gold/resolve.cc

   1 // resolve.cc -- symbol resolution for gold
   2
   3 // Copyright 2006, 2007, 2008, 2009 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       bits = global_flag;
 182       break;
 183
 184     case elfcpp::STB_WEAK:
 185       bits = weak_flag;
 186       break;
 187
 188     case elfcpp::STB_LOCAL:
 189       // We should only see externally visible symbols in the symbol
 190       // table.
 191       gold_error(_("invalid STB_LOCAL symbol in external symbols"));
 192       bits = global_flag;
 193
 194     default:
 195       // Any target which wants to handle STB_LOOS, etc., needs to
 196       // define a resolve method.
 197       gold_error(_("unsupported symbol binding"));
 198       bits = global_flag;
 199     }
 200
 201   if (is_dynamic)
 202     bits |= dynamic_flag;
 203   else
 204     bits |= regular_flag;
 205
 206   switch (shndx)
 207     {
 208     case elfcpp::SHN_UNDEF:
 209       bits |= undef_flag;
 210       break;
 211
 212     case elfcpp::SHN_COMMON:
 213       if (!is_ordinary)
 214         bits |= common_flag;
 215       break;
 216
 217     default:
 218       if (type == elfcpp::STT_COMMON)
 219         bits |= common_flag;
 220       else if (!is_ordinary && Symbol::is_common_shndx(shndx))
 221         bits |= common_flag;
 222       else
 223         bits |= def_flag;
 224       break;
 225     }
 226
 227   return bits;
 228 }
 229
 230 // Resolve a symbol.  This is called the second and subsequent times
 231 // we see a symbol.  TO is the pre-existing symbol.  ST_SHNDX is the
 232 // section index for SYM, possibly adjusted for many sections.
 233 // IS_ORDINARY is whether ST_SHNDX is a normal section index rather
 234 // than a special code.  ORIG_ST_SHNDX is the original section index,
 235 // before any munging because of discarded sections, except that all
 236 // non-ordinary section indexes are mapped to SHN_UNDEF.  VERSION is
 237 // the version of SYM.
 238
 239 template<int size, bool big_endian>
 240 void
 241 Symbol_table::resolve(Sized_symbol<size>* to,
 242                       const elfcpp::Sym<size, big_endian>& sym,
 243                       unsigned int st_shndx, bool is_ordinary,
 244                       unsigned int orig_st_shndx,
 245                       Object* object, const char* version)
 246 {
 247   if (parameters->target().has_resolve())
 248     {
 249       Sized_target<size, big_endian>* sized_target;
 250       sized_target = parameters->sized_target<size, big_endian>();
 251       sized_target->resolve(to, sym, object, version);
 252       return;
 253     }
 254
 255   if (!object->is_dynamic())
 256     {
 257       // Record that we've seen this symbol in a regular object.
 258       to->set_in_reg();
 259     }
 260   else if (st_shndx == elfcpp::SHN_UNDEF
 261            && (to->visibility() == elfcpp::STV_HIDDEN
 262                || to->visibility() == elfcpp::STV_INTERNAL))
 263     {
 264       // A dynamic object cannot reference a hidden or internal symbol
 265       // defined in another object.
 266       gold_warning(_("%s symbol '%s' in %s is referenced by DSO %s"),
 267                    (to->visibility() == elfcpp::STV_HIDDEN
 268                     ? "hidden"
 269                     : "internal"),
 270                    to->demangled_name().c_str(),
 271                    to->object()->name().c_str(),
 272                    object->name().c_str());
 273       return;
 274     }
 275   else
 276     {
 277       // Record that we've seen this symbol in a dynamic object.
 278       to->set_in_dyn();
 279     }
 280
 281   // Record if we've seen this symbol in a real ELF object (i.e., the
 282   // symbol is referenced from outside the world known to the plugin).
 283   if (object->pluginobj() == NULL)
 284     to->set_in_real_elf();
 285
 286   // If we're processing replacement files, allow new symbols to override
 287   // the placeholders from the plugin objects.
 288   if (to->source() == Symbol::FROM_OBJECT)
 289     {
 290       Pluginobj* obj = to->object()->pluginobj();
 291       if (obj != NULL
 292           && parameters->options().plugins()->in_replacement_phase())
 293         {
 294           this->override(to, sym, st_shndx, is_ordinary, object, version);
 295           return;
 296         }
 297     }
 298
 299   unsigned int frombits = symbol_to_bits(sym.get_st_bind(),
 300                                          object->is_dynamic(),
 301                                          st_shndx, is_ordinary,
 302                                          sym.get_st_type());
 303
 304   bool adjust_common_sizes;
 305   if (Symbol_table::should_override(to, frombits, object,
 306                                     &adjust_common_sizes))
 307     {
 308       typename Sized_symbol<size>::Size_type tosize = to->symsize();
 309
 310       this->override(to, sym, st_shndx, is_ordinary, object, version);
 311
 312       if (adjust_common_sizes && tosize > to->symsize())
 313         to->set_symsize(tosize);
 314     }
 315   else
 316     {
 317       if (adjust_common_sizes && sym.get_st_size() > to->symsize())
 318         to->set_symsize(sym.get_st_size());
 319       // The ELF ABI says that even for a reference to a symbol we
 320       // merge the visibility.
 321       to->override_visibility(sym.get_st_visibility());
 322     }
 323
 324   // A new weak undefined reference, merging with an old weak
 325   // reference, could be a One Definition Rule (ODR) violation --
 326   // especially if the types or sizes of the references differ.  We'll
 327   // store such pairs and look them up later to make sure they
 328   // actually refer to the same lines of code.  (Note: not all ODR
 329   // violations can be found this way, and not everything this finds
 330   // is an ODR violation.  But it's helpful to warn about.)
 331   bool to_is_ordinary;
 332   if (parameters->options().detect_odr_violations()
 333       && sym.get_st_bind() == elfcpp::STB_WEAK
 334       && to->binding() == elfcpp::STB_WEAK
 335       && orig_st_shndx != elfcpp::SHN_UNDEF
 336       && to->shndx(&to_is_ordinary) != elfcpp::SHN_UNDEF
 337       && to_is_ordinary
 338       && sym.get_st_size() != 0    // Ignore weird 0-sized symbols.
 339       && to->symsize() != 0
 340       && (sym.get_st_type() != to->type()
 341           || sym.get_st_size() != to->symsize())
 342       // C does not have a concept of ODR, so we only need to do this
 343       // on C++ symbols.  These have (mangled) names starting with _Z.
 344       && to->name()[0] == '_' && to->name()[1] == 'Z')
 345     {
 346       Symbol_location fromloc
 347           = { object, orig_st_shndx, sym.get_st_value() };
 348       Symbol_location toloc = { to->object(), to->shndx(&to_is_ordinary),
 349                                 to->value() };
 350       this->candidate_odr_violations_[to->name()].insert(fromloc);
 351       this->candidate_odr_violations_[to->name()].insert(toloc);
 352     }
 353 }
 354
 355 // Handle the core of symbol resolution.  This is called with the
 356 // existing symbol, TO, and a bitflag describing the new symbol.  This
 357 // returns true if we should override the existing symbol with the new
 358 // one, and returns false otherwise.  It sets *ADJUST_COMMON_SIZES to
 359 // true if we should set the symbol size to the maximum of the TO and
 360 // FROM sizes.  It handles error conditions.
 361
 362 bool
 363 Symbol_table::should_override(const Symbol* to, unsigned int frombits,
 364                               Object* object, bool* adjust_common_sizes)
 365 {
 366   *adjust_common_sizes = false;
 367
 368   unsigned int tobits;
 369   if (to->source() == Symbol::IS_UNDEFINED)
 370     tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_UNDEF, true,
 371                             to->type());
 372   else if (to->source() != Symbol::FROM_OBJECT)
 373     tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_ABS, false,
 374                             to->type());
 375   else
 376     {
 377       bool is_ordinary;
 378       unsigned int shndx = to->shndx(&is_ordinary);
 379       tobits = symbol_to_bits(to->binding(),
 380                               to->object()->is_dynamic(),
 381                               shndx,
 382                               is_ordinary,
 383                               to->type());
 384     }
 385
 386   // FIXME: Warn if either but not both of TO and SYM are STT_TLS.
 387
 388   // We use a giant switch table for symbol resolution.  This code is
 389   // unwieldy, but: 1) it is efficient; 2) we definitely handle all
 390   // cases; 3) it is easy to change the handling of a particular case.
 391   // The alternative would be a series of conditionals, but it is easy
 392   // to get the ordering wrong.  This could also be done as a table,
 393   // but that is no easier to understand than this large switch
 394   // statement.
 395
 396   // These are the values generated by the bit codes.
 397   enum
 398   {
 399     DEF =              global_flag | regular_flag | def_flag,
 400     WEAK_DEF =         weak_flag   | regular_flag | def_flag,
 401     DYN_DEF =          global_flag | dynamic_flag | def_flag,
 402     DYN_WEAK_DEF =     weak_flag   | dynamic_flag | def_flag,
 403     UNDEF =            global_flag | regular_flag | undef_flag,
 404     WEAK_UNDEF =       weak_flag   | regular_flag | undef_flag,
 405     DYN_UNDEF =        global_flag | dynamic_flag | undef_flag,
 406     DYN_WEAK_UNDEF =   weak_flag   | dynamic_flag | undef_flag,
 407     COMMON =           global_flag | regular_flag | common_flag,
 408     WEAK_COMMON =      weak_flag   | regular_flag | common_flag,
 409     DYN_COMMON =       global_flag | dynamic_flag | common_flag,
 410     DYN_WEAK_COMMON =  weak_flag   | dynamic_flag | common_flag
 411   };
 412
 413   switch (tobits * 16 + frombits)
 414     {
 415     case DEF * 16 + DEF:
 416       // Two definitions of the same symbol.
 417
 418       // If either symbol is defined by an object included using
 419       // --just-symbols, then don't warn.  This is for compatibility
 420       // with the GNU linker.  FIXME: This is a hack.
 421       if ((to->source() == Symbol::FROM_OBJECT && to->object()->just_symbols())
 422           || object->just_symbols())
 423         return false;
 424
 425       // FIXME: Do a better job of reporting locations.
 426       gold_error(_("%s: multiple definition of %s"),
 427                  object != NULL ? object->name().c_str() : _("command line"),
 428                  to->demangled_name().c_str());
 429       gold_error(_("%s: previous definition here"),
 430                  (to->source() == Symbol::FROM_OBJECT
 431                   ? to->object()->name().c_str()
 432                   : _("command line")));
 433       return false;
 434
 435     case WEAK_DEF * 16 + DEF:
 436       // We've seen a weak definition, and now we see a strong
 437       // definition.  In the original SVR4 linker, this was treated as
 438       // a multiple definition error.  In the Solaris linker and the
 439       // GNU linker, a weak definition followed by a regular
 440       // definition causes the weak definition to be overridden.  We
 441       // are currently compatible with the GNU linker.  In the future
 442       // we should add a target specific option to change this.
 443       // FIXME.
 444       return true;
 445
 446     case DYN_DEF * 16 + DEF:
 447     case DYN_WEAK_DEF * 16 + DEF:
 448       // We've seen a definition in a dynamic object, and now we see a
 449       // definition in a regular object.  The definition in the
 450       // regular object overrides the definition in the dynamic
 451       // object.
 452       return true;
 453
 454     case UNDEF * 16 + DEF:
 455     case WEAK_UNDEF * 16 + DEF:
 456     case DYN_UNDEF * 16 + DEF:
 457     case DYN_WEAK_UNDEF * 16 + DEF:
 458       // We've seen an undefined reference, and now we see a
 459       // definition.  We use the definition.
 460       return true;
 461
 462     case COMMON * 16 + DEF:
 463     case WEAK_COMMON * 16 + DEF:
 464     case DYN_COMMON * 16 + DEF:
 465     case DYN_WEAK_COMMON * 16 + DEF:
 466       // We've seen a common symbol and now we see a definition.  The
 467       // definition overrides.  FIXME: We should optionally issue, version a
 468       // warning.
 469       return true;
 470
 471     case DEF * 16 + WEAK_DEF:
 472     case WEAK_DEF * 16 + WEAK_DEF:
 473       // We've seen a definition and now we see a weak definition.  We
 474       // ignore the new weak definition.
 475       return false;
 476
 477     case DYN_DEF * 16 + WEAK_DEF:
 478     case DYN_WEAK_DEF * 16 + WEAK_DEF:
 479       // We've seen a dynamic definition and now we see a regular weak
 480       // definition.  The regular weak definition overrides.
 481       return true;
 482
 483     case UNDEF * 16 + WEAK_DEF:
 484     case WEAK_UNDEF * 16 + WEAK_DEF:
 485     case DYN_UNDEF * 16 + WEAK_DEF:
 486     case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
 487       // A weak definition of a currently undefined symbol.
 488       return true;
 489
 490     case COMMON * 16 + WEAK_DEF:
 491     case WEAK_COMMON * 16 + WEAK_DEF:
 492       // A weak definition does not override a common definition.
 493       return false;
 494
 495     case DYN_COMMON * 16 + WEAK_DEF:
 496     case DYN_WEAK_COMMON * 16 + WEAK_DEF:
 497       // A weak definition does override a definition in a dynamic
 498       // object.  FIXME: We should optionally issue a warning.
 499       return true;
 500
 501     case DEF * 16 + DYN_DEF:
 502     case WEAK_DEF * 16 + DYN_DEF:
 503     case DYN_DEF * 16 + DYN_DEF:
 504     case DYN_WEAK_DEF * 16 + DYN_DEF:
 505       // Ignore a dynamic definition if we already have a definition.
 506       return false;
 507
 508     case UNDEF * 16 + DYN_DEF:
 509     case WEAK_UNDEF * 16 + DYN_DEF:
 510     case DYN_UNDEF * 16 + DYN_DEF:
 511     case DYN_WEAK_UNDEF * 16 + DYN_DEF:
 512       // Use a dynamic definition if we have a reference.
 513       return true;
 514
 515     case COMMON * 16 + DYN_DEF:
 516     case WEAK_COMMON * 16 + DYN_DEF:
 517     case DYN_COMMON * 16 + DYN_DEF:
 518     case DYN_WEAK_COMMON * 16 + DYN_DEF:
 519       // Ignore a dynamic definition if we already have a common
 520       // definition.
 521       return false;
 522
 523     case DEF * 16 + DYN_WEAK_DEF:
 524     case WEAK_DEF * 16 + DYN_WEAK_DEF:
 525     case DYN_DEF * 16 + DYN_WEAK_DEF:
 526     case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
 527       // Ignore a weak dynamic definition if we already have a
 528       // definition.
 529       return false;
 530
 531     case UNDEF * 16 + DYN_WEAK_DEF:
 532     case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 533     case DYN_UNDEF * 16 + DYN_WEAK_DEF:
 534     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 535       // Use a weak dynamic definition if we have a reference.
 536       return true;
 537
 538     case COMMON * 16 + DYN_WEAK_DEF:
 539     case WEAK_COMMON * 16 + DYN_WEAK_DEF:
 540     case DYN_COMMON * 16 + DYN_WEAK_DEF:
 541     case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
 542       // Ignore a weak dynamic definition if we already have a common
 543       // definition.
 544       return false;
 545
 546     case DEF * 16 + UNDEF:
 547     case WEAK_DEF * 16 + UNDEF:
 548     case DYN_DEF * 16 + UNDEF:
 549     case DYN_WEAK_DEF * 16 + UNDEF:
 550     case UNDEF * 16 + UNDEF:
 551       // A new undefined reference tells us nothing.
 552       return false;
 553
 554     case WEAK_UNDEF * 16 + UNDEF:
 555     case DYN_UNDEF * 16 + UNDEF:
 556     case DYN_WEAK_UNDEF * 16 + UNDEF:
 557       // A strong undef overrides a dynamic or weak undef.
 558       return true;
 559
 560     case COMMON * 16 + UNDEF:
 561     case WEAK_COMMON * 16 + UNDEF:
 562     case DYN_COMMON * 16 + UNDEF:
 563     case DYN_WEAK_COMMON * 16 + UNDEF:
 564       // A new undefined reference tells us nothing.
 565       return false;
 566
 567     case DEF * 16 + WEAK_UNDEF:
 568     case WEAK_DEF * 16 + WEAK_UNDEF:
 569     case DYN_DEF * 16 + WEAK_UNDEF:
 570     case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
 571     case UNDEF * 16 + WEAK_UNDEF:
 572     case WEAK_UNDEF * 16 + WEAK_UNDEF:
 573     case DYN_UNDEF * 16 + WEAK_UNDEF:
 574     case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
 575     case COMMON * 16 + WEAK_UNDEF:
 576     case WEAK_COMMON * 16 + WEAK_UNDEF:
 577     case DYN_COMMON * 16 + WEAK_UNDEF:
 578     case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
 579       // A new weak undefined reference tells us nothing.
 580       return false;
 581
 582     case DEF * 16 + DYN_UNDEF:
 583     case WEAK_DEF * 16 + DYN_UNDEF:
 584     case DYN_DEF * 16 + DYN_UNDEF:
 585     case DYN_WEAK_DEF * 16 + DYN_UNDEF:
 586     case UNDEF * 16 + DYN_UNDEF:
 587     case WEAK_UNDEF * 16 + DYN_UNDEF:
 588     case DYN_UNDEF * 16 + DYN_UNDEF:
 589     case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
 590     case COMMON * 16 + DYN_UNDEF:
 591     case WEAK_COMMON * 16 + DYN_UNDEF:
 592     case DYN_COMMON * 16 + DYN_UNDEF:
 593     case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
 594       // A new dynamic undefined reference tells us nothing.
 595       return false;
 596
 597     case DEF * 16 + DYN_WEAK_UNDEF:
 598     case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 599     case DYN_DEF * 16 + DYN_WEAK_UNDEF:
 600     case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 601     case UNDEF * 16 + DYN_WEAK_UNDEF:
 602     case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 603     case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
 604     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 605     case COMMON * 16 + DYN_WEAK_UNDEF:
 606     case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 607     case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
 608     case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 609       // A new weak dynamic undefined reference tells us nothing.
 610       return false;
 611
 612     case DEF * 16 + COMMON:
 613       // A common symbol does not override a definition.
 614       return false;
 615
 616     case WEAK_DEF * 16 + COMMON:
 617     case DYN_DEF * 16 + COMMON:
 618     case DYN_WEAK_DEF * 16 + COMMON:
 619       // A common symbol does override a weak definition or a dynamic
 620       // definition.
 621       return true;
 622
 623     case UNDEF * 16 + COMMON:
 624     case WEAK_UNDEF * 16 + COMMON:
 625     case DYN_UNDEF * 16 + COMMON:
 626     case DYN_WEAK_UNDEF * 16 + COMMON:
 627       // A common symbol is a definition for a reference.
 628       return true;
 629
 630     case COMMON * 16 + COMMON:
 631       // Set the size to the maximum.
 632       *adjust_common_sizes = true;
 633       return false;
 634
 635     case WEAK_COMMON * 16 + COMMON:
 636       // I'm not sure just what a weak common symbol means, but
 637       // presumably it can be overridden by a regular common symbol.
 638       return true;
 639
 640     case DYN_COMMON * 16 + COMMON:
 641     case DYN_WEAK_COMMON * 16 + COMMON:
 642       // Use the real common symbol, but adjust the size if necessary.
 643       *adjust_common_sizes = true;
 644       return true;
 645
 646     case DEF * 16 + WEAK_COMMON:
 647     case WEAK_DEF * 16 + WEAK_COMMON:
 648     case DYN_DEF * 16 + WEAK_COMMON:
 649     case DYN_WEAK_DEF * 16 + WEAK_COMMON:
 650       // Whatever a weak common symbol is, it won't override a
 651       // definition.
 652       return false;
 653
 654     case UNDEF * 16 + WEAK_COMMON:
 655     case WEAK_UNDEF * 16 + WEAK_COMMON:
 656     case DYN_UNDEF * 16 + WEAK_COMMON:
 657     case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
 658       // A weak common symbol is better than an undefined symbol.
 659       return true;
 660
 661     case COMMON * 16 + WEAK_COMMON:
 662     case WEAK_COMMON * 16 + WEAK_COMMON:
 663     case DYN_COMMON * 16 + WEAK_COMMON:
 664     case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
 665       // Ignore a weak common symbol in the presence of a real common
 666       // symbol.
 667       return false;
 668
 669     case DEF * 16 + DYN_COMMON:
 670     case WEAK_DEF * 16 + DYN_COMMON:
 671     case DYN_DEF * 16 + DYN_COMMON:
 672     case DYN_WEAK_DEF * 16 + DYN_COMMON:
 673       // Ignore a dynamic common symbol in the presence of a
 674       // definition.
 675       return false;
 676
 677     case UNDEF * 16 + DYN_COMMON:
 678     case WEAK_UNDEF * 16 + DYN_COMMON:
 679     case DYN_UNDEF * 16 + DYN_COMMON:
 680     case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
 681       // A dynamic common symbol is a definition of sorts.
 682       return true;
 683
 684     case COMMON * 16 + DYN_COMMON:
 685     case WEAK_COMMON * 16 + DYN_COMMON:
 686     case DYN_COMMON * 16 + DYN_COMMON:
 687     case DYN_WEAK_COMMON * 16 + DYN_COMMON:
 688       // Set the size to the maximum.
 689       *adjust_common_sizes = true;
 690       return false;
 691
 692     case DEF * 16 + DYN_WEAK_COMMON:
 693     case WEAK_DEF * 16 + DYN_WEAK_COMMON:
 694     case DYN_DEF * 16 + DYN_WEAK_COMMON:
 695     case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
 696       // A common symbol is ignored in the face of a definition.
 697       return false;
 698
 699     case UNDEF * 16 + DYN_WEAK_COMMON:
 700     case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 701     case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
 702     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 703       // I guess a weak common symbol is better than a definition.
 704       return true;
 705
 706     case COMMON * 16 + DYN_WEAK_COMMON:
 707     case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 708     case DYN_COMMON * 16 + DYN_WEAK_COMMON:
 709     case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 710       // Set the size to the maximum.
 711       *adjust_common_sizes = true;
 712       return false;
 713
 714     default:
 715       gold_unreachable();
 716     }
 717 }
 718
 719 // A special case of should_override which is only called for a strong
 720 // defined symbol from a regular object file.  This is used when
 721 // defining special symbols.
 722
 723 bool
 724 Symbol_table::should_override_with_special(const Symbol* to)
 725 {
 726   bool adjust_common_sizes;
 727   unsigned int frombits = global_flag | regular_flag | def_flag;
 728   bool ret = Symbol_table::should_override(to, frombits, NULL,
 729                                            &adjust_common_sizes);
 730   gold_assert(!adjust_common_sizes);
 731   return ret;
 732 }
 733
 734 // Override symbol base with a special symbol.
 735
 736 void
 737 Symbol::override_base_with_special(const Symbol* from)
 738 {
 739   gold_assert(this->name_ == from->name_ || this->has_alias());
 740
 741   this->source_ = from->source_;
 742   switch (from->source_)
 743     {
 744     case FROM_OBJECT:
 745       this->u_.from_object = from->u_.from_object;
 746       break;
 747     case IN_OUTPUT_DATA:
 748       this->u_.in_output_data = from->u_.in_output_data;
 749       break;
 750     case IN_OUTPUT_SEGMENT:
 751       this->u_.in_output_segment = from->u_.in_output_segment;
 752       break;
 753     case IS_CONSTANT:
 754     case IS_UNDEFINED:
 755       break;
 756     default:
 757       gold_unreachable();
 758       break;
 759     }
 760
 761   this->override_version(from->version_);
 762   this->type_ = from->type_;
 763   this->binding_ = from->binding_;
 764   this->override_visibility(from->visibility_);
 765   this->nonvis_ = from->nonvis_;
 766
 767   // Special symbols are always considered to be regular symbols.
 768   this->in_reg_ = true;
 769
 770   if (from->needs_dynsym_entry_)
 771     this->needs_dynsym_entry_ = true;
 772   if (from->needs_dynsym_value_)
 773     this->needs_dynsym_value_ = true;
 774
 775   // We shouldn't see these flags.  If we do, we need to handle them
 776   // somehow.
 777   gold_assert(!from->is_target_special_ || this->is_target_special_);
 778   gold_assert(!from->is_forwarder_);
 779   gold_assert(!from->has_plt_offset_);
 780   gold_assert(!from->has_warning_);
 781   gold_assert(!from->is_copied_from_dynobj_);
 782   gold_assert(!from->is_forced_local_);
 783 }
 784
 785 // Override a symbol with a special symbol.
 786
 787 template<int size>
 788 void
 789 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from)
 790 {
 791   this->override_base_with_special(from);
 792   this->value_ = from->value_;
 793   this->symsize_ = from->symsize_;
 794 }
 795
 796 // Override TOSYM with the special symbol FROMSYM.  This handles all
 797 // aliases of TOSYM.
 798
 799 template<int size>
 800 void
 801 Symbol_table::override_with_special(Sized_symbol<size>* tosym,
 802                                     const Sized_symbol<size>* fromsym)
 803 {
 804   tosym->override_with_special(fromsym);
 805   if (tosym->has_alias())
 806     {
 807       Symbol* sym = this->weak_aliases_[tosym];
 808       gold_assert(sym != NULL);
 809       Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
 810       do
 811         {
 812           ssym->override_with_special(fromsym);
 813           sym = this->weak_aliases_[ssym];
 814           gold_assert(sym != NULL);
 815           ssym = this->get_sized_symbol<size>(sym);
 816         }
 817       while (ssym != tosym);
 818     }
 819   if (tosym->binding() == elfcpp::STB_LOCAL
 820       || ((tosym->visibility() == elfcpp::STV_HIDDEN
 821            || tosym->visibility() == elfcpp::STV_INTERNAL)
 822           && (tosym->binding() == elfcpp::STB_GLOBAL
 823               || tosym->binding() == elfcpp::STB_WEAK)
 824           && !parameters->options().relocatable()))
 825     this->force_local(tosym);
 826 }
 827
 828 // Instantiate the templates we need.  We could use the configure
 829 // script to restrict this to only the ones needed for implemented
 830 // targets.
 831
 832 #ifdef HAVE_TARGET_32_LITTLE
 833 template
 834 void
 835 Symbol_table::resolve<32, false>(
 836     Sized_symbol<32>* to,
 837     const elfcpp::Sym<32, false>& sym,
 838     unsigned int st_shndx,
 839     bool is_ordinary,
 840     unsigned int orig_st_shndx,
 841     Object* object,
 842     const char* version);
 843 #endif
 844
 845 #ifdef HAVE_TARGET_32_BIG
 846 template
 847 void
 848 Symbol_table::resolve<32, true>(
 849     Sized_symbol<32>* to,
 850     const elfcpp::Sym<32, true>& sym,
 851     unsigned int st_shndx,
 852     bool is_ordinary,
 853     unsigned int orig_st_shndx,
 854     Object* object,
 855     const char* version);
 856 #endif
 857
 858 #ifdef HAVE_TARGET_64_LITTLE
 859 template
 860 void
 861 Symbol_table::resolve<64, false>(
 862     Sized_symbol<64>* to,
 863     const elfcpp::Sym<64, false>& sym,
 864     unsigned int st_shndx,
 865     bool is_ordinary,
 866     unsigned int orig_st_shndx,
 867     Object* object,
 868     const char* version);
 869 #endif
 870
 871 #ifdef HAVE_TARGET_64_BIG
 872 template
 873 void
 874 Symbol_table::resolve<64, true>(
 875     Sized_symbol<64>* to,
 876     const elfcpp::Sym<64, true>& sym,
 877     unsigned int st_shndx,
 878     bool is_ordinary,
 879     unsigned int orig_st_shndx,
 880     Object* object,
 881     const char* version);
 882 #endif
 883
 884 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
 885 template
 886 void
 887 Symbol_table::override_with_special<32>(Sized_symbol<32>*,
 888                                         const Sized_symbol<32>*);
 889 #endif
 890
 891 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
 892 template
 893 void
 894 Symbol_table::override_with_special<64>(Sized_symbol<64>*,
 895                                         const Sized_symbol<64>*);
 896 #endif
 897
 898 } // End namespace gold.