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       fprintf(stderr,
 137               _("%s: %s: invalid STB_LOCAL symbol %s in external symbols\n"),
 138               program_name, object->name().c_str(), to->name());
 139       gold_exit(false);
 140
 141     default:
 142       fprintf(stderr,
 143               _("%s: %s: unsupported symbol binding %d for symbol %s\n"),
 144               program_name, object->name().c_str(),
 145               static_cast<int>(sym.get_st_bind()), to->name());
 146       gold_exit(false);
 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       fprintf(stderr, _("%s: multiple definition of %s\n"),
 280               program_name, to->name());
 281       // FIXME: Report locations.  Record that we have seen an error.
 282       return false;
 283
 284     case WEAK_DEF * 16 + DEF:
 285       // We've seen a weak definition, and now we see a strong
 286       // definition.  In the original SVR4 linker, this was treated as
 287       // a multiple definition error.  In the Solaris linker and the
 288       // GNU linker, a weak definition followed by a regular
 289       // definition causes the weak definition to be overridden.  We
 290       // are currently compatible with the GNU linker.  In the future
 291       // we should add a target specific option to change this.
 292       // FIXME.
 293       return true;
 294
 295     case DYN_DEF * 16 + DEF:
 296     case DYN_WEAK_DEF * 16 + DEF:
 297       // We've seen a definition in a dynamic object, and now we see a
 298       // definition in a regular object.  The definition in the
 299       // regular object overrides the definition in the dynamic
 300       // object.
 301       return true;
 302
 303     case UNDEF * 16 + DEF:
 304     case WEAK_UNDEF * 16 + DEF:
 305     case DYN_UNDEF * 16 + DEF:
 306     case DYN_WEAK_UNDEF * 16 + DEF:
 307       // We've seen an undefined reference, and now we see a
 308       // definition.  We use the definition.
 309       return true;
 310
 311     case COMMON * 16 + DEF:
 312     case WEAK_COMMON * 16 + DEF:
 313     case DYN_COMMON * 16 + DEF:
 314     case DYN_WEAK_COMMON * 16 + DEF:
 315       // We've seen a common symbol and now we see a definition.  The
 316       // definition overrides.  FIXME: We should optionally issue, version a
 317       // warning.
 318       return true;
 319
 320     case DEF * 16 + WEAK_DEF:
 321     case WEAK_DEF * 16 + WEAK_DEF:
 322       // We've seen a definition and now we see a weak definition.  We
 323       // ignore the new weak definition.
 324       return false;
 325
 326     case DYN_DEF * 16 + WEAK_DEF:
 327     case DYN_WEAK_DEF * 16 + WEAK_DEF:
 328       // We've seen a dynamic definition and now we see a regular weak
 329       // definition.  The regular weak definition overrides.
 330       return true;
 331
 332     case UNDEF * 16 + WEAK_DEF:
 333     case WEAK_UNDEF * 16 + WEAK_DEF:
 334     case DYN_UNDEF * 16 + WEAK_DEF:
 335     case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
 336       // A weak definition of a currently undefined symbol.
 337       return true;
 338
 339     case COMMON * 16 + WEAK_DEF:
 340     case WEAK_COMMON * 16 + WEAK_DEF:
 341       // A weak definition does not override a common definition.
 342       return false;
 343
 344     case DYN_COMMON * 16 + WEAK_DEF:
 345     case DYN_WEAK_COMMON * 16 + WEAK_DEF:
 346       // A weak definition does override a definition in a dynamic
 347       // object.  FIXME: We should optionally issue a warning.
 348       return true;
 349
 350     case DEF * 16 + DYN_DEF:
 351     case WEAK_DEF * 16 + DYN_DEF:
 352     case DYN_DEF * 16 + DYN_DEF:
 353     case DYN_WEAK_DEF * 16 + DYN_DEF:
 354       // Ignore a dynamic definition if we already have a definition.
 355       return false;
 356
 357     case UNDEF * 16 + DYN_DEF:
 358     case WEAK_UNDEF * 16 + DYN_DEF:
 359     case DYN_UNDEF * 16 + DYN_DEF:
 360     case DYN_WEAK_UNDEF * 16 + DYN_DEF:
 361       // Use a dynamic definition if we have a reference.
 362       return true;
 363
 364     case COMMON * 16 + DYN_DEF:
 365     case WEAK_COMMON * 16 + DYN_DEF:
 366     case DYN_COMMON * 16 + DYN_DEF:
 367     case DYN_WEAK_COMMON * 16 + DYN_DEF:
 368       // Ignore a dynamic definition if we already have a common
 369       // definition.
 370       return false;
 371
 372     case DEF * 16 + DYN_WEAK_DEF:
 373     case WEAK_DEF * 16 + DYN_WEAK_DEF:
 374     case DYN_DEF * 16 + DYN_WEAK_DEF:
 375     case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
 376       // Ignore a weak dynamic definition if we already have a
 377       // definition.
 378       return false;
 379
 380     case UNDEF * 16 + DYN_WEAK_DEF:
 381     case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 382     case DYN_UNDEF * 16 + DYN_WEAK_DEF:
 383     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 384       // Use a weak dynamic definition if we have a reference.
 385       return true;
 386
 387     case COMMON * 16 + DYN_WEAK_DEF:
 388     case WEAK_COMMON * 16 + DYN_WEAK_DEF:
 389     case DYN_COMMON * 16 + DYN_WEAK_DEF:
 390     case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
 391       // Ignore a weak dynamic definition if we already have a common
 392       // definition.
 393       return false;
 394
 395     case DEF * 16 + UNDEF:
 396     case WEAK_DEF * 16 + UNDEF:
 397     case DYN_DEF * 16 + UNDEF:
 398     case DYN_WEAK_DEF * 16 + UNDEF:
 399     case UNDEF * 16 + UNDEF:
 400       // A new undefined reference tells us nothing.
 401       return false;
 402
 403     case WEAK_UNDEF * 16 + UNDEF:
 404     case DYN_UNDEF * 16 + UNDEF:
 405     case DYN_WEAK_UNDEF * 16 + UNDEF:
 406       // A strong undef overrides a dynamic or weak undef.
 407       return true;
 408
 409     case COMMON * 16 + UNDEF:
 410     case WEAK_COMMON * 16 + UNDEF:
 411     case DYN_COMMON * 16 + UNDEF:
 412     case DYN_WEAK_COMMON * 16 + UNDEF:
 413       // A new undefined reference tells us nothing.
 414       return false;
 415
 416     case DEF * 16 + WEAK_UNDEF:
 417     case WEAK_DEF * 16 + WEAK_UNDEF:
 418     case DYN_DEF * 16 + WEAK_UNDEF:
 419     case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
 420     case UNDEF * 16 + WEAK_UNDEF:
 421     case WEAK_UNDEF * 16 + WEAK_UNDEF:
 422     case DYN_UNDEF * 16 + WEAK_UNDEF:
 423     case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
 424     case COMMON * 16 + WEAK_UNDEF:
 425     case WEAK_COMMON * 16 + WEAK_UNDEF:
 426     case DYN_COMMON * 16 + WEAK_UNDEF:
 427     case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
 428       // A new weak undefined reference tells us nothing.
 429       return false;
 430
 431     case DEF * 16 + DYN_UNDEF:
 432     case WEAK_DEF * 16 + DYN_UNDEF:
 433     case DYN_DEF * 16 + DYN_UNDEF:
 434     case DYN_WEAK_DEF * 16 + DYN_UNDEF:
 435     case UNDEF * 16 + DYN_UNDEF:
 436     case WEAK_UNDEF * 16 + DYN_UNDEF:
 437     case DYN_UNDEF * 16 + DYN_UNDEF:
 438     case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
 439     case COMMON * 16 + DYN_UNDEF:
 440     case WEAK_COMMON * 16 + DYN_UNDEF:
 441     case DYN_COMMON * 16 + DYN_UNDEF:
 442     case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
 443       // A new dynamic undefined reference tells us nothing.
 444       return false;
 445
 446     case DEF * 16 + DYN_WEAK_UNDEF:
 447     case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 448     case DYN_DEF * 16 + DYN_WEAK_UNDEF:
 449     case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 450     case UNDEF * 16 + DYN_WEAK_UNDEF:
 451     case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 452     case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
 453     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 454     case COMMON * 16 + DYN_WEAK_UNDEF:
 455     case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 456     case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
 457     case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 458       // A new weak dynamic undefined reference tells us nothing.
 459       return false;
 460
 461     case DEF * 16 + COMMON:
 462       // A common symbol does not override a definition.
 463       return false;
 464
 465     case WEAK_DEF * 16 + COMMON:
 466     case DYN_DEF * 16 + COMMON:
 467     case DYN_WEAK_DEF * 16 + COMMON:
 468       // A common symbol does override a weak definition or a dynamic
 469       // definition.
 470       return true;
 471
 472     case UNDEF * 16 + COMMON:
 473     case WEAK_UNDEF * 16 + COMMON:
 474     case DYN_UNDEF * 16 + COMMON:
 475     case DYN_WEAK_UNDEF * 16 + COMMON:
 476       // A common symbol is a definition for a reference.
 477       return true;
 478
 479     case COMMON * 16 + COMMON:
 480       // Set the size to the maximum.
 481       *adjust_common_sizes = true;
 482       return false;
 483
 484     case WEAK_COMMON * 16 + COMMON:
 485       // I'm not sure just what a weak common symbol means, but
 486       // presumably it can be overridden by a regular common symbol.
 487       return true;
 488
 489     case DYN_COMMON * 16 + COMMON:
 490     case DYN_WEAK_COMMON * 16 + COMMON:
 491       // Use the real common symbol, but adjust the size if necessary.
 492       *adjust_common_sizes = true;
 493       return true;
 494
 495     case DEF * 16 + WEAK_COMMON:
 496     case WEAK_DEF * 16 + WEAK_COMMON:
 497     case DYN_DEF * 16 + WEAK_COMMON:
 498     case DYN_WEAK_DEF * 16 + WEAK_COMMON:
 499       // Whatever a weak common symbol is, it won't override a
 500       // definition.
 501       return false;
 502
 503     case UNDEF * 16 + WEAK_COMMON:
 504     case WEAK_UNDEF * 16 + WEAK_COMMON:
 505     case DYN_UNDEF * 16 + WEAK_COMMON:
 506     case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
 507       // A weak common symbol is better than an undefined symbol.
 508       return true;
 509
 510     case COMMON * 16 + WEAK_COMMON:
 511     case WEAK_COMMON * 16 + WEAK_COMMON:
 512     case DYN_COMMON * 16 + WEAK_COMMON:
 513     case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
 514       // Ignore a weak common symbol in the presence of a real common
 515       // symbol.
 516       return false;
 517
 518     case DEF * 16 + DYN_COMMON:
 519     case WEAK_DEF * 16 + DYN_COMMON:
 520     case DYN_DEF * 16 + DYN_COMMON:
 521     case DYN_WEAK_DEF * 16 + DYN_COMMON:
 522       // Ignore a dynamic common symbol in the presence of a
 523       // definition.
 524       return false;
 525
 526     case UNDEF * 16 + DYN_COMMON:
 527     case WEAK_UNDEF * 16 + DYN_COMMON:
 528     case DYN_UNDEF * 16 + DYN_COMMON:
 529     case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
 530       // A dynamic common symbol is a definition of sorts.
 531       return true;
 532
 533     case COMMON * 16 + DYN_COMMON:
 534     case WEAK_COMMON * 16 + DYN_COMMON:
 535     case DYN_COMMON * 16 + DYN_COMMON:
 536     case DYN_WEAK_COMMON * 16 + DYN_COMMON:
 537       // Set the size to the maximum.
 538       *adjust_common_sizes = true;
 539       return false;
 540
 541     case DEF * 16 + DYN_WEAK_COMMON:
 542     case WEAK_DEF * 16 + DYN_WEAK_COMMON:
 543     case DYN_DEF * 16 + DYN_WEAK_COMMON:
 544     case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
 545       // A common symbol is ignored in the face of a definition.
 546       return false;
 547
 548     case UNDEF * 16 + DYN_WEAK_COMMON:
 549     case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 550     case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
 551     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 552       // I guess a weak common symbol is better than a definition.
 553       return true;
 554
 555     case COMMON * 16 + DYN_WEAK_COMMON:
 556     case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 557     case DYN_COMMON * 16 + DYN_WEAK_COMMON:
 558     case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 559       // Set the size to the maximum.
 560       *adjust_common_sizes = true;
 561       return false;
 562
 563     default:
 564       gold_unreachable();
 565     }
 566 }
 567
 568 // A special case of should_override which is only called for a strong
 569 // defined symbol from a regular object file.  This is used when
 570 // defining special symbols.
 571
 572 bool
 573 Symbol_table::should_override_with_special(const Symbol* to)
 574 {
 575   bool adjust_common_sizes;
 576   unsigned int frombits = global_flag | regular_flag | def_flag;
 577   bool ret = Symbol_table::should_override(to, frombits, &adjust_common_sizes);
 578   gold_assert(!adjust_common_sizes);
 579   return ret;
 580 }
 581
 582 // Override symbol base with a special symbol.
 583
 584 void
 585 Symbol::override_base_with_special(const Symbol* from)
 586 {
 587   this->source_ = from->source_;
 588   switch (from->source_)
 589     {
 590     case FROM_OBJECT:
 591       this->u_.from_object = from->u_.from_object;
 592       break;
 593     case IN_OUTPUT_DATA:
 594       this->u_.in_output_data = from->u_.in_output_data;
 595       break;
 596     case IN_OUTPUT_SEGMENT:
 597       this->u_.in_output_segment = from->u_.in_output_segment;
 598       break;
 599     case CONSTANT:
 600       break;
 601     default:
 602       gold_unreachable();
 603       break;
 604     }
 605
 606   if (from->version_ != NULL && this->version_ != from->version_)
 607     {
 608       gold_assert(this->version_ == NULL);
 609       this->version_ = from->version_;
 610     }
 611
 612   this->type_ = from->type_;
 613   this->binding_ = from->binding_;
 614   this->visibility_ = from->visibility_;
 615   this->nonvis_ = from->nonvis_;
 616
 617   // Special symbols are always considered to be regular symbols.
 618   this->in_reg_ = true;
 619 }
 620
 621 // Override a symbol with a special symbol.
 622
 623 template<int size>
 624 void
 625 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from)
 626 {
 627   this->override_base_with_special(from);
 628   this->value_ = from->value_;
 629   this->symsize_ = from->symsize_;
 630 }
 631
 632 // Instantiate the templates we need.  We could use the configure
 633 // script to restrict this to only the ones needed for implemented
 634 // targets.
 635
 636 #ifdef HAVE_TARGET_32_LITTLE
 637 template
 638 void
 639 Symbol_table::resolve<32, false>(
 640     Sized_symbol<32>* to,
 641     const elfcpp::Sym<32, false>& sym,
 642     Object* object,
 643     const char* version);
 644 #endif
 645
 646 #ifdef HAVE_TARGET_32_BIG
 647 template
 648 void
 649 Symbol_table::resolve<32, true>(
 650     Sized_symbol<32>* to,
 651     const elfcpp::Sym<32, true>& sym,
 652     Object* object,
 653     const char* version);
 654 #endif
 655
 656 #ifdef HAVE_TARGET_64_LITTLE
 657 template
 658 void
 659 Symbol_table::resolve<64, false>(
 660     Sized_symbol<64>* to,
 661     const elfcpp::Sym<64, false>& sym,
 662     Object* object,
 663     const char* version);
 664 #endif
 665
 666 #ifdef HAVE_TARGET_64_BIG
 667 template
 668 void
 669 Symbol_table::resolve<64, true>(
 670     Sized_symbol<64>* to,
 671     const elfcpp::Sym<64, true>& sym,
 672     Object* object,
 673     const char* version);
 674 #endif
 675
 676 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
 677 template
 678 void
 679 Sized_symbol<32>::override_with_special(const Sized_symbol<32>*);
 680 #endif
 681
 682 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
 683 template
 684 void
 685 Sized_symbol<64>::override_with_special(const Sized_symbol<64>*);
 686 #endif
 687
 688 } // End namespace gold.