text: //===- 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_COFF_SYMBOL_TABLE_H
  #define LLD_COFF_SYMBOL_TABLE_H
  
  #include "InputFiles.h"
  #include "LTO.h"
  #include "llvm/ADT/CachedHashString.h"
  #include "llvm/ADT/DenseMap.h"
  #include "llvm/ADT/DenseMapInfo.h"
  #include "llvm/Support/raw_ostream.h"
  
  namespace llvm {
  struct LTOCodeGenerator;
  }
  
  namespace lld {
  namespace coff {
  
  class Chunk;
  class CommonChunk;
  class Defined;
  class DefinedAbsolute;
  class DefinedRegular;
  class DefinedRelative;
  class LazyArchive;
  class SectionChunk;
  class Symbol;
  
  // 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 {
  public:
    void addFile(InputFile *file);
  
    // Emit errors for symbols that cannot be resolved.
    void reportUnresolvable();
  
    // Try to resolve any undefined symbols and update the symbol table
    // accordingly, then print an error message for any remaining undefined
    // symbols and warn about imported local symbols.
    void resolveRemainingUndefines();
  
    void loadMinGWAutomaticImports();
    bool handleMinGWAutomaticImport(Symbol *sym, StringRef name);
  
    // Returns a list of chunks of selected symbols.
    std::vector<Chunk *> getChunks();
  
    // Returns a symbol for a given name. Returns a nullptr if not found.
    Symbol *find(StringRef name);
    Symbol *findUnderscore(StringRef name);
  
    // Occasionally we have to resolve an undefined symbol to its
    // mangled symbol. This function tries to find a mangled name
    // for U from the symbol table, and if found, set the symbol as
    // a weak alias for U.
    Symbol *findMangle(StringRef name);
  
    // Build a set of COFF objects representing the combined contents of
    // BitcodeFiles and add them to the symbol table. Called after all files are
    // added and before the writer writes results to a file.
    void addCombinedLTOObjects();
    std::vector<StringRef> compileBitcodeFiles();
  
    // Creates an Undefined symbol for a given name.
    Symbol *addUndefined(StringRef name);
  
    Symbol *addSynthetic(StringRef n, Chunk *c);
    Symbol *addAbsolute(StringRef n, uint64_t va);
  
    Symbol *addUndefined(StringRef name, InputFile *f, bool isWeakAlias);
    void addLazyArchive(ArchiveFile *f, const Archive::Symbol &sym);
    void addLazyObject(LazyObjFile *f, StringRef n);
    Symbol *addAbsolute(StringRef n, COFFSymbolRef s);
    Symbol *addRegular(InputFile *f, StringRef n,
                       const llvm::object::coff_symbol_generic *s = nullptr,
                       SectionChunk *c = nullptr, uint32_t sectionOffset = 0);
    std::pair<DefinedRegular *, bool>
    addComdat(InputFile *f, StringRef n,
              const llvm::object::coff_symbol_generic *s = nullptr);
    Symbol *addCommon(InputFile *f, StringRef n, uint64_t size,
                      const llvm::object::coff_symbol_generic *s = nullptr,
                      CommonChunk *c = nullptr);
    Symbol *addImportData(StringRef n, ImportFile *f);
    Symbol *addImportThunk(StringRef name, DefinedImportData *s,
                           uint16_t machine);
    void addLibcall(StringRef name);
  
    void reportDuplicate(Symbol *existing, InputFile *newFile,
                         SectionChunk *newSc = nullptr,
                         uint32_t newSectionOffset = 0);
  
    // A list of chunks which to be added to .rdata.
    std::vector<Chunk *> localImportChunks;
  
    // Iterates symbols in non-determinstic hash table order.
    template <typename T> void forEachSymbol(T callback) {
      for (auto &pair : symMap)
        callback(pair.second);
    }
  
  private:
    /// Given a name without "__imp_" prefix, returns a defined symbol
    /// with the "__imp_" prefix, if it exists.
    Defined *impSymbol(StringRef name);
    /// Inserts symbol if not already present.
    std::pair<Symbol *, bool> insert(StringRef name);
    /// Same as insert(Name), but also sets isUsedInRegularObj.
    std::pair<Symbol *, bool> insert(StringRef name, InputFile *f);
  
    std::vector<Symbol *> getSymsWithPrefix(StringRef prefix);
  
    llvm::DenseMap<llvm::CachedHashStringRef, Symbol *> symMap;
    std::unique_ptr<BitcodeCompiler> lto;
  };
  
  extern SymbolTable *symtab;
  
  std::vector<std::string> getSymbolLocations(ObjFile *file, uint32_t symIndex);
  
  } // namespace coff
  } // namespace lld
  
  #endif
  