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 #include "llvm/Support/Compiler.h" 16 17 namespace lld::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 *> getSymbols() const { return symVector; } 37 38 void wrap(Symbol *sym, Symbol *real, Symbol *wrap); 39 40 Symbol *insert(StringRef name); 41 42 template <typename T> Symbol *addSymbol(const T &newSym) { 43 Symbol *sym = insert(newSym.getName()); 44 sym->resolve(newSym); 45 return sym; 46 } 47 Symbol *addAndCheckDuplicate(const Defined &newSym); 48 49 void scanVersionScript(); 50 51 Symbol *find(StringRef name); 52 53 void handleDynamicList(); 54 55 // Set of .so files to not link the same shared object file more than once. 56 llvm::DenseMap<llvm::CachedHashStringRef, SharedFile *> soNames; 57 58 // Comdat groups define "link once" sections. If two comdat groups have the 59 // same name, only one of them is linked, and the other is ignored. This map 60 // is used to uniquify them. 61 llvm::DenseMap<llvm::CachedHashStringRef, const InputFile *> comdatGroups; 62 63 private: 64 SmallVector<Symbol *, 0> findByVersion(SymbolVersion ver); 65 SmallVector<Symbol *, 0> findAllByVersion(SymbolVersion ver, 66 bool includeNonDefault); 67 68 llvm::StringMap<SmallVector<Symbol *, 0>> &getDemangledSyms(); 69 bool assignExactVersion(SymbolVersion ver, uint16_t versionId, 70 StringRef versionName, bool includeNonDefault); 71 void assignWildcardVersion(SymbolVersion ver, uint16_t versionId, 72 bool includeNonDefault); 73 74 // The order the global symbols are in is not defined. We can use an arbitrary 75 // order, but it has to be reproducible. That is true even when cross linking. 76 // The default hashing of StringRef produces different results on 32 and 64 77 // bit systems so we use a map to a vector. That is arbitrary, deterministic 78 // but a bit inefficient. 79 // FIXME: Experiment with passing in a custom hashing or sorting the symbols 80 // once symbol resolution is finished. 81 llvm::DenseMap<llvm::CachedHashStringRef, int> symMap; 82 SmallVector<Symbol *, 0> symVector; 83 84 // A map from demangled symbol names to their symbol objects. 85 // This mapping is 1:N because two symbols with different versions 86 // can have the same name. We use this map to handle "extern C++ {}" 87 // directive in version scripts. 88 std::optional<llvm::StringMap<SmallVector<Symbol *, 0>>> demangledSyms; 89 }; 90 91 LLVM_LIBRARY_VISIBILITY extern SymbolTable symtab; 92 93 } // namespace lld::elf 94 95 #endif 96