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https://sourceware.org/git/binutils-gdb.git
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537 lines
15 KiB
C++
537 lines
15 KiB
C++
// resolve.cc -- symbol resolution for gold
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#include "gold.h"
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#include "elfcpp.h"
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#include "target.h"
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#include "object.h"
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#include "symtab.h"
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namespace gold
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{
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// Symbol methods used in this file.
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// Override the fields in Symbol.
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template<int size, bool big_endian>
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void
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Symbol::override_base(const elfcpp::Sym<size, big_endian>& sym,
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Object* object)
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{
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assert(this->source_ == FROM_OBJECT);
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this->u_.from_object.object = object;
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// FIXME: Handle SHN_XINDEX.
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this->u_.from_object.shnum = sym.get_st_shndx();
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this->type_ = sym.get_st_type();
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this->binding_ = sym.get_st_bind();
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this->visibility_ = sym.get_st_visibility();
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this->nonvis_ = sym.get_st_nonvis();
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}
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// Override the fields in Sized_symbol.
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template<int size>
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template<bool big_endian>
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void
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Sized_symbol<size>::override(const elfcpp::Sym<size, big_endian>& sym,
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Object* object)
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{
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this->override_base(sym, object);
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this->value_ = sym.get_st_value();
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this->symsize_ = sym.get_st_size();
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}
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// Resolve a symbol. This is called the second and subsequent times
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// we see a symbol. TO is the pre-existing symbol. SYM is the new
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// symbol, seen in OBJECT.
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template<int size, bool big_endian>
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void
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Symbol_table::resolve(Sized_symbol<size>* to,
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const elfcpp::Sym<size, big_endian>& sym,
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Object* object)
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{
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if (object->target()->has_resolve())
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{
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Sized_target<size, big_endian>* sized_target;
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sized_target = object->sized_target
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SELECT_SIZE_ENDIAN_NAME(size, big_endian) (
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SELECT_SIZE_ENDIAN_ONLY(size, big_endian));
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sized_target->resolve(to, sym, object);
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return;
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}
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// Build a little code for each symbol.
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// Bit 0: 0 for global, 1 for weak.
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// Bit 1: 0 for regular object, 1 for shared object
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// Bits 2-3: 0 for normal, 1 for undefined, 2 for common
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// This gives us values from 0 to 11:
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enum
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{
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DEF = 0,
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WEAK_DEF = 1,
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DYN_DEF = 2,
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DYN_WEAK_DEF = 3,
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UNDEF = 4,
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WEAK_UNDEF = 5,
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DYN_UNDEF = 6,
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DYN_WEAK_UNDEF = 7,
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COMMON = 8,
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WEAK_COMMON = 9,
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DYN_COMMON = 10,
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DYN_WEAK_COMMON = 11
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};
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int tobits;
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switch (to->binding())
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{
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case elfcpp::STB_GLOBAL:
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tobits = 0;
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break;
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case elfcpp::STB_WEAK:
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tobits = 1;
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break;
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case elfcpp::STB_LOCAL:
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// We should only see externally visible symbols in the symbol
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// table.
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abort();
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default:
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// Any target which wants to handle STB_LOOS, etc., needs to
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// define a resolve method.
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abort();
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}
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if (to->object() != NULL && to->object()->is_dynamic())
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tobits |= (1 << 1);
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switch (to->shnum())
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{
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case elfcpp::SHN_UNDEF:
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tobits |= (1 << 2);
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break;
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case elfcpp::SHN_COMMON:
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tobits |= (2 << 2);
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break;
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default:
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if (to->type() == elfcpp::STT_COMMON)
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tobits |= (2 << 2);
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break;
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}
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int frombits;
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switch (sym.get_st_bind())
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{
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case elfcpp::STB_GLOBAL:
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frombits = 0;
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break;
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case elfcpp::STB_WEAK:
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frombits = 1;
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break;
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case elfcpp::STB_LOCAL:
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fprintf(stderr,
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_("%s: %s: invalid STB_LOCAL symbol %s in external symbols\n"),
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program_name, object->name().c_str(), to->name());
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gold_exit(false);
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default:
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fprintf(stderr,
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_("%s: %s: unsupported symbol binding %d for symbol %s\n"),
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program_name, object->name().c_str(),
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static_cast<int>(sym.get_st_bind()), to->name());
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gold_exit(false);
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}
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if (object->is_dynamic())
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{
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frombits |= (1 << 1);
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// Record that we've seen this symbol in a dynamic object.
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to->set_in_dyn();
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}
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switch (sym.get_st_shndx())
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{
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case elfcpp::SHN_UNDEF:
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frombits |= (1 << 2);
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break;
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case elfcpp::SHN_COMMON:
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frombits |= (2 << 2);
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break;
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default:
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if (sym.get_st_type() == elfcpp::STT_COMMON)
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frombits |= (2 << 2);
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break;
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}
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// FIXME: Warn if either but not both of TO and SYM are STT_TLS.
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// We use a giant switch table for symbol resolution. This code is
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// unwieldy, but: 1) it is efficient; 2) we definitely handle all
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// cases; 3) it is easy to change the handling of a particular case.
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// The alternative would be a series of conditionals, but it is easy
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// to get the ordering wrong. This could also be done as a table,
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// but that is no easier to understand than this large switch
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// statement.
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switch (tobits * 16 + frombits)
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{
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case DEF * 16 + DEF:
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// Two definitions of the same symbol.
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fprintf(stderr, "%s: %s: multiple definition of %s\n",
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program_name, object->name().c_str(), to->name());
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// FIXME: Report locations. Record that we have seen an error.
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return;
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case WEAK_DEF * 16 + DEF:
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// We've seen a weak definition, and now we see a strong
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// definition. In the original SVR4 linker, this was treated as
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// a multiple definition error. In the Solaris linker and the
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// GNU linker, a weak definition followed by a regular
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// definition causes the weak definition to be overridden. We
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// are currently compatible with the GNU linker. In the future
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// we should add a target specific option to change this.
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// FIXME.
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to->override(sym, object);
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return;
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case DYN_DEF * 16 + DEF:
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case DYN_WEAK_DEF * 16 + DEF:
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// We've seen a definition in a dynamic object, and now we see a
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// definition in a regular object. The definition in the
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// regular object overrides the definition in the dynamic
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// object.
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to->override(sym, object);
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return;
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case UNDEF * 16 + DEF:
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case WEAK_UNDEF * 16 + DEF:
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case DYN_UNDEF * 16 + DEF:
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case DYN_WEAK_UNDEF * 16 + DEF:
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// We've seen an undefined reference, and now we see a
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// definition. We use the definition.
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to->override(sym, object);
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return;
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case COMMON * 16 + DEF:
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case WEAK_COMMON * 16 + DEF:
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case DYN_COMMON * 16 + DEF:
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case DYN_WEAK_COMMON * 16 + DEF:
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// We've seen a common symbol and now we see a definition. The
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// definition overrides. FIXME: We should optionally issue a
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// warning.
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to->override(sym, object);
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return;
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case DEF * 16 + WEAK_DEF:
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case WEAK_DEF * 16 + WEAK_DEF:
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// We've seen a definition and now we see a weak definition. We
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// ignore the new weak definition.
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return;
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case DYN_DEF * 16 + WEAK_DEF:
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case DYN_WEAK_DEF * 16 + WEAK_DEF:
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// We've seen a dynamic definition and now we see a regular weak
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// definition. The regular weak definition overrides.
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to->override(sym, object);
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return;
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case UNDEF * 16 + WEAK_DEF:
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case WEAK_UNDEF * 16 + WEAK_DEF:
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case DYN_UNDEF * 16 + WEAK_DEF:
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case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
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// A weak definition of a currently undefined symbol.
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to->override(sym, object);
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return;
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case COMMON * 16 + WEAK_DEF:
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case WEAK_COMMON * 16 + WEAK_DEF:
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// A weak definition does not override a common definition.
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return;
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case DYN_COMMON * 16 + WEAK_DEF:
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case DYN_WEAK_COMMON * 16 + WEAK_DEF:
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// A weak definition does override a definition in a dynamic
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// object. FIXME: We should optionally issue a warning.
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to->override(sym, object);
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return;
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case DEF * 16 + DYN_DEF:
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case WEAK_DEF * 16 + DYN_DEF:
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case DYN_DEF * 16 + DYN_DEF:
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case DYN_WEAK_DEF * 16 + DYN_DEF:
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// Ignore a dynamic definition if we already have a definition.
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return;
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case UNDEF * 16 + DYN_DEF:
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case WEAK_UNDEF * 16 + DYN_DEF:
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case DYN_UNDEF * 16 + DYN_DEF:
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case DYN_WEAK_UNDEF * 16 + DYN_DEF:
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// Use a dynamic definition if we have a reference.
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to->override(sym, object);
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return;
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case COMMON * 16 + DYN_DEF:
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case WEAK_COMMON * 16 + DYN_DEF:
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case DYN_COMMON * 16 + DYN_DEF:
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case DYN_WEAK_COMMON * 16 + DYN_DEF:
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// Ignore a dynamic definition if we already have a common
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// definition.
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return;
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case DEF * 16 + DYN_WEAK_DEF:
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case WEAK_DEF * 16 + DYN_WEAK_DEF:
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case DYN_DEF * 16 + DYN_WEAK_DEF:
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case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
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// Ignore a weak dynamic definition if we already have a
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// definition.
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return;
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case UNDEF * 16 + DYN_WEAK_DEF:
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case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
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case DYN_UNDEF * 16 + DYN_WEAK_DEF:
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case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
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// Use a weak dynamic definition if we have a reference.
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to->override(sym, object);
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return;
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case COMMON * 16 + DYN_WEAK_DEF:
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case WEAK_COMMON * 16 + DYN_WEAK_DEF:
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case DYN_COMMON * 16 + DYN_WEAK_DEF:
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case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
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// Ignore a weak dynamic definition if we already have a common
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// definition.
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return;
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case DEF * 16 + UNDEF:
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case WEAK_DEF * 16 + UNDEF:
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case DYN_DEF * 16 + UNDEF:
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case DYN_WEAK_DEF * 16 + UNDEF:
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case UNDEF * 16 + UNDEF:
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// A new undefined reference tells us nothing.
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return;
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case WEAK_UNDEF * 16 + UNDEF:
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case DYN_UNDEF * 16 + UNDEF:
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case DYN_WEAK_UNDEF * 16 + UNDEF:
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// A strong undef overrides a dynamic or weak undef.
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to->override(sym, object);
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return;
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case COMMON * 16 + UNDEF:
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case WEAK_COMMON * 16 + UNDEF:
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case DYN_COMMON * 16 + UNDEF:
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case DYN_WEAK_COMMON * 16 + UNDEF:
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// A new undefined reference tells us nothing.
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return;
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case DEF * 16 + WEAK_UNDEF:
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case WEAK_DEF * 16 + WEAK_UNDEF:
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case DYN_DEF * 16 + WEAK_UNDEF:
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case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
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case UNDEF * 16 + WEAK_UNDEF:
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case WEAK_UNDEF * 16 + WEAK_UNDEF:
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case DYN_UNDEF * 16 + WEAK_UNDEF:
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case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
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case COMMON * 16 + WEAK_UNDEF:
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case WEAK_COMMON * 16 + WEAK_UNDEF:
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case DYN_COMMON * 16 + WEAK_UNDEF:
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case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
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// A new weak undefined reference tells us nothing.
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return;
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case DEF * 16 + DYN_UNDEF:
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case WEAK_DEF * 16 + DYN_UNDEF:
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case DYN_DEF * 16 + DYN_UNDEF:
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case DYN_WEAK_DEF * 16 + DYN_UNDEF:
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case UNDEF * 16 + DYN_UNDEF:
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case WEAK_UNDEF * 16 + DYN_UNDEF:
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case DYN_UNDEF * 16 + DYN_UNDEF:
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case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
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case COMMON * 16 + DYN_UNDEF:
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case WEAK_COMMON * 16 + DYN_UNDEF:
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case DYN_COMMON * 16 + DYN_UNDEF:
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case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
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// A new dynamic undefined reference tells us nothing.
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return;
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case DEF * 16 + DYN_WEAK_UNDEF:
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case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
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case DYN_DEF * 16 + DYN_WEAK_UNDEF:
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case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
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case UNDEF * 16 + DYN_WEAK_UNDEF:
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case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
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case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
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case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
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case COMMON * 16 + DYN_WEAK_UNDEF:
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case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
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case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
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case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
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// A new weak dynamic undefined reference tells us nothing.
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return;
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case DEF * 16 + COMMON:
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// A common symbol does not override a definition.
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return;
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case WEAK_DEF * 16 + COMMON:
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case DYN_DEF * 16 + COMMON:
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case DYN_WEAK_DEF * 16 + COMMON:
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// A common symbol does override a weak definition or a dynamic
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// definition.
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to->override(sym, object);
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return;
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case UNDEF * 16 + COMMON:
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case WEAK_UNDEF * 16 + COMMON:
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case DYN_UNDEF * 16 + COMMON:
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case DYN_WEAK_UNDEF * 16 + COMMON:
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// A common symbol is a definition for a reference.
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to->override(sym, object);
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return;
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case COMMON * 16 + COMMON:
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// Set the size to the maximum.
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if (sym.get_st_size() > to->symsize())
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to->set_symsize(sym.get_st_size());
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return;
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case WEAK_COMMON * 16 + COMMON:
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// I'm not sure just what a weak common symbol means, but
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// presumably it can be overridden by a regular common symbol.
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to->override(sym, object);
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return;
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case DYN_COMMON * 16 + COMMON:
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case DYN_WEAK_COMMON * 16 + COMMON:
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{
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// Use the real common symbol, but adjust the size if necessary.
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typename Sized_symbol<size>::Size_type symsize = to->symsize();
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to->override(sym, object);
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if (to->symsize() < symsize)
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to->set_symsize(symsize);
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}
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return;
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case DEF * 16 + WEAK_COMMON:
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case WEAK_DEF * 16 + WEAK_COMMON:
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case DYN_DEF * 16 + WEAK_COMMON:
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case DYN_WEAK_DEF * 16 + WEAK_COMMON:
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// Whatever a weak common symbol is, it won't override a
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// definition.
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return;
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case UNDEF * 16 + WEAK_COMMON:
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case WEAK_UNDEF * 16 + WEAK_COMMON:
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case DYN_UNDEF * 16 + WEAK_COMMON:
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case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
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// A weak common symbol is better than an undefined symbol.
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to->override(sym, object);
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return;
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case COMMON * 16 + WEAK_COMMON:
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case WEAK_COMMON * 16 + WEAK_COMMON:
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case DYN_COMMON * 16 + WEAK_COMMON:
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case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
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// Ignore a weak common symbol in the presence of a real common
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// symbol.
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return;
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case DEF * 16 + DYN_COMMON:
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case WEAK_DEF * 16 + DYN_COMMON:
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case DYN_DEF * 16 + DYN_COMMON:
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case DYN_WEAK_DEF * 16 + DYN_COMMON:
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// Ignore a dynamic common symbol in the presence of a
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// definition.
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return;
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case UNDEF * 16 + DYN_COMMON:
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case WEAK_UNDEF * 16 + DYN_COMMON:
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case DYN_UNDEF * 16 + DYN_COMMON:
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case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
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// A dynamic common symbol is a definition of sorts.
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to->override(sym, object);
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return;
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case COMMON * 16 + DYN_COMMON:
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case WEAK_COMMON * 16 + DYN_COMMON:
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case DYN_COMMON * 16 + DYN_COMMON:
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case DYN_WEAK_COMMON * 16 + DYN_COMMON:
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// Set the size to the maximum.
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if (sym.get_st_size() > to->symsize())
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to->set_symsize(sym.get_st_size());
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return;
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case DEF * 16 + DYN_WEAK_COMMON:
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case WEAK_DEF * 16 + DYN_WEAK_COMMON:
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case DYN_DEF * 16 + DYN_WEAK_COMMON:
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case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
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// A common symbol is ignored in the face of a definition.
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return;
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case UNDEF * 16 + DYN_WEAK_COMMON:
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case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
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case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
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case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
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// I guess a weak common symbol is better than a definition.
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to->override(sym, object);
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return;
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case COMMON * 16 + DYN_WEAK_COMMON:
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case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
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case DYN_COMMON * 16 + DYN_WEAK_COMMON:
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case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
|
|
// Set the size to the maximum.
|
|
if (sym.get_st_size() > to->symsize())
|
|
to->set_symsize(sym.get_st_size());
|
|
return;
|
|
|
|
default:
|
|
abort();
|
|
}
|
|
}
|
|
|
|
// Instantiate the templates we need. We could use the configure
|
|
// script to restrict this to only the ones needed for implemented
|
|
// targets.
|
|
|
|
template
|
|
void
|
|
Symbol_table::resolve<32, true>(
|
|
Sized_symbol<32>* to,
|
|
const elfcpp::Sym<32, true>& sym,
|
|
Object* object);
|
|
|
|
template
|
|
void
|
|
Symbol_table::resolve<32, false>(
|
|
Sized_symbol<32>* to,
|
|
const elfcpp::Sym<32, false>& sym,
|
|
Object* object);
|
|
|
|
template
|
|
void
|
|
Symbol_table::resolve<64, true>(
|
|
Sized_symbol<64>* to,
|
|
const elfcpp::Sym<64, true>& sym,
|
|
Object* object);
|
|
|
|
template
|
|
void
|
|
Symbol_table::resolve<64, false>(
|
|
Sized_symbol<64>* to,
|
|
const elfcpp::Sym<64, false>& sym,
|
|
Object* object);
|
|
|
|
} // End namespace gold.
|