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   unsigned int frombits = symbol_to_bits(sym.get_st_bind(),
 301                                          object->is_dynamic(),
 302                                          st_shndx, is_ordinary,
 303                                          sym.get_st_type());
 304
 305   bool adjust_common_sizes;
 306   typename Sized_symbol<size>::Size_type tosize = to->symsize();
 307   if (Symbol_table::should_override(to, frombits, OBJECT, object,
 308                                     &adjust_common_sizes))
 309     {
 310       this->override(to, sym, st_shndx, is_ordinary, object, version);
 311       if (adjust_common_sizes && tosize > to->symsize())
 312         to->set_symsize(tosize);
 313     }
 314   else
 315     {
 316       if (adjust_common_sizes && sym.get_st_size() > tosize)
 317         to->set_symsize(sym.get_st_size());
 318       // The ELF ABI says that even for a reference to a symbol we
 319       // merge the visibility.
 320       to->override_visibility(sym.get_st_visibility());
 321     }
 322
 323   if (adjust_common_sizes && parameters->options().warn_common())
 324     {
 325       if (tosize > sym.get_st_size())
 326         Symbol_table::report_resolve_problem(false,
 327                                              _("common of '%s' overriding "
 328                                                "smaller common"),
 329                                              to, OBJECT, object);
 330       else if (tosize < sym.get_st_size())
 331         Symbol_table::report_resolve_problem(false,
 332                                              _("common of '%s' overidden by "
 333                                                "larger common"),
 334                                              to, OBJECT, object);
 335       else
 336         Symbol_table::report_resolve_problem(false,
 337                                              _("multiple common of '%s'"),
 338                                              to, OBJECT, object);
 339     }
 340
 341   // A new weak undefined reference, merging with an old weak
 342   // reference, could be a One Definition Rule (ODR) violation --
 343   // especially if the types or sizes of the references differ.  We'll
 344   // store such pairs and look them up later to make sure they
 345   // actually refer to the same lines of code.  (Note: not all ODR
 346   // violations can be found this way, and not everything this finds
 347   // is an ODR violation.  But it's helpful to warn about.)
 348   bool to_is_ordinary;
 349   if (parameters->options().detect_odr_violations()
 350       && sym.get_st_bind() == elfcpp::STB_WEAK
 351       && to->binding() == elfcpp::STB_WEAK
 352       && orig_st_shndx != elfcpp::SHN_UNDEF
 353       && to->shndx(&to_is_ordinary) != elfcpp::SHN_UNDEF
 354       && to_is_ordinary
 355       && sym.get_st_size() != 0    // Ignore weird 0-sized symbols.
 356       && to->symsize() != 0
 357       && (sym.get_st_type() != to->type()
 358           || sym.get_st_size() != to->symsize())
 359       // C does not have a concept of ODR, so we only need to do this
 360       // on C++ symbols.  These have (mangled) names starting with _Z.
 361       && to->name()[0] == '_' && to->name()[1] == 'Z')
 362     {
 363       Symbol_location fromloc
 364           = { object, orig_st_shndx, sym.get_st_value() };
 365       Symbol_location toloc = { to->object(), to->shndx(&to_is_ordinary),
 366                                 to->value() };
 367       this->candidate_odr_violations_[to->name()].insert(fromloc);
 368       this->candidate_odr_violations_[to->name()].insert(toloc);
 369     }
 370 }
 371
 372 // Handle the core of symbol resolution.  This is called with the
 373 // existing symbol, TO, and a bitflag describing the new symbol.  This
 374 // returns true if we should override the existing symbol with the new
 375 // one, and returns false otherwise.  It sets *ADJUST_COMMON_SIZES to
 376 // true if we should set the symbol size to the maximum of the TO and
 377 // FROM sizes.  It handles error conditions.
 378
 379 bool
 380 Symbol_table::should_override(const Symbol* to, unsigned int frombits,
 381                               Defined defined, Object* object,
 382                               bool* adjust_common_sizes)
 383 {
 384   *adjust_common_sizes = false;
 385
 386   unsigned int tobits;
 387   if (to->source() == Symbol::IS_UNDEFINED)
 388     tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_UNDEF, true,
 389                             to->type());
 390   else if (to->source() != Symbol::FROM_OBJECT)
 391     tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_ABS, false,
 392                             to->type());
 393   else
 394     {
 395       bool is_ordinary;
 396       unsigned int shndx = to->shndx(&is_ordinary);
 397       tobits = symbol_to_bits(to->binding(),
 398                               to->object()->is_dynamic(),
 399                               shndx,
 400                               is_ordinary,
 401                               to->type());
 402     }
 403
 404   // FIXME: Warn if either but not both of TO and SYM are STT_TLS.
 405
 406   // We use a giant switch table for symbol resolution.  This code is
 407   // unwieldy, but: 1) it is efficient; 2) we definitely handle all
 408   // cases; 3) it is easy to change the handling of a particular case.
 409   // The alternative would be a series of conditionals, but it is easy
 410   // to get the ordering wrong.  This could also be done as a table,
 411   // but that is no easier to understand than this large switch
 412   // statement.
 413
 414   // These are the values generated by the bit codes.
 415   enum
 416   {
 417     DEF =              global_flag | regular_flag | def_flag,
 418     WEAK_DEF =         weak_flag   | regular_flag | def_flag,
 419     DYN_DEF =          global_flag | dynamic_flag | def_flag,
 420     DYN_WEAK_DEF =     weak_flag   | dynamic_flag | def_flag,
 421     UNDEF =            global_flag | regular_flag | undef_flag,
 422     WEAK_UNDEF =       weak_flag   | regular_flag | undef_flag,
 423     DYN_UNDEF =        global_flag | dynamic_flag | undef_flag,
 424     DYN_WEAK_UNDEF =   weak_flag   | dynamic_flag | undef_flag,
 425     COMMON =           global_flag | regular_flag | common_flag,
 426     WEAK_COMMON =      weak_flag   | regular_flag | common_flag,
 427     DYN_COMMON =       global_flag | dynamic_flag | common_flag,
 428     DYN_WEAK_COMMON =  weak_flag   | dynamic_flag | common_flag
 429   };
 430
 431   switch (tobits * 16 + frombits)
 432     {
 433     case DEF * 16 + DEF:
 434       // Two definitions of the same symbol.
 435
 436       // If either symbol is defined by an object included using
 437       // --just-symbols, then don't warn.  This is for compatibility
 438       // with the GNU linker.  FIXME: This is a hack.
 439       if ((to->source() == Symbol::FROM_OBJECT && to->object()->just_symbols())
 440           || (object != NULL && object->just_symbols()))
 441         return false;
 442
 443       if (!parameters->options().muldefs())
 444         Symbol_table::report_resolve_problem(true,
 445                                              _("multiple definition of '%s'"),
 446                                              to, defined, object);
 447       return false;
 448
 449     case WEAK_DEF * 16 + DEF:
 450       // We've seen a weak definition, and now we see a strong
 451       // definition.  In the original SVR4 linker, this was treated as
 452       // a multiple definition error.  In the Solaris linker and the
 453       // GNU linker, a weak definition followed by a regular
 454       // definition causes the weak definition to be overridden.  We
 455       // are currently compatible with the GNU linker.  In the future
 456       // we should add a target specific option to change this.
 457       // FIXME.
 458       return true;
 459
 460     case DYN_DEF * 16 + DEF:
 461     case DYN_WEAK_DEF * 16 + DEF:
 462       // We've seen a definition in a dynamic object, and now we see a
 463       // definition in a regular object.  The definition in the
 464       // regular object overrides the definition in the dynamic
 465       // object.
 466       return true;
 467
 468     case UNDEF * 16 + DEF:
 469     case WEAK_UNDEF * 16 + DEF:
 470     case DYN_UNDEF * 16 + DEF:
 471     case DYN_WEAK_UNDEF * 16 + DEF:
 472       // We've seen an undefined reference, and now we see a
 473       // definition.  We use the definition.
 474       return true;
 475
 476     case COMMON * 16 + DEF:
 477     case WEAK_COMMON * 16 + DEF:
 478     case DYN_COMMON * 16 + DEF:
 479     case DYN_WEAK_COMMON * 16 + DEF:
 480       // We've seen a common symbol and now we see a definition.  The
 481       // definition overrides.
 482       if (parameters->options().warn_common())
 483         Symbol_table::report_resolve_problem(false,
 484                                              _("definition of '%s' overriding "
 485                                                "common"),
 486                                              to, defined, object);
 487       return true;
 488
 489     case DEF * 16 + WEAK_DEF:
 490     case WEAK_DEF * 16 + WEAK_DEF:
 491       // We've seen a definition and now we see a weak definition.  We
 492       // ignore the new weak definition.
 493       return false;
 494
 495     case DYN_DEF * 16 + WEAK_DEF:
 496     case DYN_WEAK_DEF * 16 + WEAK_DEF:
 497       // We've seen a dynamic definition and now we see a regular weak
 498       // definition.  The regular weak definition overrides.
 499       return true;
 500
 501     case UNDEF * 16 + WEAK_DEF:
 502     case WEAK_UNDEF * 16 + WEAK_DEF:
 503     case DYN_UNDEF * 16 + WEAK_DEF:
 504     case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
 505       // A weak definition of a currently undefined symbol.
 506       return true;
 507
 508     case COMMON * 16 + WEAK_DEF:
 509     case WEAK_COMMON * 16 + WEAK_DEF:
 510       // A weak definition does not override a common definition.
 511       return false;
 512
 513     case DYN_COMMON * 16 + WEAK_DEF:
 514     case DYN_WEAK_COMMON * 16 + WEAK_DEF:
 515       // A weak definition does override a definition in a dynamic
 516       // object.
 517       if (parameters->options().warn_common())
 518         Symbol_table::report_resolve_problem(false,
 519                                              _("definition of '%s' overriding "
 520                                                "dynamic common definition"),
 521                                              to, defined, object);
 522       return true;
 523
 524     case DEF * 16 + DYN_DEF:
 525     case WEAK_DEF * 16 + DYN_DEF:
 526     case DYN_DEF * 16 + DYN_DEF:
 527     case DYN_WEAK_DEF * 16 + DYN_DEF:
 528       // Ignore a dynamic definition if we already have a definition.
 529       return false;
 530
 531     case UNDEF * 16 + DYN_DEF:
 532     case WEAK_UNDEF * 16 + DYN_DEF:
 533     case DYN_UNDEF * 16 + DYN_DEF:
 534     case DYN_WEAK_UNDEF * 16 + DYN_DEF:
 535       // Use a dynamic definition if we have a reference.
 536       return true;
 537
 538     case COMMON * 16 + DYN_DEF:
 539     case WEAK_COMMON * 16 + DYN_DEF:
 540     case DYN_COMMON * 16 + DYN_DEF:
 541     case DYN_WEAK_COMMON * 16 + DYN_DEF:
 542       // Ignore a dynamic definition if we already have a common
 543       // definition.
 544       return false;
 545
 546     case DEF * 16 + DYN_WEAK_DEF:
 547     case WEAK_DEF * 16 + DYN_WEAK_DEF:
 548     case DYN_DEF * 16 + DYN_WEAK_DEF:
 549     case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
 550       // Ignore a weak dynamic definition if we already have a
 551       // definition.
 552       return false;
 553
 554     case UNDEF * 16 + DYN_WEAK_DEF:
 555     case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 556     case DYN_UNDEF * 16 + DYN_WEAK_DEF:
 557     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
 558       // Use a weak dynamic definition if we have a reference.
 559       return true;
 560
 561     case COMMON * 16 + DYN_WEAK_DEF:
 562     case WEAK_COMMON * 16 + DYN_WEAK_DEF:
 563     case DYN_COMMON * 16 + DYN_WEAK_DEF:
 564     case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
 565       // Ignore a weak dynamic definition if we already have a common
 566       // definition.
 567       return false;
 568
 569     case DEF * 16 + UNDEF:
 570     case WEAK_DEF * 16 + UNDEF:
 571     case DYN_DEF * 16 + UNDEF:
 572     case DYN_WEAK_DEF * 16 + UNDEF:
 573     case UNDEF * 16 + UNDEF:
 574       // A new undefined reference tells us nothing.
 575       return false;
 576
 577     case WEAK_UNDEF * 16 + UNDEF:
 578     case DYN_UNDEF * 16 + UNDEF:
 579     case DYN_WEAK_UNDEF * 16 + UNDEF:
 580       // A strong undef overrides a dynamic or weak undef.
 581       return true;
 582
 583     case COMMON * 16 + UNDEF:
 584     case WEAK_COMMON * 16 + UNDEF:
 585     case DYN_COMMON * 16 + UNDEF:
 586     case DYN_WEAK_COMMON * 16 + UNDEF:
 587       // A new undefined reference tells us nothing.
 588       return false;
 589
 590     case DEF * 16 + WEAK_UNDEF:
 591     case WEAK_DEF * 16 + WEAK_UNDEF:
 592     case DYN_DEF * 16 + WEAK_UNDEF:
 593     case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
 594     case UNDEF * 16 + WEAK_UNDEF:
 595     case WEAK_UNDEF * 16 + WEAK_UNDEF:
 596     case DYN_UNDEF * 16 + WEAK_UNDEF:
 597     case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
 598     case COMMON * 16 + WEAK_UNDEF:
 599     case WEAK_COMMON * 16 + WEAK_UNDEF:
 600     case DYN_COMMON * 16 + WEAK_UNDEF:
 601     case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
 602       // A new weak undefined reference tells us nothing.
 603       return false;
 604
 605     case DEF * 16 + DYN_UNDEF:
 606     case WEAK_DEF * 16 + DYN_UNDEF:
 607     case DYN_DEF * 16 + DYN_UNDEF:
 608     case DYN_WEAK_DEF * 16 + DYN_UNDEF:
 609     case UNDEF * 16 + DYN_UNDEF:
 610     case WEAK_UNDEF * 16 + DYN_UNDEF:
 611     case DYN_UNDEF * 16 + DYN_UNDEF:
 612     case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
 613     case COMMON * 16 + DYN_UNDEF:
 614     case WEAK_COMMON * 16 + DYN_UNDEF:
 615     case DYN_COMMON * 16 + DYN_UNDEF:
 616     case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
 617       // A new dynamic undefined reference tells us nothing.
 618       return false;
 619
 620     case DEF * 16 + DYN_WEAK_UNDEF:
 621     case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 622     case DYN_DEF * 16 + DYN_WEAK_UNDEF:
 623     case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
 624     case UNDEF * 16 + DYN_WEAK_UNDEF:
 625     case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 626     case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
 627     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
 628     case COMMON * 16 + DYN_WEAK_UNDEF:
 629     case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 630     case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
 631     case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
 632       // A new weak dynamic undefined reference tells us nothing.
 633       return false;
 634
 635     case DEF * 16 + COMMON:
 636       // A common symbol does not override a definition.
 637       if (parameters->options().warn_common())
 638         Symbol_table::report_resolve_problem(false,
 639                                              _("common '%s' overridden by "
 640                                                "previous definition"),
 641                                              to, defined, object);
 642       return false;
 643
 644     case WEAK_DEF * 16 + COMMON:
 645     case DYN_DEF * 16 + COMMON:
 646     case DYN_WEAK_DEF * 16 + COMMON:
 647       // A common symbol does override a weak definition or a dynamic
 648       // definition.
 649       return true;
 650
 651     case UNDEF * 16 + COMMON:
 652     case WEAK_UNDEF * 16 + COMMON:
 653     case DYN_UNDEF * 16 + COMMON:
 654     case DYN_WEAK_UNDEF * 16 + COMMON:
 655       // A common symbol is a definition for a reference.
 656       return true;
 657
 658     case COMMON * 16 + COMMON:
 659       // Set the size to the maximum.
 660       *adjust_common_sizes = true;
 661       return false;
 662
 663     case WEAK_COMMON * 16 + COMMON:
 664       // I'm not sure just what a weak common symbol means, but
 665       // presumably it can be overridden by a regular common symbol.
 666       return true;
 667
 668     case DYN_COMMON * 16 + COMMON:
 669     case DYN_WEAK_COMMON * 16 + COMMON:
 670       // Use the real common symbol, but adjust the size if necessary.
 671       *adjust_common_sizes = true;
 672       return true;
 673
 674     case DEF * 16 + WEAK_COMMON:
 675     case WEAK_DEF * 16 + WEAK_COMMON:
 676     case DYN_DEF * 16 + WEAK_COMMON:
 677     case DYN_WEAK_DEF * 16 + WEAK_COMMON:
 678       // Whatever a weak common symbol is, it won't override a
 679       // definition.
 680       return false;
 681
 682     case UNDEF * 16 + WEAK_COMMON:
 683     case WEAK_UNDEF * 16 + WEAK_COMMON:
 684     case DYN_UNDEF * 16 + WEAK_COMMON:
 685     case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
 686       // A weak common symbol is better than an undefined symbol.
 687       return true;
 688
 689     case COMMON * 16 + WEAK_COMMON:
 690     case WEAK_COMMON * 16 + WEAK_COMMON:
 691     case DYN_COMMON * 16 + WEAK_COMMON:
 692     case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
 693       // Ignore a weak common symbol in the presence of a real common
 694       // symbol.
 695       return false;
 696
 697     case DEF * 16 + DYN_COMMON:
 698     case WEAK_DEF * 16 + DYN_COMMON:
 699     case DYN_DEF * 16 + DYN_COMMON:
 700     case DYN_WEAK_DEF * 16 + DYN_COMMON:
 701       // Ignore a dynamic common symbol in the presence of a
 702       // definition.
 703       return false;
 704
 705     case UNDEF * 16 + DYN_COMMON:
 706     case WEAK_UNDEF * 16 + DYN_COMMON:
 707     case DYN_UNDEF * 16 + DYN_COMMON:
 708     case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
 709       // A dynamic common symbol is a definition of sorts.
 710       return true;
 711
 712     case COMMON * 16 + DYN_COMMON:
 713     case WEAK_COMMON * 16 + DYN_COMMON:
 714     case DYN_COMMON * 16 + DYN_COMMON:
 715     case DYN_WEAK_COMMON * 16 + DYN_COMMON:
 716       // Set the size to the maximum.
 717       *adjust_common_sizes = true;
 718       return false;
 719
 720     case DEF * 16 + DYN_WEAK_COMMON:
 721     case WEAK_DEF * 16 + DYN_WEAK_COMMON:
 722     case DYN_DEF * 16 + DYN_WEAK_COMMON:
 723     case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
 724       // A common symbol is ignored in the face of a definition.
 725       return false;
 726
 727     case UNDEF * 16 + DYN_WEAK_COMMON:
 728     case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 729     case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
 730     case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
 731       // I guess a weak common symbol is better than a definition.
 732       return true;
 733
 734     case COMMON * 16 + DYN_WEAK_COMMON:
 735     case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 736     case DYN_COMMON * 16 + DYN_WEAK_COMMON:
 737     case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
 738       // Set the size to the maximum.
 739       *adjust_common_sizes = true;
 740       return false;
 741
 742     default:
 743       gold_unreachable();
 744     }
 745 }
 746
 747 // Issue an error or warning due to symbol resolution.  IS_ERROR
 748 // indicates an error rather than a warning.  MSG is the error
 749 // message; it is expected to have a %s for the symbol name.  TO is
 750 // the existing symbol.  DEFINED/OBJECT is where the new symbol was
 751 // found.
 752
 753 // FIXME: We should have better location information here.  When the
 754 // symbol is defined, we should be able to pull the location from the
 755 // debug info if there is any.
 756
 757 void
 758 Symbol_table::report_resolve_problem(bool is_error, const char* msg,
 759                                      const Symbol* to, Defined defined,
 760                                      Object* object)
 761 {
 762   std::string demangled(to->demangled_name());
 763   size_t len = strlen(msg) + demangled.length() + 10;
 764   char* buf = new char[len];
 765   snprintf(buf, len, msg, demangled.c_str());
 766
 767   const char* objname;
 768   switch (defined)
 769     {
 770     case OBJECT:
 771       objname = object->name().c_str();
 772       break;
 773     case COPY:
 774       objname = _("COPY reloc");
 775       break;
 776     case DEFSYM:
 777     case UNDEFINED:
 778       objname = _("command line");
 779       break;
 780     case SCRIPT:
 781       objname = _("linker script");
 782       break;
 783     case PREDEFINED:
 784       objname = _("linker defined");
 785       break;
 786     default:
 787       gold_unreachable();
 788     }
 789
 790   if (is_error)
 791     gold_error("%s: %s", objname, buf);
 792   else
 793     gold_warning("%s: %s", objname, buf);
 794
 795   delete[] buf;
 796
 797   if (to->source() == Symbol::FROM_OBJECT)
 798     objname = to->object()->name().c_str();
 799   else
 800     objname = _("command line");
 801   gold_info("%s: %s: previous definition here", program_name, objname);
 802 }
 803
 804 // A special case of should_override which is only called for a strong
 805 // defined symbol from a regular object file.  This is used when
 806 // defining special symbols.
 807
 808 bool
 809 Symbol_table::should_override_with_special(const Symbol* to, Defined defined)
 810 {
 811   bool adjust_common_sizes;
 812   unsigned int frombits = global_flag | regular_flag | def_flag;
 813   bool ret = Symbol_table::should_override(to, frombits, defined, NULL,
 814                                            &adjust_common_sizes);
 815   gold_assert(!adjust_common_sizes);
 816   return ret;
 817 }
 818
 819 // Override symbol base with a special symbol.
 820
 821 void
 822 Symbol::override_base_with_special(const Symbol* from)
 823 {
 824   gold_assert(this->name_ == from->name_ || this->has_alias());
 825
 826   this->source_ = from->source_;
 827   switch (from->source_)
 828     {
 829     case FROM_OBJECT:
 830       this->u_.from_object = from->u_.from_object;
 831       break;
 832     case IN_OUTPUT_DATA:
 833       this->u_.in_output_data = from->u_.in_output_data;
 834       break;
 835     case IN_OUTPUT_SEGMENT:
 836       this->u_.in_output_segment = from->u_.in_output_segment;
 837       break;
 838     case IS_CONSTANT:
 839     case IS_UNDEFINED:
 840       break;
 841     default:
 842       gold_unreachable();
 843       break;
 844     }
 845
 846   this->override_version(from->version_);
 847   this->type_ = from->type_;
 848   this->binding_ = from->binding_;
 849   this->override_visibility(from->visibility_);
 850   this->nonvis_ = from->nonvis_;
 851
 852   // Special symbols are always considered to be regular symbols.
 853   this->in_reg_ = true;
 854
 855   if (from->needs_dynsym_entry_)
 856     this->needs_dynsym_entry_ = true;
 857   if (from->needs_dynsym_value_)
 858     this->needs_dynsym_value_ = true;
 859
 860   // We shouldn't see these flags.  If we do, we need to handle them
 861   // somehow.
 862   gold_assert(!from->is_target_special_ || this->is_target_special_);
 863   gold_assert(!from->is_forwarder_);
 864   gold_assert(!from->has_plt_offset_);
 865   gold_assert(!from->has_warning_);
 866   gold_assert(!from->is_copied_from_dynobj_);
 867   gold_assert(!from->is_forced_local_);
 868 }
 869
 870 // Override a symbol with a special symbol.
 871
 872 template<int size>
 873 void
 874 Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from)
 875 {
 876   this->override_base_with_special(from);
 877   this->value_ = from->value_;
 878   this->symsize_ = from->symsize_;
 879 }
 880
 881 // Override TOSYM with the special symbol FROMSYM.  This handles all
 882 // aliases of TOSYM.
 883
 884 template<int size>
 885 void
 886 Symbol_table::override_with_special(Sized_symbol<size>* tosym,
 887                                     const Sized_symbol<size>* fromsym)
 888 {
 889   tosym->override_with_special(fromsym);
 890   if (tosym->has_alias())
 891     {
 892       Symbol* sym = this->weak_aliases_[tosym];
 893       gold_assert(sym != NULL);
 894       Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
 895       do
 896         {
 897           ssym->override_with_special(fromsym);
 898           sym = this->weak_aliases_[ssym];
 899           gold_assert(sym != NULL);
 900           ssym = this->get_sized_symbol<size>(sym);
 901         }
 902       while (ssym != tosym);
 903     }
 904   if (tosym->binding() == elfcpp::STB_LOCAL
 905       || ((tosym->visibility() == elfcpp::STV_HIDDEN
 906            || tosym->visibility() == elfcpp::STV_INTERNAL)
 907           && (tosym->binding() == elfcpp::STB_GLOBAL
 908               || tosym->binding() == elfcpp::STB_GNU_UNIQUE
 909               || tosym->binding() == elfcpp::STB_WEAK)
 910           && !parameters->options().relocatable()))
 911     this->force_local(tosym);
 912 }
 913
 914 // Instantiate the templates we need.  We could use the configure
 915 // script to restrict this to only the ones needed for implemented
 916 // targets.
 917
 918 #ifdef HAVE_TARGET_32_LITTLE
 919 template
 920 void
 921 Symbol_table::resolve<32, false>(
 922     Sized_symbol<32>* to,
 923     const elfcpp::Sym<32, false>& sym,
 924     unsigned int st_shndx,
 925     bool is_ordinary,
 926     unsigned int orig_st_shndx,
 927     Object* object,
 928     const char* version);
 929 #endif
 930
 931 #ifdef HAVE_TARGET_32_BIG
 932 template
 933 void
 934 Symbol_table::resolve<32, true>(
 935     Sized_symbol<32>* to,
 936     const elfcpp::Sym<32, true>& sym,
 937     unsigned int st_shndx,
 938     bool is_ordinary,
 939     unsigned int orig_st_shndx,
 940     Object* object,
 941     const char* version);
 942 #endif
 943
 944 #ifdef HAVE_TARGET_64_LITTLE
 945 template
 946 void
 947 Symbol_table::resolve<64, false>(
 948     Sized_symbol<64>* to,
 949     const elfcpp::Sym<64, false>& sym,
 950     unsigned int st_shndx,
 951     bool is_ordinary,
 952     unsigned int orig_st_shndx,
 953     Object* object,
 954     const char* version);
 955 #endif
 956
 957 #ifdef HAVE_TARGET_64_BIG
 958 template
 959 void
 960 Symbol_table::resolve<64, true>(
 961     Sized_symbol<64>* to,
 962     const elfcpp::Sym<64, true>& sym,
 963     unsigned int st_shndx,
 964     bool is_ordinary,
 965     unsigned int orig_st_shndx,
 966     Object* object,
 967     const char* version);
 968 #endif
 969
 970 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
 971 template
 972 void
 973 Symbol_table::override_with_special<32>(Sized_symbol<32>*,
 974                                         const Sized_symbol<32>*);
 975 #endif
 976
 977 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
 978 template
 979 void
 980 Symbol_table::override_with_special<64>(Sized_symbol<64>*,
 981                                         const Sized_symbol<64>*);
 982 #endif
 983
 984 } // End namespace gold.