Linker.h revision 208954
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 21namespace llvm { 22 namespace sys { class Path; } 23 24class Module; 25class 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. 40class 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 /// @} 62 /// @name Constructors 63 /// @{ 64 public: 65 /// Construct the Linker with an empty module which will be given the 66 /// name \p progname. \p progname will also be used for error messages. 67 /// @brief Construct with empty module 68 Linker(StringRef progname, ///< name of tool running linker 69 StringRef modulename, ///< name of linker's end-result module 70 LLVMContext &C, ///< Context for global info 71 unsigned Flags = 0 ///< ControlFlags (one or more |'d together) 72 ); 73 74 /// Construct the Linker with a previously defined module, \p aModule. Use 75 /// \p progname for the name of the program in error messages. 76 /// @brief Construct with existing module 77 Linker(StringRef progname, Module* aModule, unsigned Flags = 0); 78 79 /// Destruct the Linker. 80 /// @brief Destructor 81 ~Linker(); 82 83 /// @} 84 /// @name Accessors 85 /// @{ 86 public: 87 /// This method gets the composite module into which linking is being 88 /// done. The Composite module starts out empty and accumulates modules 89 /// linked into it via the various LinkIn* methods. This method does not 90 /// release the Module to the caller. The Linker retains ownership and will 91 /// destruct the Module when the Linker is destructed. 92 /// @see releaseModule 93 /// @brief Get the linked/composite module. 94 Module* getModule() const { return Composite; } 95 96 /// This method releases the composite Module into which linking is being 97 /// done. Ownership of the composite Module is transferred to the caller who 98 /// must arrange for its destruct. After this method is called, the Linker 99 /// terminates the linking session for the returned Module. It will no 100 /// longer utilize the returned Module but instead resets itself for 101 /// subsequent linking as if the constructor had been called. The Linker's 102 /// LibPaths and flags to be reset, and memory will be released. 103 /// @brief Release the linked/composite module. 104 Module* releaseModule(); 105 106 /// This method gets the list of libraries that form the path that the 107 /// Linker will search when it is presented with a library name. 108 /// @brief Get the Linkers library path 109 const std::vector<sys::Path>& getLibPaths() const { return LibPaths; } 110 111 /// This method returns an error string suitable for printing to the user. 112 /// The return value will be empty unless an error occurred in one of the 113 /// LinkIn* methods. In those cases, the LinkIn* methods will have returned 114 /// true, indicating an error occurred. At most one error is retained so 115 /// this function always returns the last error that occurred. Note that if 116 /// the Quiet control flag is not set, the error string will have already 117 /// been printed to stderr. 118 /// @brief Get the text of the last error that occurred. 119 const std::string &getLastError() const { return Error; } 120 121 /// @} 122 /// @name Mutators 123 /// @{ 124 public: 125 /// Add a path to the list of paths that the Linker will search. The Linker 126 /// accumulates the set of libraries added 127 /// library paths for the target platform. The standard libraries will 128 /// always be searched last. The added libraries will be searched in the 129 /// order added. 130 /// @brief Add a path. 131 void addPath(const sys::Path& path); 132 133 /// Add a set of paths to the list of paths that the linker will search. The 134 /// Linker accumulates the set of libraries added. The \p paths will be 135 /// added to the end of the Linker's list. Order will be retained. 136 /// @brief Add a set of paths. 137 void addPaths(const std::vector<std::string>& paths); 138 139 /// This method augments the Linker's list of library paths with the system 140 /// paths of the host operating system, include LLVM_LIB_SEARCH_PATH. 141 /// @brief Add the system paths. 142 void addSystemPaths(); 143 144 /// Control optional linker behavior by setting a group of flags. The flags 145 /// are defined in the ControlFlags enumeration. 146 /// @see ControlFlags 147 /// @brief Set control flags. 148 void setFlags(unsigned flags) { Flags = flags; } 149 150 /// This method is the main interface to the linker. It can be used to 151 /// link a set of linkage items into a module. A linkage item is either a 152 /// file name with fully qualified path, or a library for which the Linker's 153 /// LibraryPath will be utilized to locate the library. The bool value in 154 /// the LinkItemKind should be set to true for libraries. This function 155 /// allows linking to preserve the order of specification associated with 156 /// the command line, or for other purposes. Each item will be linked in 157 /// turn as it occurs in \p Items. 158 /// @returns true if an error occurred, false otherwise 159 /// @see LinkItemKind 160 /// @see getLastError 161 /// @throws nothing 162 bool LinkInItems ( 163 const ItemList& Items, ///< Set of libraries/files to link in 164 ItemList& NativeItems ///< Output list of native files/libs 165 ); 166 167 /// This function links the bitcode \p Files into the composite module. 168 /// Note that this does not do any linking of unresolved symbols. The \p 169 /// Files are all completely linked into \p HeadModule regardless of 170 /// unresolved symbols. This function just loads each bitcode file and 171 /// calls LinkInModule on them. 172 /// @returns true if an error occurs, false otherwise 173 /// @see getLastError 174 /// @brief Link in multiple files. 175 bool LinkInFiles ( 176 const std::vector<sys::Path> & Files ///< Files to link in 177 ); 178 179 /// This function links a single bitcode file, \p File, into the composite 180 /// module. Note that this does not attempt to resolve symbols. This method 181 /// just loads the bitcode file and calls LinkInModule on it. If an error 182 /// occurs, the Linker's error string is set. 183 /// @returns true if an error occurs, false otherwise 184 /// @see getLastError 185 /// @brief Link in a single file. 186 bool LinkInFile( 187 const sys::Path& File, ///< File to link in. 188 bool &is_native ///< Indicates if the file is native object file 189 ); 190 191 /// This function provides a way to selectively link in a set of modules, 192 /// found in libraries, based on the unresolved symbols in the composite 193 /// module. Each item in \p Libraries should be the base name of a library, 194 /// as if given with the -l option of a linker tool. The Linker's LibPaths 195 /// are searched for the \p Libraries and any found will be linked in with 196 /// LinkInArchive. If an error occurs, the Linker's error string is set. 197 /// @see LinkInArchive 198 /// @see getLastError 199 /// @returns true if an error occurs, false otherwise 200 /// @brief Link libraries into the module 201 bool LinkInLibraries ( 202 const std::vector<std::string> & Libraries ///< Libraries to link in 203 ); 204 205 /// This function provides a way to selectively link in a set of modules, 206 /// found in one library, based on the unresolved symbols in the composite 207 /// module.The \p Library should be the base name of a library, as if given 208 /// with the -l option of a linker tool. The Linker's LibPaths are searched 209 /// for the \p Library and if found, it will be linked in with via the 210 /// LinkInArchive method. If an error occurs, the Linker's error string is 211 /// set. 212 /// @see LinkInArchive 213 /// @see getLastError 214 /// @returns true if an error occurs, false otherwise 215 /// @brief Link one library into the module 216 bool LinkInLibrary ( 217 StringRef Library, ///< The library to link in 218 bool& is_native ///< Indicates if lib a native library 219 ); 220 221 /// This function links one bitcode archive, \p Filename, into the module. 222 /// The archive is searched to resolve outstanding symbols. Any modules in 223 /// the archive that resolve outstanding symbols will be linked in. The 224 /// library is searched repeatedly until no more modules that resolve 225 /// symbols can be found. If an error occurs, the error string is set. 226 /// To speed up this function, ensure the archive has been processed 227 /// llvm-ranlib or the S option was given to llvm-ar when the archive was 228 /// created. These tools add a symbol table to the archive which makes the 229 /// search for undefined symbols much faster. 230 /// @see getLastError 231 /// @returns true if an error occurs, otherwise false. 232 /// @brief Link in one archive. 233 bool LinkInArchive( 234 const sys::Path& Filename, ///< Filename of the archive to link 235 bool& is_native ///< Indicates if archive is a native archive 236 ); 237 238 /// This method links the \p Src module into the Linker's Composite module 239 /// by calling LinkModules. All the other LinkIn* methods eventually 240 /// result in calling this method to link a Module into the Linker's 241 /// composite. 242 /// @see LinkModules 243 /// @returns True if an error occurs, false otherwise. 244 /// @brief Link in a module. 245 bool LinkInModule( 246 Module* Src, ///< Module linked into \p Dest 247 std::string* ErrorMsg = 0 /// Error/diagnostic string 248 ) { 249 return LinkModules(Composite, Src, ErrorMsg ); 250 } 251 252 /// This is the heart of the linker. This method will take unconditional 253 /// control of the \p Src module and link it into the \p Dest module. The 254 /// \p Src module will be destructed or subsumed by this method. In either 255 /// case it is not usable by the caller after this method is invoked. Only 256 /// the \p Dest module will remain. The \p Src module is linked into the 257 /// Linker's composite module such that types, global variables, functions, 258 /// and etc. are matched and resolved. If an error occurs, this function 259 /// returns true and ErrorMsg is set to a descriptive message about the 260 /// error. 261 /// @returns True if an error occurs, false otherwise. 262 /// @brief Generically link two modules together. 263 static bool LinkModules(Module* Dest, Module* Src, std::string* ErrorMsg); 264 265 /// This function looks through the Linker's LibPaths to find a library with 266 /// the name \p Filename. If the library cannot be found, the returned path 267 /// will be empty (i.e. sys::Path::isEmpty() will return true). 268 /// @returns A sys::Path to the found library 269 /// @brief Find a library from its short name. 270 sys::Path FindLib(StringRef Filename); 271 272 /// @} 273 /// @name Implementation 274 /// @{ 275 private: 276 /// Read in and parse the bitcode file named by FN and return the 277 /// Module it contains (wrapped in an auto_ptr), or 0 if an error occurs. 278 std::auto_ptr<Module> LoadObject(const sys::Path& FN); 279 280 bool warning(StringRef message); 281 bool error(StringRef message); 282 void verbose(StringRef message); 283 284 /// @} 285 /// @name Data 286 /// @{ 287 private: 288 LLVMContext& Context; ///< The context for global information 289 Module* Composite; ///< The composite module linked together 290 std::vector<sys::Path> LibPaths; ///< The library search paths 291 unsigned Flags; ///< Flags to control optional behavior. 292 std::string Error; ///< Text of error that occurred. 293 std::string ProgramName; ///< Name of the program being linked 294 /// @} 295 296}; 297 298} // End llvm namespace 299 300#endif 301