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