Check_Case_Choices is new + Generic_Check_Choices + (Process_Empty_Choice => No_OP, + Process_Non_Static_Choice => Non_Static_Choice_Error, + Process_Associated_Node => No_OP); + use Check_Case_Choices; + -- 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 procedures to analyzwe and check discrete choices + + Analyze_Choices (Alternatives (N), Exp_Type); + Check_Choices (N, Alternatives (N), Exp_Type, Others_Present); + + -- Case statement with single OTHERS alternative not allowed in SPARK + + if Others_Present and then List_Length (Alternatives (N)) = 1 then + Check_SPARK_05_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 the expander is active it will detect the case of a statically + -- determined single alternative and remove warnings for the case, but + -- if we are not doing expansion, that circuit won't be active. Here we + -- duplicate the effect of removing warnings in the same way, so that + -- we will get the same set of warnings in -gnatc mode. + + 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 := Empty; -- initialize to prevent warning + 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_05_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_05_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_05_Restriction + ("exit must be in IF without ELSIF", N); + else + Check_SPARK_05_Restriction ("exit must be directly in IF", N); + end if; + + elsif Nkind (Parent (Parent (N))) /= N_Loop_Statement then + Check_SPARK_05_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_05_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_05_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_05_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 + Check_Error_Detected; + 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 not Ekind_In (Scope_Id, E_Block, E_Loop, 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 processing for 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; + + -- Warn on redundant if statement that has no effect + + -- Note, we could also check empty ELSIF parts ??? + + if Warn_On_Redundant_Constructs + + -- If statement must be from source + + and then Comes_From_Source (N) + + -- Condition must not have obvious side effect + + and then Has_No_Obvious_Side_Effects (Condition (N)) + + -- No elsif parts of else part + + and then No (Elsif_Parts (N)) + and then No (Else_Statements (N)) + + -- Then must be a single null statement + + and then List_Length (Then_Statements (N)) = 1 + then + -- Go to original node, since we may have rewritten something as + -- a null statement (e.g. a case we could figure the outcome of). + + declare + T : constant Node_Id := First (Then_Statements (N)); + S : constant Node_Id := Original_Node (T); + + begin + if Comes_From_Source (S) and then Nkind (S) = N_Null_Statement then + Error_Msg_N ("if statement has no effect?r?", N); + end if; + end; + 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 + Cond : Node_Id; + Iter_Spec : Node_Id; + Loop_Spec : Node_Id; + + begin + -- For an infinite loop, there is no iteration scheme + + if No (N) then + return; + end if; + + Cond := Condition (N); + Iter_Spec := Iterator_Specification (N); + Loop_Spec := Loop_Parameter_Specification (N); + + if Present (Cond) then + Analyze_And_Resolve (Cond, Any_Boolean); + Check_Unset_Reference (Cond); + Set_Current_Value_Condition (N); + + elsif Present (Iter_Spec) then + Analyze_Iterator_Specification (Iter_Spec); + + else + Analyze_Loop_Parameter_Specification (Loop_Spec); + end if; + end Analyze_Iteration_Scheme; + + ------------------------------------ + -- Analyze_Iterator_Specification -- + ------------------------------------ + + procedure Analyze_Iterator_Specification (N : Node_Id) is + procedure Check_Reverse_Iteration (Typ : Entity_Id); + -- For an iteration over a container, if the loop carries the Reverse + -- indicator, verify that the container type has an Iterate aspect that + -- implements the reversible iterator interface. + + function Get_Cursor_Type (Typ : Entity_Id) return Entity_Id; + -- For containers with Iterator and related aspects, the cursor is + -- obtained by locating an entity with the proper name in the scope + -- of the type. + + ----------------------------- + -- Check_Reverse_Iteration -- + ----------------------------- + + procedure Check_Reverse_Iteration (Typ : Entity_Id) is + begin + if Reverse_Present (N) then + if Is_Array_Type (Typ) + or else Is_Reversible_Iterator (Typ) + or else + (Present (Find_Aspect (Typ, Aspect_Iterable)) + and then + Present + (Get_Iterable_Type_Primitive (Typ, Name_Previous))) + then + null; + else + Error_Msg_NE + ("container type does not support reverse iteration", N, Typ); + end if; + end if; + end Check_Reverse_Iteration; + + --------------------- + -- Get_Cursor_Type -- + --------------------- + + function Get_Cursor_Type (Typ : Entity_Id) return Entity_Id is + Ent : Entity_Id; + + begin + -- If iterator type is derived, the cursor is declared in the scope + -- of the parent type. + + if Is_Derived_Type (Typ) then + Ent := First_Entity (Scope (Etype (Typ))); + else + Ent := First_Entity (Scope (Typ)); + end if; + + while Present (Ent) loop + exit when Chars (Ent) = Name_Cursor; + Next_Entity (Ent); + end loop; + + if No (Ent) then + return Any_Type; + end if; + + -- The cursor is the target of generated assignments in the + -- loop, and cannot have a limited type. + + if Is_Limited_Type (Etype (Ent)) then + Error_Msg_N ("cursor type cannot be limited", N); + end if; + + return Etype (Ent); + end Get_Cursor_Type; + + -- Local variables + + Def_Id : constant Node_Id := Defining_Identifier (N); + Iter_Name : constant Node_Id := Name (N); + Loc : constant Source_Ptr := Sloc (N); + Subt : constant Node_Id := Subtype_Indication (N); + + Bas : Entity_Id := Empty; -- initialize to prevent warning + Typ : Entity_Id; + + -- Start of processing for Analyze_Iterator_Specification + + begin + Enter_Name (Def_Id); + + -- AI12-0151 specifies that when the subtype indication is present, it + -- must statically match the type of the array or container element. + -- To simplify this check, we introduce a subtype declaration with the + -- given subtype indication when it carries a constraint, and rewrite + -- the original as a reference to the created subtype entity. + + if Present (Subt) then + if Nkind (Subt) = N_Subtype_Indication then + declare + S : constant Entity_Id := Make_Temporary (Sloc (Subt), 'S'); + Decl : constant Node_Id := + Make_Subtype_Declaration (Loc, + Defining_Identifier => S, + Subtype_Indication => New_Copy_Tree (Subt)); + begin + Insert_Before (Parent (Parent (N)), Decl); + Analyze (Decl); + Rewrite (Subt, New_Occurrence_Of (S, Sloc (Subt))); + end; + else + Analyze (Subt); + end if; + + -- Save entity of subtype indication for subsequent check + + Bas := Entity (Subt); + end if; + + Preanalyze_Range (Iter_Name); + + -- Set the kind of the loop variable, which is not visible within the + -- iterator name. + + Set_Ekind (Def_Id, E_Variable); + + -- Provide a link between the iterator variable and the container, for + -- subsequent use in cross-reference and modification information. + + if Of_Present (N) then + Set_Related_Expression (Def_Id, Iter_Name); + + -- For a container, the iterator is specified through the aspect + + if not Is_Array_Type (Etype (Iter_Name)) then + declare + Iterator : constant Entity_Id := + Find_Value_Of_Aspect + (Etype (Iter_Name), Aspect_Default_Iterator); + + I : Interp_Index; + It : Interp; + + begin + if No (Iterator) then + null; -- error reported below + + elsif not Is_Overloaded (Iterator) then + Check_Reverse_Iteration (Etype (Iterator)); + + -- If Iterator is overloaded, use reversible iterator if one is + -- available. + + elsif Is_Overloaded (Iterator) then + Get_First_Interp (Iterator, I, It); + while Present (It.Nam) loop + if Ekind (It.Nam) = E_Function + and then Is_Reversible_Iterator (Etype (It.Nam)) + then + Set_Etype (Iterator, It.Typ); + Set_Entity (Iterator, It.Nam); + exit; + end if; + + Get_Next_Interp (I, It); + end loop; + + Check_Reverse_Iteration (Etype (Iterator)); + end if; + end; + end if; + end if; + + -- If the 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) + + -- When the context is a quantified expression, the renaming + -- declaration is delayed until the expansion phase if we are + -- doing expansion. + + and then (Nkind (Parent (N)) /= N_Quantified_Expression + or else Operating_Mode = Check_Semantics) + + -- Do not perform this expansion for ASIS and when expansion is + -- disabled, where the temporary may hide the transformation of a + -- selected component into a prefixed function call, and references + -- need to see the original expression. + + and then Expander_Active + then + declare + Id : constant Entity_Id := Make_Temporary (Loc, 'R', Iter_Name); + Decl : Node_Id; + Act_S : Node_Id; + + begin + + -- If the domain of iteration is an array component that depends + -- on a discriminant, create actual subtype for it. Pre-analysis + -- does not generate the actual subtype of a selected component. + + if Nkind (Iter_Name) = N_Selected_Component + and then Is_Array_Type (Etype (Iter_Name)) + then + Act_S := + Build_Actual_Subtype_Of_Component + (Etype (Selector_Name (Iter_Name)), Iter_Name); + Insert_Action (N, Act_S); + + if Present (Act_S) then + Typ := Defining_Identifier (Act_S); + else + Typ := Etype (Iter_Name); + end if; + + else + Typ := Etype (Iter_Name); + + -- Verify that the expression produces an iterator + + if not Of_Present (N) and then not Is_Iterator (Typ) + and then not Is_Array_Type (Typ) + and then No (Find_Aspect (Typ, Aspect_Iterable)) + then + Error_Msg_N + ("expect object that implements iterator interface", + Iter_Name); + end if; + end if; + + -- Protect against malformed iterator + + if Typ = Any_Type then + Error_Msg_N ("invalid expression in loop iterator", Iter_Name); + return; + end if; + + if not Of_Present (N) then + Check_Reverse_Iteration (Typ); + end if; + + -- 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 matters is that the return type + -- of the function is an iterator type. + + elsif Is_Entity_Name (Iter_Name) then + 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; + + if not Of_Present (N) then + Check_Reverse_Iteration (Etype (Iter_Name)); + end if; + end if; + + -- Get base type of container, for proper retrieval of Cursor type + -- and primitive operations. + + Typ := Base_Type (Etype (Iter_Name)); + + if Is_Array_Type (Typ) then + if Of_Present (N) then + Set_Etype (Def_Id, Component_Type (Typ)); + + -- The loop variable is aliased if the array components are + -- aliased. + + Set_Is_Aliased (Def_Id, Has_Aliased_Components (Typ)); + + -- AI12-0047 stipulates that the domain (array or container) + -- cannot be a component that depends on a discriminant if the + -- enclosing object is mutable, to prevent a modification of the + -- dowmain of iteration in the course of an iteration. + + -- If the object is an expression it has been captured in a + -- temporary, so examine original node. + + if Nkind (Original_Node (Iter_Name)) = N_Selected_Component + and then Is_Dependent_Component_Of_Mutable_Object + (Original_Node (Iter_Name)) + then + Error_Msg_N + ("iterable name cannot be a discriminant-dependent " + & "component of a mutable object", N); + end if; + + if Present (Subt) + and then + (Base_Type (Bas) /= Base_Type (Component_Type (Typ)) + or else + not Subtypes_Statically_Match (Bas, Component_Type (Typ))) + then + Error_Msg_N + ("subtype indication does not match component type", Subt); + end if; + + -- 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); + Error_Msg_Ada_2012_Feature ("container iterator", Sloc (N)); + + -- OF present + + if Of_Present (N) then + if Has_Aspect (Typ, Aspect_Iterable) then + declare + Elt : constant Entity_Id := + Get_Iterable_Type_Primitive (Typ, Name_Element); + begin + if No (Elt) then + Error_Msg_N + ("missing Element primitive for iteration", N); + else + Set_Etype (Def_Id, Etype (Elt)); + Check_Reverse_Iteration (Typ); + end if; + end; + + -- For a predefined container, The type of the loop variable is + -- the Iterator_Element aspect of the container type. + + else + declare + Element : constant Entity_Id := + Find_Value_Of_Aspect + (Typ, Aspect_Iterator_Element); + Iterator : constant Entity_Id := + Find_Value_Of_Aspect + (Typ, Aspect_Default_Iterator); + Orig_Iter_Name : constant Node_Id := + Original_Node (Iter_Name); + Cursor_Type : Entity_Id; + + begin + if No (Element) then + Error_Msg_NE ("cannot iterate over&", N, Typ); + return; + + else + Set_Etype (Def_Id, Entity (Element)); + Cursor_Type := Get_Cursor_Type (Typ); + pragma Assert (Present (Cursor_Type)); + + -- If subtype indication was given, verify that it covers + -- the element type of the container. + + if Present (Subt) + and then (not Covers (Bas, Etype (Def_Id)) + or else not Subtypes_Statically_Match + (Bas, Etype (Def_Id))) + then + Error_Msg_N + ("subtype indication does not match element type", + Subt); + end if; + + -- If the container has a variable indexing aspect, the + -- element is a variable and is modifiable in the loop. + + if Has_Aspect (Typ, Aspect_Variable_Indexing) then + Set_Ekind (Def_Id, E_Variable); + end if; + + -- If the container is a constant, iterating over it + -- requires a Constant_Indexing operation. + + if not Is_Variable (Iter_Name) + and then not Has_Aspect (Typ, Aspect_Constant_Indexing) + then + Error_Msg_N + ("iteration over constant container require " + & "constant_indexing aspect", N); + + -- The Iterate function may have an in_out parameter, + -- and a constant container is thus illegal. + + elsif Present (Iterator) + and then Ekind (Entity (Iterator)) = E_Function + and then Ekind (First_Formal (Entity (Iterator))) /= + E_In_Parameter + and then not Is_Variable (Iter_Name) + then + Error_Msg_N ("variable container expected", N); + end if; + + -- Detect a case where the iterator denotes a component + -- of a mutable object which depends on a discriminant. + -- Note that the iterator may denote a function call in + -- qualified form, in which case this check should not + -- be performed. + + if Nkind (Orig_Iter_Name) = N_Selected_Component + and then + Present (Entity (Selector_Name (Orig_Iter_Name))) + and then Ekind_In + (Entity (Selector_Name (Orig_Iter_Name)), + E_Component, + E_Discriminant) + and then Is_Dependent_Component_Of_Mutable_Object + (Orig_Iter_Name) + then + Error_Msg_N + ("container cannot be a discriminant-dependent " + & "component of a mutable object", N); + end if; + end if; + end; + end if; + + -- IN iterator, domain is a range, or a call to Iterate function + + 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. + + -- The type may be a formal container type, which has to have + -- an Iterable aspect detailing the required primitives. + + if Is_Entity_Name (Original_Node (Name (N))) + and then not Is_Iterator (Typ) + then + if Has_Aspect (Typ, Aspect_Iterable) then + null; + + elsif not Has_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; + + if Has_Aspect (Typ, Aspect_Iterable) then + null; + else + Error_Msg_NE + ("\to iterate directly over the elements of a container, " + & "write `of &`", Name (N), Original_Node (Name (N))); + + -- No point in continuing analysis of iterator spec + + return; + end if; + end if; + + -- If the name is a call (typically prefixed) to some Iterate + -- function, it has been rewritten as an object declaration. + -- If that object is a selected component, verify that it is not + -- a component of an unconstrained mutable object. + + if Nkind (Iter_Name) = N_Identifier + or else (not Expander_Active and Comes_From_Source (Iter_Name)) + then + declare + Orig_Node : constant Node_Id := Original_Node (Iter_Name); + Iter_Kind : constant Node_Kind := Nkind (Orig_Node); + Obj : Node_Id; + + begin + if Iter_Kind = N_Selected_Component then + Obj := Prefix (Orig_Node); + + elsif Iter_Kind = N_Function_Call then + Obj := First_Actual (Orig_Node); + + -- If neither, the name comes from source + + else + Obj := Iter_Name; + end if; + + if Nkind (Obj) = N_Selected_Component + and then Is_Dependent_Component_Of_Mutable_Object (Obj) + then + Error_Msg_N + ("container cannot be a discriminant-dependent " + & "component of a mutable object", N); + end if; + end; + 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. We obtain it by name for a predefined + -- container, or through the Iterable aspect for a formal one. + + if Has_Aspect (Typ, Aspect_Iterable) then + Set_Etype (Def_Id, + Get_Cursor_Type + (Parent (Find_Value_Of_Aspect (Typ, Aspect_Iterable)), + Typ)); + + else + Set_Etype (Def_Id, Get_Cursor_Type (Typ)); + Check_Reverse_Iteration (Etype (Iter_Name)); + end if; + + 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_Parameter_Specification -- + ------------------------------------------ + + procedure Analyze_Loop_Parameter_Specification (N : Node_Id) is + Loop_Nod : constant Node_Id := Parent (Parent (N)); + + 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. + + procedure Check_Predicate_Use (T : Entity_Id); + -- Diagnose Attempt to iterate through non-static predicate. Note that + -- a type with inherited predicates may have both static and dynamic + -- forms. In this case it is not sufficent to check the static predicate + -- function only, look for a dynamic predicate aspect as well. + + 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. + + 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. + + -------------------------------------- + -- 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_Occurrence_Of (Indx, Loc), + Constraint => + Make_Range_Constraint (Loc, Relocate_Node (DS)))); + Insert_Before (Loop_Nod, Decl); + Analyze (Decl); + + Rewrite (DS, + Make_Attribute_Reference (Loc, + Prefix => New_Occurrence_Of (Subt, Loc), + Attribute_Name => Attribute_Name (DS))); + + Analyze (DS); + end; + end if; + end Check_Controlled_Array_Attribute; + + ------------------------- + -- Check_Predicate_Use -- + ------------------------- + + procedure Check_Predicate_Use (T : Entity_Id) is + begin + -- A predicated subtype is illegal in loops and related constructs + -- if the predicate is not static, or if it is a non-static subtype + -- of a statically predicated subtype. + + if Is_Discrete_Type (T) + and then Has_Predicates (T) + and then (not Has_Static_Predicate (T) + or else not Is_Static_Subtype (T) + or else Has_Dynamic_Predicate_Aspect (T)) + then + -- Seems a confusing message for the case of a static predicate + -- with a non-static subtype??? + + Bad_Predicated_Subtype_Use + ("cannot use subtype& with non-static predicate for loop " + & "iteration", Discrete_Subtype_Definition (N), + T, Suggest_Static => True); + + elsif Inside_A_Generic + and then Is_Generic_Formal (T) + and then Is_Discrete_Type (T) + then + Set_No_Dynamic_Predicate_On_Actual (T); + end if; + end Check_Predicate_Use; + + ------------------------------------ + -- 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); + + -- Call using a selected component notation or Ada 2005 object + -- operation notation + + elsif Nkind (Nam) = N_Selected_Component then + Subp := Entity (Selector_Name (Nam)); + + -- Common 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; + + -------------------- + -- Process_Bounds -- + -------------------- + + procedure Process_Bounds (R : Node_Id) is + Loc : constant Source_Ptr := Sloc (N); + + function One_Bound + (Original_Bound : Node_Id; + Analyzed_Bound : Node_Id; + Typ : Entity_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; + Typ : Entity_Id) return Node_Id + is + Assign : Node_Id; + Decl : Node_Id; + Id : Entity_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; + + -- 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 (Analyzed_Bound) then + Analyze_And_Resolve (Original_Bound, Typ); + + -- Ensure that the bound is valid. This check should not be + -- generated when the range belongs to a quantified expression + -- as the construct is still not expanded into its final form. + + if Nkind (Parent (R)) /= N_Loop_Parameter_Specification + or else Nkind (Parent (Parent (R))) /= N_Quantified_Expression + then + Ensure_Valid (Original_Bound); + end if; + + 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)); + + Insert_Actions (Loop_Nod, 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; + + Hi : constant Node_Id := High_Bound (R); + Lo : constant Node_Id := Low_Bound (R); + R_Copy : constant Node_Id := New_Copy_Tree (R); + New_Hi : Node_Id; + New_Lo : Node_Id; + Typ : Entity_Id; + + -- Start of processing for Process_Bounds + + begin + Set_Parent (R_Copy, Parent (R)); + Preanalyze_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 := One_Bound (Lo, Low_Bound (R_Copy), Typ); + New_Hi := One_Bound (Hi, High_Bound (R_Copy), Typ); + + -- Propagate staticness to loop range itself, in case the + -- corresponding subtype is static. + + if New_Lo /= Lo and then Is_OK_Static_Expression (New_Lo) then + Rewrite (Low_Bound (R), New_Copy (New_Lo)); + end if; + + if New_Hi /= Hi and then Is_OK_Static_Expression (New_Hi) then + Rewrite (High_Bound (R), New_Copy (New_Hi)); + end if; + end Process_Bounds; + + -- Local variables + + DS : constant Node_Id := Discrete_Subtype_Definition (N); + Id : constant Entity_Id := Defining_Identifier (N); + + DS_Copy : Node_Id; + + -- Start of processing for Analyze_Loop_Parameter_Specification + + 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 Ekind (H) = E_Variable + and then Is_Discrete_Type (Etype (H)) + and then Enclosing_Dynamic_Scope (H) = Enclosing_Dynamic_Scope (Id) + 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_05_Restriction + ("loop parameter specification must include subtype mark", N); + end if; + + -- Analyze the subtype definition and create temporaries for the bounds. + -- Do not evaluate the range when preanalyzing a quantified expression + -- because bounds expressed as function calls with side effects will be + -- incorrectly replicated. + + if Nkind (DS) = N_Range + and then Expander_Active + and then Nkind (Parent (N)) /= N_Quantified_Expression + then + Process_Bounds (DS); + + -- Either the expander not active or the range of iteration is a subtype + -- indication, an entity, or a function call that yields an aggregate or + -- a container. + + else + DS_Copy := New_Copy_Tree (DS); + Set_Parent (DS_Copy, Parent (DS)); + Preanalyze_Range (DS_Copy); + + -- Ada 2012: If the domain of iteration is: + + -- a) a function call, + -- b) an identifier that is not a type, + -- c) an attribute reference 'Old (within a postcondition), + -- d) an unchecked conversion or a qualified expression with + -- the proper iterator type. + + -- then it is an iteration over a container. It was classified as + -- a loop specification by the parser, and must be rewritten now + -- to activate container iteration. The last case will occur within + -- an expanded inlined call, where the expansion wraps an actual in + -- an unchecked conversion when needed. The expression of the + -- conversion is always an object. + + if Nkind (DS_Copy) = N_Function_Call + + or else (Is_Entity_Name (DS_Copy) + and then not Is_Type (Entity (DS_Copy))) + + or else (Nkind (DS_Copy) = N_Attribute_Reference + and then Nam_In (Attribute_Name (DS_Copy), + Name_Loop_Entry, Name_Old)) + + or else Has_Aspect (Etype (DS_Copy), Aspect_Iterable) + + or else Nkind (DS_Copy) = N_Unchecked_Type_Conversion + or else (Nkind (DS_Copy) = N_Qualified_Expression + and then Is_Iterator (Etype (DS_Copy))) + then + -- This is an iterator specification. Rewrite it as such and + -- analyze it to capture function calls that may require + -- finalization actions. + + declare + I_Spec : constant Node_Id := + Make_Iterator_Specification (Sloc (N), + Defining_Identifier => Relocate_Node (Id), + Name => DS_Copy, + Subtype_Indication => Empty, + Reverse_Present => Reverse_Present (N)); + Scheme : constant Node_Id := Parent (N); + + begin + Set_Iterator_Specification (Scheme, I_Spec); + Set_Loop_Parameter_Specification (Scheme, 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 + -- A quantified expression that appears in a pre/post condition + -- is pre-analyzed several times. If the range is given by an + -- attribute reference it is rewritten as a range, and this is + -- done even with expansion disabled. If the type is already set + -- do not reanalyze, because a range with static bounds may be + -- typed Integer by default. + + if Nkind (Parent (N)) = N_Quantified_Expression + and then Present (Etype (DS)) + then + null; + else + Analyze (DS); + end if; + 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; + + Check_Predicate_Use (Entity (DS)); + 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); + + if Nkind (DS) = N_Subtype_Indication then + Check_Predicate_Use (Entity (Subtype_Mark (DS))); + end if; + + Make_Index (DS, N, In_Iter_Schm => True); + Set_Ekind (Id, E_Loop_Parameter); + + -- A quantified expression which appears in a pre- or post-condition may + -- be analyzed multiple times. The analysis of the range creates several + -- itypes which reside in different scopes depending on whether the pre- + -- or post-condition has been expanded. Update the type of the loop + -- variable to reflect the proper itype at each stage of analysis. + + if No (Etype (Id)) + or else Etype (Id) = Any_Type + or else + (Present (Etype (Id)) + and then Is_Itype (Etype (Id)) + and then Nkind (Parent (Loop_Nod)) = N_Expression_With_Actions + and then Nkind (Original_Node (Parent (Loop_Nod))) = + N_Quantified_Expression) + 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 loop variable must be + -- frozen explicitly. Do not freeze while preanalyzing a quantified + -- expression because the freeze node will not be inserted into the + -- tree due to flag Is_Spec_Expression being set. + + if Nkind (Parent (N)) /= N_Quantified_Expression then + declare + Flist : constant List_Id := Freeze_Entity (Id, N); + begin + if Is_Non_Empty_List (Flist) then + Insert_Actions (N, Flist); + end if; + end; + end if; + + -- Case where we have a range or a subtype, get type bounds + + if Nkind_In (DS, N_Range, N_Subtype_Indication) + and then not Error_Posted (DS) + and then Etype (DS) /= Any_Type + and then Is_Discrete_Type (Etype (DS)) + then + declare + L : Node_Id; + H : Node_Id; + + begin + if Nkind (DS) = N_Range then + L := Low_Bound (DS); + H := High_Bound (DS); + else + L := + Type_Low_Bound (Underlying_Type (Etype (Subtype_Mark (DS)))); + H := + Type_High_Bound (Underlying_Type (Etype (Subtype_Mark (DS)))); + end if; + + -- 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. The + -- check applies as well to rewritten array element loops where a + -- null range may be detected statically. + + 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 parameterization. + + 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 + -- 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 (Loop_Nod); + + if Comes_From_Source (N) then + Error_Msg_N + ("??loop range is null, loop will not execute", DS); + end if; + + -- 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. + + elsif Comes_From_Source (N) then + 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 (Loop_Nod); + + -- 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 may exceed this value. + + -- 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 (N) + 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 + -- Lower bound may in fact be known and known not to exceed + -- upper bound (e.g. reverse 0 .. 1) and that's OK. + + if Compile_Time_Known_Value (L) + and then Expr_Value (L) <= Expr_Value (H) + then + null; + + -- Otherwise warning is warranted + + else + Error_Msg_N ("??loop range may be null", DS); + Error_Msg_N ("\??bounds may be wrong way round", DS); + end if; + end if; + + -- Check if either bound is known to be outside the range of the + -- loop parameter type, this is e.g. the case of a loop from + -- 20..X where the type is 1..19. + + -- Such a loop is dubious since either it raises CE or it executes + -- zero times, and that cannot be useful! + + if Etype (DS) /= Any_Type + and then not Error_Posted (DS) + and then Nkind (DS) = N_Subtype_Indication + and then Nkind (Constraint (DS)) = N_Range_Constraint + then + declare + LLo : constant Node_Id := + Low_Bound (Range_Expression (Constraint (DS))); + LHi : constant Node_Id := + High_Bound (Range_Expression (Constraint (DS))); + + Bad_Bound : Node_Id := Empty; + -- Suspicious loop bound + + begin + -- At this stage L, H are the bounds of the type, and LLo + -- Lhi are the low bound and high bound of the loop. + + if Compile_Time_Compare (LLo, L, Assume_Valid => True) = LT + or else + Compile_Time_Compare (LLo, H, Assume_Valid => True) = GT + then + Bad_Bound := LLo; + end if; + + if Compile_Time_Compare (LHi, L, Assume_Valid => True) = LT + or else + Compile_Time_Compare (LHi, H, Assume_Valid => True) = GT + then + Bad_Bound := LHi; + end if; + + if Present (Bad_Bound) then + Error_Msg_N + ("suspicious loop bound out of range of " + & "loop subtype??", Bad_Bound); + Error_Msg_N + ("\loop executes zero times or raises " + & "Constraint_Error??", Bad_Bound); + end if; + end; + end if; + + -- This declare block is about warnings, if we get an exception while + -- testing for warnings, we simply abandon the attempt silently. This + -- most likely occurs as the result of a previous error, but might + -- just be an obscure case we have missed. In either case, not giving + -- the warning is perfectly acceptable. + + exception + when others => null; + end; + end if; + + -- A loop parameter cannot be effectively volatile (SPARK RM 7.1.3(4)). + -- This check is relevant only when SPARK_Mode is on as it is not a + -- standard Ada legality check. + + if SPARK_Mode = On and then Is_Effectively_Volatile (Id) then + Error_Msg_N ("loop parameter cannot be volatile", Id); + end if; + end Analyze_Loop_Parameter_Specification; + + ---------------------------- + -- 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 loop statement N has been wrapped in a block to + -- capture finalization actions that may be generated for container + -- iterators. Prevents infinite recursion when block is analyzed. + -- Routine is a noop if loop is single statement within source 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)); + Preanalyze_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)); + Preanalyze_Range (DS_Copy); + + -- Check for a call to Iterate () or an expression with + -- an iterator type. + + return + (Nkind (DS_Copy) = N_Function_Call + and then Needs_Finalization (Etype (DS_Copy))) + or else Is_Iterator (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 : Node_Id; + Stat : Node_Id; + + begin + + -- Check if current scope is a block that is not a transient block. + + if Ekind (Current_Scope) /= E_Block + or else No (Block_Node (Current_Scope)) + then + return False; + + else + HSS := + Handled_Statement_Sequence (Parent (Block_Node (Current_Scope))); + + -- Skip leading pragmas that may be introduced for invariant and + -- predicate checks. + + Stat := First (Statements (HSS)); + while Present (Stat) and then Nkind (Stat) = N_Pragma loop + Stat := Next (Stat); + end loop; + + return Stat = N and then No (Next (Stat)); + end if; + 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; + Stmt : Node_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; + + -- Verify that the loop name is hot hidden by an unrelated + -- declaration in an inner scope. + + elsif Ekind (Ent) /= E_Label and then Ekind (Ent) /= E_Loop then + Error_Msg_Sloc := Sloc (Ent); + Error_Msg_N ("implicit label declaration for & is hidden#", Id); + + if Present (Homonym (Ent)) + and then Ekind (Homonym (Ent)) = E_Label + then + Set_Entity (Id, Ent); + Set_Ekind (Ent, E_Loop); + 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. Create one and attach it to the + -- loop statement for use as a scope and as a reference for later + -- expansions. Indicate that the label does not come from source, + -- and attach it to the loop statement so it is part of the tree, + -- even without a full declaration. + + else + Ent := New_Internal_Entity (E_Loop, Current_Scope, Loc, 'L'); + Set_Etype (Ent, Standard_Void_Type); + Set_Identifier (N, New_Occurrence_Of (Ent, Loc)); + Set_Parent (Ent, N); + Set_Has_Created_Identifier (N); + end if; + + -- If the iterator specification has a syntactic error, transform + -- construct into an infinite loop to prevent a crash and perform + -- some analysis. + + if Present (Iter) + and then Present (Iterator_Specification (Iter)) + and then Error_Posted (Iterator_Specification (Iter)) + then + Set_Iteration_Scheme (N, Empty); + Analyze (N); + return; + 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. + -- The same applies to the use of secondary stack when obtaining an + -- iterator. + + if Ada_Version >= Ada_2012 + and then Is_Container_Iterator (Iter) + and then not Is_Wrapped_In_Block (N) + then + declare + Block_Nod : Node_Id; + Block_Id : Entity_Id; + + begin + Block_Nod := + Make_Block_Statement (Loc, + Declarations => New_List, + Handled_Statement_Sequence => + Make_Handled_Sequence_Of_Statements (Loc, + Statements => New_List (Relocate_Node (N)))); + + Add_Block_Identifier (Block_Nod, Block_Id); + + -- The expansion of iterator loops generates an iterator in order + -- to traverse the elements of a container: + + -- Iter : <iterator type> := Iterate (Container)'reference; + + -- The iterator is controlled and returned on the secondary stack. + -- The analysis of the call to Iterate establishes a transient + -- scope to deal with the secondary stack management, but never + -- really creates a physical block as this would kill the iterator + -- too early (see Wrap_Transient_Declaration). To address this + -- case, mark the generated block as needing secondary stack + -- management. + + Set_Uses_Sec_Stack (Block_Id); + + Rewrite (N, Block_Nod); + Analyze (N); + return; + end; + 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); + + -- Check for following case which merits a warning if the type E of is + -- a multi-dimensional array (and no explicit subscript ranges present). + + -- for J in E'Range + -- for K in E'Range + + if Present (Iter) + and then Present (Loop_Parameter_Specification (Iter)) + then + declare + LPS : constant Node_Id := Loop_Parameter_Specification (Iter); + DSD : constant Node_Id := + Original_Node (Discrete_Subtype_Definition (LPS)); + begin + if Nkind (DSD) = N_Attribute_Reference + and then Attribute_Name (DSD) = Name_Range + and then No (Expressions (DSD)) + then + declare + Typ : constant Entity_Id := Etype (Prefix (DSD)); + begin + if Is_Array_Type (Typ) + and then Number_Dimensions (Typ) > 1 + and then Nkind (Parent (N)) = N_Loop_Statement + and then Present (Iteration_Scheme (Parent (N))) + then + declare + OIter : constant Node_Id := + Iteration_Scheme (Parent (N)); + OLPS : constant Node_Id := + Loop_Parameter_Specification (OIter); + ODSD : constant Node_Id := + Original_Node (Discrete_Subtype_Definition (OLPS)); + begin + if Nkind (ODSD) = N_Attribute_Reference + and then Attribute_Name (ODSD) = Name_Range + and then No (Expressions (ODSD)) + and then Etype (Prefix (ODSD)) = Typ + then + Error_Msg_Sloc := Sloc (ODSD); + Error_Msg_N + ("inner range same as outer range#??", DSD); + end if; + end; + end if; + end; + end if; + end; + end if; + + -- 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. Set its kind properly to detect + -- improper uses in the loop body. + + -- In GNATprove mode, we do one of the above depending on the kind of + -- loop. If it is an iterator over an array, then we do not analyze the + -- loop now. We will analyze it after it has been rewritten by the + -- special SPARK expansion which is activated in GNATprove mode. We need + -- to do this so that other expansions that should occur in GNATprove + -- mode take into account the specificities of the rewritten loop, in + -- particular the introduction of a renaming (which needs to be + -- expanded). + + -- In other cases in GNATprove mode then we want to analyze the loop + -- body now, since no rewriting will occur. Within a generic the + -- GNATprove mode is irrelevant, we must analyze the generic for + -- non-local name capture. + + if Present (Iter) + and then Present (Iterator_Specification (Iter)) + then + if GNATprove_Mode + and then Is_Iterator_Over_Array (Iterator_Specification (Iter)) + and then not Inside_A_Generic + then + null; + + elsif not Expander_Active then + declare + I_Spec : constant Node_Id := Iterator_Specification (Iter); + Id : constant Entity_Id := Defining_Identifier (I_Spec); + + begin + if Scope (Id) /= Current_Scope then + Enter_Name (Id); + end if; + + -- In an element iterator, The loop parameter is a variable if + -- the domain of iteration (container or array) is a variable. + + if not Of_Present (I_Spec) + or else not Is_Variable (Name (I_Spec)) + then + Set_Ekind (Id, E_Loop_Parameter); + end if; + end; + + Analyze_Statements (Statements (N)); + end if; + + else + -- Pre-Ada2012 for-loops and while loops + + Analyze_Statements (Statements (N)); + end if; + + -- When the iteration scheme of a loop contains attribute 'Loop_Entry, + -- the loop is transformed into a conditional block. Retrieve the loop. + + Stmt := N; + + if Subject_To_Loop_Entry_Attributes (Stmt) then + Stmt := Find_Loop_In_Conditional_Block (Stmt); + 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 (Stmt, '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 (Stmt) then + Check_Infinite_Loop_Warning (Stmt); + 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 (Stmt); + 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_Target_Name -- + ------------------------- + + procedure Analyze_Target_Name (N : Node_Id) is + begin + -- A target name has the type of the left-hand side of the enclosing + -- assignment. + + Set_Etype (N, Etype (Name (Current_Assignment))); + end Analyze_Target_Name; + + ------------------------ + -- Analyze_Statements -- + ------------------------ + + procedure Analyze_Statements (L : List_Id) is + Lab : Entity_Id; + S : Node_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)); + + -- Skip past pragmas + + while Nkind (Nxt) = N_Pragma loop + Nxt := Original_Node (Next (Nxt)); + end loop; + + -- 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_05) + 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 + -- or CodePeer 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 or loses useful + -- information in the CodePeer tree. + + -- 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 + and then not CodePeer_Mode + 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_05) then + Check_SPARK_05_Restriction + ("unreachable code is not allowed", Error_Node); + else + Error_Msg + ("??unreachable code!", Sloc (Error_Node), 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 + -- The original loop is now placed inside a block statement + -- due to the expansion of attribute 'Loop_Entry. Return as + -- this is not a "real" block for the purposes of exit + -- counting. + + if Nkind (N) = N_Loop_Statement + and then Subject_To_Loop_Entry_Attributes (N) + then + return; + end if; + + -- 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; + + ---------------------- + -- Preanalyze_Range -- + ---------------------- + + procedure Preanalyze_Range (R_Copy : Node_Id) is + Save_Analysis : constant Boolean := Full_Analysis; + Typ : Entity_Id; + + 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 + -- check for array or iterable construct for "of" iterator, 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; + + elsif Nkind (Parent (R_Copy)) = N_Iterator_Specification + and then Of_Present (Parent (R_Copy)) + then + if Is_Array_Type (It.Typ) + or else Has_Aspect (It.Typ, Aspect_Iterator_Element) + or else Has_Aspect (It.Typ, Aspect_Constant_Indexing) + or else Has_Aspect (It.Typ, Aspect_Variable_Indexing) + then + if No (Found) then + Found := It.Typ; + Set_Etype (R_Copy, It.Typ); + + else + Error_Msg_N ("ambiguous domain of iteration", R_Copy); + 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); + Typ := Etype (R_Copy); + + if Is_Discrete_Type (Typ) then + null; + + -- Check that the resulting object is an iterable container + + elsif Has_Aspect (Typ, Aspect_Iterator_Element) + or else Has_Aspect (Typ, Aspect_Constant_Indexing) + or else Has_Aspect (Typ, Aspect_Variable_Indexing) + then + null; + + -- The expression may yield an implicit reference to an iterable + -- container. Insert explicit dereference so that proper type is + -- visible in the loop. + + elsif Has_Implicit_Dereference (Etype (R_Copy)) then + declare + Disc : Entity_Id; + + begin + Disc := First_Discriminant (Typ); + while Present (Disc) loop + if Has_Implicit_Dereference (Disc) then + Build_Explicit_Dereference (R_Copy, Disc); + exit; + end if; + + Next_Discriminant (Disc); + end loop; + end; + + end if; + end if; + + Expander_Mode_Restore; + Full_Analysis := Save_Analysis; + end Preanalyze_Range; + +end Sem_Ch5;