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