SymbolTable.h
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//===- SymbolTable.h --------------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef LLD_ELF_SYMBOL_TABLE_H
#define LLD_ELF_SYMBOL_TABLE_H
#include "InputFiles.h"
#include "Symbols.h"
#include "lld/Common/Strings.h"
#include "llvm/ADT/CachedHashString.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
namespace lld {
namespace elf {
// SymbolTable is a bucket of all known symbols, including defined,
// undefined, or lazy symbols (the last one is symbols in archive
// files whose archive members are not yet loaded).
//
// We put all symbols of all files to a SymbolTable, and the
// SymbolTable selects the "best" symbols if there are name
// conflicts. For example, obviously, a defined symbol is better than
// an undefined symbol. Or, if there's a conflict between a lazy and a
// undefined, it'll read an archive member to read a real definition
// to replace the lazy symbol. The logic is implemented in the
// add*() functions, which are called by input files as they are parsed. There
// is one add* function per symbol type.
class SymbolTable {
struct FilterOutPlaceholder {
bool operator()(Symbol *S) const { return !S->isPlaceholder(); }
};
using iterator = llvm::filter_iterator<std::vector<Symbol *>::const_iterator,
FilterOutPlaceholder>;
public:
llvm::iterator_range<iterator> symbols() const {
return llvm::make_filter_range(symVector, FilterOutPlaceholder());
}
void wrap(Symbol *sym, Symbol *real, Symbol *wrap);
Symbol *insert(StringRef name);
Symbol *addSymbol(const Symbol &newSym);
void scanVersionScript();
Symbol *find(StringRef name);
void handleDynamicList();
// Set of .so files to not link the same shared object file more than once.
llvm::DenseMap<StringRef, SharedFile *> soNames;
// Comdat groups define "link once" sections. If two comdat groups have the
// same name, only one of them is linked, and the other is ignored. This map
// is used to uniquify them.
llvm::DenseMap<llvm::CachedHashStringRef, const InputFile *> comdatGroups;
private:
std::vector<Symbol *> findByVersion(SymbolVersion ver);
std::vector<Symbol *> findAllByVersion(SymbolVersion ver);
llvm::StringMap<std::vector<Symbol *>> &getDemangledSyms();
void assignExactVersion(SymbolVersion ver, uint16_t versionId,
StringRef versionName);
void assignWildcardVersion(SymbolVersion ver, uint16_t versionId);
// The order the global symbols are in is not defined. We can use an arbitrary
// order, but it has to be reproducible. That is true even when cross linking.
// The default hashing of StringRef produces different results on 32 and 64
// bit systems so we use a map to a vector. That is arbitrary, deterministic
// but a bit inefficient.
// FIXME: Experiment with passing in a custom hashing or sorting the symbols
// once symbol resolution is finished.
llvm::DenseMap<llvm::CachedHashStringRef, int> symMap;
std::vector<Symbol *> symVector;
// A map from demangled symbol names to their symbol objects.
// This mapping is 1:N because two symbols with different versions
// can have the same name. We use this map to handle "extern C++ {}"
// directive in version scripts.
llvm::Optional<llvm::StringMap<std::vector<Symbol *>>> demangledSyms;
};
extern SymbolTable *symtab;
} // namespace elf
} // namespace lld
#endif