------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- S E M _ W A R N -- -- -- -- B o d y -- -- -- -- Copyright (C) 1999-2004 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 2, 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 COPYING. If not, write -- -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, -- -- MA 02111-1307, USA. -- -- -- -- GNAT was originally developed by the GNAT team at New York University. -- -- Extensive contributions were provided by Ada Core Technologies Inc. -- -- -- ------------------------------------------------------------------------------ with Alloc; with Atree; use Atree; with Einfo; use Einfo; with Errout; use Errout; with Fname; use Fname; with Lib; use Lib; with Nlists; use Nlists; with Opt; use Opt; with Sem; use Sem; with Sem_Ch8; use Sem_Ch8; with Sem_Util; use Sem_Util; with Sinfo; use Sinfo; with Sinput; use Sinput; with Snames; use Snames; with Stand; use Stand; with Table; package body Sem_Warn is -- The following table collects Id's of entities that are potentially -- unreferenced. See Check_Unset_Reference for further details. package Unreferenced_Entities is new Table.Table ( Table_Component_Type => Entity_Id, Table_Index_Type => Nat, Table_Low_Bound => 1, Table_Initial => Alloc.Unreferenced_Entities_Initial, Table_Increment => Alloc.Unreferenced_Entities_Increment, Table_Name => "Unreferenced_Entities"); ------------------------------ -- Handling of Conditionals -- ------------------------------ -- Note: this is work in progress, the data structures and general -- approach are defined, but are not in use yet. ??? -- One entry is made in the following table for each branch of -- a conditional, e.g. an if-then-elsif-else-endif structure -- creates three entries in this table. type Branch_Entry is record Sloc : Source_Ptr; -- Location for warnings associated with this branch Defs : Elist_Id; -- List of entities defined for the first time in this branch. On -- exit from a conditional structure, any entity that is in the -- list of all branches is removed (and the entity flagged as -- defined by the conditional as a whole). Thus after processing -- a conditional, Defs contains a list of entities defined in this -- branch for the first time, but not defined at all in some other -- branch of the same conditional. A value of No_Elist is used to -- represent the initial empty list. Next : Nat; -- Index of next branch for this conditional, zero = last branch end record; package Branch_Table is new Table.Table ( Table_Component_Type => Branch_Entry, Table_Index_Type => Nat, Table_Low_Bound => 1, Table_Initial => Alloc.Branches_Initial, Table_Increment => Alloc.Branches_Increment, Table_Name => "Branches"); -- The following table is used to represent conditionals, there is -- one entry in this table for each conditional structure. type Conditional_Entry is record If_Stmt : Boolean; -- True for IF statement, False for CASE statement First_Branch : Nat; -- Index in Branch table of first branch, zero = none yet Current_Branch : Nat; -- Index in Branch table of current branch, zero = none yet end record; package Conditional_Table is new Table.Table ( Table_Component_Type => Conditional_Entry, Table_Index_Type => Nat, Table_Low_Bound => 1, Table_Initial => Alloc.Conditionals_Initial, Table_Increment => Alloc.Conditionals_Increment, Table_Name => "Conditionals"); -- The following table is a stack that keeps track of the current -- conditional. The Last entry is the top of the stack. An Empty -- entry represents the start of a compilation unit. Non-zero -- entries in the stack are indexes into the conditional table. package Conditional_Stack is new Table.Table ( Table_Component_Type => Nat, Table_Index_Type => Nat, Table_Low_Bound => 1, Table_Initial => Alloc.Conditional_Stack_Initial, Table_Increment => Alloc.Conditional_Stack_Increment, Table_Name => "Conditional_Stack"); pragma Warnings (Off, Branch_Table); pragma Warnings (Off, Conditional_Table); pragma Warnings (Off, Conditional_Stack); -- Not yet referenced, see note above ??? ----------------------- -- Local Subprograms -- ----------------------- function Generic_Package_Spec_Entity (E : Entity_Id) return Boolean; -- This returns true if the entity E is declared within a generic package. -- The point of this is to detect variables which are not assigned within -- the generic, but might be assigned outside the package for any given -- instance. These are cases where we leave the warnings to be posted -- for the instance, when we will know more. function Operand_Has_Warnings_Suppressed (N : Node_Id) return Boolean; -- This function traverses the expression tree represented by the node -- N and determines if any sub-operand is a reference to an entity for -- which the Warnings_Off flag is set. True is returned if such an -- entity is encountered, and False otherwise. ---------------------- -- Check_References -- ---------------------- procedure Check_References (E : Entity_Id; Anod : Node_Id := Empty) is E1 : Entity_Id; UR : Node_Id; function Missing_Subunits return Boolean; -- We suppress warnings when there are missing subunits, because this -- may generate too many false positives: entities in a parent may -- only be referenced in one of the subunits. We make an exception -- for subunits that contain no other stubs. procedure Output_Reference_Error (M : String); -- Used to output an error message. Deals with posting the error on -- the body formal in the accept case. function Publicly_Referenceable (Ent : Entity_Id) return Boolean; -- This is true if the entity in question is potentially referenceable -- from another unit. This is true for entities in packages that are -- at the library level. ---------------------- -- Missing_Subunits -- ---------------------- function Missing_Subunits return Boolean is D : Node_Id; begin if not Unloaded_Subunits then -- Normal compilation, all subunits are present return False; elsif E /= Main_Unit_Entity then -- No warnings on a stub that is not the main unit return True; elsif Nkind (Unit_Declaration_Node (E)) in N_Proper_Body then D := First (Declarations (Unit_Declaration_Node (E))); while Present (D) loop -- No warnings if the proper body contains nested stubs if Nkind (D) in N_Body_Stub then return True; end if; Next (D); end loop; return False; else -- Missing stubs elsewhere return True; end if; end Missing_Subunits; ---------------------------- -- Output_Reference_Error -- ---------------------------- procedure Output_Reference_Error (M : String) is begin -- Other than accept case, post error on defining identifier if No (Anod) then Error_Msg_N (M, E1); -- Accept case, find body formal to post the message else declare Parm : Node_Id; Enod : Node_Id; Defid : Entity_Id; begin Enod := Anod; if Present (Parameter_Specifications (Anod)) then Parm := First (Parameter_Specifications (Anod)); while Present (Parm) loop Defid := Defining_Identifier (Parm); if Chars (E1) = Chars (Defid) then Enod := Defid; exit; end if; Next (Parm); end loop; end if; Error_Msg_NE (M, Enod, E1); end; end if; end Output_Reference_Error; ---------------------------- -- Publicly_Referenceable -- ---------------------------- function Publicly_Referenceable (Ent : Entity_Id) return Boolean is P : Node_Id; Prev : Node_Id; begin -- Examine parents to look for a library level package spec -- But if we find a body or block or other similar construct -- along the way, we cannot be referenced. Prev := Ent; P := Parent (Ent); loop case Nkind (P) is -- If we get to top of tree, then publicly referenceable when N_Empty => return True; -- If we reach a generic package declaration, then always -- consider this referenceable, since any instantiation will -- have access to the entities in the generic package. Note -- that the package itself may not be instantiated, but then -- we will get a warning for the package entity -- Note that generic formal parameters are themselves not -- publicly referenceable in an instance, and warnings on -- them are useful. when N_Generic_Package_Declaration => return not Is_List_Member (Prev) or else List_Containing (Prev) /= Generic_Formal_Declarations (P); -- if we reach a subprogram body, entity is not referenceable -- unless it is the defining entity of the body. This will -- happen, e.g. when a function is an attribute renaming that -- is rewritten as a body. when N_Subprogram_Body => if Ent /= Defining_Entity (P) then return False; else P := Parent (P); end if; -- If we reach any other body, definitely not referenceable when N_Package_Body | N_Task_Body | N_Entry_Body | N_Protected_Body | N_Block_Statement | N_Subunit => return False; -- For all other cases, keep looking up tree when others => Prev := P; P := Parent (P); end case; end loop; end Publicly_Referenceable; -- Start of processing for Check_References begin -- No messages if warnings are suppressed, or if we have detected -- any real errors so far (this last check avoids junk messages -- resulting from errors, e.g. a subunit that is not loaded). if Warning_Mode = Suppress or else Serious_Errors_Detected /= 0 then return; end if; -- We also skip the messages if any subunits were not loaded (see -- comment in Sem_Ch10 to understand how this is set, and why it is -- necessary to suppress the warnings in this case). if Missing_Subunits then return; end if; -- Otherwise loop through entities, looking for suspicious stuff E1 := First_Entity (E); while Present (E1) loop -- We only look at source entities with warning flag on if Comes_From_Source (E1) and then not Warnings_Off (E1) then -- We are interested in variables and out parameters, but we -- exclude protected types, too complicated to worry about. if Ekind (E1) = E_Variable or else (Ekind (E1) = E_Out_Parameter and then not Is_Protected_Type (Current_Scope)) then -- Post warning if this object not assigned. Note that we -- do not consider the implicit initialization of an access -- type to be the assignment of a value for this purpose. if Ekind (E1) = E_Out_Parameter and then Present (Spec_Entity (E1)) then UR := Unset_Reference (Spec_Entity (E1)); else UR := Unset_Reference (E1); end if; -- If the entity is an out parameter of the current subprogram -- body, check the warning status of the parameter in the spec. if Ekind (E1) = E_Out_Parameter and then Present (Spec_Entity (E1)) and then Warnings_Off (Spec_Entity (E1)) then null; elsif Present (UR) and then Is_Access_Type (Etype (E1)) then -- For access types, the only time we made a UR -- entry was for a dereference, and so we post -- the appropriate warning here (note that the -- dereference may not be explicit in the source, -- for example in the case of a dispatching call -- with an anonymous access controlling formal, or -- of an assignment of a pointer involving a -- discriminant check on the designated object). Error_Msg_NE ("& may be null?", UR, E1); goto Continue; elsif Never_Set_In_Source (E1) and then not Generic_Package_Spec_Entity (E1) then if Warn_On_No_Value_Assigned then -- Do not output complaint about never being assigned a -- value if a pragma Unreferenced applies to the variable -- or if it is a parameter, to the corresponding spec. if Has_Pragma_Unreferenced (E1) or else (Is_Formal (E1) and then Present (Spec_Entity (E1)) and then Has_Pragma_Unreferenced (Spec_Entity (E1))) then null; -- Pragma Unreferenced not set, so output message else Output_Reference_Error ("& is never assigned a value?"); -- Deal with special case where this variable is -- hidden by a loop variable if Ekind (E1) = E_Variable and then Present (Hiding_Loop_Variable (E1)) then Error_Msg_Sloc := Sloc (E1); Error_Msg_N ("declaration hides &#?", Hiding_Loop_Variable (E1)); Error_Msg_N ("for loop implicitly declares loop variable?", Hiding_Loop_Variable (E1)); end if; end if; end if; goto Continue; -- Case of variable that could be a constant. Note that we -- never signal such messages for generic package entities, -- since a given instance could have modifications outside -- the package. elsif Warn_On_Constant and then Ekind (E1) = E_Variable and then Is_True_Constant (E1) and then not Generic_Package_Spec_Entity (E1) then Error_Msg_N ("& is not modified, could be declared constant?", E1); end if; -- Check for unset reference, note that we exclude access -- types from this check, since access types do always have -- a null value, and that seems legitimate in this case. if Warn_On_No_Value_Assigned and then Present (UR) then -- For other than access type, go back to original node -- to deal with case where original unset reference -- has been rewritten during expansion. UR := Original_Node (UR); -- In some cases, the original node may be a type -- conversion or qualification, and in this case -- we want the object entity inside. while Nkind (UR) = N_Type_Conversion or else Nkind (UR) = N_Qualified_Expression loop UR := Expression (UR); end loop; -- Here we issue the warning, all checks completed -- If the unset reference is prefix of a selected -- component that comes from source, mention the -- component as well. If the selected component comes -- from expansion, all we know is that the entity is -- not fully initialized at the point of the reference. -- Locate an unintialized component to get a better -- error message. if Nkind (Parent (UR)) = N_Selected_Component then Error_Msg_Node_2 := Selector_Name (Parent (UR)); if not Comes_From_Source (Parent (UR)) then declare Comp : Entity_Id; begin Comp := First_Entity (Etype (E1)); while Present (Comp) loop if Ekind (Comp) = E_Component and then Nkind (Parent (Comp)) = N_Component_Declaration and then No (Expression (Parent (Comp))) then Error_Msg_Node_2 := Comp; exit; end if; Next_Entity (Comp); end loop; end; end if; Error_Msg_N ("`&.&` may be referenced before it has a value?", UR); else Error_Msg_N ("& may be referenced before it has a value?", UR); end if; goto Continue; end if; end if; -- Then check for unreferenced entities. Note that we are only -- interested in entities which do not have the Referenced flag -- set. The Referenced_As_LHS flag is interesting only if the -- Referenced flag is not set. if not Referenced (E1) -- Check that warnings on unreferenced entities are enabled and then ((Check_Unreferenced and then not Is_Formal (E1)) or else (Check_Unreferenced_Formals and then Is_Formal (E1)) or else (Warn_On_Modified_Unread and then Referenced_As_LHS (E1))) -- Labels, and enumeration literals, and exceptions. The -- warnings are also placed on local packages that cannot -- be referenced from elsewhere, including those declared -- within a package body. and then (Is_Object (E1) or else Is_Type (E1) or else Ekind (E1) = E_Label or else Ekind (E1) = E_Exception or else Ekind (E1) = E_Named_Integer or else Ekind (E1) = E_Named_Real or else Is_Overloadable (E1) or else (Ekind (E1) = E_Package and then (Ekind (E) = E_Function or else Ekind (E) = E_Package_Body or else Ekind (E) = E_Procedure or else Ekind (E) = E_Subprogram_Body or else Ekind (E) = E_Block))) -- Exclude instantiations, since there is no reason why -- every entity in an instantiation should be referenced. and then Instantiation_Location (Sloc (E1)) = No_Location -- Exclude formal parameters from bodies if the corresponding -- spec entity has been referenced in the case where there is -- a separate spec. and then not (Is_Formal (E1) and then Ekind (Scope (E1)) = E_Subprogram_Body and then Present (Spec_Entity (E1)) and then Referenced (Spec_Entity (E1))) -- Consider private type referenced if full view is referenced -- If there is not full view, this is a generic type on which -- warnings are also useful. and then not (Is_Private_Type (E1) and then Present (Full_View (E1)) and then Referenced (Full_View (E1))) -- Don't worry about full view, only about private type and then not Has_Private_Declaration (E1) -- Eliminate dispatching operations from consideration, we -- cannot tell if these are referenced or not in any easy -- manner (note this also catches Adjust/Finalize/Initialize) and then not Is_Dispatching_Operation (E1) -- Check entity that can be publicly referenced (we do not -- give messages for such entities, since there could be -- other units, not involved in this compilation, that -- contain relevant references. and then not Publicly_Referenceable (E1) -- Class wide types are marked as source entities, but -- they are not really source entities, and are always -- created, so we do not care if they are not referenced. and then Ekind (E1) /= E_Class_Wide_Type -- Objects other than parameters of task types are allowed -- to be non-referenced, since they start up tasks! and then ((Ekind (E1) /= E_Variable and then Ekind (E1) /= E_Constant and then Ekind (E1) /= E_Component) or else not Is_Task_Type (Etype (E1))) -- For subunits, only place warnings on the main unit -- itself, since parent units are not completely compiled and then (Nkind (Unit (Cunit (Main_Unit))) /= N_Subunit or else Get_Source_Unit (E1) = Main_Unit) then -- Suppress warnings in internal units if not in -gnatg -- mode (these would be junk warnings for an applications -- program, since they refer to problems in internal units) if GNAT_Mode or else not Is_Internal_File_Name (Unit_File_Name (Get_Source_Unit (E1))) then -- We do not immediately flag the error. This is because -- we have not expanded generic bodies yet, and they may -- have the missing reference. So instead we park the -- entity on a list, for later processing. However, for -- the accept case, post the error right here, since we -- have the information now in this case. if Present (Anod) then Output_Reference_Error ("& is not referenced?"); else Unreferenced_Entities.Increment_Last; Unreferenced_Entities.Table (Unreferenced_Entities.Last) := E1; end if; end if; -- Generic units are referenced in the generic body, -- but if they are not public and never instantiated -- we want to force a warning on them. We treat them -- as redundant constructs to minimize noise. elsif Is_Generic_Subprogram (E1) and then not Is_Instantiated (E1) and then not Publicly_Referenceable (E1) and then Instantiation_Depth (Sloc (E1)) = 0 and then Warn_On_Redundant_Constructs then Unreferenced_Entities.Increment_Last; Unreferenced_Entities.Table (Unreferenced_Entities.Last) := E1; -- Force warning on entity Set_Referenced (E1, False); end if; end if; -- Recurse into nested package or block. Do not recurse into a -- formal package, because the correponding body is not analyzed. <<Continue>> if ((Ekind (E1) = E_Package or else Ekind (E1) = E_Generic_Package) and then Nkind (Parent (E1)) = N_Package_Specification and then Nkind (Original_Node (Unit_Declaration_Node (E1))) /= N_Formal_Package_Declaration) or else Ekind (E1) = E_Block then Check_References (E1); end if; Next_Entity (E1); end loop; end Check_References; --------------------------- -- Check_Unset_Reference -- --------------------------- procedure Check_Unset_Reference (N : Node_Id) is begin -- Nothing to do if warnings suppressed if Warning_Mode = Suppress then return; end if; -- Ignore reference to non-scalar if not from source. Almost always -- such references are bogus (e.g. calls to init procs to set -- default discriminant values). if not Comes_From_Source (N) and then not Is_Scalar_Type (Etype (N)) then return; end if; -- Otherwise see what kind of node we have. If the entity already -- has an unset reference, it is not necessarily the earliest in -- the text, because resolution of the prefix of selected components -- is completed before the resolution of the selected component itself. -- as a result, given (R /= null and then R.X > 0), the occurrences -- of R are examined in right-to-left order. If there is already an -- unset reference, we check whether N is earlier before proceeding. case Nkind (N) is when N_Identifier | N_Expanded_Name => declare E : constant Entity_Id := Entity (N); begin if (Ekind (E) = E_Variable or else Ekind (E) = E_Out_Parameter) and then Never_Set_In_Source (E) and then (No (Unset_Reference (E)) or else Earlier_In_Extended_Unit (Sloc (N), Sloc (Unset_Reference (E)))) and then not Warnings_Off (E) then -- We may have an unset reference. The first test is -- whether we are accessing a discriminant of a record -- or a component with default initialization. Both of -- these cases can be ignored, since the actual object -- that is referenced is definitely initialized. Note -- that this covers the case of reading discriminants -- of an out parameter, which is OK even in Ada 83. -- Note that we are only interested in a direct reference -- to a record component here. If the reference is via an -- access type, then the access object is being referenced, -- not the record, and still deserves an unset reference. if Nkind (Parent (N)) = N_Selected_Component and not Is_Access_Type (Etype (N)) then declare ES : constant Entity_Id := Entity (Selector_Name (Parent (N))); begin if Ekind (ES) = E_Discriminant or else Present (Expression (Declaration_Node (ES))) then return; end if; end; end if; -- Here we have a potential unset reference. But before we -- get worried about it, we have to make sure that the -- entity declaration is in the same procedure as the -- reference, since if they are in separate procedures, -- then we have no idea about sequential execution. -- The tests in the loop below catch all such cases, but -- do allow the reference to appear in a loop, block, or -- package spec that is nested within the declaring scope. -- As always, it is possible to construct cases where the -- warning is wrong, that is why it is a warning! declare SR : Entity_Id; SE : constant Entity_Id := Scope (E); begin SR := Current_Scope; while SR /= SE loop if SR = Standard_Standard or else Is_Subprogram (SR) or else Is_Concurrent_Body (SR) or else Is_Concurrent_Type (SR) then return; end if; SR := Scope (SR); end loop; -- Case of reference has an access type. This is a -- special case since access types are always set to -- null so cannot be truly uninitialized, but we still -- want to warn about cases of obvious null dereference. if Is_Access_Type (Etype (N)) then declare P : Node_Id; function Process (N : Node_Id) return Traverse_Result; -- Process function for instantation of Traverse -- below. Checks if N contains reference to E -- other than a dereference. function Ref_In (Nod : Node_Id) return Boolean; -- Determines whether Nod contains a reference -- to the entity E that is not a dereference. function Process (N : Node_Id) return Traverse_Result is begin if Is_Entity_Name (N) and then Entity (N) = E and then not Is_Dereferenced (N) then return Abandon; else return OK; end if; end Process; function Ref_In (Nod : Node_Id) return Boolean is function Traverse is new Traverse_Func (Process); begin return Traverse (Nod) = Abandon; end Ref_In; begin -- Don't bother if we are inside an instance, -- since the compilation of the generic template -- is where the warning should be issued. if In_Instance then return; end if; -- Don't bother if this is not the main unit. -- If we try to give this warning for with'ed -- units, we get some false positives, since -- we do not record references in other units. if not In_Extended_Main_Source_Unit (E) or else not In_Extended_Main_Source_Unit (N) then return; end if; -- We are only interested in deferences if not Is_Dereferenced (N) then return; end if; -- One more check, don't bother with references -- that are inside conditional statements or while -- loops if the condition references the entity in -- question. This avoids most false positives. P := Parent (N); loop P := Parent (P); exit when No (P); if (Nkind (P) = N_If_Statement or else Nkind (P) = N_Elsif_Part) and then Ref_In (Condition (P)) then return; elsif Nkind (P) = N_Loop_Statement and then Present (Iteration_Scheme (P)) and then Ref_In (Condition (Iteration_Scheme (P))) then return; end if; end loop; end; end if; -- Here we definitely have a case for giving a warning -- for a reference to an unset value. But we don't give -- the warning now. Instead we set the Unset_Reference -- field of the identifier involved. The reason for this -- is that if we find the variable is never ever assigned -- a value then that warning is more important and there -- is no point in giving the reference warning. -- If this is an identifier, set the field directly if Nkind (N) = N_Identifier then Set_Unset_Reference (E, N); -- Otherwise it is an expanded name, so set the field -- of the actual identifier for the reference. else Set_Unset_Reference (E, Selector_Name (N)); end if; end; end if; end; when N_Indexed_Component | N_Slice => Check_Unset_Reference (Prefix (N)); when N_Selected_Component => if Present (Entity (Selector_Name (N))) and then Ekind (Entity (Selector_Name (N))) = E_Discriminant then -- A discriminant is always initialized null; else Check_Unset_Reference (Prefix (N)); end if; when N_Type_Conversion | N_Qualified_Expression => Check_Unset_Reference (Expression (N)); when others => null; end case; end Check_Unset_Reference; ------------------------ -- Check_Unused_Withs -- ------------------------ procedure Check_Unused_Withs (Spec_Unit : Unit_Number_Type := No_Unit) is Cnode : Node_Id; Item : Node_Id; Lunit : Node_Id; Ent : Entity_Id; Munite : constant Entity_Id := Cunit_Entity (Main_Unit); -- This is needed for checking the special renaming case procedure Check_One_Unit (Unit : Unit_Number_Type); -- Subsidiary procedure, performs checks for specified unit -------------------- -- Check_One_Unit -- -------------------- procedure Check_One_Unit (Unit : Unit_Number_Type) is Is_Visible_Renaming : Boolean := False; Pack : Entity_Id; procedure Check_Inner_Package (Pack : Entity_Id); -- Pack is a package local to a unit in a with_clause. Both the -- unit and Pack are referenced. If none of the entities in Pack -- are referenced, then the only occurrence of Pack is in a use -- clause or a pragma, and a warning is worthwhile as well. function Check_System_Aux return Boolean; -- Before giving a warning on a with_clause for System, check -- whether a system extension is present. function Find_Package_Renaming (P : Entity_Id; L : Entity_Id) return Entity_Id; -- The only reference to a context unit may be in a renaming -- declaration. If this renaming declares a visible entity, do -- not warn that the context clause could be moved to the body, -- because the renaming may be intented to re-export the unit. ------------------------- -- Check_Inner_Package -- ------------------------- procedure Check_Inner_Package (Pack : Entity_Id) is E : Entity_Id; Un : constant Node_Id := Sinfo.Unit (Cnode); function Check_Use_Clause (N : Node_Id) return Traverse_Result; -- If N is a use_clause for Pack, emit warning procedure Check_Use_Clauses is new Traverse_Proc (Check_Use_Clause); ---------------------- -- Check_Use_Clause -- ---------------------- function Check_Use_Clause (N : Node_Id) return Traverse_Result is Nam : Node_Id; begin if Nkind (N) = N_Use_Package_Clause then Nam := First (Names (N)); while Present (Nam) loop if Entity (Nam) = Pack then Error_Msg_Qual_Level := 1; Error_Msg_NE ("no entities of package& are referenced?", Nam, Pack); Error_Msg_Qual_Level := 0; end if; Next (Nam); end loop; end if; return OK; end Check_Use_Clause; -- Start of processing for Check_Inner_Package begin E := First_Entity (Pack); while Present (E) loop if Referenced (E) then return; end if; Next_Entity (E); end loop; -- No entities of the package are referenced. Check whether -- the reference to the package itself is a use clause, and -- if so place a warning on it. Check_Use_Clauses (Un); end Check_Inner_Package; ---------------------- -- Check_System_Aux -- ---------------------- function Check_System_Aux return Boolean is Ent : Entity_Id; begin if Chars (Lunit) = Name_System and then Scope (Lunit) = Standard_Standard and then Present_System_Aux then Ent := First_Entity (System_Aux_Id); while Present (Ent) loop if Referenced (Ent) then return True; end if; Next_Entity (Ent); end loop; end if; return False; end Check_System_Aux; --------------------------- -- Find_Package_Renaming -- --------------------------- function Find_Package_Renaming (P : Entity_Id; L : Entity_Id) return Entity_Id is E1 : Entity_Id; R : Entity_Id; begin Is_Visible_Renaming := False; E1 := First_Entity (P); while Present (E1) loop if Ekind (E1) = E_Package and then Renamed_Object (E1) = L then Is_Visible_Renaming := not Is_Hidden (E1); return E1; elsif Ekind (E1) = E_Package and then No (Renamed_Object (E1)) and then not Is_Generic_Instance (E1) then R := Find_Package_Renaming (E1, L); if Present (R) then Is_Visible_Renaming := not Is_Hidden (R); return R; end if; end if; Next_Entity (E1); end loop; return Empty; end Find_Package_Renaming; -- Start of processing for Check_One_Unit begin Cnode := Cunit (Unit); -- Only do check in units that are part of the extended main -- unit. This is actually a necessary restriction, because in -- the case of subprogram acting as its own specification, -- there can be with's in subunits that we will not see. if not In_Extended_Main_Source_Unit (Cnode) then return; -- In configurable run time mode, we remove the bodies of -- non-inlined subprograms, which may lead to spurious warnings, -- which are clearly undesirable. elsif Configurable_Run_Time_Mode and then Is_Predefined_File_Name (Unit_File_Name (Unit)) then return; end if; -- Loop through context items in this unit Item := First (Context_Items (Cnode)); while Present (Item) loop if Nkind (Item) = N_With_Clause and then not Implicit_With (Item) and then In_Extended_Main_Source_Unit (Item) then Lunit := Entity (Name (Item)); -- Check if this unit is referenced if not Referenced (Lunit) then -- Suppress warnings in internal units if not in -gnatg -- mode (these would be junk warnings for an applications -- program, since they refer to problems in internal units) if GNAT_Mode or else not Is_Internal_File_Name (Unit_File_Name (Unit)) then -- Here we definitely have a non-referenced unit. If -- it is the special call for a spec unit, then just -- set the flag to be read later. if Unit = Spec_Unit then Set_Unreferenced_In_Spec (Item); -- Otherwise simple unreferenced message else Error_Msg_N ("unit& is not referenced?", Name (Item)); end if; end if; -- If main unit is a renaming of this unit, then we consider -- the with to be OK (obviously it is needed in this case!) elsif Present (Renamed_Entity (Munite)) and then Renamed_Entity (Munite) = Lunit then null; -- If this unit is referenced, and it is a package, we -- do another test, to see if any of the entities in the -- package are referenced. If none of the entities are -- referenced, we still post a warning. This occurs if -- the only use of the package is in a use clause, or -- in a package renaming declaration. elsif Ekind (Lunit) = E_Package then -- If Is_Instantiated is set, it means that the package -- is implicitly instantiated (this is the case of a -- parent instance or an actual for a generic package -- formal), and this counts as a reference. if Is_Instantiated (Lunit) then null; -- If no entities in package, and there is a pragma -- Elaborate_Body present, then assume that this with -- is done for purposes of this elaboration. elsif No (First_Entity (Lunit)) and then Has_Pragma_Elaborate_Body (Lunit) then null; -- Otherwise see if any entities have been referenced else Ent := First_Entity (Lunit); loop -- No more entities, and we did not find one -- that was referenced. Means we have a definite -- case of a with none of whose entities was -- referenced. if No (Ent) then -- If in spec, just set the flag if Unit = Spec_Unit then Set_No_Entities_Ref_In_Spec (Item); elsif Check_System_Aux then null; -- Else give the warning else Error_Msg_N ("no entities of & are referenced?", Name (Item)); -- Look for renamings of this package, and -- flag them as well. If the original package -- has warnings off, we suppress the warning -- on the renaming as well. Pack := Find_Package_Renaming (Munite, Lunit); if Present (Pack) and then not Warnings_Off (Lunit) then Error_Msg_NE ("no entities of & are referenced?", Unit_Declaration_Node (Pack), Pack); end if; end if; exit; -- Case of next entity is referenced elsif Referenced (Ent) or else Referenced_As_LHS (Ent) then -- This means that the with is indeed fine, in -- that it is definitely needed somewhere, and -- we can quite worrying about this one. -- Except for one little detail, if either of -- the flags was set during spec processing, -- this is where we complain that the with -- could be moved from the spec. If the spec -- contains a visible renaming of the package, -- inhibit warning to move with_clause to body. if Ekind (Munite) = E_Package_Body then Pack := Find_Package_Renaming (Spec_Entity (Munite), Lunit); end if; if Unreferenced_In_Spec (Item) then Error_Msg_N ("unit& is not referenced in spec?", Name (Item)); elsif No_Entities_Ref_In_Spec (Item) then Error_Msg_N ("no entities of & are referenced in spec?", Name (Item)); else if Ekind (Ent) = E_Package then Check_Inner_Package (Ent); end if; exit; end if; if not Is_Visible_Renaming then Error_Msg_N ("\with clause might be moved to body?", Name (Item)); end if; exit; -- Move to next entity to continue search else Next_Entity (Ent); end if; end loop; end if; -- For a generic package, the only interesting kind of -- reference is an instantiation, since entities cannot -- be referenced directly. elsif Is_Generic_Unit (Lunit) then -- Unit was never instantiated, set flag for case of spec -- call, or give warning for normal call. if not Is_Instantiated (Lunit) then if Unit = Spec_Unit then Set_Unreferenced_In_Spec (Item); else Error_Msg_N ("unit& is never instantiated?", Name (Item)); end if; -- If unit was indeed instantiated, make sure that -- flag is not set showing it was uninstantiated in -- the spec, and if so, give warning. elsif Unreferenced_In_Spec (Item) then Error_Msg_N ("unit& is not instantiated in spec?", Name (Item)); Error_Msg_N ("\with clause can be moved to body?", Name (Item)); end if; end if; end if; Next (Item); end loop; end Check_One_Unit; -- Start of processing for Check_Unused_Withs begin if not Opt.Check_Withs or else Operating_Mode = Check_Syntax then return; end if; -- Flag any unused with clauses, but skip this step if we are -- compiling a subunit on its own, since we do not have enough -- information to determine whether with's are used. We will get -- the relevant warnings when we compile the parent. This is the -- normal style of GNAT compilation in any case. if Nkind (Unit (Cunit (Main_Unit))) = N_Subunit then return; end if; -- Process specified units if Spec_Unit = No_Unit then -- For main call, check all units for Unit in Main_Unit .. Last_Unit loop Check_One_Unit (Unit); end loop; else -- For call for spec, check only the spec Check_One_Unit (Spec_Unit); end if; end Check_Unused_Withs; --------------------------------- -- Generic_Package_Spec_Entity -- --------------------------------- function Generic_Package_Spec_Entity (E : Entity_Id) return Boolean is S : Entity_Id; begin if Is_Package_Body_Entity (E) then return False; else S := Scope (E); loop if S = Standard_Standard then return False; elsif Ekind (S) = E_Generic_Package then return True; elsif Ekind (S) = E_Package then S := Scope (S); else return False; end if; end loop; end if; end Generic_Package_Spec_Entity; ------------------------------------- -- Operand_Has_Warnings_Suppressed -- ------------------------------------- function Operand_Has_Warnings_Suppressed (N : Node_Id) return Boolean is function Check_For_Warnings (N : Node_Id) return Traverse_Result; -- Function used to check one node to see if it is or was originally -- a reference to an entity for which Warnings are off. If so, Abandon -- is returned, otherwise OK_Orig is returned to continue the traversal -- of the original expression. function Traverse is new Traverse_Func (Check_For_Warnings); -- Function used to traverse tree looking for warnings ------------------------ -- Check_For_Warnings -- ------------------------ function Check_For_Warnings (N : Node_Id) return Traverse_Result is R : constant Node_Id := Original_Node (N); begin if Nkind (R) in N_Has_Entity and then Present (Entity (R)) and then Warnings_Off (Entity (R)) then return Abandon; else return OK_Orig; end if; end Check_For_Warnings; -- Start of processing for Operand_Has_Warnings_Suppressed begin return Traverse (N) = Abandon; -- If any exception occurs, then something has gone wrong, and this is -- only a minor aesthetic issue anyway, so just say we did not find what -- we are looking for, rather than blow up. exception when others => return False; end Operand_Has_Warnings_Suppressed; ---------------------------------- -- Output_Unreferenced_Messages -- ---------------------------------- procedure Output_Unreferenced_Messages is E : Entity_Id; begin for J in Unreferenced_Entities.First .. Unreferenced_Entities.Last loop E := Unreferenced_Entities.Table (J); if not Referenced (E) and then not Warnings_Off (E) then case Ekind (E) is when E_Variable => -- Case of variable that is assigned but not read. We -- suppress the message if the variable is volatile, -- has an address clause, or is imported. if Referenced_As_LHS (E) and then No (Address_Clause (E)) and then not Is_Volatile (E) then if Warn_On_Modified_Unread and then not Is_Imported (E) -- Suppress the message for aliased or renamed -- variables, since there may be other entities -- read the same memory location. and then not Is_Aliased (E) and then No (Renamed_Object (E)) then Error_Msg_N ("variable & is assigned but never read?", E); end if; -- Normal case of neither assigned nor read else if Present (Renamed_Object (E)) and then Comes_From_Source (Renamed_Object (E)) then Error_Msg_N ("renamed variable & is not referenced?", E); else Error_Msg_N ("variable & is not referenced?", E); end if; end if; when E_Constant => if Present (Renamed_Object (E)) and then Comes_From_Source (Renamed_Object (E)) then Error_Msg_N ("renamed constant & is not referenced?", E); else Error_Msg_N ("constant & is not referenced?", E); end if; when E_In_Parameter | E_Out_Parameter | E_In_Out_Parameter => -- Do not emit message for formals of a renaming, because -- they are never referenced explicitly. if Nkind (Original_Node (Unit_Declaration_Node (Scope (E)))) /= N_Subprogram_Renaming_Declaration then Error_Msg_N ("formal parameter & is not referenced?", E); end if; when E_Named_Integer | E_Named_Real => Error_Msg_N ("named number & is not referenced?", E); when E_Enumeration_Literal => Error_Msg_N ("literal & is not referenced?", E); when E_Function => Error_Msg_N ("function & is not referenced?", E); when E_Procedure => Error_Msg_N ("procedure & is not referenced?", E); when E_Generic_Procedure => Error_Msg_N ("generic procedure & is never instantiated?", E); when E_Generic_Function => Error_Msg_N ("generic function & is never instantiated?", E); when Type_Kind => Error_Msg_N ("type & is not referenced?", E); when others => Error_Msg_N ("& is not referenced?", E); end case; Set_Warnings_Off (E); end if; end loop; end Output_Unreferenced_Messages; ----------------------------- -- Warn_On_Known_Condition -- ----------------------------- procedure Warn_On_Known_Condition (C : Node_Id) is P : Node_Id; begin -- Argument replacement in an inlined body can make conditions -- static. Do not emit warnings in this case. if In_Inlined_Body then return; end if; if Constant_Condition_Warnings and then Nkind (C) = N_Identifier and then (Entity (C) = Standard_False or else Entity (C) = Standard_True) and then Comes_From_Source (Original_Node (C)) and then not In_Instance then -- See if this is in a statement or a declaration P := Parent (C); loop -- If tree is not attached, do not issue warning (this is very -- peculiar, and probably arises from some other error condition) if No (P) then return; -- If we are in a declaration, then no warning, since in practice -- conditionals in declarations are used for intended tests which -- may be known at compile time, e.g. things like -- x : constant Integer := 2 + (Word'Size = 32); -- And a warning is annoying in such cases elsif Nkind (P) in N_Declaration or else Nkind (P) in N_Later_Decl_Item then return; -- Don't warn in assert pragma, since presumably tests in such -- a context are very definitely intended, and might well be -- known at compile time. Note that we have to test the original -- node, since assert pragmas get rewritten at analysis time. elsif Nkind (Original_Node (P)) = N_Pragma and then Chars (Original_Node (P)) = Name_Assert then return; end if; exit when Is_Statement (P); P := Parent (P); end loop; -- Here we issue the warning unless some sub-operand has warnings -- set off, in which case we suppress the warning for the node. if not Operand_Has_Warnings_Suppressed (C) then if Entity (C) = Standard_True then Error_Msg_N ("condition is always True?", C); else Error_Msg_N ("condition is always False?", C); end if; end if; end if; end Warn_On_Known_Condition; end Sem_Warn;