gold/resolve.cc

   1 // resolve.cc -- symbol resolution for gold
   2
   3 // Copyright 2006, 2007 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 // The resolve functions build a little code for each symbol.
  75 // Bit 0: 0 for global, 1 for weak.
  76 // Bit 1: 0 for regular object, 1 for shared object
  77 // Bits 2-3: 0 for normal, 1 for undefined, 2 for common
  78 // This gives us values from 0 to 11.
  79
  80 static const int global_or_weak_shift = 0;
  81 static const unsigned int global_flag = 0 << global_or_weak_shift;
  82 static const unsigned int weak_flag = 1 << global_or_weak_shift;
  83
  84 static const int regular_or_dynamic_shift = 1;
  85 static const unsigned int regular_flag = 0 << regular_or_dynamic_shift;
  86 static const unsigned int dynamic_flag = 1 << regular_or_dynamic_shift;
  87
  88 static const int def_undef_or_common_shift = 2;
  89 static const unsigned int def_flag = 0 << def_undef_or_common_shift;
  90 static const unsigned int undef_flag = 1 << def_undef_or_common_shift;
  91 static const unsigned int common_flag = 2 << def_undef_or_common_shift;
  92
  93 // Resolve a symbol.  This is called the second and subsequent times
  94 // we see a symbol.  TO is the pre-existing symbol.  SYM is the new
  95 // symbol, seen in OBJECT.  VERSION of the version of SYM.
  96
  97 template<int size, bool big_endian>
  98 void
  99 Symbol_table::resolve(Sized_symbol<size>* to,
 100                       const elfcpp::Sym<size, big_endian>& sym,
 101                       Object* object, const char* version)
 102 {
 103   if (object->target()->has_resolve())
 104     {
 105       Sized_target<size, big_endian>* sized_target;
 106       sized_target = object->sized_target
 107                      SELECT_SIZE_ENDIAN_NAME(size, big_endian) (
 108                          SELECT_SIZE_ENDIAN_ONLY(size, big_endian));
 109       sized_target->resolve(to, sym, object, version);
 110       return;
 111     }
 112
 113   if (!object->is_dynamic())
 114     {
 115       // Record that we've seen this symbol in a regular object.
 116       to->set_in_reg();
 117     }
 118   else
 119     {
 120       // Record that we've seen this symbol in a dynamic object.
 121       to->set_in_dyn();
 122     }
 123
 124   unsigned int frombits;
 125   switch (sym.get_st_bind())
 126     {
 127     case elfcpp::STB_GLOBAL:
 128       frombits = global_flag;
 129       break;
 130
 131     case elfcpp::STB_WEAK:
 132       frombits = weak_flag;
 133       break;
 134
 135     case elfcpp::STB_LOCAL:
 136       gold_error(_("%s: invalid STB_LOCAL symbol %s in external symbols"),
 137                  object->name().c_str(), to->name());
 138       frombits = global_flag;
 139       break;
 140
 141     default:
 142       gold_error(_("%s: unsupported symbol binding %d for symbol %s"),
 143                  object->name().c_str(),
 144                  static_cast<int>(sym.get_st_bind()), to->name());
 145       frombits = global_flag;
 146       break;
 147     }
 148
 149   if (!object->is_dynamic())
 150     frombits |= regular_flag;
 151   else
 152     frombits |= dynamic_flag;
 153
 154   switch (sym.get_st_shndx())
 155     {
 156     case elfcpp::SHN_UNDEF:
 157       frombits |= undef_flag;
 158       break;
 159
 160     case elfcpp::SHN_COMMON:
 161       frombits |= common_flag;
 162       break;
 163
 164     default:
 165       if (sym.get_st_type() == elfcpp::STT_COMMON)
 166         frombits |= common_flag;
 167       else
 168         frombits |= def_flag;
 169       break;
 170     }
 171
 172   bool adjust_common_sizes;
 173   if (Symbol_table::should_override(to, frombits, &adjust_common_sizes))
 174     {
 175       typename Sized_symbol<size>::Size_type tosize = to->symsize();
 176
 177       to->override(sym, object, version);
 178
 179       if (adjust_common_sizes && tosize > to->symsize())
 180         to->set_symsize(tosize);
 181     }
 182   else
 183     {
 184       if (adjust_common_sizes && sym.get_st_size() > to->symsize())
 185         to->set_symsize(sym.get_st_size());
 186     }
 187 }
 188
 189 // Handle the core of symbol resolution.  This is called with the
 190 // existing symbol, TO, and a bitflag describing the new symbol.  This
 191 // returns true if we should override the existing symbol with the new
 192 // one, and returns false otherwise.  It sets *ADJUST_COMMON_SIZES to
 193 // true if we should set the symbol size to the maximum of the TO and
 194 // FROM sizes.  It handles error conditions.
 195
 196 bool
 197 Symbol_table::should_override(const Symbol* to, unsigned int frombits,
 198                               bool* adjust_common_sizes)
 199 {
 200   *adjust_common_sizes = false;
 201
 202   unsigned int tobits;
 203   switch (to->binding())
 204     {
 205     case elfcpp::STB_GLOBAL:
 206       tobits = global_flag;
 207       break;
 208
 209     case elfcpp::STB_WEAK:
 210       tobits = weak_flag;
 211       break;
 212
 213     case elfcpp::STB_LOCAL:
 214       // We should only see externally visible symbols in the symbol
 215       // table.
 216       gold_unreachable();
 217
 218     default:
 219       // Any target which wants to handle STB_LOOS, etc., needs to
 220       // define a resolve method.
 221       gold_unreachable();
 222     }
 223
 224   if (to->source() == Symbol::FROM_OBJECT
 225       && to->object()->is_dynamic())
 226     tobits |= dynamic_flag;
 227   else
 228     tobits |= regular_flag;
 229
 230   switch (to->shndx())
 231     {
 232     case elfcpp::SHN_UNDEF:
 233       tobits |= undef_flag;
 234       break;
 235
 236     case elfcpp::SHN_COMMON:
 237       tobits |= common_flag;
 238       break;
 239
 240     default:
 241       if (to->type() == elfcpp::STT_COMMON)
 242         tobits |= common_flag;
 243       else
 244         tobits |= def_flag;
 245       break;
 246     }
 247
 248   // FIXME: Warn if either but not both of TO and SYM are STT_TLS.
 249
 250   // We use a giant switch table for symbol resolution.  This code is
 251   // unwieldy, but: 1) it is efficient; 2) we definitely handle all
 252   // cases; 3) it is easy to change the handling of a particular case.
 253   // The alternative would be a series of conditionals, but it is easy
 254   // to get the ordering wrong.  This could also be done as a table,
 255   // but that is no easier to understand than this large switch
 256   // statement.
 257
 258   // These are the values generated by the bit codes.
 259   enum
 260   {
 261     DEF =              global_flag | regular_flag | def_flag,
 262     WEAK_DEF =         weak_flag   | regular_flag | def_flag,
 263     DYN_DEF =          global_flag | dynamic_flag | def_flag,
 264     DYN_WEAK_DEF =     weak_flag   | dynamic_flag | def_flag,
 265     UNDEF =            global_flag | regular_flag | undef_flag,
 266     WEAK_UNDEF =       weak_flag   | regular_flag | undef_flag,
 267     DYN_UNDEF =        global_flag | dynamic_flag | undef_flag,
 268     DYN_WEAK_UNDEF =   weak_flag   | dynamic_flag | undef_flag,
 269     COMMON =           global_flag | regular_flag | common_flag,
 270     WEAK_COMMON =      weak_flag   | regular_flag | common_flag,
 271     DYN_COMMON =       global_flag | dynamic_flag | common_flag,
 272     DYN_WEAK_COMMON =  weak_flag   | dynamic_flag | common_flag
 273   };
 274
 275   switch (tobits * 16 + frombits)
 276     {
 277     case DEF * 16 + DEF:
 278       // Two definitions of the same symbol.
 279       // FIXME: Report locations.
 280       gold_error(_("multiple definition of %s\n"), to->name());
 281       return false;
 282
 283     case WEAK_DEF * 16 + DEF:
 284       // We've seen a weak definition, and now we see a strong
 285       // definition.  In the original SVR4 linker, this was treated as
 286       // a multiple definition error.  In the Solaris linker and the
 287       // GNU linker, a weak definition followed by a regular
 288       // definition causes the weak definition to be overridden.  We
 289       // are currently compatible with the GNU linker.  In the future
 290       // we should add a target specific option to change this.
 291       // FIXME.
 292       return true;
 293
 294     case DYN_DEF * 16 + DEF:
 295     case DYN_WEAK_DEF * 16 + DEF:
 296       // We've seen a definition in a dynamic object, and now we see a
 297       // definition in a regular object.  The definition in the
 298       // regular object overrides the definition in the dynamic
 299       // object.
 300       return true;
 301
 302     case UNDEF * 16 + DEF:
 303     case WEAK_UNDEF * 16 + DEF:
 304     case DYN_UNDEF * 16 + DEF:
 305     case DYN_WEAK_UNDEF * 16 + DEF:
 306       // We've seen an undefined reference, and now we see a
 307       // definition.  We use the definition.
 308       return true;
 309
 310     case COMMON * 16 + DEF:
 311     case WEAK_COMMON * 16 + DEF:
 312     case DYN_COMMON * 16 + DEF:
 313     case DYN_WEAK_COMMON * 16 + DEF:
 314       // We've seen a common symbol and now we see a definition.  The
 315       // definition overrides.  FIXME: We should optionally issue, version a
 316       // warning.
 317       return true;
 318
 319     case DEF * 16 + WEAK_DEF:
 320     case WEAK_DEF * 16 + WEAK_DEF:
 321       // We've seen a definition and now we see a weak definition.  We
 322       // ignore the new weak definition.
 323       return false;
 324
 325     case DYN_DEF * 16 + WEAK_DEF:
 326     case DYN_WEAK_DEF * 16 + WEAK_DEF:
 327       // We've seen a dynamic definition and now we see a regular weak
 328       // definition.  The regular weak definition overrides.
 329       return true;
 330
 331     case UNDEF * 16 + WEAK_DEF:
 332     case WEAK_UNDEF * 16 + WEAK_DEF:
 333     case DYN_UNDEF * 16 + WEAK_DEF:
 334     case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
 335       // A weak definition of a currently undefined symbol.
 336       return true;
 337
 338     case COMMON * 16 + WEAK_DEF:
 339     case WEAK_COMMON * 16 + WEAK_DEF:
 340       // A weak definition does not override a common definition.
 341       return false;
 342
 343     case DYN_COMMON * 16 + WEAK_DEF:
 344     case DYN_WEAK_COMMON * 16 + WEAK_DEF:
 345       // A weak definition does override a definition in a dynamic
 346       // object.  FIXME: We should optionally issue a warning.
 347       return true;
 348
 349     case DEF * 16 + DYN_DEF:
 350     case WEAK_DEF * 16 + DYN_DEF:
 351     case DYN_DEF * 16 + DYN_DEF:
 352     case DYN_WEAK_DEF * 16 + DYN_DEF:
 353       // Ignore a dynamic definition if we already have a definition.
 354       return false;
 355
 356     case UNDEF * 16 + DYN_DEF:
 357     case WEAK_UNDEF * 16 + DYN_DEF:
 358     case DYN_UNDEF * 16 + DYN_DEF:
 359     case DYN_WEAK_UNDEF * 16 + DYN_DEF:
 360       // Use a dynamic definition if we have a reference.
 361       return true;
 362
 363     case COMMON * 16 + DYN_DEF:
 364     case WEAK_COMMON * 16 + DYN_DEF:
 365     case DYN_COMMON * 16 + DYN_DEF:
 366     case DYN_WEAK_COMMON * 16 + DYN_DEF:
 367       // Ignore a dynamic definition if we already have a common
 368       // definition.
 369       return false;
 370
 371     case DEF * 16 + DYN_WEAK_DEF:
 372     case WEAK_DEF * 16 + DYN_WEAK_DEF:
 373     case DYN_DEF * 16 + DYN_WEAK_DEF:
 374     case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
 375       // Ignore a weak dynamic definition if we already have a
 376       // definition.
 377       return false;
 378
 379     case UNDEF * 16 + DYN_WEAK_DEF:
 380     case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 381     case DYN_UNDEF * 16 + DYN_WEAK_DEF:
 382     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 383       // Use a weak dynamic definition if we have a reference.
 384       return true;
 385
 386     case COMMON * 16 + DYN_WEAK_DEF:
 387     case WEAK_COMMON * 16 + DYN_WEAK_DEF:
 388     case DYN_COMMON * 16 + DYN_WEAK_DEF:
 389     case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
 390       // Ignore a weak dynamic definition if we already have a common
 391       // definition.
 392       return false;
 393
 394     case DEF * 16 + UNDEF:
 395     case WEAK_DEF * 16 + UNDEF:
 396     case DYN_DEF * 16 + UNDEF:
 397     case DYN_WEAK_DEF * 16 + UNDEF:
 398     case UNDEF * 16 + UNDEF:
 399       // A new undefined reference tells us nothing.
 400       return false;
 401
 402     case WEAK_UNDEF * 16 + UNDEF:
 403     case DYN_UNDEF * 16 + UNDEF:
 404     case DYN_WEAK_UNDEF * 16 + UNDEF:
 405       // A strong undef overrides a dynamic or weak undef.
 406       return true;
 407
 408     case COMMON * 16 + UNDEF:
 409     case WEAK_COMMON * 16 + UNDEF:
 410     case DYN_COMMON * 16 + UNDEF:
 411     case DYN_WEAK_COMMON * 16 + UNDEF:
 412       // A new undefined reference tells us nothing.
 413       return false;
 414
 415     case DEF * 16 + WEAK_UNDEF:
 416     case WEAK_DEF * 16 + WEAK_UNDEF:
 417     case DYN_DEF * 16 + WEAK_UNDEF:
 418     case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
 419     case UNDEF * 16 + WEAK_UNDEF:
 420     case WEAK_UNDEF * 16 + WEAK_UNDEF:
 421     case DYN_UNDEF * 16 + WEAK_UNDEF:
 422     case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
 423     case COMMON * 16 + WEAK_UNDEF:
 424     case WEAK_COMMON * 16 + WEAK_UNDEF:
 425     case DYN_COMMON * 16 + WEAK_UNDEF:
 426     case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
 427       // A new weak undefined reference tells us nothing.
 428       return false;
 429
 430     case DEF * 16 + DYN_UNDEF:
 431     case WEAK_DEF * 16 + DYN_UNDEF:
 432     case DYN_DEF * 16 + DYN_UNDEF:
 433     case DYN_WEAK_DEF * 16 + DYN_UNDEF:
 434     case UNDEF * 16 + DYN_UNDEF:
 435     case WEAK_UNDEF * 16 + DYN_UNDEF:
 436     case DYN_UNDEF * 16 + DYN_UNDEF:
 437     case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
 438     case COMMON * 16 + DYN_UNDEF:
 439     case WEAK_COMMON * 16 + DYN_UNDEF:
 440     case DYN_COMMON * 16 + DYN_UNDEF:
 441     case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
 442       // A new dynamic undefined reference tells us nothing.
 443       return false;
 444
 445     case DEF * 16 + DYN_WEAK_UNDEF:
 446     case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 447     case DYN_DEF * 16 + DYN_WEAK_UNDEF:
 448     case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 449     case UNDEF * 16 + DYN_WEAK_UNDEF:
 450     case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 451     case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
 452     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 453     case COMMON * 16 + DYN_WEAK_UNDEF:
 454     case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 455     case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
 456     case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 457       // A new weak dynamic undefined reference tells us nothing.
 458       return false;
 459
 460     case DEF * 16 + COMMON:
 461       // A common symbol does not override a definition.
 462       return false;
 463
 464     case WEAK_DEF * 16 + COMMON:
 465     case DYN_DEF * 16 + COMMON:
 466     case DYN_WEAK_DEF * 16 + COMMON:
 467       // A common symbol does override a weak definition or a dynamic
 468       // definition.
 469       return true;
 470
 471     case UNDEF * 16 + COMMON:
 472     case WEAK_UNDEF * 16 + COMMON:
 473     case DYN_UNDEF * 16 + COMMON:
 474     case DYN_WEAK_UNDEF * 16 + COMMON:
 475       // A common symbol is a definition for a reference.
 476       return true;
 477
 478     case COMMON * 16 + COMMON:
 479       // Set the size to the maximum.
 480       *adjust_common_sizes = true;
 481       return false;
 482
 483     case WEAK_COMMON * 16 + COMMON:
 484       // I'm not sure just what a weak common symbol means, but
 485       // presumably it can be overridden by a regular common symbol.
 486       return true;
 487
 488     case DYN_COMMON * 16 + COMMON:
 489     case DYN_WEAK_COMMON * 16 + COMMON:
 490       // Use the real common symbol, but adjust the size if necessary.
 491       *adjust_common_sizes = true;
 492       return true;
 493
 494     case DEF * 16 + WEAK_COMMON:
 495     case WEAK_DEF * 16 + WEAK_COMMON:
 496     case DYN_DEF * 16 + WEAK_COMMON:
 497     case DYN_WEAK_DEF * 16 + WEAK_COMMON:
 498       // Whatever a weak common symbol is, it won't override a
 499       // definition.
 500       return false;
 501
 502     case UNDEF * 16 + WEAK_COMMON:
 503     case WEAK_UNDEF * 16 + WEAK_COMMON:
 504     case DYN_UNDEF * 16 + WEAK_COMMON:
 505     case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
 506       // A weak common symbol is better than an undefined symbol.
 507       return true;
 508
 509     case COMMON * 16 + WEAK_COMMON:
 510     case WEAK_COMMON * 16 + WEAK_COMMON:
 511     case DYN_COMMON * 16 + WEAK_COMMON:
 512     case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
 513       // Ignore a weak common symbol in the presence of a real common
 514       // symbol.
 515       return false;
 516
 517     case DEF * 16 + DYN_COMMON:
 518     case WEAK_DEF * 16 + DYN_COMMON:
 519     case DYN_DEF * 16 + DYN_COMMON:
 520     case DYN_WEAK_DEF * 16 + DYN_COMMON:
 521       // Ignore a dynamic common symbol in the presence of a
 522       // definition.
 523       return false;
 524
 525     case UNDEF * 16 + DYN_COMMON:
 526     case WEAK_UNDEF * 16 + DYN_COMMON:
 527     case DYN_UNDEF * 16 + DYN_COMMON:
 528     case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
 529       // A dynamic common symbol is a definition of sorts.
 530       return true;
 531
 532     case COMMON * 16 + DYN_COMMON:
 533     case WEAK_COMMON * 16 + DYN_COMMON:
 534     case DYN_COMMON * 16 + DYN_COMMON:
 535     case DYN_WEAK_COMMON * 16 + DYN_COMMON:
 536       // Set the size to the maximum.
 537       *adjust_common_sizes = true;
 538       return false;
 539
 540     case DEF * 16 + DYN_WEAK_COMMON:
 541     case WEAK_DEF * 16 + DYN_WEAK_COMMON:
 542     case DYN_DEF * 16 + DYN_WEAK_COMMON:
 543     case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
 544       // A common symbol is ignored in the face of a definition.
 545       return false;
 546
 547     case UNDEF * 16 + DYN_WEAK_COMMON:
 548     case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 549     case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
 550     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 551       // I guess a weak common symbol is better than a definition.
 552       return true;
 553
 554     case COMMON * 16 + DYN_WEAK_COMMON:
 555     case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 556     case DYN_COMMON * 16 + DYN_WEAK_COMMON:
 557     case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 558       // Set the size to the maximum.
 559       *adjust_common_sizes = true;
 560       return false;
 561
 562     default:
 563       gold_unreachable();
 564     }
 565 }
 566
 567 // A special case of should_override which is only called for a strong
 568 // defined symbol from a regular object file.  This is used when
 569 // defining special symbols.
 570
 571 bool
 572 Symbol_table::should_override_with_special(const Symbol* to)
 573 {
 574   bool adjust_common_sizes;
 575   unsigned int frombits = global_flag | regular_flag | def_flag;
 576   bool ret = Symbol_table::should_override(to, frombits, &adjust_common_sizes);
 577   gold_assert(!adjust_common_sizes);
 578   return ret;
 579 }
 580
 581 // Override symbol base with a special symbol.
 582
 583 void
 584 Symbol::override_base_with_special(const Symbol* from)
 585 {
 586   this->source_ = from->source_;
 587   switch (from->source_)
 588     {
 589     case FROM_OBJECT:
 590       this->u_.from_object = from->u_.from_object;
 591       break;
 592     case IN_OUTPUT_DATA:
 593       this->u_.in_output_data = from->u_.in_output_data;
 594       break;
 595     case IN_OUTPUT_SEGMENT:
 596       this->u_.in_output_segment = from->u_.in_output_segment;
 597       break;
 598     case CONSTANT:
 599       break;
 600     default:
 601       gold_unreachable();
 602       break;
 603     }
 604
 605   if (from->version_ != NULL && this->version_ != from->version_)
 606     {
 607       gold_assert(this->version_ == NULL);
 608       this->version_ = from->version_;
 609     }
 610
 611   this->type_ = from->type_;
 612   this->binding_ = from->binding_;
 613   this->visibility_ = from->visibility_;
 614   this->nonvis_ = from->nonvis_;
 615
 616   // Special symbols are always considered to be regular symbols.
 617   this->in_reg_ = true;
 618 }
 619
 620 // Override a symbol with a special symbol.
 621
 622 template<int size>
 623 void
 624 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from)
 625 {
 626   this->override_base_with_special(from);
 627   this->value_ = from->value_;
 628   this->symsize_ = from->symsize_;
 629 }
 630
 631 // Instantiate the templates we need.  We could use the configure
 632 // script to restrict this to only the ones needed for implemented
 633 // targets.
 634
 635 #ifdef HAVE_TARGET_32_LITTLE
 636 template
 637 void
 638 Symbol_table::resolve<32, false>(
 639     Sized_symbol<32>* to,
 640     const elfcpp::Sym<32, false>& sym,
 641     Object* object,
 642     const char* version);
 643 #endif
 644
 645 #ifdef HAVE_TARGET_32_BIG
 646 template
 647 void
 648 Symbol_table::resolve<32, true>(
 649     Sized_symbol<32>* to,
 650     const elfcpp::Sym<32, true>& sym,
 651     Object* object,
 652     const char* version);
 653 #endif
 654
 655 #ifdef HAVE_TARGET_64_LITTLE
 656 template
 657 void
 658 Symbol_table::resolve<64, false>(
 659     Sized_symbol<64>* to,
 660     const elfcpp::Sym<64, false>& sym,
 661     Object* object,
 662     const char* version);
 663 #endif
 664
 665 #ifdef HAVE_TARGET_64_BIG
 666 template
 667 void
 668 Symbol_table::resolve<64, true>(
 669     Sized_symbol<64>* to,
 670     const elfcpp::Sym<64, true>& sym,
 671     Object* object,
 672     const char* version);
 673 #endif
 674
 675 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
 676 template
 677 void
 678 Sized_symbol<32>::override_with_special(const Sized_symbol<32>*);
 679 #endif
 680
 681 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
 682 template
 683 void
 684 Sized_symbol<64>::override_with_special(const Sized_symbol<64>*);
 685 #endif
 686
 687 } // End namespace gold.