lld/COFF/SymbolTable.h

   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_COFF_SYMBOL_TABLE_H
  10 #define LLD_COFF_SYMBOL_TABLE_H
  11
  12 #include "InputFiles.h"
  13 #include "LTO.h"
  14 #include "llvm/ADT/CachedHashString.h"
  15 #include "llvm/ADT/DenseMap.h"
  16 #include "llvm/ADT/DenseMapInfo.h"
  17 #include "llvm/Support/raw_ostream.h"
  18
  19 namespace llvm {
  20 struct LTOCodeGenerator;
  21 }
  22
  23 namespace lld::coff {
  24
  25 class Chunk;
  26 class CommonChunk;
  27 class COFFLinkerContext;
  28 class Defined;
  29 class DefinedAbsolute;
  30 class DefinedRegular;
  31 class LazyArchive;
  32 class SectionChunk;
  33 class Symbol;
  34
  35 // SymbolTable is a bucket of all known symbols, including defined,
  36 // undefined, or lazy symbols (the last one is symbols in archive
  37 // files whose archive members are not yet loaded).
  38 //
  39 // We put all symbols of all files to a SymbolTable, and the
  40 // SymbolTable selects the "best" symbols if there are name
  41 // conflicts. For example, obviously, a defined symbol is better than
  42 // an undefined symbol. Or, if there's a conflict between a lazy and a
  43 // undefined, it'll read an archive member to read a real definition
  44 // to replace the lazy symbol. The logic is implemented in the
  45 // add*() functions, which are called by input files as they are parsed.
  46 // There is one add* function per symbol type.
  47 class SymbolTable {
  48 public:
  49   SymbolTable(COFFLinkerContext &c) : ctx(c) {}
  50
  51   void addFile(InputFile *file);
  52
  53   // Emit errors for symbols that cannot be resolved.
  54   void reportUnresolvable();
  55
  56   // Try to resolve any undefined symbols and update the symbol table
  57   // accordingly, then print an error message for any remaining undefined
  58   // symbols and warn about imported local symbols.
  59   void resolveRemainingUndefines();
  60
  61   // Load lazy objects that are needed for MinGW automatic import and for
  62   // doing stdcall fixups.
  63   void loadMinGWSymbols();
  64   bool handleMinGWAutomaticImport(Symbol *sym, StringRef name);
  65
  66   // Returns a list of chunks of selected symbols.
  67   std::vector<Chunk *> getChunks() const;
  68
  69   // Returns a symbol for a given name. Returns a nullptr if not found.
  70   Symbol *find(StringRef name) const;
  71   Symbol *findUnderscore(StringRef name) const;
  72
  73   // Occasionally we have to resolve an undefined symbol to its
  74   // mangled symbol. This function tries to find a mangled name
  75   // for U from the symbol table, and if found, set the symbol as
  76   // a weak alias for U.
  77   Symbol *findMangle(StringRef name);
  78
  79   // Build a set of COFF objects representing the combined contents of
  80   // BitcodeFiles and add them to the symbol table. Called after all files are
  81   // added and before the writer writes results to a file.
  82   void compileBitcodeFiles();
  83
  84   // Creates an Undefined symbol for a given name.
  85   Symbol *addUndefined(StringRef name);
  86
  87   Symbol *addSynthetic(StringRef n, Chunk *c);
  88   Symbol *addAbsolute(StringRef n, uint64_t va);
  89
  90   Symbol *addUndefined(StringRef name, InputFile *f, bool isWeakAlias);
  91   void addLazyArchive(ArchiveFile *f, const Archive::Symbol &sym);
  92   void addLazyObject(InputFile *f, StringRef n);
  93   void addLazyDLLSymbol(DLLFile *f, DLLFile::Symbol *sym, StringRef n);
  94   Symbol *addAbsolute(StringRef n, COFFSymbolRef s);
  95   Symbol *addRegular(InputFile *f, StringRef n,
  96                      const llvm::object::coff_symbol_generic *s = nullptr,
  97                      SectionChunk *c = nullptr, uint32_t sectionOffset = 0,
  98                      bool isWeak = false);
  99   std::pair<DefinedRegular *, bool>
 100   addComdat(InputFile *f, StringRef n,
 101             const llvm::object::coff_symbol_generic *s = nullptr);
 102   Symbol *addCommon(InputFile *f, StringRef n, uint64_t size,
 103                     const llvm::object::coff_symbol_generic *s = nullptr,
 104                     CommonChunk *c = nullptr);
 105   Symbol *addImportData(StringRef n, ImportFile *f);
 106   Symbol *addImportThunk(StringRef name, DefinedImportData *s,
 107                          uint16_t machine);
 108   void addLibcall(StringRef name);
 109
 110   void reportDuplicate(Symbol *existing, InputFile *newFile,
 111                        SectionChunk *newSc = nullptr,
 112                        uint32_t newSectionOffset = 0);
 113
 114   // A list of chunks which to be added to .rdata.
 115   std::vector<Chunk *> localImportChunks;
 116
 117   // Iterates symbols in non-determinstic hash table order.
 118   template <typename T> void forEachSymbol(T callback) {
 119     for (auto &pair : symMap)
 120       callback(pair.second);
 121   }
 122
 123 private:
 124   /// Given a name without "__imp_" prefix, returns a defined symbol
 125   /// with the "__imp_" prefix, if it exists.
 126   Defined *impSymbol(StringRef name);
 127   /// Inserts symbol if not already present.
 128   std::pair<Symbol *, bool> insert(StringRef name);
 129   /// Same as insert(Name), but also sets isUsedInRegularObj.
 130   std::pair<Symbol *, bool> insert(StringRef name, InputFile *f);
 131
 132   std::vector<Symbol *> getSymsWithPrefix(StringRef prefix);
 133
 134   llvm::DenseMap<llvm::CachedHashStringRef, Symbol *> symMap;
 135   std::unique_ptr<BitcodeCompiler> lto;
 136
 137   COFFLinkerContext &ctx;
 138 };
 139
 140 std::vector<std::string> getSymbolLocations(ObjFile *file, uint32_t symIndex);
 141
 142 StringRef ltrim1(StringRef s, const char *chars);
 143
 144 } // namespace lld::coff
 145
 146 #endif