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 {
  24 namespace coff {
  25
  26 class Chunk;
  27 class CommonChunk;
  28 class COFFLinkerContext;
  29 class Defined;
  30 class DefinedAbsolute;
  31 class DefinedRegular;
  32 class DefinedRelative;
  33 class LazyArchive;
  34 class SectionChunk;
  35 class Symbol;
  36
  37 // SymbolTable is a bucket of all known symbols, including defined,
  38 // undefined, or lazy symbols (the last one is symbols in archive
  39 // files whose archive members are not yet loaded).
  40 //
  41 // We put all symbols of all files to a SymbolTable, and the
  42 // SymbolTable selects the "best" symbols if there are name
  43 // conflicts. For example, obviously, a defined symbol is better than
  44 // an undefined symbol. Or, if there's a conflict between a lazy and a
  45 // undefined, it'll read an archive member to read a real definition
  46 // to replace the lazy symbol. The logic is implemented in the
  47 // add*() functions, which are called by input files as they are parsed.
  48 // There is one add* function per symbol type.
  49 class SymbolTable {
  50 public:
  51   SymbolTable(COFFLinkerContext &ctx) : ctx(ctx) {}
  52
  53   void addFile(InputFile *file);
  54
  55   // Emit errors for symbols that cannot be resolved.
  56   void reportUnresolvable();
  57
  58   // Try to resolve any undefined symbols and update the symbol table
  59   // accordingly, then print an error message for any remaining undefined
  60   // symbols and warn about imported local symbols.
  61   void resolveRemainingUndefines();
  62
  63   // Load lazy objects that are needed for MinGW automatic import and for
  64   // doing stdcall fixups.
  65   void loadMinGWSymbols();
  66   bool handleMinGWAutomaticImport(Symbol *sym, StringRef name);
  67
  68   // Returns a list of chunks of selected symbols.
  69   std::vector<Chunk *> getChunks() const;
  70
  71   // Returns a symbol for a given name. Returns a nullptr if not found.
  72   Symbol *find(StringRef name) const;
  73   Symbol *findUnderscore(StringRef name) const;
  74
  75   // Occasionally we have to resolve an undefined symbol to its
  76   // mangled symbol. This function tries to find a mangled name
  77   // for U from the symbol table, and if found, set the symbol as
  78   // a weak alias for U.
  79   Symbol *findMangle(StringRef name);
  80
  81   // Build a set of COFF objects representing the combined contents of
  82   // BitcodeFiles and add them to the symbol table. Called after all files are
  83   // added and before the writer writes results to a file.
  84   void compileBitcodeFiles();
  85
  86   // Creates an Undefined symbol for a given name.
  87   Symbol *addUndefined(StringRef name);
  88
  89   Symbol *addSynthetic(StringRef n, Chunk *c);
  90   Symbol *addAbsolute(StringRef n, uint64_t va);
  91
  92   Symbol *addUndefined(StringRef name, InputFile *f, bool isWeakAlias);
  93   void addLazyArchive(ArchiveFile *f, const Archive::Symbol &sym);
  94   void addLazyObject(InputFile *f, StringRef n);
  95   void addLazyDLLSymbol(DLLFile *f, DLLFile::Symbol *sym, StringRef n);
  96   Symbol *addAbsolute(StringRef n, COFFSymbolRef s);
  97   Symbol *addRegular(InputFile *f, StringRef n,
  98                      const llvm::object::coff_symbol_generic *s = nullptr,
  99                      SectionChunk *c = nullptr, uint32_t sectionOffset = 0);
 100   std::pair<DefinedRegular *, bool>
 101   addComdat(InputFile *f, StringRef n,
 102             const llvm::object::coff_symbol_generic *s = nullptr);
 103   Symbol *addCommon(InputFile *f, StringRef n, uint64_t size,
 104                     const llvm::object::coff_symbol_generic *s = nullptr,
 105                     CommonChunk *c = nullptr);
 106   Symbol *addImportData(StringRef n, ImportFile *f);
 107   Symbol *addImportThunk(StringRef name, DefinedImportData *s,
 108                          uint16_t machine);
 109   void addLibcall(StringRef name);
 110
 111   void reportDuplicate(Symbol *existing, InputFile *newFile,
 112                        SectionChunk *newSc = nullptr,
 113                        uint32_t newSectionOffset = 0);
 114
 115   // A list of chunks which to be added to .rdata.
 116   std::vector<Chunk *> localImportChunks;
 117
 118   // Iterates symbols in non-determinstic hash table order.
 119   template <typename T> void forEachSymbol(T callback) {
 120     for (auto &pair : symMap)
 121       callback(pair.second);
 122   }
 123
 124 private:
 125   /// Given a name without "__imp_" prefix, returns a defined symbol
 126   /// with the "__imp_" prefix, if it exists.
 127   Defined *impSymbol(StringRef name);
 128   /// Inserts symbol if not already present.
 129   std::pair<Symbol *, bool> insert(StringRef name);
 130   /// Same as insert(Name), but also sets isUsedInRegularObj.
 131   std::pair<Symbol *, bool> insert(StringRef name, InputFile *f);
 132
 133   std::vector<Symbol *> getSymsWithPrefix(StringRef prefix);
 134
 135   llvm::DenseMap<llvm::CachedHashStringRef, Symbol *> symMap;
 136   std::unique_ptr<BitcodeCompiler> lto;
 137
 138   COFFLinkerContext &ctx;
 139 };
 140
 141 std::vector<std::string> getSymbolLocations(ObjFile *file, uint32_t symIndex);
 142
 143 StringRef ltrim1(StringRef s, const char *chars);
 144
 145 } // namespace coff
 146 } // namespace lld
 147
 148 #endif