gold/resolve.cc

   1 // resolve.cc -- symbol resolution for gold
   2
   3 // Copyright 2006, 2007, 2008 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
  30 namespace gold
  31 {
  32
  33 // Symbol methods used in this file.
  34
  35 // Override the fields in Symbol.
  36
  37 template<int size, bool big_endian>
  38 void
  39 Symbol::override_base(const elfcpp::Sym<size, big_endian>& sym,
  40                       Object* object, const char* version)
  41 {
  42   gold_assert(this->source_ == FROM_OBJECT);
  43   this->u_.from_object.object = object;
  44   if (version != NULL && this->version() != version)
  45     {
  46       gold_assert(this->version() == NULL);
  47       this->version_ = version;
  48     }
  49   // FIXME: Handle SHN_XINDEX.
  50   this->u_.from_object.shndx = sym.get_st_shndx();
  51   this->type_ = sym.get_st_type();
  52   this->binding_ = sym.get_st_bind();
  53   this->visibility_ = sym.get_st_visibility();
  54   this->nonvis_ = sym.get_st_nonvis();
  55   if (object->is_dynamic())
  56     this->in_dyn_ = true;
  57   else
  58     this->in_reg_ = true;
  59 }
  60
  61 // Override the fields in Sized_symbol.
  62
  63 template<int size>
  64 template<bool big_endian>
  65 void
  66 Sized_symbol<size>::override(const elfcpp::Sym<size, big_endian>& sym,
  67                              Object* object, const char* version)
  68 {
  69   this->override_base(sym, object, version);
  70   this->value_ = sym.get_st_value();
  71   this->symsize_ = sym.get_st_size();
  72 }
  73
  74 // Override TOSYM with symbol FROMSYM, defined in OBJECT, with version
  75 // VERSION.  This handles all aliases of TOSYM.
  76
  77 template<int size, bool big_endian>
  78 void
  79 Symbol_table::override(Sized_symbol<size>* tosym,
  80                        const elfcpp::Sym<size, big_endian>& fromsym,
  81                        Object* object, const char* version)
  82 {
  83   tosym->override(fromsym, object, version);
  84   if (tosym->has_alias())
  85     {
  86       Symbol* sym = this->weak_aliases_[tosym];
  87       gold_assert(sym != NULL);
  88       Sized_symbol<size>* ssym;
  89       ssym = this->get_sized_symbol SELECT_SIZE_NAME(size) (sym
  90                                                             SELECT_SIZE(size));
  91       do
  92         {
  93           ssym->override(fromsym, object, version);
  94           sym = this->weak_aliases_[ssym];
  95           gold_assert(sym != NULL);
  96           ssym = this->get_sized_symbol SELECT_SIZE_NAME(size) (
  97                                                 sym SELECT_SIZE(size));
  98         }
  99       while (ssym != tosym);
 100     }
 101 }
 102
 103 // The resolve functions build a little code for each symbol.
 104 // Bit 0: 0 for global, 1 for weak.
 105 // Bit 1: 0 for regular object, 1 for shared object
 106 // Bits 2-3: 0 for normal, 1 for undefined, 2 for common
 107 // This gives us values from 0 to 11.
 108
 109 static const int global_or_weak_shift = 0;
 110 static const unsigned int global_flag = 0 << global_or_weak_shift;
 111 static const unsigned int weak_flag = 1 << global_or_weak_shift;
 112
 113 static const int regular_or_dynamic_shift = 1;
 114 static const unsigned int regular_flag = 0 << regular_or_dynamic_shift;
 115 static const unsigned int dynamic_flag = 1 << regular_or_dynamic_shift;
 116
 117 static const int def_undef_or_common_shift = 2;
 118 static const unsigned int def_flag = 0 << def_undef_or_common_shift;
 119 static const unsigned int undef_flag = 1 << def_undef_or_common_shift;
 120 static const unsigned int common_flag = 2 << def_undef_or_common_shift;
 121
 122 // This convenience function combines all the flags based on facts
 123 // about the symbol.
 124
 125 static unsigned int
 126 symbol_to_bits(elfcpp::STB binding, bool is_dynamic,
 127                unsigned int shndx, elfcpp::STT type)
 128 {
 129   unsigned int bits;
 130
 131   switch (binding)
 132     {
 133     case elfcpp::STB_GLOBAL:
 134       bits = global_flag;
 135       break;
 136
 137     case elfcpp::STB_WEAK:
 138       bits = weak_flag;
 139       break;
 140
 141     case elfcpp::STB_LOCAL:
 142       // We should only see externally visible symbols in the symbol
 143       // table.
 144       gold_error(_("invalid STB_LOCAL symbol in external symbols"));
 145       bits = global_flag;
 146
 147     default:
 148       // Any target which wants to handle STB_LOOS, etc., needs to
 149       // define a resolve method.
 150       gold_error(_("unsupported symbol binding"));
 151       bits = global_flag;
 152     }
 153
 154   if (is_dynamic)
 155     bits |= dynamic_flag;
 156   else
 157     bits |= regular_flag;
 158
 159   switch (shndx)
 160     {
 161     case elfcpp::SHN_UNDEF:
 162       bits |= undef_flag;
 163       break;
 164
 165     case elfcpp::SHN_COMMON:
 166       bits |= common_flag;
 167       break;
 168
 169     default:
 170       if (type == elfcpp::STT_COMMON)
 171         bits |= common_flag;
 172       else
 173         bits |= def_flag;
 174       break;
 175     }
 176
 177   return bits;
 178 }
 179
 180 // Resolve a symbol.  This is called the second and subsequent times
 181 // we see a symbol.  TO is the pre-existing symbol.  ORIG_SYM is the
 182 // new symbol, seen in OBJECT.  SYM is almost always identical to
 183 // ORIG_SYM, but may be munged (for instance, if we determine the
 184 // symbol is in a to-be-discarded section, we'll set sym's shndx to
 185 // UNDEFINED).  VERSION of the version of SYM.
 186
 187 template<int size, bool big_endian>
 188 void
 189 Symbol_table::resolve(Sized_symbol<size>* to,
 190                       const elfcpp::Sym<size, big_endian>& sym,
 191                       const elfcpp::Sym<size, big_endian>& orig_sym,
 192                       Object* object, const char* version)
 193 {
 194   if (object->target()->has_resolve())
 195     {
 196       Sized_target<size, big_endian>* sized_target;
 197       sized_target = object->sized_target
 198                      SELECT_SIZE_ENDIAN_NAME(size, big_endian) (
 199                          SELECT_SIZE_ENDIAN_ONLY(size, big_endian));
 200       sized_target->resolve(to, sym, object, version);
 201       return;
 202     }
 203
 204   if (!object->is_dynamic())
 205     {
 206       // Record that we've seen this symbol in a regular object.
 207       to->set_in_reg();
 208     }
 209   else
 210     {
 211       // Record that we've seen this symbol in a dynamic object.
 212       to->set_in_dyn();
 213     }
 214
 215   unsigned int frombits = symbol_to_bits(sym.get_st_bind(),
 216                                          object->is_dynamic(),
 217                                          sym.get_st_shndx(),
 218                                          sym.get_st_type());
 219
 220   bool adjust_common_sizes;
 221   if (Symbol_table::should_override(to, frombits, object,
 222                                     &adjust_common_sizes))
 223     {
 224       typename Sized_symbol<size>::Size_type tosize = to->symsize();
 225
 226       this->override(to, sym, object, version);
 227
 228       if (adjust_common_sizes && tosize > to->symsize())
 229         to->set_symsize(tosize);
 230     }
 231   else
 232     {
 233       if (adjust_common_sizes && sym.get_st_size() > to->symsize())
 234         to->set_symsize(sym.get_st_size());
 235     }
 236
 237   // A new weak undefined reference, merging with an old weak
 238   // reference, could be a One Definition Rule (ODR) violation --
 239   // especially if the types or sizes of the references differ.  We'll
 240   // store such pairs and look them up later to make sure they
 241   // actually refer to the same lines of code.  (Note: not all ODR
 242   // violations can be found this way, and not everything this finds
 243   // is an ODR violation.  But it's helpful to warn about.)
 244   // We use orig_sym here because we want the symbol exactly as it
 245   // appears in the object file, not munged via our future processing.
 246   if (parameters->options().detect_odr_violations()
 247       && orig_sym.get_st_bind() == elfcpp::STB_WEAK
 248       && to->binding() == elfcpp::STB_WEAK
 249       && orig_sym.get_st_shndx() != elfcpp::SHN_UNDEF
 250       && to->shndx() != elfcpp::SHN_UNDEF
 251       && orig_sym.get_st_size() != 0    // Ignore weird 0-sized symbols.
 252       && to->symsize() != 0
 253       && (orig_sym.get_st_type() != to->type()
 254           || orig_sym.get_st_size() != to->symsize())
 255       // C does not have a concept of ODR, so we only need to do this
 256       // on C++ symbols.  These have (mangled) names starting with _Z.
 257       && to->name()[0] == '_' && to->name()[1] == 'Z')
 258     {
 259       Symbol_location fromloc
 260           = { object, orig_sym.get_st_shndx(), orig_sym.get_st_value() };
 261       Symbol_location toloc = { to->object(), to->shndx(), to->value() };
 262       this->candidate_odr_violations_[to->name()].insert(fromloc);
 263       this->candidate_odr_violations_[to->name()].insert(toloc);
 264     }
 265 }
 266
 267 // Handle the core of symbol resolution.  This is called with the
 268 // existing symbol, TO, and a bitflag describing the new symbol.  This
 269 // returns true if we should override the existing symbol with the new
 270 // one, and returns false otherwise.  It sets *ADJUST_COMMON_SIZES to
 271 // true if we should set the symbol size to the maximum of the TO and
 272 // FROM sizes.  It handles error conditions.
 273
 274 bool
 275 Symbol_table::should_override(const Symbol* to, unsigned int frombits,
 276                               Object* object, bool* adjust_common_sizes)
 277 {
 278   *adjust_common_sizes = false;
 279
 280   unsigned int tobits;
 281   if (to->source() == Symbol::FROM_OBJECT)
 282     tobits = symbol_to_bits(to->binding(),
 283                             to->object()->is_dynamic(),
 284                             to->shndx(),
 285                             to->type());
 286   else
 287     tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_ABS,
 288                             to->type());
 289
 290   // FIXME: Warn if either but not both of TO and SYM are STT_TLS.
 291
 292   // We use a giant switch table for symbol resolution.  This code is
 293   // unwieldy, but: 1) it is efficient; 2) we definitely handle all
 294   // cases; 3) it is easy to change the handling of a particular case.
 295   // The alternative would be a series of conditionals, but it is easy
 296   // to get the ordering wrong.  This could also be done as a table,
 297   // but that is no easier to understand than this large switch
 298   // statement.
 299
 300   // These are the values generated by the bit codes.
 301   enum
 302   {
 303     DEF =              global_flag | regular_flag | def_flag,
 304     WEAK_DEF =         weak_flag   | regular_flag | def_flag,
 305     DYN_DEF =          global_flag | dynamic_flag | def_flag,
 306     DYN_WEAK_DEF =     weak_flag   | dynamic_flag | def_flag,
 307     UNDEF =            global_flag | regular_flag | undef_flag,
 308     WEAK_UNDEF =       weak_flag   | regular_flag | undef_flag,
 309     DYN_UNDEF =        global_flag | dynamic_flag | undef_flag,
 310     DYN_WEAK_UNDEF =   weak_flag   | dynamic_flag | undef_flag,
 311     COMMON =           global_flag | regular_flag | common_flag,
 312     WEAK_COMMON =      weak_flag   | regular_flag | common_flag,
 313     DYN_COMMON =       global_flag | dynamic_flag | common_flag,
 314     DYN_WEAK_COMMON =  weak_flag   | dynamic_flag | common_flag
 315   };
 316
 317   switch (tobits * 16 + frombits)
 318     {
 319     case DEF * 16 + DEF:
 320       // Two definitions of the same symbol.
 321       // FIXME: Do a better job of reporting locations.
 322       gold_error(_("%s: multiple definition of %s"),
 323                  object != NULL ? object->name().c_str() : _("command line"),
 324                  to->demangled_name().c_str());
 325       gold_error(_("%s: previous definition here"),
 326                  (to->source() == Symbol::FROM_OBJECT
 327                   ? to->object()->name().c_str()
 328                   : _("command line")));
 329       return false;
 330
 331     case WEAK_DEF * 16 + DEF:
 332       // We've seen a weak definition, and now we see a strong
 333       // definition.  In the original SVR4 linker, this was treated as
 334       // a multiple definition error.  In the Solaris linker and the
 335       // GNU linker, a weak definition followed by a regular
 336       // definition causes the weak definition to be overridden.  We
 337       // are currently compatible with the GNU linker.  In the future
 338       // we should add a target specific option to change this.
 339       // FIXME.
 340       return true;
 341
 342     case DYN_DEF * 16 + DEF:
 343     case DYN_WEAK_DEF * 16 + DEF:
 344       // We've seen a definition in a dynamic object, and now we see a
 345       // definition in a regular object.  The definition in the
 346       // regular object overrides the definition in the dynamic
 347       // object.
 348       return true;
 349
 350     case UNDEF * 16 + DEF:
 351     case WEAK_UNDEF * 16 + DEF:
 352     case DYN_UNDEF * 16 + DEF:
 353     case DYN_WEAK_UNDEF * 16 + DEF:
 354       // We've seen an undefined reference, and now we see a
 355       // definition.  We use the definition.
 356       return true;
 357
 358     case COMMON * 16 + DEF:
 359     case WEAK_COMMON * 16 + DEF:
 360     case DYN_COMMON * 16 + DEF:
 361     case DYN_WEAK_COMMON * 16 + DEF:
 362       // We've seen a common symbol and now we see a definition.  The
 363       // definition overrides.  FIXME: We should optionally issue, version a
 364       // warning.
 365       return true;
 366
 367     case DEF * 16 + WEAK_DEF:
 368     case WEAK_DEF * 16 + WEAK_DEF:
 369       // We've seen a definition and now we see a weak definition.  We
 370       // ignore the new weak definition.
 371       return false;
 372
 373     case DYN_DEF * 16 + WEAK_DEF:
 374     case DYN_WEAK_DEF * 16 + WEAK_DEF:
 375       // We've seen a dynamic definition and now we see a regular weak
 376       // definition.  The regular weak definition overrides.
 377       return true;
 378
 379     case UNDEF * 16 + WEAK_DEF:
 380     case WEAK_UNDEF * 16 + WEAK_DEF:
 381     case DYN_UNDEF * 16 + WEAK_DEF:
 382     case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
 383       // A weak definition of a currently undefined symbol.
 384       return true;
 385
 386     case COMMON * 16 + WEAK_DEF:
 387     case WEAK_COMMON * 16 + WEAK_DEF:
 388       // A weak definition does not override a common definition.
 389       return false;
 390
 391     case DYN_COMMON * 16 + WEAK_DEF:
 392     case DYN_WEAK_COMMON * 16 + WEAK_DEF:
 393       // A weak definition does override a definition in a dynamic
 394       // object.  FIXME: We should optionally issue a warning.
 395       return true;
 396
 397     case DEF * 16 + DYN_DEF:
 398     case WEAK_DEF * 16 + DYN_DEF:
 399     case DYN_DEF * 16 + DYN_DEF:
 400     case DYN_WEAK_DEF * 16 + DYN_DEF:
 401       // Ignore a dynamic definition if we already have a definition.
 402       return false;
 403
 404     case UNDEF * 16 + DYN_DEF:
 405     case WEAK_UNDEF * 16 + DYN_DEF:
 406     case DYN_UNDEF * 16 + DYN_DEF:
 407     case DYN_WEAK_UNDEF * 16 + DYN_DEF:
 408       // Use a dynamic definition if we have a reference.
 409       return true;
 410
 411     case COMMON * 16 + DYN_DEF:
 412     case WEAK_COMMON * 16 + DYN_DEF:
 413     case DYN_COMMON * 16 + DYN_DEF:
 414     case DYN_WEAK_COMMON * 16 + DYN_DEF:
 415       // Ignore a dynamic definition if we already have a common
 416       // definition.
 417       return false;
 418
 419     case DEF * 16 + DYN_WEAK_DEF:
 420     case WEAK_DEF * 16 + DYN_WEAK_DEF:
 421     case DYN_DEF * 16 + DYN_WEAK_DEF:
 422     case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
 423       // Ignore a weak dynamic definition if we already have a
 424       // definition.
 425       return false;
 426
 427     case UNDEF * 16 + DYN_WEAK_DEF:
 428     case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 429     case DYN_UNDEF * 16 + DYN_WEAK_DEF:
 430     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 431       // Use a weak dynamic definition if we have a reference.
 432       return true;
 433
 434     case COMMON * 16 + DYN_WEAK_DEF:
 435     case WEAK_COMMON * 16 + DYN_WEAK_DEF:
 436     case DYN_COMMON * 16 + DYN_WEAK_DEF:
 437     case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
 438       // Ignore a weak dynamic definition if we already have a common
 439       // definition.
 440       return false;
 441
 442     case DEF * 16 + UNDEF:
 443     case WEAK_DEF * 16 + UNDEF:
 444     case DYN_DEF * 16 + UNDEF:
 445     case DYN_WEAK_DEF * 16 + UNDEF:
 446     case UNDEF * 16 + UNDEF:
 447       // A new undefined reference tells us nothing.
 448       return false;
 449
 450     case WEAK_UNDEF * 16 + UNDEF:
 451     case DYN_UNDEF * 16 + UNDEF:
 452     case DYN_WEAK_UNDEF * 16 + UNDEF:
 453       // A strong undef overrides a dynamic or weak undef.
 454       return true;
 455
 456     case COMMON * 16 + UNDEF:
 457     case WEAK_COMMON * 16 + UNDEF:
 458     case DYN_COMMON * 16 + UNDEF:
 459     case DYN_WEAK_COMMON * 16 + UNDEF:
 460       // A new undefined reference tells us nothing.
 461       return false;
 462
 463     case DEF * 16 + WEAK_UNDEF:
 464     case WEAK_DEF * 16 + WEAK_UNDEF:
 465     case DYN_DEF * 16 + WEAK_UNDEF:
 466     case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
 467     case UNDEF * 16 + WEAK_UNDEF:
 468     case WEAK_UNDEF * 16 + WEAK_UNDEF:
 469     case DYN_UNDEF * 16 + WEAK_UNDEF:
 470     case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
 471     case COMMON * 16 + WEAK_UNDEF:
 472     case WEAK_COMMON * 16 + WEAK_UNDEF:
 473     case DYN_COMMON * 16 + WEAK_UNDEF:
 474     case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
 475       // A new weak undefined reference tells us nothing.
 476       return false;
 477
 478     case DEF * 16 + DYN_UNDEF:
 479     case WEAK_DEF * 16 + DYN_UNDEF:
 480     case DYN_DEF * 16 + DYN_UNDEF:
 481     case DYN_WEAK_DEF * 16 + DYN_UNDEF:
 482     case UNDEF * 16 + DYN_UNDEF:
 483     case WEAK_UNDEF * 16 + DYN_UNDEF:
 484     case DYN_UNDEF * 16 + DYN_UNDEF:
 485     case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
 486     case COMMON * 16 + DYN_UNDEF:
 487     case WEAK_COMMON * 16 + DYN_UNDEF:
 488     case DYN_COMMON * 16 + DYN_UNDEF:
 489     case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
 490       // A new dynamic undefined reference tells us nothing.
 491       return false;
 492
 493     case DEF * 16 + DYN_WEAK_UNDEF:
 494     case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 495     case DYN_DEF * 16 + DYN_WEAK_UNDEF:
 496     case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 497     case UNDEF * 16 + DYN_WEAK_UNDEF:
 498     case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 499     case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
 500     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 501     case COMMON * 16 + DYN_WEAK_UNDEF:
 502     case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 503     case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
 504     case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 505       // A new weak dynamic undefined reference tells us nothing.
 506       return false;
 507
 508     case DEF * 16 + COMMON:
 509       // A common symbol does not override a definition.
 510       return false;
 511
 512     case WEAK_DEF * 16 + COMMON:
 513     case DYN_DEF * 16 + COMMON:
 514     case DYN_WEAK_DEF * 16 + COMMON:
 515       // A common symbol does override a weak definition or a dynamic
 516       // definition.
 517       return true;
 518
 519     case UNDEF * 16 + COMMON:
 520     case WEAK_UNDEF * 16 + COMMON:
 521     case DYN_UNDEF * 16 + COMMON:
 522     case DYN_WEAK_UNDEF * 16 + COMMON:
 523       // A common symbol is a definition for a reference.
 524       return true;
 525
 526     case COMMON * 16 + COMMON:
 527       // Set the size to the maximum.
 528       *adjust_common_sizes = true;
 529       return false;
 530
 531     case WEAK_COMMON * 16 + COMMON:
 532       // I'm not sure just what a weak common symbol means, but
 533       // presumably it can be overridden by a regular common symbol.
 534       return true;
 535
 536     case DYN_COMMON * 16 + COMMON:
 537     case DYN_WEAK_COMMON * 16 + COMMON:
 538       // Use the real common symbol, but adjust the size if necessary.
 539       *adjust_common_sizes = true;
 540       return true;
 541
 542     case DEF * 16 + WEAK_COMMON:
 543     case WEAK_DEF * 16 + WEAK_COMMON:
 544     case DYN_DEF * 16 + WEAK_COMMON:
 545     case DYN_WEAK_DEF * 16 + WEAK_COMMON:
 546       // Whatever a weak common symbol is, it won't override a
 547       // definition.
 548       return false;
 549
 550     case UNDEF * 16 + WEAK_COMMON:
 551     case WEAK_UNDEF * 16 + WEAK_COMMON:
 552     case DYN_UNDEF * 16 + WEAK_COMMON:
 553     case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
 554       // A weak common symbol is better than an undefined symbol.
 555       return true;
 556
 557     case COMMON * 16 + WEAK_COMMON:
 558     case WEAK_COMMON * 16 + WEAK_COMMON:
 559     case DYN_COMMON * 16 + WEAK_COMMON:
 560     case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
 561       // Ignore a weak common symbol in the presence of a real common
 562       // symbol.
 563       return false;
 564
 565     case DEF * 16 + DYN_COMMON:
 566     case WEAK_DEF * 16 + DYN_COMMON:
 567     case DYN_DEF * 16 + DYN_COMMON:
 568     case DYN_WEAK_DEF * 16 + DYN_COMMON:
 569       // Ignore a dynamic common symbol in the presence of a
 570       // definition.
 571       return false;
 572
 573     case UNDEF * 16 + DYN_COMMON:
 574     case WEAK_UNDEF * 16 + DYN_COMMON:
 575     case DYN_UNDEF * 16 + DYN_COMMON:
 576     case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
 577       // A dynamic common symbol is a definition of sorts.
 578       return true;
 579
 580     case COMMON * 16 + DYN_COMMON:
 581     case WEAK_COMMON * 16 + DYN_COMMON:
 582     case DYN_COMMON * 16 + DYN_COMMON:
 583     case DYN_WEAK_COMMON * 16 + DYN_COMMON:
 584       // Set the size to the maximum.
 585       *adjust_common_sizes = true;
 586       return false;
 587
 588     case DEF * 16 + DYN_WEAK_COMMON:
 589     case WEAK_DEF * 16 + DYN_WEAK_COMMON:
 590     case DYN_DEF * 16 + DYN_WEAK_COMMON:
 591     case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
 592       // A common symbol is ignored in the face of a definition.
 593       return false;
 594
 595     case UNDEF * 16 + DYN_WEAK_COMMON:
 596     case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 597     case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
 598     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 599       // I guess a weak common symbol is better than a definition.
 600       return true;
 601
 602     case COMMON * 16 + DYN_WEAK_COMMON:
 603     case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 604     case DYN_COMMON * 16 + DYN_WEAK_COMMON:
 605     case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 606       // Set the size to the maximum.
 607       *adjust_common_sizes = true;
 608       return false;
 609
 610     default:
 611       gold_unreachable();
 612     }
 613 }
 614
 615 // A special case of should_override which is only called for a strong
 616 // defined symbol from a regular object file.  This is used when
 617 // defining special symbols.
 618
 619 bool
 620 Symbol_table::should_override_with_special(const Symbol* to)
 621 {
 622   bool adjust_common_sizes;
 623   unsigned int frombits = global_flag | regular_flag | def_flag;
 624   bool ret = Symbol_table::should_override(to, frombits, NULL,
 625                                            &adjust_common_sizes);
 626   gold_assert(!adjust_common_sizes);
 627   return ret;
 628 }
 629
 630 // Override symbol base with a special symbol.
 631
 632 void
 633 Symbol::override_base_with_special(const Symbol* from)
 634 {
 635   gold_assert(this->name_ == from->name_ || this->has_alias());
 636
 637   this->source_ = from->source_;
 638   switch (from->source_)
 639     {
 640     case FROM_OBJECT:
 641       this->u_.from_object = from->u_.from_object;
 642       break;
 643     case IN_OUTPUT_DATA:
 644       this->u_.in_output_data = from->u_.in_output_data;
 645       break;
 646     case IN_OUTPUT_SEGMENT:
 647       this->u_.in_output_segment = from->u_.in_output_segment;
 648       break;
 649     case CONSTANT:
 650       break;
 651     default:
 652       gold_unreachable();
 653       break;
 654     }
 655
 656   if (from->version_ != NULL && this->version_ != from->version_)
 657     {
 658       gold_assert(this->version_ == NULL);
 659       this->version_ = from->version_;
 660     }
 661
 662   this->type_ = from->type_;
 663   this->binding_ = from->binding_;
 664   this->visibility_ = from->visibility_;
 665   this->nonvis_ = from->nonvis_;
 666
 667   // Special symbols are always considered to be regular symbols.
 668   this->in_reg_ = true;
 669
 670   if (from->needs_dynsym_entry_)
 671     this->needs_dynsym_entry_ = true;
 672   if (from->needs_dynsym_value_)
 673     this->needs_dynsym_value_ = true;
 674
 675   // We shouldn't see these flags.  If we do, we need to handle them
 676   // somehow.
 677   gold_assert(!from->is_target_special_ || this->is_target_special_);
 678   gold_assert(!from->is_forwarder_);
 679   gold_assert(!from->has_got_offset_);
 680   gold_assert(!from->has_plt_offset_);
 681   gold_assert(!from->has_warning_);
 682   gold_assert(!from->is_copied_from_dynobj_);
 683   gold_assert(!from->is_forced_local_);
 684 }
 685
 686 // Override a symbol with a special symbol.
 687
 688 template<int size>
 689 void
 690 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from)
 691 {
 692   this->override_base_with_special(from);
 693   this->value_ = from->value_;
 694   this->symsize_ = from->symsize_;
 695 }
 696
 697 // Override TOSYM with the special symbol FROMSYM.  This handles all
 698 // aliases of TOSYM.
 699
 700 template<int size>
 701 void
 702 Symbol_table::override_with_special(Sized_symbol<size>* tosym,
 703                                     const Sized_symbol<size>* fromsym)
 704 {
 705   tosym->override_with_special(fromsym);
 706   if (tosym->has_alias())
 707     {
 708       Symbol* sym = this->weak_aliases_[tosym];
 709       gold_assert(sym != NULL);
 710       Sized_symbol<size>* ssym;
 711       ssym = this->get_sized_symbol SELECT_SIZE_NAME(size) (sym
 712                                                             SELECT_SIZE(size));
 713       do
 714         {
 715           ssym->override_with_special(fromsym);
 716           sym = this->weak_aliases_[ssym];
 717           gold_assert(sym != NULL);
 718           ssym = this->get_sized_symbol SELECT_SIZE_NAME(size) (
 719                                                 sym SELECT_SIZE(size));
 720         }
 721       while (ssym != tosym);
 722     }
 723   if (tosym->binding() == elfcpp::STB_LOCAL)
 724     this->force_local(tosym);
 725 }
 726
 727 // Instantiate the templates we need.  We could use the configure
 728 // script to restrict this to only the ones needed for implemented
 729 // targets.
 730
 731 #ifdef HAVE_TARGET_32_LITTLE
 732 template
 733 void
 734 Symbol_table::resolve<32, false>(
 735     Sized_symbol<32>* to,
 736     const elfcpp::Sym<32, false>& sym,
 737     const elfcpp::Sym<32, false>& orig_sym,
 738     Object* object,
 739     const char* version);
 740 #endif
 741
 742 #ifdef HAVE_TARGET_32_BIG
 743 template
 744 void
 745 Symbol_table::resolve<32, true>(
 746     Sized_symbol<32>* to,
 747     const elfcpp::Sym<32, true>& sym,
 748     const elfcpp::Sym<32, true>& orig_sym,
 749     Object* object,
 750     const char* version);
 751 #endif
 752
 753 #ifdef HAVE_TARGET_64_LITTLE
 754 template
 755 void
 756 Symbol_table::resolve<64, false>(
 757     Sized_symbol<64>* to,
 758     const elfcpp::Sym<64, false>& sym,
 759     const elfcpp::Sym<64, false>& orig_sym,
 760     Object* object,
 761     const char* version);
 762 #endif
 763
 764 #ifdef HAVE_TARGET_64_BIG
 765 template
 766 void
 767 Symbol_table::resolve<64, true>(
 768     Sized_symbol<64>* to,
 769     const elfcpp::Sym<64, true>& sym,
 770     const elfcpp::Sym<64, true>& orig_sym,
 771     Object* object,
 772     const char* version);
 773 #endif
 774
 775 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
 776 template
 777 void
 778 Symbol_table::override_with_special<32>(Sized_symbol<32>*,
 779                                         const Sized_symbol<32>*);
 780 #endif
 781
 782 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
 783 template
 784 void
 785 Symbol_table::override_with_special<64>(Sized_symbol<64>*,
 786                                         const Sized_symbol<64>*);
 787 #endif
 788
 789 } // End namespace gold.