270 lines
14 KiB
Ada
270 lines
14 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT COMPILER COMPONENTS --
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-- --
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-- S E M _ W A R N --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 1999-2020, Free Software Foundation, Inc. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
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-- for more details. You should have received a copy of the GNU General --
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-- Public License distributed with GNAT; see file COPYING3. If not, go to --
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-- http://www.gnu.org/licenses for a complete copy of the license. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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-- This package contains the routines used to deal with issuing warnings
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-- about uses of uninitialized variables and unused with's. It also has
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-- some unrelated routines related to the generation of warnings.
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with Alloc;
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with Table;
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with Types; use Types;
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package Sem_Warn is
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------------------------
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-- Warnings Off Table --
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------------------------
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type Warnings_Off_Entry is record
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N : Node_Id;
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-- A pragma Warnings (Off, ent [,Reason]) node
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E : Entity_Id;
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-- The entity involved
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R : String_Id;
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-- Warning reason if present, or null if not (not currently used)
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end record;
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-- An entry is made in the following table for any valid Pragma Warnings
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-- (Off, entity) encountered while Opt.Warn_On_Warnings_Off is True. It
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-- is used to generate warnings on any of these pragmas that turn out not
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-- to be needed, or that could be replaced by Unmodified/Unreferenced.
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package Warnings_Off_Pragmas is new Table.Table (
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Table_Component_Type => Warnings_Off_Entry,
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Table_Index_Type => Int,
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Table_Low_Bound => 0,
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Table_Initial => Alloc.Warnings_Off_Pragmas_Initial,
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Table_Increment => Alloc.Warnings_Off_Pragmas_Increment,
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Table_Name => "Name_Warnings_Off_Pragmas");
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--------------------
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-- Initialization --
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--------------------
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procedure Initialize;
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-- Initialize this package for new compilation
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------------------------------------------
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-- Routines to Handle Unused References --
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------------------------------------------
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procedure Check_References (E : Entity_Id; Anod : Node_Id := Empty);
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-- Called at the end of processing a declarative region. The entity E
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-- is the entity for the scope. All entities declared in the region,
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-- as indicated by First_Entity and the entity chain, are checked to
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-- see if they are variables for which warnings need to be posted for
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-- either no assignments, or a use before an assignment or no references
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-- at all. The Anod node is present for the case of an accept statement,
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-- and references the accept statement. This is used to place the warning
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-- messages in the right place.
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procedure Check_Unset_Reference (N : Node_Id);
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-- N is the node for an expression which occurs in a reference position,
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-- e.g. as the right side of an assignment. This procedure checks to see
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-- if the node is a reference to a variable entity where the entity has
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-- Not_Assigned set. If so, the Unset_Reference field is set if it is not
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-- the first occurrence. No warning is posted, instead warnings will be
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-- posted later by Check_References. The reason we do things that
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-- way is that if there are no assignments anywhere, we prefer to flag
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-- the entity, rather than a reference to it. Note that for the purposes
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-- of this routine, a type conversion or qualified expression whose
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-- expression is an entity is also processed. The reason that we do not
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-- process these at the point of occurrence is that both these constructs
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-- can occur in non-reference positions (e.g. as out parameters).
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procedure Check_Unused_Withs (Spec_Unit : Unit_Number_Type := No_Unit);
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-- This routine performs two kinds of checks. It checks that all with'ed
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-- units are referenced, and that at least one entity of each with'ed
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-- unit is referenced (the latter check catches units that are only
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-- referenced in a use or package renaming statement). Appropriate
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-- warning messages are generated if either of these situations is
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-- detected.
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--
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-- A special case arises when a package body or a subprogram body with
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-- a separate spec is being compiled. In this case, a with may appear
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-- on the spec, but be needed only by the body. This still generates
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-- a warning, but the text is different (the with is not redundant,
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-- it is misplaced).
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--
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-- This special case is implemented by making an initial call to this
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-- procedure with Spec_Unit set to the unit number of the separate spec.
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-- This call does not generate any warning messages, but instead may
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-- result in flags being set in the N_With_Clause node that record that
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-- there was no use in the spec.
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--
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-- The main call (made after all units have been analyzed, with Spec_Unit
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-- set to the default value of No_Unit) generates the required warnings
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-- using the flags set by the initial call where appropriate to specialize
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-- the text of the warning messages.
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---------------------
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-- Output Routines --
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---------------------
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procedure Output_Non_Modified_In_Out_Warnings;
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-- Warnings about IN OUT parameters that could be IN are collected till
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-- the end of the compilation process (see body of this routine for a
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-- discussion of why this is done). This procedure outputs the warnings.
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-- Note: this should be called before Output_Unreferenced_Messages, since
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-- if we have an IN OUT warning, that's the one we want to see.
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procedure Output_Obsolescent_Entity_Warnings (N : Node_Id; E : Entity_Id);
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-- N is a reference to obsolescent entity E, for which appropriate warning
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-- messages are to be generated (caller has already checked that warnings
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-- are active and appropriate for this entity).
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procedure Output_Unreferenced_Messages;
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-- Warnings about unreferenced entities are collected till the end of
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-- the compilation process (see Check_Unset_Reference for further
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-- details). This procedure outputs waiting warnings, if any.
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procedure Output_Unused_Warnings_Off_Warnings;
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-- Warnings about pragma Warnings (Off, ent) statements that are unused,
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-- or could be replaced by Unmodified/Unreferenced pragmas, are collected
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-- till the end of the compilation process. This procedure outputs waiting
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-- warnings if any.
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----------------------------
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-- Other Warning Routines --
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----------------------------
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procedure Check_Code_Statement (N : Node_Id);
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-- Perform warning checks on a code statement node
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procedure Check_Infinite_Loop_Warning (Loop_Statement : Node_Id);
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-- N is the node for a loop statement. This procedure checks if a warning
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-- for a possible infinite loop should be given for a suspicious WHILE or
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-- EXIT WHEN condition.
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procedure Check_Low_Bound_Tested (Expr : Node_Id);
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-- Expr is the node for a comparison operation. This procedure checks if
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-- the comparison is a source comparison of P'First with some other value
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-- and if so, sets the Low_Bound_Tested flag on entity P to suppress
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-- warnings about improper low bound assumptions (we assume that if the
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-- code has a test that explicitly checks P'First, then it is not operating
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-- in blind assumption mode).
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procedure Warn_On_Constant_Valid_Condition (Op : Node_Id);
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-- Determine the outcome of evaluating conditional or relational operator
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-- Op assuming that its scalar operands are valid. Emit a warning when the
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-- result of the evaluation is True or False.
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procedure Warn_On_Known_Condition (C : Node_Id);
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-- C is a node for a boolean expression resulting from a relational
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-- or membership operation. If the expression has a compile time known
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-- value, then a warning is output if all the following conditions hold:
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--
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-- 1. Original expression comes from source. We don't want to generate
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-- warnings for internally generated conditionals.
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--
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-- 2. As noted above, the expression is a relational or membership
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-- test, we don't want to generate warnings for boolean variables
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-- since this is typical of conditional compilation in Ada.
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--
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-- 3. The expression appears in a statement, rather than a declaration.
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-- In practice, most occurrences in declarations are legitimate
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-- conditionalizations, but occurrences in statements are often
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-- errors for which the warning is useful.
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--
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-- 4. The expression does not occur within an instantiation. A non-
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-- static expression in a generic may become constant because of
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-- the attributes of the actuals, and we do not want to warn on
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-- these legitimate constant foldings.
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--
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-- If all these conditions are met, the warning is issued noting that
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-- the result of the test is always false or always true as appropriate.
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function Warn_On_Modified_As_Out_Parameter (E : Entity_Id) return Boolean;
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-- Returns True if we should activate warnings for entity E being modified
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-- as an out parameter. True if either Warn_On_Modified_Unread is set for
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-- an only OUT parameter, or if Warn_On_All_Unread_Out_Parameters is set.
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procedure Warn_On_Overlapping_Actuals (Subp : Entity_Id; N : Node_Id);
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-- Called on a subprogram call. Checks whether an IN OUT actual that is
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-- not by-copy may overlap with another actual, thus leading to aliasing
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-- in the body of the called subprogram. This is indeed a warning in Ada
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-- versions prior to Ada 2012, but, unless Opt.Error_To_Warning is set by
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-- use of debug flag -gnatd.E, this is illegal and generates an error.
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procedure Warn_On_Suspicious_Index (Name : Entity_Id; X : Node_Id);
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-- This is called after resolving an indexed component or a slice. Name
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-- is the entity for the name of the indexed array, and X is the subscript
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-- for the indexed component case, or one of the bounds in the slice case.
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-- If Name is an unconstrained parameter of a standard string type, and
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-- the index is of the form of a literal or Name'Length [- literal], then
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-- a warning is generated that the subscripting operation is possibly
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-- incorrectly assuming a lower bound of 1.
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procedure Warn_On_Suspicious_Update (N : Node_Id);
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-- N is a semantically analyzed attribute reference Prefix'Update. Issue
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-- a warning if Warn_On_Suspicious_Contract is set, and N is the left-hand
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-- side or right-hand side of an equality or inequality of the form:
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-- Prefix = Prefix'Update(...)
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-- or
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-- Prefix'Update(...) = Prefix
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procedure Warn_On_Unassigned_Out_Parameter
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(Return_Node : Node_Id;
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Scope_Id : Entity_Id);
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-- Called when processing a return statement given by Return_Node. Scope_Id
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-- is the Entity_Id for the procedure in which the return statement lives.
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-- A check is made for the case of a procedure with out parameters that
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-- have not yet been assigned, and appropriate warnings are given.
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procedure Warn_On_Useless_Assignment
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(Ent : Entity_Id;
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N : Node_Id := Empty);
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-- Called to check if we have a case of a useless assignment to the given
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-- entity Ent, as indicated by a non-empty Last_Assignment field. This call
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-- should only be made if at least one of the flags Warn_On_Modified_Unread
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-- or Warn_On_All_Unread_Out_Parameters is True, and if Ent is in the
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-- extended main source unit. N is Empty for the end of block call
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-- (warning message says value unreferenced), or it is the node for
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-- an overwriting assignment (warning message points to this assignment).
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procedure Warn_On_Useless_Assignments (E : Entity_Id);
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pragma Inline (Warn_On_Useless_Assignments);
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-- Called at the end of a block or subprogram. Scans the entities of the
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-- block or subprogram to see if there are any variables for which useless
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-- assignments were made (assignments whose values were never read).
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----------------------
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-- Utility Routines --
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----------------------
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function Has_Junk_Name (E : Entity_Id) return Boolean;
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-- Return True if the entity name contains any of the following substrings:
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-- discard
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-- dummy
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-- ignore
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-- junk
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-- unused
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-- Used to suppress warnings on names matching these patterns. The contents
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-- of Name_Buffer and Name_Len are destroyed by this call.
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end Sem_Warn;
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