gold/resolve.cc

   1 // resolve.cc -- symbol resolution for gold
   2
   3 // Copyright 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
   4 // Written by Ian Lance Taylor <iant@google.com>.
   5
   6 // This file is part of gold.
   7
   8 // This program is free software; you can redistribute it and/or modify
   9 // it under the terms of the GNU General Public License as published by
  10 // the Free Software Foundation; either version 3 of the License, or
  11 // (at your option) any later version.
  12
  13 // This program is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 // GNU General Public License for more details.
  17
  18 // You should have received a copy of the GNU General Public License
  19 // along with this program; if not, write to the Free Software
  20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  21 // MA 02110-1301, USA.
  22
  23 #include "gold.h"
  24
  25 #include "elfcpp.h"
  26 #include "target.h"
  27 #include "object.h"
  28 #include "symtab.h"
  29 #include "plugin.h"
  30
  31 namespace gold
  32 {
  33
  34 // Symbol methods used in this file.
  35
  36 // This symbol is being overridden by another symbol whose version is
  37 // VERSION.  Update the VERSION_ field accordingly.
  38
  39 inline void
  40 Symbol::override_version(const char* version)
  41 {
  42   if (version == NULL)
  43     {
  44       // This is the case where this symbol is NAME/VERSION, and the
  45       // version was not marked as hidden.  That makes it the default
  46       // version, so we create NAME/NULL.  Later we see another symbol
  47       // NAME/NULL, and that symbol is overriding this one.  In this
  48       // case, since NAME/VERSION is the default, we make NAME/NULL
  49       // override NAME/VERSION as well.  They are already the same
  50       // Symbol structure.  Setting the VERSION_ field to NULL ensures
  51       // that it will be output with the correct, empty, version.
  52       this->version_ = version;
  53     }
  54   else
  55     {
  56       // This is the case where this symbol is NAME/VERSION_ONE, and
  57       // now we see NAME/VERSION_TWO, and NAME/VERSION_TWO is
  58       // overriding NAME.  If VERSION_ONE and VERSION_TWO are
  59       // different, then this can only happen when VERSION_ONE is NULL
  60       // and VERSION_TWO is not hidden.
  61       gold_assert(this->version_ == version || this->version_ == NULL);
  62       this->version_ = version;
  63     }
  64 }
  65
  66 // This symbol is being overidden by another symbol whose visibility
  67 // is VISIBILITY.  Updated the VISIBILITY_ field accordingly.
  68
  69 inline void
  70 Symbol::override_visibility(elfcpp::STV visibility)
  71 {
  72   // The rule for combining visibility is that we always choose the
  73   // most constrained visibility.  In order of increasing constraint,
  74   // visibility goes PROTECTED, HIDDEN, INTERNAL.  This is the reverse
  75   // of the numeric values, so the effect is that we always want the
  76   // smallest non-zero value.
  77   if (visibility != elfcpp::STV_DEFAULT)
  78     {
  79       if (this->visibility_ == elfcpp::STV_DEFAULT)
  80         this->visibility_ = visibility;
  81       else if (this->visibility_ > visibility)
  82         this->visibility_ = visibility;
  83     }
  84 }
  85
  86 // Override the fields in Symbol.
  87
  88 template<int size, bool big_endian>
  89 void
  90 Symbol::override_base(const elfcpp::Sym<size, big_endian>& sym,
  91                       unsigned int st_shndx, bool is_ordinary,
  92                       Object* object, const char* version)
  93 {
  94   gold_assert(this->source_ == FROM_OBJECT);
  95   this->u_.from_object.object = object;
  96   this->override_version(version);
  97   this->u_.from_object.shndx = st_shndx;
  98   this->is_ordinary_shndx_ = is_ordinary;
  99   this->type_ = sym.get_st_type();
 100   this->binding_ = sym.get_st_bind();
 101   this->override_visibility(sym.get_st_visibility());
 102   this->nonvis_ = sym.get_st_nonvis();
 103   if (object->is_dynamic())
 104     this->in_dyn_ = true;
 105   else
 106     this->in_reg_ = true;
 107 }
 108
 109 // Override the fields in Sized_symbol.
 110
 111 template<int size>
 112 template<bool big_endian>
 113 void
 114 Sized_symbol<size>::override(const elfcpp::Sym<size, big_endian>& sym,
 115                              unsigned st_shndx, bool is_ordinary,
 116                              Object* object, const char* version)
 117 {
 118   this->override_base(sym, st_shndx, is_ordinary, object, version);
 119   this->value_ = sym.get_st_value();
 120   this->symsize_ = sym.get_st_size();
 121 }
 122
 123 // Override TOSYM with symbol FROMSYM, defined in OBJECT, with version
 124 // VERSION.  This handles all aliases of TOSYM.
 125
 126 template<int size, bool big_endian>
 127 void
 128 Symbol_table::override(Sized_symbol<size>* tosym,
 129                        const elfcpp::Sym<size, big_endian>& fromsym,
 130                        unsigned int st_shndx, bool is_ordinary,
 131                        Object* object, const char* version)
 132 {
 133   tosym->override(fromsym, st_shndx, is_ordinary, object, version);
 134   if (tosym->has_alias())
 135     {
 136       Symbol* sym = this->weak_aliases_[tosym];
 137       gold_assert(sym != NULL);
 138       Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
 139       do
 140         {
 141           ssym->override(fromsym, st_shndx, is_ordinary, object, version);
 142           sym = this->weak_aliases_[ssym];
 143           gold_assert(sym != NULL);
 144           ssym = this->get_sized_symbol<size>(sym);
 145         }
 146       while (ssym != tosym);
 147     }
 148 }
 149
 150 // The resolve functions build a little code for each symbol.
 151 // Bit 0: 0 for global, 1 for weak.
 152 // Bit 1: 0 for regular object, 1 for shared object
 153 // Bits 2-3: 0 for normal, 1 for undefined, 2 for common
 154 // This gives us values from 0 to 11.
 155
 156 static const int global_or_weak_shift = 0;
 157 static const unsigned int global_flag = 0 << global_or_weak_shift;
 158 static const unsigned int weak_flag = 1 << global_or_weak_shift;
 159
 160 static const int regular_or_dynamic_shift = 1;
 161 static const unsigned int regular_flag = 0 << regular_or_dynamic_shift;
 162 static const unsigned int dynamic_flag = 1 << regular_or_dynamic_shift;
 163
 164 static const int def_undef_or_common_shift = 2;
 165 static const unsigned int def_flag = 0 << def_undef_or_common_shift;
 166 static const unsigned int undef_flag = 1 << def_undef_or_common_shift;
 167 static const unsigned int common_flag = 2 << def_undef_or_common_shift;
 168
 169 // This convenience function combines all the flags based on facts
 170 // about the symbol.
 171
 172 static unsigned int
 173 symbol_to_bits(elfcpp::STB binding, bool is_dynamic,
 174                unsigned int shndx, bool is_ordinary, elfcpp::STT type)
 175 {
 176   unsigned int bits;
 177
 178   switch (binding)
 179     {
 180     case elfcpp::STB_GLOBAL:
 181     case elfcpp::STB_GNU_UNIQUE:
 182       bits = global_flag;
 183       break;
 184
 185     case elfcpp::STB_WEAK:
 186       bits = weak_flag;
 187       break;
 188
 189     case elfcpp::STB_LOCAL:
 190       // We should only see externally visible symbols in the symbol
 191       // table.
 192       gold_error(_("invalid STB_LOCAL symbol in external symbols"));
 193       bits = global_flag;
 194
 195     default:
 196       // Any target which wants to handle STB_LOOS, etc., needs to
 197       // define a resolve method.
 198       gold_error(_("unsupported symbol binding"));
 199       bits = global_flag;
 200     }
 201
 202   if (is_dynamic)
 203     bits |= dynamic_flag;
 204   else
 205     bits |= regular_flag;
 206
 207   switch (shndx)
 208     {
 209     case elfcpp::SHN_UNDEF:
 210       bits |= undef_flag;
 211       break;
 212
 213     case elfcpp::SHN_COMMON:
 214       if (!is_ordinary)
 215         bits |= common_flag;
 216       break;
 217
 218     default:
 219       if (type == elfcpp::STT_COMMON)
 220         bits |= common_flag;
 221       else if (!is_ordinary && Symbol::is_common_shndx(shndx))
 222         bits |= common_flag;
 223       else
 224         bits |= def_flag;
 225       break;
 226     }
 227
 228   return bits;
 229 }
 230
 231 // Resolve a symbol.  This is called the second and subsequent times
 232 // we see a symbol.  TO is the pre-existing symbol.  ST_SHNDX is the
 233 // section index for SYM, possibly adjusted for many sections.
 234 // IS_ORDINARY is whether ST_SHNDX is a normal section index rather
 235 // than a special code.  ORIG_ST_SHNDX is the original section index,
 236 // before any munging because of discarded sections, except that all
 237 // non-ordinary section indexes are mapped to SHN_UNDEF.  VERSION is
 238 // the version of SYM.
 239
 240 template<int size, bool big_endian>
 241 void
 242 Symbol_table::resolve(Sized_symbol<size>* to,
 243                       const elfcpp::Sym<size, big_endian>& sym,
 244                       unsigned int st_shndx, bool is_ordinary,
 245                       unsigned int orig_st_shndx,
 246                       Object* object, const char* version)
 247 {
 248   if (parameters->target().has_resolve())
 249     {
 250       Sized_target<size, big_endian>* sized_target;
 251       sized_target = parameters->sized_target<size, big_endian>();
 252       sized_target->resolve(to, sym, object, version);
 253       return;
 254     }
 255
 256   if (!object->is_dynamic())
 257     {
 258       // Record that we've seen this symbol in a regular object.
 259       to->set_in_reg();
 260     }
 261   else if (st_shndx == elfcpp::SHN_UNDEF
 262            && (to->visibility() == elfcpp::STV_HIDDEN
 263                || to->visibility() == elfcpp::STV_INTERNAL))
 264     {
 265       // A dynamic object cannot reference a hidden or internal symbol
 266       // defined in another object.
 267       gold_warning(_("%s symbol '%s' in %s is referenced by DSO %s"),
 268                    (to->visibility() == elfcpp::STV_HIDDEN
 269                     ? "hidden"
 270                     : "internal"),
 271                    to->demangled_name().c_str(),
 272                    to->object()->name().c_str(),
 273                    object->name().c_str());
 274       return;
 275     }
 276   else
 277     {
 278       // Record that we've seen this symbol in a dynamic object.
 279       to->set_in_dyn();
 280     }
 281
 282   // Record if we've seen this symbol in a real ELF object (i.e., the
 283   // symbol is referenced from outside the world known to the plugin).
 284   if (object->pluginobj() == NULL)
 285     to->set_in_real_elf();
 286
 287   // If we're processing replacement files, allow new symbols to override
 288   // the placeholders from the plugin objects.
 289   if (to->source() == Symbol::FROM_OBJECT)
 290     {
 291       Pluginobj* obj = to->object()->pluginobj();
 292       if (obj != NULL
 293           && parameters->options().plugins()->in_replacement_phase())
 294         {
 295           this->override(to, sym, st_shndx, is_ordinary, object, version);
 296           return;
 297         }
 298     }
 299
 300   // A new weak undefined reference, merging with an old weak
 301   // reference, could be a One Definition Rule (ODR) violation --
 302   // especially if the types or sizes of the references differ.  We'll
 303   // store such pairs and look them up later to make sure they
 304   // actually refer to the same lines of code.  We also check
 305   // combinations of weak and strong, which might occur if one case is
 306   // inline and the other is not.  (Note: not all ODR violations can
 307   // be found this way, and not everything this finds is an ODR
 308   // violation.  But it's helpful to warn about.)
 309   bool to_is_ordinary;
 310   if (parameters->options().detect_odr_violations()
 311       && (sym.get_st_bind() == elfcpp::STB_WEAK
 312           || to->binding() == elfcpp::STB_WEAK)
 313       && orig_st_shndx != elfcpp::SHN_UNDEF
 314       && to->shndx(&to_is_ordinary) != elfcpp::SHN_UNDEF
 315       && to_is_ordinary
 316       && sym.get_st_size() != 0    // Ignore weird 0-sized symbols.
 317       && to->symsize() != 0
 318       && (sym.get_st_type() != to->type()
 319           || sym.get_st_size() != to->symsize())
 320       // C does not have a concept of ODR, so we only need to do this
 321       // on C++ symbols.  These have (mangled) names starting with _Z.
 322       && to->name()[0] == '_' && to->name()[1] == 'Z')
 323     {
 324       Symbol_location fromloc
 325           = { object, orig_st_shndx, sym.get_st_value() };
 326       Symbol_location toloc = { to->object(), to->shndx(&to_is_ordinary),
 327                                 to->value() };
 328       this->candidate_odr_violations_[to->name()].insert(fromloc);
 329       this->candidate_odr_violations_[to->name()].insert(toloc);
 330     }
 331
 332   unsigned int frombits = symbol_to_bits(sym.get_st_bind(),
 333                                          object->is_dynamic(),
 334                                          st_shndx, is_ordinary,
 335                                          sym.get_st_type());
 336
 337   bool adjust_common_sizes;
 338   typename Sized_symbol<size>::Size_type tosize = to->symsize();
 339   if (Symbol_table::should_override(to, frombits, OBJECT, object,
 340                                     &adjust_common_sizes))
 341     {
 342       this->override(to, sym, st_shndx, is_ordinary, object, version);
 343       if (adjust_common_sizes && tosize > to->symsize())
 344         to->set_symsize(tosize);
 345     }
 346   else
 347     {
 348       if (adjust_common_sizes && sym.get_st_size() > tosize)
 349         to->set_symsize(sym.get_st_size());
 350       // The ELF ABI says that even for a reference to a symbol we
 351       // merge the visibility.
 352       to->override_visibility(sym.get_st_visibility());
 353     }
 354
 355   if (adjust_common_sizes && parameters->options().warn_common())
 356     {
 357       if (tosize > sym.get_st_size())
 358         Symbol_table::report_resolve_problem(false,
 359                                              _("common of '%s' overriding "
 360                                                "smaller common"),
 361                                              to, OBJECT, object);
 362       else if (tosize < sym.get_st_size())
 363         Symbol_table::report_resolve_problem(false,
 364                                              _("common of '%s' overidden by "
 365                                                "larger common"),
 366                                              to, OBJECT, object);
 367       else
 368         Symbol_table::report_resolve_problem(false,
 369                                              _("multiple common of '%s'"),
 370                                              to, OBJECT, object);
 371     }
 372 }
 373
 374 // Handle the core of symbol resolution.  This is called with the
 375 // existing symbol, TO, and a bitflag describing the new symbol.  This
 376 // returns true if we should override the existing symbol with the new
 377 // one, and returns false otherwise.  It sets *ADJUST_COMMON_SIZES to
 378 // true if we should set the symbol size to the maximum of the TO and
 379 // FROM sizes.  It handles error conditions.
 380
 381 bool
 382 Symbol_table::should_override(const Symbol* to, unsigned int frombits,
 383                               Defined defined, Object* object,
 384                               bool* adjust_common_sizes)
 385 {
 386   *adjust_common_sizes = false;
 387
 388   unsigned int tobits;
 389   if (to->source() == Symbol::IS_UNDEFINED)
 390     tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_UNDEF, true,
 391                             to->type());
 392   else if (to->source() != Symbol::FROM_OBJECT)
 393     tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_ABS, false,
 394                             to->type());
 395   else
 396     {
 397       bool is_ordinary;
 398       unsigned int shndx = to->shndx(&is_ordinary);
 399       tobits = symbol_to_bits(to->binding(),
 400                               to->object()->is_dynamic(),
 401                               shndx,
 402                               is_ordinary,
 403                               to->type());
 404     }
 405
 406   // FIXME: Warn if either but not both of TO and SYM are STT_TLS.
 407
 408   // We use a giant switch table for symbol resolution.  This code is
 409   // unwieldy, but: 1) it is efficient; 2) we definitely handle all
 410   // cases; 3) it is easy to change the handling of a particular case.
 411   // The alternative would be a series of conditionals, but it is easy
 412   // to get the ordering wrong.  This could also be done as a table,
 413   // but that is no easier to understand than this large switch
 414   // statement.
 415
 416   // These are the values generated by the bit codes.
 417   enum
 418   {
 419     DEF =              global_flag | regular_flag | def_flag,
 420     WEAK_DEF =         weak_flag   | regular_flag | def_flag,
 421     DYN_DEF =          global_flag | dynamic_flag | def_flag,
 422     DYN_WEAK_DEF =     weak_flag   | dynamic_flag | def_flag,
 423     UNDEF =            global_flag | regular_flag | undef_flag,
 424     WEAK_UNDEF =       weak_flag   | regular_flag | undef_flag,
 425     DYN_UNDEF =        global_flag | dynamic_flag | undef_flag,
 426     DYN_WEAK_UNDEF =   weak_flag   | dynamic_flag | undef_flag,
 427     COMMON =           global_flag | regular_flag | common_flag,
 428     WEAK_COMMON =      weak_flag   | regular_flag | common_flag,
 429     DYN_COMMON =       global_flag | dynamic_flag | common_flag,
 430     DYN_WEAK_COMMON =  weak_flag   | dynamic_flag | common_flag
 431   };
 432
 433   switch (tobits * 16 + frombits)
 434     {
 435     case DEF * 16 + DEF:
 436       // Two definitions of the same symbol.
 437
 438       // If either symbol is defined by an object included using
 439       // --just-symbols, then don't warn.  This is for compatibility
 440       // with the GNU linker.  FIXME: This is a hack.
 441       if ((to->source() == Symbol::FROM_OBJECT && to->object()->just_symbols())
 442           || (object != NULL && object->just_symbols()))
 443         return false;
 444
 445       if (!parameters->options().muldefs())
 446         Symbol_table::report_resolve_problem(true,
 447                                              _("multiple definition of '%s'"),
 448                                              to, defined, object);
 449       return false;
 450
 451     case WEAK_DEF * 16 + DEF:
 452       // We've seen a weak definition, and now we see a strong
 453       // definition.  In the original SVR4 linker, this was treated as
 454       // a multiple definition error.  In the Solaris linker and the
 455       // GNU linker, a weak definition followed by a regular
 456       // definition causes the weak definition to be overridden.  We
 457       // are currently compatible with the GNU linker.  In the future
 458       // we should add a target specific option to change this.
 459       // FIXME.
 460       return true;
 461
 462     case DYN_DEF * 16 + DEF:
 463     case DYN_WEAK_DEF * 16 + DEF:
 464       // We've seen a definition in a dynamic object, and now we see a
 465       // definition in a regular object.  The definition in the
 466       // regular object overrides the definition in the dynamic
 467       // object.
 468       return true;
 469
 470     case UNDEF * 16 + DEF:
 471     case WEAK_UNDEF * 16 + DEF:
 472     case DYN_UNDEF * 16 + DEF:
 473     case DYN_WEAK_UNDEF * 16 + DEF:
 474       // We've seen an undefined reference, and now we see a
 475       // definition.  We use the definition.
 476       return true;
 477
 478     case COMMON * 16 + DEF:
 479     case WEAK_COMMON * 16 + DEF:
 480     case DYN_COMMON * 16 + DEF:
 481     case DYN_WEAK_COMMON * 16 + DEF:
 482       // We've seen a common symbol and now we see a definition.  The
 483       // definition overrides.
 484       if (parameters->options().warn_common())
 485         Symbol_table::report_resolve_problem(false,
 486                                              _("definition of '%s' overriding "
 487                                                "common"),
 488                                              to, defined, object);
 489       return true;
 490
 491     case DEF * 16 + WEAK_DEF:
 492     case WEAK_DEF * 16 + WEAK_DEF:
 493       // We've seen a definition and now we see a weak definition.  We
 494       // ignore the new weak definition.
 495       return false;
 496
 497     case DYN_DEF * 16 + WEAK_DEF:
 498     case DYN_WEAK_DEF * 16 + WEAK_DEF:
 499       // We've seen a dynamic definition and now we see a regular weak
 500       // definition.  The regular weak definition overrides.
 501       return true;
 502
 503     case UNDEF * 16 + WEAK_DEF:
 504     case WEAK_UNDEF * 16 + WEAK_DEF:
 505     case DYN_UNDEF * 16 + WEAK_DEF:
 506     case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
 507       // A weak definition of a currently undefined symbol.
 508       return true;
 509
 510     case COMMON * 16 + WEAK_DEF:
 511     case WEAK_COMMON * 16 + WEAK_DEF:
 512       // A weak definition does not override a common definition.
 513       return false;
 514
 515     case DYN_COMMON * 16 + WEAK_DEF:
 516     case DYN_WEAK_COMMON * 16 + WEAK_DEF:
 517       // A weak definition does override a definition in a dynamic
 518       // object.
 519       if (parameters->options().warn_common())
 520         Symbol_table::report_resolve_problem(false,
 521                                              _("definition of '%s' overriding "
 522                                                "dynamic common definition"),
 523                                              to, defined, object);
 524       return true;
 525
 526     case DEF * 16 + DYN_DEF:
 527     case WEAK_DEF * 16 + DYN_DEF:
 528     case DYN_DEF * 16 + DYN_DEF:
 529     case DYN_WEAK_DEF * 16 + DYN_DEF:
 530       // Ignore a dynamic definition if we already have a definition.
 531       return false;
 532
 533     case UNDEF * 16 + DYN_DEF:
 534     case WEAK_UNDEF * 16 + DYN_DEF:
 535     case DYN_UNDEF * 16 + DYN_DEF:
 536     case DYN_WEAK_UNDEF * 16 + DYN_DEF:
 537       // Use a dynamic definition if we have a reference.
 538       return true;
 539
 540     case COMMON * 16 + DYN_DEF:
 541     case WEAK_COMMON * 16 + DYN_DEF:
 542     case DYN_COMMON * 16 + DYN_DEF:
 543     case DYN_WEAK_COMMON * 16 + DYN_DEF:
 544       // Ignore a dynamic definition if we already have a common
 545       // definition.
 546       return false;
 547
 548     case DEF * 16 + DYN_WEAK_DEF:
 549     case WEAK_DEF * 16 + DYN_WEAK_DEF:
 550     case DYN_DEF * 16 + DYN_WEAK_DEF:
 551     case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
 552       // Ignore a weak dynamic definition if we already have a
 553       // definition.
 554       return false;
 555
 556     case UNDEF * 16 + DYN_WEAK_DEF:
 557     case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 558     case DYN_UNDEF * 16 + DYN_WEAK_DEF:
 559     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 560       // Use a weak dynamic definition if we have a reference.
 561       return true;
 562
 563     case COMMON * 16 + DYN_WEAK_DEF:
 564     case WEAK_COMMON * 16 + DYN_WEAK_DEF:
 565     case DYN_COMMON * 16 + DYN_WEAK_DEF:
 566     case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
 567       // Ignore a weak dynamic definition if we already have a common
 568       // definition.
 569       return false;
 570
 571     case DEF * 16 + UNDEF:
 572     case WEAK_DEF * 16 + UNDEF:
 573     case DYN_DEF * 16 + UNDEF:
 574     case DYN_WEAK_DEF * 16 + UNDEF:
 575     case UNDEF * 16 + UNDEF:
 576       // A new undefined reference tells us nothing.
 577       return false;
 578
 579     case WEAK_UNDEF * 16 + UNDEF:
 580     case DYN_UNDEF * 16 + UNDEF:
 581     case DYN_WEAK_UNDEF * 16 + UNDEF:
 582       // A strong undef overrides a dynamic or weak undef.
 583       return true;
 584
 585     case COMMON * 16 + UNDEF:
 586     case WEAK_COMMON * 16 + UNDEF:
 587     case DYN_COMMON * 16 + UNDEF:
 588     case DYN_WEAK_COMMON * 16 + UNDEF:
 589       // A new undefined reference tells us nothing.
 590       return false;
 591
 592     case DEF * 16 + WEAK_UNDEF:
 593     case WEAK_DEF * 16 + WEAK_UNDEF:
 594     case DYN_DEF * 16 + WEAK_UNDEF:
 595     case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
 596     case UNDEF * 16 + WEAK_UNDEF:
 597     case WEAK_UNDEF * 16 + WEAK_UNDEF:
 598     case DYN_UNDEF * 16 + WEAK_UNDEF:
 599     case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
 600     case COMMON * 16 + WEAK_UNDEF:
 601     case WEAK_COMMON * 16 + WEAK_UNDEF:
 602     case DYN_COMMON * 16 + WEAK_UNDEF:
 603     case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
 604       // A new weak undefined reference tells us nothing.
 605       return false;
 606
 607     case DEF * 16 + DYN_UNDEF:
 608     case WEAK_DEF * 16 + DYN_UNDEF:
 609     case DYN_DEF * 16 + DYN_UNDEF:
 610     case DYN_WEAK_DEF * 16 + DYN_UNDEF:
 611     case UNDEF * 16 + DYN_UNDEF:
 612     case WEAK_UNDEF * 16 + DYN_UNDEF:
 613     case DYN_UNDEF * 16 + DYN_UNDEF:
 614     case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
 615     case COMMON * 16 + DYN_UNDEF:
 616     case WEAK_COMMON * 16 + DYN_UNDEF:
 617     case DYN_COMMON * 16 + DYN_UNDEF:
 618     case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
 619       // A new dynamic undefined reference tells us nothing.
 620       return false;
 621
 622     case DEF * 16 + DYN_WEAK_UNDEF:
 623     case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 624     case DYN_DEF * 16 + DYN_WEAK_UNDEF:
 625     case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 626     case UNDEF * 16 + DYN_WEAK_UNDEF:
 627     case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 628     case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
 629     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 630     case COMMON * 16 + DYN_WEAK_UNDEF:
 631     case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 632     case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
 633     case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 634       // A new weak dynamic undefined reference tells us nothing.
 635       return false;
 636
 637     case DEF * 16 + COMMON:
 638       // A common symbol does not override a definition.
 639       if (parameters->options().warn_common())
 640         Symbol_table::report_resolve_problem(false,
 641                                              _("common '%s' overridden by "
 642                                                "previous definition"),
 643                                              to, defined, object);
 644       return false;
 645
 646     case WEAK_DEF * 16 + COMMON:
 647     case DYN_DEF * 16 + COMMON:
 648     case DYN_WEAK_DEF * 16 + COMMON:
 649       // A common symbol does override a weak definition or a dynamic
 650       // definition.
 651       return true;
 652
 653     case UNDEF * 16 + COMMON:
 654     case WEAK_UNDEF * 16 + COMMON:
 655     case DYN_UNDEF * 16 + COMMON:
 656     case DYN_WEAK_UNDEF * 16 + COMMON:
 657       // A common symbol is a definition for a reference.
 658       return true;
 659
 660     case COMMON * 16 + COMMON:
 661       // Set the size to the maximum.
 662       *adjust_common_sizes = true;
 663       return false;
 664
 665     case WEAK_COMMON * 16 + COMMON:
 666       // I'm not sure just what a weak common symbol means, but
 667       // presumably it can be overridden by a regular common symbol.
 668       return true;
 669
 670     case DYN_COMMON * 16 + COMMON:
 671     case DYN_WEAK_COMMON * 16 + COMMON:
 672       // Use the real common symbol, but adjust the size if necessary.
 673       *adjust_common_sizes = true;
 674       return true;
 675
 676     case DEF * 16 + WEAK_COMMON:
 677     case WEAK_DEF * 16 + WEAK_COMMON:
 678     case DYN_DEF * 16 + WEAK_COMMON:
 679     case DYN_WEAK_DEF * 16 + WEAK_COMMON:
 680       // Whatever a weak common symbol is, it won't override a
 681       // definition.
 682       return false;
 683
 684     case UNDEF * 16 + WEAK_COMMON:
 685     case WEAK_UNDEF * 16 + WEAK_COMMON:
 686     case DYN_UNDEF * 16 + WEAK_COMMON:
 687     case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
 688       // A weak common symbol is better than an undefined symbol.
 689       return true;
 690
 691     case COMMON * 16 + WEAK_COMMON:
 692     case WEAK_COMMON * 16 + WEAK_COMMON:
 693     case DYN_COMMON * 16 + WEAK_COMMON:
 694     case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
 695       // Ignore a weak common symbol in the presence of a real common
 696       // symbol.
 697       return false;
 698
 699     case DEF * 16 + DYN_COMMON:
 700     case WEAK_DEF * 16 + DYN_COMMON:
 701     case DYN_DEF * 16 + DYN_COMMON:
 702     case DYN_WEAK_DEF * 16 + DYN_COMMON:
 703       // Ignore a dynamic common symbol in the presence of a
 704       // definition.
 705       return false;
 706
 707     case UNDEF * 16 + DYN_COMMON:
 708     case WEAK_UNDEF * 16 + DYN_COMMON:
 709     case DYN_UNDEF * 16 + DYN_COMMON:
 710     case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
 711       // A dynamic common symbol is a definition of sorts.
 712       return true;
 713
 714     case COMMON * 16 + DYN_COMMON:
 715     case WEAK_COMMON * 16 + DYN_COMMON:
 716     case DYN_COMMON * 16 + DYN_COMMON:
 717     case DYN_WEAK_COMMON * 16 + DYN_COMMON:
 718       // Set the size to the maximum.
 719       *adjust_common_sizes = true;
 720       return false;
 721
 722     case DEF * 16 + DYN_WEAK_COMMON:
 723     case WEAK_DEF * 16 + DYN_WEAK_COMMON:
 724     case DYN_DEF * 16 + DYN_WEAK_COMMON:
 725     case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
 726       // A common symbol is ignored in the face of a definition.
 727       return false;
 728
 729     case UNDEF * 16 + DYN_WEAK_COMMON:
 730     case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 731     case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
 732     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 733       // I guess a weak common symbol is better than a definition.
 734       return true;
 735
 736     case COMMON * 16 + DYN_WEAK_COMMON:
 737     case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 738     case DYN_COMMON * 16 + DYN_WEAK_COMMON:
 739     case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 740       // Set the size to the maximum.
 741       *adjust_common_sizes = true;
 742       return false;
 743
 744     default:
 745       gold_unreachable();
 746     }
 747 }
 748
 749 // Issue an error or warning due to symbol resolution.  IS_ERROR
 750 // indicates an error rather than a warning.  MSG is the error
 751 // message; it is expected to have a %s for the symbol name.  TO is
 752 // the existing symbol.  DEFINED/OBJECT is where the new symbol was
 753 // found.
 754
 755 // FIXME: We should have better location information here.  When the
 756 // symbol is defined, we should be able to pull the location from the
 757 // debug info if there is any.
 758
 759 void
 760 Symbol_table::report_resolve_problem(bool is_error, const char* msg,
 761                                      const Symbol* to, Defined defined,
 762                                      Object* object)
 763 {
 764   std::string demangled(to->demangled_name());
 765   size_t len = strlen(msg) + demangled.length() + 10;
 766   char* buf = new char[len];
 767   snprintf(buf, len, msg, demangled.c_str());
 768
 769   const char* objname;
 770   switch (defined)
 771     {
 772     case OBJECT:
 773       objname = object->name().c_str();
 774       break;
 775     case COPY:
 776       objname = _("COPY reloc");
 777       break;
 778     case DEFSYM:
 779     case UNDEFINED:
 780       objname = _("command line");
 781       break;
 782     case SCRIPT:
 783       objname = _("linker script");
 784       break;
 785     case PREDEFINED:
 786       objname = _("linker defined");
 787       break;
 788     default:
 789       gold_unreachable();
 790     }
 791
 792   if (is_error)
 793     gold_error("%s: %s", objname, buf);
 794   else
 795     gold_warning("%s: %s", objname, buf);
 796
 797   delete[] buf;
 798
 799   if (to->source() == Symbol::FROM_OBJECT)
 800     objname = to->object()->name().c_str();
 801   else
 802     objname = _("command line");
 803   gold_info("%s: %s: previous definition here", program_name, objname);
 804 }
 805
 806 // A special case of should_override which is only called for a strong
 807 // defined symbol from a regular object file.  This is used when
 808 // defining special symbols.
 809
 810 bool
 811 Symbol_table::should_override_with_special(const Symbol* to, Defined defined)
 812 {
 813   bool adjust_common_sizes;
 814   unsigned int frombits = global_flag | regular_flag | def_flag;
 815   bool ret = Symbol_table::should_override(to, frombits, defined, NULL,
 816                                            &adjust_common_sizes);
 817   gold_assert(!adjust_common_sizes);
 818   return ret;
 819 }
 820
 821 // Override symbol base with a special symbol.
 822
 823 void
 824 Symbol::override_base_with_special(const Symbol* from)
 825 {
 826   gold_assert(this->name_ == from->name_ || this->has_alias());
 827
 828   this->source_ = from->source_;
 829   switch (from->source_)
 830     {
 831     case FROM_OBJECT:
 832       this->u_.from_object = from->u_.from_object;
 833       break;
 834     case IN_OUTPUT_DATA:
 835       this->u_.in_output_data = from->u_.in_output_data;
 836       break;
 837     case IN_OUTPUT_SEGMENT:
 838       this->u_.in_output_segment = from->u_.in_output_segment;
 839       break;
 840     case IS_CONSTANT:
 841     case IS_UNDEFINED:
 842       break;
 843     default:
 844       gold_unreachable();
 845       break;
 846     }
 847
 848   this->override_version(from->version_);
 849   this->type_ = from->type_;
 850   this->binding_ = from->binding_;
 851   this->override_visibility(from->visibility_);
 852   this->nonvis_ = from->nonvis_;
 853
 854   // Special symbols are always considered to be regular symbols.
 855   this->in_reg_ = true;
 856
 857   if (from->needs_dynsym_entry_)
 858     this->needs_dynsym_entry_ = true;
 859   if (from->needs_dynsym_value_)
 860     this->needs_dynsym_value_ = true;
 861
 862   // We shouldn't see these flags.  If we do, we need to handle them
 863   // somehow.
 864   gold_assert(!from->is_forwarder_);
 865   gold_assert(!from->has_plt_offset());
 866   gold_assert(!from->has_warning_);
 867   gold_assert(!from->is_copied_from_dynobj_);
 868   gold_assert(!from->is_forced_local_);
 869 }
 870
 871 // Override a symbol with a special symbol.
 872
 873 template<int size>
 874 void
 875 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from)
 876 {
 877   this->override_base_with_special(from);
 878   this->value_ = from->value_;
 879   this->symsize_ = from->symsize_;
 880 }
 881
 882 // Override TOSYM with the special symbol FROMSYM.  This handles all
 883 // aliases of TOSYM.
 884
 885 template<int size>
 886 void
 887 Symbol_table::override_with_special(Sized_symbol<size>* tosym,
 888                                     const Sized_symbol<size>* fromsym)
 889 {
 890   tosym->override_with_special(fromsym);
 891   if (tosym->has_alias())
 892     {
 893       Symbol* sym = this->weak_aliases_[tosym];
 894       gold_assert(sym != NULL);
 895       Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
 896       do
 897         {
 898           ssym->override_with_special(fromsym);
 899           sym = this->weak_aliases_[ssym];
 900           gold_assert(sym != NULL);
 901           ssym = this->get_sized_symbol<size>(sym);
 902         }
 903       while (ssym != tosym);
 904     }
 905   if (tosym->binding() == elfcpp::STB_LOCAL
 906       || ((tosym->visibility() == elfcpp::STV_HIDDEN
 907            || tosym->visibility() == elfcpp::STV_INTERNAL)
 908           && (tosym->binding() == elfcpp::STB_GLOBAL
 909               || tosym->binding() == elfcpp::STB_GNU_UNIQUE
 910               || tosym->binding() == elfcpp::STB_WEAK)
 911           && !parameters->options().relocatable()))
 912     this->force_local(tosym);
 913 }
 914
 915 // Instantiate the templates we need.  We could use the configure
 916 // script to restrict this to only the ones needed for implemented
 917 // targets.
 918
 919 #ifdef HAVE_TARGET_32_LITTLE
 920 template
 921 void
 922 Symbol_table::resolve<32, false>(
 923     Sized_symbol<32>* to,
 924     const elfcpp::Sym<32, false>& sym,
 925     unsigned int st_shndx,
 926     bool is_ordinary,
 927     unsigned int orig_st_shndx,
 928     Object* object,
 929     const char* version);
 930 #endif
 931
 932 #ifdef HAVE_TARGET_32_BIG
 933 template
 934 void
 935 Symbol_table::resolve<32, true>(
 936     Sized_symbol<32>* to,
 937     const elfcpp::Sym<32, true>& sym,
 938     unsigned int st_shndx,
 939     bool is_ordinary,
 940     unsigned int orig_st_shndx,
 941     Object* object,
 942     const char* version);
 943 #endif
 944
 945 #ifdef HAVE_TARGET_64_LITTLE
 946 template
 947 void
 948 Symbol_table::resolve<64, false>(
 949     Sized_symbol<64>* to,
 950     const elfcpp::Sym<64, false>& sym,
 951     unsigned int st_shndx,
 952     bool is_ordinary,
 953     unsigned int orig_st_shndx,
 954     Object* object,
 955     const char* version);
 956 #endif
 957
 958 #ifdef HAVE_TARGET_64_BIG
 959 template
 960 void
 961 Symbol_table::resolve<64, true>(
 962     Sized_symbol<64>* to,
 963     const elfcpp::Sym<64, true>& sym,
 964     unsigned int st_shndx,
 965     bool is_ordinary,
 966     unsigned int orig_st_shndx,
 967     Object* object,
 968     const char* version);
 969 #endif
 970
 971 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
 972 template
 973 void
 974 Symbol_table::override_with_special<32>(Sized_symbol<32>*,
 975                                         const Sized_symbol<32>*);
 976 #endif
 977
 978 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
 979 template
 980 void
 981 Symbol_table::override_with_special<64>(Sized_symbol<64>*,
 982                                         const Sized_symbol<64>*);
 983 #endif
 984
 985 } // End namespace gold.