1 //===- llvm/Linker.h - Module Linker Interface ------------------*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file defines the interface to the module/file/archive linker. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #ifndef LLVM_LINKER_H 15 #define LLVM_LINKER_H 16 17 #include <memory> 18 #include <string> 19 #include <vector> 20 21 namespace llvm { 22 namespace sys { class Path; } 23 24 class Module; 25 class LLVMContext; 26 class StringRef; 27 28 /// This class provides the core functionality of linking in LLVM. It retains a 29 /// Module object which is the composite of the modules and libraries linked 30 /// into it. The composite Module can be retrieved via the getModule() method. 31 /// In this case the Linker still retains ownership of the Module. If the 32 /// releaseModule() method is used, the ownership of the Module is transferred 33 /// to the caller and the Linker object is only suitable for destruction. 34 /// The Linker can link Modules from memory, bitcode files, or bitcode 35 /// archives. It retains a set of search paths in which to find any libraries 36 /// presented to it. By default, the linker will generate error and warning 37 /// messages to stderr but this capability can be turned off with the 38 /// QuietWarnings and QuietErrors flags. It can also be instructed to verbosely 39 /// print out the linking actions it is taking with the Verbose flag. 40 /// @brief The LLVM Linker. 41 class Linker { 42 43 /// @name Types 44 /// @{ 45 public: 46 /// This type is used to pass the linkage items (libraries and files) to 47 /// the LinkItems function. It is composed of string/bool pairs. The string 48 /// provides the name of the file or library (as with the -l option). The 49 /// bool should be true for libraries and false for files, signifying 50 /// "isLibrary". 51 /// @brief A list of linkage items 52 typedef std::vector<std::pair<std::string,bool> > ItemList; 53 54 /// This enumeration is used to control various optional features of the 55 /// linker. 56 enum ControlFlags { 57 Verbose = 1, ///< Print to stderr what steps the linker is taking 58 QuietWarnings = 2, ///< Don't print warnings to stderr. 59 QuietErrors = 4 ///< Don't print errors to stderr. 60 }; 61 62 enum LinkerMode { 63 DestroySource = 0, // Allow source module to be destroyed. 64 PreserveSource = 1 // Preserve the source module. 65 }; 66 67 /// @} 68 /// @name Constructors 69 /// @{ 70 public: 71 /// Construct the Linker with an empty module which will be given the 72 /// name \p progname. \p progname will also be used for error messages. 73 /// @brief Construct with empty module 74 Linker(StringRef progname, ///< name of tool running linker 75 StringRef modulename, ///< name of linker's end-result module 76 LLVMContext &C, ///< Context for global info 77 unsigned Flags = 0 ///< ControlFlags (one or more |'d together) 78 ); 79 80 /// Construct the Linker with a previously defined module, \p aModule. Use 81 /// \p progname for the name of the program in error messages. 82 /// @brief Construct with existing module 83 Linker(StringRef progname, Module* aModule, unsigned Flags = 0); 84 85 /// Destruct the Linker. 86 /// @brief Destructor 87 ~Linker(); 88 89 /// @} 90 /// @name Accessors 91 /// @{ 92 public: 93 /// This method gets the composite module into which linking is being 94 /// done. The Composite module starts out empty and accumulates modules 95 /// linked into it via the various LinkIn* methods. This method does not 96 /// release the Module to the caller. The Linker retains ownership and will 97 /// destruct the Module when the Linker is destructed. 98 /// @see releaseModule 99 /// @brief Get the linked/composite module. getModule()100 Module* getModule() const { return Composite; } 101 102 /// This method releases the composite Module into which linking is being 103 /// done. Ownership of the composite Module is transferred to the caller who 104 /// must arrange for its destruct. After this method is called, the Linker 105 /// terminates the linking session for the returned Module. It will no 106 /// longer utilize the returned Module but instead resets itself for 107 /// subsequent linking as if the constructor had been called. The Linker's 108 /// LibPaths and flags to be reset, and memory will be released. 109 /// @brief Release the linked/composite module. 110 Module* releaseModule(); 111 112 /// This method gets the list of libraries that form the path that the 113 /// Linker will search when it is presented with a library name. 114 /// @brief Get the Linkers library path getLibPaths()115 const std::vector<sys::Path>& getLibPaths() const { return LibPaths; } 116 117 /// This method returns an error string suitable for printing to the user. 118 /// The return value will be empty unless an error occurred in one of the 119 /// LinkIn* methods. In those cases, the LinkIn* methods will have returned 120 /// true, indicating an error occurred. At most one error is retained so 121 /// this function always returns the last error that occurred. Note that if 122 /// the Quiet control flag is not set, the error string will have already 123 /// been printed to stderr. 124 /// @brief Get the text of the last error that occurred. getLastError()125 const std::string &getLastError() const { return Error; } 126 127 /// @} 128 /// @name Mutators 129 /// @{ 130 public: 131 /// Add a path to the list of paths that the Linker will search. The Linker 132 /// accumulates the set of libraries added 133 /// library paths for the target platform. The standard libraries will 134 /// always be searched last. The added libraries will be searched in the 135 /// order added. 136 /// @brief Add a path. 137 void addPath(const sys::Path& path); 138 139 /// Add a set of paths to the list of paths that the linker will search. The 140 /// Linker accumulates the set of libraries added. The \p paths will be 141 /// added to the end of the Linker's list. Order will be retained. 142 /// @brief Add a set of paths. 143 void addPaths(const std::vector<std::string>& paths); 144 145 /// This method augments the Linker's list of library paths with the system 146 /// paths of the host operating system, include LLVM_LIB_SEARCH_PATH. 147 /// @brief Add the system paths. 148 void addSystemPaths(); 149 150 /// Control optional linker behavior by setting a group of flags. The flags 151 /// are defined in the ControlFlags enumeration. 152 /// @see ControlFlags 153 /// @brief Set control flags. setFlags(unsigned flags)154 void setFlags(unsigned flags) { Flags = flags; } 155 156 /// This method is the main interface to the linker. It can be used to 157 /// link a set of linkage items into a module. A linkage item is either a 158 /// file name with fully qualified path, or a library for which the Linker's 159 /// LibraryPath will be utilized to locate the library. The bool value in 160 /// the LinkItemKind should be set to true for libraries. This function 161 /// allows linking to preserve the order of specification associated with 162 /// the command line, or for other purposes. Each item will be linked in 163 /// turn as it occurs in \p Items. 164 /// @returns true if an error occurred, false otherwise 165 /// @see LinkItemKind 166 /// @see getLastError 167 bool LinkInItems ( 168 const ItemList& Items, ///< Set of libraries/files to link in 169 ItemList& NativeItems ///< Output list of native files/libs 170 ); 171 172 /// This function links the bitcode \p Files into the composite module. 173 /// Note that this does not do any linking of unresolved symbols. The \p 174 /// Files are all completely linked into \p HeadModule regardless of 175 /// unresolved symbols. This function just loads each bitcode file and 176 /// calls LinkInModule on them. 177 /// @returns true if an error occurs, false otherwise 178 /// @see getLastError 179 /// @brief Link in multiple files. 180 bool LinkInFiles ( 181 const std::vector<sys::Path> & Files ///< Files to link in 182 ); 183 184 /// This function links a single bitcode file, \p File, into the composite 185 /// module. Note that this does not attempt to resolve symbols. This method 186 /// just loads the bitcode file and calls LinkInModule on it. If an error 187 /// occurs, the Linker's error string is set. 188 /// @returns true if an error occurs, false otherwise 189 /// @see getLastError 190 /// @brief Link in a single file. 191 bool LinkInFile( 192 const sys::Path& File, ///< File to link in. 193 bool &is_native ///< Indicates if the file is native object file 194 ); 195 196 /// This function provides a way to selectively link in a set of modules, 197 /// found in libraries, based on the unresolved symbols in the composite 198 /// module. Each item in \p Libraries should be the base name of a library, 199 /// as if given with the -l option of a linker tool. The Linker's LibPaths 200 /// are searched for the \p Libraries and any found will be linked in with 201 /// LinkInArchive. If an error occurs, the Linker's error string is set. 202 /// @see LinkInArchive 203 /// @see getLastError 204 /// @returns true if an error occurs, false otherwise 205 /// @brief Link libraries into the module 206 bool LinkInLibraries ( 207 const std::vector<std::string> & Libraries ///< Libraries to link in 208 ); 209 210 /// This function provides a way to selectively link in a set of modules, 211 /// found in one library, based on the unresolved symbols in the composite 212 /// module.The \p Library should be the base name of a library, as if given 213 /// with the -l option of a linker tool. The Linker's LibPaths are searched 214 /// for the \p Library and if found, it will be linked in with via the 215 /// LinkInArchive method. If an error occurs, the Linker's error string is 216 /// set. 217 /// @see LinkInArchive 218 /// @see getLastError 219 /// @returns true if an error occurs, false otherwise 220 /// @brief Link one library into the module 221 bool LinkInLibrary ( 222 StringRef Library, ///< The library to link in 223 bool& is_native ///< Indicates if lib a native library 224 ); 225 226 /// This function links one bitcode archive, \p Filename, into the module. 227 /// The archive is searched to resolve outstanding symbols. Any modules in 228 /// the archive that resolve outstanding symbols will be linked in. The 229 /// library is searched repeatedly until no more modules that resolve 230 /// symbols can be found. If an error occurs, the error string is set. 231 /// To speed up this function, ensure the archive has been processed 232 /// llvm-ranlib or the S option was given to llvm-ar when the archive was 233 /// created. These tools add a symbol table to the archive which makes the 234 /// search for undefined symbols much faster. 235 /// @see getLastError 236 /// @returns true if an error occurs, otherwise false. 237 /// @brief Link in one archive. 238 bool LinkInArchive( 239 const sys::Path& Filename, ///< Filename of the archive to link 240 bool& is_native ///< Indicates if archive is a native archive 241 ); 242 243 /// This method links the \p Src module into the Linker's Composite module 244 /// by calling LinkModules. All the other LinkIn* methods eventually 245 /// result in calling this method to link a Module into the Linker's 246 /// composite. 247 /// @see LinkModules 248 /// @returns True if an error occurs, false otherwise. 249 /// @brief Link in a module. 250 bool LinkInModule( 251 Module* Src, ///< Module linked into \p Dest 252 std::string* ErrorMsg = 0 /// Error/diagnostic string 253 ) { 254 return LinkModules(Composite, Src, Linker::DestroySource, ErrorMsg ); 255 } 256 257 /// This is the heart of the linker. This method will take unconditional 258 /// control of the \p Src module and link it into the \p Dest module. The 259 /// \p Src module will be destructed or subsumed by this method. In either 260 /// case it is not usable by the caller after this method is invoked. Only 261 /// the \p Dest module will remain. The \p Src module is linked into the 262 /// Linker's composite module such that types, global variables, functions, 263 /// and etc. are matched and resolved. If an error occurs, this function 264 /// returns true and ErrorMsg is set to a descriptive message about the 265 /// error. 266 /// @returns True if an error occurs, false otherwise. 267 /// @brief Generically link two modules together. 268 static bool LinkModules(Module* Dest, Module* Src, unsigned Mode, 269 std::string* ErrorMsg); 270 271 /// This function looks through the Linker's LibPaths to find a library with 272 /// the name \p Filename. If the library cannot be found, the returned path 273 /// will be empty (i.e. sys::Path::isEmpty() will return true). 274 /// @returns A sys::Path to the found library 275 /// @brief Find a library from its short name. 276 sys::Path FindLib(StringRef Filename); 277 278 /// @} 279 /// @name Implementation 280 /// @{ 281 private: 282 /// Read in and parse the bitcode file named by FN and return the 283 /// Module it contains (wrapped in an auto_ptr), or 0 if an error occurs. 284 std::auto_ptr<Module> LoadObject(const sys::Path& FN); 285 286 bool warning(StringRef message); 287 bool error(StringRef message); 288 void verbose(StringRef message); 289 290 /// @} 291 /// @name Data 292 /// @{ 293 private: 294 LLVMContext& Context; ///< The context for global information 295 Module* Composite; ///< The composite module linked together 296 std::vector<sys::Path> LibPaths; ///< The library search paths 297 unsigned Flags; ///< Flags to control optional behavior. 298 std::string Error; ///< Text of error that occurred. 299 std::string ProgramName; ///< Name of the program being linked 300 /// @} 301 302 }; 303 304 } // End llvm namespace 305 306 #endif 307