Merge branch 'vinoski/sys-get-rep-state2'

* vinoski/sys-get-rep-state2:
  remove tuple funs from special process documentation
  fix sys:get_state/1,2 and sys:replace_state/2,3 when sys suspended

OTP-11817

1 files changed, 36 insertions, 13 deletions

diff --git a/system/doc/design_principles/spec_proc.xml b/system/doc/design_principles/spec_proc.xml
index 8de7a5fe03..69bf2e0448 100644
--- a/system/doc/design_principles/spec_proc.xml
+++ b/system/doc/design_principles/spec_proc.xml
@@ -130,7 +130,8 @@ ok
 -export([alloc/0, free/1]).
 -export([init/1]).
 -export([system_continue/3, system_terminate/4,
-         write_debug/3]).
+         write_debug/3,
+         system_get_state/1, system_replace_state/2]).
 
 start_link() ->
     proc_lib:start_link(ch4, init, [self()]).
@@ -156,15 +157,15 @@ init(Parent) ->
 loop(Chs, Parent, Deb) ->
     receive
         {From, alloc} ->
-            Deb2 = sys:handle_debug(Deb, {ch4, write_debug},
+            Deb2 = sys:handle_debug(Deb, fun ch4:write_debug/3,
                                     ch4, {in, alloc, From}),
             {Ch, Chs2} = alloc(Chs),
             From ! {ch4, Ch},
-            Deb3 = sys:handle_debug(Deb2, {ch4, write_debug},
+            Deb3 = sys:handle_debug(Deb2, fun ch4:write_debug/3,
                                     ch4, {out, {ch4, Ch}, From}),
             loop(Chs2, Parent, Deb3);
         {free, Ch} ->
-            Deb2 = sys:handle_debug(Deb, {ch4, write_debug},
+            Deb2 = sys:handle_debug(Deb, fun ch4:write_debug/3,
                                     ch4, {in, {free, Ch}}),
             Chs2 = free(Ch, Chs),
             loop(Chs2, Parent, Deb2);
@@ -177,9 +178,16 @@ loop(Chs, Parent, Deb) ->
 system_continue(Parent, Deb, Chs) ->
     loop(Chs, Parent, Deb).
 
-system_terminate(Reason, Parent, Deb, Chs) ->
+system_terminate(Reason, _Parent, _Deb, _Chs) ->
     exit(Reason).
 
+system_get_state(Chs) ->
+    {ok, Chs}.
+
+system_replace_state(StateFun, Chs) ->
+    NChs = StateFun(Chs),
+    {ok, NChs, NChs}.
+
 write_debug(Dev, Event, Name) ->
     io:format(Dev, "~p event = ~p~n", [Name, Event]).</pre>
       <p>Example on how the simple debugging functions in <c>sys</c> can
@@ -281,10 +289,10 @@ sys:handle_debug(Deb, Func, Info, Event) => Deb1</code>
           <p><c>Deb</c> is the debug structure.</p>
         </item>
         <item>
-          <p><c>Func</c> is a tuple <c>{Module, Name}</c> (or a fun) and
-            should specify a (user defined) function used to format
+          <p><c>Func</c> is a fun specifying
+            a (user defined) function used to format
             trace output. For each system event, the format function is
-            called as <c>Module:Name(Dev, Event, Info)</c>, where:</p>
+            called as <c>Func(Dev, Event, Info)</c>, where:</p>
           <list type="bulleted">
             <item>
               <p><c>Dev</c> is the IO device to which the output should
@@ -319,15 +327,15 @@ sys:handle_debug(Deb, Func, Info, Event) => Deb1</code>
 loop(Chs, Parent, Deb) ->
     receive
         {From, alloc} ->
-            Deb2 = sys:handle_debug(Deb, {ch4, write_debug},
+            Deb2 = sys:handle_debug(Deb, fun ch4:write_debug/3,
                                     ch4, {in, alloc, From}),
             {Ch, Chs2} = alloc(Chs),
             From ! {ch4, Ch},
-            Deb3 = sys:handle_debug(Deb2, {ch4, write_debug},
+            Deb3 = sys:handle_debug(Deb2, fun ch4:write_debug/3,
                                     ch4, {out, {ch4, Ch}, From}),
             loop(Chs2, Parent, Deb3);
         {free, Ch} ->
-            Deb2 = sys:handle_debug(Deb, {ch4, write_debug},
+            Deb2 = sys:handle_debug(Deb, fun ch4:write_debug/3,
                                     ch4, {in, {free, Ch}}),
             Chs2 = free(Ch, Chs),
             loop(Chs2, Parent, Deb2);
@@ -366,8 +374,15 @@ Module:system_terminate(Reason, Parent, Deb, State)</code>
         <item><c>Module</c> is the name of the module.</item>
         <item><c>Deb</c> is the debug structure.</item>
         <item><c>State</c> is a term describing the internal state and
-         is passed to <c>system_continue</c>/<c>system_terminate</c>.</item>
+         is passed to <c>system_continue</c>/<c>system_terminate</c>/
+         <c>system_get_state</c>/<c>system_replace_state</c>.</item>
       </list>
+      <p>If the process should return its state <c>handle_system_msg</c> will call:</p>
+      <code type="none">
+Module:system_get_state(State)</code>
+      <p>or if the process should replace its state using the fun <c>StateFun</c>:</p>
+      <code type="none">
+Module:system_replace_state(StateFun, State)</code>
       <p>In the example:</p>
       <code type="none">
 loop(Chs, Parent, Deb) ->
@@ -383,7 +398,15 @@ system_continue(Parent, Deb, Chs) ->
     loop(Chs, Parent, Deb).
 
 system_terminate(Reason, Parent, Deb, Chs) ->
-    exit(Reason).</code>
+    exit(Reason).
+
+system_get_state(Chs) ->
+    {ok, Chs, Chs}.
+
+system_replace_state(StateFun, Chs) ->
+    NChs = StateFun(Chs),
+    {ok, NChs, NChs}.
+</code>
       <p>If the special process is set to trap exits, note that if
         the parent process terminates, the expected behavior is to
         terminate with the same reason:</p>