1------------------------------------------------------------------------------ 2-- -- 3-- GNAT COMPILER COMPONENTS -- 4-- -- 5-- S E M _ W A R N -- 6-- -- 7-- B o d y -- 8-- -- 9-- Copyright (C) 1999-2019, 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 26with Atree; use Atree; 27with Debug; use Debug; 28with Einfo; use Einfo; 29with Errout; use Errout; 30with Exp_Code; use Exp_Code; 31with Lib; use Lib; 32with Lib.Xref; use Lib.Xref; 33with Namet; use Namet; 34with Nlists; use Nlists; 35with Opt; use Opt; 36with Par_SCO; use Par_SCO; 37with Rtsfind; use Rtsfind; 38with Sem; use Sem; 39with Sem_Ch8; use Sem_Ch8; 40with Sem_Aux; use Sem_Aux; 41with Sem_Eval; use Sem_Eval; 42with Sem_Prag; use Sem_Prag; 43with Sem_Util; use Sem_Util; 44with Sinfo; use Sinfo; 45with Sinput; use Sinput; 46with Snames; use Snames; 47with Stand; use Stand; 48with Stringt; use Stringt; 49with Tbuild; use Tbuild; 50with Uintp; use Uintp; 51 52package body Sem_Warn is 53 54 -- The following table collects Id's of entities that are potentially 55 -- unreferenced. See Check_Unset_Reference for further details. 56 -- ??? Check_Unset_Reference has zero information about this table. 57 58 package Unreferenced_Entities is new Table.Table ( 59 Table_Component_Type => Entity_Id, 60 Table_Index_Type => Nat, 61 Table_Low_Bound => 1, 62 Table_Initial => Alloc.Unreferenced_Entities_Initial, 63 Table_Increment => Alloc.Unreferenced_Entities_Increment, 64 Table_Name => "Unreferenced_Entities"); 65 66 -- The following table collects potential warnings for IN OUT parameters 67 -- that are referenced but not modified. These warnings are processed when 68 -- the front end calls the procedure Output_Non_Modified_In_Out_Warnings. 69 -- The reason that we defer output of these messages is that we want to 70 -- detect the case where the relevant procedure is used as a generic actual 71 -- in an instantiation, since we suppress the warnings in this case. The 72 -- flag Used_As_Generic_Actual will be set in this case, but only at the 73 -- point of usage. Similarly, we suppress the message if the address of the 74 -- procedure is taken, where the flag Address_Taken may be set later. 75 76 package In_Out_Warnings is new Table.Table ( 77 Table_Component_Type => Entity_Id, 78 Table_Index_Type => Nat, 79 Table_Low_Bound => 1, 80 Table_Initial => Alloc.In_Out_Warnings_Initial, 81 Table_Increment => Alloc.In_Out_Warnings_Increment, 82 Table_Name => "In_Out_Warnings"); 83 84 -------------------------------------------------------- 85 -- Handling of Warnings Off, Unmodified, Unreferenced -- 86 -------------------------------------------------------- 87 88 -- The functions Has_Warnings_Off, Has_Unmodified, Has_Unreferenced must 89 -- generally be used instead of Warnings_Off, Has_Pragma_Unmodified and 90 -- Has_Pragma_Unreferenced, as noted in the specs in Einfo. 91 92 -- In order to avoid losing warnings in -gnatw.w (warn on unnecessary 93 -- warnings off pragma) mode, i.e. to avoid false negatives, the code 94 -- must follow some important rules. 95 96 -- Call these functions as late as possible, after completing all other 97 -- tests, just before the warnings is given. For example, don't write: 98 99 -- if not Has_Warnings_Off (E) 100 -- and then some-other-predicate-on-E then .. 101 102 -- Instead the following is preferred 103 104 -- if some-other-predicate-on-E 105 -- and then Has_Warnings_Off (E) 106 107 -- This way if some-other-predicate is false, we avoid a false indication 108 -- that a Warnings (Off, E) pragma was useful in preventing a warning. 109 110 -- The second rule is that if both Has_Unmodified and Has_Warnings_Off, or 111 -- Has_Unreferenced and Has_Warnings_Off are called, make sure that the 112 -- call to Has_Unmodified/Has_Unreferenced comes first, this way we record 113 -- that the Warnings (Off) could have been Unreferenced or Unmodified. In 114 -- fact Has_Unmodified/Has_Unreferenced includes a test for Warnings Off, 115 -- and so a subsequent test is not needed anyway (though it is harmless). 116 117 ----------------------- 118 -- Local Subprograms -- 119 ----------------------- 120 121 function Generic_Package_Spec_Entity (E : Entity_Id) return Boolean; 122 -- This returns true if the entity E is declared within a generic package. 123 -- The point of this is to detect variables which are not assigned within 124 -- the generic, but might be assigned outside the package for any given 125 -- instance. These are cases where we leave the warnings to be posted for 126 -- the instance, when we will know more. 127 128 function Goto_Spec_Entity (E : Entity_Id) return Entity_Id; 129 -- If E is a parameter entity for a subprogram body, then this function 130 -- returns the corresponding spec entity, if not, E is returned unchanged. 131 132 function Has_Pragma_Unmodified_Check_Spec (E : Entity_Id) return Boolean; 133 -- Tests Has_Pragma_Unmodified flag for entity E. If E is not a formal, 134 -- this is simply the setting of the flag Has_Pragma_Unmodified. If E is 135 -- a body formal, the setting of the flag in the corresponding spec is 136 -- also checked (and True returned if either flag is True). 137 138 function Has_Pragma_Unreferenced_Check_Spec (E : Entity_Id) return Boolean; 139 -- Tests Has_Pragma_Unreferenced flag for entity E. If E is not a formal, 140 -- this is simply the setting of the flag Has_Pragma_Unreferenced. If E is 141 -- a body formal, the setting of the flag in the corresponding spec is 142 -- also checked (and True returned if either flag is True). 143 144 function Is_Attribute_And_Known_Value_Comparison 145 (Op : Node_Id) return Boolean; 146 -- Determine whether operator Op denotes a comparison where the left 147 -- operand is an attribute reference and the value of the right operand is 148 -- known at compile time. 149 150 function Never_Set_In_Source_Check_Spec (E : Entity_Id) return Boolean; 151 -- Tests Never_Set_In_Source status for entity E. If E is not a formal, 152 -- this is simply the setting of the flag Never_Set_In_Source. If E is 153 -- a body formal, the setting of the flag in the corresponding spec is 154 -- also checked (and False returned if either flag is False). 155 156 function Operand_Has_Warnings_Suppressed (N : Node_Id) return Boolean; 157 -- This function traverses the expression tree represented by the node N 158 -- and determines if any sub-operand is a reference to an entity for which 159 -- the Warnings_Off flag is set. True is returned if such an entity is 160 -- encountered, and False otherwise. 161 162 function Referenced_Check_Spec (E : Entity_Id) return Boolean; 163 -- Tests Referenced status for entity E. If E is not a formal, this is 164 -- simply the setting of the flag Referenced. If E is a body formal, the 165 -- setting of the flag in the corresponding spec is also checked (and True 166 -- returned if either flag is True). 167 168 function Referenced_As_LHS_Check_Spec (E : Entity_Id) return Boolean; 169 -- Tests Referenced_As_LHS status for entity E. If E is not a formal, this 170 -- is simply the setting of the flag Referenced_As_LHS. If E is a body 171 -- formal, the setting of the flag in the corresponding spec is also 172 -- checked (and True returned if either flag is True). 173 174 function Referenced_As_Out_Parameter_Check_Spec 175 (E : Entity_Id) return Boolean; 176 -- Tests Referenced_As_Out_Parameter status for entity E. If E is not a 177 -- formal, this is simply the setting of Referenced_As_Out_Parameter. If E 178 -- is a body formal, the setting of the flag in the corresponding spec is 179 -- also checked (and True returned if either flag is True). 180 181 procedure Warn_On_Unreferenced_Entity 182 (Spec_E : Entity_Id; 183 Body_E : Entity_Id := Empty); 184 -- Output warnings for unreferenced entity E. For the case of an entry 185 -- formal, Body_E is the corresponding body entity for a particular 186 -- accept statement, and the message is posted on Body_E. In all other 187 -- cases, Body_E is ignored and must be Empty. 188 189 function Warnings_Off_Check_Spec (E : Entity_Id) return Boolean; 190 -- Returns True if Warnings_Off is set for the entity E or (in the case 191 -- where there is a Spec_Entity), Warnings_Off is set for the Spec_Entity. 192 193 -------------------------- 194 -- Check_Code_Statement -- 195 -------------------------- 196 197 procedure Check_Code_Statement (N : Node_Id) is 198 begin 199 -- If volatile, nothing to worry about 200 201 if Is_Asm_Volatile (N) then 202 return; 203 end if; 204 205 -- Warn if no input or no output 206 207 Setup_Asm_Inputs (N); 208 209 if No (Asm_Input_Value) then 210 Error_Msg_F 211 ("??code statement with no inputs should usually be Volatile!", N); 212 return; 213 end if; 214 215 Setup_Asm_Outputs (N); 216 217 if No (Asm_Output_Variable) then 218 Error_Msg_F 219 ("??code statement with no outputs should usually be Volatile!", N); 220 return; 221 end if; 222 end Check_Code_Statement; 223 224 --------------------------------- 225 -- Check_Infinite_Loop_Warning -- 226 --------------------------------- 227 228 -- The case we look for is a while loop which tests a local variable, where 229 -- there is no obvious direct or possible indirect update of the variable 230 -- within the body of the loop. 231 232 procedure Check_Infinite_Loop_Warning (Loop_Statement : Node_Id) is 233 Expression : Node_Id := Empty; 234 -- Set to WHILE or EXIT WHEN condition to be tested 235 236 Ref : Node_Id := Empty; 237 -- Reference in Expression to variable that might not be modified 238 -- in loop, indicating a possible infinite loop. 239 240 Var : Entity_Id := Empty; 241 -- Corresponding entity (entity of Ref) 242 243 Function_Call_Found : Boolean := False; 244 -- True if Find_Var found a function call in the condition 245 246 procedure Find_Var (N : Node_Id); 247 -- Inspect condition to see if it depends on a single entity reference. 248 -- If so, Ref is set to point to the reference node, and Var is set to 249 -- the referenced Entity. 250 251 function Has_Condition_Actions (Iter : Node_Id) return Boolean; 252 -- Determine whether iteration scheme Iter has meaningful condition 253 -- actions. 254 255 function Has_Indirection (T : Entity_Id) return Boolean; 256 -- If the controlling variable is an access type, or is a record type 257 -- with access components, assume that it is changed indirectly and 258 -- suppress the warning. As a concession to low-level programming, in 259 -- particular within Declib, we also suppress warnings on a record 260 -- type that contains components of type Address or Short_Address. 261 262 function Is_Suspicious_Function_Name (E : Entity_Id) return Boolean; 263 -- Given an entity name, see if the name appears to have something to 264 -- do with I/O or network stuff, and if so, return True. Used to kill 265 -- some false positives on a heuristic basis that such functions will 266 -- likely have some strange side effect dependencies. A rather strange 267 -- test, but warning messages are in the heuristics business. 268 269 function Test_Ref (N : Node_Id) return Traverse_Result; 270 -- Test for reference to variable in question. Returns Abandon if 271 -- matching reference found. Used in instantiation of No_Ref_Found. 272 273 function No_Ref_Found is new Traverse_Func (Test_Ref); 274 -- Function to traverse body of procedure. Returns Abandon if matching 275 -- reference found. 276 277 -------------- 278 -- Find_Var -- 279 -------------- 280 281 procedure Find_Var (N : Node_Id) is 282 begin 283 -- Condition is a direct variable reference 284 285 if Is_Entity_Name (N) then 286 Ref := N; 287 Var := Entity (Ref); 288 289 -- Case of condition is a comparison with compile time known value 290 291 elsif Nkind (N) in N_Op_Compare then 292 if Compile_Time_Known_Value (Right_Opnd (N)) then 293 Find_Var (Left_Opnd (N)); 294 295 elsif Compile_Time_Known_Value (Left_Opnd (N)) then 296 Find_Var (Right_Opnd (N)); 297 298 -- Ignore any other comparison 299 300 else 301 return; 302 end if; 303 304 -- If condition is a negation, check its operand 305 306 elsif Nkind (N) = N_Op_Not then 307 Find_Var (Right_Opnd (N)); 308 309 -- Case of condition is function call 310 311 elsif Nkind (N) = N_Function_Call then 312 313 Function_Call_Found := True; 314 315 -- Forget it if function name is not entity, who knows what 316 -- we might be calling? 317 318 if not Is_Entity_Name (Name (N)) then 319 return; 320 321 -- Forget it if function name is suspicious. A strange test 322 -- but warning generation is in the heuristics business. 323 324 elsif Is_Suspicious_Function_Name (Entity (Name (N))) then 325 return; 326 327 -- Forget it if function is marked Volatile_Function 328 329 elsif Is_Volatile_Function (Entity (Name (N))) then 330 return; 331 332 -- Forget it if warnings are suppressed on function entity 333 334 elsif Has_Warnings_Off (Entity (Name (N))) then 335 return; 336 337 -- Forget it if the parameter is not In 338 339 elsif Has_Out_Or_In_Out_Parameter (Entity (Name (N))) then 340 return; 341 end if; 342 343 -- OK, see if we have one argument 344 345 declare 346 PA : constant List_Id := Parameter_Associations (N); 347 348 begin 349 -- One argument, so check the argument 350 351 if Present (PA) and then List_Length (PA) = 1 then 352 if Nkind (First (PA)) = N_Parameter_Association then 353 Find_Var (Explicit_Actual_Parameter (First (PA))); 354 else 355 Find_Var (First (PA)); 356 end if; 357 358 -- Not one argument 359 360 else 361 return; 362 end if; 363 end; 364 365 -- Any other kind of node is not something we warn for 366 367 else 368 return; 369 end if; 370 end Find_Var; 371 372 --------------------------- 373 -- Has_Condition_Actions -- 374 --------------------------- 375 376 function Has_Condition_Actions (Iter : Node_Id) return Boolean is 377 Action : Node_Id; 378 379 begin 380 -- A call marker is not considered a meaningful action because it 381 -- acts as an annotation and has no runtime semantics. 382 383 Action := First (Condition_Actions (Iter)); 384 while Present (Action) loop 385 if Nkind (Action) /= N_Call_Marker then 386 return True; 387 end if; 388 389 Next (Action); 390 end loop; 391 392 return False; 393 end Has_Condition_Actions; 394 395 --------------------- 396 -- Has_Indirection -- 397 --------------------- 398 399 function Has_Indirection (T : Entity_Id) return Boolean is 400 Comp : Entity_Id; 401 Rec : Entity_Id; 402 403 begin 404 if Is_Access_Type (T) then 405 return True; 406 407 elsif Is_Private_Type (T) 408 and then Present (Full_View (T)) 409 and then Is_Access_Type (Full_View (T)) 410 then 411 return True; 412 413 elsif Is_Record_Type (T) then 414 Rec := T; 415 416 elsif Is_Private_Type (T) 417 and then Present (Full_View (T)) 418 and then Is_Record_Type (Full_View (T)) 419 then 420 Rec := Full_View (T); 421 else 422 return False; 423 end if; 424 425 Comp := First_Component (Rec); 426 while Present (Comp) loop 427 if Is_Access_Type (Etype (Comp)) 428 or else Is_Descendant_Of_Address (Etype (Comp)) 429 then 430 return True; 431 end if; 432 433 Next_Component (Comp); 434 end loop; 435 436 return False; 437 end Has_Indirection; 438 439 --------------------------------- 440 -- Is_Suspicious_Function_Name -- 441 --------------------------------- 442 443 function Is_Suspicious_Function_Name (E : Entity_Id) return Boolean is 444 S : Entity_Id; 445 446 function Substring_Present (S : String) return Boolean; 447 -- Returns True if name buffer has given string delimited by non- 448 -- alphabetic characters or by end of string. S is lower case. 449 450 ----------------------- 451 -- Substring_Present -- 452 ----------------------- 453 454 function Substring_Present (S : String) return Boolean is 455 Len : constant Natural := S'Length; 456 457 begin 458 for J in 1 .. Name_Len - (Len - 1) loop 459 if Name_Buffer (J .. J + (Len - 1)) = S 460 and then (J = 1 or else Name_Buffer (J - 1) not in 'a' .. 'z') 461 and then 462 (J + Len > Name_Len 463 or else Name_Buffer (J + Len) not in 'a' .. 'z') 464 then 465 return True; 466 end if; 467 end loop; 468 469 return False; 470 end Substring_Present; 471 472 -- Start of processing for Is_Suspicious_Function_Name 473 474 begin 475 S := E; 476 while Present (S) and then S /= Standard_Standard loop 477 Get_Name_String (Chars (S)); 478 479 if Substring_Present ("io") 480 or else Substring_Present ("file") 481 or else Substring_Present ("network") 482 then 483 return True; 484 else 485 S := Scope (S); 486 end if; 487 end loop; 488 489 return False; 490 end Is_Suspicious_Function_Name; 491 492 -------------- 493 -- Test_Ref -- 494 -------------- 495 496 function Test_Ref (N : Node_Id) return Traverse_Result is 497 begin 498 -- Waste of time to look at the expression we are testing 499 500 if N = Expression then 501 return Skip; 502 503 -- Direct reference to variable in question 504 505 elsif Is_Entity_Name (N) 506 and then Present (Entity (N)) 507 and then Entity (N) = Var 508 then 509 -- If this is an lvalue, then definitely abandon, since 510 -- this could be a direct modification of the variable. 511 512 if May_Be_Lvalue (N) then 513 return Abandon; 514 end if; 515 516 -- If the condition contains a function call, we consider it may 517 -- be modified by side effects from a procedure call. Otherwise, 518 -- we consider the condition may not be modified, although that 519 -- might happen if Variable is itself a by-reference parameter, 520 -- and the procedure called modifies the global object referred to 521 -- by Variable, but we actually prefer to issue a warning in this 522 -- odd case. Note that the case where the procedure called has 523 -- visibility over Variable is treated in another case below. 524 525 if Function_Call_Found then 526 declare 527 P : Node_Id; 528 529 begin 530 P := N; 531 loop 532 P := Parent (P); 533 exit when P = Loop_Statement; 534 535 -- Abandon if at procedure call, or something strange is 536 -- going on (perhaps a node with no parent that should 537 -- have one but does not?) As always, for a warning we 538 -- prefer to just abandon the warning than get into the 539 -- business of complaining about the tree structure here. 540 541 if No (P) 542 or else Nkind (P) = N_Procedure_Call_Statement 543 then 544 return Abandon; 545 end if; 546 end loop; 547 end; 548 end if; 549 550 -- Reference to variable renaming variable in question 551 552 elsif Is_Entity_Name (N) 553 and then Present (Entity (N)) 554 and then Ekind (Entity (N)) = E_Variable 555 and then Present (Renamed_Object (Entity (N))) 556 and then Is_Entity_Name (Renamed_Object (Entity (N))) 557 and then Entity (Renamed_Object (Entity (N))) = Var 558 and then May_Be_Lvalue (N) 559 then 560 return Abandon; 561 562 -- Call to subprogram 563 564 elsif Nkind (N) in N_Subprogram_Call then 565 566 -- If subprogram is within the scope of the entity we are dealing 567 -- with as the loop variable, then it could modify this parameter, 568 -- so we abandon in this case. In the case of a subprogram that is 569 -- not an entity we also abandon. The check for no entity being 570 -- present is a defense against previous errors. 571 572 if not Is_Entity_Name (Name (N)) 573 or else No (Entity (Name (N))) 574 or else Scope_Within (Entity (Name (N)), Scope (Var)) 575 then 576 return Abandon; 577 end if; 578 579 -- If any of the arguments are of type access to subprogram, then 580 -- we may have funny side effects, so no warning in this case. 581 582 declare 583 Actual : Node_Id; 584 begin 585 Actual := First_Actual (N); 586 while Present (Actual) loop 587 if Is_Access_Subprogram_Type (Etype (Actual)) then 588 return Abandon; 589 else 590 Next_Actual (Actual); 591 end if; 592 end loop; 593 end; 594 595 -- Declaration of the variable in question 596 597 elsif Nkind (N) = N_Object_Declaration 598 and then Defining_Identifier (N) = Var 599 then 600 return Abandon; 601 end if; 602 603 -- All OK, continue scan 604 605 return OK; 606 end Test_Ref; 607 608 -- Start of processing for Check_Infinite_Loop_Warning 609 610 begin 611 -- Skip processing if debug flag gnatd.w is set 612 613 if Debug_Flag_Dot_W then 614 return; 615 end if; 616 617 -- Deal with Iteration scheme present 618 619 declare 620 Iter : constant Node_Id := Iteration_Scheme (Loop_Statement); 621 622 begin 623 if Present (Iter) then 624 625 -- While iteration 626 627 if Present (Condition (Iter)) then 628 629 -- Skip processing for while iteration with conditions actions, 630 -- since they make it too complicated to get the warning right. 631 632 if Has_Condition_Actions (Iter) then 633 return; 634 end if; 635 636 -- Capture WHILE condition 637 638 Expression := Condition (Iter); 639 640 -- For Loop_Parameter_Specification, do not process, since loop 641 -- will always terminate. For Iterator_Specification, also do not 642 -- process. Either it will always terminate (e.g. "for X of 643 -- Some_Array ..."), or we can't tell if it's going to terminate 644 -- without looking at the iterator, so any warning here would be 645 -- noise. 646 647 elsif Present (Loop_Parameter_Specification (Iter)) 648 or else Present (Iterator_Specification (Iter)) 649 then 650 return; 651 end if; 652 end if; 653 end; 654 655 -- Check chain of EXIT statements, we only process loops that have a 656 -- single exit condition (either a single EXIT WHEN statement, or a 657 -- WHILE loop not containing any EXIT WHEN statements). 658 659 declare 660 Ident : constant Node_Id := Identifier (Loop_Statement); 661 Exit_Stmt : Node_Id; 662 663 begin 664 -- If we don't have a proper chain set, ignore call entirely. This 665 -- happens because of previous errors. 666 667 if No (Entity (Ident)) 668 or else Ekind (Entity (Ident)) /= E_Loop 669 then 670 Check_Error_Detected; 671 return; 672 end if; 673 674 -- Otherwise prepare to scan list of EXIT statements 675 676 Exit_Stmt := First_Exit_Statement (Entity (Ident)); 677 while Present (Exit_Stmt) loop 678 679 -- Check for EXIT WHEN 680 681 if Present (Condition (Exit_Stmt)) then 682 683 -- Quit processing if EXIT WHEN in WHILE loop, or more than 684 -- one EXIT WHEN statement present in the loop. 685 686 if Present (Expression) then 687 return; 688 689 -- Otherwise capture condition from EXIT WHEN statement 690 691 else 692 Expression := Condition (Exit_Stmt); 693 end if; 694 695 -- If an unconditional exit statement is the last statement in the 696 -- loop, assume that no warning is needed, without any attempt at 697 -- checking whether the exit is reachable. 698 699 elsif Exit_Stmt = Last (Statements (Loop_Statement)) then 700 return; 701 end if; 702 703 Exit_Stmt := Next_Exit_Statement (Exit_Stmt); 704 end loop; 705 end; 706 707 -- Return if no condition to test 708 709 if No (Expression) then 710 return; 711 end if; 712 713 -- Initial conditions met, see if condition is of right form 714 715 Find_Var (Expression); 716 717 -- Nothing to do if local variable from source not found. If it's a 718 -- renaming, it is probably renaming something too complicated to deal 719 -- with here. 720 721 if No (Var) 722 or else Ekind (Var) /= E_Variable 723 or else Is_Library_Level_Entity (Var) 724 or else not Comes_From_Source (Var) 725 or else Nkind (Parent (Var)) = N_Object_Renaming_Declaration 726 then 727 return; 728 729 -- Nothing to do if there is some indirection involved (assume that the 730 -- designated variable might be modified in some way we don't see). 731 -- However, if no function call was found, then we don't care about 732 -- indirections, because the condition must be something like "while X 733 -- /= null loop", so we don't care if X.all is modified in the loop. 734 735 elsif Function_Call_Found and then Has_Indirection (Etype (Var)) then 736 return; 737 738 -- Same sort of thing for volatile variable, might be modified by 739 -- some other task or by the operating system in some way. 740 741 elsif Is_Volatile (Var) then 742 return; 743 end if; 744 745 -- Filter out case of original statement sequence starting with delay. 746 -- We assume this is a multi-tasking program and that the condition 747 -- is affected by other threads (some kind of busy wait). 748 749 declare 750 Fstm : constant Node_Id := 751 Original_Node (First (Statements (Loop_Statement))); 752 begin 753 if Nkind (Fstm) = N_Delay_Relative_Statement 754 or else Nkind (Fstm) = N_Delay_Until_Statement 755 then 756 return; 757 end if; 758 end; 759 760 -- We have a variable reference of the right form, now we scan the loop 761 -- body to see if it looks like it might not be modified 762 763 if No_Ref_Found (Loop_Statement) = OK then 764 Error_Msg_NE 765 ("??variable& is not modified in loop body!", Ref, Var); 766 Error_Msg_N 767 ("\??possible infinite loop!", Ref); 768 end if; 769 end Check_Infinite_Loop_Warning; 770 771 ---------------------------- 772 -- Check_Low_Bound_Tested -- 773 ---------------------------- 774 775 procedure Check_Low_Bound_Tested (Expr : Node_Id) is 776 procedure Check_Low_Bound_Tested_For (Opnd : Node_Id); 777 -- Determine whether operand Opnd denotes attribute 'First whose prefix 778 -- is a formal parameter. If this is the case, mark the entity of the 779 -- prefix as having its low bound tested. 780 781 -------------------------------- 782 -- Check_Low_Bound_Tested_For -- 783 -------------------------------- 784 785 procedure Check_Low_Bound_Tested_For (Opnd : Node_Id) is 786 begin 787 if Nkind (Opnd) = N_Attribute_Reference 788 and then Attribute_Name (Opnd) = Name_First 789 and then Is_Entity_Name (Prefix (Opnd)) 790 and then Present (Entity (Prefix (Opnd))) 791 and then Is_Formal (Entity (Prefix (Opnd))) 792 then 793 Set_Low_Bound_Tested (Entity (Prefix (Opnd))); 794 end if; 795 end Check_Low_Bound_Tested_For; 796 797 -- Start of processing for Check_Low_Bound_Tested 798 799 begin 800 if Comes_From_Source (Expr) then 801 Check_Low_Bound_Tested_For (Left_Opnd (Expr)); 802 Check_Low_Bound_Tested_For (Right_Opnd (Expr)); 803 end if; 804 end Check_Low_Bound_Tested; 805 806 ---------------------- 807 -- Check_References -- 808 ---------------------- 809 810 procedure Check_References (E : Entity_Id; Anod : Node_Id := Empty) is 811 E1 : Entity_Id; 812 E1T : Entity_Id; 813 UR : Node_Id; 814 815 function Body_Formal 816 (E : Entity_Id; 817 Accept_Statement : Node_Id) return Entity_Id; 818 -- For an entry formal entity from an entry declaration, find the 819 -- corresponding body formal from the given accept statement. 820 821 function Generic_Body_Formal (E : Entity_Id) return Entity_Id; 822 -- Warnings on unused formals of subprograms are placed on the entity 823 -- in the subprogram body, which seems preferable because it suggests 824 -- a better codefix for GNAT Studio. The analysis of generic subprogram 825 -- bodies uses a different circuitry, so the choice for the proper 826 -- placement of the warning in the generic case takes place here, by 827 -- finding the body entity that corresponds to a formal in a spec. 828 829 procedure May_Need_Initialized_Actual (Ent : Entity_Id); 830 -- If an entity of a generic type has default initialization, then the 831 -- corresponding actual type should be fully initialized, or else there 832 -- will be uninitialized components in the instantiation, that might go 833 -- unreported. This routine marks the type of the uninitialized variable 834 -- appropriately to allow the compiler to emit an appropriate warning 835 -- in the instance. In a sense, the use of a type that requires full 836 -- initialization is a weak part of the generic contract. 837 838 function Missing_Subunits return Boolean; 839 -- We suppress warnings when there are missing subunits, because this 840 -- may generate too many false positives: entities in a parent may only 841 -- be referenced in one of the subunits. We make an exception for 842 -- subunits that contain no other stubs. 843 844 procedure Output_Reference_Error (M : String); 845 -- Used to output an error message. Deals with posting the error on the 846 -- body formal in the accept case. 847 848 function Publicly_Referenceable (Ent : Entity_Id) return Boolean; 849 -- This is true if the entity in question is potentially referenceable 850 -- from another unit. This is true for entities in packages that are at 851 -- the library level. 852 853 function Warnings_Off_E1 return Boolean; 854 -- Return True if Warnings_Off is set for E1, or for its Etype (E1T), 855 -- or for the base type of E1T. 856 857 ----------------- 858 -- Body_Formal -- 859 ----------------- 860 861 function Body_Formal 862 (E : Entity_Id; 863 Accept_Statement : Node_Id) return Entity_Id 864 is 865 Body_Param : Node_Id; 866 Body_E : Entity_Id; 867 868 begin 869 -- Loop to find matching parameter in accept statement 870 871 Body_Param := First (Parameter_Specifications (Accept_Statement)); 872 while Present (Body_Param) loop 873 Body_E := Defining_Identifier (Body_Param); 874 875 if Chars (Body_E) = Chars (E) then 876 return Body_E; 877 end if; 878 879 Next (Body_Param); 880 end loop; 881 882 -- Should never fall through, should always find a match 883 884 raise Program_Error; 885 end Body_Formal; 886 887 ------------------------- 888 -- Generic_Body_Formal -- 889 ------------------------- 890 891 function Generic_Body_Formal (E : Entity_Id) return Entity_Id is 892 Gen_Decl : constant Node_Id := Unit_Declaration_Node (Scope (E)); 893 Gen_Body : constant Entity_Id := Corresponding_Body (Gen_Decl); 894 Form : Entity_Id; 895 896 begin 897 if No (Gen_Body) then 898 return E; 899 900 else 901 Form := First_Entity (Gen_Body); 902 while Present (Form) loop 903 if Chars (Form) = Chars (E) then 904 return Form; 905 end if; 906 907 Next_Entity (Form); 908 end loop; 909 end if; 910 911 -- Should never fall through, should always find a match 912 913 raise Program_Error; 914 end Generic_Body_Formal; 915 916 --------------------------------- 917 -- May_Need_Initialized_Actual -- 918 --------------------------------- 919 920 procedure May_Need_Initialized_Actual (Ent : Entity_Id) is 921 T : constant Entity_Id := Etype (Ent); 922 Par : constant Node_Id := Parent (T); 923 924 begin 925 if not Is_Generic_Type (T) then 926 null; 927 928 elsif (Nkind (Par)) = N_Private_Extension_Declaration then 929 930 -- We only indicate the first such variable in the generic. 931 932 if No (Uninitialized_Variable (Par)) then 933 Set_Uninitialized_Variable (Par, Ent); 934 end if; 935 936 elsif (Nkind (Par)) = N_Formal_Type_Declaration 937 and then Nkind (Formal_Type_Definition (Par)) = 938 N_Formal_Private_Type_Definition 939 then 940 if No (Uninitialized_Variable (Formal_Type_Definition (Par))) then 941 Set_Uninitialized_Variable (Formal_Type_Definition (Par), Ent); 942 end if; 943 end if; 944 end May_Need_Initialized_Actual; 945 946 ---------------------- 947 -- Missing_Subunits -- 948 ---------------------- 949 950 function Missing_Subunits return Boolean is 951 D : Node_Id; 952 953 begin 954 if not Unloaded_Subunits then 955 956 -- Normal compilation, all subunits are present 957 958 return False; 959 960 elsif E /= Main_Unit_Entity then 961 962 -- No warnings on a stub that is not the main unit 963 964 return True; 965 966 elsif Nkind (Unit_Declaration_Node (E)) in N_Proper_Body then 967 D := First (Declarations (Unit_Declaration_Node (E))); 968 while Present (D) loop 969 970 -- No warnings if the proper body contains nested stubs 971 972 if Nkind (D) in N_Body_Stub then 973 return True; 974 end if; 975 976 Next (D); 977 end loop; 978 979 return False; 980 981 else 982 -- Missing stubs elsewhere 983 984 return True; 985 end if; 986 end Missing_Subunits; 987 988 ---------------------------- 989 -- Output_Reference_Error -- 990 ---------------------------- 991 992 procedure Output_Reference_Error (M : String) is 993 begin 994 -- Never issue messages for internal names or renamings 995 996 if Is_Internal_Name (Chars (E1)) 997 or else Nkind (Parent (E1)) = N_Object_Renaming_Declaration 998 then 999 return; 1000 end if; 1001 1002 -- Don't output message for IN OUT formal unless we have the warning 1003 -- flag specifically set. It is a bit odd to distinguish IN OUT 1004 -- formals from other cases. This distinction is historical in 1005 -- nature. Warnings for IN OUT formals were added fairly late. 1006 1007 if Ekind (E1) = E_In_Out_Parameter 1008 and then not Check_Unreferenced_Formals 1009 then 1010 return; 1011 end if; 1012 1013 -- Other than accept case, post error on defining identifier 1014 1015 if No (Anod) then 1016 Error_Msg_N (M, E1); 1017 1018 -- Accept case, find body formal to post the message 1019 1020 else 1021 Error_Msg_NE (M, Body_Formal (E1, Accept_Statement => Anod), E1); 1022 1023 end if; 1024 end Output_Reference_Error; 1025 1026 ---------------------------- 1027 -- Publicly_Referenceable -- 1028 ---------------------------- 1029 1030 function Publicly_Referenceable (Ent : Entity_Id) return Boolean is 1031 P : Node_Id; 1032 Prev : Node_Id; 1033 1034 begin 1035 -- A formal parameter is never referenceable outside the body of its 1036 -- subprogram or entry. 1037 1038 if Is_Formal (Ent) then 1039 return False; 1040 end if; 1041 1042 -- Examine parents to look for a library level package spec. But if 1043 -- we find a body or block or other similar construct along the way, 1044 -- we cannot be referenced. 1045 1046 Prev := Ent; 1047 P := Parent (Ent); 1048 loop 1049 case Nkind (P) is 1050 1051 -- If we get to top of tree, then publicly referenceable 1052 1053 when N_Empty => 1054 return True; 1055 1056 -- If we reach a generic package declaration, then always 1057 -- consider this referenceable, since any instantiation will 1058 -- have access to the entities in the generic package. Note 1059 -- that the package itself may not be instantiated, but then 1060 -- we will get a warning for the package entity. 1061 1062 -- Note that generic formal parameters are themselves not 1063 -- publicly referenceable in an instance, and warnings on them 1064 -- are useful. 1065 1066 when N_Generic_Package_Declaration => 1067 return 1068 not Is_List_Member (Prev) 1069 or else List_Containing (Prev) /= 1070 Generic_Formal_Declarations (P); 1071 1072 -- Similarly, the generic formals of a generic subprogram are 1073 -- not accessible. 1074 1075 when N_Generic_Subprogram_Declaration => 1076 if Is_List_Member (Prev) 1077 and then List_Containing (Prev) = 1078 Generic_Formal_Declarations (P) 1079 then 1080 return False; 1081 else 1082 P := Parent (P); 1083 end if; 1084 1085 -- If we reach a subprogram body, entity is not referenceable 1086 -- unless it is the defining entity of the body. This will 1087 -- happen, e.g. when a function is an attribute renaming that 1088 -- is rewritten as a body. 1089 1090 when N_Subprogram_Body => 1091 if Ent /= Defining_Entity (P) then 1092 return False; 1093 else 1094 P := Parent (P); 1095 end if; 1096 1097 -- If we reach any other body, definitely not referenceable 1098 1099 when N_Block_Statement 1100 | N_Entry_Body 1101 | N_Package_Body 1102 | N_Protected_Body 1103 | N_Subunit 1104 | N_Task_Body 1105 => 1106 return False; 1107 1108 -- For all other cases, keep looking up tree 1109 1110 when others => 1111 Prev := P; 1112 P := Parent (P); 1113 end case; 1114 end loop; 1115 end Publicly_Referenceable; 1116 1117 --------------------- 1118 -- Warnings_Off_E1 -- 1119 --------------------- 1120 1121 function Warnings_Off_E1 return Boolean is 1122 begin 1123 return Has_Warnings_Off (E1T) 1124 or else Has_Warnings_Off (Base_Type (E1T)) 1125 or else Warnings_Off_Check_Spec (E1); 1126 end Warnings_Off_E1; 1127 1128 -- Start of processing for Check_References 1129 1130 begin 1131 Process_Deferred_References; 1132 1133 -- No messages if warnings are suppressed, or if we have detected any 1134 -- real errors so far (this last check avoids junk messages resulting 1135 -- from errors, e.g. a subunit that is not loaded). 1136 1137 if Warning_Mode = Suppress or else Serious_Errors_Detected /= 0 then 1138 return; 1139 end if; 1140 1141 -- We also skip the messages if any subunits were not loaded (see 1142 -- comment in Sem_Ch10 to understand how this is set, and why it is 1143 -- necessary to suppress the warnings in this case). 1144 1145 if Missing_Subunits then 1146 return; 1147 end if; 1148 1149 -- Otherwise loop through entities, looking for suspicious stuff 1150 1151 E1 := First_Entity (E); 1152 while Present (E1) loop 1153 E1T := Etype (E1); 1154 1155 -- We are only interested in source entities. We also don't issue 1156 -- warnings within instances, since the proper place for such 1157 -- warnings is on the template when it is compiled, and we don't 1158 -- issue warnings for variables with names like Junk, Discard etc. 1159 1160 if Comes_From_Source (E1) 1161 and then Instantiation_Location (Sloc (E1)) = No_Location 1162 then 1163 -- We are interested in variables and out/in-out parameters, but 1164 -- we exclude protected types, too complicated to worry about. 1165 1166 if Ekind (E1) = E_Variable 1167 or else 1168 (Ekind_In (E1, E_Out_Parameter, E_In_Out_Parameter) 1169 and then not Is_Protected_Type (Current_Scope)) 1170 then 1171 -- If the formal has a class-wide type, retrieve its type 1172 -- because checks below depend on its private nature. 1173 1174 if Is_Class_Wide_Type (E1T) then 1175 E1T := Etype (E1T); 1176 end if; 1177 1178 -- Case of an unassigned variable 1179 1180 -- First gather any Unset_Reference indication for E1. In the 1181 -- case of a parameter, it is the Spec_Entity that is relevant. 1182 1183 if Ekind (E1) = E_Out_Parameter 1184 and then Present (Spec_Entity (E1)) 1185 then 1186 UR := Unset_Reference (Spec_Entity (E1)); 1187 else 1188 UR := Unset_Reference (E1); 1189 end if; 1190 1191 -- Special processing for access types 1192 1193 if Present (UR) and then Is_Access_Type (E1T) then 1194 1195 -- For access types, the only time we made a UR entry was 1196 -- for a dereference, and so we post the appropriate warning 1197 -- here (note that the dereference may not be explicit in 1198 -- the source, for example in the case of a dispatching call 1199 -- with an anonymous access controlling formal, or of an 1200 -- assignment of a pointer involving discriminant check on 1201 -- the designated object). 1202 1203 if not Warnings_Off_E1 then 1204 Error_Msg_NE ("??& may be null!", UR, E1); 1205 end if; 1206 1207 goto Continue; 1208 1209 -- Case of variable that could be a constant. Note that we 1210 -- never signal such messages for generic package entities, 1211 -- since a given instance could have modifications outside 1212 -- the package. 1213 1214 -- Note that we used to check Address_Taken here, but we don't 1215 -- want to do that since it can be set for non-source cases, 1216 -- e.g. the Unrestricted_Access from a valid attribute, and 1217 -- the wanted effect is included in Never_Set_In_Source. 1218 1219 elsif Warn_On_Constant 1220 and then (Ekind (E1) = E_Variable 1221 and then Has_Initial_Value (E1)) 1222 and then Never_Set_In_Source_Check_Spec (E1) 1223 and then not Generic_Package_Spec_Entity (E1) 1224 then 1225 -- A special case, if this variable is volatile and not 1226 -- imported, it is not helpful to tell the programmer 1227 -- to mark the variable as constant, since this would be 1228 -- illegal by virtue of RM C.6(13). Instead we suggest 1229 -- using pragma Export (can't be Import because of the 1230 -- initial value). 1231 1232 if (Is_Volatile (E1) or else Has_Volatile_Components (E1)) 1233 and then not Is_Imported (E1) 1234 then 1235 Error_Msg_N 1236 ("?k?& is not modified, consider pragma Export for " 1237 & "volatile variable!", E1); 1238 1239 -- Another special case, Exception_Occurrence, this catches 1240 -- the case of exception choice (and a bit more too, but not 1241 -- worth doing more investigation here). 1242 1243 elsif Is_RTE (E1T, RE_Exception_Occurrence) then 1244 null; 1245 1246 -- Here we give the warning if referenced and no pragma 1247 -- Unreferenced or Unmodified is present. 1248 1249 else 1250 -- Variable case 1251 1252 if Ekind (E1) = E_Variable then 1253 if Referenced_Check_Spec (E1) 1254 and then not Has_Pragma_Unreferenced_Check_Spec (E1) 1255 and then not Has_Pragma_Unmodified_Check_Spec (E1) 1256 then 1257 if not Warnings_Off_E1 1258 and then not Has_Junk_Name (E1) 1259 then 1260 Error_Msg_N -- CODEFIX 1261 ("?k?& is not modified, " 1262 & "could be declared constant!", 1263 E1); 1264 end if; 1265 end if; 1266 end if; 1267 end if; 1268 1269 -- Other cases of a variable or parameter never set in source 1270 1271 elsif Never_Set_In_Source_Check_Spec (E1) 1272 1273 -- No warning if warning for this case turned off 1274 1275 and then Warn_On_No_Value_Assigned 1276 1277 -- No warning if address taken somewhere 1278 1279 and then not Address_Taken (E1) 1280 1281 -- No warning if explicit initial value 1282 1283 and then not Has_Initial_Value (E1) 1284 1285 -- No warning for generic package spec entities, since we 1286 -- might set them in a child unit or something like that 1287 1288 and then not Generic_Package_Spec_Entity (E1) 1289 1290 -- No warning if fully initialized type, except that for 1291 -- this purpose we do not consider access types to qualify 1292 -- as fully initialized types (relying on an access type 1293 -- variable being null when it is never set is a bit odd). 1294 1295 -- Also we generate warning for an out parameter that is 1296 -- never referenced, since again it seems odd to rely on 1297 -- default initialization to set an out parameter value. 1298 1299 and then (Is_Access_Type (E1T) 1300 or else Ekind (E1) = E_Out_Parameter 1301 or else not Is_Fully_Initialized_Type (E1T)) 1302 then 1303 -- Do not output complaint about never being assigned a 1304 -- value if a pragma Unmodified applies to the variable 1305 -- we are examining, or if it is a parameter, if there is 1306 -- a pragma Unreferenced for the corresponding spec, or 1307 -- if the type is marked as having unreferenced objects. 1308 -- The last is a little peculiar, but better too few than 1309 -- too many warnings in this situation. 1310 1311 if Has_Pragma_Unreferenced_Objects (E1T) 1312 or else Has_Pragma_Unmodified_Check_Spec (E1) 1313 then 1314 null; 1315 1316 -- IN OUT parameter case where parameter is referenced. We 1317 -- separate this out, since this is the case where we delay 1318 -- output of the warning until more information is available 1319 -- (about use in an instantiation or address being taken). 1320 1321 elsif Ekind (E1) = E_In_Out_Parameter 1322 and then Referenced_Check_Spec (E1) 1323 then 1324 -- Suppress warning if private type, and the procedure 1325 -- has a separate declaration in a different unit. This 1326 -- is the case where the client of a package sees only 1327 -- the private type, and it may be quite reasonable 1328 -- for the logical view to be IN OUT, even if the 1329 -- implementation ends up using access types or some 1330 -- other method to achieve the local effect of a 1331 -- modification. On the other hand if the spec and body 1332 -- are in the same unit, we are in the package body and 1333 -- there we have less excuse for a junk IN OUT parameter. 1334 1335 if Has_Private_Declaration (E1T) 1336 and then Present (Spec_Entity (E1)) 1337 and then not In_Same_Source_Unit (E1, Spec_Entity (E1)) 1338 then 1339 null; 1340 1341 -- Suppress warning for any parameter of a dispatching 1342 -- operation, since it is quite reasonable to have an 1343 -- operation that is overridden, and for some subclasses 1344 -- needs the formal to be IN OUT and for others happens 1345 -- not to assign it. 1346 1347 elsif Is_Dispatching_Operation 1348 (Scope (Goto_Spec_Entity (E1))) 1349 then 1350 null; 1351 1352 -- Suppress warning if composite type contains any access 1353 -- component, since the logical effect of modifying a 1354 -- parameter may be achieved by modifying a referenced 1355 -- object. 1356 1357 elsif Is_Composite_Type (E1T) 1358 and then Has_Access_Values (E1T) 1359 then 1360 null; 1361 1362 -- Suppress warning on formals of an entry body. All 1363 -- references are attached to the formal in the entry 1364 -- declaration, which are marked Is_Entry_Formal. 1365 1366 elsif Ekind (Scope (E1)) = E_Entry 1367 and then not Is_Entry_Formal (E1) 1368 then 1369 null; 1370 1371 -- OK, looks like warning for an IN OUT parameter that 1372 -- could be IN makes sense, but we delay the output of 1373 -- the warning, pending possibly finding out later on 1374 -- that the associated subprogram is used as a generic 1375 -- actual, or its address/access is taken. In these two 1376 -- cases, we suppress the warning because the context may 1377 -- force use of IN OUT, even if in this particular case 1378 -- the formal is not modified. 1379 1380 else 1381 -- Suppress the warnings for a junk name 1382 1383 if not Has_Junk_Name (E1) then 1384 In_Out_Warnings.Append (E1); 1385 end if; 1386 end if; 1387 1388 -- Other cases of formals 1389 1390 elsif Is_Formal (E1) then 1391 if not Is_Trivial_Subprogram (Scope (E1)) then 1392 if Referenced_Check_Spec (E1) then 1393 if not Has_Pragma_Unmodified_Check_Spec (E1) 1394 and then not Warnings_Off_E1 1395 and then not Has_Junk_Name (E1) 1396 then 1397 Output_Reference_Error 1398 ("?f?formal parameter& is read but " 1399 & "never assigned!"); 1400 end if; 1401 1402 elsif not Has_Pragma_Unreferenced_Check_Spec (E1) 1403 and then not Warnings_Off_E1 1404 and then not Has_Junk_Name (E1) 1405 then 1406 Output_Reference_Error 1407 ("?f?formal parameter& is not referenced!"); 1408 end if; 1409 end if; 1410 1411 -- Case of variable 1412 1413 else 1414 if Referenced (E1) then 1415 if not Has_Unmodified (E1) 1416 and then not Warnings_Off_E1 1417 and then not Has_Junk_Name (E1) 1418 then 1419 Output_Reference_Error 1420 ("?v?variable& is read but never assigned!"); 1421 May_Need_Initialized_Actual (E1); 1422 end if; 1423 1424 elsif not Has_Unreferenced (E1) 1425 and then not Warnings_Off_E1 1426 and then not Has_Junk_Name (E1) 1427 then 1428 Output_Reference_Error -- CODEFIX 1429 ("?v?variable& is never read and never assigned!"); 1430 end if; 1431 1432 -- Deal with special case where this variable is hidden 1433 -- by a loop variable. 1434 1435 if Ekind (E1) = E_Variable 1436 and then Present (Hiding_Loop_Variable (E1)) 1437 and then not Warnings_Off_E1 1438 then 1439 Error_Msg_N 1440 ("?v?for loop implicitly declares loop variable!", 1441 Hiding_Loop_Variable (E1)); 1442 1443 Error_Msg_Sloc := Sloc (E1); 1444 Error_Msg_N 1445 ("\?v?declaration hides & declared#!", 1446 Hiding_Loop_Variable (E1)); 1447 end if; 1448 end if; 1449 1450 goto Continue; 1451 end if; 1452 1453 -- Check for unset reference. If type of object has 1454 -- preelaborable initialization, warning is misleading. 1455 1456 if Warn_On_No_Value_Assigned 1457 and then Present (UR) 1458 and then not Known_To_Have_Preelab_Init (Etype (E1)) 1459 then 1460 1461 -- For other than access type, go back to original node to 1462 -- deal with case where original unset reference has been 1463 -- rewritten during expansion. 1464 1465 -- In some cases, the original node may be a type 1466 -- conversion, a qualification or an attribute reference and 1467 -- in this case we want the object entity inside. Same for 1468 -- an expression with actions. 1469 1470 UR := Original_Node (UR); 1471 loop 1472 if Nkind_In (UR, N_Expression_With_Actions, 1473 N_Qualified_Expression, 1474 N_Type_Conversion) 1475 then 1476 UR := Expression (UR); 1477 1478 elsif Nkind (UR) = N_Attribute_Reference then 1479 UR := Prefix (UR); 1480 1481 else 1482 exit; 1483 end if; 1484 end loop; 1485 1486 -- Don't issue warning if appearing inside Initial_Condition 1487 -- pragma or aspect, since that expression is not evaluated 1488 -- at the point where it occurs in the source. 1489 1490 if In_Pragma_Expression (UR, Name_Initial_Condition) then 1491 goto Continue; 1492 end if; 1493 1494 -- Here we issue the warning, all checks completed 1495 1496 -- If we have a return statement, this was a case of an OUT 1497 -- parameter not being set at the time of the return. (Note: 1498 -- it can't be N_Extended_Return_Statement, because those 1499 -- are only for functions, and functions do not allow OUT 1500 -- parameters.) 1501 1502 if not Is_Trivial_Subprogram (Scope (E1)) then 1503 if Nkind (UR) = N_Simple_Return_Statement 1504 and then not Has_Pragma_Unmodified_Check_Spec (E1) 1505 then 1506 if not Warnings_Off_E1 1507 and then not Has_Junk_Name (E1) 1508 then 1509 Error_Msg_NE 1510 ("?v?OUT parameter& not set before return", 1511 UR, E1); 1512 end if; 1513 1514 -- If the unset reference is a selected component 1515 -- prefix from source, mention the component as well. 1516 -- If the selected component comes from expansion, all 1517 -- we know is that the entity is not fully initialized 1518 -- at the point of the reference. Locate a random 1519 -- uninitialized component to get a better message. 1520 1521 elsif Nkind (Parent (UR)) = N_Selected_Component then 1522 Error_Msg_Node_2 := Selector_Name (Parent (UR)); 1523 1524 if not Comes_From_Source (Parent (UR)) then 1525 declare 1526 Comp : Entity_Id; 1527 1528 begin 1529 Comp := First_Entity (E1T); 1530 while Present (Comp) loop 1531 if Ekind (Comp) = E_Component 1532 and then Nkind (Parent (Comp)) = 1533 N_Component_Declaration 1534 and then No (Expression (Parent (Comp))) 1535 then 1536 Error_Msg_Node_2 := Comp; 1537 exit; 1538 end if; 1539 1540 Next_Entity (Comp); 1541 end loop; 1542 end; 1543 end if; 1544 1545 -- Issue proper warning. This is a case of referencing 1546 -- a variable before it has been explicitly assigned. 1547 -- For access types, UR was only set for dereferences, 1548 -- so the issue is that the value may be null. 1549 1550 if not Is_Trivial_Subprogram (Scope (E1)) then 1551 if not Warnings_Off_E1 then 1552 if Is_Access_Type (Etype (Parent (UR))) then 1553 Error_Msg_N ("??`&.&` may be null!", UR); 1554 else 1555 Error_Msg_N 1556 ("??`&.&` may be referenced before " 1557 & "it has a value!", UR); 1558 end if; 1559 end if; 1560 end if; 1561 1562 -- All other cases of unset reference active 1563 1564 elsif not Warnings_Off_E1 then 1565 Error_Msg_N 1566 ("??& may be referenced before it has a value!", UR); 1567 end if; 1568 end if; 1569 1570 goto Continue; 1571 1572 end if; 1573 end if; 1574 1575 -- Then check for unreferenced entities. Note that we are only 1576 -- interested in entities whose Referenced flag is not set. 1577 1578 if not Referenced_Check_Spec (E1) 1579 1580 -- If Referenced_As_LHS is set, then that's still interesting 1581 -- (potential "assigned but never read" case), but not if we 1582 -- have pragma Unreferenced, which cancels this warning. 1583 1584 and then (not Referenced_As_LHS_Check_Spec (E1) 1585 or else not Has_Unreferenced (E1)) 1586 1587 -- Check that warnings on unreferenced entities are enabled 1588 1589 and then 1590 ((Check_Unreferenced and then not Is_Formal (E1)) 1591 1592 -- Case of warning on unreferenced formal 1593 1594 or else (Check_Unreferenced_Formals and then Is_Formal (E1)) 1595 1596 -- Case of warning on unread variables modified by an 1597 -- assignment, or an OUT parameter if it is the only one. 1598 1599 or else (Warn_On_Modified_Unread 1600 and then Referenced_As_LHS_Check_Spec (E1)) 1601 1602 -- Case of warning on any unread OUT parameter (note such 1603 -- indications are only set if the appropriate warning 1604 -- options were set, so no need to recheck here.) 1605 1606 or else Referenced_As_Out_Parameter_Check_Spec (E1)) 1607 1608 -- All other entities, including local packages that cannot be 1609 -- referenced from elsewhere, including those declared within a 1610 -- package body. 1611 1612 and then (Is_Object (E1) 1613 or else Is_Type (E1) 1614 or else Ekind (E1) = E_Label 1615 or else Ekind_In (E1, E_Exception, 1616 E_Named_Integer, 1617 E_Named_Real) 1618 or else Is_Overloadable (E1) 1619 1620 -- Package case, if the main unit is a package spec 1621 -- or generic package spec, then there may be a 1622 -- corresponding body that references this package 1623 -- in some other file. Otherwise we can be sure 1624 -- that there is no other reference. 1625 1626 or else 1627 (Ekind (E1) = E_Package 1628 and then 1629 not Is_Package_Or_Generic_Package 1630 (Cunit_Entity (Current_Sem_Unit)))) 1631 1632 -- Exclude instantiations, since there is no reason why every 1633 -- entity in an instantiation should be referenced. 1634 1635 and then Instantiation_Location (Sloc (E1)) = No_Location 1636 1637 -- Exclude formal parameters from bodies if the corresponding 1638 -- spec entity has been referenced in the case where there is 1639 -- a separate spec. 1640 1641 and then not (Is_Formal (E1) 1642 and then Ekind (Scope (E1)) = E_Subprogram_Body 1643 and then Present (Spec_Entity (E1)) 1644 and then Referenced (Spec_Entity (E1))) 1645 1646 -- Consider private type referenced if full view is referenced. 1647 -- If there is not full view, this is a generic type on which 1648 -- warnings are also useful. 1649 1650 and then 1651 not (Is_Private_Type (E1) 1652 and then Present (Full_View (E1)) 1653 and then Referenced (Full_View (E1))) 1654 1655 -- Don't worry about full view, only about private type 1656 1657 and then not Has_Private_Declaration (E1) 1658 1659 -- Eliminate dispatching operations from consideration, we 1660 -- cannot tell if these are referenced or not in any easy 1661 -- manner (note this also catches Adjust/Finalize/Initialize). 1662 1663 and then not Is_Dispatching_Operation (E1) 1664 1665 -- Check entity that can be publicly referenced (we do not give 1666 -- messages for such entities, since there could be other 1667 -- units, not involved in this compilation, that contain 1668 -- relevant references. 1669 1670 and then not Publicly_Referenceable (E1) 1671 1672 -- Class wide types are marked as source entities, but they are 1673 -- not really source entities, and are always created, so we do 1674 -- not care if they are not referenced. 1675 1676 and then Ekind (E1) /= E_Class_Wide_Type 1677 1678 -- Objects other than parameters of task types are allowed to 1679 -- be non-referenced, since they start up tasks. 1680 1681 and then ((Ekind (E1) /= E_Variable 1682 and then Ekind (E1) /= E_Constant 1683 and then Ekind (E1) /= E_Component) 1684 or else not Is_Task_Type (E1T)) 1685 1686 -- For subunits, only place warnings on the main unit itself, 1687 -- since parent units are not completely compiled. 1688 1689 and then (Nkind (Unit (Cunit (Main_Unit))) /= N_Subunit 1690 or else Get_Source_Unit (E1) = Main_Unit) 1691 1692 -- No warning on a return object, because these are often 1693 -- created with a single expression and an implicit return. 1694 -- If the object is a variable there will be a warning 1695 -- indicating that it could be declared constant. 1696 1697 and then not 1698 (Ekind (E1) = E_Constant and then Is_Return_Object (E1)) 1699 then 1700 -- Suppress warnings in internal units if not in -gnatg mode 1701 -- (these would be junk warnings for an applications program, 1702 -- since they refer to problems in internal units). 1703 1704 if GNAT_Mode or else not In_Internal_Unit (E1) then 1705 -- We do not immediately flag the error. This is because we 1706 -- have not expanded generic bodies yet, and they may have 1707 -- the missing reference. So instead we park the entity on a 1708 -- list, for later processing. However for the case of an 1709 -- accept statement we want to output messages now, since 1710 -- we know we already have all information at hand, and we 1711 -- also want to have separate warnings for each accept 1712 -- statement for the same entry. 1713 1714 if Present (Anod) then 1715 pragma Assert (Is_Formal (E1)); 1716 1717 -- The unreferenced entity is E1, but post the warning 1718 -- on the body entity for this accept statement. 1719 1720 if not Warnings_Off_E1 then 1721 Warn_On_Unreferenced_Entity 1722 (E1, Body_Formal (E1, Accept_Statement => Anod)); 1723 end if; 1724 1725 elsif not Warnings_Off_E1 1726 and then not Has_Junk_Name (E1) 1727 then 1728 if Is_Formal (E1) 1729 and then Nkind (Unit_Declaration_Node (Scope (E1))) 1730 = N_Generic_Subprogram_Declaration 1731 then 1732 Unreferenced_Entities.Append 1733 (Generic_Body_Formal (E1)); 1734 else 1735 Unreferenced_Entities.Append (E1); 1736 end if; 1737 end if; 1738 end if; 1739 1740 -- Generic units are referenced in the generic body, but if they 1741 -- are not public and never instantiated we want to force a 1742 -- warning on them. We treat them as redundant constructs to 1743 -- minimize noise. 1744 1745 elsif Is_Generic_Subprogram (E1) 1746 and then not Is_Instantiated (E1) 1747 and then not Publicly_Referenceable (E1) 1748 and then Instantiation_Depth (Sloc (E1)) = 0 1749 and then Warn_On_Redundant_Constructs 1750 then 1751 if not Warnings_Off_E1 and then not Has_Junk_Name (E1) then 1752 Unreferenced_Entities.Append (E1); 1753 1754 -- Force warning on entity 1755 1756 Set_Referenced (E1, False); 1757 end if; 1758 end if; 1759 end if; 1760 1761 -- Recurse into nested package or block. Do not recurse into a formal 1762 -- package, because the corresponding body is not analyzed. 1763 1764 <<Continue>> 1765 if (Is_Package_Or_Generic_Package (E1) 1766 and then Nkind (Parent (E1)) = N_Package_Specification 1767 and then 1768 Nkind (Original_Node (Unit_Declaration_Node (E1))) /= 1769 N_Formal_Package_Declaration) 1770 1771 or else Ekind (E1) = E_Block 1772 then 1773 Check_References (E1); 1774 end if; 1775 1776 Next_Entity (E1); 1777 end loop; 1778 end Check_References; 1779 1780 --------------------------- 1781 -- Check_Unset_Reference -- 1782 --------------------------- 1783 1784 procedure Check_Unset_Reference (N : Node_Id) is 1785 Typ : constant Entity_Id := Etype (N); 1786 1787 function Is_OK_Fully_Initialized return Boolean; 1788 -- This function returns true if the given node N is fully initialized 1789 -- so that the reference is safe as far as this routine is concerned. 1790 -- Safe generally means that the type of N is a fully initialized type. 1791 -- The one special case is that for access types, which are always fully 1792 -- initialized, we don't consider a dereference OK since it will surely 1793 -- be dereferencing a null value, which won't do. 1794 1795 function Prefix_Has_Dereference (Pref : Node_Id) return Boolean; 1796 -- Used to test indexed or selected component or slice to see if the 1797 -- evaluation of the prefix depends on a dereference, and if so, returns 1798 -- True, in which case we always check the prefix, even if we know that 1799 -- the referenced component is initialized. Pref is the prefix to test. 1800 1801 ----------------------------- 1802 -- Is_OK_Fully_Initialized -- 1803 ----------------------------- 1804 1805 function Is_OK_Fully_Initialized return Boolean is 1806 begin 1807 if Is_Access_Type (Typ) and then Is_Dereferenced (N) then 1808 return False; 1809 1810 -- A type subject to pragma Default_Initial_Condition may be fully 1811 -- default initialized depending on inheritance and the argument of 1812 -- the pragma (SPARK RM 3.1 and SPARK RM 7.3.3). 1813 1814 elsif Has_Fully_Default_Initializing_DIC_Pragma (Typ) then 1815 return True; 1816 1817 else 1818 return Is_Fully_Initialized_Type (Typ); 1819 end if; 1820 end Is_OK_Fully_Initialized; 1821 1822 ---------------------------- 1823 -- Prefix_Has_Dereference -- 1824 ---------------------------- 1825 1826 function Prefix_Has_Dereference (Pref : Node_Id) return Boolean is 1827 begin 1828 -- If prefix is of an access type, it certainly needs a dereference 1829 1830 if Is_Access_Type (Etype (Pref)) then 1831 return True; 1832 1833 -- If prefix is explicit dereference, that's a dereference for sure 1834 1835 elsif Nkind (Pref) = N_Explicit_Dereference then 1836 return True; 1837 1838 -- If prefix is itself a component reference or slice check prefix 1839 1840 elsif Nkind (Pref) = N_Slice 1841 or else Nkind (Pref) = N_Indexed_Component 1842 or else Nkind (Pref) = N_Selected_Component 1843 then 1844 return Prefix_Has_Dereference (Prefix (Pref)); 1845 1846 -- All other cases do not involve a dereference 1847 1848 else 1849 return False; 1850 end if; 1851 end Prefix_Has_Dereference; 1852 1853 -- Start of processing for Check_Unset_Reference 1854 1855 begin 1856 -- Nothing to do if warnings suppressed 1857 1858 if Warning_Mode = Suppress then 1859 return; 1860 end if; 1861 1862 -- Nothing to do for numeric or string literal. Do this test early to 1863 -- save time in a common case (it does not matter that we do not include 1864 -- character literal here, since that will be caught later on in the 1865 -- when others branch of the case statement). 1866 1867 if Nkind (N) in N_Numeric_Or_String_Literal then 1868 return; 1869 end if; 1870 1871 -- Ignore reference unless it comes from source. Almost always if we 1872 -- have a reference from generated code, it is bogus (e.g. calls to init 1873 -- procs to set default discriminant values). 1874 1875 if not Comes_From_Source (N) then 1876 return; 1877 end if; 1878 1879 -- Otherwise see what kind of node we have. If the entity already has an 1880 -- unset reference, it is not necessarily the earliest in the text, 1881 -- because resolution of the prefix of selected components is completed 1882 -- before the resolution of the selected component itself. As a result, 1883 -- given (R /= null and then R.X > 0), the occurrences of R are examined 1884 -- in right-to-left order. If there is already an unset reference, we 1885 -- check whether N is earlier before proceeding. 1886 1887 case Nkind (N) is 1888 1889 -- For identifier or expanded name, examine the entity involved 1890 1891 when N_Expanded_Name 1892 | N_Identifier 1893 => 1894 declare 1895 E : constant Entity_Id := Entity (N); 1896 1897 begin 1898 if Ekind_In (E, E_Variable, E_Out_Parameter) 1899 and then Never_Set_In_Source_Check_Spec (E) 1900 and then not Has_Initial_Value (E) 1901 and then (No (Unset_Reference (E)) 1902 or else 1903 Earlier_In_Extended_Unit 1904 (Sloc (N), Sloc (Unset_Reference (E)))) 1905 and then not Has_Pragma_Unmodified_Check_Spec (E) 1906 and then not Warnings_Off_Check_Spec (E) 1907 and then not Has_Junk_Name (E) 1908 then 1909 -- We may have an unset reference. The first test is whether 1910 -- this is an access to a discriminant of a record or a 1911 -- component with default initialization. Both of these 1912 -- cases can be ignored, since the actual object that is 1913 -- referenced is definitely initialized. Note that this 1914 -- covers the case of reading discriminants of an OUT 1915 -- parameter, which is OK even in Ada 83. 1916 1917 -- Note that we are only interested in a direct reference to 1918 -- a record component here. If the reference is through an 1919 -- access type, then the access object is being referenced, 1920 -- not the record, and still deserves an unset reference. 1921 1922 if Nkind (Parent (N)) = N_Selected_Component 1923 and not Is_Access_Type (Typ) 1924 then 1925 declare 1926 ES : constant Entity_Id := 1927 Entity (Selector_Name (Parent (N))); 1928 begin 1929 if Ekind (ES) = E_Discriminant 1930 or else 1931 (Present (Declaration_Node (ES)) 1932 and then 1933 Present (Expression (Declaration_Node (ES)))) 1934 then 1935 return; 1936 end if; 1937 end; 1938 end if; 1939 1940 -- Exclude fully initialized types 1941 1942 if Is_OK_Fully_Initialized then 1943 return; 1944 end if; 1945 1946 -- Here we have a potential unset reference. But before we 1947 -- get worried about it, we have to make sure that the 1948 -- entity declaration is in the same procedure as the 1949 -- reference, since if they are in separate procedures, then 1950 -- we have no idea about sequential execution. 1951 1952 -- The tests in the loop below catch all such cases, but do 1953 -- allow the reference to appear in a loop, block, or 1954 -- package spec that is nested within the declaring scope. 1955 -- As always, it is possible to construct cases where the 1956 -- warning is wrong, that is why it is a warning. 1957 1958 Potential_Unset_Reference : declare 1959 SR : Entity_Id; 1960 SE : constant Entity_Id := Scope (E); 1961 1962 function Within_Postcondition return Boolean; 1963 -- Returns True if N is within a Postcondition, a 1964 -- Refined_Post, an Ensures component in a Test_Case, 1965 -- or a Contract_Cases. 1966 1967 -------------------------- 1968 -- Within_Postcondition -- 1969 -------------------------- 1970 1971 function Within_Postcondition return Boolean is 1972 Nod, P : Node_Id; 1973 1974 begin 1975 Nod := Parent (N); 1976 while Present (Nod) loop 1977 if Nkind (Nod) = N_Pragma 1978 and then Nam_In (Pragma_Name_Unmapped (Nod), 1979 Name_Postcondition, 1980 Name_Refined_Post, 1981 Name_Contract_Cases) 1982 then 1983 return True; 1984 1985 elsif Present (Parent (Nod)) then 1986 P := Parent (Nod); 1987 1988 if Nkind (P) = N_Pragma 1989 and then Pragma_Name (P) = 1990 Name_Test_Case 1991 and then Nod = Test_Case_Arg (P, Name_Ensures) 1992 then 1993 return True; 1994 end if; 1995 end if; 1996 1997 Nod := Parent (Nod); 1998 end loop; 1999 2000 return False; 2001 end Within_Postcondition; 2002 2003 -- Start of processing for Potential_Unset_Reference 2004 2005 begin 2006 SR := Current_Scope; 2007 while SR /= SE loop 2008 if SR = Standard_Standard 2009 or else Is_Subprogram (SR) 2010 or else Is_Concurrent_Body (SR) 2011 or else Is_Concurrent_Type (SR) 2012 then 2013 return; 2014 end if; 2015 2016 SR := Scope (SR); 2017 end loop; 2018 2019 -- Case of reference has an access type. This is a 2020 -- special case since access types are always set to null 2021 -- so cannot be truly uninitialized, but we still want to 2022 -- warn about cases of obvious null dereference. 2023 2024 if Is_Access_Type (Typ) then 2025 Access_Type_Case : declare 2026 P : Node_Id; 2027 2028 function Process 2029 (N : Node_Id) return Traverse_Result; 2030 -- Process function for instantiation of Traverse 2031 -- below. Checks if N contains reference to E other 2032 -- than a dereference. 2033 2034 function Ref_In (Nod : Node_Id) return Boolean; 2035 -- Determines whether Nod contains a reference to 2036 -- the entity E that is not a dereference. 2037 2038 ------------- 2039 -- Process -- 2040 ------------- 2041 2042 function Process 2043 (N : Node_Id) return Traverse_Result 2044 is 2045 begin 2046 if Is_Entity_Name (N) 2047 and then Entity (N) = E 2048 and then not Is_Dereferenced (N) 2049 then 2050 return Abandon; 2051 else 2052 return OK; 2053 end if; 2054 end Process; 2055 2056 ------------ 2057 -- Ref_In -- 2058 ------------ 2059 2060 function Ref_In (Nod : Node_Id) return Boolean is 2061 function Traverse is new Traverse_Func (Process); 2062 begin 2063 return Traverse (Nod) = Abandon; 2064 end Ref_In; 2065 2066 -- Start of processing for Access_Type_Case 2067 2068 begin 2069 -- Don't bother if we are inside an instance, since 2070 -- the compilation of the generic template is where 2071 -- the warning should be issued. 2072 2073 if In_Instance then 2074 return; 2075 end if; 2076 2077 -- Don't bother if this is not the main unit. If we 2078 -- try to give this warning for with'ed units, we 2079 -- get some false positives, since we do not record 2080 -- references in other units. 2081 2082 if not In_Extended_Main_Source_Unit (E) 2083 or else 2084 not In_Extended_Main_Source_Unit (N) 2085 then 2086 return; 2087 end if; 2088 2089 -- We are only interested in dereferences 2090 2091 if not Is_Dereferenced (N) then 2092 return; 2093 end if; 2094 2095 -- One more check, don't bother with references 2096 -- that are inside conditional statements or WHILE 2097 -- loops if the condition references the entity in 2098 -- question. This avoids most false positives. 2099 2100 P := Parent (N); 2101 loop 2102 P := Parent (P); 2103 exit when No (P); 2104 2105 if Nkind_In (P, N_If_Statement, N_Elsif_Part) 2106 and then Ref_In (Condition (P)) 2107 then 2108 return; 2109 2110 elsif Nkind (P) = N_Loop_Statement 2111 and then Present (Iteration_Scheme (P)) 2112 and then 2113 Ref_In (Condition (Iteration_Scheme (P))) 2114 then 2115 return; 2116 end if; 2117 end loop; 2118 end Access_Type_Case; 2119 end if; 2120 2121 -- One more check, don't bother if we are within a 2122 -- postcondition, since the expression occurs in a 2123 -- place unrelated to the actual test. 2124 2125 if not Within_Postcondition then 2126 2127 -- Here we definitely have a case for giving a warning 2128 -- for a reference to an unset value. But we don't 2129 -- give the warning now. Instead set Unset_Reference 2130 -- in the identifier involved. The reason for this is 2131 -- that if we find the variable is never ever assigned 2132 -- a value then that warning is more important and 2133 -- there is no point in giving the reference warning. 2134 2135 -- If this is an identifier, set the field directly 2136 2137 if Nkind (N) = N_Identifier then 2138 Set_Unset_Reference (E, N); 2139 2140 -- Otherwise it is an expanded name, so set the field 2141 -- of the actual identifier for the reference. 2142 2143 else 2144 Set_Unset_Reference (E, Selector_Name (N)); 2145 end if; 2146 end if; 2147 end Potential_Unset_Reference; 2148 end if; 2149 end; 2150 2151 -- Indexed component or slice 2152 2153 when N_Indexed_Component 2154 | N_Slice 2155 => 2156 -- If prefix does not involve dereferencing an access type, then 2157 -- we know we are OK if the component type is fully initialized, 2158 -- since the component will have been set as part of the default 2159 -- initialization. 2160 2161 if not Prefix_Has_Dereference (Prefix (N)) 2162 and then Is_OK_Fully_Initialized 2163 then 2164 return; 2165 2166 -- Look at prefix in access type case, or if the component is not 2167 -- fully initialized. 2168 2169 else 2170 Check_Unset_Reference (Prefix (N)); 2171 end if; 2172 2173 -- Record component 2174 2175 when N_Selected_Component => 2176 declare 2177 Pref : constant Node_Id := Prefix (N); 2178 Ent : constant Entity_Id := Entity (Selector_Name (N)); 2179 2180 begin 2181 -- If prefix involves dereferencing an access type, always 2182 -- check the prefix, since the issue then is whether this 2183 -- access value is null. 2184 2185 if Prefix_Has_Dereference (Pref) then 2186 null; 2187 2188 -- Always go to prefix if no selector entity is set. Can this 2189 -- happen in the normal case? Not clear, but it definitely can 2190 -- happen in error cases. 2191 2192 elsif No (Ent) then 2193 null; 2194 2195 -- For a record component, check some cases where we have 2196 -- reasonable cause to consider that the component is known to 2197 -- be or probably is initialized. In this case, we don't care 2198 -- if the prefix itself was explicitly initialized. 2199 2200 -- Discriminants are always considered initialized 2201 2202 elsif Ekind (Ent) = E_Discriminant then 2203 return; 2204 2205 -- An explicitly initialized component is certainly initialized 2206 2207 elsif Nkind (Parent (Ent)) = N_Component_Declaration 2208 and then Present (Expression (Parent (Ent))) 2209 then 2210 return; 2211 2212 -- A fully initialized component is initialized 2213 2214 elsif Is_OK_Fully_Initialized then 2215 return; 2216 end if; 2217 2218 -- If none of those cases apply, check the record type prefix 2219 2220 Check_Unset_Reference (Pref); 2221 end; 2222 2223 -- For type conversions, qualifications, or expressions with actions, 2224 -- examine the expression. 2225 2226 when N_Expression_With_Actions 2227 | N_Qualified_Expression 2228 | N_Type_Conversion 2229 => 2230 Check_Unset_Reference (Expression (N)); 2231 2232 -- For explicit dereference, always check prefix, which will generate 2233 -- an unset reference (since this is a case of dereferencing null). 2234 2235 when N_Explicit_Dereference => 2236 Check_Unset_Reference (Prefix (N)); 2237 2238 -- All other cases are not cases of an unset reference 2239 2240 when others => 2241 null; 2242 end case; 2243 end Check_Unset_Reference; 2244 2245 ------------------------ 2246 -- Check_Unused_Withs -- 2247 ------------------------ 2248 2249 procedure Check_Unused_Withs (Spec_Unit : Unit_Number_Type := No_Unit) is 2250 Cnode : Node_Id; 2251 Item : Node_Id; 2252 Lunit : Node_Id; 2253 Ent : Entity_Id; 2254 2255 Munite : constant Entity_Id := Cunit_Entity (Main_Unit); 2256 -- This is needed for checking the special renaming case 2257 2258 procedure Check_One_Unit (Unit : Unit_Number_Type); 2259 -- Subsidiary procedure, performs checks for specified unit 2260 2261 -------------------- 2262 -- Check_One_Unit -- 2263 -------------------- 2264 2265 procedure Check_One_Unit (Unit : Unit_Number_Type) is 2266 Is_Visible_Renaming : Boolean := False; 2267 Pack : Entity_Id; 2268 2269 procedure Check_Inner_Package (Pack : Entity_Id); 2270 -- Pack is a package local to a unit in a with_clause. Both the unit 2271 -- and Pack are referenced. If none of the entities in Pack are 2272 -- referenced, then the only occurrence of Pack is in a USE clause 2273 -- or a pragma, and a warning is worthwhile as well. 2274 2275 function Check_System_Aux return Boolean; 2276 -- Before giving a warning on a with_clause for System, check whether 2277 -- a system extension is present. 2278 2279 function Find_Package_Renaming 2280 (P : Entity_Id; 2281 L : Entity_Id) return Entity_Id; 2282 -- The only reference to a context unit may be in a renaming 2283 -- declaration. If this renaming declares a visible entity, do not 2284 -- warn that the context clause could be moved to the body, because 2285 -- the renaming may be intended to re-export the unit. 2286 2287 function Has_Visible_Entities (P : Entity_Id) return Boolean; 2288 -- This function determines if a package has any visible entities. 2289 -- True is returned if there is at least one declared visible entity, 2290 -- otherwise False is returned (e.g. case of only pragmas present). 2291 2292 ------------------------- 2293 -- Check_Inner_Package -- 2294 ------------------------- 2295 2296 procedure Check_Inner_Package (Pack : Entity_Id) is 2297 E : Entity_Id; 2298 Un : constant Node_Id := Sinfo.Unit (Cnode); 2299 2300 function Check_Use_Clause (N : Node_Id) return Traverse_Result; 2301 -- If N is a use_clause for Pack, emit warning 2302 2303 procedure Check_Use_Clauses is new 2304 Traverse_Proc (Check_Use_Clause); 2305 2306 ---------------------- 2307 -- Check_Use_Clause -- 2308 ---------------------- 2309 2310 function Check_Use_Clause (N : Node_Id) return Traverse_Result is 2311 begin 2312 if Nkind (N) = N_Use_Package_Clause 2313 and then Entity (Name (N)) = Pack 2314 then 2315 -- Suppress message if any serious errors detected that turn 2316 -- off expansion, and thus result in false positives for 2317 -- this warning. 2318 2319 if Serious_Errors_Detected = 0 then 2320 Error_Msg_Qual_Level := 1; 2321 Error_Msg_NE -- CODEFIX 2322 ("?u?no entities of package& are referenced!", 2323 Name (N), Pack); 2324 Error_Msg_Qual_Level := 0; 2325 end if; 2326 end if; 2327 2328 return OK; 2329 end Check_Use_Clause; 2330 2331 -- Start of processing for Check_Inner_Package 2332 2333 begin 2334 E := First_Entity (Pack); 2335 while Present (E) loop 2336 if Referenced_Check_Spec (E) then 2337 return; 2338 end if; 2339 2340 Next_Entity (E); 2341 end loop; 2342 2343 -- No entities of the package are referenced. Check whether the 2344 -- reference to the package itself is a use clause, and if so 2345 -- place a warning on it. 2346 2347 Check_Use_Clauses (Un); 2348 end Check_Inner_Package; 2349 2350 ---------------------- 2351 -- Check_System_Aux -- 2352 ---------------------- 2353 2354 function Check_System_Aux return Boolean is 2355 Ent : Entity_Id; 2356 2357 begin 2358 if Chars (Lunit) = Name_System 2359 and then Scope (Lunit) = Standard_Standard 2360 and then Present_System_Aux 2361 then 2362 Ent := First_Entity (System_Aux_Id); 2363 while Present (Ent) loop 2364 if Referenced_Check_Spec (Ent) then 2365 return True; 2366 end if; 2367 2368 Next_Entity (Ent); 2369 end loop; 2370 end if; 2371 2372 return False; 2373 end Check_System_Aux; 2374 2375 --------------------------- 2376 -- Find_Package_Renaming -- 2377 --------------------------- 2378 2379 function Find_Package_Renaming 2380 (P : Entity_Id; 2381 L : Entity_Id) return Entity_Id 2382 is 2383 E1 : Entity_Id; 2384 R : Entity_Id; 2385 2386 begin 2387 Is_Visible_Renaming := False; 2388 2389 E1 := First_Entity (P); 2390 while Present (E1) loop 2391 if Ekind (E1) = E_Package and then Renamed_Object (E1) = L then 2392 Is_Visible_Renaming := not Is_Hidden (E1); 2393 return E1; 2394 2395 elsif Ekind (E1) = E_Package 2396 and then No (Renamed_Object (E1)) 2397 and then not Is_Generic_Instance (E1) 2398 then 2399 R := Find_Package_Renaming (E1, L); 2400 2401 if Present (R) then 2402 Is_Visible_Renaming := not Is_Hidden (R); 2403 return R; 2404 end if; 2405 end if; 2406 2407 Next_Entity (E1); 2408 end loop; 2409 2410 return Empty; 2411 end Find_Package_Renaming; 2412 2413 -------------------------- 2414 -- Has_Visible_Entities -- 2415 -------------------------- 2416 2417 function Has_Visible_Entities (P : Entity_Id) return Boolean is 2418 E : Entity_Id; 2419 2420 begin 2421 -- If unit in context is not a package, it is a subprogram that 2422 -- is not called or a generic unit that is not instantiated 2423 -- in the current unit, and warning is appropriate. 2424 2425 if Ekind (P) /= E_Package then 2426 return True; 2427 end if; 2428 2429 -- If unit comes from a limited_with clause, look for declaration 2430 -- of shadow entities. 2431 2432 if Present (Limited_View (P)) then 2433 E := First_Entity (Limited_View (P)); 2434 else 2435 E := First_Entity (P); 2436 end if; 2437 2438 while Present (E) and then E /= First_Private_Entity (P) loop 2439 if Comes_From_Source (E) or else Present (Limited_View (P)) then 2440 return True; 2441 end if; 2442 2443 Next_Entity (E); 2444 end loop; 2445 2446 return False; 2447 end Has_Visible_Entities; 2448 2449 -- Start of processing for Check_One_Unit 2450 2451 begin 2452 Cnode := Cunit (Unit); 2453 2454 -- Only do check in units that are part of the extended main unit. 2455 -- This is actually a necessary restriction, because in the case of 2456 -- subprogram acting as its own specification, there can be with's in 2457 -- subunits that we will not see. 2458 2459 if not In_Extended_Main_Source_Unit (Cnode) then 2460 return; 2461 end if; 2462 2463 -- Loop through context items in this unit 2464 2465 Item := First (Context_Items (Cnode)); 2466 while Present (Item) loop 2467 if Nkind (Item) = N_With_Clause 2468 and then not Implicit_With (Item) 2469 and then In_Extended_Main_Source_Unit (Item) 2470 2471 -- Guard for no entity present. Not clear under what conditions 2472 -- this happens, but it does occur, and since this is only a 2473 -- warning, we just suppress the warning in this case. 2474 2475 and then Nkind (Name (Item)) in N_Has_Entity 2476 and then Present (Entity (Name (Item))) 2477 then 2478 Lunit := Entity (Name (Item)); 2479 2480 -- Check if this unit is referenced (skip the check if this 2481 -- is explicitly marked by a pragma Unreferenced). 2482 2483 if not Referenced (Lunit) and then not Has_Unreferenced (Lunit) 2484 then 2485 -- Suppress warnings in internal units if not in -gnatg mode 2486 -- (these would be junk warnings for an application program, 2487 -- since they refer to problems in internal units). 2488 2489 if GNAT_Mode or else not Is_Internal_Unit (Unit) then 2490 -- Here we definitely have a non-referenced unit. If it 2491 -- is the special call for a spec unit, then just set the 2492 -- flag to be read later. 2493 2494 if Unit = Spec_Unit then 2495 Set_Unreferenced_In_Spec (Item); 2496 2497 -- Otherwise simple unreferenced message, but skip this 2498 -- if no visible entities, because that is most likely a 2499 -- case where warning would be false positive (e.g. a 2500 -- package with only a linker options pragma and nothing 2501 -- else or a pragma elaborate with a body library task). 2502 2503 elsif Has_Visible_Entities (Entity (Name (Item))) then 2504 Error_Msg_N -- CODEFIX 2505 ("?u?unit& is not referenced!", Name (Item)); 2506 end if; 2507 end if; 2508 2509 -- If main unit is a renaming of this unit, then we consider 2510 -- the with to be OK (obviously it is needed in this case). 2511 -- This may be transitive: the unit in the with_clause may 2512 -- itself be a renaming, in which case both it and the main 2513 -- unit rename the same ultimate package. 2514 2515 elsif Present (Renamed_Entity (Munite)) 2516 and then 2517 (Renamed_Entity (Munite) = Lunit 2518 or else Renamed_Entity (Munite) = Renamed_Entity (Lunit)) 2519 then 2520 null; 2521 2522 -- If this unit is referenced, and it is a package, we do 2523 -- another test, to see if any of the entities in the package 2524 -- are referenced. If none of the entities are referenced, we 2525 -- still post a warning. This occurs if the only use of the 2526 -- package is in a use clause, or in a package renaming 2527 -- declaration. This check is skipped for packages that are 2528 -- renamed in a spec, since the entities in such a package are 2529 -- visible to clients via the renaming. 2530 2531 elsif Ekind (Lunit) = E_Package 2532 and then not Renamed_In_Spec (Lunit) 2533 then 2534 -- If Is_Instantiated is set, it means that the package is 2535 -- implicitly instantiated (this is the case of parent 2536 -- instance or an actual for a generic package formal), and 2537 -- this counts as a reference. 2538 2539 if Is_Instantiated (Lunit) then 2540 null; 2541 2542 -- If no entities in package, and there is a pragma 2543 -- Elaborate_Body present, then assume that this with is 2544 -- done for purposes of this elaboration. 2545 2546 elsif No (First_Entity (Lunit)) 2547 and then Has_Pragma_Elaborate_Body (Lunit) 2548 then 2549 null; 2550 2551 -- Otherwise see if any entities have been referenced 2552 2553 else 2554 if Limited_Present (Item) then 2555 Ent := First_Entity (Limited_View (Lunit)); 2556 else 2557 Ent := First_Entity (Lunit); 2558 end if; 2559 2560 loop 2561 -- No more entities, and we did not find one that was 2562 -- referenced. Means we have a definite case of a with 2563 -- none of whose entities was referenced. 2564 2565 if No (Ent) then 2566 2567 -- If in spec, just set the flag 2568 2569 if Unit = Spec_Unit then 2570 Set_No_Entities_Ref_In_Spec (Item); 2571 2572 elsif Check_System_Aux then 2573 null; 2574 2575 -- Else the warning may be needed 2576 2577 else 2578 declare 2579 Eitem : constant Entity_Id := 2580 Entity (Name (Item)); 2581 2582 begin 2583 -- Warn if we unreferenced flag set and we 2584 -- have not had serious errors. The reason we 2585 -- inhibit the message if there are errors is 2586 -- to prevent false positives from disabling 2587 -- expansion. 2588 2589 if not Has_Unreferenced (Eitem) 2590 and then Serious_Errors_Detected = 0 2591 then 2592 -- Get possible package renaming 2593 2594 Pack := 2595 Find_Package_Renaming (Munite, Lunit); 2596 2597 -- No warning if either the package or its 2598 -- renaming is used as a generic actual. 2599 2600 if Used_As_Generic_Actual (Eitem) 2601 or else 2602 (Present (Pack) 2603 and then 2604 Used_As_Generic_Actual (Pack)) 2605 then 2606 exit; 2607 end if; 2608 2609 -- Here we give the warning 2610 2611 Error_Msg_N -- CODEFIX 2612 ("?u?no entities of & are referenced!", 2613 Name (Item)); 2614 2615 -- Flag renaming of package as well. If 2616 -- the original package has warnings off, 2617 -- we suppress the warning on the renaming 2618 -- as well. 2619 2620 if Present (Pack) 2621 and then not Has_Warnings_Off (Lunit) 2622 and then not Has_Unreferenced (Pack) 2623 then 2624 Error_Msg_NE -- CODEFIX 2625 ("?u?no entities of& are referenced!", 2626 Unit_Declaration_Node (Pack), Pack); 2627 end if; 2628 end if; 2629 end; 2630 end if; 2631 2632 exit; 2633 2634 -- Case of entity being referenced. The reference may 2635 -- come from a limited_with_clause, in which case the 2636 -- limited view of the entity carries the flag. 2637 2638 elsif Referenced_Check_Spec (Ent) 2639 or else Referenced_As_LHS_Check_Spec (Ent) 2640 or else Referenced_As_Out_Parameter_Check_Spec (Ent) 2641 or else 2642 (From_Limited_With (Ent) 2643 and then Is_Incomplete_Type (Ent) 2644 and then Present (Non_Limited_View (Ent)) 2645 and then Referenced (Non_Limited_View (Ent))) 2646 then 2647 -- This means that the with is indeed fine, in that 2648 -- it is definitely needed somewhere, and we can 2649 -- quit worrying about this one... 2650 2651 -- Except for one little detail: if either of the 2652 -- flags was set during spec processing, this is 2653 -- where we complain that the with could be moved 2654 -- from the spec. If the spec contains a visible 2655 -- renaming of the package, inhibit warning to move 2656 -- with_clause to body. 2657 2658 if Ekind (Munite) = E_Package_Body then 2659 Pack := 2660 Find_Package_Renaming 2661 (Spec_Entity (Munite), Lunit); 2662 else 2663 Pack := Empty; 2664 end if; 2665 2666 -- If a renaming is present in the spec do not warn 2667 -- because the body or child unit may depend on it. 2668 2669 if Present (Pack) 2670 and then Renamed_Entity (Pack) = Lunit 2671 then 2672 exit; 2673 2674 elsif Unreferenced_In_Spec (Item) then 2675 Error_Msg_N -- CODEFIX 2676 ("?u?unit& is not referenced in spec!", 2677 Name (Item)); 2678 2679 elsif No_Entities_Ref_In_Spec (Item) then 2680 Error_Msg_N -- CODEFIX 2681 ("?u?no entities of & are referenced in spec!", 2682 Name (Item)); 2683 2684 else 2685 if Ekind (Ent) = E_Package then 2686 Check_Inner_Package (Ent); 2687 end if; 2688 2689 exit; 2690 end if; 2691 2692 if not Is_Visible_Renaming then 2693 Error_Msg_N -- CODEFIX 2694 ("\?u?with clause might be moved to body!", 2695 Name (Item)); 2696 end if; 2697 2698 exit; 2699 2700 -- Move to next entity to continue search 2701 2702 else 2703 Next_Entity (Ent); 2704 end if; 2705 end loop; 2706 end if; 2707 2708 -- For a generic package, the only interesting kind of 2709 -- reference is an instantiation, since entities cannot be 2710 -- referenced directly. 2711 2712 elsif Is_Generic_Unit (Lunit) then 2713 2714 -- Unit was never instantiated, set flag for case of spec 2715 -- call, or give warning for normal call. 2716 2717 if not Is_Instantiated (Lunit) then 2718 if Unit = Spec_Unit then 2719 Set_Unreferenced_In_Spec (Item); 2720 else 2721 Error_Msg_N -- CODEFIX 2722 ("?u?unit& is never instantiated!", Name (Item)); 2723 end if; 2724 2725 -- If unit was indeed instantiated, make sure that flag is 2726 -- not set showing it was uninstantiated in the spec, and if 2727 -- so, give warning. 2728 2729 elsif Unreferenced_In_Spec (Item) then 2730 Error_Msg_N 2731 ("?u?unit& is not instantiated in spec!", Name (Item)); 2732 Error_Msg_N -- CODEFIX 2733 ("\?u?with clause can be moved to body!", Name (Item)); 2734 end if; 2735 end if; 2736 end if; 2737 2738 Next (Item); 2739 end loop; 2740 end Check_One_Unit; 2741 2742 -- Start of processing for Check_Unused_Withs 2743 2744 begin 2745 -- Immediate return if no semantics or warning flag not set 2746 2747 if not Opt.Check_Withs or else Operating_Mode = Check_Syntax then 2748 return; 2749 end if; 2750 2751 Process_Deferred_References; 2752 2753 -- Flag any unused with clauses. For a subunit, check only the units 2754 -- in its context, not those of the parent, which may be needed by other 2755 -- subunits. We will get the full warnings when we compile the parent, 2756 -- but the following is helpful when compiling a subunit by itself. 2757 2758 if Nkind (Unit (Cunit (Main_Unit))) = N_Subunit then 2759 if Current_Sem_Unit = Main_Unit then 2760 Check_One_Unit (Main_Unit); 2761 end if; 2762 2763 return; 2764 end if; 2765 2766 -- Process specified units 2767 2768 if Spec_Unit = No_Unit then 2769 2770 -- For main call, check all units 2771 2772 for Unit in Main_Unit .. Last_Unit loop 2773 Check_One_Unit (Unit); 2774 end loop; 2775 2776 else 2777 -- For call for spec, check only the spec 2778 2779 Check_One_Unit (Spec_Unit); 2780 end if; 2781 end Check_Unused_Withs; 2782 2783 --------------------------------- 2784 -- Generic_Package_Spec_Entity -- 2785 --------------------------------- 2786 2787 function Generic_Package_Spec_Entity (E : Entity_Id) return Boolean is 2788 S : Entity_Id; 2789 2790 begin 2791 if Is_Package_Body_Entity (E) then 2792 return False; 2793 2794 else 2795 S := Scope (E); 2796 loop 2797 if S = Standard_Standard then 2798 return False; 2799 2800 elsif Ekind (S) = E_Generic_Package then 2801 return True; 2802 2803 elsif Ekind (S) = E_Package then 2804 S := Scope (S); 2805 2806 else 2807 return False; 2808 end if; 2809 end loop; 2810 end if; 2811 end Generic_Package_Spec_Entity; 2812 2813 ---------------------- 2814 -- Goto_Spec_Entity -- 2815 ---------------------- 2816 2817 function Goto_Spec_Entity (E : Entity_Id) return Entity_Id is 2818 begin 2819 if Is_Formal (E) and then Present (Spec_Entity (E)) then 2820 return Spec_Entity (E); 2821 else 2822 return E; 2823 end if; 2824 end Goto_Spec_Entity; 2825 2826 ------------------- 2827 -- Has_Junk_Name -- 2828 ------------------- 2829 2830 function Has_Junk_Name (E : Entity_Id) return Boolean is 2831 function Match (S : String) return Boolean; 2832 -- Return true if substring S is found in Name_Buffer (1 .. Name_Len) 2833 2834 ----------- 2835 -- Match -- 2836 ----------- 2837 2838 function Match (S : String) return Boolean is 2839 Slen1 : constant Integer := S'Length - 1; 2840 2841 begin 2842 for J in 1 .. Name_Len - S'Length + 1 loop 2843 if Name_Buffer (J .. J + Slen1) = S then 2844 return True; 2845 end if; 2846 end loop; 2847 2848 return False; 2849 end Match; 2850 2851 -- Start of processing for Has_Junk_Name 2852 2853 begin 2854 Get_Unqualified_Decoded_Name_String (Chars (E)); 2855 2856 return 2857 Match ("discard") or else 2858 Match ("dummy") or else 2859 Match ("ignore") or else 2860 Match ("junk") or else 2861 Match ("unused"); 2862 end Has_Junk_Name; 2863 2864 -------------------------------------- 2865 -- Has_Pragma_Unmodified_Check_Spec -- 2866 -------------------------------------- 2867 2868 function Has_Pragma_Unmodified_Check_Spec 2869 (E : Entity_Id) return Boolean 2870 is 2871 begin 2872 if Is_Formal (E) and then Present (Spec_Entity (E)) then 2873 2874 -- Note: use of OR instead of OR ELSE here is deliberate, we want 2875 -- to mess with Unmodified flags on both body and spec entities. 2876 -- Has_Unmodified has side effects! 2877 2878 return Has_Unmodified (E) 2879 or 2880 Has_Unmodified (Spec_Entity (E)); 2881 2882 else 2883 return Has_Unmodified (E); 2884 end if; 2885 end Has_Pragma_Unmodified_Check_Spec; 2886 2887 ---------------------------------------- 2888 -- Has_Pragma_Unreferenced_Check_Spec -- 2889 ---------------------------------------- 2890 2891 function Has_Pragma_Unreferenced_Check_Spec 2892 (E : Entity_Id) return Boolean 2893 is 2894 begin 2895 if Is_Formal (E) and then Present (Spec_Entity (E)) then 2896 2897 -- Note: use of OR here instead of OR ELSE is deliberate, we want 2898 -- to mess with flags on both entities. 2899 2900 return Has_Unreferenced (E) 2901 or 2902 Has_Unreferenced (Spec_Entity (E)); 2903 2904 else 2905 return Has_Unreferenced (E); 2906 end if; 2907 end Has_Pragma_Unreferenced_Check_Spec; 2908 2909 ---------------- 2910 -- Initialize -- 2911 ---------------- 2912 2913 procedure Initialize is 2914 begin 2915 Warnings_Off_Pragmas.Init; 2916 Unreferenced_Entities.Init; 2917 In_Out_Warnings.Init; 2918 end Initialize; 2919 2920 --------------------------------------------- 2921 -- Is_Attribute_And_Known_Value_Comparison -- 2922 --------------------------------------------- 2923 2924 function Is_Attribute_And_Known_Value_Comparison 2925 (Op : Node_Id) return Boolean 2926 is 2927 Orig_Op : constant Node_Id := Original_Node (Op); 2928 2929 begin 2930 return 2931 Nkind (Orig_Op) in N_Op_Compare 2932 and then Nkind (Original_Node (Left_Opnd (Orig_Op))) = 2933 N_Attribute_Reference 2934 and then Compile_Time_Known_Value (Right_Opnd (Orig_Op)); 2935 end Is_Attribute_And_Known_Value_Comparison; 2936 2937 ------------------------------------ 2938 -- Never_Set_In_Source_Check_Spec -- 2939 ------------------------------------ 2940 2941 function Never_Set_In_Source_Check_Spec (E : Entity_Id) return Boolean is 2942 begin 2943 if Is_Formal (E) and then Present (Spec_Entity (E)) then 2944 return Never_Set_In_Source (E) 2945 and then 2946 Never_Set_In_Source (Spec_Entity (E)); 2947 else 2948 return Never_Set_In_Source (E); 2949 end if; 2950 end Never_Set_In_Source_Check_Spec; 2951 2952 ------------------------------------- 2953 -- Operand_Has_Warnings_Suppressed -- 2954 ------------------------------------- 2955 2956 function Operand_Has_Warnings_Suppressed (N : Node_Id) return Boolean is 2957 2958 function Check_For_Warnings (N : Node_Id) return Traverse_Result; 2959 -- Function used to check one node to see if it is or was originally 2960 -- a reference to an entity for which Warnings are off. If so, Abandon 2961 -- is returned, otherwise OK_Orig is returned to continue the traversal 2962 -- of the original expression. 2963 2964 function Traverse is new Traverse_Func (Check_For_Warnings); 2965 -- Function used to traverse tree looking for warnings 2966 2967 ------------------------ 2968 -- Check_For_Warnings -- 2969 ------------------------ 2970 2971 function Check_For_Warnings (N : Node_Id) return Traverse_Result is 2972 R : constant Node_Id := Original_Node (N); 2973 2974 begin 2975 if Nkind (R) in N_Has_Entity 2976 and then Present (Entity (R)) 2977 and then Has_Warnings_Off (Entity (R)) 2978 then 2979 return Abandon; 2980 else 2981 return OK_Orig; 2982 end if; 2983 end Check_For_Warnings; 2984 2985 -- Start of processing for Operand_Has_Warnings_Suppressed 2986 2987 begin 2988 return Traverse (N) = Abandon; 2989 2990 -- If any exception occurs, then something has gone wrong, and this is 2991 -- only a minor aesthetic issue anyway, so just say we did not find what 2992 -- we are looking for, rather than blow up. 2993 2994 exception 2995 when others => 2996 return False; 2997 end Operand_Has_Warnings_Suppressed; 2998 2999 ----------------------------------------- 3000 -- Output_Non_Modified_In_Out_Warnings -- 3001 ----------------------------------------- 3002 3003 procedure Output_Non_Modified_In_Out_Warnings is 3004 3005 function No_Warn_On_In_Out (E : Entity_Id) return Boolean; 3006 -- Given a formal parameter entity E, determines if there is a reason to 3007 -- suppress IN OUT warnings (not modified, could be IN) for formals of 3008 -- the subprogram. We suppress these warnings if Warnings Off is set, or 3009 -- if we have seen the address of the subprogram being taken, or if the 3010 -- subprogram is used as a generic actual (in the latter cases the 3011 -- context may force use of IN OUT, even if the parameter is not 3012 -- modifies for this particular case. 3013 3014 ----------------------- 3015 -- No_Warn_On_In_Out -- 3016 ----------------------- 3017 3018 function No_Warn_On_In_Out (E : Entity_Id) return Boolean is 3019 S : constant Entity_Id := Scope (E); 3020 SE : constant Entity_Id := Spec_Entity (E); 3021 3022 begin 3023 -- Do not warn if address is taken, since funny business may be going 3024 -- on in treating the parameter indirectly as IN OUT. 3025 3026 if Address_Taken (S) 3027 or else (Present (SE) and then Address_Taken (Scope (SE))) 3028 then 3029 return True; 3030 3031 -- Do not warn if used as a generic actual, since the generic may be 3032 -- what is forcing the use of an "unnecessary" IN OUT. 3033 3034 elsif Used_As_Generic_Actual (S) 3035 or else (Present (SE) and then Used_As_Generic_Actual (Scope (SE))) 3036 then 3037 return True; 3038 3039 -- Else test warnings off 3040 3041 elsif Warnings_Off_Check_Spec (S) then 3042 return True; 3043 3044 -- All tests for suppressing warning failed 3045 3046 else 3047 return False; 3048 end if; 3049 end No_Warn_On_In_Out; 3050 3051 -- Start of processing for Output_Non_Modified_In_Out_Warnings 3052 3053 begin 3054 -- Loop through entities for which a warning may be needed 3055 3056 for J in In_Out_Warnings.First .. In_Out_Warnings.Last loop 3057 declare 3058 E1 : constant Entity_Id := In_Out_Warnings.Table (J); 3059 3060 begin 3061 -- Suppress warning in specific cases (see details in comments for 3062 -- No_Warn_On_In_Out), or if there is a pragma Unmodified. 3063 3064 if Has_Pragma_Unmodified_Check_Spec (E1) 3065 or else No_Warn_On_In_Out (E1) 3066 then 3067 null; 3068 3069 -- Here we generate the warning 3070 3071 else 3072 -- If -gnatwc is set then output message that we could be IN 3073 3074 if not Is_Trivial_Subprogram (Scope (E1)) then 3075 if Warn_On_Constant then 3076 Error_Msg_N 3077 ("?u?formal parameter & is not modified!", E1); 3078 Error_Msg_N 3079 ("\?u?mode could be IN instead of `IN OUT`!", E1); 3080 3081 -- We do not generate warnings for IN OUT parameters 3082 -- unless we have at least -gnatwu. This is deliberately 3083 -- inconsistent with the treatment of variables, but 3084 -- otherwise we get too many unexpected warnings in 3085 -- default mode. 3086 3087 elsif Check_Unreferenced then 3088 Error_Msg_N 3089 ("?u?formal parameter& is read but " 3090 & "never assigned!", E1); 3091 end if; 3092 end if; 3093 3094 -- Kill any other warnings on this entity, since this is the 3095 -- one that should dominate any other unreferenced warning. 3096 3097 Set_Warnings_Off (E1); 3098 end if; 3099 end; 3100 end loop; 3101 end Output_Non_Modified_In_Out_Warnings; 3102 3103 ---------------------------------------- 3104 -- Output_Obsolescent_Entity_Warnings -- 3105 ---------------------------------------- 3106 3107 procedure Output_Obsolescent_Entity_Warnings (N : Node_Id; E : Entity_Id) is 3108 P : constant Node_Id := Parent (N); 3109 S : Entity_Id; 3110 3111 begin 3112 S := Current_Scope; 3113 3114 -- Do not output message if we are the scope of standard. This means 3115 -- we have a reference from a context clause from when it is originally 3116 -- processed, and that's too early to tell whether it is an obsolescent 3117 -- unit doing the with'ing. In Sem_Ch10.Analyze_Compilation_Unit we make 3118 -- sure that we have a later call when the scope is available. This test 3119 -- also eliminates all messages for use clauses, which is fine (we do 3120 -- not want messages for use clauses, since they are always redundant 3121 -- with respect to the associated with clause). 3122 3123 if S = Standard_Standard then 3124 return; 3125 end if; 3126 3127 -- Do not output message if we are in scope of an obsolescent package 3128 -- or subprogram. 3129 3130 loop 3131 if Is_Obsolescent (S) then 3132 return; 3133 end if; 3134 3135 S := Scope (S); 3136 exit when S = Standard_Standard; 3137 end loop; 3138 3139 -- Here we will output the message 3140 3141 Error_Msg_Sloc := Sloc (E); 3142 3143 -- Case of with clause 3144 3145 if Nkind (P) = N_With_Clause then 3146 if Ekind (E) = E_Package then 3147 Error_Msg_NE 3148 ("?j?with of obsolescent package& declared#", N, E); 3149 elsif Ekind (E) = E_Procedure then 3150 Error_Msg_NE 3151 ("?j?with of obsolescent procedure& declared#", N, E); 3152 else 3153 Error_Msg_NE 3154 ("??with of obsolescent function& declared#", N, E); 3155 end if; 3156 3157 -- If we do not have a with clause, then ignore any reference to an 3158 -- obsolescent package name. We only want to give the one warning of 3159 -- withing the package, not one each time it is used to qualify. 3160 3161 elsif Ekind (E) = E_Package then 3162 return; 3163 3164 -- Procedure call statement 3165 3166 elsif Nkind (P) = N_Procedure_Call_Statement then 3167 Error_Msg_NE 3168 ("??call to obsolescent procedure& declared#", N, E); 3169 3170 -- Function call 3171 3172 elsif Nkind (P) = N_Function_Call then 3173 Error_Msg_NE 3174 ("??call to obsolescent function& declared#", N, E); 3175 3176 -- Reference to obsolescent type 3177 3178 elsif Is_Type (E) then 3179 Error_Msg_NE 3180 ("??reference to obsolescent type& declared#", N, E); 3181 3182 -- Reference to obsolescent component 3183 3184 elsif Ekind_In (E, E_Component, E_Discriminant) then 3185 Error_Msg_NE 3186 ("??reference to obsolescent component& declared#", N, E); 3187 3188 -- Reference to obsolescent variable 3189 3190 elsif Ekind (E) = E_Variable then 3191 Error_Msg_NE 3192 ("??reference to obsolescent variable& declared#", N, E); 3193 3194 -- Reference to obsolescent constant 3195 3196 elsif Ekind (E) = E_Constant or else Ekind (E) in Named_Kind then 3197 Error_Msg_NE 3198 ("??reference to obsolescent constant& declared#", N, E); 3199 3200 -- Reference to obsolescent enumeration literal 3201 3202 elsif Ekind (E) = E_Enumeration_Literal then 3203 Error_Msg_NE 3204 ("??reference to obsolescent enumeration literal& declared#", N, E); 3205 3206 -- Generic message for any other case we missed 3207 3208 else 3209 Error_Msg_NE 3210 ("??reference to obsolescent entity& declared#", N, E); 3211 end if; 3212 3213 -- Output additional warning if present 3214 3215 for J in Obsolescent_Warnings.First .. Obsolescent_Warnings.Last loop 3216 if Obsolescent_Warnings.Table (J).Ent = E then 3217 String_To_Name_Buffer (Obsolescent_Warnings.Table (J).Msg); 3218 Error_Msg_Strlen := Name_Len; 3219 Error_Msg_String (1 .. Name_Len) := Name_Buffer (1 .. Name_Len); 3220 Error_Msg_N ("\\??~", N); 3221 exit; 3222 end if; 3223 end loop; 3224 end Output_Obsolescent_Entity_Warnings; 3225 3226 ---------------------------------- 3227 -- Output_Unreferenced_Messages -- 3228 ---------------------------------- 3229 3230 procedure Output_Unreferenced_Messages is 3231 begin 3232 for J in Unreferenced_Entities.First .. Unreferenced_Entities.Last loop 3233 Warn_On_Unreferenced_Entity (Unreferenced_Entities.Table (J)); 3234 end loop; 3235 end Output_Unreferenced_Messages; 3236 3237 ----------------------------------------- 3238 -- Output_Unused_Warnings_Off_Warnings -- 3239 ----------------------------------------- 3240 3241 procedure Output_Unused_Warnings_Off_Warnings is 3242 begin 3243 for J in Warnings_Off_Pragmas.First .. Warnings_Off_Pragmas.Last loop 3244 declare 3245 Wentry : Warnings_Off_Entry renames Warnings_Off_Pragmas.Table (J); 3246 N : Node_Id renames Wentry.N; 3247 E : Node_Id renames Wentry.E; 3248 3249 begin 3250 -- Turn off Warnings_Off, or we won't get the warning 3251 3252 Set_Warnings_Off (E, False); 3253 3254 -- Nothing to do if pragma was used to suppress a general warning 3255 3256 if Warnings_Off_Used (E) then 3257 null; 3258 3259 -- If pragma was used both in unmodified and unreferenced contexts 3260 -- then that's as good as the general case, no warning. 3261 3262 elsif Warnings_Off_Used_Unmodified (E) 3263 and 3264 Warnings_Off_Used_Unreferenced (E) 3265 then 3266 null; 3267 3268 -- Used only in context where Unmodified would have worked 3269 3270 elsif Warnings_Off_Used_Unmodified (E) then 3271 Error_Msg_NE 3272 ("?W?could use Unmodified instead of " 3273 & "Warnings Off for &", Pragma_Identifier (N), E); 3274 3275 -- Used only in context where Unreferenced would have worked 3276 3277 elsif Warnings_Off_Used_Unreferenced (E) then 3278 Error_Msg_NE 3279 ("?W?could use Unreferenced instead of " 3280 & "Warnings Off for &", Pragma_Identifier (N), E); 3281 3282 -- Not used at all 3283 3284 else 3285 Error_Msg_NE 3286 ("?W?pragma Warnings Off for & unused, " 3287 & "could be omitted", N, E); 3288 end if; 3289 end; 3290 end loop; 3291 end Output_Unused_Warnings_Off_Warnings; 3292 3293 --------------------------- 3294 -- Referenced_Check_Spec -- 3295 --------------------------- 3296 3297 function Referenced_Check_Spec (E : Entity_Id) return Boolean is 3298 begin 3299 if Is_Formal (E) and then Present (Spec_Entity (E)) then 3300 return Referenced (E) or else Referenced (Spec_Entity (E)); 3301 else 3302 return Referenced (E); 3303 end if; 3304 end Referenced_Check_Spec; 3305 3306 ---------------------------------- 3307 -- Referenced_As_LHS_Check_Spec -- 3308 ---------------------------------- 3309 3310 function Referenced_As_LHS_Check_Spec (E : Entity_Id) return Boolean is 3311 begin 3312 if Is_Formal (E) and then Present (Spec_Entity (E)) then 3313 return Referenced_As_LHS (E) 3314 or else Referenced_As_LHS (Spec_Entity (E)); 3315 else 3316 return Referenced_As_LHS (E); 3317 end if; 3318 end Referenced_As_LHS_Check_Spec; 3319 3320 -------------------------------------------- 3321 -- Referenced_As_Out_Parameter_Check_Spec -- 3322 -------------------------------------------- 3323 3324 function Referenced_As_Out_Parameter_Check_Spec 3325 (E : Entity_Id) return Boolean 3326 is 3327 begin 3328 if Is_Formal (E) and then Present (Spec_Entity (E)) then 3329 return Referenced_As_Out_Parameter (E) 3330 or else Referenced_As_Out_Parameter (Spec_Entity (E)); 3331 else 3332 return Referenced_As_Out_Parameter (E); 3333 end if; 3334 end Referenced_As_Out_Parameter_Check_Spec; 3335 3336 -------------------------------------- 3337 -- Warn_On_Constant_Valid_Condition -- 3338 -------------------------------------- 3339 3340 procedure Warn_On_Constant_Valid_Condition (Op : Node_Id) is 3341 Left : constant Node_Id := Left_Opnd (Op); 3342 Right : constant Node_Id := Right_Opnd (Op); 3343 3344 True_Result : Boolean; 3345 False_Result : Boolean; 3346 3347 begin 3348 -- Determine the potential outcome of the comparison assuming that the 3349 -- scalar operands are valid. 3350 3351 if Constant_Condition_Warnings 3352 and then Comes_From_Source (Original_Node (Op)) 3353 and then Is_Scalar_Type (Etype (Left)) 3354 and then Is_Scalar_Type (Etype (Right)) 3355 3356 -- Do not consider instances because the check was already performed 3357 -- in the generic. 3358 3359 and then not In_Instance 3360 3361 -- Do not consider comparisons between two static expressions such as 3362 -- constants or literals because those values cannot be invalidated. 3363 3364 and then not (Is_Static_Expression (Left) 3365 and then Is_Static_Expression (Right)) 3366 3367 -- Do not consider comparison between an attribute reference and a 3368 -- compile-time known value since this is most likely a conditional 3369 -- compilation. 3370 3371 and then not Is_Attribute_And_Known_Value_Comparison (Op) 3372 3373 -- Do not consider internal files to allow for various assertions and 3374 -- safeguards within our runtime. 3375 3376 and then not In_Internal_Unit (Op) 3377 then 3378 Test_Comparison 3379 (Op => Op, 3380 Assume_Valid => True, 3381 True_Result => True_Result, 3382 False_Result => False_Result); 3383 3384 -- Warn on a possible evaluation to False / True in the presence of 3385 -- invalid values. 3386 3387 if True_Result then 3388 Error_Msg_N 3389 ("condition can only be False if invalid values present??", Op); 3390 3391 elsif False_Result then 3392 Error_Msg_N 3393 ("condition can only be True if invalid values present??", Op); 3394 end if; 3395 end if; 3396 end Warn_On_Constant_Valid_Condition; 3397 3398 ----------------------------- 3399 -- Warn_On_Known_Condition -- 3400 ----------------------------- 3401 3402 procedure Warn_On_Known_Condition (C : Node_Id) is 3403 Test_Result : Boolean := False; 3404 -- Force initialization to facilitate static analysis 3405 3406 function Is_Known_Branch return Boolean; 3407 -- If the type of the condition is Boolean, the constant value of the 3408 -- condition is a boolean literal. If the type is a derived boolean 3409 -- type, the constant is wrapped in a type conversion of the derived 3410 -- literal. If the value of the condition is not a literal, no warnings 3411 -- can be produced. This function returns True if the result can be 3412 -- determined, and Test_Result is set True/False accordingly. Otherwise 3413 -- False is returned, and Test_Result is unchanged. 3414 3415 procedure Track (N : Node_Id; Loc : Node_Id); 3416 -- Adds continuation warning(s) pointing to reason (assignment or test) 3417 -- for the operand of the conditional having a known value (or at least 3418 -- enough is known about the value to issue the warning). N is the node 3419 -- which is judged to have a known value. Loc is the warning location. 3420 3421 --------------------- 3422 -- Is_Known_Branch -- 3423 --------------------- 3424 3425 function Is_Known_Branch return Boolean is 3426 begin 3427 if Etype (C) = Standard_Boolean 3428 and then Is_Entity_Name (C) 3429 and then 3430 (Entity (C) = Standard_False or else Entity (C) = Standard_True) 3431 then 3432 Test_Result := Entity (C) = Standard_True; 3433 return True; 3434 3435 elsif Is_Boolean_Type (Etype (C)) 3436 and then Nkind (C) = N_Unchecked_Type_Conversion 3437 and then Is_Entity_Name (Expression (C)) 3438 and then Ekind (Entity (Expression (C))) = E_Enumeration_Literal 3439 then 3440 Test_Result := 3441 Chars (Entity (Expression (C))) = Chars (Standard_True); 3442 return True; 3443 3444 else 3445 return False; 3446 end if; 3447 end Is_Known_Branch; 3448 3449 ----------- 3450 -- Track -- 3451 ----------- 3452 3453 procedure Track (N : Node_Id; Loc : Node_Id) is 3454 Nod : constant Node_Id := Original_Node (N); 3455 3456 begin 3457 if Nkind (Nod) in N_Op_Compare then 3458 Track (Left_Opnd (Nod), Loc); 3459 Track (Right_Opnd (Nod), Loc); 3460 3461 elsif Is_Entity_Name (Nod) and then Is_Object (Entity (Nod)) then 3462 declare 3463 CV : constant Node_Id := Current_Value (Entity (Nod)); 3464 3465 begin 3466 if Present (CV) then 3467 Error_Msg_Sloc := Sloc (CV); 3468 3469 if Nkind (CV) not in N_Subexpr then 3470 Error_Msg_N ("\\??(see test #)", Loc); 3471 3472 elsif Nkind (Parent (CV)) = 3473 N_Case_Statement_Alternative 3474 then 3475 Error_Msg_N ("\\??(see case alternative #)", Loc); 3476 3477 else 3478 Error_Msg_N ("\\??(see assignment #)", Loc); 3479 end if; 3480 end if; 3481 end; 3482 end if; 3483 end Track; 3484 3485 -- Local variables 3486 3487 Orig : constant Node_Id := Original_Node (C); 3488 P : Node_Id; 3489 3490 -- Start of processing for Warn_On_Known_Condition 3491 3492 begin 3493 -- Adjust SCO condition if from source 3494 3495 if Generate_SCO 3496 and then Comes_From_Source (Orig) 3497 and then Is_Known_Branch 3498 then 3499 declare 3500 Atrue : Boolean; 3501 3502 begin 3503 Atrue := Test_Result; 3504 3505 if Present (Parent (C)) and then Nkind (Parent (C)) = N_Op_Not then 3506 Atrue := not Atrue; 3507 end if; 3508 3509 Set_SCO_Condition (Orig, Atrue); 3510 end; 3511 end if; 3512 3513 -- Argument replacement in an inlined body can make conditions static. 3514 -- Do not emit warnings in this case. 3515 3516 if In_Inlined_Body then 3517 return; 3518 end if; 3519 3520 if Constant_Condition_Warnings 3521 and then Is_Known_Branch 3522 and then Comes_From_Source (Orig) 3523 and then not In_Instance 3524 then 3525 -- Don't warn if comparison of result of attribute against a constant 3526 -- value, since this is likely legitimate conditional compilation. 3527 3528 if Is_Attribute_And_Known_Value_Comparison (C) then 3529 return; 3530 end if; 3531 3532 -- See if this is in a statement or a declaration 3533 3534 P := Parent (C); 3535 loop 3536 -- If tree is not attached, do not issue warning (this is very 3537 -- peculiar, and probably arises from some other error condition). 3538 3539 if No (P) then 3540 return; 3541 3542 -- If we are in a declaration, then no warning, since in practice 3543 -- conditionals in declarations are used for intended tests which 3544 -- may be known at compile time, e.g. things like 3545 3546 -- x : constant Integer := 2 + (Word'Size = 32); 3547 3548 -- And a warning is annoying in such cases 3549 3550 elsif Nkind (P) in N_Declaration 3551 or else 3552 Nkind (P) in N_Later_Decl_Item 3553 then 3554 return; 3555 3556 -- Don't warn in assert or check pragma, since presumably tests in 3557 -- such a context are very definitely intended, and might well be 3558 -- known at compile time. Note that we have to test the original 3559 -- node, since assert pragmas get rewritten at analysis time. 3560 3561 elsif Nkind (Original_Node (P)) = N_Pragma 3562 and then Nam_In (Pragma_Name_Unmapped (Original_Node (P)), 3563 Name_Assert, Name_Check) 3564 then 3565 return; 3566 end if; 3567 3568 exit when Is_Statement (P); 3569 P := Parent (P); 3570 end loop; 3571 3572 -- Here we issue the warning unless some sub-operand has warnings 3573 -- set off, in which case we suppress the warning for the node. If 3574 -- the original expression is an inequality, it has been expanded 3575 -- into a negation, and the value of the original expression is the 3576 -- negation of the equality. If the expression is an entity that 3577 -- appears within a negation, it is clearer to flag the negation 3578 -- itself, and report on its constant value. 3579 3580 if not Operand_Has_Warnings_Suppressed (C) then 3581 declare 3582 True_Branch : Boolean := Test_Result; 3583 Cond : Node_Id := C; 3584 3585 begin 3586 if Present (Parent (C)) 3587 and then Nkind (Parent (C)) = N_Op_Not 3588 then 3589 True_Branch := not True_Branch; 3590 Cond := Parent (C); 3591 end if; 3592 3593 -- Condition always True 3594 3595 if True_Branch then 3596 if Is_Entity_Name (Original_Node (C)) 3597 and then Nkind (Cond) /= N_Op_Not 3598 then 3599 Error_Msg_NE 3600 ("object & is always True at this point?c?", 3601 Cond, Original_Node (C)); 3602 Track (Original_Node (C), Cond); 3603 3604 else 3605 Error_Msg_N ("condition is always True?c?", Cond); 3606 Track (Cond, Cond); 3607 end if; 3608 3609 -- Condition always False 3610 3611 else 3612 if Is_Entity_Name (Original_Node (C)) 3613 and then Nkind (Cond) /= N_Op_Not 3614 then 3615 Error_Msg_NE 3616 ("object & is always False at this point?c?", 3617 Cond, Original_Node (C)); 3618 Track (Original_Node (C), Cond); 3619 3620 else 3621 Error_Msg_N ("condition is always False?c?", Cond); 3622 Track (Cond, Cond); 3623 end if; 3624 end if; 3625 end; 3626 end if; 3627 end if; 3628 end Warn_On_Known_Condition; 3629 3630 --------------------------------------- 3631 -- Warn_On_Modified_As_Out_Parameter -- 3632 --------------------------------------- 3633 3634 function Warn_On_Modified_As_Out_Parameter (E : Entity_Id) return Boolean is 3635 begin 3636 return 3637 (Warn_On_Modified_Unread and then Is_Only_Out_Parameter (E)) 3638 or else Warn_On_All_Unread_Out_Parameters; 3639 end Warn_On_Modified_As_Out_Parameter; 3640 3641 --------------------------------- 3642 -- Warn_On_Overlapping_Actuals -- 3643 --------------------------------- 3644 3645 procedure Warn_On_Overlapping_Actuals (Subp : Entity_Id; N : Node_Id) is 3646 function Is_Covered_Formal (Formal : Node_Id) return Boolean; 3647 -- Return True if Formal is covered by the rule 3648 3649 function Refer_Same_Object 3650 (Act1 : Node_Id; 3651 Act2 : Node_Id) return Boolean; 3652 -- Two names are known to refer to the same object if the two names 3653 -- are known to denote the same object; or one of the names is a 3654 -- selected_component, indexed_component, or slice and its prefix is 3655 -- known to refer to the same object as the other name; or one of the 3656 -- two names statically denotes a renaming declaration whose renamed 3657 -- object_name is known to refer to the same object as the other name 3658 -- (RM 6.4.1(6.11/3)) 3659 3660 ----------------------- 3661 -- Is_Covered_Formal -- 3662 ----------------------- 3663 3664 function Is_Covered_Formal (Formal : Node_Id) return Boolean is 3665 begin 3666 return 3667 Ekind_In (Formal, E_Out_Parameter, E_In_Out_Parameter) 3668 and then (Is_Elementary_Type (Etype (Formal)) 3669 or else Is_Record_Type (Etype (Formal)) 3670 or else Is_Array_Type (Etype (Formal))); 3671 end Is_Covered_Formal; 3672 3673 ----------------------- 3674 -- Refer_Same_Object -- 3675 ----------------------- 3676 3677 function Refer_Same_Object 3678 (Act1 : Node_Id; 3679 Act2 : Node_Id) return Boolean 3680 is 3681 begin 3682 return 3683 Denotes_Same_Object (Act1, Act2) 3684 or else Denotes_Same_Prefix (Act1, Act2); 3685 end Refer_Same_Object; 3686 3687 -- Local variables 3688 3689 Act1 : Node_Id; 3690 Act2 : Node_Id; 3691 Form1 : Entity_Id; 3692 Form2 : Entity_Id; 3693 Warn_Only : Boolean; 3694 -- GNAT warns on overlapping in-out parameters of any type, not just for 3695 -- elementary in-out parameters (as specified in RM 6.4.1 (15/3-17/3)). 3696 3697 -- Start of processing for Warn_On_Overlapping_Actuals 3698 3699 begin 3700 3701 if Ada_Version < Ada_2012 and then not Warn_On_Overlap then 3702 return; 3703 end if; 3704 3705 -- The call is illegal only if there are at least two in-out parameters 3706 -- of the same elementary type. 3707 3708 Warn_Only := True; 3709 Form1 := First_Formal (Subp); 3710 while Present (Form1) loop 3711 Form2 := Next_Formal (Form1); 3712 while Present (Form2) loop 3713 if Is_Elementary_Type (Etype (Form1)) 3714 and then Is_Elementary_Type (Etype (Form2)) 3715 and then Ekind (Form1) /= E_In_Parameter 3716 and then Ekind (Form2) /= E_In_Parameter 3717 then 3718 Warn_Only := False; 3719 exit; 3720 end if; 3721 3722 Next_Formal (Form2); 3723 end loop; 3724 3725 Next_Formal (Form1); 3726 end loop; 3727 3728 -- Exclude calls rewritten as enumeration literals 3729 3730 if Nkind (N) not in N_Subprogram_Call 3731 and then Nkind (N) /= N_Entry_Call_Statement 3732 then 3733 return; 3734 end if; 3735 3736 -- If a call C has two or more parameters of mode in out or out that are 3737 -- of an elementary type, then the call is legal only if for each name 3738 -- N that is passed as a parameter of mode in out or out to the call C, 3739 -- there is no other name among the other parameters of mode in out or 3740 -- out to C that is known to denote the same object (RM 6.4.1(6.15/3)) 3741 3742 -- If appropriate warning switch is set, we also report warnings on 3743 -- overlapping parameters that are record types or array types. 3744 3745 Form1 := First_Formal (Subp); 3746 Act1 := First_Actual (N); 3747 while Present (Form1) and then Present (Act1) loop 3748 if Is_Covered_Formal (Form1) then 3749 Form2 := First_Formal (Subp); 3750 Act2 := First_Actual (N); 3751 while Present (Form2) and then Present (Act2) loop 3752 if Form1 /= Form2 3753 and then Is_Covered_Formal (Form2) 3754 and then Refer_Same_Object (Act1, Act2) 3755 then 3756 -- Guard against previous errors 3757 3758 if Error_Posted (N) 3759 or else No (Etype (Act1)) 3760 or else No (Etype (Act2)) 3761 then 3762 null; 3763 3764 -- If the actual is a function call in prefix notation, 3765 -- there is no real overlap. 3766 3767 elsif Nkind (Act2) = N_Function_Call then 3768 null; 3769 3770 -- If type is not by-copy, assume that aliasing is intended 3771 3772 elsif 3773 Present (Underlying_Type (Etype (Form1))) 3774 and then 3775 (Is_By_Reference_Type (Underlying_Type (Etype (Form1))) 3776 or else 3777 Convention (Underlying_Type (Etype (Form1))) = 3778 Convention_Ada_Pass_By_Reference) 3779 then 3780 null; 3781 3782 -- Under Ada 2012 we only report warnings on overlapping 3783 -- arrays and record types if switch is set. 3784 3785 elsif Ada_Version >= Ada_2012 3786 and then not Is_Elementary_Type (Etype (Form1)) 3787 and then not Warn_On_Overlap 3788 then 3789 null; 3790 3791 -- Here we may need to issue overlap message 3792 3793 else 3794 Error_Msg_Warn := 3795 3796 -- Overlap checking is an error only in Ada 2012. For 3797 -- earlier versions of Ada, this is a warning. 3798 3799 Ada_Version < Ada_2012 3800 3801 -- Overlap is only illegal in Ada 2012 in the case of 3802 -- elementary types (passed by copy). For other types, 3803 -- we always have a warning in all Ada versions. 3804 3805 or else not Is_Elementary_Type (Etype (Form1)) 3806 3807 -- debug flag -gnatd.E changes the error to a warning 3808 -- even in Ada 2012 mode. 3809 3810 or else Error_To_Warning 3811 or else Warn_Only; 3812 3813 declare 3814 Act : Node_Id; 3815 Form : Entity_Id; 3816 3817 begin 3818 -- Find matching actual 3819 3820 Act := First_Actual (N); 3821 Form := First_Formal (Subp); 3822 while Act /= Act2 loop 3823 Next_Formal (Form); 3824 Next_Actual (Act); 3825 end loop; 3826 3827 if Is_Elementary_Type (Etype (Act1)) 3828 and then Ekind (Form2) = E_In_Parameter 3829 then 3830 null; -- No real aliasing 3831 3832 elsif Is_Elementary_Type (Etype (Act2)) 3833 and then Ekind (Form2) = E_In_Parameter 3834 then 3835 null; -- Ditto 3836 3837 -- If the call was written in prefix notation, and 3838 -- thus its prefix before rewriting was a selected 3839 -- component, count only visible actuals in the call. 3840 3841 elsif Is_Entity_Name (First_Actual (N)) 3842 and then Nkind (Original_Node (N)) = Nkind (N) 3843 and then Nkind (Name (Original_Node (N))) = 3844 N_Selected_Component 3845 and then 3846 Is_Entity_Name (Prefix (Name (Original_Node (N)))) 3847 and then 3848 Entity (Prefix (Name (Original_Node (N)))) = 3849 Entity (First_Actual (N)) 3850 then 3851 if Act1 = First_Actual (N) then 3852 Error_Msg_FE 3853 ("<<`IN OUT` prefix overlaps with " 3854 & "actual for&", Act1, Form); 3855 3856 else 3857 -- For greater clarity, give name of formal 3858 3859 Error_Msg_Node_2 := Form; 3860 Error_Msg_FE 3861 ("<<writable actual for & overlaps with " 3862 & "actual for&", Act1, Form); 3863 end if; 3864 3865 else 3866 -- For greater clarity, give name of formal 3867 3868 Error_Msg_Node_2 := Form; 3869 3870 -- This is one of the messages 3871 3872 Error_Msg_FE 3873 ("<<writable actual for & overlaps with " 3874 & "actual for&", Act1, Form1); 3875 end if; 3876 end; 3877 end if; 3878 3879 return; 3880 end if; 3881 3882 Next_Formal (Form2); 3883 Next_Actual (Act2); 3884 end loop; 3885 end if; 3886 3887 Next_Formal (Form1); 3888 Next_Actual (Act1); 3889 end loop; 3890 end Warn_On_Overlapping_Actuals; 3891 3892 ------------------------------ 3893 -- Warn_On_Suspicious_Index -- 3894 ------------------------------ 3895 3896 procedure Warn_On_Suspicious_Index (Name : Entity_Id; X : Node_Id) is 3897 3898 Low_Bound : Uint; 3899 -- Set to lower bound for a suspicious type 3900 3901 Ent : Entity_Id; 3902 -- Entity for array reference 3903 3904 Typ : Entity_Id; 3905 -- Array type 3906 3907 function Is_Suspicious_Type (Typ : Entity_Id) return Boolean; 3908 -- Tests to see if Typ is a type for which we may have a suspicious 3909 -- index, namely an unconstrained array type, whose lower bound is 3910 -- either zero or one. If so, True is returned, and Low_Bound is set 3911 -- to this lower bound. If not, False is returned, and Low_Bound is 3912 -- undefined on return. 3913 -- 3914 -- For now, we limit this to standard string types, so any other 3915 -- unconstrained types return False. We may change our minds on this 3916 -- later on, but strings seem the most important case. 3917 3918 procedure Test_Suspicious_Index; 3919 -- Test if index is of suspicious type and if so, generate warning 3920 3921 ------------------------ 3922 -- Is_Suspicious_Type -- 3923 ------------------------ 3924 3925 function Is_Suspicious_Type (Typ : Entity_Id) return Boolean is 3926 LB : Node_Id; 3927 3928 begin 3929 if Is_Array_Type (Typ) 3930 and then not Is_Constrained (Typ) 3931 and then Number_Dimensions (Typ) = 1 3932 and then Is_Standard_String_Type (Typ) 3933 and then not Has_Warnings_Off (Typ) 3934 then 3935 LB := Type_Low_Bound (Etype (First_Index (Typ))); 3936 3937 if Compile_Time_Known_Value (LB) then 3938 Low_Bound := Expr_Value (LB); 3939 return Low_Bound = Uint_0 or else Low_Bound = Uint_1; 3940 end if; 3941 end if; 3942 3943 return False; 3944 end Is_Suspicious_Type; 3945 3946 --------------------------- 3947 -- Test_Suspicious_Index -- 3948 --------------------------- 3949 3950 procedure Test_Suspicious_Index is 3951 3952 function Length_Reference (N : Node_Id) return Boolean; 3953 -- Check if node N is of the form Name'Length 3954 3955 procedure Warn1; 3956 -- Generate first warning line 3957 3958 procedure Warn_On_Index_Below_Lower_Bound; 3959 -- Generate a warning on indexing the array with a literal value 3960 -- below the lower bound of the index type. 3961 3962 procedure Warn_On_Literal_Index; 3963 -- Generate a warning on indexing the array with a literal value 3964 3965 ---------------------- 3966 -- Length_Reference -- 3967 ---------------------- 3968 3969 function Length_Reference (N : Node_Id) return Boolean is 3970 R : constant Node_Id := Original_Node (N); 3971 begin 3972 return 3973 Nkind (R) = N_Attribute_Reference 3974 and then Attribute_Name (R) = Name_Length 3975 and then Is_Entity_Name (Prefix (R)) 3976 and then Entity (Prefix (R)) = Ent; 3977 end Length_Reference; 3978 3979 ----------- 3980 -- Warn1 -- 3981 ----------- 3982 3983 procedure Warn1 is 3984 begin 3985 Error_Msg_Uint_1 := Low_Bound; 3986 Error_Msg_FE -- CODEFIX 3987 ("?w?index for& may assume lower bound of^", X, Ent); 3988 end Warn1; 3989 3990 ------------------------------------- 3991 -- Warn_On_Index_Below_Lower_Bound -- 3992 ------------------------------------- 3993 3994 procedure Warn_On_Index_Below_Lower_Bound is 3995 begin 3996 if Is_Standard_String_Type (Typ) then 3997 Discard_Node 3998 (Compile_Time_Constraint_Error 3999 (N => X, 4000 Msg => "?w?string index should be positive")); 4001 else 4002 Discard_Node 4003 (Compile_Time_Constraint_Error 4004 (N => X, 4005 Msg => "?w?index out of the allowed range")); 4006 end if; 4007 end Warn_On_Index_Below_Lower_Bound; 4008 4009 --------------------------- 4010 -- Warn_On_Literal_Index -- 4011 --------------------------- 4012 4013 procedure Warn_On_Literal_Index is 4014 begin 4015 Warn1; 4016 4017 -- Case where original form of subscript is an integer literal 4018 4019 if Nkind (Original_Node (X)) = N_Integer_Literal then 4020 if Intval (X) = Low_Bound then 4021 Error_Msg_FE -- CODEFIX 4022 ("\?w?suggested replacement: `&''First`", X, Ent); 4023 else 4024 Error_Msg_Uint_1 := Intval (X) - Low_Bound; 4025 Error_Msg_FE -- CODEFIX 4026 ("\?w?suggested replacement: `&''First + ^`", X, Ent); 4027 4028 end if; 4029 4030 -- Case where original form of subscript is more complex 4031 4032 else 4033 -- Build string X'First - 1 + expression where the expression 4034 -- is the original subscript. If the expression starts with "1 4035 -- + ", then the "- 1 + 1" is elided. 4036 4037 Error_Msg_String (1 .. 13) := "'First - 1 + "; 4038 Error_Msg_Strlen := 13; 4039 4040 declare 4041 Sref : Source_Ptr := Sloc (First_Node (Original_Node (X))); 4042 Tref : constant Source_Buffer_Ptr := 4043 Source_Text (Get_Source_File_Index (Sref)); 4044 -- Tref (Sref) is used to scan the subscript 4045 4046 Pctr : Natural; 4047 -- Parentheses counter when scanning subscript 4048 4049 begin 4050 -- Tref (Sref) points to start of subscript 4051 4052 -- Elide - 1 if subscript starts with 1 + 4053 4054 if Tref (Sref .. Sref + 2) = "1 +" then 4055 Error_Msg_Strlen := Error_Msg_Strlen - 6; 4056 Sref := Sref + 2; 4057 4058 elsif Tref (Sref .. Sref + 1) = "1+" then 4059 Error_Msg_Strlen := Error_Msg_Strlen - 6; 4060 Sref := Sref + 1; 4061 end if; 4062 4063 -- Now we will copy the subscript to the string buffer 4064 4065 Pctr := 0; 4066 loop 4067 -- Count parens, exit if terminating right paren. Note 4068 -- check to ignore paren appearing as character literal. 4069 4070 if Tref (Sref + 1) = ''' 4071 and then 4072 Tref (Sref - 1) = ''' 4073 then 4074 null; 4075 else 4076 if Tref (Sref) = '(' then 4077 Pctr := Pctr + 1; 4078 elsif Tref (Sref) = ')' then 4079 exit when Pctr = 0; 4080 Pctr := Pctr - 1; 4081 end if; 4082 end if; 4083 4084 -- Done if terminating double dot (slice case) 4085 4086 exit when Pctr = 0 4087 and then (Tref (Sref .. Sref + 1) = ".." 4088 or else 4089 Tref (Sref .. Sref + 2) = " .."); 4090 4091 -- Quit if we have hit EOF character, something wrong 4092 4093 if Tref (Sref) = EOF then 4094 return; 4095 end if; 4096 4097 -- String literals are too much of a pain to handle 4098 4099 if Tref (Sref) = '"' or else Tref (Sref) = '%' then 4100 return; 4101 end if; 4102 4103 -- If we have a 'Range reference, then this is a case 4104 -- where we cannot easily give a replacement. Don't try. 4105 4106 if Tref (Sref .. Sref + 4) = "range" 4107 and then Tref (Sref - 1) < 'A' 4108 and then Tref (Sref + 5) < 'A' 4109 then 4110 return; 4111 end if; 4112 4113 -- Else store next character 4114 4115 Error_Msg_Strlen := Error_Msg_Strlen + 1; 4116 Error_Msg_String (Error_Msg_Strlen) := Tref (Sref); 4117 Sref := Sref + 1; 4118 4119 -- If we get more than 40 characters then the expression 4120 -- is too long to copy, or something has gone wrong. In 4121 -- either case, just skip the attempt at a suggested fix. 4122 4123 if Error_Msg_Strlen > 40 then 4124 return; 4125 end if; 4126 end loop; 4127 end; 4128 4129 -- Replacement subscript is now in string buffer 4130 4131 Error_Msg_FE -- CODEFIX 4132 ("\?w?suggested replacement: `&~`", Original_Node (X), Ent); 4133 end if; 4134 end Warn_On_Literal_Index; 4135 4136 -- Start of processing for Test_Suspicious_Index 4137 4138 begin 4139 -- Nothing to do if subscript does not come from source (we don't 4140 -- want to give garbage warnings on compiler expanded code, e.g. the 4141 -- loops generated for slice assignments. Such junk warnings would 4142 -- be placed on source constructs with no subscript in sight). 4143 4144 if not Comes_From_Source (Original_Node (X)) then 4145 return; 4146 end if; 4147 4148 -- Case where subscript is a constant integer 4149 4150 if Nkind (X) = N_Integer_Literal then 4151 4152 -- Case where subscript is lower than the lowest possible bound. 4153 -- This might be the case for example when programmers try to 4154 -- access a string at index 0, as they are used to in other 4155 -- programming languages like C. 4156 4157 if Intval (X) < Low_Bound then 4158 Warn_On_Index_Below_Lower_Bound; 4159 else 4160 Warn_On_Literal_Index; 4161 end if; 4162 4163 -- Case where subscript is of the form X'Length 4164 4165 elsif Length_Reference (X) then 4166 Warn1; 4167 Error_Msg_Node_2 := Ent; 4168 Error_Msg_FE 4169 ("\?w?suggest replacement of `&''Length` by `&''Last`", 4170 X, Ent); 4171 4172 -- Case where subscript is of the form X'Length - expression 4173 4174 elsif Nkind (X) = N_Op_Subtract 4175 and then Length_Reference (Left_Opnd (X)) 4176 then 4177 Warn1; 4178 Error_Msg_Node_2 := Ent; 4179 Error_Msg_FE 4180 ("\?w?suggest replacement of `&''Length` by `&''Last`", 4181 Left_Opnd (X), Ent); 4182 end if; 4183 end Test_Suspicious_Index; 4184 4185 -- Start of processing for Warn_On_Suspicious_Index 4186 4187 begin 4188 -- Only process if warnings activated 4189 4190 if Warn_On_Assumed_Low_Bound then 4191 4192 -- Test if array is simple entity name 4193 4194 if Is_Entity_Name (Name) then 4195 4196 -- Test if array is parameter of unconstrained string type 4197 4198 Ent := Entity (Name); 4199 Typ := Etype (Ent); 4200 4201 if Is_Formal (Ent) 4202 and then Is_Suspicious_Type (Typ) 4203 and then not Low_Bound_Tested (Ent) 4204 then 4205 Test_Suspicious_Index; 4206 end if; 4207 end if; 4208 end if; 4209 end Warn_On_Suspicious_Index; 4210 4211 ------------------------------- 4212 -- Warn_On_Suspicious_Update -- 4213 ------------------------------- 4214 4215 procedure Warn_On_Suspicious_Update (N : Node_Id) is 4216 Par : constant Node_Id := Parent (N); 4217 Arg : Node_Id; 4218 4219 begin 4220 -- Only process if warnings activated 4221 4222 if Warn_On_Suspicious_Contract then 4223 if Nkind_In (Par, N_Op_Eq, N_Op_Ne) then 4224 if N = Left_Opnd (Par) then 4225 Arg := Right_Opnd (Par); 4226 else 4227 Arg := Left_Opnd (Par); 4228 end if; 4229 4230 if Same_Object (Prefix (N), Arg) then 4231 if Nkind (Par) = N_Op_Eq then 4232 Error_Msg_N 4233 ("suspicious equality test with modified version of " 4234 & "same object?T?", Par); 4235 else 4236 Error_Msg_N 4237 ("suspicious inequality test with modified version of " 4238 & "same object?T?", Par); 4239 end if; 4240 end if; 4241 end if; 4242 end if; 4243 end Warn_On_Suspicious_Update; 4244 4245 -------------------------------------- 4246 -- Warn_On_Unassigned_Out_Parameter -- 4247 -------------------------------------- 4248 4249 procedure Warn_On_Unassigned_Out_Parameter 4250 (Return_Node : Node_Id; 4251 Scope_Id : Entity_Id) 4252 is 4253 Form : Entity_Id; 4254 Form2 : Entity_Id; 4255 4256 begin 4257 -- Ignore if procedure or return statement does not come from source 4258 4259 if not Comes_From_Source (Scope_Id) 4260 or else not Comes_From_Source (Return_Node) 4261 then 4262 return; 4263 end if; 4264 4265 -- Loop through formals 4266 4267 Form := First_Formal (Scope_Id); 4268 while Present (Form) loop 4269 4270 -- We are only interested in OUT parameters that come from source 4271 -- and are never set in the source, and furthermore only in scalars 4272 -- since non-scalars generate too many false positives. 4273 4274 if Ekind (Form) = E_Out_Parameter 4275 and then Never_Set_In_Source_Check_Spec (Form) 4276 and then Is_Scalar_Type (Etype (Form)) 4277 and then not Present (Unset_Reference (Form)) 4278 then 4279 -- Before we issue the warning, an add ad hoc defence against the 4280 -- most common case of false positives with this warning which is 4281 -- the case where there is a Boolean OUT parameter that has been 4282 -- set, and whose meaning is "ignore the values of the other 4283 -- parameters". We can't of course reliably tell this case at 4284 -- compile time, but the following test kills a lot of false 4285 -- positives, without generating a significant number of false 4286 -- negatives (missed real warnings). 4287 4288 Form2 := First_Formal (Scope_Id); 4289 while Present (Form2) loop 4290 if Ekind (Form2) = E_Out_Parameter 4291 and then Root_Type (Etype (Form2)) = Standard_Boolean 4292 and then not Never_Set_In_Source_Check_Spec (Form2) 4293 then 4294 return; 4295 end if; 4296 4297 Next_Formal (Form2); 4298 end loop; 4299 4300 -- Here all conditions are met, record possible unset reference 4301 4302 Set_Unset_Reference (Form, Return_Node); 4303 end if; 4304 4305 Next_Formal (Form); 4306 end loop; 4307 end Warn_On_Unassigned_Out_Parameter; 4308 4309 --------------------------------- 4310 -- Warn_On_Unreferenced_Entity -- 4311 --------------------------------- 4312 4313 procedure Warn_On_Unreferenced_Entity 4314 (Spec_E : Entity_Id; 4315 Body_E : Entity_Id := Empty) 4316 is 4317 E : Entity_Id := Spec_E; 4318 4319 begin 4320 if not Referenced_Check_Spec (E) 4321 and then not Has_Pragma_Unreferenced_Check_Spec (E) 4322 and then not Warnings_Off_Check_Spec (E) 4323 and then not Has_Junk_Name (Spec_E) 4324 and then not Is_Exported (Spec_E) 4325 then 4326 case Ekind (E) is 4327 when E_Variable => 4328 4329 -- Case of variable that is assigned but not read. We suppress 4330 -- the message if the variable is volatile, has an address 4331 -- clause, is aliased, or is a renaming, or is imported. 4332 4333 if Referenced_As_LHS_Check_Spec (E) 4334 and then No (Address_Clause (E)) 4335 and then not Is_Volatile (E) 4336 then 4337 if Warn_On_Modified_Unread 4338 and then not Is_Imported (E) 4339 and then not Is_Aliased (E) 4340 and then No (Renamed_Object (E)) 4341 then 4342 if not Has_Pragma_Unmodified_Check_Spec (E) then 4343 Error_Msg_N -- CODEFIX 4344 ("?m?variable & is assigned but never read!", E); 4345 end if; 4346 4347 Set_Last_Assignment (E, Empty); 4348 end if; 4349 4350 -- Normal case of neither assigned nor read (exclude variables 4351 -- referenced as out parameters, since we already generated 4352 -- appropriate warnings at the call point in this case). 4353 4354 elsif not Referenced_As_Out_Parameter (E) then 4355 4356 -- We suppress the message for types for which a valid 4357 -- pragma Unreferenced_Objects has been given, otherwise 4358 -- we go ahead and give the message. 4359 4360 if not Has_Pragma_Unreferenced_Objects (Etype (E)) then 4361 4362 -- Distinguish renamed case in message 4363 4364 if Present (Renamed_Object (E)) 4365 and then Comes_From_Source (Renamed_Object (E)) 4366 then 4367 Error_Msg_N -- CODEFIX 4368 ("?u?renamed variable & is not referenced!", E); 4369 else 4370 Error_Msg_N -- CODEFIX 4371 ("?u?variable & is not referenced!", E); 4372 end if; 4373 end if; 4374 end if; 4375 4376 when E_Constant => 4377 if not Has_Pragma_Unreferenced_Objects (Etype (E)) then 4378 if Present (Renamed_Object (E)) 4379 and then Comes_From_Source (Renamed_Object (E)) 4380 then 4381 Error_Msg_N -- CODEFIX 4382 ("?u?renamed constant & is not referenced!", E); 4383 else 4384 Error_Msg_N -- CODEFIX 4385 ("?u?constant & is not referenced!", E); 4386 end if; 4387 end if; 4388 4389 when E_In_Out_Parameter 4390 | E_In_Parameter 4391 => 4392 -- Do not emit message for formals of a renaming, because they 4393 -- are never referenced explicitly. 4394 4395 if Nkind (Original_Node (Unit_Declaration_Node (Scope (E)))) /= 4396 N_Subprogram_Renaming_Declaration 4397 then 4398 -- Suppress this message for an IN OUT parameter of a 4399 -- non-scalar type, since it is normal to have only an 4400 -- assignment in such a case. 4401 4402 if Ekind (E) = E_In_Parameter 4403 or else not Referenced_As_LHS_Check_Spec (E) 4404 or else Is_Scalar_Type (Etype (E)) 4405 then 4406 if Present (Body_E) then 4407 E := Body_E; 4408 end if; 4409 4410 declare 4411 B : constant Node_Id := Parent (Parent (Scope (E))); 4412 S : Entity_Id := Empty; 4413 begin 4414 if Nkind_In (B, 4415 N_Expression_Function, 4416 N_Subprogram_Body, 4417 N_Subprogram_Renaming_Declaration) 4418 then 4419 S := Corresponding_Spec (B); 4420 end if; 4421 4422 -- Do not warn for dispatching operations, because 4423 -- that causes too much noise. Also do not warn for 4424 -- trivial subprograms. 4425 4426 if (not Present (S) 4427 or else not Is_Dispatching_Operation (S)) 4428 and then not Is_Trivial_Subprogram (Scope (E)) 4429 then 4430 Error_Msg_NE -- CODEFIX 4431 ("?u?formal parameter & is not referenced!", 4432 E, Spec_E); 4433 end if; 4434 end; 4435 end if; 4436 end if; 4437 4438 when E_Out_Parameter => 4439 null; 4440 4441 when E_Discriminant => 4442 Error_Msg_N ("?u?discriminant & is not referenced!", E); 4443 4444 when E_Named_Integer 4445 | E_Named_Real 4446 => 4447 Error_Msg_N -- CODEFIX 4448 ("?u?named number & is not referenced!", E); 4449 4450 when Formal_Object_Kind => 4451 Error_Msg_N -- CODEFIX 4452 ("?u?formal object & is not referenced!", E); 4453 4454 when E_Enumeration_Literal => 4455 Error_Msg_N -- CODEFIX 4456 ("?u?literal & is not referenced!", E); 4457 4458 when E_Function => 4459 Error_Msg_N -- CODEFIX 4460 ("?u?function & is not referenced!", E); 4461 4462 when E_Procedure => 4463 Error_Msg_N -- CODEFIX 4464 ("?u?procedure & is not referenced!", E); 4465 4466 when E_Package => 4467 Error_Msg_N -- CODEFIX 4468 ("?u?package & is not referenced!", E); 4469 4470 when E_Exception => 4471 Error_Msg_N -- CODEFIX 4472 ("?u?exception & is not referenced!", E); 4473 4474 when E_Label => 4475 Error_Msg_N -- CODEFIX 4476 ("?u?label & is not referenced!", E); 4477 4478 when E_Generic_Procedure => 4479 Error_Msg_N -- CODEFIX 4480 ("?u?generic procedure & is never instantiated!", E); 4481 4482 when E_Generic_Function => 4483 Error_Msg_N -- CODEFIX 4484 ("?u?generic function & is never instantiated!", E); 4485 4486 when Type_Kind => 4487 Error_Msg_N -- CODEFIX 4488 ("?u?type & is not referenced!", E); 4489 4490 when others => 4491 Error_Msg_N -- CODEFIX 4492 ("?u?& is not referenced!", E); 4493 end case; 4494 4495 -- Kill warnings on the entity on which the message has been posted 4496 -- (nothing is posted on out parameters because back end might be 4497 -- able to uncover an uninitialized path, and warn accordingly). 4498 4499 if Ekind (E) /= E_Out_Parameter then 4500 Set_Warnings_Off (E); 4501 end if; 4502 end if; 4503 end Warn_On_Unreferenced_Entity; 4504 4505 -------------------------------- 4506 -- Warn_On_Useless_Assignment -- 4507 -------------------------------- 4508 4509 procedure Warn_On_Useless_Assignment 4510 (Ent : Entity_Id; 4511 N : Node_Id := Empty) 4512 is 4513 P : Node_Id; 4514 X : Node_Id; 4515 4516 function Check_Ref (N : Node_Id) return Traverse_Result; 4517 -- Used to instantiate Traverse_Func. Returns Abandon if a reference to 4518 -- the entity in question is found. 4519 4520 function Test_No_Refs is new Traverse_Func (Check_Ref); 4521 4522 --------------- 4523 -- Check_Ref -- 4524 --------------- 4525 4526 function Check_Ref (N : Node_Id) return Traverse_Result is 4527 begin 4528 -- Check reference to our identifier. We use name equality here 4529 -- because the exception handlers have not yet been analyzed. This 4530 -- is not quite right, but it really does not matter that we fail 4531 -- to output the warning in some obscure cases of name clashes. 4532 4533 if Nkind (N) = N_Identifier and then Chars (N) = Chars (Ent) then 4534 return Abandon; 4535 else 4536 return OK; 4537 end if; 4538 end Check_Ref; 4539 4540 -- Start of processing for Warn_On_Useless_Assignment 4541 4542 begin 4543 -- Check if this is a case we want to warn on, a scalar or access 4544 -- variable with the last assignment field set, with warnings enabled, 4545 -- and which is not imported or exported. We also check that it is OK 4546 -- to capture the value. We are not going to capture any value, but 4547 -- the warning message depends on the same kind of conditions. 4548 4549 -- If the assignment appears as an out-parameter in a call within an 4550 -- expression function it may be detected twice: once when expression 4551 -- itself is analyzed, and once when the constructed body is analyzed. 4552 -- We don't want to emit a spurious warning in this case. 4553 4554 if Is_Assignable (Ent) 4555 and then not Is_Return_Object (Ent) 4556 and then Present (Last_Assignment (Ent)) 4557 and then Last_Assignment (Ent) /= N 4558 and then not Is_Imported (Ent) 4559 and then not Is_Exported (Ent) 4560 and then Safe_To_Capture_Value (N, Ent) 4561 and then not Has_Pragma_Unreferenced_Check_Spec (Ent) 4562 and then not Has_Junk_Name (Ent) 4563 then 4564 -- Before we issue the message, check covering exception handlers. 4565 -- Search up tree for enclosing statement sequences and handlers. 4566 4567 P := Parent (Last_Assignment (Ent)); 4568 while Present (P) loop 4569 4570 -- Something is really wrong if we don't find a handled statement 4571 -- sequence, so just suppress the warning. 4572 4573 if No (P) then 4574 Set_Last_Assignment (Ent, Empty); 4575 return; 4576 4577 -- When we hit a package/subprogram body, issue warning and exit 4578 4579 elsif Nkind_In (P, N_Entry_Body, 4580 N_Package_Body, 4581 N_Subprogram_Body, 4582 N_Task_Body) 4583 then 4584 -- Case of assigned value never referenced 4585 4586 if No (N) then 4587 declare 4588 LA : constant Node_Id := Last_Assignment (Ent); 4589 4590 begin 4591 -- Don't give this for OUT and IN OUT formals, since 4592 -- clearly caller may reference the assigned value. Also 4593 -- never give such warnings for internal variables. In 4594 -- either case, word the warning in a conditional way, 4595 -- because in the case of a component of a controlled 4596 -- type, the assigned value might be referenced in the 4597 -- Finalize operation, so we can't make a definitive 4598 -- statement that it's never referenced. 4599 4600 if Ekind (Ent) = E_Variable 4601 and then not Is_Internal_Name (Chars (Ent)) 4602 then 4603 -- Give appropriate message, distinguishing between 4604 -- assignment statements and out parameters. 4605 4606 if Nkind_In (Parent (LA), N_Parameter_Association, 4607 N_Procedure_Call_Statement) 4608 then 4609 Error_Msg_NE 4610 ("?m?& modified by call, but value might not be " 4611 & "referenced", LA, Ent); 4612 4613 else 4614 Error_Msg_NE -- CODEFIX 4615 ("?m?possibly useless assignment to&, value " 4616 & "might not be referenced!", LA, Ent); 4617 end if; 4618 end if; 4619 end; 4620 4621 -- Case of assigned value overwritten 4622 4623 else 4624 declare 4625 LA : constant Node_Id := Last_Assignment (Ent); 4626 4627 begin 4628 Error_Msg_Sloc := Sloc (N); 4629 4630 -- Give appropriate message, distinguishing between 4631 -- assignment statements and out parameters. 4632 4633 if Nkind_In (Parent (LA), N_Procedure_Call_Statement, 4634 N_Parameter_Association) 4635 then 4636 Error_Msg_NE 4637 ("?m?& modified by call, but value overwritten #!", 4638 LA, Ent); 4639 else 4640 Error_Msg_NE -- CODEFIX 4641 ("?m?useless assignment to&, value overwritten #!", 4642 LA, Ent); 4643 end if; 4644 end; 4645 end if; 4646 4647 -- Clear last assignment indication and we are done 4648 4649 Set_Last_Assignment (Ent, Empty); 4650 return; 4651 4652 -- Enclosing handled sequence of statements 4653 4654 elsif Nkind (P) = N_Handled_Sequence_Of_Statements then 4655 4656 -- Check exception handlers present 4657 4658 if Present (Exception_Handlers (P)) then 4659 4660 -- If we are not at the top level, we regard an inner 4661 -- exception handler as a decisive indicator that we should 4662 -- not generate the warning, since the variable in question 4663 -- may be accessed after an exception in the outer block. 4664 4665 if not Nkind_In (Parent (P), N_Entry_Body, 4666 N_Package_Body, 4667 N_Subprogram_Body, 4668 N_Task_Body) 4669 then 4670 Set_Last_Assignment (Ent, Empty); 4671 return; 4672 4673 -- Otherwise we are at the outer level. An exception 4674 -- handler is significant only if it references the 4675 -- variable in question, or if the entity in question 4676 -- is an OUT or IN OUT parameter, in which case 4677 -- the caller can reference it after the exception 4678 -- handler completes. 4679 4680 else 4681 if Is_Formal (Ent) then 4682 Set_Last_Assignment (Ent, Empty); 4683 return; 4684 4685 else 4686 X := First (Exception_Handlers (P)); 4687 while Present (X) loop 4688 if Test_No_Refs (X) = Abandon then 4689 Set_Last_Assignment (Ent, Empty); 4690 return; 4691 end if; 4692 4693 X := Next (X); 4694 end loop; 4695 end if; 4696 end if; 4697 end if; 4698 end if; 4699 4700 P := Parent (P); 4701 end loop; 4702 end if; 4703 end Warn_On_Useless_Assignment; 4704 4705 --------------------------------- 4706 -- Warn_On_Useless_Assignments -- 4707 --------------------------------- 4708 4709 procedure Warn_On_Useless_Assignments (E : Entity_Id) is 4710 Ent : Entity_Id; 4711 4712 begin 4713 Process_Deferred_References; 4714 4715 if Warn_On_Modified_Unread 4716 and then In_Extended_Main_Source_Unit (E) 4717 then 4718 Ent := First_Entity (E); 4719 while Present (Ent) loop 4720 Warn_On_Useless_Assignment (Ent); 4721 Next_Entity (Ent); 4722 end loop; 4723 end if; 4724 end Warn_On_Useless_Assignments; 4725 4726 ----------------------------- 4727 -- Warnings_Off_Check_Spec -- 4728 ----------------------------- 4729 4730 function Warnings_Off_Check_Spec (E : Entity_Id) return Boolean is 4731 begin 4732 if Is_Formal (E) and then Present (Spec_Entity (E)) then 4733 4734 -- Note: use of OR here instead of OR ELSE is deliberate, we want 4735 -- to mess with flags on both entities. 4736 4737 return Has_Warnings_Off (E) 4738 or 4739 Has_Warnings_Off (Spec_Entity (E)); 4740 4741 else 4742 return Has_Warnings_Off (E); 4743 end if; 4744 end Warnings_Off_Check_Spec; 4745 4746end Sem_Warn; 4747