ircd::mods: Add sym_ptr/sym_ref to link symbols with a typed object.

include/ircd/mods.h

@@ -41,6 +41,8 @@ using mapi::version_t;
 IRCD_EXCEPTION(ircd::error, error)
 IRCD_EXCEPTION(error, filesystem_error)
 IRCD_EXCEPTION(error, invalid_export)
+IRCD_EXCEPTION(error, expired_symbol)
+IRCD_EXCEPTION(error, undefined_symbol)
 
 extern struct log::log log;
 
@@ -80,6 +82,38 @@ struct module
 template<> const uint8_t *module::ptr<const uint8_t>(const std::string &name) const;
 template<> uint8_t *module::ptr<uint8_t>(const std::string &name);
 
+class sym_ptr
+:std::weak_ptr<mod>
+{
+	void *ptr;
+
+  public:
+	operator bool() const                        { return !expired();                              }
+	bool operator!() const                       { return expired();                               }
+
+	template<class T> const T *get() const;
+	template<class T> T *get();
+
+	template<class T> const T *operator->() const;
+	template<class T> T *operator->();
+
+	template<class T> const T &operator*() const;
+	template<class T> T &operator*();
+
+	sym_ptr(const std::string &modname, const std::string &symname);
+	~sym_ptr() noexcept;
+};
+
+template<class T>
+struct sym_ref
+:protected sym_ptr
+{
+	operator const T &() const                   { return sym_ptr::operator*<T>();                 }
+	operator T &()                               { return sym_ptr::operator*<T>();                 }
+
+	using sym_ptr::sym_ptr;
+};
+
 std::vector<std::string> symbols(const std::string &fullpath, const std::string &section);
 std::vector<std::string> symbols(const std::string &fullpath);
 std::vector<std::string> sections(const std::string &fullpath);
@@ -114,6 +148,57 @@ using mods::module;                              // Bring struct module into mai
 
 } // namespace ircd
 
+template<class T>
+T &
+ircd::mods::sym_ptr::operator*()
+{
+	if(unlikely(expired()))
+		throw expired_symbol("The reference to a symbol in another module is no longer valid");
+
+	return *get<T>();
+}
+
+template<class T>
+T *
+ircd::mods::sym_ptr::operator->()
+{
+	return get<T>();
+}
+
+template<class T>
+T *
+ircd::mods::sym_ptr::get()
+{
+	return reinterpret_cast<T *>(ptr);
+}
+
+template<class T>
+const T &
+ircd::mods::sym_ptr::operator*()
+const
+{
+	if(unlikely(expired()))
+		throw expired_symbol("The const reference to a symbol in another module is no longer valid");
+
+	return *get<T>();
+}
+
+template<class T>
+const T *
+ircd::mods::sym_ptr::operator->()
+const
+{
+	return get<T>();
+}
+
+template<class T>
+const T *
+ircd::mods::sym_ptr::get()
+const
+{
+	return reinterpret_cast<const T *>(ptr);
+}
+
 template<class T>
 T &
 ircd::mods::module::get(const std::string &name)

ircd/ircd.cc

@@ -105,8 +105,8 @@ try
 
 	module listener("listen.so");
 	module client_versions("client_versions.so");
-	module client_login("client_login.so");
 	module client_register("client_register.so");
+	module client_login("client_login.so");
 
 	// This is the main program loop. Right now all it does is sleep until notified
 	// to shutdown, but it can do other things eventually. Other subsystems may have

ircd/mods.cc

@@ -174,8 +174,8 @@ const
 template<> uint8_t *
 ircd::mods::module::ptr<uint8_t>(const std::string &name)
 {
-	const auto &mod(**this);
+	auto &mod(**this);
-	return &mod.handle.get<uint8_t>(name);
+	return mod.ptr<uint8_t>(name);
 }
 
 template<>
@@ -184,7 +184,7 @@ ircd::mods::module::ptr<const uint8_t>(const std::string &name)
 const
 {
 	const auto &mod(**this);
-	return &mod.handle.get<const uint8_t>(name);
+	return mod.ptr<const uint8_t>(name);
 }
 
 bool
@@ -195,7 +195,35 @@ const
 		return false;
 
 	const auto &mod(**this);
-	return mod.handle.has(name);
+	return mod.has(name);
+}
+
+///////////////////////////////////////////////////////////////////////////////
+//
+// sym_ptr
+//
+
+ircd::mods::sym_ptr::sym_ptr(const std::string &modname,
+                             const std::string &symname)
+:std::weak_ptr<mod>
+{
+	module(modname)
+}
+,ptr{[this, &modname, &symname]
+{
+	const life_guard<mods::mod> mod(*this);
+
+	if(unlikely(!mod->has(symname)))
+		throw undefined_symbol("Could not find symbol '%s' in module '%s'", symname, mod->name());
+
+	return mod->ptr(symname);
+}()}
+{
+}
+
+ircd::mods::sym_ptr::~sym_ptr()
+noexcept
+{
 }
 
 ///////////////////////////////////////////////////////////////////////////////