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) 1999-2018, 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; 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 [,Reason]) node 43 44 E : Entity_Id; 45 -- The entity involved 46 47 R : String_Id; 48 -- Warning reason if present, or null if not (not currently used) 49 end record; 50 51 -- An entry is made in the following table for any valid Pragma Warnings 52 -- (Off, entity) encountered while Opt.Warn_On_Warnings_Off is True. It 53 -- is used to generate warnings on any of these pragmas that turn out not 54 -- to be needed, or that could be replaced by Unmodified/Unreferenced. 55 56 package Warnings_Off_Pragmas is new Table.Table ( 57 Table_Component_Type => Warnings_Off_Entry, 58 Table_Index_Type => Int, 59 Table_Low_Bound => 0, 60 Table_Initial => Alloc.Warnings_Off_Pragmas_Initial, 61 Table_Increment => Alloc.Warnings_Off_Pragmas_Increment, 62 Table_Name => "Name_Warnings_Off_Pragmas"); 63 64 -------------------- 65 -- Initialization -- 66 -------------------- 67 68 procedure Initialize; 69 -- Initialize this package for new compilation 70 71 ------------------------------------------ 72 -- Routines to Handle Unused References -- 73 ------------------------------------------ 74 75 procedure Check_References (E : Entity_Id; Anod : Node_Id := Empty); 76 -- Called at the end of processing a declarative region. The entity E 77 -- is the entity for the scope. All entities declared in the region, 78 -- as indicated by First_Entity and the entity chain, are checked to 79 -- see if they are variables for which warnings need to be posted for 80 -- either no assignments, or a use before an assignment or no references 81 -- at all. The Anod node is present for the case of an accept statement, 82 -- and references the accept statement. This is used to place the warning 83 -- messages in the right place. 84 85 procedure Check_Unset_Reference (N : Node_Id); 86 -- N is the node for an expression which occurs in a reference position, 87 -- e.g. as the right side of an assignment. This procedure checks to see 88 -- if the node is a reference to a variable entity where the entity has 89 -- Not_Assigned set. If so, the Unset_Reference field is set if it is not 90 -- the first occurrence. No warning is posted, instead warnings will be 91 -- posted later by Check_References. The reason we do things that 92 -- way is that if there are no assignments anywhere, we prefer to flag 93 -- the entity, rather than a reference to it. Note that for the purposes 94 -- of this routine, a type conversion or qualified expression whose 95 -- expression is an entity is also processed. The reason that we do not 96 -- process these at the point of occurrence is that both these constructs 97 -- can occur in non-reference positions (e.g. as out parameters). 98 99 procedure Check_Unused_Withs (Spec_Unit : Unit_Number_Type := No_Unit); 100 -- This routine performs two kinds of checks. It checks that all with'ed 101 -- units are referenced, and that at least one entity of each with'ed 102 -- unit is referenced (the latter check catches units that are only 103 -- referenced in a use or package renaming statement). Appropriate 104 -- warning messages are generated if either of these situations is 105 -- detected. 106 -- 107 -- A special case arises when a package body or a subprogram body with 108 -- a separate spec is being compiled. In this case, a with may appear 109 -- on the spec, but be needed only by the body. This still generates 110 -- a warning, but the text is different (the with is not redundant, 111 -- it is misplaced). 112 -- 113 -- This special case is implemented by making an initial call to this 114 -- procedure with Spec_Unit set to the unit number of the separate spec. 115 -- This call does not generate any warning messages, but instead may 116 -- result in flags being set in the N_With_Clause node that record that 117 -- there was no use in the spec. 118 -- 119 -- The main call (made after all units have been analyzed, with Spec_Unit 120 -- set to the default value of No_Unit) generates the required warnings 121 -- using the flags set by the initial call where appropriate to specialize 122 -- the text of the warning messages. 123 124 --------------------- 125 -- Output Routines -- 126 --------------------- 127 128 procedure Output_Non_Modified_In_Out_Warnings; 129 -- Warnings about IN OUT parameters that could be IN are collected till 130 -- the end of the compilation process (see body of this routine for a 131 -- discussion of why this is done). This procedure outputs the warnings. 132 -- Note: this should be called before Output_Unreferenced_Messages, since 133 -- if we have an IN OUT warning, that's the one we want to see. 134 135 procedure Output_Obsolescent_Entity_Warnings (N : Node_Id; E : Entity_Id); 136 -- N is a reference to obsolescent entity E, for which appropriate warning 137 -- messages are to be generated (caller has already checked that warnings 138 -- are active and appropriate for this entity). 139 140 procedure Output_Unreferenced_Messages; 141 -- Warnings about unreferenced entities are collected till the end of 142 -- the compilation process (see Check_Unset_Reference for further 143 -- details). This procedure outputs waiting warnings, if any. 144 145 procedure Output_Unused_Warnings_Off_Warnings; 146 -- Warnings about pragma Warnings (Off, ent) statements that are unused, 147 -- or could be replaced by Unmodified/Unreferenced pragmas, are collected 148 -- till the end of the compilation process. This procedure outputs waiting 149 -- warnings if any. 150 151 ---------------------------- 152 -- Other Warning Routines -- 153 ---------------------------- 154 155 procedure Check_Code_Statement (N : Node_Id); 156 -- Perform warning checks on a code statement node 157 158 procedure Check_Infinite_Loop_Warning (Loop_Statement : Node_Id); 159 -- N is the node for a loop statement. This procedure checks if a warning 160 -- for a possible infinite loop should be given for a suspicious WHILE or 161 -- EXIT WHEN condition. 162 163 procedure Check_Low_Bound_Tested (Expr : Node_Id); 164 -- Expr is the node for a comparison operation. This procedure checks if 165 -- the comparison is a source comparison of P'First with some other value 166 -- and if so, sets the Low_Bound_Tested flag on entity P to suppress 167 -- warnings about improper low bound assumptions (we assume that if the 168 -- code has a test that explicitly checks P'First, then it is not operating 169 -- in blind assumption mode). 170 171 procedure Warn_On_Constant_Valid_Condition (Op : Node_Id); 172 -- Determine the outcome of evaluating conditional or relational operator 173 -- Op assuming that its scalar operands are valid. Emit a warning when the 174 -- result of the evaluation is True or False. 175 176 procedure Warn_On_Known_Condition (C : Node_Id); 177 -- C is a node for a boolean expression resulting from a relational 178 -- or membership operation. If the expression has a compile time known 179 -- value, then a warning is output if all the following conditions hold: 180 -- 181 -- 1. Original expression comes from source. We don't want to generate 182 -- warnings for internally generated conditionals. 183 -- 184 -- 2. As noted above, the expression is a relational or membership 185 -- test, we don't want to generate warnings for boolean variables 186 -- since this is typical of conditional compilation in Ada. 187 -- 188 -- 3. The expression appears in a statement, rather than a declaration. 189 -- In practice, most occurrences in declarations are legitimate 190 -- conditionalizations, but occurrences in statements are often 191 -- errors for which the warning is useful. 192 -- 193 -- 4. The expression does not occur within an instantiation. A non- 194 -- static expression in a generic may become constant because of 195 -- the attributes of the actuals, and we do not want to warn on 196 -- these legitimate constant foldings. 197 -- 198 -- If all these conditions are met, the warning is issued noting that 199 -- the result of the test is always false or always true as appropriate. 200 201 function Warn_On_Modified_As_Out_Parameter (E : Entity_Id) return Boolean; 202 -- Returns True if we should activate warnings for entity E being modified 203 -- as an out parameter. True if either Warn_On_Modified_Unread is set for 204 -- an only OUT parameter, or if Warn_On_All_Unread_Out_Parameters is set. 205 206 procedure Warn_On_Overlapping_Actuals (Subp : Entity_Id; N : Node_Id); 207 -- Called on a subprogram call. Checks whether an IN OUT actual that is 208 -- not by-copy may overlap with another actual, thus leading to aliasing 209 -- in the body of the called subprogram. This is indeed a warning in Ada 210 -- versions prior to Ada 2012, but, unless Opt.Error_To_Warning is set by 211 -- use of debug flag -gnatd.E, this is illegal and generates an error. 212 213 procedure Warn_On_Suspicious_Index (Name : Entity_Id; X : Node_Id); 214 -- This is called after resolving an indexed component or a slice. Name 215 -- is the entity for the name of the indexed array, and X is the subscript 216 -- for the indexed component case, or one of the bounds in the slice case. 217 -- If Name is an unconstrained parameter of a standard string type, and 218 -- the index is of the form of a literal or Name'Length [- literal], then 219 -- a warning is generated that the subscripting operation is possibly 220 -- incorrectly assuming a lower bound of 1. 221 222 procedure Warn_On_Suspicious_Update (N : Node_Id); 223 -- N is a semantically analyzed attribute reference Prefix'Update. Issue 224 -- a warning if Warn_On_Suspicious_Contract is set, and N is the left-hand 225 -- side or right-hand side of an equality or inequality of the form: 226 -- Prefix = Prefix'Update(...) 227 -- or 228 -- Prefix'Update(...) = Prefix 229 230 procedure Warn_On_Unassigned_Out_Parameter 231 (Return_Node : Node_Id; 232 Scope_Id : Entity_Id); 233 -- Called when processing a return statement given by Return_Node. Scope_Id 234 -- is the Entity_Id for the procedure in which the return statement lives. 235 -- A check is made for the case of a procedure with out parameters that 236 -- have not yet been assigned, and appropriate warnings are given. 237 238 procedure Warn_On_Useless_Assignment 239 (Ent : Entity_Id; 240 N : Node_Id := Empty); 241 -- Called to check if we have a case of a useless assignment to the given 242 -- entity Ent, as indicated by a non-empty Last_Assignment field. This call 243 -- should only be made if at least one of the flags Warn_On_Modified_Unread 244 -- or Warn_On_All_Unread_Out_Parameters is True, and if Ent is in the 245 -- extended main source unit. N is Empty for the end of block call 246 -- (warning message says value unreferenced), or it is the node for 247 -- an overwriting assignment (warning message points to this assignment). 248 249 procedure Warn_On_Useless_Assignments (E : Entity_Id); 250 pragma Inline (Warn_On_Useless_Assignments); 251 -- Called at the end of a block or subprogram. Scans the entities of the 252 -- block or subprogram to see if there are any variables for which useless 253 -- assignments were made (assignments whose values were never read). 254 255 ---------------------- 256 -- Utility Routines -- 257 ---------------------- 258 259 function Has_Junk_Name (E : Entity_Id) return Boolean; 260 -- Return True if the entity name contains any of the following substrings: 261 -- discard 262 -- dummy 263 -- ignore 264 -- junk 265 -- unused 266 -- Used to suppress warnings on names matching these patterns. The contents 267 -- of Name_Buffer and Name_Len are destroyed by this call. 268 269end Sem_Warn; 270