proc_lib: Add format/3

We'll need a way to limit the size of the crash report produced
by proc_lib:format(). Add format/3, where the third argument is
a depth argument.

3 files changed, 100 insertions, 25 deletions

diff --git a/lib/stdlib/doc/src/proc_lib.xml b/lib/stdlib/doc/src/proc_lib.xml
index 86ade8840f..85f0c0c908 100644
--- a/lib/stdlib/doc/src/proc_lib.xml
+++ b/lib/stdlib/doc/src/proc_lib.xml
@@ -227,6 +227,17 @@ init(Parent) ->
       </desc>
     </func>
     <func>
+      <name name="format" arity="3"/>
+      <fsummary>Format a crash report.</fsummary>
+      <desc>
+        <p>This function can be used by a user defined event handler to
+          format a crash report. When <anno>Depth</anno> is given as an
+	  positive integer, it will be used in the format string to
+	  limit the output as follows: <c>io_lib:format("~P",
+	  [Term,<anno>Depth</anno>])</c>.</p>
+      </desc>
+    </func>
+    <func>
       <name name="initial_call" arity="1"/>
       <fsummary>Extract the initial call of a <c>proc_lib</c>spawned process.</fsummary>
       <desc>
diff --git a/lib/stdlib/src/proc_lib.erl b/lib/stdlib/src/proc_lib.erl
index bbf4f573f5..10c476a6f5 100644
--- a/lib/stdlib/src/proc_lib.erl
+++ b/lib/stdlib/src/proc_lib.erl
@@ -30,7 +30,8 @@
 	 start/3, start/4, start/5, start_link/3, start_link/4, start_link/5,
 	 hibernate/3,
 	 init_ack/1, init_ack/2,
-	 init_p/3,init_p/5,format/1,format/2,initial_call/1,
+	 init_p/3,init_p/5,format/1,format/2,format/3,
+	 initial_call/1,
          translate_initial_call/1,
 	 stop/1, stop/3]).
 
@@ -700,53 +701,71 @@ format(CrashReport) ->
       CrashReport :: [term()],
       Encoding :: latin1 | unicode | utf8.
 
-format([OwnReport,LinkReport], Encoding) ->
-    OwnFormat = format_report(OwnReport, Encoding),
-    LinkFormat = format_report(LinkReport, Encoding),
+format(CrashReport, Encoding) ->
+    format(CrashReport, Encoding, unlimited).
+
+-spec format(CrashReport, Encoding, Depth) -> string() when
+      CrashReport :: [term()],
+      Encoding :: latin1 | unicode | utf8,
+      Depth :: unlimited | pos_integer().
+
+format([OwnReport,LinkReport], Encoding, Depth) ->
+    Extra = {Encoding,Depth},
+    OwnFormat = format_report(OwnReport, Extra),
+    LinkFormat = format_report(LinkReport, Extra),
     Str = io_lib:format("  crasher:~n~ts  neighbours:~n~ts",
                         [OwnFormat, LinkFormat]),
     lists:flatten(Str).
 
-format_report(Rep, Enc) when is_list(Rep) ->
-    format_rep(Rep,Enc);
-format_report(Rep, Enc) ->
+format_report(Rep, Extra) when is_list(Rep) ->
+    format_rep(Rep, Extra);
+format_report(Rep, {Enc,_}) ->
     io_lib:format("~"++modifier(Enc)++"p~n", [Rep]).
 
-format_rep([{initial_call,InitialCall}|Rep], Enc) ->
-    [format_mfa(InitialCall)|format_rep(Rep, Enc)];
-format_rep([{error_info,{Class,Reason,StackTrace}}|Rep], Enc) ->
-    [format_exception(Class, Reason, StackTrace, Enc)|format_rep(Rep, Enc)];
-format_rep([{Tag,Data}|Rep], Enc) ->
-    [format_tag(Tag, Data)|format_rep(Rep, Enc)];
-format_rep(_, _Enc) ->
+format_rep([{initial_call,InitialCall}|Rep], {_Enc,Depth}=Extra) ->
+    [format_mfa(InitialCall, Depth)|format_rep(Rep, Extra)];
+format_rep([{error_info,{Class,Reason,StackTrace}}|Rep], Extra) ->
+    [format_exception(Class, Reason, StackTrace, Extra)|format_rep(Rep, Extra)];
+format_rep([{Tag,Data}|Rep], Extra) ->
+    [format_tag(Tag, Data, Extra)|format_rep(Rep, Extra)];
+format_rep(_, _Extra) ->
     [].
 
-format_exception(Class, Reason, StackTrace, Enc) ->
-    PF = pp_fun(Enc),
+format_exception(Class, Reason, StackTrace, {Enc,_}=Extra) ->
+    PF = pp_fun(Extra),
     StackFun = fun(M, _F, _A) -> (M =:= erl_eval) or (M =:= ?MODULE) end,
     %% EI = "    exception: ",
     EI = "    ",
     [EI, lib:format_exception(1+length(EI), Class, Reason, 
                               StackTrace, StackFun, PF, Enc), "\n"].
 
-format_mfa({M,F,Args}=StartF) ->
+format_mfa({M,F,Args}=StartF, Depth) ->
     try
 	A = length(Args),
 	["    initial call: ",atom_to_list(M),$:,atom_to_list(F),$/,
 	 integer_to_list(A),"\n"]
     catch
 	error:_ ->
-	    format_tag(initial_call, StartF)
+	    format_tag(initial_call, StartF, Depth)
     end.
 
-pp_fun(Enc) ->
-    P = modifier(Enc) ++ "p",
+pp_fun({Enc,Depth}) ->
+    {Letter,Tl} = case Depth of
+		      unlimited -> {"p",[]};
+		      _ -> {"P",[Depth]}
+		  end,
+    P = modifier(Enc) ++ Letter,
     fun(Term, I) -> 
-            io_lib:format("~." ++ integer_to_list(I) ++ P, [Term])
+            io_lib:format("~." ++ integer_to_list(I) ++ P, [Term|Tl])
     end.
 
-format_tag(Tag, Data) ->
-    io_lib:format("    ~p: ~80.18p~n", [Tag, Data]).
+format_tag(Tag, Data, {_Enc,Depth}) ->
+    case Depth of
+	unlimited ->
+	    io_lib:format("    ~p: ~80.18p~n", [Tag, Data]);
+	_ ->
+	    io_lib:format("    ~p: ~80.18P~n", [Tag, Data, Depth])
+    end.
 
 modifier(latin1) -> "";
 modifier(_) -> "t".
diff --git a/lib/stdlib/test/proc_lib_SUITE.erl b/lib/stdlib/test/proc_lib_SUITE.erl
index 437c981461..3a8fa74d36 100644
--- a/lib/stdlib/test/proc_lib_SUITE.erl
+++ b/lib/stdlib/test/proc_lib_SUITE.erl
@@ -28,7 +28,7 @@
 	 init_per_group/2,end_per_group/2, 
 	 crash/1, sync_start_nolink/1, sync_start_link/1,
          spawn_opt/1, sp1/0, sp2/0, sp3/1, sp4/2, sp5/1,
-	 hibernate/1, stop/1]).
+	 hibernate/1, stop/1, t_format/1]).
 -export([ otp_6345/1, init_dont_hang/1]).
 
 -export([hib_loop/1, awaken/1]).
@@ -51,7 +51,7 @@ suite() -> [{ct_hooks,[ts_install_cth]}].
 
 all() -> 
     [crash, {group, sync_start}, spawn_opt, hibernate,
-     {group, tickets}, stop].
+     {group, tickets}, stop, t_format].
 
 groups() -> 
     [{tickets, [], [otp_6345, init_dont_hang]},
@@ -457,6 +457,51 @@ system_terminate(crash,_Parent,_Deb,_State) ->
 system_terminate(Reason,_Parent,_Deb,_State) ->
     exit(Reason).
 
+
+t_format(_Config) ->
+    error_logger:tty(false),
+    try
+	t_format()
+    after
+	error_logger:tty(true)
+    end,
+    ok.
+
+t_format() ->
+    error_logger:add_report_handler(?MODULE, self()),
+    Pid = proc_lib:spawn(fun t_format_looper/0),
+    HugeData = gb_sets:from_list(lists:seq(1, 100)),
+    Pid ! {die,HugeData},
+    Report = receive
+		 {crash_report, Pid, Report0} -> Report0
+	     end,
+    Usz = do_test_format(Report, unlimited),
+    Tsz = do_test_format(Report, 20),
+
+    if
+	Tsz >= Usz ->
+	    ?t:fail();
+	true ->
+	    ok
+    end,
+
+    ok.
+
+do_test_format(Report, Depth) ->
+    io:format("*** Depth = ~p", [Depth]),
+    S0 = proc_lib:format(Report, latin1, Depth),
+    S = lists:flatten(S0),
+    io:put_chars(S),
+    length(S).
+
+t_format_looper() ->
+    receive
+	{die,Data} ->
+	    exit(Data);
+	_ ->
+	    t_format_looper()
+    end.
+
 %%-----------------------------------------------------------------
 %% The error_logger handler used.
 %%-----------------------------------------------------------------