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Diffstat (limited to 'gcc-4.2.1/gcc/ada/sem_warn.adb')
| -rw-r--r-- | gcc-4.2.1/gcc/ada/sem_warn.adb | 1884 |
1 files changed, 1884 insertions, 0 deletions
diff --git a/gcc-4.2.1/gcc/ada/sem_warn.adb b/gcc-4.2.1/gcc/ada/sem_warn.adb new file mode 100644 index 000000000..5f8394e79 --- /dev/null +++ b/gcc-4.2.1/gcc/ada/sem_warn.adb @@ -0,0 +1,1884 @@ +------------------------------------------------------------------------------ +-- -- +-- GNAT COMPILER COMPONENTS -- +-- -- +-- S E M _ W A R N -- +-- -- +-- B o d y -- +-- -- +-- Copyright (C) 1999-2006, 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, 51 Franklin Street, Fifth Floor, -- +-- Boston, MA 02110-1301, 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. ??? + + -- An entry is made in the following table for each branch of 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); + + -- Similarly, the generic formals of a generic subprogram + -- are not accessible. + + when N_Generic_Subprogram_Declaration => + if Is_List_Member (Prev) + and then List_Containing (Prev) = + Generic_Formal_Declarations (P) + then + return False; + else + P := Parent (P); + end if; + + -- 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 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 + -- A special case, if this variable is volatile and not + -- imported, it is not helpful to tell the programmer + -- to mark the variable as constant, since this would be + -- illegal by virtue of RM C.6(13). + + if (Is_Volatile (E1) or else Has_Volatile_Components (E1)) + and then not Is_Imported (E1) + then + Error_Msg_N + ("& is not modified, volatile has no effect?", E1); + else + Error_Msg_N + ("& is not modified, could be declared constant?", E1); + end if; + 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 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 + Access_Type_Case : 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 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. + + ------------- + -- Process -- + ------------- + + 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; + + ------------ + -- Ref_In -- + ------------ + + function Ref_In (Nod : Node_Id) return Boolean is + function Traverse is new Traverse_Func (Process); + begin + return Traverse (Nod) = Abandon; + end Ref_In; + + -- Start of processing for Access_Type_Case + + 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 Access_Type_Case; + 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 application 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 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 + if Limited_Present (Item) then + Ent := First_Entity (Limited_View (Lunit)); + else + Ent := First_Entity (Lunit); + end if; + + 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; + + ------------------------ + -- Set_Warning_Switch -- + ------------------------ + + function Set_Warning_Switch (C : Character) return Boolean is + begin + case C is + when 'a' => + Check_Unreferenced := True; + Check_Unreferenced_Formals := True; + Check_Withs := True; + Constant_Condition_Warnings := True; + Implementation_Unit_Warnings := True; + Ineffective_Inline_Warnings := True; + Warn_On_Ada_2005_Compatibility := True; + Warn_On_Bad_Fixed_Value := True; + Warn_On_Constant := True; + Warn_On_Export_Import := True; + Warn_On_Modified_Unread := True; + Warn_On_No_Value_Assigned := True; + Warn_On_Obsolescent_Feature := True; + Warn_On_Redundant_Constructs := True; + Warn_On_Unchecked_Conversion := True; + Warn_On_Unrecognized_Pragma := True; + + when 'A' => + Check_Unreferenced := False; + Check_Unreferenced_Formals := False; + Check_Withs := False; + Constant_Condition_Warnings := False; + Elab_Warnings := False; + Implementation_Unit_Warnings := False; + Ineffective_Inline_Warnings := False; + Warn_On_Ada_2005_Compatibility := False; + Warn_On_Bad_Fixed_Value := False; + Warn_On_Constant := False; + Warn_On_Dereference := False; + Warn_On_Export_Import := False; + Warn_On_Hiding := False; + Warn_On_Modified_Unread := False; + Warn_On_No_Value_Assigned := False; + Warn_On_Obsolescent_Feature := False; + Warn_On_Redundant_Constructs := False; + Warn_On_Unchecked_Conversion := False; + Warn_On_Unrecognized_Pragma := False; + + when 'b' => + Warn_On_Bad_Fixed_Value := True; + + when 'B' => + Warn_On_Bad_Fixed_Value := False; + + when 'c' => + Constant_Condition_Warnings := True; + + when 'C' => + Constant_Condition_Warnings := False; + + when 'd' => + Warn_On_Dereference := True; + + when 'D' => + Warn_On_Dereference := False; + + when 'e' => + Warning_Mode := Treat_As_Error; + + when 'f' => + Check_Unreferenced_Formals := True; + + when 'F' => + Check_Unreferenced_Formals := False; + + when 'g' => + Warn_On_Unrecognized_Pragma := True; + + when 'G' => + Warn_On_Unrecognized_Pragma := False; + + when 'h' => + Warn_On_Hiding := True; + + when 'H' => + Warn_On_Hiding := False; + + when 'i' => + Implementation_Unit_Warnings := True; + + when 'I' => + Implementation_Unit_Warnings := False; + + when 'j' => + Warn_On_Obsolescent_Feature := True; + + when 'J' => + Warn_On_Obsolescent_Feature := False; + + when 'k' => + Warn_On_Constant := True; + + when 'K' => + Warn_On_Constant := False; + + when 'l' => + Elab_Warnings := True; + + when 'L' => + Elab_Warnings := False; + + when 'm' => + Warn_On_Modified_Unread := True; + + when 'M' => + Warn_On_Modified_Unread := False; + + when 'n' => + Warning_Mode := Normal; + + when 'o' => + Address_Clause_Overlay_Warnings := True; + + when 'O' => + Address_Clause_Overlay_Warnings := False; + + when 'p' => + Ineffective_Inline_Warnings := True; + + when 'P' => + Ineffective_Inline_Warnings := False; + + when 'r' => + Warn_On_Redundant_Constructs := True; + + when 'R' => + Warn_On_Redundant_Constructs := False; + + when 's' => + Warning_Mode := Suppress; + + when 'u' => + Check_Unreferenced := True; + Check_Withs := True; + Check_Unreferenced_Formals := True; + + when 'U' => + Check_Unreferenced := False; + Check_Withs := False; + Check_Unreferenced_Formals := False; + + when 'v' => + Warn_On_No_Value_Assigned := True; + + when 'V' => + Warn_On_No_Value_Assigned := False; + + when 'x' => + Warn_On_Export_Import := True; + + when 'X' => + Warn_On_Export_Import := False; + + when 'y' => + Warn_On_Ada_2005_Compatibility := True; + + when 'Y' => + Warn_On_Ada_2005_Compatibility := False; + + when 'z' => + Warn_On_Unchecked_Conversion := True; + + when 'Z' => + Warn_On_Unchecked_Conversion := False; + + -- Allow and ignore 'w' so that the old + -- format (e.g. -gnatwuwl) will work. + + when 'w' => + null; + + when others => + return False; + end case; + + return True; + end Set_Warning_Switch; + + ----------------------------- + -- 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 + -- the original expression is an inequality, it has been expanded + -- into a negation, and the value of the original expression is the + -- negation of the equality. If the expression is an entity that + -- appears within a negation, it is clearer to flag the negation + -- itself, and report on its constant value. + + if not Operand_Has_Warnings_Suppressed (C) then + declare + True_Branch : Boolean := Entity (C) = Standard_True; + Cond : Node_Id := C; + + begin + if Present (Parent (C)) + and then Nkind (Parent (C)) = N_Op_Not + then + True_Branch := not True_Branch; + Cond := Parent (C); + end if; + + if True_Branch then + if Is_Entity_Name (Original_Node (C)) + and then Nkind (Cond) /= N_Op_Not + then + Error_Msg_NE + ("object & is always True?", Cond, Original_Node (C)); + else + Error_Msg_N ("condition is always True?", Cond); + end if; + else + Error_Msg_N ("condition is always False?", Cond); + end if; + end; + end if; + end if; + end Warn_On_Known_Condition; + +end Sem_Warn; |