+/// This class provides the core functionality of linking in LLVM. It retains a
+/// Module object which is the composite of the modules and libraries linked
+/// into it. The composite Module can be retrieved via the getModule() method.
+/// In this case the Linker still retains ownership of the Module. If the
+/// releaseModule() method is used, the ownership of the Module is transferred
+/// to the caller and the Linker object is only suitable for destruction.
+/// The Linker can link Modules from memory. By default, the linker
+/// will generate error and warning messages to stderr but this capability can
+/// be turned off with the QuietWarnings and QuietErrors flags. It can also be
+/// instructed to verbosely print out the linking actions it is taking with
+/// the Verbose flag.
+/// @brief The LLVM Linker.
+class Linker {
+
+ /// @name Types
+ /// @{
+ public:
+ /// This enumeration is used to control various optional features of the
+ /// linker.
+ enum ControlFlags {
+ Verbose = 1, ///< Print to stderr what steps the linker is taking
+ QuietWarnings = 2, ///< Don't print warnings to stderr.
+ QuietErrors = 4 ///< Don't print errors to stderr.
+ };
+
+ enum LinkerMode {
+ DestroySource = 0, // Allow source module to be destroyed.
+ PreserveSource = 1 // Preserve the source module.
+ };
+
+ /// @}
+ /// @name Constructors
+ /// @{
+ public:
+ /// Construct the Linker with an empty module which will be given the
+ /// name \p progname. \p progname will also be used for error messages.
+ /// @brief Construct with empty module
+ Linker(StringRef progname, ///< name of tool running linker
+ StringRef modulename, ///< name of linker's end-result module
+ LLVMContext &C, ///< Context for global info
+ unsigned Flags = 0 ///< ControlFlags (one or more |'d together)
+ );
+
+ /// Construct the Linker with a previously defined module, \p aModule. Use
+ /// \p progname for the name of the program in error messages.
+ /// @brief Construct with existing module
+ Linker(StringRef progname, Module* aModule, unsigned Flags = 0);
+
+ /// Destruct the Linker.
+ /// @brief Destructor
+ ~Linker();
+
+ /// @}
+ /// @name Accessors
+ /// @{
+ public:
+ /// This method gets the composite module into which linking is being
+ /// done. The Composite module starts out empty and accumulates modules
+ /// linked into it via the various LinkIn* methods. This method does not
+ /// release the Module to the caller. The Linker retains ownership and will
+ /// destruct the Module when the Linker is destructed.
+ /// @see releaseModule
+ /// @brief Get the linked/composite module.
+ Module* getModule() const { return Composite; }
+
+ /// This method releases the composite Module into which linking is being
+ /// done. Ownership of the composite Module is transferred to the caller who
+ /// must arrange for its destruct. After this method is called, the Linker
+ /// terminates the linking session for the returned Module. It will no
+ /// longer utilize the returned Module but instead resets itself for
+ /// subsequent linking as if the constructor had been called.
+ /// @brief Release the linked/composite module.
+ Module* releaseModule();
+
+ /// This method returns an error string suitable for printing to the user.
+ /// The return value will be empty unless an error occurred in one of the
+ /// LinkIn* methods. In those cases, the LinkIn* methods will have returned
+ /// true, indicating an error occurred. At most one error is retained so
+ /// this function always returns the last error that occurred. Note that if
+ /// the Quiet control flag is not set, the error string will have already
+ /// been printed to stderr.
+ /// @brief Get the text of the last error that occurred.
+ const std::string &getLastError() const { return Error; }
+
+ /// @}
+ /// @name Mutators
+ /// @{
+ public:
+ /// This method links the \p Src module into the Linker's Composite module
+ /// by calling LinkModules.
+ /// @see LinkModules
+ /// @returns True if an error occurs, false otherwise.
+ /// @brief Link in a module.
+ bool LinkInModule(
+ Module* Src, ///< Module linked into \p Dest
+ std::string* ErrorMsg = 0 /// Error/diagnostic string
+ ) {
+ return LinkModules(Composite, Src, Linker::DestroySource, ErrorMsg);
+ }
+
+ /// This is the heart of the linker. This method will take unconditional
+ /// control of the \p Src module and link it into the \p Dest module. The
+ /// \p Src module will be destructed or subsumed by this method. In either
+ /// case it is not usable by the caller after this method is invoked. Only
+ /// the \p Dest module will remain. The \p Src module is linked into the
+ /// Linker's composite module such that types, global variables, functions,
+ /// and etc. are matched and resolved. If an error occurs, this function
+ /// returns true and ErrorMsg is set to a descriptive message about the
+ /// error.
+ /// @returns True if an error occurs, false otherwise.
+ /// @brief Generically link two modules together.
+ static bool LinkModules(Module* Dest, Module* Src, unsigned Mode,
+ std::string* ErrorMsg);
+
+ /// @}
+ /// @name Implementation
+ /// @{
+ private:
+ bool warning(StringRef message);
+ bool error(StringRef message);
+ void verbose(StringRef message);
+
+ /// @}
+ /// @name Data
+ /// @{
+ private:
+ LLVMContext& Context; ///< The context for global information
+ Module* Composite; ///< The composite module linked together
+ unsigned Flags; ///< Flags to control optional behavior.
+ std::string Error; ///< Text of error that occurred.
+ std::string ProgramName; ///< Name of the program being linked
+ /// @}
+
+};
+
+} // End llvm namespace