gold/resolve.cc

   1 // resolve.cc -- symbol resolution for gold
   2
   3 // Copyright 2006, 2007, 2008 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 // This symbol is being overridden by another symbol whose version is
  36 // VERSION.  Update the VERSION_ field accordingly.
  37
  38 inline void
  39 Symbol::override_version(const char* version)
  40 {
  41   if (version == NULL)
  42     {
  43       // This is the case where this symbol is NAME/VERSION, and the
  44       // version was not marked as hidden.  That makes it the default
  45       // version, so we create NAME/NULL.  Later we see another symbol
  46       // NAME/NULL, and that symbol is overriding this one.  In this
  47       // case, since NAME/VERSION is the default, we make NAME/NULL
  48       // override NAME/VERSION as well.  They are already the same
  49       // Symbol structure.  Setting the VERSION_ field to NULL ensures
  50       // that it will be output with the correct, empty, version.
  51       this->version_ = version;
  52     }
  53   else
  54     {
  55       // This is the case where this symbol is NAME/VERSION_ONE, and
  56       // now we see NAME/VERSION_TWO, and NAME/VERSION_TWO is
  57       // overriding NAME.  If VERSION_ONE and VERSION_TWO are
  58       // different, then this can only happen when VERSION_ONE is NULL
  59       // and VERSION_TWO is not hidden.
  60       gold_assert(this->version_ == version || this->version_ == NULL);
  61       this->version_ = version;
  62     }
  63 }
  64
  65 // Override the fields in Symbol.
  66
  67 template<int size, bool big_endian>
  68 void
  69 Symbol::override_base(const elfcpp::Sym<size, big_endian>& sym,
  70                       unsigned int st_shndx, bool is_ordinary,
  71                       Object* object, const char* version)
  72 {
  73   gold_assert(this->source_ == FROM_OBJECT);
  74   this->u_.from_object.object = object;
  75   this->override_version(version);
  76   this->u_.from_object.shndx = st_shndx;
  77   this->is_ordinary_shndx_ = is_ordinary;
  78   this->type_ = sym.get_st_type();
  79   this->binding_ = sym.get_st_bind();
  80   this->visibility_ = sym.get_st_visibility();
  81   this->nonvis_ = sym.get_st_nonvis();
  82   if (object->is_dynamic())
  83     this->in_dyn_ = true;
  84   else
  85     this->in_reg_ = true;
  86 }
  87
  88 // Override the fields in Sized_symbol.
  89
  90 template<int size>
  91 template<bool big_endian>
  92 void
  93 Sized_symbol<size>::override(const elfcpp::Sym<size, big_endian>& sym,
  94                              unsigned st_shndx, bool is_ordinary,
  95                              Object* object, const char* version)
  96 {
  97   this->override_base(sym, st_shndx, is_ordinary, object, version);
  98   this->value_ = sym.get_st_value();
  99   this->symsize_ = sym.get_st_size();
 100 }
 101
 102 // Override TOSYM with symbol FROMSYM, defined in OBJECT, with version
 103 // VERSION.  This handles all aliases of TOSYM.
 104
 105 template<int size, bool big_endian>
 106 void
 107 Symbol_table::override(Sized_symbol<size>* tosym,
 108                        const elfcpp::Sym<size, big_endian>& fromsym,
 109                        unsigned int st_shndx, bool is_ordinary,
 110                        Object* object, const char* version)
 111 {
 112   tosym->override(fromsym, st_shndx, is_ordinary, object, version);
 113   if (tosym->has_alias())
 114     {
 115       Symbol* sym = this->weak_aliases_[tosym];
 116       gold_assert(sym != NULL);
 117       Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
 118       do
 119         {
 120           ssym->override(fromsym, st_shndx, is_ordinary, object, version);
 121           sym = this->weak_aliases_[ssym];
 122           gold_assert(sym != NULL);
 123           ssym = this->get_sized_symbol<size>(sym);
 124         }
 125       while (ssym != tosym);
 126     }
 127 }
 128
 129 // The resolve functions build a little code for each symbol.
 130 // Bit 0: 0 for global, 1 for weak.
 131 // Bit 1: 0 for regular object, 1 for shared object
 132 // Bits 2-3: 0 for normal, 1 for undefined, 2 for common
 133 // This gives us values from 0 to 11.
 134
 135 static const int global_or_weak_shift = 0;
 136 static const unsigned int global_flag = 0 << global_or_weak_shift;
 137 static const unsigned int weak_flag = 1 << global_or_weak_shift;
 138
 139 static const int regular_or_dynamic_shift = 1;
 140 static const unsigned int regular_flag = 0 << regular_or_dynamic_shift;
 141 static const unsigned int dynamic_flag = 1 << regular_or_dynamic_shift;
 142
 143 static const int def_undef_or_common_shift = 2;
 144 static const unsigned int def_flag = 0 << def_undef_or_common_shift;
 145 static const unsigned int undef_flag = 1 << def_undef_or_common_shift;
 146 static const unsigned int common_flag = 2 << def_undef_or_common_shift;
 147
 148 // This convenience function combines all the flags based on facts
 149 // about the symbol.
 150
 151 static unsigned int
 152 symbol_to_bits(elfcpp::STB binding, bool is_dynamic,
 153                unsigned int shndx, bool is_ordinary, elfcpp::STT type)
 154 {
 155   unsigned int bits;
 156
 157   switch (binding)
 158     {
 159     case elfcpp::STB_GLOBAL:
 160       bits = global_flag;
 161       break;
 162
 163     case elfcpp::STB_WEAK:
 164       bits = weak_flag;
 165       break;
 166
 167     case elfcpp::STB_LOCAL:
 168       // We should only see externally visible symbols in the symbol
 169       // table.
 170       gold_error(_("invalid STB_LOCAL symbol in external symbols"));
 171       bits = global_flag;
 172
 173     default:
 174       // Any target which wants to handle STB_LOOS, etc., needs to
 175       // define a resolve method.
 176       gold_error(_("unsupported symbol binding"));
 177       bits = global_flag;
 178     }
 179
 180   if (is_dynamic)
 181     bits |= dynamic_flag;
 182   else
 183     bits |= regular_flag;
 184
 185   switch (shndx)
 186     {
 187     case elfcpp::SHN_UNDEF:
 188       bits |= undef_flag;
 189       break;
 190
 191     case elfcpp::SHN_COMMON:
 192       if (!is_ordinary)
 193         bits |= common_flag;
 194       break;
 195
 196     default:
 197       if (type == elfcpp::STT_COMMON)
 198         bits |= common_flag;
 199       else
 200         bits |= def_flag;
 201       break;
 202     }
 203
 204   return bits;
 205 }
 206
 207 // Resolve a symbol.  This is called the second and subsequent times
 208 // we see a symbol.  TO is the pre-existing symbol.  ST_SHNDX is the
 209 // section index for SYM, possibly adjusted for many sections.
 210 // IS_ORDINARY is whether ST_SHNDX is a normal section index rather
 211 // than a special code.  ORIG_ST_SHNDX is the original section index,
 212 // before any munging because of discarded sections, except that all
 213 // non-ordinary section indexes are mapped to SHN_UNDEF.  VERSION is
 214 // the version of SYM.
 215
 216 template<int size, bool big_endian>
 217 void
 218 Symbol_table::resolve(Sized_symbol<size>* to,
 219                       const elfcpp::Sym<size, big_endian>& sym,
 220                       unsigned int st_shndx, bool is_ordinary,
 221                       unsigned int orig_st_shndx,
 222                       Object* object, const char* version)
 223 {
 224   if (object->target()->has_resolve())
 225     {
 226       Sized_target<size, big_endian>* sized_target;
 227       sized_target = object->sized_target<size, big_endian>();
 228       sized_target->resolve(to, sym, object, version);
 229       return;
 230     }
 231
 232   if (!object->is_dynamic())
 233     {
 234       // Record that we've seen this symbol in a regular object.
 235       to->set_in_reg();
 236     }
 237   else
 238     {
 239       // Record that we've seen this symbol in a dynamic object.
 240       to->set_in_dyn();
 241     }
 242
 243   unsigned int frombits = symbol_to_bits(sym.get_st_bind(),
 244                                          object->is_dynamic(),
 245                                          st_shndx, is_ordinary,
 246                                          sym.get_st_type());
 247
 248   bool adjust_common_sizes;
 249   if (Symbol_table::should_override(to, frombits, object,
 250                                     &adjust_common_sizes))
 251     {
 252       typename Sized_symbol<size>::Size_type tosize = to->symsize();
 253
 254       this->override(to, sym, st_shndx, is_ordinary, object, version);
 255
 256       if (adjust_common_sizes && tosize > to->symsize())
 257         to->set_symsize(tosize);
 258     }
 259   else
 260     {
 261       if (adjust_common_sizes && sym.get_st_size() > to->symsize())
 262         to->set_symsize(sym.get_st_size());
 263     }
 264
 265   // A new weak undefined reference, merging with an old weak
 266   // reference, could be a One Definition Rule (ODR) violation --
 267   // especially if the types or sizes of the references differ.  We'll
 268   // store such pairs and look them up later to make sure they
 269   // actually refer to the same lines of code.  (Note: not all ODR
 270   // violations can be found this way, and not everything this finds
 271   // is an ODR violation.  But it's helpful to warn about.)
 272   bool to_is_ordinary;
 273   if (parameters->options().detect_odr_violations()
 274       && sym.get_st_bind() == elfcpp::STB_WEAK
 275       && to->binding() == elfcpp::STB_WEAK
 276       && orig_st_shndx != elfcpp::SHN_UNDEF
 277       && to->shndx(&to_is_ordinary) != elfcpp::SHN_UNDEF
 278       && to_is_ordinary
 279       && sym.get_st_size() != 0    // Ignore weird 0-sized symbols.
 280       && to->symsize() != 0
 281       && (sym.get_st_type() != to->type()
 282           || sym.get_st_size() != to->symsize())
 283       // C does not have a concept of ODR, so we only need to do this
 284       // on C++ symbols.  These have (mangled) names starting with _Z.
 285       && to->name()[0] == '_' && to->name()[1] == 'Z')
 286     {
 287       Symbol_location fromloc
 288           = { object, orig_st_shndx, sym.get_st_value() };
 289       Symbol_location toloc = { to->object(), to->shndx(&to_is_ordinary),
 290                                 to->value() };
 291       this->candidate_odr_violations_[to->name()].insert(fromloc);
 292       this->candidate_odr_violations_[to->name()].insert(toloc);
 293     }
 294 }
 295
 296 // Handle the core of symbol resolution.  This is called with the
 297 // existing symbol, TO, and a bitflag describing the new symbol.  This
 298 // returns true if we should override the existing symbol with the new
 299 // one, and returns false otherwise.  It sets *ADJUST_COMMON_SIZES to
 300 // true if we should set the symbol size to the maximum of the TO and
 301 // FROM sizes.  It handles error conditions.
 302
 303 bool
 304 Symbol_table::should_override(const Symbol* to, unsigned int frombits,
 305                               Object* object, bool* adjust_common_sizes)
 306 {
 307   *adjust_common_sizes = false;
 308
 309   unsigned int tobits;
 310   if (to->source() == Symbol::IS_UNDEFINED)
 311     tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_UNDEF, true,
 312                             to->type());
 313   else if (to->source() != Symbol::FROM_OBJECT)
 314     tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_ABS, false,
 315                             to->type());
 316   else
 317     {
 318       bool is_ordinary;
 319       unsigned int shndx = to->shndx(&is_ordinary);
 320       tobits = symbol_to_bits(to->binding(),
 321                               to->object()->is_dynamic(),
 322                               shndx,
 323                               is_ordinary,
 324                               to->type());
 325     }
 326
 327   // FIXME: Warn if either but not both of TO and SYM are STT_TLS.
 328
 329   // We use a giant switch table for symbol resolution.  This code is
 330   // unwieldy, but: 1) it is efficient; 2) we definitely handle all
 331   // cases; 3) it is easy to change the handling of a particular case.
 332   // The alternative would be a series of conditionals, but it is easy
 333   // to get the ordering wrong.  This could also be done as a table,
 334   // but that is no easier to understand than this large switch
 335   // statement.
 336
 337   // These are the values generated by the bit codes.
 338   enum
 339   {
 340     DEF =              global_flag | regular_flag | def_flag,
 341     WEAK_DEF =         weak_flag   | regular_flag | def_flag,
 342     DYN_DEF =          global_flag | dynamic_flag | def_flag,
 343     DYN_WEAK_DEF =     weak_flag   | dynamic_flag | def_flag,
 344     UNDEF =            global_flag | regular_flag | undef_flag,
 345     WEAK_UNDEF =       weak_flag   | regular_flag | undef_flag,
 346     DYN_UNDEF =        global_flag | dynamic_flag | undef_flag,
 347     DYN_WEAK_UNDEF =   weak_flag   | dynamic_flag | undef_flag,
 348     COMMON =           global_flag | regular_flag | common_flag,
 349     WEAK_COMMON =      weak_flag   | regular_flag | common_flag,
 350     DYN_COMMON =       global_flag | dynamic_flag | common_flag,
 351     DYN_WEAK_COMMON =  weak_flag   | dynamic_flag | common_flag
 352   };
 353
 354   switch (tobits * 16 + frombits)
 355     {
 356     case DEF * 16 + DEF:
 357       // Two definitions of the same symbol.
 358
 359       // If either symbol is defined by an object included using
 360       // --just-symbols, then don't warn.  This is for compatibility
 361       // with the GNU linker.  FIXME: This is a hack.
 362       if ((to->source() == Symbol::FROM_OBJECT && to->object()->just_symbols())
 363           || object->just_symbols())
 364         return false;
 365
 366       // FIXME: Do a better job of reporting locations.
 367       gold_error(_("%s: multiple definition of %s"),
 368                  object != NULL ? object->name().c_str() : _("command line"),
 369                  to->demangled_name().c_str());
 370       gold_error(_("%s: previous definition here"),
 371                  (to->source() == Symbol::FROM_OBJECT
 372                   ? to->object()->name().c_str()
 373                   : _("command line")));
 374       return false;
 375
 376     case WEAK_DEF * 16 + DEF:
 377       // We've seen a weak definition, and now we see a strong
 378       // definition.  In the original SVR4 linker, this was treated as
 379       // a multiple definition error.  In the Solaris linker and the
 380       // GNU linker, a weak definition followed by a regular
 381       // definition causes the weak definition to be overridden.  We
 382       // are currently compatible with the GNU linker.  In the future
 383       // we should add a target specific option to change this.
 384       // FIXME.
 385       return true;
 386
 387     case DYN_DEF * 16 + DEF:
 388     case DYN_WEAK_DEF * 16 + DEF:
 389       // We've seen a definition in a dynamic object, and now we see a
 390       // definition in a regular object.  The definition in the
 391       // regular object overrides the definition in the dynamic
 392       // object.
 393       return true;
 394
 395     case UNDEF * 16 + DEF:
 396     case WEAK_UNDEF * 16 + DEF:
 397     case DYN_UNDEF * 16 + DEF:
 398     case DYN_WEAK_UNDEF * 16 + DEF:
 399       // We've seen an undefined reference, and now we see a
 400       // definition.  We use the definition.
 401       return true;
 402
 403     case COMMON * 16 + DEF:
 404     case WEAK_COMMON * 16 + DEF:
 405     case DYN_COMMON * 16 + DEF:
 406     case DYN_WEAK_COMMON * 16 + DEF:
 407       // We've seen a common symbol and now we see a definition.  The
 408       // definition overrides.  FIXME: We should optionally issue, version a
 409       // warning.
 410       return true;
 411
 412     case DEF * 16 + WEAK_DEF:
 413     case WEAK_DEF * 16 + WEAK_DEF:
 414       // We've seen a definition and now we see a weak definition.  We
 415       // ignore the new weak definition.
 416       return false;
 417
 418     case DYN_DEF * 16 + WEAK_DEF:
 419     case DYN_WEAK_DEF * 16 + WEAK_DEF:
 420       // We've seen a dynamic definition and now we see a regular weak
 421       // definition.  The regular weak definition overrides.
 422       return true;
 423
 424     case UNDEF * 16 + WEAK_DEF:
 425     case WEAK_UNDEF * 16 + WEAK_DEF:
 426     case DYN_UNDEF * 16 + WEAK_DEF:
 427     case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
 428       // A weak definition of a currently undefined symbol.
 429       return true;
 430
 431     case COMMON * 16 + WEAK_DEF:
 432     case WEAK_COMMON * 16 + WEAK_DEF:
 433       // A weak definition does not override a common definition.
 434       return false;
 435
 436     case DYN_COMMON * 16 + WEAK_DEF:
 437     case DYN_WEAK_COMMON * 16 + WEAK_DEF:
 438       // A weak definition does override a definition in a dynamic
 439       // object.  FIXME: We should optionally issue a warning.
 440       return true;
 441
 442     case DEF * 16 + DYN_DEF:
 443     case WEAK_DEF * 16 + DYN_DEF:
 444     case DYN_DEF * 16 + DYN_DEF:
 445     case DYN_WEAK_DEF * 16 + DYN_DEF:
 446       // Ignore a dynamic definition if we already have a definition.
 447       return false;
 448
 449     case UNDEF * 16 + DYN_DEF:
 450     case WEAK_UNDEF * 16 + DYN_DEF:
 451     case DYN_UNDEF * 16 + DYN_DEF:
 452     case DYN_WEAK_UNDEF * 16 + DYN_DEF:
 453       // Use a dynamic definition if we have a reference.
 454       return true;
 455
 456     case COMMON * 16 + DYN_DEF:
 457     case WEAK_COMMON * 16 + DYN_DEF:
 458     case DYN_COMMON * 16 + DYN_DEF:
 459     case DYN_WEAK_COMMON * 16 + DYN_DEF:
 460       // Ignore a dynamic definition if we already have a common
 461       // definition.
 462       return false;
 463
 464     case DEF * 16 + DYN_WEAK_DEF:
 465     case WEAK_DEF * 16 + DYN_WEAK_DEF:
 466     case DYN_DEF * 16 + DYN_WEAK_DEF:
 467     case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
 468       // Ignore a weak dynamic definition if we already have a
 469       // definition.
 470       return false;
 471
 472     case UNDEF * 16 + DYN_WEAK_DEF:
 473     case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 474     case DYN_UNDEF * 16 + DYN_WEAK_DEF:
 475     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 476       // Use a weak dynamic definition if we have a reference.
 477       return true;
 478
 479     case COMMON * 16 + DYN_WEAK_DEF:
 480     case WEAK_COMMON * 16 + DYN_WEAK_DEF:
 481     case DYN_COMMON * 16 + DYN_WEAK_DEF:
 482     case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
 483       // Ignore a weak dynamic definition if we already have a common
 484       // definition.
 485       return false;
 486
 487     case DEF * 16 + UNDEF:
 488     case WEAK_DEF * 16 + UNDEF:
 489     case DYN_DEF * 16 + UNDEF:
 490     case DYN_WEAK_DEF * 16 + UNDEF:
 491     case UNDEF * 16 + UNDEF:
 492       // A new undefined reference tells us nothing.
 493       return false;
 494
 495     case WEAK_UNDEF * 16 + UNDEF:
 496     case DYN_UNDEF * 16 + UNDEF:
 497     case DYN_WEAK_UNDEF * 16 + UNDEF:
 498       // A strong undef overrides a dynamic or weak undef.
 499       return true;
 500
 501     case COMMON * 16 + UNDEF:
 502     case WEAK_COMMON * 16 + UNDEF:
 503     case DYN_COMMON * 16 + UNDEF:
 504     case DYN_WEAK_COMMON * 16 + UNDEF:
 505       // A new undefined reference tells us nothing.
 506       return false;
 507
 508     case DEF * 16 + WEAK_UNDEF:
 509     case WEAK_DEF * 16 + WEAK_UNDEF:
 510     case DYN_DEF * 16 + WEAK_UNDEF:
 511     case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
 512     case UNDEF * 16 + WEAK_UNDEF:
 513     case WEAK_UNDEF * 16 + WEAK_UNDEF:
 514     case DYN_UNDEF * 16 + WEAK_UNDEF:
 515     case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
 516     case COMMON * 16 + WEAK_UNDEF:
 517     case WEAK_COMMON * 16 + WEAK_UNDEF:
 518     case DYN_COMMON * 16 + WEAK_UNDEF:
 519     case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
 520       // A new weak undefined reference tells us nothing.
 521       return false;
 522
 523     case DEF * 16 + DYN_UNDEF:
 524     case WEAK_DEF * 16 + DYN_UNDEF:
 525     case DYN_DEF * 16 + DYN_UNDEF:
 526     case DYN_WEAK_DEF * 16 + DYN_UNDEF:
 527     case UNDEF * 16 + DYN_UNDEF:
 528     case WEAK_UNDEF * 16 + DYN_UNDEF:
 529     case DYN_UNDEF * 16 + DYN_UNDEF:
 530     case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
 531     case COMMON * 16 + DYN_UNDEF:
 532     case WEAK_COMMON * 16 + DYN_UNDEF:
 533     case DYN_COMMON * 16 + DYN_UNDEF:
 534     case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
 535       // A new dynamic undefined reference tells us nothing.
 536       return false;
 537
 538     case DEF * 16 + DYN_WEAK_UNDEF:
 539     case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 540     case DYN_DEF * 16 + DYN_WEAK_UNDEF:
 541     case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 542     case UNDEF * 16 + DYN_WEAK_UNDEF:
 543     case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 544     case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
 545     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 546     case COMMON * 16 + DYN_WEAK_UNDEF:
 547     case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 548     case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
 549     case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 550       // A new weak dynamic undefined reference tells us nothing.
 551       return false;
 552
 553     case DEF * 16 + COMMON:
 554       // A common symbol does not override a definition.
 555       return false;
 556
 557     case WEAK_DEF * 16 + COMMON:
 558     case DYN_DEF * 16 + COMMON:
 559     case DYN_WEAK_DEF * 16 + COMMON:
 560       // A common symbol does override a weak definition or a dynamic
 561       // definition.
 562       return true;
 563
 564     case UNDEF * 16 + COMMON:
 565     case WEAK_UNDEF * 16 + COMMON:
 566     case DYN_UNDEF * 16 + COMMON:
 567     case DYN_WEAK_UNDEF * 16 + COMMON:
 568       // A common symbol is a definition for a reference.
 569       return true;
 570
 571     case COMMON * 16 + COMMON:
 572       // Set the size to the maximum.
 573       *adjust_common_sizes = true;
 574       return false;
 575
 576     case WEAK_COMMON * 16 + COMMON:
 577       // I'm not sure just what a weak common symbol means, but
 578       // presumably it can be overridden by a regular common symbol.
 579       return true;
 580
 581     case DYN_COMMON * 16 + COMMON:
 582     case DYN_WEAK_COMMON * 16 + COMMON:
 583       // Use the real common symbol, but adjust the size if necessary.
 584       *adjust_common_sizes = true;
 585       return true;
 586
 587     case DEF * 16 + WEAK_COMMON:
 588     case WEAK_DEF * 16 + WEAK_COMMON:
 589     case DYN_DEF * 16 + WEAK_COMMON:
 590     case DYN_WEAK_DEF * 16 + WEAK_COMMON:
 591       // Whatever a weak common symbol is, it won't override a
 592       // definition.
 593       return false;
 594
 595     case UNDEF * 16 + WEAK_COMMON:
 596     case WEAK_UNDEF * 16 + WEAK_COMMON:
 597     case DYN_UNDEF * 16 + WEAK_COMMON:
 598     case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
 599       // A weak common symbol is better than an undefined symbol.
 600       return true;
 601
 602     case COMMON * 16 + WEAK_COMMON:
 603     case WEAK_COMMON * 16 + WEAK_COMMON:
 604     case DYN_COMMON * 16 + WEAK_COMMON:
 605     case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
 606       // Ignore a weak common symbol in the presence of a real common
 607       // symbol.
 608       return false;
 609
 610     case DEF * 16 + DYN_COMMON:
 611     case WEAK_DEF * 16 + DYN_COMMON:
 612     case DYN_DEF * 16 + DYN_COMMON:
 613     case DYN_WEAK_DEF * 16 + DYN_COMMON:
 614       // Ignore a dynamic common symbol in the presence of a
 615       // definition.
 616       return false;
 617
 618     case UNDEF * 16 + DYN_COMMON:
 619     case WEAK_UNDEF * 16 + DYN_COMMON:
 620     case DYN_UNDEF * 16 + DYN_COMMON:
 621     case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
 622       // A dynamic common symbol is a definition of sorts.
 623       return true;
 624
 625     case COMMON * 16 + DYN_COMMON:
 626     case WEAK_COMMON * 16 + DYN_COMMON:
 627     case DYN_COMMON * 16 + DYN_COMMON:
 628     case DYN_WEAK_COMMON * 16 + DYN_COMMON:
 629       // Set the size to the maximum.
 630       *adjust_common_sizes = true;
 631       return false;
 632
 633     case DEF * 16 + DYN_WEAK_COMMON:
 634     case WEAK_DEF * 16 + DYN_WEAK_COMMON:
 635     case DYN_DEF * 16 + DYN_WEAK_COMMON:
 636     case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
 637       // A common symbol is ignored in the face of a definition.
 638       return false;
 639
 640     case UNDEF * 16 + DYN_WEAK_COMMON:
 641     case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 642     case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
 643     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 644       // I guess a weak common symbol is better than a definition.
 645       return true;
 646
 647     case COMMON * 16 + DYN_WEAK_COMMON:
 648     case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 649     case DYN_COMMON * 16 + DYN_WEAK_COMMON:
 650     case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 651       // Set the size to the maximum.
 652       *adjust_common_sizes = true;
 653       return false;
 654
 655     default:
 656       gold_unreachable();
 657     }
 658 }
 659
 660 // A special case of should_override which is only called for a strong
 661 // defined symbol from a regular object file.  This is used when
 662 // defining special symbols.
 663
 664 bool
 665 Symbol_table::should_override_with_special(const Symbol* to)
 666 {
 667   bool adjust_common_sizes;
 668   unsigned int frombits = global_flag | regular_flag | def_flag;
 669   bool ret = Symbol_table::should_override(to, frombits, NULL,
 670                                            &adjust_common_sizes);
 671   gold_assert(!adjust_common_sizes);
 672   return ret;
 673 }
 674
 675 // Override symbol base with a special symbol.
 676
 677 void
 678 Symbol::override_base_with_special(const Symbol* from)
 679 {
 680   gold_assert(this->name_ == from->name_ || this->has_alias());
 681
 682   this->source_ = from->source_;
 683   switch (from->source_)
 684     {
 685     case FROM_OBJECT:
 686       this->u_.from_object = from->u_.from_object;
 687       break;
 688     case IN_OUTPUT_DATA:
 689       this->u_.in_output_data = from->u_.in_output_data;
 690       break;
 691     case IN_OUTPUT_SEGMENT:
 692       this->u_.in_output_segment = from->u_.in_output_segment;
 693       break;
 694     case IS_CONSTANT:
 695     case IS_UNDEFINED:
 696       break;
 697     default:
 698       gold_unreachable();
 699       break;
 700     }
 701
 702   this->override_version(from->version_);
 703   this->type_ = from->type_;
 704   this->binding_ = from->binding_;
 705   this->visibility_ = from->visibility_;
 706   this->nonvis_ = from->nonvis_;
 707
 708   // Special symbols are always considered to be regular symbols.
 709   this->in_reg_ = true;
 710
 711   if (from->needs_dynsym_entry_)
 712     this->needs_dynsym_entry_ = true;
 713   if (from->needs_dynsym_value_)
 714     this->needs_dynsym_value_ = true;
 715
 716   // We shouldn't see these flags.  If we do, we need to handle them
 717   // somehow.
 718   gold_assert(!from->is_target_special_ || this->is_target_special_);
 719   gold_assert(!from->is_forwarder_);
 720   gold_assert(!from->has_plt_offset_);
 721   gold_assert(!from->has_warning_);
 722   gold_assert(!from->is_copied_from_dynobj_);
 723   gold_assert(!from->is_forced_local_);
 724 }
 725
 726 // Override a symbol with a special symbol.
 727
 728 template<int size>
 729 void
 730 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from)
 731 {
 732   this->override_base_with_special(from);
 733   this->value_ = from->value_;
 734   this->symsize_ = from->symsize_;
 735 }
 736
 737 // Override TOSYM with the special symbol FROMSYM.  This handles all
 738 // aliases of TOSYM.
 739
 740 template<int size>
 741 void
 742 Symbol_table::override_with_special(Sized_symbol<size>* tosym,
 743                                     const Sized_symbol<size>* fromsym)
 744 {
 745   tosym->override_with_special(fromsym);
 746   if (tosym->has_alias())
 747     {
 748       Symbol* sym = this->weak_aliases_[tosym];
 749       gold_assert(sym != NULL);
 750       Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
 751       do
 752         {
 753           ssym->override_with_special(fromsym);
 754           sym = this->weak_aliases_[ssym];
 755           gold_assert(sym != NULL);
 756           ssym = this->get_sized_symbol<size>(sym);
 757         }
 758       while (ssym != tosym);
 759     }
 760   if (tosym->binding() == elfcpp::STB_LOCAL)
 761     this->force_local(tosym);
 762 }
 763
 764 // Instantiate the templates we need.  We could use the configure
 765 // script to restrict this to only the ones needed for implemented
 766 // targets.
 767
 768 #ifdef HAVE_TARGET_32_LITTLE
 769 template
 770 void
 771 Symbol_table::resolve<32, false>(
 772     Sized_symbol<32>* to,
 773     const elfcpp::Sym<32, false>& sym,
 774     unsigned int st_shndx,
 775     bool is_ordinary,
 776     unsigned int orig_st_shndx,
 777     Object* object,
 778     const char* version);
 779 #endif
 780
 781 #ifdef HAVE_TARGET_32_BIG
 782 template
 783 void
 784 Symbol_table::resolve<32, true>(
 785     Sized_symbol<32>* to,
 786     const elfcpp::Sym<32, true>& sym,
 787     unsigned int st_shndx,
 788     bool is_ordinary,
 789     unsigned int orig_st_shndx,
 790     Object* object,
 791     const char* version);
 792 #endif
 793
 794 #ifdef HAVE_TARGET_64_LITTLE
 795 template
 796 void
 797 Symbol_table::resolve<64, false>(
 798     Sized_symbol<64>* to,
 799     const elfcpp::Sym<64, false>& sym,
 800     unsigned int st_shndx,
 801     bool is_ordinary,
 802     unsigned int orig_st_shndx,
 803     Object* object,
 804     const char* version);
 805 #endif
 806
 807 #ifdef HAVE_TARGET_64_BIG
 808 template
 809 void
 810 Symbol_table::resolve<64, true>(
 811     Sized_symbol<64>* to,
 812     const elfcpp::Sym<64, true>& sym,
 813     unsigned int st_shndx,
 814     bool is_ordinary,
 815     unsigned int orig_st_shndx,
 816     Object* object,
 817     const char* version);
 818 #endif
 819
 820 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
 821 template
 822 void
 823 Symbol_table::override_with_special<32>(Sized_symbol<32>*,
 824                                         const Sized_symbol<32>*);
 825 #endif
 826
 827 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
 828 template
 829 void
 830 Symbol_table::override_with_special<64>(Sized_symbol<64>*,
 831                                         const Sized_symbol<64>*);
 832 #endif
 833
 834 } // End namespace gold.