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