1 // resolve.cc -- symbol resolution for gold 2 3 // Copyright 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc. 4 // Written by Ian Lance Taylor <iant@google.com>. 5 6 // This file is part of gold. 7 8 // This program is free software; you can redistribute it and/or modify 9 // it under the terms of the GNU General Public License as published by 10 // the Free Software Foundation; either version 3 of the License, or 11 // (at your option) any later version. 12 13 // This program is distributed in the hope that it will be useful, 14 // but WITHOUT ANY WARRANTY; without even the implied warranty of 15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16 // GNU General Public License for more details. 17 18 // You should have received a copy of the GNU General Public License 19 // along with this program; if not, write to the Free Software 20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, 21 // MA 02110-1301, USA. 22 23 #include "gold.h" 24 25 #include "elfcpp.h" 26 #include "target.h" 27 #include "object.h" 28 #include "symtab.h" 29 #include "plugin.h" 30 31 namespace gold 32 { 33 34 // Symbol methods used in this file. 35 36 // This symbol is being overridden by another symbol whose version is 37 // VERSION. Update the VERSION_ field accordingly. 38 39 inline void 40 Symbol::override_version(const char* version) 41 { 42 if (version == NULL) 43 { 44 // This is the case where this symbol is NAME/VERSION, and the 45 // version was not marked as hidden. That makes it the default 46 // version, so we create NAME/NULL. Later we see another symbol 47 // NAME/NULL, and that symbol is overriding this one. In this 48 // case, since NAME/VERSION is the default, we make NAME/NULL 49 // override NAME/VERSION as well. They are already the same 50 // Symbol structure. Setting the VERSION_ field to NULL ensures 51 // that it will be output with the correct, empty, version. 52 this->version_ = version; 53 } 54 else 55 { 56 // This is the case where this symbol is NAME/VERSION_ONE, and 57 // now we see NAME/VERSION_TWO, and NAME/VERSION_TWO is 58 // overriding NAME. If VERSION_ONE and VERSION_TWO are 59 // different, then this can only happen when VERSION_ONE is NULL 60 // and VERSION_TWO is not hidden. 61 gold_assert(this->version_ == version || this->version_ == NULL); 62 this->version_ = version; 63 } 64 } 65 66 // This symbol is being overidden by another symbol whose visibility 67 // is VISIBILITY. Updated the VISIBILITY_ field accordingly. 68 69 inline void 70 Symbol::override_visibility(elfcpp::STV visibility) 71 { 72 // The rule for combining visibility is that we always choose the 73 // most constrained visibility. In order of increasing constraint, 74 // visibility goes PROTECTED, HIDDEN, INTERNAL. This is the reverse 75 // of the numeric values, so the effect is that we always want the 76 // smallest non-zero value. 77 if (visibility != elfcpp::STV_DEFAULT) 78 { 79 if (this->visibility_ == elfcpp::STV_DEFAULT) 80 this->visibility_ = visibility; 81 else if (this->visibility_ > visibility) 82 this->visibility_ = visibility; 83 } 84 } 85 86 // Override the fields in Symbol. 87 88 template<int size, bool big_endian> 89 void 90 Symbol::override_base(const elfcpp::Sym<size, big_endian>& sym, 91 unsigned int st_shndx, bool is_ordinary, 92 Object* object, const char* version) 93 { 94 gold_assert(this->source_ == FROM_OBJECT); 95 this->u_.from_object.object = object; 96 this->override_version(version); 97 this->u_.from_object.shndx = st_shndx; 98 this->is_ordinary_shndx_ = is_ordinary; 99 this->type_ = sym.get_st_type(); 100 this->binding_ = sym.get_st_bind(); 101 this->override_visibility(sym.get_st_visibility()); 102 this->nonvis_ = sym.get_st_nonvis(); 103 if (object->is_dynamic()) 104 this->in_dyn_ = true; 105 else 106 this->in_reg_ = true; 107 } 108 109 // Override the fields in Sized_symbol. 110 111 template<int size> 112 template<bool big_endian> 113 void 114 Sized_symbol<size>::override(const elfcpp::Sym<size, big_endian>& sym, 115 unsigned st_shndx, bool is_ordinary, 116 Object* object, const char* version) 117 { 118 this->override_base(sym, st_shndx, is_ordinary, object, version); 119 this->value_ = sym.get_st_value(); 120 this->symsize_ = sym.get_st_size(); 121 } 122 123 // Override TOSYM with symbol FROMSYM, defined in OBJECT, with version 124 // VERSION. This handles all aliases of TOSYM. 125 126 template<int size, bool big_endian> 127 void 128 Symbol_table::override(Sized_symbol<size>* tosym, 129 const elfcpp::Sym<size, big_endian>& fromsym, 130 unsigned int st_shndx, bool is_ordinary, 131 Object* object, const char* version) 132 { 133 tosym->override(fromsym, st_shndx, is_ordinary, object, version); 134 if (tosym->has_alias()) 135 { 136 Symbol* sym = this->weak_aliases_[tosym]; 137 gold_assert(sym != NULL); 138 Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym); 139 do 140 { 141 ssym->override(fromsym, st_shndx, is_ordinary, object, version); 142 sym = this->weak_aliases_[ssym]; 143 gold_assert(sym != NULL); 144 ssym = this->get_sized_symbol<size>(sym); 145 } 146 while (ssym != tosym); 147 } 148 } 149 150 // The resolve functions build a little code for each symbol. 151 // Bit 0: 0 for global, 1 for weak. 152 // Bit 1: 0 for regular object, 1 for shared object 153 // Bits 2-3: 0 for normal, 1 for undefined, 2 for common 154 // This gives us values from 0 to 11. 155 156 static const int global_or_weak_shift = 0; 157 static const unsigned int global_flag = 0 << global_or_weak_shift; 158 static const unsigned int weak_flag = 1 << global_or_weak_shift; 159 160 static const int regular_or_dynamic_shift = 1; 161 static const unsigned int regular_flag = 0 << regular_or_dynamic_shift; 162 static const unsigned int dynamic_flag = 1 << regular_or_dynamic_shift; 163 164 static const int def_undef_or_common_shift = 2; 165 static const unsigned int def_flag = 0 << def_undef_or_common_shift; 166 static const unsigned int undef_flag = 1 << def_undef_or_common_shift; 167 static const unsigned int common_flag = 2 << def_undef_or_common_shift; 168 169 // This convenience function combines all the flags based on facts 170 // about the symbol. 171 172 static unsigned int 173 symbol_to_bits(elfcpp::STB binding, bool is_dynamic, 174 unsigned int shndx, bool is_ordinary, elfcpp::STT type) 175 { 176 unsigned int bits; 177 178 switch (binding) 179 { 180 case elfcpp::STB_GLOBAL: 181 case elfcpp::STB_GNU_UNIQUE: 182 bits = global_flag; 183 break; 184 185 case elfcpp::STB_WEAK: 186 bits = weak_flag; 187 break; 188 189 case elfcpp::STB_LOCAL: 190 // We should only see externally visible symbols in the symbol 191 // table. 192 gold_error(_("invalid STB_LOCAL symbol in external symbols")); 193 bits = global_flag; 194 195 default: 196 // Any target which wants to handle STB_LOOS, etc., needs to 197 // define a resolve method. 198 gold_error(_("unsupported symbol binding %d"), static_cast<int>(binding)); 199 bits = global_flag; 200 } 201 202 if (is_dynamic) 203 bits |= dynamic_flag; 204 else 205 bits |= regular_flag; 206 207 switch (shndx) 208 { 209 case elfcpp::SHN_UNDEF: 210 bits |= undef_flag; 211 break; 212 213 case elfcpp::SHN_COMMON: 214 if (!is_ordinary) 215 bits |= common_flag; 216 break; 217 218 default: 219 if (type == elfcpp::STT_COMMON) 220 bits |= common_flag; 221 else if (!is_ordinary && Symbol::is_common_shndx(shndx)) 222 bits |= common_flag; 223 else 224 bits |= def_flag; 225 break; 226 } 227 228 return bits; 229 } 230 231 // Resolve a symbol. This is called the second and subsequent times 232 // we see a symbol. TO is the pre-existing symbol. ST_SHNDX is the 233 // section index for SYM, possibly adjusted for many sections. 234 // IS_ORDINARY is whether ST_SHNDX is a normal section index rather 235 // than a special code. ORIG_ST_SHNDX is the original section index, 236 // before any munging because of discarded sections, except that all 237 // non-ordinary section indexes are mapped to SHN_UNDEF. VERSION is 238 // the version of SYM. 239 240 template<int size, bool big_endian> 241 void 242 Symbol_table::resolve(Sized_symbol<size>* to, 243 const elfcpp::Sym<size, big_endian>& sym, 244 unsigned int st_shndx, bool is_ordinary, 245 unsigned int orig_st_shndx, 246 Object* object, const char* version) 247 { 248 if (parameters->target().has_resolve()) 249 { 250 Sized_target<size, big_endian>* sized_target; 251 sized_target = parameters->sized_target<size, big_endian>(); 252 sized_target->resolve(to, sym, object, version); 253 return; 254 } 255 256 if (!object->is_dynamic()) 257 { 258 // Record that we've seen this symbol in a regular object. 259 to->set_in_reg(); 260 } 261 else if (st_shndx == elfcpp::SHN_UNDEF 262 && (to->visibility() == elfcpp::STV_HIDDEN 263 || to->visibility() == elfcpp::STV_INTERNAL)) 264 { 265 // A dynamic object cannot reference a hidden or internal symbol 266 // defined in another object. 267 gold_warning(_("%s symbol '%s' in %s is referenced by DSO %s"), 268 (to->visibility() == elfcpp::STV_HIDDEN 269 ? "hidden" 270 : "internal"), 271 to->demangled_name().c_str(), 272 to->object()->name().c_str(), 273 object->name().c_str()); 274 return; 275 } 276 else 277 { 278 // Record that we've seen this symbol in a dynamic object. 279 to->set_in_dyn(); 280 } 281 282 // Record if we've seen this symbol in a real ELF object (i.e., the 283 // symbol is referenced from outside the world known to the plugin). 284 if (object->pluginobj() == NULL) 285 to->set_in_real_elf(); 286 287 // If we're processing replacement files, allow new symbols to override 288 // the placeholders from the plugin objects. 289 if (to->source() == Symbol::FROM_OBJECT) 290 { 291 Pluginobj* obj = to->object()->pluginobj(); 292 if (obj != NULL 293 && parameters->options().plugins()->in_replacement_phase()) 294 { 295 this->override(to, sym, st_shndx, is_ordinary, object, version); 296 return; 297 } 298 } 299 300 // A new weak undefined reference, merging with an old weak 301 // reference, could be a One Definition Rule (ODR) violation -- 302 // especially if the types or sizes of the references differ. We'll 303 // store such pairs and look them up later to make sure they 304 // actually refer to the same lines of code. We also check 305 // combinations of weak and strong, which might occur if one case is 306 // inline and the other is not. (Note: not all ODR violations can 307 // be found this way, and not everything this finds is an ODR 308 // violation. But it's helpful to warn about.) 309 bool to_is_ordinary; 310 if (parameters->options().detect_odr_violations() 311 && (sym.get_st_bind() == elfcpp::STB_WEAK 312 || to->binding() == elfcpp::STB_WEAK) 313 && orig_st_shndx != elfcpp::SHN_UNDEF 314 && to->shndx(&to_is_ordinary) != elfcpp::SHN_UNDEF 315 && to_is_ordinary 316 && sym.get_st_size() != 0 // Ignore weird 0-sized symbols. 317 && to->symsize() != 0 318 && (sym.get_st_type() != to->type() 319 || sym.get_st_size() != to->symsize()) 320 // C does not have a concept of ODR, so we only need to do this 321 // on C++ symbols. These have (mangled) names starting with _Z. 322 && to->name()[0] == '_' && to->name()[1] == 'Z') 323 { 324 Symbol_location fromloc 325 = { object, orig_st_shndx, sym.get_st_value() }; 326 Symbol_location toloc = { to->object(), to->shndx(&to_is_ordinary), 327 to->value() }; 328 this->candidate_odr_violations_[to->name()].insert(fromloc); 329 this->candidate_odr_violations_[to->name()].insert(toloc); 330 } 331 332 unsigned int frombits = symbol_to_bits(sym.get_st_bind(), 333 object->is_dynamic(), 334 st_shndx, is_ordinary, 335 sym.get_st_type()); 336 337 bool adjust_common_sizes; 338 bool adjust_dyndef; 339 typename Sized_symbol<size>::Size_type tosize = to->symsize(); 340 if (Symbol_table::should_override(to, frombits, OBJECT, object, 341 &adjust_common_sizes, 342 &adjust_dyndef)) 343 { 344 elfcpp::STB tobinding = to->binding(); 345 this->override(to, sym, st_shndx, is_ordinary, object, version); 346 if (adjust_common_sizes && tosize > to->symsize()) 347 to->set_symsize(tosize); 348 if (adjust_dyndef) 349 { 350 // We are overriding an UNDEF or WEAK UNDEF with a DYN DEF. 351 // Remember which kind of UNDEF it was for future reference. 352 to->set_undef_binding(tobinding); 353 } 354 } 355 else 356 { 357 if (adjust_common_sizes && sym.get_st_size() > tosize) 358 to->set_symsize(sym.get_st_size()); 359 if (adjust_dyndef) 360 { 361 // We are keeping a DYN DEF after seeing an UNDEF or WEAK UNDEF. 362 // Remember which kind of UNDEF it was. 363 to->set_undef_binding(sym.get_st_bind()); 364 } 365 // The ELF ABI says that even for a reference to a symbol we 366 // merge the visibility. 367 to->override_visibility(sym.get_st_visibility()); 368 } 369 370 if (adjust_common_sizes && parameters->options().warn_common()) 371 { 372 if (tosize > sym.get_st_size()) 373 Symbol_table::report_resolve_problem(false, 374 _("common of '%s' overriding " 375 "smaller common"), 376 to, OBJECT, object); 377 else if (tosize < sym.get_st_size()) 378 Symbol_table::report_resolve_problem(false, 379 _("common of '%s' overidden by " 380 "larger common"), 381 to, OBJECT, object); 382 else 383 Symbol_table::report_resolve_problem(false, 384 _("multiple common of '%s'"), 385 to, OBJECT, object); 386 } 387 } 388 389 // Handle the core of symbol resolution. This is called with the 390 // existing symbol, TO, and a bitflag describing the new symbol. This 391 // returns true if we should override the existing symbol with the new 392 // one, and returns false otherwise. It sets *ADJUST_COMMON_SIZES to 393 // true if we should set the symbol size to the maximum of the TO and 394 // FROM sizes. It handles error conditions. 395 396 bool 397 Symbol_table::should_override(const Symbol* to, unsigned int frombits, 398 Defined defined, Object* object, 399 bool* adjust_common_sizes, 400 bool* adjust_dyndef) 401 { 402 *adjust_common_sizes = false; 403 *adjust_dyndef = false; 404 405 unsigned int tobits; 406 if (to->source() == Symbol::IS_UNDEFINED) 407 tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_UNDEF, true, 408 to->type()); 409 else if (to->source() != Symbol::FROM_OBJECT) 410 tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_ABS, false, 411 to->type()); 412 else 413 { 414 bool is_ordinary; 415 unsigned int shndx = to->shndx(&is_ordinary); 416 tobits = symbol_to_bits(to->binding(), 417 to->object()->is_dynamic(), 418 shndx, 419 is_ordinary, 420 to->type()); 421 } 422 423 // FIXME: Warn if either but not both of TO and SYM are STT_TLS. 424 425 // We use a giant switch table for symbol resolution. This code is 426 // unwieldy, but: 1) it is efficient; 2) we definitely handle all 427 // cases; 3) it is easy to change the handling of a particular case. 428 // The alternative would be a series of conditionals, but it is easy 429 // to get the ordering wrong. This could also be done as a table, 430 // but that is no easier to understand than this large switch 431 // statement. 432 433 // These are the values generated by the bit codes. 434 enum 435 { 436 DEF = global_flag | regular_flag | def_flag, 437 WEAK_DEF = weak_flag | regular_flag | def_flag, 438 DYN_DEF = global_flag | dynamic_flag | def_flag, 439 DYN_WEAK_DEF = weak_flag | dynamic_flag | def_flag, 440 UNDEF = global_flag | regular_flag | undef_flag, 441 WEAK_UNDEF = weak_flag | regular_flag | undef_flag, 442 DYN_UNDEF = global_flag | dynamic_flag | undef_flag, 443 DYN_WEAK_UNDEF = weak_flag | dynamic_flag | undef_flag, 444 COMMON = global_flag | regular_flag | common_flag, 445 WEAK_COMMON = weak_flag | regular_flag | common_flag, 446 DYN_COMMON = global_flag | dynamic_flag | common_flag, 447 DYN_WEAK_COMMON = weak_flag | dynamic_flag | common_flag 448 }; 449 450 switch (tobits * 16 + frombits) 451 { 452 case DEF * 16 + DEF: 453 // Two definitions of the same symbol. 454 455 // If either symbol is defined by an object included using 456 // --just-symbols, then don't warn. This is for compatibility 457 // with the GNU linker. FIXME: This is a hack. 458 if ((to->source() == Symbol::FROM_OBJECT && to->object()->just_symbols()) 459 || (object != NULL && object->just_symbols())) 460 return false; 461 462 if (!parameters->options().muldefs()) 463 Symbol_table::report_resolve_problem(true, 464 _("multiple definition of '%s'"), 465 to, defined, object); 466 return false; 467 468 case WEAK_DEF * 16 + DEF: 469 // We've seen a weak definition, and now we see a strong 470 // definition. In the original SVR4 linker, this was treated as 471 // a multiple definition error. In the Solaris linker and the 472 // GNU linker, a weak definition followed by a regular 473 // definition causes the weak definition to be overridden. We 474 // are currently compatible with the GNU linker. In the future 475 // we should add a target specific option to change this. 476 // FIXME. 477 return true; 478 479 case DYN_DEF * 16 + DEF: 480 case DYN_WEAK_DEF * 16 + DEF: 481 // We've seen a definition in a dynamic object, and now we see a 482 // definition in a regular object. The definition in the 483 // regular object overrides the definition in the dynamic 484 // object. 485 return true; 486 487 case UNDEF * 16 + DEF: 488 case WEAK_UNDEF * 16 + DEF: 489 case DYN_UNDEF * 16 + DEF: 490 case DYN_WEAK_UNDEF * 16 + DEF: 491 // We've seen an undefined reference, and now we see a 492 // definition. We use the definition. 493 return true; 494 495 case COMMON * 16 + DEF: 496 case WEAK_COMMON * 16 + DEF: 497 case DYN_COMMON * 16 + DEF: 498 case DYN_WEAK_COMMON * 16 + DEF: 499 // We've seen a common symbol and now we see a definition. The 500 // definition overrides. 501 if (parameters->options().warn_common()) 502 Symbol_table::report_resolve_problem(false, 503 _("definition of '%s' overriding " 504 "common"), 505 to, defined, object); 506 return true; 507 508 case DEF * 16 + WEAK_DEF: 509 case WEAK_DEF * 16 + WEAK_DEF: 510 // We've seen a definition and now we see a weak definition. We 511 // ignore the new weak definition. 512 return false; 513 514 case DYN_DEF * 16 + WEAK_DEF: 515 case DYN_WEAK_DEF * 16 + WEAK_DEF: 516 // We've seen a dynamic definition and now we see a regular weak 517 // definition. The regular weak definition overrides. 518 return true; 519 520 case UNDEF * 16 + WEAK_DEF: 521 case WEAK_UNDEF * 16 + WEAK_DEF: 522 case DYN_UNDEF * 16 + WEAK_DEF: 523 case DYN_WEAK_UNDEF * 16 + WEAK_DEF: 524 // A weak definition of a currently undefined symbol. 525 return true; 526 527 case COMMON * 16 + WEAK_DEF: 528 case WEAK_COMMON * 16 + WEAK_DEF: 529 // A weak definition does not override a common definition. 530 return false; 531 532 case DYN_COMMON * 16 + WEAK_DEF: 533 case DYN_WEAK_COMMON * 16 + WEAK_DEF: 534 // A weak definition does override a definition in a dynamic 535 // object. 536 if (parameters->options().warn_common()) 537 Symbol_table::report_resolve_problem(false, 538 _("definition of '%s' overriding " 539 "dynamic common definition"), 540 to, defined, object); 541 return true; 542 543 case DEF * 16 + DYN_DEF: 544 case WEAK_DEF * 16 + DYN_DEF: 545 case DYN_DEF * 16 + DYN_DEF: 546 case DYN_WEAK_DEF * 16 + DYN_DEF: 547 // Ignore a dynamic definition if we already have a definition. 548 return false; 549 550 case UNDEF * 16 + DYN_DEF: 551 case DYN_UNDEF * 16 + DYN_DEF: 552 case DYN_WEAK_UNDEF * 16 + DYN_DEF: 553 // Use a dynamic definition if we have a reference. 554 return true; 555 556 case WEAK_UNDEF * 16 + DYN_DEF: 557 // When overriding a weak undef by a dynamic definition, 558 // we need to remember that the original undef was weak. 559 *adjust_dyndef = true; 560 return true; 561 562 case COMMON * 16 + DYN_DEF: 563 case WEAK_COMMON * 16 + DYN_DEF: 564 case DYN_COMMON * 16 + DYN_DEF: 565 case DYN_WEAK_COMMON * 16 + DYN_DEF: 566 // Ignore a dynamic definition if we already have a common 567 // definition. 568 return false; 569 570 case DEF * 16 + DYN_WEAK_DEF: 571 case WEAK_DEF * 16 + DYN_WEAK_DEF: 572 case DYN_DEF * 16 + DYN_WEAK_DEF: 573 case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF: 574 // Ignore a weak dynamic definition if we already have a 575 // definition. 576 return false; 577 578 case UNDEF * 16 + DYN_WEAK_DEF: 579 // When overriding an undef by a dynamic weak definition, 580 // we need to remember that the original undef was not weak. 581 *adjust_dyndef = true; 582 return true; 583 584 case DYN_UNDEF * 16 + DYN_WEAK_DEF: 585 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF: 586 // Use a weak dynamic definition if we have a reference. 587 return true; 588 589 case WEAK_UNDEF * 16 + DYN_WEAK_DEF: 590 // When overriding a weak undef by a dynamic definition, 591 // we need to remember that the original undef was weak. 592 *adjust_dyndef = true; 593 return true; 594 595 case COMMON * 16 + DYN_WEAK_DEF: 596 case WEAK_COMMON * 16 + DYN_WEAK_DEF: 597 case DYN_COMMON * 16 + DYN_WEAK_DEF: 598 case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF: 599 // Ignore a weak dynamic definition if we already have a common 600 // definition. 601 return false; 602 603 case DEF * 16 + UNDEF: 604 case WEAK_DEF * 16 + UNDEF: 605 case UNDEF * 16 + UNDEF: 606 // A new undefined reference tells us nothing. 607 return false; 608 609 case DYN_DEF * 16 + UNDEF: 610 case DYN_WEAK_DEF * 16 + UNDEF: 611 // For a dynamic def, we need to remember which kind of undef we see. 612 *adjust_dyndef = true; 613 return false; 614 615 case WEAK_UNDEF * 16 + UNDEF: 616 case DYN_UNDEF * 16 + UNDEF: 617 case DYN_WEAK_UNDEF * 16 + UNDEF: 618 // A strong undef overrides a dynamic or weak undef. 619 return true; 620 621 case COMMON * 16 + UNDEF: 622 case WEAK_COMMON * 16 + UNDEF: 623 case DYN_COMMON * 16 + UNDEF: 624 case DYN_WEAK_COMMON * 16 + UNDEF: 625 // A new undefined reference tells us nothing. 626 return false; 627 628 case DEF * 16 + WEAK_UNDEF: 629 case WEAK_DEF * 16 + WEAK_UNDEF: 630 case UNDEF * 16 + WEAK_UNDEF: 631 case WEAK_UNDEF * 16 + WEAK_UNDEF: 632 case DYN_UNDEF * 16 + WEAK_UNDEF: 633 case COMMON * 16 + WEAK_UNDEF: 634 case WEAK_COMMON * 16 + WEAK_UNDEF: 635 case DYN_COMMON * 16 + WEAK_UNDEF: 636 case DYN_WEAK_COMMON * 16 + WEAK_UNDEF: 637 // A new weak undefined reference tells us nothing unless the 638 // exisiting symbol is a dynamic weak reference. 639 return false; 640 641 case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF: 642 // A new weak reference overrides an existing dynamic weak reference. 643 // This is necessary because a dynamic weak reference remembers 644 // the old binding, which may not be weak. If we keeps the existing 645 // dynamic weak reference, the weakness may be dropped in the output. 646 return true; 647 648 case DYN_DEF * 16 + WEAK_UNDEF: 649 case DYN_WEAK_DEF * 16 + WEAK_UNDEF: 650 // For a dynamic def, we need to remember which kind of undef we see. 651 *adjust_dyndef = true; 652 return false; 653 654 case DEF * 16 + DYN_UNDEF: 655 case WEAK_DEF * 16 + DYN_UNDEF: 656 case DYN_DEF * 16 + DYN_UNDEF: 657 case DYN_WEAK_DEF * 16 + DYN_UNDEF: 658 case UNDEF * 16 + DYN_UNDEF: 659 case WEAK_UNDEF * 16 + DYN_UNDEF: 660 case DYN_UNDEF * 16 + DYN_UNDEF: 661 case DYN_WEAK_UNDEF * 16 + DYN_UNDEF: 662 case COMMON * 16 + DYN_UNDEF: 663 case WEAK_COMMON * 16 + DYN_UNDEF: 664 case DYN_COMMON * 16 + DYN_UNDEF: 665 case DYN_WEAK_COMMON * 16 + DYN_UNDEF: 666 // A new dynamic undefined reference tells us nothing. 667 return false; 668 669 case DEF * 16 + DYN_WEAK_UNDEF: 670 case WEAK_DEF * 16 + DYN_WEAK_UNDEF: 671 case DYN_DEF * 16 + DYN_WEAK_UNDEF: 672 case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF: 673 case UNDEF * 16 + DYN_WEAK_UNDEF: 674 case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF: 675 case DYN_UNDEF * 16 + DYN_WEAK_UNDEF: 676 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF: 677 case COMMON * 16 + DYN_WEAK_UNDEF: 678 case WEAK_COMMON * 16 + DYN_WEAK_UNDEF: 679 case DYN_COMMON * 16 + DYN_WEAK_UNDEF: 680 case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF: 681 // A new weak dynamic undefined reference tells us nothing. 682 return false; 683 684 case DEF * 16 + COMMON: 685 // A common symbol does not override a definition. 686 if (parameters->options().warn_common()) 687 Symbol_table::report_resolve_problem(false, 688 _("common '%s' overridden by " 689 "previous definition"), 690 to, defined, object); 691 return false; 692 693 case WEAK_DEF * 16 + COMMON: 694 case DYN_DEF * 16 + COMMON: 695 case DYN_WEAK_DEF * 16 + COMMON: 696 // A common symbol does override a weak definition or a dynamic 697 // definition. 698 return true; 699 700 case UNDEF * 16 + COMMON: 701 case WEAK_UNDEF * 16 + COMMON: 702 case DYN_UNDEF * 16 + COMMON: 703 case DYN_WEAK_UNDEF * 16 + COMMON: 704 // A common symbol is a definition for a reference. 705 return true; 706 707 case COMMON * 16 + COMMON: 708 // Set the size to the maximum. 709 *adjust_common_sizes = true; 710 return false; 711 712 case WEAK_COMMON * 16 + COMMON: 713 // I'm not sure just what a weak common symbol means, but 714 // presumably it can be overridden by a regular common symbol. 715 return true; 716 717 case DYN_COMMON * 16 + COMMON: 718 case DYN_WEAK_COMMON * 16 + COMMON: 719 // Use the real common symbol, but adjust the size if necessary. 720 *adjust_common_sizes = true; 721 return true; 722 723 case DEF * 16 + WEAK_COMMON: 724 case WEAK_DEF * 16 + WEAK_COMMON: 725 case DYN_DEF * 16 + WEAK_COMMON: 726 case DYN_WEAK_DEF * 16 + WEAK_COMMON: 727 // Whatever a weak common symbol is, it won't override a 728 // definition. 729 return false; 730 731 case UNDEF * 16 + WEAK_COMMON: 732 case WEAK_UNDEF * 16 + WEAK_COMMON: 733 case DYN_UNDEF * 16 + WEAK_COMMON: 734 case DYN_WEAK_UNDEF * 16 + WEAK_COMMON: 735 // A weak common symbol is better than an undefined symbol. 736 return true; 737 738 case COMMON * 16 + WEAK_COMMON: 739 case WEAK_COMMON * 16 + WEAK_COMMON: 740 case DYN_COMMON * 16 + WEAK_COMMON: 741 case DYN_WEAK_COMMON * 16 + WEAK_COMMON: 742 // Ignore a weak common symbol in the presence of a real common 743 // symbol. 744 return false; 745 746 case DEF * 16 + DYN_COMMON: 747 case WEAK_DEF * 16 + DYN_COMMON: 748 case DYN_DEF * 16 + DYN_COMMON: 749 case DYN_WEAK_DEF * 16 + DYN_COMMON: 750 // Ignore a dynamic common symbol in the presence of a 751 // definition. 752 return false; 753 754 case UNDEF * 16 + DYN_COMMON: 755 case WEAK_UNDEF * 16 + DYN_COMMON: 756 case DYN_UNDEF * 16 + DYN_COMMON: 757 case DYN_WEAK_UNDEF * 16 + DYN_COMMON: 758 // A dynamic common symbol is a definition of sorts. 759 return true; 760 761 case COMMON * 16 + DYN_COMMON: 762 case WEAK_COMMON * 16 + DYN_COMMON: 763 case DYN_COMMON * 16 + DYN_COMMON: 764 case DYN_WEAK_COMMON * 16 + DYN_COMMON: 765 // Set the size to the maximum. 766 *adjust_common_sizes = true; 767 return false; 768 769 case DEF * 16 + DYN_WEAK_COMMON: 770 case WEAK_DEF * 16 + DYN_WEAK_COMMON: 771 case DYN_DEF * 16 + DYN_WEAK_COMMON: 772 case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON: 773 // A common symbol is ignored in the face of a definition. 774 return false; 775 776 case UNDEF * 16 + DYN_WEAK_COMMON: 777 case WEAK_UNDEF * 16 + DYN_WEAK_COMMON: 778 case DYN_UNDEF * 16 + DYN_WEAK_COMMON: 779 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON: 780 // I guess a weak common symbol is better than a definition. 781 return true; 782 783 case COMMON * 16 + DYN_WEAK_COMMON: 784 case WEAK_COMMON * 16 + DYN_WEAK_COMMON: 785 case DYN_COMMON * 16 + DYN_WEAK_COMMON: 786 case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON: 787 // Set the size to the maximum. 788 *adjust_common_sizes = true; 789 return false; 790 791 default: 792 gold_unreachable(); 793 } 794 } 795 796 // Issue an error or warning due to symbol resolution. IS_ERROR 797 // indicates an error rather than a warning. MSG is the error 798 // message; it is expected to have a %s for the symbol name. TO is 799 // the existing symbol. DEFINED/OBJECT is where the new symbol was 800 // found. 801 802 // FIXME: We should have better location information here. When the 803 // symbol is defined, we should be able to pull the location from the 804 // debug info if there is any. 805 806 void 807 Symbol_table::report_resolve_problem(bool is_error, const char* msg, 808 const Symbol* to, Defined defined, 809 Object* object) 810 { 811 std::string demangled(to->demangled_name()); 812 size_t len = strlen(msg) + demangled.length() + 10; 813 char* buf = new char[len]; 814 snprintf(buf, len, msg, demangled.c_str()); 815 816 const char* objname; 817 switch (defined) 818 { 819 case OBJECT: 820 objname = object->name().c_str(); 821 break; 822 case COPY: 823 objname = _("COPY reloc"); 824 break; 825 case DEFSYM: 826 case UNDEFINED: 827 objname = _("command line"); 828 break; 829 case SCRIPT: 830 objname = _("linker script"); 831 break; 832 case PREDEFINED: 833 objname = _("linker defined"); 834 break; 835 default: 836 gold_unreachable(); 837 } 838 839 if (is_error) 840 gold_error("%s: %s", objname, buf); 841 else 842 gold_warning("%s: %s", objname, buf); 843 844 delete[] buf; 845 846 if (to->source() == Symbol::FROM_OBJECT) 847 objname = to->object()->name().c_str(); 848 else 849 objname = _("command line"); 850 gold_info("%s: %s: previous definition here", program_name, objname); 851 } 852 853 // A special case of should_override which is only called for a strong 854 // defined symbol from a regular object file. This is used when 855 // defining special symbols. 856 857 bool 858 Symbol_table::should_override_with_special(const Symbol* to, Defined defined) 859 { 860 bool adjust_common_sizes; 861 bool adjust_dyn_def; 862 unsigned int frombits = global_flag | regular_flag | def_flag; 863 bool ret = Symbol_table::should_override(to, frombits, defined, NULL, 864 &adjust_common_sizes, 865 &adjust_dyn_def); 866 gold_assert(!adjust_common_sizes && !adjust_dyn_def); 867 return ret; 868 } 869 870 // Override symbol base with a special symbol. 871 872 void 873 Symbol::override_base_with_special(const Symbol* from) 874 { 875 gold_assert(this->name_ == from->name_ || this->has_alias()); 876 877 this->source_ = from->source_; 878 switch (from->source_) 879 { 880 case FROM_OBJECT: 881 this->u_.from_object = from->u_.from_object; 882 break; 883 case IN_OUTPUT_DATA: 884 this->u_.in_output_data = from->u_.in_output_data; 885 break; 886 case IN_OUTPUT_SEGMENT: 887 this->u_.in_output_segment = from->u_.in_output_segment; 888 break; 889 case IS_CONSTANT: 890 case IS_UNDEFINED: 891 break; 892 default: 893 gold_unreachable(); 894 break; 895 } 896 897 this->override_version(from->version_); 898 this->type_ = from->type_; 899 this->binding_ = from->binding_; 900 this->override_visibility(from->visibility_); 901 this->nonvis_ = from->nonvis_; 902 903 // Special symbols are always considered to be regular symbols. 904 this->in_reg_ = true; 905 906 if (from->needs_dynsym_entry_) 907 this->needs_dynsym_entry_ = true; 908 if (from->needs_dynsym_value_) 909 this->needs_dynsym_value_ = true; 910 911 // We shouldn't see these flags. If we do, we need to handle them 912 // somehow. 913 gold_assert(!from->is_forwarder_); 914 gold_assert(!from->has_plt_offset()); 915 gold_assert(!from->has_warning_); 916 gold_assert(!from->is_copied_from_dynobj_); 917 gold_assert(!from->is_forced_local_); 918 } 919 920 // Override a symbol with a special symbol. 921 922 template<int size> 923 void 924 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from) 925 { 926 this->override_base_with_special(from); 927 this->value_ = from->value_; 928 this->symsize_ = from->symsize_; 929 } 930 931 // Override TOSYM with the special symbol FROMSYM. This handles all 932 // aliases of TOSYM. 933 934 template<int size> 935 void 936 Symbol_table::override_with_special(Sized_symbol<size>* tosym, 937 const Sized_symbol<size>* fromsym) 938 { 939 tosym->override_with_special(fromsym); 940 if (tosym->has_alias()) 941 { 942 Symbol* sym = this->weak_aliases_[tosym]; 943 gold_assert(sym != NULL); 944 Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym); 945 do 946 { 947 ssym->override_with_special(fromsym); 948 sym = this->weak_aliases_[ssym]; 949 gold_assert(sym != NULL); 950 ssym = this->get_sized_symbol<size>(sym); 951 } 952 while (ssym != tosym); 953 } 954 if (tosym->binding() == elfcpp::STB_LOCAL 955 || ((tosym->visibility() == elfcpp::STV_HIDDEN 956 || tosym->visibility() == elfcpp::STV_INTERNAL) 957 && (tosym->binding() == elfcpp::STB_GLOBAL 958 || tosym->binding() == elfcpp::STB_GNU_UNIQUE 959 || tosym->binding() == elfcpp::STB_WEAK) 960 && !parameters->options().relocatable())) 961 this->force_local(tosym); 962 } 963 964 // Instantiate the templates we need. We could use the configure 965 // script to restrict this to only the ones needed for implemented 966 // targets. 967 968 // We have to instantiate both big and little endian versions because 969 // these are used by other templates that depends on size only. 970 971 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG) 972 template 973 void 974 Symbol_table::resolve<32, false>( 975 Sized_symbol<32>* to, 976 const elfcpp::Sym<32, false>& sym, 977 unsigned int st_shndx, 978 bool is_ordinary, 979 unsigned int orig_st_shndx, 980 Object* object, 981 const char* version); 982 983 template 984 void 985 Symbol_table::resolve<32, true>( 986 Sized_symbol<32>* to, 987 const elfcpp::Sym<32, true>& sym, 988 unsigned int st_shndx, 989 bool is_ordinary, 990 unsigned int orig_st_shndx, 991 Object* object, 992 const char* version); 993 #endif 994 995 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG) 996 template 997 void 998 Symbol_table::resolve<64, false>( 999 Sized_symbol<64>* to, 1000 const elfcpp::Sym<64, false>& sym, 1001 unsigned int st_shndx, 1002 bool is_ordinary, 1003 unsigned int orig_st_shndx, 1004 Object* object, 1005 const char* version); 1006 1007 template 1008 void 1009 Symbol_table::resolve<64, true>( 1010 Sized_symbol<64>* to, 1011 const elfcpp::Sym<64, true>& sym, 1012 unsigned int st_shndx, 1013 bool is_ordinary, 1014 unsigned int orig_st_shndx, 1015 Object* object, 1016 const char* version); 1017 #endif 1018 1019 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG) 1020 template 1021 void 1022 Symbol_table::override_with_special<32>(Sized_symbol<32>*, 1023 const Sized_symbol<32>*); 1024 #endif 1025 1026 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG) 1027 template 1028 void 1029 Symbol_table::override_with_special<64>(Sized_symbol<64>*, 1030 const Sized_symbol<64>*); 1031 #endif 1032 1033 } // End namespace gold. 1034