File 0197-epp-Fix-inconsistent-handling-of-undefined... of Package erlang

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File 0197-epp-Fix-inconsistent-handling-of-undefined-pre-defin.patch of Package erlang (Revision 1cbc14a9258a28addda6173b430c4a37)

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From 54dde00bcc42112f3588deb330118964fe21458e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Wed, 23 Jun 2021 09:05:12 +0200
Subject: [PATCH] epp: Fix inconsistent handling of undefined pre-defined
 macros

The `?MODULE` pre-defined macro would be considered defined even before
a `-module()` definition had been seen. For example:

-ifdef(MODULE).
    -error("?MODULE is incorrectly considered defined").
    -endif.
    -module(t).

When attempting to compile this module, the following error would
be produced:

t.erl:2:2: -error("?MODULE is incorrectly considered defined").
    %    2| -error("?MODULE is incorrectly considered defined").
    %     |  ^

The behavior is inconsistent with how an attempt to use ?MODULE before
the `-module()` definition has been seen is handled (there will be
an "undefined macro" error).

This bug matters in practice because Elixir is pre-processing `.hrl`
files containing record declarations in order to build helper
functions. Pre-processing the following header file will fail when
pre-processed in isolation by Elixir:

-ifdef(MODULE).
    -record(r, {x = ?MODULE}).
    -endif.

Fixes #4995.
---
 lib/stdlib/src/epp.erl        | 31 +++++++++++++++++++------------
 lib/stdlib/test/epp_SUITE.erl | 15 +++++++++++++--
 2 files changed, 32 insertions(+), 14 deletions(-)

diff --git a/lib/stdlib/src/epp.erl b/lib/stdlib/src/epp.erl
index 8577fca072..9db34afdad 100644
--- a/lib/stdlib/src/epp.erl
+++ b/lib/stdlib/src/epp.erl
@@ -1088,17 +1088,17 @@ scan_include_lib1(Toks, Inc, From, St) ->
 %%  Report a badly formed if[n]def test and then treat as undefined macro.
 
 scan_ifdef([{'(',_Alp},{atom,_Am,M},{')',_Arp},{dot,_Ad}], _IfD, From, St) ->
-    case St#epp.macs of
-	#{M:=_Def} ->
+    case is_macro_defined(M, St) of
+        true ->
 	    scan_toks(From, St#epp{istk=[ifdef|St#epp.istk]});
-	_ ->
+        false ->
 	    skip_toks(From, St, [ifdef])
     end;
 scan_ifdef([{'(',_Alp},{var,_Am,M},{')',_Arp},{dot,_Ad}], _IfD, From, St) ->
-    case St#epp.macs of
-	#{M:=_Def} ->
+    case is_macro_defined(M, St) of
+        true ->
 	    scan_toks(From, St#epp{istk=[ifdef|St#epp.istk]});
-	_ ->
+        false ->
 	    skip_toks(From, St, [ifdef])
     end;
 scan_ifdef(Toks, IfDef, From, St) ->
@@ -1107,17 +1107,17 @@ scan_ifdef(Toks, IfDef, From, St) ->
     wait_req_skip(St, [ifdef]).
 
 scan_ifndef([{'(',_Alp},{atom,_Am,M},{')',_Arp},{dot,_Ad}], _IfnD, From, St) ->
-    case St#epp.macs of
-	#{M:=_Def} ->
+    case is_macro_defined(M, St) of
+        true ->
 	    skip_toks(From, St, [ifndef]);
-	_ ->
+        false ->
 	    scan_toks(From, St#epp{istk=[ifndef|St#epp.istk]})
     end;
 scan_ifndef([{'(',_Alp},{var,_Am,M},{')',_Arp},{dot,_Ad}], _IfnD, From, St) ->
-    case St#epp.macs of
-	#{M:=_Def} ->
+    case is_macro_defined(M, St) of
+        true ->
 	    skip_toks(From, St, [ifndef]);
-	_ ->
+        false ->
 	    scan_toks(From, St#epp{istk=[ifndef|St#epp.istk]})
     end;
 scan_ifndef(Toks, IfnDef, From, St) ->
@@ -1125,6 +1125,13 @@ scan_ifndef(Toks, IfnDef, From, St) ->
     epp_reply(From, {error,{loc(T),epp,{bad,ifndef}}}),
     wait_req_skip(St, [ifndef]).
 
+is_macro_defined(Name, #epp{macs=Macs}) ->
+    case Macs of
+        #{Name := undefined} -> false;
+        #{Name := _Def} -> true;
+        #{} -> false
+    end.
+
 %% scan_else(Tokens, ElseToken, From, EppState)
 %%  If we are in an if body then convert to else and skip, if we are in an
 %%  else or not in anything report an error.
diff --git a/lib/stdlib/test/epp_SUITE.erl b/lib/stdlib/test/epp_SUITE.erl
index 11f3bb4adb..8ec9b7acb8 100644
--- a/lib/stdlib/test/epp_SUITE.erl
+++ b/lib/stdlib/test/epp_SUITE.erl
@@ -24,7 +24,7 @@
 -export([rec_1/1, include_local/1, predef_mac/1,
 	 upcase_mac_1/1, upcase_mac_2/1,
 	 variable_1/1, otp_4870/1, otp_4871/1, otp_5362/1,
-         pmod/1, not_circular/1, skip_header/1, otp_6277/1, otp_7702/1,
+         pmod/1, not_circular/1, skip_header/1, otp_6277/1, gh_4995/1, otp_7702/1,
          otp_8130/1, overload_mac/1, otp_8388/1, otp_8470/1,
          otp_8562/1, otp_8665/1, otp_8911/1, otp_10302/1, otp_10820/1,
          otp_11728/1, encoding/1, extends/1,  function_macro/1,
@@ -66,7 +66,7 @@ suite() ->
 all() -> 
     [rec_1, {group, upcase_mac}, include_local, predef_mac,
      {group, variable}, otp_4870, otp_4871, otp_5362, pmod,
-     not_circular, skip_header, otp_6277, otp_7702, otp_8130,
+     not_circular, skip_header, otp_6277, gh_4995, otp_7702, otp_8130,
      overload_mac, otp_8388, otp_8470, otp_8562,
      otp_8665, otp_8911, otp_10302, otp_10820, otp_11728,
      encoding, extends, function_macro, test_error, test_warning,
@@ -479,6 +479,17 @@ otp_6277(Config) when is_list(Config) ->
     [] = check(Config, Ts),
     ok.
 
+%% Test -ifdef(MODULE) before module declaration. Should not be
+%% considered defined.
+gh_4995(Config) when is_list(Config) ->
+    Ts = [{gh_4995,
+           <<"-ifdef(MODULE).
+              -record(r, {x = ?MODULE}).
+              -endif.">>,
+           []}],
+    [] = check(Config, Ts),
+    ok.
+
 %% OTP-7702. Wrong line number in stringifying macro expansion.
 otp_7702(Config) when is_list(Config) ->
     Dir = proplists:get_value(priv_dir, Config),
-- 
2.26.2

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File 0197-epp-Fix-inconsistent-handling-of-undefined-pre-defin.patch of Package erlang (Revision 1cbc14a9258a28addda6173b430c4a37)

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