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