Merge branch 'ta/werror' into dev

* ta/werror:
  snmp: extend warnings_as_errors test
  systools: add warnings_as_errors option
  asn1ct: add warnings_as_errors option
  leex: optimize werror/1
  yecc: optimize werror/1
  yecc: use more descriptive name: 'werror'
  leex: use more descriptive name: 'werror'
  compile: optimize werror/1
  compile: log warnings as errors if -Werror is enabled
  yecc: log warnings as errors if -Werror is enabled
  leex: log warnings as errors if -Werror is enabled
  yecc: honour -Werror passed from erlc
  leex: honour -Werror passed from erlc
  Do not write beam file if Werr and warnings /= []
  parsetools: test if warnings_as_errors writes file

OTP-9536

18 files changed, 472 insertions, 192 deletions

diff --git a/erts/test/erlc_SUITE.erl b/erts/test/erlc_SUITE.erl
index 2b5cb11f02..a9e28672e3 100644
--- a/erts/test/erlc_SUITE.erl
+++ b/erts/test/erlc_SUITE.erl
@@ -79,7 +79,7 @@ compile_erl(Config) when is_list(Config) ->
 
     ?line run(Config, Cmd, FileName, "-Werror",
 	      ["compile: warnings being treated as errors\$",
-	       "Warning: function foo/0 is unused\$",
+	       "function foo/0 is unused\$",
 	       "_ERROR_"]),
 
     %% Check a bad file.
diff --git a/lib/asn1/doc/src/asn1ct.xml b/lib/asn1/doc/src/asn1ct.xml
index 265f8735c2..50458b4a9a 100644
--- a/lib/asn1/doc/src/asn1ct.xml
+++ b/lib/asn1/doc/src/asn1ct.xml
@@ -53,7 +53,7 @@
         <v>Option = ber_bin | per_bin | uper_bin | der | compact_bit_string | 
 	noobj | {n2n,EnumTypeName} |{outdir,Dir} | {i,IncludeDir} | optimize | 
 	driver | asn1config | undec_rest | {inline,OutputName} | inline |
-	{macro_name_prefix, Prefix} | {record_name_prefix, Prefix} | verbose</v>
+	{macro_name_prefix, Prefix} | {record_name_prefix, Prefix} | verbose | warnings_as_errors</v>
         <v>OldOption = ber | per</v> 
         <v>Reason = term()</v>
         <v>Prefix = string()</v>
@@ -289,6 +289,10 @@ Binary = binary()
             <p>Causes more verbose information from the compiler
               describing what it is doing.</p>
           </item>
+          <tag><c>warnings_as_errors</c></tag>
+          <item>
+            <p>Causes warnings to be treated as errors.</p>
+          </item>
         </taglist>
         <p>Any additional option that is applied will be passed to
           the final step when the generated .erl file is compiled.
diff --git a/lib/asn1/src/asn1ct.erl b/lib/asn1/src/asn1ct.erl
index a167d27f82..e26fadd160 100644
--- a/lib/asn1/src/asn1ct.erl
+++ b/lib/asn1/src/asn1ct.erl
@@ -39,7 +39,7 @@
 	 add_tobe_refed_func/1,add_generated_refed_func/1,
 	 maybe_rename_function/3,latest_sindex/0,current_sindex/0,
 	 set_current_sindex/1,next_sindex/0,maybe_saved_sindex/2,
-	 parse_and_save/2,verbose/3,warning/3,error/3]).
+	 parse_and_save/2,verbose/3,warning/3,warning/4,error/3]).
 
 -include("asn1_records.hrl").
 -include_lib("stdlib/include/erl_compile.hrl").
@@ -825,10 +825,13 @@ generate({true,{M,_Module,GenTOrV}},OutFile,EncodingRule,Options) ->
     case catch specialized_decode_prepare(EncodingRule,M,GenTOrV,Options) of
 	{error, enoent} -> ok;
 	{error, Reason} -> warning("Error in configuration "
-				   "file: ~n~p~n",[Reason],Options);
+				   "file: ~n~p~n",[Reason],Options,
+				   "Error in configuration file");
 	{'EXIT',Reason} -> warning("Internal error when "
 				   "analyzing configuration "
-				   "file: ~n~p~n",[Reason],Options);
+				   "file: ~n~p~n",[Reason],Options,
+				   "Internal error when "
+				   "analyzing configuration");
 	_ -> ok
     end,
 
@@ -2524,14 +2527,14 @@ type_check(#'Externaltypereference'{}) ->
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %% Report functions.
 %%
-%% Errors messages are controlled with the 'errors' compiler option
+%% Error messages are controlled with the 'errors' compiler option
 %% Warning messages are controlled with the 'warnings' compiler option
 %% Verbose messages are controlled with the 'verbose' compiler option
 
 error(Format, Args, S) ->
     case is_error(S) of
 	true ->
-	    io:format("Error: " ++ Format, Args);
+	    io:format(Format, Args);
 	false ->
 	    ok
     end.
@@ -2544,6 +2547,17 @@ warning(Format, Args, S) ->
 	    ok
     end.
 
+warning(Format, Args, S, Reason) ->
+    case {is_werr(S), is_error(S), is_warning(S)} of
+	{true, true, _} ->
+	    io:format(Format, Args),
+	    throw({error, Reason});
+	{false, _, true} ->
+	    io:format(Format, Args);
+	_ ->
+	    ok
+    end.
+
 verbose(Format, Args, S) ->
     case is_verbose(S) of
 	true ->
@@ -2566,3 +2580,8 @@ is_verbose(S) when is_record(S, state) ->
     is_verbose(S#state.options);
 is_verbose(O) ->
     lists:member(verbose, O).
+
+is_werr(S) when is_record(S, state) ->
+    is_werr(S#state.options);
+is_werr(O) ->
+    lists:member(warnings_as_errors, O).
diff --git a/lib/asn1/src/asn1ct_check.erl b/lib/asn1/src/asn1ct_check.erl
index efd731f052..e318477234 100644
--- a/lib/asn1/src/asn1ct_check.erl
+++ b/lib/asn1/src/asn1ct_check.erl
@@ -2031,7 +2031,7 @@ get_objectset_def2(_S,T = #typedef{typespec=#'ObjectSet'{}},_CField) ->
     T;
 get_objectset_def2(S,T,_CField) ->
     asn1ct:warning("get_objectset_def2: uncontrolled object set structure:~n~p~n",
-		   [T],S).
+		   [T],S,"get_objectset_def2: uncontrolled object set structure").
     
 type_name(S,#type{def=Def}) ->
     CurrMod = S#state.mname,
@@ -2705,7 +2705,7 @@ normalize_value(S,Type,{'DEFAULT',Value},NameList) ->
 	    normalize_objectclassfieldvalue(S,Value,NL);
 	Err ->
 	    asn1ct:warning("could not check default value ~p~nType:~n~p~nNameList:~n~p~n",
-			   [Value,Type,Err],S),
+			   [Value,Type,Err],S,"could not check default value"),
 	    Value
     end;
 normalize_value(S,Type,Val,NameList) ->
@@ -2791,22 +2791,27 @@ normalize_bitstring(S,Value,Type)->
 		    case catch lists:map(F,RecList) of
 			{error,Reason} ->
 			    asn1ct:warning("default value not "
-				      "compatible with type definition ~p~n",
-				      [Reason],S),
+					   "compatible with type definition ~p~n",
+					   [Reason],S,
+					   "default value not "
+					   "compatible with type definition"),
 			    Value;
 			NewList ->
 			    NewList
 		    end;
 		_ ->
 		    asn1ct:warning("default value not "
-			      "compatible with type definition ~p~n",
-			      [RecList],S),
+				   "compatible with type definition ~p~n",
+				   [RecList],S,
+				   "default value not "
+				   "compatible with type definition"),
 		    Value
 	    end;
 	{Name,String} when is_atom(Name) ->
 	    normalize_bitstring(S,String,Type);
 	Other ->
-	    asn1ct:warning("illegal default value ~p~n",[Other],S),
+	    asn1ct:warning("illegal default value ~p~n",[Other],S,
+			   "illegal default value"),
 	    Value
     end.
 
@@ -2846,12 +2851,14 @@ normalize_octetstring(S,Value,CType) ->
 	    lists:map(fun([])-> ok;
 			 (H)when H > 255->
 			      asn1ct:warning("not legal octet value ~p in OCTET STRING, ~p~n",
-					     [H,List],S);
+					     [H,List],S,
+					     "not legal octet value ~p in OCTET STRING");
 			 (_)-> ok
 		      end, List),
 	    List;
 	Other ->
-	    asn1ct:warning("unknown default value ~p~n",[Other],S),
+	    asn1ct:warning("unknown default value ~p~n",[Other],S,
+			   "unknown default value"),
 	    Value
     end.
 
@@ -2908,13 +2915,15 @@ normalize_enumerated(S,{Name,EnumV},CType) when is_atom(Name) ->
 normalize_enumerated(S,Value,{CType1,CType2}) when is_list(CType1), is_list(CType2)->
     normalize_enumerated(S,Value,CType1++CType2);
 normalize_enumerated(S,V,CType) ->
-    asn1ct:warning("Enumerated unknown type ~p~n",[CType],S),
+    asn1ct:warning("Enumerated unknown type ~p~n",[CType],S,
+		   "Enumerated unknown type"),
     V.
 normalize_enumerated2(S,V,Enum) ->
     case lists:keysearch(V,1,Enum) of
 	{value,{Val,_}} -> Val;
 	_ -> 
-	    asn1ct:warning("Enumerated value is not correct ~p~n",[V],S),
+	    asn1ct:warning("enumerated value is not correct ~p~n",[V],S,
+			   "enumerated value is not correct"),
 	    V
     end.
 
@@ -2925,7 +2934,8 @@ normalize_choice(S,{'CHOICE',{C,V}},CType,NameList) when is_atom(C) ->
 	    {C,normalize_value(S,CT,{'DEFAULT',V},
 			       [Name|NameList])};
 	Other ->
-	    asn1ct:warning("Wrong format of type/value ~p/~p~n",[Other,V],S),
+	    asn1ct:warning("Wrong format of type/value ~p/~p~n",[Other,V],S,
+			   "Wrong format of type/value"),
 	    {C,V}
     end;
 normalize_choice(S,{'DEFAULT',ValueList},CType,NameList) when is_list(ValueList) ->
@@ -3101,7 +3111,8 @@ normalize_s_of(SorS,S,Value,Type,NameList) when is_list(Value) ->
 	List when is_list(List) ->
 	    List;
 	_ ->
-	    asn1ct:warning("~p could not handle value ~p~n",[SorS,Value],S),
+	    asn1ct:warning("~p could not handle value ~p~n",[SorS,Value],S,
+			   "could not handle value"),
 	    Value
     end;
 normalize_s_of(SorS,S,Value,Type,NameList) 
@@ -3159,7 +3170,8 @@ get_normalized_value(S,Val,Type,Func,AddArg) ->
 	    V2 = sort_val_if_set(AddArg,NewVal,Type),
 	    call_Func(update_state(S,ExtM),V2,Type,Func,AddArg);
 	_ ->
-	    asn1ct:warning("default value not comparable ~p~n",[Val],S),
+	    asn1ct:warning("default value not comparable ~p~n",[Val],S,
+			   "default value not comparable"),
 	    Val
     end.
 
@@ -5756,7 +5768,8 @@ ascending_order_check1(S,TypeName,
 		       [C1 = #'ComponentType'{tags=[{_,T}|_]},
 			C2 = #'ComponentType'{tags=[{_,T}|_]}|Rest]) ->
     asn1ct:warning("Indistinct tag ~p in SET ~p, components ~p and ~p~n",
-	      [T,TypeName,C1#'ComponentType'.name,C2#'ComponentType'.name],S),
+		   [T,TypeName,C1#'ComponentType'.name,C2#'ComponentType'.name],S,
+		   "Indistinct tag in SET"),
     ascending_order_check1(S,TypeName,[C2|Rest]);
 ascending_order_check1(S,TypeName,
 		       [C1 = #'ComponentType'{tags=[{'UNIVERSAL',T1}|_]},
@@ -5764,9 +5777,10 @@ ascending_order_check1(S,TypeName,
     case (decode_type(T1) == decode_type(T2)) of
 	true ->
 	    asn1ct:warning("Indistinct tags ~p and ~p in"
-		      " SET ~p, components ~p and ~p~n",
-		      [T1,T2,TypeName,C1#'ComponentType'.name,
-		       C2#'ComponentType'.name],S),
+			   " SET ~p, components ~p and ~p~n",
+			   [T1,T2,TypeName,C1#'ComponentType'.name,
+			    C2#'ComponentType'.name],S,
+			   "Indistinct tags and in SET"),
 	    ascending_order_check1(S,TypeName,[C2|Rest]);
 	_ ->
 	    ascending_order_check1(S,TypeName,[C2|Rest])
diff --git a/lib/asn1/test/asn1_SUITE.erl.src b/lib/asn1/test/asn1_SUITE.erl.src
index 582ccd877c..e7f93a4053 100644
--- a/lib/asn1/test/asn1_SUITE.erl.src
+++ b/lib/asn1/test/asn1_SUITE.erl.src
@@ -2236,8 +2236,10 @@ test_compile_options(Config) ->
     	  ?line ok = test_compile_options:path(Config),
     	  ?line ok = test_compile_options:noobj(Config),
 	  ?line ok = test_compile_options:record_name_prefix(Config),
-	  ?line ok = test_compile_options:verbose(Config)
+	  ?line ok = test_compile_options:verbose(Config),
+	  ?line ok = test_compile_options:warnings_as_errors(Config)
     end.
+
 testDoubleEllipses(suite) ->  [];
 testDoubleEllipses(Config) ->
     ?line testDoubleEllipses:compile(Config,?BER,[]),
diff --git a/lib/asn1/test/test_compile_options.erl b/lib/asn1/test/test_compile_options.erl
index 5e027cdedb..5cb212eddf 100644
--- a/lib/asn1/test/test_compile_options.erl
+++ b/lib/asn1/test/test_compile_options.erl
@@ -24,7 +24,7 @@
 
 
 -export([wrong_path/1,comp/2,path/1,ticket_6143/1,noobj/1,
-	 record_name_prefix/1,verbose/1]).
+	 record_name_prefix/1,verbose/1,warnings_as_errors/1]).
 
 %% OTP-5689
 wrong_path(Config) ->
@@ -141,6 +141,43 @@ verbose(Config) when is_list(Config) ->
     ?line [] = test_server:capture_get(),
     ok.
 
+warnings_as_errors(Config) when is_list(Config) ->
+    PrivDir = ?config(priv_dir,Config),
+    Asn1File = filename:join([PrivDir,"WERROR.asn1"]),
+    OutFile = filename:join([PrivDir,"WERROR.erl"]),
+    Opts = [{outdir,PrivDir},noobj,verbose],
+
+    %% Generate WERR.asn to emit warning
+    %% Warning: Wrong format of type/value
+    %%     false/{'Externalvaluereference',_,'WERR',noInvokeId}
+    Warn = <<"WERROR DEFINITIONS IMPLICIT TAGS ::=\n"
+	     "\n"
+	     "BEGIN\n"
+	     "\n"
+	     "InvokeId ::= CHOICE\n"
+	     "{\n"
+	     "    present INTEGER,\n"
+	     "    absent NULL\n"
+	     "}\n"
+	     "\n"
+	     "noInvokeId InvokeId ::= absent:NULL\n"
+	     "\n"
+	     "NoInvokeId InvokeId ::= {noInvokeId}\n"
+	     "\n"
+	     "END -- end of useful definitions.\n">>,
+    ?line ok = file:write_file(Asn1File, Warn),
+
+    %% Test warnings_as_errors compile
+    ?line false = filelib:is_regular(OutFile),
+    ?line {error, _} = asn1ct:compile(Asn1File, [warnings_as_errors|Opts]),
+    ?line false = filelib:is_regular(OutFile),
+
+    %% Test normal compile
+    ?line ok = asn1ct:compile(Asn1File, Opts),
+    ?line true = filelib:is_regular(OutFile),
+    ?line ok = file:delete(OutFile),
+    ok.
+
 outfiles_check(OutDir) ->
     outfiles_check(OutDir,outfiles1()).
 
diff --git a/lib/compiler/src/compile.erl b/lib/compiler/src/compile.erl
index ce8a5bf864..e46c667e47 100644
--- a/lib/compiler/src/compile.erl
+++ b/lib/compiler/src/compile.erl
@@ -113,7 +113,7 @@ noenv_forms(Forms, Opt) when is_atom(Opt) ->
 
 noenv_output_generated(Opts) ->
     {_,Passes} = passes(file, expand_opts(Opts)),
-    any(fun ({save_binary,_F}) -> true;
+    any(fun ({save_binary,_T,_F}) -> true;
 	    (_Other) -> false
 	end, Passes).
 
@@ -122,6 +122,7 @@ noenv_output_generated(Opts) ->
 %%
 
 -define(pass(P), {P,fun P/1}).
+-define(pass(P,T), {P,fun T/1,fun P/1}).
 
 env_default_opts() ->
     Key = "ERL_COMPILER_OPTIONS",
@@ -304,7 +305,7 @@ run_tc({Name,Fun}, St) ->
     Val.
 
 comp_ret_ok(#compile{code=Code,warnings=Warn0,module=Mod,options=Opts}=St) ->
-    case member(warnings_as_errors, Opts) andalso length(Warn0) > 0 of
+    case werror(St) of
         true ->
             case member(report_warnings, Opts) of
                 true ->
@@ -339,6 +340,11 @@ comp_ret_err(#compile{warnings=Warn0,errors=Err0,options=Opts}=St) ->
 	false -> error
     end.
 
+not_werror(St) -> not werror(St).
+
+werror(#compile{options=Opts,warnings=Ws}) ->
+    Ws =/= [] andalso member(warnings_as_errors, Opts).
+
 %% messages_per_file([{File,[Message]}]) -> [{File,[Message]}]
 messages_per_file(Ms) ->
     T = lists:sort([{File,M} || {File,Messages} <- Ms, M <- Messages]),
@@ -373,7 +379,7 @@ passes(Type, Opts) ->
     %% insert a first pass to remove the file (unless the
     %% source file is a BEAM file).
     {Ext,case last(Passes) of
-	     {save_binary,_Fun} ->
+	     {save_binary,_TestFun,_Fun} ->
 		 case Passes of
 		     [{read_beam_file,_}|_] ->
 			 %% The BEAM is both input and output.
@@ -655,7 +661,7 @@ asm_passes() ->
 
 binary_passes() ->
     [{native_compile,fun test_native/1,fun native_compile/1},
-     {unless,binary,?pass(save_binary)}].
+     {unless,binary,?pass(save_binary,not_werror)}].
 
 %%%
 %%% Compiler passes.
@@ -1379,28 +1385,34 @@ report_errors(#compile{options=Opts,errors=Errors}) ->
     end.
 
 report_warnings(#compile{options=Opts,warnings=Ws0}) ->
-    case member(report_warnings, Opts) of
+    Werror = member(warnings_as_errors, Opts),
+    P = case Werror of
+	    true -> "";
+	    false -> "Warning: "
+	end,
+    ReportWerror = Werror andalso member(report_errors, Opts),
+    case member(report_warnings, Opts) orelse ReportWerror of
 	true ->
-	    Ws1 = flatmap(fun({{F,_L},Eds}) -> format_message(F, Eds);
-			     ({F,Eds}) -> format_message(F, Eds) end,
+	    Ws1 = flatmap(fun({{F,_L},Eds}) -> format_message(F, P, Eds);
+			     ({F,Eds}) -> format_message(F, P, Eds) end,
 			  Ws0),
 	    Ws = lists:sort(Ws1),
 	    foreach(fun({_,Str}) -> io:put_chars(Str) end, Ws);
 	false -> ok
     end.
 
-format_message(F, [{{Line,Column}=Loc,Mod,E}|Es]) ->
-    M = {{F,Loc},io_lib:format("~s:~w:~w Warning: ~s\n",
-                                [F,Line,Column,Mod:format_error(E)])},
-    [M|format_message(F, Es)];
-format_message(F, [{Line,Mod,E}|Es]) ->
-    M = {{F,{Line,0}},io_lib:format("~s:~w: Warning: ~s\n",
-                                [F,Line,Mod:format_error(E)])},
-    [M|format_message(F, Es)];
-format_message(F, [{Mod,E}|Es]) ->
-    M = {none,io_lib:format("~s: Warning: ~s\n", [F,Mod:format_error(E)])},
-    [M|format_message(F, Es)];
-format_message(_, []) -> [].
+format_message(F, P, [{{Line,Column}=Loc,Mod,E}|Es]) ->
+    M = {{F,Loc},io_lib:format("~s:~w:~w ~s~s\n",
+                                [F,Line,Column,P,Mod:format_error(E)])},
+    [M|format_message(F, P, Es)];
+format_message(F, P, [{Line,Mod,E}|Es]) ->
+    M = {{F,{Line,0}},io_lib:format("~s:~w: ~s~s\n",
+                                [F,Line,P,Mod:format_error(E)])},
+    [M|format_message(F, P, Es)];
+format_message(F, P, [{Mod,E}|Es]) ->
+    M = {none,io_lib:format("~s: ~s~s\n", [F,P,Mod:format_error(E)])},
+    [M|format_message(F, P, Es)];
+format_message(_, _, []) -> [].
 
 %% list_errors(File, ErrorDescriptors) -> ok
 
diff --git a/lib/compiler/test/error_SUITE.erl b/lib/compiler/test/error_SUITE.erl
index 6e0aadf007..eb5e50818e 100644
--- a/lib/compiler/test/error_SUITE.erl
+++ b/lib/compiler/test/error_SUITE.erl
@@ -183,23 +183,47 @@ get_compilation_errors(Config, Filename) ->
     E.
 
 warnings_as_errors(Config) when is_list(Config) ->
-    Ts = [{warnings_as_errors,
+    ?line TestFile = test_filename(Config),
+    ?line BeamFile = filename:rootname(TestFile, ".erl") ++ ".beam",
+    ?line OutDir = ?config(priv_dir, Config),
+
+    Ts1 = [{warnings_as_errors,
            <<"
                t() ->
                  A = unused,
                  ok.
              ">>,
-           [export_all,warnings_as_errors],
-          {error,
-           [],
-           [{3,erl_lint,{unused_var,'A'}}]} }],
-    ?line [] = run(Config, Ts),
+	    [warnings_as_errors, export_all, {outdir, OutDir}],
+	    {error,
+	     [],
+	     [{3,erl_lint,{unused_var,'A'}}]} }],
+    ?line [] = run(Ts1, TestFile, write_beam),
+    ?line false = filelib:is_regular(BeamFile),
+
+    Ts2 = [{warning_unused_var,
+           <<"
+               t() ->
+                 A = unused,
+                 ok.
+             ">>,
+	    [return_warnings, export_all, {outdir, OutDir}],
+	    {warning,
+	       [{3,erl_lint,{unused_var,'A'}}]} }],
+
+    ?line [] = run(Ts2, TestFile, write_beam),
+    ?line true = filelib:is_regular(BeamFile),
+    ?line ok = file:delete(BeamFile),
+
     ok.
 
 
 run(Config, Tests) ->
+    ?line File = test_filename(Config),
+    run(Tests, File, dont_write_beam).
+
+run(Tests, File, WriteBeam) ->
     F = fun({N,P,Ws,E}, BadL) ->
-                case catch run_test(Config, P, Ws) of
+                case catch run_test(P, File, Ws, WriteBeam) of
                     E -> 
                         BadL;
                     Bad -> 
@@ -211,8 +235,12 @@ run(Config, Tests) ->
     lists:foldl(F, [], Tests).
 
 run2(Config, Tests) ->
+    ?line File = test_filename(Config),
+    run2(Tests, File, dont_write_beam).
+
+run2(Tests, File, WriteBeam) ->
     F = fun({N,P,Ws,E}, BadL) ->
-                case catch filter(run_test(Config, P, Ws)) of
+                case catch filter(run_test(P, File, Ws, WriteBeam)) of
                     E ->
                         BadL;
                     Bad ->
@@ -231,12 +259,19 @@ filter(X) ->
 
 %% Compiles a test module and returns the list of errors and warnings.
 
-run_test(Conf, Test0, Warnings) ->
-    Filename = 'errors_test.erl',
-    ?line DataDir = ?config(priv_dir, Conf),
+test_filename(Conf) ->
+    Filename = "errors_test.erl",
+    DataDir = ?config(priv_dir, Conf),
+    filename:join(DataDir, Filename).
+
+run_test(Test0, File, Warnings, WriteBeam) ->
     ?line Test = ["-module(errors_test). ", Test0],
-    ?line File = filename:join(DataDir, Filename),
-    ?line Opts = [binary,return_errors|Warnings],
+    ?line Opts = case WriteBeam of
+		     dont_write_beam ->
+			 [binary,return_errors|Warnings];
+		     write_beam ->
+			 [return_errors|Warnings]
+		 end,
     ?line ok = file:write_file(File, Test),
 
     %% Compile once just to print all errors and warnings.
@@ -252,6 +287,10 @@ run_test(Conf, Test0, Warnings) ->
 			%io:format("compile:file(~s,~p) ->~n~p~n",
 			%	  [File,Opts,Ws]),
 			[];
+		    {ok,errors_test,[{_File,Ws}]} ->
+			{warning,Ws};
+		    {ok,errors_test,[]} ->
+			[];
 		    {error,[{XFile,Es}],Ws} = _ZZ when is_list(XFile) ->
 			%io:format("compile:file(~s,~p) ->~n~p~n",
 			%	  [File,Opts,_ZZ]),
diff --git a/lib/parsetools/src/leex.erl b/lib/parsetools/src/leex.erl
index 942e9928b1..cdf20461d9 100644
--- a/lib/parsetools/src/leex.erl
+++ b/lib/parsetools/src/leex.erl
@@ -73,12 +73,15 @@
 %%% Interface to erl_compile.
 
 compile(Input0, Output0,
-        #options{warning = WarnLevel, verbose=Verbose, includes=Includes}) ->
+        #options{warning = WarnLevel, verbose=Verbose, includes=Includes,
+		 specific=Specific}) ->
     Input = assure_extension(shorten_filename(Input0), ".xrl"),
     Output = assure_extension(shorten_filename(Output0), ".erl"),
     Includefile = lists:sublist(Includes, 1),
+    Werror = proplists:get_bool(warnings_as_errors, Specific),
     Opts = [{scannerfile,Output},{includefile,Includefile},{verbose,Verbose},
-            {report_errors,true},{report_warnings,WarnLevel > 0}],
+            {report_errors,true},{report_warnings,WarnLevel > 0},
+	    {warnings_as_errors, Werror}],
     case file(Input, Opts) of
         {ok, _} ->
             ok;
@@ -107,7 +110,7 @@ file(File, Opts0) ->
     St = try
              {ok,REAs,Actions,Code,St2} = parse_file(St1),
              {DFA,DF} = make_dfa(REAs, St2),
-             case werr(St2) of
+             case werror(St2) of
                  false ->
                      St3 = out_file(St2, DFA, DF, Actions, Code),
                      case lists:member(dfa_graph, St3#leex.opts) of
@@ -259,9 +262,9 @@ leex_ret(St) ->
     report_warnings(St),
     Es = pack_errors(St#leex.errors),
     Ws = pack_warnings(St#leex.warnings),
-    Werr = werr(St),
+    Werror = werror(St),
     if 
-        Werr ->
+        Werror ->
             do_error_return(St, Es, Ws);
         Es =:= [] -> 
             case member(return_warnings, St#leex.opts) of
@@ -278,9 +281,9 @@ do_error_return(St, Es, Ws) ->
         false -> error
     end.
 
-werr(St) ->
-    member(warnings_as_errors, St#leex.opts)
-        andalso length(St#leex.warnings) > 0.
+werror(St) ->
+    St#leex.warnings =/= []
+	andalso member(warnings_as_errors, St#leex.opts).
 
 pack_errors([{File,_} | _] = Es) ->
     [{File, flatmap(fun({_,E}) -> [E] end, sort(Es))}];
@@ -304,15 +307,24 @@ report_errors(St) ->
              end, report_errors, St#leex.opts).
 
 report_warnings(St) ->
-    when_opt(fun () ->
-                     foreach(fun({File,{none,Mod,W}}) -> 
-                                     io:fwrite("~s: Warning: ~s\n",
-                                               [File,Mod:format_error(W)]);
-                                ({File,{Line,Mod,W}}) -> 
-                                     io:fwrite("~s:~w: Warning: ~s\n",
-                                               [File,Line,Mod:format_error(W)])
-                             end, sort(St#leex.warnings))
-             end, report_warnings, St#leex.opts).
+    Werror = member(warnings_as_errors, St#leex.opts),
+    Prefix = case Werror of
+		 true -> "";
+		 false -> "Warning: "
+	     end,
+    ReportWerror = Werror andalso member(report_errors, St#leex.opts),
+    ShouldReport = member(report_warnings, St#leex.opts) orelse ReportWerror,
+    when_bool(fun () ->
+		      foreach(fun({File,{none,Mod,W}}) ->
+				      io:fwrite("~s: ~s~s\n",
+						[File,Prefix,
+						 Mod:format_error(W)]);
+				 ({File,{Line,Mod,W}}) ->
+				      io:fwrite("~s:~w: ~s~s\n",
+						[File,Line,Prefix,
+						 Mod:format_error(W)])
+			      end, sort(St#leex.warnings))
+	      end, ShouldReport).
 
 -spec add_error(_, #leex{}) -> no_return().
 add_error(E, St) ->
@@ -360,6 +372,12 @@ when_opt(Do, Opt, Opts) ->
         false -> ok
     end.
 
+when_bool(Do, Bool) ->
+    case Bool of
+	true -> Do();
+	false -> ok
+    end.
+
 verbose_print(St, Format, Args) ->
     when_opt(fun () -> io:fwrite(Format, Args) end, verbose, St#leex.opts).
 
diff --git a/lib/parsetools/src/yecc.erl b/lib/parsetools/src/yecc.erl
index 72cff3af92..354d56527d 100644
--- a/lib/parsetools/src/yecc.erl
+++ b/lib/parsetools/src/yecc.erl
@@ -133,12 +133,15 @@
 %%% Interface to erl_compile.
 
 compile(Input0, Output0, 
-        #options{warning = WarnLevel, verbose=Verbose, includes=Includes}) ->
+        #options{warning = WarnLevel, verbose=Verbose, includes=Includes,
+		 specific=Specific}) ->
     Input = shorten_filename(Input0),
     Output = shorten_filename(Output0),
     Includefile = lists:sublist(Includes, 1),
+    Werror = proplists:get_bool(warnings_as_errors, Specific),
     Opts = [{parserfile,Output}, {includefile,Includefile}, {verbose,Verbose},
-            {report_errors, true}, {report_warnings, WarnLevel > 0}],
+            {report_errors, true}, {report_warnings, WarnLevel > 0},
+	    {warnings_as_errors, Werror}],
     case file(Input, Opts) of
         {ok, _OutFile} ->
             ok;
@@ -411,15 +414,15 @@ infile(Parent, Infilex, Options) ->
              {error, Reason} ->
                  add_error(St0#yecc.infile, none, {file_error, Reason}, St0)
          end,
-    case {St#yecc.errors, werr(St)} of
+    case {St#yecc.errors, werror(St)} of
         {[], false} -> ok;
         _ -> _ = file:delete(St#yecc.outfile)
     end,
     Parent ! {self(), yecc_ret(St)}.
 
-werr(St) ->
-    member(warnings_as_errors, St#yecc.options)
-        andalso length(St#yecc.warnings) > 0.
+werror(St) ->
+    St#yecc.warnings =/= []
+	andalso member(warnings_as_errors, St#yecc.options).
 
 outfile(St0) ->
     case file:open(St0#yecc.outfile, [write, delayed_write]) of
@@ -783,9 +786,9 @@ yecc_ret(St0) ->
     report_warnings(St),
     Es = pack_errors(St#yecc.errors),
     Ws = pack_warnings(St#yecc.warnings),
-    Werr = werr(St),
+    Werror = werror(St),
     if 
-        Werr ->
+        Werror ->
             do_error_return(St, Es, Ws);
         Es =:= [] -> 
             case member(return_warnings, St#yecc.options) of
@@ -849,14 +852,22 @@ report_errors(St) ->
     end.
 
 report_warnings(St) ->
-    case member(report_warnings, St#yecc.options) of
+    Werror = member(warnings_as_errors, St#yecc.options),
+    Prefix = case Werror of
+		 true -> "";
+		 false -> "Warning: "
+	     end,
+    ReportWerror = Werror andalso member(report_errors, St#yecc.options),
+    case member(report_warnings, St#yecc.options) orelse ReportWerror of
         true ->
             foreach(fun({File,{none,Mod,W}}) -> 
-                            io:fwrite(<<"~s: Warning: ~s\n">>, 
-                                      [File,Mod:format_error(W)]);
+                            io:fwrite(<<"~s: ~s~s\n">>,
+                                      [File,Prefix,
+				       Mod:format_error(W)]);
                        ({File,{Line,Mod,W}}) -> 
-                            io:fwrite(<<"~s:~w: Warning: ~s\n">>, 
-                                      [File,Line,Mod:format_error(W)])
+                            io:fwrite(<<"~s:~w: ~s~s\n">>,
+                                      [File,Line,Prefix,
+				       Mod:format_error(W)])
                     end, sort(St#yecc.warnings));
         false -> 
             ok
diff --git a/lib/parsetools/test/leex_SUITE.erl b/lib/parsetools/test/leex_SUITE.erl
index 48312445ef..1e50aedf07 100644
--- a/lib/parsetools/test/leex_SUITE.erl
+++ b/lib/parsetools/test/leex_SUITE.erl
@@ -152,6 +152,7 @@ file(Config) when is_list(Config) ->
     ?line writable(Dotfile),
     file:delete(Dotfile),
 
+    ok = file:delete(Scannerfile),
     Warn = <<"Definitions.1998\n"
              "D  = [0-9]\n"
              "Rules.\n"
@@ -159,11 +160,15 @@ file(Config) when is_list(Config) ->
              "Erlang code.\n">>,
     ok = file:write_file(Filename, Warn),
     error = leex:file(Filename, [warnings_as_errors]),
+    false = filelib:is_regular(Scannerfile),
     error = leex:file(Filename, [return_warnings,warnings_as_errors]),
-    {ok,Scannerfile,[{Filename,[{1,leex,ignored_characters}]}]} =
-	leex:file(Filename, [return_warnings]),
+    false = filelib:is_regular(Scannerfile),
     {error,_,[{Filename,[{1,leex,ignored_characters}]}]} =
-	leex:file(Filename, [return_errors,warnings_as_errors]),
+        leex:file(Filename, [return_errors,warnings_as_errors]),
+    false = filelib:is_regular(Scannerfile),
+    {ok,Scannerfile,[{Filename,[{1,leex,ignored_characters}]}]} =
+        leex:file(Filename, [return_warnings]),
+    true = filelib:is_regular(Scannerfile),
 
     file:delete(Filename),
     ok.
diff --git a/lib/parsetools/test/yecc_SUITE.erl b/lib/parsetools/test/yecc_SUITE.erl
index 0133524950..a5f66b48e9 100644
--- a/lib/parsetools/test/yecc_SUITE.erl
+++ b/lib/parsetools/test/yecc_SUITE.erl
@@ -173,6 +173,7 @@ syntax(Config) when is_list(Config) ->
     %% Report errors. Very simple test of format_error/1.
     Ret = [return, {report, true}],
     Filename = filename:join(Dir, "file.yrl"),
+    Parserfile = filename:join(Dir, "file.erl"),
     Parserfile1 = filename:join(Dir, "a file"),
 
     ?line ok = file:write_file(Filename, <<"">>),
@@ -248,12 +249,17 @@ syntax(Config) when is_list(Config) ->
         yecc:file(Filename, Ret),
 
     %% Bad declaration with warnings_as_errors.
+    ok = file:delete(Parserfile),
     error = yecc:file(Filename, [warnings_as_errors]),
+    false = filelib:is_regular(Parserfile),
     error = yecc:file(Filename, [return_warnings,warnings_as_errors]),
-    {ok,_,[{_,[{2,yecc,bad_declaration}]}]} =
-        yecc:file(Filename, [return_warnings]),
+    false = filelib:is_regular(Parserfile),
     {error,_,[{_,[{2,yecc,bad_declaration}]}]} =
         yecc:file(Filename, [return_errors,warnings_as_errors]),
+    false = filelib:is_regular(Parserfile),
+    {ok,_,[{_,[{2,yecc,bad_declaration}]}]} =
+        yecc:file(Filename, [return_warnings]),
+    true = filelib:is_regular(Parserfile),
 
     %% Bad declaration.
     ?line ok = file:write_file(Filename, 
diff --git a/lib/sasl/doc/src/systools.xml b/lib/sasl/doc/src/systools.xml
index 883c9c372b..8c1c327d74 100644
--- a/lib/sasl/doc/src/systools.xml
+++ b/lib/sasl/doc/src/systools.xml
@@ -45,7 +45,8 @@
         <v>Name = string()</v>
         <v>UpFrom = DownTo = [Name | {Name,Descr}]</v>
         <v>&nbsp;Descr = term()</v>
-        <v>Opt = {path,[Dir]} | restart_emulator | silent | noexec | {outdir,Dir}</v>
+        <v>Opt = {path,[Dir]} | restart_emulator | silent | noexec | {outdir,Dir}
+	| warnings_as_errors</v>
         <v>&nbsp;Dir = string()</v>
         <v>Result = ok | error | {ok,Relup,Module,Warnings} | {error,Module,Error}</v>
         <v>&nbsp;Relup - see relup(4)</v>
@@ -122,6 +123,8 @@
         <p>If the option <c>noexec</c> is provided, the function returns
           the same values as for <c>silent</c> but no <c>relup</c> file
           is created.</p>
+	<p>If the option <c>warnings_as_errors</c> is provided, warnings
+	   are treated as errors.</p>
       </desc>
     </func>
     <func>
@@ -130,7 +133,8 @@
       <fsummary>Generate a boot script <c>.script/.boot</c>.</fsummary>
       <type>
         <v>Name = string()</v>
-        <v>Opt = src_tests | {path,[Dir]} | local | {variables,[Var]} | exref | {exref,[App]}] | silent | {outdir,Dir}</v>
+        <v>Opt = src_tests | {path,[Dir]} | local | {variables,[Var]} | exref | {exref,[App]}]
+	| silent | {outdir,Dir} | warnings_as_errors</v>
         <v>&nbsp;Dir = string()</v>
         <v>&nbsp;Var = {VarName,Prefix}</v>
         <v>&nbsp;&nbsp;VarName = Prefix = string()</v>
@@ -232,6 +236,8 @@
           Warnings and errors can be converted to strings by calling
           <c>Module:format_warning(Warnings)</c> or
           <c>Module:format_error(Error)</c>.</p>
+	<p>If the option <c>warnings_as_errors</c> is provided, warnings
+	   are treated as errors.</p>
       </desc>
     </func>
     <func>
diff --git a/lib/sasl/src/systools_lib.erl b/lib/sasl/src/systools_lib.erl
index f951647b79..1b6ea125d9 100644
--- a/lib/sasl/src/systools_lib.erl
+++ b/lib/sasl/src/systools_lib.erl
@@ -24,7 +24,7 @@
 %%         
 
 -export([file_term2binary/2, read_term/1, read_term_from_stream/2,
-	 get_dirs/1, get_path/1]).
+	 get_dirs/1, get_path/1, werror/2]).
 
 -include_lib("kernel/include/file.hrl").
 
@@ -219,6 +219,7 @@ flat([H|T], Ack) ->
     flat(T, [H|Ack]);
 flat([], Ack) ->
     lists:reverse(Ack).
-    
-			       
+
+werror(Options, Warnings) ->
+    lists:member(warnings_as_errors, Options) andalso Warnings =/= [].
 
diff --git a/lib/sasl/src/systools_make.erl b/lib/sasl/src/systools_make.erl
index 5dc83e7b2a..7f400f5cce 100644
--- a/lib/sasl/src/systools_make.erl
+++ b/lib/sasl/src/systools_make.erl
@@ -44,10 +44,12 @@
 
 %%-----------------------------------------------------------------
 %% Create a boot script from a release file.
-%% Options is a list of {path, Path} | silent | local where path sets
-%% the search path, silent supresses error message printing on console,
-%% local generates a script with references to the directories there
-%% the applications are found.
+%% Options is a list of {path, Path} | silent | local
+%%         | warnings_as_errors
+%% where path sets the search path, silent supresses error message
+%% printing on console, local generates a script with references
+%% to the directories there the applications are found,
+%% and warnings_as_errors treats warnings as errors.
 %%
 %% New options: {path,Path} can contain wildcards
 %%              src_tests
@@ -85,11 +87,16 @@ make_script(RelName, Output, Flags) when is_list(RelName),
 	    ModTestP = {member(src_tests, Flags),xref_p(Flags)},
 	    case get_release(RelName, Path, ModTestP, machine(Flags)) of
 		{ok, Release, Appls, Warnings} ->
-		    case generate_script(Output,Release,Appls,Flags) of
-			ok ->
+		    case systools_lib:werror(Flags, Warnings) of
+			true ->
 			    return(ok,Warnings,Flags);
-			Error ->
-			    return(Error,Warnings,Flags)
+			false ->
+			    case generate_script(Output,Release,Appls,Flags) of
+				ok ->
+				    return(ok,Warnings,Flags);
+				Error ->
+				    return(Error,Warnings,Flags)
+			    end
 		    end;
 		Error ->
 		    return(Error,[],Flags)
@@ -130,10 +137,21 @@ get_outdir(Flags) ->
 return(ok,Warnings,Flags) ->
     case member(silent,Flags) of
 	true ->
-	    {ok,?MODULE,Warnings};
+	    case systools_lib:werror(Flags, Warnings) of
+		true ->
+		    error;
+		false ->
+		    {ok,?MODULE,Warnings}
+	    end;
 	_ ->
-	    io:format("~s",[format_warning(Warnings)]),
-	    ok
+	    case member(warnings_as_errors,Flags) of
+		true ->
+		    io:format("~s",[format_warning(Warnings, true)]),
+		    error;
+		false ->
+		    io:format("~s",[format_warning(Warnings)]),
+		    ok
+	    end
     end;
 return({error,Mod,Error},_,Flags) ->
     case member(silent,Flags) of
@@ -1833,78 +1851,89 @@ get_flag(_,_)         -> false.
 %% Check Options for make_script
 check_args_script(Args) ->
     cas(Args,
-	{undef, undef, undef, undef, undef, undef, undef, undef, []}). 
+	{undef, undef, undef, undef, undef, undef, undef, undef,
+	 undef, []}).
 
-cas([], {_Path,_Sil,_Loc,_Test,_Var,_Mach,_Xref,_XrefApps, X}) ->
+cas([], {_Path,_Sil,_Loc,_Test,_Var,_Mach,_Xref,_XrefApps,_Werror, X}) ->
     X;
 %%% path ---------------------------------------------------------------
-cas([{path, P} | Args], {Path, Sil, Loc, Test, Var, Mach, 
-			 Xref, XrefApps, X}) when is_list(P) -> 
+cas([{path, P} | Args], {Path, Sil, Loc, Test, Var, Mach, Xref,
+			 XrefApps, Werror, X}) when is_list(P) ->
     case check_path(P) of
 	ok ->
-	    cas(Args, {P, Sil, Loc, Test, Var, Mach, Xref, XrefApps,X});
+	    cas(Args, {P, Sil, Loc, Test, Var, Mach, Xref, XrefApps,
+		       Werror, X});
 	error ->
 	    cas(Args, {Path, Sil, Loc, Test, Var, Mach, Xref, XrefApps,
-		       X++[{path,P}]})
+		       Werror, X++[{path,P}]})
     end;
 %%% silent -------------------------------------------------------------
-cas([silent | Args], {Path, _Sil, Loc, Test, Var, Mach,
-		      Xref, XrefApps, X}) ->
-    cas(Args, {Path, silent, Loc, Test, Var, Mach, Xref, XrefApps, X});
+cas([silent | Args], {Path, _Sil, Loc, Test, Var, Mach, Xref,
+		      XrefApps, Werror, X}) ->
+    cas(Args, {Path, silent, Loc, Test, Var, Mach, Xref, XrefApps,
+	       Werror, X});
 %%% local --------------------------------------------------------------
-cas([local | Args], {Path, Sil, _Loc, Test, Var, Mach,
-		     Xref, XrefApps, X}) ->
-    cas(Args, {Path, Sil, local, Test, Var, Mach, Xref, XrefApps, X});
+cas([local | Args], {Path, Sil, _Loc, Test, Var, Mach, Xref,
+		     XrefApps, Werror, X}) ->
+    cas(Args, {Path, Sil, local, Test, Var, Mach, Xref, XrefApps,
+	       Werror, X});
 %%% src_tests -------------------------------------------------------
-cas([src_tests | Args], {Path, Sil, Loc, _Test, Var, Mach,
-			    Xref, XrefApps, X}) ->
+cas([src_tests | Args], {Path, Sil, Loc, _Test, Var, Mach, Xref,
+			 XrefApps, Werror, X}) ->
     cas(Args,
-	{Path, Sil, Loc, src_tests, Var, Mach, Xref, XrefApps,X});
+	{Path, Sil, Loc, src_tests, Var, Mach, Xref, Werror, XrefApps,X});
 %%% variables ----------------------------------------------------------
-cas([{variables, V} | Args], {Path, Sil, Loc, Test, Var, Mach, 
-				 Xref, XrefApps, X}) when is_list(V) ->
+cas([{variables, V} | Args], {Path, Sil, Loc, Test, Var, Mach, Xref,
+			      XrefApps, Werror, X}) when is_list(V) ->
     case check_vars(V) of
 	ok ->
 	    cas(Args,
-		{Path, Sil, Loc, Test, V, Mach, Xref, XrefApps, X});
+		{Path, Sil, Loc, Test, V, Mach, Xref, XrefApps, Werror, X});
 	error ->
 	    cas(Args, {Path, Sil, Loc, Test, Var, Mach, Xref, XrefApps,
-		       X++[{variables, V}]})
+		       Werror, X++[{variables, V}]})
     end;
 %%% machine ------------------------------------------------------------
-cas([{machine, M} | Args], {Path, Sil, Loc, Test, Var, Mach, 
-			    Xref, XrefApps, X}) when is_atom(M) ->
-    cas(Args, {Path, Sil, Loc, Test, Var, Mach, Xref, XrefApps, X});
+cas([{machine, M} | Args], {Path, Sil, Loc, Test, Var, Mach, Xref,
+			    XrefApps, Werror, X}) when is_atom(M) ->
+    cas(Args, {Path, Sil, Loc, Test, Var, Mach, Xref, XrefApps, Werror, X});
 %%% exref --------------------------------------------------------------
-cas([exref | Args], {Path, Sil, Loc, Test, Var, Mach,
-		     _Xref, XrefApps, X})  ->
-    cas(Args, {Path, Sil, Loc, Test, Var, Mach, exref, XrefApps, X});
+cas([exref | Args], {Path, Sil, Loc, Test, Var, Mach, _Xref,
+		     XrefApps, Werror, X})  ->
+    cas(Args, {Path, Sil, Loc, Test, Var, Mach, exref, XrefApps, Werror, X});
 %%% exref Apps ---------------------------------------------------------
-cas([{exref, Apps} | Args], {Path, Sil, Loc, Test, Var, Mach, 
-			     Xref, XrefApps, X}) when is_list(Apps) ->
+cas([{exref, Apps} | Args], {Path, Sil, Loc, Test, Var, Mach, Xref,
+			     XrefApps, Werror, X}) when is_list(Apps) ->
     case check_apps(Apps) of 
 	ok ->
 	    cas(Args, {Path, Sil, Loc, Test, Var, Mach, 
-			     Xref, Apps, X});
+		       Xref, Apps, Werror, X});
 	error ->
 	    cas(Args, {Path, Sil, Loc, Test, Var, Mach, 
-			     Xref, XrefApps, X++[{exref, Apps}]})
+		       Xref, XrefApps, Werror, X++[{exref, Apps}]})
     end;
 %%% outdir Dir ---------------------------------------------------------
-cas([{outdir, Dir} | Args], {Path, Sil, Loc, Test, Var, Mach,
-			     Xref, XrefApps, X}) when is_list(Dir) ->
-    cas(Args, {Path, Sil, Loc, Test, Var, Mach, Xref, XrefApps, X});
+cas([{outdir, Dir} | Args], {Path, Sil, Loc, Test, Var, Mach, Xref,
+			     XrefApps, Werror, X}) when is_list(Dir) ->
+    cas(Args, {Path, Sil, Loc, Test, Var, Mach, Xref, XrefApps, Werror, X});
 %%% otp_build (secret, not documented) ---------------------------------
-cas([otp_build | Args], {Path, Sil, Loc, Test, Var, Mach,
-			 Xref, XrefApps, X}) ->
-    cas(Args, {Path, Sil, Loc, Test, Var, Mach, Xref, XrefApps, X});
+cas([otp_build | Args], {Path, Sil, Loc, Test, Var, Mach, Xref,
+			 XrefApps, Werror, X}) ->
+    cas(Args, {Path, Sil, Loc, Test, Var, Mach, Xref, XrefApps, Werror, X});
 %%% no_module_tests (kept for backwards compatibility, but ignored) ----
-cas([no_module_tests | Args], {Path, Sil, Loc, Test, Var, Mach,
-			       Xref, XrefApps, X}) ->
-    cas(Args, {Path, Sil, Loc, Test, Var, Mach, Xref, XrefApps,X});
+cas([no_module_tests | Args], {Path, Sil, Loc, Test, Var, Mach, Xref,
+			       XrefApps, Werror, X}) ->
+    cas(Args, {Path, Sil, Loc, Test, Var, Mach, Xref, XrefApps, Werror, X});
+%%% warnings_as_errors (kept for backwards compatibility, but ignored) ----
+cas([warnings_as_errors | Args], {Path, Sil, Loc, Test, Var, Mach, Xref,
+				  XrefApps, _Werror, X}) ->
+    cas(Args, {Path, Sil, Loc, Test, Var, Mach, Xref, XrefApps,
+	       warnings_as_errors, X});
 %%% ERROR --------------------------------------------------------------
-cas([Y | Args], {Path, Sil, Loc, Test, Var, Mach, Xref, XrefApps, X}) ->
-    cas(Args, {Path, Sil, Loc, Test, Var, Mach, Xref, XrefApps,X++[Y]}).
+cas([Y | Args], {Path, Sil, Loc, Test, Var, Mach, Xref, XrefApps,
+		 Werror, X}) ->
+    cas(Args, {Path, Sil, Loc, Test, Var, Mach, Xref, XrefApps, Werror,
+	       X++[Y]}).
 
 
 
@@ -2030,7 +2059,6 @@ check_apps([H|T]) when is_atom(H) ->
 check_apps(_) ->
     error.
 
-
 %% Format error
 
 format_error(badly_formatted_release) ->
@@ -2144,21 +2172,31 @@ form_tar_err({add, File, Error}) ->
 %% Format warning
 
 format_warning(Warnings) ->
-    map(fun({warning,W}) -> form_warn(W) end, Warnings).
-
-form_warn({source_not_found,{Mod,_,App,_,_}}) ->
-    io_lib:format("*WARNING* ~p: Source code not found: ~p.erl~n",
-		  [App,Mod]);
-form_warn({{parse_error, File},{_,_,App,_,_}}) ->
-    io_lib:format("*WARNING* ~p: Parse error: ~p~n",
-		  [App,File]);
-form_warn({obj_out_of_date,{Mod,_,App,_,_}}) ->
-    io_lib:format("*WARNING* ~p: Object code (~p) out of date~n",[App,Mod]);
-form_warn({exref_undef, Undef}) ->
-    F = fun({M,F,A}) -> 
-		io_lib:format("*WARNING* Undefined function ~p:~p/~p~n", 
-			      [M,F,A])
+    format_warning(Warnings, false).
+
+format_warning(Warnings, Werror) ->
+    Prefix = case Werror of
+		 true ->
+		     "";
+		 false ->
+		     "*WARNING* "
+	     end,
+    map(fun({warning,W}) -> form_warn(Prefix, W) end, Warnings).
+
+form_warn(Prefix, {source_not_found,{Mod,_,App,_,_}}) ->
+    io_lib:format("~s~p: Source code not found: ~p.erl~n",
+		  [Prefix,App,Mod]);
+form_warn(Prefix, {{parse_error, File},{_,_,App,_,_}}) ->
+    io_lib:format("~s~p: Parse error: ~p~n",
+		  [Prefix,App,File]);
+form_warn(Prefix, {obj_out_of_date,{Mod,_,App,_,_}}) ->
+    io_lib:format("~s~p: Object code (~p) out of date~n",
+		  [Prefix,App,Mod]);
+form_warn(Prefix, {exref_undef, Undef}) ->
+    F = fun({M,F,A}) ->
+		io_lib:format("~sUndefined function ~p:~p/~p~n",
+			      [Prefix,M,F,A])
 	end,
     map(F, Undef);
-form_warn(What) ->
-    io_lib:format("*WARNING* ~p~n", [What]).
+form_warn(Prefix, What) ->
+    io_lib:format("~s ~p~n", [Prefix,What]).
diff --git a/lib/sasl/src/systools_relup.erl b/lib/sasl/src/systools_relup.erl
index ec5486226c..6d9e922900 100644
--- a/lib/sasl/src/systools_relup.erl
+++ b/lib/sasl/src/systools_relup.erl
@@ -122,7 +122,7 @@
 %% rel_filename() = description() = string()
 %% Opts = [opt()]
 %% opt() = {path, [path()]} | silent | noexec | restart_emulator
-%%       | {outdir, string()}
+%%       | {outdir, string()} | warnings_as_errors
 %% path() = [string()]
 %% Ret = ok | error | {ok, Relup, Module, Warnings} | {error, Module, Error}
 %%
@@ -139,8 +139,9 @@
 %% 
 %% The option `path' sets search path, `silent' suppresses printing of
 %% error messages to the console, `noexec' inhibits the creation of
-%% the output "relup" file, and restart_emulator ensures that the new
-%% emulator is restarted (as the final step).
+%% the output "relup" file, restart_emulator ensures that the new
+%% emulator is restarted (as the final step), and `warnings_as_errors'
+%% treats warnings as errors.
 %% ----------------------------------------------------------------
 mk_relup(TopRelFile, BaseUpRelDcs, BaseDnRelDcs) ->
     mk_relup(TopRelFile, BaseUpRelDcs, BaseDnRelDcs, []).
@@ -153,14 +154,29 @@ mk_relup(TopRelFile, BaseUpRelDcs, BaseDnRelDcs, Opts) ->
 		{false, false} ->
 		    case R of
 			{ok, _Res, _Mod, Ws} -> 
-			    print_warnings(Ws),
-			    ok;
+			    print_warnings(Ws, Opts),
+			    case systools_lib:werror(Opts, Ws) of
+				true ->
+				    error;
+				false ->
+				    ok
+			    end;
 			Other -> 
 			    print_error(Other),
 			    error
 		    end;
-		_ -> 
-		    R
+		_ ->
+		    case R of
+			{ok, _Res, _Mod, Ws} ->
+			    case systools_lib:werror(Opts, Ws) of
+				true ->
+				    error;
+				false ->
+				    R
+			    end;
+			R ->
+			    R
+		    end
 	    end;
 	BadArg ->
 	    erlang:error({badarg, BadArg})
@@ -195,7 +211,12 @@ do_mk_relup(TopRelFile, BaseUpRelDcs, BaseDnRelDcs, Path, Opts) ->
 	    {Dn, Ws2} = foreach_baserel_dn(TopRel, TopApps, BaseDnRelDcs, 
 					  Path, Opts, Ws1),
 	    Relup = {TopRel#release.vsn, Up, Dn},
-	    write_relup_file(Relup, Opts),
+	    case systools_lib:werror(Opts, Ws2) of
+		true ->
+		    ok;
+		false ->
+		    write_relup_file(Relup, Opts)
+	    end,
 	    {ok, Relup, ?MODULE, Ws2};
 	Other -> 
 	    throw(Other)
@@ -527,20 +548,29 @@ format_error(Error) ->
     io:format("~p~n", [Error]).
 
 
-print_warnings(Ws) when is_list(Ws) ->
-    lists:foreach(fun(W) -> print_warning(W) end, Ws);
-print_warnings(W) ->
-    print_warning(W).
+print_warnings(Ws, Opts) when is_list(Ws) ->
+    lists:foreach(fun(W) -> print_warning(W, Opts) end, Ws);
+print_warnings(W, Opts) ->
+    print_warning(W, Opts).
 
-print_warning(W) ->
-    S = format_warning(W),
+print_warning(W, Opts) ->
+    Prefix = case lists:member(warnings_as_errors, Opts) of
+		 true ->
+		     "";
+		 false ->
+		     "*WARNING* "
+	     end,
+    S = format_warning(Prefix, W),
     io:format("~s", [S]).
 
-format_warning({erts_vsn_changed, {Rel1, Rel2}}) ->
-    io_lib:format("*WARNING* The ERTS version changed between ~p and ~p~n",
-		  [Rel1, Rel2]);
-format_warning(What) ->
-    io_lib:format("*WARNING* ~p~n",[What]).
+format_warning(W) ->
+    format_warning("*WARNING* ", W).
+
+format_warning(Prefix, {erts_vsn_changed, {Rel1, Rel2}}) ->
+    io_lib:format("~sThe ERTS version changed between ~p and ~p~n",
+		  [Prefix, Rel1, Rel2]);
+format_warning(Prefix, What) ->
+    io_lib:format("~s~p~n",[Prefix, What]).
 
 
 get_reason({error, {open, _, _}}) -> open;
diff --git a/lib/sasl/test/systools_SUITE.erl b/lib/sasl/test/systools_SUITE.erl
index 539f6de99d..e352247d44 100644
--- a/lib/sasl/test/systools_SUITE.erl
+++ b/lib/sasl/test/systools_SUITE.erl
@@ -396,6 +396,7 @@ src_tests_script(Config) when is_list(Config) ->
     ?line PSAVE = code:get_path(),		% Save path
 
     ?line {LatestDir, LatestName} = create_script(latest,Config),
+    ?line BootFile = LatestName ++ ".boot",
 
     ?line DataDir = filename:absname(?copydir),
     ?line LibDir = fname([DataDir, d_missing_src, lib]),
@@ -416,14 +417,32 @@ src_tests_script(Config) when is_list(Config) ->
     ?line Erl2 = filename:join([P1,"..","src","db2.erl"]),
     ?line file:delete(Erl2),
 
-    %% Then make script - two warnings should be issued when
-    %% src_tests is given
+    %% Then make script
+
+    %% .boot file should not exist
+    ?line ok = file:delete(BootFile),
+    ?line false = filelib:is_regular(BootFile),
+    %% With warnings_as_errors and src_tests option, an error should be issued
+    ?line error =
+	systools:make_script(LatestName, [silent, {path, N}, src_tests,
+					  warnings_as_errors]),
+    ?line error =
+	systools:make_script(LatestName, [{path, N}, src_tests,
+					  warnings_as_errors]),
+
+    %% due to warnings_as_errors .boot file should still not exist
+    ?line false = filelib:is_regular(BootFile),
+
+    %% Two warnings should be issued when src_tests is given
     %% 1. old object code for db1.beam
     %% 2. missing source code for db2.beam
     ?line {ok, _, [{warning,{obj_out_of_date,_}},
 		   {warning,{source_not_found,_}}]} =
 	systools:make_script(LatestName, [silent, {path, N}, src_tests]),
 
+    %% .boot file should exist now
+    ?line true = filelib:is_regular(BootFile),
+
     %% Without the src_tests option, no warning should be issued
     ?line {ok, _, []} =
 	systools:make_script(LatestName, [silent, {path, N}]),
@@ -1150,6 +1169,21 @@ normal_relup(Config) when is_list(Config) ->
 			    [{path, P}, silent]),
     ?line ok = check_relup([{db, "2.1"}], [{db, "1.0"}]),
 
+    %% file should not be written if warnings_as_errors is enabled.
+    %% delete before running tests.
+    ?line ok = file:delete("relup"),
+
+    %% Check that warnings are treated as errors
+    ?line error =
+	systools:make_relup(LatestName, [LatestName2], [LatestName1],
+			    [{path, P}, warnings_as_errors]),
+    ?line error =
+	systools:make_relup(LatestName, [LatestName2], [LatestName1],
+			    [{path, P}, silent, warnings_as_errors]),
+
+    %% relup file should not exist
+    ?line false = filelib:is_regular("relup"),
+
     %% Check that warnings get through
     ?line ok = systools:make_relup(LatestName, [LatestName2], [LatestName1],
 				   [{path, P}]),
@@ -1159,6 +1193,9 @@ normal_relup(Config) when is_list(Config) ->
 			    [{path, P}, silent]),
     ?line ok = check_relup([{fe, "3.1"}, {db, "2.1"}], [{db, "1.0"}]),
 
+    %% relup file should exist now
+    ?line true = filelib:is_regular("relup"),
+
     ?line ok = file:set_cwd(OldDir),
     ok.
 
diff --git a/lib/snmp/test/snmp_compiler_test.erl b/lib/snmp/test/snmp_compiler_test.erl
index cee11ba97a..c964b08168 100644
--- a/lib/snmp/test/snmp_compiler_test.erl
+++ b/lib/snmp/test/snmp_compiler_test.erl
@@ -47,7 +47,7 @@
 	 module_identity/1,
 	 agent_capabilities/1,
 	 module_compliance/1, 
-	 warnings_as_errors/1, 
+	 warnings_as_errors/1,
 
 	 otp_6150/1,
 	 otp_8574/1, 
@@ -101,7 +101,7 @@ all() ->
      module_identity, 
      agent_capabilities, 
      module_compliance, 
-     warnings_as_errors, 
+     warnings_as_errors,
      {group, tickets}
     ].
 
@@ -282,8 +282,8 @@ warnings_as_errors(Config) when is_list(Config) ->
     MibDir  = ?config(mib_dir,  Config),
     MibFile = join(MibDir, "OTP8574-MIB.mib"),
     OutFile = join(Dir, "OTP8574-MIB.bin"),
-    Opts =  [{group_check, false}, 
-	     {outdir,      Dir}, 
+    Opts =  [{group_check, false},
+	     {outdir,      Dir},
 	     {verbosity,   trace},
 	     relaxed_row_name_assign_check],
     {error, compilation_failed} =
@@ -291,6 +291,7 @@ warnings_as_errors(Config) when is_list(Config) ->
     false = filelib:is_regular(OutFile),
     {ok, _} = snmpc:compile(MibFile, Opts),
     true = filelib:is_regular(OutFile),
+    ok = file:delete(OutFile),
     ok.