Convert observers to C++

This converts observers from using a special source-generating script
to be plain C++.  This version of the patch takes advantage of C++11
by using std::function and variadic templates; incorporates Pedro's
patches; and renames the header file to "observable.h" (this change
eliminates the need for a clean rebuild).

Note that Pedro's patches used a template lambda in tui-hooks.c, but
this failed to compile on some buildbot instances (presumably due to
differing C++ versions); I replaced this with an ordinary template
function.

Regression tested on the buildbot.

gdb/ChangeLog
2018-03-19  Pedro Alves  <palves@redhat.com>
	    Tom Tromey  <tom@tromey.com>

	* unittests/observable-selftests.c: New file.
	* common/observable.h: New file.
	* observable.h: New file.
	* ada-lang.c, ada-tasks.c, agent.c, aix-thread.c, annotate.c,
	arm-tdep.c, auto-load.c, auxv.c, break-catch-syscall.c,
	breakpoint.c, bsd-uthread.c, cli/cli-interp.c, cli/cli-setshow.c,
	corefile.c, dummy-frame.c, event-loop.c, event-top.c, exec.c,
	extension.c, frame.c, gdbarch.c, guile/scm-breakpoint.c,
	infcall.c, infcmd.c, inferior.c, inflow.c, infrun.c, jit.c,
	linux-tdep.c, linux-thread-db.c, m68klinux-tdep.c,
	mi/mi-cmd-break.c, mi/mi-interp.c, mi/mi-main.c, objfiles.c,
	ppc-linux-nat.c, ppc-linux-tdep.c, printcmd.c, procfs.c,
	python/py-breakpoint.c, python/py-finishbreakpoint.c,
	python/py-inferior.c, python/py-unwind.c, ravenscar-thread.c,
	record-btrace.c, record-full.c, record.c, regcache.c, remote.c,
	riscv-tdep.c, sol-thread.c, solib-aix.c, solib-spu.c, solib.c,
	spu-multiarch.c, spu-tdep.c, stack.c, symfile-mem.c, symfile.c,
	symtab.c, thread.c, top.c, tracepoint.c, tui/tui-hooks.c,
	tui/tui-interp.c, valops.c: Update all users.
	* tui/tui-hooks.c (tui_bp_created_observer)
	(tui_bp_deleted_observer, tui_bp_modified_observer)
	(tui_inferior_exit_observer, tui_before_prompt_observer)
	(tui_normal_stop_observer, tui_register_changed_observer):
	Remove.
	(tui_observers_token): New global.
	(attach_or_detach, tui_attach_detach_observers): New functions.
	(tui_install_hooks, tui_remove_hooks): Use
	tui_attach_detach_observers.
	* record-btrace.c (record_btrace_thread_observer): Remove.
	(record_btrace_thread_observer_token): New global.
	* observer.sh: Remove.
	* observer.c: Rename to observable.c.
	* observable.c (namespace gdb_observers): Define new objects.
	(observer_debug): Move into gdb_observers namespace.
	(struct observer, struct observer_list, xalloc_observer_list_node)
	(xfree_observer_list_node, generic_observer_attach)
	(generic_observer_detach, generic_observer_notify): Remove.
	(_initialize_observer): Update.
	Don't include observer.inc.
	* Makefile.in (generated_files): Remove observer.h, observer.inc.
	(clean mostlyclean): Likewise.
	(observer.h, observer.inc): Remove targets.
	(SUBDIR_UNITTESTS_SRCS): Add observable-selftests.c.
	(COMMON_SFILES): Use observable.c, not observer.c.
	* .gitignore: Remove observer.h.

gdb/doc/ChangeLog
2018-03-19  Tom Tromey  <tom@tromey.com>

	* observer.texi: Remove.

gdb/testsuite/ChangeLog
2018-03-19  Tom Tromey  <tom@tromey.com>

	* gdb.gdb/observer.exp: Remove.

gdb/common/observable.h

@@ -0,0 +1,119 @@
+/* Observers
+
+   Copyright (C) 2016-2018 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#if !defined (GDB_COMMON_OBSERVABLE_H)
+#define GDB_COMMON_OBSERVABLE_H
+
+#include <algorithm>
+#include <functional>
+#include <vector>
+
+namespace gdb
+{
+
+namespace observers
+{
+
+extern unsigned int observer_debug;
+
+/* An observer is an entity which is interested in being notified
+   when GDB reaches certain states, or certain events occur in GDB.
+   The entity being observed is called the observable.  To receive
+   notifications, the observer attaches a callback to the observable.
+   One observable can have several observers.
+
+   The observer implementation is also currently not reentrant.  In
+   particular, it is therefore not possible to call the attach or
+   detach routines during a notification.  */
+
+/* The type of a key that can be passed to attach, which can be passed
+   to detach to remove associated observers.  Tokens have address
+   identity, and are thus usually const globals.  */
+struct token
+{
+  token () = default;
+
+  DISABLE_COPY_AND_ASSIGN (token);
+};
+
+template<typename... T>
+class observable
+{
+public:
+
+  typedef std::function<void (T...)> func_type;
+
+  explicit observable (const char *name)
+    : m_name (name)
+  {
+  }
+
+  DISABLE_COPY_AND_ASSIGN (observable);
+
+  /* Attach F as an observer to this observable.  F cannot be
+     detached.  */
+  void attach (const func_type &f)
+  {
+    m_observers.emplace_back (nullptr, f);
+  }
+
+  /* Attach F as an observer to this observable.  T is a reference to
+     a token that can be used to later remove F.  */
+  void attach (const func_type &f, const token &t)
+  {
+    m_observers.emplace_back (&t, f);
+  }
+
+  /* Remove observers associated with T from this observable.  T is
+     the token that was previously passed to any number of "attach"
+     calls.  */
+  void detach (const token &t)
+  {
+    auto iter = std::remove_if (m_observers.begin (),
+				m_observers.end (),
+				[&] (const std::pair<const token *,
+				     func_type> &e)
+				{
+				  return e.first == &t;
+				});
+
+    m_observers.erase (iter, m_observers.end ());
+  }
+
+  /* Notify all observers that are attached to this observable.  */
+  void notify (T... args) const
+  {
+    if (observer_debug)
+      fprintf_unfiltered (gdb_stdlog, "observable %s notify() called\n",
+			  m_name);
+    for (auto &&e : m_observers)
+      e.second (args...);
+  }
+
+private:
+
+  std::vector<std::pair<const token *, func_type>> m_observers;
+  const char *m_name;
+};
+
+} /* namespace observers */
+
+} /* namespace gdb */
+
+#endif /* GDB_COMMON_OBSERVABLE_H */