1------------------------------------------------------------------------------ 2-- -- 3-- GNAT COMPILER COMPONENTS -- 4-- -- 5-- S E M _ W A R N -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 1999-2011, Free Software Foundation, Inc. -- 10-- -- 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. -- 20-- -- 21-- GNAT was originally developed by the GNAT team at New York University. -- 22-- Extensive contributions were provided by Ada Core Technologies Inc. -- 23-- -- 24------------------------------------------------------------------------------ 25 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. 29 30with Alloc; use Alloc; 31with Table; 32with Types; use Types; 33 34package Sem_Warn is 35 36 ------------------------ 37 -- Warnings Off Table -- 38 ------------------------ 39 40 type Warnings_Off_Entry is record 41 N : Node_Id; 42 -- A pragma Warnings (Off, ent) node 43 44 E : Entity_Id; 45 -- The entity involved 46 end record; 47 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. 52 53 package Warnings_Off_Pragmas is new Table.Table ( 54 Table_Component_Type => Warnings_Off_Entry, 55 Table_Index_Type => Int, 56 Table_Low_Bound => 0, 57 Table_Initial => Alloc.Warnings_Off_Pragmas_Initial, 58 Table_Increment => Alloc.Warnings_Off_Pragmas_Increment, 59 Table_Name => "Name_Warnings_Off_Pragmas"); 60 61 -------------------- 62 -- Initialization -- 63 -------------------- 64 65 procedure Initialize; 66 -- Initialize this package for new compilation 67 68 ------------------------------------------ 69 -- Routines to Handle Unused References -- 70 ------------------------------------------ 71 72 procedure Check_References (E : Entity_Id; Anod : Node_Id := Empty); 73 -- Called at the end of processing a declarative region. The entity E 74 -- is the entity for the scope. All entities declared in the region, 75 -- as indicated by First_Entity and the entity chain, are checked to 76 -- see if they are variables for which warnings need to be posted for 77 -- either no assignments, or a use before an assignment or no references 78 -- at all. The Anod node is present for the case of an accept statement, 79 -- and references the accept statement. This is used to place the warning 80 -- messages in the right place. 81 82 procedure Check_Unset_Reference (N : Node_Id); 83 -- N is the node for an expression which occurs in a reference position, 84 -- e.g. as the right side of an assignment. This procedure checks to see 85 -- if the node is a reference to a variable entity where the entity has 86 -- Not_Assigned set. If so, the Unset_Reference field is set if it is not 87 -- the first occurrence. No warning is posted, instead warnings will be 88 -- posted later by Check_References. The reason we do things that 89 -- way is that if there are no assignments anywhere, we prefer to flag 90 -- the entity, rather than a reference to it. Note that for the purposes 91 -- of this routine, a type conversion or qualified expression whose 92 -- expression is an entity is also processed. The reason that we do not 93 -- process these at the point of occurrence is that both these constructs 94 -- can occur in non-reference positions (e.g. as out parameters). 95 96 procedure Check_Unused_Withs (Spec_Unit : Unit_Number_Type := No_Unit); 97 -- This routine performs two kinds of checks. It checks that all with'ed 98 -- units are referenced, and that at least one entity of each with'ed 99 -- unit is referenced (the latter check catches units that are only 100 -- referenced in a use or package renaming statement). Appropriate 101 -- warning messages are generated if either of these situations is 102 -- detected. 103 -- 104 -- A special case arises when a package body or a subprogram body with 105 -- a separate spec is being compiled. In this case, a with may appear 106 -- on the spec, but be needed only by the body. This still generates 107 -- a warning, but the text is different (the with is not redundant, 108 -- it is misplaced). 109 -- 110 -- This special case is implemented by making an initial call to this 111 -- procedure with Spec_Unit set to the unit number of the separate spec. 112 -- This call does not generate any warning messages, but instead may 113 -- result in flags being set in the N_With_Clause node that record that 114 -- there was no use in the spec. 115 -- 116 -- The main call (made after all units have been analyzed, with Spec_Unit 117 -- set to the default value of No_Unit) generates the required warnings 118 -- using the flags set by the initial call where appropriate to specialize 119 -- the text of the warning messages. 120 121 --------------------- 122 -- Output Routines -- 123 --------------------- 124 125 procedure Output_Non_Modified_In_Out_Warnings; 126 -- Warnings about IN OUT parameters that could be IN are collected till 127 -- the end of the compilation process (see body of this routine for a 128 -- discussion of why this is done). This procedure outputs the warnings. 129 -- Note: this should be called before Output_Unreferenced_Messages, since 130 -- if we have an IN OUT warning, that's the one we want to see! 131 132 procedure Output_Obsolescent_Entity_Warnings (N : Node_Id; E : Entity_Id); 133 -- N is a reference to obsolescent entity E, for which appropriate warning 134 -- messages are to be generated (caller has already checked that warnings 135 -- are active and appropriate for this entity). 136 137 procedure Output_Unreferenced_Messages; 138 -- Warnings about unreferenced entities are collected till the end of 139 -- the compilation process (see Check_Unset_Reference for further 140 -- details). This procedure outputs waiting warnings, if any. 141 142 procedure Output_Unused_Warnings_Off_Warnings; 143 -- Warnings about pragma Warnings (Off, ent) statements that are unused, 144 -- or could be replaced by Unmodified/Unreferenced pragmas, are collected 145 -- till the end of the compilation process. This procedure outputs waiting 146 -- warnings if any. 147 148 ---------------------------- 149 -- Other Warning Routines -- 150 ---------------------------- 151 152 procedure Check_Code_Statement (N : Node_Id); 153 -- Perform warning checks on a code statement node 154 155 procedure Check_Infinite_Loop_Warning (Loop_Statement : Node_Id); 156 -- N is the node for a loop statement. This procedure checks if a warning 157 -- for a possible infinite loop should be given for a suspicious WHILE or 158 -- EXIT WHEN condition. 159 160 procedure Check_Low_Bound_Tested (Expr : Node_Id); 161 -- Expr is the node for a comparison operation. This procedure checks if 162 -- the comparison is a source comparison of P'First with some other value 163 -- and if so, sets the Low_Bound_Tested flag on entity P to suppress 164 -- warnings about improper low bound assumptions (we assume that if the 165 -- code has a test that explicitly checks P'First, then it is not operating 166 -- in blind assumption mode). 167 168 procedure Warn_On_Known_Condition (C : Node_Id); 169 -- C is a node for a boolean expression resulting from a relational 170 -- or membership operation. If the expression has a compile time known 171 -- value, then a warning is output if all the following conditions hold: 172 -- 173 -- 1. Original expression comes from source. We don't want to generate 174 -- warnings for internally generated conditionals. 175 -- 176 -- 2. As noted above, the expression is a relational or membership 177 -- test, we don't want to generate warnings for boolean variables 178 -- since this is typical of conditional compilation in Ada. 179 -- 180 -- 3. The expression appears in a statement, rather than a declaration. 181 -- In practice, most occurrences in declarations are legitimate 182 -- conditionalizations, but occurrences in statements are often 183 -- errors for which the warning is useful. 184 -- 185 -- 4. The expression does not occur within an instantiation. A non- 186 -- static expression in a generic may become constant because of 187 -- the attributes of the actuals, and we do not want to warn on 188 -- these legitimate constant foldings. 189 -- 190 -- If all these conditions are met, the warning is issued noting that 191 -- the result of the test is always false or always true as appropriate. 192 193 function Warn_On_Modified_As_Out_Parameter (E : Entity_Id) return Boolean; 194 -- Returns True if we should activate warnings for entity E being modified 195 -- as an out parameter. True if either Warn_On_Modified_Unread is set for 196 -- an only OUT parameter, or if Warn_On_All_Unread_Out_Parameters is set. 197 198 procedure Warn_On_Overlapping_Actuals (Subp : Entity_Id; N : Node_Id); 199 -- Called on a subprogram call. Checks whether an IN OUT actual that is 200 -- not by-copy may overlap with another actual, thus leading to aliasing 201 -- in the body of the called subprogram. 202 203 procedure Warn_On_Suspicious_Index (Name : Entity_Id; X : Node_Id); 204 -- This is called after resolving an indexed component or a slice. Name 205 -- is the entity for the name of the indexed array, and X is the subscript 206 -- for the indexed component case, or one of the bounds in the slice case. 207 -- If Name is an unconstrained parameter of a standard string type, and 208 -- the index is of the form of a literal or Name'Length [- literal], then 209 -- a warning is generated that the subscripting operation is possibly 210 -- incorrectly assuming a lower bound of 1. 211 212 procedure Warn_On_Unassigned_Out_Parameter 213 (Return_Node : Node_Id; 214 Scope_Id : Entity_Id); 215 -- Called when processing a return statement given by Return_Node. Scope_Id 216 -- is the Entity_Id for the procedure in which the return statement lives. 217 -- A check is made for the case of a procedure with out parameters that 218 -- have not yet been assigned, and appropriate warnings are given. 219 220 procedure Warn_On_Useless_Assignment 221 (Ent : Entity_Id; 222 N : Node_Id := Empty); 223 -- Called to check if we have a case of a useless assignment to the given 224 -- entity Ent, as indicated by a non-empty Last_Assignment field. This call 225 -- should only be made if at least one of the flags Warn_On_Modified_Unread 226 -- or Warn_On_All_Unread_Out_Parameters is True, and if Ent is in the 227 -- extended main source unit. N is Empty for the end of block call 228 -- (warning message says value unreferenced), or the it is the node for 229 -- an overwriting assignment (warning message points to this assignment). 230 231 procedure Warn_On_Useless_Assignments (E : Entity_Id); 232 pragma Inline (Warn_On_Useless_Assignments); 233 -- Called at the end of a block or subprogram. Scans the entities of the 234 -- block or subprogram to see if there are any variables for which useless 235 -- assignments were made (assignments whose values were never read). 236 237end Sem_Warn; 238