1 //===- SymbolTable.h --------------------------------------------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef LLD_ELF_SYMBOL_TABLE_H 10 #define LLD_ELF_SYMBOL_TABLE_H 11 12 #include "Symbols.h" 13 #include "llvm/ADT/CachedHashString.h" 14 #include "llvm/ADT/DenseMap.h" 15 16 namespace lld { 17 namespace elf { 18 19 class InputFile; 20 class SharedFile; 21 22 // SymbolTable is a bucket of all known symbols, including defined, 23 // undefined, or lazy symbols (the last one is symbols in archive 24 // files whose archive members are not yet loaded). 25 // 26 // We put all symbols of all files to a SymbolTable, and the 27 // SymbolTable selects the "best" symbols if there are name 28 // conflicts. For example, obviously, a defined symbol is better than 29 // an undefined symbol. Or, if there's a conflict between a lazy and a 30 // undefined, it'll read an archive member to read a real definition 31 // to replace the lazy symbol. The logic is implemented in the 32 // add*() functions, which are called by input files as they are parsed. There 33 // is one add* function per symbol type. 34 class SymbolTable { 35 public: 36 ArrayRef<Symbol *> symbols() const { return symVector; } 37 38 void wrap(Symbol *sym, Symbol *real, Symbol *wrap); 39 40 Symbol *insert(StringRef name); 41 42 Symbol *addSymbol(const Symbol &newSym); 43 Symbol *addAndCheckDuplicate(const Defined &newSym); 44 45 void scanVersionScript(); 46 47 Symbol *find(StringRef name); 48 49 void handleDynamicList(); 50 51 // Set of .so files to not link the same shared object file more than once. 52 llvm::DenseMap<llvm::CachedHashStringRef, SharedFile *> soNames; 53 54 // Comdat groups define "link once" sections. If two comdat groups have the 55 // same name, only one of them is linked, and the other is ignored. This map 56 // is used to uniquify them. 57 llvm::DenseMap<llvm::CachedHashStringRef, const InputFile *> comdatGroups; 58 59 private: 60 SmallVector<Symbol *, 0> findByVersion(SymbolVersion ver); 61 SmallVector<Symbol *, 0> findAllByVersion(SymbolVersion ver, 62 bool includeNonDefault); 63 64 llvm::StringMap<SmallVector<Symbol *, 0>> &getDemangledSyms(); 65 bool assignExactVersion(SymbolVersion ver, uint16_t versionId, 66 StringRef versionName, bool includeNonDefault); 67 void assignWildcardVersion(SymbolVersion ver, uint16_t versionId, 68 bool includeNonDefault); 69 70 // The order the global symbols are in is not defined. We can use an arbitrary 71 // order, but it has to be reproducible. That is true even when cross linking. 72 // The default hashing of StringRef produces different results on 32 and 64 73 // bit systems so we use a map to a vector. That is arbitrary, deterministic 74 // but a bit inefficient. 75 // FIXME: Experiment with passing in a custom hashing or sorting the symbols 76 // once symbol resolution is finished. 77 llvm::DenseMap<llvm::CachedHashStringRef, int> symMap; 78 SmallVector<Symbol *, 0> symVector; 79 80 // A map from demangled symbol names to their symbol objects. 81 // This mapping is 1:N because two symbols with different versions 82 // can have the same name. We use this map to handle "extern C++ {}" 83 // directive in version scripts. 84 llvm::Optional<llvm::StringMap<SmallVector<Symbol *, 0>>> demangledSyms; 85 }; 86 87 extern std::unique_ptr<SymbolTable> symtab; 88 89 } // namespace elf 90 } // namespace lld 91 92 #endif 93