gold/resolve.cc

   1 // resolve.cc -- symbol resolution for gold
   2
   3 // Copyright 2006, 2007, 2008, 2009 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       bits = global_flag;
 182       break;
 183
 184     case elfcpp::STB_WEAK:
 185       bits = weak_flag;
 186       break;
 187
 188     case elfcpp::STB_LOCAL:
 189       // We should only see externally visible symbols in the symbol
 190       // table.
 191       gold_error(_("invalid STB_LOCAL symbol in external symbols"));
 192       bits = global_flag;
 193
 194     default:
 195       // Any target which wants to handle STB_LOOS, etc., needs to
 196       // define a resolve method.
 197       gold_error(_("unsupported symbol binding"));
 198       bits = global_flag;
 199     }
 200
 201   if (is_dynamic)
 202     bits |= dynamic_flag;
 203   else
 204     bits |= regular_flag;
 205
 206   switch (shndx)
 207     {
 208     case elfcpp::SHN_UNDEF:
 209       bits |= undef_flag;
 210       break;
 211
 212     case elfcpp::SHN_COMMON:
 213       if (!is_ordinary)
 214         bits |= common_flag;
 215       break;
 216
 217     default:
 218       if (type == elfcpp::STT_COMMON)
 219         bits |= common_flag;
 220       else
 221         bits |= def_flag;
 222       break;
 223     }
 224
 225   return bits;
 226 }
 227
 228 // Resolve a symbol.  This is called the second and subsequent times
 229 // we see a symbol.  TO is the pre-existing symbol.  ST_SHNDX is the
 230 // section index for SYM, possibly adjusted for many sections.
 231 // IS_ORDINARY is whether ST_SHNDX is a normal section index rather
 232 // than a special code.  ORIG_ST_SHNDX is the original section index,
 233 // before any munging because of discarded sections, except that all
 234 // non-ordinary section indexes are mapped to SHN_UNDEF.  VERSION is
 235 // the version of SYM.
 236
 237 template<int size, bool big_endian>
 238 void
 239 Symbol_table::resolve(Sized_symbol<size>* to,
 240                       const elfcpp::Sym<size, big_endian>& sym,
 241                       unsigned int st_shndx, bool is_ordinary,
 242                       unsigned int orig_st_shndx,
 243                       Object* object, const char* version)
 244 {
 245   if (object->target()->has_resolve())
 246     {
 247       Sized_target<size, big_endian>* sized_target;
 248       sized_target = object->sized_target<size, big_endian>();
 249       sized_target->resolve(to, sym, object, version);
 250       return;
 251     }
 252
 253   if (!object->is_dynamic())
 254     {
 255       // Record that we've seen this symbol in a regular object.
 256       to->set_in_reg();
 257     }
 258   else
 259     {
 260       // Record that we've seen this symbol in a dynamic object.
 261       to->set_in_dyn();
 262     }
 263
 264   // Record if we've seen this symbol in a real ELF object (i.e., the
 265   // symbol is referenced from outside the world known to the plugin).
 266   if (object->pluginobj() == NULL)
 267     to->set_in_real_elf();
 268
 269   // If we're processing replacement files, allow new symbols to override
 270   // the placeholders from the plugin objects.
 271   if (to->source() == Symbol::FROM_OBJECT)
 272     {
 273       Pluginobj* obj = to->object()->pluginobj();
 274       if (obj != NULL
 275           && parameters->options().plugins()->in_replacement_phase())
 276         {
 277           this->override(to, sym, st_shndx, is_ordinary, object, version);
 278           return;
 279         }
 280     }
 281
 282   unsigned int frombits = symbol_to_bits(sym.get_st_bind(),
 283                                          object->is_dynamic(),
 284                                          st_shndx, is_ordinary,
 285                                          sym.get_st_type());
 286
 287   bool adjust_common_sizes;
 288   if (Symbol_table::should_override(to, frombits, object,
 289                                     &adjust_common_sizes))
 290     {
 291       typename Sized_symbol<size>::Size_type tosize = to->symsize();
 292
 293       this->override(to, sym, st_shndx, is_ordinary, object, version);
 294
 295       if (adjust_common_sizes && tosize > to->symsize())
 296         to->set_symsize(tosize);
 297     }
 298   else
 299     {
 300       if (adjust_common_sizes && sym.get_st_size() > to->symsize())
 301         to->set_symsize(sym.get_st_size());
 302       // The ELF ABI says that even for a reference to a symbol we
 303       // merge the visibility.
 304       to->override_visibility(sym.get_st_visibility());
 305     }
 306
 307   // A new weak undefined reference, merging with an old weak
 308   // reference, could be a One Definition Rule (ODR) violation --
 309   // especially if the types or sizes of the references differ.  We'll
 310   // store such pairs and look them up later to make sure they
 311   // actually refer to the same lines of code.  (Note: not all ODR
 312   // violations can be found this way, and not everything this finds
 313   // is an ODR violation.  But it's helpful to warn about.)
 314   bool to_is_ordinary;
 315   if (parameters->options().detect_odr_violations()
 316       && sym.get_st_bind() == elfcpp::STB_WEAK
 317       && to->binding() == elfcpp::STB_WEAK
 318       && orig_st_shndx != elfcpp::SHN_UNDEF
 319       && to->shndx(&to_is_ordinary) != elfcpp::SHN_UNDEF
 320       && to_is_ordinary
 321       && sym.get_st_size() != 0    // Ignore weird 0-sized symbols.
 322       && to->symsize() != 0
 323       && (sym.get_st_type() != to->type()
 324           || sym.get_st_size() != to->symsize())
 325       // C does not have a concept of ODR, so we only need to do this
 326       // on C++ symbols.  These have (mangled) names starting with _Z.
 327       && to->name()[0] == '_' && to->name()[1] == 'Z')
 328     {
 329       Symbol_location fromloc
 330           = { object, orig_st_shndx, sym.get_st_value() };
 331       Symbol_location toloc = { to->object(), to->shndx(&to_is_ordinary),
 332                                 to->value() };
 333       this->candidate_odr_violations_[to->name()].insert(fromloc);
 334       this->candidate_odr_violations_[to->name()].insert(toloc);
 335     }
 336 }
 337
 338 // Handle the core of symbol resolution.  This is called with the
 339 // existing symbol, TO, and a bitflag describing the new symbol.  This
 340 // returns true if we should override the existing symbol with the new
 341 // one, and returns false otherwise.  It sets *ADJUST_COMMON_SIZES to
 342 // true if we should set the symbol size to the maximum of the TO and
 343 // FROM sizes.  It handles error conditions.
 344
 345 bool
 346 Symbol_table::should_override(const Symbol* to, unsigned int frombits,
 347                               Object* object, bool* adjust_common_sizes)
 348 {
 349   *adjust_common_sizes = false;
 350
 351   unsigned int tobits;
 352   if (to->source() == Symbol::IS_UNDEFINED)
 353     tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_UNDEF, true,
 354                             to->type());
 355   else if (to->source() != Symbol::FROM_OBJECT)
 356     tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_ABS, false,
 357                             to->type());
 358   else
 359     {
 360       bool is_ordinary;
 361       unsigned int shndx = to->shndx(&is_ordinary);
 362       tobits = symbol_to_bits(to->binding(),
 363                               to->object()->is_dynamic(),
 364                               shndx,
 365                               is_ordinary,
 366                               to->type());
 367     }
 368
 369   // FIXME: Warn if either but not both of TO and SYM are STT_TLS.
 370
 371   // We use a giant switch table for symbol resolution.  This code is
 372   // unwieldy, but: 1) it is efficient; 2) we definitely handle all
 373   // cases; 3) it is easy to change the handling of a particular case.
 374   // The alternative would be a series of conditionals, but it is easy
 375   // to get the ordering wrong.  This could also be done as a table,
 376   // but that is no easier to understand than this large switch
 377   // statement.
 378
 379   // These are the values generated by the bit codes.
 380   enum
 381   {
 382     DEF =              global_flag | regular_flag | def_flag,
 383     WEAK_DEF =         weak_flag   | regular_flag | def_flag,
 384     DYN_DEF =          global_flag | dynamic_flag | def_flag,
 385     DYN_WEAK_DEF =     weak_flag   | dynamic_flag | def_flag,
 386     UNDEF =            global_flag | regular_flag | undef_flag,
 387     WEAK_UNDEF =       weak_flag   | regular_flag | undef_flag,
 388     DYN_UNDEF =        global_flag | dynamic_flag | undef_flag,
 389     DYN_WEAK_UNDEF =   weak_flag   | dynamic_flag | undef_flag,
 390     COMMON =           global_flag | regular_flag | common_flag,
 391     WEAK_COMMON =      weak_flag   | regular_flag | common_flag,
 392     DYN_COMMON =       global_flag | dynamic_flag | common_flag,
 393     DYN_WEAK_COMMON =  weak_flag   | dynamic_flag | common_flag
 394   };
 395
 396   switch (tobits * 16 + frombits)
 397     {
 398     case DEF * 16 + DEF:
 399       // Two definitions of the same symbol.
 400
 401       // If either symbol is defined by an object included using
 402       // --just-symbols, then don't warn.  This is for compatibility
 403       // with the GNU linker.  FIXME: This is a hack.
 404       if ((to->source() == Symbol::FROM_OBJECT && to->object()->just_symbols())
 405           || object->just_symbols())
 406         return false;
 407
 408       // FIXME: Do a better job of reporting locations.
 409       gold_error(_("%s: multiple definition of %s"),
 410                  object != NULL ? object->name().c_str() : _("command line"),
 411                  to->demangled_name().c_str());
 412       gold_error(_("%s: previous definition here"),
 413                  (to->source() == Symbol::FROM_OBJECT
 414                   ? to->object()->name().c_str()
 415                   : _("command line")));
 416       return false;
 417
 418     case WEAK_DEF * 16 + DEF:
 419       // We've seen a weak definition, and now we see a strong
 420       // definition.  In the original SVR4 linker, this was treated as
 421       // a multiple definition error.  In the Solaris linker and the
 422       // GNU linker, a weak definition followed by a regular
 423       // definition causes the weak definition to be overridden.  We
 424       // are currently compatible with the GNU linker.  In the future
 425       // we should add a target specific option to change this.
 426       // FIXME.
 427       return true;
 428
 429     case DYN_DEF * 16 + DEF:
 430     case DYN_WEAK_DEF * 16 + DEF:
 431       // We've seen a definition in a dynamic object, and now we see a
 432       // definition in a regular object.  The definition in the
 433       // regular object overrides the definition in the dynamic
 434       // object.
 435       return true;
 436
 437     case UNDEF * 16 + DEF:
 438     case WEAK_UNDEF * 16 + DEF:
 439     case DYN_UNDEF * 16 + DEF:
 440     case DYN_WEAK_UNDEF * 16 + DEF:
 441       // We've seen an undefined reference, and now we see a
 442       // definition.  We use the definition.
 443       return true;
 444
 445     case COMMON * 16 + DEF:
 446     case WEAK_COMMON * 16 + DEF:
 447     case DYN_COMMON * 16 + DEF:
 448     case DYN_WEAK_COMMON * 16 + DEF:
 449       // We've seen a common symbol and now we see a definition.  The
 450       // definition overrides.  FIXME: We should optionally issue, version a
 451       // warning.
 452       return true;
 453
 454     case DEF * 16 + WEAK_DEF:
 455     case WEAK_DEF * 16 + WEAK_DEF:
 456       // We've seen a definition and now we see a weak definition.  We
 457       // ignore the new weak definition.
 458       return false;
 459
 460     case DYN_DEF * 16 + WEAK_DEF:
 461     case DYN_WEAK_DEF * 16 + WEAK_DEF:
 462       // We've seen a dynamic definition and now we see a regular weak
 463       // definition.  The regular weak definition overrides.
 464       return true;
 465
 466     case UNDEF * 16 + WEAK_DEF:
 467     case WEAK_UNDEF * 16 + WEAK_DEF:
 468     case DYN_UNDEF * 16 + WEAK_DEF:
 469     case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
 470       // A weak definition of a currently undefined symbol.
 471       return true;
 472
 473     case COMMON * 16 + WEAK_DEF:
 474     case WEAK_COMMON * 16 + WEAK_DEF:
 475       // A weak definition does not override a common definition.
 476       return false;
 477
 478     case DYN_COMMON * 16 + WEAK_DEF:
 479     case DYN_WEAK_COMMON * 16 + WEAK_DEF:
 480       // A weak definition does override a definition in a dynamic
 481       // object.  FIXME: We should optionally issue a warning.
 482       return true;
 483
 484     case DEF * 16 + DYN_DEF:
 485     case WEAK_DEF * 16 + DYN_DEF:
 486     case DYN_DEF * 16 + DYN_DEF:
 487     case DYN_WEAK_DEF * 16 + DYN_DEF:
 488       // Ignore a dynamic definition if we already have a definition.
 489       return false;
 490
 491     case UNDEF * 16 + DYN_DEF:
 492     case WEAK_UNDEF * 16 + DYN_DEF:
 493     case DYN_UNDEF * 16 + DYN_DEF:
 494     case DYN_WEAK_UNDEF * 16 + DYN_DEF:
 495       // Use a dynamic definition if we have a reference.
 496       return true;
 497
 498     case COMMON * 16 + DYN_DEF:
 499     case WEAK_COMMON * 16 + DYN_DEF:
 500     case DYN_COMMON * 16 + DYN_DEF:
 501     case DYN_WEAK_COMMON * 16 + DYN_DEF:
 502       // Ignore a dynamic definition if we already have a common
 503       // definition.
 504       return false;
 505
 506     case DEF * 16 + DYN_WEAK_DEF:
 507     case WEAK_DEF * 16 + DYN_WEAK_DEF:
 508     case DYN_DEF * 16 + DYN_WEAK_DEF:
 509     case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
 510       // Ignore a weak dynamic definition if we already have a
 511       // definition.
 512       return false;
 513
 514     case UNDEF * 16 + DYN_WEAK_DEF:
 515     case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 516     case DYN_UNDEF * 16 + DYN_WEAK_DEF:
 517     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 518       // Use a weak dynamic definition if we have a reference.
 519       return true;
 520
 521     case COMMON * 16 + DYN_WEAK_DEF:
 522     case WEAK_COMMON * 16 + DYN_WEAK_DEF:
 523     case DYN_COMMON * 16 + DYN_WEAK_DEF:
 524     case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
 525       // Ignore a weak dynamic definition if we already have a common
 526       // definition.
 527       return false;
 528
 529     case DEF * 16 + UNDEF:
 530     case WEAK_DEF * 16 + UNDEF:
 531     case DYN_DEF * 16 + UNDEF:
 532     case DYN_WEAK_DEF * 16 + UNDEF:
 533     case UNDEF * 16 + UNDEF:
 534       // A new undefined reference tells us nothing.
 535       return false;
 536
 537     case WEAK_UNDEF * 16 + UNDEF:
 538     case DYN_UNDEF * 16 + UNDEF:
 539     case DYN_WEAK_UNDEF * 16 + UNDEF:
 540       // A strong undef overrides a dynamic or weak undef.
 541       return true;
 542
 543     case COMMON * 16 + UNDEF:
 544     case WEAK_COMMON * 16 + UNDEF:
 545     case DYN_COMMON * 16 + UNDEF:
 546     case DYN_WEAK_COMMON * 16 + UNDEF:
 547       // A new undefined reference tells us nothing.
 548       return false;
 549
 550     case DEF * 16 + WEAK_UNDEF:
 551     case WEAK_DEF * 16 + WEAK_UNDEF:
 552     case DYN_DEF * 16 + WEAK_UNDEF:
 553     case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
 554     case UNDEF * 16 + WEAK_UNDEF:
 555     case WEAK_UNDEF * 16 + WEAK_UNDEF:
 556     case DYN_UNDEF * 16 + WEAK_UNDEF:
 557     case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
 558     case COMMON * 16 + WEAK_UNDEF:
 559     case WEAK_COMMON * 16 + WEAK_UNDEF:
 560     case DYN_COMMON * 16 + WEAK_UNDEF:
 561     case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
 562       // A new weak undefined reference tells us nothing.
 563       return false;
 564
 565     case DEF * 16 + DYN_UNDEF:
 566     case WEAK_DEF * 16 + DYN_UNDEF:
 567     case DYN_DEF * 16 + DYN_UNDEF:
 568     case DYN_WEAK_DEF * 16 + DYN_UNDEF:
 569     case UNDEF * 16 + DYN_UNDEF:
 570     case WEAK_UNDEF * 16 + DYN_UNDEF:
 571     case DYN_UNDEF * 16 + DYN_UNDEF:
 572     case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
 573     case COMMON * 16 + DYN_UNDEF:
 574     case WEAK_COMMON * 16 + DYN_UNDEF:
 575     case DYN_COMMON * 16 + DYN_UNDEF:
 576     case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
 577       // A new dynamic undefined reference tells us nothing.
 578       return false;
 579
 580     case DEF * 16 + DYN_WEAK_UNDEF:
 581     case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 582     case DYN_DEF * 16 + DYN_WEAK_UNDEF:
 583     case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 584     case UNDEF * 16 + DYN_WEAK_UNDEF:
 585     case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 586     case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
 587     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 588     case COMMON * 16 + DYN_WEAK_UNDEF:
 589     case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 590     case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
 591     case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 592       // A new weak dynamic undefined reference tells us nothing.
 593       return false;
 594
 595     case DEF * 16 + COMMON:
 596       // A common symbol does not override a definition.
 597       return false;
 598
 599     case WEAK_DEF * 16 + COMMON:
 600     case DYN_DEF * 16 + COMMON:
 601     case DYN_WEAK_DEF * 16 + COMMON:
 602       // A common symbol does override a weak definition or a dynamic
 603       // definition.
 604       return true;
 605
 606     case UNDEF * 16 + COMMON:
 607     case WEAK_UNDEF * 16 + COMMON:
 608     case DYN_UNDEF * 16 + COMMON:
 609     case DYN_WEAK_UNDEF * 16 + COMMON:
 610       // A common symbol is a definition for a reference.
 611       return true;
 612
 613     case COMMON * 16 + COMMON:
 614       // Set the size to the maximum.
 615       *adjust_common_sizes = true;
 616       return false;
 617
 618     case WEAK_COMMON * 16 + COMMON:
 619       // I'm not sure just what a weak common symbol means, but
 620       // presumably it can be overridden by a regular common symbol.
 621       return true;
 622
 623     case DYN_COMMON * 16 + COMMON:
 624     case DYN_WEAK_COMMON * 16 + COMMON:
 625       // Use the real common symbol, but adjust the size if necessary.
 626       *adjust_common_sizes = true;
 627       return true;
 628
 629     case DEF * 16 + WEAK_COMMON:
 630     case WEAK_DEF * 16 + WEAK_COMMON:
 631     case DYN_DEF * 16 + WEAK_COMMON:
 632     case DYN_WEAK_DEF * 16 + WEAK_COMMON:
 633       // Whatever a weak common symbol is, it won't override a
 634       // definition.
 635       return false;
 636
 637     case UNDEF * 16 + WEAK_COMMON:
 638     case WEAK_UNDEF * 16 + WEAK_COMMON:
 639     case DYN_UNDEF * 16 + WEAK_COMMON:
 640     case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
 641       // A weak common symbol is better than an undefined symbol.
 642       return true;
 643
 644     case COMMON * 16 + WEAK_COMMON:
 645     case WEAK_COMMON * 16 + WEAK_COMMON:
 646     case DYN_COMMON * 16 + WEAK_COMMON:
 647     case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
 648       // Ignore a weak common symbol in the presence of a real common
 649       // symbol.
 650       return false;
 651
 652     case DEF * 16 + DYN_COMMON:
 653     case WEAK_DEF * 16 + DYN_COMMON:
 654     case DYN_DEF * 16 + DYN_COMMON:
 655     case DYN_WEAK_DEF * 16 + DYN_COMMON:
 656       // Ignore a dynamic common symbol in the presence of a
 657       // definition.
 658       return false;
 659
 660     case UNDEF * 16 + DYN_COMMON:
 661     case WEAK_UNDEF * 16 + DYN_COMMON:
 662     case DYN_UNDEF * 16 + DYN_COMMON:
 663     case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
 664       // A dynamic common symbol is a definition of sorts.
 665       return true;
 666
 667     case COMMON * 16 + DYN_COMMON:
 668     case WEAK_COMMON * 16 + DYN_COMMON:
 669     case DYN_COMMON * 16 + DYN_COMMON:
 670     case DYN_WEAK_COMMON * 16 + DYN_COMMON:
 671       // Set the size to the maximum.
 672       *adjust_common_sizes = true;
 673       return false;
 674
 675     case DEF * 16 + DYN_WEAK_COMMON:
 676     case WEAK_DEF * 16 + DYN_WEAK_COMMON:
 677     case DYN_DEF * 16 + DYN_WEAK_COMMON:
 678     case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
 679       // A common symbol is ignored in the face of a definition.
 680       return false;
 681
 682     case UNDEF * 16 + DYN_WEAK_COMMON:
 683     case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 684     case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
 685     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 686       // I guess a weak common symbol is better than a definition.
 687       return true;
 688
 689     case COMMON * 16 + DYN_WEAK_COMMON:
 690     case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 691     case DYN_COMMON * 16 + DYN_WEAK_COMMON:
 692     case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 693       // Set the size to the maximum.
 694       *adjust_common_sizes = true;
 695       return false;
 696
 697     default:
 698       gold_unreachable();
 699     }
 700 }
 701
 702 // A special case of should_override which is only called for a strong
 703 // defined symbol from a regular object file.  This is used when
 704 // defining special symbols.
 705
 706 bool
 707 Symbol_table::should_override_with_special(const Symbol* to)
 708 {
 709   bool adjust_common_sizes;
 710   unsigned int frombits = global_flag | regular_flag | def_flag;
 711   bool ret = Symbol_table::should_override(to, frombits, NULL,
 712                                            &adjust_common_sizes);
 713   gold_assert(!adjust_common_sizes);
 714   return ret;
 715 }
 716
 717 // Override symbol base with a special symbol.
 718
 719 void
 720 Symbol::override_base_with_special(const Symbol* from)
 721 {
 722   gold_assert(this->name_ == from->name_ || this->has_alias());
 723
 724   this->source_ = from->source_;
 725   switch (from->source_)
 726     {
 727     case FROM_OBJECT:
 728       this->u_.from_object = from->u_.from_object;
 729       break;
 730     case IN_OUTPUT_DATA:
 731       this->u_.in_output_data = from->u_.in_output_data;
 732       break;
 733     case IN_OUTPUT_SEGMENT:
 734       this->u_.in_output_segment = from->u_.in_output_segment;
 735       break;
 736     case IS_CONSTANT:
 737     case IS_UNDEFINED:
 738       break;
 739     default:
 740       gold_unreachable();
 741       break;
 742     }
 743
 744   this->override_version(from->version_);
 745   this->type_ = from->type_;
 746   this->binding_ = from->binding_;
 747   this->override_visibility(from->visibility_);
 748   this->nonvis_ = from->nonvis_;
 749
 750   // Special symbols are always considered to be regular symbols.
 751   this->in_reg_ = true;
 752
 753   if (from->needs_dynsym_entry_)
 754     this->needs_dynsym_entry_ = true;
 755   if (from->needs_dynsym_value_)
 756     this->needs_dynsym_value_ = true;
 757
 758   // We shouldn't see these flags.  If we do, we need to handle them
 759   // somehow.
 760   gold_assert(!from->is_target_special_ || this->is_target_special_);
 761   gold_assert(!from->is_forwarder_);
 762   gold_assert(!from->has_plt_offset_);
 763   gold_assert(!from->has_warning_);
 764   gold_assert(!from->is_copied_from_dynobj_);
 765   gold_assert(!from->is_forced_local_);
 766 }
 767
 768 // Override a symbol with a special symbol.
 769
 770 template<int size>
 771 void
 772 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from)
 773 {
 774   this->override_base_with_special(from);
 775   this->value_ = from->value_;
 776   this->symsize_ = from->symsize_;
 777 }
 778
 779 // Override TOSYM with the special symbol FROMSYM.  This handles all
 780 // aliases of TOSYM.
 781
 782 template<int size>
 783 void
 784 Symbol_table::override_with_special(Sized_symbol<size>* tosym,
 785                                     const Sized_symbol<size>* fromsym)
 786 {
 787   tosym->override_with_special(fromsym);
 788   if (tosym->has_alias())
 789     {
 790       Symbol* sym = this->weak_aliases_[tosym];
 791       gold_assert(sym != NULL);
 792       Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
 793       do
 794         {
 795           ssym->override_with_special(fromsym);
 796           sym = this->weak_aliases_[ssym];
 797           gold_assert(sym != NULL);
 798           ssym = this->get_sized_symbol<size>(sym);
 799         }
 800       while (ssym != tosym);
 801     }
 802   if (tosym->binding() == elfcpp::STB_LOCAL
 803       || ((tosym->visibility() == elfcpp::STV_HIDDEN
 804            || tosym->visibility() == elfcpp::STV_INTERNAL)
 805           && (tosym->binding() == elfcpp::STB_GLOBAL
 806               || tosym->binding() == elfcpp::STB_WEAK)
 807           && !parameters->options().relocatable()))
 808     this->force_local(tosym);
 809 }
 810
 811 // Instantiate the templates we need.  We could use the configure
 812 // script to restrict this to only the ones needed for implemented
 813 // targets.
 814
 815 #ifdef HAVE_TARGET_32_LITTLE
 816 template
 817 void
 818 Symbol_table::resolve<32, false>(
 819     Sized_symbol<32>* to,
 820     const elfcpp::Sym<32, false>& sym,
 821     unsigned int st_shndx,
 822     bool is_ordinary,
 823     unsigned int orig_st_shndx,
 824     Object* object,
 825     const char* version);
 826 #endif
 827
 828 #ifdef HAVE_TARGET_32_BIG
 829 template
 830 void
 831 Symbol_table::resolve<32, true>(
 832     Sized_symbol<32>* to,
 833     const elfcpp::Sym<32, true>& sym,
 834     unsigned int st_shndx,
 835     bool is_ordinary,
 836     unsigned int orig_st_shndx,
 837     Object* object,
 838     const char* version);
 839 #endif
 840
 841 #ifdef HAVE_TARGET_64_LITTLE
 842 template
 843 void
 844 Symbol_table::resolve<64, false>(
 845     Sized_symbol<64>* to,
 846     const elfcpp::Sym<64, false>& sym,
 847     unsigned int st_shndx,
 848     bool is_ordinary,
 849     unsigned int orig_st_shndx,
 850     Object* object,
 851     const char* version);
 852 #endif
 853
 854 #ifdef HAVE_TARGET_64_BIG
 855 template
 856 void
 857 Symbol_table::resolve<64, true>(
 858     Sized_symbol<64>* to,
 859     const elfcpp::Sym<64, true>& sym,
 860     unsigned int st_shndx,
 861     bool is_ordinary,
 862     unsigned int orig_st_shndx,
 863     Object* object,
 864     const char* version);
 865 #endif
 866
 867 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
 868 template
 869 void
 870 Symbol_table::override_with_special<32>(Sized_symbol<32>*,
 871                                         const Sized_symbol<32>*);
 872 #endif
 873
 874 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
 875 template
 876 void
 877 Symbol_table::override_with_special<64>(Sized_symbol<64>*,
 878                                         const Sized_symbol<64>*);
 879 #endif
 880
 881 } // End namespace gold.