From 615e41b3810cecc7a30668193ce1fb0207cc42c7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn-Egil=20Dahlberg?= <egil@erlang.org>
Date: Thu, 27 Feb 2014 17:50:58 +0100
Subject: erts: Fix Map cmp exact equal of an empty map

The expression,

  #{} =:= M

where M was any Map, would always result in 'true'.

This commit fixes this issue by first comparing sizes for
both terms and then checking for size zero.
---
 erts/emulator/beam/utils.c       |  6 +++++-
 erts/emulator/test/map_SUITE.erl | 19 +++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/erts/emulator/beam/utils.c b/erts/emulator/beam/utils.c
index 5b43d25e3c..738f793020 100644
--- a/erts/emulator/beam/utils.c
+++ b/erts/emulator/beam/utils.c
@@ -2125,7 +2125,11 @@ tailrecur_ne:
 		    if (!is_boxed(b) || *boxed_val_rel(b,b_base) != *aa)
 			goto not_equal;
 		    bb = map_val_rel(b,b_base);
-		    if ((sz = map_get_size((map_t*)aa)) == 0) goto pop_next;
+		    sz = map_get_size((map_t*)aa);
+
+		    if (sz != map_get_size((map_t*)bb)) goto not_equal;
+		    if (sz == 0) goto pop_next;
+
 		    aa += 2;
 		    bb += 2;
 		    sz += 1; /* increment for tuple-keys */
diff --git a/erts/emulator/test/map_SUITE.erl b/erts/emulator/test/map_SUITE.erl
index 8cc5621181..753d6f7727 100644
--- a/erts/emulator/test/map_SUITE.erl
+++ b/erts/emulator/test/map_SUITE.erl
@@ -29,6 +29,7 @@
 	t_guard_receive/1, t_guard_fun/1,
 	t_list_comprehension/1,
 	t_map_sort_literals/1,
+	t_map_equal/1,
 	%t_size/1,
 	t_map_size/1,
 
@@ -74,6 +75,7 @@ all() -> [
 	t_update_assoc,t_update_exact,
 	t_guard_bifs, t_guard_sequence, t_guard_update,
 	t_guard_receive,t_guard_fun, t_list_comprehension,
+	t_map_equal,
 	t_map_sort_literals,
 
 	%% Specific Map BIFs
@@ -450,6 +452,23 @@ t_map_sort_literals(Config) when is_list(Config) ->
 
     ok.
 
+t_map_equal(Config) when is_list(Config) ->
+    true  = id(#{}) =:= id(#{}),
+    false = id(#{}) =:= id(#{a=>1}),
+    false = id(#{a=>1}) =:= id(#{}),
+    true  = id(#{ "a" => "hi", b => 134 }) =:= id(#{ b => 134,"a" => "hi"}),
+
+    false = id(#{ a => 1 }) =:= id(#{ a => 2}),
+    false = id(#{ a => 2 }) =:= id(#{ a => 1}),
+    false = id(#{ a => 2, b => 1 }) =:= id(#{ a => 1, b => 3}),
+    false = id(#{ a => 1, b => 1 }) =:= id(#{ a => 1, b => 3}),
+
+    true = id(#{ a => 1 }) =:= id(#{ a => 1}),
+    true = id(#{ "a" => 2 }) =:= id(#{ "a" => 2}),
+    true = id(#{ "a" => 2, b => 3 }) =:= id(#{ "a" => 2, b => 3}),
+    true = id(#{ a => 1, b => 3, c => <<"wat">> }) =:= id(#{ a => 1, b => 3, c=><<"wat">>}),
+    ok.
+
 %% BIFs
 t_bif_map_get(Config) when is_list(Config) ->
 
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