1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1999-2008, Free Software Foundation, Inc. --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 3, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING3. If not, go to --
19 -- http://www.gnu.org/licenses for a complete copy of the license. --
21 -- GNAT was originally developed by the GNAT team at New York University. --
22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
24 ------------------------------------------------------------------------------
26 -- This package contains the routines used to deal with issuing warnings
27 -- about uses of uninitialized variables and unused with's. It also has
28 -- some unrelated routines related to the generation of warnings.
30 with Alloc; use Alloc;
32 with Types; use Types;
36 ------------------------
37 -- Warnings Off Table --
38 ------------------------
40 type Warnings_Off_Entry is record
42 -- A pragma Warnings (Off, ent) node
45 -- The entity involved
48 -- An entry is made in the following table for any valid Pragma Warnings
49 -- (Off, entity) encountered while Opt.Warn_On_Warnings_Off is True. It
50 -- is used to generate warnings on any of these pragmas that turn out not
51 -- to be needed, or that could be replaced by Unmodified/Unreferenced.
53 package Warnings_Off_Pragmas is new Table.Table (
54 Table_Component_Type => Warnings_Off_Entry,
55 Table_Index_Type => Int,
57 Table_Initial => Alloc.Warnings_Off_Pragmas_Initial,
58 Table_Increment => Alloc.Warnings_Off_Pragmas_Increment,
59 Table_Name => "Name_Warnings_Off_Pragmas");
66 -- Initialize this package for new compilation
68 function Set_Warning_Switch (C : Character) return Boolean;
69 -- This function sets the warning switch or switches corresponding to the
70 -- given character. It is used to process a -gnatw switch on the command
71 -- line, or a character in a string literal in pragma Warnings. Returns
72 -- True for valid warning character C, False for invalid character.
74 function Set_Dot_Warning_Switch (C : Character) return Boolean;
75 -- This function sets the warning switch or switches corresponding to the
76 -- given character preceded by a dot. Used to process a -gnatw. switch on
77 -- the command line or .C in a string literal in pragma Warnings. Returns
78 -- True for valid warning character C, False for invalid character.
80 ------------------------------------------
81 -- Routines to Handle Unused References --
82 ------------------------------------------
84 procedure Check_References (E : Entity_Id; Anod : Node_Id := Empty);
85 -- Called at the end of processing a declarative region. The entity E
86 -- is the entity for the scope. All entities declared in the region,
87 -- as indicated by First_Entity and the entity chain, are checked to
88 -- see if they are variables for which warnings need to be posted for
89 -- either no assignments, or a use before an assignment or no references
90 -- at all. The Anod node is present for the case of an accept statement,
91 -- and references the accept statement. This is used to place the warning
92 -- messages in the right place.
94 procedure Check_Unset_Reference (N : Node_Id);
95 -- N is the node for an expression which occurs in a reference position,
96 -- e.g. as the right side of an assignment. This procedure checks to see
97 -- if the node is a reference to a variable entity where the entity has
98 -- Not_Assigned set. If so, the Unset_Reference field is set if it is not
99 -- the first occurrence. No warning is posted, instead warnings will be
100 -- posted later by Check_References. The reason we do things that
101 -- way is that if there are no assignments anywhere, we prefer to flag
102 -- the entity, rather than a reference to it. Note that for the purposes
103 -- of this routine, a type conversion or qualified expression whose
104 -- expression is an entity is also processed. The reason that we do not
105 -- process these at the point of occurrence is that both these constructs
106 -- can occur in non-reference positions (e.g. as out parameters).
108 procedure Check_Unused_Withs (Spec_Unit : Unit_Number_Type := No_Unit);
109 -- This routine performs two kinds of checks. It checks that all with'ed
110 -- units are referenced, and that at least one entity of each with'ed
111 -- unit is referenced (the latter check catches units that are only
112 -- referenced in a use or package renaming statement). Appropriate
113 -- warning messages are generated if either of these situations is
116 -- A special case arises when a package body or a subprogram body with
117 -- a separate spec is being compiled. In this case, a with may appear
118 -- on the spec, but be needed only by the body. This still generates
119 -- a warning, but the text is different (the with is not redundant,
122 -- This special case is implemented by making an initial call to this
123 -- procedure with Spec_Unit set to the unit number of the separate spec.
124 -- This call does not generate any warning messages, but instead may
125 -- result in flags being set in the N_With_Clause node that record that
126 -- there was no use in the spec.
128 -- The main call (made after all units have been analyzed, with Spec_Unit
129 -- set to the default value of No_Unit) generates the required warnings
130 -- using the flags set by the initial call where appropriate to specialize
131 -- the text of the warning messages.
133 ---------------------
134 -- Output Routines --
135 ---------------------
137 procedure Output_Non_Modifed_In_Out_Warnings;
138 -- Warnings about IN OUT parameters that could be IN are collected till
139 -- the end of the compilation process (see body of this routine for a
140 -- discussion of why this is done). This procedure outputs the warnings.
141 -- Note: this should be called before Output_Unreferenced_Messages, since
142 -- if we have an IN OUT warning, that's the one we want to see!
144 procedure Output_Obsolescent_Entity_Warnings (N : Node_Id; E : Entity_Id);
145 -- N is a reference to obsolescent entity E, for which appropriate warning
146 -- messages are to be generated (caller has already checked that warnings
147 -- are active and appropriate for this entity).
149 procedure Output_Unreferenced_Messages;
150 -- Warnings about unreferenced entities are collected till the end of
151 -- the compilation process (see Check_Unset_Reference for further
152 -- details). This procedure outputs waiting warnings, if any.
154 procedure Output_Unused_Warnings_Off_Warnings;
155 -- Warnings about pragma Warnings (Off, ent) statements that are unused,
156 -- or could be replaced by Unmodified/Unreferenced pragmas, are collected
157 -- till the end of the compilation process. This procedure outputs waiting
160 ----------------------------
161 -- Other Warning Routines --
162 ----------------------------
164 procedure Check_Code_Statement (N : Node_Id);
165 -- Perform warning checks on a code statement node
167 procedure Check_Infinite_Loop_Warning (Loop_Statement : Node_Id);
168 -- N is the node for a loop statement. This procedure checks if a warning
169 -- should be given for a possible infinite loop, and if so issues it.
171 procedure Check_Low_Bound_Tested (Expr : Node_Id);
172 -- Expr is the node for a comparison operation. This procedure checks if
173 -- the comparison is a source comparison of P'First with some other value
174 -- and if so, sets the Low_Bound_Tested flag on entity P to suppress
175 -- warnings about improper low bound assumptions (we assume that if the
176 -- code has a test that explicitly checks P'First, then it is not operating
177 -- in blind assumption mode).
179 procedure Warn_On_Known_Condition (C : Node_Id);
180 -- C is a node for a boolean expression resulting from a relational
181 -- or membership operation. If the expression has a compile time known
182 -- value, then a warning is output if all the following conditions hold:
184 -- 1. Original expression comes from source. We don't want to generate
185 -- warnings for internally generated conditionals.
187 -- 2. As noted above, the expression is a relational or membership
188 -- test, we don't want to generate warnings for boolean variables
189 -- since this is typical of conditional compilation in Ada.
191 -- 3. The expression appears in a statement, rather than a declaration.
192 -- In practice, most occurrences in declarations are legitimate
193 -- conditionalizations, but occurrences in statements are often
194 -- errors for which the warning is useful.
196 -- 4. The expression does not occur within an instantiation. A non-
197 -- static expression in a generic may become constant because of
198 -- the attributes of the actuals, and we do not want to warn on
199 -- these legitimate constant foldings.
201 -- If all these conditions are met, the warning is issued noting that
202 -- the result of the test is always false or always true as appropriate.
204 function Warn_On_Modified_As_Out_Parameter (E : Entity_Id) return Boolean;
205 -- Returns True if we should activate warnings for entity E being modified
206 -- as an out parameter. True if either Warn_On_Modified_Unread is set for
207 -- an only OUT parameter, or if Warn_On_All_Unread_Out_Parameters is set.
209 procedure Warn_On_Suspicious_Index (Name : Entity_Id; X : Node_Id);
210 -- This is called after resolving an indexed component or a slice. Name
211 -- is the entity for the name of the indexed array, and X is the subscript
212 -- for the indexed component case, or one of the bounds in the slice case.
213 -- If Name is an unconstrained parameter of a standard string type, and
214 -- the index is of the form of a literal or Name'Length [- literal], then
215 -- a warning is generated that the subscripting operation is possibly
216 -- incorrectly assuming a lower bound of 1.
218 procedure Warn_On_Unassigned_Out_Parameter
219 (Return_Node : Node_Id;
220 Scope_Id : Entity_Id);
221 -- Called when processing a return statement given by Return_Node. Scope_Id
222 -- is the Entity_Id for the procedure in which the return statement lives.
223 -- A check is made for the case of a procedure with out parameters that
224 -- have not yet been assigned, and appropriate warnings are given.
226 procedure Warn_On_Useless_Assignment
228 N : Node_Id := Empty);
229 -- Called to check if we have a case of a useless assignment to the given
230 -- entity Ent, as indicated by a non-empty Last_Assignment field. This call
231 -- should only be made if at least one of the flags Warn_On_Modified_Unread
232 -- or Warn_On_All_Unread_Out_Parameters is True, and if Ent is in the
233 -- extended main source unit. N is Empty for the end of block call
234 -- (warning message says value unreferenced), or the it is the node for
235 -- an overwriting assignment (warning message points to this assignment).
237 procedure Warn_On_Useless_Assignments (E : Entity_Id);
238 pragma Inline (Warn_On_Useless_Assignments);
239 -- Called at the end of a block or subprogram. Scans the entities of the
240 -- block or subprogram to see if there are any variables for which useless
241 -- assignments were made (assignments whose values were never read).
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