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, sym.get_st_value() };
 340       Symbol_location toloc = { to->object(), to->shndx(&to_is_ordinary),
 341                                 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       this->override(to, sym, st_shndx, is_ordinary, object, version);
 360       if (adjust_common_sizes && tosize > to->symsize())
 361         to->set_symsize(tosize);
 362       if (adjust_dyndef)
 363         {
 364           // We are overriding an UNDEF or WEAK UNDEF with a DYN DEF.
 365           // Remember which kind of UNDEF it was for future reference.
 366           to->set_undef_binding(tobinding);
 367         }
 368     }
 369   else
 370     {
 371       if (adjust_common_sizes && sym.get_st_size() > tosize)
 372         to->set_symsize(sym.get_st_size());
 373       if (adjust_dyndef)
 374         {
 375           // We are keeping a DYN DEF after seeing an UNDEF or WEAK UNDEF.
 376           // Remember which kind of UNDEF it was.
 377           to->set_undef_binding(sym.get_st_bind());
 378         }
 379       // The ELF ABI says that even for a reference to a symbol we
 380       // merge the visibility.
 381       to->override_visibility(sym.get_st_visibility());
 382     }
 383
 384   if (adjust_common_sizes && parameters->options().warn_common())
 385     {
 386       if (tosize > sym.get_st_size())
 387         Symbol_table::report_resolve_problem(false,
 388                                              _("common of '%s' overriding "
 389                                                "smaller common"),
 390                                              to, OBJECT, object);
 391       else if (tosize < sym.get_st_size())
 392         Symbol_table::report_resolve_problem(false,
 393                                              _("common of '%s' overidden by "
 394                                                "larger common"),
 395                                              to, OBJECT, object);
 396       else
 397         Symbol_table::report_resolve_problem(false,
 398                                              _("multiple common of '%s'"),
 399                                              to, OBJECT, object);
 400     }
 401 }
 402
 403 // Handle the core of symbol resolution.  This is called with the
 404 // existing symbol, TO, and a bitflag describing the new symbol.  This
 405 // returns true if we should override the existing symbol with the new
 406 // one, and returns false otherwise.  It sets *ADJUST_COMMON_SIZES to
 407 // true if we should set the symbol size to the maximum of the TO and
 408 // FROM sizes.  It handles error conditions.
 409
 410 bool
 411 Symbol_table::should_override(const Symbol* to, unsigned int frombits,
 412                               elfcpp::STT fromtype, Defined defined,
 413                               Object* object, bool* adjust_common_sizes,
 414                               bool* adjust_dyndef)
 415 {
 416   *adjust_common_sizes = false;
 417   *adjust_dyndef = false;
 418
 419   unsigned int tobits;
 420   if (to->source() == Symbol::IS_UNDEFINED)
 421     tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_UNDEF, true,
 422                             to->type());
 423   else if (to->source() != Symbol::FROM_OBJECT)
 424     tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_ABS, false,
 425                             to->type());
 426   else
 427     {
 428       bool is_ordinary;
 429       unsigned int shndx = to->shndx(&is_ordinary);
 430       tobits = symbol_to_bits(to->binding(),
 431                               to->object()->is_dynamic(),
 432                               shndx,
 433                               is_ordinary,
 434                               to->type());
 435     }
 436
 437   if (to->type() == elfcpp::STT_TLS
 438       ? fromtype != elfcpp::STT_TLS
 439       : fromtype == elfcpp::STT_TLS)
 440     Symbol_table::report_resolve_problem(true,
 441                                          _("symbol '%s' used as both __thread "
 442                                            "and non-__thread"),
 443                                          to, defined, object);
 444
 445   // We use a giant switch table for symbol resolution.  This code is
 446   // unwieldy, but: 1) it is efficient; 2) we definitely handle all
 447   // cases; 3) it is easy to change the handling of a particular case.
 448   // The alternative would be a series of conditionals, but it is easy
 449   // to get the ordering wrong.  This could also be done as a table,
 450   // but that is no easier to understand than this large switch
 451   // statement.
 452
 453   // These are the values generated by the bit codes.
 454   enum
 455   {
 456     DEF =              global_flag | regular_flag | def_flag,
 457     WEAK_DEF =         weak_flag   | regular_flag | def_flag,
 458     DYN_DEF =          global_flag | dynamic_flag | def_flag,
 459     DYN_WEAK_DEF =     weak_flag   | dynamic_flag | def_flag,
 460     UNDEF =            global_flag | regular_flag | undef_flag,
 461     WEAK_UNDEF =       weak_flag   | regular_flag | undef_flag,
 462     DYN_UNDEF =        global_flag | dynamic_flag | undef_flag,
 463     DYN_WEAK_UNDEF =   weak_flag   | dynamic_flag | undef_flag,
 464     COMMON =           global_flag | regular_flag | common_flag,
 465     WEAK_COMMON =      weak_flag   | regular_flag | common_flag,
 466     DYN_COMMON =       global_flag | dynamic_flag | common_flag,
 467     DYN_WEAK_COMMON =  weak_flag   | dynamic_flag | common_flag
 468   };
 469
 470   switch (tobits * 16 + frombits)
 471     {
 472     case DEF * 16 + DEF:
 473       // Two definitions of the same symbol.
 474
 475       // If either symbol is defined by an object included using
 476       // --just-symbols, then don't warn.  This is for compatibility
 477       // with the GNU linker.  FIXME: This is a hack.
 478       if ((to->source() == Symbol::FROM_OBJECT && to->object()->just_symbols())
 479           || (object != NULL && object->just_symbols()))
 480         return false;
 481
 482       if (!parameters->options().muldefs())
 483         Symbol_table::report_resolve_problem(true,
 484                                              _("multiple definition of '%s'"),
 485                                              to, defined, object);
 486       return false;
 487
 488     case WEAK_DEF * 16 + DEF:
 489       // We've seen a weak definition, and now we see a strong
 490       // definition.  In the original SVR4 linker, this was treated as
 491       // a multiple definition error.  In the Solaris linker and the
 492       // GNU linker, a weak definition followed by a regular
 493       // definition causes the weak definition to be overridden.  We
 494       // are currently compatible with the GNU linker.  In the future
 495       // we should add a target specific option to change this.
 496       // FIXME.
 497       return true;
 498
 499     case DYN_DEF * 16 + DEF:
 500     case DYN_WEAK_DEF * 16 + DEF:
 501       // We've seen a definition in a dynamic object, and now we see a
 502       // definition in a regular object.  The definition in the
 503       // regular object overrides the definition in the dynamic
 504       // object.
 505       return true;
 506
 507     case UNDEF * 16 + DEF:
 508     case WEAK_UNDEF * 16 + DEF:
 509     case DYN_UNDEF * 16 + DEF:
 510     case DYN_WEAK_UNDEF * 16 + DEF:
 511       // We've seen an undefined reference, and now we see a
 512       // definition.  We use the definition.
 513       return true;
 514
 515     case COMMON * 16 + DEF:
 516     case WEAK_COMMON * 16 + DEF:
 517     case DYN_COMMON * 16 + DEF:
 518     case DYN_WEAK_COMMON * 16 + DEF:
 519       // We've seen a common symbol and now we see a definition.  The
 520       // definition overrides.
 521       if (parameters->options().warn_common())
 522         Symbol_table::report_resolve_problem(false,
 523                                              _("definition of '%s' overriding "
 524                                                "common"),
 525                                              to, defined, object);
 526       return true;
 527
 528     case DEF * 16 + WEAK_DEF:
 529     case WEAK_DEF * 16 + WEAK_DEF:
 530       // We've seen a definition and now we see a weak definition.  We
 531       // ignore the new weak definition.
 532       return false;
 533
 534     case DYN_DEF * 16 + WEAK_DEF:
 535     case DYN_WEAK_DEF * 16 + WEAK_DEF:
 536       // We've seen a dynamic definition and now we see a regular weak
 537       // definition.  The regular weak definition overrides.
 538       return true;
 539
 540     case UNDEF * 16 + WEAK_DEF:
 541     case WEAK_UNDEF * 16 + WEAK_DEF:
 542     case DYN_UNDEF * 16 + WEAK_DEF:
 543     case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
 544       // A weak definition of a currently undefined symbol.
 545       return true;
 546
 547     case COMMON * 16 + WEAK_DEF:
 548     case WEAK_COMMON * 16 + WEAK_DEF:
 549       // A weak definition does not override a common definition.
 550       return false;
 551
 552     case DYN_COMMON * 16 + WEAK_DEF:
 553     case DYN_WEAK_COMMON * 16 + WEAK_DEF:
 554       // A weak definition does override a definition in a dynamic
 555       // object.
 556       if (parameters->options().warn_common())
 557         Symbol_table::report_resolve_problem(false,
 558                                              _("definition of '%s' overriding "
 559                                                "dynamic common definition"),
 560                                              to, defined, object);
 561       return true;
 562
 563     case DEF * 16 + DYN_DEF:
 564     case WEAK_DEF * 16 + DYN_DEF:
 565     case DYN_DEF * 16 + DYN_DEF:
 566     case DYN_WEAK_DEF * 16 + DYN_DEF:
 567       // Ignore a dynamic definition if we already have a definition.
 568       return false;
 569
 570     case UNDEF * 16 + DYN_DEF:
 571     case DYN_UNDEF * 16 + DYN_DEF:
 572     case DYN_WEAK_UNDEF * 16 + DYN_DEF:
 573       // Use a dynamic definition if we have a reference.
 574       return true;
 575
 576     case WEAK_UNDEF * 16 + DYN_DEF:
 577       // When overriding a weak undef by a dynamic definition,
 578       // we need to remember that the original undef was weak.
 579       *adjust_dyndef = true;
 580       return true;
 581
 582     case COMMON * 16 + DYN_DEF:
 583     case WEAK_COMMON * 16 + DYN_DEF:
 584     case DYN_COMMON * 16 + DYN_DEF:
 585     case DYN_WEAK_COMMON * 16 + DYN_DEF:
 586       // Ignore a dynamic definition if we already have a common
 587       // definition.
 588       return false;
 589
 590     case DEF * 16 + DYN_WEAK_DEF:
 591     case WEAK_DEF * 16 + DYN_WEAK_DEF:
 592     case DYN_DEF * 16 + DYN_WEAK_DEF:
 593     case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
 594       // Ignore a weak dynamic definition if we already have a
 595       // definition.
 596       return false;
 597
 598     case UNDEF * 16 + DYN_WEAK_DEF:
 599       // When overriding an undef by a dynamic weak definition,
 600       // we need to remember that the original undef was not weak.
 601       *adjust_dyndef = true;
 602       return true;
 603
 604     case DYN_UNDEF * 16 + DYN_WEAK_DEF:
 605     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 606       // Use a weak dynamic definition if we have a reference.
 607       return true;
 608
 609     case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 610       // When overriding a weak undef by a dynamic definition,
 611       // we need to remember that the original undef was weak.
 612       *adjust_dyndef = true;
 613       return true;
 614
 615     case COMMON * 16 + DYN_WEAK_DEF:
 616     case WEAK_COMMON * 16 + DYN_WEAK_DEF:
 617     case DYN_COMMON * 16 + DYN_WEAK_DEF:
 618     case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
 619       // Ignore a weak dynamic definition if we already have a common
 620       // definition.
 621       return false;
 622
 623     case DEF * 16 + UNDEF:
 624     case WEAK_DEF * 16 + UNDEF:
 625     case UNDEF * 16 + UNDEF:
 626       // A new undefined reference tells us nothing.
 627       return false;
 628
 629     case DYN_DEF * 16 + UNDEF:
 630     case DYN_WEAK_DEF * 16 + UNDEF:
 631       // For a dynamic def, we need to remember which kind of undef we see.
 632       *adjust_dyndef = true;
 633       return false;
 634
 635     case WEAK_UNDEF * 16 + UNDEF:
 636     case DYN_UNDEF * 16 + UNDEF:
 637     case DYN_WEAK_UNDEF * 16 + UNDEF:
 638       // A strong undef overrides a dynamic or weak undef.
 639       return true;
 640
 641     case COMMON * 16 + UNDEF:
 642     case WEAK_COMMON * 16 + UNDEF:
 643     case DYN_COMMON * 16 + UNDEF:
 644     case DYN_WEAK_COMMON * 16 + UNDEF:
 645       // A new undefined reference tells us nothing.
 646       return false;
 647
 648     case DEF * 16 + WEAK_UNDEF:
 649     case WEAK_DEF * 16 + WEAK_UNDEF:
 650     case UNDEF * 16 + WEAK_UNDEF:
 651     case WEAK_UNDEF * 16 + WEAK_UNDEF:
 652     case DYN_UNDEF * 16 + WEAK_UNDEF:
 653     case COMMON * 16 + WEAK_UNDEF:
 654     case WEAK_COMMON * 16 + WEAK_UNDEF:
 655     case DYN_COMMON * 16 + WEAK_UNDEF:
 656     case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
 657       // A new weak undefined reference tells us nothing unless the
 658       // exisiting symbol is a dynamic weak reference.
 659       return false;
 660
 661     case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
 662       // A new weak reference overrides an existing dynamic weak reference.
 663       // This is necessary because a dynamic weak reference remembers
 664       // the old binding, which may not be weak.  If we keeps the existing
 665       // dynamic weak reference, the weakness may be dropped in the output.
 666       return true;
 667
 668     case DYN_DEF * 16 + WEAK_UNDEF:
 669     case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
 670       // For a dynamic def, we need to remember which kind of undef we see.
 671       *adjust_dyndef = true;
 672       return false;
 673
 674     case DEF * 16 + DYN_UNDEF:
 675     case WEAK_DEF * 16 + DYN_UNDEF:
 676     case DYN_DEF * 16 + DYN_UNDEF:
 677     case DYN_WEAK_DEF * 16 + DYN_UNDEF:
 678     case UNDEF * 16 + DYN_UNDEF:
 679     case WEAK_UNDEF * 16 + DYN_UNDEF:
 680     case DYN_UNDEF * 16 + DYN_UNDEF:
 681     case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
 682     case COMMON * 16 + DYN_UNDEF:
 683     case WEAK_COMMON * 16 + DYN_UNDEF:
 684     case DYN_COMMON * 16 + DYN_UNDEF:
 685     case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
 686       // A new dynamic undefined reference tells us nothing.
 687       return false;
 688
 689     case DEF * 16 + DYN_WEAK_UNDEF:
 690     case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 691     case DYN_DEF * 16 + DYN_WEAK_UNDEF:
 692     case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 693     case UNDEF * 16 + DYN_WEAK_UNDEF:
 694     case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 695     case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
 696     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 697     case COMMON * 16 + DYN_WEAK_UNDEF:
 698     case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 699     case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
 700     case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 701       // A new weak dynamic undefined reference tells us nothing.
 702       return false;
 703
 704     case DEF * 16 + COMMON:
 705       // A common symbol does not override a definition.
 706       if (parameters->options().warn_common())
 707         Symbol_table::report_resolve_problem(false,
 708                                              _("common '%s' overridden by "
 709                                                "previous definition"),
 710                                              to, defined, object);
 711       return false;
 712
 713     case WEAK_DEF * 16 + COMMON:
 714     case DYN_DEF * 16 + COMMON:
 715     case DYN_WEAK_DEF * 16 + COMMON:
 716       // A common symbol does override a weak definition or a dynamic
 717       // definition.
 718       return true;
 719
 720     case UNDEF * 16 + COMMON:
 721     case WEAK_UNDEF * 16 + COMMON:
 722     case DYN_UNDEF * 16 + COMMON:
 723     case DYN_WEAK_UNDEF * 16 + COMMON:
 724       // A common symbol is a definition for a reference.
 725       return true;
 726
 727     case COMMON * 16 + COMMON:
 728       // Set the size to the maximum.
 729       *adjust_common_sizes = true;
 730       return false;
 731
 732     case WEAK_COMMON * 16 + COMMON:
 733       // I'm not sure just what a weak common symbol means, but
 734       // presumably it can be overridden by a regular common symbol.
 735       return true;
 736
 737     case DYN_COMMON * 16 + COMMON:
 738     case DYN_WEAK_COMMON * 16 + COMMON:
 739       // Use the real common symbol, but adjust the size if necessary.
 740       *adjust_common_sizes = true;
 741       return true;
 742
 743     case DEF * 16 + WEAK_COMMON:
 744     case WEAK_DEF * 16 + WEAK_COMMON:
 745     case DYN_DEF * 16 + WEAK_COMMON:
 746     case DYN_WEAK_DEF * 16 + WEAK_COMMON:
 747       // Whatever a weak common symbol is, it won't override a
 748       // definition.
 749       return false;
 750
 751     case UNDEF * 16 + WEAK_COMMON:
 752     case WEAK_UNDEF * 16 + WEAK_COMMON:
 753     case DYN_UNDEF * 16 + WEAK_COMMON:
 754     case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
 755       // A weak common symbol is better than an undefined symbol.
 756       return true;
 757
 758     case COMMON * 16 + WEAK_COMMON:
 759     case WEAK_COMMON * 16 + WEAK_COMMON:
 760     case DYN_COMMON * 16 + WEAK_COMMON:
 761     case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
 762       // Ignore a weak common symbol in the presence of a real common
 763       // symbol.
 764       return false;
 765
 766     case DEF * 16 + DYN_COMMON:
 767     case WEAK_DEF * 16 + DYN_COMMON:
 768     case DYN_DEF * 16 + DYN_COMMON:
 769     case DYN_WEAK_DEF * 16 + DYN_COMMON:
 770       // Ignore a dynamic common symbol in the presence of a
 771       // definition.
 772       return false;
 773
 774     case UNDEF * 16 + DYN_COMMON:
 775     case WEAK_UNDEF * 16 + DYN_COMMON:
 776     case DYN_UNDEF * 16 + DYN_COMMON:
 777     case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
 778       // A dynamic common symbol is a definition of sorts.
 779       return true;
 780
 781     case COMMON * 16 + DYN_COMMON:
 782     case WEAK_COMMON * 16 + DYN_COMMON:
 783     case DYN_COMMON * 16 + DYN_COMMON:
 784     case DYN_WEAK_COMMON * 16 + DYN_COMMON:
 785       // Set the size to the maximum.
 786       *adjust_common_sizes = true;
 787       return false;
 788
 789     case DEF * 16 + DYN_WEAK_COMMON:
 790     case WEAK_DEF * 16 + DYN_WEAK_COMMON:
 791     case DYN_DEF * 16 + DYN_WEAK_COMMON:
 792     case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
 793       // A common symbol is ignored in the face of a definition.
 794       return false;
 795
 796     case UNDEF * 16 + DYN_WEAK_COMMON:
 797     case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 798     case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
 799     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 800       // I guess a weak common symbol is better than a definition.
 801       return true;
 802
 803     case COMMON * 16 + DYN_WEAK_COMMON:
 804     case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 805     case DYN_COMMON * 16 + DYN_WEAK_COMMON:
 806     case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 807       // Set the size to the maximum.
 808       *adjust_common_sizes = true;
 809       return false;
 810
 811     default:
 812       gold_unreachable();
 813     }
 814 }
 815
 816 // Issue an error or warning due to symbol resolution.  IS_ERROR
 817 // indicates an error rather than a warning.  MSG is the error
 818 // message; it is expected to have a %s for the symbol name.  TO is
 819 // the existing symbol.  DEFINED/OBJECT is where the new symbol was
 820 // found.
 821
 822 // FIXME: We should have better location information here.  When the
 823 // symbol is defined, we should be able to pull the location from the
 824 // debug info if there is any.
 825
 826 void
 827 Symbol_table::report_resolve_problem(bool is_error, const char* msg,
 828                                      const Symbol* to, Defined defined,
 829                                      Object* object)
 830 {
 831   std::string demangled(to->demangled_name());
 832   size_t len = strlen(msg) + demangled.length() + 10;
 833   char* buf = new char[len];
 834   snprintf(buf, len, msg, demangled.c_str());
 835
 836   const char* objname;
 837   switch (defined)
 838     {
 839     case OBJECT:
 840       objname = object->name().c_str();
 841       break;
 842     case COPY:
 843       objname = _("COPY reloc");
 844       break;
 845     case DEFSYM:
 846     case UNDEFINED:
 847       objname = _("command line");
 848       break;
 849     case SCRIPT:
 850       objname = _("linker script");
 851       break;
 852     case PREDEFINED:
 853     case INCREMENTAL_BASE:
 854       objname = _("linker defined");
 855       break;
 856     default:
 857       gold_unreachable();
 858     }
 859
 860   if (is_error)
 861     gold_error("%s: %s", objname, buf);
 862   else
 863     gold_warning("%s: %s", objname, buf);
 864
 865   delete[] buf;
 866
 867   if (to->source() == Symbol::FROM_OBJECT)
 868     objname = to->object()->name().c_str();
 869   else
 870     objname = _("command line");
 871   gold_info("%s: %s: previous definition here", program_name, objname);
 872 }
 873
 874 // A special case of should_override which is only called for a strong
 875 // defined symbol from a regular object file.  This is used when
 876 // defining special symbols.
 877
 878 bool
 879 Symbol_table::should_override_with_special(const Symbol* to,
 880                                            elfcpp::STT fromtype,
 881                                            Defined defined)
 882 {
 883   bool adjust_common_sizes;
 884   bool adjust_dyn_def;
 885   unsigned int frombits = global_flag | regular_flag | def_flag;
 886   bool ret = Symbol_table::should_override(to, frombits, fromtype, defined,
 887                                            NULL, &adjust_common_sizes,
 888                                            &adjust_dyn_def);
 889   gold_assert(!adjust_common_sizes && !adjust_dyn_def);
 890   return ret;
 891 }
 892
 893 // Override symbol base with a special symbol.
 894
 895 void
 896 Symbol::override_base_with_special(const Symbol* from)
 897 {
 898   bool same_name = this->name_ == from->name_;
 899   gold_assert(same_name || this->has_alias());
 900
 901   this->source_ = from->source_;
 902   switch (from->source_)
 903     {
 904     case FROM_OBJECT:
 905       this->u_.from_object = from->u_.from_object;
 906       break;
 907     case IN_OUTPUT_DATA:
 908       this->u_.in_output_data = from->u_.in_output_data;
 909       break;
 910     case IN_OUTPUT_SEGMENT:
 911       this->u_.in_output_segment = from->u_.in_output_segment;
 912       break;
 913     case IS_CONSTANT:
 914     case IS_UNDEFINED:
 915       break;
 916     default:
 917       gold_unreachable();
 918       break;
 919     }
 920
 921   if (same_name)
 922     {
 923       // When overriding a versioned symbol with a special symbol, we
 924       // may be changing the version.  This will happen if we see a
 925       // special symbol such as "_end" defined in a shared object with
 926       // one version (from a version script), but we want to define it
 927       // here with a different version (from a different version
 928       // script).
 929       this->version_ = from->version_;
 930     }
 931   this->type_ = from->type_;
 932   this->binding_ = from->binding_;
 933   this->override_visibility(from->visibility_);
 934   this->nonvis_ = from->nonvis_;
 935
 936   // Special symbols are always considered to be regular symbols.
 937   this->in_reg_ = true;
 938
 939   if (from->needs_dynsym_entry_)
 940     this->needs_dynsym_entry_ = true;
 941   if (from->needs_dynsym_value_)
 942     this->needs_dynsym_value_ = true;
 943
 944   this->is_predefined_ = from->is_predefined_;
 945
 946   // We shouldn't see these flags.  If we do, we need to handle them
 947   // somehow.
 948   gold_assert(!from->is_forwarder_);
 949   gold_assert(!from->has_plt_offset());
 950   gold_assert(!from->has_warning_);
 951   gold_assert(!from->is_copied_from_dynobj_);
 952   gold_assert(!from->is_forced_local_);
 953 }
 954
 955 // Override a symbol with a special symbol.
 956
 957 template<int size>
 958 void
 959 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from)
 960 {
 961   this->override_base_with_special(from);
 962   this->value_ = from->value_;
 963   this->symsize_ = from->symsize_;
 964 }
 965
 966 // Override TOSYM with the special symbol FROMSYM.  This handles all
 967 // aliases of TOSYM.
 968
 969 template<int size>
 970 void
 971 Symbol_table::override_with_special(Sized_symbol<size>* tosym,
 972                                     const Sized_symbol<size>* fromsym)
 973 {
 974   tosym->override_with_special(fromsym);
 975   if (tosym->has_alias())
 976     {
 977       Symbol* sym = this->weak_aliases_[tosym];
 978       gold_assert(sym != NULL);
 979       Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
 980       do
 981         {
 982           ssym->override_with_special(fromsym);
 983           sym = this->weak_aliases_[ssym];
 984           gold_assert(sym != NULL);
 985           ssym = this->get_sized_symbol<size>(sym);
 986         }
 987       while (ssym != tosym);
 988     }
 989   if (tosym->binding() == elfcpp::STB_LOCAL
 990       || ((tosym->visibility() == elfcpp::STV_HIDDEN
 991            || tosym->visibility() == elfcpp::STV_INTERNAL)
 992           && (tosym->binding() == elfcpp::STB_GLOBAL
 993               || tosym->binding() == elfcpp::STB_GNU_UNIQUE
 994               || tosym->binding() == elfcpp::STB_WEAK)
 995           && !parameters->options().relocatable()))
 996     this->force_local(tosym);
 997 }
 998
 999 // Instantiate the templates we need.  We could use the configure
1000 // script to restrict this to only the ones needed for implemented
1001 // targets.
1002
1003 // We have to instantiate both big and little endian versions because
1004 // these are used by other templates that depends on size only.
1005
1006 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
1007 template
1008 void
1009 Symbol_table::resolve<32, false>(
1010     Sized_symbol<32>* to,
1011     const elfcpp::Sym<32, false>& sym,
1012     unsigned int st_shndx,
1013     bool is_ordinary,
1014     unsigned int orig_st_shndx,
1015     Object* object,
1016     const char* version);
1017
1018 template
1019 void
1020 Symbol_table::resolve<32, true>(
1021     Sized_symbol<32>* to,
1022     const elfcpp::Sym<32, true>& sym,
1023     unsigned int st_shndx,
1024     bool is_ordinary,
1025     unsigned int orig_st_shndx,
1026     Object* object,
1027     const char* version);
1028 #endif
1029
1030 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
1031 template
1032 void
1033 Symbol_table::resolve<64, false>(
1034     Sized_symbol<64>* to,
1035     const elfcpp::Sym<64, 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<64, true>(
1045     Sized_symbol<64>* to,
1046     const elfcpp::Sym<64, 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_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
1055 template
1056 void
1057 Symbol_table::override_with_special<32>(Sized_symbol<32>*,
1058                                         const Sized_symbol<32>*);
1059 #endif
1060
1061 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
1062 template
1063 void
1064 Symbol_table::override_with_special<64>(Sized_symbol<64>*,
1065                                         const Sized_symbol<64>*);
1066 #endif
1067
1068 } // End namespace gold.