compile: add flag warnings_as_errors to treat warnings as errors

With this flag, warnings are treated as errors, like gcc flag '-Werror'.

3 files changed, 48 insertions, 13 deletions

diff --git a/lib/compiler/doc/src/compile.xml b/lib/compiler/doc/src/compile.xml
index c39c9b25eb..d6e81165d8 100644
--- a/lib/compiler/doc/src/compile.xml
+++ b/lib/compiler/doc/src/compile.xml
@@ -212,6 +212,12 @@
               success.</p>
           </item>
 
+          <tag><c>warnings_as_errors</c></tag>
+          <item>
+            <p>Causes warnings to be treated as errors. This option is supported
+            since R13B04.</p>
+          </item>
+
           <tag><c>return</c></tag>
           <item>
             <p>This is a short form for both <c>return_errors</c> and
diff --git a/lib/compiler/src/compile.erl b/lib/compiler/src/compile.erl
index a10c75c9da..8dd7cea38c 100644
--- a/lib/compiler/src/compile.erl
+++ b/lib/compiler/src/compile.erl
@@ -318,17 +318,30 @@ run_tc({Name,Fun}, St) ->
     Val.
 
 comp_ret_ok(#compile{code=Code,warnings=Warn0,module=Mod,options=Opts}=St) ->
-    Warn = messages_per_file(Warn0),
-    report_warnings(St#compile{warnings = Warn}),
-    Ret1 = case member(binary, Opts) andalso not member(no_code_generation, Opts) of
-	       true -> [Code];
-	       false -> []
-	   end,
-    Ret2 = case member(return_warnings, Opts) of
-	       true -> Ret1 ++ [Warn];
-	       false -> Ret1
-	   end,
-    list_to_tuple([ok,Mod|Ret2]).
+    case member(warnings_as_errors, Opts) andalso length(Warn0) > 0 of
+        true ->
+            case member(report_warnings, Opts) of
+                true ->
+		    io:format("~p: warnings being treated as errors\n",
+			      [?MODULE]);
+                false ->
+		    ok
+            end,
+            comp_ret_err(St);
+        false ->
+            Warn = messages_per_file(Warn0),
+            report_warnings(St#compile{warnings = Warn}),
+            Ret1 = case member(binary, Opts) andalso
+		       not member(no_code_generation, Opts) of
+                       true -> [Code];
+                       false -> []
+                   end,
+            Ret2 = case member(return_warnings, Opts) of
+                       true -> Ret1 ++ [Warn];
+                       false -> Ret1
+                   end,
+            list_to_tuple([ok,Mod|Ret2])
+    end.
 
 comp_ret_err(#compile{warnings=Warn0,errors=Err0,options=Opts}=St) ->
     Warn = messages_per_file(Warn0),
diff --git a/lib/compiler/test/error_SUITE.erl b/lib/compiler/test/error_SUITE.erl
index 477730c3ac..757e1c5725 100644
--- a/lib/compiler/test/error_SUITE.erl
+++ b/lib/compiler/test/error_SUITE.erl
@@ -21,11 +21,11 @@
 -include("test_server.hrl").
 
 -export([all/1,
-	 head_mismatch_line/1,r11b_binaries/1]).
+	 head_mismatch_line/1,r11b_binaries/1,warnings_as_errors/1]).
 
 all(suite) ->
     test_lib:recompile(?MODULE),
-    [head_mismatch_line,r11b_binaries].
+    [head_mismatch_line,r11b_binaries,warnings_as_errors].
 
 %% Tests that a head mismatch is reported on the correct line (OTP-2125).
 head_mismatch_line(Config) when is_list(Config) ->
@@ -73,6 +73,20 @@ r11b_binaries(Config) when is_list(Config) ->
     ?line [] = run(Config, Ts),
     ok.
 
+warnings_as_errors(Config) when is_list(Config) ->
+    Ts = [{warnings_as_errors,
+           <<"
+               t() ->
+                 A = unused,
+                 ok.
+             ">>,
+           [warnings_as_errors],
+          {error,
+           [],
+           [{3,erl_lint,{unused_var,'A'}}]} }],
+    ?line [] = run(Config, Ts),
+    ok.
+
 
 run(Config, Tests) ->
     F = fun({N,P,Ws,E}, BadL) ->
@@ -104,6 +118,8 @@ run_test(Conf, Test0, Warnings) ->
     %% Test result of compilation.
     ?line Res = case compile:file(File, Opts) of
 		    {error,[{_File,Es}],Ws} ->
+			{error,Es,Ws};
+		    {error,Es,[{_File,Ws}]} ->
 			{error,Es,Ws}
 		end,
     file:delete(File),