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and has largely been superseded by the pg2 module from the kernel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.

9 files changed, 3 insertions, 315 deletions

diff --git a/lib/kernel/doc/src/pg2.xml b/lib/kernel/doc/src/pg2.xml
index 5eb63c1ef6..35cf85470a 100644
--- a/lib/kernel/doc/src/pg2.xml
+++ b/lib/kernel/doc/src/pg2.xml
@@ -34,11 +34,8 @@
   <module>pg2</module>
   <modulesummary>Distributed Named Process Groups</modulesummary>
   <description>
-    <p>This module implements process groups. The groups in this
-      module differ from the groups in the module <c>pg</c> in several
-      ways. In <c>pg</c>, each message is sent to all members in the
-      group. In this module, each message may be sent to one, some, or
-      all members.
+    <p>This module implements process groups. Each message may be sent
+      to one, some, or all members of the group.
       </p>
     <p>A group of processes can be accessed by a common name. For
       example, if there is a group named <c>foobar</c>, there can be a
@@ -160,8 +157,7 @@
 
   <section>
     <title>See Also</title>
-    <p><seealso marker="kernel_app">kernel(6)</seealso>, 
-       <seealso marker="stdlib:pg">pg(3)</seealso></p>
+    <p><seealso marker="kernel_app">kernel(6)</seealso></p>
   </section>
 </erlref>
 
diff --git a/lib/stdlib/doc/src/Makefile b/lib/stdlib/doc/src/Makefile
index ff77c3eea0..f5d8b2072a 100644
--- a/lib/stdlib/doc/src/Makefile
+++ b/lib/stdlib/doc/src/Makefile
@@ -76,7 +76,6 @@ XML_REF3_FILES = \
 	ms_transform.xml \
 	orddict.xml \
 	ordsets.xml \
-	pg.xml \
 	pool.xml \
 	proc_lib.xml \
 	proplists.xml \
diff --git a/lib/stdlib/doc/src/pg.xml b/lib/stdlib/doc/src/pg.xml
deleted file mode 100644
index a3b69884b6..0000000000
--- a/lib/stdlib/doc/src/pg.xml
+++ /dev/null
@@ -1,114 +0,0 @@
-<?xml version="1.0" encoding="utf-8" ?>
-<!DOCTYPE erlref SYSTEM "erlref.dtd">
-
-<erlref>
-  <header>
-    <copyright>
-      <year>1996</year>
-      <year>2014</year>
-      <holder>Ericsson AB, All Rights Reserved</holder>
-    </copyright>
-    <legalnotice>
-  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.
-
-  The Initial Developer of the Original Code is Ericsson AB.
-    </legalnotice>
-
-    <title>pg</title>
-    <prepared></prepared>
-    <docno></docno>
-    <date></date>
-    <rev></rev>
-  </header>
-  <module>pg</module>
-  <modulesummary>Distributed, Named Process Groups</modulesummary>
-  <description>
-    <warning>
-      <p>This module is deprecated and will be removed in Erlang/OTP 18.</p>
-    </warning>
-    <p>This (experimental) module implements process groups. A process
-      group is a group of processes that can be accessed by a common
-      name. For example, a group named <c>foobar</c> can include a set
-      of processes as members of this group and they can be located on
-      different nodes.</p>
-    <p>When messages are sent to the named group, all members of
-      the group receive the message. The messages are serialized. If
-      the process <c>P1</c> sends the message <c>M1</c> to the group,
-      and process <c>P2</c> simultaneously sends message <c>M2</c>, then
-      all members of the group receive the two messages in the same
-      order. If members of a group terminate, they are automatically 
-      removed from the group.</p>
-    <p>This module is not complete. The module is inspired by the ISIS
-      system and the causal order protocol of the ISIS system should 
-      also be implemented. At the moment, all messages are serialized
-      by sending them through a group master process.</p>
-  </description>
-  <funcs>
-    <func>
-      <name name="create" arity="1"/>
-      <fsummary>Create an empty group</fsummary>
-      <desc>
-        <p>Creates an empty group named <c><anno>PgName</anno></c> on the current
-          node.</p>
-      </desc>
-    </func>
-    <func>
-      <name name="create" arity="2"/>
-      <fsummary>Create an empty group on another node</fsummary>
-      <desc>
-        <p>Creates an empty group named <c><anno>PgName</anno></c> on the node
-          <c><anno>Node</anno></c>.</p>
-      </desc>
-    </func>
-    <func>
-      <name name="join" arity="2"/>
-      <fsummary>Join a pid to a process group</fsummary>
-      <desc>
-        <p>Joins the pid <c><anno>Pid</anno></c> to the process group
-          <c><anno>PgName</anno></c>.
-          Returns a list of all old members of the group.</p>
-      </desc>
-    </func>
-    <func>
-      <name name="send" arity="2"/>
-      <fsummary>Send a message to all members of a process group</fsummary>
-      <desc>
-        <p>Sends the tuple <c>{pg_message, From, PgName, Msg}</c> to
-          all members of the process group <c><anno>PgName</anno></c>.</p>
-        <p>Failure: <c>{badarg, {<anno>PgName</anno>, <anno>Msg</anno>}}</c>
-          if <c><anno>PgName</anno></c> is
-          not a process group (a globally registered name).</p>
-      </desc>
-    </func>
-    <func>
-      <name name="esend" arity="2"/>
-      <fsummary>Send a message to all members of a process group, except ourselves</fsummary>
-      <desc>
-        <p>Sends the tuple <c>{pg_message, From, PgName, Msg}</c> to
-          all members of the process group <c><anno>PgName</anno></c>, except
-          ourselves.</p>
-        <p>Failure: <c>{badarg, {<anno>PgName</anno>, <anno>Msg</anno>}}</c>
-          if <c><anno>PgName</anno></c> is
-          not a process group (a globally registered name).</p>
-      </desc>
-    </func>
-    <func>
-      <name name="members" arity="1"/>
-      <fsummary>Return a list of all members of a process group</fsummary>
-      <desc>
-        <p>Returns a list of all members of the process group
-          <c>PgName</c>.</p>
-      </desc>
-    </func>
-  </funcs>
-</erlref>
-
diff --git a/lib/stdlib/doc/src/ref_man.xml b/lib/stdlib/doc/src/ref_man.xml
index 6c35578bdf..ea4009dc3e 100644
--- a/lib/stdlib/doc/src/ref_man.xml
+++ b/lib/stdlib/doc/src/ref_man.xml
@@ -73,7 +73,6 @@
   <xi:include href="ms_transform.xml"/>
   <xi:include href="orddict.xml"/>
   <xi:include href="ordsets.xml"/>
-  <xi:include href="pg.xml"/>
   <xi:include href="pool.xml"/>
   <xi:include href="proc_lib.xml"/>
   <xi:include href="proplists.xml"/>
diff --git a/lib/stdlib/doc/src/specs.xml b/lib/stdlib/doc/src/specs.xml
index 60a04ed5e7..fd77b52da6 100644
--- a/lib/stdlib/doc/src/specs.xml
+++ b/lib/stdlib/doc/src/specs.xml
@@ -39,7 +39,6 @@
   <xi:include href="../specs/specs_ms_transform.xml"/>
   <xi:include href="../specs/specs_orddict.xml"/>
   <xi:include href="../specs/specs_ordsets.xml"/>
-  <xi:include href="../specs/specs_pg.xml"/>
   <xi:include href="../specs/specs_pool.xml"/>
   <xi:include href="../specs/specs_proc_lib.xml"/>
   <xi:include href="../specs/specs_proplists.xml"/>
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,