Imported from /home/lorry/working-area/delta_binutils-tarball/binutils-2.25.tar.bz2.HEADbinutils-2.25master

1 files changed, 1107 insertions, 0 deletions

diff --git a/gold/resolve.cc b/gold/resolve.cc
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+// resolve.cc -- symbol resolution for gold
+
+// Copyright (C) 2006-2014 Free Software Foundation, Inc.
+// Written by Ian Lance Taylor <iant@google.com>.
+
+// This file is part of gold.
+
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
+// MA 02110-1301, USA.
+
+#include "gold.h"
+
+#include "elfcpp.h"
+#include "target.h"
+#include "object.h"
+#include "symtab.h"
+#include "plugin.h"
+
+namespace gold
+{
+
+// Symbol methods used in this file.
+
+// This symbol is being overridden by another symbol whose version is
+// VERSION.  Update the VERSION_ field accordingly.
+
+inline void
+Symbol::override_version(const char* version)
+{
+  if (version == NULL)
+    {
+      // This is the case where this symbol is NAME/VERSION, and the
+      // version was not marked as hidden.  That makes it the default
+      // version, so we create NAME/NULL.  Later we see another symbol
+      // NAME/NULL, and that symbol is overriding this one.  In this
+      // case, since NAME/VERSION is the default, we make NAME/NULL
+      // override NAME/VERSION as well.  They are already the same
+      // Symbol structure.  Setting the VERSION_ field to NULL ensures
+      // that it will be output with the correct, empty, version.
+      this->version_ = version;
+    }
+  else
+    {
+      // This is the case where this symbol is NAME/VERSION_ONE, and
+      // now we see NAME/VERSION_TWO, and NAME/VERSION_TWO is
+      // overriding NAME.  If VERSION_ONE and VERSION_TWO are
+      // different, then this can only happen when VERSION_ONE is NULL
+      // and VERSION_TWO is not hidden.
+      gold_assert(this->version_ == version || this->version_ == NULL);
+      this->version_ = version;
+    }
+}
+
+// This symbol is being overidden by another symbol whose visibility
+// is VISIBILITY.  Updated the VISIBILITY_ field accordingly.
+
+inline void
+Symbol::override_visibility(elfcpp::STV visibility)
+{
+  // The rule for combining visibility is that we always choose the
+  // most constrained visibility.  In order of increasing constraint,
+  // visibility goes PROTECTED, HIDDEN, INTERNAL.  This is the reverse
+  // of the numeric values, so the effect is that we always want the
+  // smallest non-zero value.
+  if (visibility != elfcpp::STV_DEFAULT)
+    {
+      if (this->visibility_ == elfcpp::STV_DEFAULT)
+	this->visibility_ = visibility;
+      else if (this->visibility_ > visibility)
+	this->visibility_ = visibility;
+    }
+}
+
+// Override the fields in Symbol.
+
+template<int size, bool big_endian>
+void
+Symbol::override_base(const elfcpp::Sym<size, big_endian>& sym,
+		      unsigned int st_shndx, bool is_ordinary,
+		      Object* object, const char* version)
+{
+  gold_assert(this->source_ == FROM_OBJECT);
+  this->u_.from_object.object = object;
+  this->override_version(version);
+  this->u_.from_object.shndx = st_shndx;
+  this->is_ordinary_shndx_ = is_ordinary;
+  // Don't override st_type from plugin placeholder symbols.
+  if (object->pluginobj() == NULL)
+    this->type_ = sym.get_st_type();
+  this->binding_ = sym.get_st_bind();
+  this->override_visibility(sym.get_st_visibility());
+  this->nonvis_ = sym.get_st_nonvis();
+  if (object->is_dynamic())
+    this->in_dyn_ = true;
+  else
+    this->in_reg_ = true;
+}
+
+// Override the fields in Sized_symbol.
+
+template<int size>
+template<bool big_endian>
+void
+Sized_symbol<size>::override(const elfcpp::Sym<size, big_endian>& sym,
+			     unsigned st_shndx, bool is_ordinary,
+			     Object* object, const char* version)
+{
+  this->override_base(sym, st_shndx, is_ordinary, object, version);
+  this->value_ = sym.get_st_value();
+  this->symsize_ = sym.get_st_size();
+}
+
+// Override TOSYM with symbol FROMSYM, defined in OBJECT, with version
+// VERSION.  This handles all aliases of TOSYM.
+
+template<int size, bool big_endian>
+void
+Symbol_table::override(Sized_symbol<size>* tosym,
+		       const elfcpp::Sym<size, big_endian>& fromsym,
+		       unsigned int st_shndx, bool is_ordinary,
+		       Object* object, const char* version)
+{
+  tosym->override(fromsym, st_shndx, is_ordinary, object, version);
+  if (tosym->has_alias())
+    {
+      Symbol* sym = this->weak_aliases_[tosym];
+      gold_assert(sym != NULL);
+      Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
+      do
+	{
+	  ssym->override(fromsym, st_shndx, is_ordinary, object, version);
+	  sym = this->weak_aliases_[ssym];
+	  gold_assert(sym != NULL);
+	  ssym = this->get_sized_symbol<size>(sym);
+	}
+      while (ssym != tosym);
+    }
+}
+
+// The resolve functions build a little code for each symbol.
+// Bit 0: 0 for global, 1 for weak.
+// Bit 1: 0 for regular object, 1 for shared object
+// Bits 2-3: 0 for normal, 1 for undefined, 2 for common
+// This gives us values from 0 to 11.
+
+static const int global_or_weak_shift = 0;
+static const unsigned int global_flag = 0 << global_or_weak_shift;
+static const unsigned int weak_flag = 1 << global_or_weak_shift;
+
+static const int regular_or_dynamic_shift = 1;
+static const unsigned int regular_flag = 0 << regular_or_dynamic_shift;
+static const unsigned int dynamic_flag = 1 << regular_or_dynamic_shift;
+
+static const int def_undef_or_common_shift = 2;
+static const unsigned int def_flag = 0 << def_undef_or_common_shift;
+static const unsigned int undef_flag = 1 << def_undef_or_common_shift;
+static const unsigned int common_flag = 2 << def_undef_or_common_shift;
+
+// This convenience function combines all the flags based on facts
+// about the symbol.
+
+static unsigned int
+symbol_to_bits(elfcpp::STB binding, bool is_dynamic,
+	       unsigned int shndx, bool is_ordinary, elfcpp::STT type)
+{
+  unsigned int bits;
+
+  switch (binding)
+    {
+    case elfcpp::STB_GLOBAL:
+    case elfcpp::STB_GNU_UNIQUE:
+      bits = global_flag;
+      break;
+
+    case elfcpp::STB_WEAK:
+      bits = weak_flag;
+      break;
+
+    case elfcpp::STB_LOCAL:
+      // We should only see externally visible symbols in the symbol
+      // table.
+      gold_error(_("invalid STB_LOCAL symbol in external symbols"));
+      bits = global_flag;
+
+    default:
+      // Any target which wants to handle STB_LOOS, etc., needs to
+      // define a resolve method.
+      gold_error(_("unsupported symbol binding %d"), static_cast<int>(binding));
+      bits = global_flag;
+    }
+
+  if (is_dynamic)
+    bits |= dynamic_flag;
+  else
+    bits |= regular_flag;
+
+  switch (shndx)
+    {
+    case elfcpp::SHN_UNDEF:
+      bits |= undef_flag;
+      break;
+
+    case elfcpp::SHN_COMMON:
+      if (!is_ordinary)
+	bits |= common_flag;
+      break;
+
+    default:
+      if (type == elfcpp::STT_COMMON)
+	bits |= common_flag;
+      else if (!is_ordinary && Symbol::is_common_shndx(shndx))
+	bits |= common_flag;
+      else
+        bits |= def_flag;
+      break;
+    }
+
+  return bits;
+}
+
+// Resolve a symbol.  This is called the second and subsequent times
+// we see a symbol.  TO is the pre-existing symbol.  ST_SHNDX is the
+// section index for SYM, possibly adjusted for many sections.
+// IS_ORDINARY is whether ST_SHNDX is a normal section index rather
+// than a special code.  ORIG_ST_SHNDX is the original section index,
+// before any munging because of discarded sections, except that all
+// non-ordinary section indexes are mapped to SHN_UNDEF.  VERSION is
+// the version of SYM.
+
+template<int size, bool big_endian>
+void
+Symbol_table::resolve(Sized_symbol<size>* to,
+		      const elfcpp::Sym<size, big_endian>& sym,
+		      unsigned int st_shndx, bool is_ordinary,
+		      unsigned int orig_st_shndx,
+		      Object* object, const char* version)
+{
+  // It's possible for a symbol to be defined in an object file
+  // using .symver to give it a version, and for there to also be
+  // a linker script giving that symbol the same version.  We
+  // don't want to give a multiple-definition error for this
+  // harmless redefinition.
+  bool to_is_ordinary;
+  if (to->source() == Symbol::FROM_OBJECT
+      && to->object() == object
+      && is_ordinary
+      && to->is_defined()
+      && to->shndx(&to_is_ordinary) == st_shndx
+      && to_is_ordinary
+      && to->value() == sym.get_st_value())
+    return;
+
+  if (parameters->target().has_resolve())
+    {
+      Sized_target<size, big_endian>* sized_target;
+      sized_target = parameters->sized_target<size, big_endian>();
+      sized_target->resolve(to, sym, object, version);
+      return;
+    }
+
+  if (!object->is_dynamic())
+    {
+      // Record that we've seen this symbol in a regular object.
+      to->set_in_reg();
+    }
+  else if (st_shndx == elfcpp::SHN_UNDEF
+           && (to->visibility() == elfcpp::STV_HIDDEN
+               || to->visibility() == elfcpp::STV_INTERNAL))
+    {
+      // A dynamic object cannot reference a hidden or internal symbol
+      // defined in another object.
+      gold_warning(_("%s symbol '%s' in %s is referenced by DSO %s"),
+                   (to->visibility() == elfcpp::STV_HIDDEN
+                    ? "hidden"
+                    : "internal"),
+                   to->demangled_name().c_str(),
+                   to->object()->name().c_str(),
+                   object->name().c_str());
+      return;
+    }
+  else
+    {
+      // Record that we've seen this symbol in a dynamic object.
+      to->set_in_dyn();
+    }
+
+  // Record if we've seen this symbol in a real ELF object (i.e., the
+  // symbol is referenced from outside the world known to the plugin).
+  if (object->pluginobj() == NULL && !object->is_dynamic())
+    to->set_in_real_elf();
+
+  // If we're processing replacement files, allow new symbols to override
+  // the placeholders from the plugin objects.
+  // Treat common symbols specially since it is possible that an ELF
+  // file increased the size of the alignment.
+  if (to->source() == Symbol::FROM_OBJECT)
+    {
+      Pluginobj* obj = to->object()->pluginobj();
+      if (obj != NULL
+          && parameters->options().plugins()->in_replacement_phase())
+        {
+	  bool adjust_common = false;
+	  typename Sized_symbol<size>::Size_type tosize = 0;
+	  typename Sized_symbol<size>::Value_type tovalue = 0;
+	  if (to->is_common() && !is_ordinary && st_shndx == elfcpp::SHN_COMMON)
+	    {
+	      adjust_common = true;
+	      tosize = to->symsize();
+	      tovalue = to->value();
+	    }
+	  this->override(to, sym, st_shndx, is_ordinary, object, version);
+	  if (adjust_common)
+	    {
+	      if (tosize > to->symsize())
+		to->set_symsize(tosize);
+	      if (tovalue > to->value())
+		to->set_value(tovalue);
+	    }
+	  return;
+        }
+    }
+
+  // A new weak undefined reference, merging with an old weak
+  // reference, could be a One Definition Rule (ODR) violation --
+  // especially if the types or sizes of the references differ.  We'll
+  // store such pairs and look them up later to make sure they
+  // actually refer to the same lines of code.  We also check
+  // combinations of weak and strong, which might occur if one case is
+  // inline and the other is not.  (Note: not all ODR violations can
+  // be found this way, and not everything this finds is an ODR
+  // violation.  But it's helpful to warn about.)
+  if (parameters->options().detect_odr_violations()
+      && (sym.get_st_bind() == elfcpp::STB_WEAK
+	  || to->binding() == elfcpp::STB_WEAK)
+      && orig_st_shndx != elfcpp::SHN_UNDEF
+      && to->shndx(&to_is_ordinary) != elfcpp::SHN_UNDEF
+      && to_is_ordinary
+      && sym.get_st_size() != 0    // Ignore weird 0-sized symbols.
+      && to->symsize() != 0
+      && (sym.get_st_type() != to->type()
+          || sym.get_st_size() != to->symsize())
+      // C does not have a concept of ODR, so we only need to do this
+      // on C++ symbols.  These have (mangled) names starting with _Z.
+      && to->name()[0] == '_' && to->name()[1] == 'Z')
+    {
+      Symbol_location fromloc
+          = { object, orig_st_shndx, static_cast<off_t>(sym.get_st_value()) };
+      Symbol_location toloc = { to->object(), to->shndx(&to_is_ordinary),
+				static_cast<off_t>(to->value()) };
+      this->candidate_odr_violations_[to->name()].insert(fromloc);
+      this->candidate_odr_violations_[to->name()].insert(toloc);
+    }
+
+  // Plugins don't provide a symbol type, so adopt the existing type
+  // if the FROM symbol is from a plugin.
+  elfcpp::STT fromtype = (object->pluginobj() != NULL
+			  ? to->type()
+			  : sym.get_st_type());
+  unsigned int frombits = symbol_to_bits(sym.get_st_bind(),
+                                         object->is_dynamic(),
+					 st_shndx, is_ordinary,
+                                         fromtype);
+
+  bool adjust_common_sizes;
+  bool adjust_dyndef;
+  typename Sized_symbol<size>::Size_type tosize = to->symsize();
+  if (Symbol_table::should_override(to, frombits, fromtype, OBJECT,
+				    object, &adjust_common_sizes,
+				    &adjust_dyndef))
+    {
+      elfcpp::STB tobinding = to->binding();
+      typename Sized_symbol<size>::Value_type tovalue = to->value();
+      this->override(to, sym, st_shndx, is_ordinary, object, version);
+      if (adjust_common_sizes)
+	{
+	  if (tosize > to->symsize())
+	    to->set_symsize(tosize);
+	  if (tovalue > to->value())
+	    to->set_value(tovalue);
+	}
+      if (adjust_dyndef)
+	{
+	  // We are overriding an UNDEF or WEAK UNDEF with a DYN DEF.
+	  // Remember which kind of UNDEF it was for future reference.
+	  to->set_undef_binding(tobinding);
+	}
+    }
+  else
+    {
+      if (adjust_common_sizes)
+	{
+	  if (sym.get_st_size() > tosize)
+	    to->set_symsize(sym.get_st_size());
+	  if (sym.get_st_value() > to->value())
+	    to->set_value(sym.get_st_value());
+	}
+      if (adjust_dyndef)
+	{
+	  // We are keeping a DYN DEF after seeing an UNDEF or WEAK UNDEF.
+	  // Remember which kind of UNDEF it was.
+	  to->set_undef_binding(sym.get_st_bind());
+	}
+      // The ELF ABI says that even for a reference to a symbol we
+      // merge the visibility.
+      to->override_visibility(sym.get_st_visibility());
+    }
+
+  if (adjust_common_sizes && parameters->options().warn_common())
+    {
+      if (tosize > sym.get_st_size())
+	Symbol_table::report_resolve_problem(false,
+					     _("common of '%s' overriding "
+					       "smaller common"),
+					     to, OBJECT, object);
+      else if (tosize < sym.get_st_size())
+	Symbol_table::report_resolve_problem(false,
+					     _("common of '%s' overidden by "
+					       "larger common"),
+					     to, OBJECT, object);
+      else
+	Symbol_table::report_resolve_problem(false,
+					     _("multiple common of '%s'"),
+					     to, OBJECT, object);
+    }
+}
+
+// Handle the core of symbol resolution.  This is called with the
+// existing symbol, TO, and a bitflag describing the new symbol.  This
+// returns true if we should override the existing symbol with the new
+// one, and returns false otherwise.  It sets *ADJUST_COMMON_SIZES to
+// true if we should set the symbol size to the maximum of the TO and
+// FROM sizes.  It handles error conditions.
+
+bool
+Symbol_table::should_override(const Symbol* to, unsigned int frombits,
+			      elfcpp::STT fromtype, Defined defined,
+			      Object* object, bool* adjust_common_sizes,
+			      bool* adjust_dyndef)
+{
+  *adjust_common_sizes = false;
+  *adjust_dyndef = false;
+
+  unsigned int tobits;
+  if (to->source() == Symbol::IS_UNDEFINED)
+    tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_UNDEF, true,
+			    to->type());
+  else if (to->source() != Symbol::FROM_OBJECT)
+    tobits = symbol_to_bits(to->binding(), false, elfcpp::SHN_ABS, false,
+			    to->type());
+  else
+    {
+      bool is_ordinary;
+      unsigned int shndx = to->shndx(&is_ordinary);
+      tobits = symbol_to_bits(to->binding(),
+			      to->object()->is_dynamic(),
+			      shndx,
+			      is_ordinary,
+			      to->type());
+    }
+
+  if ((to->type() == elfcpp::STT_TLS) ^ (fromtype == elfcpp::STT_TLS)
+      && !to->is_placeholder())
+    Symbol_table::report_resolve_problem(true,
+					 _("symbol '%s' used as both __thread "
+					   "and non-__thread"),
+					 to, defined, object);
+
+  // We use a giant switch table for symbol resolution.  This code is
+  // unwieldy, but: 1) it is efficient; 2) we definitely handle all
+  // cases; 3) it is easy to change the handling of a particular case.
+  // The alternative would be a series of conditionals, but it is easy
+  // to get the ordering wrong.  This could also be done as a table,
+  // but that is no easier to understand than this large switch
+  // statement.
+
+  // These are the values generated by the bit codes.
+  enum
+  {
+    DEF =              global_flag | regular_flag | def_flag,
+    WEAK_DEF =         weak_flag   | regular_flag | def_flag,
+    DYN_DEF =          global_flag | dynamic_flag | def_flag,
+    DYN_WEAK_DEF =     weak_flag   | dynamic_flag | def_flag,
+    UNDEF =            global_flag | regular_flag | undef_flag,
+    WEAK_UNDEF =       weak_flag   | regular_flag | undef_flag,
+    DYN_UNDEF =        global_flag | dynamic_flag | undef_flag,
+    DYN_WEAK_UNDEF =   weak_flag   | dynamic_flag | undef_flag,
+    COMMON =           global_flag | regular_flag | common_flag,
+    WEAK_COMMON =      weak_flag   | regular_flag | common_flag,
+    DYN_COMMON =       global_flag | dynamic_flag | common_flag,
+    DYN_WEAK_COMMON =  weak_flag   | dynamic_flag | common_flag
+  };
+
+  switch (tobits * 16 + frombits)
+    {
+    case DEF * 16 + DEF:
+      // Two definitions of the same symbol.
+
+      // If either symbol is defined by an object included using
+      // --just-symbols, then don't warn.  This is for compatibility
+      // with the GNU linker.  FIXME: This is a hack.
+      if ((to->source() == Symbol::FROM_OBJECT && to->object()->just_symbols())
+          || (object != NULL && object->just_symbols()))
+        return false;
+
+      if (!parameters->options().muldefs())
+	Symbol_table::report_resolve_problem(true,
+					     _("multiple definition of '%s'"),
+					     to, defined, object);
+      return false;
+
+    case WEAK_DEF * 16 + DEF:
+      // We've seen a weak definition, and now we see a strong
+      // definition.  In the original SVR4 linker, this was treated as
+      // a multiple definition error.  In the Solaris linker and the
+      // GNU linker, a weak definition followed by a regular
+      // definition causes the weak definition to be overridden.  We
+      // are currently compatible with the GNU linker.  In the future
+      // we should add a target specific option to change this.
+      // FIXME.
+      return true;
+
+    case DYN_DEF * 16 + DEF:
+    case DYN_WEAK_DEF * 16 + DEF:
+      // We've seen a definition in a dynamic object, and now we see a
+      // definition in a regular object.  The definition in the
+      // regular object overrides the definition in the dynamic
+      // object.
+      return true;
+
+    case UNDEF * 16 + DEF:
+    case WEAK_UNDEF * 16 + DEF:
+    case DYN_UNDEF * 16 + DEF:
+    case DYN_WEAK_UNDEF * 16 + DEF:
+      // We've seen an undefined reference, and now we see a
+      // definition.  We use the definition.
+      return true;
+
+    case COMMON * 16 + DEF:
+    case WEAK_COMMON * 16 + DEF:
+    case DYN_COMMON * 16 + DEF:
+    case DYN_WEAK_COMMON * 16 + DEF:
+      // We've seen a common symbol and now we see a definition.  The
+      // definition overrides.
+      if (parameters->options().warn_common())
+	Symbol_table::report_resolve_problem(false,
+					     _("definition of '%s' overriding "
+					       "common"),
+					     to, defined, object);
+      return true;
+
+    case DEF * 16 + WEAK_DEF:
+    case WEAK_DEF * 16 + WEAK_DEF:
+      // We've seen a definition and now we see a weak definition.  We
+      // ignore the new weak definition.
+      return false;
+
+    case DYN_DEF * 16 + WEAK_DEF:
+    case DYN_WEAK_DEF * 16 + WEAK_DEF:
+      // We've seen a dynamic definition and now we see a regular weak
+      // definition.  The regular weak definition overrides.
+      return true;
+
+    case UNDEF * 16 + WEAK_DEF:
+    case WEAK_UNDEF * 16 + WEAK_DEF:
+    case DYN_UNDEF * 16 + WEAK_DEF:
+    case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
+      // A weak definition of a currently undefined symbol.
+      return true;
+
+    case COMMON * 16 + WEAK_DEF:
+    case WEAK_COMMON * 16 + WEAK_DEF:
+      // A weak definition does not override a common definition.
+      return false;
+
+    case DYN_COMMON * 16 + WEAK_DEF:
+    case DYN_WEAK_COMMON * 16 + WEAK_DEF:
+      // A weak definition does override a definition in a dynamic
+      // object.
+      if (parameters->options().warn_common())
+	Symbol_table::report_resolve_problem(false,
+					     _("definition of '%s' overriding "
+					       "dynamic common definition"),
+					     to, defined, object);
+      return true;
+
+    case DEF * 16 + DYN_DEF:
+    case WEAK_DEF * 16 + DYN_DEF:
+    case DYN_DEF * 16 + DYN_DEF:
+    case DYN_WEAK_DEF * 16 + DYN_DEF:
+      // Ignore a dynamic definition if we already have a definition.
+      return false;
+
+    case UNDEF * 16 + DYN_DEF:
+    case DYN_UNDEF * 16 + DYN_DEF:
+    case DYN_WEAK_UNDEF * 16 + DYN_DEF:
+      // Use a dynamic definition if we have a reference.
+      return true;
+
+    case WEAK_UNDEF * 16 + DYN_DEF:
+      // When overriding a weak undef by a dynamic definition,
+      // we need to remember that the original undef was weak.
+      *adjust_dyndef = true;
+      return true;
+
+    case COMMON * 16 + DYN_DEF:
+    case WEAK_COMMON * 16 + DYN_DEF:
+    case DYN_COMMON * 16 + DYN_DEF:
+    case DYN_WEAK_COMMON * 16 + DYN_DEF:
+      // Ignore a dynamic definition if we already have a common
+      // definition.
+      return false;
+
+    case DEF * 16 + DYN_WEAK_DEF:
+    case WEAK_DEF * 16 + DYN_WEAK_DEF:
+    case DYN_DEF * 16 + DYN_WEAK_DEF:
+    case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
+      // Ignore a weak dynamic definition if we already have a
+      // definition.
+      return false;
+
+    case UNDEF * 16 + DYN_WEAK_DEF:
+      // When overriding an undef by a dynamic weak definition,
+      // we need to remember that the original undef was not weak.
+      *adjust_dyndef = true;
+      return true;
+
+    case DYN_UNDEF * 16 + DYN_WEAK_DEF:
+    case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
+      // Use a weak dynamic definition if we have a reference.
+      return true;
+
+    case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
+      // When overriding a weak undef by a dynamic definition,
+      // we need to remember that the original undef was weak.
+      *adjust_dyndef = true;
+      return true;
+
+    case COMMON * 16 + DYN_WEAK_DEF:
+    case WEAK_COMMON * 16 + DYN_WEAK_DEF:
+    case DYN_COMMON * 16 + DYN_WEAK_DEF:
+    case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
+      // Ignore a weak dynamic definition if we already have a common
+      // definition.
+      return false;
+
+    case DEF * 16 + UNDEF:
+    case WEAK_DEF * 16 + UNDEF:
+    case UNDEF * 16 + UNDEF:
+      // A new undefined reference tells us nothing.
+      return false;
+
+    case DYN_DEF * 16 + UNDEF:
+    case DYN_WEAK_DEF * 16 + UNDEF:
+      // For a dynamic def, we need to remember which kind of undef we see.
+      *adjust_dyndef = true;
+      return false;
+
+    case WEAK_UNDEF * 16 + UNDEF:
+    case DYN_UNDEF * 16 + UNDEF:
+    case DYN_WEAK_UNDEF * 16 + UNDEF:
+      // A strong undef overrides a dynamic or weak undef.
+      return true;
+
+    case COMMON * 16 + UNDEF:
+    case WEAK_COMMON * 16 + UNDEF:
+    case DYN_COMMON * 16 + UNDEF:
+    case DYN_WEAK_COMMON * 16 + UNDEF:
+      // A new undefined reference tells us nothing.
+      return false;
+
+    case DEF * 16 + WEAK_UNDEF:
+    case WEAK_DEF * 16 + WEAK_UNDEF:
+    case UNDEF * 16 + WEAK_UNDEF:
+    case WEAK_UNDEF * 16 + WEAK_UNDEF:
+    case DYN_UNDEF * 16 + WEAK_UNDEF:
+    case COMMON * 16 + WEAK_UNDEF:
+    case WEAK_COMMON * 16 + WEAK_UNDEF:
+    case DYN_COMMON * 16 + WEAK_UNDEF:
+    case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
+      // A new weak undefined reference tells us nothing unless the
+      // exisiting symbol is a dynamic weak reference.
+      return false;
+
+    case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
+      // A new weak reference overrides an existing dynamic weak reference.
+      // This is necessary because a dynamic weak reference remembers
+      // the old binding, which may not be weak.  If we keeps the existing
+      // dynamic weak reference, the weakness may be dropped in the output.
+      return true;
+
+    case DYN_DEF * 16 + WEAK_UNDEF:
+    case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
+      // For a dynamic def, we need to remember which kind of undef we see.
+      *adjust_dyndef = true;
+      return false;
+
+    case DEF * 16 + DYN_UNDEF:
+    case WEAK_DEF * 16 + DYN_UNDEF:
+    case DYN_DEF * 16 + DYN_UNDEF:
+    case DYN_WEAK_DEF * 16 + DYN_UNDEF:
+    case UNDEF * 16 + DYN_UNDEF:
+    case WEAK_UNDEF * 16 + DYN_UNDEF:
+    case DYN_UNDEF * 16 + DYN_UNDEF:
+    case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
+    case COMMON * 16 + DYN_UNDEF:
+    case WEAK_COMMON * 16 + DYN_UNDEF:
+    case DYN_COMMON * 16 + DYN_UNDEF:
+    case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
+      // A new dynamic undefined reference tells us nothing.
+      return false;
+
+    case DEF * 16 + DYN_WEAK_UNDEF:
+    case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
+    case DYN_DEF * 16 + DYN_WEAK_UNDEF:
+    case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
+    case UNDEF * 16 + DYN_WEAK_UNDEF:
+    case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
+    case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
+    case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
+    case COMMON * 16 + DYN_WEAK_UNDEF:
+    case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
+    case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
+    case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
+      // A new weak dynamic undefined reference tells us nothing.
+      return false;
+
+    case DEF * 16 + COMMON:
+      // A common symbol does not override a definition.
+      if (parameters->options().warn_common())
+	Symbol_table::report_resolve_problem(false,
+					     _("common '%s' overridden by "
+					       "previous definition"),
+					     to, defined, object);
+      return false;
+
+    case WEAK_DEF * 16 + COMMON:
+    case DYN_DEF * 16 + COMMON:
+    case DYN_WEAK_DEF * 16 + COMMON:
+      // A common symbol does override a weak definition or a dynamic
+      // definition.
+      return true;
+
+    case UNDEF * 16 + COMMON:
+    case WEAK_UNDEF * 16 + COMMON:
+    case DYN_UNDEF * 16 + COMMON:
+    case DYN_WEAK_UNDEF * 16 + COMMON:
+      // A common symbol is a definition for a reference.
+      return true;
+
+    case COMMON * 16 + COMMON:
+      // Set the size to the maximum.
+      *adjust_common_sizes = true;
+      return false;
+
+    case WEAK_COMMON * 16 + COMMON:
+      // I'm not sure just what a weak common symbol means, but
+      // presumably it can be overridden by a regular common symbol.
+      return true;
+
+    case DYN_COMMON * 16 + COMMON:
+    case DYN_WEAK_COMMON * 16 + COMMON:
+      // Use the real common symbol, but adjust the size if necessary.
+      *adjust_common_sizes = true;
+      return true;
+
+    case DEF * 16 + WEAK_COMMON:
+    case WEAK_DEF * 16 + WEAK_COMMON:
+    case DYN_DEF * 16 + WEAK_COMMON:
+    case DYN_WEAK_DEF * 16 + WEAK_COMMON:
+      // Whatever a weak common symbol is, it won't override a
+      // definition.
+      return false;
+
+    case UNDEF * 16 + WEAK_COMMON:
+    case WEAK_UNDEF * 16 + WEAK_COMMON:
+    case DYN_UNDEF * 16 + WEAK_COMMON:
+    case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
+      // A weak common symbol is better than an undefined symbol.
+      return true;
+
+    case COMMON * 16 + WEAK_COMMON:
+    case WEAK_COMMON * 16 + WEAK_COMMON:
+    case DYN_COMMON * 16 + WEAK_COMMON:
+    case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
+      // Ignore a weak common symbol in the presence of a real common
+      // symbol.
+      return false;
+
+    case DEF * 16 + DYN_COMMON:
+    case WEAK_DEF * 16 + DYN_COMMON:
+    case DYN_DEF * 16 + DYN_COMMON:
+    case DYN_WEAK_DEF * 16 + DYN_COMMON:
+      // Ignore a dynamic common symbol in the presence of a
+      // definition.
+      return false;
+
+    case UNDEF * 16 + DYN_COMMON:
+    case WEAK_UNDEF * 16 + DYN_COMMON:
+    case DYN_UNDEF * 16 + DYN_COMMON:
+    case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
+      // A dynamic common symbol is a definition of sorts.
+      return true;
+
+    case COMMON * 16 + DYN_COMMON:
+    case WEAK_COMMON * 16 + DYN_COMMON:
+    case DYN_COMMON * 16 + DYN_COMMON:
+    case DYN_WEAK_COMMON * 16 + DYN_COMMON:
+      // Set the size to the maximum.
+      *adjust_common_sizes = true;
+      return false;
+
+    case DEF * 16 + DYN_WEAK_COMMON:
+    case WEAK_DEF * 16 + DYN_WEAK_COMMON:
+    case DYN_DEF * 16 + DYN_WEAK_COMMON:
+    case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
+      // A common symbol is ignored in the face of a definition.
+      return false;
+
+    case UNDEF * 16 + DYN_WEAK_COMMON:
+    case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
+    case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
+    case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
+      // I guess a weak common symbol is better than a definition.
+      return true;
+
+    case COMMON * 16 + DYN_WEAK_COMMON:
+    case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
+    case DYN_COMMON * 16 + DYN_WEAK_COMMON:
+    case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
+      // Set the size to the maximum.
+      *adjust_common_sizes = true;
+      return false;
+
+    default:
+      gold_unreachable();
+    }
+}
+
+// Issue an error or warning due to symbol resolution.  IS_ERROR
+// indicates an error rather than a warning.  MSG is the error
+// message; it is expected to have a %s for the symbol name.  TO is
+// the existing symbol.  DEFINED/OBJECT is where the new symbol was
+// found.
+
+// FIXME: We should have better location information here.  When the
+// symbol is defined, we should be able to pull the location from the
+// debug info if there is any.
+
+void
+Symbol_table::report_resolve_problem(bool is_error, const char* msg,
+				     const Symbol* to, Defined defined,
+				     Object* object)
+{
+  std::string demangled(to->demangled_name());
+  size_t len = strlen(msg) + demangled.length() + 10;
+  char* buf = new char[len];
+  snprintf(buf, len, msg, demangled.c_str());
+
+  const char* objname;
+  switch (defined)
+    {
+    case OBJECT:
+      objname = object->name().c_str();
+      break;
+    case COPY:
+      objname = _("COPY reloc");
+      break;
+    case DEFSYM:
+    case UNDEFINED:
+      objname = _("command line");
+      break;
+    case SCRIPT:
+      objname = _("linker script");
+      break;
+    case PREDEFINED:
+    case INCREMENTAL_BASE:
+      objname = _("linker defined");
+      break;
+    default:
+      gold_unreachable();
+    }
+
+  if (is_error)
+    gold_error("%s: %s", objname, buf);
+  else
+    gold_warning("%s: %s", objname, buf);
+
+  delete[] buf;
+
+  if (to->source() == Symbol::FROM_OBJECT)
+    objname = to->object()->name().c_str();
+  else
+    objname = _("command line");
+  gold_info("%s: %s: previous definition here", program_name, objname);
+}
+
+// A special case of should_override which is only called for a strong
+// defined symbol from a regular object file.  This is used when
+// defining special symbols.
+
+bool
+Symbol_table::should_override_with_special(const Symbol* to,
+					   elfcpp::STT fromtype,
+					   Defined defined)
+{
+  bool adjust_common_sizes;
+  bool adjust_dyn_def;
+  unsigned int frombits = global_flag | regular_flag | def_flag;
+  bool ret = Symbol_table::should_override(to, frombits, fromtype, defined,
+					   NULL, &adjust_common_sizes,
+					   &adjust_dyn_def);
+  gold_assert(!adjust_common_sizes && !adjust_dyn_def);
+  return ret;
+}
+
+// Override symbol base with a special symbol.
+
+void
+Symbol::override_base_with_special(const Symbol* from)
+{
+  bool same_name = this->name_ == from->name_;
+  gold_assert(same_name || this->has_alias());
+
+  // If we are overriding an undef, remember the original binding.
+  if (this->is_undefined())
+    this->set_undef_binding(this->binding_);
+
+  this->source_ = from->source_;
+  switch (from->source_)
+    {
+    case FROM_OBJECT:
+      this->u_.from_object = from->u_.from_object;
+      break;
+    case IN_OUTPUT_DATA:
+      this->u_.in_output_data = from->u_.in_output_data;
+      break;
+    case IN_OUTPUT_SEGMENT:
+      this->u_.in_output_segment = from->u_.in_output_segment;
+      break;
+    case IS_CONSTANT:
+    case IS_UNDEFINED:
+      break;
+    default:
+      gold_unreachable();
+      break;
+    }
+
+  if (same_name)
+    {
+      // When overriding a versioned symbol with a special symbol, we
+      // may be changing the version.  This will happen if we see a
+      // special symbol such as "_end" defined in a shared object with
+      // one version (from a version script), but we want to define it
+      // here with a different version (from a different version
+      // script).
+      this->version_ = from->version_;
+    }
+  this->type_ = from->type_;
+  this->binding_ = from->binding_;
+  this->override_visibility(from->visibility_);
+  this->nonvis_ = from->nonvis_;
+
+  // Special symbols are always considered to be regular symbols.
+  this->in_reg_ = true;
+
+  if (from->needs_dynsym_entry_)
+    this->needs_dynsym_entry_ = true;
+  if (from->needs_dynsym_value_)
+    this->needs_dynsym_value_ = true;
+
+  this->is_predefined_ = from->is_predefined_;
+
+  // We shouldn't see these flags.  If we do, we need to handle them
+  // somehow.
+  gold_assert(!from->is_forwarder_);
+  gold_assert(!from->has_plt_offset());
+  gold_assert(!from->has_warning_);
+  gold_assert(!from->is_copied_from_dynobj_);
+  gold_assert(!from->is_forced_local_);
+}
+
+// Override a symbol with a special symbol.
+
+template<int size>
+void
+Sized_symbol<size>::override_with_special(const Sized_symbol<size>* from)
+{
+  this->override_base_with_special(from);
+  this->value_ = from->value_;
+  this->symsize_ = from->symsize_;
+}
+
+// Override TOSYM with the special symbol FROMSYM.  This handles all
+// aliases of TOSYM.
+
+template<int size>
+void
+Symbol_table::override_with_special(Sized_symbol<size>* tosym,
+				    const Sized_symbol<size>* fromsym)
+{
+  tosym->override_with_special(fromsym);
+  if (tosym->has_alias())
+    {
+      Symbol* sym = this->weak_aliases_[tosym];
+      gold_assert(sym != NULL);
+      Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
+      do
+	{
+	  ssym->override_with_special(fromsym);
+	  sym = this->weak_aliases_[ssym];
+	  gold_assert(sym != NULL);
+	  ssym = this->get_sized_symbol<size>(sym);
+	}
+      while (ssym != tosym);
+    }
+  if (tosym->binding() == elfcpp::STB_LOCAL
+      || ((tosym->visibility() == elfcpp::STV_HIDDEN
+	   || tosym->visibility() == elfcpp::STV_INTERNAL)
+	  && (tosym->binding() == elfcpp::STB_GLOBAL
+	      || tosym->binding() == elfcpp::STB_GNU_UNIQUE
+	      || tosym->binding() == elfcpp::STB_WEAK)
+	  && !parameters->options().relocatable()))
+    this->force_local(tosym);
+}
+
+// Instantiate the templates we need.  We could use the configure
+// script to restrict this to only the ones needed for implemented
+// targets.
+
+// We have to instantiate both big and little endian versions because
+// these are used by other templates that depends on size only.
+
+#if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
+template
+void
+Symbol_table::resolve<32, false>(
+    Sized_symbol<32>* to,
+    const elfcpp::Sym<32, false>& sym,
+    unsigned int st_shndx,
+    bool is_ordinary,
+    unsigned int orig_st_shndx,
+    Object* object,
+    const char* version);
+
+template
+void
+Symbol_table::resolve<32, true>(
+    Sized_symbol<32>* to,
+    const elfcpp::Sym<32, true>& sym,
+    unsigned int st_shndx,
+    bool is_ordinary,
+    unsigned int orig_st_shndx,
+    Object* object,
+    const char* version);
+#endif
+
+#if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
+template
+void
+Symbol_table::resolve<64, false>(
+    Sized_symbol<64>* to,
+    const elfcpp::Sym<64, false>& sym,
+    unsigned int st_shndx,
+    bool is_ordinary,
+    unsigned int orig_st_shndx,
+    Object* object,
+    const char* version);
+
+template
+void
+Symbol_table::resolve<64, true>(
+    Sized_symbol<64>* to,
+    const elfcpp::Sym<64, true>& sym,
+    unsigned int st_shndx,
+    bool is_ordinary,
+    unsigned int orig_st_shndx,
+    Object* object,
+    const char* version);
+#endif
+
+#if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
+template
+void
+Symbol_table::override_with_special<32>(Sized_symbol<32>*,
+					const Sized_symbol<32>*);
+#endif
+
+#if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
+template
+void
+Symbol_table::override_with_special<64>(Sized_symbol<64>*,
+					const Sized_symbol<64>*);
+#endif
+
+} // End namespace gold.