File 2786-epp-Fix-error-return-for-an-incorrect-preprocessor-i.patch of Package erlang

From f932c79a121a54fbf47c69e282b0933d5a694d9c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Wed, 26 Aug 2020 06:01:38 +0200
Subject: [PATCH] epp: Fix error return for an incorrect preprocessor -if
 directive

Referencing an undefined preprocessor symbol in an `-if` directive
would return an invalid error term not recognized by
`epp:format_error/1`.

https://bugs.erlang.org/browse/ERL-1310
---
 lib/stdlib/src/epp.erl        |  2 ++
 lib/stdlib/test/epp_SUITE.erl | 17 +++++++++++++++--
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/lib/stdlib/src/epp.erl b/lib/stdlib/src/epp.erl
index 181a524db6..92b43a89ce 100644
--- a/lib/stdlib/src/epp.erl
+++ b/lib/stdlib/src/epp.erl
@@ -1106,6 +1106,8 @@ scan_if([{'(',_}|_]=Toks, If, From, St) ->
 	    Error = case Error0 of
 			{_,erl_parse,_} ->
 			    {error,Error0};
+                        {error,ErrL,What} ->
+                            {error,{ErrL,epp,What}};
 			_ ->
 			    {error,{loc(If),epp,Error0}}
 		    end,
diff --git a/lib/stdlib/test/epp_SUITE.erl b/lib/stdlib/test/epp_SUITE.erl
index a90beed4f3..cb1638670c 100644
--- a/lib/stdlib/test/epp_SUITE.erl
+++ b/lib/stdlib/test/epp_SUITE.erl
@@ -1154,7 +1154,12 @@ test_if(Config) ->
 	  {if_7c,
 	   <<"-if(begin true end).\n"		%Not a guard expression.
 	     "-endif.\n">>,
-	   {errors,[{1,epp,{bad,'if'}}],[]}}
+	   {errors,[{1,epp,{bad,'if'}}],[]}},
+
+	  {if_8c,
+	   <<"-if(?foo).\n"                     %Undefined symbol.
+	     "-endif.\n">>,
+	   {errors,[{1,epp,{undefined,foo,none}}],[]}}
 
 	 ],
     [] = compile(Config, Cs),
@@ -1730,6 +1735,12 @@ eval_tests(Config, Fun, Tests) ->
                 Return = Fun(Config, P),
                 case message_compare(E, Return) of
                     true ->
+                        case E of
+                            {errors, Errors} ->
+                                call_format_error(Errors);
+                            _ ->
+                                ok
+                        end,
                         BadL;
                     false ->
                         io:format("~nTest ~p failed. Expected~n  ~p~n"
@@ -1739,7 +1750,6 @@ eval_tests(Config, Fun, Tests) ->
         end,
     lists:foldl(F, [], Tests).
 
-
 check_test(Config, Test) ->
     Filename = "epp_test.erl",
     PrivDir = proplists:get_value(priv_dir, Config),
@@ -1763,6 +1773,9 @@ compile_test(Config, Test0) ->
     Opts = [export_all,nowarn_export_all,return,nowarn_unused_record,{outdir,PrivDir}],
     case compile_file(File, Opts) of
         {ok, Ws} -> warnings(File, Ws);
+        {errors, Errors}=Else ->
+            call_format_error(Errors),
+            Else;
         Else -> Else
     end.
 
-- 
2.26.2