gold/resolve.cc

   1 // resolve.cc -- symbol resolution for gold
   2
   3 // Copyright (C) 2006-2014 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   // Don't override st_type from plugin placeholder symbols.
 100   if (object->pluginobj() == NULL)
 101     this->type_ = sym.get_st_type();
 102   this->binding_ = sym.get_st_bind();
 103   this->override_visibility(sym.get_st_visibility());
 104   this->nonvis_ = sym.get_st_nonvis();
 105   if (object->is_dynamic())
 106     this->in_dyn_ = true;
 107   else
 108     this->in_reg_ = true;
 109 }
 110
 111 // Override the fields in Sized_symbol.
 112
 113 template<int size>
 114 template<bool big_endian>
 115 void
 116 Sized_symbol<size>::override(const elfcpp::Sym<size, big_endian>& sym,
 117                              unsigned st_shndx, bool is_ordinary,
 118                              Object* object, const char* version)
 119 {
 120   this->override_base(sym, st_shndx, is_ordinary, object, version);
 121   this->value_ = sym.get_st_value();
 122   this->symsize_ = sym.get_st_size();
 123 }
 124
 125 // Override TOSYM with symbol FROMSYM, defined in OBJECT, with version
 126 // VERSION.  This handles all aliases of TOSYM.
 127
 128 template<int size, bool big_endian>
 129 void
 130 Symbol_table::override(Sized_symbol<size>* tosym,
 131                        const elfcpp::Sym<size, big_endian>& fromsym,
 132                        unsigned int st_shndx, bool is_ordinary,
 133                        Object* object, const char* version)
 134 {
 135   tosym->override(fromsym, st_shndx, is_ordinary, object, version);
 136   if (tosym->has_alias())
 137     {
 138       Symbol* sym = this->weak_aliases_[tosym];
 139       gold_assert(sym != NULL);
 140       Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
 141       do
 142         {
 143           ssym->override(fromsym, st_shndx, is_ordinary, object, version);
 144           sym = this->weak_aliases_[ssym];
 145           gold_assert(sym != NULL);
 146           ssym = this->get_sized_symbol<size>(sym);
 147         }
 148       while (ssym != tosym);
 149     }
 150 }
 151
 152 // The resolve functions build a little code for each symbol.
 153 // Bit 0: 0 for global, 1 for weak.
 154 // Bit 1: 0 for regular object, 1 for shared object
 155 // Bits 2-3: 0 for normal, 1 for undefined, 2 for common
 156 // This gives us values from 0 to 11.
 157
 158 static const int global_or_weak_shift = 0;
 159 static const unsigned int global_flag = 0 << global_or_weak_shift;
 160 static const unsigned int weak_flag = 1 << global_or_weak_shift;
 161
 162 static const int regular_or_dynamic_shift = 1;
 163 static const unsigned int regular_flag = 0 << regular_or_dynamic_shift;
 164 static const unsigned int dynamic_flag = 1 << regular_or_dynamic_shift;
 165
 166 static const int def_undef_or_common_shift = 2;
 167 static const unsigned int def_flag = 0 << def_undef_or_common_shift;
 168 static const unsigned int undef_flag = 1 << def_undef_or_common_shift;
 169 static const unsigned int common_flag = 2 << def_undef_or_common_shift;
 170
 171 // This convenience function combines all the flags based on facts
 172 // about the symbol.
 173
 174 static unsigned int
 175 symbol_to_bits(elfcpp::STB binding, bool is_dynamic,
 176                unsigned int shndx, bool is_ordinary, elfcpp::STT type)
 177 {
 178   unsigned int bits;
 179
 180   switch (binding)
 181     {
 182     case elfcpp::STB_GLOBAL:
 183     case elfcpp::STB_GNU_UNIQUE:
 184       bits = global_flag;
 185       break;
 186
 187     case elfcpp::STB_WEAK:
 188       bits = weak_flag;
 189       break;
 190
 191     case elfcpp::STB_LOCAL:
 192       // We should only see externally visible symbols in the symbol
 193       // table.
 194       gold_error(_("invalid STB_LOCAL symbol in external symbols"));
 195       bits = global_flag;
 196
 197     default:
 198       // Any target which wants to handle STB_LOOS, etc., needs to
 199       // define a resolve method.
 200       gold_error(_("unsupported symbol binding %d"), static_cast<int>(binding));
 201       bits = global_flag;
 202     }
 203
 204   if (is_dynamic)
 205     bits |= dynamic_flag;
 206   else
 207     bits |= regular_flag;
 208
 209   switch (shndx)
 210     {
 211     case elfcpp::SHN_UNDEF:
 212       bits |= undef_flag;
 213       break;
 214
 215     case elfcpp::SHN_COMMON:
 216       if (!is_ordinary)
 217         bits |= common_flag;
 218       break;
 219
 220     default:
 221       if (type == elfcpp::STT_COMMON)
 222         bits |= common_flag;
 223       else if (!is_ordinary && Symbol::is_common_shndx(shndx))
 224         bits |= common_flag;
 225       else
 226         bits |= def_flag;
 227       break;
 228     }
 229
 230   return bits;
 231 }
 232
 233 // Resolve a symbol.  This is called the second and subsequent times
 234 // we see a symbol.  TO is the pre-existing symbol.  ST_SHNDX is the
 235 // section index for SYM, possibly adjusted for many sections.
 236 // IS_ORDINARY is whether ST_SHNDX is a normal section index rather
 237 // than a special code.  ORIG_ST_SHNDX is the original section index,
 238 // before any munging because of discarded sections, except that all
 239 // non-ordinary section indexes are mapped to SHN_UNDEF.  VERSION is
 240 // the version of SYM.
 241
 242 template<int size, bool big_endian>
 243 void
 244 Symbol_table::resolve(Sized_symbol<size>* to,
 245                       const elfcpp::Sym<size, big_endian>& sym,
 246                       unsigned int st_shndx, bool is_ordinary,
 247                       unsigned int orig_st_shndx,
 248                       Object* object, const char* version)
 249 {
 250   // It's possible for a symbol to be defined in an object file
 251   // using .symver to give it a version, and for there to also be
 252   // a linker script giving that symbol the same version.  We
 253   // don't want to give a multiple-definition error for this
 254   // harmless redefinition.
 255   bool to_is_ordinary;
 256   if (to->source() == Symbol::FROM_OBJECT
 257       && to->object() == object
 258       && is_ordinary
 259       && to->is_defined()
 260       && to->shndx(&to_is_ordinary) == st_shndx
 261       && to_is_ordinary
 262       && to->value() == sym.get_st_value())
 263     return;
 264
 265   if (parameters->target().has_resolve())
 266     {
 267       Sized_target<size, big_endian>* sized_target;
 268       sized_target = parameters->sized_target<size, big_endian>();
 269       sized_target->resolve(to, sym, object, version);
 270       return;
 271     }
 272
 273   if (!object->is_dynamic())
 274     {
 275       // Record that we've seen this symbol in a regular object.
 276       to->set_in_reg();
 277     }
 278   else if (st_shndx == elfcpp::SHN_UNDEF
 279            && (to->visibility() == elfcpp::STV_HIDDEN
 280                || to->visibility() == elfcpp::STV_INTERNAL))
 281     {
 282       // A dynamic object cannot reference a hidden or internal symbol
 283       // defined in another object.
 284       gold_warning(_("%s symbol '%s' in %s is referenced by DSO %s"),
 285                    (to->visibility() == elfcpp::STV_HIDDEN
 286                     ? "hidden"
 287                     : "internal"),
 288                    to->demangled_name().c_str(),
 289                    to->object()->name().c_str(),
 290                    object->name().c_str());
 291       return;
 292     }
 293   else
 294     {
 295       // Record that we've seen this symbol in a dynamic object.
 296       to->set_in_dyn();
 297     }
 298
 299   // Record if we've seen this symbol in a real ELF object (i.e., the
 300   // symbol is referenced from outside the world known to the plugin).
 301   if (object->pluginobj() == NULL && !object->is_dynamic())
 302     to->set_in_real_elf();
 303
 304   // If we're processing replacement files, allow new symbols to override
 305   // the placeholders from the plugin objects.
 306   // Treat common symbols specially since it is possible that an ELF
 307   // file increased the size of the alignment.
 308   if (to->source() == Symbol::FROM_OBJECT)
 309     {
 310       Pluginobj* obj = to->object()->pluginobj();
 311       if (obj != NULL
 312           && parameters->options().plugins()->in_replacement_phase()
 313           && !to->is_common())
 314         {
 315           this->override(to, sym, st_shndx, is_ordinary, object, version);
 316           return;
 317         }
 318     }
 319
 320   // A new weak undefined reference, merging with an old weak
 321   // reference, could be a One Definition Rule (ODR) violation --
 322   // especially if the types or sizes of the references differ.  We'll
 323   // store such pairs and look them up later to make sure they
 324   // actually refer to the same lines of code.  We also check
 325   // combinations of weak and strong, which might occur if one case is
 326   // inline and the other is not.  (Note: not all ODR violations can
 327   // be found this way, and not everything this finds is an ODR
 328   // violation.  But it's helpful to warn about.)
 329   if (parameters->options().detect_odr_violations()
 330       && (sym.get_st_bind() == elfcpp::STB_WEAK
 331           || to->binding() == elfcpp::STB_WEAK)
 332       && orig_st_shndx != elfcpp::SHN_UNDEF
 333       && to->shndx(&to_is_ordinary) != elfcpp::SHN_UNDEF
 334       && to_is_ordinary
 335       && sym.get_st_size() != 0    // Ignore weird 0-sized symbols.
 336       && to->symsize() != 0
 337       && (sym.get_st_type() != to->type()
 338           || sym.get_st_size() != to->symsize())
 339       // C does not have a concept of ODR, so we only need to do this
 340       // on C++ symbols.  These have (mangled) names starting with _Z.
 341       && to->name()[0] == '_' && to->name()[1] == 'Z')
 342     {
 343       Symbol_location fromloc
 344           = { object, orig_st_shndx, static_cast<off_t>(sym.get_st_value()) };
 345       Symbol_location toloc = { to->object(), to->shndx(&to_is_ordinary),
 346                                 static_cast<off_t>(to->value()) };
 347       this->candidate_odr_violations_[to->name()].insert(fromloc);
 348       this->candidate_odr_violations_[to->name()].insert(toloc);
 349     }
 350
 351   // Plugins don't provide a symbol type, so adopt the existing type
 352   // if the FROM symbol is from a plugin.
 353   elfcpp::STT fromtype = (object->pluginobj() != NULL
 354                           ? to->type()
 355                           : sym.get_st_type());
 356   unsigned int frombits = symbol_to_bits(sym.get_st_bind(),
 357                                          object->is_dynamic(),
 358                                          st_shndx, is_ordinary,
 359                                          fromtype);
 360
 361   bool adjust_common_sizes;
 362   bool adjust_dyndef;
 363   typename Sized_symbol<size>::Size_type tosize = to->symsize();
 364   if (Symbol_table::should_override(to, frombits, fromtype, OBJECT,
 365                                     object, &adjust_common_sizes,
 366                                     &adjust_dyndef))
 367     {
 368       elfcpp::STB tobinding = to->binding();
 369       typename Sized_symbol<size>::Value_type tovalue = to->value();
 370       this->override(to, sym, st_shndx, is_ordinary, object, version);
 371       if (adjust_common_sizes)
 372         {
 373           if (tosize > to->symsize())
 374             to->set_symsize(tosize);
 375           if (tovalue > to->value())
 376             to->set_value(tovalue);
 377         }
 378       if (adjust_dyndef)
 379         {
 380           // We are overriding an UNDEF or WEAK UNDEF with a DYN DEF.
 381           // Remember which kind of UNDEF it was for future reference.
 382           to->set_undef_binding(tobinding);
 383         }
 384     }
 385   else
 386     {
 387       if (adjust_common_sizes)
 388         {
 389           if (sym.get_st_size() > tosize)
 390             to->set_symsize(sym.get_st_size());
 391           if (sym.get_st_value() > to->value())
 392             to->set_value(sym.get_st_value());
 393         }
 394       if (adjust_dyndef)
 395         {
 396           // We are keeping a DYN DEF after seeing an UNDEF or WEAK UNDEF.
 397           // Remember which kind of UNDEF it was.
 398           to->set_undef_binding(sym.get_st_bind());
 399         }
 400       // The ELF ABI says that even for a reference to a symbol we
 401       // merge the visibility.
 402       to->override_visibility(sym.get_st_visibility());
 403     }
 404
 405   if (adjust_common_sizes && parameters->options().warn_common())
 406     {
 407       if (tosize > sym.get_st_size())
 408         Symbol_table::report_resolve_problem(false,
 409                                              _("common of '%s' overriding "
 410                                                "smaller common"),
 411                                              to, OBJECT, object);
 412       else if (tosize < sym.get_st_size())
 413         Symbol_table::report_resolve_problem(false,
 414                                              _("common of '%s' overidden by "
 415                                                "larger common"),
 416                                              to, OBJECT, object);
 417       else
 418         Symbol_table::report_resolve_problem(false,
 419                                              _("multiple common of '%s'"),
 420                                              to, OBJECT, object);
 421     }
 422 }
 423
 424 // Handle the core of symbol resolution.  This is called with the
 425 // existing symbol, TO, and a bitflag describing the new symbol.  This
 426 // returns true if we should override the existing symbol with the new
 427 // one, and returns false otherwise.  It sets *ADJUST_COMMON_SIZES to
 428 // true if we should set the symbol size to the maximum of the TO and
 429 // FROM sizes.  It handles error conditions.
 430
 431 bool
 432 Symbol_table::should_override(const Symbol* to, unsigned int frombits,
 433                               elfcpp::STT fromtype, Defined defined,
 434                               Object* object, bool* adjust_common_sizes,
 435                               bool* adjust_dyndef)
 436 {
 437   *adjust_common_sizes = false;
 438   *adjust_dyndef = false;
 439
 440   unsigned int tobits;
 441   if (to->source() == Symbol::IS_UNDEFINED)
 442     tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_UNDEF, true,
 443                             to->type());
 444   else if (to->source() != Symbol::FROM_OBJECT)
 445     tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_ABS, false,
 446                             to->type());
 447   else
 448     {
 449       bool is_ordinary;
 450       unsigned int shndx = to->shndx(&is_ordinary);
 451       tobits = symbol_to_bits(to->binding(),
 452                               to->object()->is_dynamic(),
 453                               shndx,
 454                               is_ordinary,
 455                               to->type());
 456     }
 457
 458   if ((to->type() == elfcpp::STT_TLS) ^ (fromtype == elfcpp::STT_TLS)
 459       && !to->is_placeholder())
 460     Symbol_table::report_resolve_problem(true,
 461                                          _("symbol '%s' used as both __thread "
 462                                            "and non-__thread"),
 463                                          to, defined, object);
 464
 465   // We use a giant switch table for symbol resolution.  This code is
 466   // unwieldy, but: 1) it is efficient; 2) we definitely handle all
 467   // cases; 3) it is easy to change the handling of a particular case.
 468   // The alternative would be a series of conditionals, but it is easy
 469   // to get the ordering wrong.  This could also be done as a table,
 470   // but that is no easier to understand than this large switch
 471   // statement.
 472
 473   // These are the values generated by the bit codes.
 474   enum
 475   {
 476     DEF =              global_flag | regular_flag | def_flag,
 477     WEAK_DEF =         weak_flag   | regular_flag | def_flag,
 478     DYN_DEF =          global_flag | dynamic_flag | def_flag,
 479     DYN_WEAK_DEF =     weak_flag   | dynamic_flag | def_flag,
 480     UNDEF =            global_flag | regular_flag | undef_flag,
 481     WEAK_UNDEF =       weak_flag   | regular_flag | undef_flag,
 482     DYN_UNDEF =        global_flag | dynamic_flag | undef_flag,
 483     DYN_WEAK_UNDEF =   weak_flag   | dynamic_flag | undef_flag,
 484     COMMON =           global_flag | regular_flag | common_flag,
 485     WEAK_COMMON =      weak_flag   | regular_flag | common_flag,
 486     DYN_COMMON =       global_flag | dynamic_flag | common_flag,
 487     DYN_WEAK_COMMON =  weak_flag   | dynamic_flag | common_flag
 488   };
 489
 490   switch (tobits * 16 + frombits)
 491     {
 492     case DEF * 16 + DEF:
 493       // Two definitions of the same symbol.
 494
 495       // If either symbol is defined by an object included using
 496       // --just-symbols, then don't warn.  This is for compatibility
 497       // with the GNU linker.  FIXME: This is a hack.
 498       if ((to->source() == Symbol::FROM_OBJECT && to->object()->just_symbols())
 499           || (object != NULL && object->just_symbols()))
 500         return false;
 501
 502       if (!parameters->options().muldefs())
 503         Symbol_table::report_resolve_problem(true,
 504                                              _("multiple definition of '%s'"),
 505                                              to, defined, object);
 506       return false;
 507
 508     case WEAK_DEF * 16 + DEF:
 509       // We've seen a weak definition, and now we see a strong
 510       // definition.  In the original SVR4 linker, this was treated as
 511       // a multiple definition error.  In the Solaris linker and the
 512       // GNU linker, a weak definition followed by a regular
 513       // definition causes the weak definition to be overridden.  We
 514       // are currently compatible with the GNU linker.  In the future
 515       // we should add a target specific option to change this.
 516       // FIXME.
 517       return true;
 518
 519     case DYN_DEF * 16 + DEF:
 520     case DYN_WEAK_DEF * 16 + DEF:
 521       // We've seen a definition in a dynamic object, and now we see a
 522       // definition in a regular object.  The definition in the
 523       // regular object overrides the definition in the dynamic
 524       // object.
 525       return true;
 526
 527     case UNDEF * 16 + DEF:
 528     case WEAK_UNDEF * 16 + DEF:
 529     case DYN_UNDEF * 16 + DEF:
 530     case DYN_WEAK_UNDEF * 16 + DEF:
 531       // We've seen an undefined reference, and now we see a
 532       // definition.  We use the definition.
 533       return true;
 534
 535     case COMMON * 16 + DEF:
 536     case WEAK_COMMON * 16 + DEF:
 537     case DYN_COMMON * 16 + DEF:
 538     case DYN_WEAK_COMMON * 16 + DEF:
 539       // We've seen a common symbol and now we see a definition.  The
 540       // definition overrides.
 541       if (parameters->options().warn_common())
 542         Symbol_table::report_resolve_problem(false,
 543                                              _("definition of '%s' overriding "
 544                                                "common"),
 545                                              to, defined, object);
 546       return true;
 547
 548     case DEF * 16 + WEAK_DEF:
 549     case WEAK_DEF * 16 + WEAK_DEF:
 550       // We've seen a definition and now we see a weak definition.  We
 551       // ignore the new weak definition.
 552       return false;
 553
 554     case DYN_DEF * 16 + WEAK_DEF:
 555     case DYN_WEAK_DEF * 16 + WEAK_DEF:
 556       // We've seen a dynamic definition and now we see a regular weak
 557       // definition.  The regular weak definition overrides.
 558       return true;
 559
 560     case UNDEF * 16 + WEAK_DEF:
 561     case WEAK_UNDEF * 16 + WEAK_DEF:
 562     case DYN_UNDEF * 16 + WEAK_DEF:
 563     case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
 564       // A weak definition of a currently undefined symbol.
 565       return true;
 566
 567     case COMMON * 16 + WEAK_DEF:
 568     case WEAK_COMMON * 16 + WEAK_DEF:
 569       // A weak definition does not override a common definition.
 570       return false;
 571
 572     case DYN_COMMON * 16 + WEAK_DEF:
 573     case DYN_WEAK_COMMON * 16 + WEAK_DEF:
 574       // A weak definition does override a definition in a dynamic
 575       // object.
 576       if (parameters->options().warn_common())
 577         Symbol_table::report_resolve_problem(false,
 578                                              _("definition of '%s' overriding "
 579                                                "dynamic common definition"),
 580                                              to, defined, object);
 581       return true;
 582
 583     case DEF * 16 + DYN_DEF:
 584     case WEAK_DEF * 16 + DYN_DEF:
 585     case DYN_DEF * 16 + DYN_DEF:
 586     case DYN_WEAK_DEF * 16 + DYN_DEF:
 587       // Ignore a dynamic definition if we already have a definition.
 588       return false;
 589
 590     case UNDEF * 16 + DYN_DEF:
 591     case DYN_UNDEF * 16 + DYN_DEF:
 592     case DYN_WEAK_UNDEF * 16 + DYN_DEF:
 593       // Use a dynamic definition if we have a reference.
 594       return true;
 595
 596     case WEAK_UNDEF * 16 + DYN_DEF:
 597       // When overriding a weak undef by a dynamic definition,
 598       // we need to remember that the original undef was weak.
 599       *adjust_dyndef = true;
 600       return true;
 601
 602     case COMMON * 16 + DYN_DEF:
 603     case WEAK_COMMON * 16 + DYN_DEF:
 604     case DYN_COMMON * 16 + DYN_DEF:
 605     case DYN_WEAK_COMMON * 16 + DYN_DEF:
 606       // Ignore a dynamic definition if we already have a common
 607       // definition.
 608       return false;
 609
 610     case DEF * 16 + DYN_WEAK_DEF:
 611     case WEAK_DEF * 16 + DYN_WEAK_DEF:
 612     case DYN_DEF * 16 + DYN_WEAK_DEF:
 613     case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
 614       // Ignore a weak dynamic definition if we already have a
 615       // definition.
 616       return false;
 617
 618     case UNDEF * 16 + DYN_WEAK_DEF:
 619       // When overriding an undef by a dynamic weak definition,
 620       // we need to remember that the original undef was not weak.
 621       *adjust_dyndef = true;
 622       return true;
 623
 624     case DYN_UNDEF * 16 + DYN_WEAK_DEF:
 625     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 626       // Use a weak dynamic definition if we have a reference.
 627       return true;
 628
 629     case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 630       // When overriding a weak undef by a dynamic definition,
 631       // we need to remember that the original undef was weak.
 632       *adjust_dyndef = true;
 633       return true;
 634
 635     case COMMON * 16 + DYN_WEAK_DEF:
 636     case WEAK_COMMON * 16 + DYN_WEAK_DEF:
 637     case DYN_COMMON * 16 + DYN_WEAK_DEF:
 638     case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
 639       // Ignore a weak dynamic definition if we already have a common
 640       // definition.
 641       return false;
 642
 643     case DEF * 16 + UNDEF:
 644     case WEAK_DEF * 16 + UNDEF:
 645     case UNDEF * 16 + UNDEF:
 646       // A new undefined reference tells us nothing.
 647       return false;
 648
 649     case DYN_DEF * 16 + UNDEF:
 650     case DYN_WEAK_DEF * 16 + UNDEF:
 651       // For a dynamic def, we need to remember which kind of undef we see.
 652       *adjust_dyndef = true;
 653       return false;
 654
 655     case WEAK_UNDEF * 16 + UNDEF:
 656     case DYN_UNDEF * 16 + UNDEF:
 657     case DYN_WEAK_UNDEF * 16 + UNDEF:
 658       // A strong undef overrides a dynamic or weak undef.
 659       return true;
 660
 661     case COMMON * 16 + UNDEF:
 662     case WEAK_COMMON * 16 + UNDEF:
 663     case DYN_COMMON * 16 + UNDEF:
 664     case DYN_WEAK_COMMON * 16 + UNDEF:
 665       // A new undefined reference tells us nothing.
 666       return false;
 667
 668     case DEF * 16 + WEAK_UNDEF:
 669     case WEAK_DEF * 16 + WEAK_UNDEF:
 670     case UNDEF * 16 + WEAK_UNDEF:
 671     case WEAK_UNDEF * 16 + WEAK_UNDEF:
 672     case DYN_UNDEF * 16 + WEAK_UNDEF:
 673     case COMMON * 16 + WEAK_UNDEF:
 674     case WEAK_COMMON * 16 + WEAK_UNDEF:
 675     case DYN_COMMON * 16 + WEAK_UNDEF:
 676     case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
 677       // A new weak undefined reference tells us nothing unless the
 678       // exisiting symbol is a dynamic weak reference.
 679       return false;
 680
 681     case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
 682       // A new weak reference overrides an existing dynamic weak reference.
 683       // This is necessary because a dynamic weak reference remembers
 684       // the old binding, which may not be weak.  If we keeps the existing
 685       // dynamic weak reference, the weakness may be dropped in the output.
 686       return true;
 687
 688     case DYN_DEF * 16 + WEAK_UNDEF:
 689     case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
 690       // For a dynamic def, we need to remember which kind of undef we see.
 691       *adjust_dyndef = true;
 692       return false;
 693
 694     case DEF * 16 + DYN_UNDEF:
 695     case WEAK_DEF * 16 + DYN_UNDEF:
 696     case DYN_DEF * 16 + DYN_UNDEF:
 697     case DYN_WEAK_DEF * 16 + DYN_UNDEF:
 698     case UNDEF * 16 + DYN_UNDEF:
 699     case WEAK_UNDEF * 16 + DYN_UNDEF:
 700     case DYN_UNDEF * 16 + DYN_UNDEF:
 701     case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
 702     case COMMON * 16 + DYN_UNDEF:
 703     case WEAK_COMMON * 16 + DYN_UNDEF:
 704     case DYN_COMMON * 16 + DYN_UNDEF:
 705     case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
 706       // A new dynamic undefined reference tells us nothing.
 707       return false;
 708
 709     case DEF * 16 + DYN_WEAK_UNDEF:
 710     case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 711     case DYN_DEF * 16 + DYN_WEAK_UNDEF:
 712     case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 713     case UNDEF * 16 + DYN_WEAK_UNDEF:
 714     case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 715     case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
 716     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 717     case COMMON * 16 + DYN_WEAK_UNDEF:
 718     case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 719     case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
 720     case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 721       // A new weak dynamic undefined reference tells us nothing.
 722       return false;
 723
 724     case DEF * 16 + COMMON:
 725       // A common symbol does not override a definition.
 726       if (parameters->options().warn_common())
 727         Symbol_table::report_resolve_problem(false,
 728                                              _("common '%s' overridden by "
 729                                                "previous definition"),
 730                                              to, defined, object);
 731       return false;
 732
 733     case WEAK_DEF * 16 + COMMON:
 734     case DYN_DEF * 16 + COMMON:
 735     case DYN_WEAK_DEF * 16 + COMMON:
 736       // A common symbol does override a weak definition or a dynamic
 737       // definition.
 738       return true;
 739
 740     case UNDEF * 16 + COMMON:
 741     case WEAK_UNDEF * 16 + COMMON:
 742     case DYN_UNDEF * 16 + COMMON:
 743     case DYN_WEAK_UNDEF * 16 + COMMON:
 744       // A common symbol is a definition for a reference.
 745       return true;
 746
 747     case COMMON * 16 + COMMON:
 748       // Set the size to the maximum.
 749       *adjust_common_sizes = true;
 750       return false;
 751
 752     case WEAK_COMMON * 16 + COMMON:
 753       // I'm not sure just what a weak common symbol means, but
 754       // presumably it can be overridden by a regular common symbol.
 755       return true;
 756
 757     case DYN_COMMON * 16 + COMMON:
 758     case DYN_WEAK_COMMON * 16 + COMMON:
 759       // Use the real common symbol, but adjust the size if necessary.
 760       *adjust_common_sizes = true;
 761       return true;
 762
 763     case DEF * 16 + WEAK_COMMON:
 764     case WEAK_DEF * 16 + WEAK_COMMON:
 765     case DYN_DEF * 16 + WEAK_COMMON:
 766     case DYN_WEAK_DEF * 16 + WEAK_COMMON:
 767       // Whatever a weak common symbol is, it won't override a
 768       // definition.
 769       return false;
 770
 771     case UNDEF * 16 + WEAK_COMMON:
 772     case WEAK_UNDEF * 16 + WEAK_COMMON:
 773     case DYN_UNDEF * 16 + WEAK_COMMON:
 774     case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
 775       // A weak common symbol is better than an undefined symbol.
 776       return true;
 777
 778     case COMMON * 16 + WEAK_COMMON:
 779     case WEAK_COMMON * 16 + WEAK_COMMON:
 780     case DYN_COMMON * 16 + WEAK_COMMON:
 781     case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
 782       // Ignore a weak common symbol in the presence of a real common
 783       // symbol.
 784       return false;
 785
 786     case DEF * 16 + DYN_COMMON:
 787     case WEAK_DEF * 16 + DYN_COMMON:
 788     case DYN_DEF * 16 + DYN_COMMON:
 789     case DYN_WEAK_DEF * 16 + DYN_COMMON:
 790       // Ignore a dynamic common symbol in the presence of a
 791       // definition.
 792       return false;
 793
 794     case UNDEF * 16 + DYN_COMMON:
 795     case WEAK_UNDEF * 16 + DYN_COMMON:
 796     case DYN_UNDEF * 16 + DYN_COMMON:
 797     case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
 798       // A dynamic common symbol is a definition of sorts.
 799       return true;
 800
 801     case COMMON * 16 + DYN_COMMON:
 802     case WEAK_COMMON * 16 + DYN_COMMON:
 803     case DYN_COMMON * 16 + DYN_COMMON:
 804     case DYN_WEAK_COMMON * 16 + DYN_COMMON:
 805       // Set the size to the maximum.
 806       *adjust_common_sizes = true;
 807       return false;
 808
 809     case DEF * 16 + DYN_WEAK_COMMON:
 810     case WEAK_DEF * 16 + DYN_WEAK_COMMON:
 811     case DYN_DEF * 16 + DYN_WEAK_COMMON:
 812     case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
 813       // A common symbol is ignored in the face of a definition.
 814       return false;
 815
 816     case UNDEF * 16 + DYN_WEAK_COMMON:
 817     case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 818     case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
 819     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 820       // I guess a weak common symbol is better than a definition.
 821       return true;
 822
 823     case COMMON * 16 + DYN_WEAK_COMMON:
 824     case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 825     case DYN_COMMON * 16 + DYN_WEAK_COMMON:
 826     case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 827       // Set the size to the maximum.
 828       *adjust_common_sizes = true;
 829       return false;
 830
 831     default:
 832       gold_unreachable();
 833     }
 834 }
 835
 836 // Issue an error or warning due to symbol resolution.  IS_ERROR
 837 // indicates an error rather than a warning.  MSG is the error
 838 // message; it is expected to have a %s for the symbol name.  TO is
 839 // the existing symbol.  DEFINED/OBJECT is where the new symbol was
 840 // found.
 841
 842 // FIXME: We should have better location information here.  When the
 843 // symbol is defined, we should be able to pull the location from the
 844 // debug info if there is any.
 845
 846 void
 847 Symbol_table::report_resolve_problem(bool is_error, const char* msg,
 848                                      const Symbol* to, Defined defined,
 849                                      Object* object)
 850 {
 851   std::string demangled(to->demangled_name());
 852   size_t len = strlen(msg) + demangled.length() + 10;
 853   char* buf = new char[len];
 854   snprintf(buf, len, msg, demangled.c_str());
 855
 856   const char* objname;
 857   switch (defined)
 858     {
 859     case OBJECT:
 860       objname = object->name().c_str();
 861       break;
 862     case COPY:
 863       objname = _("COPY reloc");
 864       break;
 865     case DEFSYM:
 866     case UNDEFINED:
 867       objname = _("command line");
 868       break;
 869     case SCRIPT:
 870       objname = _("linker script");
 871       break;
 872     case PREDEFINED:
 873     case INCREMENTAL_BASE:
 874       objname = _("linker defined");
 875       break;
 876     default:
 877       gold_unreachable();
 878     }
 879
 880   if (is_error)
 881     gold_error("%s: %s", objname, buf);
 882   else
 883     gold_warning("%s: %s", objname, buf);
 884
 885   delete[] buf;
 886
 887   if (to->source() == Symbol::FROM_OBJECT)
 888     objname = to->object()->name().c_str();
 889   else
 890     objname = _("command line");
 891   gold_info("%s: %s: previous definition here", program_name, objname);
 892 }
 893
 894 // A special case of should_override which is only called for a strong
 895 // defined symbol from a regular object file.  This is used when
 896 // defining special symbols.
 897
 898 bool
 899 Symbol_table::should_override_with_special(const Symbol* to,
 900                                            elfcpp::STT fromtype,
 901                                            Defined defined)
 902 {
 903   bool adjust_common_sizes;
 904   bool adjust_dyn_def;
 905   unsigned int frombits = global_flag | regular_flag | def_flag;
 906   bool ret = Symbol_table::should_override(to, frombits, fromtype, defined,
 907                                            NULL, &adjust_common_sizes,
 908                                            &adjust_dyn_def);
 909   gold_assert(!adjust_common_sizes && !adjust_dyn_def);
 910   return ret;
 911 }
 912
 913 // Override symbol base with a special symbol.
 914
 915 void
 916 Symbol::override_base_with_special(const Symbol* from)
 917 {
 918   bool same_name = this->name_ == from->name_;
 919   gold_assert(same_name || this->has_alias());
 920
 921   // If we are overriding an undef, remember the original binding.
 922   if (this->is_undefined())
 923     this->set_undef_binding(this->binding_);
 924
 925   this->source_ = from->source_;
 926   switch (from->source_)
 927     {
 928     case FROM_OBJECT:
 929       this->u_.from_object = from->u_.from_object;
 930       break;
 931     case IN_OUTPUT_DATA:
 932       this->u_.in_output_data = from->u_.in_output_data;
 933       break;
 934     case IN_OUTPUT_SEGMENT:
 935       this->u_.in_output_segment = from->u_.in_output_segment;
 936       break;
 937     case IS_CONSTANT:
 938     case IS_UNDEFINED:
 939       break;
 940     default:
 941       gold_unreachable();
 942       break;
 943     }
 944
 945   if (same_name)
 946     {
 947       // When overriding a versioned symbol with a special symbol, we
 948       // may be changing the version.  This will happen if we see a
 949       // special symbol such as "_end" defined in a shared object with
 950       // one version (from a version script), but we want to define it
 951       // here with a different version (from a different version
 952       // script).
 953       this->version_ = from->version_;
 954     }
 955   this->type_ = from->type_;
 956   this->binding_ = from->binding_;
 957   this->override_visibility(from->visibility_);
 958   this->nonvis_ = from->nonvis_;
 959
 960   // Special symbols are always considered to be regular symbols.
 961   this->in_reg_ = true;
 962
 963   if (from->needs_dynsym_entry_)
 964     this->needs_dynsym_entry_ = true;
 965   if (from->needs_dynsym_value_)
 966     this->needs_dynsym_value_ = true;
 967
 968   this->is_predefined_ = from->is_predefined_;
 969
 970   // We shouldn't see these flags.  If we do, we need to handle them
 971   // somehow.
 972   gold_assert(!from->is_forwarder_);
 973   gold_assert(!from->has_plt_offset());
 974   gold_assert(!from->has_warning_);
 975   gold_assert(!from->is_copied_from_dynobj_);
 976   gold_assert(!from->is_forced_local_);
 977 }
 978
 979 // Override a symbol with a special symbol.
 980
 981 template<int size>
 982 void
 983 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from)
 984 {
 985   this->override_base_with_special(from);
 986   this->value_ = from->value_;
 987   this->symsize_ = from->symsize_;
 988 }
 989
 990 // Override TOSYM with the special symbol FROMSYM.  This handles all
 991 // aliases of TOSYM.
 992
 993 template<int size>
 994 void
 995 Symbol_table::override_with_special(Sized_symbol<size>* tosym,
 996                                     const Sized_symbol<size>* fromsym)
 997 {
 998   tosym->override_with_special(fromsym);
 999   if (tosym->has_alias())
1000     {
1001       Symbol* sym = this->weak_aliases_[tosym];
1002       gold_assert(sym != NULL);
1003       Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
1004       do
1005         {
1006           ssym->override_with_special(fromsym);
1007           sym = this->weak_aliases_[ssym];
1008           gold_assert(sym != NULL);
1009           ssym = this->get_sized_symbol<size>(sym);
1010         }
1011       while (ssym != tosym);
1012     }
1013   if (tosym->binding() == elfcpp::STB_LOCAL
1014       || ((tosym->visibility() == elfcpp::STV_HIDDEN
1015            || tosym->visibility() == elfcpp::STV_INTERNAL)
1016           && (tosym->binding() == elfcpp::STB_GLOBAL
1017               || tosym->binding() == elfcpp::STB_GNU_UNIQUE
1018               || tosym->binding() == elfcpp::STB_WEAK)
1019           && !parameters->options().relocatable()))
1020     this->force_local(tosym);
1021 }
1022
1023 // Instantiate the templates we need.  We could use the configure
1024 // script to restrict this to only the ones needed for implemented
1025 // targets.
1026
1027 // We have to instantiate both big and little endian versions because
1028 // these are used by other templates that depends on size only.
1029
1030 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
1031 template
1032 void
1033 Symbol_table::resolve<32, false>(
1034     Sized_symbol<32>* to,
1035     const elfcpp::Sym<32, false>& sym,
1036     unsigned int st_shndx,
1037     bool is_ordinary,
1038     unsigned int orig_st_shndx,
1039     Object* object,
1040     const char* version);
1041
1042 template
1043 void
1044 Symbol_table::resolve<32, true>(
1045     Sized_symbol<32>* to,
1046     const elfcpp::Sym<32, true>& sym,
1047     unsigned int st_shndx,
1048     bool is_ordinary,
1049     unsigned int orig_st_shndx,
1050     Object* object,
1051     const char* version);
1052 #endif
1053
1054 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
1055 template
1056 void
1057 Symbol_table::resolve<64, false>(
1058     Sized_symbol<64>* to,
1059     const elfcpp::Sym<64, false>& sym,
1060     unsigned int st_shndx,
1061     bool is_ordinary,
1062     unsigned int orig_st_shndx,
1063     Object* object,
1064     const char* version);
1065
1066 template
1067 void
1068 Symbol_table::resolve<64, true>(
1069     Sized_symbol<64>* to,
1070     const elfcpp::Sym<64, true>& sym,
1071     unsigned int st_shndx,
1072     bool is_ordinary,
1073     unsigned int orig_st_shndx,
1074     Object* object,
1075     const char* version);
1076 #endif
1077
1078 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
1079 template
1080 void
1081 Symbol_table::override_with_special<32>(Sized_symbol<32>*,
1082                                         const Sized_symbol<32>*);
1083 #endif
1084
1085 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
1086 template
1087 void
1088 Symbol_table::override_with_special<64>(Sized_symbol<64>*,
1089                                         const Sized_symbol<64>*);
1090 #endif
1091
1092 } // End namespace gold.