gold/resolve.cc

   1 // resolve.cc -- symbol resolution for gold
   2
   3 // Copyright 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
   4 // Written by Ian Lance Taylor <iant@google.com>.
   5
   6 // This file is part of gold.
   7
   8 // This program is free software; you can redistribute it and/or modify
   9 // it under the terms of the GNU General Public License as published by
  10 // the Free Software Foundation; either version 3 of the License, or
  11 // (at your option) any later version.
  12
  13 // This program is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 // GNU General Public License for more details.
  17
  18 // You should have received a copy of the GNU General Public License
  19 // along with this program; if not, write to the Free Software
  20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  21 // MA 02110-1301, USA.
  22
  23 #include "gold.h"
  24
  25 #include "elfcpp.h"
  26 #include "target.h"
  27 #include "object.h"
  28 #include "symtab.h"
  29 #include "plugin.h"
  30
  31 namespace gold
  32 {
  33
  34 // Symbol methods used in this file.
  35
  36 // This symbol is being overridden by another symbol whose version is
  37 // VERSION.  Update the VERSION_ field accordingly.
  38
  39 inline void
  40 Symbol::override_version(const char* version)
  41 {
  42   if (version == NULL)
  43     {
  44       // This is the case where this symbol is NAME/VERSION, and the
  45       // version was not marked as hidden.  That makes it the default
  46       // version, so we create NAME/NULL.  Later we see another symbol
  47       // NAME/NULL, and that symbol is overriding this one.  In this
  48       // case, since NAME/VERSION is the default, we make NAME/NULL
  49       // override NAME/VERSION as well.  They are already the same
  50       // Symbol structure.  Setting the VERSION_ field to NULL ensures
  51       // that it will be output with the correct, empty, version.
  52       this->version_ = version;
  53     }
  54   else
  55     {
  56       // This is the case where this symbol is NAME/VERSION_ONE, and
  57       // now we see NAME/VERSION_TWO, and NAME/VERSION_TWO is
  58       // overriding NAME.  If VERSION_ONE and VERSION_TWO are
  59       // different, then this can only happen when VERSION_ONE is NULL
  60       // and VERSION_TWO is not hidden.
  61       gold_assert(this->version_ == version || this->version_ == NULL);
  62       this->version_ = version;
  63     }
  64 }
  65
  66 // This symbol is being overidden by another symbol whose visibility
  67 // is VISIBILITY.  Updated the VISIBILITY_ field accordingly.
  68
  69 inline void
  70 Symbol::override_visibility(elfcpp::STV visibility)
  71 {
  72   // The rule for combining visibility is that we always choose the
  73   // most constrained visibility.  In order of increasing constraint,
  74   // visibility goes PROTECTED, HIDDEN, INTERNAL.  This is the reverse
  75   // of the numeric values, so the effect is that we always want the
  76   // smallest non-zero value.
  77   if (visibility != elfcpp::STV_DEFAULT)
  78     {
  79       if (this->visibility_ == elfcpp::STV_DEFAULT)
  80         this->visibility_ = visibility;
  81       else if (this->visibility_ > visibility)
  82         this->visibility_ = visibility;
  83     }
  84 }
  85
  86 // Override the fields in Symbol.
  87
  88 template<int size, bool big_endian>
  89 void
  90 Symbol::override_base(const elfcpp::Sym<size, big_endian>& sym,
  91                       unsigned int st_shndx, bool is_ordinary,
  92                       Object* object, const char* version)
  93 {
  94   gold_assert(this->source_ == FROM_OBJECT);
  95   this->u_.from_object.object = object;
  96   this->override_version(version);
  97   this->u_.from_object.shndx = st_shndx;
  98   this->is_ordinary_shndx_ = is_ordinary;
  99   this->type_ = sym.get_st_type();
 100   this->binding_ = sym.get_st_bind();
 101   this->override_visibility(sym.get_st_visibility());
 102   this->nonvis_ = sym.get_st_nonvis();
 103   if (object->is_dynamic())
 104     this->in_dyn_ = true;
 105   else
 106     this->in_reg_ = true;
 107 }
 108
 109 // Override the fields in Sized_symbol.
 110
 111 template<int size>
 112 template<bool big_endian>
 113 void
 114 Sized_symbol<size>::override(const elfcpp::Sym<size, big_endian>& sym,
 115                              unsigned st_shndx, bool is_ordinary,
 116                              Object* object, const char* version)
 117 {
 118   this->override_base(sym, st_shndx, is_ordinary, object, version);
 119   this->value_ = sym.get_st_value();
 120   this->symsize_ = sym.get_st_size();
 121 }
 122
 123 // Override TOSYM with symbol FROMSYM, defined in OBJECT, with version
 124 // VERSION.  This handles all aliases of TOSYM.
 125
 126 template<int size, bool big_endian>
 127 void
 128 Symbol_table::override(Sized_symbol<size>* tosym,
 129                        const elfcpp::Sym<size, big_endian>& fromsym,
 130                        unsigned int st_shndx, bool is_ordinary,
 131                        Object* object, const char* version)
 132 {
 133   tosym->override(fromsym, st_shndx, is_ordinary, object, version);
 134   if (tosym->has_alias())
 135     {
 136       Symbol* sym = this->weak_aliases_[tosym];
 137       gold_assert(sym != NULL);
 138       Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
 139       do
 140         {
 141           ssym->override(fromsym, st_shndx, is_ordinary, object, version);
 142           sym = this->weak_aliases_[ssym];
 143           gold_assert(sym != NULL);
 144           ssym = this->get_sized_symbol<size>(sym);
 145         }
 146       while (ssym != tosym);
 147     }
 148 }
 149
 150 // The resolve functions build a little code for each symbol.
 151 // Bit 0: 0 for global, 1 for weak.
 152 // Bit 1: 0 for regular object, 1 for shared object
 153 // Bits 2-3: 0 for normal, 1 for undefined, 2 for common
 154 // This gives us values from 0 to 11.
 155
 156 static const int global_or_weak_shift = 0;
 157 static const unsigned int global_flag = 0 << global_or_weak_shift;
 158 static const unsigned int weak_flag = 1 << global_or_weak_shift;
 159
 160 static const int regular_or_dynamic_shift = 1;
 161 static const unsigned int regular_flag = 0 << regular_or_dynamic_shift;
 162 static const unsigned int dynamic_flag = 1 << regular_or_dynamic_shift;
 163
 164 static const int def_undef_or_common_shift = 2;
 165 static const unsigned int def_flag = 0 << def_undef_or_common_shift;
 166 static const unsigned int undef_flag = 1 << def_undef_or_common_shift;
 167 static const unsigned int common_flag = 2 << def_undef_or_common_shift;
 168
 169 // This convenience function combines all the flags based on facts
 170 // about the symbol.
 171
 172 static unsigned int
 173 symbol_to_bits(elfcpp::STB binding, bool is_dynamic,
 174                unsigned int shndx, bool is_ordinary, elfcpp::STT type)
 175 {
 176   unsigned int bits;
 177
 178   switch (binding)
 179     {
 180     case elfcpp::STB_GLOBAL:
 181     case elfcpp::STB_GNU_UNIQUE:
 182       bits = global_flag;
 183       break;
 184
 185     case elfcpp::STB_WEAK:
 186       bits = weak_flag;
 187       break;
 188
 189     case elfcpp::STB_LOCAL:
 190       // We should only see externally visible symbols in the symbol
 191       // table.
 192       gold_error(_("invalid STB_LOCAL symbol in external symbols"));
 193       bits = global_flag;
 194
 195     default:
 196       // Any target which wants to handle STB_LOOS, etc., needs to
 197       // define a resolve method.
 198       gold_error(_("unsupported symbol binding %d"), static_cast<int>(binding));
 199       bits = global_flag;
 200     }
 201
 202   if (is_dynamic)
 203     bits |= dynamic_flag;
 204   else
 205     bits |= regular_flag;
 206
 207   switch (shndx)
 208     {
 209     case elfcpp::SHN_UNDEF:
 210       bits |= undef_flag;
 211       break;
 212
 213     case elfcpp::SHN_COMMON:
 214       if (!is_ordinary)
 215         bits |= common_flag;
 216       break;
 217
 218     default:
 219       if (type == elfcpp::STT_COMMON)
 220         bits |= common_flag;
 221       else if (!is_ordinary && Symbol::is_common_shndx(shndx))
 222         bits |= common_flag;
 223       else
 224         bits |= def_flag;
 225       break;
 226     }
 227
 228   return bits;
 229 }
 230
 231 // Resolve a symbol.  This is called the second and subsequent times
 232 // we see a symbol.  TO is the pre-existing symbol.  ST_SHNDX is the
 233 // section index for SYM, possibly adjusted for many sections.
 234 // IS_ORDINARY is whether ST_SHNDX is a normal section index rather
 235 // than a special code.  ORIG_ST_SHNDX is the original section index,
 236 // before any munging because of discarded sections, except that all
 237 // non-ordinary section indexes are mapped to SHN_UNDEF.  VERSION is
 238 // the version of SYM.
 239
 240 template<int size, bool big_endian>
 241 void
 242 Symbol_table::resolve(Sized_symbol<size>* to,
 243                       const elfcpp::Sym<size, big_endian>& sym,
 244                       unsigned int st_shndx, bool is_ordinary,
 245                       unsigned int orig_st_shndx,
 246                       Object* object, const char* version)
 247 {
 248   // It's possible for a symbol to be defined in an object file
 249   // using .symver to give it a version, and for there to also be
 250   // a linker script giving that symbol the same version.  We
 251   // don't want to give a multiple-definition error for this
 252   // harmless redefinition.
 253   bool to_is_ordinary;
 254   if (to->source() == Symbol::FROM_OBJECT
 255       && to->object() == object
 256       && is_ordinary
 257       && to->is_defined()
 258       && to->shndx(&to_is_ordinary) == st_shndx
 259       && to_is_ordinary
 260       && to->value() == sym.get_st_value())
 261     return;
 262
 263   if (parameters->target().has_resolve())
 264     {
 265       Sized_target<size, big_endian>* sized_target;
 266       sized_target = parameters->sized_target<size, big_endian>();
 267       sized_target->resolve(to, sym, object, version);
 268       return;
 269     }
 270
 271   if (!object->is_dynamic())
 272     {
 273       // Record that we've seen this symbol in a regular object.
 274       to->set_in_reg();
 275     }
 276   else if (st_shndx == elfcpp::SHN_UNDEF
 277            && (to->visibility() == elfcpp::STV_HIDDEN
 278                || to->visibility() == elfcpp::STV_INTERNAL))
 279     {
 280       // A dynamic object cannot reference a hidden or internal symbol
 281       // defined in another object.
 282       gold_warning(_("%s symbol '%s' in %s is referenced by DSO %s"),
 283                    (to->visibility() == elfcpp::STV_HIDDEN
 284                     ? "hidden"
 285                     : "internal"),
 286                    to->demangled_name().c_str(),
 287                    to->object()->name().c_str(),
 288                    object->name().c_str());
 289       return;
 290     }
 291   else
 292     {
 293       // Record that we've seen this symbol in a dynamic object.
 294       to->set_in_dyn();
 295     }
 296
 297   // Record if we've seen this symbol in a real ELF object (i.e., the
 298   // symbol is referenced from outside the world known to the plugin).
 299   if (object->pluginobj() == NULL && !object->is_dynamic())
 300     to->set_in_real_elf();
 301
 302   // If we're processing replacement files, allow new symbols to override
 303   // the placeholders from the plugin objects.
 304   if (to->source() == Symbol::FROM_OBJECT)
 305     {
 306       Pluginobj* obj = to->object()->pluginobj();
 307       if (obj != NULL
 308           && parameters->options().plugins()->in_replacement_phase())
 309         {
 310           this->override(to, sym, st_shndx, is_ordinary, object, version);
 311           return;
 312         }
 313     }
 314
 315   // A new weak undefined reference, merging with an old weak
 316   // reference, could be a One Definition Rule (ODR) violation --
 317   // especially if the types or sizes of the references differ.  We'll
 318   // store such pairs and look them up later to make sure they
 319   // actually refer to the same lines of code.  We also check
 320   // combinations of weak and strong, which might occur if one case is
 321   // inline and the other is not.  (Note: not all ODR violations can
 322   // be found this way, and not everything this finds is an ODR
 323   // violation.  But it's helpful to warn about.)
 324   if (parameters->options().detect_odr_violations()
 325       && (sym.get_st_bind() == elfcpp::STB_WEAK
 326           || to->binding() == elfcpp::STB_WEAK)
 327       && orig_st_shndx != elfcpp::SHN_UNDEF
 328       && to->shndx(&to_is_ordinary) != elfcpp::SHN_UNDEF
 329       && to_is_ordinary
 330       && sym.get_st_size() != 0    // Ignore weird 0-sized symbols.
 331       && to->symsize() != 0
 332       && (sym.get_st_type() != to->type()
 333           || sym.get_st_size() != to->symsize())
 334       // C does not have a concept of ODR, so we only need to do this
 335       // on C++ symbols.  These have (mangled) names starting with _Z.
 336       && to->name()[0] == '_' && to->name()[1] == 'Z')
 337     {
 338       Symbol_location fromloc
 339           = { object, orig_st_shndx, static_cast<off_t>(sym.get_st_value()) };
 340       Symbol_location toloc = { to->object(), to->shndx(&to_is_ordinary),
 341                                 static_cast<off_t>(to->value()) };
 342       this->candidate_odr_violations_[to->name()].insert(fromloc);
 343       this->candidate_odr_violations_[to->name()].insert(toloc);
 344     }
 345
 346   unsigned int frombits = symbol_to_bits(sym.get_st_bind(),
 347                                          object->is_dynamic(),
 348                                          st_shndx, is_ordinary,
 349                                          sym.get_st_type());
 350
 351   bool adjust_common_sizes;
 352   bool adjust_dyndef;
 353   typename Sized_symbol<size>::Size_type tosize = to->symsize();
 354   if (Symbol_table::should_override(to, frombits, sym.get_st_type(), OBJECT,
 355                                     object, &adjust_common_sizes,
 356                                     &adjust_dyndef))
 357     {
 358       elfcpp::STB tobinding = to->binding();
 359       typename Sized_symbol<size>::Value_type tovalue = to->value();
 360       this->override(to, sym, st_shndx, is_ordinary, object, version);
 361       if (adjust_common_sizes)
 362         {
 363           if (tosize > to->symsize())
 364             to->set_symsize(tosize);
 365           if (tovalue > to->value())
 366             to->set_value(tovalue);
 367         }
 368       if (adjust_dyndef)
 369         {
 370           // We are overriding an UNDEF or WEAK UNDEF with a DYN DEF.
 371           // Remember which kind of UNDEF it was for future reference.
 372           to->set_undef_binding(tobinding);
 373         }
 374     }
 375   else
 376     {
 377       if (adjust_common_sizes)
 378         {
 379           if (sym.get_st_size() > tosize)
 380             to->set_symsize(sym.get_st_size());
 381           if (sym.get_st_value() > to->value())
 382             to->set_value(sym.get_st_value());
 383         }
 384       if (adjust_dyndef)
 385         {
 386           // We are keeping a DYN DEF after seeing an UNDEF or WEAK UNDEF.
 387           // Remember which kind of UNDEF it was.
 388           to->set_undef_binding(sym.get_st_bind());
 389         }
 390       // The ELF ABI says that even for a reference to a symbol we
 391       // merge the visibility.
 392       to->override_visibility(sym.get_st_visibility());
 393     }
 394
 395   if (adjust_common_sizes && parameters->options().warn_common())
 396     {
 397       if (tosize > sym.get_st_size())
 398         Symbol_table::report_resolve_problem(false,
 399                                              _("common of '%s' overriding "
 400                                                "smaller common"),
 401                                              to, OBJECT, object);
 402       else if (tosize < sym.get_st_size())
 403         Symbol_table::report_resolve_problem(false,
 404                                              _("common of '%s' overidden by "
 405                                                "larger common"),
 406                                              to, OBJECT, object);
 407       else
 408         Symbol_table::report_resolve_problem(false,
 409                                              _("multiple common of '%s'"),
 410                                              to, OBJECT, object);
 411     }
 412 }
 413
 414 // Handle the core of symbol resolution.  This is called with the
 415 // existing symbol, TO, and a bitflag describing the new symbol.  This
 416 // returns true if we should override the existing symbol with the new
 417 // one, and returns false otherwise.  It sets *ADJUST_COMMON_SIZES to
 418 // true if we should set the symbol size to the maximum of the TO and
 419 // FROM sizes.  It handles error conditions.
 420
 421 bool
 422 Symbol_table::should_override(const Symbol* to, unsigned int frombits,
 423                               elfcpp::STT fromtype, Defined defined,
 424                               Object* object, bool* adjust_common_sizes,
 425                               bool* adjust_dyndef)
 426 {
 427   *adjust_common_sizes = false;
 428   *adjust_dyndef = false;
 429
 430   unsigned int tobits;
 431   if (to->source() == Symbol::IS_UNDEFINED)
 432     tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_UNDEF, true,
 433                             to->type());
 434   else if (to->source() != Symbol::FROM_OBJECT)
 435     tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_ABS, false,
 436                             to->type());
 437   else
 438     {
 439       bool is_ordinary;
 440       unsigned int shndx = to->shndx(&is_ordinary);
 441       tobits = symbol_to_bits(to->binding(),
 442                               to->object()->is_dynamic(),
 443                               shndx,
 444                               is_ordinary,
 445                               to->type());
 446     }
 447
 448   if (to->type() == elfcpp::STT_TLS
 449       ? fromtype != elfcpp::STT_TLS
 450       : fromtype == elfcpp::STT_TLS)
 451     Symbol_table::report_resolve_problem(true,
 452                                          _("symbol '%s' used as both __thread "
 453                                            "and non-__thread"),
 454                                          to, defined, object);
 455
 456   // We use a giant switch table for symbol resolution.  This code is
 457   // unwieldy, but: 1) it is efficient; 2) we definitely handle all
 458   // cases; 3) it is easy to change the handling of a particular case.
 459   // The alternative would be a series of conditionals, but it is easy
 460   // to get the ordering wrong.  This could also be done as a table,
 461   // but that is no easier to understand than this large switch
 462   // statement.
 463
 464   // These are the values generated by the bit codes.
 465   enum
 466   {
 467     DEF =              global_flag | regular_flag | def_flag,
 468     WEAK_DEF =         weak_flag   | regular_flag | def_flag,
 469     DYN_DEF =          global_flag | dynamic_flag | def_flag,
 470     DYN_WEAK_DEF =     weak_flag   | dynamic_flag | def_flag,
 471     UNDEF =            global_flag | regular_flag | undef_flag,
 472     WEAK_UNDEF =       weak_flag   | regular_flag | undef_flag,
 473     DYN_UNDEF =        global_flag | dynamic_flag | undef_flag,
 474     DYN_WEAK_UNDEF =   weak_flag   | dynamic_flag | undef_flag,
 475     COMMON =           global_flag | regular_flag | common_flag,
 476     WEAK_COMMON =      weak_flag   | regular_flag | common_flag,
 477     DYN_COMMON =       global_flag | dynamic_flag | common_flag,
 478     DYN_WEAK_COMMON =  weak_flag   | dynamic_flag | common_flag
 479   };
 480
 481   switch (tobits * 16 + frombits)
 482     {
 483     case DEF * 16 + DEF:
 484       // Two definitions of the same symbol.
 485
 486       // If either symbol is defined by an object included using
 487       // --just-symbols, then don't warn.  This is for compatibility
 488       // with the GNU linker.  FIXME: This is a hack.
 489       if ((to->source() == Symbol::FROM_OBJECT && to->object()->just_symbols())
 490           || (object != NULL && object->just_symbols()))
 491         return false;
 492
 493       if (!parameters->options().muldefs())
 494         Symbol_table::report_resolve_problem(true,
 495                                              _("multiple definition of '%s'"),
 496                                              to, defined, object);
 497       return false;
 498
 499     case WEAK_DEF * 16 + DEF:
 500       // We've seen a weak definition, and now we see a strong
 501       // definition.  In the original SVR4 linker, this was treated as
 502       // a multiple definition error.  In the Solaris linker and the
 503       // GNU linker, a weak definition followed by a regular
 504       // definition causes the weak definition to be overridden.  We
 505       // are currently compatible with the GNU linker.  In the future
 506       // we should add a target specific option to change this.
 507       // FIXME.
 508       return true;
 509
 510     case DYN_DEF * 16 + DEF:
 511     case DYN_WEAK_DEF * 16 + DEF:
 512       // We've seen a definition in a dynamic object, and now we see a
 513       // definition in a regular object.  The definition in the
 514       // regular object overrides the definition in the dynamic
 515       // object.
 516       return true;
 517
 518     case UNDEF * 16 + DEF:
 519     case WEAK_UNDEF * 16 + DEF:
 520     case DYN_UNDEF * 16 + DEF:
 521     case DYN_WEAK_UNDEF * 16 + DEF:
 522       // We've seen an undefined reference, and now we see a
 523       // definition.  We use the definition.
 524       return true;
 525
 526     case COMMON * 16 + DEF:
 527     case WEAK_COMMON * 16 + DEF:
 528     case DYN_COMMON * 16 + DEF:
 529     case DYN_WEAK_COMMON * 16 + DEF:
 530       // We've seen a common symbol and now we see a definition.  The
 531       // definition overrides.
 532       if (parameters->options().warn_common())
 533         Symbol_table::report_resolve_problem(false,
 534                                              _("definition of '%s' overriding "
 535                                                "common"),
 536                                              to, defined, object);
 537       return true;
 538
 539     case DEF * 16 + WEAK_DEF:
 540     case WEAK_DEF * 16 + WEAK_DEF:
 541       // We've seen a definition and now we see a weak definition.  We
 542       // ignore the new weak definition.
 543       return false;
 544
 545     case DYN_DEF * 16 + WEAK_DEF:
 546     case DYN_WEAK_DEF * 16 + WEAK_DEF:
 547       // We've seen a dynamic definition and now we see a regular weak
 548       // definition.  The regular weak definition overrides.
 549       return true;
 550
 551     case UNDEF * 16 + WEAK_DEF:
 552     case WEAK_UNDEF * 16 + WEAK_DEF:
 553     case DYN_UNDEF * 16 + WEAK_DEF:
 554     case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
 555       // A weak definition of a currently undefined symbol.
 556       return true;
 557
 558     case COMMON * 16 + WEAK_DEF:
 559     case WEAK_COMMON * 16 + WEAK_DEF:
 560       // A weak definition does not override a common definition.
 561       return false;
 562
 563     case DYN_COMMON * 16 + WEAK_DEF:
 564     case DYN_WEAK_COMMON * 16 + WEAK_DEF:
 565       // A weak definition does override a definition in a dynamic
 566       // object.
 567       if (parameters->options().warn_common())
 568         Symbol_table::report_resolve_problem(false,
 569                                              _("definition of '%s' overriding "
 570                                                "dynamic common definition"),
 571                                              to, defined, object);
 572       return true;
 573
 574     case DEF * 16 + DYN_DEF:
 575     case WEAK_DEF * 16 + DYN_DEF:
 576     case DYN_DEF * 16 + DYN_DEF:
 577     case DYN_WEAK_DEF * 16 + DYN_DEF:
 578       // Ignore a dynamic definition if we already have a definition.
 579       return false;
 580
 581     case UNDEF * 16 + DYN_DEF:
 582     case DYN_UNDEF * 16 + DYN_DEF:
 583     case DYN_WEAK_UNDEF * 16 + DYN_DEF:
 584       // Use a dynamic definition if we have a reference.
 585       return true;
 586
 587     case WEAK_UNDEF * 16 + DYN_DEF:
 588       // When overriding a weak undef by a dynamic definition,
 589       // we need to remember that the original undef was weak.
 590       *adjust_dyndef = true;
 591       return true;
 592
 593     case COMMON * 16 + DYN_DEF:
 594     case WEAK_COMMON * 16 + DYN_DEF:
 595     case DYN_COMMON * 16 + DYN_DEF:
 596     case DYN_WEAK_COMMON * 16 + DYN_DEF:
 597       // Ignore a dynamic definition if we already have a common
 598       // definition.
 599       return false;
 600
 601     case DEF * 16 + DYN_WEAK_DEF:
 602     case WEAK_DEF * 16 + DYN_WEAK_DEF:
 603     case DYN_DEF * 16 + DYN_WEAK_DEF:
 604     case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
 605       // Ignore a weak dynamic definition if we already have a
 606       // definition.
 607       return false;
 608
 609     case UNDEF * 16 + DYN_WEAK_DEF:
 610       // When overriding an undef by a dynamic weak definition,
 611       // we need to remember that the original undef was not weak.
 612       *adjust_dyndef = true;
 613       return true;
 614
 615     case DYN_UNDEF * 16 + DYN_WEAK_DEF:
 616     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 617       // Use a weak dynamic definition if we have a reference.
 618       return true;
 619
 620     case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 621       // When overriding a weak undef by a dynamic definition,
 622       // we need to remember that the original undef was weak.
 623       *adjust_dyndef = true;
 624       return true;
 625
 626     case COMMON * 16 + DYN_WEAK_DEF:
 627     case WEAK_COMMON * 16 + DYN_WEAK_DEF:
 628     case DYN_COMMON * 16 + DYN_WEAK_DEF:
 629     case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
 630       // Ignore a weak dynamic definition if we already have a common
 631       // definition.
 632       return false;
 633
 634     case DEF * 16 + UNDEF:
 635     case WEAK_DEF * 16 + UNDEF:
 636     case UNDEF * 16 + UNDEF:
 637       // A new undefined reference tells us nothing.
 638       return false;
 639
 640     case DYN_DEF * 16 + UNDEF:
 641     case DYN_WEAK_DEF * 16 + UNDEF:
 642       // For a dynamic def, we need to remember which kind of undef we see.
 643       *adjust_dyndef = true;
 644       return false;
 645
 646     case WEAK_UNDEF * 16 + UNDEF:
 647     case DYN_UNDEF * 16 + UNDEF:
 648     case DYN_WEAK_UNDEF * 16 + UNDEF:
 649       // A strong undef overrides a dynamic or weak undef.
 650       return true;
 651
 652     case COMMON * 16 + UNDEF:
 653     case WEAK_COMMON * 16 + UNDEF:
 654     case DYN_COMMON * 16 + UNDEF:
 655     case DYN_WEAK_COMMON * 16 + UNDEF:
 656       // A new undefined reference tells us nothing.
 657       return false;
 658
 659     case DEF * 16 + WEAK_UNDEF:
 660     case WEAK_DEF * 16 + WEAK_UNDEF:
 661     case UNDEF * 16 + WEAK_UNDEF:
 662     case WEAK_UNDEF * 16 + WEAK_UNDEF:
 663     case DYN_UNDEF * 16 + WEAK_UNDEF:
 664     case COMMON * 16 + WEAK_UNDEF:
 665     case WEAK_COMMON * 16 + WEAK_UNDEF:
 666     case DYN_COMMON * 16 + WEAK_UNDEF:
 667     case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
 668       // A new weak undefined reference tells us nothing unless the
 669       // exisiting symbol is a dynamic weak reference.
 670       return false;
 671
 672     case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
 673       // A new weak reference overrides an existing dynamic weak reference.
 674       // This is necessary because a dynamic weak reference remembers
 675       // the old binding, which may not be weak.  If we keeps the existing
 676       // dynamic weak reference, the weakness may be dropped in the output.
 677       return true;
 678
 679     case DYN_DEF * 16 + WEAK_UNDEF:
 680     case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
 681       // For a dynamic def, we need to remember which kind of undef we see.
 682       *adjust_dyndef = true;
 683       return false;
 684
 685     case DEF * 16 + DYN_UNDEF:
 686     case WEAK_DEF * 16 + DYN_UNDEF:
 687     case DYN_DEF * 16 + DYN_UNDEF:
 688     case DYN_WEAK_DEF * 16 + DYN_UNDEF:
 689     case UNDEF * 16 + DYN_UNDEF:
 690     case WEAK_UNDEF * 16 + DYN_UNDEF:
 691     case DYN_UNDEF * 16 + DYN_UNDEF:
 692     case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
 693     case COMMON * 16 + DYN_UNDEF:
 694     case WEAK_COMMON * 16 + DYN_UNDEF:
 695     case DYN_COMMON * 16 + DYN_UNDEF:
 696     case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
 697       // A new dynamic undefined reference tells us nothing.
 698       return false;
 699
 700     case DEF * 16 + DYN_WEAK_UNDEF:
 701     case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 702     case DYN_DEF * 16 + DYN_WEAK_UNDEF:
 703     case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 704     case UNDEF * 16 + DYN_WEAK_UNDEF:
 705     case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 706     case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
 707     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 708     case COMMON * 16 + DYN_WEAK_UNDEF:
 709     case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 710     case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
 711     case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 712       // A new weak dynamic undefined reference tells us nothing.
 713       return false;
 714
 715     case DEF * 16 + COMMON:
 716       // A common symbol does not override a definition.
 717       if (parameters->options().warn_common())
 718         Symbol_table::report_resolve_problem(false,
 719                                              _("common '%s' overridden by "
 720                                                "previous definition"),
 721                                              to, defined, object);
 722       return false;
 723
 724     case WEAK_DEF * 16 + COMMON:
 725     case DYN_DEF * 16 + COMMON:
 726     case DYN_WEAK_DEF * 16 + COMMON:
 727       // A common symbol does override a weak definition or a dynamic
 728       // definition.
 729       return true;
 730
 731     case UNDEF * 16 + COMMON:
 732     case WEAK_UNDEF * 16 + COMMON:
 733     case DYN_UNDEF * 16 + COMMON:
 734     case DYN_WEAK_UNDEF * 16 + COMMON:
 735       // A common symbol is a definition for a reference.
 736       return true;
 737
 738     case COMMON * 16 + COMMON:
 739       // Set the size to the maximum.
 740       *adjust_common_sizes = true;
 741       return false;
 742
 743     case WEAK_COMMON * 16 + COMMON:
 744       // I'm not sure just what a weak common symbol means, but
 745       // presumably it can be overridden by a regular common symbol.
 746       return true;
 747
 748     case DYN_COMMON * 16 + COMMON:
 749     case DYN_WEAK_COMMON * 16 + COMMON:
 750       // Use the real common symbol, but adjust the size if necessary.
 751       *adjust_common_sizes = true;
 752       return true;
 753
 754     case DEF * 16 + WEAK_COMMON:
 755     case WEAK_DEF * 16 + WEAK_COMMON:
 756     case DYN_DEF * 16 + WEAK_COMMON:
 757     case DYN_WEAK_DEF * 16 + WEAK_COMMON:
 758       // Whatever a weak common symbol is, it won't override a
 759       // definition.
 760       return false;
 761
 762     case UNDEF * 16 + WEAK_COMMON:
 763     case WEAK_UNDEF * 16 + WEAK_COMMON:
 764     case DYN_UNDEF * 16 + WEAK_COMMON:
 765     case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
 766       // A weak common symbol is better than an undefined symbol.
 767       return true;
 768
 769     case COMMON * 16 + WEAK_COMMON:
 770     case WEAK_COMMON * 16 + WEAK_COMMON:
 771     case DYN_COMMON * 16 + WEAK_COMMON:
 772     case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
 773       // Ignore a weak common symbol in the presence of a real common
 774       // symbol.
 775       return false;
 776
 777     case DEF * 16 + DYN_COMMON:
 778     case WEAK_DEF * 16 + DYN_COMMON:
 779     case DYN_DEF * 16 + DYN_COMMON:
 780     case DYN_WEAK_DEF * 16 + DYN_COMMON:
 781       // Ignore a dynamic common symbol in the presence of a
 782       // definition.
 783       return false;
 784
 785     case UNDEF * 16 + DYN_COMMON:
 786     case WEAK_UNDEF * 16 + DYN_COMMON:
 787     case DYN_UNDEF * 16 + DYN_COMMON:
 788     case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
 789       // A dynamic common symbol is a definition of sorts.
 790       return true;
 791
 792     case COMMON * 16 + DYN_COMMON:
 793     case WEAK_COMMON * 16 + DYN_COMMON:
 794     case DYN_COMMON * 16 + DYN_COMMON:
 795     case DYN_WEAK_COMMON * 16 + DYN_COMMON:
 796       // Set the size to the maximum.
 797       *adjust_common_sizes = true;
 798       return false;
 799
 800     case DEF * 16 + DYN_WEAK_COMMON:
 801     case WEAK_DEF * 16 + DYN_WEAK_COMMON:
 802     case DYN_DEF * 16 + DYN_WEAK_COMMON:
 803     case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
 804       // A common symbol is ignored in the face of a definition.
 805       return false;
 806
 807     case UNDEF * 16 + DYN_WEAK_COMMON:
 808     case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 809     case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
 810     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 811       // I guess a weak common symbol is better than a definition.
 812       return true;
 813
 814     case COMMON * 16 + DYN_WEAK_COMMON:
 815     case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 816     case DYN_COMMON * 16 + DYN_WEAK_COMMON:
 817     case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 818       // Set the size to the maximum.
 819       *adjust_common_sizes = true;
 820       return false;
 821
 822     default:
 823       gold_unreachable();
 824     }
 825 }
 826
 827 // Issue an error or warning due to symbol resolution.  IS_ERROR
 828 // indicates an error rather than a warning.  MSG is the error
 829 // message; it is expected to have a %s for the symbol name.  TO is
 830 // the existing symbol.  DEFINED/OBJECT is where the new symbol was
 831 // found.
 832
 833 // FIXME: We should have better location information here.  When the
 834 // symbol is defined, we should be able to pull the location from the
 835 // debug info if there is any.
 836
 837 void
 838 Symbol_table::report_resolve_problem(bool is_error, const char* msg,
 839                                      const Symbol* to, Defined defined,
 840                                      Object* object)
 841 {
 842   std::string demangled(to->demangled_name());
 843   size_t len = strlen(msg) + demangled.length() + 10;
 844   char* buf = new char[len];
 845   snprintf(buf, len, msg, demangled.c_str());
 846
 847   const char* objname;
 848   switch (defined)
 849     {
 850     case OBJECT:
 851       objname = object->name().c_str();
 852       break;
 853     case COPY:
 854       objname = _("COPY reloc");
 855       break;
 856     case DEFSYM:
 857     case UNDEFINED:
 858       objname = _("command line");
 859       break;
 860     case SCRIPT:
 861       objname = _("linker script");
 862       break;
 863     case PREDEFINED:
 864     case INCREMENTAL_BASE:
 865       objname = _("linker defined");
 866       break;
 867     default:
 868       gold_unreachable();
 869     }
 870
 871   if (is_error)
 872     gold_error("%s: %s", objname, buf);
 873   else
 874     gold_warning("%s: %s", objname, buf);
 875
 876   delete[] buf;
 877
 878   if (to->source() == Symbol::FROM_OBJECT)
 879     objname = to->object()->name().c_str();
 880   else
 881     objname = _("command line");
 882   gold_info("%s: %s: previous definition here", program_name, objname);
 883 }
 884
 885 // A special case of should_override which is only called for a strong
 886 // defined symbol from a regular object file.  This is used when
 887 // defining special symbols.
 888
 889 bool
 890 Symbol_table::should_override_with_special(const Symbol* to,
 891                                            elfcpp::STT fromtype,
 892                                            Defined defined)
 893 {
 894   bool adjust_common_sizes;
 895   bool adjust_dyn_def;
 896   unsigned int frombits = global_flag | regular_flag | def_flag;
 897   bool ret = Symbol_table::should_override(to, frombits, fromtype, defined,
 898                                            NULL, &adjust_common_sizes,
 899                                            &adjust_dyn_def);
 900   gold_assert(!adjust_common_sizes && !adjust_dyn_def);
 901   return ret;
 902 }
 903
 904 // Override symbol base with a special symbol.
 905
 906 void
 907 Symbol::override_base_with_special(const Symbol* from)
 908 {
 909   bool same_name = this->name_ == from->name_;
 910   gold_assert(same_name || this->has_alias());
 911
 912   this->source_ = from->source_;
 913   switch (from->source_)
 914     {
 915     case FROM_OBJECT:
 916       this->u_.from_object = from->u_.from_object;
 917       break;
 918     case IN_OUTPUT_DATA:
 919       this->u_.in_output_data = from->u_.in_output_data;
 920       break;
 921     case IN_OUTPUT_SEGMENT:
 922       this->u_.in_output_segment = from->u_.in_output_segment;
 923       break;
 924     case IS_CONSTANT:
 925     case IS_UNDEFINED:
 926       break;
 927     default:
 928       gold_unreachable();
 929       break;
 930     }
 931
 932   if (same_name)
 933     {
 934       // When overriding a versioned symbol with a special symbol, we
 935       // may be changing the version.  This will happen if we see a
 936       // special symbol such as "_end" defined in a shared object with
 937       // one version (from a version script), but we want to define it
 938       // here with a different version (from a different version
 939       // script).
 940       this->version_ = from->version_;
 941     }
 942   this->type_ = from->type_;
 943   this->binding_ = from->binding_;
 944   this->override_visibility(from->visibility_);
 945   this->nonvis_ = from->nonvis_;
 946
 947   // Special symbols are always considered to be regular symbols.
 948   this->in_reg_ = true;
 949
 950   if (from->needs_dynsym_entry_)
 951     this->needs_dynsym_entry_ = true;
 952   if (from->needs_dynsym_value_)
 953     this->needs_dynsym_value_ = true;
 954
 955   this->is_predefined_ = from->is_predefined_;
 956
 957   // We shouldn't see these flags.  If we do, we need to handle them
 958   // somehow.
 959   gold_assert(!from->is_forwarder_);
 960   gold_assert(!from->has_plt_offset());
 961   gold_assert(!from->has_warning_);
 962   gold_assert(!from->is_copied_from_dynobj_);
 963   gold_assert(!from->is_forced_local_);
 964 }
 965
 966 // Override a symbol with a special symbol.
 967
 968 template<int size>
 969 void
 970 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from)
 971 {
 972   this->override_base_with_special(from);
 973   this->value_ = from->value_;
 974   this->symsize_ = from->symsize_;
 975 }
 976
 977 // Override TOSYM with the special symbol FROMSYM.  This handles all
 978 // aliases of TOSYM.
 979
 980 template<int size>
 981 void
 982 Symbol_table::override_with_special(Sized_symbol<size>* tosym,
 983                                     const Sized_symbol<size>* fromsym)
 984 {
 985   tosym->override_with_special(fromsym);
 986   if (tosym->has_alias())
 987     {
 988       Symbol* sym = this->weak_aliases_[tosym];
 989       gold_assert(sym != NULL);
 990       Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
 991       do
 992         {
 993           ssym->override_with_special(fromsym);
 994           sym = this->weak_aliases_[ssym];
 995           gold_assert(sym != NULL);
 996           ssym = this->get_sized_symbol<size>(sym);
 997         }
 998       while (ssym != tosym);
 999     }
1000   if (tosym->binding() == elfcpp::STB_LOCAL
1001       || ((tosym->visibility() == elfcpp::STV_HIDDEN
1002            || tosym->visibility() == elfcpp::STV_INTERNAL)
1003           && (tosym->binding() == elfcpp::STB_GLOBAL
1004               || tosym->binding() == elfcpp::STB_GNU_UNIQUE
1005               || tosym->binding() == elfcpp::STB_WEAK)
1006           && !parameters->options().relocatable()))
1007     this->force_local(tosym);
1008 }
1009
1010 // Instantiate the templates we need.  We could use the configure
1011 // script to restrict this to only the ones needed for implemented
1012 // targets.
1013
1014 // We have to instantiate both big and little endian versions because
1015 // these are used by other templates that depends on size only.
1016
1017 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
1018 template
1019 void
1020 Symbol_table::resolve<32, false>(
1021     Sized_symbol<32>* to,
1022     const elfcpp::Sym<32, false>& sym,
1023     unsigned int st_shndx,
1024     bool is_ordinary,
1025     unsigned int orig_st_shndx,
1026     Object* object,
1027     const char* version);
1028
1029 template
1030 void
1031 Symbol_table::resolve<32, true>(
1032     Sized_symbol<32>* to,
1033     const elfcpp::Sym<32, true>& sym,
1034     unsigned int st_shndx,
1035     bool is_ordinary,
1036     unsigned int orig_st_shndx,
1037     Object* object,
1038     const char* version);
1039 #endif
1040
1041 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
1042 template
1043 void
1044 Symbol_table::resolve<64, false>(
1045     Sized_symbol<64>* to,
1046     const elfcpp::Sym<64, false>& sym,
1047     unsigned int st_shndx,
1048     bool is_ordinary,
1049     unsigned int orig_st_shndx,
1050     Object* object,
1051     const char* version);
1052
1053 template
1054 void
1055 Symbol_table::resolve<64, true>(
1056     Sized_symbol<64>* to,
1057     const elfcpp::Sym<64, true>& sym,
1058     unsigned int st_shndx,
1059     bool is_ordinary,
1060     unsigned int orig_st_shndx,
1061     Object* object,
1062     const char* version);
1063 #endif
1064
1065 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
1066 template
1067 void
1068 Symbol_table::override_with_special<32>(Sized_symbol<32>*,
1069                                         const Sized_symbol<32>*);
1070 #endif
1071
1072 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
1073 template
1074 void
1075 Symbol_table::override_with_special<64>(Sized_symbol<64>*,
1076                                         const Sized_symbol<64>*);
1077 #endif
1078
1079 } // End namespace gold.