Remove the pg module and related documentation

This module has been marked experimental for more than 15 years,
and has largely been superseded by the pg2 module from the kernel
application. The original pg also has no tests and has not been
updated in the last 15 years other than small maintenance edits
(like adding specs or replacing pid/1 by is_pid/1). It is pretty
unlikely that anyone uses it today and its presence is simply
confusing as people should be using pg2 anyway.

4 files changed, 0 insertions, 191 deletions

diff --git a/lib/stdlib/src/Makefile b/lib/stdlib/src/Makefile
index 9ab2cd4134..1b3744b6fb 100644
--- a/lib/stdlib/src/Makefile
+++ b/lib/stdlib/src/Makefile
@@ -97,7 +97,6 @@ MODULES= \
 	otp_internal \
 	orddict \
 	ordsets \
-	pg \
 	re \
 	pool \
 	proc_lib \
diff --git a/lib/stdlib/src/otp_internal.erl b/lib/stdlib/src/otp_internal.erl
index c0ee8799c8..662a0aca74 100644
--- a/lib/stdlib/src/otp_internal.erl
+++ b/lib/stdlib/src/otp_internal.erl
@@ -577,8 +577,6 @@ obsolete_1(asn1rt, utf8_binary_to_list, 1) ->
     {deprecated,{unicode,characters_to_list,1}};
 obsolete_1(asn1rt, utf8_list_to_binary, 1) ->
     {deprecated,{unicode,characters_to_binary,1}};
-obsolete_1(pg, _, _) ->
-    {deprecated,"deprecated; will be removed in OTP 18"};
 
 obsolete_1(_, _, _) ->
     no.
diff --git a/lib/stdlib/src/pg.erl b/lib/stdlib/src/pg.erl
deleted file mode 100644
index a41fd329c2..0000000000
--- a/lib/stdlib/src/pg.erl
+++ /dev/null
@@ -1,187 +0,0 @@
-%%
-%% %CopyrightBegin%
-%% 
-%% Copyright Ericsson AB 1996-2014. All Rights Reserved.
-%% 
-%% The contents of this file are subject to the Erlang Public License,
-%% Version 1.1, (the "License"); you may not use this file except in
-%% compliance with the License. You should have received a copy of the
-%% Erlang Public License along with this software. If not, it can be
-%% retrieved online at http://www.erlang.org/.
-%% 
-%% Software distributed under the License is distributed on an "AS IS"
-%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
-%% the License for the specific language governing rights and limitations
-%% under the License.
-%% 
-%% %CopyrightEnd%
-%%
--module(pg).
--deprecated(module).
-
-%% pg provides a process group facility. Messages 
-%% can be multicasted to all members in the group
-
--export([create/1,
-	 create/2,
-	 standby/2,
-	 join/2,
-	 send/2,
-	 esend/2,
-	 members/1,
-	 name_to_pid/1,
-	 master/1]).
-
-
-%% Create a brand new empty process group with the master residing 
-%% at the local node
-
--spec create(PgName) -> 'ok' | {'error', Reason} when
-      PgName :: term(),
-      Reason :: 'already_created' | term().
-
-create(PgName) -> 
-    catch begin check(PgName),
-    Pid = spawn(pg,master,[PgName]),
-    global:register_name(PgName,Pid),
-    ok end.
-
-%% Create a brand new empty process group with the master 
-%% residing at Node
-
--spec create(PgName, Node) -> 'ok' | {'error', Reason} when
-      PgName :: term(),
-      Node :: node(),
-      Reason :: 'already_created' | term().
-
-create(PgName, Node) ->
-    catch begin check(PgName),
-    Pid = spawn(Node,pg,master,[PgName]),
-    global:register_name(PgName,Pid),
-    ok end.
-
-%% Have a process on Node that will act as a standby for the process
-%% group manager. So if the node where the manager runs fails, the
-%% process group will continue to function.
-
--spec standby(term(), node()) -> 'ok'.
-
-standby(_PgName, _Node) ->
-    ok.
-
-%% Tell process group PgName that Pid is a new member of the group
-%% synchronously return a list of all old members in the group
-
--spec join(PgName, Pid) -> Members when
-      PgName :: term(),
-      Pid :: pid(),
-      Members :: [pid()].
-
-join(PgName, Pid) when is_atom(PgName) -> 
-    global:send(PgName, {join,self(),Pid}),
-    receive
-	{_P,{members,Members}} ->
-	    Members
-    end.
-
-%% Multi cast Mess to all members in the group
-
--spec send(PgName, Msg) -> 'ok' when
-      PgName :: term(),
-      Msg :: term().
-
-send(PgName, Mess) when is_atom(PgName) ->
-    global:send(PgName, {send, self(), Mess}),
-    ok;
-send(Pg, Mess) when is_pid(Pg) ->
-    Pg ! {send,self(),Mess},
-    ok.
-
-%% multi cast a message to all members in the group but ourselves
-%% If we are a member
-
--spec esend(PgName, Msg) -> 'ok' when
-      PgName :: term(),
-      Msg :: term().
-
-esend(PgName, Mess) when is_atom(PgName) ->
-    global:send(PgName, {esend,self(),Mess}),
-    ok;
-esend(Pg, Mess) when is_pid(Pg) ->
-    Pg ! {esend,self(),Mess},
-    ok.
-
-%% Return the members of the group
-
--spec members(PgName) -> Members when
-      PgName :: term(),
-      Members :: [pid()].
-
-members(PgName) when is_atom(PgName) ->
-    global:send(PgName, {self() ,members}),
-    receive
-	{_P,{members,Members}} ->
-	    Members
-    end;
-members(Pg) when is_pid(Pg) ->
-    Pg ! {self,members},
-    receive
-	{_P,{members,Members}} ->
-	    Members
-    end.
-
--spec name_to_pid(atom()) -> pid() | 'undefined'.
-
-name_to_pid(PgName) when is_atom(PgName) ->
-    global:whereis_name(PgName).
-
--spec master(term()) -> no_return().
-
-master(PgName) ->
-    process_flag(trap_exit, true),
-    master_loop(PgName, []).
-
-master_loop(PgName,Members) ->
-    receive
-	{send,From,Message} ->
-	    send_all(Members,{pg_message,From,PgName,Message}),
-	    master_loop(PgName,Members);
-	{esend,From,Message} ->
-	    send_all(lists:delete(From,Members),
-		     {pg_message,From,PgName,Message}),
-	    master_loop(PgName,Members);
-	{join,From,Pid} ->
-	    link(Pid),
-	    send_all(Members,{new_member,PgName,Pid}),
-	    From ! {self(),{members,Members}},
-	    master_loop(PgName,[Pid|Members]);
-	{From,members} ->
-	    From ! {self(),{members,Members}},
-	    master_loop(PgName,Members);
-	{'EXIT',From,_} ->
-	    L =
-		case lists:member(From,Members) of
-		    true ->
-			NewMembers = lists:delete(From,Members),
-			send_all(NewMembers, {crashed_member,PgName,From}),
-			NewMembers;
-		    false ->
-			Members
-		end,
-	    master_loop(PgName,L)  
-    end.
-
-send_all([], _) -> ok;
-send_all([P|Ps], M) ->
-    P ! M,
-    send_all(Ps, M).
-
-%% Check if the process group already exists
-
-check(PgName) ->
-    case global:whereis_name(PgName) of
-        Pid when is_pid(Pid) -> 
-            throw({error,already_created});
-        undefined ->
-	    ok
-    end.
diff --git a/lib/stdlib/src/stdlib.app.src b/lib/stdlib/src/stdlib.app.src
index d388410de0..42a787dacf 100644
--- a/lib/stdlib/src/stdlib.app.src
+++ b/lib/stdlib/src/stdlib.app.src
@@ -77,7 +77,6 @@
 	     orddict,
 	     ordsets,
 	     otp_internal,
-	     pg,
 	     pool,
 	     proc_lib,
 	     proplists,