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