| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT COMPILER COMPONENTS -- |
| -- -- |
| -- S E M _ W A R N -- |
| -- -- |
| -- S p e c -- |
| -- -- |
| -- Copyright (C) 1999-2022, Free Software Foundation, Inc. -- |
| -- -- |
| -- GNAT is free software; you can redistribute it and/or modify it under -- |
| -- terms of the GNU General Public License as published by the Free Soft- -- |
| -- ware Foundation; either version 3, or (at your option) any later ver- -- |
| -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- |
| -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- |
| -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- |
| -- for more details. You should have received a copy of the GNU General -- |
| -- Public License distributed with GNAT; see file COPYING3. If not, go to -- |
| -- http://www.gnu.org/licenses for a complete copy of the license. -- |
| -- -- |
| -- GNAT was originally developed by the GNAT team at New York University. -- |
| -- Extensive contributions were provided by Ada Core Technologies Inc. -- |
| -- -- |
| ------------------------------------------------------------------------------ |
| |
| -- This package contains the routines used to deal with issuing warnings |
| -- about uses of uninitialized variables and unused with's. It also has |
| -- some unrelated routines related to the generation of warnings. |
| |
| with Alloc; |
| with Table; |
| with Types; use Types; |
| |
| package Sem_Warn is |
| |
| ------------------------ |
| -- Warnings Off Table -- |
| ------------------------ |
| |
| type Warnings_Off_Entry is record |
| N : Node_Id; |
| -- A pragma Warnings (Off, ent [,Reason]) node |
| |
| E : Entity_Id; |
| -- The entity involved |
| |
| R : String_Id; |
| -- Warning reason if present, or null if not (not currently used) |
| end record; |
| |
| -- An entry is made in the following table for any valid Pragma Warnings |
| -- (Off, entity) encountered while Opt.Warn_On_Warnings_Off is True. It |
| -- is used to generate warnings on any of these pragmas that turn out not |
| -- to be needed, or that could be replaced by Unmodified/Unreferenced. |
| |
| package Warnings_Off_Pragmas is new Table.Table ( |
| Table_Component_Type => Warnings_Off_Entry, |
| Table_Index_Type => Int, |
| Table_Low_Bound => 0, |
| Table_Initial => Alloc.Warnings_Off_Pragmas_Initial, |
| Table_Increment => Alloc.Warnings_Off_Pragmas_Increment, |
| Table_Name => "Name_Warnings_Off_Pragmas"); |
| |
| -------------------- |
| -- Initialization -- |
| -------------------- |
| |
| procedure Initialize; |
| -- Initialize this package for new compilation |
| |
| ------------------------------------------ |
| -- Routines to Handle Unused References -- |
| ------------------------------------------ |
| |
| procedure Check_References (E : Entity_Id; Anod : Node_Id := Empty); |
| -- Called at the end of processing a declarative region. The entity E |
| -- is the entity for the scope. All entities declared in the region, |
| -- as indicated by First_Entity and the entity chain, are checked to |
| -- see if they are variables for which warnings need to be posted for |
| -- either no assignments, or a use before an assignment or no references |
| -- at all. The Anod node is present for the case of an accept statement, |
| -- and references the accept statement. This is used to place the warning |
| -- messages in the right place. |
| |
| procedure Check_Unset_Reference (N : Node_Id); |
| -- N is the node for an expression which occurs in a reference position, |
| -- e.g. as the right side of an assignment. This procedure checks to see |
| -- if the node is a reference to a variable entity where the entity has |
| -- Not_Assigned set. If so, the Unset_Reference field is set if it is not |
| -- the first occurrence. No warning is posted, instead warnings will be |
| -- posted later by Check_References. The reason we do things that |
| -- way is that if there are no assignments anywhere, we prefer to flag |
| -- the entity, rather than a reference to it. Note that for the purposes |
| -- of this routine, a type conversion or qualified expression whose |
| -- expression is an entity is also processed. The reason that we do not |
| -- process these at the point of occurrence is that both these constructs |
| -- can occur in non-reference positions (e.g. as out parameters). |
| |
| procedure Check_Unused_Withs (Spec_Unit : Unit_Number_Type := No_Unit); |
| -- This routine performs two kinds of checks. It checks that all with'ed |
| -- units are referenced, and that at least one entity of each with'ed |
| -- unit is referenced (the latter check catches units that are only |
| -- referenced in a use or package renaming statement). Appropriate |
| -- warning messages are generated if either of these situations is |
| -- detected. |
| -- |
| -- A special case arises when a package body or a subprogram body with |
| -- a separate spec is being compiled. In this case, a with may appear |
| -- on the spec, but be needed only by the body. This still generates |
| -- a warning, but the text is different (the with is not redundant, |
| -- it is misplaced). |
| -- |
| -- This special case is implemented by making an initial call to this |
| -- procedure with Spec_Unit set to the unit number of the separate spec. |
| -- This call does not generate any warning messages, but instead may |
| -- result in flags being set in the N_With_Clause node that record that |
| -- there was no use in the spec. |
| -- |
| -- The main call (made after all units have been analyzed, with Spec_Unit |
| -- set to the default value of No_Unit) generates the required warnings |
| -- using the flags set by the initial call where appropriate to specialize |
| -- the text of the warning messages. |
| |
| --------------------- |
| -- Output Routines -- |
| --------------------- |
| |
| procedure Output_Non_Modified_In_Out_Warnings; |
| -- Warnings about IN OUT parameters that could be IN are collected till |
| -- the end of the compilation process (see body of this routine for a |
| -- discussion of why this is done). This procedure outputs the warnings. |
| -- Note: this should be called before Output_Unreferenced_Messages, since |
| -- if we have an IN OUT warning, that's the one we want to see. |
| |
| procedure Output_Obsolescent_Entity_Warnings (N : Node_Id; E : Entity_Id); |
| -- N is a reference to obsolescent entity E, for which appropriate warning |
| -- messages are to be generated (caller has already checked that warnings |
| -- are active and appropriate for this entity). |
| |
| procedure Output_Unreferenced_Messages; |
| -- Warnings about unreferenced entities are collected till the end of |
| -- the compilation process (see Check_Unset_Reference for further |
| -- details). This procedure outputs waiting warnings, if any. |
| |
| procedure Output_Unused_Warnings_Off_Warnings; |
| -- Warnings about pragma Warnings (Off, ent) statements that are unused, |
| -- or could be replaced by Unmodified/Unreferenced pragmas, are collected |
| -- till the end of the compilation process. This procedure outputs waiting |
| -- warnings if any. |
| |
| ---------------------------- |
| -- Other Warning Routines -- |
| ---------------------------- |
| |
| procedure Check_Code_Statement (N : Node_Id); |
| -- Perform warning checks on a code statement node |
| |
| procedure Check_Infinite_Loop_Warning (Loop_Statement : Node_Id); |
| -- N is the node for a loop statement. This procedure checks if a warning |
| -- for a possible infinite loop should be given for a suspicious WHILE or |
| -- EXIT WHEN condition. |
| |
| procedure Check_Low_Bound_Tested (Expr : Node_Id); |
| -- Expr is the node for a comparison operation. This procedure checks if |
| -- the comparison is a source comparison of P'First with some other value |
| -- and if so, sets the Low_Bound_Tested flag on entity P to suppress |
| -- warnings about improper low bound assumptions (we assume that if the |
| -- code has a test that explicitly checks P'First, then it is not operating |
| -- in blind assumption mode). |
| |
| procedure Warn_On_Constant_Valid_Condition (Op : Node_Id); |
| -- Determine the outcome of evaluating conditional or relational operator |
| -- Op assuming that its scalar operands are valid. Emit a warning when the |
| -- result of the evaluation is True or False. |
| |
| procedure Warn_On_Known_Condition (C : Node_Id); |
| -- C is a node for a boolean expression resulting from a relational |
| -- or membership operation. If the expression has a compile time known |
| -- value, then a warning is output if all the following conditions hold: |
| -- |
| -- 1. Original expression comes from source. We don't want to generate |
| -- warnings for internally generated conditionals. |
| -- |
| -- 2. As noted above, the expression is a relational or membership |
| -- test, we don't want to generate warnings for boolean variables |
| -- since this is typical of conditional compilation in Ada. |
| -- |
| -- 3. The expression appears in a statement, rather than a declaration. |
| -- In practice, most occurrences in declarations are legitimate |
| -- conditionalizations, but occurrences in statements are often |
| -- errors for which the warning is useful. |
| -- |
| -- 4. The expression does not occur within an instantiation. A non- |
| -- static expression in a generic may become constant because of |
| -- the attributes of the actuals, and we do not want to warn on |
| -- these legitimate constant foldings. |
| -- |
| -- If all these conditions are met, the warning is issued noting that |
| -- the result of the test is always false or always true as appropriate. |
| |
| function Warn_On_Modified_As_Out_Parameter (E : Entity_Id) return Boolean; |
| -- Returns True if we should activate warnings for entity E being modified |
| -- as an out parameter. True if either Warn_On_Modified_Unread is set for |
| -- an only OUT parameter, or if Warn_On_All_Unread_Out_Parameters is set. |
| |
| procedure Warn_On_Overlapping_Actuals (Subp : Entity_Id; N : Node_Id); |
| -- Called on a subprogram call. Checks whether an IN OUT actual that is |
| -- not by-copy may overlap with another actual, thus leading to aliasing |
| -- in the body of the called subprogram. This is indeed a warning in Ada |
| -- versions prior to Ada 2012, but, unless Opt.Error_To_Warning is set by |
| -- use of debug flag -gnatd.E, this is illegal and generates an error. |
| |
| procedure Warn_On_Suspicious_Index (Name : Entity_Id; X : Node_Id); |
| -- This is called after resolving an indexed component or a slice. Name |
| -- is the entity for the name of the indexed array, and X is the subscript |
| -- for the indexed component case, or one of the bounds in the slice case. |
| -- If Name is an unconstrained parameter of a standard string type, and |
| -- the index is of the form of a literal or Name'Length [- literal], then |
| -- a warning is generated that the subscripting operation is possibly |
| -- incorrectly assuming a lower bound of 1. |
| |
| procedure Warn_On_Suspicious_Update (N : Node_Id); |
| -- N is a semantically analyzed attribute reference Prefix'Update. Issue |
| -- a warning if Warn_On_Suspicious_Contract is set, and N is the left-hand |
| -- side or right-hand side of an equality or inequality of the form: |
| -- Prefix = Prefix'Update(...) |
| -- or |
| -- Prefix'Update(...) = Prefix |
| |
| procedure Warn_On_Unassigned_Out_Parameter |
| (Return_Node : Node_Id; |
| Scope_Id : Entity_Id); |
| -- Called when processing a return statement given by Return_Node. Scope_Id |
| -- is the Entity_Id for the procedure in which the return statement lives. |
| -- A check is made for the case of a procedure with out parameters that |
| -- have not yet been assigned, and appropriate warnings are given. |
| |
| procedure Warn_On_Useless_Assignment |
| (Ent : Entity_Id; |
| N : Node_Id := Empty); |
| -- Called to check if we have a case of a useless assignment to the given |
| -- entity Ent, as indicated by a non-empty Last_Assignment field. This call |
| -- should only be made if at least one of the flags Warn_On_Modified_Unread |
| -- or Warn_On_All_Unread_Out_Parameters is True, and if Ent is in the |
| -- extended main source unit. N is Empty for the end of block call |
| -- (warning message says value unreferenced), or it is the node for |
| -- an overwriting assignment (warning message points to this assignment). |
| |
| procedure Warn_On_Useless_Assignments (E : Entity_Id); |
| pragma Inline (Warn_On_Useless_Assignments); |
| -- Called at the end of a block or subprogram. Scans the entities of the |
| -- block or subprogram to see if there are any variables for which useless |
| -- assignments were made (assignments whose values were never read). |
| |
| ---------------------- |
| -- Utility Routines -- |
| ---------------------- |
| |
| function Has_Junk_Name (E : Entity_Id) return Boolean; |
| -- Return True if the entity name contains any of the following substrings: |
| -- discard |
| -- dummy |
| -- ignore |
| -- junk |
| -- unused |
| -- Used to suppress warnings on names matching these patterns. The contents |
| -- of Name_Buffer and Name_Len are destroyed by this call. |
| |
| end Sem_Warn; |
