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)
 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, OBJECT, object,
 355                                     &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                               Defined defined, Object* object,
 413                               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   // FIXME: Warn if either but not both of TO and SYM are STT_TLS.
 438
 439   // We use a giant switch table for symbol resolution.  This code is
 440   // unwieldy, but: 1) it is efficient; 2) we definitely handle all
 441   // cases; 3) it is easy to change the handling of a particular case.
 442   // The alternative would be a series of conditionals, but it is easy
 443   // to get the ordering wrong.  This could also be done as a table,
 444   // but that is no easier to understand than this large switch
 445   // statement.
 446
 447   // These are the values generated by the bit codes.
 448   enum
 449   {
 450     DEF =              global_flag | regular_flag | def_flag,
 451     WEAK_DEF =         weak_flag   | regular_flag | def_flag,
 452     DYN_DEF =          global_flag | dynamic_flag | def_flag,
 453     DYN_WEAK_DEF =     weak_flag   | dynamic_flag | def_flag,
 454     UNDEF =            global_flag | regular_flag | undef_flag,
 455     WEAK_UNDEF =       weak_flag   | regular_flag | undef_flag,
 456     DYN_UNDEF =        global_flag | dynamic_flag | undef_flag,
 457     DYN_WEAK_UNDEF =   weak_flag   | dynamic_flag | undef_flag,
 458     COMMON =           global_flag | regular_flag | common_flag,
 459     WEAK_COMMON =      weak_flag   | regular_flag | common_flag,
 460     DYN_COMMON =       global_flag | dynamic_flag | common_flag,
 461     DYN_WEAK_COMMON =  weak_flag   | dynamic_flag | common_flag
 462   };
 463
 464   switch (tobits * 16 + frombits)
 465     {
 466     case DEF * 16 + DEF:
 467       // Two definitions of the same symbol.
 468
 469       // If either symbol is defined by an object included using
 470       // --just-symbols, then don't warn.  This is for compatibility
 471       // with the GNU linker.  FIXME: This is a hack.
 472       if ((to->source() == Symbol::FROM_OBJECT && to->object()->just_symbols())
 473           || (object != NULL && object->just_symbols()))
 474         return false;
 475
 476       if (!parameters->options().muldefs())
 477         Symbol_table::report_resolve_problem(true,
 478                                              _("multiple definition of '%s'"),
 479                                              to, defined, object);
 480       return false;
 481
 482     case WEAK_DEF * 16 + DEF:
 483       // We've seen a weak definition, and now we see a strong
 484       // definition.  In the original SVR4 linker, this was treated as
 485       // a multiple definition error.  In the Solaris linker and the
 486       // GNU linker, a weak definition followed by a regular
 487       // definition causes the weak definition to be overridden.  We
 488       // are currently compatible with the GNU linker.  In the future
 489       // we should add a target specific option to change this.
 490       // FIXME.
 491       return true;
 492
 493     case DYN_DEF * 16 + DEF:
 494     case DYN_WEAK_DEF * 16 + DEF:
 495       // We've seen a definition in a dynamic object, and now we see a
 496       // definition in a regular object.  The definition in the
 497       // regular object overrides the definition in the dynamic
 498       // object.
 499       return true;
 500
 501     case UNDEF * 16 + DEF:
 502     case WEAK_UNDEF * 16 + DEF:
 503     case DYN_UNDEF * 16 + DEF:
 504     case DYN_WEAK_UNDEF * 16 + DEF:
 505       // We've seen an undefined reference, and now we see a
 506       // definition.  We use the definition.
 507       return true;
 508
 509     case COMMON * 16 + DEF:
 510     case WEAK_COMMON * 16 + DEF:
 511     case DYN_COMMON * 16 + DEF:
 512     case DYN_WEAK_COMMON * 16 + DEF:
 513       // We've seen a common symbol and now we see a definition.  The
 514       // definition overrides.
 515       if (parameters->options().warn_common())
 516         Symbol_table::report_resolve_problem(false,
 517                                              _("definition of '%s' overriding "
 518                                                "common"),
 519                                              to, defined, object);
 520       return true;
 521
 522     case DEF * 16 + WEAK_DEF:
 523     case WEAK_DEF * 16 + WEAK_DEF:
 524       // We've seen a definition and now we see a weak definition.  We
 525       // ignore the new weak definition.
 526       return false;
 527
 528     case DYN_DEF * 16 + WEAK_DEF:
 529     case DYN_WEAK_DEF * 16 + WEAK_DEF:
 530       // We've seen a dynamic definition and now we see a regular weak
 531       // definition.  The regular weak definition overrides.
 532       return true;
 533
 534     case UNDEF * 16 + WEAK_DEF:
 535     case WEAK_UNDEF * 16 + WEAK_DEF:
 536     case DYN_UNDEF * 16 + WEAK_DEF:
 537     case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
 538       // A weak definition of a currently undefined symbol.
 539       return true;
 540
 541     case COMMON * 16 + WEAK_DEF:
 542     case WEAK_COMMON * 16 + WEAK_DEF:
 543       // A weak definition does not override a common definition.
 544       return false;
 545
 546     case DYN_COMMON * 16 + WEAK_DEF:
 547     case DYN_WEAK_COMMON * 16 + WEAK_DEF:
 548       // A weak definition does override a definition in a dynamic
 549       // object.
 550       if (parameters->options().warn_common())
 551         Symbol_table::report_resolve_problem(false,
 552                                              _("definition of '%s' overriding "
 553                                                "dynamic common definition"),
 554                                              to, defined, object);
 555       return true;
 556
 557     case DEF * 16 + DYN_DEF:
 558     case WEAK_DEF * 16 + DYN_DEF:
 559     case DYN_DEF * 16 + DYN_DEF:
 560     case DYN_WEAK_DEF * 16 + DYN_DEF:
 561       // Ignore a dynamic definition if we already have a definition.
 562       return false;
 563
 564     case UNDEF * 16 + DYN_DEF:
 565     case DYN_UNDEF * 16 + DYN_DEF:
 566     case DYN_WEAK_UNDEF * 16 + DYN_DEF:
 567       // Use a dynamic definition if we have a reference.
 568       return true;
 569
 570     case WEAK_UNDEF * 16 + DYN_DEF:
 571       // When overriding a weak undef by a dynamic definition,
 572       // we need to remember that the original undef was weak.
 573       *adjust_dyndef = true;
 574       return true;
 575
 576     case COMMON * 16 + DYN_DEF:
 577     case WEAK_COMMON * 16 + DYN_DEF:
 578     case DYN_COMMON * 16 + DYN_DEF:
 579     case DYN_WEAK_COMMON * 16 + DYN_DEF:
 580       // Ignore a dynamic definition if we already have a common
 581       // definition.
 582       return false;
 583
 584     case DEF * 16 + DYN_WEAK_DEF:
 585     case WEAK_DEF * 16 + DYN_WEAK_DEF:
 586     case DYN_DEF * 16 + DYN_WEAK_DEF:
 587     case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
 588       // Ignore a weak dynamic definition if we already have a
 589       // definition.
 590       return false;
 591
 592     case UNDEF * 16 + DYN_WEAK_DEF:
 593       // When overriding an undef by a dynamic weak definition,
 594       // we need to remember that the original undef was not weak.
 595       *adjust_dyndef = true;
 596       return true;
 597
 598     case DYN_UNDEF * 16 + DYN_WEAK_DEF:
 599     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 600       // Use a weak dynamic definition if we have a reference.
 601       return true;
 602
 603     case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 604       // When overriding a weak undef by a dynamic definition,
 605       // we need to remember that the original undef was weak.
 606       *adjust_dyndef = true;
 607       return true;
 608
 609     case COMMON * 16 + DYN_WEAK_DEF:
 610     case WEAK_COMMON * 16 + DYN_WEAK_DEF:
 611     case DYN_COMMON * 16 + DYN_WEAK_DEF:
 612     case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
 613       // Ignore a weak dynamic definition if we already have a common
 614       // definition.
 615       return false;
 616
 617     case DEF * 16 + UNDEF:
 618     case WEAK_DEF * 16 + UNDEF:
 619     case UNDEF * 16 + UNDEF:
 620       // A new undefined reference tells us nothing.
 621       return false;
 622
 623     case DYN_DEF * 16 + UNDEF:
 624     case DYN_WEAK_DEF * 16 + UNDEF:
 625       // For a dynamic def, we need to remember which kind of undef we see.
 626       *adjust_dyndef = true;
 627       return false;
 628
 629     case WEAK_UNDEF * 16 + UNDEF:
 630     case DYN_UNDEF * 16 + UNDEF:
 631     case DYN_WEAK_UNDEF * 16 + UNDEF:
 632       // A strong undef overrides a dynamic or weak undef.
 633       return true;
 634
 635     case COMMON * 16 + UNDEF:
 636     case WEAK_COMMON * 16 + UNDEF:
 637     case DYN_COMMON * 16 + UNDEF:
 638     case DYN_WEAK_COMMON * 16 + UNDEF:
 639       // A new undefined reference tells us nothing.
 640       return false;
 641
 642     case DEF * 16 + WEAK_UNDEF:
 643     case WEAK_DEF * 16 + WEAK_UNDEF:
 644     case UNDEF * 16 + WEAK_UNDEF:
 645     case WEAK_UNDEF * 16 + WEAK_UNDEF:
 646     case DYN_UNDEF * 16 + WEAK_UNDEF:
 647     case COMMON * 16 + WEAK_UNDEF:
 648     case WEAK_COMMON * 16 + WEAK_UNDEF:
 649     case DYN_COMMON * 16 + WEAK_UNDEF:
 650     case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
 651       // A new weak undefined reference tells us nothing unless the
 652       // exisiting symbol is a dynamic weak reference.
 653       return false;
 654
 655     case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
 656       // A new weak reference overrides an existing dynamic weak reference.
 657       // This is necessary because a dynamic weak reference remembers
 658       // the old binding, which may not be weak.  If we keeps the existing
 659       // dynamic weak reference, the weakness may be dropped in the output.
 660       return true;
 661
 662     case DYN_DEF * 16 + WEAK_UNDEF:
 663     case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
 664       // For a dynamic def, we need to remember which kind of undef we see.
 665       *adjust_dyndef = true;
 666       return false;
 667
 668     case DEF * 16 + DYN_UNDEF:
 669     case WEAK_DEF * 16 + DYN_UNDEF:
 670     case DYN_DEF * 16 + DYN_UNDEF:
 671     case DYN_WEAK_DEF * 16 + DYN_UNDEF:
 672     case UNDEF * 16 + DYN_UNDEF:
 673     case WEAK_UNDEF * 16 + DYN_UNDEF:
 674     case DYN_UNDEF * 16 + DYN_UNDEF:
 675     case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
 676     case COMMON * 16 + DYN_UNDEF:
 677     case WEAK_COMMON * 16 + DYN_UNDEF:
 678     case DYN_COMMON * 16 + DYN_UNDEF:
 679     case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
 680       // A new dynamic undefined reference tells us nothing.
 681       return false;
 682
 683     case DEF * 16 + DYN_WEAK_UNDEF:
 684     case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 685     case DYN_DEF * 16 + DYN_WEAK_UNDEF:
 686     case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 687     case UNDEF * 16 + DYN_WEAK_UNDEF:
 688     case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 689     case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
 690     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 691     case COMMON * 16 + DYN_WEAK_UNDEF:
 692     case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 693     case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
 694     case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 695       // A new weak dynamic undefined reference tells us nothing.
 696       return false;
 697
 698     case DEF * 16 + COMMON:
 699       // A common symbol does not override a definition.
 700       if (parameters->options().warn_common())
 701         Symbol_table::report_resolve_problem(false,
 702                                              _("common '%s' overridden by "
 703                                                "previous definition"),
 704                                              to, defined, object);
 705       return false;
 706
 707     case WEAK_DEF * 16 + COMMON:
 708     case DYN_DEF * 16 + COMMON:
 709     case DYN_WEAK_DEF * 16 + COMMON:
 710       // A common symbol does override a weak definition or a dynamic
 711       // definition.
 712       return true;
 713
 714     case UNDEF * 16 + COMMON:
 715     case WEAK_UNDEF * 16 + COMMON:
 716     case DYN_UNDEF * 16 + COMMON:
 717     case DYN_WEAK_UNDEF * 16 + COMMON:
 718       // A common symbol is a definition for a reference.
 719       return true;
 720
 721     case COMMON * 16 + COMMON:
 722       // Set the size to the maximum.
 723       *adjust_common_sizes = true;
 724       return false;
 725
 726     case WEAK_COMMON * 16 + COMMON:
 727       // I'm not sure just what a weak common symbol means, but
 728       // presumably it can be overridden by a regular common symbol.
 729       return true;
 730
 731     case DYN_COMMON * 16 + COMMON:
 732     case DYN_WEAK_COMMON * 16 + COMMON:
 733       // Use the real common symbol, but adjust the size if necessary.
 734       *adjust_common_sizes = true;
 735       return true;
 736
 737     case DEF * 16 + WEAK_COMMON:
 738     case WEAK_DEF * 16 + WEAK_COMMON:
 739     case DYN_DEF * 16 + WEAK_COMMON:
 740     case DYN_WEAK_DEF * 16 + WEAK_COMMON:
 741       // Whatever a weak common symbol is, it won't override a
 742       // definition.
 743       return false;
 744
 745     case UNDEF * 16 + WEAK_COMMON:
 746     case WEAK_UNDEF * 16 + WEAK_COMMON:
 747     case DYN_UNDEF * 16 + WEAK_COMMON:
 748     case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
 749       // A weak common symbol is better than an undefined symbol.
 750       return true;
 751
 752     case COMMON * 16 + WEAK_COMMON:
 753     case WEAK_COMMON * 16 + WEAK_COMMON:
 754     case DYN_COMMON * 16 + WEAK_COMMON:
 755     case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
 756       // Ignore a weak common symbol in the presence of a real common
 757       // symbol.
 758       return false;
 759
 760     case DEF * 16 + DYN_COMMON:
 761     case WEAK_DEF * 16 + DYN_COMMON:
 762     case DYN_DEF * 16 + DYN_COMMON:
 763     case DYN_WEAK_DEF * 16 + DYN_COMMON:
 764       // Ignore a dynamic common symbol in the presence of a
 765       // definition.
 766       return false;
 767
 768     case UNDEF * 16 + DYN_COMMON:
 769     case WEAK_UNDEF * 16 + DYN_COMMON:
 770     case DYN_UNDEF * 16 + DYN_COMMON:
 771     case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
 772       // A dynamic common symbol is a definition of sorts.
 773       return true;
 774
 775     case COMMON * 16 + DYN_COMMON:
 776     case WEAK_COMMON * 16 + DYN_COMMON:
 777     case DYN_COMMON * 16 + DYN_COMMON:
 778     case DYN_WEAK_COMMON * 16 + DYN_COMMON:
 779       // Set the size to the maximum.
 780       *adjust_common_sizes = true;
 781       return false;
 782
 783     case DEF * 16 + DYN_WEAK_COMMON:
 784     case WEAK_DEF * 16 + DYN_WEAK_COMMON:
 785     case DYN_DEF * 16 + DYN_WEAK_COMMON:
 786     case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
 787       // A common symbol is ignored in the face of a definition.
 788       return false;
 789
 790     case UNDEF * 16 + DYN_WEAK_COMMON:
 791     case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 792     case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
 793     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 794       // I guess a weak common symbol is better than a definition.
 795       return true;
 796
 797     case COMMON * 16 + DYN_WEAK_COMMON:
 798     case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 799     case DYN_COMMON * 16 + DYN_WEAK_COMMON:
 800     case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 801       // Set the size to the maximum.
 802       *adjust_common_sizes = true;
 803       return false;
 804
 805     default:
 806       gold_unreachable();
 807     }
 808 }
 809
 810 // Issue an error or warning due to symbol resolution.  IS_ERROR
 811 // indicates an error rather than a warning.  MSG is the error
 812 // message; it is expected to have a %s for the symbol name.  TO is
 813 // the existing symbol.  DEFINED/OBJECT is where the new symbol was
 814 // found.
 815
 816 // FIXME: We should have better location information here.  When the
 817 // symbol is defined, we should be able to pull the location from the
 818 // debug info if there is any.
 819
 820 void
 821 Symbol_table::report_resolve_problem(bool is_error, const char* msg,
 822                                      const Symbol* to, Defined defined,
 823                                      Object* object)
 824 {
 825   std::string demangled(to->demangled_name());
 826   size_t len = strlen(msg) + demangled.length() + 10;
 827   char* buf = new char[len];
 828   snprintf(buf, len, msg, demangled.c_str());
 829
 830   const char* objname;
 831   switch (defined)
 832     {
 833     case OBJECT:
 834       objname = object->name().c_str();
 835       break;
 836     case COPY:
 837       objname = _("COPY reloc");
 838       break;
 839     case DEFSYM:
 840     case UNDEFINED:
 841       objname = _("command line");
 842       break;
 843     case SCRIPT:
 844       objname = _("linker script");
 845       break;
 846     case PREDEFINED:
 847     case INCREMENTAL_BASE:
 848       objname = _("linker defined");
 849       break;
 850     default:
 851       gold_unreachable();
 852     }
 853
 854   if (is_error)
 855     gold_error("%s: %s", objname, buf);
 856   else
 857     gold_warning("%s: %s", objname, buf);
 858
 859   delete[] buf;
 860
 861   if (to->source() == Symbol::FROM_OBJECT)
 862     objname = to->object()->name().c_str();
 863   else
 864     objname = _("command line");
 865   gold_info("%s: %s: previous definition here", program_name, objname);
 866 }
 867
 868 // A special case of should_override which is only called for a strong
 869 // defined symbol from a regular object file.  This is used when
 870 // defining special symbols.
 871
 872 bool
 873 Symbol_table::should_override_with_special(const Symbol* to, Defined defined)
 874 {
 875   bool adjust_common_sizes;
 876   bool adjust_dyn_def;
 877   unsigned int frombits = global_flag | regular_flag | def_flag;
 878   bool ret = Symbol_table::should_override(to, frombits, defined, NULL,
 879                                            &adjust_common_sizes,
 880                                            &adjust_dyn_def);
 881   gold_assert(!adjust_common_sizes && !adjust_dyn_def);
 882   return ret;
 883 }
 884
 885 // Override symbol base with a special symbol.
 886
 887 void
 888 Symbol::override_base_with_special(const Symbol* from)
 889 {
 890   bool same_name = this->name_ == from->name_;
 891   gold_assert(same_name || this->has_alias());
 892
 893   this->source_ = from->source_;
 894   switch (from->source_)
 895     {
 896     case FROM_OBJECT:
 897       this->u_.from_object = from->u_.from_object;
 898       break;
 899     case IN_OUTPUT_DATA:
 900       this->u_.in_output_data = from->u_.in_output_data;
 901       break;
 902     case IN_OUTPUT_SEGMENT:
 903       this->u_.in_output_segment = from->u_.in_output_segment;
 904       break;
 905     case IS_CONSTANT:
 906     case IS_UNDEFINED:
 907       break;
 908     default:
 909       gold_unreachable();
 910       break;
 911     }
 912
 913   if (same_name)
 914     {
 915       // When overriding a versioned symbol with a special symbol, we
 916       // may be changing the version.  This will happen if we see a
 917       // special symbol such as "_end" defined in a shared object with
 918       // one version (from a version script), but we want to define it
 919       // here with a different version (from a different version
 920       // script).
 921       this->version_ = from->version_;
 922     }
 923   this->type_ = from->type_;
 924   this->binding_ = from->binding_;
 925   this->override_visibility(from->visibility_);
 926   this->nonvis_ = from->nonvis_;
 927
 928   // Special symbols are always considered to be regular symbols.
 929   this->in_reg_ = true;
 930
 931   if (from->needs_dynsym_entry_)
 932     this->needs_dynsym_entry_ = true;
 933   if (from->needs_dynsym_value_)
 934     this->needs_dynsym_value_ = true;
 935
 936   this->is_predefined_ = from->is_predefined_;
 937
 938   // We shouldn't see these flags.  If we do, we need to handle them
 939   // somehow.
 940   gold_assert(!from->is_forwarder_);
 941   gold_assert(!from->has_plt_offset());
 942   gold_assert(!from->has_warning_);
 943   gold_assert(!from->is_copied_from_dynobj_);
 944   gold_assert(!from->is_forced_local_);
 945 }
 946
 947 // Override a symbol with a special symbol.
 948
 949 template<int size>
 950 void
 951 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from)
 952 {
 953   this->override_base_with_special(from);
 954   this->value_ = from->value_;
 955   this->symsize_ = from->symsize_;
 956 }
 957
 958 // Override TOSYM with the special symbol FROMSYM.  This handles all
 959 // aliases of TOSYM.
 960
 961 template<int size>
 962 void
 963 Symbol_table::override_with_special(Sized_symbol<size>* tosym,
 964                                     const Sized_symbol<size>* fromsym)
 965 {
 966   tosym->override_with_special(fromsym);
 967   if (tosym->has_alias())
 968     {
 969       Symbol* sym = this->weak_aliases_[tosym];
 970       gold_assert(sym != NULL);
 971       Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
 972       do
 973         {
 974           ssym->override_with_special(fromsym);
 975           sym = this->weak_aliases_[ssym];
 976           gold_assert(sym != NULL);
 977           ssym = this->get_sized_symbol<size>(sym);
 978         }
 979       while (ssym != tosym);
 980     }
 981   if (tosym->binding() == elfcpp::STB_LOCAL
 982       || ((tosym->visibility() == elfcpp::STV_HIDDEN
 983            || tosym->visibility() == elfcpp::STV_INTERNAL)
 984           && (tosym->binding() == elfcpp::STB_GLOBAL
 985               || tosym->binding() == elfcpp::STB_GNU_UNIQUE
 986               || tosym->binding() == elfcpp::STB_WEAK)
 987           && !parameters->options().relocatable()))
 988     this->force_local(tosym);
 989 }
 990
 991 // Instantiate the templates we need.  We could use the configure
 992 // script to restrict this to only the ones needed for implemented
 993 // targets.
 994
 995 // We have to instantiate both big and little endian versions because
 996 // these are used by other templates that depends on size only.
 997
 998 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
 999 template
1000 void
1001 Symbol_table::resolve<32, false>(
1002     Sized_symbol<32>* to,
1003     const elfcpp::Sym<32, false>& sym,
1004     unsigned int st_shndx,
1005     bool is_ordinary,
1006     unsigned int orig_st_shndx,
1007     Object* object,
1008     const char* version);
1009
1010 template
1011 void
1012 Symbol_table::resolve<32, true>(
1013     Sized_symbol<32>* to,
1014     const elfcpp::Sym<32, true>& sym,
1015     unsigned int st_shndx,
1016     bool is_ordinary,
1017     unsigned int orig_st_shndx,
1018     Object* object,
1019     const char* version);
1020 #endif
1021
1022 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
1023 template
1024 void
1025 Symbol_table::resolve<64, false>(
1026     Sized_symbol<64>* to,
1027     const elfcpp::Sym<64, false>& sym,
1028     unsigned int st_shndx,
1029     bool is_ordinary,
1030     unsigned int orig_st_shndx,
1031     Object* object,
1032     const char* version);
1033
1034 template
1035 void
1036 Symbol_table::resolve<64, true>(
1037     Sized_symbol<64>* to,
1038     const elfcpp::Sym<64, true>& sym,
1039     unsigned int st_shndx,
1040     bool is_ordinary,
1041     unsigned int orig_st_shndx,
1042     Object* object,
1043     const char* version);
1044 #endif
1045
1046 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
1047 template
1048 void
1049 Symbol_table::override_with_special<32>(Sized_symbol<32>*,
1050                                         const Sized_symbol<32>*);
1051 #endif
1052
1053 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
1054 template
1055 void
1056 Symbol_table::override_with_special<64>(Sized_symbol<64>*,
1057                                         const Sized_symbol<64>*);
1058 #endif
1059
1060 } // End namespace gold.