------------------------------------------------------------------------------ -- -- -- GNAT COMPILER COMPONENTS -- -- -- -- S E M _ W A R N -- -- -- -- S p e c -- -- -- -- Copyright (C) 1999-2013, 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; use 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_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_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 the 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). end Sem_Warn;