Patchwork [RFA,v3] Convert observers to C++

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Submitter Tom Tromey
Date March 10, 2018, 5:03 a.m.
Message ID <20180310050337.6516-1-tom@tromey.com>
Download mbox | patch
Permalink /patch/26272/
State New
Headers show

Comments

Tom Tromey - March 10, 2018, 5:03 a.m.
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
2018-03-09  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
2017-11-04  Tom Tromey  <tom@tromey.com>

	* observer.texi: Remove.

gdb/testsuite/ChangeLog
2017-11-04  Tom Tromey  <tom@tromey.com>

	* gdb.gdb/observer.exp: Remove.
---
 gdb/.gitignore                       |   1 -
 gdb/ChangeLog                        |  49 ++++++
 gdb/Makefile.in                      |  13 +-
 gdb/ada-lang.c                       |   8 +-
 gdb/ada-tasks.c                      |   6 +-
 gdb/agent.c                          |   4 +-
 gdb/aix-thread.c                     |   6 +-
 gdb/annotate.c                       |   8 +-
 gdb/arm-linux-nat.c                  |   2 +-
 gdb/arm-tdep.c                       |   4 +-
 gdb/auto-load.c                      |   6 +-
 gdb/auxv.c                           |   8 +-
 gdb/break-catch-syscall.c            |   4 +-
 gdb/breakpoint.c                     |  52 +++---
 gdb/bsd-uthread.c                    |   8 +-
 gdb/cli/cli-interp.c                 |  20 +--
 gdb/cli/cli-setshow.c                |  12 +-
 gdb/common/observable.h              | 119 +++++++++++++
 gdb/corefile.c                       |   4 +-
 gdb/defs.h                           |   2 +-
 gdb/doc/ChangeLog                    |   4 +
 gdb/doc/observer.texi                | 313 -----------------------------------
 gdb/dummy-frame.c                    |   4 +-
 gdb/event-loop.c                     |   4 +-
 gdb/event-top.c                      |   4 +-
 gdb/exec.c                           |   4 +-
 gdb/extension.c                      |   4 +-
 gdb/frame.c                          |   4 +-
 gdb/gdbarch.c                        |   4 +-
 gdb/guile/scm-breakpoint.c           |   6 +-
 gdb/inf-loop.c                       |   2 +-
 gdb/infcall.c                        |   6 +-
 gdb/infcmd.c                         |   4 +-
 gdb/inferior.c                       |  15 +-
 gdb/inflow.c                         |   4 +-
 gdb/infrun.c                         |  28 ++--
 gdb/jit.c                            |   8 +-
 gdb/linux-tdep.c                     |   6 +-
 gdb/linux-thread-db.c                |   8 +-
 gdb/m68k-linux-tdep.c                |   4 +-
 gdb/mi/mi-cmd-break.c                |   6 +-
 gdb/mi/mi-interp.c                   |  58 +++----
 gdb/mi/mi-main.c                     |  10 +-
 gdb/objfiles.c                       |   4 +-
 gdb/observable.c                     |  99 +++++++++++
 gdb/observable.h                     | 235 ++++++++++++++++++++++++++
 gdb/observer.c                       | 215 ------------------------
 gdb/observer.sh                      | 200 ----------------------
 gdb/ppc-linux-nat.c                  |   4 +-
 gdb/ppc-linux-tdep.c                 |   8 +-
 gdb/printcmd.c                       |   4 +-
 gdb/procfs.c                         |   4 +-
 gdb/python/py-breakpoint.c           |   8 +-
 gdb/python/py-finishbreakpoint.c     |   6 +-
 gdb/python/py-inferior.c             |  26 +--
 gdb/python/py-unwind.c               |   4 +-
 gdb/ravenscar-thread.c               |   4 +-
 gdb/record-btrace.c                  |  22 +--
 gdb/record-full.c                    |   4 +-
 gdb/record.c                         |   4 +-
 gdb/regcache.c                       |   7 +-
 gdb/remote-notif.c                   |   2 +-
 gdb/remote.c                         |  10 +-
 gdb/riscv-tdep.c                     |   6 +-
 gdb/rs6000-nat.c                     |   2 +-
 gdb/sol-thread.c                     |   4 +-
 gdb/solib-aix.c                      |   4 +-
 gdb/solib-spu.c                      |   4 +-
 gdb/solib-svr4.c                     |   2 +-
 gdb/solib.c                          |  10 +-
 gdb/spu-multiarch.c                  |   8 +-
 gdb/spu-tdep.c                       |   8 +-
 gdb/stack.c                          |  10 +-
 gdb/symfile-debug.c                  |   2 +-
 gdb/symfile-mem.c                    |   4 +-
 gdb/symfile.c                        |  16 +-
 gdb/symtab.c                         |   8 +-
 gdb/testsuite/ChangeLog              |   4 +
 gdb/testsuite/gdb.gdb/observer.exp   | 143 ----------------
 gdb/thread.c                         |  20 +--
 gdb/top.c                            |   4 +-
 gdb/tracepoint.c                     |  18 +-
 gdb/tui/tui-hooks.c                  |  79 ++++-----
 gdb/tui/tui-interp.c                 |  20 +--
 gdb/unittests/observable-selftests.c | 135 +++++++++++++++
 gdb/valops.c                         |   6 +-
 86 files changed, 999 insertions(+), 1234 deletions(-)
 create mode 100644 gdb/common/observable.h
 delete mode 100644 gdb/doc/observer.texi
 create mode 100644 gdb/observable.c
 create mode 100644 gdb/observable.h
 delete mode 100644 gdb/observer.c
 delete mode 100755 gdb/observer.sh
 delete mode 100644 gdb/testsuite/gdb.gdb/observer.exp
 create mode 100644 gdb/unittests/observable-selftests.c
Pedro Alves - March 19, 2018, 10:38 a.m.
Hi Tom,

On 03/10/2018 05:03 AM, Tom Tromey wrote:
> 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.

This version LGTM.

Thanks,
Pedro Alves
Joel Brobecker - March 19, 2018, 10:18 p.m.
Hi Tom,

In the new file gdb/observable.h, I can't help but notice that
the observer's documentation is less clear than before when
the observer has some arguments. For instance, taking one observer
as an example:

> +/* The status of process record for inferior inferior in gdb has
> +   changed.  The process record is started if started is true, and
> +   the process record is stopped if started is false.
> +
> +   When started is true, method indicates the short name of the
> +   method used for recording.  If the method supports multiple
> +   formats, format indicates which one is being used, otherwise it
> +   is NULL.  When started is false, they are both NULL.  */
> +extern observable<struct inferior *, int, const char *, const char *>
> +    record_changed;

The documentation mentions the arguments by name, except we don't have
the name. For some observers where the arguments are strongly typed
and with obvious names, it's relatively easy to find your way around,
but it's much harder I think in the case above.

Is there something C++ can do, for us? Otherwise, would people consider
the idea of adding the variable name as a comment? Eg:

    extern observable<struct inferior * /* inferior */,
                      int /* started */,
                      const char * /* method */,
                      const char * /* format */>
        record_changed;

In addition to making the documentation clear, I think it's nicer to
have the parameter names here, as it provides a "suggestion" as to
what the name of the parameter should be in the function passed as
the callback, which helps keeping things consistent.

I'll agree that the above suggestion with the comment as a parameter
name is not very appealing - it's the only thing that comes to mind
at the moment.

Thanks!
Tom Tromey - March 23, 2018, 4:04 p.m.
>>>>> "Joel" == Joel Brobecker <brobecker@adacore.com> writes:

Joel> In the new file gdb/observable.h, I can't help but notice that
Joel> the observer's documentation is less clear than before when
Joel> the observer has some arguments.

That's a good point.

Joel> Is there something C++ can do, for us? Otherwise, would people consider
Joel> the idea of adding the variable name as a comment? Eg:

I think the comments would be fine.
I will try soon to write a patch to do this.

Tom

Patch

diff --git a/gdb/.gitignore b/gdb/.gitignore
index e7e108768e..b9b2c6f2d1 100644
--- a/gdb/.gitignore
+++ b/gdb/.gitignore
@@ -21,7 +21,6 @@ 
 /jv-exp.c
 /m2-exp.c
 /objc-exp.c
-/observer.h
 /observer.inc
 /p-exp.c
 /rust-exp.c
diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index 690653ac04..cf703fefd2 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -421,6 +421,7 @@  SUBDIR_UNITTESTS_SRCS = \
 	unittests/memory-map-selftests.c \
 	unittests/memrange-selftests.c \
 	unittests/offset-type-selftests.c \
+	unittests/observable-selftests.c \
 	unittests/optional-selftests.c \
 	unittests/ptid-selftests.c \
 	unittests/rsp-low-selftests.c \
@@ -1054,7 +1055,7 @@  COMMON_SFILES = \
 	namespace.c \
 	objc-lang.c \
 	objfiles.c \
-	observer.c \
+	observable.c \
 	opencl-lang.c \
 	osabi.c \
 	osdata.c \
@@ -1586,8 +1587,6 @@  generated_files = \
 	config.h \
 	gcore \
 	jit-reader.h \
-	observer.h \
-	observer.inc \
 	$(GNULIB_H) \
 	$(NAT_GENERATED_FILES)
 
@@ -1946,7 +1945,7 @@  tags: TAGS
 clean mostlyclean: $(CONFIG_CLEAN)
 	@$(MAKE) $(FLAGS_TO_PASS) DO=clean "DODIRS=$(CLEANDIRS)" subdir_do
 	rm -f *.o *.a $(ADD_FILES) *~ init.c-tmp init.l-tmp version.c-tmp
-	rm -f init.c version.c observer.h observer.inc
+	rm -f init.c version.c
 	rm -f gdb$(EXEEXT) core make.log
 	rm -f gdb[0-9]$(EXEEXT)
 	rm -f test-cp-name-parser$(EXEEXT)
@@ -2133,12 +2132,6 @@  version.c: Makefile version.in $(srcdir)/../bfd/version.h $(srcdir)/common/creat
 	$(SHELL) $(srcdir)/common/create-version.sh $(srcdir) \
 	    $(host_alias) $(target_alias) version.c
 
-observer.h: observer.sh doc/observer.texi
-	${srcdir}/observer.sh h ${srcdir}/doc/observer.texi observer.h
-
-observer.inc: observer.sh doc/observer.texi
-	${srcdir}/observer.sh inc ${srcdir}/doc/observer.texi observer.inc
-
 lint: $(LINTFILES)
 	$(LINT) $(INCLUDE_CFLAGS) $(LINTFLAGS) $(LINTFILES) \
 	   `echo $(DEPFILES) $(CONFIG_OBS) | sed 's/\.o /\.c /g'`
diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index ff9dff50d7..f8cefc15fb 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -48,7 +48,7 @@ 
 #include "annotate.h"
 #include "valprint.h"
 #include "source.h"
-#include "observer.h"
+#include "observable.h"
 #include "vec.h"
 #include "stack.h"
 #include "gdb_vecs.h"
@@ -14720,9 +14720,9 @@  DWARF attribute."),
      NULL, xcalloc, xfree);
 
   /* The ada-lang observers.  */
-  observer_attach_new_objfile (ada_new_objfile_observer);
-  observer_attach_free_objfile (ada_free_objfile_observer);
-  observer_attach_inferior_exit (ada_inferior_exit);
+  gdb::observers::new_objfile.attach (ada_new_objfile_observer);
+  gdb::observers::free_objfile.attach (ada_free_objfile_observer);
+  gdb::observers::inferior_exit.attach (ada_inferior_exit);
 
   /* Setup various context-specific data.  */
   ada_inferior_data
diff --git a/gdb/ada-tasks.c b/gdb/ada-tasks.c
index d95d8b092d..bbc0375571 100644
--- a/gdb/ada-tasks.c
+++ b/gdb/ada-tasks.c
@@ -16,7 +16,7 @@ 
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include "defs.h"
-#include "observer.h"
+#include "observable.h"
 #include "gdbcmd.h"
 #include "target.h"
 #include "ada-lang.h"
@@ -1444,8 +1444,8 @@  _initialize_tasks (void)
   ada_tasks_inferior_data_handle = register_inferior_data ();
 
   /* Attach various observers.  */
-  observer_attach_normal_stop (ada_tasks_normal_stop_observer);
-  observer_attach_new_objfile (ada_tasks_new_objfile_observer);
+  gdb::observers::normal_stop.attach (ada_tasks_normal_stop_observer);
+  gdb::observers::new_objfile.attach (ada_tasks_new_objfile_observer);
 
   /* Some new commands provided by this module.  */
   add_info ("tasks", info_tasks_command,
diff --git a/gdb/agent.c b/gdb/agent.c
index 2b7fc8ad6f..1d1f00461c 100644
--- a/gdb/agent.c
+++ b/gdb/agent.c
@@ -51,7 +51,7 @@  set_can_use_agent (const char *args, int from_tty, struct cmd_list_element *c)
     can_use_agent = can_use_agent_off;
 }
 
-#include "observer.h"
+#include "observable.h"
 #include "objfiles.h"
 
 static void
@@ -66,7 +66,7 @@  agent_new_objfile (struct objfile *objfile)
 void
 _initialize_agent (void)
 {
-  observer_attach_new_objfile (agent_new_objfile);
+  gdb::observers::new_objfile.attach (agent_new_objfile);
 
   add_setshow_enum_cmd ("agent", class_run,
 			can_use_agent_enum,
diff --git a/gdb/aix-thread.c b/gdb/aix-thread.c
index 09d5175d90..d2b951d94d 100644
--- a/gdb/aix-thread.c
+++ b/gdb/aix-thread.c
@@ -46,7 +46,7 @@ 
 #include "regcache.h"
 #include "gdbcmd.h"
 #include "ppc-tdep.h"
-#include "observer.h"
+#include "observable.h"
 #include "objfiles.h"
 
 #include <procinfo.h>
@@ -1859,11 +1859,11 @@  _initialize_aix_thread (void)
   complete_target_initialization (&aix_thread_ops);
 
   /* Notice when object files get loaded and unloaded.  */
-  observer_attach_new_objfile (new_objfile);
+  gdb::observers::new_objfile.attach (new_objfile);
 
   /* Add ourselves to inferior_created event chain.
      This is needed to enable the thread target on "attach".  */
-  observer_attach_inferior_created (aix_thread_inferior_created);
+  gdb::observers::inferior_created.attach (aix_thread_inferior_created);
 
   add_setshow_boolean_cmd ("aix-thread", class_maintenance, &debug_aix_thread,
 			   _("Set debugging of AIX thread module."),
diff --git a/gdb/annotate.c b/gdb/annotate.c
index 0c70ff9553..495aa2dba6 100644
--- a/gdb/annotate.c
+++ b/gdb/annotate.c
@@ -22,7 +22,7 @@ 
 #include "target.h"
 #include "gdbtypes.h"
 #include "breakpoint.h"
-#include "observer.h"
+#include "observable.h"
 #include "inferior.h"
 #include "infrun.h"
 #include "top.h"
@@ -592,7 +592,7 @@  breakpoint_changed (struct breakpoint *b)
 void
 _initialize_annotate (void)
 {
-  observer_attach_breakpoint_created (breakpoint_changed);
-  observer_attach_breakpoint_deleted (breakpoint_changed);
-  observer_attach_breakpoint_modified (breakpoint_changed);
+  gdb::observers::breakpoint_created.attach (breakpoint_changed);
+  gdb::observers::breakpoint_deleted.attach (breakpoint_changed);
+  gdb::observers::breakpoint_modified.attach (breakpoint_changed);
 }
diff --git a/gdb/arm-linux-nat.c b/gdb/arm-linux-nat.c
index 484bd4e4c4..d41ef723ff 100644
--- a/gdb/arm-linux-nat.c
+++ b/gdb/arm-linux-nat.c
@@ -24,7 +24,7 @@ 
 #include "linux-nat.h"
 #include "target-descriptions.h"
 #include "auxv.h"
-#include "observer.h"
+#include "observable.h"
 #include "gdbthread.h"
 
 #include "arm-tdep.h"
diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index ef7e66b36a..d71e4ff96b 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -44,7 +44,7 @@ 
 #include "remote.h"
 #include "target-descriptions.h"
 #include "user-regs.h"
-#include "observer.h"
+#include "observable.h"
 
 #include "arch/arm.h"
 #include "arch/arm-get-next-pcs.h"
@@ -9556,7 +9556,7 @@  _initialize_arm_tdep (void)
     = register_objfile_data_with_cleanup (NULL, arm_objfile_data_free);
 
   /* Add ourselves to objfile event chain.  */
-  observer_attach_new_objfile (arm_exidx_new_objfile);
+  gdb::observers::new_objfile.attach (arm_exidx_new_objfile);
   arm_exidx_data_key
     = register_objfile_data_with_cleanup (NULL, arm_exidx_data_free);
 
diff --git a/gdb/auto-load.c b/gdb/auto-load.c
index 70bddbc862..288adb1ba3 100644
--- a/gdb/auto-load.c
+++ b/gdb/auto-load.c
@@ -25,7 +25,7 @@ 
 #include "ui-out.h"
 #include "filenames.h"
 #include "command.h"
-#include "observer.h"
+#include "observable.h"
 #include "objfiles.h"
 #include "cli/cli-script.h"
 #include "gdbcmd.h"
@@ -1553,7 +1553,7 @@  _initialize_auto_load (void)
     = register_program_space_data_with_cleanup (NULL,
 						auto_load_pspace_data_cleanup);
 
-  observer_attach_new_objfile (auto_load_new_objfile);
+  gdb::observers::new_objfile.attach (auto_load_new_objfile);
 
   add_setshow_boolean_cmd ("gdb-scripts", class_support,
 			   &auto_load_gdb_scripts, _("\
@@ -1663,7 +1663,7 @@  This options has security implications for untrusted inferiors."),
 				     show_auto_load_safe_path,
 				     auto_load_set_cmdlist_get (),
 				     auto_load_show_cmdlist_get ());
-  observer_attach_gdb_datadir_changed (auto_load_gdb_datadir_changed);
+  gdb::observers::gdb_datadir_changed.attach (auto_load_gdb_datadir_changed);
 
   cmd = add_cmd ("add-auto-load-safe-path", class_support,
 		 add_auto_load_safe_path,
diff --git a/gdb/auxv.c b/gdb/auxv.c
index 3a4d914326..26cc63e020 100644
--- a/gdb/auxv.c
+++ b/gdb/auxv.c
@@ -24,7 +24,7 @@ 
 #include "inferior.h"
 #include "valprint.h"
 #include "gdbcore.h"
-#include "observer.h"
+#include "observable.h"
 #include "filestuff.h"
 #include "objfiles.h"
 
@@ -579,7 +579,7 @@  This is information provided by the operating system at program startup."));
     = register_inferior_data_with_cleanup (NULL, auxv_inferior_data_cleanup);
 
   /* Observers used to invalidate the auxv cache when needed.  */
-  observer_attach_inferior_exit (invalidate_auxv_cache_inf);
-  observer_attach_inferior_appeared (invalidate_auxv_cache_inf);
-  observer_attach_executable_changed (invalidate_auxv_cache);
+  gdb::observers::inferior_exit.attach (invalidate_auxv_cache_inf);
+  gdb::observers::inferior_appeared.attach (invalidate_auxv_cache_inf);
+  gdb::observers::executable_changed.attach (invalidate_auxv_cache);
 }
diff --git a/gdb/break-catch-syscall.c b/gdb/break-catch-syscall.c
index 42d49387e2..2fb5e6157b 100644
--- a/gdb/break-catch-syscall.c
+++ b/gdb/break-catch-syscall.c
@@ -27,7 +27,7 @@ 
 #include "mi/mi-common.h"
 #include "valprint.h"
 #include "arch-utils.h"
-#include "observer.h"
+#include "observable.h"
 #include "xml-syscall.h"
 
 /* An instance of this type is used to represent a syscall catchpoint.
@@ -632,7 +632,7 @@  _initialize_break_catch_syscall (void)
 {
   initialize_syscall_catchpoint_ops ();
 
-  observer_attach_inferior_exit (clear_syscall_counts);
+  gdb::observers::inferior_exit.attach (clear_syscall_counts);
   catch_syscall_inferior_data
     = register_inferior_data_with_cleanup (NULL,
 					   catch_syscall_inferior_data_cleanup);
diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index 454fda7684..85f2fd800c 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -49,7 +49,7 @@ 
 #include "block.h"
 #include "solib.h"
 #include "solist.h"
-#include "observer.h"
+#include "observable.h"
 #include "memattr.h"
 #include "ada-lang.h"
 #include "top.h"
@@ -903,7 +903,7 @@  set_breakpoint_condition (struct breakpoint *b, const char *exp,
     }
   mark_breakpoint_modified (b);
 
-  observer_notify_breakpoint_modified (b);
+  gdb::observers::breakpoint_modified.notify (b);
 }
 
 /* Completion for the "condition" command.  */
@@ -1172,7 +1172,7 @@  breakpoint_set_commands (struct breakpoint *b,
   validate_commands_for_breakpoint (b, commands.get ());
 
   b->commands = std::move (commands);
-  observer_notify_breakpoint_modified (b);
+  gdb::observers::breakpoint_modified.notify (b);
 }
 
 /* Set the internal `silent' flag on the breakpoint.  Note that this
@@ -1186,7 +1186,7 @@  breakpoint_set_silent (struct breakpoint *b, int silent)
 
   b->silent = silent;
   if (old_silent != silent)
-    observer_notify_breakpoint_modified (b);
+    gdb::observers::breakpoint_modified.notify (b);
 }
 
 /* Set the thread for this breakpoint.  If THREAD is -1, make the
@@ -1199,7 +1199,7 @@  breakpoint_set_thread (struct breakpoint *b, int thread)
 
   b->thread = thread;
   if (old_thread != thread)
-    observer_notify_breakpoint_modified (b);
+    gdb::observers::breakpoint_modified.notify (b);
 }
 
 /* Set the task for this breakpoint.  If TASK is 0, make the
@@ -1212,7 +1212,7 @@  breakpoint_set_task (struct breakpoint *b, int task)
 
   b->task = task;
   if (old_task != task)
-    observer_notify_breakpoint_modified (b);
+    gdb::observers::breakpoint_modified.notify (b);
 }
 
 void
@@ -1269,7 +1269,7 @@  commands_command_1 (const char *arg, int from_tty,
 	 {
 	   validate_commands_for_breakpoint (b, cmd.get ());
 	   b->commands = cmd;
-	   observer_notify_breakpoint_modified (b);
+	   gdb::observers::breakpoint_modified.notify (b);
 	 }
      });
 }
@@ -2655,7 +2655,7 @@  insert_bp_location (struct bp_location *bl,
 	    {
 	      /* See also: disable_breakpoints_in_shlibs.  */
 	      bl->shlib_disabled = 1;
-	      observer_notify_breakpoint_modified (bl->owner);
+	      gdb::observers::breakpoint_modified.notify (bl->owner);
 	      if (!*disabled_breaks)
 		{
 		  fprintf_unfiltered (tmp_error_stream, 
@@ -5321,7 +5321,7 @@  bpstat_check_breakpoint_conditions (bpstat bs, ptid_t ptid)
       bs->stop = 0;
       /* Increase the hit count even though we don't stop.  */
       ++(b->hit_count);
-      observer_notify_breakpoint_modified (b);
+      gdb::observers::breakpoint_modified.notify (b);
     }	
 }
 
@@ -5476,7 +5476,7 @@  bpstat_stop_status (const address_space *aspace,
 	  if (bs->stop)
 	    {
 	      ++(b->hit_count);
-	      observer_notify_breakpoint_modified (b);
+	      gdb::observers::breakpoint_modified.notify (b);
 
 	      /* We will stop here.  */
 	      if (b->disposition == disp_disable)
@@ -7639,7 +7639,7 @@  disable_breakpoints_in_unloaded_shlib (struct so_list *solib)
 	loc->inserted = 0;
 
 	/* This may cause duplicate notifications for the same breakpoint.  */
-	observer_notify_breakpoint_modified (b);
+	gdb::observers::breakpoint_modified.notify (b);
 
 	if (!disabled_shlib_breaks)
 	  {
@@ -7722,7 +7722,7 @@  disable_breakpoints_in_freed_objfile (struct objfile *objfile)
 	}
 
       if (bp_modified)
-	observer_notify_breakpoint_modified (b);
+	gdb::observers::breakpoint_modified.notify (b);
     }
 }
 
@@ -8250,7 +8250,7 @@  install_breakpoint (int internal, std::unique_ptr<breakpoint> &&arg, int update_
     set_tracepoint_count (breakpoint_count);
   if (!internal)
     mention (b);
-  observer_notify_breakpoint_created (b);
+  gdb::observers::breakpoint_created.notify (b);
 
   if (update_gll)
     update_global_location_list (UGLL_MAY_INSERT);
@@ -9989,7 +9989,7 @@  break_range_command (const char *arg, int from_tty)
   b->loc->length = length;
 
   mention (b);
-  observer_notify_breakpoint_created (b);
+  gdb::observers::breakpoint_created.notify (b);
   update_global_location_list (UGLL_MAY_INSERT);
 }
 
@@ -11744,7 +11744,7 @@  download_tracepoint_locations (void)
       t = (struct tracepoint *) b;
       t->number_on_target = b->number;
       if (bp_location_downloaded)
-	observer_notify_breakpoint_modified (b);
+	gdb::observers::breakpoint_modified.notify (b);
     }
 }
 
@@ -13257,7 +13257,7 @@  delete_breakpoint (struct breakpoint *bpt)
      a problem in that process, we'll be asked to delete the half-created
      watchpoint.  In that case, don't announce the deletion.  */
   if (bpt->number)
-    observer_notify_breakpoint_deleted (bpt);
+    gdb::observers::breakpoint_deleted.notify (bpt);
 
   if (breakpoint_chain == bpt)
     breakpoint_chain = bpt->next;
@@ -13732,7 +13732,7 @@  update_breakpoint_locations (struct breakpoint *b,
   }
 
   if (!locations_are_equal (existing_locations, b->loc))
-    observer_notify_breakpoint_modified (b);
+    gdb::observers::breakpoint_modified.notify (b);
 }
 
 /* Find the SaL locations corresponding to the given LOCATION.
@@ -14029,7 +14029,7 @@  set_ignore_count (int bptnum, int count, int from_tty)
 			       "crossings of breakpoint %d."),
 			     count, bptnum);
 	}
-      observer_notify_breakpoint_modified (b);
+      gdb::observers::breakpoint_modified.notify (b);
       return;
     }
 
@@ -14332,7 +14332,7 @@  disable_breakpoint (struct breakpoint *bpt)
 
   update_global_location_list (UGLL_DONT_INSERT);
 
-  observer_notify_breakpoint_modified (bpt);
+  gdb::observers::breakpoint_modified.notify (bpt);
 }
 
 /* Enable or disable the breakpoint(s) or breakpoint location(s)
@@ -14458,7 +14458,7 @@  enable_breakpoint_disp (struct breakpoint *bpt, enum bpdisp disposition,
   bpt->enable_count = count;
   update_global_location_list (UGLL_MAY_INSERT);
 
-  observer_notify_breakpoint_modified (bpt);
+  gdb::observers::breakpoint_modified.notify (bpt);
 }
 
 
@@ -14938,7 +14938,7 @@  static void
 trace_pass_set_count (struct tracepoint *tp, int count, int from_tty)
 {
   tp->pass_count = count;
-  observer_notify_breakpoint_modified (tp);
+  gdb::observers::breakpoint_modified.notify (tp);
   if (from_tty)
     printf_filtered (_("Setting tracepoint %d's passcount to %d\n"),
 		     tp->number, count);
@@ -15578,9 +15578,9 @@  _initialize_breakpoint (void)
 
   initialize_breakpoint_ops ();
 
-  observer_attach_solib_unloaded (disable_breakpoints_in_unloaded_shlib);
-  observer_attach_free_objfile (disable_breakpoints_in_freed_objfile);
-  observer_attach_memory_changed (invalidate_bp_value_on_memory_change);
+  gdb::observers::solib_unloaded.attach (disable_breakpoints_in_unloaded_shlib);
+  gdb::observers::free_objfile.attach (disable_breakpoints_in_freed_objfile);
+  gdb::observers::memory_changed.attach (invalidate_bp_value_on_memory_change);
 
   breakpoint_objfile_key
     = register_objfile_data_with_cleanup (NULL, free_breakpoint_objfile_data);
@@ -16131,6 +16131,6 @@  agent-printf \"printf format string\", arg1, arg2, arg3, ..., argn\n\
 
   automatic_hardware_breakpoints = 1;
 
-  observer_attach_about_to_proceed (breakpoint_about_to_proceed);
-  observer_attach_thread_exit (remove_threaded_breakpoints);
+  gdb::observers::about_to_proceed.attach (breakpoint_about_to_proceed);
+  gdb::observers::thread_exit.attach (remove_threaded_breakpoints);
 }
diff --git a/gdb/bsd-uthread.c b/gdb/bsd-uthread.c
index fdcac41e6a..6c9e3af77f 100644
--- a/gdb/bsd-uthread.c
+++ b/gdb/bsd-uthread.c
@@ -22,7 +22,7 @@ 
 #include "gdbthread.h"
 #include "inferior.h"
 #include "objfiles.h"
-#include "observer.h"
+#include "observable.h"
 #include "regcache.h"
 #include "solib.h"
 #include "solist.h"
@@ -554,7 +554,7 @@  _initialize_bsd_uthread (void)
 
   bsd_uthread_data = gdbarch_data_register_pre_init (bsd_uthread_init);
 
-  observer_attach_inferior_created (bsd_uthread_inferior_created);
-  observer_attach_solib_loaded (bsd_uthread_solib_loaded);
-  observer_attach_solib_unloaded (bsd_uthread_solib_unloaded);
+  gdb::observers::inferior_created.attach (bsd_uthread_inferior_created);
+  gdb::observers::solib_loaded.attach (bsd_uthread_solib_loaded);
+  gdb::observers::solib_unloaded.attach (bsd_uthread_solib_unloaded);
 }
diff --git a/gdb/cli/cli-interp.c b/gdb/cli/cli-interp.c
index 12b677fa7e..bbee809880 100644
--- a/gdb/cli/cli-interp.c
+++ b/gdb/cli/cli-interp.c
@@ -26,7 +26,7 @@ 
 #include "top.h"		/* for "execute_command" */
 #include "event-top.h"
 #include "infrun.h"
-#include "observer.h"
+#include "observable.h"
 #include "gdbthread.h"
 #include "thread-fsm.h"
 
@@ -461,14 +461,14 @@  _initialize_cli_interp (void)
   interp_factory_register (INTERP_CONSOLE, cli_interp_factory);
 
   /* If changing this, remember to update tui-interp.c as well.  */
-  observer_attach_normal_stop (cli_on_normal_stop);
-  observer_attach_end_stepping_range (cli_on_end_stepping_range);
-  observer_attach_signal_received (cli_on_signal_received);
-  observer_attach_signal_exited (cli_on_signal_exited);
-  observer_attach_exited (cli_on_exited);
-  observer_attach_no_history (cli_on_no_history);
-  observer_attach_sync_execution_done (cli_on_sync_execution_done);
-  observer_attach_command_error (cli_on_command_error);
-  observer_attach_user_selected_context_changed
+  gdb::observers::normal_stop.attach (cli_on_normal_stop);
+  gdb::observers::end_stepping_range.attach (cli_on_end_stepping_range);
+  gdb::observers::signal_received.attach (cli_on_signal_received);
+  gdb::observers::signal_exited.attach (cli_on_signal_exited);
+  gdb::observers::exited.attach (cli_on_exited);
+  gdb::observers::no_history.attach (cli_on_no_history);
+  gdb::observers::sync_execution_done.attach (cli_on_sync_execution_done);
+  gdb::observers::command_error.attach (cli_on_command_error);
+  gdb::observers::user_selected_context_changed.attach
     (cli_on_user_selected_context_changed);
 }
diff --git a/gdb/cli/cli-setshow.c b/gdb/cli/cli-setshow.c
index f74a8acf36..bb444688f9 100644
--- a/gdb/cli/cli-setshow.c
+++ b/gdb/cli/cli-setshow.c
@@ -20,7 +20,7 @@ 
 #include "value.h"
 #include <ctype.h>
 #include "arch-utils.h"
-#include "observer.h"
+#include "observable.h"
 
 #include "ui-out.h"
 
@@ -511,20 +511,20 @@  do_set_command (const char *arg, int from_tty, struct cmd_list_element *c)
 	case var_filename:
 	case var_optional_filename:
 	case var_enum:
-	  observer_notify_command_param_changed (name, *(char **) c->var);
+	  gdb::observers::command_param_changed.notify (name, *(char **) c->var);
 	  break;
 	case var_boolean:
 	  {
 	    const char *opt = *(int *) c->var ? "on" : "off";
 
-	    observer_notify_command_param_changed (name, opt);
+	    gdb::observers::command_param_changed.notify (name, opt);
 	  }
 	  break;
 	case var_auto_boolean:
 	  {
 	    const char *s = auto_boolean_enums[*(enum auto_boolean *) c->var];
 
-	    observer_notify_command_param_changed (name, s);
+	    gdb::observers::command_param_changed.notify (name, s);
 	  }
 	  break;
 	case var_uinteger:
@@ -533,7 +533,7 @@  do_set_command (const char *arg, int from_tty, struct cmd_list_element *c)
 	    char s[64];
 
 	    xsnprintf (s, sizeof s, "%u", *(unsigned int *) c->var);
-	    observer_notify_command_param_changed (name, s);
+	    gdb::observers::command_param_changed.notify (name, s);
 	  }
 	  break;
 	case var_integer:
@@ -543,7 +543,7 @@  do_set_command (const char *arg, int from_tty, struct cmd_list_element *c)
 	    char s[64];
 
 	    xsnprintf (s, sizeof s, "%d", *(int *) c->var);
-	    observer_notify_command_param_changed (name, s);
+	    gdb::observers::command_param_changed.notify (name, s);
 	  }
 	  break;
 	}
diff --git a/gdb/common/observable.h b/gdb/common/observable.h
new file mode 100644
index 0000000000..f5666c14e5
--- /dev/null
+++ b/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 */
diff --git a/gdb/corefile.c b/gdb/corefile.c
index abf9ea675d..5a735264ef 100644
--- a/gdb/corefile.c
+++ b/gdb/corefile.c
@@ -30,7 +30,7 @@ 
 #include "dis-asm.h"
 #include <sys/stat.h>
 #include "completer.h"
-#include "observer.h"
+#include "observable.h"
 #include "cli/cli-utils.h"
 
 /* You can have any number of hooks for `exec_file_command' command to
@@ -408,7 +408,7 @@  write_memory_with_notification (CORE_ADDR memaddr, const bfd_byte *myaddr,
 				ssize_t len)
 {
   write_memory (memaddr, myaddr, len);
-  observer_notify_memory_changed (current_inferior (), memaddr, len, myaddr);
+  gdb::observers::memory_changed.notify (current_inferior (), memaddr, len, myaddr);
 }
 
 /* Store VALUE at ADDR in the inferior as a LEN-byte unsigned
diff --git a/gdb/defs.h b/gdb/defs.h
index 91988758a3..ff3599ddac 100644
--- a/gdb/defs.h
+++ b/gdb/defs.h
@@ -658,7 +658,7 @@  enum block_enum
   FIRST_LOCAL_BLOCK = 2
 };
 
-/* User selection used in observer.h and multiple print functions.  */
+/* User selection used in observable.h and multiple print functions.  */
 
 enum user_selected_what_flag
   {
diff --git a/gdb/doc/observer.texi b/gdb/doc/observer.texi
deleted file mode 100644
index 8ab8da709d..0000000000
--- a/gdb/doc/observer.texi
+++ /dev/null
@@ -1,313 +0,0 @@ 
-@c -*-texinfo-*-
-
-@c This file is part of the GDB manual.
-@c
-@c Copyright (C) 2003-2018 Free Software Foundation, Inc.
-@c
-@c See the file gdbint.texinfo for copying conditions.
-@c
-@c Also, the @deftypefun lines from this file are processed into a
-@c header file during the GDB build process.  Permission is granted
-@c to redistribute and/or modify those lines under the terms of the
-@c GNU General Public License as published by the Free Software
-@c Foundation; either version 3 of the License, or (at your option)
-@c any later version.
-
-@node GDB Observers
-@appendix @value{GDBN} Currently available observers
-
-@section Implementation rationale
-@cindex observers implementation rationale
-
-An @dfn{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 @dfn{subject}.  To receive
-notifications, the observer attaches a callback to the subject.
-One subject can have several observers.
-
-@file{observer.c} implements an internal generic low-level event
-notification mechanism.  This generic event notification mechanism is
-then re-used to implement the exported high-level notification
-management routines for all possible notifications.
-
-The current implementation of the generic observer provides support
-for contextual data.  This contextual data is given to the subject
-when attaching the callback.  In return, the subject will provide
-this contextual data back to the observer as a parameter of the
-callback.
-
-Note that the current support for the contextual data is only partial,
-as it lacks a mechanism that would deallocate this data when the
-callback is detached.  This is not a problem so far, as this contextual
-data is only used internally to hold a function pointer.  Later on, if
-a certain observer needs to provide support for user-level contextual
-data, then the generic notification mechanism will need to be
-enhanced to allow the observer to provide a routine to deallocate the
-data when attaching the callback.
-
-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.
-
-@section Debugging
-Observer notifications can be traced using the command @samp{set debug
-observer 1} (@pxref{Debugging Output, , Optional messages about
-internal happenings, gdb, Debugging with @var{GDBN}}).
-
-@section @code{normal_stop} Notifications
-@cindex @code{normal_stop} observer
-@cindex notification about inferior execution stop
-
-@value{GDBN} notifies all @code{normal_stop} observers when the
-inferior execution has just stopped, the associated messages and
-annotations have been printed, and the control is about to be returned
-to the user.
-
-Note that the @code{normal_stop} notification is not emitted when
-the execution stops due to a breakpoint, and this breakpoint has
-a condition that is not met.  If the breakpoint has any associated
-commands list, the commands are executed after the notification
-is emitted.
-
-The following interfaces are available to manage observers:
-
-@deftypefun extern struct observer *observer_attach_@var{event} (observer_@var{event}_ftype *@var{f})
-Using the function @var{f}, create an observer that is notified when
-ever @var{event} occurs, return the observer.
-@end deftypefun
-
-@deftypefun extern void observer_detach_@var{event} (struct observer *@var{observer});
-Remove @var{observer} from the list of observers to be notified when
-@var{event} occurs.
-@end deftypefun
-
-@deftypefun extern void observer_notify_@var{event} (void);
-Send a notification to all @var{event} observers.
-@end deftypefun
-
-The following observable events are defined:
-
-@deftypefun void normal_stop (struct bpstats *@var{bs}, int @var{print_frame})
-The inferior has stopped for real.  The  @var{bs} argument describes
-the breakpoints were are stopped at, if any.  Second argument
-@var{print_frame} non-zero means display the location where the
-inferior has stopped.
-@end deftypefun
-
-@deftypefun void signal_received (enum gdb_signal @var{siggnal})
-The inferior was stopped by a signal.
-@end deftypefun
-
-@deftypefun void end_stepping_range (void)
-We are done with a step/next/si/ni command.
-@end deftypefun
-
-@deftypefun void signal_exited (enum gdb_signal @var{siggnal})
-The inferior was terminated by a signal.
-@end deftypefun
-
-@deftypefun void exited (int @var{exitstatus})
-The inferior program is finished.
-@end deftypefun
-
-@deftypefun void no_history (void)
-Reverse execution: target ran out of history info.
-@end deftypefun
-
-@deftypefun void sync_execution_done (void)
-A synchronous command finished.
-@end deftypefun
-
-@deftypefun void command_error (void)
-An error was caught while executing a command.
-@end deftypefun
-
-@deftypefun void target_changed (struct target_ops *@var{target})
-The target's register contents have changed.
-@end deftypefun
-
-@deftypefun void executable_changed (void)
-The executable being debugged by GDB has changed: The user decided
-to debug a different program, or the program he was debugging has
-been modified since being loaded by the debugger (by being recompiled,
-for instance).
-@end deftypefun
-
-@deftypefun void inferior_created (struct target_ops *@var{objfile}, int @var{from_tty})
-@value{GDBN} has just connected to an inferior.  For @samp{run},
-@value{GDBN} calls this observer while the inferior is still stopped
-at the entry-point instruction.  For @samp{attach} and @samp{core},
-@value{GDBN} calls this observer immediately after connecting to the
-inferior, and before any information on the inferior has been printed.
-@end deftypefun
-
-@deftypefun void record_changed (struct inferior *@var{inferior}, int @var{started}, const char *@var{method}, const char *@var{format})
-The status of process record for inferior @var{inferior} in
-@value{GDBN} has changed.  The process record is started if
-@var{started} is true, and the process record is stopped if
-@var{started} is false.
-
-When @var{started} is true, @var{method} indicates the short name of the method
-used for recording.  If the method supports multiple formats, @var{format}
-indicates which one is being used, otherwise it is NULL.  When @var{started} is
-false, they are both NULL.
-@end deftypefun
-
-@deftypefun void solib_loaded (struct so_list *@var{solib})
-The shared library specified by @var{solib} has been loaded.  Note that
-when @value{GDBN} calls this observer, the library's symbols probably
-haven't been loaded yet.
-@end deftypefun
-
-@deftypefun void solib_unloaded (struct so_list *@var{solib})
-The shared library specified by @var{solib} has been unloaded.
-Note that when @value{GDBN} calls this observer, the library's
-symbols have not been unloaded yet, and thus are still available.
-@end deftypefun
-
-@deftypefun void new_objfile (struct objfile *@var{objfile})
-The symbol file specified by @var{objfile} has been loaded.
-Called with @var{objfile} equal to @code{NULL} to indicate
-previously loaded symbol table data has now been invalidated.
-@end deftypefun
-
-@deftypefun void free_objfile (struct objfile *@var{objfile})
-The object file specified by @var{objfile} is about to be freed.
-@end deftypefun
-
-@deftypefun void new_thread (struct thread_info *@var{t})
-The thread specified by @var{t} has been created.
-@end deftypefun
-
-@deftypefun void thread_exit (struct thread_info *@var{t}, int @var{silent})
-The thread specified by @var{t} has exited.  The @var{silent} argument
-indicates that @value{GDBN} is removing the thread from its tables
-without wanting to notify the user about it.
-@end deftypefun
-
-@deftypefun void thread_stop_requested (ptid_t @var{ptid})
-An explicit stop request was issued to @var{ptid}.  If @var{ptid}
-equals @var{minus_one_ptid}, the request applied to all threads.  If
-@code{ptid_is_pid(ptid)} returns true, the request applied to all
-threads of the process pointed at by @var{ptid}.  Otherwise, the
-request applied to the single thread pointed at by @var{ptid}.
-@end deftypefun
-
-@deftypefun void target_resumed (ptid_t @var{ptid})
-The target was resumed.  The @var{ptid} parameter specifies which
-thread was resume, and may be RESUME_ALL if all threads are resumed.
-@end deftypefun
-
-@deftypefun void about_to_proceed (void)
-The target is about to be proceeded.
-@end deftypefun
-
-@deftypefun void breakpoint_created (struct breakpoint *@var{b})
-A new breakpoint @var{b} has been created.
-@end deftypefun
-
-@deftypefun void breakpoint_deleted (struct breakpoint *@var{b})
-A breakpoint has been destroyed.  The argument @var{b} is the
-pointer to the destroyed breakpoint.
-@end deftypefun
-
-@deftypefun void breakpoint_modified (struct breakpoint *@var{b})
-A breakpoint has been modified in some way.  The argument @var{b}
-is the modified breakpoint.
-@end deftypefun
-
-@deftypefun void traceframe_changed (int @var{tfnum}, int @var{tpnum})
-The trace frame is changed to @var{tfnum} (e.g., by using the
-@code{tfind} command).  If @var{tfnum} is negative, it means
-@value{GDBN} resumes live debugging.  The number of the tracepoint
-associated with this traceframe is @var{tpnum}.
-@end deftypefun
-
-@deftypefun void architecture_changed (struct gdbarch *@var{newarch})
-The current architecture has changed.  The argument @var{newarch} is
-a pointer to the new architecture.
-@end deftypefun
-
-@deftypefun void thread_ptid_changed (ptid_t @var{old_ptid}, ptid_t @var{new_ptid})
-The thread's ptid has changed.  The @var{old_ptid} parameter specifies
-the old value, and @var{new_ptid} specifies the new value.
-@end deftypefun
-
-@deftypefun void inferior_added (struct inferior *@var{inf})
-The inferior @var{inf} has been added to the list of inferiors.  At
-this point, it might not be associated with any process.
-@end deftypefun
-
-@deftypefun void inferior_appeared (struct inferior *@var{inf})
-The inferior identified by @var{inf} has been attached to a process.
-@end deftypefun
-
-@deftypefun void inferior_exit (struct inferior *@var{inf})
-Either the inferior associated with @var{inf} has been detached from the
-process, or the process has exited.
-@end deftypefun
-
-@deftypefun void inferior_removed (struct inferior *@var{inf})
-The inferior @var{inf} has been removed from the list of inferiors.
-This method is called immediately before freeing @var{inf}.
-@end deftypefun
-
-@deftypefun void memory_changed (struct inferior *@var{inferior}, CORE_ADDR @var{addr}, ssize_t @var{len}, const bfd_byte *@var{data})
-Bytes from @var{data} to @var{data} + @var{len} have been written
-to the @var{inferior} at @var{addr}.
-@end deftypefun
-
-@deftypefun void before_prompt (const char *@var{current_prompt})
-Called before a top-level prompt is displayed.  @var{current_prompt} is
-the current top-level prompt.
-@end deftypefun
-
-@deftypefun void gdb_datadir_changed (void)
-Variable gdb_datadir has been set.  The value may not necessarily change.
-@end deftypefun
-
-@deftypefun void command_param_changed (const char *@var{param}, const char *@var{value})
-The parameter of some @code{set} commands in console are changed.  This
-method is called after a command @code{set @var{param} @var{value}}.
-@var{param} is the parameter of @code{set} command, and @var{value}
-is the value of changed parameter.
-@end deftypefun
-
-@deftypefun void tsv_created (const struct trace_state_variable *@var{tsv})
-The new trace state variable @var{tsv} is created.
-@end deftypefun
-
-@deftypefun void tsv_deleted (const struct trace_state_variable *@var{tsv})
-The trace state variable @var{tsv} is deleted.  If @var{tsv} is
-@code{NULL}, all trace state variables are deleted.
-@end deftypefun
-
-@deftypefun void tsv_modified (const struct trace_state_variable *@var{tsv})
-The trace state value @var{tsv} is modified.
-@end deftypefun
-
-@deftypefun void inferior_call_pre (ptid_t @var{thread}, CORE_ADDR @var{address})
-An inferior function at @var{address} is about to be called in thread
-@var{thread}.
-@end deftypefun
-
-@deftypefun void inferior_call_post (ptid_t @var{thread}, CORE_ADDR @var{address})
-The inferior function at @var{address} has just been called.  This observer
-is called even if the inferior exits during the call.  @var{thread} is the
-thread in which the function was called, which may be different from the
-current thread.
-@end deftypefun
-
-@deftypefun void register_changed (struct frame_info *@var{frame}, int @var{regnum})
-A register in the inferior has been modified by the @value{GDBN} user.
-@end deftypefun
-
-@deftypefun void test_notification (int @var{somearg})
-This observer is used for internal testing.  Do not use.  
-See testsuite/gdb.gdb/observer.exp.
-@end deftypefun
-
-@deftypefun void user_selected_context_changed (user_selected_what @var{selection})
-The user-selected inferior, thread and/or frame has changed.  The user_select_what
-flag specifies if the inferior, thread and/or frame has changed.
-@end deftypefun
diff --git a/gdb/dummy-frame.c b/gdb/dummy-frame.c
index a67033e6f2..82e7251cce 100644
--- a/gdb/dummy-frame.c
+++ b/gdb/dummy-frame.c
@@ -26,7 +26,7 @@ 
 #include "frame-unwind.h"
 #include "command.h"
 #include "gdbcmd.h"
-#include "observer.h"
+#include "observable.h"
 #include "gdbthread.h"
 #include "infcall.h"
 
@@ -424,5 +424,5 @@  _initialize_dummy_frame (void)
 	   _("Print the contents of the internal dummy-frame stack."),
 	   &maintenanceprintlist);
 
-  observer_attach_inferior_created (cleanup_dummy_frames);
+  gdb::observers::inferior_created.attach (cleanup_dummy_frames);
 }
diff --git a/gdb/event-loop.c b/gdb/event-loop.c
index 7934ab4c82..9ca473e7b5 100644
--- a/gdb/event-loop.c
+++ b/gdb/event-loop.c
@@ -34,7 +34,7 @@ 
 #include <sys/types.h>
 #include "gdb_sys_time.h"
 #include "gdb_select.h"
-#include "observer.h"
+#include "observable.h"
 #include "top.h"
 
 /* Tell create_file_handler what events we are interested in.
@@ -382,7 +382,7 @@  start_event_loop (void)
 	     get around to resetting the prompt, which leaves readline
 	     in a messed-up state.  Reset it here.  */
 	  current_ui->prompt_state = PROMPT_NEEDED;
-	  observer_notify_command_error ();
+	  gdb::observers::command_error.notify ();
 	  /* This call looks bizarre, but it is required.  If the user
 	     entered a command that caused an error,
 	     after_char_processing_hook won't be called from
diff --git a/gdb/event-top.c b/gdb/event-top.c
index 0c1528e5eb..5852089f09 100644
--- a/gdb/event-top.c
+++ b/gdb/event-top.c
@@ -32,7 +32,7 @@ 
 #include "cli/cli-script.h"     /* for reset_command_nest_depth */
 #include "main.h"
 #include "gdbthread.h"
-#include "observer.h"
+#include "observable.h"
 #include "continuations.h"
 #include "gdbcmd.h"		/* for dont_repeat() */
 #include "annotate.h"
@@ -428,7 +428,7 @@  top_level_prompt (void)
 
   /* Give observers a chance of changing the prompt.  E.g., the python
      `gdb.prompt_hook' is installed as an observer.  */
-  observer_notify_before_prompt (get_prompt ());
+  gdb::observers::before_prompt.notify (get_prompt ());
 
   prompt = get_prompt ();
 
diff --git a/gdb/exec.c b/gdb/exec.c
index 6b910e8f54..f94c15f1f5 100644
--- a/gdb/exec.c
+++ b/gdb/exec.c
@@ -29,7 +29,7 @@ 
 #include "completer.h"
 #include "value.h"
 #include "exec.h"
-#include "observer.h"
+#include "observable.h"
 #include "arch-utils.h"
 #include "gdbthread.h"
 #include "progspace.h"
@@ -378,7 +378,7 @@  exec_file_attach (const char *filename, int from_tty)
     }
 
   bfd_cache_close_all ();
-  observer_notify_executable_changed ();
+  gdb::observers::executable_changed.notify ();
 }
 
 /*  Process the first arg in ARGS as the new exec file.
diff --git a/gdb/extension.c b/gdb/extension.c
index 67f83b4bcd..4e3b3e94bb 100644
--- a/gdb/extension.c
+++ b/gdb/extension.c
@@ -28,7 +28,7 @@ 
 #include "event-top.h"
 #include "extension.h"
 #include "extension-priv.h"
-#include "observer.h"
+#include "observable.h"
 #include "cli/cli-script.h"
 #include "python/python.h"
 #include "guile/guile.h"
@@ -945,5 +945,5 @@  ext_lang_before_prompt (const char *current_gdb_prompt)
 void
 _initialize_extension (void)
 {
-  observer_attach_before_prompt (ext_lang_before_prompt);
+  gdb::observers::before_prompt.attach (ext_lang_before_prompt);
 }
diff --git a/gdb/frame.c b/gdb/frame.c
index 0b04a4ebac..c792d1f4e1 100644
--- a/gdb/frame.c
+++ b/gdb/frame.c
@@ -34,7 +34,7 @@ 
 #include "frame-base.h"
 #include "command.h"
 #include "gdbcmd.h"
-#include "observer.h"
+#include "observable.h"
 #include "objfiles.h"
 #include "gdbthread.h"
 #include "block.h"
@@ -2923,7 +2923,7 @@  _initialize_frame (void)
 
   frame_stash_create ();
 
-  observer_attach_target_changed (frame_observer_target_changed);
+  gdb::observers::target_changed.attach (frame_observer_target_changed);
 
   add_prefix_cmd ("backtrace", class_maintenance, set_backtrace_cmd, _("\
 Set backtrace specific variables.\n\
diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c
index b8703e5a55..ddafe25d4d 100644
--- a/gdb/gdbarch.c
+++ b/gdb/gdbarch.c
@@ -44,7 +44,7 @@ 
 #include "reggroups.h"
 #include "osabi.h"
 #include "gdb_obstack.h"
-#include "observer.h"
+#include "observable.h"
 #include "regcache.h"
 #include "objfiles.h"
 #include "auxv.h"
@@ -5457,7 +5457,7 @@  set_target_gdbarch (struct gdbarch *new_gdbarch)
   gdb_assert (new_gdbarch != NULL);
   gdb_assert (new_gdbarch->initialized_p);
   current_inferior ()->gdbarch = new_gdbarch;
-  observer_notify_architecture_changed (new_gdbarch);
+  gdb::observers::architecture_changed.notify (new_gdbarch);
   registers_changed ();
 }
 
diff --git a/gdb/guile/scm-breakpoint.c b/gdb/guile/scm-breakpoint.c
index 642eefd71e..75c24a5235 100644
--- a/gdb/guile/scm-breakpoint.c
+++ b/gdb/guile/scm-breakpoint.c
@@ -25,7 +25,7 @@ 
 #include "breakpoint.h"
 #include "gdbcmd.h"
 #include "gdbthread.h"
-#include "observer.h"
+#include "observable.h"
 #include "cli/cli-script.h"
 #include "ada-lang.h"
 #include "arch-utils.h"
@@ -1327,8 +1327,8 @@  gdbscm_initialize_breakpoints (void)
   scm_set_smob_free (breakpoint_smob_tag, bpscm_free_breakpoint_smob);
   scm_set_smob_print (breakpoint_smob_tag, bpscm_print_breakpoint_smob);
 
-  observer_attach_breakpoint_created (bpscm_breakpoint_created);
-  observer_attach_breakpoint_deleted (bpscm_breakpoint_deleted);
+  gdb::observers::breakpoint_created.attach (bpscm_breakpoint_created);
+  gdb::observers::breakpoint_deleted.attach (bpscm_breakpoint_deleted);
 
   gdbscm_define_integer_constants (breakpoint_integer_constants, 1);
   gdbscm_define_functions (breakpoint_functions, 1);
diff --git a/gdb/inf-loop.c b/gdb/inf-loop.c
index eaaa8443e4..bb6ad25bb7 100644
--- a/gdb/inf-loop.c
+++ b/gdb/inf-loop.c
@@ -29,7 +29,7 @@ 
 #include "continuations.h"
 #include "interps.h"
 #include "top.h"
-#include "observer.h"
+#include "observable.h"
 
 /* General function to handle events in the inferior.  */
 
diff --git a/gdb/infcall.c b/gdb/infcall.c
index 54f82ba02c..9f02674bdf 100644
--- a/gdb/infcall.c
+++ b/gdb/infcall.c
@@ -35,7 +35,7 @@ 
 #include "ada-lang.h"
 #include "gdbthread.h"
 #include "event-top.h"
-#include "observer.h"
+#include "observable.h"
 #include "top.h"
 #include "interps.h"
 #include "thread-fsm.h"
@@ -903,7 +903,7 @@  call_function_by_hand_dummy (struct value *function,
       target_values_type = values_type;
     }
 
-  observer_notify_inferior_call_pre (inferior_ptid, funaddr);
+  gdb::observers::inferior_call_pre.notify (inferior_ptid, funaddr);
 
   /* Determine the location of the breakpoint (and possibly other
      stuff) that the called function will return to.  The SPARC, for a
@@ -1176,7 +1176,7 @@  call_function_by_hand_dummy (struct value *function,
 
     e = run_inferior_call (sm, tp, real_pc);
 
-    observer_notify_inferior_call_post (call_thread_ptid, funaddr);
+    gdb::observers::inferior_call_post.notify (call_thread_ptid, funaddr);
 
     tp = find_thread_ptid (call_thread_ptid);
     if (tp != NULL)
diff --git a/gdb/infcmd.c b/gdb/infcmd.c
index c10a49892e..9c236b8e70 100644
--- a/gdb/infcmd.c
+++ b/gdb/infcmd.c
@@ -42,7 +42,7 @@ 
 #include "block.h"
 #include "solib.h"
 #include <ctype.h>
-#include "observer.h"
+#include "observable.h"
 #include "target-descriptions.h"
 #include "user-regs.h"
 #include "cli/cli-decode.h"
@@ -499,7 +499,7 @@  post_create_inferior (struct target_ops *target, int from_tty)
      if the now pushed target supports hardware watchpoints.  */
   breakpoint_re_set ();
 
-  observer_notify_inferior_created (target, from_tty);
+  gdb::observers::inferior_created.notify (target, from_tty);
 }
 
 /* Kill the inferior if already running.  This function is designed
diff --git a/gdb/inferior.c b/gdb/inferior.c
index c88a23c241..4ff5712d75 100644
--- a/gdb/inferior.c
+++ b/gdb/inferior.c
@@ -26,7 +26,7 @@ 
 #include "gdbcmd.h"
 #include "gdbthread.h"
 #include "ui-out.h"
-#include "observer.h"
+#include "observable.h"
 #include "gdbcore.h"
 #include "symfile.h"
 #include "environ.h"
@@ -109,7 +109,7 @@  add_inferior_silent (int pid)
       last->next = inf;
     }
 
-  observer_notify_inferior_added (inf);
+  gdb::observers::inferior_added.notify (inf);
 
   if (pid != 0)
     inferior_appeared (inf, pid);
@@ -176,7 +176,7 @@  delete_inferior (struct inferior *todel)
   else
     inferior_list = inf->next;
 
-  observer_notify_inferior_removed (inf);
+  gdb::observers::inferior_removed.notify (inf);
 
   /* If this program space is rendered useless, remove it. */
   if (program_space_empty_p (inf->pspace))
@@ -206,7 +206,7 @@  exit_inferior_1 (struct inferior *inftoex, int silent)
 
   iterate_over_threads (delete_thread_of_inferior, &arg);
 
-  observer_notify_inferior_exit (inf);
+  gdb::observers::inferior_exit.notify (inf);
 
   inf->pid = 0;
   inf->fake_pid_p = 0;
@@ -284,7 +284,7 @@  inferior_appeared (struct inferior *inf, int pid)
   inf->has_exit_code = 0;
   inf->exit_code = 0;
 
-  observer_notify_inferior_appeared (inf);
+  gdb::observers::inferior_appeared.notify (inf);
 }
 
 void
@@ -713,7 +713,7 @@  inferior_command (const char *args, int from_tty)
 	  switch_to_thread (tp->ptid);
 	}
 
-      observer_notify_user_selected_context_changed
+      gdb::observers::user_selected_context_changed.notify
 	(USER_SELECTED_INFERIOR
 	 | USER_SELECTED_THREAD
 	 | USER_SELECTED_FRAME);
@@ -724,7 +724,8 @@  inferior_command (const char *args, int from_tty)
       switch_to_thread (null_ptid);
       set_current_program_space (inf->pspace);
 
-      observer_notify_user_selected_context_changed (USER_SELECTED_INFERIOR);
+      gdb::observers::user_selected_context_changed.notify
+	(USER_SELECTED_INFERIOR);
     }
 }
 
diff --git a/gdb/inflow.c b/gdb/inflow.c
index d971543a28..08e47d65cb 100644
--- a/gdb/inflow.c
+++ b/gdb/inflow.c
@@ -24,7 +24,7 @@ 
 #include "terminal.h"
 #include "target.h"
 #include "gdbthread.h"
-#include "observer.h"
+#include "observable.h"
 #include <signal.h>
 #include <fcntl.h>
 #include "gdb_select.h"
@@ -989,7 +989,7 @@  _initialize_inflow (void)
   /* OK, figure out whether we have job control.  */
   have_job_control ();
 
-  observer_attach_inferior_exit (inflow_inferior_exit);
+  gdb::observers::inferior_exit.attach (inflow_inferior_exit);
 
   inflow_inferior_data
     = register_inferior_data_with_cleanup (NULL, inflow_inferior_data_cleanup);
diff --git a/gdb/infrun.c b/gdb/infrun.c
index 5aeafef08b..6648698df6 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -38,7 +38,7 @@ 
 #include "inf-loop.h"
 #include "regcache.h"
 #include "value.h"
-#include "observer.h"
+#include "observable.h"
 #include "language.h"
 #include "solib.h"
 #include "main.h"
@@ -2899,7 +2899,7 @@  clear_proceed_status (int step)
       inferior->control.stop_soon = NO_STOP_QUIETLY;
     }
 
-  observer_notify_about_to_proceed ();
+  gdb::observers::about_to_proceed.notify ();
 }
 
 /* Returns true if TP is still stopped at a breakpoint that needs
@@ -3816,7 +3816,7 @@  check_curr_ui_sync_execution_done (void)
       && !gdb_in_secondary_prompt_p (ui))
     {
       target_terminal::ours ();
-      observer_notify_sync_execution_done ();
+      gdb::observers::sync_execution_done.notify ();
       ui_register_input_event_handler (ui);
     }
 }
@@ -5069,7 +5069,7 @@  handle_inferior_event_1 (struct execution_control_state *ecs)
 	  /* Support the --return-child-result option.  */
 	  return_child_result_value = ecs->ws.value.integer;
 
-	  observer_notify_exited (ecs->ws.value.integer);
+	  gdb::observers::exited.notify (ecs->ws.value.integer);
 	}
       else
 	{
@@ -5098,7 +5098,7 @@  handle_inferior_event_1 (struct execution_control_state *ecs)
 Cannot fill $_exitsignal with the correct signal number.\n"));
 	    }
 
-	  observer_notify_signal_exited (ecs->ws.value.sig);
+	  gdb::observers::signal_exited.notify (ecs->ws.value.sig);
 	}
 
       gdb_flush (gdb_stdout);
@@ -5392,7 +5392,7 @@  Cannot fill $_exitsignal with the correct signal number.\n"));
       if (handle_stop_requested (ecs))
 	return;
 
-      observer_notify_no_history ();
+      gdb::observers::no_history.notify ();
       stop_waiting (ecs);
       return;
     }
@@ -6096,7 +6096,7 @@  handle_signal_stop (struct execution_control_state *ecs)
 	{
 	  /* The signal table tells us to print about this signal.  */
 	  target_terminal::ours_for_output ();
-	  observer_notify_signal_received (ecs->event_thread->suspend.stop_signal);
+	  gdb::observers::signal_received.notify (ecs->event_thread->suspend.stop_signal);
 	  target_terminal::inferior ();
 	}
 
@@ -8205,7 +8205,7 @@  normal_stop (void)
   update_thread_list ();
 
   if (last.kind == TARGET_WAITKIND_STOPPED && stopped_by_random_signal)
-    observer_notify_signal_received (inferior_thread ()->suspend.stop_signal);
+    gdb::observers::signal_received.notify (inferior_thread ()->suspend.stop_signal);
 
   /* As with the notification of thread events, we want to delay
      notifying the user that we've switched thread context until
@@ -8330,10 +8330,10 @@  normal_stop (void)
   /* Notify observers about the stop.  This is where the interpreters
      print the stop event.  */
   if (!ptid_equal (inferior_ptid, null_ptid))
-    observer_notify_normal_stop (inferior_thread ()->control.stop_bpstat,
+    gdb::observers::normal_stop.notify (inferior_thread ()->control.stop_bpstat,
 				 stop_print_frame);
   else
-    observer_notify_normal_stop (NULL, stop_print_frame);
+    gdb::observers::normal_stop.notify (NULL, stop_print_frame);
 
   annotate_stopped ();
 
@@ -9438,10 +9438,10 @@  enabled by default on some platforms."),
   inferior_ptid = null_ptid;
   target_last_wait_ptid = minus_one_ptid;
 
-  observer_attach_thread_ptid_changed (infrun_thread_ptid_changed);
-  observer_attach_thread_stop_requested (infrun_thread_stop_requested);
-  observer_attach_thread_exit (infrun_thread_thread_exit);
-  observer_attach_inferior_exit (infrun_inferior_exit);
+  gdb::observers::thread_ptid_changed.attach (infrun_thread_ptid_changed);
+  gdb::observers::thread_stop_requested.attach (infrun_thread_stop_requested);
+  gdb::observers::thread_exit.attach (infrun_thread_thread_exit);
+  gdb::observers::inferior_exit.attach (infrun_inferior_exit);
 
   /* Explicitly create without lookup, since that tries to create a
      value with a void typed value, and when we get here, gdbarch
diff --git a/gdb/jit.c b/gdb/jit.c
index 62d6634541..313e2d30e8 100644
--- a/gdb/jit.c
+++ b/gdb/jit.c
@@ -30,7 +30,7 @@ 
 #include "gdbcmd.h"
 #include "gdbcore.h"
 #include "inferior.h"
-#include "observer.h"
+#include "observable.h"
 #include "objfiles.h"
 #include "regcache.h"
 #include "symfile.h"
@@ -1506,9 +1506,9 @@  _initialize_jit (void)
 			     show_jit_debug,
 			     &setdebuglist, &showdebuglist);
 
-  observer_attach_inferior_created (jit_inferior_created);
-  observer_attach_inferior_exit (jit_inferior_exit_hook);
-  observer_attach_breakpoint_deleted (jit_breakpoint_deleted);
+  gdb::observers::inferior_created.attach (jit_inferior_created);
+  gdb::observers::inferior_exit.attach (jit_inferior_exit_hook);
+  gdb::observers::breakpoint_deleted.attach (jit_breakpoint_deleted);
 
   jit_objfile_data =
     register_objfile_data_with_cleanup (NULL, free_objfile_data);
diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c
index b5bb16215d..b4b87dd8af 100644
--- a/gdb/linux-tdep.c
+++ b/gdb/linux-tdep.c
@@ -32,7 +32,7 @@ 
 #include "cli/cli-utils.h"
 #include "arch-utils.h"
 #include "gdb_obstack.h"
-#include "observer.h"
+#include "observable.h"
 #include "objfiles.h"
 #include "infcall.h"
 #include "gdbcmd.h"
@@ -2513,8 +2513,8 @@  _initialize_linux_tdep (void)
   linux_inferior_data
     = register_inferior_data_with_cleanup (NULL, linux_inferior_data_cleanup);
   /* Observers used to invalidate the cache when needed.  */
-  observer_attach_inferior_exit (invalidate_linux_cache_inf);
-  observer_attach_inferior_appeared (invalidate_linux_cache_inf);
+  gdb::observers::inferior_exit.attach (invalidate_linux_cache_inf);
+  gdb::observers::inferior_appeared.attach (invalidate_linux_cache_inf);
 
   add_setshow_boolean_cmd ("use-coredump-filter", class_files,
 			   &use_coredump_filter, _("\
diff --git a/gdb/linux-thread-db.c b/gdb/linux-thread-db.c
index 4da27b6600..cfedd98bd8 100644
--- a/gdb/linux-thread-db.c
+++ b/gdb/linux-thread-db.c
@@ -35,7 +35,7 @@ 
 #include "solib.h"
 #include "solib-svr4.h"
 #include "gdbcore.h"
-#include "observer.h"
+#include "observable.h"
 #include "linux-nat.h"
 #include "nat/linux-procfs.h"
 #include "nat/linux-ptrace.h"
@@ -960,7 +960,7 @@  thread_db_new_objfile (struct objfile *objfile)
   if (objfile != NULL
       /* libpthread with separate debug info has its debug info file already
 	 loaded (and notified without successful thread_db initialization)
-	 the time observer_notify_new_objfile is called for the library itself.
+	 the time gdb::observers::new_objfile.notify is called for the library itself.
 	 Static executables have their separate debug info loaded already
 	 before the inferior has started.  */
       && objfile->separate_debug_objfile_backlink == NULL
@@ -1715,10 +1715,10 @@  Usage: info auto-load libthread-db"),
 	   auto_load_info_cmdlist_get ());
 
   /* Add ourselves to objfile event chain.  */
-  observer_attach_new_objfile (thread_db_new_objfile);
+  gdb::observers::new_objfile.attach (thread_db_new_objfile);
 
   /* Add ourselves to inferior_created event chain.
      This is needed to handle debugging statically linked programs where
      the new_objfile observer won't get called for libpthread.  */
-  observer_attach_inferior_created (thread_db_inferior_created);
+  gdb::observers::inferior_created.attach (thread_db_inferior_created);
 }
diff --git a/gdb/m68k-linux-tdep.c b/gdb/m68k-linux-tdep.c
index e26ceab513..11cde0b09f 100644
--- a/gdb/m68k-linux-tdep.c
+++ b/gdb/m68k-linux-tdep.c
@@ -32,7 +32,7 @@ 
 #include "glibc-tdep.h"
 #include "solib-svr4.h"
 #include "auxv.h"
-#include "observer.h"
+#include "observable.h"
 #include "elf/common.h"
 #include "linux-tdep.h"
 #include "regset.h"
@@ -426,5 +426,5 @@  _initialize_m68k_linux_tdep (void)
 {
   gdbarch_register_osabi (bfd_arch_m68k, 0, GDB_OSABI_LINUX,
 			  m68k_linux_init_abi);
-  observer_attach_inferior_created (m68k_linux_inferior_created);
+  gdb::observers::inferior_created.attach (m68k_linux_inferior_created);
 }
diff --git a/gdb/mi/mi-cmd-break.c b/gdb/mi/mi-cmd-break.c
index 243a9d03a8..c1f5e2d924 100644
--- a/gdb/mi/mi-cmd-break.c
+++ b/gdb/mi/mi-cmd-break.c
@@ -24,7 +24,7 @@ 
 #include "mi-out.h"
 #include "breakpoint.h"
 #include "mi-getopt.h"
-#include "observer.h"
+#include "observable.h"
 #include "mi-main.h"
 #include "mi-cmd-break.h"
 #include "language.h"
@@ -84,7 +84,7 @@  setup_breakpoint_reporting (void)
 {
   if (! mi_breakpoint_observers_installed)
     {
-      observer_attach_breakpoint_created (breakpoint_notify);
+      gdb::observers::breakpoint_created.attach (breakpoint_notify);
       mi_breakpoint_observers_installed = 1;
     }
 
@@ -394,7 +394,7 @@  mi_cmd_break_passcount (const char *command, char **argv, int argc)
   if (t)
     {
       t->pass_count = p;
-      observer_notify_breakpoint_modified (t);
+      gdb::observers::breakpoint_modified.notify (t);
     }
   else
     {
diff --git a/gdb/mi/mi-interp.c b/gdb/mi/mi-interp.c
index 2ec1d693b1..0a9613804f 100644
--- a/gdb/mi/mi-interp.c
+++ b/gdb/mi/mi-interp.c
@@ -30,7 +30,7 @@ 
 #include "mi-out.h"
 #include "mi-console.h"
 #include "mi-common.h"
-#include "observer.h"
+#include "observable.h"
 #include "gdbthread.h"
 #include "solist.h"
 #include "objfiles.h"
@@ -1353,33 +1353,33 @@  _initialize_mi_interp (void)
   interp_factory_register (INTERP_MI3, mi_interp_factory);
   interp_factory_register (INTERP_MI, mi_interp_factory);
 
-  observer_attach_signal_received (mi_on_signal_received);
-  observer_attach_end_stepping_range (mi_on_end_stepping_range);
-  observer_attach_signal_exited (mi_on_signal_exited);
-  observer_attach_exited (mi_on_exited);
-  observer_attach_no_history (mi_on_no_history);
-  observer_attach_new_thread (mi_new_thread);
-  observer_attach_thread_exit (mi_thread_exit);
-  observer_attach_inferior_added (mi_inferior_added);
-  observer_attach_inferior_appeared (mi_inferior_appeared);
-  observer_attach_inferior_exit (mi_inferior_exit);
-  observer_attach_inferior_removed (mi_inferior_removed);
-  observer_attach_record_changed (mi_record_changed);
-  observer_attach_normal_stop (mi_on_normal_stop);
-  observer_attach_target_resumed (mi_on_resume);
-  observer_attach_solib_loaded (mi_solib_loaded);
-  observer_attach_solib_unloaded (mi_solib_unloaded);
-  observer_attach_about_to_proceed (mi_about_to_proceed);
-  observer_attach_traceframe_changed (mi_traceframe_changed);
-  observer_attach_tsv_created (mi_tsv_created);
-  observer_attach_tsv_deleted (mi_tsv_deleted);
-  observer_attach_tsv_modified (mi_tsv_modified);
-  observer_attach_breakpoint_created (mi_breakpoint_created);
-  observer_attach_breakpoint_deleted (mi_breakpoint_deleted);
-  observer_attach_breakpoint_modified (mi_breakpoint_modified);
-  observer_attach_command_param_changed (mi_command_param_changed);
-  observer_attach_memory_changed (mi_memory_changed);
-  observer_attach_sync_execution_done (mi_on_sync_execution_done);
-  observer_attach_user_selected_context_changed
+  gdb::observers::signal_received.attach (mi_on_signal_received);
+  gdb::observers::end_stepping_range.attach (mi_on_end_stepping_range);
+  gdb::observers::signal_exited.attach (mi_on_signal_exited);
+  gdb::observers::exited.attach (mi_on_exited);
+  gdb::observers::no_history.attach (mi_on_no_history);
+  gdb::observers::new_thread.attach (mi_new_thread);
+  gdb::observers::thread_exit.attach (mi_thread_exit);
+  gdb::observers::inferior_added.attach (mi_inferior_added);
+  gdb::observers::inferior_appeared.attach (mi_inferior_appeared);
+  gdb::observers::inferior_exit.attach (mi_inferior_exit);
+  gdb::observers::inferior_removed.attach (mi_inferior_removed);
+  gdb::observers::record_changed.attach (mi_record_changed);
+  gdb::observers::normal_stop.attach (mi_on_normal_stop);
+  gdb::observers::target_resumed.attach (mi_on_resume);
+  gdb::observers::solib_loaded.attach (mi_solib_loaded);
+  gdb::observers::solib_unloaded.attach (mi_solib_unloaded);
+  gdb::observers::about_to_proceed.attach (mi_about_to_proceed);
+  gdb::observers::traceframe_changed.attach (mi_traceframe_changed);
+  gdb::observers::tsv_created.attach (mi_tsv_created);
+  gdb::observers::tsv_deleted.attach (mi_tsv_deleted);
+  gdb::observers::tsv_modified.attach (mi_tsv_modified);
+  gdb::observers::breakpoint_created.attach (mi_breakpoint_created);
+  gdb::observers::breakpoint_deleted.attach (mi_breakpoint_deleted);
+  gdb::observers::breakpoint_modified.attach (mi_breakpoint_modified);
+  gdb::observers::command_param_changed.attach (mi_command_param_changed);
+  gdb::observers::memory_changed.attach (mi_memory_changed);
+  gdb::observers::sync_execution_done.attach (mi_on_sync_execution_done);
+  gdb::observers::user_selected_context_changed.attach
     (mi_user_selected_context_changed);
 }
diff --git a/gdb/mi/mi-main.c b/gdb/mi/mi-main.c
index 1716a7fe44..9c4e44ba6b 100644
--- a/gdb/mi/mi-main.c
+++ b/gdb/mi/mi-main.c
@@ -52,7 +52,7 @@ 
 #include "linespec.h"
 #include "extension.h"
 #include "gdbcmd.h"
-#include "observer.h"
+#include "observable.h"
 #include "common/gdb_optional.h"
 #include "common/byte-vector.h"
 
@@ -573,8 +573,8 @@  mi_cmd_thread_select (const char *command, char **argv, int argc)
   /* Notify if the thread has effectively changed.  */
   if (!ptid_equal (inferior_ptid, previous_ptid))
     {
-      observer_notify_user_selected_context_changed (USER_SELECTED_THREAD
-						     | USER_SELECTED_FRAME);
+      gdb::observers::user_selected_context_changed.notify
+	(USER_SELECTED_THREAD | USER_SELECTED_FRAME);
     }
 }
 
@@ -2024,8 +2024,8 @@  mi_execute_command (const char *cmd, int from_tty)
 
 	  if (report_change)
 	    {
-		observer_notify_user_selected_context_changed
-		  (USER_SELECTED_THREAD | USER_SELECTED_FRAME);
+	      gdb::observers::user_selected_context_changed.notify
+		(USER_SELECTED_THREAD | USER_SELECTED_FRAME);
 	    }
 	}
     }
diff --git a/gdb/objfiles.c b/gdb/objfiles.c
index a9aaf89540..ef3510b058 100644
--- a/gdb/objfiles.c
+++ b/gdb/objfiles.c
@@ -46,7 +46,7 @@ 
 #include "addrmap.h"
 #include "arch-utils.h"
 #include "exec.h"
-#include "observer.h"
+#include "observable.h"
 #include "complaints.h"
 #include "psymtab.h"
 #include "solist.h"
@@ -617,7 +617,7 @@  free_objfile_separate_debug (struct objfile *objfile)
 objfile::~objfile ()
 {
   /* First notify observers that this objfile is about to be freed.  */
-  observer_notify_free_objfile (this);
+  gdb::observers::free_objfile.notify (this);
 
   /* Free all separate debug objfiles.  */
   free_objfile_separate_debug (this);
diff --git a/gdb/observable.c b/gdb/observable.c
new file mode 100644
index 0000000000..5539b9837b
--- /dev/null
+++ b/gdb/observable.c
@@ -0,0 +1,99 @@ 
+/* GDB Notifications to Observers.
+
+   Copyright (C) 2003-2018 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/>.  */
+
+#include "defs.h"
+#include "observable.h"
+#include "command.h"
+#include "gdbcmd.h"
+
+namespace gdb
+{
+
+namespace observers
+{
+
+unsigned int observer_debug;
+
+#define DEFINE_OBSERVABLE(name) decltype (name) name (# name)
+
+DEFINE_OBSERVABLE (normal_stop);
+DEFINE_OBSERVABLE (signal_received);
+DEFINE_OBSERVABLE (end_stepping_range);
+DEFINE_OBSERVABLE (signal_exited);
+DEFINE_OBSERVABLE (exited);
+DEFINE_OBSERVABLE (no_history);
+DEFINE_OBSERVABLE (sync_execution_done);
+DEFINE_OBSERVABLE (command_error);
+DEFINE_OBSERVABLE (target_changed);
+DEFINE_OBSERVABLE (executable_changed);
+DEFINE_OBSERVABLE (inferior_created);
+DEFINE_OBSERVABLE (record_changed);
+DEFINE_OBSERVABLE (solib_loaded);
+DEFINE_OBSERVABLE (solib_unloaded);
+DEFINE_OBSERVABLE (new_objfile);
+DEFINE_OBSERVABLE (free_objfile);
+DEFINE_OBSERVABLE (new_thread);
+DEFINE_OBSERVABLE (thread_exit);
+DEFINE_OBSERVABLE (thread_stop_requested);
+DEFINE_OBSERVABLE (target_resumed);
+DEFINE_OBSERVABLE (about_to_proceed);
+DEFINE_OBSERVABLE (breakpoint_created);
+DEFINE_OBSERVABLE (breakpoint_deleted);
+DEFINE_OBSERVABLE (breakpoint_modified);
+DEFINE_OBSERVABLE (traceframe_changed);
+DEFINE_OBSERVABLE (architecture_changed);
+DEFINE_OBSERVABLE (thread_ptid_changed);
+DEFINE_OBSERVABLE (inferior_added);
+DEFINE_OBSERVABLE (inferior_appeared);
+DEFINE_OBSERVABLE (inferior_exit);
+DEFINE_OBSERVABLE (inferior_removed);
+DEFINE_OBSERVABLE (memory_changed);
+DEFINE_OBSERVABLE (before_prompt);
+DEFINE_OBSERVABLE (gdb_datadir_changed);
+DEFINE_OBSERVABLE (command_param_changed);
+DEFINE_OBSERVABLE (tsv_created);
+DEFINE_OBSERVABLE (tsv_deleted);
+DEFINE_OBSERVABLE (tsv_modified);
+DEFINE_OBSERVABLE (inferior_call_pre);
+DEFINE_OBSERVABLE (inferior_call_post);
+DEFINE_OBSERVABLE (register_changed);
+DEFINE_OBSERVABLE (user_selected_context_changed);
+
+} /* namespace observers */
+} /* namespace gdb */
+
+static void
+show_observer_debug (struct ui_file *file, int from_tty,
+		     struct cmd_list_element *c, const char *value)
+{
+  fprintf_filtered (file, _("Observer debugging is %s.\n"), value);
+}
+
+void
+_initialize_observer (void)
+{
+  add_setshow_zuinteger_cmd ("observer", class_maintenance,
+			     &gdb::observers::observer_debug, _("\
+Set observer debugging."), _("\
+Show observer debugging."), _("\
+When non-zero, observer debugging is enabled."),
+			     NULL,
+			     show_observer_debug,
+			     &setdebuglist, &showdebuglist);
+}
diff --git a/gdb/observable.h b/gdb/observable.h
new file mode 100644
index 0000000000..34447b90bb
--- /dev/null
+++ b/gdb/observable.h
@@ -0,0 +1,235 @@ 
+/* 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_OBSERVER_H)
+#define GDB_OBSERVER_H
+
+#include "common/observable.h"
+
+struct bpstats;
+struct so_list;
+struct objfile;
+struct thread_info;
+struct inferior;
+struct trace_state_variable;
+
+namespace gdb
+{
+
+namespace observers
+{
+
+/* The inferior has stopped for real.  The bs argument describes the
+   breakpoints were are stopped at, if any.  Second argument
+   print_frame non-zero means display the location where the
+   inferior has stopped.
+
+   gdb notifies all normal_stop observers when the inferior execution
+   has just stopped, the associated messages and annotations have been
+   printed, and the control is about to be returned to the user.
+
+   Note that the normal_stop notification is not emitted when the
+   execution stops due to a breakpoint, and this breakpoint has a
+   condition that is not met.  If the breakpoint has any associated
+   commands list, the commands are executed after the notification is
+   emitted.  */
+extern observable<struct bpstats *, int> normal_stop;
+
+/* The inferior was stopped by a signal.  */
+extern observable<enum gdb_signal> signal_received;
+
+/* We are done with a step/next/si/ni command.  */
+extern observable<> end_stepping_range;
+
+/* The inferior was terminated by a signal.  */
+extern observable<enum gdb_signal> signal_exited;
+
+/* The inferior program is finished.  */
+extern observable<int> exited;
+
+/* Reverse execution: target ran out of history info.  */
+extern observable<> no_history;
+
+/* A synchronous command finished.  */
+extern observable<> sync_execution_done;
+
+/* An error was caught while executing a command.  */
+extern observable<> command_error;
+
+/* The target's register contents have changed.  */
+extern observable<struct target_ops *> target_changed;
+
+/* The executable being debugged by GDB has changed: The user
+   decided to debug a different program, or the program he was
+   debugging has been modified since being loaded by the debugger
+   (by being recompiled, for instance).  */
+extern observable<> executable_changed;
+
+/* gdb has just connected to an inferior.  For 'run', gdb calls this
+   observer while the inferior is still stopped at the entry-point
+   instruction.  For 'attach' and 'core', gdb calls this observer
+   immediately after connecting to the inferior, and before any
+   information on the inferior has been printed.  */
+extern observable<struct target_ops *, int> inferior_created;
+
+/* The status of process record for inferior inferior in gdb has
+   changed.  The process record is started if started is true, and
+   the process record is stopped if started is false.
+
+   When started is true, method indicates the short name of the
+   method used for recording.  If the method supports multiple
+   formats, format indicates which one is being used, otherwise it
+   is NULL.  When started is false, they are both NULL.  */
+extern observable<struct inferior *, int, const char *, const char *>
+    record_changed;
+
+/* The shared library specified by solib has been loaded.  Note that
+   when gdb calls this observer, the library's symbols probably
+   haven't been loaded yet.  */
+extern observable<struct so_list *> solib_loaded;
+
+/* The shared library specified by solib has been unloaded.  Note
+   that when gdb calls this observer, the library's symbols have not
+   been unloaded yet, and thus are still available.  */
+extern observable<struct so_list *> solib_unloaded;
+
+/* The symbol file specified by objfile has been loaded.  Called
+   with objfile equal to NULL to indicate previously loaded symbol
+   table data has now been invalidated.  */
+extern observable<struct objfile *> new_objfile;
+
+/* The object file specified by objfile is about to be freed.  */
+extern observable<struct objfile *> free_objfile;
+
+/* The thread specified by t has been created.  */
+extern observable<struct thread_info *> new_thread;
+
+/* The thread specified by t has exited.  The silent argument
+   indicates that gdb is removing the thread from its tables without
+   wanting to notify the user about it.  */
+extern observable<struct thread_info *, int> thread_exit;
+
+/* An explicit stop request was issued to ptid.  If ptid equals
+   minus_one_ptid, the request applied to all threads.  If
+   ptid_is_pid(ptid) returns true, the request applied to all
+   threads of the process pointed at by ptid.  Otherwise, the
+   request applied to the single thread pointed at by ptid.  */
+extern observable<ptid_t> thread_stop_requested;
+
+/* The target was resumed.  The ptid parameter specifies which
+   thread was resume, and may be RESUME_ALL if all threads are
+   resumed.  */
+extern observable<ptid_t> target_resumed;
+
+/* The target is about to be proceeded.  */
+extern observable<> about_to_proceed;
+
+/* A new breakpoint b has been created.  */
+extern observable<struct breakpoint *> breakpoint_created;
+
+/* A breakpoint has been destroyed.  The argument b is the
+   pointer to the destroyed breakpoint.  */
+extern observable<struct breakpoint *> breakpoint_deleted;
+
+/* A breakpoint has been modified in some way.  The argument b
+   is the modified breakpoint.  */
+extern observable<struct breakpoint *> breakpoint_modified;
+
+/* The trace frame is changed to tfnum (e.g., by using the 'tfind'
+   command).  If tfnum is negative, it means gdb resumes live
+   debugging.  The number of the tracepoint associated with this
+   traceframe is tpnum.  */
+extern observable<int, int> traceframe_changed;
+
+/* The current architecture has changed.  The argument newarch is a
+   pointer to the new architecture.  */
+extern observable<struct gdbarch *> architecture_changed;
+
+/* The thread's ptid has changed.  The old_ptid parameter specifies
+   the old value, and new_ptid specifies the new value.  */
+extern observable<ptid_t, ptid_t> thread_ptid_changed;
+
+/* The inferior inf has been added to the list of inferiors.  At
+   this point, it might not be associated with any process.  */
+extern observable<struct inferior *> inferior_added;
+
+/* The inferior identified by inf has been attached to a
+   process.  */
+extern observable<struct inferior *> inferior_appeared;
+
+/* Either the inferior associated with inf has been detached from
+   the process, or the process has exited.  */
+extern observable<struct inferior *> inferior_exit;
+
+/* The inferior inf has been removed from the list of inferiors.
+   This method is called immediately before freeing inf.  */
+extern observable<struct inferior *> inferior_removed;
+
+/* Bytes from data to data + len have been written to the inferior
+   at addr.  */
+extern observable<struct inferior *, CORE_ADDR, ssize_t, const bfd_byte *>
+    memory_changed;
+
+/* Called before a top-level prompt is displayed.  current_prompt is
+   the current top-level prompt.  */
+extern observable<const char *> before_prompt;
+
+/* Variable gdb_datadir has been set.  The value may not necessarily
+   change.  */
+extern observable<> gdb_datadir_changed;
+
+/* The parameter of some 'set' commands in console are changed.
+   This method is called after a command 'set param value'.  param
+   is the parameter of 'set' command, and value is the value of
+   changed parameter.  */
+extern observable<const char *, const char *> command_param_changed;
+
+/* The new trace state variable tsv is created.  */
+extern observable<const struct trace_state_variable *> tsv_created;
+
+/* The trace state variable tsv is deleted.  If tsv is NULL, all
+   trace state variables are deleted.  */
+extern observable<const struct trace_state_variable *> tsv_deleted;
+
+/* The trace state value tsv is modified.  */
+extern observable<const struct trace_state_variable *> tsv_modified;
+
+/* An inferior function at address is about to be called in thread
+   thread.  */
+extern observable<ptid_t, CORE_ADDR> inferior_call_pre;
+
+/* The inferior function at address has just been called.  This
+   observer is called even if the inferior exits during the call.
+   thread is the thread in which the function was called, which may
+   be different from the current thread.  */
+extern observable<ptid_t, CORE_ADDR> inferior_call_post;
+
+/* A register in the inferior has been modified by the gdb user.  */
+extern observable<struct frame_info *, int> register_changed;
+
+/* The user-selected inferior, thread and/or frame has changed.  The
+   user_select_what flag specifies if the inferior, thread and/or
+   frame has changed.  */
+extern observable<user_selected_what> user_selected_context_changed;
+
+} /* namespace observers */
+
+} /* namespace gdb */
+
+#endif /* GDB_OBSERVER_H */
diff --git a/gdb/observer.c b/gdb/observer.c
deleted file mode 100644
index 3c0ec2a2ee..0000000000
--- a/gdb/observer.c
+++ /dev/null
@@ -1,215 +0,0 @@ 
-/* GDB Notifications to Observers.
-
-   Copyright (C) 2003-2018 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/>.  */
-
-/* An observer is an entity who is interested in being notified when GDB
-   reaches certain states, or certain events occur in GDB.  The entity being
-   observed is called the Subject.  To receive notifications, the observer
-   attaches a callback to the subject.  One subject can have several
-   observers.
-
-   This file implements an internal generic low-level event notification
-   mechanism based on the Observer paradigm described in the book "Design
-   Patterns".  This generic event notification mechansim is then re-used
-   to implement the exported high-level notification management routines
-   for all possible notifications.
-
-   The current implementation of the generic observer provides support
-   for contextual data.  This contextual data is given to the subject
-   when attaching the callback.  In return, the subject will provide
-   this contextual data back to the observer as a parameter of the
-   callback.
-
-   FIXME: The current support for the contextual data is only partial,
-   as it lacks a mechanism that would deallocate this data when the
-   callback is detached.  This is not a problem so far, as this contextual
-   data is only used internally to hold a function pointer.  Later on,
-   if a certain observer needs to provide support for user-level
-   contextual data, then the generic notification mechanism will need
-   need to be enhanced to allow the observer to provide a routine to
-   deallocate the data when attaching the callback.
-
-   This file is currently maintained by hand, but the long term plan
-   if the number of different notifications starts growing is to create
-   a new script (observer.sh) that would generate this file, and the
-   associated documentation.  */
-
-#include "defs.h"
-#include "observer.h"
-#include "command.h"
-#include "gdbcmd.h"
-
-static unsigned int observer_debug;
-static void
-show_observer_debug (struct ui_file *file, int from_tty,
-		     struct cmd_list_element *c, const char *value)
-{
-  fprintf_filtered (file, _("Observer debugging is %s.\n"), value);
-}
-
-/* The internal generic observer.  */
-
-typedef void (generic_observer_notification_ftype) (const void *data,
-						    const void *args);
-
-struct observer
-{
-  generic_observer_notification_ftype *notify;
-  /* No memory management needed for the following field for now.  */
-  void *data;
-};
-
-/* A list of observers, maintained by the subject.  A subject is
-   actually represented by its list of observers.  */
-
-struct observer_list
-{
-  struct observer_list *next;
-  struct observer *observer;
-};
-
-/* Allocate a struct observer_list, intended to be used as a node
-   in the list of observers maintained by a subject.  */
-
-static struct observer_list *
-xalloc_observer_list_node (void)
-{
-  struct observer_list *node = XNEW (struct observer_list);
-
-  node->observer = XNEW (struct observer);
-  return node;
-}
-
-/* The opposite of xalloc_observer_list_node, frees the memory for
-   the given node.  */
-
-static void
-xfree_observer_list_node (struct observer_list *node)
-{
-  xfree (node->observer);
-  xfree (node);
-}
-
-/* Attach the callback NOTIFY to a SUBJECT.  The DATA is also stored,
-   in order for the subject to provide it back to the observer during
-   a notification.  */
-
-static struct observer *
-generic_observer_attach (struct observer_list **subject,
-			 generic_observer_notification_ftype * notify,
-			 void *data)
-{
-  struct observer_list *observer_list = xalloc_observer_list_node ();
-
-  observer_list->next = *subject;
-  observer_list->observer->notify = notify;
-  observer_list->observer->data = data;
-  *subject = observer_list;
-
-  return observer_list->observer;
-}
-
-/* Remove the given OBSERVER from the SUBJECT.  Once detached, OBSERVER
-   should no longer be used, as it is no longer valid.  */
-
-static void
-generic_observer_detach (struct observer_list **subject,
-			 const struct observer *observer)
-{
-  struct observer_list *previous_node = NULL;
-  struct observer_list *current_node = *subject;
-
-  while (current_node != NULL)
-    {
-      if (current_node->observer == observer)
-	{
-	  if (previous_node != NULL)
-	    previous_node->next = current_node->next;
-	  else
-	    *subject = current_node->next;
-	  xfree_observer_list_node (current_node);
-	  return;
-	}
-      previous_node = current_node;
-      current_node = current_node->next;
-    }
-
-  /* We should never reach this point.  However, this should not be
-     a very serious error, so simply report a warning to the user.  */
-  warning (_("Failed to detach observer"));
-}
-
-/* Send a notification to all the observers of SUBJECT.  ARGS is passed to
-   all observers as an argument to the notification callback.  */
-
-static void
-generic_observer_notify (struct observer_list *subject, const void *args)
-{
-  struct observer_list *current_node = subject;
-
-  while (current_node != NULL)
-    {
-      (*current_node->observer->notify) (current_node->observer->data, args);
-      current_node = current_node->next;
-    }
-}
-
-
-/* The following code is only used to unit-test the observers from our
-   testsuite.  DO NOT USE IT within observer.c (or anywhere else for
-   that matter)!  */
-
-/* If we define these variables and functions as `static', the
-   compiler will optimize them out.  */
- 
-int observer_test_first_observer = 0;
-int observer_test_second_observer = 0;
-int observer_test_third_observer = 0;
-
-void
-observer_test_first_notification_function (int arg)
-{
-  observer_test_first_observer++;
-}
-
-void
-observer_test_second_notification_function (int arg)
-{
-  observer_test_second_observer++;
-}
-
-void
-observer_test_third_notification_function (int arg)
-{
-  observer_test_third_observer++;
-}
-
-void
-_initialize_observer (void)
-{
-  add_setshow_zuinteger_cmd ("observer", class_maintenance,
-			     &observer_debug, _("\
-Set observer debugging."), _("\
-Show observer debugging."), _("\
-When non-zero, observer debugging is enabled."),
-			     NULL,
-			     show_observer_debug,
-			     &setdebuglist, &showdebuglist);
-}
-
-#include "observer.inc"
diff --git a/gdb/observer.sh b/gdb/observer.sh
deleted file mode 100755
index fa3dcc505f..0000000000
--- a/gdb/observer.sh
+++ /dev/null
@@ -1,200 +0,0 @@ 
-#!/bin/sh -e
-
-# Make certain that the script is not running in an internationalized
-# environment.
-LANG=C ; export LANG
-LC_ALL=C ; export LC_ALL
-
-if test $# -ne 3
-then
-    echo "Usage: $0 <h|inc> <observer.texi> <observer.out>" 1>&2
-    exit 0
-fi
-
-lang=$1 ; shift
-texi=$1 ; shift
-o=$1
-case $lang in
-  h) tmp=htmp ;;
-  inc) tmp=itmp ;;
-esac
-otmp="`echo $1 | sed -e 's,\.[^.]*$,,'`.$tmp"; shift
-echo "Creating ${otmp}" 1>&2
-rm -f ${otmp}
-
-# Can use any of the following: cat cmp cp diff echo egrep expr false
-# grep install-info ln ls mkdir mv pwd rm rmdir sed sleep sort tar
-# test touch true
-
-cat <<EOF >>${otmp}
-/* GDB Notifications to Observers.
-
-   Copyright (C) 2004-2018 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/>.
-
-   --
-
-   This file was generated using observer.sh and observer.texi.  */
-
-EOF
-
-
-case $lang in
-    h) cat <<EOF >>${otmp}
-#ifndef OBSERVER_H
-#define OBSERVER_H
-
-struct observer;
-struct bpstats;
-struct so_list;
-struct objfile;
-struct thread_info;
-struct inferior;
-struct trace_state_variable;
-EOF
-        ;;
-esac
-
-# We are about to set IFS=:, so DOS-style file names with a drive
-# letter and a colon will be in trouble.
-
-if test -n "$DJGPP"
-then
-     texi=`echo $texi | sed -e 's,^\([a-zA-Z]\):/,/dev/\1/,'`
-fi
-
-# generate a list of events that can be observed
-
-IFS=:
-sed -n '
-/@deftypefun void/{
-# Save original line for later processing into the actual parameter
-    h
-# Convert from: @deftypefun void EVENT (TYPE @var{PARAM},...)
-# to event and formals: EVENT:TYPE PARAM, ...:
-    s/^.* void \([a-z_][a-z_]*\) (\(.*\))$/\1:\2/
-    s/@var{//g
-    s/}//g
-# Switch to held
-    x
-# Convert from: @deftypefun void FUNC (TYPE @var{PARAM},...)
-# to actuals: PARAM, ...
-    s/^[^{]*[{]*//
-    s/[}]*[^}]*$//
-    s/}[^{]*{/, /g
-# Combine held (EVENT:TYPE PARAM, ...:) and pattern (PARAM, ...) into
-# FUNC:TYPE PARAM, ...:PARAM, ...
-    H
-    x
-    s/\n/:/g
-    p
-}
-' $texi | while read event formal actual
-do
-  case $lang in
-      h) cat <<EOF >>${otmp}
-
-/* ${event} notifications.  */
-
-typedef void (observer_${event}_ftype) (${formal});
-
-extern struct observer *observer_attach_${event} (observer_${event}_ftype *f);
-extern void observer_detach_${event} (struct observer *observer);
-extern void observer_notify_${event} (${formal});
-EOF
-	;;
-
-      inc)
-      	cat <<EOF >>${otmp}
-
-/* ${event} notifications.  */
-
-static struct observer_list *${event}_subject = NULL;
-
-EOF
-	if test "$formal" != "void"; then
-	    cat<<EOF >>${otmp}
-struct ${event}_args { `echo "${formal}" | sed -e 's/,/;/g'`; };
-
-EOF
-	fi
-	cat <<EOF >>${otmp}
-static void
-observer_${event}_notification_stub (const void *data, const void *args_data)
-{
-  observer_${event}_ftype *notify = (observer_${event}_ftype *) data;
-EOF
-
-	notify_args=`echo ${actual} | sed -e 's/\([a-z0-9_][a-z0-9_]*\)/args->\1/g'`
-
-	if test ! -z "${notify_args}"; then
-	    cat<<EOF >>${otmp}
-  const struct ${event}_args *args = (const struct ${event}_args *) args_data;
-EOF
-	fi
-	cat <<EOF >>${otmp}
-  notify (${notify_args});
-}
-
-struct observer *
-observer_attach_${event} (observer_${event}_ftype *f)
-{
-  return generic_observer_attach (&${event}_subject,
-				  &observer_${event}_notification_stub,
-				  (void *) f);
-}
-
-void
-observer_detach_${event} (struct observer *observer)
-{
-  generic_observer_detach (&${event}_subject, observer);
-}
-
-void
-observer_notify_${event} (${formal})
-{
-EOF
-	if test "$formal" != "void"; then
-	    cat<<EOF >>${otmp}
-  struct ${event}_args args;
-  `echo ${actual} | sed -e 's/\([a-z0-9_][a-z0-9_]*\)/args.\1 = \1/g'`;
-
-EOF
-	else
-	    echo "char *args = NULL;" >> ${otmp}
-	fi
-	cat<<EOF >>${otmp}
-  if (observer_debug)
-    fprintf_unfiltered (gdb_stdlog, "observer_notify_${event}() called\n");
-  generic_observer_notify (${event}_subject, &args);
-}
-EOF
-	;;
-    esac
-done
-
-
-case $lang in
-    h) cat <<EOF >>${otmp}
-
-#endif /* OBSERVER_H */
-EOF
-esac
-
-
-echo Moving ${otmp} to ${o}
-mv ${otmp} ${o}
diff --git a/gdb/ppc-linux-nat.c b/gdb/ppc-linux-nat.c
index 8418e4d35d..1d2769a983 100644
--- a/gdb/ppc-linux-nat.c
+++ b/gdb/ppc-linux-nat.c
@@ -18,7 +18,7 @@ 
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include "defs.h"
-#include "observer.h"
+#include "observable.h"
 #include "frame.h"
 #include "inferior.h"
 #include "gdbthread.h"
@@ -2500,7 +2500,7 @@  _initialize_ppc_linux_nat (void)
   t->to_read_description = ppc_linux_read_description;
   t->to_auxv_parse = ppc_linux_auxv_parse;
 
-  observer_attach_thread_exit (ppc_linux_thread_exit);
+  gdb::observers::thread_exit.attach (ppc_linux_thread_exit);
 
   /* Register the target.  */
   linux_nat_add_target (t);
diff --git a/gdb/ppc-linux-tdep.c b/gdb/ppc-linux-tdep.c
index d6a98fc0db..04487e7b15 100644
--- a/gdb/ppc-linux-tdep.c
+++ b/gdb/ppc-linux-tdep.c
@@ -41,7 +41,7 @@ 
 #include "trad-frame.h"
 #include "frame-unwind.h"
 #include "tramp-frame.h"
-#include "observer.h"
+#include "observable.h"
 #include "auxv.h"
 #include "elf/common.h"
 #include "elf/ppc64.h"
@@ -1857,9 +1857,9 @@  _initialize_ppc_linux_tdep (void)
                          ppc_linux_init_abi);
 
   /* Attach to observers to track __spe_current_active_context.  */
-  observer_attach_inferior_created (ppc_linux_spe_context_inferior_created);
-  observer_attach_solib_loaded (ppc_linux_spe_context_solib_loaded);
-  observer_attach_solib_unloaded (ppc_linux_spe_context_solib_unloaded);
+  gdb::observers::inferior_created.attach (ppc_linux_spe_context_inferior_created);
+  gdb::observers::solib_loaded.attach (ppc_linux_spe_context_solib_loaded);
+  gdb::observers::solib_unloaded.attach (ppc_linux_spe_context_solib_unloaded);
 
   /* Initialize the Linux target descriptions.  */
   initialize_tdesc_powerpc_32l ();
diff --git a/gdb/printcmd.c b/gdb/printcmd.c
index fc9d7e4dd9..5f43a0b83a 100644
--- a/gdb/printcmd.c
+++ b/gdb/printcmd.c
@@ -39,7 +39,7 @@ 
 #include "block.h"
 #include "disasm.h"
 #include "target-float.h"
-#include "observer.h"
+#include "observable.h"
 #include "solist.h"
 #include "parser-defs.h"
 #include "charset.h"
@@ -2612,7 +2612,7 @@  _initialize_printcmd (void)
 
   current_display_number = -1;
 
-  observer_attach_free_objfile (clear_dangling_display_expressions);
+  gdb::observers::free_objfile.attach (clear_dangling_display_expressions);
 
   add_info ("address", info_address_command,
 	    _("Describe where symbol SYM is stored."));
diff --git a/gdb/procfs.c b/gdb/procfs.c
index cd6dcaad57..5ca7477fa5 100644
--- a/gdb/procfs.c
+++ b/gdb/procfs.c
@@ -45,7 +45,7 @@ 
 #include "inflow.h"
 #include "auxv.h"
 #include "procfs.h"
-#include "observer.h"
+#include "observable.h"
 #include "common/scoped_fd.h"
 
 /* This module provides the interface between GDB and the
@@ -3751,7 +3751,7 @@  proc_untrace_sysexit_cmd (const char *args, int from_tty)
 void
 _initialize_procfs (void)
 {
-  observer_attach_inferior_created (procfs_inferior_created);
+  gdb::observers::inferior_created.attach (procfs_inferior_created);
 
   add_com ("proc-trace-entry", no_class, proc_trace_sysentry_cmd,
 	   _("Give a trace of entries into the syscall."));
diff --git a/gdb/python/py-breakpoint.c b/gdb/python/py-breakpoint.c
index 5ac3f98641..d654b92a8c 100644
--- a/gdb/python/py-breakpoint.c
+++ b/gdb/python/py-breakpoint.c
@@ -25,7 +25,7 @@ 
 #include "breakpoint.h"
 #include "gdbcmd.h"
 #include "gdbthread.h"
-#include "observer.h"
+#include "observable.h"
 #include "cli/cli-script.h"
 #include "ada-lang.h"
 #include "arch-utils.h"
@@ -1086,9 +1086,9 @@  gdbpy_initialize_breakpoints (void)
 			      (PyObject *) &breakpoint_object_type) < 0)
     return -1;
 
-  observer_attach_breakpoint_created (gdbpy_breakpoint_created);
-  observer_attach_breakpoint_deleted (gdbpy_breakpoint_deleted);
-  observer_attach_breakpoint_modified (gdbpy_breakpoint_modified);
+  gdb::observers::breakpoint_created.attach (gdbpy_breakpoint_created);
+  gdb::observers::breakpoint_deleted.attach (gdbpy_breakpoint_deleted);
+  gdb::observers::breakpoint_modified.attach (gdbpy_breakpoint_modified);
 
   /* Add breakpoint types constants.  */
   for (i = 0; pybp_codes[i].name; ++i)
diff --git a/gdb/python/py-finishbreakpoint.c b/gdb/python/py-finishbreakpoint.c
index 7a05ad3195..b3978f717d 100644
--- a/gdb/python/py-finishbreakpoint.c
+++ b/gdb/python/py-finishbreakpoint.c
@@ -26,7 +26,7 @@ 
 #include "gdbthread.h"
 #include "arch-utils.h"
 #include "language.h"
-#include "observer.h"
+#include "observable.h"
 #include "inferior.h"
 #include "block.h"
 #include "location.h"
@@ -416,8 +416,8 @@  gdbpy_initialize_finishbreakpoints (void)
 			      (PyObject *) &finish_breakpoint_object_type) < 0)
     return -1;
 
-  observer_attach_normal_stop (bpfinishpy_handle_stop);
-  observer_attach_inferior_exit (bpfinishpy_handle_exit);
+  gdb::observers::normal_stop.attach (bpfinishpy_handle_stop);
+  gdb::observers::inferior_exit.attach (bpfinishpy_handle_exit);
 
   return 0;
 }
diff --git a/gdb/python/py-inferior.c b/gdb/python/py-inferior.c
index 564aa79f17..d199aaa1f8 100644
--- a/gdb/python/py-inferior.c
+++ b/gdb/python/py-inferior.c
@@ -22,7 +22,7 @@ 
 #include "gdbthread.h"
 #include "inferior.h"
 #include "objfiles.h"
-#include "observer.h"
+#include "observable.h"
 #include "python-internal.h"
 #include "arch-utils.h"
 #include "language.h"
@@ -926,18 +926,18 @@  gdbpy_initialize_inferior (void)
   infpy_inf_data_key =
     register_inferior_data_with_cleanup (NULL, py_free_inferior);
 
-  observer_attach_new_thread (add_thread_object);
-  observer_attach_thread_exit (delete_thread_object);
-  observer_attach_normal_stop (python_on_normal_stop);
-  observer_attach_target_resumed (python_on_resume);
-  observer_attach_inferior_call_pre (python_on_inferior_call_pre);
-  observer_attach_inferior_call_post (python_on_inferior_call_post);
-  observer_attach_memory_changed (python_on_memory_change);
-  observer_attach_register_changed (python_on_register_change);
-  observer_attach_inferior_exit (python_inferior_exit);
-  observer_attach_new_objfile (python_new_objfile);
-  observer_attach_inferior_added (python_new_inferior);
-  observer_attach_inferior_removed (python_inferior_deleted);
+  gdb::observers::new_thread.attach (add_thread_object);
+  gdb::observers::thread_exit.attach (delete_thread_object);
+  gdb::observers::normal_stop.attach (python_on_normal_stop);
+  gdb::observers::target_resumed.attach (python_on_resume);
+  gdb::observers::inferior_call_pre.attach (python_on_inferior_call_pre);
+  gdb::observers::inferior_call_post.attach (python_on_inferior_call_post);
+  gdb::observers::memory_changed.attach (python_on_memory_change);
+  gdb::observers::register_changed.attach (python_on_register_change);
+  gdb::observers::inferior_exit.attach (python_inferior_exit);
+  gdb::observers::new_objfile.attach (python_new_objfile);
+  gdb::observers::inferior_added.attach (python_new_inferior);
+  gdb::observers::inferior_removed.attach (python_inferior_deleted);
 
   membuf_object_type.tp_new = PyType_GenericNew;
   if (PyType_Ready (&membuf_object_type) < 0)
diff --git a/gdb/python/py-unwind.c b/gdb/python/py-unwind.c
index 906a00447e..1d235fceed 100644
--- a/gdb/python/py-unwind.c
+++ b/gdb/python/py-unwind.c
@@ -23,7 +23,7 @@ 
 #include "gdb_obstack.h"
 #include "gdbcmd.h"
 #include "language.h"
-#include "observer.h"
+#include "observable.h"
 #include "python-internal.h"
 #include "regcache.h"
 #include "valprint.h"
@@ -662,7 +662,7 @@  gdbpy_initialize_unwind (void)
         &setdebuglist, &showdebuglist);
   pyuw_gdbarch_data
       = gdbarch_data_register_post_init (pyuw_gdbarch_data_init);
-  observer_attach_architecture_changed (pyuw_on_new_gdbarch);
+  gdb::observers::architecture_changed.attach (pyuw_on_new_gdbarch);
 
   if (PyType_Ready (&pending_frame_object_type) < 0)
     return -1;
diff --git a/gdb/ravenscar-thread.c b/gdb/ravenscar-thread.c
index 19bdd7dc8d..46e454a6a8 100644
--- a/gdb/ravenscar-thread.c
+++ b/gdb/ravenscar-thread.c
@@ -25,7 +25,7 @@ 
 #include "inferior.h"
 #include "command.h"
 #include "ravenscar-thread.h"
-#include "observer.h"
+#include "observable.h"
 #include "gdbcmd.h"
 #include "top.h"
 #include "regcache.h"
@@ -632,7 +632,7 @@  _initialize_ravenscar (void)
 
   /* Notice when the inferior is created in order to push the
      ravenscar ops if needed.  */
-  observer_attach_inferior_created (ravenscar_inferior_created);
+  gdb::observers::inferior_created.attach (ravenscar_inferior_created);
 
   complete_target_initialization (&ravenscar_ops);
 
diff --git a/gdb/record-btrace.c b/gdb/record-btrace.c
index e77a6a7d21..7264b8ed2b 100644
--- a/gdb/record-btrace.c
+++ b/gdb/record-btrace.c
@@ -26,7 +26,7 @@ 
 #include "target.h"
 #include "gdbcmd.h"
 #include "disasm.h"
-#include "observer.h"
+#include "observable.h"
 #include "cli/cli-utils.h"
 #include "source.h"
 #include "ui-out.h"
@@ -44,8 +44,9 @@ 
 /* The target_ops of record-btrace.  */
 static struct target_ops record_btrace_ops;
 
-/* A new thread observer enabling branch tracing for the new thread.  */
-static struct observer *record_btrace_thread_observer;
+/* Token associated with a new-thread observer enabling branch tracing
+   for the new thread.  */
+static const gdb::observers::token record_btrace_thread_observer_token;
 
 /* Memory access types used in set/show record btrace replay-memory-access.  */
 static const char replay_memory_access_read_only[] = "read-only";
@@ -166,8 +167,8 @@  record_btrace_auto_enable (void)
 {
   DEBUG ("attach thread observer");
 
-  record_btrace_thread_observer
-    = observer_attach_new_thread (record_btrace_enable_warn);
+  gdb::observers::new_thread.attach (record_btrace_enable_warn,
+				     record_btrace_thread_observer_token);
 }
 
 /* Disable automatic tracing of new threads.  */
@@ -175,14 +176,9 @@  record_btrace_auto_enable (void)
 static void
 record_btrace_auto_disable (void)
 {
-  /* The observer may have been detached, already.  */
-  if (record_btrace_thread_observer == NULL)
-    return;
-
   DEBUG ("detach thread observer");
 
-  observer_detach_new_thread (record_btrace_thread_observer);
-  record_btrace_thread_observer = NULL;
+  gdb::observers::new_thread.detach (record_btrace_thread_observer_token);
 }
 
 /* The record-btrace async event handler function.  */
@@ -210,7 +206,7 @@  record_btrace_push_target (void)
   record_btrace_generating_corefile = 0;
 
   format = btrace_format_short_string (record_btrace_conf.format);
-  observer_notify_record_changed (current_inferior (), 1, "btrace", format);
+  gdb::observers::record_changed.notify (current_inferior (), 1, "btrace", format);
 }
 
 /* Disable btrace on a set of threads on scope exit.  */
@@ -258,8 +254,6 @@  record_btrace_open (const char *args, int from_tty)
   if (!target_has_execution)
     error (_("The program is not being run."));
 
-  gdb_assert (record_btrace_thread_observer == NULL);
-
   ALL_NON_EXITED_THREADS (tp)
     if (args == NULL || *args == 0 || number_is_in_list (args, tp->global_num))
       {
diff --git a/gdb/record-full.c b/gdb/record-full.c
index 82b3c74451..abaf99bab9 100644
--- a/gdb/record-full.c
+++ b/gdb/record-full.c
@@ -33,7 +33,7 @@ 
 #include "event-loop.h"
 #include "inf-loop.h"
 #include "gdb_bfd.h"
-#include "observer.h"
+#include "observable.h"
 #include "infrun.h"
 #include "common/gdb_unlinker.h"
 #include "common/byte-vector.h"
@@ -851,7 +851,7 @@  record_full_open (const char *name, int from_tty)
 
   record_full_init_record_breakpoints ();
 
-  observer_notify_record_changed (current_inferior (),  1, "full", NULL);
+  gdb::observers::record_changed.notify (current_inferior (),  1, "full", NULL);
 }
 
 /* "to_close" target method.  Close the process record target.  */
diff --git a/gdb/record.c b/gdb/record.c
index cd83b99a33..7c35dc8989 100644
--- a/gdb/record.c
+++ b/gdb/record.c
@@ -21,7 +21,7 @@ 
 #include "gdbcmd.h"
 #include "completer.h"
 #include "record.h"
-#include "observer.h"
+#include "observable.h"
 #include "inferior.h"
 #include "common/common-utils.h"
 #include "cli/cli-utils.h"
@@ -311,7 +311,7 @@  cmd_record_stop (const char *args, int from_tty)
   printf_unfiltered (_("Process record is stopped and all execution "
 		       "logs are deleted.\n"));
 
-  observer_notify_record_changed (current_inferior (), 0, NULL, NULL);
+  gdb::observers::record_changed.notify (current_inferior (), 0, NULL, NULL);
 }
 
 /* The "set record" command.  */
diff --git a/gdb/regcache.c b/gdb/regcache.c
index 8e843b2030..3af8ca9699 100644
--- a/gdb/regcache.c
+++ b/gdb/regcache.c
@@ -24,7 +24,7 @@ 
 #include "gdbcmd.h"
 #include "regcache.h"
 #include "reggroups.h"
-#include "observer.h"
+#include "observable.h"
 #include "regset.h"
 #include <forward_list>
 
@@ -1868,8 +1868,9 @@  _initialize_regcache (void)
   regcache_descr_handle
     = gdbarch_data_register_post_init (init_regcache_descr);
 
-  observer_attach_target_changed (regcache_observer_target_changed);
-  observer_attach_thread_ptid_changed (regcache::regcache_thread_ptid_changed);
+  gdb::observers::target_changed.attach (regcache_observer_target_changed);
+  gdb::observers::thread_ptid_changed.attach
+    (regcache::regcache_thread_ptid_changed);
 
   add_com ("flushregs", class_maintenance, reg_flush_command,
 	   _("Force gdb to flush its register cache (maintainer command)"));
diff --git a/gdb/remote-notif.c b/gdb/remote-notif.c
index e009d815f3..85612b1e39 100644
--- a/gdb/remote-notif.c
+++ b/gdb/remote-notif.c
@@ -34,7 +34,7 @@ 
 #include "defs.h"
 #include "remote.h"
 #include "remote-notif.h"
-#include "observer.h"
+#include "observable.h"
 #include "event-loop.h"
 #include "target.h"
 #include "inferior.h"
diff --git a/gdb/remote.c b/gdb/remote.c
index 7f409fdb1d..501c443bb9 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -36,7 +36,7 @@ 
 #include "remote-notif.h"
 #include "regcache.h"
 #include "value.h"
-#include "observer.h"
+#include "observable.h"
 #include "solib.h"
 #include "cli/cli-decode.h"
 #include "cli/cli-setshow.h"
@@ -3824,9 +3824,9 @@  print_one_stopped_thread (struct thread_info *thread)
       enum gdb_signal sig = ws->value.sig;
 
       if (signal_print_state (sig))
-	observer_notify_signal_received (sig);
+	gdb::observers::signal_received.notify (sig);
     }
-  observer_notify_normal_stop (NULL, 1);
+  gdb::observers::normal_stop.notify (NULL, 1);
 }
 
 /* Process all initial stop replies the remote side sent in response
@@ -13925,10 +13925,10 @@  _initialize_remote (void)
   add_target (&extended_remote_ops);
 
   /* Hook into new objfile notification.  */
-  observer_attach_new_objfile (remote_new_objfile);
+  gdb::observers::new_objfile.attach (remote_new_objfile);
   /* We're no longer interested in notification events of an inferior
      when it exits.  */
-  observer_attach_inferior_exit (discard_pending_stop_replies);
+  gdb::observers::inferior_exit.attach (discard_pending_stop_replies);
 
 #if 0
   init_remote_threadtests ();
diff --git a/gdb/riscv-tdep.c b/gdb/riscv-tdep.c
index 11b1227932..8b1d7232aa 100644
--- a/gdb/riscv-tdep.c
+++ b/gdb/riscv-tdep.c
@@ -53,7 +53,7 @@ 
 #include "common-defs.h"
 #include "opcode/riscv-opc.h"
 #include "cli/cli-decode.h"
-#include "observer.h"
+#include "observable.h"
 
 /* The stack must be 16-byte aligned.  */
 #define SP_ALIGNMENT 16
@@ -2642,8 +2642,8 @@  _initialize_riscv_tdep (void)
     = register_inferior_data_with_cleanup (NULL, riscv_inferior_data_cleanup);
 
   /* Observers used to invalidate the inferior data when needed.  */
-  observer_attach_inferior_exit (riscv_invalidate_inferior_data);
-  observer_attach_inferior_appeared (riscv_invalidate_inferior_data);
+  gdb::observers::inferior_exit.attach (riscv_invalidate_inferior_data);
+  gdb::observers::inferior_appeared.attach (riscv_invalidate_inferior_data);
 
   /* Add root prefix command for all "set debug riscv" and "show debug
      riscv" commands.  */
diff --git a/gdb/rs6000-nat.c b/gdb/rs6000-nat.c
index 8c54dc219a..4f05cd6b6a 100644
--- a/gdb/rs6000-nat.c
+++ b/gdb/rs6000-nat.c
@@ -33,7 +33,7 @@ 
 #include "rs6000-tdep.h"
 #include "rs6000-aix-tdep.h"
 #include "exec.h"
-#include "observer.h"
+#include "observable.h"
 #include "xcoffread.h"
 
 #include <sys/ptrace.h>
diff --git a/gdb/sol-thread.c b/gdb/sol-thread.c
index 2c7dd0e15d..62d839cd41 100644
--- a/gdb/sol-thread.c
+++ b/gdb/sol-thread.c
@@ -63,7 +63,7 @@ 
 #include "regcache.h"
 #include "solib.h"
 #include "symfile.h"
-#include "observer.h"
+#include "observable.h"
 #include "procfs.h"
 #include "symtab.h"
 #include "minsyms.h"
@@ -1229,7 +1229,7 @@  _initialize_sol_thread (void)
 	   _("Show info on Solaris user threads."), &maintenanceinfolist);
 
   /* Hook into new_objfile notification.  */
-  observer_attach_new_objfile (sol_thread_new_objfile);
+  gdb::observers::new_objfile.attach (sol_thread_new_objfile);
   return;
 
  die:
diff --git a/gdb/solib-aix.c b/gdb/solib-aix.c
index f11cbcd243..5339f11261 100644
--- a/gdb/solib-aix.c
+++ b/gdb/solib-aix.c
@@ -24,7 +24,7 @@ 
 #include "objfiles.h"
 #include "symtab.h"
 #include "xcoffread.h"
-#include "observer.h"
+#include "observable.h"
 #include "gdbcmd.h"
 
 /* Variable controlling the output of the debugging traces for
@@ -791,7 +791,7 @@  _initialize_solib_aix (void)
 
   solib_aix_inferior_data_handle = register_inferior_data ();
 
-  observer_attach_normal_stop (solib_aix_normal_stop_observer);
+  gdb::observers::normal_stop.attach (solib_aix_normal_stop_observer);
 
   /* Debug this file's internals.  */
   add_setshow_boolean_cmd ("aix-solib", class_maintenance,
diff --git a/gdb/solib-spu.c b/gdb/solib-spu.c
index 943ebf5ee3..cb735fd451 100644
--- a/gdb/solib-spu.c
+++ b/gdb/solib-spu.c
@@ -30,7 +30,7 @@ 
 #include "solist.h"
 #include "inferior.h"
 #include "objfiles.h"
-#include "observer.h"
+#include "observable.h"
 #include "breakpoint.h"
 #include "gdbthread.h"
 #include "gdb_bfd.h"
@@ -545,7 +545,7 @@  spu_solib_loaded (struct so_list *so)
 void
 _initialize_spu_solib (void)
 {
-  observer_attach_solib_loaded (spu_solib_loaded);
+  gdb::observers::solib_loaded.attach (spu_solib_loaded);
   ocl_program_data_key = register_objfile_data ();
 }
 
diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c
index c8f5e935a9..29e74daa51 100644
--- a/gdb/solib-svr4.c
+++ b/gdb/solib-svr4.c
@@ -33,7 +33,7 @@ 
 #include "infrun.h"
 #include "regcache.h"
 #include "gdbthread.h"
-#include "observer.h"
+#include "observable.h"
 
 #include "solist.h"
 #include "solib.h"
diff --git a/gdb/solib.c b/gdb/solib.c
index 1c78845938..9bdc0d391c 100644
--- a/gdb/solib.c
+++ b/gdb/solib.c
@@ -38,7 +38,7 @@ 
 #include "filenames.h"		/* for DOSish file names */
 #include "exec.h"
 #include "solist.h"
-#include "observer.h"
+#include "observable.h"
 #include "readline/readline.h"
 #include "remote.h"
 #include "solib.h"
@@ -826,7 +826,7 @@  update_solib_list (int from_tty)
 	{
 	  /* Notify any observer that the shared object has been
 	     unloaded before we remove it from GDB's tables.  */
-	  observer_notify_solib_unloaded (gdb);
+	  gdb::observers::solib_unloaded.notify (gdb);
 
 	  current_program_space->deleted_solibs.push_back (gdb->so_name);
 
@@ -887,7 +887,7 @@  update_solib_list (int from_tty)
 
 	  /* Notify any observer that the shared object has been
 	     loaded now that we've added it to GDB's tables.  */
-	  observer_notify_solib_loaded (i);
+	  gdb::observers::solib_loaded.notify (i);
 	}
 
       /* If a library was not found, issue an appropriate warning
@@ -1195,7 +1195,7 @@  clear_solib (void)
       struct so_list *so = so_list_head;
 
       so_list_head = so->next;
-      observer_notify_solib_unloaded (so);
+      gdb::observers::solib_unloaded.notify (so);
       remove_target_sections (so);
       free_so (so);
     }
@@ -1599,7 +1599,7 @@  _initialize_solib (void)
 {
   solib_data = gdbarch_data_register_pre_init (solib_init);
 
-  observer_attach_free_objfile (remove_user_added_objfile);
+  gdb::observers::free_objfile.attach (remove_user_added_objfile);
 
   add_com ("sharedlibrary", class_files, sharedlibrary_command,
 	   _("Load shared object library symbols for files matching REGEXP."));
diff --git a/gdb/spu-multiarch.c b/gdb/spu-multiarch.c
index 7152ddabbd..86782abc8b 100644
--- a/gdb/spu-multiarch.c
+++ b/gdb/spu-multiarch.c
@@ -22,7 +22,7 @@ 
 #include "gdbcore.h"
 #include "gdbcmd.h"
 #include "arch-utils.h"
-#include "observer.h"
+#include "observable.h"
 #include "inferior.h"
 #include "regcache.h"
 #include "symfile.h"
@@ -410,8 +410,8 @@  _initialize_spu_multiarch (void)
   complete_target_initialization (&spu_ops);
 
   /* Install observers to watch for SPU objects.  */
-  observer_attach_inferior_created (spu_multiarch_inferior_created);
-  observer_attach_solib_loaded (spu_multiarch_solib_loaded);
-  observer_attach_solib_unloaded (spu_multiarch_solib_unloaded);
+  gdb::observers::inferior_created.attach (spu_multiarch_inferior_created);
+  gdb::observers::solib_loaded.attach (spu_multiarch_solib_loaded);
+  gdb::observers::solib_unloaded.attach (spu_multiarch_solib_unloaded);
 }
 
diff --git a/gdb/spu-tdep.c b/gdb/spu-tdep.c
index 695b5cca0d..783ef5b247 100644
--- a/gdb/spu-tdep.c
+++ b/gdb/spu-tdep.c
@@ -39,7 +39,7 @@ 
 #include "regcache.h"
 #include "reggroups.h"
 #include "block.h"
-#include "observer.h"
+#include "observable.h"
 #include "infcall.h"
 #include "dwarf2.h"
 #include "dwarf2-frame.h"
@@ -2771,14 +2771,14 @@  _initialize_spu_tdep (void)
   register_gdbarch_init (bfd_arch_spu, spu_gdbarch_init);
 
   /* Add ourselves to objfile event chain.  */
-  observer_attach_new_objfile (spu_overlay_new_objfile);
+  gdb::observers::new_objfile.attach (spu_overlay_new_objfile);
   spu_overlay_data = register_objfile_data ();
 
   /* Install spu stop-on-load handler.  */
-  observer_attach_new_objfile (spu_catch_start);
+  gdb::observers::new_objfile.attach (spu_catch_start);
 
   /* Add ourselves to normal_stop event chain.  */
-  observer_attach_normal_stop (spu_attach_normal_stop);
+  gdb::observers::normal_stop.attach (spu_attach_normal_stop);
 
   /* Add root prefix command for all "set spu"/"show spu" commands.  */
   add_prefix_cmd ("spu", no_class, set_spu_command,
diff --git a/gdb/stack.c b/gdb/stack.c
index ebc49d4264..aad8fcd987 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -51,7 +51,7 @@ 
 #include "safe-ctype.h"
 #include "symfile.h"
 #include "extension.h"
-#include "observer.h"
+#include "observable.h"
 #include "common/def-vector.h"
 
 /* The possible choices of "set print frame-arguments", and the value
@@ -2277,7 +2277,7 @@  select_frame_command (const char *level_exp, int from_tty)
 
   select_frame (parse_frame_specification (level_exp, NULL));
   if (get_selected_frame_if_set () != prev_frame)
-    observer_notify_user_selected_context_changed (USER_SELECTED_FRAME);
+    gdb::observers::user_selected_context_changed.notify (USER_SELECTED_FRAME);
 }
 
 /* The "frame" command.  With no argument, print the selected frame
@@ -2291,7 +2291,7 @@  frame_command (const char *level_exp, int from_tty)
 
   select_frame (parse_frame_specification (level_exp, NULL));
   if (get_selected_frame_if_set () != prev_frame)
-    observer_notify_user_selected_context_changed (USER_SELECTED_FRAME);
+    gdb::observers::user_selected_context_changed.notify (USER_SELECTED_FRAME);
   else
     print_selected_thread_frame (current_uiout, USER_SELECTED_FRAME);
 }
@@ -2324,7 +2324,7 @@  static void
 up_command (const char *count_exp, int from_tty)
 {
   up_silently_base (count_exp);
-  observer_notify_user_selected_context_changed (USER_SELECTED_FRAME);
+  gdb::observers::user_selected_context_changed.notify (USER_SELECTED_FRAME);
 }
 
 /* Select the frame down one or COUNT_EXP stack levels from the previously
@@ -2363,7 +2363,7 @@  static void
 down_command (const char *count_exp, int from_tty)
 {
   down_silently_base (count_exp);
-  observer_notify_user_selected_context_changed (USER_SELECTED_FRAME);
+  gdb::observers::user_selected_context_changed.notify (USER_SELECTED_FRAME);
 }
 
 void
diff --git a/gdb/symfile-debug.c b/gdb/symfile-debug.c
index 8b2df55031..0f95da81f7 100644
--- a/gdb/symfile-debug.c
+++ b/gdb/symfile-debug.c
@@ -28,7 +28,7 @@ 
 #include "defs.h"
 #include "gdbcmd.h"
 #include "objfiles.h"
-#include "observer.h"
+#include "observable.h"
 #include "source.h"
 #include "symtab.h"
 #include "symfile.h"
diff --git a/gdb/symfile-mem.c b/gdb/symfile-mem.c
index 8d91c729a5..f4e3a9c204 100644
--- a/gdb/symfile-mem.c
+++ b/gdb/symfile-mem.c
@@ -49,7 +49,7 @@ 
 #include "target.h"
 #include "value.h"
 #include "symfile.h"
-#include "observer.h"
+#include "observable.h"
 #include "auxv.h"
 #include "elf/common.h"
 #include "gdb_bfd.h"
@@ -229,5 +229,5 @@  _initialize_symfile_mem (void)
 
   /* Want to know of each new inferior so that its vsyscall info can
      be extracted.  */
-  observer_attach_inferior_created (add_vsyscall_page);
+  gdb::observers::inferior_created.attach (add_vsyscall_page);
 }
diff --git a/gdb/symfile.c b/gdb/symfile.c
index 58747d545b..9e14df8ea8 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -46,7 +46,7 @@ 
 #include "hashtab.h"
 #include "readline/readline.h"
 #include "block.h"
-#include "observer.h"
+#include "observable.h"
 #include "exec.h"
 #include "parser-defs.h"
 #include "varobj.h"
@@ -1211,13 +1211,13 @@  symbol_file_add_with_addrs (bfd *abfd, const char *name,
 
   if (objfile->sf == NULL)
     {
-      observer_notify_new_objfile (objfile);
+      gdb::observers::new_objfile.notify (objfile);
       return objfile;	/* No symbols.  */
     }
 
   finish_new_objfile (objfile, add_flags);
 
-  observer_notify_new_objfile (objfile);
+  gdb::observers::new_objfile.notify (objfile);
 
   bfd_cache_close_all ();
   return (objfile);
@@ -2599,14 +2599,14 @@  reread_symbols (void)
       clear_symtab_users (0);
 
       /* clear_objfile_data for each objfile was called before freeing it and
-	 observer_notify_new_objfile (NULL) has been called by
+	 gdb::observers::new_objfile.notify (NULL) has been called by
 	 clear_symtab_users above.  Notify the new files now.  */
       for (auto iter : new_objfiles)
-	observer_notify_new_objfile (iter);
+	gdb::observers::new_objfile.notify (objfile);
 
       /* At least one objfile has changed, so we can consider that
          the executable we're debugging has changed too.  */
-      observer_notify_executable_changed ();
+      gdb::observers::executable_changed.notify ();
     }
 }
 
@@ -2843,7 +2843,7 @@  clear_symtab_users (symfile_add_flags add_flags)
   clear_displays ();
   clear_last_displayed_sal ();
   clear_pc_function_cache ();
-  observer_notify_new_objfile (NULL);
+  gdb::observers::new_objfile.notify (NULL);
 
   /* Clear globals which might have pointed into a removed objfile.
      FIXME: It's not clear which of these are supposed to persist
@@ -3849,7 +3849,7 @@  _initialize_symfile (void)
 {
   struct cmd_list_element *c;
 
-  observer_attach_free_objfile (symfile_free_objfile);
+  gdb::observers::free_objfile.attach (symfile_free_objfile);
 
 #define READNOW_READNEVER_HELP \
   "The '-readnow' option will cause GDB to read the entire symbol file\n\
diff --git a/gdb/symtab.c b/gdb/symtab.c
index 567195304f..894a2537d6 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -54,7 +54,7 @@ 
 #include <ctype.h>
 #include "cp-abi.h"
 #include "cp-support.h"
-#include "observer.h"
+#include "observable.h"
 #include "solist.h"
 #include "macrotab.h"
 #include "macroscope.h"
@@ -5917,7 +5917,7 @@  If zero then the symbol cache is disabled."),
 	   _("Flush the symbol cache for each program space."),
 	   &maintenancelist);
 
-  observer_attach_executable_changed (symtab_observer_executable_changed);
-  observer_attach_new_objfile (symtab_new_objfile_observer);
-  observer_attach_free_objfile (symtab_free_objfile_observer);
+  gdb::observers::executable_changed.attach (symtab_observer_executable_changed);
+  gdb::observers::new_objfile.attach (symtab_new_objfile_observer);
+  gdb::observers::free_objfile.attach (symtab_free_objfile_observer);
 }
diff --git a/gdb/testsuite/gdb.gdb/observer.exp b/gdb/testsuite/gdb.gdb/observer.exp
deleted file mode 100644
index 1b514640d3..0000000000
--- a/gdb/testsuite/gdb.gdb/observer.exp
+++ /dev/null
@@ -1,143 +0,0 @@ 
-# Copyright 2003-2018 Free Software Foundation, Inc.
-
-# 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/>.
-
-# This file was written by Joel Brobecker (brobecker@gnat.com), derived
-# from xfullpath.exp.
-
-load_lib selftest-support.exp
-
-proc attach_first_observer { message } {
-    gdb_test_no_output "set \$first_obs = observer_attach_test_notification (&observer_test_first_notification_function)" \
-	"$message; attach first observer"
-}
-
-proc attach_second_observer { message } {
-    gdb_test_no_output "set \$second_obs = observer_attach_test_notification (&observer_test_second_notification_function)" \
-	"$message; attach second observer"
-}
-
-proc attach_third_observer { message } {
-    gdb_test_no_output "set \$third_obs = observer_attach_test_notification (&observer_test_third_notification_function)" \
-	"$message; attach third observer"
-}
-
-proc detach_first_observer { message } {
-    gdb_test_no_output "call observer_detach_test_notification (\$first_obs)" \
-	"$message; detach first observer"
-}
-
-proc detach_second_observer { message } {
-    gdb_test_no_output "call observer_detach_test_notification (\$second_obs)" \
-	"$message; detach second observer"
-}
-
-proc detach_third_observer { message } {
-    gdb_test_no_output "call observer_detach_test_notification (\$third_obs)" \
-	"$message; detach third observer"
-}
-
-proc check_counters { first second third message } {
-    gdb_test "print observer_test_first_observer" \
-	".\[0-9\]+ =.*$first" \
-	"$message; check first observer counter value"
-    gdb_test "print observer_test_second_observer" \
-	".\[0-9\]+ =.*$second" \
-	"$message; check second observer counter value"
-    gdb_test "print observer_test_third_observer" \
-	".\[0-9\]+ =.*$third" \
-	"$message; check third observer counter value"
-}
-
-proc reset_counters { message } {
-    gdb_test_no_output "set variable observer_test_first_observer = 0" \
-	"$message; reset first observer counter"
-    gdb_test_no_output "set variable observer_test_second_observer = 0" \
-	"$message; reset second observer counter"
-    gdb_test_no_output "set variable observer_test_third_observer = 0" \
-	"$message; reset third observer counter"
-}
-
-proc test_notifications { first second third message args } {
-    # Do any initialization
-    for {set i 0} {$i < [llength $args]} {incr i} {
-	[lindex $args $i] $message
-    }
-    reset_counters $message
-    # Call observer_notify_test_notification.  Note that this procedure
-    # takes one argument, but this argument is ignored by the observer
-    # callbacks we have installed.  So we just pass an arbitrary value.
-    gdb_test_no_output "call observer_notify_test_notification (0)" \
-	"$message; sending notification"
-    check_counters $first $second $third $message
-}
-
-proc test_observer {} {
-    # First, try sending a notification without any observer attached.
-    test_notifications 0 0 0 "no observer attached"
-
-    # Now, attach one observer, and send a notification.
-    test_notifications 0 1 0 "second observer attached" \
-	attach_second_observer
-
-    # Remove the observer, and send a notification.
-    test_notifications 0 0 0 "second observer detached" \
-	detach_second_observer
-
-    # With a new observer.
-    test_notifications 1 0 0 "1st observer added" \
-	attach_first_observer
-
-    # With 2 observers.
-    test_notifications 1 1 0 "2nd observer added" \
-	attach_second_observer
-
-    # With 3 observers.
-    test_notifications 1 1 1 "3rd observer added" \
-	attach_third_observer
-
-    # Remove middle observer.
-    test_notifications 1 0 1 "2nd observer removed" \
-	detach_second_observer
-
-    # Remove first observer.
-    test_notifications 0 0 1 "1st observer removed" \
-	detach_first_observer
-
-    # Remove last observer.
-    test_notifications 0 0 0 "3rd observer removed" \
-	detach_third_observer
-
-    # Go back to 3 observers, and remove them in a different order...
-    test_notifications 1 1 1 "three observers added" \
-	attach_first_observer \
-	attach_second_observer \
-	attach_third_observer 
-
-    # Remove the third observer.
-    test_notifications 1 1 0 "third observer removed" \
-	detach_third_observer
-
-    # Remove the second observer.
-    test_notifications 1 0 0 "second observer removed" \
-	detach_second_observer
-
-    # Remove the first observer, no more observers.
-    test_notifications 0 0 0 "first observer removed" \
-	detach_first_observer
-
-    return 0
-}
-
-do_self_tests captured_main test_observer
diff --git a/gdb/thread.c b/gdb/thread.c
index a99fbdc170..99f3f5be63 100644
--- a/gdb/thread.c
+++ b/gdb/thread.c
@@ -36,7 +36,7 @@ 
 #include <sys/types.h>
 #include <signal.h>
 #include "ui-out.h"
-#include "observer.h"
+#include "observable.h"
 #include "annotate.h"
 #include "cli/cli-decode.h"
 #include "gdb_regex.h"
@@ -207,7 +207,7 @@  set_thread_exited (thread_info *tp, int silent)
 
   if (tp->state != THREAD_EXITED)
     {
-      observer_notify_thread_exit (tp, silent);
+      gdb::observers::thread_exit.notify (tp, silent);
 
       /* Tag it as exited.  */
       tp->state = THREAD_EXITED;
@@ -299,7 +299,7 @@  add_thread_silent (ptid_t ptid)
 	  tp->state = THREAD_STOPPED;
 	  switch_to_thread (ptid);
 
-	  observer_notify_new_thread (tp);
+	  gdb::observers::new_thread.notify (tp);
 
 	  /* All done.  */
 	  return tp;
@@ -310,7 +310,7 @@  add_thread_silent (ptid_t ptid)
     }
 
   tp = new_thread (inf, ptid);
-  observer_notify_new_thread (tp);
+  gdb::observers::new_thread.notify (tp);
 
   return tp;
 }
@@ -821,7 +821,7 @@  thread_change_ptid (ptid_t old_ptid, ptid_t new_ptid)
   tp = find_thread_ptid (old_ptid);
   tp->ptid = new_ptid;
 
-  observer_notify_thread_ptid_changed (old_ptid, new_ptid);
+  gdb::observers::thread_ptid_changed.notify (old_ptid, new_ptid);
 }
 
 /* See gdbthread.h.  */
@@ -901,7 +901,7 @@  set_running (ptid_t ptid, int running)
 	any_started = 1;
     }
   if (any_started)
-    observer_notify_target_resumed (ptid);
+    gdb::observers::target_resumed.notify (ptid);
 }
 
 static int
@@ -1000,7 +1000,7 @@  set_stop_requested (ptid_t ptid, int stop)
   /* Call the stop requested observer so other components of GDB can
      react to this request.  */
   if (stop)
-    observer_notify_thread_stop_requested (ptid);
+    gdb::observers::thread_stop_requested.notify (ptid);
 }
 
 void
@@ -1037,7 +1037,7 @@  finish_thread_state (ptid_t ptid)
     }
 
   if (any_started)
-    observer_notify_target_resumed (ptid);
+    gdb::observers::target_resumed.notify (ptid);
 }
 
 void
@@ -1786,8 +1786,8 @@  thread_command (const char *tidstr, int from_tty)
 	}
       else
 	{
-	  observer_notify_user_selected_context_changed (USER_SELECTED_THREAD
-							 | USER_SELECTED_FRAME);
+	  gdb::observers::user_selected_context_changed.notify
+	    (USER_SELECTED_THREAD | USER_SELECTED_FRAME);
 	}
     }
 }
diff --git a/gdb/top.c b/gdb/top.c
index 72b3fd9e4e..14387b9f1a 100644
--- a/gdb/top.c
+++ b/gdb/top.c
@@ -46,7 +46,7 @@ 
 #include "gdbthread.h"
 #include "extension.h"
 #include "interps.h"
-#include "observer.h"
+#include "observable.h"
 #include "maint.h"
 #include "filenames.h"
 #include "frame.h"
@@ -1959,7 +1959,7 @@  static void
 set_gdb_datadir (const char *args, int from_tty, struct cmd_list_element *c)
 {
   set_gdb_data_directory (staged_gdb_datadir);
-  observer_notify_gdb_datadir_changed ();
+  gdb::observers::gdb_datadir_changed.notify ();
 }
 
 /* "show" command for the gdb_datadir configuration variable.  */
diff --git a/gdb/tracepoint.c b/gdb/tracepoint.c
index f34f103875..30fe206973 100644
--- a/gdb/tracepoint.c
+++ b/gdb/tracepoint.c
@@ -36,7 +36,7 @@ 
 #include "completer.h"
 #include "block.h"
 #include "dictionary.h"
-#include "observer.h"
+#include "observable.h"
 #include "user-regs.h"
 #include "valprint.h"
 #include "gdbcore.h"
@@ -315,7 +315,7 @@  delete_trace_state_variable (const char *name)
   for (ix = 0; VEC_iterate (tsv_s, tvariables, ix, tsv); ++ix)
     if (strcmp (name, tsv->name) == 0)
       {
-	observer_notify_tsv_deleted (tsv);
+	gdb::observers::tsv_deleted.notify (tsv);
 
 	xfree ((void *)tsv->name);
 	VEC_unordered_remove (tsv_s, tvariables, ix);
@@ -390,7 +390,7 @@  trace_variable_command (const char *args, int from_tty)
       if (tsv->initial_value != initval)
 	{
 	  tsv->initial_value = initval;
-	  observer_notify_tsv_modified (tsv);
+	  gdb::observers::tsv_modified.notify (tsv);
 	}
       printf_filtered (_("Trace state variable $%s "
 			 "now has initial value %s.\n"),
@@ -402,7 +402,7 @@  trace_variable_command (const char *args, int from_tty)
   tsv = create_trace_state_variable (name.c_str ());
   tsv->initial_value = initval;
 
-  observer_notify_tsv_created (tsv);
+  gdb::observers::tsv_created.notify (tsv);
 
   printf_filtered (_("Trace state variable $%s "
 		     "created, with initial value %s.\n"),
@@ -417,7 +417,7 @@  delete_trace_variable_command (const char *args, int from_tty)
       if (query (_("Delete all trace state variables? ")))
 	VEC_free (tsv_s, tvariables);
       dont_repeat ();
-      observer_notify_tsv_deleted (NULL);
+      gdb::observers::tsv_deleted.notify (NULL);
       return;
     }
 
@@ -1659,7 +1659,7 @@  start_tracing (const char *notes)
 					  loc->gdbarch);
 
       if (bp_location_downloaded)
-	observer_notify_breakpoint_modified (b);
+	gdb::observers::breakpoint_modified.notify (b);
     }
   VEC_free (breakpoint_p, tp_vec);
 
@@ -2175,7 +2175,7 @@  tfind_1 (enum trace_find_type type, int num,
   set_tracepoint_num (tp ? tp->number : target_tracept);
 
   if (target_frameno != get_traceframe_number ())
-    observer_notify_traceframe_changed (target_frameno, tracepoint_number);
+    gdb::observers::traceframe_changed.notify (target_frameno, tracepoint_number);
 
   set_current_traceframe (target_frameno);
 
@@ -3240,7 +3240,7 @@  merge_uploaded_tracepoints (struct uploaded_tp **uploaded_tps)
   /* Notify 'breakpoint-modified' observer that at least one of B's
      locations was changed.  */
   for (ix = 0; VEC_iterate (breakpoint_p, modified_tp, ix, b); ix++)
-    observer_notify_breakpoint_modified (b);
+    gdb::observers::breakpoint_modified.notify (b);
 
   VEC_free (breakpoint_p, modified_tp);
   free_uploaded_tps (uploaded_tps);
@@ -3287,7 +3287,7 @@  create_tsv_from_upload (struct uploaded_tsv *utsv)
   tsv->initial_value = utsv->initial_value;
   tsv->builtin = utsv->builtin;
 
-  observer_notify_tsv_created (tsv);
+  gdb::observers::tsv_created.notify (tsv);
 
   return tsv;
 }
diff --git a/gdb/tui/tui-hooks.c b/gdb/tui/tui-hooks.c
index 84e416e756..efa02e2f08 100644
--- a/gdb/tui/tui-hooks.c
+++ b/gdb/tui/tui-hooks.c
@@ -32,7 +32,7 @@ 
 #include "breakpoint.h"
 #include "ui-out.h"
 #include "top.h"
-#include "observer.h"
+#include "observable.h"
 #include <unistd.h>
 #include <fcntl.h>
 
@@ -203,14 +203,42 @@  tui_normal_stop (struct bpstats *bs, int print_frame)
   tui_refresh_frame_and_register_information (/*registers_too_p=*/1);
 }
 
-/* Observers created when installing TUI hooks.  */
-static struct observer *tui_bp_created_observer;
-static struct observer *tui_bp_deleted_observer;
-static struct observer *tui_bp_modified_observer;
-static struct observer *tui_inferior_exit_observer;
-static struct observer *tui_before_prompt_observer;
-static struct observer *tui_normal_stop_observer;
-static struct observer *tui_register_changed_observer;
+/* Token associated with observers registered while TUI hooks are
+   installed.  */
+static const gdb::observers::token tui_observers_token;
+
+/* Attach or detach a single observer, according to ATTACH.  */
+
+template<typename T>
+static void
+attach_or_detach (T &observable, typename T::func_type func, bool attach)
+{
+  if (attach)
+    observable.attach (func, tui_observers_token);
+  else
+    observable.detach (tui_observers_token);
+}
+
+/* Attach or detach TUI observers, according to ATTACH.  */
+
+static void
+tui_attach_detach_observers (bool attach)
+{
+  attach_or_detach (gdb::observers::breakpoint_created,
+		    tui_event_create_breakpoint, attach);
+  attach_or_detach (gdb::observers::breakpoint_deleted,
+		    tui_event_delete_breakpoint, attach);
+  attach_or_detach (gdb::observers::breakpoint_modified,
+		    tui_event_modify_breakpoint, attach);
+  attach_or_detach (gdb::observers::inferior_exit,
+		    tui_inferior_exit, attach);
+  attach_or_detach (gdb::observers::before_prompt,
+		    tui_before_prompt, attach);
+  attach_or_detach (gdb::observers::normal_stop,
+		    tui_normal_stop, attach);
+  attach_or_detach (gdb::observers::register_changed,
+		    tui_register_changed, attach);
+}
 
 /* Install the TUI specific hooks.  */
 void
@@ -224,20 +252,7 @@  tui_install_hooks (void)
     = tui_dummy_print_frame_info_listing_hook;
 
   /* Install the event hooks.  */
-  tui_bp_created_observer
-    = observer_attach_breakpoint_created (tui_event_create_breakpoint);
-  tui_bp_deleted_observer
-    = observer_attach_breakpoint_deleted (tui_event_delete_breakpoint);
-  tui_bp_modified_observer
-    = observer_attach_breakpoint_modified (tui_event_modify_breakpoint);
-  tui_inferior_exit_observer
-    = observer_attach_inferior_exit (tui_inferior_exit);
-  tui_before_prompt_observer
-    = observer_attach_before_prompt (tui_before_prompt);
-  tui_normal_stop_observer
-    = observer_attach_normal_stop (tui_normal_stop);
-  tui_register_changed_observer
-    = observer_attach_register_changed (tui_register_changed);
+  tui_attach_detach_observers (true);
 }
 
 /* Remove the TUI specific hooks.  */
@@ -246,26 +261,14 @@  tui_remove_hooks (void)
 {
   deprecated_print_frame_info_listing_hook = 0;
   deprecated_query_hook = 0;
+
   /* Remove our observers.  */
-  observer_detach_breakpoint_created (tui_bp_created_observer);
-  tui_bp_created_observer = NULL;
-  observer_detach_breakpoint_deleted (tui_bp_deleted_observer);
-  tui_bp_deleted_observer = NULL;
-  observer_detach_breakpoint_modified (tui_bp_modified_observer);
-  tui_bp_modified_observer = NULL;
-  observer_detach_inferior_exit (tui_inferior_exit_observer);
-  tui_inferior_exit_observer = NULL;
-  observer_detach_before_prompt (tui_before_prompt_observer);
-  tui_before_prompt_observer = NULL;
-  observer_detach_normal_stop (tui_normal_stop_observer);
-  tui_normal_stop_observer = NULL;
-  observer_detach_register_changed (tui_register_changed_observer);
-  tui_register_changed_observer = NULL;
+  tui_attach_detach_observers (false);
 }
 
 void
 _initialize_tui_hooks (void)
 {
   /* Install the permanent hooks.  */
-  observer_attach_new_objfile (tui_new_objfile_hook);
+  gdb::observers::new_objfile.attach (tui_new_objfile_hook);
 }
diff --git a/gdb/tui/tui-interp.c b/gdb/tui/tui-interp.c
index 3c87198696..cf32c905c5 100644
--- a/gdb/tui/tui-interp.c
+++ b/gdb/tui/tui-interp.c
@@ -31,7 +31,7 @@ 
 #include "tui/tui.h"
 #include "tui/tui-io.h"
 #include "infrun.h"
-#include "observer.h"
+#include "observable.h"
 #include "gdbthread.h"
 
 /* Set to 1 when the TUI mode must be activated when we first start
@@ -326,14 +326,14 @@  _initialize_tui_interp (void)
     }
 
   /* If changing this, remember to update cli-interp.c as well.  */
-  observer_attach_normal_stop (tui_on_normal_stop);
-  observer_attach_signal_received (tui_on_signal_received);
-  observer_attach_end_stepping_range (tui_on_end_stepping_range);
-  observer_attach_signal_exited (tui_on_signal_exited);
-  observer_attach_exited (tui_on_exited);
-  observer_attach_no_history (tui_on_no_history);
-  observer_attach_sync_execution_done (tui_on_sync_execution_done);
-  observer_attach_command_error (tui_on_command_error);
-  observer_attach_user_selected_context_changed
+  gdb::observers::normal_stop.attach (tui_on_normal_stop);
+  gdb::observers::signal_received.attach (tui_on_signal_received);
+  gdb::observers::end_stepping_range.attach (tui_on_end_stepping_range);
+  gdb::observers::signal_exited.attach (tui_on_signal_exited);
+  gdb::observers::exited.attach (tui_on_exited);
+  gdb::observers::no_history.attach (tui_on_no_history);
+  gdb::observers::sync_execution_done.attach (tui_on_sync_execution_done);
+  gdb::observers::command_error.attach (tui_on_command_error);
+  gdb::observers::user_selected_context_changed.attach
     (tui_on_user_selected_context_changed);
 }
diff --git a/gdb/unittests/observable-selftests.c b/gdb/unittests/observable-selftests.c
new file mode 100644
index 0000000000..6f2f7e8bcc
--- /dev/null
+++ b/gdb/unittests/observable-selftests.c
@@ -0,0 +1,135 @@ 
+/* Self tests for gdb::observers, GDB notifications to observers.
+
+   Copyright (C) 2003-2018 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/>.  */
+
+#include "defs.h"
+#include "selftest.h"
+#include "common/observable.h"
+
+namespace selftests {
+namespace observers {
+
+gdb::observers::observable<int> test_notification ("test_notification");
+
+static int test_first_observer = 0;
+static int test_second_observer = 0;
+static int test_third_observer = 0;
+
+static void
+test_first_notification_function (int arg)
+{
+  test_first_observer++;
+}
+
+static void
+test_second_notification_function (int arg)
+{
+  test_second_observer++;
+}
+
+static void
+test_third_notification_function (int arg)
+{
+  test_third_observer++;
+}
+
+static void
+notify_check_counters (int one, int two, int three)
+{
+  /* Reset.  */
+  test_first_observer = 0;
+  test_second_observer = 0;
+  test_third_observer = 0;
+  /* Notify.  */
+  test_notification.notify (0);
+  /* Check.  */
+  SELF_CHECK (one == test_first_observer);
+  SELF_CHECK (two == test_second_observer);
+  SELF_CHECK (three == test_third_observer);
+}
+
+static void
+run_tests ()
+{
+  /* First, try sending a notification without any observer
+     attached.  */
+  notify_check_counters (0, 0, 0);
+
+  const gdb::observers::token token1, token2, token3;
+
+  /* Now, attach one observer, and send a notification.  */
+  test_notification.attach (&test_second_notification_function, token2);
+  notify_check_counters (0, 1, 0);
+
+  /* Remove the observer, and send a notification.  */
+  test_notification.detach (token2);
+  notify_check_counters (0, 0, 0);
+
+  /* With a new observer.  */
+  test_notification.attach (&test_first_notification_function, token1);
+  notify_check_counters (1, 0, 0);
+
+  /* With 2 observers.  */
+  test_notification.attach (&test_second_notification_function, token2);
+  notify_check_counters (1, 1, 0);
+
+  /* With 3 observers.  */
+  test_notification.attach (&test_third_notification_function, token3);
+  notify_check_counters (1, 1, 1);
+
+  /* Remove middle observer.  */
+  test_notification.detach (token2);
+  notify_check_counters (1, 0, 1);
+
+  /* Remove first observer.  */
+  test_notification.detach (token1);
+  notify_check_counters (0, 0, 1);
+
+  /* Remove last observer.  */
+  test_notification.detach (token3);
+  notify_check_counters (0, 0, 0);
+
+  /* Go back to 3 observers, and remove them in a different
+     order...  */
+  test_notification.attach (&test_first_notification_function, token1);
+  test_notification.attach (&test_second_notification_function, token2);
+  test_notification.attach (&test_third_notification_function, token3);
+  notify_check_counters (1, 1, 1);
+
+  /* Remove the third observer.  */
+  test_notification.detach (token3);
+  notify_check_counters (1, 1, 0);
+
+  /* Remove the second observer.  */
+  test_notification.detach (token2);
+  notify_check_counters (1, 0, 0);
+
+  /* Remove first observer, no more observers.  */
+  test_notification.detach (token1);
+  notify_check_counters (0, 0, 0);
+}
+
+} /* namespace observers */
+} /* namespace selftests */
+
+void
+_initialize_observer_selftest ()
+{
+  selftests::register_test ("gdb::observers",
+			    selftests::observers::run_tests);
+}
diff --git a/gdb/valops.c b/gdb/valops.c
index bf028fd7a3..1f655b5187 100644
--- a/gdb/valops.c
+++ b/gdb/valops.c
@@ -36,7 +36,7 @@ 
 #include "cp-support.h"
 #include "target-float.h"
 #include "tracepoint.h"
-#include "observer.h"
+#include "observable.h"
 #include "objfiles.h"
 #include "extension.h"
 #include "byte-vector.h"
@@ -1177,7 +1177,7 @@  value_assign (struct value *toval, struct value *fromval)
 	      }
 	  }
 
-	observer_notify_register_changed (frame, value_reg);
+	gdb::observers::register_changed.notify (frame, value_reg);
 	break;
       }
 
@@ -1208,7 +1208,7 @@  value_assign (struct value *toval, struct value *fromval)
     case lval_register:
     case lval_computed:
 
-      observer_notify_target_changed (&current_target);
+      gdb::observers::target_changed.notify (&current_target);
 
       /* Having destroyed the frame cache, restore the selected
 	 frame.  */