gold/resolve.cc

   1 // resolve.cc -- symbol resolution for gold
   2
   3 // Copyright 2006, 2007 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
  30 namespace gold
  31 {
  32
  33 // Symbol methods used in this file.
  34
  35 // Override the fields in Symbol.
  36
  37 template<int size, bool big_endian>
  38 void
  39 Symbol::override_base(const elfcpp::Sym<size, big_endian>& sym,
  40                       Object* object, const char* version)
  41 {
  42   gold_assert(this->source_ == FROM_OBJECT);
  43   this->u_.from_object.object = object;
  44   if (version != NULL && this->version() != version)
  45     {
  46       gold_assert(this->version() == NULL);
  47       this->version_ = version;
  48     }
  49   // FIXME: Handle SHN_XINDEX.
  50   this->u_.from_object.shndx = sym.get_st_shndx();
  51   this->type_ = sym.get_st_type();
  52   this->binding_ = sym.get_st_bind();
  53   this->visibility_ = sym.get_st_visibility();
  54   this->nonvis_ = sym.get_st_nonvis();
  55   if (object->is_dynamic())
  56     this->in_dyn_ = true;
  57   else
  58     this->in_reg_ = true;
  59 }
  60
  61 // Override the fields in Sized_symbol.
  62
  63 template<int size>
  64 template<bool big_endian>
  65 void
  66 Sized_symbol<size>::override(const elfcpp::Sym<size, big_endian>& sym,
  67                              Object* object, const char* version)
  68 {
  69   this->override_base(sym, object, version);
  70   this->value_ = sym.get_st_value();
  71   this->symsize_ = sym.get_st_size();
  72 }
  73
  74 // Override TOSYM with symbol FROMSYM, defined in OBJECT, with version
  75 // VERSION.  This handles all aliases of TOSYM.
  76
  77 template<int size, bool big_endian>
  78 void
  79 Symbol_table::override(Sized_symbol<size>* tosym,
  80                        const elfcpp::Sym<size, big_endian>& fromsym,
  81                        Object* object, const char* version)
  82 {
  83   tosym->override(fromsym, object, version);
  84   if (tosym->has_alias())
  85     {
  86       Symbol* sym = this->weak_aliases_[tosym];
  87       gold_assert(sym != NULL);
  88       Sized_symbol<size>* ssym;
  89       ssym = this->get_sized_symbol SELECT_SIZE_NAME(size) (sym
  90                                                             SELECT_SIZE(size));
  91       do
  92         {
  93           ssym->override(fromsym, object, version);
  94           sym = this->weak_aliases_[ssym];
  95           gold_assert(sym != NULL);
  96           ssym = this->get_sized_symbol SELECT_SIZE_NAME(size) (
  97                                                 sym SELECT_SIZE(size));
  98         }
  99       while (ssym != tosym);
 100     }
 101 }
 102
 103 // The resolve functions build a little code for each symbol.
 104 // Bit 0: 0 for global, 1 for weak.
 105 // Bit 1: 0 for regular object, 1 for shared object
 106 // Bits 2-3: 0 for normal, 1 for undefined, 2 for common
 107 // This gives us values from 0 to 11.
 108
 109 static const int global_or_weak_shift = 0;
 110 static const unsigned int global_flag = 0 << global_or_weak_shift;
 111 static const unsigned int weak_flag = 1 << global_or_weak_shift;
 112
 113 static const int regular_or_dynamic_shift = 1;
 114 static const unsigned int regular_flag = 0 << regular_or_dynamic_shift;
 115 static const unsigned int dynamic_flag = 1 << regular_or_dynamic_shift;
 116
 117 static const int def_undef_or_common_shift = 2;
 118 static const unsigned int def_flag = 0 << def_undef_or_common_shift;
 119 static const unsigned int undef_flag = 1 << def_undef_or_common_shift;
 120 static const unsigned int common_flag = 2 << def_undef_or_common_shift;
 121
 122 // Resolve a symbol.  This is called the second and subsequent times
 123 // we see a symbol.  TO is the pre-existing symbol.  SYM is the new
 124 // symbol, seen in OBJECT.  VERSION of the version of SYM.
 125
 126 template<int size, bool big_endian>
 127 void
 128 Symbol_table::resolve(Sized_symbol<size>* to,
 129                       const elfcpp::Sym<size, big_endian>& sym,
 130                       Object* object, const char* version)
 131 {
 132   if (object->target()->has_resolve())
 133     {
 134       Sized_target<size, big_endian>* sized_target;
 135       sized_target = object->sized_target
 136                      SELECT_SIZE_ENDIAN_NAME(size, big_endian) (
 137                          SELECT_SIZE_ENDIAN_ONLY(size, big_endian));
 138       sized_target->resolve(to, sym, object, version);
 139       return;
 140     }
 141
 142   if (!object->is_dynamic())
 143     {
 144       // Record that we've seen this symbol in a regular object.
 145       to->set_in_reg();
 146     }
 147   else
 148     {
 149       // Record that we've seen this symbol in a dynamic object.
 150       to->set_in_dyn();
 151     }
 152
 153   unsigned int frombits;
 154   switch (sym.get_st_bind())
 155     {
 156     case elfcpp::STB_GLOBAL:
 157       frombits = global_flag;
 158       break;
 159
 160     case elfcpp::STB_WEAK:
 161       frombits = weak_flag;
 162       break;
 163
 164     case elfcpp::STB_LOCAL:
 165       gold_error(_("%s: invalid STB_LOCAL symbol %s in external symbols"),
 166                  object->name().c_str(), to->name());
 167       frombits = global_flag;
 168       break;
 169
 170     default:
 171       gold_error(_("%s: unsupported symbol binding %d for symbol %s"),
 172                  object->name().c_str(),
 173                  static_cast<int>(sym.get_st_bind()), to->name());
 174       frombits = global_flag;
 175       break;
 176     }
 177
 178   if (!object->is_dynamic())
 179     frombits |= regular_flag;
 180   else
 181     frombits |= dynamic_flag;
 182
 183   switch (sym.get_st_shndx())
 184     {
 185     case elfcpp::SHN_UNDEF:
 186       frombits |= undef_flag;
 187       break;
 188
 189     case elfcpp::SHN_COMMON:
 190       frombits |= common_flag;
 191       break;
 192
 193     default:
 194       if (sym.get_st_type() == elfcpp::STT_COMMON)
 195         frombits |= common_flag;
 196       else
 197         frombits |= def_flag;
 198       break;
 199     }
 200
 201   bool adjust_common_sizes;
 202   if (Symbol_table::should_override(to, frombits, object,
 203                                     &adjust_common_sizes))
 204     {
 205       typename Sized_symbol<size>::Size_type tosize = to->symsize();
 206
 207       this->override(to, sym, object, version);
 208
 209       if (adjust_common_sizes && tosize > to->symsize())
 210         to->set_symsize(tosize);
 211     }
 212   else
 213     {
 214       if (adjust_common_sizes && sym.get_st_size() > to->symsize())
 215         to->set_symsize(sym.get_st_size());
 216     }
 217 }
 218
 219 // Handle the core of symbol resolution.  This is called with the
 220 // existing symbol, TO, and a bitflag describing the new symbol.  This
 221 // returns true if we should override the existing symbol with the new
 222 // one, and returns false otherwise.  It sets *ADJUST_COMMON_SIZES to
 223 // true if we should set the symbol size to the maximum of the TO and
 224 // FROM sizes.  It handles error conditions.
 225
 226 bool
 227 Symbol_table::should_override(const Symbol* to, unsigned int frombits,
 228                               Object* object, bool* adjust_common_sizes)
 229 {
 230   *adjust_common_sizes = false;
 231
 232   unsigned int tobits;
 233   switch (to->binding())
 234     {
 235     case elfcpp::STB_GLOBAL:
 236       tobits = global_flag;
 237       break;
 238
 239     case elfcpp::STB_WEAK:
 240       tobits = weak_flag;
 241       break;
 242
 243     case elfcpp::STB_LOCAL:
 244       // We should only see externally visible symbols in the symbol
 245       // table.
 246       gold_unreachable();
 247
 248     default:
 249       // Any target which wants to handle STB_LOOS, etc., needs to
 250       // define a resolve method.
 251       gold_unreachable();
 252     }
 253
 254   if (to->source() == Symbol::FROM_OBJECT
 255       && to->object()->is_dynamic())
 256     tobits |= dynamic_flag;
 257   else
 258     tobits |= regular_flag;
 259
 260   switch (to->shndx())
 261     {
 262     case elfcpp::SHN_UNDEF:
 263       tobits |= undef_flag;
 264       break;
 265
 266     case elfcpp::SHN_COMMON:
 267       tobits |= common_flag;
 268       break;
 269
 270     default:
 271       if (to->type() == elfcpp::STT_COMMON)
 272         tobits |= common_flag;
 273       else
 274         tobits |= def_flag;
 275       break;
 276     }
 277
 278   // FIXME: Warn if either but not both of TO and SYM are STT_TLS.
 279
 280   // We use a giant switch table for symbol resolution.  This code is
 281   // unwieldy, but: 1) it is efficient; 2) we definitely handle all
 282   // cases; 3) it is easy to change the handling of a particular case.
 283   // The alternative would be a series of conditionals, but it is easy
 284   // to get the ordering wrong.  This could also be done as a table,
 285   // but that is no easier to understand than this large switch
 286   // statement.
 287
 288   // These are the values generated by the bit codes.
 289   enum
 290   {
 291     DEF =              global_flag | regular_flag | def_flag,
 292     WEAK_DEF =         weak_flag   | regular_flag | def_flag,
 293     DYN_DEF =          global_flag | dynamic_flag | def_flag,
 294     DYN_WEAK_DEF =     weak_flag   | dynamic_flag | def_flag,
 295     UNDEF =            global_flag | regular_flag | undef_flag,
 296     WEAK_UNDEF =       weak_flag   | regular_flag | undef_flag,
 297     DYN_UNDEF =        global_flag | dynamic_flag | undef_flag,
 298     DYN_WEAK_UNDEF =   weak_flag   | dynamic_flag | undef_flag,
 299     COMMON =           global_flag | regular_flag | common_flag,
 300     WEAK_COMMON =      weak_flag   | regular_flag | common_flag,
 301     DYN_COMMON =       global_flag | dynamic_flag | common_flag,
 302     DYN_WEAK_COMMON =  weak_flag   | dynamic_flag | common_flag
 303   };
 304
 305   switch (tobits * 16 + frombits)
 306     {
 307     case DEF * 16 + DEF:
 308       // Two definitions of the same symbol.
 309       // FIXME: Do a better job of reporting locations.
 310       gold_error(_("%s: multiple definition of %s"),
 311                  object != NULL ? object->name().c_str() : _("command line"),
 312                  to->name());
 313       gold_error(_("%s: previous definition here"),
 314                  (to->source() == Symbol::FROM_OBJECT
 315                   ? to->object()->name().c_str()
 316                   : _("command line")));
 317       return false;
 318
 319     case WEAK_DEF * 16 + DEF:
 320       // We've seen a weak definition, and now we see a strong
 321       // definition.  In the original SVR4 linker, this was treated as
 322       // a multiple definition error.  In the Solaris linker and the
 323       // GNU linker, a weak definition followed by a regular
 324       // definition causes the weak definition to be overridden.  We
 325       // are currently compatible with the GNU linker.  In the future
 326       // we should add a target specific option to change this.
 327       // FIXME.
 328       return true;
 329
 330     case DYN_DEF * 16 + DEF:
 331     case DYN_WEAK_DEF * 16 + DEF:
 332       // We've seen a definition in a dynamic object, and now we see a
 333       // definition in a regular object.  The definition in the
 334       // regular object overrides the definition in the dynamic
 335       // object.
 336       return true;
 337
 338     case UNDEF * 16 + DEF:
 339     case WEAK_UNDEF * 16 + DEF:
 340     case DYN_UNDEF * 16 + DEF:
 341     case DYN_WEAK_UNDEF * 16 + DEF:
 342       // We've seen an undefined reference, and now we see a
 343       // definition.  We use the definition.
 344       return true;
 345
 346     case COMMON * 16 + DEF:
 347     case WEAK_COMMON * 16 + DEF:
 348     case DYN_COMMON * 16 + DEF:
 349     case DYN_WEAK_COMMON * 16 + DEF:
 350       // We've seen a common symbol and now we see a definition.  The
 351       // definition overrides.  FIXME: We should optionally issue, version a
 352       // warning.
 353       return true;
 354
 355     case DEF * 16 + WEAK_DEF:
 356     case WEAK_DEF * 16 + WEAK_DEF:
 357       // We've seen a definition and now we see a weak definition.  We
 358       // ignore the new weak definition.
 359       return false;
 360
 361     case DYN_DEF * 16 + WEAK_DEF:
 362     case DYN_WEAK_DEF * 16 + WEAK_DEF:
 363       // We've seen a dynamic definition and now we see a regular weak
 364       // definition.  The regular weak definition overrides.
 365       return true;
 366
 367     case UNDEF * 16 + WEAK_DEF:
 368     case WEAK_UNDEF * 16 + WEAK_DEF:
 369     case DYN_UNDEF * 16 + WEAK_DEF:
 370     case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
 371       // A weak definition of a currently undefined symbol.
 372       return true;
 373
 374     case COMMON * 16 + WEAK_DEF:
 375     case WEAK_COMMON * 16 + WEAK_DEF:
 376       // A weak definition does not override a common definition.
 377       return false;
 378
 379     case DYN_COMMON * 16 + WEAK_DEF:
 380     case DYN_WEAK_COMMON * 16 + WEAK_DEF:
 381       // A weak definition does override a definition in a dynamic
 382       // object.  FIXME: We should optionally issue a warning.
 383       return true;
 384
 385     case DEF * 16 + DYN_DEF:
 386     case WEAK_DEF * 16 + DYN_DEF:
 387     case DYN_DEF * 16 + DYN_DEF:
 388     case DYN_WEAK_DEF * 16 + DYN_DEF:
 389       // Ignore a dynamic definition if we already have a definition.
 390       return false;
 391
 392     case UNDEF * 16 + DYN_DEF:
 393     case WEAK_UNDEF * 16 + DYN_DEF:
 394     case DYN_UNDEF * 16 + DYN_DEF:
 395     case DYN_WEAK_UNDEF * 16 + DYN_DEF:
 396       // Use a dynamic definition if we have a reference.
 397       return true;
 398
 399     case COMMON * 16 + DYN_DEF:
 400     case WEAK_COMMON * 16 + DYN_DEF:
 401     case DYN_COMMON * 16 + DYN_DEF:
 402     case DYN_WEAK_COMMON * 16 + DYN_DEF:
 403       // Ignore a dynamic definition if we already have a common
 404       // definition.
 405       return false;
 406
 407     case DEF * 16 + DYN_WEAK_DEF:
 408     case WEAK_DEF * 16 + DYN_WEAK_DEF:
 409     case DYN_DEF * 16 + DYN_WEAK_DEF:
 410     case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
 411       // Ignore a weak dynamic definition if we already have a
 412       // definition.
 413       return false;
 414
 415     case UNDEF * 16 + DYN_WEAK_DEF:
 416     case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 417     case DYN_UNDEF * 16 + DYN_WEAK_DEF:
 418     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 419       // Use a weak dynamic definition if we have a reference.
 420       return true;
 421
 422     case COMMON * 16 + DYN_WEAK_DEF:
 423     case WEAK_COMMON * 16 + DYN_WEAK_DEF:
 424     case DYN_COMMON * 16 + DYN_WEAK_DEF:
 425     case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
 426       // Ignore a weak dynamic definition if we already have a common
 427       // definition.
 428       return false;
 429
 430     case DEF * 16 + UNDEF:
 431     case WEAK_DEF * 16 + UNDEF:
 432     case DYN_DEF * 16 + UNDEF:
 433     case DYN_WEAK_DEF * 16 + UNDEF:
 434     case UNDEF * 16 + UNDEF:
 435       // A new undefined reference tells us nothing.
 436       return false;
 437
 438     case WEAK_UNDEF * 16 + UNDEF:
 439     case DYN_UNDEF * 16 + UNDEF:
 440     case DYN_WEAK_UNDEF * 16 + UNDEF:
 441       // A strong undef overrides a dynamic or weak undef.
 442       return true;
 443
 444     case COMMON * 16 + UNDEF:
 445     case WEAK_COMMON * 16 + UNDEF:
 446     case DYN_COMMON * 16 + UNDEF:
 447     case DYN_WEAK_COMMON * 16 + UNDEF:
 448       // A new undefined reference tells us nothing.
 449       return false;
 450
 451     case DEF * 16 + WEAK_UNDEF:
 452     case WEAK_DEF * 16 + WEAK_UNDEF:
 453     case DYN_DEF * 16 + WEAK_UNDEF:
 454     case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
 455     case UNDEF * 16 + WEAK_UNDEF:
 456     case WEAK_UNDEF * 16 + WEAK_UNDEF:
 457     case DYN_UNDEF * 16 + WEAK_UNDEF:
 458     case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
 459     case COMMON * 16 + WEAK_UNDEF:
 460     case WEAK_COMMON * 16 + WEAK_UNDEF:
 461     case DYN_COMMON * 16 + WEAK_UNDEF:
 462     case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
 463       // A new weak undefined reference tells us nothing.
 464       return false;
 465
 466     case DEF * 16 + DYN_UNDEF:
 467     case WEAK_DEF * 16 + DYN_UNDEF:
 468     case DYN_DEF * 16 + DYN_UNDEF:
 469     case DYN_WEAK_DEF * 16 + DYN_UNDEF:
 470     case UNDEF * 16 + DYN_UNDEF:
 471     case WEAK_UNDEF * 16 + DYN_UNDEF:
 472     case DYN_UNDEF * 16 + DYN_UNDEF:
 473     case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
 474     case COMMON * 16 + DYN_UNDEF:
 475     case WEAK_COMMON * 16 + DYN_UNDEF:
 476     case DYN_COMMON * 16 + DYN_UNDEF:
 477     case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
 478       // A new dynamic undefined reference tells us nothing.
 479       return false;
 480
 481     case DEF * 16 + DYN_WEAK_UNDEF:
 482     case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 483     case DYN_DEF * 16 + DYN_WEAK_UNDEF:
 484     case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 485     case UNDEF * 16 + DYN_WEAK_UNDEF:
 486     case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 487     case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
 488     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 489     case COMMON * 16 + DYN_WEAK_UNDEF:
 490     case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 491     case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
 492     case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 493       // A new weak dynamic undefined reference tells us nothing.
 494       return false;
 495
 496     case DEF * 16 + COMMON:
 497       // A common symbol does not override a definition.
 498       return false;
 499
 500     case WEAK_DEF * 16 + COMMON:
 501     case DYN_DEF * 16 + COMMON:
 502     case DYN_WEAK_DEF * 16 + COMMON:
 503       // A common symbol does override a weak definition or a dynamic
 504       // definition.
 505       return true;
 506
 507     case UNDEF * 16 + COMMON:
 508     case WEAK_UNDEF * 16 + COMMON:
 509     case DYN_UNDEF * 16 + COMMON:
 510     case DYN_WEAK_UNDEF * 16 + COMMON:
 511       // A common symbol is a definition for a reference.
 512       return true;
 513
 514     case COMMON * 16 + COMMON:
 515       // Set the size to the maximum.
 516       *adjust_common_sizes = true;
 517       return false;
 518
 519     case WEAK_COMMON * 16 + COMMON:
 520       // I'm not sure just what a weak common symbol means, but
 521       // presumably it can be overridden by a regular common symbol.
 522       return true;
 523
 524     case DYN_COMMON * 16 + COMMON:
 525     case DYN_WEAK_COMMON * 16 + COMMON:
 526       // Use the real common symbol, but adjust the size if necessary.
 527       *adjust_common_sizes = true;
 528       return true;
 529
 530     case DEF * 16 + WEAK_COMMON:
 531     case WEAK_DEF * 16 + WEAK_COMMON:
 532     case DYN_DEF * 16 + WEAK_COMMON:
 533     case DYN_WEAK_DEF * 16 + WEAK_COMMON:
 534       // Whatever a weak common symbol is, it won't override a
 535       // definition.
 536       return false;
 537
 538     case UNDEF * 16 + WEAK_COMMON:
 539     case WEAK_UNDEF * 16 + WEAK_COMMON:
 540     case DYN_UNDEF * 16 + WEAK_COMMON:
 541     case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
 542       // A weak common symbol is better than an undefined symbol.
 543       return true;
 544
 545     case COMMON * 16 + WEAK_COMMON:
 546     case WEAK_COMMON * 16 + WEAK_COMMON:
 547     case DYN_COMMON * 16 + WEAK_COMMON:
 548     case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
 549       // Ignore a weak common symbol in the presence of a real common
 550       // symbol.
 551       return false;
 552
 553     case DEF * 16 + DYN_COMMON:
 554     case WEAK_DEF * 16 + DYN_COMMON:
 555     case DYN_DEF * 16 + DYN_COMMON:
 556     case DYN_WEAK_DEF * 16 + DYN_COMMON:
 557       // Ignore a dynamic common symbol in the presence of a
 558       // definition.
 559       return false;
 560
 561     case UNDEF * 16 + DYN_COMMON:
 562     case WEAK_UNDEF * 16 + DYN_COMMON:
 563     case DYN_UNDEF * 16 + DYN_COMMON:
 564     case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
 565       // A dynamic common symbol is a definition of sorts.
 566       return true;
 567
 568     case COMMON * 16 + DYN_COMMON:
 569     case WEAK_COMMON * 16 + DYN_COMMON:
 570     case DYN_COMMON * 16 + DYN_COMMON:
 571     case DYN_WEAK_COMMON * 16 + DYN_COMMON:
 572       // Set the size to the maximum.
 573       *adjust_common_sizes = true;
 574       return false;
 575
 576     case DEF * 16 + DYN_WEAK_COMMON:
 577     case WEAK_DEF * 16 + DYN_WEAK_COMMON:
 578     case DYN_DEF * 16 + DYN_WEAK_COMMON:
 579     case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
 580       // A common symbol is ignored in the face of a definition.
 581       return false;
 582
 583     case UNDEF * 16 + DYN_WEAK_COMMON:
 584     case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 585     case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
 586     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 587       // I guess a weak common symbol is better than a definition.
 588       return true;
 589
 590     case COMMON * 16 + DYN_WEAK_COMMON:
 591     case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 592     case DYN_COMMON * 16 + DYN_WEAK_COMMON:
 593     case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 594       // Set the size to the maximum.
 595       *adjust_common_sizes = true;
 596       return false;
 597
 598     default:
 599       gold_unreachable();
 600     }
 601 }
 602
 603 // A special case of should_override which is only called for a strong
 604 // defined symbol from a regular object file.  This is used when
 605 // defining special symbols.
 606
 607 bool
 608 Symbol_table::should_override_with_special(const Symbol* to)
 609 {
 610   bool adjust_common_sizes;
 611   unsigned int frombits = global_flag | regular_flag | def_flag;
 612   bool ret = Symbol_table::should_override(to, frombits, NULL,
 613                                            &adjust_common_sizes);
 614   gold_assert(!adjust_common_sizes);
 615   return ret;
 616 }
 617
 618 // Override symbol base with a special symbol.
 619
 620 void
 621 Symbol::override_base_with_special(const Symbol* from)
 622 {
 623   gold_assert(this->name_ == from->name_ || this->has_alias());
 624
 625   this->source_ = from->source_;
 626   switch (from->source_)
 627     {
 628     case FROM_OBJECT:
 629       this->u_.from_object = from->u_.from_object;
 630       break;
 631     case IN_OUTPUT_DATA:
 632       this->u_.in_output_data = from->u_.in_output_data;
 633       break;
 634     case IN_OUTPUT_SEGMENT:
 635       this->u_.in_output_segment = from->u_.in_output_segment;
 636       break;
 637     case CONSTANT:
 638       break;
 639     default:
 640       gold_unreachable();
 641       break;
 642     }
 643
 644   if (from->version_ != NULL && this->version_ != from->version_)
 645     {
 646       gold_assert(this->version_ == NULL);
 647       this->version_ = from->version_;
 648     }
 649
 650   this->type_ = from->type_;
 651   this->binding_ = from->binding_;
 652   this->visibility_ = from->visibility_;
 653   this->nonvis_ = from->nonvis_;
 654
 655   // Special symbols are always considered to be regular symbols.
 656   this->in_reg_ = true;
 657
 658   if (from->needs_dynsym_entry_)
 659     this->needs_dynsym_entry_ = true;
 660   if (from->needs_dynsym_value_)
 661     this->needs_dynsym_value_ = true;
 662
 663   // We shouldn't see these flags.  If we do, we need to handle them
 664   // somehow.
 665   gold_assert(!from->is_target_special_ || this->is_target_special_);
 666   gold_assert(!from->is_forwarder_);
 667   gold_assert(!from->has_got_offset_);
 668   gold_assert(!from->has_plt_offset_);
 669   gold_assert(!from->has_warning_);
 670   gold_assert(!from->is_copied_from_dynobj_);
 671 }
 672
 673 // Override a symbol with a special symbol.
 674
 675 template<int size>
 676 void
 677 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from)
 678 {
 679   this->override_base_with_special(from);
 680   this->value_ = from->value_;
 681   this->symsize_ = from->symsize_;
 682 }
 683
 684 // Override TOSYM with the special symbol FROMSYM.  This handles all
 685 // aliases of TOSYM.
 686
 687 template<int size>
 688 void
 689 Symbol_table::override_with_special(Sized_symbol<size>* tosym,
 690                                     const Sized_symbol<size>* fromsym)
 691 {
 692   tosym->override_with_special(fromsym);
 693   if (tosym->has_alias())
 694     {
 695       Symbol* sym = this->weak_aliases_[tosym];
 696       gold_assert(sym != NULL);
 697       Sized_symbol<size>* ssym;
 698       ssym = this->get_sized_symbol SELECT_SIZE_NAME(size) (sym
 699                                                             SELECT_SIZE(size));
 700       do
 701         {
 702           ssym->override_with_special(fromsym);
 703           sym = this->weak_aliases_[ssym];
 704           gold_assert(sym != NULL);
 705           ssym = this->get_sized_symbol SELECT_SIZE_NAME(size) (
 706                                                 sym SELECT_SIZE(size));
 707         }
 708       while (ssym != tosym);
 709     }
 710 }
 711
 712 // Instantiate the templates we need.  We could use the configure
 713 // script to restrict this to only the ones needed for implemented
 714 // targets.
 715
 716 #ifdef HAVE_TARGET_32_LITTLE
 717 template
 718 void
 719 Symbol_table::resolve<32, false>(
 720     Sized_symbol<32>* to,
 721     const elfcpp::Sym<32, false>& sym,
 722     Object* object,
 723     const char* version);
 724 #endif
 725
 726 #ifdef HAVE_TARGET_32_BIG
 727 template
 728 void
 729 Symbol_table::resolve<32, true>(
 730     Sized_symbol<32>* to,
 731     const elfcpp::Sym<32, true>& sym,
 732     Object* object,
 733     const char* version);
 734 #endif
 735
 736 #ifdef HAVE_TARGET_64_LITTLE
 737 template
 738 void
 739 Symbol_table::resolve<64, false>(
 740     Sized_symbol<64>* to,
 741     const elfcpp::Sym<64, false>& sym,
 742     Object* object,
 743     const char* version);
 744 #endif
 745
 746 #ifdef HAVE_TARGET_64_BIG
 747 template
 748 void
 749 Symbol_table::resolve<64, true>(
 750     Sized_symbol<64>* to,
 751     const elfcpp::Sym<64, true>& sym,
 752     Object* object,
 753     const char* version);
 754 #endif
 755
 756 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
 757 template
 758 void
 759 Symbol_table::override_with_special<32>(Sized_symbol<32>*,
 760                                         const Sized_symbol<32>*);
 761 #endif
 762
 763 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
 764 template
 765 void
 766 Symbol_table::override_with_special<64>(Sized_symbol<64>*,
 767                                         const Sized_symbol<64>*);
 768 #endif
 769
 770 } // End namespace gold.