1 /* Language-level data type conversion for GNU C++. 2 Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 3 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 4 2011 Free Software Foundation, Inc. 5 Hacked by Michael Tiemann (tiemann@cygnus.com) 6 7 This file is part of GCC. 8 9 GCC is free software; you can redistribute it and/or modify 10 it under the terms of the GNU General Public License as published by 11 the Free Software Foundation; either version 3, or (at your option) 12 any later version. 13 14 GCC is distributed in the hope that it will be useful, 15 but WITHOUT ANY WARRANTY; without even the implied warranty of 16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17 GNU General Public License for more details. 18 19 You should have received a copy of the GNU General Public License 20 along with GCC; see the file COPYING3. If not see 21 <http://www.gnu.org/licenses/>. */ 22 23 24 /* This file contains the functions for converting C++ expressions 25 to different data types. The only entry point is `convert'. 26 Every language front end must have a `convert' function 27 but what kind of conversions it does will depend on the language. */ 28 29 #include "config.h" 30 #include "system.h" 31 #include "coretypes.h" 32 #include "tm.h" 33 #include "tree.h" 34 #include "flags.h" 35 #include "cp-tree.h" 36 #include "intl.h" 37 #include "convert.h" 38 #include "decl.h" 39 #include "target.h" 40 41 static tree cp_convert_to_pointer (tree, tree); 42 static tree convert_to_pointer_force (tree, tree); 43 static tree build_type_conversion (tree, tree); 44 static tree build_up_reference (tree, tree, int, tree); 45 static void warn_ref_binding (tree, tree, tree); 46 47 /* Change of width--truncation and extension of integers or reals-- 48 is represented with NOP_EXPR. Proper functioning of many things 49 assumes that no other conversions can be NOP_EXPRs. 50 51 Conversion between integer and pointer is represented with CONVERT_EXPR. 52 Converting integer to real uses FLOAT_EXPR 53 and real to integer uses FIX_TRUNC_EXPR. 54 55 Here is a list of all the functions that assume that widening and 56 narrowing is always done with a NOP_EXPR: 57 In convert.c, convert_to_integer. 58 In c-typeck.c, build_binary_op_nodefault (boolean ops), 59 and c_common_truthvalue_conversion. 60 In expr.c: expand_expr, for operands of a MULT_EXPR. 61 In fold-const.c: fold. 62 In tree.c: get_narrower and get_unwidened. 63 64 C++: in multiple-inheritance, converting between pointers may involve 65 adjusting them by a delta stored within the class definition. */ 66 67 /* Subroutines of `convert'. */ 68 69 /* if converting pointer to pointer 70 if dealing with classes, check for derived->base or vice versa 71 else if dealing with method pointers, delegate 72 else convert blindly 73 else if converting class, pass off to build_type_conversion 74 else try C-style pointer conversion. */ 75 76 static tree 77 cp_convert_to_pointer (tree type, tree expr) 78 { 79 tree intype = TREE_TYPE (expr); 80 enum tree_code form; 81 tree rval; 82 if (intype == error_mark_node) 83 return error_mark_node; 84 85 if (MAYBE_CLASS_TYPE_P (intype)) 86 { 87 intype = complete_type (intype); 88 if (!COMPLETE_TYPE_P (intype)) 89 { 90 error ("can%'t convert from incomplete type %qT to %qT", 91 intype, type); 92 return error_mark_node; 93 } 94 95 rval = build_type_conversion (type, expr); 96 if (rval) 97 { 98 if (rval == error_mark_node) 99 error ("conversion of %qE from %qT to %qT is ambiguous", 100 expr, intype, type); 101 return rval; 102 } 103 } 104 105 /* Handle anachronistic conversions from (::*)() to cv void* or (*)(). */ 106 if (TREE_CODE (type) == POINTER_TYPE 107 && (TREE_CODE (TREE_TYPE (type)) == FUNCTION_TYPE 108 || VOID_TYPE_P (TREE_TYPE (type)))) 109 { 110 if (TYPE_PTRMEMFUNC_P (intype) 111 || TREE_CODE (intype) == METHOD_TYPE) 112 return convert_member_func_to_ptr (type, expr); 113 if (TREE_CODE (TREE_TYPE (expr)) == POINTER_TYPE) 114 return build_nop (type, expr); 115 intype = TREE_TYPE (expr); 116 } 117 118 if (expr == error_mark_node) 119 return error_mark_node; 120 121 form = TREE_CODE (intype); 122 123 if (POINTER_TYPE_P (intype)) 124 { 125 intype = TYPE_MAIN_VARIANT (intype); 126 127 if (TYPE_MAIN_VARIANT (type) != intype 128 && TREE_CODE (type) == POINTER_TYPE 129 && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE 130 && MAYBE_CLASS_TYPE_P (TREE_TYPE (type)) 131 && MAYBE_CLASS_TYPE_P (TREE_TYPE (intype)) 132 && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE) 133 { 134 enum tree_code code = PLUS_EXPR; 135 tree binfo; 136 tree intype_class; 137 tree type_class; 138 bool same_p; 139 140 intype_class = TREE_TYPE (intype); 141 type_class = TREE_TYPE (type); 142 143 same_p = same_type_p (TYPE_MAIN_VARIANT (intype_class), 144 TYPE_MAIN_VARIANT (type_class)); 145 binfo = NULL_TREE; 146 /* Try derived to base conversion. */ 147 if (!same_p) 148 binfo = lookup_base (intype_class, type_class, ba_check, NULL); 149 if (!same_p && !binfo) 150 { 151 /* Try base to derived conversion. */ 152 binfo = lookup_base (type_class, intype_class, ba_check, NULL); 153 code = MINUS_EXPR; 154 } 155 if (binfo == error_mark_node) 156 return error_mark_node; 157 if (binfo || same_p) 158 { 159 if (binfo) 160 expr = build_base_path (code, expr, binfo, 0, 161 tf_warning_or_error); 162 /* Add any qualifier conversions. */ 163 return build_nop (type, expr); 164 } 165 } 166 167 if (TYPE_PTRMEMFUNC_P (type)) 168 { 169 error ("cannot convert %qE from type %qT to type %qT", 170 expr, intype, type); 171 return error_mark_node; 172 } 173 174 return build_nop (type, expr); 175 } 176 else if ((TYPE_PTRMEM_P (type) && TYPE_PTRMEM_P (intype)) 177 || (TYPE_PTRMEMFUNC_P (type) && TYPE_PTRMEMFUNC_P (intype))) 178 return convert_ptrmem (type, expr, /*allow_inverse_p=*/false, 179 /*c_cast_p=*/false, tf_warning_or_error); 180 else if (TYPE_PTRMEMFUNC_P (intype)) 181 { 182 if (!warn_pmf2ptr) 183 { 184 if (TREE_CODE (expr) == PTRMEM_CST) 185 return cp_convert_to_pointer (type, 186 PTRMEM_CST_MEMBER (expr)); 187 else if (TREE_CODE (expr) == OFFSET_REF) 188 { 189 tree object = TREE_OPERAND (expr, 0); 190 return get_member_function_from_ptrfunc (&object, 191 TREE_OPERAND (expr, 1)); 192 } 193 } 194 error ("cannot convert %qE from type %qT to type %qT", 195 expr, intype, type); 196 return error_mark_node; 197 } 198 199 if (null_ptr_cst_p (expr)) 200 { 201 tree val; 202 203 if (c_inhibit_evaluation_warnings == 0 204 && !NULLPTR_TYPE_P (TREE_TYPE (expr))) 205 warning (OPT_Wzero_as_null_pointer_constant, 206 "zero as null pointer constant"); 207 208 if (TYPE_PTRMEMFUNC_P (type)) 209 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), expr, 0, 210 /*c_cast_p=*/false, tf_warning_or_error); 211 212 /* A NULL pointer-to-data-member is represented by -1, not by 213 zero. */ 214 val = (TYPE_PTRMEM_P (type) 215 ? build_int_cst_type (type, -1) 216 : build_int_cst (type, 0)); 217 218 return (TREE_SIDE_EFFECTS (expr) 219 ? build2 (COMPOUND_EXPR, type, expr, val) : val); 220 } 221 else if (TYPE_PTR_TO_MEMBER_P (type) && INTEGRAL_CODE_P (form)) 222 { 223 error ("invalid conversion from %qT to %qT", intype, type); 224 return error_mark_node; 225 } 226 227 if (INTEGRAL_CODE_P (form)) 228 { 229 if (TYPE_PRECISION (intype) == POINTER_SIZE) 230 return build1 (CONVERT_EXPR, type, expr); 231 expr = cp_convert (c_common_type_for_size (POINTER_SIZE, 0), expr); 232 /* Modes may be different but sizes should be the same. There 233 is supposed to be some integral type that is the same width 234 as a pointer. */ 235 gcc_assert (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (expr))) 236 == GET_MODE_SIZE (TYPE_MODE (type))); 237 238 return convert_to_pointer (type, expr); 239 } 240 241 if (type_unknown_p (expr)) 242 return instantiate_type (type, expr, tf_warning_or_error); 243 244 error ("cannot convert %qE from type %qT to type %qT", 245 expr, intype, type); 246 return error_mark_node; 247 } 248 249 /* Like convert, except permit conversions to take place which 250 are not normally allowed due to access restrictions 251 (such as conversion from sub-type to private super-type). */ 252 253 static tree 254 convert_to_pointer_force (tree type, tree expr) 255 { 256 tree intype = TREE_TYPE (expr); 257 enum tree_code form = TREE_CODE (intype); 258 259 if (form == POINTER_TYPE) 260 { 261 intype = TYPE_MAIN_VARIANT (intype); 262 263 if (TYPE_MAIN_VARIANT (type) != intype 264 && TREE_CODE (TREE_TYPE (type)) == RECORD_TYPE 265 && MAYBE_CLASS_TYPE_P (TREE_TYPE (type)) 266 && MAYBE_CLASS_TYPE_P (TREE_TYPE (intype)) 267 && TREE_CODE (TREE_TYPE (intype)) == RECORD_TYPE) 268 { 269 enum tree_code code = PLUS_EXPR; 270 tree binfo; 271 272 binfo = lookup_base (TREE_TYPE (intype), TREE_TYPE (type), 273 ba_unique, NULL); 274 if (!binfo) 275 { 276 binfo = lookup_base (TREE_TYPE (type), TREE_TYPE (intype), 277 ba_unique, NULL); 278 code = MINUS_EXPR; 279 } 280 if (binfo == error_mark_node) 281 return error_mark_node; 282 if (binfo) 283 { 284 expr = build_base_path (code, expr, binfo, 0, 285 tf_warning_or_error); 286 if (expr == error_mark_node) 287 return error_mark_node; 288 /* Add any qualifier conversions. */ 289 if (!same_type_p (TREE_TYPE (TREE_TYPE (expr)), 290 TREE_TYPE (type))) 291 expr = build_nop (type, expr); 292 return expr; 293 } 294 } 295 } 296 297 return cp_convert_to_pointer (type, expr); 298 } 299 300 /* We are passing something to a function which requires a reference. 301 The type we are interested in is in TYPE. The initial 302 value we have to begin with is in ARG. 303 304 FLAGS controls how we manage access checking. 305 DIRECT_BIND in FLAGS controls how any temporaries are generated. 306 If DIRECT_BIND is set, DECL is the reference we're binding to. */ 307 308 static tree 309 build_up_reference (tree type, tree arg, int flags, tree decl) 310 { 311 tree rval; 312 tree argtype = TREE_TYPE (arg); 313 tree target_type = TREE_TYPE (type); 314 315 gcc_assert (TREE_CODE (type) == REFERENCE_TYPE); 316 317 if ((flags & DIRECT_BIND) && ! real_lvalue_p (arg)) 318 { 319 /* Create a new temporary variable. We can't just use a TARGET_EXPR 320 here because it needs to live as long as DECL. */ 321 tree targ = arg; 322 323 arg = make_temporary_var_for_ref_to_temp (decl, target_type); 324 325 /* Process the initializer for the declaration. */ 326 DECL_INITIAL (arg) = targ; 327 cp_finish_decl (arg, targ, /*init_const_expr_p=*/false, NULL_TREE, 328 LOOKUP_ONLYCONVERTING|DIRECT_BIND); 329 } 330 else if (!(flags & DIRECT_BIND) && ! lvalue_p (arg)) 331 return get_target_expr (arg); 332 333 /* If we had a way to wrap this up, and say, if we ever needed its 334 address, transform all occurrences of the register, into a memory 335 reference we could win better. */ 336 rval = cp_build_addr_expr (arg, tf_warning_or_error); 337 if (rval == error_mark_node) 338 return error_mark_node; 339 340 if ((flags & LOOKUP_PROTECT) 341 && TYPE_MAIN_VARIANT (argtype) != TYPE_MAIN_VARIANT (target_type) 342 && MAYBE_CLASS_TYPE_P (argtype) 343 && MAYBE_CLASS_TYPE_P (target_type)) 344 { 345 /* We go through lookup_base for the access control. */ 346 tree binfo = lookup_base (argtype, target_type, ba_check, NULL); 347 if (binfo == error_mark_node) 348 return error_mark_node; 349 if (binfo == NULL_TREE) 350 return error_not_base_type (target_type, argtype); 351 rval = build_base_path (PLUS_EXPR, rval, binfo, 1, 352 tf_warning_or_error); 353 } 354 else 355 rval 356 = convert_to_pointer_force (build_pointer_type (target_type), rval); 357 return build_nop (type, rval); 358 } 359 360 /* Subroutine of convert_to_reference. REFTYPE is the target reference type. 361 INTYPE is the original rvalue type and DECL is an optional _DECL node 362 for diagnostics. 363 364 [dcl.init.ref] says that if an rvalue is used to 365 initialize a reference, then the reference must be to a 366 non-volatile const type. */ 367 368 static void 369 warn_ref_binding (tree reftype, tree intype, tree decl) 370 { 371 tree ttl = TREE_TYPE (reftype); 372 373 if (!CP_TYPE_CONST_NON_VOLATILE_P (ttl)) 374 { 375 const char *msg; 376 377 if (CP_TYPE_VOLATILE_P (ttl) && decl) 378 msg = G_("initialization of volatile reference type %q#T from " 379 "rvalue of type %qT"); 380 else if (CP_TYPE_VOLATILE_P (ttl)) 381 msg = G_("conversion to volatile reference type %q#T " 382 "from rvalue of type %qT"); 383 else if (decl) 384 msg = G_("initialization of non-const reference type %q#T from " 385 "rvalue of type %qT"); 386 else 387 msg = G_("conversion to non-const reference type %q#T from " 388 "rvalue of type %qT"); 389 390 permerror (input_location, msg, reftype, intype); 391 } 392 } 393 394 /* For C++: Only need to do one-level references, but cannot 395 get tripped up on signed/unsigned differences. 396 397 DECL is either NULL_TREE or the _DECL node for a reference that is being 398 initialized. It can be error_mark_node if we don't know the _DECL but 399 we know it's an initialization. */ 400 401 tree 402 convert_to_reference (tree reftype, tree expr, int convtype, 403 int flags, tree decl) 404 { 405 tree type = TYPE_MAIN_VARIANT (TREE_TYPE (reftype)); 406 tree intype; 407 tree rval = NULL_TREE; 408 tree rval_as_conversion = NULL_TREE; 409 bool can_convert_intype_to_type; 410 411 if (TREE_CODE (type) == FUNCTION_TYPE 412 && TREE_TYPE (expr) == unknown_type_node) 413 expr = instantiate_type (type, expr, 414 (flags & LOOKUP_COMPLAIN) 415 ? tf_warning_or_error : tf_none); 416 417 if (expr == error_mark_node) 418 return error_mark_node; 419 420 intype = TREE_TYPE (expr); 421 422 gcc_assert (TREE_CODE (intype) != REFERENCE_TYPE); 423 gcc_assert (TREE_CODE (reftype) == REFERENCE_TYPE); 424 425 intype = TYPE_MAIN_VARIANT (intype); 426 427 can_convert_intype_to_type = can_convert (type, intype); 428 if (!can_convert_intype_to_type 429 && (convtype & CONV_IMPLICIT) && MAYBE_CLASS_TYPE_P (intype) 430 && ! (flags & LOOKUP_NO_CONVERSION)) 431 { 432 /* Look for a user-defined conversion to lvalue that we can use. */ 433 434 rval_as_conversion 435 = build_type_conversion (reftype, expr); 436 437 if (rval_as_conversion && rval_as_conversion != error_mark_node 438 && real_lvalue_p (rval_as_conversion)) 439 { 440 expr = rval_as_conversion; 441 rval_as_conversion = NULL_TREE; 442 intype = type; 443 can_convert_intype_to_type = 1; 444 } 445 } 446 447 if (((convtype & CONV_STATIC) && can_convert (intype, type)) 448 || ((convtype & CONV_IMPLICIT) && can_convert_intype_to_type)) 449 { 450 if (flags & LOOKUP_COMPLAIN) 451 { 452 tree ttl = TREE_TYPE (reftype); 453 tree ttr = lvalue_type (expr); 454 455 if (! real_lvalue_p (expr)) 456 warn_ref_binding (reftype, intype, decl); 457 458 if (! (convtype & CONV_CONST) 459 && !at_least_as_qualified_p (ttl, ttr)) 460 permerror (input_location, "conversion from %qT to %qT discards qualifiers", 461 ttr, reftype); 462 } 463 464 return build_up_reference (reftype, expr, flags, decl); 465 } 466 else if ((convtype & CONV_REINTERPRET) && lvalue_p (expr)) 467 { 468 /* When casting an lvalue to a reference type, just convert into 469 a pointer to the new type and deference it. This is allowed 470 by San Diego WP section 5.2.9 paragraph 12, though perhaps it 471 should be done directly (jason). (int &)ri ---> *(int*)&ri */ 472 473 /* B* bp; A& ar = (A&)bp; is valid, but it's probably not what they 474 meant. */ 475 if (TREE_CODE (intype) == POINTER_TYPE 476 && (comptypes (TREE_TYPE (intype), type, 477 COMPARE_BASE | COMPARE_DERIVED))) 478 warning (0, "casting %qT to %qT does not dereference pointer", 479 intype, reftype); 480 481 rval = cp_build_addr_expr (expr, tf_warning_or_error); 482 if (rval != error_mark_node) 483 rval = convert_force (build_pointer_type (TREE_TYPE (reftype)), 484 rval, 0); 485 if (rval != error_mark_node) 486 rval = build1 (NOP_EXPR, reftype, rval); 487 } 488 else 489 { 490 rval = convert_for_initialization (NULL_TREE, type, expr, flags, 491 ICR_CONVERTING, 0, 0, 492 tf_warning_or_error); 493 if (rval == NULL_TREE || rval == error_mark_node) 494 return rval; 495 warn_ref_binding (reftype, intype, decl); 496 rval = build_up_reference (reftype, rval, flags, decl); 497 } 498 499 if (rval) 500 { 501 /* If we found a way to convert earlier, then use it. */ 502 return rval; 503 } 504 505 if (flags & LOOKUP_COMPLAIN) 506 error ("cannot convert type %qT to type %qT", intype, reftype); 507 508 return error_mark_node; 509 } 510 511 /* We are using a reference VAL for its value. Bash that reference all the 512 way down to its lowest form. */ 513 514 tree 515 convert_from_reference (tree val) 516 { 517 if (TREE_TYPE (val) 518 && TREE_CODE (TREE_TYPE (val)) == REFERENCE_TYPE) 519 { 520 tree t = TREE_TYPE (TREE_TYPE (val)); 521 tree ref = build1 (INDIRECT_REF, t, val); 522 523 mark_exp_read (val); 524 /* We *must* set TREE_READONLY when dereferencing a pointer to const, 525 so that we get the proper error message if the result is used 526 to assign to. Also, &* is supposed to be a no-op. */ 527 TREE_READONLY (ref) = CP_TYPE_CONST_P (t); 528 TREE_THIS_VOLATILE (ref) = CP_TYPE_VOLATILE_P (t); 529 TREE_SIDE_EFFECTS (ref) 530 = (TREE_THIS_VOLATILE (ref) || TREE_SIDE_EFFECTS (val)); 531 val = ref; 532 } 533 534 return val; 535 } 536 537 /* Really perform an lvalue-to-rvalue conversion, including copying an 538 argument of class type into a temporary. */ 539 540 tree 541 force_rvalue (tree expr, tsubst_flags_t complain) 542 { 543 tree type = TREE_TYPE (expr); 544 if (MAYBE_CLASS_TYPE_P (type) && TREE_CODE (expr) != TARGET_EXPR) 545 { 546 VEC(tree,gc) *args = make_tree_vector_single (expr); 547 expr = build_special_member_call (NULL_TREE, complete_ctor_identifier, 548 &args, type, LOOKUP_NORMAL, complain); 549 release_tree_vector (args); 550 expr = build_cplus_new (type, expr, complain); 551 } 552 else 553 expr = decay_conversion (expr); 554 555 return expr; 556 } 557 558 559 /* If EXPR and ORIG are INTEGER_CSTs, return a version of EXPR that has 560 TREE_OVERFLOW set only if it is set in ORIG. Otherwise, return EXPR 561 unchanged. */ 562 563 static tree 564 ignore_overflows (tree expr, tree orig) 565 { 566 if (TREE_CODE (expr) == INTEGER_CST 567 && TREE_CODE (orig) == INTEGER_CST 568 && TREE_OVERFLOW (expr) != TREE_OVERFLOW (orig)) 569 { 570 gcc_assert (!TREE_OVERFLOW (orig)); 571 /* Ensure constant sharing. */ 572 expr = build_int_cst_wide (TREE_TYPE (expr), 573 TREE_INT_CST_LOW (expr), 574 TREE_INT_CST_HIGH (expr)); 575 } 576 return expr; 577 } 578 579 /* Fold away simple conversions, but make sure TREE_OVERFLOW is set 580 properly. */ 581 582 tree 583 cp_fold_convert (tree type, tree expr) 584 { 585 tree conv = fold_convert (type, expr); 586 conv = ignore_overflows (conv, expr); 587 return conv; 588 } 589 590 /* C++ conversions, preference to static cast conversions. */ 591 592 tree 593 cp_convert (tree type, tree expr) 594 { 595 return ocp_convert (type, expr, CONV_OLD_CONVERT, LOOKUP_NORMAL); 596 } 597 598 /* C++ equivalent of convert_and_check but using cp_convert as the 599 conversion function. 600 601 Convert EXPR to TYPE, warning about conversion problems with constants. 602 Invoke this function on every expression that is converted implicitly, 603 i.e. because of language rules and not because of an explicit cast. */ 604 605 tree 606 cp_convert_and_check (tree type, tree expr) 607 { 608 tree result; 609 610 if (TREE_TYPE (expr) == type) 611 return expr; 612 613 result = cp_convert (type, expr); 614 615 if (c_inhibit_evaluation_warnings == 0 616 && !TREE_OVERFLOW_P (expr) 617 && result != error_mark_node) 618 warnings_for_convert_and_check (type, expr, result); 619 620 return result; 621 } 622 623 /* Conversion... 624 625 FLAGS indicates how we should behave. */ 626 627 tree 628 ocp_convert (tree type, tree expr, int convtype, int flags) 629 { 630 tree e = expr; 631 enum tree_code code = TREE_CODE (type); 632 const char *invalid_conv_diag; 633 tree e1; 634 635 if (error_operand_p (e) || type == error_mark_node) 636 return error_mark_node; 637 638 complete_type (type); 639 complete_type (TREE_TYPE (expr)); 640 641 if ((invalid_conv_diag 642 = targetm.invalid_conversion (TREE_TYPE (expr), type))) 643 { 644 error (invalid_conv_diag); 645 return error_mark_node; 646 } 647 648 /* FIXME remove when moving to c_fully_fold model. */ 649 /* FIXME do we still need this test? */ 650 if (!CLASS_TYPE_P (type)) 651 e = integral_constant_value (e); 652 if (error_operand_p (e)) 653 return error_mark_node; 654 655 if (MAYBE_CLASS_TYPE_P (type) && (convtype & CONV_FORCE_TEMP)) 656 /* We need a new temporary; don't take this shortcut. */; 657 else if (same_type_ignoring_top_level_qualifiers_p (type, TREE_TYPE (e))) 658 { 659 if (same_type_p (type, TREE_TYPE (e))) 660 /* The call to fold will not always remove the NOP_EXPR as 661 might be expected, since if one of the types is a typedef; 662 the comparison in fold is just equality of pointers, not a 663 call to comptypes. We don't call fold in this case because 664 that can result in infinite recursion; fold will call 665 convert, which will call ocp_convert, etc. */ 666 return e; 667 /* For complex data types, we need to perform componentwise 668 conversion. */ 669 else if (TREE_CODE (type) == COMPLEX_TYPE) 670 return fold_if_not_in_template (convert_to_complex (type, e)); 671 else if (TREE_CODE (e) == TARGET_EXPR) 672 { 673 /* Don't build a NOP_EXPR of class type. Instead, change the 674 type of the temporary. */ 675 TREE_TYPE (e) = TREE_TYPE (TARGET_EXPR_SLOT (e)) = type; 676 return e; 677 } 678 else 679 { 680 /* We shouldn't be treating objects of ADDRESSABLE type as 681 rvalues. */ 682 gcc_assert (!TREE_ADDRESSABLE (type)); 683 return fold_if_not_in_template (build_nop (type, e)); 684 } 685 } 686 687 e1 = targetm.convert_to_type (type, e); 688 if (e1) 689 return e1; 690 691 if (code == VOID_TYPE && (convtype & CONV_STATIC)) 692 { 693 e = convert_to_void (e, ICV_CAST, tf_warning_or_error); 694 return e; 695 } 696 697 if (INTEGRAL_CODE_P (code)) 698 { 699 tree intype = TREE_TYPE (e); 700 tree converted; 701 702 if (TREE_CODE (type) == ENUMERAL_TYPE) 703 { 704 /* enum = enum, enum = int, enum = float, (enum)pointer are all 705 errors. */ 706 if (((INTEGRAL_OR_ENUMERATION_TYPE_P (intype) 707 || TREE_CODE (intype) == REAL_TYPE) 708 && ! (convtype & CONV_STATIC)) 709 || TREE_CODE (intype) == POINTER_TYPE) 710 { 711 if (flags & LOOKUP_COMPLAIN) 712 permerror (input_location, "conversion from %q#T to %q#T", intype, type); 713 714 if (!flag_permissive) 715 return error_mark_node; 716 } 717 718 /* [expr.static.cast] 719 720 8. A value of integral or enumeration type can be explicitly 721 converted to an enumeration type. The value is unchanged if 722 the original value is within the range of the enumeration 723 values. Otherwise, the resulting enumeration value is 724 unspecified. */ 725 if (TREE_CODE (expr) == INTEGER_CST 726 && !int_fits_type_p (expr, ENUM_UNDERLYING_TYPE (type))) 727 warning (OPT_Wconversion, 728 "the result of the conversion is unspecified because " 729 "%qE is outside the range of type %qT", 730 expr, type); 731 } 732 if (MAYBE_CLASS_TYPE_P (intype)) 733 { 734 tree rval; 735 rval = build_type_conversion (type, e); 736 if (rval) 737 return rval; 738 if (flags & LOOKUP_COMPLAIN) 739 error ("%q#T used where a %qT was expected", intype, type); 740 return error_mark_node; 741 } 742 if (code == BOOLEAN_TYPE) 743 { 744 /* We can't implicitly convert a scoped enum to bool, so convert 745 to the underlying type first. */ 746 if (SCOPED_ENUM_P (intype) && (convtype & CONV_STATIC)) 747 e = build_nop (ENUM_UNDERLYING_TYPE (intype), e); 748 return cp_truthvalue_conversion (e); 749 } 750 751 converted = fold_if_not_in_template (convert_to_integer (type, e)); 752 753 /* Ignore any integer overflow caused by the conversion. */ 754 return ignore_overflows (converted, e); 755 } 756 if (NULLPTR_TYPE_P (type) && e && null_ptr_cst_p (e)) 757 return nullptr_node; 758 if (POINTER_TYPE_P (type) || TYPE_PTR_TO_MEMBER_P (type)) 759 return fold_if_not_in_template (cp_convert_to_pointer (type, e)); 760 if (code == VECTOR_TYPE) 761 { 762 tree in_vtype = TREE_TYPE (e); 763 if (MAYBE_CLASS_TYPE_P (in_vtype)) 764 { 765 tree ret_val; 766 ret_val = build_type_conversion (type, e); 767 if (ret_val) 768 return ret_val; 769 if (flags & LOOKUP_COMPLAIN) 770 error ("%q#T used where a %qT was expected", in_vtype, type); 771 return error_mark_node; 772 } 773 return fold_if_not_in_template (convert_to_vector (type, e)); 774 } 775 if (code == REAL_TYPE || code == COMPLEX_TYPE) 776 { 777 if (MAYBE_CLASS_TYPE_P (TREE_TYPE (e))) 778 { 779 tree rval; 780 rval = build_type_conversion (type, e); 781 if (rval) 782 return rval; 783 else 784 if (flags & LOOKUP_COMPLAIN) 785 error ("%q#T used where a floating point value was expected", 786 TREE_TYPE (e)); 787 } 788 if (code == REAL_TYPE) 789 return fold_if_not_in_template (convert_to_real (type, e)); 790 else if (code == COMPLEX_TYPE) 791 return fold_if_not_in_template (convert_to_complex (type, e)); 792 } 793 794 /* New C++ semantics: since assignment is now based on 795 memberwise copying, if the rhs type is derived from the 796 lhs type, then we may still do a conversion. */ 797 if (RECORD_OR_UNION_CODE_P (code)) 798 { 799 tree dtype = TREE_TYPE (e); 800 tree ctor = NULL_TREE; 801 802 dtype = TYPE_MAIN_VARIANT (dtype); 803 804 /* Conversion between aggregate types. New C++ semantics allow 805 objects of derived type to be cast to objects of base type. 806 Old semantics only allowed this between pointers. 807 808 There may be some ambiguity between using a constructor 809 vs. using a type conversion operator when both apply. */ 810 811 ctor = e; 812 813 if (abstract_virtuals_error (NULL_TREE, type)) 814 return error_mark_node; 815 816 if (BRACE_ENCLOSED_INITIALIZER_P (ctor)) 817 ctor = perform_implicit_conversion (type, ctor, tf_warning_or_error); 818 else if ((flags & LOOKUP_ONLYCONVERTING) 819 && ! (CLASS_TYPE_P (dtype) && DERIVED_FROM_P (type, dtype))) 820 /* For copy-initialization, first we create a temp of the proper type 821 with a user-defined conversion sequence, then we direct-initialize 822 the target with the temp (see [dcl.init]). */ 823 ctor = build_user_type_conversion (type, ctor, flags); 824 else 825 { 826 VEC(tree,gc) *ctor_vec = make_tree_vector_single (ctor); 827 ctor = build_special_member_call (NULL_TREE, 828 complete_ctor_identifier, 829 &ctor_vec, 830 type, flags, 831 tf_warning_or_error); 832 release_tree_vector (ctor_vec); 833 } 834 if (ctor) 835 return build_cplus_new (type, ctor, tf_warning_or_error); 836 } 837 838 if (flags & LOOKUP_COMPLAIN) 839 { 840 /* If the conversion failed and expr was an invalid use of pointer to 841 member function, try to report a meaningful error. */ 842 if (invalid_nonstatic_memfn_p (expr, tf_warning_or_error)) 843 /* We displayed the error message. */; 844 else 845 error ("conversion from %qT to non-scalar type %qT requested", 846 TREE_TYPE (expr), type); 847 } 848 return error_mark_node; 849 } 850 851 /* When an expression is used in a void context, its value is discarded and 852 no lvalue-rvalue and similar conversions happen [expr.static.cast/4, 853 stmt.expr/1, expr.comma/1]. This permits dereferencing an incomplete type 854 in a void context. The C++ standard does not define what an `access' to an 855 object is, but there is reason to believe that it is the lvalue to rvalue 856 conversion -- if it were not, `*&*p = 1' would violate [expr]/4 in that it 857 accesses `*p' not to calculate the value to be stored. But, dcl.type.cv/8 858 indicates that volatile semantics should be the same between C and C++ 859 where ever possible. C leaves it implementation defined as to what 860 constitutes an access to a volatile. So, we interpret `*vp' as a read of 861 the volatile object `vp' points to, unless that is an incomplete type. For 862 volatile references we do not do this interpretation, because that would 863 make it impossible to ignore the reference return value from functions. We 864 issue warnings in the confusing cases. 865 866 The IMPLICIT is ICV_CAST when the user is explicitly converting an expression 867 to void via a cast. If an expression is being implicitly converted, IMPLICIT 868 indicates the context of the implicit conversion. */ 869 870 tree 871 convert_to_void (tree expr, impl_conv_void implicit, tsubst_flags_t complain) 872 { 873 if (expr == error_mark_node 874 || TREE_TYPE (expr) == error_mark_node) 875 return error_mark_node; 876 877 if (implicit == ICV_CAST) 878 mark_exp_read (expr); 879 else 880 { 881 tree exprv = expr; 882 883 while (TREE_CODE (exprv) == COMPOUND_EXPR) 884 exprv = TREE_OPERAND (exprv, 1); 885 if (DECL_P (exprv) 886 || handled_component_p (exprv) 887 || TREE_CODE (exprv) == INDIRECT_REF) 888 /* Expr is not being 'used' here, otherwise we whould have 889 called mark_{rl}value_use use here, which would have in turn 890 called mark_exp_read. Rather, we call mark_exp_read directly 891 to avoid some warnings when 892 -Wunused-but-set-{variable,parameter} is in effect. */ 893 mark_exp_read (exprv); 894 } 895 896 if (!TREE_TYPE (expr)) 897 return expr; 898 if (invalid_nonstatic_memfn_p (expr, complain)) 899 return error_mark_node; 900 if (TREE_CODE (expr) == PSEUDO_DTOR_EXPR) 901 { 902 if (complain & tf_error) 903 error ("pseudo-destructor is not called"); 904 return error_mark_node; 905 } 906 if (VOID_TYPE_P (TREE_TYPE (expr))) 907 return expr; 908 switch (TREE_CODE (expr)) 909 { 910 case COND_EXPR: 911 { 912 /* The two parts of a cond expr might be separate lvalues. */ 913 tree op1 = TREE_OPERAND (expr,1); 914 tree op2 = TREE_OPERAND (expr,2); 915 bool side_effects = ((op1 && TREE_SIDE_EFFECTS (op1)) 916 || TREE_SIDE_EFFECTS (op2)); 917 tree new_op1, new_op2; 918 new_op1 = NULL_TREE; 919 if (implicit != ICV_CAST && !side_effects) 920 { 921 if (op1) 922 new_op1 = convert_to_void (op1, ICV_SECOND_OF_COND, complain); 923 new_op2 = convert_to_void (op2, ICV_THIRD_OF_COND, complain); 924 } 925 else 926 { 927 if (op1) 928 new_op1 = convert_to_void (op1, ICV_CAST, complain); 929 new_op2 = convert_to_void (op2, ICV_CAST, complain); 930 } 931 932 expr = build3 (COND_EXPR, TREE_TYPE (new_op2), 933 TREE_OPERAND (expr, 0), new_op1, new_op2); 934 break; 935 } 936 937 case COMPOUND_EXPR: 938 { 939 /* The second part of a compound expr contains the value. */ 940 tree op1 = TREE_OPERAND (expr,1); 941 tree new_op1; 942 if (implicit != ICV_CAST && !TREE_NO_WARNING (expr)) 943 new_op1 = convert_to_void (op1, ICV_RIGHT_OF_COMMA, complain); 944 else 945 new_op1 = convert_to_void (op1, ICV_CAST, complain); 946 947 if (new_op1 != op1) 948 { 949 tree t = build2 (COMPOUND_EXPR, TREE_TYPE (new_op1), 950 TREE_OPERAND (expr, 0), new_op1); 951 expr = t; 952 } 953 954 break; 955 } 956 957 case NON_LVALUE_EXPR: 958 case NOP_EXPR: 959 /* These have already decayed to rvalue. */ 960 break; 961 962 case CALL_EXPR: /* We have a special meaning for volatile void fn(). */ 963 break; 964 965 case INDIRECT_REF: 966 { 967 tree type = TREE_TYPE (expr); 968 int is_reference = TREE_CODE (TREE_TYPE (TREE_OPERAND (expr, 0))) 969 == REFERENCE_TYPE; 970 int is_volatile = TYPE_VOLATILE (type); 971 int is_complete = COMPLETE_TYPE_P (complete_type (type)); 972 973 /* Can't load the value if we don't know the type. */ 974 if (is_volatile && !is_complete) 975 { 976 if (complain & tf_warning) 977 switch (implicit) 978 { 979 case ICV_CAST: 980 warning (0, "conversion to void will not access " 981 "object of incomplete type %qT", type); 982 break; 983 case ICV_SECOND_OF_COND: 984 warning (0, "indirection will not access object of " 985 "incomplete type %qT in second operand " 986 "of conditional expression", type); 987 break; 988 case ICV_THIRD_OF_COND: 989 warning (0, "indirection will not access object of " 990 "incomplete type %qT in third operand " 991 "of conditional expression", type); 992 break; 993 case ICV_RIGHT_OF_COMMA: 994 warning (0, "indirection will not access object of " 995 "incomplete type %qT in right operand of " 996 "comma operator", type); 997 break; 998 case ICV_LEFT_OF_COMMA: 999 warning (0, "indirection will not access object of " 1000 "incomplete type %qT in left operand of " 1001 "comma operator", type); 1002 break; 1003 case ICV_STATEMENT: 1004 warning (0, "indirection will not access object of " 1005 "incomplete type %qT in statement", type); 1006 break; 1007 case ICV_THIRD_IN_FOR: 1008 warning (0, "indirection will not access object of " 1009 "incomplete type %qT in for increment " 1010 "expression", type); 1011 break; 1012 default: 1013 gcc_unreachable (); 1014 } 1015 } 1016 /* Don't load the value if this is an implicit dereference, or if 1017 the type needs to be handled by ctors/dtors. */ 1018 else if (is_volatile && is_reference) 1019 { 1020 if (complain & tf_warning) 1021 switch (implicit) 1022 { 1023 case ICV_CAST: 1024 warning (0, "conversion to void will not access " 1025 "object of type %qT", type); 1026 break; 1027 case ICV_SECOND_OF_COND: 1028 warning (0, "implicit dereference will not access object " 1029 "of type %qT in second operand of " 1030 "conditional expression", type); 1031 break; 1032 case ICV_THIRD_OF_COND: 1033 warning (0, "implicit dereference will not access object " 1034 "of type %qT in third operand of " 1035 "conditional expression", type); 1036 break; 1037 case ICV_RIGHT_OF_COMMA: 1038 warning (0, "implicit dereference will not access object " 1039 "of type %qT in right operand of " 1040 "comma operator", type); 1041 break; 1042 case ICV_LEFT_OF_COMMA: 1043 warning (0, "implicit dereference will not access object " 1044 "of type %qT in left operand of comma operator", 1045 type); 1046 break; 1047 case ICV_STATEMENT: 1048 warning (0, "implicit dereference will not access object " 1049 "of type %qT in statement", type); 1050 break; 1051 case ICV_THIRD_IN_FOR: 1052 warning (0, "implicit dereference will not access object " 1053 "of type %qT in for increment expression", 1054 type); 1055 break; 1056 default: 1057 gcc_unreachable (); 1058 } 1059 } 1060 else if (is_volatile && TREE_ADDRESSABLE (type)) 1061 { 1062 if (complain & tf_warning) 1063 switch (implicit) 1064 { 1065 case ICV_CAST: 1066 warning (0, "conversion to void will not access " 1067 "object of non-trivially-copyable type %qT", 1068 type); 1069 break; 1070 case ICV_SECOND_OF_COND: 1071 warning (0, "indirection will not access object of " 1072 "non-trivially-copyable type %qT in second " 1073 "operand of conditional expression", type); 1074 break; 1075 case ICV_THIRD_OF_COND: 1076 warning (0, "indirection will not access object of " 1077 "non-trivially-copyable type %qT in third " 1078 "operand of conditional expression", type); 1079 break; 1080 case ICV_RIGHT_OF_COMMA: 1081 warning (0, "indirection will not access object of " 1082 "non-trivially-copyable type %qT in right " 1083 "operand of comma operator", type); 1084 break; 1085 case ICV_LEFT_OF_COMMA: 1086 warning (0, "indirection will not access object of " 1087 "non-trivially-copyable type %qT in left " 1088 "operand of comma operator", type); 1089 break; 1090 case ICV_STATEMENT: 1091 warning (0, "indirection will not access object of " 1092 "non-trivially-copyable type %qT in statement", 1093 type); 1094 break; 1095 case ICV_THIRD_IN_FOR: 1096 warning (0, "indirection will not access object of " 1097 "non-trivially-copyable type %qT in for " 1098 "increment expression", type); 1099 break; 1100 default: 1101 gcc_unreachable (); 1102 } 1103 } 1104 if (is_reference || !is_volatile || !is_complete || TREE_ADDRESSABLE (type)) 1105 { 1106 /* Emit a warning (if enabled) when the "effect-less" INDIRECT_REF 1107 operation is stripped off. Note that we don't warn about 1108 - an expression with TREE_NO_WARNING set. (For an example of 1109 such expressions, see build_over_call in call.c.) 1110 - automatic dereferencing of references, since the user cannot 1111 control it. (See also warn_if_unused_value() in stmt.c.) */ 1112 if (warn_unused_value 1113 && implicit != ICV_CAST 1114 && (complain & tf_warning) 1115 && !TREE_NO_WARNING (expr) 1116 && !is_reference) 1117 warning (OPT_Wunused_value, "value computed is not used"); 1118 expr = TREE_OPERAND (expr, 0); 1119 } 1120 1121 break; 1122 } 1123 1124 case VAR_DECL: 1125 { 1126 /* External variables might be incomplete. */ 1127 tree type = TREE_TYPE (expr); 1128 int is_complete = COMPLETE_TYPE_P (complete_type (type)); 1129 1130 if (TYPE_VOLATILE (type) && !is_complete && (complain & tf_warning)) 1131 switch (implicit) 1132 { 1133 case ICV_CAST: 1134 warning (0, "conversion to void will not access " 1135 "object %qE of incomplete type %qT", expr, type); 1136 break; 1137 case ICV_SECOND_OF_COND: 1138 warning (0, "variable %qE of incomplete type %qT will not " 1139 "be accessed in second operand of " 1140 "conditional expression", expr, type); 1141 break; 1142 case ICV_THIRD_OF_COND: 1143 warning (0, "variable %qE of incomplete type %qT will not " 1144 "be accessed in third operand of " 1145 "conditional expression", expr, type); 1146 break; 1147 case ICV_RIGHT_OF_COMMA: 1148 warning (0, "variable %qE of incomplete type %qT will not " 1149 "be accessed in right operand of comma operator", 1150 expr, type); 1151 break; 1152 case ICV_LEFT_OF_COMMA: 1153 warning (0, "variable %qE of incomplete type %qT will not " 1154 "be accessed in left operand of comma operator", 1155 expr, type); 1156 break; 1157 case ICV_STATEMENT: 1158 warning (0, "variable %qE of incomplete type %qT will not " 1159 "be accessed in statement", expr, type); 1160 break; 1161 case ICV_THIRD_IN_FOR: 1162 warning (0, "variable %qE of incomplete type %qT will not " 1163 "be accessed in for increment expression", 1164 expr, type); 1165 break; 1166 default: 1167 gcc_unreachable (); 1168 } 1169 1170 break; 1171 } 1172 1173 case TARGET_EXPR: 1174 /* Don't bother with the temporary object returned from a function if 1175 we don't use it and don't need to destroy it. We'll still 1176 allocate space for it in expand_call or declare_return_variable, 1177 but we don't need to track it through all the tree phases. */ 1178 if (TARGET_EXPR_IMPLICIT_P (expr) 1179 && TYPE_HAS_TRIVIAL_DESTRUCTOR (TREE_TYPE (expr))) 1180 { 1181 tree init = TARGET_EXPR_INITIAL (expr); 1182 if (TREE_CODE (init) == AGGR_INIT_EXPR 1183 && !AGGR_INIT_VIA_CTOR_P (init)) 1184 { 1185 tree fn = AGGR_INIT_EXPR_FN (init); 1186 expr = build_call_array_loc (input_location, 1187 TREE_TYPE (TREE_TYPE (TREE_TYPE (fn))), 1188 fn, 1189 aggr_init_expr_nargs (init), 1190 AGGR_INIT_EXPR_ARGP (init)); 1191 } 1192 } 1193 break; 1194 1195 default:; 1196 } 1197 expr = resolve_nondeduced_context (expr); 1198 { 1199 tree probe = expr; 1200 1201 if (TREE_CODE (probe) == ADDR_EXPR) 1202 probe = TREE_OPERAND (expr, 0); 1203 if (type_unknown_p (probe)) 1204 { 1205 /* [over.over] enumerates the places where we can take the address 1206 of an overloaded function, and this is not one of them. */ 1207 if (complain & tf_error) 1208 switch (implicit) 1209 { 1210 case ICV_CAST: 1211 error ("conversion to void " 1212 "cannot resolve address of overloaded function"); 1213 break; 1214 case ICV_SECOND_OF_COND: 1215 error ("second operand of conditional expression " 1216 "cannot resolve address of overloaded function"); 1217 break; 1218 case ICV_THIRD_OF_COND: 1219 error ("third operand of conditional expression " 1220 "cannot resolve address of overloaded function"); 1221 break; 1222 case ICV_RIGHT_OF_COMMA: 1223 error ("right operand of comma operator " 1224 "cannot resolve address of overloaded function"); 1225 break; 1226 case ICV_LEFT_OF_COMMA: 1227 error ("left operand of comma operator " 1228 "cannot resolve address of overloaded function"); 1229 break; 1230 case ICV_STATEMENT: 1231 error ("statement " 1232 "cannot resolve address of overloaded function"); 1233 break; 1234 case ICV_THIRD_IN_FOR: 1235 error ("for increment expression " 1236 "cannot resolve address of overloaded function"); 1237 break; 1238 } 1239 else 1240 return error_mark_node; 1241 expr = void_zero_node; 1242 } 1243 else if (implicit != ICV_CAST && probe == expr && is_overloaded_fn (probe)) 1244 { 1245 /* Only warn when there is no &. */ 1246 if (complain & tf_warning) 1247 switch (implicit) 1248 { 1249 case ICV_SECOND_OF_COND: 1250 warning (OPT_Waddress, 1251 "second operand of conditional expression " 1252 "is a reference, not call, to function %qE", expr); 1253 break; 1254 case ICV_THIRD_OF_COND: 1255 warning (OPT_Waddress, 1256 "third operand of conditional expression " 1257 "is a reference, not call, to function %qE", expr); 1258 break; 1259 case ICV_RIGHT_OF_COMMA: 1260 warning (OPT_Waddress, 1261 "right operand of comma operator " 1262 "is a reference, not call, to function %qE", expr); 1263 break; 1264 case ICV_LEFT_OF_COMMA: 1265 warning (OPT_Waddress, 1266 "left operand of comma operator " 1267 "is a reference, not call, to function %qE", expr); 1268 break; 1269 case ICV_STATEMENT: 1270 warning (OPT_Waddress, 1271 "statement is a reference, not call, to function %qE", 1272 expr); 1273 break; 1274 case ICV_THIRD_IN_FOR: 1275 warning (OPT_Waddress, 1276 "for increment expression " 1277 "is a reference, not call, to function %qE", expr); 1278 break; 1279 default: 1280 gcc_unreachable (); 1281 } 1282 1283 if (TREE_CODE (expr) == COMPONENT_REF) 1284 expr = TREE_OPERAND (expr, 0); 1285 } 1286 } 1287 1288 if (expr != error_mark_node && !VOID_TYPE_P (TREE_TYPE (expr))) 1289 { 1290 if (implicit != ICV_CAST 1291 && warn_unused_value 1292 && !TREE_NO_WARNING (expr) 1293 && !processing_template_decl) 1294 { 1295 /* The middle end does not warn about expressions that have 1296 been explicitly cast to void, so we must do so here. */ 1297 if (!TREE_SIDE_EFFECTS (expr)) { 1298 if (complain & tf_warning) 1299 switch (implicit) 1300 { 1301 case ICV_SECOND_OF_COND: 1302 warning (OPT_Wunused_value, 1303 "second operand of conditional expression has no effect"); 1304 break; 1305 case ICV_THIRD_OF_COND: 1306 warning (OPT_Wunused_value, 1307 "third operand of conditional expression has no effect"); 1308 break; 1309 case ICV_RIGHT_OF_COMMA: 1310 warning (OPT_Wunused_value, 1311 "right operand of comma operator has no effect"); 1312 break; 1313 case ICV_LEFT_OF_COMMA: 1314 warning (OPT_Wunused_value, 1315 "left operand of comma operator has no effect"); 1316 break; 1317 case ICV_STATEMENT: 1318 warning (OPT_Wunused_value, 1319 "statement has no effect"); 1320 break; 1321 case ICV_THIRD_IN_FOR: 1322 warning (OPT_Wunused_value, 1323 "for increment expression has no effect"); 1324 break; 1325 default: 1326 gcc_unreachable (); 1327 } 1328 } 1329 else 1330 { 1331 tree e; 1332 enum tree_code code; 1333 enum tree_code_class tclass; 1334 1335 e = expr; 1336 /* We might like to warn about (say) "(int) f()", as the 1337 cast has no effect, but the compiler itself will 1338 generate implicit conversions under some 1339 circumstances. (For example a block copy will be 1340 turned into a call to "__builtin_memcpy", with a 1341 conversion of the return value to an appropriate 1342 type.) So, to avoid false positives, we strip 1343 conversions. Do not use STRIP_NOPs because it will 1344 not strip conversions to "void", as that is not a 1345 mode-preserving conversion. */ 1346 while (TREE_CODE (e) == NOP_EXPR) 1347 e = TREE_OPERAND (e, 0); 1348 1349 code = TREE_CODE (e); 1350 tclass = TREE_CODE_CLASS (code); 1351 if ((tclass == tcc_comparison 1352 || tclass == tcc_unary 1353 || (tclass == tcc_binary 1354 && !(code == MODIFY_EXPR 1355 || code == INIT_EXPR 1356 || code == PREDECREMENT_EXPR 1357 || code == PREINCREMENT_EXPR 1358 || code == POSTDECREMENT_EXPR 1359 || code == POSTINCREMENT_EXPR))) 1360 && (complain & tf_warning)) 1361 warning (OPT_Wunused_value, "value computed is not used"); 1362 } 1363 } 1364 expr = build1 (CONVERT_EXPR, void_type_node, expr); 1365 } 1366 if (! TREE_SIDE_EFFECTS (expr)) 1367 expr = void_zero_node; 1368 return expr; 1369 } 1370 1371 /* Create an expression whose value is that of EXPR, 1372 converted to type TYPE. The TREE_TYPE of the value 1373 is always TYPE. This function implements all reasonable 1374 conversions; callers should filter out those that are 1375 not permitted by the language being compiled. 1376 1377 Most of this routine is from build_reinterpret_cast. 1378 1379 The back end cannot call cp_convert (what was convert) because 1380 conversions to/from basetypes may involve memory references 1381 (vbases) and adding or subtracting small values (multiple 1382 inheritance), but it calls convert from the constant folding code 1383 on subtrees of already built trees after it has ripped them apart. 1384 1385 Also, if we ever support range variables, we'll probably also have to 1386 do a little bit more work. */ 1387 1388 tree 1389 convert (tree type, tree expr) 1390 { 1391 tree intype; 1392 1393 if (type == error_mark_node || expr == error_mark_node) 1394 return error_mark_node; 1395 1396 intype = TREE_TYPE (expr); 1397 1398 if (POINTER_TYPE_P (type) && POINTER_TYPE_P (intype)) 1399 return fold_if_not_in_template (build_nop (type, expr)); 1400 1401 return ocp_convert (type, expr, CONV_OLD_CONVERT, 1402 LOOKUP_NORMAL|LOOKUP_NO_CONVERSION); 1403 } 1404 1405 /* Like cp_convert, except permit conversions to take place which 1406 are not normally allowed due to access restrictions 1407 (such as conversion from sub-type to private super-type). */ 1408 1409 tree 1410 convert_force (tree type, tree expr, int convtype) 1411 { 1412 tree e = expr; 1413 enum tree_code code = TREE_CODE (type); 1414 1415 if (code == REFERENCE_TYPE) 1416 return (fold_if_not_in_template 1417 (convert_to_reference (type, e, CONV_C_CAST, LOOKUP_COMPLAIN, 1418 NULL_TREE))); 1419 1420 if (code == POINTER_TYPE) 1421 return fold_if_not_in_template (convert_to_pointer_force (type, e)); 1422 1423 /* From typeck.c convert_for_assignment */ 1424 if (((TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE && TREE_CODE (e) == ADDR_EXPR 1425 && TREE_CODE (TREE_TYPE (e)) == POINTER_TYPE 1426 && TREE_CODE (TREE_TYPE (TREE_TYPE (e))) == METHOD_TYPE) 1427 || integer_zerop (e) 1428 || TYPE_PTRMEMFUNC_P (TREE_TYPE (e))) 1429 && TYPE_PTRMEMFUNC_P (type)) 1430 /* compatible pointer to member functions. */ 1431 return build_ptrmemfunc (TYPE_PTRMEMFUNC_FN_TYPE (type), e, 1, 1432 /*c_cast_p=*/1, tf_warning_or_error); 1433 1434 return ocp_convert (type, e, CONV_C_CAST|convtype, LOOKUP_NORMAL); 1435 } 1436 1437 /* Convert an aggregate EXPR to type XTYPE. If a conversion 1438 exists, return the attempted conversion. This may 1439 return ERROR_MARK_NODE if the conversion is not 1440 allowed (references private members, etc). 1441 If no conversion exists, NULL_TREE is returned. 1442 1443 FIXME: Ambiguity checking is wrong. Should choose one by the implicit 1444 object parameter, or by the second standard conversion sequence if 1445 that doesn't do it. This will probably wait for an overloading rewrite. 1446 (jason 8/9/95) */ 1447 1448 static tree 1449 build_type_conversion (tree xtype, tree expr) 1450 { 1451 /* C++: check to see if we can convert this aggregate type 1452 into the required type. */ 1453 return build_user_type_conversion (xtype, expr, LOOKUP_NORMAL); 1454 } 1455 1456 /* Convert the given EXPR to one of a group of types suitable for use in an 1457 expression. DESIRES is a combination of various WANT_* flags (q.v.) 1458 which indicates which types are suitable. If COMPLAIN is true, complain 1459 about ambiguity; otherwise, the caller will deal with it. */ 1460 1461 tree 1462 build_expr_type_conversion (int desires, tree expr, bool complain) 1463 { 1464 tree basetype = TREE_TYPE (expr); 1465 tree conv = NULL_TREE; 1466 tree winner = NULL_TREE; 1467 1468 if (expr == null_node 1469 && (desires & WANT_INT) 1470 && !(desires & WANT_NULL)) 1471 warning_at (input_location, OPT_Wconversion_null, 1472 "converting NULL to non-pointer type"); 1473 1474 basetype = TREE_TYPE (expr); 1475 1476 if (basetype == error_mark_node) 1477 return error_mark_node; 1478 1479 if (! MAYBE_CLASS_TYPE_P (basetype)) 1480 switch (TREE_CODE (basetype)) 1481 { 1482 case INTEGER_TYPE: 1483 if ((desires & WANT_NULL) && null_ptr_cst_p (expr)) 1484 return expr; 1485 /* else fall through... */ 1486 1487 case BOOLEAN_TYPE: 1488 return (desires & WANT_INT) ? expr : NULL_TREE; 1489 case ENUMERAL_TYPE: 1490 return (desires & WANT_ENUM) ? expr : NULL_TREE; 1491 case REAL_TYPE: 1492 return (desires & WANT_FLOAT) ? expr : NULL_TREE; 1493 case POINTER_TYPE: 1494 return (desires & WANT_POINTER) ? expr : NULL_TREE; 1495 1496 case FUNCTION_TYPE: 1497 case ARRAY_TYPE: 1498 return (desires & WANT_POINTER) ? decay_conversion (expr) 1499 : NULL_TREE; 1500 1501 case COMPLEX_TYPE: 1502 case VECTOR_TYPE: 1503 if ((desires & WANT_VECTOR_OR_COMPLEX) == 0) 1504 return NULL_TREE; 1505 switch (TREE_CODE (TREE_TYPE (basetype))) 1506 { 1507 case INTEGER_TYPE: 1508 case BOOLEAN_TYPE: 1509 return (desires & WANT_INT) ? expr : NULL_TREE; 1510 case ENUMERAL_TYPE: 1511 return (desires & WANT_ENUM) ? expr : NULL_TREE; 1512 case REAL_TYPE: 1513 return (desires & WANT_FLOAT) ? expr : NULL_TREE; 1514 default: 1515 return NULL_TREE; 1516 } 1517 1518 default: 1519 return NULL_TREE; 1520 } 1521 1522 /* The code for conversions from class type is currently only used for 1523 delete expressions. Other expressions are handled by build_new_op. */ 1524 if (!complete_type_or_maybe_complain (basetype, expr, complain)) 1525 return error_mark_node; 1526 if (!TYPE_HAS_CONVERSION (basetype)) 1527 return NULL_TREE; 1528 1529 for (conv = lookup_conversions (basetype); conv; conv = TREE_CHAIN (conv)) 1530 { 1531 int win = 0; 1532 tree candidate; 1533 tree cand = TREE_VALUE (conv); 1534 cand = OVL_CURRENT (cand); 1535 1536 if (winner && winner == cand) 1537 continue; 1538 1539 if (DECL_NONCONVERTING_P (cand)) 1540 continue; 1541 1542 candidate = non_reference (TREE_TYPE (TREE_TYPE (cand))); 1543 1544 switch (TREE_CODE (candidate)) 1545 { 1546 case BOOLEAN_TYPE: 1547 case INTEGER_TYPE: 1548 win = (desires & WANT_INT); break; 1549 case ENUMERAL_TYPE: 1550 win = (desires & WANT_ENUM); break; 1551 case REAL_TYPE: 1552 win = (desires & WANT_FLOAT); break; 1553 case POINTER_TYPE: 1554 win = (desires & WANT_POINTER); break; 1555 1556 case COMPLEX_TYPE: 1557 case VECTOR_TYPE: 1558 if ((desires & WANT_VECTOR_OR_COMPLEX) == 0) 1559 break; 1560 switch (TREE_CODE (TREE_TYPE (candidate))) 1561 { 1562 case BOOLEAN_TYPE: 1563 case INTEGER_TYPE: 1564 win = (desires & WANT_INT); break; 1565 case ENUMERAL_TYPE: 1566 win = (desires & WANT_ENUM); break; 1567 case REAL_TYPE: 1568 win = (desires & WANT_FLOAT); break; 1569 default: 1570 break; 1571 } 1572 break; 1573 1574 default: 1575 /* A wildcard could be instantiated to match any desired 1576 type, but we can't deduce the template argument. */ 1577 if (WILDCARD_TYPE_P (candidate)) 1578 win = true; 1579 break; 1580 } 1581 1582 if (win) 1583 { 1584 if (TREE_CODE (cand) == TEMPLATE_DECL) 1585 { 1586 if (complain) 1587 error ("default type conversion can't deduce template" 1588 " argument for %qD", cand); 1589 return error_mark_node; 1590 } 1591 1592 if (winner) 1593 { 1594 if (complain) 1595 { 1596 error ("ambiguous default type conversion from %qT", 1597 basetype); 1598 error (" candidate conversions include %qD and %qD", 1599 winner, cand); 1600 } 1601 return error_mark_node; 1602 } 1603 else 1604 winner = cand; 1605 } 1606 } 1607 1608 if (winner) 1609 { 1610 tree type = non_reference (TREE_TYPE (TREE_TYPE (winner))); 1611 return build_user_type_conversion (type, expr, LOOKUP_NORMAL); 1612 } 1613 1614 return NULL_TREE; 1615 } 1616 1617 /* Implements integral promotion (4.1) and float->double promotion. */ 1618 1619 tree 1620 type_promotes_to (tree type) 1621 { 1622 tree promoted_type; 1623 1624 if (type == error_mark_node) 1625 return error_mark_node; 1626 1627 type = TYPE_MAIN_VARIANT (type); 1628 1629 /* Check for promotions of target-defined types first. */ 1630 promoted_type = targetm.promoted_type (type); 1631 if (promoted_type) 1632 return promoted_type; 1633 1634 /* bool always promotes to int (not unsigned), even if it's the same 1635 size. */ 1636 if (TREE_CODE (type) == BOOLEAN_TYPE) 1637 type = integer_type_node; 1638 1639 /* Scoped enums don't promote, but pretend they do for backward ABI bug 1640 compatibility wrt varargs. */ 1641 else if (SCOPED_ENUM_P (type) && abi_version_at_least (6)) 1642 ; 1643 1644 /* Normally convert enums to int, but convert wide enums to something 1645 wider. */ 1646 else if (TREE_CODE (type) == ENUMERAL_TYPE 1647 || type == char16_type_node 1648 || type == char32_type_node 1649 || type == wchar_type_node) 1650 { 1651 int precision = MAX (TYPE_PRECISION (type), 1652 TYPE_PRECISION (integer_type_node)); 1653 tree totype = c_common_type_for_size (precision, 0); 1654 if (SCOPED_ENUM_P (type)) 1655 warning (OPT_Wabi, "scoped enum %qT will not promote to an integral " 1656 "type in a future version of GCC", type); 1657 if (TREE_CODE (type) == ENUMERAL_TYPE) 1658 type = ENUM_UNDERLYING_TYPE (type); 1659 if (TYPE_UNSIGNED (type) 1660 && ! int_fits_type_p (TYPE_MAX_VALUE (type), totype)) 1661 type = c_common_type_for_size (precision, 1); 1662 else 1663 type = totype; 1664 } 1665 else if (c_promoting_integer_type_p (type)) 1666 { 1667 /* Retain unsignedness if really not getting bigger. */ 1668 if (TYPE_UNSIGNED (type) 1669 && TYPE_PRECISION (type) == TYPE_PRECISION (integer_type_node)) 1670 type = unsigned_type_node; 1671 else 1672 type = integer_type_node; 1673 } 1674 else if (type == float_type_node) 1675 type = double_type_node; 1676 1677 return type; 1678 } 1679 1680 /* The routines below this point are carefully written to conform to 1681 the standard. They use the same terminology, and follow the rules 1682 closely. Although they are used only in pt.c at the moment, they 1683 should presumably be used everywhere in the future. */ 1684 1685 /* Attempt to perform qualification conversions on EXPR to convert it 1686 to TYPE. Return the resulting expression, or error_mark_node if 1687 the conversion was impossible. */ 1688 1689 tree 1690 perform_qualification_conversions (tree type, tree expr) 1691 { 1692 tree expr_type; 1693 1694 expr_type = TREE_TYPE (expr); 1695 1696 if (same_type_p (type, expr_type)) 1697 return expr; 1698 else if (TYPE_PTR_P (type) && TYPE_PTR_P (expr_type) 1699 && comp_ptr_ttypes (TREE_TYPE (type), TREE_TYPE (expr_type))) 1700 return build_nop (type, expr); 1701 else if (TYPE_PTR_TO_MEMBER_P (type) 1702 && TYPE_PTR_TO_MEMBER_P (expr_type) 1703 && same_type_p (TYPE_PTRMEM_CLASS_TYPE (type), 1704 TYPE_PTRMEM_CLASS_TYPE (expr_type)) 1705 && comp_ptr_ttypes (TYPE_PTRMEM_POINTED_TO_TYPE (type), 1706 TYPE_PTRMEM_POINTED_TO_TYPE (expr_type))) 1707 return build_nop (type, expr); 1708 else 1709 return error_mark_node; 1710 } 1711